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WELDER, NSQF LEVEL - 4, , 1st Semester, TRADE THEORY, SECTOR: Fabrication, , DIRECTORATE GENERAL OF TRAINING, MINISTRY OF SKILL DEVELOPMENT & ENTREPRENEURSHIP, GOVERNMENT OF INDIA, , NATIONAL INSTRUCTIONAL, MEDIA INSTITUTE, CHENNAI, Post Box No. 3142, CTI Campus, Guindy, Chennai - 600 032, (i)

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Sector, , : Fabrication, , Duration : 1 - Year, Trade, , : Welder 1st Semester - Trade Theory - NSQF LEVEL 4, , Copyright © 2018 National Instructional Media Institute, Chennai, , All rights reserved., , Copies : 1,000, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Rs.240/-, , August 2018, , Co, , First Edition :, , No part of this publication can be reproduced or transmitted in any form or by any means, electronic or mechanical, including, photocopy, recording or any information storage and retrieval system, without permission in writing from the National, Instructional Media Institute, Chennai., , Published by:, NATIONAL INSTRUCTIONAL MEDIA INSTITUTE, P. B. No.3142, CTI Campus, Guindy Industrial Estate,, Guindy, Chennai - 600 032., Phone : 044 - 2250 0248, 2250 0657, 2250 2421, Fax : 91 - 44 - 2250 0791, email : nimi_bsnl@dataone.in, chennai-nic.in, Website: www.nimi.gov.in, (ii)

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FOREWORD, , The Government of India has set an ambitious target of imparting skills to 30 crores people, one out of every, four Indians, by 2020 to help them secure jobs as part of the National Skills Development Policy. Industrial, Training Institutes (ITIs) play a vital role in this process especially in terms of providing skilled manpower., Keeping this in mind, and for providing the current industry relevant skill training to Trainees, ITI syllabus, has been recently updated with the help of Mentor Councils comprising various stakeholder's viz. Industries,, Entrepreneurs, Academicians and representatives from ITIs., The National Instructional Media Institute (NIMI), Chennai, an autonomous body under the Directorate, General of Training (DGT), Ministry of Skill Development & Entrepreneurship is entrusted with developing, producing and disseminating Instructional Media Packages (IMPs) required for ITIs and other related, institutions., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The institute has now come up with instructional material to suit the revised curriculum for Welder, 1st Semester Trade Theory NSQF Level - 4 in Fabrication Sector under Semester Pattern. The, NSQF Level - 4 Trade Theory will help the trainees to get an international equivalency standard where their, skill proficiency and competency will be duly recognized across the globe and this will also increase the, scope of recognition of prior learning. NSQF Level - 4 trainees will also get the opportunities to promote life, long learning and skill development. I have no doubt that with NSQF Level - 4 the trainers and trainees of, ITIs, and all stakeholders will derive maximum benefits from these IMPs and that NIMI's effort will go a long, way in improving the quality of Vocational training in the country., The Executive Director & Staff of NIMI and members of Media Development Committee deserve appreciation, for their contribution in bringing out this publication., , Co, , Jai Hind, , ASHEESH SHARMA, Joint Secretary, Ministry of Skill Development & Entrepreneurship,, Government of India., , New Delhi - 110 001, , (iii)

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PREFACE, The National Instructional Media Institute (NIMI) was established in 1986 at Chennai by then Directorate, General of Employment and Training (D.G.E & T), Ministry of Labour and Employment, (now under Directorate, General of Training, Ministry of Skill Development and Entrepreneurship) Government of India, with technical, assistance from the Govt. of the Federal Republic of Germany. The prime objective of this institute is to, develop and provide instructional materials for various trades as per the prescribed syllabi (NSQF) under the, Craftsman and Apprenticeship Training Schemes., The instructional materials are created keeping in mind, the main objective of Vocational Training under, NCVT/NAC in India, which is to help an individual to master skills to do a job. The instructional materials are, generated in the form of Instructional Media Packages (IMPs). An IMP consists of Theory book, Practical, book, Test and Assignment book, Instructor Guide, Audio Visual Aid (Wall charts and Transparencies) and, other support materials., The trade practical book consists of series of exercises to be completed by the trainees in the workshop., These exercises are designed to ensure that all the skills in the prescribed syllabus are covered. The trade, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , theory book provides related theoretical knowledge required to enable the trainee to do a job. The test and, assignments will enable the instructor to give assignments for the evaluation of the performance of a trainee., The wall charts and transparencies are unique, as they not only help the instructor to effectively present a, topic but also help him to assess the trainee's understanding. The instructor guide enables the instructor to, plan his schedule of instruction, plan the raw material requirements, day to day lessons and demonstrations., In order to perform the skills in a productive manner instructional videos are embedded in QR code of the, exercise in this instructional material so as to integrate the skill learning with the procedural practical steps, given in the exercise. The instructional videos will improve the quality of standard on practical training and, will motivate the trainees to focus and perform the skill seamlessly., , Co, , IMPs also deals with the complex skills required to be developed for effective team work. Necessary care, has also been taken to include important skill areas of allied trades as prescribed in the syllabus., The availability of a complete Instructional Media Package in an institute helps both the trainer and, management to impart effective training., The IMPs are the outcome of collective efforts of the staff members of NIMI and the members of the Media, Development Committees specially drawn from Public and Private sector industries, various training institutes, under the Directorate General of Training (DGT), Government and Private ITIs., NIMI would like to take this opportunity to convey sincere thanks to the Directors of Employment & Training, of various State Governments, Training Departments of Industries both in the Public and Private sectors,, Officers of DGT and DGT field institutes, proof readers, individual media developers and coordinators, but for, whose active support NIMI would not have been able to bring out this materials., , R. P. DHINGRA, EXECUTIVE DIRECTOR, , Chennai - 600 032, , (iv)

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INTRODUCTION, This manual for trade practical is intended for use in the ITI workshop. It consists of a series of practical exercises, that are to be completed by the trainees during the first semester of course is the Welder trade under, Fabrication Sector. It is National Skills Qualifications Framework (NSQF) - Level 4, supplemented and, supported by instructions/information to assist the trainees in performing the exercise. The exercises are designed, to ensure that all the skills prescribed in the syllabus are covered including the allied trades.The syllabus for the1st, Semester Welder Trade under Fabrication Sector Trade Theory is divided into six modules.The allocation of time, for the various modules is given below:, Module 1 - Induction Training and Welding Process, , 16 Exercises, , 117 Hrs, , Module 2 - Welding Techiniques, , 08 Exercises, , 75 Hrs, , Module 3 - Weldability of steel (OAW, SMAW), , 32 Exercises, , 333 Hrs, , 56 Exercises, , 525 Hrs, , Total, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The syllabus and the content in the modules are interlinked. As the number of workstations available in the electrical, section is limited by the machinery and equipment, it is necessary to interpolate the exercises in the modules to, form a proper teaching and learning sequence. The sequence of instruction is given in the schedule of instruction, which is incorporated in the Instructor's Guide. With 25 practical hours a week of 5 working days 100 hours of, practical per month is available., Contents of Trade Theory, , The procedure for working through the 64 exercises for the 1st semester with the specific objectives as the learning, out comes at the end of each exercise is given is this book., , Co, , The skill objectives and tools/instruments, equipment/machines and materials required to perform the exercise are, given in the beginning of each exercise.Skill training in the shop floor is planned through a series of practical, exercises/experiments to support the related theory to make the trainees get hands on trainning in the Electrician, trade along with the relevant cognitive skills appropriate for the level. A minimum number of projects have been, included to make the training more effective and develop attitude to work in a team. Pictorial, schematic, wiring and, circuit diagrams have been included in the exercises, wherever necessary, to assist the trainees broaden their views., The symbols used in the diagrams comply with the Bureau of Indian Standards (BIS) specifications., Illustrations in this manual, help trainess visual perspective of the ideas and concepts.The procedures to be followed, for completing the exercises is also given. Different forms of intermediate test questions have been included in the, exercises, to enhance the trainee to trainee and trainee to instructor interactions., Skill Information, Skill areas which are repetitive in nature are given as separate skill information sheets. Skills which are to be, developed in specific areas are included in the exercises itself. Some subexercises are developed to fulfill the, sequence of exercises in keeping with the syllabus., This manual on trade practical forms part of the Written Instructional Material (WIM). Which includes manual on, trade theory and assignment/test., , (vi)

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CONTENTS, Lesson No., , Title of the Lesson, , Page No., , Module 1 : Induction Training and Welding Process (OAW, SMAW), 1.1.01, , Importance of welder trade training, , 1, , General discipline in the institute, , 2, , Elementary first aid, , 3, , Safety rules for gas cylinders, , 5, , 1.1.03, , Importance of welding in industry, , 7, , 1.1.04, , Hacksaw frames and blades, , 8, , Files-Grades and specification, , 9, , Cut of files, , 10, , File specifications and grades, , 11, , 1.1.02, , File shapes, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Cleaning of files, , 12, , Try square, , 13, , Bench vice, , 14, , Introduction and definition of welding, , 15, , Safety in shielded metal arc welding, , 16, , Safety in gas cutting process, , 19, , Length measurement, , 21, , Steel rule, , 21, , Co, , 1.1.05, , Mallets, , Types of calipers, , 22, , Marking media, , 23, , Jenny calipers, , 24, , Scribers, , 1.1 06, , Dividers, , 25, , Surface gauges, , 26, , Types of marking punches, , 28, , Angular measuring instruments (Semi-precision), , 29, , Datum, , 29, , Hammer, , 30, , Arc welding machines, , 32, , Arc welding accessories, , 33, , High pressure oxy-acetylene welding equipment and accessories, , 35, , (vii)

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Lesson No., , Title of the Lesson, , Page No., , Gas welding hand tools, , 37, , Various welding processes and its application, , 40, , Shielded metal arc welding, , 41, , 1.1.08, , Welding terms & Its definition, , 43, , 1.1.09, , Bolted joints, , 44, , Rivet joints, , 46, , Soldering, , 47, , Soldering iron (Soldering bit), , 48, , Solder, , 49, , Soldering flux, , 50, , Portable hand forge with blower, , 52, , 1.1.07, , Dipping solution, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Safety precautions in soldering, Soft soldering, , 53, , Soldered joint, , 54, , Blow lamp, , 55, , Factors considered while soldering, , 56, , Seaming and machine, , 60, , Basic welding joints and Nomenclature of Butt and fillet weld., , 62, , Material preparation method, , 64, , Co, , 1.1.10, , Soft soldering, brazing and silver brazing, , Edge preparation, , Methods of cleaning the base metals before welding, , 66, , 1.1.11, , Basic electricity as applied to welding, , 67, , 1.1.12, , Heat and temperature, , 69, , Principle of arc welding, , 70, , 1.1.13, , Gases used for welding and gas flame combinations, , 73, , 1.1.14, , Chemistry of oxy-acetylene flame, , 74, , Types of oxy-acetylene flames, , 75, , 1.1.15, , Principle of gas cutting and application, , 76, , 1.1.16, , Oxy-acetylene hand cutting - Piercing hole and profile cutting, , 78, , Oxy-acetylene cutting equipment, , 81, , 1.1.17, , Oxy-acetylene machine cutting, , 83, , 1.1.18, , Common defects in gas cutting, , 86, , (viii)

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Lesson No., , Title of the Lesson, , Page No., , Module 2 : Welding techniques, Power source selection criteria, , 88, , 1.2.20, , A.C. Welding transformer DC welding Generator and its construction, , 89, , AC/DC Welding rectifier and its construction, , 91, , Inverters, , 92, , 1.2.21, , Advantages and disadvantages of AC and DC welding, , 93, , 1.2.22, , Basic welding positions, , 94, , 1.2.23, , Weld slope and rotation, , 95, , 1.2.24, , Weld symbol and welding symbol - Description and uses, , 97, , American Welding Society Welding Symbol Chart, , 103, , Arc length and its effects, , 104, , Metal transfer across the arc (Characteristics of arc), , 105, , Polarity in DC arc welding, , 106, , Weld quality and inspection (Visual inspection), , 109, , Weld gauges and its uses, , 111, , Calcium carbide properties and its uses, , 113, , Acetylene gas - Properties, , 114, , 1.2.25, , 1.2.26, 1.2.27, 1.2.28, 1.2.29, 1.2.30, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 1.2.19, , Acetylene gas generation, , 1.2.31, , Water to carbide acetylene gas generator, , 115, , Carbide to water type acetylene gas generator, , 116, , Acetylene gas purifier, , 118, , Co, , Hydraulic back pressure valve, Flash Back Arrestor, , 119, , Oxygen gas - Properties and production, , 121, , Oxygen gas cylinder, , 123, , Dissolved acetylene gas cylinder, , 124, , Welding gas regulator, , 125, , 1.2.34, , Systems of oxy-acetylene welding, , 137, , 1.2.35, , Gas welding torch its type and construction, , 129, , 1.2.36, , Welding technique of oxy-acetylene welding, , 131, , Rightward technique of oxy-acetylene gas welding ×, , 132, , 1.2.37, , Arc blow its causes and remedial measures, , 134, , 1.2.38, , Distortion and its control, , 136, , 1.2.39, , Defects in arc welding - Its effect, , 142, , Defects in arc welding - Definition, causes and remedies, , 143, , Pipe joints, , 148, , Pipe welding by arc in fixed positions, , 154, , 1.2.32, 1.2.33, , 1.2.40, , (ix)

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Lesson No., , Title of the Lesson, , Page No., , Welding of M.S. pipe, , 157, , 1.2.41, , Difference between plate welding and pipe welding, , 163, , 1.2.42, , Development of a pipe elbow joint, , 165, , Development of a pipe "T" joint, , 166, , Pipe development for "Y" joint, , 169, , Development of 45° and 90° branch pipe, , 171, , 1.2.43, , Manifold system, , 172, , 1.2.44, , Different types of filler rods used in gas welding, , 173, , Gas welding fluxes and function, Module 3 : Weldability of steel (OAW, 8mAW), , 1.3.46, , 1.3.47, , Defects in gas welding, , 179, , Weld defects - Causes and remedies, , 181, , Arc welding electrodes, , 183, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 1.3.45, , Composition/Characteristics flux, , 184, , Sizes of mild steel electrodes, , 185, , Coding of electrodes as per BIS, AWS and BS, , 188, , Effects of moisture pick up storage and baking of electrodes, , 195, , Special purpose electrodes and their applications, Weldability of metals, , 197, , 1.3.49, , Importances of preheating, post-heating and maintenance of, inter-pass temperature, , 198, , 1.3.50, , Classification of steels, , 200, , 1.3.51, , Co, , 1.3.48, , Welding of low carbon steel, medium and high carbon steel, , 202, , Alloying elements and their functions on steel, , 204, , 1.3.53, , Stainless steel properties types weld decay and weldability, , 205, , 1.3.54, , Welding of brass, , 207, , 1.3.55, , Copper-properties-types and weldability, , 208, , 1.3.56, , Bronze welding of copper, , 210, , 1.3.57, , Welding of aluminium and its alloys, , 212, , 1.3.58, , Metallic arc cutting and gouging, , 214, , 1.3.59, , Carbon arc cutting and gouging, , 216, , 1.3.60, , Cast iron-properties-types and weldability, , 219, , 1.3.61, , Bronze welding of cast iron, , 221, , 1.3.52, , (x)

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Fabrication, Related Theory for Exercise 1.1.01, Welder - Induction Training & Welding Process, Importance of welder trade training, Objectives : At the end of this lesson you shall be able to, • state the competencies achieved in this welder trade, • describe the further learning path ways craftsman training scheme, • explain the employement opportunities on completion of welder trade., This trade is meant for the candidates who aspire to, become a professional WELDER The duration of the trade, is two semesters under craftsam training scheme., , Organization, further for a period of one year under, Apprenticeship Training sheme to acquire practical skills, and knowledge., , Competencies achieved, , Employment Opportunities, , After successful completion of this trade trainee shall be, able to perform the following skills with proper sequence., , On successful completion of this trade, the candidates, shall gain to be fully employed in the following industries:, , 1 welding of M.S. sheet and M.S. pipe by Gas welding, process., , 1 Structural fabrication like bridges, Roof structures,, Building & construction., , 2 Welding of M.S. plate in all position by SMAW, processs., , 2 Automobile and allied industries, 3 Site construction activities for power stations, process, industries and mining., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 3 Staight, bevel & circular cutting on MS. plate by Oxyacetylene cutting process., 4 Repair & Maintenance works, , 4 Service industries like road transportation and, railways., , 5 GMAW welding on M.S sheet & M.S plate., , 5 Ship building and repair, , 6 Operating skills of spot welding machine, PUG cutting, machine,, , 6 Infrastructure and defence organizations, , 7 Welding C.I using SMAW process., Further learning pathways, , 8 Petrochemical industries like ONGC, LOCL, and, HPCL etc, 9 Self employment, , Co, , Also on successful completion of the trade the candidate, can pursue apprenticeship training in Registered Industries/, , 7 In public sector industries like BHEL, NTPC, etc and, private industries in India & Abroad., , 1

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General discipline in the Institute, Objectives: At the end of this lesson you shall be able to, • follow the general discipline laid down by the institute, • avoid any undesirable actions as a learner, • keep up the moral image and reputation of the institute., General discipline: always be polite, courteous while, speaking to any person, (Principal, Training and Office, staff, your co-trainee and any other person visiting your, institute), Do not get into argument with others on matters related to, your training and with the office while seeking clarifications., Do not bring bad name to your institute by your improper, actions., Do not waste your precious time in gossiping with your, friends and on activities other than training., , Do not make noise or be playful while undergoing, training., Keep the institute premises neat and avoid polluting the, environment., Do not take away any material from the institute which, does not belong to you., Always attend the institute well dressed and with good, physical appearance., , Do not be late to the theory and practical classes., , Be regular to attend the training without fail and avoid, abstaining from the theory or practicl classes for simple, reasons., , Do not unnecessarily interfere in other’s activities., , Prepare well before writing a test/examination., , Be very attentive and listen to the lecture carefully during, the theory classes and practical demonstration given by, the training staff., , Aviod any malpractice during the test/examination., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Write your theory and practical records regularly and, submit them on time for correction, , Give respect to your trainer and all other training staff,, office staff and co-trainees., , Take care of your safety as well as other’s safety while, doing the practicals., , Co, , Be interested in all the training activities., , 2, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.01

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Fabrication, Related Theory for Exercise 1.1.02, Welder - Induction Training & Welding Process, Elementary first aid, Objectives : At the end of this lesson you shall be able to, • understand the first aid treatment to be given for, • breathing problems, • electric shock, • burns caused by direct flame or by chemical, • large wounds with or without severe bleeding, • eye injuries due to hot flying particles., Electical shock and breathing problems: The severity, of an electric shock will depend on the level of the current, which passes through the body and the length of time of, contact, Do not delay to disconnect the contact., , Electric burns on the victim may not cover a big area but, may be deep seated. All you can do is to cover the area, with a clean, sterile dressing and treat for shock, Get expert help as quickly as possible., If the affected person is unconscious but is breathing,, loosen the clothing about the neck, chest and waist and, place the affected person in the recovery position.(Fig.3), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , If the person is still in contact with the electric supplybreak, the contact either by switching off the power by removing, the plug or wrenching the cable free.If not, stand on some, insulating material such as dry wood, rubber or plastic,, or using whatever is at hand to insulate yourself and, break the contact by pushing or pulling the person free., (Fig. 1 & 2), , If the victim is at a height from the ground level, proper, safety actions must be taken to prevent him from falling or, atleast make him fall safely., , Keep a constant check on the breathing and pulse rate., , Co, , Keep the affected person warm and comfortable.(Fig.4), , If you remain un-insulated, do not touch the victim with, your bare hands until the circuit is made dead or he is, moved away from the equipment., , Send for help., , Do not give an unconscious person anything, by mouth., Do not leave an unconscious person unattended., , 3

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if the casuality is not breathing-act once-don’t waste time!, Electric shock: The severity of an electric shock will depend on the level of the current which passes through the, body and the length of time of the contact., Other factors that contribute to the severity of shocks are:, -the age of the person, -not wearing insulating footwear or wearing wet footwear, -Weather condition, -floor is wet, - main voltage etc., Effects of an electric shock: The effect of the current at, very low levels may only be an unpleasant tingling, sensation,but this itself may be sufficient to cause one to, lose his balance and fall., , Electrical burns: A person receiving an electric shock, may also get burns when the current passes through his, body. Do not waste time by applying first aid to the burns, until breathing has been restored and the patient can, breathe normally - unaided., Burns and scalds: Burns are very painful. If a large area, of the body is burnt, give no treatment, except to exclude, the air. eg, by covering with water, clean paper, or a clean, shirt. This relieves the pain., Severe bleeding: Any wound which is bleeding profusely, especially in the wrist, hand or fingers must be, considered serious and must receive professiomal attention. As an immediate first aid measure, pressure on the, wound itself is the best means of stopping the bleeding, and avoiding infection., Immediate action: Always in cases of severe bleeding:, , At higher levels of current, the person receiving the shock, may be thrown off his feet and will experience severe pain,, and possibly minor burns at the point of contact., , - make the patient lie down and rest, , At an excessive level of current flow, the muscles may, contract and the person may be unable to release his grip, on the conductor, He may lose consciousness and the, muscles of the heart may contract spasmodically (Fibrillation). This may be fatal., , - apply pressure on the wound, , - if possible, raise the injured part above the level of the, body(Fig,6), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - Call for assistance., , Electric shock can also cause burning of the skin at the, point of contact., Treatment for electric shock:, , Prompt treatment is essential., , If assistance is available nearby. send for medical aid,, then carry on with emergency treatment., , Co, , Switch off the curent, if this can be done without undue, delay. Otherwise, remove the victim from contact with the, live conductor, using dry non-conducting materials such, as a wooden bar, rope, a scarf, the victim’s coat-tails, any, dry article of clothing, a belt, rolled-up newspaper, nonmetalic hose, PVC tubling, bakelite paper, tube etc. (Fig,5), , To control severe bleeding: Squeeze together the sides, of the wound. Apply pressure as long as it is necessaary, to stop the bleeding. When the bleeding has stopped, put, a dressing over the wound, and cover it with a pad of soft, material. (Fig,7), , Avoid direct contact with the victim. Wrap your hands in, dry material if rubber gloves are not available, , For an abdominal stab wound, which may be caused by, falling on a sharp tool, keep the patient bending over the, wound to stop internal bleeding., Large wound: Apply a clean pad (Preferably an individual dressing) and bandage firmly in place, If the bleeding is very severe apply more than one dressing. (Fig.8), , 4, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.02

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Follow the right methods of artifical respiration., Eye injury: For eye irritation caused by arc flashes, use, a mild eye drop and apply 2 to 3 drops for 3 or 4 times a, day. If the injury is due to a metal chip or slag particles, entering the eye then take the injured person to an eye, doctor immediately for treatment. Never rub the eye for, any type of eye injury. It will cause a permanent vision, problem. Also do not apply any eye drop or ointment, without consulting an eye doctor., , Safety rules for gas cylinders, Objectives : At the end of this lesson you shall be able to, • stae various improper practices, while working in gas cylinders, • state different precautions to be taken for the gas cylinders, Never apply undue force to open or close a, cylinder valve., Avoid the use of hammer or wrench., Always use a proper cylinder (or spindle) key to open or, close the cylinder valves., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , oxy- acetylene equipment is safe if it is properly, handled. but it may become a great destructive power, if handled carelessly. It is important that the operator, be familiar with all the safety rules before handling, gas cylinders., Keep the cylinders free of oil, grease or any type of, lubrication., Check leakage before use., , Do not remove the cylinder key from the cylinder valve, when it is in use. It may be needed immediately to close, the gas in case of emergency., , Open cylinder valves slowly., , Never fall or trip over gas cylinders., A valve broken in the oxygen cylinder will cause, it to become a rocket with tremendous force., , Co, , keep the gas cylinders away from exposure to high temperature., Remember the pressure in the gas cylinders, increases with the temperature., , Store full and empty gas cylinders separately in a well, ventilated place., Mark the empty cylinders (MT/EMPTY)with chalk., , If a cylinder leaks due to defective valve or safety plug, do, not try to repair it yourself, but move it to a safe area with, a tag to indicate the fault and then inform the supplier to, pick it up., When the cylinders are not in use or they are being moved,, at on the valve protection caps., Cylinders should always be kept in upright position and, properly chained when in use., Close the cylinder valves both when the gases are full or, empty., , Smoking or naked lights should be strictly, prohibited near gas cylinders., , Never strike an arc or direct gas flame on a gas cylinder., Safety procedure for handling an internally, fired dissolved acetylene (D A) cylinder, , In the case of severe backfire of flashback the DA cylinder, may catch fire., Close the blowpipe valve immediately (oxygen first)., No damage will occur to the cylinder if the backfire is, arrested at the blowpipe., The signs of severe backfire or flashback are:, -, , a squeezing or hissing noise in the blowpipe, , -, , a heavy black smoke and sparks coming out of the, nozzie, , -, , over heating of the blowpipe handle., , To control this:, -, , Close the cylinder valves, , -, , Disconnect the regulator from the cylinder valve, , -, , Check the hosepipes and blowpipe before re-use., , Never remove the valves protection cap while lifting cylinders., , If the cylinder catch fire externally due to the leakage of, gas at the connection:, , Avoid exposing the cylinders to furness heat, open fire or, sparks from the torch., , -, , Close the cylinder valve immediately(wearing asbestos gloves as a safety measure), , - Use carbon dioxide fire extinguisher to extinguish the, Never move a cylinder by dragging. sliding or rolling it on, fire, its sides., Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.02, 5

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-, , rectify the leakage thoroughly before putting into, further use., , -, , cool the cylinder by spraying with water, , -, , inform the gas cylinder supplier immediately., , If the cylinder becomes overheated due to internal or, external fire:, close the cylinder valve, , -, , detach the regulator from the cylinder, , -, , remove the cylinder to an open space, away rom, smoking or naked light, , Never keep such defective cylinders with the, other cylinders., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , 6, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.02

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Fabrication, Related Theory for Exercise 1.1.03, Welder - Induction Training & Welding Process, Importance of welding in Industry, Objectives : At the end of this lesson you shall be able to, • realise and state the importance of welding in industry, • state the advantages of welding over other methods of joining metals., In engineering industry, joining of different type of metals, is necessary to make various components/parts having, different shapes. Various type of parts are joined by bolting, or rivetting if thickness of metal is more. Example: lron, bridges, steam boilers, roof trusses, etc. For joining thin, sheets (2mm thick and below) sheet metal joints are used., Example: Tin containers, oil drums, buckets, funnels,, hoppers etc, also thin sheets can be joined by soldering, and brazing., , Riveting, assembling with bolt, seaming, soldering and, brazing all result in temporary joints. Welding is the, only method to join metals permanently., The temporary joints can be separated if:, -, , the head of the rivet is cut, , -, , nut of the bolt is unscrewed, , -, , hook of the seam is opened, , -, , more heat is given than that required for soldering and, brazing., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , But very heavy thick plates used in heavy industries are, not joined by rivetting or bolting as the joints will not be, able to withstand heavy loads. Also the cost of production, wil be more. So many special materials for special, applications like space ships, atomic power generation,, thin walled containers for storing chemicals. etc have, been developed in the recent years. They can be joined, easily at a lower cost with good joint strength by using, welding. A welded joint is the strongest joint of all the, other types of joints, The effiiency of a welded joint is, 100% whereas the efficiency of other types of joints are, less than 70%, , Comparison between welding and other metal, joining methods, , Advantages of welding, , Welding is superior to other metal joining methods, because it:, -, , is a permanent pressure tight joint, , -, , occupies less space, , -, , gives more economy of material, , -, , has less weight, , Advantages of welding over methods of joining, metals, , -, , Withstands high temperature and pressure equal to, joined material, , Welding method: Welding is metal joining method in, which the joining edges are heated and fused together, to form permanent (homogeneous) bond/joint., , -, , can be done quickly, , -, , gives no colour change to joints, , Co, , So all industries are using welding for the fabrication of, various structures., , it is the strongest joint and any type of metal of any, thickness can be joined., , 7

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Fabrication, Related Theory for Exercise 1.1.04, Welder - Induction Training & Welding Process, Hacksaw frames and blades, objectives: At the end of this lesson you shall be able to, • identify the parts of a hacksaw frame, • specify hacksaw blades, • state the different types of hacksaw frames and their uses., The hand hacksaw is used along with a blade to cut metals, of different sections. It is also used to cut slots and, contours. See fig. 1 to identify the parts., , All hard blades: The full blade is hardened between the, pin holes., Flexible blades: For these types of blades, only the, teeth are hardened. Because of their flexibility, these, blades are useful for cutting along curved lines., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Pitch of Blade (Fig.3): The distance between adjacent, teeth is known as the ‘pitch’ of the blade., , Types of hacksaw frames: The two different types of, hacksaw frames are solid frames and adjustable frames., Solid frame: Only a particular standard length of blade, can be fitted to this frame., , Adjustable frame (Flat type): Different standard lengths, of blades can be fitted to this frame., Adjustable frame (Tubular type): This is the most, commonly used type. It gives a better grip and control,, while sawing. Fig. 1, , Co, , For proper working, it is necessary to have frames of, rigid construction., Hacksaw blades (Fig.2): A hacksaw blade is a thin, narrow steel band with teeth cut on one edge and two, pin holes at the ends. It is used along with a hacksaw, frame. The blade is made of either low alloy steel or, high speed steel and is available in standard lengths of, 250 mm and 300 mm., , Classification pitch, Coarse, , 1.8 mm, , Medium 1.4 mm & 1.0 mm, Fine, , 0.8 mm, , Hacksaw blades are specified according to the length,, pitch and type., Setting of the saw: To prevent the saw blade bending, between the cut edges when penetrating into the material, and to allow free movement of the blade, the width of cut, is to be broader than the thickness of the saw blade. This, is achieved by the setting of the saw teeth. There are two, types of saw settings., Staggered set (Fig.4): Alternate teeth or groups of teeth, are staggered. This arrangement helps for cutting, and, provides for good chip clearance., Wave Set (Fig.5): In this, the teeth of the blade are, arranged in a wave form., , Type of Hacksaw Blades: Two types of hacksaw blades, are available - all hard blades and flexible blades., , 8

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The set of blades can be classified as follows., Pitch, , Type of Set, , 0.8 mm, , Wave set, , 1.0 mm, , Wave or staggered, , For best result, the blade with the right pitch, should be selected and fitted correctly onto the, hacksaw frame., , Over 1.0 mm staggered, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -----------------------, , Files - Grades and specification, , Objectives: At the end of this lesson you shall be able to, • identify the parts of a file., Parts of a file (Fig. 1): The parts of a file as can be, seen in fig. 1, are, , Heel: The portion of the broad part without teeth near the, tang., , Tip or point: The end opposite to tang, , Shoulder: The curved part of the file joining tang from the, body., , Co, , Tang; The narrow and thin part of a file which fits into the, handle, Handle: The part fitted to the tang for holding the file, Ferrule; A protective metal ring to prevent cracking of the, handle., Materials: Generally files are made of high carbon or, high grade cast steel. The body portion is hardened and, tempered. The tang is, however, not hardened., , Face or side: The broad part of the file with teeth cut on, its surface., Edge The thin part of the file with a Single row of parallel, teeth., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04, , 9

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Cut of files, Objectives: At the end of this lesson you shall be able to, • name the different cuts of files, • state the uses of each type of cut., The teeth of a file is formed by cuts made on its face., Files have cuts of different types. Files with different cuts, have different uses., Type of cuts: Basically there are four types., , Rasp Cut File (Fig.3): The rasp cut has individual, sharp,, pointed teeth in a line, and is useful for filing wood, leather, and other soft materials. These files are available only in, half round shape., , Single cut, Double cut, Rasp cut and curved cut., Single cut File (Fig. 1): a single cut file has rows of, teeth cut in one direction across its face. The teeth are at, an angle of 60° to the center line. It can cut chips as wide, as the cut of the file. Files with this cut are useful for filing, soft metals like brass, aluminium, bronze and copper., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Curved cut file (Fig.4): These files have deeper cutting, action and are useful for filing soft materials like- aluminium, tin, copper and plastic. The curved cut are, available only in a flat shape., , Single cut files do not remove stock as fast as double cut, files, but the surface finish obatained is much smoother., , Co, , Double cut cile (Fig.2): A double cut file has two rows of, teeth cut diagonal to each other. The first row of teeth is, known as OVERCUT and they are cut at an angle of 70°, The other cut, mde diagonal to this, is known as UPCUT,, and is at an angle of 51°. This removes stock faster than, the single cut file., , 10, , The selection of a file with a particular type of cut is based, on the material to be filed. Single cut files are used for, filing soft materials., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04

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File specifications and grades, Objectives: At the end of this lesson you shall be able to, • state how files are specified, • name the different grades of files, • state the application of each grade of file., Files are manufactured in different types and grades to, meet the various needs., Files are specified according to their length, grade, cut, and shape., Length is the distance from the tip of a file to the heel. Fig, 1 under lesson parts of a File., File grades are determined by the spacing of the teeth., A rough file is used for removing rapidly a larger quantity of, metal. It is mostly used for trimming the rough edges of, soft metal castings., , File shapes, , A smooth file is used to remove small quantity of material, and to give a good finish., A dead smooth file is used to bring to accurate size with a, high degree of finish., The most used grades of files are bastard,, second cut, smooth and dead smooth. These, are the grades recommended by the Bureau, of Indian Standards. (BIS), Different sizes of files with the same grade will have varying, sizes of teeth. In longer files, the teeth will be coarser., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , A bastard file is used in cases where there is a heavy, reduction of material., , A second cut file is used to give a good finish on metals, It, is excellent to file hard metals. It is useful for bringing the, jobs close to the finishing size., , Objectives: At the end of this lesson you shall be able to, • state the features of flat and hand files, • state the application of flat and hand files., Files are made in different shapes so as to be able to file, and finish components to different shapes,, , The shape of files is usually specified by their cross section, as flat, square, triangular, round, half round and knife edge., , Hand files (Fig. 2): These files are similar to the flat files, in their cross section. The edges along the width are, parallel throughout the length. The faces are double cut., , The files useful for this this execise i,e., filing to square, are flat files and hand files., , Co, , Flat files (Fig. 1): These files are of a rectangular cross, section. The edges along the width of these files are parallel, up to two-thirds of the length. and then they taper towards, the point. The faces are double cut, and the edges single, cut. These file are used for general purpose work. They, are useful for filing and finishing external and internal, surfaces., , One edge is single cut whereas the other is safe edge., Because of the safe edge, they are useful for filing surfaces, which are at rigt angles to surfaces already finished., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04, , 11

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Cleaning of files, Objectives: At the end of this lesson you shall be able to, • understand how to clean files, During filing, the metal chips (Filings) will clog between, the teeth of the files. This is known as ‘pinning’ of the, files. Files which are pinned will produce scratches on the, surface being filed, and also will not bite well to cut the, metal properly., , When filing a work piece to a smooth finish more’ pinning’, will take place because the pitch and depth of the teeth, are less. The file can also be cleaned by rubbing a copper, or brass strip over the pinned surface. (Fig. 2), , Method of removing pinning: Pinning of the files is, removed by using a file brush. (File card), Press the file brush on the surface of pinned file and pull it, along the direction of the overcut. (Fig. 1), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Application of chalk on the face of the file will help reduce, the penetration of the teeth and ‘pinning’., Clean the file frequently in order to remove the filings, embedded in the chalk powder., , Try square, , Co, , Objectives: At the end of this lesson you shall be able to, • name the parts of the try square, • state the uses of the trysquare., Try square Fig 1 is a precision instrument which is used, to check the squareness and the flatness of surfces very, accurately., , The try square has a blade with parallel edges. This blade, is fixed to the stock at 90°. Burr slot is provided on the, stock at meeting point of blade to accommodate the burr,, if present on the component, to avoid inaccuracy in, measuring squareness., Uses: The try square is used to check the squareness of, machined of filed surfaces (Fig. 2) and check flatness of, surfaces (Fig. 3), mark line at 90° to the edges of work, pieces (Fig. 4) and set work pieces at right angles on, work holding devices. (Benchvice) Fig.5, Try squares are made of hardened steel, Try squares are, specified accroding to the length of the blade i.e 100mm,, 150mm, 200mm., , 12, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Mallets, , Objectives: At the end of this lesson you shall be able to, • state the different types of mallets, • state the uses of mallets, • state the care and maintenance., , Co, , Mallet is a shaping tool used for general purpose work like, flattening, bending and forming to required shape of sheet, metal., These are made of hard wood, , When using any metal hammer for flattening the sheet, metal, the face of the hammer may damage or leave, impression in the sheet more than what is required for the, job. To avoid such damage and a impression, mallets are, used., Types (Fig. 1), - Ordinary mallet, - Bossing mallet, - End-faked mallet, - Raw hide mallet,, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04, , 13

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Ordinary mallet: Both the faces of the mallets, are, provided a little convexity. If the face is not in convex, shape the edges of the mallet face will get broken while, beating the job., , Avoid using the mallet as hammer for doing chipping and, to drive nails and work on the sharp corners. If the mallet, is used for the above work its face will get damaged., , Mallets are specified by the dia and the shape of the face., Mallets are avilable in 50mm, 75mm and 100 mm dia, , Bench Vice, Objectives: At the end of this lesson you shall be able to, • name the parts and uses of a bench vice, • specify the size of a bench vice, • state the uses of vice clamps., These are used for holding workpieces. They are available, in different types. The vice used for bench work is bench, vice. (Engineer’s vice), , Bench vice is made of cast iron or cast steel and it is, used to hold work for filing, sawing, threading and other, hand operations. (Fig 1), , Parts of a bench vice (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The size of the vice is stated by the width of the jaws., , The following are the parts of vice:, , To hold a finished work use soft jaws (Vice claps) made of, aluminium over the regular hard jaws. This will protect the, work surface from damage., , Co, , Fixed jaw. Movable jow, Hard jaws, Spindle, Handle, Box, nut and Spring., , Vice clamp or soft jaws(Fig 3), , Do not over-tighten the vice, otherwise, the, spindle may be damaged., , The box nut and the spring are the internal parts,, , 14, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.04

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Fabrication, Related Theory for Exercise 1.1.05, Welder - Induction Training & Welding Process, Introduction and definition of welding, Objectives: At the end of this lesson you shall be able to, • state the invention of welding, • describe the different ways to weld, The history of joining metals goes back several miliennia., Called forge welding, the earliest come from the Bronze, and lron Ages in Europe and the Middle East. The middle, Ages brought advances in forge welding. in which, blacksmiths used to heat the metal repeatedly until, bonding occurred, , GMAW involves a wire fed “gun” that feeds wire at an, adjustable speed and sprays a shielding gas (generally, pure Argon or a mix of Argon and Co2) over the weld puddle, to protect it from the effect of atmosphere., GTAW involves a much smaller hand-held gun that has, a tungsten rod inside of it. With most, you use a pedal to, adjust your amount of heat and hold a filler metal with, your other hand and slowly feed it., Stick welding or Shielded Metal Arc Welding has an, electrode that has flux, the protecting for the puddle,, around it. The electrode holder holds the electrode as it, slowly melts away. Slag protects the weld puddle from, the affection of atmosphere. Flux-core is almost identical, to stick welding except once again you have a wire, feeding gun; the wire has a thin flux coating around it, that protects the weld puddle., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , In 1801, Sir Humphry Davy discovered the electrical arc., In 1802, Russian Scientist Vasily Petrov also discovered, the electric arc and subsequently proposed possible, practical applications such as welding. In 1881-82, a, Russian Inventor Nlkolai Benardos and polish Stainshlaw, olszewski created the first electric arc, welding method, known as carbon arc welding; they used carbon electrodes., , There are many different ways to weld. such as; Shielded, Metal Arc Welding (SMAW). Gas Tungsten Arc Welding, (GTAW), and Gas Metal Arc Welding (GMAW)., , The advances in arc welding continued with the invention, of metal electrodes in the late 1800’s by a Russian, Nikolai, Slavyanov (1888), and an American, C.L. Coffin (1890)., Around 1900, A.P. Strohmenger released a coated metal, electrode in Britian, which gave a more stable arc., In 1905, Russian scientist Vladmir mitkevich proposed, using a three-phase electric arc for welding. In 1919,, alternating current welding was invented by C.J. Holslag, but did not become popular for another dacade., , Co, , Welding is a fabrication process that joins materials, normally metals. This is often done by melting the work, pieces and adding a filler material to form pool of molten, material that cools to become a strong joint, with pressure, sometimes used in conjunction with the heat or by itself,, to produce the weld. This is in contrast with soldering &, brazing, which involve melting a lower-melting-point, material to form a bond between them, without melting, the work pieces., , Many different sources of energy can be used for welding,, including a gas flame, an electrical arc, a laser, an, Electron Beam (EB), Friction, and ultrasound. While, often an industrial process, welding may be performed, in many different environments, including in open air, under, water, and on outer space,. Welding is a potentially, hazardous undertaking and precautions are required to, avoid burns, elecric shock, vision damage, inhalation of, poisonous gases and fumes, and exposure to intense, ultraviolet radiation., , 15

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Safety in Shielded Metal Arc Welding, Objectives : At the end of this lesson you shall be able to, • identify the safety apparels and accesories used in arc welding, • select the safety apparels and accessories to protect from burns and injuries, • learn how to protect yourself and others from the effect of harmful arc rays and toxic fumes, • select the shielding glass for eye and face protection., Non-fusion welding, This is a method of welding in which similar or dissimilar, metals are joined together without melting the edges of, the base metal by using a low melting point filler rod but, without the application of pressure., Example: Soldering, Brazing and Bronze welding., During arc welding the welder is exposed to hazards such, injury due to harmful rays (Ultra violet and infra red rays), of the arc, burns due to excessive heat from the arc and, contact with hot jobs, electric shock. toxic fumes, flying, hot spatters and slag particles and objects falling on the, feet., , 1 Safety apparels, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The following safety apparels and accessories are used, to protect the welder and other persons working near the, welding area from the above mentioned hazards., , a, , Leather apron, , b, , Leather gloves, , c, , Leather cape with sleeves, , d, , Industrial safety shoes, , 2 a, , Hand screen, , b, , Adjustable helmet, , c, , Portable fire proof canvas screens, , Co, , 3 Chipping/grinding goggles, , 4 Respirator and exhaust ducting, , The leather apron, glooves, cape with sleeves and leg guard, Fig 3,4,5 and 6 are used to protect the body, hands, arms,, neck and chest of the welder from the heat radiation and, hot spatters from the arc and also from the hot slag, praticles flying from the weld joint during chipping off, the solidified slag., All the above safety apparels should not be loose while, wearing them and suitable size has to be selected by, the welder., , 16, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Welding hand screens and helmet: These are used to, protect the eyes and face of a welder from arc radiation, and sparks during arc welding., A hand screen is designed to hold in hand. (Fig. 6), A helmet screen is designed to wear on the head. (fig. 7), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The industrial safety boot (Fig. 5) is used to avoid slipping, injury to the toes and ankle to the foot. It also protects, the welder from the electric shock as the sole of the, shoe is specially made of shock resistat material., , Co, , Clear glasses are fitted on each side of the coloured, glass to protect it from weld spatters. (Fig. 8), , The helmet screen provides better protection and allows, the welder to use his both hands freely., Coloured (filter) glasses are made in various shades, depending on the welding current ranges. (Table1), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 17

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Table 1, Recommendations of filter glasses for manual metal, arc welding, Shade No. of, coloured glass, 8-9, 10-11, 12-14, , Range of welding, current in amperes, Upto 100, 100 to 300, Above 300, , It is made of bakelite frame fitted with clear glasses and, an elastic band to hold it securely on the operator’s head., It is designed for comfortable fit, proper ventilaon and full, protection from all sides., Sometimes toxic fumes and heavy smoke may be liberated, (given out) from the weld while welding non-ferrous alloys, like brass etc. Use a respirator and use exhaust ducts, and fans near the weld area to avoid inhaling the toxic, fumes and smoke fig. 11., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Portable fire proof canvas screens Fig. 9 are used to protect, the persons who work near the welding area from arc, flashes., , Inhaling toixc fumes will make the welder become, unconscious and fall on the hot welded job/on the floor., This causes burns or injury., , Co, , Plain goggles are used to protect the eyes while chipping, the slag or grinding the job. Fig, 10, , 18, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Safety in Gas cutting process, Objectives: At the end of this lesson you shall be able to, • describe the safety precautions to be followed by handling gas cutting equipment, • explain the safety precautions to be followed by the operator, • state the safety required during gas cutting operation., - protection of your eyes, Equipment safety: Safety precautions for gas cutting, equipment are the same as those adopted in the case of, - protection from burns, gas welding equipment., - protection of clothing, safety for the operator (Fig 1), - protection of inhaling burnt gases., protect yourself and others from the flying sparks., Ensure that the metal being cut is properly, supported and balanced so that it will not fall, on the feet of the operator or on the hoses., Keep the space clear underneath the cutting job so as to, allow the slag to run freely, and the cutting parts to fall, safely., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Be careful about flying hot metal and sparks while starting, a cut. Containers which hold combustible substance, should not be taken directly for cutting or welding. (Fig 2), Wash the containers with carbon tetrachloride and caustic soda before welding or cutting and fill them with water, before repairing., Keep fire- fighting equipment handy and, ready., , Co, , Always use safety apparel, , goggles, gloves and other protective clothing must be warn., , Safety during operation: Keep the work area free from, flammable materials., Ensure that the combustible material is atleast, 3 metres away from the cutting operation, area., , In case the flammable material is difficult to remove, suitable fire resisting guards/partitions must be provided., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 19

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Co, 20, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Length measurement, Objectives: At the end of this lesson you shall be able to, • name the base unit of length measurement as per the International System of units of measurement (SI), • state the multiples of a meter and their values., When we measure an object, we are actually comparing, it with a known standard of measurement., The base unit of length as per SI is the METRE., Length - SI UNITS and MULTIPLES, Base unit: The base unit of length as per the Systems, International is the meter. The table given below lists some, multiples of a metre., METRE (m), , = 1000 mm, , CENTIMETRE(cm), , = 10 mm, , MILLIMETRE (mm), , = 1000u, , MICROMETRE (um), , = 0.001 mm, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Measurement in engineering practice: Usually, in, engineering practice, the preferred unit of length measurement is the millimetre. (Fig 1), Both large and small dimensions are stated in millimetres., (Fig 2), , The British system of length measurement: An alternative system of length measurement is the British system. In this system, the base unit is the Imperial Standard Yard. Most countries, including Great Britain itself,, have, however, in the last few years, switched over to SI, units., , Steel rule, , Co, , Objectives: At the end of this lesson you shall be able to, • state the purpose of steel rule, • state the types of steel rule, • state the precautions to be followed while using a steel rule., Engineer’s steel rule (Fig 1) is used to measure the dimensions of work pieces., , For accurate reading it is necessary to read vertically to, avoid errors arising out of parallax.(Fig1), Steel rule in English measure, they can also be furnished, with metric and English graduation in a complete range of, size 150, 300, 500 and 1000 mm. (Fig 2), Other types of rule, - narrow steel rules, - short steel rules, - full flexible steel rule with tapered end., , Steel rules are made of spring steel or stainless steel., These rules are available in length 150mm, 300mm and, 600mm. The reading accuracy of steel rule is 0.5 mm, and 1/64 inch., Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 21

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The rules are easily inserted in the slotted end of the holder, and are rigidly clamped in place by a slight turn of the, knurreled nut at the end of the handle. Five rule lengths, are provided 1/4”, 3/8”, 1/2”, 3/4”, and 1” and each rule is, graduated in 32” nds on the reverse side., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Narrow steel rule: Narrow steel rule is used to measure, the depth of key-ways and depth of smaller dia, blind holes, and other jobs, where the ordinary steel rule can not reach., Width appoximately 5mm thickness to 2mm. (Fig 3), , Co, , Short steel rule (Fig 4): This set of five small rules together with a holder is extremely useful for measurements, in confined or hard to reach locations which prevent use of, ordinary steel rules. It is used suitably for measuring, grooves, short shoulder, recesses, key ways etc, in machining operation on shapers, millers and tool and die work., , Steel rule with tapered end: This rule is a favorite with, all mechanics since its tapered end permits measuring of, inside size of small holes, narrow sots, grooves, recesses, etc. This rule has a taper from 1/2 inch width at the 2 inch, graduation to 1/8 inch width at the end. (Fig 6), For maintaining the accuracy of a steel rule, it is important to see to it that its edges and surfaces are protected, from damage and rust., Do not place a steel rule with other cutting tools., Apply a thin layer of oil when not in use., , Types of calipers, Objectives: At the end of this lesson you shall be able to, • name the commonly used calipers, • state the advantages of spring joint calipers., Calipers are indirect measuring instruments used for transferring measurements from a steel rule to a job, and vice, versa., Calipers are classified according to their joints and their, legs., Joint, - Firm joint calipers (Fig 1a), - Spring joint calipers (Fig 1b), , 22, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Legs, - Outside caliper for external measurement. (Figs 2a), , Marking media, , Spring joint calipers have the advantage of quick setting, with the help of an adjusting nut. For setting a firm joint, caliper, tap the leg lightly on a wooden surface., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - inside caliper for internal measurement(Fig 2b), , Calipers are used along with steel rules, and the accuracy is limited to 0.5 mm; Parallelism of jobs etc. can be, checked with higher accuracy by using calipers with, sensitive feel., , Objectives: At the end of this lesson you shall be able to, • name the common type of marking media, • state the Correct marking media for different applications., Different marking media: The different marking media, are Whitewash, Prussian Blue, Copper Sulphate and Cellulose Lacquer., Whitewash: White wash is prepared in many ways, Chalk powder mixed with water, , Chalk mixed with methylated spirit, , Co, , White lead powder mixed with turpentine., , Whitewash is applied to rough forgings and castings with, oxidised surfaces. (Fig 1), , Copper Sulphate: The solution is prepared by mixing, copper sulphate in water and a few drops of nitric acid., The copper sulphate is used on filed or machine-finished, surfaces. Copper sulphate sticks to the finished surfaces, well., , Whitewash is not recommended for workpieces of high, accuracy., Prussian Blue: This is used on file or machine-finished, surfaces. This will give very clear lines but takes more, time for drying than the other marking media. (Fig 2), , Copper sulphate needs to be handled carefully as it is, poisonous. Copper sulphate coating should be dried well, before commencing marking as, otherwise, the solution, may stick on the instruments used for marking., Cellulose Lacquer: This is a commercially available, marking medium. It is made in different colours, and dries, very quickly., The selection of marking medium for a particular job depends on the surface roughness, and the accuracy of the workpiece., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 23

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Jenny calipers, Objectives: At the end of this lesson you shall be able to, • state the uses of a jenny caliper, • state the two types of legs of a jenny caliper., Jenny calipers have one leg with an adjustable divider point, while the other is a bent leg. (Fig 1) These are available, in sizes pf 150mm, 200mm, 250mm and 300mm., Jenny calipers are used:, -for marking lines parallel to the inside and outside edges, (Fig 2), -for finding the center of round bars. (Fig 3), , These calipers are avilable with the usual bent leg or with, a heel., Calipers with bent leg (Fig 2B) are used for drawing lines, parallel along an inside edge. and the heel type (Fig 2A) is, used for drawing parallel lines along the outer edges., The other names for this callper are:, - hemaphrodite callpers, - leg and point calipers, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - odd leg caliper, , Scribers, , Objectives: At the end of this lesson you shall be able to, • state the Features of scribers, • state the uses of scribers., In lay out work it is necessary to scribe lines to indicate, the dimensions of the workpiece to be filed or machined., The scriber is a tool used for this purpose. It is made of, high carbon steel and is hardened. For drawing clear and, sharp lines, the point should be ground and used frequently, for maintaining its sharpnss., Scribers are available in different shapes and sizes. The, most commonly used one is the plain scriber. (Fig 1), , 24, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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While scribing lines, the scriber is used like a pencil so, that the lines drawn are close to the straight edge. (fig 2), , scriber points are very sharp: therefore, do not put the, plain scriber in your pocket., Place a cork on the point when not in use to, prevent accidents., , Dividers, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Objectives: At the end of this lesson you shall be able to, • identify the parts of a divider, • state the uses of dividers, • state the specifications of dividers, • state some important hints on divider points., , Co, , Dividers are used for scribing circles, arc and for transferring and stepping of distances. (Fig 1,2 and 3), , The sizes of dividers range between 50 mm to 200 mm., , The distance from the point to the centre of the fulcrum, roller (pivot) is the size of the divider. (Fig 4), , Dividers are available with firm joints and spring joints., (Fig 1& 4). The measurements are set on the dividers, with a steel rule. (fig 2), , For the correct location and seating of the divider point, prick punch marks of 30° are used., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 25

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The two legs of the divider should always be of equal length., (Fig 5) Dividers are specified by the type of their joints and, length., , The divider point should be kept sharp in order to produce, fine lines, frequent sharpening with an oilstone is better, than sharpening by grinding. Sharpening by grinding will, make the points soft., , Surface gauges, Objectives: At the end of this lesson you shall be able to, • state the constructional features of surface guages, • name the types of surface guages, • state the uses of surface guages, • state the advantages of universal surface guages., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The surface guage is one of the most common marking, tools used for:- Scribing lines parallel to a datum surface. (Figs 1&2), , Co, , - setting jobs concentric to the machine spindle. (Fig 4), , Types of surface guages: Surface gauges/scribing, blocks are of two types,, - fixed and univesal, , - setting jobs on machines parallel to a datum surface and, checking the height and parallelism of jobs (Fig 3 ), , 26, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Surface guage - Fixed type (Fig 5): The fixed type of, surface guages consist of a heavy flat base and a spindle,, fixed upright, to which a scriber is attached with a snug, and a clamp nut., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Universal Surface Guage (Fig 6): This has the following, - The spindle can be set to any position., , - fine adjustrments can be made quickly., , Co, , - Can also be used on cylindrical datum surfaces., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 27

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Types of marking punches, Objectives: At the end of this lesson you shall be able to, • name the different punches in marking, • state the features of each punch and its uses., Punches are used in order to make certain dimensional, features of the layout permanently. There are two types of, punches. They are center punch and prick punch made, up of high carbon steel, hardened and ground., , The witness marks should not be too close to, one another., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Centre punch: The angle of the point is 90° in a centre, punch. The punch mark made by this is wide and not very, deep. This punch is used for locating centre of the holes., The wide punch mark gives a good seating for starting the, drill. (Fig 1a), , divider point will get a proper seating in the punch mark., The 60° punch is used for marking withness marks and, called as dot punch (Fig 2), , Co, , Prick punch/Dot punch: The angle of the prick punch is, 30° or 60°. (Fig 1b) The 30° point punch is used for marking light punch marks needed to position dividers. The, , 28, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Angular measuring instruments (Semi-precision), Objectives: At the end of this lesson you shall be able to, • state the names of semi-precision angular measuring instruments, • differentiate between bevel and universal bevel gauges, • state the features of bevel protractors., The most common instruments used to check angles are, the:, - bevel or bevel gauge (Fig 1), - Universal bevel gauge (Fig 2), - bevel protractor. (Fig 3), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Bevel gauges (Fig 1): The bevel gauges cannot measure angle directly. they are. therefore, indirect angular, measuring instruments. The angles can be set and measured with bevel protractors., , universal bevel gauges (Fig 2): The universal bevel gauge, has an additional blade. This helps in measuring angles, which cannot be checked with an ordinary bevel gauge., , Co, , Bevel protractor (Fig 3): The bevel protractor is a direct, angular measuring instrument, and has graduation marked, from 0° to 180°. This instrument can measure angle within, an accuracy of 1.0°., , Datum, , Objectives: At the end of this lesson you shall be able to, • state the need for datum while marking, • name the different datum references., Say, the height of a person is measured from the floor on, which he stands, the floor then becomes the datum of the, common basis for measurement., A datum is a referable surface. Line of point, and its purpose is to provide a common position from which measurements may be taken. The datum may be an edge or, centre line depending on the shape of the work. For positioning a point, two datum references are required. (Fig, 1,2 and 3), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 29

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Marking tables, surface plates, angle plates, ‘V’ blocks,, and parallel blocks serve as a datum. (Fig 4) Marking, tables are made up of cast iron since they are i)Self lubricating ii) Easy to cast and iii) cheaper., , Hammer, , Objectives: At the end of this lesson you shall be able to, • state the uses of an engineer’s hammer, • identify the parts of an engineer’s hammer and state their functions, • name the types of engineer’s hammers, • specify the engineer’s hammer., , The head is made of dorp-forged carbon steel, while the, wooden handle must be capable of absorbing shock., , punching, bending, straightening, chipping, forging, riveting., , The parts of a hammer-head are the, , Co, , An engineer’s hammer is a hand tool used for striking, purposes while, , face, pein, cheek, eye hole., , (See fig 2.), , (See fig 1.), , Major parts of a hammer, The major parts of a hammer are a head and handle., , 30, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05

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Face, The face is the striking portion. Slight convexity is given, to it to avoid digging of the edge., pein, The pein is the other end of the head. It is used for shaping and forming work like riveting and bending. The pein is, of different shapes like the, ball pein, cross pein, straight pein. (Fig 3), , Cheek, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The face and the pein are hardened., , The cheek is the middle portion of the hammer-head. The, weight of the hammer is stamped here., This protion of the hammer-head is left soft, Eye hole, , An eye hole is meat for fixing the handle; Eye is shaped, to fit the handle rigidly. The wedges fix the handle in the, eye hole. (See figs 4 and 5.), Specification, , The ball pein hammers are used for general work in a, machine/fittimg shop., Before Using a Hammer, , Make sure the handle is properly fixed and select a hammer with correct weight suitable for the job, Check the head and handle for any cracks and ensure the, face of the hammer is free from ail or grease., , Co, , An engineer’s hammers is specified by their weight and, the shape of the pein. Their weight varies from 125 gms to, 1500 gms., , The weight of an engineer’s hammer used for marking purposes, is 250 gms., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.05, , 31

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Fabrication, Related Theory for Exercise 1.1.06, Welder - Induction Training & Welding Process, Arc welding machines, Objectives : At the end of this lesson you shall be able to, • state the neccessity of an arc welding machine, • name the different types of arc welding machine., In arc welding process, the source of heat is electricity., (High ampere-lo voltage), , Type (Fig 2): Basically power sources are:, , The required electrical energy for welding is obtained from, an arc welding machine, a power source. (Fig 1), , - direct current welding machine., , - alternating currernt welding machine, , These may be further classified as DC machines and AC, machines., DC machines, - Motor generator set, - Engine generator set, - Rectifier set, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , AC machines, , - Transformer sets, , Necessity, - The equipment is used to, , - provide Ac or DC welding supply for arc welding, , - provide higher vollage (OCV) for striking the arc and, lower voltage (AV) for maintaining the arc, , - change the high voltage of the main supply (AC) to, low voltage and heavy current supply (AC or DC) suitable, for arc welding, , Co, , - establish a relationship between arc voltage and, welding current, , - control and adjust the required welding current during, arc welding, - weld with all gauges of electrode, , - weld thin and thick plates. both ferrous and non-ferrous, metals., , 32, , AC means alternating current. It changes or, reverses its dirction of flow of current 50 times, per second, if it is 50 cycles/sec. (Fig.3), DC means direct current. it flows steadily and, constantly in one direction. (Fig.4)

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Care and maintenace of arc welding machines and, accessories, Every machine and accessory used for any useful, purpose requires some care and maintenace to increase, its usage for a long time. In the case of arc welding, machines and accessories the following points are, important., Arc welding machines: Do not keep the machine in, open air. In a DC welding generator do not put the starting, switch on DELTA position directly: keep the switch on, START position first. Run it for a few seconds and then, put the switch in DELTA position. Do not disconnect the, cooling fan of a welding generator., Maintain the cooling oil in the transformer welding set., Periodically drain the cooling oil from the transformer, and purify, and refill the transformer. Fix the input cables, form the mains to the machine and the electrode and earth, cable firmly. Replace the carbon brushes of the DC welding, generator whenever necessary., , Do not clean any welding machine with water. The dust, and other impurities are to be removed by compressed, air only. Operate all control knobs and handles gently., Avoid loose connections at the main fuses, starting, switch.etc., Arc welding accessories: Ensure the welding and earth, cables are of standard amperage. The cables are to be, joined only by sockets. Use the right capacity electrode, holder and earth clamp. Avoid temporary arrangements, to join cables or to connect earth clamp with the table or, job. Avoid direct contact of electrode-holder with work, table or job or earth connections. For this, hang the, electrode-holder on the insulated hanger of the welding, table. Use a properly insulated electrode-holder. Avoid, over running of the trolley wheel etc. on the welding or, return cable. Avoid stray arcing on the work table or on the, job., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Arc welding accessories, , Objectives: At the end of this lesson you shall be able to, • identify the arc welding accessories, • explain the function of each accessory., Arc welding accessories: Some very important items,, used by a welder with an arc welding machine during the, welding operation, are called arc welding accessories., , Co, , Electrode-holder (Fig 1): It is a clamping device used to, grip and manipulate the electrode during arc welding. It is, made of copper/copper alloy for better electrical, conductivity., , Screw or spring-loaded earth clamps are made in various, sizes i.e. 200 - 300 - 500 amps. (Fig 3), , Partially or fully insulated holders are made in various sizes, i.e. 200 - 300 - 500 amps., The electrode-holder is connected to the welding machine, by a welding cable., Earth clamp (fig 2): It is used to connect the earth cable, firmly to the job on welding table. It is also made of copper/, copper alloys., , Welding cables/leads: These are used to carry the, welding current from the welding machine to the work and, back., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06, , 33

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The lead from the welding machine to the electrode-holder, is called electrode cable., The lead from the work or job through the earth clamp to, the welding machine is called earth (ground) cable., Cables are made of super flexible rubber insulation, having, fine copper wires and woven fabric reinforcing layers. (Fig4), Welding cables are made in various sizes (cross-sections), , Loose joints or bad contacts cause overheating of the, cables., The length of the cable has considerable effect on the, size to be used. (See Table1.), TABLE 1, Recommendations of copper cable for arc welding, , i.e. 300, 400, 600 amps etc., , Lengths of cable in metres, current capacity in amperes, 0 - 15, 15 - 30, 30 - 75, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Cable, dia., ( mm), , The same size welding cables must be used, for the electrode and the job., , 24.0, 21.0, 19.0, 18.0, 16.5, 15.5, 14.5, 13.5, , 600, 500, 400, 300, 250, 200, 150, 125, , 600, 400, 350, 300, 200, 195, 150, 100, , Co, , The cable connection must be made with, suitable cable attachments (lugs). (Fig 5), , 34, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06, , 400, 300, 300, 200, 175, 150, 100, 75

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High pressure oxy-acetylene welding equipment and accessories, Objectives: At the end of this lesson you shall be able to, • distinguish between the features of oxygen and acetylene gas cylinders, • compare the feaures of oxygen and acetylene gas regulators, • distinguish between the house-connectors used in oxygen and acetylene regulators, • describe the function of hose-protectors, • state the functions of blowpipes and nozzles., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Oxy-acetylene welding is a method of joining metals by, heating them to the melting point using a mixture of oxygen, and acetylene gases. (Fig 1), , (MAROON COLOUR), , Co, , Oxygen gas cylinders: The oxygen required for gas, welding is stored in bottle-shaped cylinders. These, cylinders are painted in black colour. (Fig 2) Oxygen, cylinders can store gas to a capacity of 7 m3 with the, pressure ranging between 120 to 150 kg/cm2 . Oxygen, gas cylinder valves are right hand threaded., Dissolved acetylene cylinders: The acetylene gas used, in gas welding is stored in steel bottles (cylinders) painted, in maroon colour. The normal storing capacity of storing, acetylene in dissolved state is 6m3 with the pressure, ranging between 15-16 kg/cm2., Oxygen pressure regulator: This is used to reduce the, oxygen cylinder gas pressure according to the required, working pressure and to control the flow of oxygen at a, constant rate to the blowpipe. The threaded connections, are right hand threaded. (Fig 3), , Acetylene regulator: As with the case of oxygen, regulator this also is used to reduce the cylinder gas, pressure to the required working pressure and to control, the flow of acetylene gas at a constant rate to the blowpipe., The threaded connections are left handed, For quickly, identifying the acetylene regulator, a groove is cut at the, corners of the but. (Fig 4), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06, , 35

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At the blowpipe end of the rubber hoses-protectors are, fitted. The hose protectors are in the shape of a connecting, union and have a non-return disc fitted inside to protect, from flashback and backfire during welding. (Fig 7), , Blowpipre and nozzle: Blowipipes are used to control, and mix the oxygen and acetylene gases to the required, proportion. (Fig 8), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Rubber hose-pipes and connections: These are used, to carry gas from the regulator to the blowpipe. These are, made of strong canvas rubber having good flexibility., Hosepipes which carry oxygen are black in colur and the, acetylene hoses are of maroon colour (Fig 5), , Co, , A set of interchangeable nozzles/tips of diffrent sizes is, available to produce smaller bigger flames. (Fig 9), , (MAROON COLOUR), , Rubber hoses are connected to regulators with the help of, unions. These unions are right hand threaded for oxygen, and left hand threaded for acetylene. Acetylene hose unions, have a groove cut on the corners. (Fig 6), , 36, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06

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The size of the nozzle varies according to the thickness, of the plates to be welded. (Table), TABLE 1, plate, thickness, mm, , Nozzle size, Number, , 0.8, 1.2, 1.6, 2.4, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, 19.0, 25.0, Over 25 .0, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 1, 2, 3, 5, 7, 10, 13, 18, 25, 35, 45, 55, 70, 90, , Gas welding hand tools, , Objectives: At the end of this lesson you shall be able to, • identify and name the hand tools used by a welder, • state their uses, • state the care and maintenance to keep the hand tool in good working condition., The following are the details of different hand tools used, by a welder., , Co, , Double ended spanner: A double ended spanner is, shown in Fig.1 and 1a. It is made of forged chrome, vanadium steel. It is used to loosen or tighten nuts, bolts, with hexagonal or square heads. The size of the spanner, is marked on it as shown in fig. 1. In welding practice the, spanners are used to fix the regulator onto the gas cylinder, valves, hose connector and protector to the regulator and, blow pipe, fix the cable lugs to the arc welding machine, output teminals, etc., Do not use any size of hammer, use the correct size of, spanner to avoid damage to the nut/bolt head,, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06, , 37

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Cylinder Key: A cylinder key is shown in Fig.2. It is used, to open or close the gas cylinder valve socket to permit or, stop the gas flow from the cylinder to the regulator., , Before cleaning the tip, select the correct drill and move, it, without turning, up and down through the tip Fig.4., , Always use correct size key to avoid damage to the square, rod used to operate the valve. The key must always be, left on the valve socket-itself so that the gas flow can be, stopped immediately in case of flash back/back fire., Nozzle or tip cleaner, Cleaning the tip: All welding torch tips are made of copper., They can be damaged by the slightest rough handling., Dropping, tapping or chopping with the tip on the work, may damage the tip beyond repair., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The smooth file is then used to clean the surface of the tip, Fig.5. While cleaning, leave the oxygen valve partly open, to blow out the dust., , Co, , Tip cleaner: A Special tip cleaner is supplied with the, torch container. For each tip there is a kind of drill and a, smooth file Fig.3., , Spark lighter: The spark lighter, as illustrated in Fig.6, &7 is used for igniting the torch. While welding, form, the habit of always employing a spark lighter to light a, torch. Never use matches. The use pf matches for this, purpose is very dangerous because the puff of the flame, produced by the ignition of the acetylene flowing from the, tip is likely to burn your hand., , 38, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06

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Chipping hammer: The chipping hammer (Fig 8) Is used, to remove the slag which covers the deposited weld bead., It is made of medium carbon steel with a mild steel handle., It is provided with a chisel edge on one end and a point on, the other end for chipping off slag in any position., , A stainless steel wire brush is used for cleaning a non, ferrous and stainless steel welded joint., It is made of bunch of steel wires fitted in three to five, rows on a wooden piece with handle. The wires are, harderned and tempered for long life and to ensure good, cleaning action., Tongs: Fig.10 and Fig.11 show a pair of tongs used to, hold hot work pieces and to hold the job in position., , Care should be taken to maintain the sharp chisel edge, and the point for effective chipping of slag., Carbon steel wire brush: A carbon steel wire brush is, shown in Fig.9. It is used for, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - Cleaning the work surface from rust, oxide and other, dirt etc. prior to welding., - Cleaning the interbead weld deposits after chipping, off the slag, , Co, , - General cleaning of the weldment., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.06, , 39

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Fabrication, Related Theory for Exercise 1.1.07, Welder - Induction Training & Welding Process, Various welding processes and their application, Objectives: At the end of this lesson you shall be able to, • state and classify the electric welding processes, • state and classify the gas welding processes, • name and classify the other welding processes, • state the applications of various welding processes., According to the sources of heat, welding processes can, be broadly classified as:, - Electric welding processes (heat source is electricity), - Gas welding processes (heat source is gas flame), , The other welding processes are:, - Thermit welding, - Forge welding, - Friction welding, - Ultrasonic welding, , Electric welding processes can be classified as:-, , - Explosive welding, , - Electric arc welding, , - Cold pressure welding, , - Electric resistance welding, , - Plastic welding., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - Other welding processes (heat source is neither, electricity nor gas flame), , code, , Welding process, , AAW, , Air Acetylene, , AHW, , Atomic Hydrogen, , Electric arc welding can be futher classified as:, , BMAW, , Bare Metal Arc, , - Shielded Metal Arc Welding/Manual Metal Arc Welding, , CAW, , Carbon Arc, , - Carbon arc welding, , EBW, , Electron Beam, , - Atomic hydrogen arc welding, , EGW, , Electro Gas, , - Gas Tungsten Arc Welding / TIG Welding, , ESM, , Electroslag, , - Gas Metal Arc Weling / MIG/MAG Welding, , FCAW, , Flux Cored Arc, , - Flux cored arc welding, , FW, , Flash, , FLOW, , Flow, , GCAW, , Gas Carbon Arc, , GMAW, , Gas Matel Arc, , Electric resistance welding can be further classified as:, , GTAW, , Gas Tungsten Arc, , - Spot welding, , IW, , Induction, , - Seam welding, , LBW, , Laser Beam, , - Butt welding, , OAW, , Oxy-Acetylence, , - Blash butt welding, , OHW, , Oxy-Hydrogen, , - Projection welding., , PAW, , Plasma Arc, , Gas welding processes can be classified as:, , PGW, , Pressure Gas, , - Oxy-acetylene gas welding, , RPW, , Resistance Projection, , - Oxy-hydrogen gas welding, , RSEW, , Resistance Seam, , - Oxy-coal gas welding, , RSW, , Resistance Spot, , - Oxy-liquified petroleum gas welding, , SAW, , Submerged Arc, , - Air acetylene gas welding., , SMAW, , Shielded Metal Arc, , - Laser welding, - Electron beam welding, , Co, , - induction welding, , - Submerged arc welding, - Electro-slag welding, - Plasma arc welding, , 40

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SCAW, , Shielded Carbon Arc, , SW, , Stud Arc, , TW, , Thermit, , UW, , Ulrosonic, , Applications of Various welding processes, Forge welding: It is used in olden days for joining metals, as a lap and butt joint., Shielded Metal arc welding is used for welding all, ferrous and non-ferrous metals using consumable stick, electrodes,, Carbon arc welding is used for welding all ferrous and, non-ferrous metals using carbon electrodes and separate, filler metal. But this is a slow welding process and so, not used now-a-days., Submerged arc welding is used for welding ferrous, metals, thicker plates and for more production., , Projection welding is used to weld two plates one over, the other on their surfaces instead of the edges by making, projection on one plate and pressing it over the othr flat, surface. Each projection acts as a spot weld during, welding., Butt welding is used to join the ends of two heavy, section rods/blocks together to lengthen it using the, resistance property of the rods under contact., Flash butt welding is used o join heavy sections of, rods/blocks similar to butt welding except that arc flashes, are produced at the joining ends to melt them before, applying heavy pressure to join them., Oxy -acetylene welding is used to join different ferrous, and non ferrous metals, generally of 3mm thickness and, below., Oxy-other fuel gases welding: Fuel gases like, hydrogen, coal gas, liquified petrolenum gas (LPG) are, used along with oxygen to get a a flame and melt the, base metal and filler rod. Since the temperature of these, flames are lower than the oxy-acetylene flame, these, welding are used to weld metals where less heat input is, required., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Co 2 Welding (Gas Metal Arc Welding) is used for, welding ferrous metals using continuously fed filler wire, and shielding the weld metal and the arc by carbon-dioxide gas., , Seam welding is used for welding thin sheets similar to, spot welding. But the adjacent weld spots will be, overlapping each other to get a continuous weld seam., , TIG welding (Gas Tungsten Arc Welding) Is used for, welding ferrous metals, stainless steel, aluminium and, thin sheet metal welding., , Atomic hydrogen welding is used for welding all ferrous, and non-ferrous metals and the arc has a higher, temperature than other arc welding processes., , Electroslag welding is used for welding very thick steel, plates in one pass using the resistance property of the, flux material., , Co, , Plasma arc welding: The arc has a very deep penetrating, ability into the metals welded and also the fusion is taking, place in a very narrow zone of the joint., , Spot weding is used for welding thin sheet metal as a, lap joint in small spots by using the resistance property of, the metals being welded., , Air-acetylene gas welding is used for soldering, heating, the job etc., Induction welding is used to weld parts that are heated, by electrical induction coils like brazing of tool tips to the, shank, joining flat rings, etc., Thermit welding is used for joining thick, heavy,, irregularly shaped rods, like rails, etc using chemical, heating process., Friction welding is used to join the ends of large dlameter, shafts, etc by generating the required heat using the friction, between their ends in contact with each other by rotating, one rod against the other rod., , Shielded Metal ARC Welding, Objectives: At the end of this lesson you shall be able to, • state the types and classify electric welding processes, • state the principle of electric arc welding, Electric welding: This is a process of welding in which, the heat energy is obtained from electricity., When electric current passes through a, medium material, it generates heat., , -, , the changes taking place in the medium, , -, , the resistance of the medium., , By adjusting current and resistance, sufficient heat can, be produced to melt the metals., , The amount of heat generated depends upon:, -, , the amount of current passing through the medium, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.07, , 41

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Principle of shielded Metal Arc Welding, , SMAW advantages / Disadvantages, , An electric arc is maintained between the end of a coated, metal electrode and work piece., , Advantages:, , The flux covering melts during welding and forms gas and, slag to shield the arc molten weld pool. The flux also, provides a method of a adding scavengers, deoxidizers, and alloying elements to the weld metal, , 2 Wide range of conusumables, , Various Name Stick Electrode welding,, , 5 Simple, inexpensive equipment, , 1 Field or shop use; less sensitive to wind and dirt, , 3 All positional; flexible, 4 Very portable; can reach limited access areas, , Electric Arc welding,, , Disadvantages:, , Shielded Metal Arc welding (SMAW), , 1 High skill factor, , Manual Metal Arc welding (MMAw), , 2 Slag inculsions, , Popularly known as Arc welding, , 3 Low deposition rate and operating factor, 4 High level of fume, , Main parts in SMAW, , 5 Hydrogen control, , •, , Welding Machine, , •, , Electrode Holder, , 6 Can’t weld low melting point (e.g.pb,sn,zn) or reactive, metals (e.g.ti), , •, , Ground Clamp(Earth), , •, , Welding Cables, , Types of power source, 1 AC welding Transformer, 2 DC motor Generator, 3 Rectifier set, , Co, , 4 Inverter, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , It is a manual & ancient welding process, 100 years old, , 42, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.07

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Fabrication, Related Theory for Exercise 1.1.08, Welder - Induction Training & Welding Process, Welding Terms & Its Definition, 1. Butt Weld: joining of two pieces placed in 180° (surface, level) & the welding performed is called as Butt weld., 2. Fillet weld: joining of two pieces placed in 90° (surface, level / one surface & another edge surface/both edge, surface) & the welding performed is called as fillet weld., 3. Weld reinforcement: the material which is above the, place surface/miter surface is called as weld, reinforcement., 4. Miter line: the straight line which is bisecting two toe, points is known as miter line., 5. Toe of weld: the point at which the weld reinforcement, is resting on base metal surface is known as toe point., 6. Toe Line: the line on which the weld reinforcement is, resting on base metal surface., , 16.Flash back arrestor: Sometimes during backfire, the, flame goes off and the burning acetylene gas travels, backward in the blowpipe, towards the regulator or, cylinder. At the time in between the device which has, to be arrested the backfire., 17.Electrode holder: A device by which electricity, provided by cable will be carried to the electrode and, which holds the electrode in desired angles. (This device, is available with different capacities and type i.e. 300, Amps, 400 Amps and 600 Amps partly, semi and fully, insulated)., 18.Earth clamp: A device by which electricity will carry, provided by cable will be carried to the job table. (This, device is available with different capacities and type, i.e. 300 Amps, 400 Amps and 600 Ams. It is prepared, by brass casting, G.I. Coated in spring or fixed form., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 7. Concave bead: the weld metal below the miter line is, known as concave bead., , 15.Flash back: When the gas flame is snapped out and, starts reverse burning towards cylinder with hissing, sound which is very hazardous is known as flash back,, , 8. Convex bead: the weld metal above the miter line is, known as convex bead., , 19. Arc welding cable: This is made of copper/aluminium, strands to carry electricity from welding machine to, electrode holder and earth cable., , 10 Gas welding torch: A device which is used for mixing,, carrying, flow control and flame igniting of gases is, known as gas welding torch., , 20.Cable Lug: This is available with different capacities, and type i.e. 300Amps, 400Amps and 600Amps. This, is preferably made of copper metal., , 11. Gas cutting torch; A device which is used for mixing,, carrying, flow control and flame igniting of gases is, known as gas cutting torch., , 21.SMAW: Shielded Metal Arc Welding. Also known as, manual metal arc welding and stick welding. (In this, process the electrode is consumable)., , 12.Gas pressure regulator: A device which monitors, content of gas pressure in cylinder and regulates, drawing/working gas pressure., , 22.GMAW: Gas Metal Arc welding covers CO2 welding, (MAG), metal inter gas arc welding (MIG) & flux cored, arc welding. (In these processes the electrode is, consumable)., , Co, , 9. Miter bead: If the weld bead is up to the level of miter, line it is known as miter bead., , 13.Gas Rubber hose pipe: A rubber hose which carries, gases from gas pressure regulators and supplies to, gas welding/cutting torches., 14.BACk fire: If gas flame is snapped out due to wrong, gas pressure setting is known as back fire., , 23.GTAW: Gas Tungsten Arc welding. (In this process, the electrode is consumable)., 24.FCAW: Flux cored Arc welding. Flux cored arc welding., (In the process the electrode is consumable)., 25.Electrode (Flux coated) A metal stick which is coated, with flux and having parts indicated as stub end, tip,bare/, core wire and flux coating. The size of this is determined, by size of bare/core wire diameter. (This is used in, shielded Metal Arc welding as consumable material)., , 43

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Fabrication, Related Theory for Exercise 1.1.09, Welder - Induction Training & Welding Process, Bolted Joints, Objectives: At the end of this lesson you shall be able to, • state the situations in which bolts and nuts are used, • state the advantages of using bolts and nuts, • identify the different types of bolts, • state the applications of the different types of bolts, • state the situations in which studs are used, • state the reason for having different pitches of threads on stud ends., Bolts and nuts (Fig 1), , Slight misalignment in the matching hole will not affect, the assembly., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Body fit bolt (Fig 3), , These are generally used to clamp two parts together., , Co, , When bolts and nuts are used, if the thread is stripped, a, new bolt and nut can be used. But in the case of a screw, directly fitted in the component, when threads are, damaged,the component may need extensive repair or, replacement., Depending on the type of application, different types of, bolts are used., Bolts with clearance hole (Fig 2), , This type of bolt assembly is used when the relative, movement between the workpieces has to be prevented., The diameter of the threaded portion is slightly smaller, than the shank diameter of the bolt., The bolt shank and the hole are accurately machined for, achieving perfect mating., Anti-fatigue bolt (Fig 4), , This is the most common type of fastening arrangement, using bolts. The size of the hole is slightly larger than, the belt (Clearance hole)., , 44

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This type of bolt is used when the assembly is subjected, to alternating load conditions continuously . Connecting, rod with big ends in engine assembly are examples of this, application., , Designation of bolts as per B.I.S. specifications, Hexagonal head bolts shall be designated by name, thread, size, nominal length, property class and number of the, Indian Standard., , The shank diameter is in contact with the hole in a few, places and other protions are relieved to give clearances., , Example, , Studs (Fig 5), , A hexagonal head bolt of size M10, nominal length 60mm, and property class 4.8 shall be designated as:, Hexagonal head bolt M10 60 - 4.8 - IS: 1363 (Part), Explanation about property class., The part of the specification 4.8 indicates the property, class (mechacical properties). In this case it is made of, steel with minimum tensile strength - 40 kgf/mm2 and, having a ratio of minimum yield stress to minimum tensile, strength = 0.8., NOTE, Indian standard bolts and screws are made of three product, grades - A, B, & C and ‘A’ being precision and the others,, of lesser grades of accuracy and finish., (For more details on the designation system, refer to IS:, 1367, Part XVI 1979.), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Studs are used in assemblies which are to be separated, frequently., , While there are many parameters given in, the B.I.S. Specification, the designation, need not cover all the aspects and it actually, depends on the fuctional requirement of the, bolt or other threaded fasteners., , Co, , When excessively tightened, the variation in the thread, pitch allows the fine thread or nut end to strip. This, prevents damage to the casting., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 45

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Rivet Joines, Objectives: At the end of this lesson you shall be able to, • state the purpose of rivets, • identify the different types of rivets, • name the different types of riveted joints, • name the materials from which rivets are made, • calculate the length of rivets., Rivets are used to join together two or more sheets of, metal permanently. In sheet metal work riveting is done, where;, , The materials used for rivets are mild steel, copper yellow, brass, aluminium and heir alloys., The length of the rivets ‘L’ is indicated by the shank length., (Fig 1), , - brazing is not suitable,, - the structure changes owing to welding heat,, - the distortion due to welding cannot be easily removed, etc., Specification of rivets, Rivets are specified by their length, material, size and, shape of head., Rivets, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , There are various kinds of rivets as shown in Fig 1., Snaphead rivets, countersink rivets and thin bevelhead, rivets are widely used in sheet metal work., , 46, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Rivet joints (Fig 2), Rivet joints are classified as lap joints and butt joints., , Therefore, the length of the rivet (L mm) to form a round, head when the total thickness of the piled plates is T mm, will be, as given below., , In the case of butt joints, a plate called a butt strap is, used., , L = T + d (1.3 - 1.6), , Rivet interference, , When forming a flat head (Fig 4) the length of the rivet, (L’mm) will be as given below., , The length required to form the head in riveting is called, rivet interference., , L’ = T + d (0.8 - 1.2), , When forming a round head (Fig 3) the interference X is, given as, , When the appropriate values of the rivet diameter and the, length for the plate thickness are found out, choose the, rivets with the standard size close to the calculated values., , X = d X (1.3, -- 1.6), where = rivet interference(mm), , Soldering, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , d = rivet diameter (mm), , Co, , Objectives: At the end of this lesson you shall be able to, • define ‘soldering’, • state the different types of soldering processes., Soldering method: There are different methods of joining, metallic sheets. Soldering is one of them., , Soldering should not be done on joints subjected to heat, and vibration and where more strength is required., , soldering is the process by which metals are joined with, the help of another alloy called solder without heating the, base metal to be joined. The melting point of the solder is, lower than that of the materials being joined., , Soldering can be classified as soft soldering and hard, soldering. Hard soldering is further divided as (a) brazing, (b) sliver brazing., , The molten solder wets the base material which helps in, binding the base metal to form a joint., , The process of joining metals using tin and lead as a, soldering alloy which melts below 420°C is known as soft, soldering., The process of joining metals using copper. zinc and tin, alloy as filler material in which the base metal is heated, above 420°C below 850°C is called brazing., Silver brazing is similar to brazing except that the filler, material used is a silver-copper alloy and the flux used is, also different., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 47

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Soldering iron (soldering bit), Objectives: At the end of this lesson you shall be able to, • state the purpose of soldering iron, • describe constructional features of soldering iron, • state different types of copper bits and there uses., Soldering iron: The soldering iron is used to melt the, solder and heat metal that are joined together., Soldering irons are normally made of copper or copper, alloys. So they are also called as copper bits., Copper is the preferred material for soldering bit because, -, , it is a very good conductor of heat, , -, , it has affinity for tin lead alloy, , -, , it is easy to maintain in serviceable condition, , -, , it can be easily forged to the required shape., , -, , Head (copper bit), , -, , Shank, , -, , Wooden handle, , -, , Edge, , Co, , SOLDERING COPPER BIT, , Soldering bits are specified by the weight of the copper, head. For general soldering process, the shape of the, head is a square pyramid but for repetition, or awkward, placed, other shapes are designated., Point soldering copper bit: This is also called a square, pointed soldering iron, The edge is shaped to an angle on, four sides to from a pyramid. This is used for tacking and, soldering. (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , A soldering iron has the following parts. (Fig 1 ), , The bits of soldering irons are made in various shapes and, sizes to suit the particular job. They should be large enough, to carry adequate heat to avoid too frequent reheating and, not too big to be awkward to manipulate., , Electric soldering copper bit: The bit of the electric, soldering iron is heated by an element. This type is, perferred, if current is available because it maintains uniform, heat. Electric soldering irons are available for different, voltages and are usually supplied with a number of, interchangeable tips. They can be made quite small and, are generally used on electrical or radio assembly work, (Fig 3), , Type of soldering copper bits: There are 7 types of, soldering copper bits in general use,, They are, -, , The pointed soldering copper bit., , -, , The electric soldering copper bit., , -, , The gas heated soldering copper bit ., , -, , Straight soldering copper bit., , -, , Hatchet soldering copper bit., , -, , Adjustable copper bit, , -, , Handy soldering copper bit., , 48, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Gas heated soldering copper bit: A gas heated, soldering copper bit is heated by a gas flame which ignites, on the back of the head. High pressure gas is used and, the bit is large enough to have a good heat storage capacity., Liquified petroleum gas (L.P.G) flame is used extensively, for this purpose. Soldering kit normally includes many, sizes and shapes of bits which can be used to make most, kinds of soldering connections. (Fig 4), , Straight soldering copper bit: This type of soldering, iron is suitable for soldering the inside bottom of a round, job. (Fig 5), , Adjustable soldering copper bit: This type of soldering, iron is used for soldering where straight or Hatchet bit, cannot be used for soldering. Adjustable slodering bit can, be adjusted in any position for soldering. (Fig 7), , Handy soldering copper bit: It is like a hatchet type, but bigger in size than the hatchet. It is used for soldering, heavy gauges of metal because additional heat will cause, the metal to buckle. (Fig 8), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Hatchet soldering copper bit: This type of soldering, iron is very much suitable for soldering on flat position hp, or grooved joint outside round or square bottom. (Fig 6), , Co, , Solder, , Objectives: At the end of this lesson you shall be able to, • define a solder, • state the types of solders, • state the constituents of soft and hard solders., Solder is a bonding filler metal used in soldering process., Pure metals or alloys are used as solders. Solders are, applied in the form of wires, sticks ingots, rods, threads,, tapes, formed sections, powder, pastes etc., , metals. Table shows different compositions of solder and, their application., In the composition of soft solder, tin is always, stated first., , TYPES OF SOLDERS, , WARNING, , There are two types of solders., , For cooking utensils, do not use solder containing lead., This could cause poisoning. Use pure tin only., , - Soft solder, - Hard solder, Soft solders: Soft solders are alloys of tin and lead in, varying proportions. They are called soft solders because, of their comparatively low melting point. One distinguishes, between soft solder whose melting points are 450°C and, hard solders whose melting points lie above 450°C These, are alloys of the materials tin, lead, anitimony,copper,, cadmium and zinc and are used for sodering heavy (thick), , Hard solder: These are alloys of copper, tin, silver, zinc,, cadmium and phosphorus and are used for soldering, heavy metals., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 49

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SI.No., , Types of solder, , Tin, , 1, , Common solder, , 50, , 2, , Fine solder, , 60, , 3, , Fine Solder, , 70, , 4, , Coarse solder, , 40, , 5, , Extra fine solder, , 66, , 6, , Eutectic alloy, , 63, , Lead, , 50, 40, 30, , 60, 34, 37, , Application, , General sheet metal applications, Because of quick setting properties, and higher strength,, they are used for copper water, electrical work., Used on glavanised iron sheets, Soldering brass, copper and jewellery, Similar to fine solder, , Soldering Flux, Objectives: At the end of this lesson you shall be able to, • state the functions of soldering fluxes, • state the criteria for the selection of fluxes, • distinguish between corrosive and non-corrosive fluxes, • state the different types of fluxes and their applications., , Function of the fluxes:, , DIFFERENT TYPES OF FLUXES, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , All metal rust to some extent, when exposed to the, atmosphere because of oxidation. The layer of the rust, must be removed before soldering. For this, a chemical, compound applied to the joint is called flux., , (A), , Inorganic fluxes, , 1, , Hydrochloric acid: Concentrated hydrochloric, acid is a liquid which fumes when it comes into, contact with air. After mixing with water 2 or 3, times the quantity of the acid, it is used as dilute, hydrochloric acid. Hydrochlotic acid combines, with zinc farmaing zinc chloride and acts as a, flux. So it cannot be used as a flux for sheet, metals other than zinc iron or galvanised sheet, this is also known as muriatic acid., , 2, , Zinc chloride: Zinc chloride is produced by, adding small pieces of clean zinc to hybrochloric, acid. It gives off hydrogen gas and heat after a, vigorous bubbling action, thus producing zinc, chloride. The zinc chloride is prepared in heat, resisting glass beakers in small quantities.(Fig1), , 3, , Ammonium chloride or sal-Ammoniac: It is a, solid white crystalline substance used when, soldering copper, brass, iron and steel. It is used, in the form of powder mixed with water. It is, also used as a cleaning agent in dipping solution., , 4, , Phosphoric acid: It is mainly used as flux for, stainless steel. It is extremely reactive. It is, stored in plastic containers because it attacks, glass., , 1 Fluxes remove oxides from the soldering surface. It, prevents corrosion., 2 It forms a liquid cover over the workpiece and, prevents further oxidation., , 3 It helps molten solder to flow easily in the required, place by lowering the surface tension of the molten, solder., , Co, , Selection of flux: The following criterias are important, for selecting a flux., - Working temperature of the solder, - Soldering process, - Material to be joined, , Different types of fluxes: Flux can be clasified as (1), Inorganic or corrosive (Active) & (2) Organic or noncorrosive, (Passive.), Inorganic fluxes are acidic and chemically active and, remove oxides by chemically dissolving them. They are, applied by brush directly on to the surface to be soldered, and should be washed immediately after the soldering, operation is completed., organic fluxes are chemically inactive. These fluxes coat, the surface of the metals to be joined and exclude the air, from the surface, to avoid further oxidation. They are, applied only to the metal surfaces which have been, previously cleaned, by mechanical abrasion. They are in, the form of lump, powder, paste or liquid., , 50, , (B), , Organic fluxes, 1, , Resin: it is an amber coloured substance, extracted from pine tree sap. It is available in, paster or powder form., Resin used for soldering copper, brass, bronze,, tin plate, cadmium, nickel, silver and some alloys, of these metals. This is used extensively for, electrical soldering work., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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2, , Tallow: It is a form of animal fat. It is used, when soldering lead, brass and copper., , The following Table shows the nature and type of flux used in soldering., , Metal to, be soldered, , Inorganic flux, , Organic flux, , Aluminium, Aluminium-bronze, , Remarks, , Commercially prepared flux and, solder required, , Brass, , Killed spirits, Sal ammoniac, , Resin, Tallow, , Commercial flux availlable, , Cadmium, , Killed spriits, , Resin, , commercial flux available, , Copper, , Killed spirits salammoniac, , Resin, , Commercial flux available, , Gold, , Monel, , Nickel, , Silver, , Killed Spirits, , Commercial flux required, , Killed spirits, , Phosphoric acid, , Steel, , Killed spirits, , Resin, , commercial flux available, , Resin, , commercial flux available, , commercial flux available, , Co, , Stainless steel, , Tin, , Tallow, Resin, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Lead, , Resin, , commercial flux available, , Killed spirits, , Killed spirits, , Resin, , Tin-zinc, , Killed spirits, , Resin, , zinc, , Muriatic acid, , Tin -bronze, Tin-lead, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 51

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Portable hand forge with blower, Objectives: At the end of this lesson you shall be able to, • state the purpose of hand forge, • describe the constructional feature of hand forge, • state the fuel used in hand forge., Hand forge: It is used for heating the soldering bit., It is made of mild steel plates and angles. It is generally, round in shape, the hand blower is attached to it for air, supply., A perforated plate is fixed at the bottom to remove burnt, residuals., The fuel zone is built up with fire bricks and coated with, the mixture of clay and sand, providing space at the centre, for fuel, (Fig 1), , Dipping solution, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The fuel used for firing is mainly charcoal. The charcoal is, prepared from hard wood., , Objectives: At the end of this lesson you shall be able to, • state the use of the dipping solution, • state the constituents of the dipping solution., It is used to dissolve oxides from solder coated faces of, the copper bit before applying it to the workpiece., It is made of, , A mixture of approximately one part of active component, and four parts of water is satisfactory as the acidity of the, solution should not be strong, , 1 Dissolving sal-ammoniac powder in water., 2 Dilute zinc-chloride with water,, , Co, , 3 Adding commercial flux with zine chloride or, ammonium chloride as active ingredients to water., , Safety pracautions in soldering, , Objectives: At the end of this lesson you shall be able to, • follow safety precautions in soldering to avoid injuries/acccidents., Safety precautions followed while soldering, , 5 Wear safety goggles when using acids for cleaning., , 1 Wear safety glasses to protect your eyes from, solder splattering and flux., , 6 When making acid solution, always pour acid into, water slowly., , 2 Be careful while storing hot soldering irons after use, to avoid burns., , 7 Never pour water into the acid., , 3 Wash your hands thoroughly after using soft solder, because it is poisonous., , 9 Wear goggles and gloves while handling corrosive, flux., , 8 All inorganic fluxes are poisonous., , 4 Tin the soldering iron in a well ventilated area to, exhaust fumes coming out while soldering., , 52, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Soft soldering, Objectives: At the end of this lesson you shall be able to, • explain soft soldering process, • state the melting characteristics of soft solders, • state the essential features of the soldering technique, • explain the importance of the attitude of the bit, • state the importance of movement of the bit in soldering, • state the characteristics of the soldered seams to be observed while inspection., Soft soldering involves the process., Preparing the workpiece., , -, , Select the correct soft solder., , -, , Correct joint design, , -, , Preparing the soldering iron., , -, , Preparation of the joint, , -, , Select and apply suitable flux., , -, , Selection of the solder, , -, , heat the soldering iron bit and the workpiece to the, correct temperature., , -, , Selection and preparation of the soldering iron., , -, , Copper bit heating, , -, , manipulating the soldering iron on the workpiece, skillfully as shown in Fig 1., , -, , Soldering bit manipulation, , -, , Complete the job to a satisfactory standard., , -, , Cleaning after soldering, , -, , Inspection of the seam., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Soldering Techniques: The following features are, essential to do soldering., , Attitude of the bit: The soldering iron bit should be placed, in a position that enables sufficient heat and solder to flow, into the joint., The angle between a working face of the bit and the joint, surface should be filled with a pocket of solder. (Fig 3), Any variation of this angle will control the amount of heat, and solder which is transferred onto the lapped surfaces., Contact between the molten solder and the joint opening, is essential for the penetration of the solder into the joint, as shown in figure., , Co, , Melting characteristics of soft solders: The eutectic, alloy of tins lead solder is a mixture of 63% tin and 37%, lead. 63/37 solder melts at 183°C and is the lowest melting, point of alloy series as shown in fig 2., , Successful use of the soldering iron is influenced by the, attitude of the bit and the movement of the bit on the, workpiece., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 53

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Movement of the bit: The bit movement along the line of, the seam, must be constant and consistent with a smooth, flow of solder. When sweating wide overlaps, in addition, to the progressive movement along the seam, it is required, to move the bit back and forth across the seam. (Fig 4), The pattern of the bit movement ensures successful heating, of the solder deposited, when the point of the bit covering, the joint opening penetrates through the lap as shown in, figure., , Flux residues and stains should be removed from the, seam, to keep clean dry surfaces for paint finishes., Inspection of the seam: A soldered seam should have, the following characteristics., -, , The solder has penetrated the lapped surface., , -, , The joint gap is sealed with a neat smooth fillet of the, solder., , -, , The upper surfaces of the seam must be smooth, thin, coating of solder, with tidy solder margins with uniform, width., , Soldered joint, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Visual inspection is good to rectify the faults of the solder., However, physical testing for air or water tight seam is, specified often. Leaks, detected by the tests are corrected, by re-cleaning, re-fluxing and re-soldering of the faulty joint, in the soldered seam., , Objectives: At the end of this lesson you shall be able to, • state the types of the soldered joints, • state the points to be considered for correct joint design., Types of soldered joints: Sheet metal components are, joined together by soldered joints. In many cases, the, edges are joined by sheet metal mechanical joints and, then soldered to make the joint stronger and leak proof., , Fig 2 shows soldered seams., , Co, , Fig 1 shows soldered lap joints., , Fig 3 shows soldered joint on round shaped parts., , 54, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Correct joint design: Sheet metal joints with overlapping, surfaces are ideal for joining or sealing with solder. Close, fitting of lapped sufaces are essential for the flow of, mobilized solder in into the joint by capillary action., , -, , Joint design suitable for silver brazing or soldering mainly, depends on the type of assembly and its intended use, following conditions., , Sheet metal joints both lapped and folded, are suitable for, silver soldering application as shown in fig 4., , Maximum strength can be achieved by observing the, following conditions., A suitable filler alloy must be used. Component metal, is of major consideration., , -, , Joint clearances should be minimum. Close fitting, surfaces helps capillary flow and gaps between 0.05, and 0.13 mm should be used., , -, , The solder must contact lapped surface suficiently., Lap width is commonly made 2 to 10 times the, component metal thickness. In case of unqual, thickness, the lap size is based on the thinner, materials., , Blow lamp, , Silver solder effects the union of lapped joints and seals, the seam openings of the interlocking folded joints., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Workpieces must be firmly supported. It is essential, to prevent the movement for the control of the solder, application, alignment and accuracy of the componet, assembly., , Objectives: At the end of this lesson you shall be able to, • state the constructional feature of blow lamp, • identify the parts of blow lamp, • describe the operation of blow lamp., , Co, , In blow lamp (Fig 1) the kerosene is pressurized to pass, through pre-heated tubes, thus becoming vaporised. The, kerosene vapour continues through a jet to mix with a air, and when ignited directed through a nozzle, producing a, forceful flame., , The flame within the housing provides the heat to maintain, vaporisation of the kerosene. The free flame at the nozzle, outlet is used to heat the soldering bit., Blow lamp is a portable heating appliance used as a direct, source of heat for soldering irons or other parts to be, soldered. Fig 1 shows parts of blow lamp., It has an tank made of brass, filler cap is fitted at its top to, fill kerosene. A pressure relief valve is connected to the, tank to switch ON/OFF and control the flame., Priming trough is provided for filling methylated spirit for, lighting the blow lamp. Set of nozzle is provided to direct, the kerosene vapour to produce forceful flame. Burner, housing is mounted on support brackets on which soldering, iron is placed for heating as shown in figure., Pump is provided to pressurise the kerosene in the tank., , Factors considered while soldering, Objectives: At the end of this lesson you shall be able to, • state the constructional feature of blow lamp, • identify the parts of blow lamp, • describe the operation of blow lamp., Soldering is joining two metal parts with a solder, i.e., a, 3 The correct solder and flux or soldering agent must, third metal that has a lower melting point., be chosen., Before soldering the following conditions must be met., 4 Proper amount of heat must be applied. If you follow, these conditions, you could get a good solder joint., 1 The metal must be clean., 2 The correct soldering device must be used and it must, be in good condition., Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, 55

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Cleanliness: Solder will never stick to a dirty, oil or oxide, coated surface. Beginners often ignore this simple point., If the metal is dirty, clean it with a liquid cleaner. If it is, black annealed sheet remove the oxide with an abrasive, cloth, and clean it until the surface is bright., , A bright metal, such as coper, can be coated with oxide, even though you cannot see it. This oxide can be removed, with any fine abrasive., , Soft soldering, brazing and silver brazing, Objectives: At the end of this lesson you shall be able to, • explain soft soldering and hard soldering, • describe the method of soft soldering, brazing and sliver brazing, • describe the difference between brazing and soldering, • explain the various methods of brazing, • explain the problems in brazing and the remedies., Soldering amd brazing: The soldering and brazing, processes differ from welding in the sense that there is, no direct melting of the base metal(s) being welded. In, brazing or soldering, the filler alloy flows between two, closely adjacent surfaces by capillary action.fig.1, , substances hydrochloric acid like zinc chloride, ammonium, chloride, hydrochloric acid. This type of flux leaves a, corrosive deposit on the base metal surface which must, be throughly washed off after soldering. This type of flux, is not used on electrical works or where the joints cannot, be effectively washed., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Non-corrosive: These are fluxes based on resin. These, leave a non-corrosive residue. They are used on electrical, works, instruments like pressure gauges, and parts where, washing is dificult., Suitable fluxes for various materials, Steel - zinc chloride, , Zinc and galvanized iron - hydrochloric acid, Tin - Zinc chloride, , Lead - tallow resin, , Brass, copper, brass - Zinc chloride, resin., Basic operations in soldering, , The parts to be soldered are fitted closely., , Co, , Soft soldering: The filler metals used in soldering have a, melting point below 427°C, The alloys used for soft soldering are:, -, , tin-lead (for general purpose soldering), , -, , tin-lead-antimony, , -, , tin-lead-cadmium,, , Paint, rust, dirt or thick oxides are removed by filing, scraping or by using emery paper or steel wool., The surfaces to be soldered are coated with flux to remove, the films of oxide. (Fig 2), , The process is referred to as ‘soft soldering’. The heat, required for ‘soft soldering’ is supplied by a soldering, iron, whose copper tip is heated either by a forge or, electrically., Composition of soft solder, Usually soft solder is an alloy of lead and tin in different, ratios depending on the base metals soldered and the, purpose of soldering., Soft solders are available in different shapes and forms, such as stick, bar, paste, tape or wire etc., TYPES OF FLUXES, Corrosive: In this type the solution contains inorganic, 56, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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The solder is applied with a copper soldering bit. (Figs 3a,, b and c) The joining takes place due to “sweating’ of the, bit the hot and tinned copper tip of the soldering iron., , It is applied on the joint in the form of a paste made by, mixing up with water., If brazing is to be done at a lower temperature, fluorides, of alkali materials are commonly used. These fluxes will, remove refractory oxides of aluminium, chromium, silicon, and berrylium., VARIOUS METHODS OF BRAZING, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Torch brazing: The base metal is heated to the required, temperature by the application of the oxy-acetylene, flame. (Fig 4), , The two sheets to be soldered are adhering to each other, due to sweating and bonding of the tinned area., , The excess solder present on the surfaces is removed, and the joint is allowed to cool., , Furnace brazing: The parts to be brazed are aligned, with the brazing material placed in the joint. The, assembly is kept in the furnace. The temperature is, controlled to provide uniform heating. (Fig 5), , Brazing: Brazing is a metal joining process which is, done at a temperature of above 450°C as compared to, soldering which is done at below 450°C, , Co, , So brazing is a process in which the following steps are, followed., , - Clean the area of the joint thoroughly by wire brushing,, emerying and by chemical solutions for removing oil,, grease, paints etc., - Fit the joints tightly using proper clamping. (Maximum, gap permitted between the two joining surfaces is only, 0.08 mm), , - Apply the flux in paste form (for brazing iron and steel, a mixture of 75% borax powder with 25% boric acid (liquid, form) to form a paste is used). Usually the brazing flux, contains chlorides, fluorides, borax, borates, flurodorates,, boric acid, wetting agents and water. So suitable flux, combination is selected based on metal being used., Brazing is employed where a ductile joints is required., Brazing filler rods/ metals melt at temperature from 860°C, to 950°C and are used to braze iron and its alloys., Brazing fluxes: Fused borax is the general purpose flux, for most metals., , Dip brazing: The parts to be brazd are submerged in a, molten metal or chemical bath (Fig 6) of brazing filler metal., Induction brazing: The parts to be brazed are heated to, the melting point of the brazing material by means of a, high frequency electric current. This is done by encircling, the joint with a water cooled iduction coil (Fig 7)., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 57

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, There is no flash or weld spatter., , The brazing technique does not require as much skill as, the technique for fusion welding., The process can be easily mechanised., The process is economical owing to the above advantages., , Wet the base metal., , Co, , Conditions to obtain satisfactory brazed or soldered, joint, , Spread the filler metal and make contact with the joint, surfaces. The solder will be drawn into the joint by capillary, action., Suggested joint designs for soldering and brazing are, shown in Fig 8, , Disadvantages of brazing, , If the joint is exposed to corrosive media, the filler metal, used may not have the required corrosive resistance., All the brazing alloys loose strength at an elevated, temperature, The colour of the brazing alloy which ranges from silver, white to copper red may not match the base metal very, closely., , Advantages of brazing, The completed joint requires little or no finishing., The relatively low temperature at which the joint made, minimizes distortion., , 58, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Brazing: Problems and remedies, Problem, , Remedy, Use more flux. Pickling or additional mechanical cleaning to remove, oxides, oils, or other surface coatings must be done, Add fresh flux., Also check for contaminated pickling acid or ‘dirty’ grinderwheels, that could spread impurities instead of removing them., , Filler metal melts but does not flow, completely through joint., , Longer preheating period required. the base metal may not be hot, enough. More thorough cleaning required. A wider or narrower, joint gap should be provided. Joint must not be too tight or too, loose. Also check for gaps or spaces where capillarity is interrupted., Apply more flux to both filler and base metal. Use a different flux, compound. Improper flux may be breaking down due to too much, heat. Eliminate this fault., , Filler metal runs out, instead of running, into the joint., , Re-position (tilt) the joint so that gravity helps the filler metal to run, into the joint. Making a small reservoir in the joint to start the, capillary action will help. Feeding the filler metal into the joint from, above rather than horizontally or from below is recommended., , Filler metal melts but will not flow., , Additional cleaning of filler metal to remove oxides is required. More, flux on both filler and base metal is required., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Filler metal ‘balls up’, does not melt and, flow into the joint., , Co, , Silver brazing: Silver brazing is also sometimes called, silver soldering. It is one of the best methods used to, connect/join parts which are to be leak proof and has to, give maximum strength of the joint. It is a very useful, and easy process for joining copper brass, bronze parts, as well as for joining dissimilar metal tubes like copper to, stainless steel tubes etc. The melting point of silver brazing, alloy filler rods will be around 600 to 800°C which is always, less than that of the base metals joined. Fig. 1 shows, silver brazing of stainless steel tube to be with a copper, tube., , Apply proper flux at the joint and on the filler rod., Heat the joint to the brazing temperature depending on, the composition of the silver brazing filler rod. The, brazing temperature may vary from 600°C to 800°. Use an, oxy-acetylene blow pipe for heating., Apply the silver brazing filler rod coated with the pasty, flux at the joint using leftward techique. Heat the filler rod, to the “flow temperature” which is usually 10 to 15° more, than its melting temperature. i.e, for the filler metal to flow, easily into the joint and for getting the wetting and capillary, action, it is necessary to heat the molten filler metal to 10, or 15° more than its melting temperture., Allow the joint to cool without removing the support given, to the joint., Clean the joint throughly to remove all residual flux., Fluxes used fo silver brazing may be chlorides or borax, made into a paste with water., Brazing and braze welding; Both brazing and braze, welding are metal joining processes which are performed, at temperatures above 840°F (450°C) as compared to, soldering which is performed temperatures below 840°F, (450°C), The American Welding soceity defines these processes, as follows:, , The process is similar to other brazing processes. The, points to be remembered while silver soldering are:, -, , The joint must be thoroughly cleaned both mechanically, and chemically., , -, , Fit the joint closely/tightly without any gap and support, the joint. (The maximum permissible gap between the, parts to be silver brazing is 0.08mm), , Brazing-” A group of welding processes which produces, coalescence of materials by heating them o a suitable, temperature and by using a filler metal having a liquidus, above 840°F (450°C) and below the solidus of the base, metal . The filler metal is distributed between the closely, fitted surfaces of the joint by capillary action” coalescence, is a joining or uniting of materials., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 59

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Braze welding-” A welding process variation in which a, filler metal, having a liquidus above 840°F (450°C) and, below the solidus of the base metal, is used. Unlike, brazing, in braze welding the filler is not distributed in the, joint by capillary action”, Brazing has been used for centuries. Blacksmiths,, jewellers, armourers and other crafters used the process, on large and small articles before recorded history. This, joining method has grown steadily both in volume and, popularity. It is an important industrial process, as well, as jewellery making and repair process. The art of brazing, has become more of a science as the knowledge of, chemistry, physics and metallurgy has increased., The usual terms Brazing and Braze welding imply the, use of a nonferrous alloy. These nonferrous alloys consist, of alloys of copper. tin, zinc, aluminum, beryllium,, magnesium, silver, gold and others., , Brazing and braze welding wrap the original metals less, and it is possible to joint dissimilar metals. For example,, steel tubing may be brazed to cast iron, copper tubing, brazed to steel and tool steel brazed to low carbon steel., Brazing is done on metals which fit together tightly. The, metal is drawn into the joint by capillary action. (A liquid, will be drawn between two tightly fitted surfaces. This, drawing action is known as capillary action). Very thin, layers of filler metal are used when brazing. The joints, and the material being brazed must be specially designed, for the purpose. When brazing, poor fit and alignment, result in poor joints and in inefficient use of brazing filler, metal., In braze welding, joint designs used for oxyfuel gas or arc, welding are satisfactory. When braze welding, thick layers, of the brazing filler metal is used., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Brass is an alloy consisting chiefy of copper and zinc., Bronze is an alloy consisting chiefly of copper and tin., Most rods used in both brazing and braze welding on, ferrous metals are brass alloys rather than bronze. The, brands which are called bronze usually contain a small, percent (about one percent) of tin., , A brazed joint is stronger than a soldered joint because of, the strength of the alloys used. In some instances it is as, strong as a welded joint. It is used where mechanical, strength and leaproof joints are desired. Brazing and braze, welding are superior to welding in some applications, since, they do not affect the heat treatment of the original metals, as much as welding., , Brazing and braze welding principles: Brazing is an, adhesion process in which the metals being joined are, heated but not melted: the brazing filler metal melts and, flows at temperatures above 840°F (450°C). Adhesion is, the molecular attraction exerted between surfaces., , Seaming and Machine, , Co, , Objectives: At the end of this lesson you shall be able to, • explain the construction of the seam closing machine, • identify the parts of the seam closing machine, • state the uses of the seam closing machine., Grooved seam can also be closed or locked mechanically, by means of the seam closing machine. This machine is, also called “Seaming machine”, , Horn: It contains grooves of various widths on, throughout the length as shown in Fig 2., , Parts shown in fig 1 are Body, Arm, Hom, Pressure roller,, carriage, Crank handle, Latch and Crank rack., , 60, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09

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Pressure roller: Two types of pressure rollers are available, alongwith the machine. One is flat roller and the other is, grooved one, Grooved roller is having grooves of 3 mm, 4, mm, 5 mm and 6 mm widths as shown in Fig 3., , If the seam is to be made from inside of the object, adjust, the suitable groove on the horn upper side and provide flat, pressure roller in carriage as shown in Fig 5., , Latch: It holds the horn rigid by when pressure roller is, functioning at the time of closing the seam., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Internal and External locks (Fig 4) can be made by, adjusting the horn and changing the pressure rollers on, the seam closing machine., , Co, , If the seam to be made on the outside of the object, adjust, the flat or plain face of the horn on the upper side, and, provide suitable grooved pressure roller in the carriage., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.09, , 61

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Fabrication, Related Theory for Exercise 1.1.10, Welder - Induction Training & Welding Process, Basic Welding Joints and Nomenclature of butt and fillet weld, Objectives: At the end of this lesson you shall be able to, • illustrate and name the basic welding joints., • explain the nomenclature of butt and fillet welds., Basic welding joints (Fig. 1), The various basic welding joints are shown in Fig. 1., , Leg length: The distance between the junction of the, metals and the point where the weld metal touches the, base metal ‘toe’ (Fig 5), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The above types mean the shape of the joint, that is, how, the joining edges of the parts are placed together., , Types of weld: There are two types of weld. (Fig .2), Groove weld/butt weld, , -, , Fillet weld, , Co, , -, , -, , Application of welding joints to the included, , Nomenclature of butt nd fillet weld (Figs 3 and 4), Root gap: It is the distance between the parts to be, joined. (Fig 3), Heat affected zone: Metallurgical properties have been, changed by the welding heat adjacent to weld., , 62, , Parent metal: The material or the part to be welded., Fusion penetration: The depth of fusion Zone in the, parent metal. (Fig.3 and 4)

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Reinforcement: Metal deposited on the surface of the, parent metal of the excess metal over the line joining, the two toes. (Fig6), , Root: The parts to be joined that are nearest together., (Fig 7), , Sealing run: A small weld deposited on the root side of, a butt or corner joint (after completion of the weld joint)., (Fig 10), , Backing run: A small weld deposited on the root side of, butt or corner joint (before welding the joint.) Fig. 6, Throat thickness: The distance between the junction, of metals and the midpoint on the line joining the two, toes. (Fig 5.), Toe of weld: The point where the weld face joins the, parent metal. (Fig 5&6.), weld face: The surface of a weld seen from the side, from which the weld was made. (Fig 5&6.), weld Juction: The boundary between the fusion zone, and the heat affected zone. (Fig 3&4), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Root face: The surface formed by squaring off the root, edge of the fusion face to avoid a sharp edge at the root., (Fig 8), , Fusion face: The portion of a surface which is to be, fused on making the weld. (Fig 11), Fusion zone: The depth to which the parent metal has, been fused. (Fig 11), , Co, , Root run: The first run deposited in the root of a joint, (Fig 9), , Root penetration: It is the projection of the root run at, the bottom of the joint (Fig. 6 and 9), Run: The metal deposited during one pass. Fig. 9., , The second run is marked as 2 which is deposited over, the root run. The third run is marked as 3 which is deposited, over the second run., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.10, , 63

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Material preparation method, Objectives: At the end of this lesson you shall be able to, • state the necessity of preparing the materials to be welded, • state different methods used to cut mild steel sheets and plates to the required size before welding, • identify different tools and equipments used to prepare the mild steel sheets and plates., Necessity of materials prepartion for welding: While, fabricating (producing or making) different components/, parts by welding, different sizes of plates, sheets pipes,, angles, channels with different dimensions are joined, together to get the final objects. For example, a railway, compartment, an aeroplane, an oil or water pipe line, a, gate,a window grill, a stainless steel milk tank, etc. So, these objects can be made to the required dimenesions, only by cutting them from the larger size sheets, plates,, pipes etc, which are available in standard sizes,, thickness, diameters and lengths in the market. Hence, cutting and preparing the base metal to the required, dimensions from the original material available in many, stores is necessary before welding them., , Different methods used to cut metals, , Also the base metals before cutting them to size will have, impurities like dirt, oil, paint, water and surface oxides,, due to long storage., , 2 Hacksaw with frame, , 2 By hacksawing, 3 By shearing using hand lever shear, 4 By using guillotine shear, 5 By gas cutting, For thin sheets the first 4 methods are used. For thick, materials method 2,4 and 5 are used., Tools and equipments used to cut metals, 1 Cold chisel, , 3 Hand lever shear, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , These impurities will affect the welding and will create some, defects in the welded joint. These defects will make the, joint weak and it is possible that the welded joint will break,, if the weld defects are present in the welded joints., , So in order to get a strong welded joint, it is necessary to, clean the surfaces to be joined and remove the dirt, oil, paint, water, surface oxide etc. from the joining sufaces, before welding., , Edge preparation, , 1 By chiseling the sheets, , 4 Guillotine shear, , 5 Oxy-acetylene cutting torch, , The cut edges of the sheet or plate are to be filed to remove, burrs and to make the edges to be square (at 90° angle), with each other. For ferrous metal plates, which are more, than 3mm thick, the edges can be prepared by grinding, them on a bench/pedestal grinding machine., , Co, , Objectives: At the end of this lesson you shall be able to, • explain the necessity of edge preparation, • describe the edge preparation for butt and fillet welds., Necessity of edge preparation: Joints are prepared to, weld metals at less cost. The preparation of edges are, also necessary prior to welding in order to obtain the, required strength to the joint. The following factors are, to be taken into consideration for the edge preparation., -, , The welding process like SMAW, oxy-acetylene welds,, Co2, eletro-slag etc., , -, , The type of metal to be joined, (i.e) mild steel, stainless, steel, alumininum, cast iron etc., , -, , The thickness of metal to be joined., , 64, , -, , The type of weld (groove and fillet weld), , -, , Economic factors, , The square butt weld is the most economical to use, since, this weld requires no chamferring, provided satisfactory, strength is attained. The joints have to be bevelled when, the parts to be welded are thick so that the root of the, joints have to be made accessible for welding in order to, obtain the required strength., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.10

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In the interest of economy, bevel butt welds should be, selected with minimum root opening and groove angles, such that the amount of weld metal to be deposited is, the smallest. “J” and “U” butt joints may be used to, further minimise weld metal when the savings are, sufficient to justify the more difficult and costly, chamferring operations. The “J” joint is usually used in, fillet welds., , TYPES OF EDGE PREPARATION AND SETUP, Different preparation generally used in arc welding are, shown in fig. 1 below., , A root gap is recommended since the spacing allows the, shrinking weld to draw the plates freely together in the, butt joint. Thus, it is possible to reduce weld cracking, and minimise distortion and increase penetration, by, providing a root gap for some welded joints., Method of edge preparation: The joining edges may, be prepared for welding by any one of the methods, mentioned below., Flame cutting, , -, , Machine tool cutting, , -, , Machine grinding or hand grinding, , -, , Filing, chipping, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.10, , 65

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Methods of cleaning the base metals before welding, Objectives: At the end of this lesson you shall be able to, • importance of cleaning, • describe the cleaning method, Every joint must be cleaned before welding to obtain a, sound weld., Importance of cleaning: The basic requirement of any, welding process is to clean the joining edges before, welding. The joining edges of surface may have oil,, paint, grease, rust, moisture, scale or any other foreign, matter. If these contaminants are not removed the weld, will become porous, brittle and weak. The success of, welding depends largely on the conditions of the surface, to be joined before welding. The oil, grease, paints and, moisture of the sheets to be welded will give out gases, while heated by arc or flame and these gases will get, into the molten metal. They will come out of the metal, when the molten metal cools to form the bead and create, small pin holes on the surface of the bead. This is known, as porosity and it weakens the joint., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Methods of cleaning: Chemical cleaning includes, washing the joining surface with solvents of diluted, hydrochloric acid to remove oil, grease, paint etc (Fig. 1), Mechanical cleaning inculdes wire brushing, grinding, filing,, sand blasting, scraping, machining or rubbing with emery, paper. (Fig. 2), , Co, , For cleaning ferrous metals a carbon steel wire brush is, used. For cleaning stainless and non-ferrous metals, a, stainless steel wire brush is used., , 66, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.10

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Fabrication, Related Theory for Exercise 1.1.11, Welder - Induction Training & Welding Process, Basic electricity as applied to welding, Objectives : At the end of this lesson you shall be able to, • define simple electrical terms, • differentiate between electric current, pressure and resistance, • state AC and DC, • explain open circuit and arc voltage, • state OHM’s law and its application, Electricity is a kind of invisible energy which is capable of, doing work such as:, , Copper, aluminium, steel, carbon, etc, are examples of, conductors. The resistance of these materials is low., , -, , burning of lamps, , -, , running of fans, motors, machines etc., , Insulators: Those substances through which electricity, does not pass are called insulators. (Fig 1), , -, , producing heat., , -, , by creating an arc, , -, , by electrical resistance of materials, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , It is dangerous to play with electricity., , Electric current: Electrons in motion is called current., The rate of flow of electrons is measured in amperes, (A). The measuring instrument is called ampere meter,, or ammeter., Electric pressure/voltage: It is the pressure which makes, the electric current to flow., , It is called voltage or electromotive force (emf). Its, measuring unit is volt(V). The measuring instrument is, called voltmeter., Electric resistance; It is the property of a substance to, oppose the flow of electric current passing through it., , Co, , Its measuring unit is ohm and the measuring instrument, is ohmmeter or megger., -, , Resistance of a metal changes as given below:, , -, , If the length is more the resistance will also be more., , -, , if the diameter is more the resistance will be less., , -, , the resistance will increase or decrease depending, on the nature of the meterial., , Conductors: Those substances through which electricity, passes are called conductors. (Fig 1), , Glass, mica, rubber. Bakelite, plastic dry wood, dry cotton,, porcelain and varnish are examples of insulators. The, resistance of these materials is high., Electric circuits: It is the path taken by the electric current, during its flow. Every electrical circuit comprises current,, resistance and voltage., The fundamental types of cricuit are:, -, , series circuit, , -, , parallel circuit., , Series circuit: The resistances of a circuit are cnnected, in a series end-to-end making only one path in which the, current flows., Parallel circuit: The resistances are connected side by, side to each other with the ends conected to power, source., Alternating current (AC): Electric current which changes, its direction of flow and magnitude at a certain number of, times per second is called alternating current. E.g. 50, cycles means it changes its direction 50 times per second., Its rate of change is called frequency i.e. hertz (Hz). (Fig.2), Direct current (DC) (Fig. 4): Electric current which always, flows in a particular direction is known as direct current., , 67

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(I.e) Negative to positive (electronic direction). Positive to, negative (conventional dirction)., Ohm’s law: It is one of the most widely applied laws of, electrical science., , welding machine, when there is no arc created/struck, between the electrode tip and the base metal then the, voltage”V” shown by the voltmeter in the circuit is called, “Open circuit voltage”., The vlue of this open circuit voltage will very from 60V to, 110V depending on the type of machine., After switching on the welding machine, if the arc is struck/, created between the tip of the electrode and the base, metal then the voltage “V’ shown by the voltmeter in the, ciruit is called “Arc voltage”., , The law states:, , In an electrical circuit, at constant temperature, the, current varies directly as the voltage, and inversely as, the resistance. i.e. current increases when voltage, increases., V=IR, Where V = Voltage, I = Current, , Use of electricity as applied to welding: For fusion, welding, the pieces to be joined are to be melted by:, - creating a high temperature (4500°C) arc between the, electrode and the work using electric voltage and high, current. (All types of arc welding), - heating the work to red hot condition by using the, resistance property of the metal and passig a very high, current for a fraction of a second and then applying a, very heavy pressure. (All types of resistance welding), - using highly concentrated electron beam on the joint, of the workpiece (Electron beam welding), , Co, , R = Resistance, , The value of this arc voltage will vary from 18V to 55V, depending on the type of machine., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , It is the relationship of current, voltage and resistance,, which was studied in 1827 by George. S.Ohm, a, mathematician., , Current decreases when resistance increases., , Application of Ohm’s law: The importance of this law, lies in its practical use for finding any one value when the, other two values are known., The three forms in which ohm’s law may be written are, shown below., , - Using the resistance of the slag and the current to, flow through the molten slag (Electroslag welding), In all the above welding processes, the electrical energy, is converted to heat energy which is used to either melt, the metal fully or heat them to red hot condition and, then melted by applying heavy pressure. So electricity, is used to a very large extent in many welding processes., , open circuit voltge and arc voltage: Fig.3 shows an, electric circuit used in arc welding. After switching on the, , I=, , V, R, , Where I = current in amps, , V = I × R Where V = Voltage in volts, , R=, , 68, , V, Where R = Resistance ohms, R, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.11

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Fabrication, Related Theory for Exercise 1.1.12, Welder - Induction Training & Welding Process, Heat and temperature, Objectives : At the end of this lesson you shall be able to, • differentiate between heat and temperature, • state the units of heat and temperature measurement, • differentiate between heat and temperature as applicable to welding, • convert centigrade to fahrenheit and vice versa, using tables., Heat and temperaure: Heat is a form of energy, capable, of flowing between two bodies which are at different, temperatures. The addition of heat energy to a body, increases the kinetic energy of motion of its molecules., Temperature is the degree of hotness or coldness of a, body measured, usually in centigrade of Fahrenheit., Temperature is a measure of the intensity of heat., Example: If we ask, ‘how hot is a substance’, the answer, will be, ‘it is so many degrees hot’. i.e. 40°C, 50°C, 150°F, etc., , -, , Centigrade scale, , -, , Fahrenheit scale, , 5, 9, Application of heat, temperature and their units, (terms) in welding, c = (122 - 32) ×, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Temperature measurement: there are two basic scales, for measuring temperature., , To check this, a reading of 100°C may be changed to the, Fahrenheit scale by substituting the value of (C) as given, below., 9, F = (100 c × ) ± 32 = 212°, 5, A reading of 122°F can be converted to centigrade scale, by subsituting the value of 122°F given below., , In both systems there are two fixed points which indicate:, -, , the temperature at which ice melts (Water freezes), , -, , the temperature at which pure water boils at standard, pressure., , Heat and temperature should not be confused with each, other., The temperature of oxy-acetylene flame is app. 3200°C., Flames produced by small and large nozzles have the, same temperatures but the large nozzle flame gives off, more heat than the small nozzle flame. More volume of, mixed gases comes out through larger size nozzles and, so more heat is produced. Refer the chart given below., Example, , Centigrade scale: This is a system for measuring, changes in temperature in which the interval of temperature, between the freezing and boiling points of pure water at, standard pressure is divided into 100 equal parts. There, freezing point is made zero of the scale (°0 C) and the, boiling point is fixed at 100 degrees (100° C), each division, part is called one centigrade degree (°C). Degree, centigrade is also called as degree celsius., , A thin piece of steel sheet 1.5 mm thick can be melted, quickly with a small oxy-acetylene flame., , Fahrenheit scale: A system for measuring changes in, temperature in which the interval of temperature between, the freezing and boiling points of pure water at standard, pressure is divided into 180 equal parts. The freezing, point is made 32 degree of the scale (32°F). The boiling, point is fixed at 212 degree (212°F)., , To speed up the melting of the thicker plate, use bigger, nozzles which will give a larger flame and more heat in, less time., , Each division part is called one Fahrenheit a degree (°F)., , When the nozzle size increases, the quantity of gas flow, per hour (rate of gas flow) increases. So more heat is, given out by larger nozzles and less heat by smaller, size nozzles., , Co, , Temperature is measured by a unit called ‘degree’., , Conversion of temperature from °C to °F, The formula used for temperature conversion is, C = (F - 32) ×, , 5, ⎡ 9 ⎤ ± 32, and F = c ×, ⎢⎣ 5 ⎥⎦, 9, , A thicker piece of steel plate (6 mm) will take a longer, time to melt with the same oxy-acetylene flame., Both pieces of steel have the same melting, points of 1530°C., , Refer to the chart given below which gives different nozzle, sizes and the corresponding volume of gasses flowing out, of them per hour, , Given below is a chart showing welded plate thickness,, nozzle size used and volume of gasses used., , 69

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Plate, thickness, (in mm), , Nozzle, size, , Approximate, consumption of each, gas litres per hour, , 0.8, 1.2, 1.6, 2.0 to 2.5, 3.0 to 3.5, 4.0, 5.0, 6.0 to 6.5, 8.0, 10.0, 12.0, , 1, 2, 3, 5, 7, 10, 13, 18, 25, 35, 45, , 28, 56, 85, 142, 200, 280, 370, 510, 710, 990, 1280, , Principle of arc welding, Carbon arc welding (Fig 3): Here the arc is formed, between a carbon electrode (non-consumable) and the, welding job., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , When high current passes through an air gap from one, conductor to another, it produces very intense and, concentrated heat in the form of a spark. The, temperature of this spark (or arc) is app. 3600°C, which, can melt and fuse the metal very quickly to produce a, homogeneous weld. (Fig 1), , Co, , Shielded metal arc welding (fig 2): This is an arc welding, process in which the welding heat is obtained from an arc,, formed between a metallic (consumable) electrode and, welding job., , A separate filler rod is usd since the carbon electrode is, a non-metal and will not melt., Atomic hydrogen arc welding (Fig 4): In this process, the arc is formed between two tungsten electrodes in an, atmosphere of hydrogen gas., the welding job remains out of the welding circuit., , A separate filler rod is used to add the filler metal., , The metal electrode itself melts and acts as a filler metal., , 70, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.12

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Tungsten inert gas arc welding (TlG) (Fig 5): In this, case the arc is formed between the tugsten electrodes, (nonconsumable) and the welding job in an atmosphere, of an inert gas (argon or helium)., A separate filler rod is used to add the filler metal., This process is also called gas tungsten arc welding, (GTAW) process., , Gas metal arc welding (GMAW) or Metal inert gas, arc welding (MIG) (Fig 6): In this process the arc is, formed between a continuous, automatically fed, metallic, consumable electrode and welding job in an atmosphere, of inert gas, and hence this is called metal inert gas arc, welding (MIG) process., When the inert gas is replaced by carbon dioxide then it, is called CO2 arc welding or metal active gas (MAG) arc, welding., The common name for this process is gas metal arc, welding (GMAW)., Submerged arc welding (Fig 7): Here the arc is formed, between a continuous, automatically fed, metallic, consumable electrode and the welding job under a heap, of powdered/granulated flux., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The arc is totally submerged in the flux (invisible)., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.12, , 71

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Plasma arc welding (Fig 9): In this process the arc is, formed between a tungsten electrode and the welding, job in an atmosphere of plasma-forming gas- nitrogen,, hydrogen and argon., , This automatic process requires special equipment and, is used only in vertical position for the welding of heavy, thick plates., , A separate filler rod is used to add the filler metal in the, joint, if necessary. But normally no filler rod is used., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Electro-slag welding (Fig 8): The arc is fomed between, a continuous, automatically fed, metalic consumable, electrode and the welding job under a thick pool of molten, flux (slag)., , The process is similar to TIG welding., , Co, , Plasma cutting is used to cut non-ferrous metals and alloys, successfully and quickly., , 72, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.12

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Fabrication, Related Theory for Exercise 1.1.13, Welder - Induction Training & Welding Process, Gases used for welding and gas flame combinations, Objectives: At the end of this lesson you shall be able to, • name the different types of gases used for welding, • compare the different types of gas flame combinations, • state the temperatures and uses of the different gas flame combinations., In the gas welding process, the welding heat is obtained, from the combustion of fuel gases in the presence of a, supporter of combustion (oxygen)., , (Oxy-acetylene gas flame combination is used in most, gas welding processes because of the high temperature, and heat intensity.), , Comparison of different gas flame combinations and their uses, Fuel gas, , Supporter, of combustion, , Name of the gas, flame, , Temperature, , Application/uses, , 1, , Acetylene, , Oxygen, , Oxy-acetylene, flame, , 3100 to 3300°C, (Highest temperature), , To weld all ferrous and, non-ferrous metals and, their alloys; gas cutting, & gouging of steel;, brazing bronze welding;, metal spraying and hard, facing., , 2, , Hydrogen, , 3, , Coal gas, , 4, , Liquid, petroleum, gas (LPG), , 5, , Acetylene, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Si., No., , Oxy-hydrogen, flame, , 2400 to 2700°C, (Medium temperature), , Only used for brazing,, silver soldering and, underwater gas cutting, of steel., , Oxygen, , Oxy-coal gas flame, , 1800 to 2200°C, (Low temperature), , Used for silver soldering, underwater gas cutting, of steel., , Oxygen, , Oxy-liquid petroleum, gas flame, , 2700 to 2800°C, (Medium temperature), , Used for gas cutting steel, heating purposes. (Has, moisture and carbon, effect in the flame.), , Air-acetylene, flame, , 1825 to 1875°C, (Low temperature), , used only for soldering,, brazing,heating, purposes and lead, burning., , Co, , Oxygen, , Air, , 73

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Fabrication, Related Theory for Exercise 1.1.14, Welder - Induction Training & Welding Process, Chemistry of oxy-acetylene flame, Objectives : At the end of this lesson you shall be able to, • identify the features and illustrate the different zones of an oxy-acetylene flame with their corresponding, temperatures, • explain the chemical reaction between oxygen and acetylene during primary and secondary combustion, in the flame., Oxy-acetylene flame is produced by the combustion of a, mixture of oxygen and acetylene in various proportions., The temperature and characteristics of the flame depend, on the ratio of the two gases in the mixture., , The flame takes an additional 1.5 litres of oxygen from the, surrounding atmosphere. (secondary combustion) (Fig 1), , Features of neutral flame: Oxy-acetylene flame, consists of the following features by appearance., , Primary combustion: It takes place in the inner cone, right in the tip of the nozzle. (Fig 1), , -, , Inner cone, , In the bright nucleus:, , -, , inner reducing zone, , C2 H2 ↑ 2C + H2 + Heat, , -, , Outer zone or envelope (Fig 1), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , To know the characteristics and effects of oxy-acetylene, flame a welder must know the chemistry of the flame., , Chemical reaction: 1 volume of acetylene combines, with 2 1/2 volumes of oxygen and burns to form 2, volumes of carbon di-oxide and 1 volume of water vapour, plus heat., , Different zones and temperature: To know and make, the best use of oxy-acetylene flame, the temperature in, different zones is shown in Fig 1., , In the inner cone - first burning stage:, 2C + H2 O2 ↑ 2CO + H2 + Heat, CO and H2 have reducing effect (no oxides are forming), Maximum heat (Hottest point) is just in front of the inner, cone., One volume of oxgen combines with one volume of, acetylene (delivered through the torch) and burns to, form.two volume of carbon monoxide and one volume of, hydrogen plus heat., , Co, , Secondary combustion: It takes place in the outer, envelope of the flame., , The greatest amount of heat is produced at just ahead, of the inner cone called the hottest point or region of, maximum temperature., , Combustion ratio of oxygen and acetylene in flame, For complete combustion/burning one volume of acetylene, requries two and a half volumes of oxygen., Acetyene, , :, , Oxygen + O, , 1 litre, , :, , 2.5 litres, , Equal volumes of acetylene and oxgen are supplied from, the blowpipe to produce a neutral flame. (Fig 1), Acetylene, 1 litre, , :, , Oxygen, , :, , 1 litre, , (primary combustion), So another 1.5 litres of oxgen is required for complete, burning of acetylene., , 74, , In the outer envelope - secondary burning, 2CO + O2 ↑ 2CO2 + Heat, , 2H2 + O2 ↑ 2H 0O + Heat, , Combustion in air (Fig 1): Two volumes of carbon, monoxide and 1 volume of hydrogen (Product of primary, combustion) combine with 1.5 volume of oxygen from, the surrounding air and burn to form. two volumes of carbon, dioxde and 1 volume of water vapour., The product of primary combustion is further, burnt in the reducing zone., The region surrounding the inner cone and, its tip is called reducing zone, The reducing zone protects the molten metal, from atmospheric effects as it uses the, atmospheric oxygen for secondary, combustion.

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Types of oxy - acetylene flames, Objectives: At the end of this lesson you shall be able to, • name the different types of oxy-acetylene flames, • state the characteristics of each type of flame, • explain the uses of each type of flame., The oxy-acetylene gas flame is used for gas welding, because, , The flame has an oxidising effect on metals which, prevents evaporation of zinc/tin in brass welding/brazing., , - it has a well controlled flame with high temperature, , Uses: Useful for welding of brass and for brazing of ferrous, metals., , - the flame can be easily manipulated for proper melting, of the base metal, - it does not change the chemical composition of the, base metal /weld., , Carburising flame (Fig 3): It receives an excess of, acetylene over oxygen from the blowpipe., , Three different types of oxy-acetylene flames as given, below can be set., - Neutral flame, - Oxidising flame, - Carburising flame., CHARACTERISTICS AND USES, Uses: Useful for stelliting (hard facing), ‘Linde’ welding of, steel pipes, and flame cleaning., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Neutral flame (Fig 1): Oxygen and acetylene are mixed, in equal proportion in the blowpipe., , The selection of the flame is based on the metal to be, welded, The neutral flame is the most commonly used flame., (See the chart given below.), , Complete combustion takes place in this flame., , Co, , This flame does not have a bad effect on the base metal/, weld i.e. the metal is not oxidised and no carbon is avilable, for reacting with the metal., , Uses: It is used to weld most of the common metals, i.e., mild steel, cast iron, stainless steel, copper and, aluminium., , Metal, , Flame, , 1 Mild steel, , Neutral, , 2 Copper (de-oxidised), , Neutral, , 3 Brass, , Oxidising, , 4 Cast iron, , Neutral, , 5 Stainless steel, , Neutral, , 6 Aluminium (Pure), , Neutral, , 7 Stellite, , Carburising, , Oxidising flame (Fig 2): It contains excess of oxygen, over acetylene as the gases come out of the nozzle., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.14, , 75

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Fabrication, Related Theory for Exercise 1.1.15, Welder - Induction Training & Welding Process, Principle of gas cutting and application, Objectives : At the end of this lesson you shall be able to, • explain the principle of gas cutting, • describe the cutting operation and its application., Introduction to gas cutting: The most common, method of cutting mild steel is by an oxy-acetylene cutting, process. With an oxy-acetylene cutting torch, the cutting, (Oxidation) can be confined to a narrow strip and with, little effect of heat on the adjoining metal. The cut, appears like a saw-cut on a wooden plank. The method, can be successfully used to cut ferrous metals i.e. mild, steel., Non-ferrous metals and their alloys cannot be cut by this, process., , Also the iron oxide is in molten condition called slag. So, the jet of oxygen coming from the cutting torch will blow, the molten slag away from the metal making a gap called, ‘Kerf’. Fig.2, Cutting operation (Fig 2): There are two operations in, oxy-acetylene gas cutting. A preheating flame is directed, on the metal to be cut and raises it to bright red hot or, ignition point (900° C app.). Then a stream of high, pressure pure oxygen is directed on to the hot metal, which oxidizes and cuts the metal., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Principle of gas cutting: When a ferrous metal is heated, to red hot condition and then exposed to pure oxygen, a, chemical reaction takes place between the heated metal, and oxygen. Due to this oxidation reaction, a large amount, of heat is produced and cutting action takes place., , When a piece of wire with a red hot tip is placed in a, container of pure oxygen, it bursts in to flame immediately, and is completely consumed. Fig 1 illustrates this, reaction. Similarly in oxy-acetylene cutting the, combination of red hot metal and pure oxygen causes, rapid burning and iron is changed into iron oxide, (oxidation)., BY this continuous process of oxidation the metal can, be cut through very rapidly., The iron oxide is less in weight than base metal., 76, , The two operations are done simultaneously with a single, torch., The torch is moved at a proper travel speed to produce, a smooth cut. The removal of oxide particles from the, line of cut is automatic by means of the force of oxygen, jet during the progress of cut., 300 litres of oxygen are required to oxidize, one kilogram of iron completely. The, ignition temperature of steel for gas cutting, is 875°C to 900°C

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Application of cutting torch: Oxy-acetylene cutting, torch is used to cut mild steel plates above 4mm, thickness. The M.S plate can be cut to its full length in, straight line either parallel to the edge or at any angle to, the edge of the plate. Bevelling the edges of a plate to, any required angle can also be done by tilting the torch., Circles and any other curved profile can also be cut using, the cutting torch by using a suitable guide or template., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Fig.3 to Fig.7 Shows the guides used to cut straight lines,, bevel and small circles., , Cutting torch guides: Guides are sometimes used during, oxy acetylene cutting., They can be either a roller guide, double support or spade, guide with single support., , Cutting guides are held onto the nozzle of the cutting, torch by tightening a clamp bolt. the clamps, where they, are fitted, are adjusted so the inner cones of the preheat, flames are approximately 2-3mm above the surface of, the metal to be cut. The tip of the cutting nozzzle is held, at distance of 5-6mm above surface of the plate being, cut., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.15, , 77

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Fabrication, Related Theory for Exercise 1.1.16, Welder - Induction Training & Welding Process, Oxy-acetylene hand cutting - piercing hole and profile cutting, Objectives : At the end of this lesson you shall be able to, • explain the special types of nozzles for gas cutting and their application, • describe the parts of a cutting equipment and their functions, • explain trouble shooting and the remedy of the faults in oxygen cutting., Table of some common cutting torch tips and their uses, Degree of, preheating, , Aplication, , Medium, , For straight line or circular, cutting of clean plates., , Light, , For splitting angle iron, trimming, plates and sheet metal cutting., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Number of preheat orfices in, cutting torch tips, , 78, , Light, , For hand cutting rivet heads and, machine cutting 30 deg. bevels., , Light, , For Straight line and shape, cutting clean plate., , Medium, , For rusty or painted surfaces., , Heavy, , For cast iron cutting and, preparing vee for cast iron, welding., , Very, heavy, , For general cutting; also for, cutting and stainless steel., , Medium, , For grooving,flame machining,, gouging and removing imperfect, welds., , Medium, , For grooving,gouging or, removing imperfect welds., , Medium, , For machine cutting 45° deg., bevel or hand cutting rivet heads., , Heavy, , Flared cutting orifices provide a, large oxygen stream of low, velocity for rivet head removal, (Washing).

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Special purpose nozzle: For profile cutting. different, types of nozzles are used for cutting metals in different, shapes., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Nozzles used for cutting profiles are shown in fig 1., , Co, , Cutting torch: Fig.2 Oxygen and fuel gas are mixed and, then the gas is carried to the tip of the orifice to form, ‘preheat’ flames. If oxygen is carried directly to the tip it, oxidises the metal and blows it away to form the cut., Method of piercing a hole: Hold the cutting blow pipe, at right angles on the point where the hole is to be made., The point will be brightened. Release the cutting oxygen, slowly. Raise the torch, tilt the nozzle slightly to the left, and right direction so that the sparks may not fuel the, nozzle. Thus the hole may be piecred., , Names and function of the parts of a cutting torch, (Fig 3 and Table 1), Table 1, , NO., , Name, , 1., , Acetylene, gas valve, Oxygen Regulator, Acetylene gas, hose joint, Oxygen conduit, Acetylene gas, conduit, Grip, Preheating, oxygen valve, Cutting oxygen, valve, Injector, , 2., 3., 4., 5., , For cutting of the profile hold the blow pipe head in such a, way that the oxygen stream is directed by the correct, tilting of the blow pipe. It is obvious that the angle between, the nozzle and the plate must remain constant and this, poses the greatest difficulty for the beginners., , 6., 7., , Position of the preheating flame as related to the plate, surface is very important., , 9., , 8., , 10., 11., 12., , Cutting oxygen, conduit, Mixed gas, conduit, Torch head, , Function, To adjust the flow rate, of acetylene gas., To connect Regulator, To connect with the, acetylene gas hose., To lead oxygen., To lead acetylene gas., To hold the torch., To adjust the preheating, flame., To adjust the cutting, oxygen flow rate., To mix the acetylene gas, with oxygen., To lead the cutting oxygen., To lead the mixture of, acetylene gas and oxygen., To attach the nozzle., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.16, , 79

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Troubleshooting, Object, , Trouble, , part to be, , Method, , Hose joint, , soap water, or water, , Tighten further, or replace., , At the beginning of the, work., , Valve &, regulator, , Soap water, or water, , Replace the torch., , At the beginning of the, work., , Cutting tip, attching, part, , soap water, or water, , Tighten further, or replace., , At the beginning of the, work., , Injector, , plug the fuel, gas hose, mouth with, your finger., , Replace., , Periodical check for the, low pressure torch., , Preheating, flame shape, , Neutral flame, visual, inspection, , Clean or replace., , At the beginning of the, work or at random., , Cutting oxy, gen flow, , Visible gas, Visual, inspection, , Clean or replace., , At the beginning of the, work or at random., , Gas leakage, Torch, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Suction of, Acetylene, , Remedy, , Care and maintenance: The cutting oxygen orifice should, be cleaned at regular intervals by using different size wire, of nozzle cleaner. (Fig 4), , Characteristics of analysis of cutting: This analysis, has been made on referring to the cutting face and the, formation of cut in this surface., This can be analysed as shown in the figure . (Fig 5), , Co, , 5, , 80, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.16

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Oxy-acetylene cutting equipment, Objectives: At the end of this lesson you shall be able to, • explain the features of the oxy-acetylene cutting equipment, its parts and cutting torch, • describe the oxy-acetylene cutting procedure, • differentiate between cutting and welding blowpipes., Cutting equipment: The oxy-acetylene cutting equipment, is similar to the welding equipment, except that istead of, using a welding blowpipe, a cutting blowpipe is used. The, cutting equipment consists of the following., -, , Acetylene gas cylinder, , -, , Oxygen gas cylinder, , -, , Acetylene gas regulator, , -, , Oxygen gas regulator (Heavy cutting requires higher, pressure oxygen regulator.), , -, , Rubber hose-pipes for acetylene and oxygen, , -, , Cutting blowpipe, , Difference between cutting blowpipe and welding, blowpipe: A cutting blowpipe has two control valves, (oxygen and acetylene) to control the preheating flame, and one lever type control valve to control the high pressure, for oxygen for making the cut., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , (Cutting accessories i.e. cylinder key, spark lighter, cylinder, trolley and other safety appliances are the same as are, used for gas welding.), , Oxy-acetylene cuttng procedure: Fix a suitable size, cutting nozzle in the cutting blowpipe. lgnite the cutting, torch the same way as was done in the case of the, welding blowpipe. Set the neutral flame for preheating., To start the cut, hold the cutting nozzle at angle 90° with, the plate surface, and the inner cone of the heating flame, 3 mm above the metal. Preheat the metal to bright red, before pressing the cutting oxygen lever. If the cut is, proceeding correctly, a shower of sparks will be seen to, fall from the punched line. If the edge of the cut appears, to be too ragged, the torch is being moved too slowly., For a bevel cut, hold the cutting torch at the desired, angle and proceed as is done in making a straight line, cut. At the end of the cut, relese the cutting oxygen, lever and close the control valves of the oxygen and, acetylene. Clean the cut and inspect., , Co, , The cutting torch (Fig 1): The cutting torch differs from, the regular welding blowpipe in most cases: it has an, additional lever for the control of the cutting oxygen used, to cut the metal. The torch has the oxygen and acetylene, control valves to control the oxygen and acetylene gases, while preheating the metal., , A welding blowpipe has only two control valves to control, the heating flame (Fig 2)., , The nozzle of the cutting blowpipe has one hole in the, center for cutting oxygen and a number of holes around, the circle for the preheating flame. (Fig 3), , The cutting tip is made with an orifice in the centre, surrounded by five smaller holes. The centre opening, permits the flow of the cutting oxygen and the smaller, holes are for the preheating flame. Usually different tip, sizes are provided for cutting metals of different, thicknesses., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.16, , 81

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The nozzle of the welding blowpipe has only one hole in, the center for the heating flame. (fig 4), , The cutting nozzle size is given by the diameter of the, cutting oxygen orifice in mm., The welding nozzle size is given by the volume of oxyacetylene mixed gas coming out of the nozzle in cubic, meter per hour., Operating data for cutting mild steel, , The angle of the cutting nozzle with the body is 90°, The angle of the welding nozzle with the neck is 120°, Cutting nozzle, size-mm, , Thickness of plate (mm), , Cutting oxygen, Pressure kgf/cm2, , 3-6, , 1.0 - 1.4, , 1.2, , 6-9, , 1.4 - 2.1, , 1.6, , 19-100, , 2.1 - 4.2, , 2.0, , 100-150, , 4.2 - 4.6, , 2.4, , 150-200, , 4.6 - 4.9, , 2.8, , 200-250, , 4.9 - 5.5, , 3.2, , 250-300, , 5.5 - 5.6, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 0.8, , Care and maintenance: The high preesure cutting, oxygen lever should be operated only for gas cutting, purposes., Care should be taken while fitting the nozzle with the torch, to avoid wrong thread. Dip the torch after each cutting, operation in water to cool the nozzle., , Co, , To remove any slag particles of dirt from the nozzle orifice, use the correct size nozzle cleaner Fig.5. Use an emery, paper if the nozzle tip is damaged to make it sharp and to, be at 90° with the nozzle axis., , However, the oxidation of metals has also certain useful, effects, i.e a stream of pure oxygen if applied (used) on, a red hot mild steel plate through a nozzle, the plate will, get cut into 2 pieces. Hence the principle of oxidation is, effectively used in gas cutting and gouging of mild steel., , 82, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.16

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Fabrication, Related Theory for Exercise 1.1.17, Welder - Induction Training & Welding Process, Oxy-acetylene machine cutting, Objectives : At the end of this lesson you shall be able to, • explain different types of gas cutting machines, • explain profile cutting using templates, • state gas cutting defects, their causes and remedies.., There are two types of cutting machines., -, , Manually driven cutting machines, , -, , Electrically driven cutting machines, , This machine can be used for straight line cutting, bevel, cutting, circular cutting and profile cutting. (Fig 2), , Manually operated cutting machines, A manually driven cutting machine normally consists of:, a crank or wheel to drive the cutter via a screw thread, and this machine can be used for straight line cutting, and bevel cutting, , -, , a system of links or rods which are used with the, machines and by which simple circles, ellipses,, squares, etc. can also be cut. (Fig. 1), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Provision is also made to enable full adjustment of the, cutting head to be carried out over the cutting area., , Co, , The electrical control unit fitted to the carriage is shown, in Fig.3., , The speed of the manually operated cutting machines is, liable to variation and the range of speed is also limited., Electrically driven cutting machines, There are two types of machines available., Portable machines, Static machines, PORTABLE MACHINES, An electrically driven portable cutting machine generally, consists of:, -, , cutting instruments, , -, , carriage (Consisting of a variable speed motor), , -, , guide (to guide the carriage)., , The speed of an electrically driven machine, when it, is, constant, and normally it is able to produce better cuts, than a manually driven machine. The speed range of an, electrically driven machine is greater than that of the manual, type and the adjustment of speed helps to control more, accurately. Multiple cutting heads can be mounted to, increase the volume of cutting, these cutting heads may, be mounted on an adjustable bar extending to either side, of the track at 90° to the direction of travel. (Fig 4), , 83

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STATIC MACHINES, These machines are generally used to produce more, accurate work than what is possible with manually, operated or portable cutters., , -, , Outside template, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , These machines can be used with radial arm and crosscarriage arrangements. In general the work is required, to be brought to the machine. With this machine straight, line cutting, circle and profile cutting can be done., (Fig 5), , Two types of templates are in use depending on their size., , -, , Inside template, , Outside template, , The outline of the template will be the shape to be cut,, reduced in size by the radius of the follower wheel or roller, which is (Knurled) attached with the motor af the machine., The size of the template is excluding the radius of the, tracing wheel (knurled wheel) - half of the kerf width., (Fig 7), , Co, , Example, , Profile cutting by using templates, Profile cutting can be done by static cutting machines as, per the shape of the templates. (Fig 6) The templates are, mainly used for reproducing the same shapes into a no., of pieces. The templates are made from wood, hardboard,, aluminium or steel., , 84, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.17

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To cut a circle using an extermal template, Radius of circle, Radius tracing wheel, Half the kerf width, Difference [(a) - (b)], So pre-radius of external, template, , 100 mm, 6.5 mm (a), 0.8 mm (b), 5.7 mm, , =, , 100-5.7 mm, 94.3 mm, , GAS CUTTING DEFECTS, Recognition of cutting and gouging defects, their causes,, prevention and permissible methods of rectification, - In a correct cut the top of the cut is both sharp and, clean, the drag lines are almost invisible, producing a, smooth side. Oxide is easily removed, the cut is sharp, and bottom edge is clearly and sharply defined., Drag lines should be vertical for profiles. A small amount, of drag is allowed on straight cuts., , NOTE:, Kerf width is variable according to the:, -, , nozzle size, type and condition, , -, , plate thickness, , -, , cutting speed, , -, , pressure of cutting oxygen, , -, , preheat flame size., , Internal template or inside template, - Due to melting, the top edge has become rounded., Gouging is pronounced at the bottom edge, which is also, rough. Scale on the cut face is difficult to remove., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The shape of the template will be the shape to be cut, increased by the radius of the following roller (knurled, wheel) + half the kerf width. (Fig 8), , Co, , To rectify: Traverse at recommended speed. Increase, the oxygen pressure., , - The top edge may not be sharp; there is a possibility, of beading., To rectify: slow down the traverse to the recommended, speed. Leave the oxygen pressure as set., , Example, To cut a circle using an internal template:, Radius of circle, Radius of tracing wheel, (knurled), Half the kerf width, Sum of (a) + (b), , -, , 100mm, , =, , 6.5 mm (a), 0.8 mm (b), 6.5 + 0.8 mm, , =, , 7.3 mm, , The radius of the external, template, =, =, , 100 + 7.3 mm, 107.3 mm, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.17, , 85

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Fabrication, Related Theory for Exercise 1.1.18, Welder - Induction Training & Welding Process, Common defects in gas cutting, Objectives : At the end of this lesson you shall be able to, • explain the principle of gas cutting, • describe the cutting operation and its application., Common faults in cutting, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , (Fig 1) The tip is too high off the steel. The top edge is, heated or rounded, the cut face is not smooth, and often, the face is slightly bevelled where preheat effectiveness, is partially lost due to the tip being held so high. The, cutting speed must be reduced because of the danger of, losing the cut., , (Fig 3) Tip too close to the steel. The cut shows grooves, and deep drag lines, caused an unstable cutting action., Part of the preheat cones burned inside the kerf, where, normal gas expansion affected the oxygen cutting, stream., , Co, , (Fig 2) Extemely slow cutting speed. Pressure marks, on the cut face indicate too much oxygen for the cutting, conditions. Either the tip is too big, the cutting oxygen, pressure is too high, or the speed is too slow as shown, by the rounded or beaded top edge. On reducing the, cutting oxygen volume to the correct proportions for the, thickness of the cut, the pressure marks will recede, toward the bottom edge until they finally disappear., , 86, , (Fig 4) Too much cutting oxygen. The cut shows pressure, marks caused by too much cutting oxygen. When more, oxygen is supplied than can be consumed in oxidation,, the remainder flow around the slags, creating gouges or, pressure marks.

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(Fig 5) Too much preheating. The cut shows a rounded, top edge caused by too much preheat. Excess, preheating does not increase the cutting speed, it only, wastes gases., , (Fig 8) Slightly too slow a cutting speed. The cut is of, high quality although there is some surface roughness, caused by the vertical drag line. The top edge is usually, slightly beaded. This quality is generally acceptable, but, faster speeds are more desirable because the labour cost, for this cut is too high., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , (Fig 6) Poor quality bevel cut. The most common fault, is gouging, caused by either excessive speed or, inadequate perheat flames. Another fault is a rounded, top edge caused by too much preheat, indicating, excessive gas consumption., , In a good cut, the edges are square, and the lines of cut, are vertical. (Fig 9), , Co, , (FIg 7) Slightly too fast a cutting speed. The drag lines, on this cut incline backwards, but a ‘drop cut’ is still, attained. The top edge is good; the cut face is smooth, and slag-free. This quality is satisfactory for most, production work., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.1.18, , 87

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.19, , Power source selection criteria, Some General Terms to Understand, , Power source selection criteria MIG/MAG:, , Insulation class- The temperature withstanding capability, of the insulation materials., , Maximum & minimum electrode wire diameter. Welding, job thickness. welding position joining materials, Circularity, of joints - Pulsed/non-pulsed, preciseness of parameter, control-step-controlled or step less. Dip tranfer/spray, transfer, shielding Gas Inductance level required, , Power factor- Ratio of active power used to the total power, drawn from the system., Efficiency- Power utility factor of the machine expressed, as a % output to input. It accounts for losses in the system, particularly transformer losses. In welding power sources, ‘no load’ loss is a very important criteria because power, source arc-on time is hardly 25% in a shopfloor situation., , Inverter its concept and application, , The first digit defines the degree of protection with respect, to person and solid ingress., , Inverters: Mains voltage is recitifed to DC. The inverter, converts to the high frequency AC. The transformer, changes the HF AC to suitable welding voltage. The AC is, rectified. Various filters remove the disturbing frequencies, and ripples in the DC current. The entire process is, monitored by a control circuit. This gives the machine, ideal static and dynamic characteristic. A CDC voltage is, availabe for welding purpose through a microprocessor, based real time adaptive process control., , The degrees range from, 0-6 where 0 means no protection, & 6 means Dust proof., , Why inverters: Traditional power sources have the, following disadvantages:, , The second digit defines the degree of protection with, respect to harmful ingress of water. The degrees range, from 0-8 where 0 means no special protection & 8 means, protection against submersion (Hermetically sealed)., , Higher weight due to low frequency of operation (50Hz), larger volume occupying more workspace. Features of,, inverter power sources,, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Ip classes define the degree of protection provided by the, closure and is indicated by various 2-digit numbers such, as 22,23,54 etc., , Power Source Selection Criteria General:, , Copper or Aluminum conductors-A total non-issue class, of insulation., , • Very light and compact-portable., • Power consumption reduced by 40-50%, • Can quickly modify static, and dynamic output, characteristics for multi-process capability., , • Excellent arc stability., , Power source selection criteria SMAW:, , • TIG welding can be done at 1ampere., , Co, , Input power - 3phase or 2line of 3phase Duty cycle., pertaining, IP class, power factor, Efficiency., , Type of welding current-AC or DC or both amperage range, determined by size & type of electrode., , Open circuit voltage (Ocv) - high OCV desirable from the, stand point of arc initiation & arc maintenance. But, electrical hazard factors & high cost are to be considered., Welding positions - If vertical & overhead welding are, planned, slope adjustment of the V-A curve is desirable., , 88, , • Hot start and adjustable arc force for SMAW,GMAWpulse and synergic MIG welding., , • Possible to achieve spray transfer at lower currents., • High switching frequencies of 50,000 hertz facilitates, microproessor based real time adaptive process control.

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.20, , A.C welding transformer and its construction, Objectives: At the end of this lesson you shall be able to, • identify the features of an AC welding transformer, DC welding generator and welding rectifier, • explain the working principle of the above welding machines, • compare the advantages and disadvntages of an Ac and a DC welding machine, • explain the care and maintenance of welding machines., AC welding transformer: This is a type of AC welding, machine which converts AC main supply into AC welding, supply. (Fig 1), , Two welding cables are attached with the output terminals., One is for the electrode and the other is for earth or job., The transformer may be air-cooled or oil-cooled., Working principle: The AC main supply (220-440 volts), is connected to the primary winding which produces a, magnetic lines of force in the iron core., The magnetic lines of force affects the secondary winding, and induces high ampere-low voltage welding supply in it., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , This action is called the principle of mutual, induction., , The voltage at the primary coil is reduced in the secondary, coil depending on the ratio of the No. of turns in the primary, to that of the secondary., Voltage at secondary coil =, Voltage at primary coil × No. of turns in the secondary, , AC main supply has high voltage-low ampere., AC welding supply has high ampere-low, voltage., It is a step down transformer, which:, , Co, , - reduces the main supply voltage (220 or 440 volts) to, welding supply open circuit voltage (OCV), between 40, and 100 volts, , - increases the main supply low current to the required, high output welding current in hundreds of amperes., , An Ac welding transformer cannot be operated without AC, main supply., Constructional features: It consists of an iron core made, out of a special alloy thin iron sheet stampings. Two coils, of wire are wound over the iron core without any, interconnection between them., One coil, called primary winding, consists of a thin, conductor and has more turns which receive energy from, the mains. The second coil, called secondary winding, consists of a thick conductor and less turns which supply, energy for welding., , No.of turns in the primary, , Advantages, , Less initial cost, , Less maintenance cost, Freedom from arc blow, NO noise, , The magnetic effect of DC disturbs the arc, the, effect of which is called ‘arc blow’., , Disadvantages, Not suitable for:, - welding of non-ferrous metals, - bare wire electrodes, - fine current setting in welding special jobs., AC cannot be used without special precautions, of safety., , A current regulator is attached to the secondary output, supply to adjust the amperes for welding suitable to the, various sizes of electrodes., , 89

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care and maintenance, Transformer body must be properly earthed., Transformer oil must be changed after recommended, period, in the oil cooled transformers., Always follow the operating instruction manual to run, and install the machine., Do not run the machine continuously on its maximum, capacity., Switch off the main supply of the machine while cleaning, internally or externally., Do not change the current when welding is going on., Always keep and install the machine on dry floor., Give proper protection to the machine while working outside, in rain or dust., D.C welding generator, Necessity of DC welding generator, , Main poles: These are connected to the body or yoke to, produce magnetic lines of force, also called FIELD COILS., Body or yoke: It is the body of the generator which covers, all the parts and helps in completing the magnetic circuit, to generate electricity., Armature: It is a laminated steel drum with longitudinal, stole which accommodate copper conductors., It is mounted on a shaft which rotates in suitable bearing, arranged at its ends., It is also mounted on the shaft along with the armature, and is connected to the armature conductors., Carbon brushes: These are mounted on the body to, have contact with the rotating commutator and are, connected to the output terminals., Fan: It is meant for cooling the generator., Prime mover: It is the driving source as motor or engine, used to rotate the armature in the generator. (Fig 3), , DC welding generators are used to:, generate DC welding supply with the help of AC main, supply, , -, , generate welding supply where electricity (main supply), is not available, with the help of engine driven sets, , -, , get relative advantages of polarity i.e. heat distribution, between the electrode and the base metal and welding, of non-ferrous metals., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Constructional features of DC welding generator, (Fig.2), , Co, , A DC welding generator (Fig.2) consists of the following, parts., , Working principle of DC welding genertor: The, armature is made to rotate with the help of a prime mover, between the main poles, where a strong magnetic field, exists, The armture cuts the magnetic lines of force, generating, emf in its conductors. The commutator, being connected, to the armature conductors, changes the generated, alternating current into DC. The generated DC is then, taken to the generator terminals through the carbon, brushes. Where the main supply electricity is availble;, a motor is used as a prime mover. For field work or, where main supply is not available, petrol or diesel engine, may be used as a prime mover., , 90, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.20

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care and maintenance of arc welding generators, To make the best use of the arc welding generator and to, ensure its longer life the following checkpoints are to be, observed., Checkpoints for engine of an engine driven, generator., Check the water level in the radiator and the oil level in the, engine daily., Change the engine oil after running for 250 hrs., Lubricate the fan bearing once in a week., , Check every week the contact of the carbon brushes with, the commutaor to ensure it is in good condition without, sparking., Lubricate the shaft bearings after six months with good, quality grease., Guard the rotaing parts with suitable covers., Do not cover the air ventilation ducts., Do not operate the polarity switch during arcing., Ensure a proper working of the cooling fan., , Check fan belts daily for their proper tightness., , Check the electrical connections and avoid loose, connections., , Check petrol or diesel pipe unions leakage daily., , Never run the motor on a weak phase., , Checkpoints for motor driven generator, , Ensure the electric motor is properlay earthed., , Blow out the dust from the inside of the generator with dry, compressed air at 1.5 to 2.0 kg/cm2 pressure after every, three months., , AC/DC welding rectifier its construction, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Constructional features of AC/DC welding rectifier: A, welding rectifier set is used to convert AC welding supply, into DC welding supply. It consists of a step down, transformer and welding current rectifier cell with a, cooling fan. (Fig, 1) The rectifier cell consists of a, supporting plate made of steel or aluminium (Fig.2) which, is plated with a thin layer of nickel or bismith, sparyed, with SELENIUM or SILICON. It is finally covered with an, alloyed film of CADMIUM, BISMITH and TIN., , Co, , The coating of nickel or bismuth over the supporting plate, serves as one electrode (ANODE) of the rectifying cell., The alloyed film (of cadmium, bismuth and tin) serves as, another electrode (CATHODE) of the rectifying cell. The, rectifier acts as a non-return valve and allows current to, flow one side of it as it offers very little resistance and on, the other side it offers very high resistance to the flow of, the current. Hence the current can flow in one direction, only., , Working principle: The output of the step down, transformer is connected to the rectifier unit, which converts, AC to DC. The DC output is connected to positive and, negative terminals, from where it is taken for welding, purposes through welding cables. It can be designed to, provide either AC or DC welding supply by operating a, switch provided on the machine., Care and maintenance of rectifier welding set, Keep all the connections in tight condition., Lubricate the fan shaft once in 3 months., Do not adjust the current or operate the AC/DC switch, when the welding arc is ‘on’., Keep the rectifier plates clean., Check and clean the set atleast once in a, month., Keep the air ventilation system in good order., Never run the machine without the fan., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.20, , 91

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Inverters, Objectives: At the end of this lesson you shall be able to, • describe the inverters, • state the advantage & disadvantage of inverter, Inverters, , 4 The AC is rectified, , Basic principle:, , 5 Various filters remove the disturbing frequencies and, ripples in the DC current. There is also a filter which, protects against exterior high frequency disturbances., , inverter basically converts DC to AC, DC derived by rectification of AC voltage with high value, electrolytic capacitors as filters, These DC is converted to AC by high frequency solid state, switching (in KHz), A small ferrite core is suffcient for converting several, kilowatts of power, , 6 The entire process is monitored by a control circuit., This gives the machine an ideal static and dynamic, characteristics., 7 A DC voltage is available for welding purpose, Advantage:, , Output of this ferrite transformer is rectified by high, frequency diodes and smoothened by a DC choke, , •, , Compact and light weight, , •, , easy to set, , The output is controlled with Sensors & suitable closed, loop electronic circuitry., , •, , precise setting, , Working principle, , Disadvantage:, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , • expensive, , 1 Main voltage is rectified to DC, , 2 The inverter converts the Dc to high frequency AC, , • difficult to repair, , • sensitive to high currents, , Co, , 3 The transformer changes the HF AC to suitable welding, current., , 92, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.20

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.21, , Advantages and disadvantages of AC and DC welding, Objectives: At the end of this lesson you shall be able to, • compare the advantages and disadvantages of AC welding, • compare the advantages and disadvantages of DC welding., Positional welding is easy due to polarity advantage., Advantages of AC welding, A welding transformer has:, , It can be run with the help of diesel or petrol engine where, electrical mains supply is not available., , -, , a low initial cost due to simple and easy construction, , -, , a low operating cost due ot less power consumption, , -, , no effect of arc blow during welding due to AC, , It can be used for welding thin sheet metal, cast iron and, non-ferrous metals successfully due to polarity, advantage., , -, , low maintenance cost due to the absence of rotating, parts, , It has less possibility for electrical shock because of less, open circuit voltage., , -, , higher working effeiciency, , It is easy to strike and maintain a stable arc., , -, , noiseless operation., , Remote control of current adjustment is possible., Disadvantages of DC welding, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Disadvantages of AC welding, It is not suitable for bare and light coated electrodes., , DC welding power source has:, , It has more possiblility for electrical shock because of, higher open circuit voltage., , -, , a higher initial cost, , -, , a higher operating cost, , Welding of thin gauge sheets, cast iron and non-ferrous, metals (in certain cases) will be difficult., , -, , a higher maintenance cost, , -, , trouble of arc blow during welding, , -, , a lower working efficiency, , Advantages of DC welding, , -, , noisy operation in the case of a welding generator, , Required heat distribution is possible between the, electrode and the base metal due to the change of polarity, (positive 2/3 and negative 1/3)., , -, , occupies more space., , it can only be used where electrical mains supply is, available., , Co, , It can be used sucessfully to weld both ferrous and nonferrous metals., Bare wires and light coated electrodes can be easily used., , 93

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.22, , Basic welding positions, Objectives : At the end of this lesson you shall be able to, • name and illustrate the basic welding positions., Basic welding positions, , - Overhead position (Fig 4), , - Flat or downhand position (Fig 1), , All welding action takes place in the molten pool, formed, in the welding joint/welding line., , - Horizontal position (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The position of the welding joint line and the weld face in, respect of ground axis indicates the welding position., All joints may be welded in all positions., , - Vertical position (Vertical up and down) (Fig 3), , Plate welding position:, EN, Welding position, Groove Fillet, Flat, PA, PA, Horizontal, PC, PB, Vertical, PG/PF PG/PF, Overhead, PE, PD, , ASME, Groove fillet, 1G, 1F, 2G, 2F, 3G, 3F, 4G, 4F, , Co, , Pipe welding position:, , ASME, , Groove, , Groove, , Welding position, , Flat, Horizontal, Multiple postion, Inclined (All position), , 94, , EN, , PA, PC, PF/PG, H-LO45, , 1G, 2G, 5G, 6G

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.23, , Weld slope and rotation, Objectives : At the end of this lesson you shall be able to, • define and explain weld slope and weld rotation with respect to butt and fillet joint, • illustrate the various weld positions with respect to slope and rotation as per I.S., Welding position: All welding is to be done in one of the, four positions mentioned below., 1 Flat or downhand, 2 Horizontal, 3 Vertical, 4 Overhead, Each of these positions can be decided by the angle formed, by the axis of the weld and the weld face with the horizontal, and vertical plane respectively., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Axis of weld: The imaginary line passing through the, weld centre lengthwise is known as axis of the weld., (Fig 1), , Co, , Face of weld: Face of weld is the exposed surface of a, weld made in a welding process on the side from which, the welding is done. (Fig 1.), , Weld slope (Fig 2): It is the angle formed between the, upper portion of the vertical reference, , Weld rotation (Fig 3): It is the angle formed between, the upper portion of the vertical reference plane passing, through the line of the weld root and that part of the, plane passing through the weld root and a point on the, face of the weld equidistant from both the edges of the, weld., Slope and rotation (Fig 4), weld in flat position. (Fig 5), , 95

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Weld in horizontal and vertical position. (Fig 6 & 7), , Weld slope and weld rotation in respect of all the four, positions are shown above., Definitions of welding positions with respect to their slope, and rotation angles a Table is given below., DEFINITIONS OF WELDING POSITIONS, Position, , Symbol, , Slope, , Flat or, downhand, , F, , Not exceeding, 10°, , Not exceeding, 10°, , Horizontal, , H, , Not exceeding, 10°, , Exceeding 10°, but not, beyond 90°, , Vertical, , V, , Exceeding 45°, , Any., , Overhead, , O, , Not exceeding, 45°., , Exceeding, 90°., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Weld in overhead position. (Fig 8), , 96, , Rotation, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.23

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.24, , Weld symbol and welding symbol - Description and uses, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Objectives : At the end of this lesson you shall be able to, • explain the necessity of weld symbol and welding symbol, • describe the elementary symbols and supplementary symbols, • describe the welding symbol and its application, as per symbol standard (BIS) and AWS., categories of welds are characterized by a symbol which, Necessity: For conveying the information required for, in general is similar to the shape of the weld to be made., welding for designers and welders, standard symbols are, (Table 1), used. The symbols described below provide the means of, placing on dawing the information concerning type, size,, Supplementary symbols: Elementary symbols may be, location of weldment., complemented by another set of symbols (supplementary), (Table 2) characterizing the shape of the external surface, Elementary symbols (As per IS 813 - 1986): The various, of the weld. Supplementary symbols on elementary, symbols indicate the type of weld surface required., (Table 3), , 97

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TABLE 1, Elementary symbols, SI., No., , Designation, , Butt weld between plates with raised edges (the, raised edges being melted down completely), , 2, , Square butt weld, , 3, , Single V butt weld, , 4, , Single bevel butt weld, , 5, , Single V butt weld with broad root face, , 6, , Single bevel butt weld with broad root face, , 7, , Single U butt weld (Parallel or sloping sides), , 8, , Single J butt weld, , 9, , Backing run; back or backing weld, , 10, , fillet weld, , 11, , plug weld; Plug or slot weld/USA, , 12, , Spot weld, , 13, , Seam weld, , 98, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 1, , Illustration, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.24, , Symbol

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TABLE 2, , TABLE 3, , Supplementary symbols, Shape of weld surface, , Examples of application of supplementary symbols, Symbol, , Designation, , Illustration, , a) Flat (Usually finished flush), Flat(flush)single V, b) Convex, Convex double V butt, weld, , c) Concave, Weld symbol: It represents the type of weld made on a, weld joint. It is also a miniature drawing of any metal, edge preparation required prior to welding,, Welding symbol: The complete welding symbol will, indicate to the welder how to prepare the base metal,, the welding proces to use, the method of finish and the, required dimensions and other details with the basic weld, symbol. They consist of 7 elements as mentioned below., (Fig 4), , Concave fillet weld, Flat (flush) single V butt, weld with flat (flush), backing run, Methods of representation (Fig 2 and 3), , 2 Arrow, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 1 Reference line, , 3 Welding elementary symbols, 4 Dimensions and other details, 5 Supplementary symbols, 6 Finish symbols, , Co, , 7 Tail (Specification, process), , The reference line, arrow-head and tail, The reference line shown in Figs 1 and 5 is always drawn, as horizontal line. It is placed on the drawing near the, joint to be welded. All other information to be given on, th welding symbols is shown above below the reference, line., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.24, , 99

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Tail: The tail is used only when necessary. If used it may, give information on specification, the welding process used., or other details required which are not shown in the welding, symbol., , Arrow: The arrow may be drawn from either end of the, reference line. The arrow always touches the line which, represents the welded joint., Welding/elementary symbol: Figs 6 and 7 illustrate, how some of the various types of weld symbols are used, in welding symbols., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , On the welding symbol the arrow side weld information is, always shown below the reference line. The other side, weld information is always shown on the dash- line side., (Figs 2 and 4), , 100, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.24

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Co, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.24, , 101

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Root opening and groove angle: The root opening, size appears inside the basic weld symbol on the complete, welding symbol. The included angle or total angle of a, groove weld is shown above the basic weld symbol., (Fig 8), , Dimensions and other details: The size of a weld is, important. The term ‘size of weld’ means different things, for the fillet weld and butt weld. The dimensions of a fillet, weld are shown to the left of the basic weld symbol. (Fig, 10) The number 300 indicates the length of the weld is, 300mm; a5 indicates that the throat thickness is 5mm;, z7 indicates the leg length is 7mm., As per AWS (American Welding Society), basic weld, symbols and their location on welding symbols is given, as per following charter., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Contour and finish symbols: The shape or contour of, the completed weld bead is shown on the welding symbol, as a straight or curved line between the basic weld symbol, and the finish symbol. The curved contour line indicates, a normal convex or concave weld bead. (Fig 9), , 102, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.24

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.25, , Arc length and its effects, Objectives : At the end of this lesson you shall be able to, • define and identify the different types of arc lengths, • explain the effects and uses of different arc lengths., , -, , Medium or normal, , -, , Long, , -, , Short, , Long arc (Fig 3): If the distance between the tip of the, electrode and the base metal is more than the diameter, of the core wire it is called a long arc., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Arc length (Fig 1): It is the straight distance between the, electrode tip and the job surface when the arc is formed., There are three of arc lengths., , Short arc (Fig 4): If the distance between the tip of the, electrode and the base metal is less than the dia. of the, core wire it is called a Short arc., , Co, , Medium, normal arc (Fig 2): The correct arc length or, normal arc length is approximately equal to the diameter, of the core wire of the electrode., , 103

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Effects of different arc length, , -, , even burning of the electrode, , Long arc, , -, , reduction in spatters, , It makes a humming sound causing:, , -, , correct fusion and penetration, , -, , Unstable arc, , -, , correct metal deposition., , -, , Oxidation of weld metal, , Uses of different arc lengths, , -, , Poor fusion and penetration, , -, , Poor control of molten metal, , -, , more spatters, indicating wastage of electrode metal., , Medium or normal arc: It is used to weld mild steel, using a medium coated electrode. It can be used for the, final covering run to avoid undercut and excessive, convex fillet/reinforcement., , Short arc: It makes a popping sound causing:, -, , the electrode melting fastly and trying to freeze with, the job, , -, , higher metal with narrow width bead, , -, , less spatters, , -, , more fusion and penetration., , Short arc: It is used for root runs to get good root, penetration, for positional welding and while using a, heavy coated electrode, low hydrogen, iron, powder and, deep penetration electrode., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Normal arc: This is a stable arc producing steady sharp, crackling sound and causing:, , Long arc: It is used in plug and slot welding. for restarting, the arc and while withdrawing the electrode at the end of a, bead after filling the crater. Generally long arc is to be, avoided as it will give a defective weld., , Metal transfer across the arc (Characteristics of arc), , Objectives: At the end of this lesson you shall be able to, • explain the factors involved in the transfer of metal across the arc due to arc characteristics., The electric arc has different arc characteristics which, help in the transfer of metal across the arc. They are:, gravity force, , -, , gas expansion force, , -, , surface tension, , -, , electromagnetic force., , Co, , -, , Gravity force (Fig 1): Molten globules formed at the arcing, end of the electrode travel downwards towards the job in, the molten pool., Gravitational force helps the transfer of metal flat or, downhand position and thus the deposition rate of weld, metal is increased., , Gas expansion force (Fig 2): Flux coating on the, electrode melts due to the arc heat, resulting in the:, -, , Production of carbon monoxide and hydrogen mainly, , - Formation of a sleeve of the flux at the arcing end due, to a little higher melting point of the flux coating than the, core wire., , 104, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.25

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These gases expand and gain velocity. The flux sleeve, direct these gases to flow in the direction of the molten, metal. The gases flowing from the tip of the electrode, have a pushing effect. Thus the metal globules are carried, deep into the weld pool and influence penetration., This effect of expanded gases is more useful in positional, welding in metal transfer and influences penetration, Surface tension (Fig 3): It is the characteristic (Force), of the base metal to attract and retain the molten metal in, it. This effect is more useful in the cse of positional welding., , Electromagnetic force (Fig 4): The current passing, through the electrode forms maganetic lines of force in, the form of concentric circles. This force exerts a pinch, effect on the molten metal globule formed at the arcing, end of the electrode. The globule is detached from the, electrode and reaches the molten pool under the influence, of the magnetic force., This effect is more useful in positional welding., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The short arc promotes more surface tension effect., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.25, , 105

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.26, , Polarity in DC arc welding, Objectives : At the end of this lesson you shall be able to, • state the kinds and importance of polarity in arc welding, • describe the uses of straight and reverse polarity, • describe the methods of determining the polarity and explain the effects of using wrong polarity., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Polarity in arc welding: Polarity indicates the direction, of current flow in the welding circuit. (Fig 1), , Importance of polarity in welding: In DC welding 2/3 of the, heat is liberated from the positive end and 1/3 from the, negative end., To have this advantage of unequal heat distribution in the, electrode and base metal, the polarity is an important factor, for successful welding., Kinds of polarity, , Direct current (DC) Always flows from:, , the positive (higher potential) terminal to the negative, (lower potential) terminal, as per the conventional theory, , -, , negative terminal to positive terminal as per electronic, theory., , Co, , -, , In older machines the electrode and earth cables are, interchanged whenever the polarity has to be changed., In the latest machines a polarity switch is used to change, the polarity., Flow of electrons is always from negative to, the positive., In AC we cannot utilise polarity as the power, source changes its poles frequently. (Fig 2), , 106, , -, , Straight polarity or electrode negative (DCEN)., , -, , Reverse polarity or electrode positive (DCEP)., , Straight polarity: In straight polarity the electrode is, connected to the negative and the work to the positive, terminal of the power source. (Fig 3)

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Reverse Polarity: In reverse polarity the electrode is, connected to the positive and the work to the negative, terminal of the power source. (Fig 4), , The pointed end of carbon will become blunt soon if it is, connected with the positive terminal, but there will be no, change with the negative., Water test (Fig 6): Put both terminals of the welding, cable (connected with DC) in a container of electrolyte, water separately., , Straight polarity is used for:, -, , welding with bare light coated and medium coated, electrodes, , -, , Welding the thicker sections in down hand position to, obtain more base metal fusion and penetration., , More and quick arising bubbles will indicate NEGATIVE, while slow arising bubbles will indicate POSITIVE., , -, , Welding of non-ferrous metals, , Indication of wrong polarity, , -, , Welding of cast iron, , If the electrode is used on wrong polarity it will result in:, , -, , Welding with heavy and super-heavy coated electrodes, , -, , excess spatter and poor penetration, , -, , Welding in horizontal, vertical and overhead positions, , -, , improper fusion of the electrode, , -, , Sheet metal welding., , -, , heavy brownish deposition on the face of the weld metal, , DC is preferred to AC for hard facing and stainless steel, welding., , -, , diffculty in manipulation of the arc, , -, , abnormal sound of the arc, , Choice of the polarity also depends on the instruction of, the electrode manufacturers., , -, , Poor weld bead appearance with surfacee defects and, more spatter., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Reverse polarity is used for:, , Co, , Determination of polarity: In order to get the best results, it is essential to attach the electrode with the correct, terminal of the welding machine., Positive/negative terminals on a DC welding machine can, be identified by the following tests., , Carbon electrode test (Fig 5): Strike an arc using normal, range current with the help of a carbon electrode pointed, at its end using DC., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.26, , 107

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.27, , Weld qualify and inspection visual inspections, Objectives : At the end of this lesson you shall be able to, • state the necessity of weld qualify and inspection, • explain the quailfy inspection- conducted to overcome the common welding trainers., • describe the appearance of good and defective welds., Introduction, Welded joint in a welded structure (e.g. a bridge) are, expected to posses certain service related capabilities., Welded joint are generally required to carry loading of, various type which is subject to stress of either a simple, or complex character as good or as bad as it may appear, to be its in surface., Welding qulify and inspection:, , 4 Toe crack: The crack occurs at the location of the toe, at weld joint of base metal and weld metal. This may, section the lorgitudinal or transverse cable., 5 Lack of fusion: It is incomplete or partial melting and, fusion of weld metal., 6 Root crack: The crack occurs at the root of a used, joint, 7 Under bead crack: It occurs under base metal due, to improper, of used metal, at heat affected zone,, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Inspection has to do with observation of the processes, and product of manufacture to ensure the presence of, desired qualities or properties., , 3 Overlap: An excess or over flow of unfused used, metal extending beyond the fusion limits over the, surface of the base metal., , In certain cases inspection may be entirely qualitative and, involve only visual observation of surface defects of welded, joints, etc. Whereas in other instances, inspection may, involve the performance of the complicated test to, determine whether specification required is met or not., Testing on the other hand, specifically refer to the physical, performance of operation (Test) to determine quantitative, measure of certain properties sucth as mechanical which, will be explained later., , Co, , Testing aims to determine quality, i.e to discover facts, regarding the implication of the result, whereas inspection, intends to control quantity throuh the application of, established criteria and involves the idea of rejection of, substandard product., 1 Porosity: It is entrapment of gases evolved during weld, metal solidification, , 2 Slag inclutions: The oxides and non-metallic solid, materials that and entraped in the weld metal or between, the base metal and used metal, , 108, , 8 Hot cracks: It occurs at elevated temperature during, cooling solidifying from the molten stage., 9 Undercut: It is a spot or continuous groove melted, into base metal along the edge of weld and let in filled, with weld metal.

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Common welding mistakes (Defects), 10 Transverse crack: The crack occurs at the location, of the weld joint of base metal and weld ,method, accross weld bead., , 12 Longitudinal crack: The crack covers at the location, of the weld joint of base metal and weld metal along, the face of weld seam, 13 HAZ - Heat affected zone: The area of base metal, which is melted and its micro structure properties, affected by welding heat., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 11 Crater: It is surface of the cavity extending into the, weld bead as shown in figures., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.27, , 109

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.28, , Weld gauger and its uses, Objectives : At the end of this lesson you shall be able to, • state the types of welding gauge, • explain the uses at weld fillet gauge., • explain the uses of AWS type weld measurement gauge., Weld fillet gauge: To check fillet weld profile for, acceptable limit, the fillet weld is checked for the leg size,, using weld fillet gauge. Also concaving in weld face is, also to be determined by comparing the weld face adjusting, the gauge. (Fig 1), The fig no.1 shown is set of weld fillet gauge, which are, marked with metric and equivalent inch standard. The, measuring blade is made of stainless steel and accordingly, finshed with are end for checking the leg size and, concaving of the weldface. (Fig 2), If one of the leg sizes is short then welding size is, undersized, and this is not acceptable, (Fig 3), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Welding gauger: A set of individual leaves having the, profile, made of, hardened and tempered , weld to straight, with a clamping arrangment, The gauge is used to measure, the leg size of weld reinforcement in buttwelds,(concave, and convexing in case of fillet welder and) The weld joints, are frequently checked for the above features, to ensure a, proper weld to meet the size requirement of the component, of structure which are inspected for coupling standards, need stage inspection and the most suitable inspection, procedure is to use the weld gauge, to attain better quality, standard. The type of weld gauge weld belong the a, category of weld ins pection, to check weld profile and its, required size of bead., •, , weld fillet gauge (Fig 1), , •, , AWS type weld measurement gauge (Fig 2), , Co, , Also the less concaving shows a gap between measuring, face to face reweld and this is also not acceptable., Causes of the throat thickness of weld is less is also not, acceptable., All weld measurement gauge:, , This gauge is more powerful than the standard fillet gauge., The following are the functions of this weld measurement, gauge., 1 Leg size of fillet used., 2 Acceptable size of convexity., 3 Acceptable size of concavity., 4 Acceptable reinforcement height on butt weld, The gauges consist of struck which can be suitably altered, according to the position of the used bead for fillet used, butt weld., It consists of blade whose alignment is adjusted according, to the weld bead surface., , 110

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3, , 3, , According to the type of measurement the blade after, positioning over the weld bead the locking screw as shown, in (Fig 1) Is tightened suitably to determine the, measurement ., , On sliding the pointer blade to touch the face of the weld, determines the concavity, formed due to under fill of the, weld bead as shown in Fig 4., 1 Leg size of fillet weld: To determine the fillet weld, leg size the slot is placed against the toe of the weld as, shown in (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , On moving the pointer blade as shown in the figure down, wards on the face of the other joint number., , Co, , The co-incidence of the graduation scale defines the fillet, issued leg measurement., , 4 Acceptable reinforcement height on butt weld: To, determine the acceptable size of reinforcement height on, butt weld, the spode portion of the gauge, flat portion may, be scated on either size of butt weld as shown in Fig 5, on, sliding the pointer blade downwards so as to touch the, reinforcement placed on the butt weld., The co-incidence of the graduated scale determines the, acceptable reinforcement height of the weld bead., , 2 Acceptable size of convexity: To determaine the, acceptable size of convexity, the stock portion of the gauge, having 45° angle sides to which both the members of the, joints is placed as shown in (fig 3), On sliding due pointer blade to touch the face of the weld,, determines the convexity of reinforcement., 3 Aceeptable size of convexity: To determine the, acceptable size of convexity the stock portion of the gauge, having 45° angle sides touching both the members of the, joints is placed as shown in Fig 4., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.28, , 111

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Fabrication, Welder, , Related Theory for Exercise 1.2.29, , Calcium carbide preparation and its uses, Objectives : At the end of this lesson you shall be able to, • state the ingredients and grades of calcium carbide, • describe the properties of calcium carbide, • explain the method of production of calcium carbide, • explain the safe storage and handling of calcium carbide., Calcium carbide is a dark-grey stone like chemical, compound which is used to produce acetylene gas., , Production of one metric ton of calcium carbide requires:, (average), , Compostion of calcium carbide: calcium carbide is a, chemical compound consisting of:, , -, , 950 to 1000 kg of lime, , -, , 600 to 610 kg coke and anthracite, , -, , 40 to 70 kg of carbon electrode material, , - calcium = 62.5%, - carbon = 37.5%, by weight i.e., in 100g of calcium, carbide, 62.5g will be calcium and 37.5g will be carbon., its chemical symbol is Ca C2, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Properties of calcium carbide: It is a solid chemical, compound of dark-grey colour. It is brittle. Its density is, 2.22 to 2.26 g/cc. It easily absorbs moisture from the, atmosphere and gradually changes into slaked lime. It is, not soluble in kerosene. If it is allowed to come into contact, with water (or any mixture containing water), it produces, acetylene gas., , It takes 0.875 kg calcium and 0.562 kg carbon to produce, one kilogram of chemically pure calcium carbide. With, the intense heat (3000 - 3600°c) of the carbon arc in the, furnace, lime and coke turn to a liquid compound called, calcium carbide., Lime+Coke+Heat= calcium, carbide+carbon monoxide., , Production of calcium carbide, , Calcium carbide is produced in an electric furnace by, smelting coke and lime in right proportion.(Fig 1), , Carbon monoxide escapes and burns at the mouth of the, furnace. Molten carbide is drawn out of the furnace and, cast into ingots. The ingots are crushed, graded to definite, sizes and packed into airtight steel drums., Grades/sizes of calcium carbide: Different grades/sizes, of calcium cardibe are available for use in different types, of acetylene generators., , Co, , These are designated as:, - LUMP, - EGG, - NUT - 14 NDT., , The sizes given above indicate the range in the screening, sizes. For example (LUMP) size 90*50 means that no, piece is larger than 90 mm nor smaller than 50 mm., Safety precautions for handling and storage of, calcium carbide: It can be stored in approved places, only, Storage building must not have either water line or, high temperature. It must be stored in perfect airtight, containers. Fire breakout in a carbide storage room must, be extinguished with Co2 fire extinguishers or dry sand, and not with water. Do not allow the carbide to come in, contact with water/mosisture outside the acetylene, generator. Never put a naked light of any kind or any other, source of ignition into or near the caridide container. Carbide, drums should be opened with tools which will not produce, sparks., Use a brass chisel and hammer., After taking out the carbide from a drum, it must be closed, and made airtinght immedialtely. Preserve carbide in, kerosene oil in case of emergencey. The person, handling, calcium carbide, must wear rubber gloves. Empty carbide, drums must be filled completely with water before disposing, off., , 112

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Fabrication, Welder, , Related Theory for Exercise 1.2.30, , Acetylene gas - Properties, Objectives : At the end of this lesson you shall be able to, • explain the composition and properties of acetylene and oxygen gas, • describe the method of producing oxygen by air liquification process and by electrolysis of water., Acetylene is a fuel gas, which produces a very high, temperature flame with the help of oxygen, because it, has more amount of carbon (92.3%) than any other fuel, gas. The temperature of oxy-acetylene flame is 3100°c, - 3300°c., Composition of acetylene gas: Acetylene is composed, of:, -, , carbon 92.3% (24 parts), , -, , hydrogen 7.7% (2 parts), , Its chemical symbol is C2 H2 which shows that two atoms, of carbon are combined with two atoms of hydrogen., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Properties of acetylene gas: It is a colourless gas,, lighter than air. It has a specific gravity of 0.9056 as, compared with air. It is highly inflammable and burns, with a brilliant flame. It is slightly soluble in water and, alcohol. Impure acetylene has pungent (garlic like) odour., It can be easily detected by its peculiar smell. Acetylene, dissolves in acetone liquid., , Impure acetylene reacts with copper and forms an, explosive compound called copper acetylide. therefore,, copper should not be used for acetylene pipeline., Acetylene gas can cause suffocation if mixed 40% or more, in air. Acetylene mixed with air becomes explosive on, ignition. It is unstable and unsafe when compressed to, high pressure i.e. its safe storage pressure in free state is, fixed as 1 kg/cm2. The normal temperature pressure, (N.T.P) is 1.091 kg/cm2.The normal temperature is 20°C, and the normal pressure 760mm of mercury or 1 kg/cm2., It can be dissolved in liquid acetone. at high pressure., One volume of liquid acetone can dissolve 25 volumes of, acetylene under N.T.P. It can dissolve 25*15=375 volume, of acetylene cylinder if it is dissolved with a pressure of, 15kg/cm2 pressure. In an acetylene cylinder it is dissolved, acetylene. For complete combution one volume unit of, acetylene requires two and a half voulme units of oxygen., , Acetylene gas generation, , Co, , Objectives: At the end of this lesson you shall be able to, • explain the principle and name the different methods of acetylene gas generation, • explain the working principle of the types of acetylene generators, • compare the types of acetylene generators, • state their care and maintenance., Composition of acetylene: Acetylene is a fuel gas, composed of:, carbon 92.3% and Hydrogen 7.7%, Its chemical symbol is C2 H2, Principle of acetylene gas generation: It is the product, of chemical reaction between calcium carbide and water., When water is added to calcium carbide it reacts and, produces acetylene gas and calcium hydroxide (slaked, lime)., , Calcium caribide is composed of calcium and carbon., Water is Composed of hydrogen and oxygen., When calcium carbide is allowed to react with water the, carbon of the calcium carbide combines with the, hydrogen of water forming acetylene gas. calcium, combines with oxygen and hydrogen in water to form, slaked lime (Calcium hydroxide)., Methods of acetylene generation: Acetylene is, produced in acetylene generators based on two methods., -, , Water-to-carbide method, , -, , Carbide-to-water method, , 113

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In the water-to-carbide method water falls on calcium, carbide to produce acetylene., Carbide-to-water means calcium carbide grains fall on a, mass of water producing acetylene., , Acetylene generators are of two types., -, , Water-to-carbide type acetylene genertor (low pressure), , - Carbide-to-water type acetylene genertor (medium, pressure), , An acetylene generator is a device which brings proper, amounts of calcium carbide and water together to generate, the acetylene gas at the required rate., , Water to carbide acetylene gas generator, The generated gas goes up in the gas collection pipe,, passes through the water in the form of bubbles (washed, and cooled) and enters the rising bell. The rising bell, rises with gas pressure and lifts the cross-bar up, thus, closing the water valve automatically and preventing further, supply of water into the carbide container., The gas is taken out through the outlet pipe from where it, goes into the purifier and then to the hydraulic safety valve, before its use in welding. A weight is provided on the top, of the rising bell to keep it in position and enable it to, supply the gas with the required pressure., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Features of water-to-carbide acetylene generator: In, this low pressure acetylene gas generator, water falls on, the carbide to generate acetylene gas. Acetylene, pressure up to 0.17 kg / cm2 can be generated. Carbide, is placed in a carbide container located at the bottom of, the generator. Water (Controlled by a float valve) is fed, into the carbide container. The generated acetylene is, collected in a gas bell which rises and then cuts off the, water supply automatically., The features of a generator are shown in fig 1., , A safety outlet pipe is also provided with the rising bell to, release excess (generated) gas in emergency., Further generation of acetylene gas is controlled, automatically by the downward and upward movement of, the rising gas bell., , Co, , When the gas is consumed, the rising bell comes down, and its cross-bar presses the float ball down to open the, water alve. Water flows down into the carbide container, to generate acetylene gas again. With the entry of the, generated gas, the rising bell moves up again and stops, the water supply to carbide container., This operation continues till all the calcium carbide in the, carbide container has reacted with water., Non-automatic type generators are also available, in which, the welder himself pours water on the carbide, by a hand, operated valve, as per his requirements of acetylene gas., , Working principle: Water is filled in the outer vessel, through the water filling pipe and the water tap is turned off, when there is sfficient water., Calcium carblde is filled in the carbide container, inserted, through the door at the bottom., Initially the rising bell is at its bottom level and the cross, (fixed to the rising bell) holds the float ball down thus, opening the water valve. Water flows down the water, supply pipe and enters the carbide container. Acetylene, gas is generated due to chemical reaction., , 114, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.30

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Carbide to water acetylene gas generator, Features of carbide-to-water type acetylene, generator: In this generator carbide falls on water, automatically to generate the acetylene gas. Acetylene, pressure up to 1 kg/cm2 can be generated., Calcium carbide is placed in the hopper at the top of the, generator. The generator is partially filled with water to, the required level. A feed mechanism in the hopper feeds, the carbide into the water and acetylene is generated. At, a predetermined acetylene pressure (inside the generator), carbide feeding stops. Carbide feeding starts, when the, acetylene is drawn out and its pressure in the generator, decreases., The features of this type of generator are shown in Fig2., , The falling carbide reacts with water to generate acetylene, gas. The acetylene gas passes up through the water, (washed and cooled) into the gas storage chamber. When, the pressure of the generated acetylene incresses in the, gas chamber more than the pressure of the compound, spring, the feeding rod moves up with the help of the, diaphragm to close the feeding valve. Thus the carbide, flow stops automatically. The generated acetylene is taken, out through the gas outlet pipe, flashback arrester cum, purifier and outlet valve. The pressure of the generated, gas is indicated on the prssure gauge fitted near the outlet, valve. When the pressure of gas in the gas chamber, decreases, the carbide falls into the water and as the, pressure increases, the carbide flow stops automatically., This operation continues until all the carbide in hopper is, exhausted., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The calcium hydroxide (slaked lime or sludge) collected, at the bottom of the generator is cleaned out through the, sludge outlet by operating the agitator. The agitator, prevents the formation of solid form of calcium hydroxide, and mixes the calcium hydroxide with water and this makes, it easy to remove (the thin milky fluid) from the generator, completely. The generation of gas in this generator is, completely automatic and is under close control of, pressure with the demand. An emergency relief valve is, provided to discharge the gas out of the generator, immediately if the pressure exceeds the safety limit and, in case of any emergency., Flashback arrestor: The purpose of the flashback arrestor, cum purifier is to save the generator from the danger of, backfire or flashback and also to purify the generated, acetylene gas before it is used for welding., , Co, , Working principle: The water tank cum gas-holder is, filled with clean water to the water level. The carbide hopper, is charged with ND 14 size calcium carbide through the, cardide hopper door. (The hopper door is closed.) The, carbide hopper is attached at the top of the water tank, tightly., , Comparison of acetylene gas generators, Water-to-carbide type, , Consumption of water is less., Recharging is not a problem., , After starting the genertor, the outlet valve and relief valve, are closed. Calcium carbide is allowed to fall into the, water by operating the feeding lever with the assistance of, the other mechanism mentioned below., , Sludge disposal is not easy., , The carbide feed valve is controlled by the feed rod and, diaphragm (all connected to one another). A compound, spring fitted to the opposite side of the diaphram is, supported by a pressure by a pressure adjusting screw., Then pressure adjusting screw controls the carbide feeding, i.e., more pressure, more feeding and vice versa. By, operating the feeding lever the pressure of the compound, spring pushes the diaphagm down and thus the feeding, rod also moves down to open the feed valve., , Has lower gas generation., , Pressure of the gas is low., , The gas is slightly hot as there is no proper cooling system., Any grade of calcium carbide can be used., May be automatic or non-automatic., Care and maintenance is not easy., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.30, , 115

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Control on working pressure difficult., , Cost of generator more., , Cost of generator less., , Both injectors and non-injector type ‘blowpipes’ can be, used., , Only injector type blowpipe can be used., Suitable for one operation and no need of the manifold, system., Carbide-to-water type, Consumption of water is very high., Recharging takes more time., Sludge disposal is easy but takes more time., Pressure of the gas is medium and high., Has higher gas generation., Gas is cool as the gas is produced at the bottom level of, water tank and travels the full height of the water., Only a particular grade (14 NDT) of calcium carbide can, be used., Operation is always automatic., , Care and maintenance of acetylene generators:, Display ‘no smoking’ boards near generators. Generators, must be fitted with safety devices, (Hydraulic back, pressure valve). Avoid overcharging of calcuim carbide in, the generator’s chamber or carbide hopper, before, recharging from the carbide chamber or generator. Avoid, the creation of sparks inside the carbide chamber generator, during cleaning. Acetylene generators should be, cleaned,checked and painted periodically by competent, persons, clean and recharge the acetylene generator in a, well ventilated place, away from naked flame of fire., Leakages in valves, connection joints or any other fitting, of acetylene generator must be checked daily (before use), using soap solution. Maintain the required water level in, the generator daily. Keep and operate the generator away, from sparks/fire or combustible materials. Disposal of, slaked lime (Sludge) should be made in sludge pits (Away, from fire or sparks) in open space. The recommended, grade/size of calcium carbide should be used in each, generator (type). Joints of carbide container and carbide, hopper must be pressure-tight joints with generators., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Care and maintenance easy., , Many operations can be done at a time and a manifold, system is essential., , Co, , Control on working pressure easy., , 116, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.30

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.31, , Acetylene gas purifier, Objectives : At the end of this lesson you shall be able to, • explain the necessity and the features of the acetylene gas purifier, • explain the working principles of a purifier., Acetylene purifier: It is a cylindrical device which is, used to purify the generated acetylene gas. It is fitted, between the acetylene generator and blowpipe of a low, pressure system of oxy-acetylene welding., Necessity of a purifier: The generated acetylene gas, will have the following impurities., Sulphurated hydrogen, , -, , Phosphorated hydrogen, , -, , Ammonia, , -, , Lime dust, , -, , Water vpour, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , These impurities, if not removed, may have the following, harmful effects., -, , Reduction in flame temperature., , - Reaction with metal and influencing welding defects, like blow holes, porosity etc., , Acetylene gas used for gas welding and cutting must be, free from impurities. To remove these impurities, a suitable, gas purifier must be used., , Co, , Gas purifier-working principle: The acetylene gas from, the generator enters the purifier at the bottom chamber, through the gas inlet pipe and passes through three, compartments and comes out at the top through the outlet, pipe. (Fig 1), , The first compartment contains pumice stone which, absorbs moisture from the acetylene. The second, compartment contains purifying chemicals, which, remove sulphurated and posphorated hydrogen. The, third compartment contains filter wool, which filters the, lime dust and other foreign materials. Ammonia is removed, within the generator when the gas passes through the, water., , Hydraulic back pressure valve, , Objectives: At the end of this lesson you shall be able to, • state the necessity of the hydraulic back pressure valve, • explain the Working principle of a hydraulic back pressure valve., Necessity of hydraulic safety valve: In the low pressure, system the oxygen pressure is always greater than the, generated acetylene gas pressure., During welding, due to backfire or nozzle hole blockage,, the high pressure oxygen may enter into the acetylene, passage and enter the acetylene generator, which will, lead to an EXPLOSION., To prevent the entry of high pressure oxygen or backfire, to the generator, a hydraulic safety valve must be fitted in, the acetylene pipe line between the blowpipe and the, generator or purifier., , Constructional features of hydraulic back pressure, valve: It is a cylindericl shaped device having 250mm, depth and 50 to 100mm dia, as per the generator’s, capacity. (Fig 1), Working principle, The cylindrical device is filled with water through the VENT, PIPE (v) up to the level of water level (D). (Fig 1), Gas enters from the generator through the inlet pipe valve, (T) and comes down the centre pipe (P), bubbles through, the outlet pipe (R) and valve (S)., , 117

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The burnt gases in case of a backire, or the back pressure, gases, pass up the vent pipe into the atmosphere and are, prevented from getting into the generator. (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Each blowpipe must have a separate hydraulic, safety valve., , The pipe (P) has a baffle plate fixed at its lower end., , In the event of BACKFIRE or FLASHBACK (BACK, PRESSURE) from the blowpipe side, the water level (A), is pushed down and water is forced up into the vent pipe, until the hole (H) is exposed., , Flash back arrestor (Fig 1), , Co, , Introduction: It is a safety device and fitted with carbide, to water acetylene generator. It is made out of mild steel, cylindrical body., Parts: Flash back arrestor has the following parts, 1. Inlet, 2. Drain plug, 3. Non-return value, 4. Water level, 5. Water, 6. Baffle plate, 7. Purifying materials, 8. Filter wool, 9. Wire screen, 10.Bursting disc, 11. Pressure gauge, 12.Gas controlling tap, , 118, , Working principle in normal stage: The acetylene gas, from the carbide to water acetylene generator enters, through the inlet connection of the flash back arrestor and, goes to water compartment through non, returm space, valve and baffle plate, filter wool. Baffle plate reduces the, velocity of acetylene gas whereas the purifying materials, purify the generated acetylene gas that goes to outlet, through the regulator and gas controlling tap., Accidental condition: Flash back from the blow pipe, enters through the outlet connection in flashback arrestor, and goes to the non-return valve through the filter wool,, baffle plate and water. Flash back creates the pressure, and pushes the water downwards when the ball of nonreturn valve comes down and closes the inlet acetylene, gas with the help of the disc. With the result, no more, gas enters inside the flash back arreestor. The acetyene, gas which is already in the flask back arrestor burns due, to this pressure, the bursting disc bursts remaining gas, in the flash back arrestor. So the damages of flash back, arrestor outside the water acetylene generator is prevented, from the accident. Thereafter water and the carbon particle, are taken out through the drain plug and fresh water is, filled in the flash back arrestor for further use., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.31

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Co, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.31, , 119

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.32, , Oxygen gas - properties and production, Objectives : At the end of this lesson you shall be able to, • explain the composition and properties of oxygen gas, • describe the method of producing oxygen by air liquification process and by electrolysis of water., Oxygen gas: Oxygen is a supporter of combustion. Its, chemical symbol is O2, Properties of oxygen gas, -, , Oxygen is colourless, odourless and tasteless gas,, , -, , It has atomic weight of 16., , -, , Its specific gracity at 32° F and at normal (atm), pressure is 1.1053, as compared with air., , -, , Production of oxygen gas, Air liquification process: This method is based upon, the idea of separating the various gases that constitute, the air by liquification process., This process is done in three stages., -, , purification, , -, , liquification, , It is slightly soluble in water., , -, , Distillation, , It does not burn itself. but readily supports combustion, of fuels., , The composition of air and the boiling points of its, components are given in table 1., , Oxygen becomes liquefied at a temperature of -182.962°C, at normal atmospheric pressure., Liquid oxygen has a pale blue colour., , Liquid oxygen becomes solid at - 218.4 C° at normal, atmospheric pressure. It combines rapidly with most of, the metals and forms oxide. i.e.,, , Co, , Iron + oxygen = Iron oxide, , Copper + oxygen = Cuprous oxide, , Aluminium + oxygen = Aluminium oxide, , The process of making oxide is called oxidation. Oxygen, is found everywhere in nature, either in free state or in a, combination with other elements. It is one of the chief, constituents of atmosphere i.e., 21% oxygen 78%, Nitrogen. Water is chemical compound of oxygen and, hydrogen, in which approximately 89% is oxygen by weight, and 1/3 by volume. One volume of liquid oxygen produces, 860 volumes of oxygen gas. One kg of liquid oxygen, produces 750 liters of gas. The weight of the container, used to store liquid oxygen is several times less than the, weight of cylinders required to store an equivalent quantity, of gaseous oxygen., , 120, , TABLE 1, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , When compressed oxygen comes in contact with finely, divided particles of combustible material (i.e., coal, dust,mineral oil,grease) it will self-ignite them, leading, to fire or explosion. Self-ignition in such cases may be, initiated by the heat given up suddenly by compressed, oxygen,, , Composition of air, , Name of, component, , Quantity by, volume %, , NITROGEN, OXYGEN, ARGON, NEON, HELIUM, KRYPTON, XENON, HYDROGEN, CARBON, DIOXIDE, , 78.0300, 20.9300, 00.9325, 00.0018, 00.0005, 00.0001, 00.000009, 00.00005, , Boiling point °C, -195.80, -182.96, -185.70, , 00.030000, , Air is a mixture of roughly 78% nitrogen, 21% oxygen, and 1% argon and other inert gases., The basis of the separation of the elements in air by this, method depends on the difference in the boiling point of, the major elements., Between nitrogen and oxygen - 13°C, Between nitrogen and argon - 10°C, Between oxygen and argon - 3°C

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Steps for separating oxygen (Fig 1), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Electrolysis of water (Fig 3): In this method. DC electricity, is passed through water causing the water to separate, into its elements which are oxygen and hydrogen oxygen, will collect at the positive terminal and hydrogen at the, negative., , Purification: Air is drawn from the atmosphere into large, containers called washing towers, where it is washed and, purified of carbon dioxide dust particles by means of caustic, soda solution. The washed air from the washing towers is, compressed by a compressor to 150 atmospheric pressure, and passed through oil purging cylinders and then through, aluminium driers, which remove the remaining carbon, dioxide and water vapours., Liquefaction: The dry, clean, compressed air then goes, into liquification columns, where it is cooled and then, expanded to change into liquid form., , Co, , Distillation: The liquid air is then rectified in the, CONDENSER column by increasing the temperature on, the basis of difference in the boiling points of its elements., Nitrogen having a lower boiling point (-195.8°C)evapo, rates first., , Argon having a boiling point (-185.70°C) evaporates second, leaving liquid oxygen in the bottom of the condenser., Liquid oxygen can be stored in liquid form as shown in the, liquid oxygen container. (Fig 2), The liquid oxygen next passes through a heated coil which, changes the liquid into a gaseous form., The gaseous oxygen goes into a storage tank from where, it is drawn and compressed into oxyen gas cylinders., , Caustic soda is added to the water to make it a good, electrolyte since pure water will not allow the current to, pass., This method produces two volumes of hydrogen and one, volume of oxygen., The cost of producing oxygen by this method is more the, oxygen contains more moisture and it is difficult to obtain, 99% purity and the process requires enormous quantity, of water and electricity. So the air liquefaction method is, more commonly used to produce commercial oxygen with, a purity of 99.99%., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.32, , 121

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.33, , Oxygen gas cylinder, Objectives : At the end of this lesson you shall be able to, • identify different gas cylinders, • explain the constructional features of oxygen gas cylinder and the method of charging., Definition of a gas cylinder: It is a steel container,, used to store different gases at high pressure safely and, in large quantity for welding or other industrial uses., Types and identifications of gas cylinders: Gas, cylinders are called by names of the gas they are holding., (Table 1), Table 1, Identification of gas cylinders, Colour, codling, , Valve, threads, , Oxygen, , Black, , Right hand, , Acetylene, , Maroon, , Left hand, , Coal, , Red (With, name coal gas), , Left hand, , Hydrogen, , Red, , Left hand, , Nitrogen, , Grey (With, black neck), , Air, , Grey, , Propane, , RED (with, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Name of gas, Cylinder, , Right hand, , Right hand, , Left hand, , larger diameter, , and name propane), Blue, , Carbon-diOxide, , Black (With, white neck), , Co, , Argon, , Right hand, , Right hand, , Gas cylinders are identified by their body colour marks, and valve threads. (Table 1), Oxygen gas cylinder: It is a seamless steel container, used to store oxygen gas safely and in large quantity, under a maximum pressure of 150 kg /cm2, for use in, gas welding and cutting., Constructional features of oxygen gas cylinder, (Fig 1), It is made from seamless solid drawn steel and tested, with a water pressure of 225kg/cm2. The cylinder top is, , 122

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fitted with a high pressure valve made from high quality, forged bronze. (Fig 2), , The capacity of the cylinder may be 3.5m3 - 8.5m3., Oxygen cylinders of 7m3 capacity are commonly used., , The cylinder valve has a pressure safety device, which, consists of a pressure disc, which will burst before the, inside cylinder pressure becomes high enough to break, the cylinder body. The cylinder valve outlet socket fitting, has standard right hand threads, to which all pressure, regulators may be attached. The cylinder valve is also, fitted with a steel spindle to operate the valve for opening, and closing. A steel cap is screwed over the valve to protect, it from damage during transportation. (Fig 1), The cylinder body is painted black., , Dissolved acetylene gas cylinder, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Objectives: At the end of this lesson you shall be able to, • describe the constructional features of the DA gas cylinder and the method of charging, • state the safety rules for handling gas cylinders, • explain the safe procedure to be followed in handling an internally fired DA cylinder., Charging of gas in oxygen cylinder: The oxygen, cylinders are filled with oxygen gas under a pressure of, 120-150 kg/cm2. The cylinders are tested regularty and, periodically. They are annealed to relieve stresses caused, during ‘on the job’ handling. They are periodically cleaned, using caustic solution., , Definition: It is a steel container used to store high, pressure acetylene gas safely in dissolved state for gas, welding or cutting purpose., , Co, , Constructional features (Fig 1): The acetylene gas, cylinder is made from seamless drawn steel tube or welded, steel container and tested with a water pressure of 100kg/, cm2 The cylinder top is fitted with a pressure valve made, from high quality forged bronze. The cylinder valve outlet, socket has standard left hand threads to which acetylene, regulators of all makes may be attached. The cylinder, valve is also fitted with a steel spindle to operate the valve, for opening and closing. A steel cap is screwed over the, valve to protect it from damage during transportation. The, body of the cylinder is painted maroon. The capacity of, the DA cylinder may be 3.5m3-8.5m3., The base of the D A cylinder (Curved inside) is fitted with, fuse plugs which will melt at a temperature of app. 100°C., (Fig 2) In case the cylinder is subjected to high, temperature, the fuse plugs will melt and allow the gas to, escape, before the pressure increases enough to harm or, rupture the cylinder. Fuse plugs are also fitted on the top, of the cylinder., , ×, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.33, , 123

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Method of charging D A gas cylinder: The storage of, acetylene gas in its gaseous form under pressure above, 1kg/cm2 is not safe. A special method is used to store, acetylene safely in cylinders as given below., The cylinders are filled with porous substances such as:, -, , pith from corm stalk, , -, , fullers earth, , -, , lime silica, , -, , specially prepared charcoal, , -, , Fiber asbestos., , Acetylene gas is then charged in the cylinder, under a, pressure of app. 15 kg//cm2., The liquid acetone dissolves the acetylene gas in large, quantity as safe storage medium: hence, it is called, dissolved acetylene. One volume of liquid acetone can, dissolve 25 volumes of acetylene gas under normal, atmospheric pressure and temperature. During the gas, charging operation one volume of liquid acetone dissolves, 25X15=375 volumes of acetylene gas under 15kg/cm2, pressure at normal temperature. While charging cold water, will be sprayed over the cylinder so that the temperature, inside the cylinder does not cross certain limit., , The hydrocarbon liquid named acetone is then charged in, the cylinder, which fills the porous substances (1/3rd of, total volume of the cylinder)., , Welding gas regulator, , Types of regulators, -, , single stage regulator, , -, , Double stage regulator, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Objectives: At the end of this lesson you shall be able to, • state the different types of regulators, • describe the working principle of a single and double stage regulator, • explain the parts of each type of regulator, • explain the care and maintenance of the regulators., , Welding regulator (Single stage), , Co, , Working principle: When the spindle of the cylinder is, opened slowly, the high pressure gas from the cylinder, enters into the regulator through the inlet valve. (Fig 1), , The outlet side is fitted with a pressure gauge which, indicates the working pressure on the blowpipe. Upon the, gas being drawn ‘off from the outlet side, the pressure, inside the regulator body falls, the diaphragm is pushed, back by the spring and the valve opens, letting more gas, ‘in’ from the cylinder. The pressure in the body, therefore,, depends on the pressure of the springs and this can be, adjusted by means of a regulator knob., (Fig 2), , The gas then enters the body of the regulator which is, controlled by the needle valve. The pressure inside the, regulator rises which pushes the diaphragm and the valve, to which it is attached, closes the valve and prevents any, more gas from entering the regulator., , 124, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.33

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Welding regulator (double stage), Working principle: The two-stage regulator (Fig 3) is, nothing but two regulators in one which operates to reduce, the pressure progressively in two stages instead of one., The first stage, which is pre-set, reduces the pressure of, the cylinder to an intermediate stage (i.e,) 5kgf/mm2 and, gas at that pressure passes into the second stage, the, gas now emerges at a pressure (Working pressure) set, by the pressure adjusting control knob attached to the, diaphragm. Two-stage regulators have two safety valves,, so that if there is any excess pressure there will be no, explosion. A major objection to the single stage regulator, is the need for frequent torch adjustment, for as the cylinder, pressure falls the regulator pressure likewise falls, necessitating torch adjustment. In the two stage regulator,, there is automatic compensation for any drop in the cylinder, pressure., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Single stage regulators may be used with pipelines and, cylinders. Two stage regulators are used with cylinders, and manifolds., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.33, , 125

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.34, , Systems of oxy-acetylene welding, Objectives : At the end of this lesson you shall be able to, • explain the low pressure and the high pressure systems of oxy-acetylene plants and systems, • distinguish between low pressure and high pressure blowpipes, • state the advantages and disadvantages of both systems., Oxy-acetylene plants: An oxy-acetylene plant can be, classified into:, -, , high pressure plant, , -, , low pressure plant., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , A high pressure plant utilises acetylene under high pressure, (15 kg/cm2). (Fig 1), , A low presure acetylene plant with a low pressure acetylene, generator and a high pressure oxygen cylinder is called a, low pressure system., , Co, , The terms low pressure and high pressure, systems used in oxy-acctylene welding, refer only to acetylene pressure, high or, low., , Dissolved acetylene (acetylene in cylinder) is the commonly, used source., Acetylene generated from a high pressure generator is, not commonly used., , A low pressure plant utilizes acetylene under low pressure, (0.017 kg/cm2) produced by the acetylene generator only., (Fig 2), High pressure and low pressure plants utilize, oxygen gas kept in compressed high pressure, cylinders only at 120 to 150 kg/cm2 pressure., Oxy acetylene systems: A high pressure oxy-acetylene, plant is also called a high pressure system., , 126, , Types of blowpipes: For the low pressure system, a, specially designed injector types blowpipe is required,, which may be used for high pressure system also., In the high pressure system, a mixer type high pressure, blowpipe is used which is not suitable for the low pressure, system., To avoid the danger of high pressure oxygen entering into, the acetylene pipeline an injector is used in a low pressure, blowpipe. In addition a non-return valve is also used in the, blowpipe connection on the acetylene hose. As a further, precaution to prevent the acetylene generator from, exploding, a hydraulic back pressure valve is used between, the acetylene generator and the blowpipe., Advantanges of high pressure system: Safe working, and less chances of accidents. The pressure adjustment, of gases in this system is easy ang accurate, hence, working efficiency is more. The gases being in cylinder, are perfectiy under control. The D.A cylinder is portable, and can be taken easily from one place to another place.

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The D.A cylinder can be fitted with a regulator quickly and, easily, thus saving time. Both injector and non-injector, type blowpipes can be used. No license is required for, keeping the D.A cylinder., Sequence of steps, Slowly open the cylinder valve., Open the shut-off valve or pressure reducing valve, Slowly screw in the adjusting screw. (The locking bolt, opens.), Watch the working pressure gauge., Turn the adjusting screw until the desired pressure is, reached. There is an equilibrium between the bottom, adjusting spring and the pressure of the gas on the, membrane, which is amplified by the spring of the locking, pin., Care and maintenance of regulators, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Check the cylinder connection and crack the cylinder before, fixing the regulator. (Fig 3), , Open the cylinder valve slowly and allow the gas to pass, to the regulator (cylinder) content gauge., , Co, , Loosen the pressure screw., , Do not use oil in regulator connections. (Fig 4), , Do not fix the oxygen and acetylene regulators close, together. (Fig 5), Do not wind the hose on the regulators. (Fig 6), , Use hose-clips before connecting to the regulator., Use soap water to check the leakage in the acetylene, regulator connections and plain water on the oxygen, regulator connections Fig 7, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.34, , 127

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.35, , Gas welding torch its type and construction, Objectives : At the end of this lesson you shall be able to, • state the uses of the different types of blowpipes, • describe the working principle of each type of blowpipes, • explain its care and maintenance., Types, There are two types of blowpipes., -, , High pressure blowpipe or non-injector types blowpipe, , -, , Low pressure blopipe or injector type blowpipe., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Uses of blow pipes: Each type consists of a variety of, designs depending on the work for which the blowpipe is, required, i,e., gas welding, brazing, very thin sheet, welding, heating before and after welding, gas cutting., , Equal or high pressure blowpipe (Fig 1): The H.P., blowpipe is simply a mixing device to supply approximately, equal volume of oxygen and acetylene to the tip, and is, fitted with valves to control the flow of the gases as required, i.e, the blow pipes/gas welding torches are used for welding, of ferrous and non-ferrous metals, joining thin sheets by, fusing the edges, preheating and post heating of jobs,, brazing, for removing the dents formed by distortion and, for gas cutting using a cutting blow pipe., , Co, , The equal pressure blow pipe (Fig.1) consists of two inlet, connections for acetylene and oxygen gases kept in high, pressure cylinders. Two control valves to control the, quantity of flow of the gases and a body inside which the, gases are mixed in the mixing chamber (Fig.2). The mixed, gases flow through a neck pipe to the nozzle and then, get ignited at the tip of the nozzle. Since the pressure of, the oxygen and acetylene gases are set at the same, pressure of 0.15 kg/cm2 they mix together at the mixing, chamber and flows through the blow pipe to the nozzle tip, on its own. This equal pressure blow pipe/torch is also, called as high pressure blow pipe/torch because this is, used in the high pressure system of gas welding., , Low pressure blowpipe (Fig 3), , This blowpipe has an injector (Fig 3) inside its body through, which the high pressure oxygen passes. This oxygen, draws the low pressure acetylene from an acetylene, generator into a mixing chamber and gives it the necessary, helps to prevent backfiring., The low pressure blow pipe is similar to the equal pressure, blow pipe except that inside its body an injector with a, very small (narrow) hole in its center through which high, pressure oxygen is passed. This high pressure oxygen, while coming out of the injector creates a vacuum in the, mixing chamber and sucks the low pressure acetylene, from the gas generator (Fig 4), It is usual for the whole head to be interchangeable in this, type, the head containing both the nozzle and injector., This is necessary, since there is a corresponding injector, size for each nozzle., , A set of nozzles is supplied with each blowpipe, the nozzles, having holes varying in diameters, and thus giving various, sized flames. The nozzles are numbered with their, consumption of gas in litres per hour., Important caution: A high pressure blowpipe, should not be used on a low pressure system., 128, , The L.P. blowpipe is more expensive than, the H.P. blowpipe but it can be used on a, high pressure system, if required.

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Care and maintenance, Welding tips made of copper may be damaged by careless, handling., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Nozzles should never be dropped or used for moving or, holding the work., , The nozzle seat and threads should be absolutely free, from foreign matter in order to prevent any scoring/scrator, on the fitting surfaces when tightening on assembly., , Co, , The nozzle orifice should only be cleaned with a tip cleaner, specially designed for this purpose. (Fig5,6 &7), , At frequent intervals the nozzle tip should be filed to remove, any damage to the tip due to the excessive heat of the, flame and the molten metal., , The inlet for acetylene has left hand thread and that for, oxygen has right hand thread. Take care to fit the correct, hose pipe with the blow pipe inlet. At frequent intervals,, put off the flame and dip the blow pipe in cold water., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.35, , 129

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.36, , Welding technique of oxy-acetylene welding, Objectives: At the end of this lesson you shall be able to, • name the different gas welding techniques and explain the leftward welding techniques, • describe the edge preparation and application of leftward techniques., There are two welding techniques on oxy-acetylene welding, process. They are:, 1 Leftward welding technique (Forehand technique), 2 Righward welding technique (Backhand technique), The leftward technique is explained below. For details of, rightward technique rfer Related Theory for exercise 2..6., Leftward welding technique: It is the most widely used, oxy-acetylene gas welding technique in which the welding, commences at the right hand edge of the welding job, and proceeds towards the left. It is also called forwrd or, forehand technique. (Fig 1), , The blowpipe is given a circular or side-to-side motion to, obtain even fusion on each side of the joint., The filler rod is added in the (Weld) molten pool by a piston, like motion and not melted off by the flame itself., If the flame is used to melt the welding rod, itself into the pool, the temperature of the, molten pool will be reduced and consequently, good fusion cannot be abtained., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , In this case welding is started at the right hand edge of, the job and proceeds towards the left. The blowpipe is, , held at an angle of 60°-70° with the welding line. The filler, rod is held at an angle of 30°-40° with the welding line., The welding blowpipe follows the welding rod. The welding, flame is directed away from the deposited weld metal., , Edge preparation for leftward technique: For fillet joints, square edge preparation is done., For butt joints the edges are prepared as shown in fig.2., the table given below gives the details for welding mild, steel by lefward technique for butt joints., , 130

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Table 1, For fillet joints one size larger nozzle is to be, used., , Flange, , NIL, , 1.6, to, 2, , 1.6, , 3, , Square 2, , 2.5, , 2, , 5, , Square 2, , 3.15, , 2.5, , 7, , Square 3, , 4, , 3.15, , 7, , 80°Vee 3, , 5, , 3.15, , 13, , 80°Vee 3, , Flux to be used, , Root gap in mm, , 1, , Above 5.0 mm thickness,the rightward technique should, be used., Application, This technique is used for the welding of:, -, , mild steel up to 5mm thick, , -, , all metals both ferrous and non-ferrous., , For gas, welding of, mild steel, no flux is, required to, be used, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Blow pipe, nozzle size, , 1.6, , C.C.M.S filler, rod diameter, in mm, , 0.8, , Metal thiickness, in mm, , Edge, preparation, , The table given below shows the details for welding mild, steel by leftward technique (For Butt joints), , Rightward technique of oxy-acetylene gas welding, Objectives: At the end of this lesson you shall be able to, • explain rightward welding technique and its advantages., • describe edge preparation and the application of rightward technique., Rightward welding technique: It is an oxy-acetylene, gas welding technique, in which the welding is begun at, the left hand edge of the welding job and it proceeds towards, the right., , Co, , This technique was developed to assist the production, work on thick steel plates (Above 5mm) so as to produce, economic welds of good qulity., It is also called backward or back hand technique., the following are its features. (Fig 1), , Welding is commenced at the left hand edge of the job, and it proceeds to the right. The blowpipe is held at an, angle of 40° - 50° with the welding line. The filler rod is, held at an angle of 30° - 40° with the welding line. The, filler rod follows the welding blowpipe. The welding flame, is directed towards the deposited weld metal., The filler rod is given a rotational or circular loop motion in, the forward direction. The blowpipe moves back in a, straight line steadily towards the right. This technique, generates more heat for fusion, which makes it economical, for thick steel plate welding., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.36, , 131

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Edge preparation for rightward technique (Fig 2), For butt joints the edges are prepared as shown in fig 2., , The table given below gives the details for welding mild, steel by rightward welding technique for Butt joints., Application: This technique is used for the welding of, steel above 5mm thickness and ‘LINDE’ WELDING, PROCESS of sheet pipes., Advantage: Less cost per length run of the weld due to, less bevel angle, less filler rod being used, and increased, speed. Welds are made much faster., It is easy to control the distortion due to less expansion, and contraction of a smaller volume of molten metal. The, flame being directed towards the deposited metal, is, allowed to cool slowly and uniformly. Greater annealing, action of the flame on the weld metal as it is always directed, towards the deposited metal during welding., We can have a better view of the molten pool giving a, better control of the weld which results in more penetration., The oxidation effect on the motion metal is minimized as, the reducing zone of the flame provides continuous, coverage., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , TABLE 1 (For Butt joints), , Blow pipe, nozzle size, , Edge preparation, , Root gap, in mm, , Flux to, be used, , 5, , 3.15, , 10, , Square, , 2.5, , For gas, , 6.3, , 4.0, , 13, , Square, , 3.0, , welding of mild, , 8, , 5.0, , 18, , 60°Vee, , 3.0, , steel no flux, , 10 to 16, , 6.3, , 18, , 60°Vee, , 4.0, , is required to, , Above 16, , 6.3, , 25, , 60° double Vee, , 3.0, , be used, , Co, , Metal thickness C.C.M.S filler rod, in mm, diameter in mm, , 132, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.36

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.37, , Arc blow its causes and remedial measures, Objectives : At the end of this lesson you shall be able to, • explain the arc blow in DC welding, • explain the effects of arc blow on welds, • describe the various methods used to control the arc blow., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Arc blow in dc welding: When the arc deviates from its, regular path due to the magnetic disturbances it is called, ‘Arc blow’. (Fig 1), , Co, , Causes and effects of arc blow: Whenever a current, flows in the electrode a magnetic field is formed around, the electrode and the arc F1 and F3 (Fig.2). Likewise a, similar magnetic field is also formed around the base metal, F2 (Fig 2). Due to the interaction of these two magnetic, fields, the arc is blown to one side of the joint. At the, starting of the weld there will be forward blow and at the, end backward blow. Fig.3, , Methods used to control the arc blow, The arc blow can be controlled by:, -, , Place the earth connection as far from the weld joint, as possible (Fig 4), , -, , changing the position of the earth connection on the, work, , -, , Changing the position of the work on the welding table, , -, , wrapping the electrode cable around the work (Fig 5), , -, , welding towards a heavy welding tack or a weld, already made, , Due to this the following effects occur., -, , more spatters with less deposition of weld metal., , -, , poor fusion/penetration., , -, , weak welds., , -, , Difficulty in depositing weld metal at the required place, in the joint., , -, , The bead appearance will be poor and slag inclusion, defect will also take place., , 133

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-, , keeping a magnetic bridge on the top of the groove, joint, , -, , holding the correct electrode angle with a short arc., use ‘run on’ and ‘run off plates. Fig6., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , If all the above methods fail to control the ‘arc blow’, change, to AC supply., , 134, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.37

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.38, , Distortion and its control, Objectives : At the end of this lesson you shall be able to, • explain the causes of distortion, • describe the types of distortion, • explain the methods of preventing distortion, • explain the methods of correcting distortion., Types of distortion, The 3 types of distortion are:, -, , longitudinal distortion, , -, , transverse distortion, , -, , angular distortion., , The figures (3,4,5) illustrate the different types of distortion., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Causes of distortion: In arc welding, the temperature at, different areas of the joint are different. (Fig 1a). The, expansions in these areas are also different depending on, the temperature (Fig 1b). In the same way after welding,, different areas of the joint contract differently, But in a, solid body (i.e., the parent metal) it cannot expand or, contract differently at different areas. This uneven expansion, and contraction of the welded joint due to uneven heating, and cooling in welding creates stresses in the joint. These, stresses make the welded job to change its size and shape, permanently (i.e.deformation) and this is called distortion, of the welded joint. (Fig 2), , 135

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Factors affecting distortion, Design, Parent metal, Joint preparation and set up, Assembly procedure, Welding process, Deposition technique, Welding sequence, Unbalanced heating about the neutral axis, Restraint imposed, Either one or more of these above factors are responsible, for distortion, in a welded job. To avoid or reduce the, distortion in a welding job these factors are to be taken, care of-before, during and after welding. The methods, adopted to avoid or reduce distortion are as follows., Prevention of distortion: The following methods are, used to prevent and control distortion., Reducing the effective shrinkage force., , -, , Making the shrinkage forces to reduce distortion., , -, , Balancing the shrinkage force with another shrinkage, force., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , -, , Methods of reducing the effective shrinkage forces, , Avoiding over-welding/Excessive reinforcement:, Excessive build up in the case of butt welds and fillet, welds should be avoided. (Fig 6), , Co, , The permissible value of reinforcement in groove and fillet, welds is T/10 where “T” is thickness of parent metal., , use of deep fillet weld: Place the weld as possible to, the neutral axis by using the deep fillet method. This will, reduce the leverage of pulling the plates out of alignment., (Fig 9), , Use of proper edge preparation and fit up: It is possible, to reduce the effective shrinkage force by correct edge, preparation. This will ensure proper fusion at the root of, the weld with a minimum of weld metal.(Fig 7), Use of few passes: Use of fewer passes with large dia., electrodes reduces distortion in the lateral direction., (Fiig 8), , 136, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.38

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Use of intermittent welds: Minimize the amount of weld, metal with the help of intermittent welds instead of, continuous welds. This can be used with fillet welds only., (Fig 10), , Use of skip welding: In this method, the weld is made, not longer than 75 mm at one time. Skip welding reduces, locked up stresses and warping due to more uniform, distribution of heat. (Fig 13), , Use of ‘back step’ welding method: The general, direction of welding progression is from left to right. But, in this method each short bead is deposited from right to, left. In this method. the plates expand to a lesser degree, with each bead because of the locking effect of each, weld. (Fig 11), , Methods used for making the shrinkage forces work, to reduce distortion, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Locating parts out of position: Distortion may be allowed, for by pre-setting the plates in the opposite way so that, the weld pulls them to the desired shape. When the weld, shrinks it will pull the plate to its correct position (Fig 14 &, 15), , Co, , Welding from center: Welding of long joints from centre, outwards breaks up the progressive effect of high, stresses on continuous weld., , Use of planned wandering method: In this method, welding starts at the centre, and thereafter portions are, completed on each side of the centre in turn. (Fig 12), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.38, , 137

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Spacing of parts to allow for shrinkage: Correct, spacing of the parts prior to welding is necessary. This, will allow the parts to be pulled in correct position by the, shrinkage force of the welding. (Fig 16), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Pre-bending: Shrinkage forces may be put to work in, many cases by pre-bending. (Fig 17), , Methods of balancing of one shrinkage force with, another shrinkage force, , Co, , Use of proper welding sequence: This places the weld, metal at different points about the structure. In this method,, welds are made from each side alternately so that when a, second run of weld metal shrinks it will counteract the, shrinkage forces of the first weld. (Figs 18, 19 a and 19b), , Divergence allowance: As there is a tendency of the, plates to extend & converge along the seam during welding,, this technique is used to diverge the plates from the point, where welding commences by placing a wedge or an, alignment clamp between the plates ahead of the weld., (Fig 21), , Peening: This is light hammering of the weld metal, immediately after it is deposited. By peening the bead, it, is actually stretched counteracting its tendency to contract, as it cools. Fig 20., , 138, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.38

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Tack-welding: A tack weld is a short weld made prior to, welding to hold the plates in perfect alignment and with, uniform root gap. Tack welds are made at regular intervals, along the joint with high current to obtain proper penetration., (Fig 25) They are necessary where the plates cannot be, held by a fixture. (Fig 26), , The spacing allowances are as follows., 3mm/m for (mild steel) Ferrous metals, 10 mm/m for non ferrous metals, While cooling, the shrinkage stresses will pull the plate in, correct alignment., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Preheating: Some metals would normally fracture if, welded in the cold state. They may be welded successfully, by preheating and subsequent controlled cooling. (Fig, 23), , Jigs and fixtures: Jigs and fixtures are used to hold the, work in a right position during welding. By using them the, shrinkage forces of the weld are balanced with sufficient, counterforce of the jigs and fixtures. (Fig 24), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.38, , 139

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Methods of correcting distortion: Distortion may take, place even after following a planned procedure as it is, difficult to control distortion to the full extent. So some, mechanical means and application of heat are used to, remove distortion after it occurs., Mechanical methods: Small parts, deformed by angular, distortion can be straightened by using a press. If the, parts of the assembly are not restrained, they can be, brought into alignment by hammering, drifting or jacking, without giving excessive force (stress}., Heating methods: The distorted part is heated locally, and rapidly keeping the surrounding metal reasonably cool., Heat small areas at a time. It should not exceed bright, red hot condition., If thin plates are buckled they can be corrected by local, spot heating on the convex side. Starting at the centre, of the buckled area heat symmetrically outwards as shown, in Fig 27., , The methods of flame straightening are shown in Fig 29., In Line heating (Fig 29a) heat from the torch is applied, along a line or a set of parallel lines. This method is, frequently used for removing the angular distortion produced, by the fillet welds attaching a plate to its stiffener., In pipe-needle (Fig 29b) heating, heat is applied along two, short lines crossing each other. This method is half way, between line heating and spot heating. Since the shrinkage, and angular distortion occur in two directions, this method, produces a uniform distortion-removal effect., In checker board (cross-directions) heating, (Fig 29c) heat, is applied along a pair of two lines crossing each other., This method is used to remove severe distortion., In spot heating. (Fig 29e) heat is applied on a wedge, shaped area, and this method is useful for the removal of, bending distortion in frames., In triangular heating (Fig 29e) heat is applied on a, wedgeshaped area, and this mehod is useful for the, removal of bending distortion in frames., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Red hot heating (Fig 29f) is used when severe distortion, has occured in a localised area, and it may be necessry, to heat the area to a high temprature and beat it with a, hammer. This method can cause metallurgical changes., , Co, , Correction of distortion caused by fillet welds is done by, local heating on the underside of the plate in a narrow, strip following the line of the joint. (Fig 28), , Straightening by flame heating: The most common, distortion-removal technique is to use a flame and heat, the part at selected spots or along certain lines and then, to aircool it. The area to be straightened is heated to, between 600 and 650°C for plain carbon and low alloy, steels and suddenly cooled in air, or if necessary with a, spray of water in low carbon steels., , 140, , Fabrication : Welder - Related Theory for Exercise 1.1.38

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Thermal treatments: To reduce distortion, various, thermal treatments are done. They inculde preheat and, postweld thermal treatments., Preheating: Weld shrinkage is generally reduced by, preheating. Actual measurements across welds during, cooling have shown that less than 30% total contraction, occured in joints preheated to 200°C, compared to, nonpreheating joints., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Stress relief: In many cases thermal stress relief is, necessary to prevent further distortion being developed, before the weldment is brought to its finished state., Residual tensile stress in welds are always balanced by, compressive reidual stresses. If a considerable portion, of the stressed material is machined out, a new balance, of residual stress will result, causing new distortion. Weld, stress-relieving prior to machining is thus very important, for prolonged dimensional accuracy of sliding and rotating, parts., , Vibration stress relieving: This technique reduces, distortion by means of vibrating the weldments. The, equipment consists of a variable speed vibrator, which is, clamped to the workpiece, and an electronic amplifier,, by varying the speed of the vibrating motor, the frequency, can be varied until a resonant frequency has been reached, for the workpiece. The piece is then allowed to vibrate for, a period which varies in relation to the weight of the, workpiece. Usually it ranges from 10 to 30 minutes. 30 to, even 50% of the residual stresses are relieved using, vibrating methods. The component thus balances roughly, its residual stresses, and it remains undistorted, , Fabrication : Welder - Related Theory for Exercise 1.1.38, , 141

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.39, , Defects in arc welding - its effect, Objectives: At the end of this lesson you shall be able to, • name different weld defects in arc welded joints, • define weld defect, • state the effect of defects on the welded joints, • differentiate between external and internal defects., Introduction: The strength of a welded joint should be, more than or equal to the strength of the base metal., If any weld defect is in a welded joint, then the joint becomes weaker than the base metal. This is not acceptable., So a strong or good weld should have uniformly rippled, surface, even contour, bead width, good penetration and, should not have defect., , Those defects, which are hidden inside the weld bead or, inside the basemetal surface and which cannot be seen, with bare eyes or lens are called internal defects., Some of the weld defects are external defects, some are, internal defects and some defects like crack, blow hole and, porosity, slag inclusion, lack of root penetration in fillet joints,, etc will occur both as external and internal defects., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Definition of a weld defect/fault: A defect or fault is one, which does not allow the finished joint to withstand or, carry the required load., , The defects which can be seen with bare eyes or with a lens, on the top of the weld bed, or on the base metal surface or, on the root side of the joint are called external defects., , External defects, , Effects of weld defect/fault: Always a defective welded, joint will have the following bad effects., – The effective thickness of the base metal is reduced., – The strength of the weld is reduced, , – The effective throat thickness is reduced, , – The joint will break, when loaded, causing accident., , 1 Undercut, 2 Cracks, , 3 Blow hole and porosity, 4 Slag inclusions, , 5 Edge plate melted off, , 6 Excessive convexity/Oversized weld/Excessive reinforcement, , – More electrodes are required which will also increase, the cost of welding., , 7 Excessive concavity/insufficient throat thickness/, insufficient fill, , Co, , – The properties of base metal will change., , – Waste of labour and materials., , 8 Incomplete root penetration/lack of penetration, , – The weld appearance will be poor., , 9 Excessive root penetration, , Since the weld defects will give bad effects on the joint,, always proper care and action has to be taken before and, during welding to avoid/prevent the defects. If the defects, have already taken place then proper action has to be, taken to correct/rectify the defect after welding., , 10 Overlap, , The action/measure taken to avoid/prevent and correct/, rectify a weld defect is also called as a remedy., , Internal defects, , So some remedies may help to avoid/prevent a weld, defect and some remedies may help to correct/rectify a, weld defect which has already taken place., Weld defect may be considered under two heads., – External defects, – Internal defects, , 142, , 11 Mismatch, , 12 Uneven/irregular bead appearance, 13 Spatters, , 1 Cracks, 2 Blow hole and porosity, 3 Slag inclusions, 4 Lack of fusion, 5 Lack of root penetration, 6 Internal stresses or locked-up stresses or restrained, joint., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39

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Defects in arc Welding - Definition, Causes and Remedies, Objectives: At the end of this lesson you shall be able to, • define common weld defects in arc welded joints, • describe the causes, remedies and corrections of weld defects., A sound or good weld will have uniformly rippled surface,, even contour, bead width, good penetration and no, defects., Definition of a defect: A defect is one which does not, allow the finished joint to withstand the required strength, (load)., Causes for weld defects means wrong actions taken which, creates the defect., , Causes, , A remedy can be, , Current too high, , a. Preventing the defect by taking proper actions before, and during welding., , Welding speed too fast, Overheating of job due continuous welding, Faulty electrode manipulation, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , b. Taking some corrective actions after welding to rectify, a defect which has already taken place., , Use of a very short arc length, , Undercut: A grooved or channel formed in the parent metal, at the toe of the weld. (Figs 1, 2 & 3), , Wrong electrode angle, REMEDIES, , (a) Preventive action, Ensure, , – proper current is set, , – correct welding speed is used, – correct arc length is used, , Co, , – correct manipulation of electrode is followed, (b) Corrective action, , – deposit a thin stringer bead at the top of the weld using, a 2mm ø electrode to fill up the undercut., Overlap, An overlap occurs when the molten metal from the, electrode flows over the parent metal surface without, fusing into it. (Fig 4), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39, , 143

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CAUSES, , REMEDIES, , Low current., , (a) Preventive actions, , Slow arc travel speed., Long arc., , Remove oil, grease, rust, paint, moisture, etc. from the, surface. Use fresh and dried electrodes. Use good fluxcoated electrodes. Avoid long arcs., , Too large a diameter electrode., , (b) Corrective action, , Use of wrist movement for electrode weaving instead of, arm movement., , If the blowhole or porosity is inside the weld then gouge, the area and reweld. If it is on the surface then grind it and, reweld., , REMEDIES, Spatter, (a) Preventive actions, Small metal particles which are thrown out of the arc, during welding along the weld and adhering to the base, metal surface. (Fig 6), , Correct current setting., Correct arc travel speed., Correct arc length., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Correct diameter electrode as per metal thickness., Proper manipulation of electrode., (b) Corrective actions, , Remove the overlap by grinding without an undercut., Blowhole and porosity, , CAUSES, , Co, , Blow hole or gas pocket is a large diameter hole inside a, bead or on the surface of the weld caused by gas entrapment. Porosity is a group of fine holes on the surface of, the weld caused by gas entrapment. (Fig 5), , Welding current too high. Wrong polarity (in DC). Use of, long arc. Arc blow. Uneven flux coated electrode., REMEDIES, , (a) Preventive actions, Use correct current., , Use correct polarity (DC)., Use correct arc length., , Use good flux-coated electrode., (b) Corrective actions, CAUSES, Presence of contaminants/impurities on the job surface, or on electrode flux, presence of high sulphur in the job or, electrode materials. Trapped moisture between joining, surfaces. Fast freezing of weld metal. Improper cleaning, of the edges., , 144, , Remove the spatters using a chipping hammer and wire, brush., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39

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Edge of plate melted off, , CAUSES, , Edge of plate melted off defect takes place in lap and, corner joints only. If there is excess melting of one of the, plate edges resulting in insufficient throat thickness then, it is called edge of plate melted off defect. (Fig 7), , Wrong selection of electrode., Presence of localized stress., A restrained joint., Fast cooling., Improper welding techniques/sequence., Poor ductility., Absence of preheating and post-heating of the joint., Excessive sulphur in base metal., REMEDIES, (a) Preventive actions, , CAUSES, Preheating and post-heating to be done on copper, cast, iron, medium and high carbon steels., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Use of oversize electrode., Use of excessive current., , Select low hydrogen electrode., , Wrong manipulation of the electrode i.e. excessive, weaving of electrode., , Cool slowly., , Use fewer passes., , REMEDIES, , Use proper welding technique/sequence., , (a) Preventive action, , Cracks, , Select correct size electrode., , (b) Corrective actions, , Set correct current., , Co, , Ensure correct manipulation of electrode., (b) Corrective action, , Deposit additional weld metal to increase throat thickness., Crack, , A hairline separation exhibits in the root or middle or surface and inside of the weld metal or parent metal. (Fig 8), , – For all external cracks to a smaller depth, take a, V groove using a diamond point chisel upto the depth, of the crack and reweld (with preheating if necessary), using low hydrogen electrode. Cool the job slowly., – For internal/hidden cracks gouge upto the depth of the, cracks and reweld (with preheating if necessary) using, low hydrogen electrode. Cool the job slowly., Incomplete penetration, Failure of weld metal to reach and fuse the root of the, joint. (Fig 9), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39, , 145

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CAUSES, , CAUSES, , Edge preparation too narrow - less bevel angle., , Incorrect edge preparation., , Welding speed too much., , Use of damaged flux coated electrode due to long storage., , Key-hole not maintained during welding the root run of a, grooved joint., , Excessive current., Long arc length., , Less current., Improper welding technique., Use of larger dia. electrode., Inadequate cleaning of each run in multi-run welding., REMEDIES, , Wrong angle of electrode., , (a) Preventive actions, , Insufficient root gap., , Use correct joint preparation., , REMEDIES, , Use correct type of flux coated electrode., , (a) Preventive actions, , Use correct arc length., , Correct edge preparation is required., , Use correct welding technique., , Ensure correct angle of bevel and required root gap., , Ensure thorough cleaning of each run in multi-run welding., , Use correct size of electrode., , (b) Corrective actions, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Inadequate cleaning or gouging before depositing sealing, run., , Correct welding speed is required., , Maintain a key-hole throughout the root run., , For external/surface slag inclusion remove them using a, diamond point chisel or by grinding and reweld that area., For internal slag inclusions use gouging upto the depth of, the defect and reweld., , Correct current setting is required., , Excessive convexity (Fig 11), , (b) Corrective actions, , Co, , For butt welds and open corner welds gouge the root of, the joint and deposit the root run from the bottom side of, the joint. For a Tee & lap fillet welds blow off the full weld, deposit and reweld the joint., , This defect is also called as oversize weld or excessive, reinforcement. It is the extra weld metal deposited in the, final layer/covering run., , Slag inclusion: Slag or other non-metallic foreign materials entrapped in a weld. (Fig 10), , 146, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39

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Excessive concavity/insufficient throat thickness, If the weld metal deposited into a butt or fillet weld is, below the line joining the toes of the weld then this defect, is called excessive concavity or insufficient throat, thickness. (Fig 12), , – Excessive speed of welding., – Wrong welding sequence when using stringer beads, to fill the groove., – Sagging of weld metal is not controlled in horizontal, position., – Electrode movement is not uniform., – Improper electrode angle between the plate surfaces., Remedies, – Lack of fusion., – Mismatch., , CAUSES, – Incorrect bead profile due to improper weaving of, electrode., , – Uneven/irregular bead appearance., – Excessive root penetration., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Use of small dia. electrode., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.39, , 147

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.40, , Pipe joints, Objectives: At the end of this lesson you shall be able to, • explain the advantages of welded pipes, • State different methods of pipes welding, • explain the types of pipe joint and pipe welding positions, • describe the methods of welding pipes in ‘1G’ position., , Specification of Pipes, In a pipe its size is measured by nominal diameter (or), nominal outside diameter (OD)., , •, , It is also mentioned as nominal pipe size (NPS)., , •, , Pipe is normally used to transport gases or liquids in a, process., , As per Indian standard 1161-1998, it is specified as steel, tubes of nominal force, and thickness having outside, diameter in mm under light, medium and heavy class., Refer Table 1 as per IS 1161:1998., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , •, , Tube is normally used for standard purpose and it is mentioned as outside diameter and its wall thickness as tube., , 148

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Outside, Diameter, , mm, (2), , 21.3, , 26.9, , 33.7, , 42.4, , 48.3, , 60.3, , 76.1, , 88.9, , 101.6, , Nominal, Bore, , mm, (1), , 15, , 20, , 25, , 32, , 40, , 50, , 65, , 80, , 90, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , (3), , Class, , 3.6, 4.0, 4.8, , 3.2, 4.0, 4.8, , 3.2, 3.6, 4.5, , 2.9, 3.6, 4.5, , 2.9, 3.2, 4.0, , 2.6, 3.2, 4.0, , 2.6, 3.2, 4.0, , 2.3, 2.6, 3.2, , 2.0, 2.6, 3.2, , mm, (4), , Thickness, , Internal, Volume, External, , Internal, , Surface, , 8.70, 9.63, 11.5, , 6.72, 8.36, 9.90, , 5.17, 6.42, 7.93, , 4.08, 5.03, 6.19, , 3.23, 3.56, 4.37, , 2.54, 3.10, 3.79, , 1.98, 2.41, 2.93, , 1.38, 1.56, 1.87, , 0.947, 1.21, 1.44, , kg/m, (5), , 11.1, 12.3, 14.6, , 8.61, 10.7, 12.7, , 7.32, 8.20, 10.1, , 5.23, 6.41, 7.88, , 4.13, 4.53, 5.56, , 3.25, 3.94, 4.82, , 2.54, 3.06, 3.73, , 1.78, 1.98, 2.38, , 1.21, 1.53, 1.82, , cm2, (6), , 6 995, 6 877, 6 644, , 5 343, 5 138, 4 936, , 3 814, 3 727, 3 534, , 2 332, 2 213, 2 066, , 1 418, 1 378, 1 275, , 1 086, 1 017, 929, , 638, 585, 518, , 390, 370, 330, , 235, 203, 174, , cm3/m, (7), , 3 192, , 2 793, , 2 391, , 1 517, , 1 332, , 1 059, , 845, , 669, , cm3/m, (8), , 2 964, 2 939, 2 889, , 2 591, 2 540, 2 490, , 2 189, 2 163, 2 107, , 1 711, 1 667, 1 611, , 1 335, 1 316, 1 265, , 1 168, 1 130, 1 080, , 895, 857, 807, , 700, 681, 644, , 543, 506, 468, , cm3/m, (9), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Area of, Cross, Section, , Co, , Mass, , 133.27, 146.32, 171.44, , 79.23, 96.36, 112.52, , 48.79, 54.02, 65.12, , 21.59, 25.88, 30.90, , 10.70, 11.59, 13.77, , 6.47, 7.62, 8.99, , 3.09, 3.61, 4.19, , 1.36, 1.48, 1.70, , 0.57, 0.69, 0.75, , cm4, (10), , Moment, of, Inertia, , (Clauses 3.1, 6.1, 6.1.1 and 6.1.2), , 26.23, 28.80, 33.75, , 17.82, 21.68, 25.31, , 12.82, 14.20, 17.1, , 7.16, 8.58, 10.2, , 4.43, 4.80, 5.70, , 3.05, 3.59, 4.24, , 1.83, 2.14, 2.48, , 1.01, 1.10, 1.26, , 0.54, 0.64, 0.70, , cm3, (11), , Modulus, of, Section, , Sizes and Properties of Steel Tubes for Structural Purposes, , Table 1, , 3.47, 3.45, 3.43, , 3.03, 3.00, 2.98, , 2.58, 2.57, 2.54, , 2.03, 2.00, 1.98, , 1.61, 1.59, 1.57, , 1.41, 1.39, 1.36, , 1.10, 1.08, 1.05, , 0.87, 0.86, 0.84, , 0.69, 0.66, 0.55, , cm, (12), , Radius, of, Gyration, , 12.03, 11.91, 11.76, , 9.19, 9.00, 8.88, , 6.66, 6.60, 6.43, , 4.13, 4.02, 3.92, , 2.59, 2.54, 2.47, , 1.98, 1.93, 1.86, , 1.21, 1.17, 1.11, , 0.76, 0.74, 0.71, , 0.47, 0.44, 0.42, , cm2, (13), , Square of, Radius of, Gyration, , IS 1161 : 1998, , 149

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150, , 114.3, , 127.0, , 139.7, , 152.4, , 165.1, , 168.3, , 193.7, , 219.1, , 244.5, , 273.0, , 323.9, , 355.6, , 110, , 125, , 135, , 150, , 150, , 175, , 200, , 225, , 250, , 300, , 350, , mm, (2), , mm, (1), , 100, , Outside, Diameter, , Nominal, Bore, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , Heavy, , Heavy, , Heavy, , Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy 1, Heavy 2, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , Light, Medium, Heavy, , (3), , Class, , 8.0, , 6.3, , 5.9, , 5.9, , 4.8, 5.6, 5.9, , 4.8, 5.4, 5.9, , 4.5, 4.8, 5.4, 6.3, , 4.5, 4.8, 5.4, , 4.5, 4.8, 5.4, , 4.5, 4.8, 5.4, , 4.5, 4.8, 5.4, , 3.6, 4.5, 5.4, , mm, (4), , Thickness, , Co, , 68.6, , 49.3, , 38.9, , 34.7, , 25.4, 29.5, 31.0, , 22.4, 25.1, 27.3, , 18.2, 19.4, 21.7, 25.2, , 17.8, 18.9, 21.3, , 16.4, 17.5, 19.6, , 15.0, 15.9, 17.9, , 87.3, , 62.8, , 49.5, , 44.2, , 32.3, 37.5, 39.5, , 28.5, 32.0, 34.8, , 23.1, 24.7, 27.6, 32.0, , 22.7, 24.2, 27.1, , 20.9, 22.2, 25.0, , 19.1, 20.3, 22.8, , 17.3, 18.4, 20.6, , 90 533, , 76 073, , 53 557, , 42 507, , 34 454, 33 930, 33 734, , 26 606, 26 260, 25 974, , 19 921, 19 771, 19 473, 19 030, , 19 128, 18 981, 18 690, , 16 142, 16 008, 15 740, , 13 410, 13 287, 13 043, , 10 930, 10 819, 10 599, , 9 004, 8 704, 8 409, , 3 990, , 3 591, , cm3/m, (8), , cm3/m, (7), , cm2, (6), 12.5, 15.5, 18.5, , External, , Internal, Volume, , Area of, Cross, Section, , 11 173, , 10 177, , 8 578, , 7 681, , 6 883, , 6 085, , 5 287, , 5 187, , 4 788, , 4 389, , 002, 983, 946, 889, , 10 663, , 9 775, , 8 202, , 7 307, , 6 578, 6 528, 6 509, , 5 781, 5 743, 5 712, , 5, 4, 4, 4, , 4 902, 4 883, 4 845, , 4 503, 4 484, 4 446, , 4 104, 4 085, 4 047, , 3 705, 3 686, 3 649, , 3 363, 3 306, 3 250, , cm3/m, (9), , Internal, , Surface, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 13.6, 14.5, 16.2, , 9.75, 12.2, 14.5, , kg/m, (5), , Mass, , 13 111, , 7 992, , 4 412, , 3 149, , 1 856.51, 2 141, 2 247, , 1 271.71, 1 417, 1 535.2, , 777.2, 824.78, 917.7, 1 053, , 732.6, 777.32, 864.7, , 572.2, 606.92, 674.5, , 437.2, 463.44, 514.5, , 325.3, 344.58, 382.0, , 192.03, 234.3, 274.5, , cm4, (10), , Moment, of, Inertia, , 737, , 493, , 323, , 258, , 169.47, 195, 205, , 131.31, 146, 158.65, , 92.4, 98.01, 109.0, 125.0, , 88.7, 94.16, 105.0, , 75.1, 79.65, 88.5, , 62.6, 66.35, 73.7, , 51.2, 54.27, 60.2, , 33.60, 41.0, 48.0, , cm3, (11), , Modulus, of, Section, , 12.3, , 11.2, , 9.45, , 8.44, , 7.58, 7.55, 7.54, , 6.68, 6.66, 6.64, , 5.79, 5.78, 5.76, 5.73, , 5.68, 5.67, 5.65, , 5.23, 5.22, 5.20, , 4.78, 4.77, 4.75, , 4.33, 4.32, 4.30, , 3.92, 3.89, 3.85, , cm, (12), , Radius, of, Gyration, , 151.29, , 125.44, , 89.30, , 71.21, , 57.45, 57.02, 56.86, , 44.63, 44.36, 41.11, , 33.56, 33.42, 33.21, 32.85, , 32.27, 32.14, 31.92, , 27.37, 27.25, 27.05, , 22.87, 22.76, 22.58, , 18.78, 18.69, 18.52, , 15.36, 15.10, 14.86, , cm2, (13), , Square of, Radius of, Gyration, , IS 1161 : 1998

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Welded pipe joints, Pipes of all types and sizes are used in great deal today, in transporting oil, gas, water etc. They are also used, extensively for piping systems in building, refineries and, industrial plants., Advantages of welded pipe, Pipes are mostly made of ferrous and non-ferrous metals, and their alloys. They possess the following advantages., – Improved overall strength., – Ultimate saving in cost including maintenance., – Improved flow characteristics., – Reduction in weight due to its compactness., – Good appearance., Method of pipes welding, , – Metallic arc welding, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The following are the methods of pipe welding by arc., , – Gas metal arc welding, , – Tungsten inert gas welding, – Submerged arc welding, – Carbon arc welding, , All these methods, except carbon arc welding are, commonly used and the choice of welding depends upon, the size of the pipe and its application., Types of pipe joints, , 2 'T' joint, 3 Lap joint, , Co, , 1 Butt joint, , (Fig 1), , 4 Angle joint, 5 composite joint, 6 Pipe flange joint, 7 Y joint, , (Fig 2), , 8 Elbow joint, , (Fig 3), , 1 G - Pipe weld in flat (roll) position i.e. pipe axis is parallel, to the ground., , Welding of pipe butt joints: Normally joints in pipes, and tubes cannot be welded from the inside of the bore., Hence before starting to learn pipe welding, a person should, be proficient in welding in all positions i.e. flat, horizontal,, vertical and overhead., , 2 G - Pipe weld in horizontal position i.e. pipe axis is, perpendicular to the ground., , All these positions are used to weld pipes., , 6 G - Pipe weld in including (fixed) position i.e. pipe axis, is including to both horizontal and vertical planes., , 5 G - Pipe weld in flat (fixed) position i.e. pipe axis is, parallel to the ground., , Pipes welding positions (Figs 4 and 5), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 151

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Setting the pipes for welding: Tack weld together with, 4 small equally spaced tacks. The gap should be equal to, the root face dimension plus 0.75 mm. Support the tacked, assembly on V blocks or rollers so that the assembly can, be rolled or rotated with the free hand., Select a 2.5 mm rutile electrode for 1st run and a, 3.15 mm rutile electrode for 2nd run., Set a current of 70-80A for 1st run and 100-110 for the, 2nd run., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Rotate the assembly as welding proceeds. (Fig 6) keeping, the welding arc within an area between vertical and 10°, from the vertical in the direction of welding Fig 7., (Use a helmet type screen)., , During the welding of butt joints the pipe may be, 1 rolled or rotated (1G position), , 2 fixed (2G, 5G and 6G position)., Welding of pipe butt joints by arc can be done in, 1G position by (a) continuous rotation method and, (b) Segmental method., , – Direct the electrode centrally at the root of the joint, and in line with the radius of the pipe at the point of, welding., , 1a Pipe welding by arc (in 1G position) by continuous, rotation method: Satisfactory welding of butt joints, in pipes depends upon the correct preparation of pipe, ends and careful assembly of the joint to be welded., Ensure that the bores and root faces are in correct, alignment and that the gap is correct., , – Strike the arc near the top dead centre and hold the, arc length as short as possible. Continue to weld as, the pipe is rotated manually at steady speed., , Clean the edges. Prepare an angle of bevel 35° by gas, cutting and filing. A root face 1.5 to 2.5 mm is to be provided., , 152, , – Deposit first run by weaving the electrode very slightly, from root face to root face., – Adjust the speed of rotation to obtain full fusion of the, root faces without excessive penetration., – Chip out tack weld as they are approached. Do not, weld over tacks otherwise loss of penetration at the, tacking points may occur., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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– Complete the weld with the second run. Adjust the, speed of rotation to secure fusion to the outer edge of, each fusion face. The amount of reinforcement should, be even around the edge of the joint., 1b Welding of a pipe butt (IG position i.e. by rotation), by segmental welding., – The edges of the pipe are bevelled to 35 to 40° angle, with a root gap of 2.5 mm., , – When a segment equivalent to 60° has been welded,, terminate/stop the weld run. Avoid the formation of a, crater., – Move the pipe until the end of the segment is at 10°, before TDC., – Strike the arc on the end of the previous weld run and, establish a weld pool., – Weld a further 60° segment. (Fig10), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Tack the pipe as before and support the assembly on, two vee blocks. (Fig 8), , – Strike the arc at 10° from Top Dead Centre (TDC) and, deposit the root run. Use a small weaving motion to, achieve fusion of the root faces. Adjust travel speed to, control root penetration. (Fig 9), , – Continue welding in segments until the root run has, been completed., – Move the pipe until the mid point of the segments is at, TDC., – Strike the arc and deposit the second (filling) run, use, a side-to-side weaving position to fill the preparation, and to achieve fusion of the pipe edges., , Co, , – Complete the filling run in 60° segments., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 153

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Pipe welding by arc in fixed positions, Objectives: At the end of this lesson you shall be able to, • state different fixed pipe welding positions, • explain different methods of pipe welding in 5G position, • explain the welding producer of M.S. pipe butt joint by arc in fixed (5G) position., Whenever the pipes to be welded cannot be rotated or, whenever the pipes are to be welded in the field i.e. at, worksite, then they are welded in fixed position. If the fixed, pipe axis is horizontal, then the welding position is called, 5G position., The other pipe welding positions in which the pipes are, fixed during welding are 2G and 6G positions. If the axis of, the fixed pipes to be welded are vertical then this position, is called 2G position. If the axis of the fixed pipes in inclined, at 45° to both horizontal and vertical planes, then the, welding position is called 6G position., In 5G position, a pipe butt joint can be welded by the, following method., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Method 1: The pipe joint circumference is divided into, four positions as A, B, C and D. First portion 'A' is welded, from 1 to 2 in more or less in flat position. Then portion B, is welded from 3 to 4 in overhead position. Next portion C, from 3 to 2 and then portion D from 4 to 1 are welded in, vertical up position. (Fig 1), , Co, , Method 3: The weld is started from 6 O'clock to 12 O'clock, position on the right side first and then again from the, 6 O'clock to 12 O'clock position on the left side (Fig4)., This method is called uphill method or vertical up method., This uphill method is used to weld pipes of 5 mm and, above wall thickness., , It is important that a key hole is maintained throughout, the welding operation to ensure proper root penetration., Also the electrode position is continuously changed as, the joint surface is curved. In addition, the starting and, ending of each weld portion i.e. A, B, C and D properly, done so that they merge with the previous portion., Method 2: The pipe outer circumference is divided into, 12 equal divisions as in a clock., The top of the pipe is 12 O'clock position and the bottom, is in 6 O'clock position. (Fig 2), , The weld is started from 12 O'clock position to 6 O'clock, position on the right side vertically downwards. Then welding, is done again from 12 O'clock to 6 O'clock position on the, left side (Fig 3). This method is called down hill method, and is normally used for thin walled pipes with wall, thickness of 3 to 4 mm., , 154, , Welding in 2G and 6G positions are done based on the, position of the pipe axis., In the 2G position, the horizontal pipe welding with its, axis being vertical, the weld joint connecting the two pipes, is in the horizontal position. The weld must be made around, the pipe. (Fig 5), In the 6G position welding is usually done by using one of, the methods i.e. uphill or downhill welding. (Fig 6), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Use electrodes specially manufactured for pipe welding to, get good penetration, appearance and strength, (low, hydrogen electrodes, deep penetration electrodes etc.), , Co, , Welding procedure of M.S. pipe butt joint by arc in, fixed (5G) position., , Edge preparation and cleaning: If the wall thickness is, 3 mm and below the edges of the pipe end is filed square, i.e. perpendicular to the pipe axis. The welding of the joint, is complete in one pass using the down hill method or by, segmental method i.e. welding the top quarter in flat, bottom, quarter in overhead and the two side quarter portion in, vertical up position. The electrode has to be held at angles, as shown in Fig 14 for welding the root pass of a thicker, pipe explained later in this lesson., For welding pipes with higher wall thickness the following, procedure is to be followed., Edge preparation: The pipe ends are bevelled by flame, cutting or machining in the shop (Figs 7 and 8) The, including angle is 75° the root face and root gap are, 2.5 mm to 3 mm. All traces of oxide from and other, contaminations must be removed before starting the weld., (Fig 9), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 155

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Setting of pipe: Pipe to be joined together must be, accurately aligned prior to welding. The inside surface of, the pipe must be blended together smoothly as in the, outer surface. Maintain the root opening 2.5 mm, use a, M.S. angle and strength bar for checking the alignment of, the pipe. (Fig 10), , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Tacking: Place a 2.5 mm bend wire between the edges., The tack length should be 3 times the metal thickness., Put the first tack at the root side and the second tack at, the opposite side of the first tack. Arrange the third and, fourth tacks at 90° from the first and second tacks., (Fig 11), , Root pass: Fix the job in the clamp and adjust the height, to a position convenient to you. The position of tack weld, should be fixed as in Fig 12. The keyhole is an essential, part in the welding of the root pass. (Fig 13) It should be, about, , 1, , of the diameter of the electrode. Maintain, 3, the electrode angle as shown in Fig 14 Weld the root, pass on side 2 of the pipe joint. (Fig 14), , 1, , The side 1 of the root pass is started at 6½ hrs position, and stopped at 11½ hrs position. The side 2 is started at, 5½ hrs position and stopped at 12½ hrs position., , After completing the root pass, depending on the wall, thickness of the pipe there will be further weld deposits, either 2 or 3 or more passes. These passes can be a, mixture of stringer beads and weaved beads by vertical, up/uphill method., The names of each pass is given in Fig 15. Usually the, second weld bead after the root pass is deposited keeping, the joint hot. So it is called hot pass., , The weld beads on side 1 and side 2 will overlap for a, short distance at the start and at the stop positions., , 156, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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For hot pass and cover pass maintain the electrode angle, as shown in the Fig 14. Each pass should start at a different, place of the joint. The second pass should fill the groove, by using side-to-side movement. The final cover pass, should be made wider than the second pass. The third, pass should be smooth and of uniform appearance, and, must have minimum reinforcement. (Fig 15), , Advantages of H/P pipe welding, – The joint is permanent., – Saving of material., – Reduction of joint weight., – Less expensive., – Multiple lines grouped together more closely., – Repair and maintenance cost is less., , Welding of M.S. pipe, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Objectives: At the end of this lesson you shall be able to, • classify and specify mild steel pipes, • state and explain different methods of welding M.S. pipes, • state the method of edge preparation, tacking and necessary of key hole maintenance, • explain the pipe welding procedure by gas welding., Welding of M.S. pipe: Mild steel pipes are classified into, two groups., , 1 Seamless pipes manufactured by piercing a hot solid, round billets/rods. (Fig 1), , Co, , 2 Resistance welded pipes manufactured by continuously, feeding a strip of metal through a machine which rolls, the strip into cylindrical shape and the seam is, electrically resistance welded. (Fig 2), , Based on the wall thickness, these pipes are further, categorised as "Standard pipes", "Extra Strong pipes" and, "Double extra strong pipes". Also the pipes are specified, by first the material then by the diameter followed by the, wall thickness. (Fig 3) For example a M.S. pipe 100 mm, long with 50 mm inside diameter and 3 mm wall thickness, is specified as M.S. ø 50 WT3 × 100 mm., In the actual usage of pipes in various applications like, transmitting water, oil, chemical, air, gases, etc. it is, necessary to weld them as a butt, elbow and Tee joints as, well as branch pipe joints at various angles., The welding of smaller diameter pipes and bigger diameter, pipes inside a welding shop can be done by rotating the, pipes on roller or manually by a helper using an angle iron, and tongs. (Fig 4 and Fig 5), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 157

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Co, , The edges of the pipe joints are prepared depending on, the type of joint and the wall thickness of the pipe. For a, pipe flange joint and for pipe butt joint with 1.5 to 3 mm, wall thickness, the pipe edges are filed or ground square, (Fig 6) for pipe butt joints above 3 mm wall thickness, the, pipe edges are bevelled as shown in Fig 7 with 1.5 mm, root face., , If the pipes are larger and are to be welded in the field/, work site or if the pipes cannot be rotated, then in such, cases, the pipes are welded in fixed position i.e. the pipe, will not ne rotated, but the welder has to move the blowpipe, and filler rod along the curved line of the joint around the, pipe to complete the weld., , 158, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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Weld defects like incomplete or lack of root penetration, cannot be rectified from inside small diameter pipes. Hence, slightly larger root gaps are given while welding pipe butt, joints to ensure proper root penetration. (Table 1) Fig 6, and Fig 7 gives the details of edge preparation., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , For pipes with wall thickness 3 mm and below, the edges, are prepared by a file. If the wall thickness is more than, 3 mm then the bevelling is done by gas cutting (Fig 8) and, the root face is prepared by filing/grinding. (Fig 9), , As welding of pipes is done either by rotating the pipe or, by the fixed method, the pipe welding procedure also, differs accordingly., The different positions used to weld pipe butt joints are, named as 1G, 2G, 5G and 6G as shown in Fig 10 to, Fig 13. These positions are decided based on the position, of the pipe axis and whether the welding is done by rotating, the pipe or by keeping the pipe fixed., But in gas welding only 1G, 2G and 5G position are used., The 6G position welding is done by arc welding and it is, usually used to test the skill/ability of a welder in pipe, welding., , Pipe welding by rotation method (Position 1G): The, method of welding pipes using pipe rotation is shown in, the Fig 14. The two pipes after cleaning and preparing the, edges, are set with proper root gap on an angle iron or, channel so that the axes of the pipes are properly aligned., Then tack weld them at 3 places at 120° intervals., (Fig 14A), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 159

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Table 1, Pipe and preparation, , Welding technique, , Root gap (g), , 3 mm or less, , Square, , Leftward, , 2.5 - 3 mm, , 5 mm or less, , Square, , Rightward or all-positional rightward, , 2.5 - 3 mm, , 3 - 5 mm, , Bevelled, , Leftward, , 1.5 - 2.5 mm, , 5 - 7 mm, , Bevelled, , Rightward or all-positional rightward, , 3 - 4 mm, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Wall thickness (t), , Co, , Start the weld at 3 O'clock position and finish at 12 O'clock, position. Now the first ¼ portion of the pipe joint, marked, as 1 in Fig 14B is welded. Rotate the pipe joint by 90° in, clockwise direction so that the 12 O'clock position on the, pipe comes to 3 O'clock position. Weld the portion marked, as 2 in Fig 14C as done in welding portion 1 already., Now rotate the pipe by 90° and weld portion 3 (Fig 14D)., On completing welding of portion 3 rotate the pipe again, by 90° so that the portion 4 can be welded (Fig 14E). The, position of blowpipe/torch and filler rods is shown in, Fig 14F and the blowpipe weaving motion is shown in Fig, 14G. It is very important to continuously maintain a key, hole both while tacking Fig 15 and during welding (Fig 16)., In this method leftward technique is used and the metal, deposition starts in vertical at 3 O'clock position and ends, with flat position at 12 O'clock position. Care should be, taken to properly overlap the previous weld deposit while, starting the 2nd, 3rd and 4th segments., Pipe welding in fixed position (position 5G): The, welding of the pipeline without rotating the pipe during, welding is called fixed position welding. (5G) In this position, the welder has to move according to the condition of the, pipeline in different positions, such as vertical, down hand, and overhead positions., , 160, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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In fixed position pipe welding, the welder has to weld, according to the conditions of the pipeline., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , In this system, the welding should be started from, 6 O'clock position and move to 12 O'clock position on either, side by moving the blowpipe and the filler rod from bottom in, the upward direction as shown in Fig 17a, 17b, 17c., , Co, , This also can be welded by the four quarter method, first, by welding two quarter distance (opposite to each other), by moving the blowpipe in the upward vertical direction., (Fig 18a and Fig 18b) Then weld the top quarter distance, in the down hand position. Finally weld the bottom quarter, distance in the overhead position. The clock face and its, relationship to pipe welding and various blowpipe and filler, rod positions are illustrated in Fig 19., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40, , 161

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pipe surface. The position of blowpipe and the filler rod are, given in Fig 20. To avoid sagging of weld metal the blowpipe, is given a motion as shown in Fig 21 and the filler rod is, fed at the top half of the molten pool., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Pipe welding in 2G position (Pipe axis is vertical): In a, pipe butt joint if the axis of the pipes is vertical and the, weld joint is in the horizontal plane then it is called pipe, welding in 2G position. (Fig 20) It is a fixed position welding, and the blowpipe and filler rod are to be moved around the, , 162, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.40

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.41, , Difference between plate welding and pipe welding, Objectives: At the end of this lesson you shall be able to, • describe plate welding, • explain pipe welding, • explain the differences between plate welding and pipe welding., Plate welding: Plate welding is a fusion welding process., It joins plate metals using the combustion of oxygen and, fuel gas. The intense heat that is produced melts and, fuses together the edges of the parts to be welded generally, with the help of a filler metal., Plate welding by gas can be done in two ways. One is, leftward welding and the other rightward welding., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , All the-position rightward welding is used for all position of, welding. (Fig 1) The path travelled by the flame and the, filler rod varies with the welding position. The angles at, which the flame and the filler rod are held also vary., Metal thickness and related techniques, Material thickness range, , Method, , Flat, , Not exceeding 5 mm, Exceeding 5 mm, , Leftward, Rightward, , Horizontalvertical, , 1 mm to 5 mm, 5 mm and above, , Leftward, All-position, Rightward, , Vertical, (single, operator), , 1 mm to 5 mm, 5 mm and above, , Leftward, All position, rightward, , Vertical (two, operatorstechnique), , 5 mm and above, , Leftward, , Overhead, , 1 mm to 5 mm, 5 mm and above, , Leftward, All-position, rightward., , Co, , Position, , Pipe welding: When welding the circumference of a mild, steel pipe, the angles of the rod and the blowpipe are, given in relation to the tangent to the pipe at the point of, welding., , When the pipe remains stationary, the following techniques, are used., Position, , Method, , At the top of the pipe,, flat position., , Leftward or rightward, , At the flank of a set on, branch when both pipe, axes are in horizontal, flat position., , Leftward or rightward, , The weld is made, along the vertical, sides of the pipe., , Leftward or rightward, or, all-position rightward, , The weld at the bottom, of a pipe is made in the, overhead position., , Leftward or rightward, or, all-position rightward, , The welding position can be seen in relation to the plane, of the joint., , The techniques used for the positional welding of plates, are also applied when welding pipes., , The techniques used will depend upon:, , For thin walled pipes up to 5 mm, the leftward technique, is used in any position. (Fig 2), , – the pipe wall thickness, – the welding positions, – whether the pipe is fixed or can be rotated., , The leftward, rightward or all-position rightward techniques, are used as appropriate on sections of 5 mm and above., (Fig 3), 163

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No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , In plate welding the sealing run can easily be deposited, when needed. In pipe welding the sealing run cannot be, deposited in small pipes. Sealing run can be deposited, only when the pipe has so large a diameter as to allow the, welder to enter into the pipe., , Co, , Possibility of distortion is higher in plate welding., Possibility of distortion is less in pipe welding., , Differences between plate welding and pipe welding, In the plate welding the total welding line can be seen at, any time. In pipe welding only a portion of the welding line, can be seen at any time., , Tip travel and hand travel will be equal in plate welding., Tip travel will be less and hand travel will be more in pipe, welding., , In plate welding, the line of weld is in only one position. In, pipe welding, welding can be done in one position when it, can be rotated. (Fig 4) Otherwise all-position welding can, be done in the pipe when the pipe is in fixed position. (Fig, 6) Sometimes the pipe may be in a fixed position and only, one position of welding will be done., Eg. 2G Position. (Fig 5), , 164, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.41

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.42, , Development of a pipe elbow joint, Objectives: At the end of this lesson you shall be able to, • develop and layout the pattern for 90° elbow joining two equal diameter pipe by parallel line method., Develop the pattern for a 90° elbow of equal, diameter pipes by parallel line method:, Draw plan as shown in Fig 1., , Now you find that the vertical lines are cutting at six different, points top and bottom in the elevation line. Number them, as shown in Fig 5., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Below this, draw the front elevation as shown in Fig 2., , Draw horizontal parallel lines from each point and number, them as shown in Fig 6., , Co, , Divide the circle in the plan into twelve equal parts and, number the points 0 to 12 as shown in Fig 3., , Extend the front elevation base line as shown in Fig 7., , Draw the perpendicular line from these points towards the, front view and number 1 to 12 as shown in Fig 4., , 165

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Take the distance equal to one division of plan and mark, twelve times on base line by a compass and draw, perpendicular lines from each point as shown in Fig 8., , Now you find that each horizontal line and corresponding, vertical line meet at a point. Number the points as 1 to 12, as shown in Fig 9., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Join these points by free hand curve as shown in Fig 10., , Development of a pipe "T" joint, , Objective: At the end of this lesson you shall be able to, • develop and layout the pattern for 90° "T" pipe of equal diameter by parallel line method., Develop the pattern for a 90° "T" pipe of equal, diameter by parallel line method:, , Co, , Draw the front view as shown in Fig 1., , Draw the side view as shown in Fig 2., Draw a semi-circle on the base line of the front elevation., (Fig 3), Divide the semi-circle into six equal parts and number, them as 0, 1, 2, 3, 2, 1, 0. (Fig 3), , 166, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42

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Divide a semi-circle in side view into six equal parts and, number as 3, 2, 1, 0, 1, 2, 3 as shown in Fig 4., , Draw the perpendicular lines from each point of the, semi-circle of the view as shown in Fig 5., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Take one division of the semi-circle in side view and transfer, it 12 times on the base line starting from: 0: and number, as 0, 1, 2, 3, 2, 1, 0, 1, 2, 3, 2, 1, 0 as shown in Fig 9., Draw perpendicular lines from these points and draw, horizontal lines from the points on the line of intersection, of "T". These line meet at their respective points. (Fig 9), , Co, , Draw horizontal lines from the side view towards the front, view as shown in Fig 6., , Join these points by free hand curve. (Fig 10), , Now the vertical lines of the front view and the horizontal, lines of side meet at their respective points., Join these points to get the line of intersection of "T" pipe, as shown in Fig 7., Extend the base line of the side view and mark the end, point as 0. (Fig 8), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42, , 167

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Provide locked grooved joint allowance as shown in Fig 11., , Check the pattern once again and cut. Thus you get the, pattern for branch pipe., For main pipe, develop and layout the pattern as follows:, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Draw the front view and end view. (Fig 12), , Co, , Extend the vertical lines 0, 1, 2, 3, 1, 0 of branch pipe from, the front view as shown in Fig 13., , Extend the two extreme end vertical lines of the main pipe, from the front view as shown in Fig 14., On one of these lines, take point "0" as starting point and, mark points 0, 1, 2, 3, 2, 1, 0, 1, 2, 3, 2, 1, 0 at equal, distances equal to one division of the semi-circle and draw, horizontal lines from these points. (Fig 15), Now these horizontal lines meet the vertical lines at their, respective points as shown in Fig 16., , 168, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42

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Join these points by free hand curve and get the pattern, for the main pipe. (Fig 17), Provide the locked grooved joint allowances as shown in, Fig 17., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Pipe development for "Y" joint, , Objectives: At the end of this lesson you shall be able to, • develop and able to layout the pattern for "Y" joint pipes intersecting at 120°, • develop and layout the pattern for "Y" joint pipes branching at 90°., Development of "Y" joint pipes intersecting at 120°:, Draw the development of intersecting cylinders of dia., 30 mm at 120°. (Fig 1), , Co, , All the cylindrical pipes are of same diameter and, intersecting each at equal angles. Hence in this case the, development of all the pipes are same and so the, development of one pipe will represent other pipes., •, , Draw the plan and elevation of the pipe 'A' and mark, the division on the plan. (Fig 1b), , •, , Draw the vertical projectors from the plan to front view, to meet the line of intersection., , •, , Draw horizontal projectors from these points on to the, development., , •, , Mark the intersecting points and join with a smooth, curve to complete the required development., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42, , 169

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Development of 'Y' joint branching at 90°: Three, cylindrical pipes of X, Y, Z form a 'Y' piece. (Fig 2) Draw, the lateral surface development of each pipe., In the three pipes XYZ, Y & Z are similar in size and shape,, hence their developments are also similar., Draw the development of pipe 'X' as in the previous, exercise., , •, , Draw the elevation and plan of pipe 'Y' as shown., , Divide the plan circle into 16 equal parts., , •, , Project the points to the elevation., , •, , Draw the rectangle ABCD in which AB is equal to ʌ D., , •, , Draw the development of pipe Y as shown in Fig 2., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , •, , •, , 170, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42

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Development of 45° and 90° branch pipe, Objective: At the end of this lesson you shall be able to, • prepare the development of pipe for 45° and 90° branch pipe., Procedure for development of 45° branch pipe: Refer, Fig 1. Draw a centre line AB., , From I, draw a horizontal line on both sides (XX'). This XX', will be the base line for drawing development., From I, plot the outside diameter of the branch pipe IJ on, the line XX'., Draw a centre line for the branch pipe. This line will cut the, main pipe's centre line AB at K., Join GK. Draw a perpendicular line to GK at K which meets, CD at H. Join KH. Now IHKHJ will be the shape (outline) of, the branch pipe., Draw a semi-circle equal to the branch pipe outside, diameter., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Divide the semi-circle into 6 equal parts as 0-1; 1-2; 2-3;, 3-4; 4-5 & 5-6., Draw vertical lines from these points 1, 2, 3, 4, 5. Already, there will be two vertical lines IG from the points 6 and JH, from point 0. These vertical lines will cut the branch pipe, lines 'GK' and 'KH' at points 6', 5', 4', 3', 2', 1', & 0'. Note, that points 6' and G as points 0' and H are the same, points. In the base line XX' plot 12 points equal to the, distance of '0-1' as 0, 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1, 0., Draw vertical lines to XX' from these 13 points., , Co, , Draw horizontal lines parallel to XX' from points 6', 5', 4', 3',, 2', 1', 0'. These 7 horizontal lines will cut the 13 vertical, lines from the base line at 13 points., Join the 13 cutting points with a regular smooth curve., Now the required development for the 45° branch pipe will, be ready. Give allowance of 3 to 5 mm at the edges of the, development. (Fig 1), For developing a hole in the base pipe: Above the, main pipe, draw 7 lines parallel to AB namely 3, 2, 1, 0, 1,, 2, 3 equal to the distance of 0-1 on the semi circle., , Mark the points C, D, E and F taking the radius and the, length of the given pipe with the centre line AB as reference, line., On the line "CD" locate the position of the 45° branch, pipe. This will be "G"., , Draw vertical lines from 0', 1', 2', 3', 4', 5', 6'. These vertical, lines will intercept the 7 horizontal lines. Join the, intercepting points with a smooth curve. The required, development for hole is now ready., , Draw a 45° angle at the point "G"., Choose a suitable height and mark the height of the branch, pipe (GI) in 45° line from point G., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.42, , 171

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.43, , Manifold system, Objectives: At the end of this lesson you shall be able to, • explain the necessity of the manifold system and its types, • describe the construction of the manifold system, • explain the advantages and disadvantages of the manifold system, • describe the care and maintenance of the manifold system., When large volumes of oxygen and acetylene gas are, required on a temporary or permanent basis for many, welding and cutting operations in a workshop, a manifold, system is most suitable one., Types, , When the demand is even more, many cylinder are coupled, together, and this is called stationary 'MANIFOLD' system., (Fig 2) Separate manifold systems are installed for oxygen, and acetylene. These manifolds usually have two banks, of cylinders. One bank is kept in reserve while the other, one is in use., , – Portable manifold system, – Stationary manifold system, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Portable manifold system means two or three cylinders, are coupled with a suitable apparatus - namely 'PIG TAIL', and connected to a main distribution pipe. (Fig 1) Separate, arrangements are made for oxygen and acetylene gases., , Co, , The use of such manifolds reduces substantially the cost, of handling the cylinders inside the workshop., , 172, , These manifolds are fitted with master regulators which, reduce the cylinder pressure to about 15 kgf/cm2 for feeding, into the distribution pipe to the various consuming points., The consuming points are fitted with an outlet value,, stop-valves and regulators for individual pressure control, at the site for gas welding or cutting operations.

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Fabrication, Welder - Welding Techniques, , Related Theory for Exercise 1.2.44, , Filler rods for gas welding, Objectives: At the end of this lesson you shall be able to, • state the necessity of filler rods and name the different types of filler rods and their sizes, • select filler rods for the jobs to be welded by gas., Filler rod and its necessity: Pieces of wires or rods of, standard diameter and length used as filler metal in the, joint during gas welding process are called filler rods or, welding rods., To obtain best results, high quality filler rods should be, used., The actual cost of welding rods, is very small compared, with cost of job, labour, gases and flux., Good quality filler rods are necessary to:, -, , reduce oxidation (effect of oxygen), , -, , Sizes as per IS: 1278 - 1972), The size of the filler rod is determined from the diameter, as: 1.00, 1.20. 1.60, 2.00, 2.50, 3.15, 4.00, 5.00 and, 6.30mm. For leftward technique filler rods upto 4mm dia., are used. For rightward technique upto 6.3 mm dia. is, used. For C.l welding filler rods of 6mm dia. and above, are used. Length of filler rod:-500mm or 1000mm., Filler rods above 4mm diameter are not used often for, welding of mild steel., The usual size of mild steel filler rods used are 1.6mm, and 3.15mm diameter. All mild steel filler rods are given a, thin layer of copper coating to protect them from oxidation, (rusting) during storage. So these filler rods are called, copper coated mild steel (C.C.M.S) filler rods., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , - Control the mechanical properties of the deposited, metal, , necessary. Each metal requires a suitable filler rod., , Metal caused by fusion., , While welding, a cavity or depression will be formed at the, joints of thin section metals. For heavy/thick plates a, groove is prepared at the joint. This groove is necessary, to get better fusion of the full thickness of the metal, so as, to get a uniform strength at the joint. This groove formed, has to be filled with metal. For this purpose a filler rod is, , All types of filler rods are to be stored in sealed plastic, covers until they are used., , Different types of filler rods used in gas welding, , Co, , Objectives: At the end of this lesson you shall be able to, • define a filler rod, • specify and state the different types of ferrous, non-ferrous and alloy filler rods, • explain the method of selection of filler rod in respect to the metal to be welded., Definition of filler rod: A filler rod is a metallic wire made, out of ferrous or non-ferrous metal to deposit the required, metal in a joint or on the base metal., , The alloy type filler contains iron, carbon, silicon and any, one or many of the following elements such as manganese,, nickel, chromium, molybdenum, etc., , Types of filler rods: The following types of filler rods are, classified in gas welding., , The non-ferrous type filler rod which contains elements of, non-ferrous metals. The composition of non-ferrous type, filler rods is similar to any non-ferrous metal such as, copper, aluminium. A non-ferrous alloy type filler rod, contains metals like copper, aluminium, tin, etc. alongwith, zinc, lead, nickel, manganese, silicon, etc., , – Ferrous filler rod, – Non-Ferrous filler rod, – Alloy type filler rod for ferrous metals, – Alloy type filler rod for non-ferrous metals, A ferrous type filler rod has a major % of iron., The ferrous type filler rod contains iron, carbon, silicon,, sulphur and phosphorous., , Selection of the correct filler rod for a particular job is a, very important step for successful welding. Cutting out a, strip from the material to be welded is not always possible, and even when it is possible, such a strip cannot replace, a recommended welding filler materials. Composition of a, filler metal is chosen with special consideration to the, metallurgical requirement of a weldment. A wrong choice, 173

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due to either ignorance or a false consideration of economy, may lead to costly failures. IS: 1278-1972* specifies, requirements that should be met by filler rods for gas, welding. There is another specification IS: 2927-1975*, which covers brazing alloys. It is strongly recommended, that filler material confirming to these specifications is used., In certain rare cases, it may be necessary to use filler, rods of composition not covered by these specifications;, in such cases filler rods with well established performances, should be used., To select a filler rod in respect to the metal to be welded,, the filler rod must have the same composition with respect, to the base metal to be welded., Factors to be considered for selection of filler rod are:, a. the type and composition of base metal, b. the base metal thickness, c. the type of edge preparation, , e. welding position, , Filler rods should be stored in clean, dry condition to prevent, deterioration., Do not mix different types of filler rods., Ensure that packages and their labels are in order for easy, and correct selection., Where it is not practicable to store filler rods under heated, conditions, an absorbent for moisture such as silico-gel, may be used in the storage area., Ensure the rod is free from contamination such as rust,, scale, oil, grease and moisture., Ensure the rod is reasonably straight to assist manipulation during welding., Each metal requires a suitable filler rod. Refer, to IS : 1278 - 1972 and IS : 2927 - 1975 attached., (Table 1: Filler metals and fluxes for gas, welding.), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , d. the weld is deposited as root run, intermediate runs or, final covering run, , Care and maintenance, , Co, , f. whether there is any corrosion effect or loss of material, from the base metal due to welding., , 174, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.44

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Table 1, Filler metals and fluxes for gas welding, , Filler metal type, , Application, , Flux, , A general purpose rod for welding mild steel where a, minimum butt-weld tensile strength of 35.0 kg/mm2, is required. (Full fusion technique with neutral flame.), , Not required., , Mild steel - Type S-FS2, , Intended for application in which minimum butt-weld, tensile strength of 44.0 kg/mm2 is required. (Full fusion, technique with neutral flame.), , Not required., , Wear-resisting alloy steel, , Building up worn out crossings and other application where, the steel surfaces are subject to extreme wear by shock, and abrasion. (Surface fusion technique with excess, acetylene flame.), , Not required., , 3 percent nickel steel, Type S-FS4, , These rods are intended to be used in repair and, reconditioning parts which have to be subsequently, hardened and tempered. (Full fusion technique with, neutral flame.), , Special flux, (if necessary)., , Stainless steel decay-resistant (nobium bearing), , These rods are intended for use in the welding of corrosionresisting steels such as those containing 18 percent, chromium and 8 percent nickel. (Full fusion technique, with neutral flame.), , Necessary, , High silicon cast ironType S-C11, , Intended for use in the welding of cast iron where an, easily machinable deposit is required. (Full fusion, technique with neutral flame.), , Flux necessary., , For welding of de-oxidized copper. (Full fusion, technique with neutral flame.), , Flux necessary., , For use in the braze welding of copper and mild steel, and for the fusion welding of material of the same or, closely similar composition. (Oxidising flame.), , Flux necessary., , Manganese bronze (high, tensile brass) - Type S-C8, , For use in braze welding of copper, cast iron and malleable, iron and for the fusion welding of materials of the same, or closely similar composition. (Oxidising flame.), , Flux necessary., , Medium nickel bronze - Type, S-C9, , For use in the braze welding of mild steel, cast iron and, malleable iron. (Oxidising flame.), , Flux required., , Aluminium (Pure) - Type, S-C13, , For use in the welding of aluminium grade 1B., (Full fusion technique with neutral flame.), , Flux necessary., , Aluminium alloy-5 percent, silicon - Type S-NG21, , For welding of aluminium casting alloys, except those, containing magnesium, or zinc as the main addition., They may also be used to weld wrought aluminiummagnesium-silicon alloys. (Full fusion technique with, neutral flame.), , Flux necessary., , Aluminium alloy-10-13 percent silicon - Type 5-NG2, , For welding high silicon aluminium alloys. Also, recommended for brazing aluminium. (Neutral flame.), , Flux necessary., , Aluminium alloy-5 percent, copper, , For welding aluminium casting particularly those, containing about 5 percent copper. (Full fusion technique, with neutral flame.), , Flux necessary., , Copper filler rod - Type, S-C1, , Co, , Brass filler rod - Type, S-C6, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Mild steel - Type S-FS1, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.44, , 175

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Filler metal type, , Application, , Flux, , Hard facing of components subjected mainly, to abrasion. (Surface fusion technique with, excess acetylene flame.), , Stellite: Grade 6, , Hard facing of components subjected to shock and abrasion,, (Surface fusion technique with excess acetylene flame.), , -do-, , Stellite: Grade 12, , Hard facing of components subjected to abrasion and, moderate shock. (Surface fusion technique with excess, acetylene flame.), , -do-, , Copper-phosphorus brazing, alloy - Type BA-CuP2, , Brazing copper, brass and bronze components. Brazing, with slightly oxidising flame on copper; neutral flame on, copper alloys., , Necessary, , Copper-phosphorus brazing, alloy - Type BA-CuP5, , For making ductile joint in copper without flux. Also widely, used on copper based alloys of the brass and bronze type in, conjunction with a suitable silver brazing flux. (Flame, slightly oxidising on copper; neutral on copper alloys.), , None for copper., A flux is necessary for brazing, copper alloys., , Silver-copper-zinc (61 percent silver) type brazing, alloys - Type BA-CuP3, , Silver-copper-zinc (61, percent silver) - Type BACu-AG6, , Silver-copper-zinc cadmium, (43 percent silver) - Type, BA-Cu-Ag 16A, , None is usually, required. A cast iron, flux may be used, if, necessary, , Similar to type BA-CuP5 but with a slightly lower tensile, strength and electrical conductivity (flame slightly, oxidising on copper; neutral on copper alloys)., NOTE: Phosphorus bearing silver brazing alloys, should not be used with ferrous metal or alloys of, high nickel content., , None for copper., A flux is necessary for brazing, copper alloys., , This brazing alloy is particularly suitable for joining, electrical components requiring high electrical, conductivity. (Flame neutral), , Flux necessary., , This is a general purpose brazing alloy and is particularly, suitable for joining electrical components requiring high, electrical conductivity. (Flame neutral), , Flux necessary., , Co, , Silver-copper-zinc (43 percent silver) - Type BA-CuAg 16, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Stellite: Grade 1, , An ideal composition for economy in brazing operation, requiring a low temperature, quick and complete, penetration. Suitable on steel, copper, brass, bronze,, copper-nickel alloys and nickel-silver. (Flame neutral), , Flux necessary., , Silver-copper-zinc-cadmium, (50 percent silver) - Type, BA-Cu-Ag 11, , This alloy is also suitable for steel, copper-nickel, alloys and nickel-silvers. (Flame neutral), , Flux necessary., , Silver-copper-zinc-cadmium, nickel (50 percent silver), -Type BA-Cu-Ag 12, , Specially suitable for brazing tungsten carbide tips to, rock drills, milling cutters, cutting and shaping tools;, also suitable for brazing steels which are difficult to, 'wet' such as stainless steels. (Flame neutral), , Flux necessary., , 176, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.44

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Gas Welding Fluxes and Function, Objectives: At the end of this lesson you shall be able to, • explain flux and its function in gas welding, • describe the types of welding fluxes and their storage., Flux is a fusible (easily melted) chemical compound to be, applied before and during welding to prevent unwanted, chemical action during welding and thus making the, welding operation easier., , Seal flux tin lids when storing especially for long periods., (Fig 2), , The function of flux in gas welding: To dissolve oxides, and to prevent impurities and other inclusion that could, affect the weld quality., Fluxes help the flow of their metal into very small gap, between the metals being joined., Fluxes act as cleaning agents to dissolve and remove, oxides and clean the metal for welding from dirt and other, impurities., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Fluxes are available in the form of paste, powder and liquid., The method of application of flux is shown in Fig 1., , Co, , Though the inner envelope of an oxy-acetylene flame offers, protection to the weld metal, it is necessary to use a flux, in most cases. Flux used during welding not only protects, the weldment from oxidation but also from a slag which, floats up and allows clean weld metal, to be deposited., After the completion of welding, flux residues should be, cleaned., Removal of flux residues: After welding or brazing is, over, it is essential to remove the flux residues. Fluxes in, general are chemically active. Therefore, flux residues, if, not properly removed, may lead to corrosion of parent metal, and weld deposit., Some hints for removal of flux residues are given below:, – Aluminium and aluminium alloys - As soon as possible, after welding, wash the joints in warm water and brush, vigorously. When conditions allow, follow up by a rapid, dip in a 5 percent solution of nitric acid; wash again,, using hot water to assist drying., , Storing of fluxes: Where the flux is in the form of a coating, on the filler rod, protect carefully at all times against damage, and dampness. (Fig 2), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.44, , 177

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When containers, such as fuel tanks, have been welded, and parts are inaccessible for the hot water scrubbing, method, use a solution of nitric and hydrofluoric acids., To each 5.0 liters of water add 400 ml of nitric acid, (specific gravity 1.42) followed by 33 ml of hydrofluoric, acid (40 percent strength). The solution used at room, temperature will generally completely remove the flux, residue in 10 minutes, producing a clean uniformly, etched surface, free from stains. Following this treatment, the parts should be rinsed with cold water and finished, with a hot water rinse. The time of immersion in hot, water should not exceed three minutes, otherwise, staining may result; after this washing with hot water, the parts should be dried. It is essential when using, this treatment that rubber gloves be worn by the operator, and the acid solution should preferably be contained in, an aluminium vessel., , – Stainless steel - Treat in boiling 5 percent caustic soda, solution, followed by washing in hot water. Alternatively,, use a de-scaling solution of equal volume of hydrochloric, acid and water to which is added 5 percent of the total, volume of nitric acid with 0.2 percent of total volume of, a suitable restrainer., – Cast iron - Residues may be removed easily by a, chipping hammer or wire brush., – Silver brazing - The flux residue can be easily removed, by soaking brazed components in hot water, followed, by wire brushing. In difficult cases the work piece, should be immersed in 5 to 10 percent sulphuric acid, solution for a period of 2 to 5 minutes, followed by hot, water rinsing and wire brushing., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Magnesium alloys - Wash in water followed quickly by, standard chromating. Acid chromate bath is, recommended., , – Copper and brass - Wash in boiling water followed by, brushing. Where possible, a 2 percent solution of nitric, or sulphuric acid is preferred to help in removing the, glassy slag, followed by a hot water wash., , 178, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.2.44

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Fabrication, Related Theory for Exercise 1.3.45, Welder - Welding of Steel (OAW, 8mAW), Defects in gas welding, Objectives: At the end of this lesson you shall be able to, • name and define various weld defects, • identify the common faults in gas welding., Definition, A fault is an imperfection in the weld which may result in, failure of the welded joint while in service., The following faults occur commonly in gas welding., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Undercut: A groove or channel formed along the toe of the, weld on one side or on both sides. (Fig 1), , Excessive penetration: Depth of fusion at the root of the, grooved joint is more than the required amount. (Fig 4), , Co, , Excessive convexity: Too much weld metal added to the, joint so that there is excessive weld reinforcement. (Fig 2), , Lack of penetration: Required amount of penetration is, not achieved, i.e. fusion does not take place up to the root, of the weld. (Fig 5), , Lack of fusion: If there is no melting of the edges of the, base metal at the root face or on the side face or between, the weld runs, then it is called lack of fusion. (Fig 6), , Overlap: Metal flowing into the surface of the base metal, without fusing it. (Fig 3), , 179

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Porosity: Number of pinholes formed on the surface of, the deposited metal. (Fig 7), , Excessive concavity/insufficient throat thickness:, Enough weld metal is not added to the joint so that there, is insufficient throat thickness. (Fig 11), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Blow-holes: These are similar to pinholes but have a, greater diameter. (Fig 8), , Unfilled crater: A depression formed at the end of the, weld. (Fig 10), , Cracks: A discontinuity in the base metal or weld metal or, both. (Fig 9), , Co, , Burn through: A collapse of the molten pool due to, excessive penetration, resulting in a hole in the weld run., (Fig 12), , 180, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.45

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Weld defects - Causes and remedies, Objectives: At the end of this lesson you shall be able to, • explain the causes of weld defects, • state the remedies to prevent the defects., , Welding defects: Possible causes and remedies, , Possible causes, , Appropriate remedies, , 1, , Fillet weld with, insufficient, throat thickness., , Incorrect angle of filler rod and, blowpipe., , Maintain filler rod and blowpipe, at the appropriate angles., , 2, , Excessive concavity, in butt weld profile., , Excess heat build-up with too, fast a speed of travel or filler, rod too small., , Use the appropriate size nozzle, and filler rod with the correct, speed of travel., , 3, , Excessive penetration., Excess fusion of root, edges., , Angle of slope of nozzle too large., Insufficient forward heat., Flame size and/or velocity too, high. Filler rod too large or too, small. Speed of travel too slow., , Maintain the nozzle at the correct, speed of travel., Select correct nozzle size., Regulate flame velocity correctly., Use correct size of filler rod., , 4, , Burn through., , Excessive penetration has produced, local collapse of weld pool resulting, in a hole in the root run., , Maintain blowpipe at the correct, angles. Check nozzle size, filler rod, size. Travel at the correct speed., , 5, , Undercut along vertical, member of filler, welded Tee joint., , Incorrect angle of tilt used in, blowpipe manipulation., , Maintain blowpipe at the, Correct angle., , 6, , Undercut in both sides, of weld face in butt, joint., , Wrong blowpipe manipulation; incorrect distance from plate surface,, excessive lateral movement., Use of too large a nozzle., , Use correct nozzle size, speed of, travel and lateral blowpipe, manipulation., , 7, , Incomplete root penetration in butt joint, (single vee or double vee)., , Incorrect set up and joint preparation., Use of unsuitable procedure and/or, welding technique., , Ensure joint preparation and set up, are correct. Appropriate procedure, and/or welding technique must be, used., , 8, , Incomplete root penetration in close square, Tee joint., , Incorrect set up and joint preparation., Use of unsuitable procedure and/or, welding technique., , Ensure joint preparation and set up, are correct. Appropriate procedure, and/or welding technique, must be used., , 9, , Lack of root penetration., , Incorrect joint preparation and set up., Gap too small. Vee preparation too, narrow. Root edges touching., , Prepare and set up the joint correctly., , 10 Lack of fusion on root, and side faces of double, Vee butt joint., , Incorrect set up and joint preparation., Use of unsuitable welding, technique., , Ensure the use of correct joint, preparation, set up and welding, technique., , 11 Lack of inter-run, fusion., , Angles of nozzle and blowpipe, manipulation incorrect., , Correct the angles of slope and tilt., Use blowpipe manipulation to control, uniform heat build-up., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Defect, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.45, , 181

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Defect, , Possible causes, , Appropriate remedies, , 12 Weld face cracks in, butt and fillet welds., , Use of incorrect welding procedure., Unbalanced expansion and, contraction stresses., Presence of impurities., Undesirable chilling effects., Use of incorrect filler rod., , Use correct procedure and filler, rod. Ensure uniform heating and, cooling. Check suitability and, surface preparation of material, before welding. Avoid draughts, and use appropriate heat treatment., , 13 Surface porosity and, gaseous intrusions., , Use of incorrect filler rod and, technique. Failure to clean, surfaces before welding., Absorption of gases due to, incorrectly stored fluxes,, unclean filler rod., Atmospheric contamination., , Clean plate surfaces. Use correct, filler rod and technique. Make, sure the flame setting is correct, to avoid gas contamination., , 14 Crater at end of weld, run. Small cracks, may be present., , Neglect to change the angle of, blowpipe, speed of travel or, increase the rate of weld metal, deposition as welding is completed, at the end of the seam., , Reduce the angle of the blowpipe, progressively with speed of travel to, lower the heat input and deposit, and, deposit sufficient metal to maintain, the toe of the weld pool at the, correct level until it has completely, solidified., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Overlap, , 182, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.45

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Fabrication, Related Theory for Exercise 1.3.46, Welder - Welding of Steel (OAW, 8mAW), Arc welding electrodes, Objectives: At the end of this lesson you shall be able to, • explain arc welding electrode, • state the types of electrodes, • explain the coating factor, • describe the characteristics of flux coating on electrode, • explain the functions of flux coating during welding., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Introduction: An electrode is a metallic wire of standard, size and length, generally coated with flux (may be bare, or without flux coating also) used to complete the welding, circuit and provide filler material to the joint by an arc,, maintained between its tip and the work. (Fig 1), , Different types of electrodes used are given in the Electrode, chart., Method of flux coating:, – Dipping, , – Cellulosic (Pipe welding electrode e.g. E6010), – Rutile (General purpose electrode e.g. E6013), , Co, , – Extrusion, , Types of flux coating, , Dipping method: The core wire is dipped in a container, carrying flux paste. The coating obtained on the core wire, is not uniform resulting in non-uniform melting; hence this, method is not popular., Extrusion method: A straightened wire is fed into an, extrusion press where the coating is applied under, pressure. The coating thus obtained on the core wire is, uniform and concentric, resulting in uniform melting of the, electrode. (Fig 2) This method is used by all the electrode, manufacturers., Coating factor (Fig 3): The ratio of the coating diameter, to the core wire diameter is called the coating factor., It is 1.25 to 1.3 for light coated,, 1.4 to 1.5 for medium coated,, , 1.6 to 2.2 for heavy coated, and above 2.2 for super heavy, coated electrodes., , – Iron powder (e.g. E7018), – Basic coated (Low hydrogen electrode e.g. E7018), Cellulosic electrode: Cellulosic electrode coatings are, mainly made of materials containing cellulose, such as, wood pulp and flour. The coating on these electrodes is, very thin and the slag is difficult to remove from deposited, welds. The coating produces high levels of hydrogen and, is therefore not suitable for high-strength steels. This type, of electrode is usually used on DC+ and suited to root, pass welding of high pressure pipes., Rutile electrodes: Rutile electrodes, are general-purpose, electrodes have coatings based on titanium dioxide. These, electrodes are widely used in the fabrication industry as, they produce acceptable weld shape and the slag on, deposited welds is easily removed. Strength of deposited, welds is acceptable for most low-carbon steels and the, majority of the electrodes in this group are suitable for, general purpose fabrication., , 183

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Basic or hydrogen-controlled electrodes: Basic or, hydrogen controlled electrode coatings are based on, calcium fluoride or calcium carbonate. This type of, electrode is suitable for welding high-strength steels, without weld cracks and the coating have to be dried. This, drying is achieved by backing at 450°C holding at 300°C, and storing at 150°C until the time of use. By maintaining, these conditions it is possible to achieve high strength, weld deposits on carbon, carbon manganese and low, alloyed steels. Most electrodes in this group deposit welds, with easily removable slags, producing acceptable weld, shape in all positions. Fumes given off by this electrode, are greater than with other types of electrodes., , Iron powder electrodes: Iron powder electrodes get their, name from the addition of iron powders to the coating which, tend to increase efficiency of the electrode. For example,, if the electrode efficiency is 120%, 100% is obtained from, the core wire and 20% from the coating. Deposited welds, are very smooth with an easily removable slag; welding, positions are limited to horizontal, vertical fillet welds and, flat or gravity position fillet and butt welds., , Composition/Characteristics Flux, Composition/characteristics flux: The coating of the, welding electrodes consists of a mixture of the following, substances., , – ferro-manganese, – ferro-silicon, – ferro-titanium., , Purpose or function of flux coating: During welding,, with the heat of the arc, the electrode coating melts and, performs the following functions., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Alloying substances: These substances compensate for, the burning of manganese, ferro-silicon. The alloying, substances are:, , These are: sodium and potassium silicates., , – It stabilizes the arc., , – It forms a gaseous shield around the arc which protects, the molten weld pool from atmospheric contamination., – It compensates the losses of certain elements which, are burnt out during welding., , Arc stabilizing substances: These are carbonates known, as chalk and marble. These are used for the stabilisation, of the arc., , Co, , Deoxidizers: These substances prevent porosity and, make the welds stronger. The deoxidising substances are, iron oxide, lamitite, magnetite., , Slag forming substances: These substances melt and, float over the molten metal and protect the hot deposited, weld metal from the atmospheric oxygen and nitrogen., Also due to the slag covering, the weld metal is prevented, from fast cooling. The slag forming substances are clay,, limestone., , – It retards the rate of cooling of the deposited metal by, covering with slags and improves its mechanical, properties., – It helps to give good appearance to the weld and, controls penetration., – It makes the welding in all positions easy., – Both AC and DC can be used for the welding., – Removes oxide, scale etc. and cleans the surfaces to, be welded., – It increases metal deposition rate by melting the, additional iron powder available in the flux coating., Types of electrodes for ferrous and alloy metals, , Fluxing/cleaning substances: These substances remove, oxides from the edges to be welded and controls the fluidity, of the molten metal. The cleaning substances are lime, stone, chlorides, fluorides., , Mild steel electrode: Mild steel is characterized by carbon, content not exceeding 0.3%. Mild steel electrode core, wire contains various alloying elements., , Gas forming substances: These substances form gases, which aid the transfer of metal. They also shield the welding, arc and weld pool. The substances are: wood flour dixtorine, and cellulose., , Carbon 0.1 to 0.3%, (Strengthening agent), , Binding and plasticizing substances: These substances help the applied coating to grip firmly around the, core wire of the electrode., , Silicon above 0.5%, (Deoxidizes, prevents weld metal porosity.), , 184, , Keep carbon as low as possible., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46

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Manganese 1.65%, (Increases strength and hardness.), Nickel, (Increases strength and notch toughness.), Chromium, (Increases tensile strength and hardness. Lowers the, ductility.), Molybdenum 0.5%, (Increases hardness and strength.), Indian Standard System laid down in IS:814-1991 a, classification and coding of covered electrodes for metal, arc welding of mild steel, and low alloy high tensile steel., Mild steel and low alloy high tensile steel electrodes are, classified into seven recognised groups, depending upon, the chemical composition of the flux coating., , Stainless steel electrodes: Selecting proper electrodes, depends primarily on the composition of the base metal, to be welded., These electrodes are available with either lime or titanium, coatings. The lime coated electrode is used only with DC, reverse polarity. Titanium coated electrodes can be used, in AC and DC reverse polarity, and will produce smoother, and stable arc., The coding system for stainless steel electrodes differs, somewhat from that for the M.S. electrode. The I.S., 5206-1969 specification for corrosion-resisting chromium, and chromium-nickel steel covered electrodes will give full, details., During welding, the electrode will tend to get red hot quickly., To avoid this, a 20 to 30% lower current than what is used, for ordinary M.S. electrode is recommended., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Sizes of Mild Steel Electrodes, , Objectives: At the end of this lesson you shall be able to, • state the size, length and current setting of M.S. electrodes, • explain the functions of electrode, • state the BIS coding for M.S. electrode., The electrode size refers to the diameter of its core wire., Each electrode has a certain current range. The welding, current increases with the electrode size (diameter)., , Metric, 1.6mm, 2.0mm, 2.5mm, 3.15mm, 4.0mm, 5.0mm, 6.0mm, 6.3mm, 8.0mm, 10.0mm, , – The core wire conducts the electric current from the, electrode holder to the base metal through the arc., – It deposits weld metal across the arc onto the base, metal., , Co, , Electrode sizes, , Functions of an electrode in shielded metal arc, welding: The two main functions of an electrode in SMAW, are: (Fig 1), , Standard length of electrodes: The electrodes are, manufactured in two different lengths, 350 or 450mm., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 185

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The flux covering melts at a slower rate than the metal, core and a cup is formed at the tip of the electrode which, helps to direct the molten metal to the required spot., For easy identification and selection of a suitable arc, welding electrode for welding mild steel plates, the, electrodes are coded by Bureau of Indian Standards (B.I.S)., According to this B.I.S., the electrodes to be used for, welding mild steel for training a beginner is coded as, ER4211., Types of electrodes: Electric arc welding electrodes are, of three general types. They are:, Flux coated electrodes are used in the manual metal arc, welding process for welding ferrous and non-ferrous metals., (Fig 4), , Carbon electrodes, Bare electrodes, Flux coated electrodes, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Carbon electrodes are used in the carbon arc welding, process (Fig 2). The arc is created between the carbon, electrode and the job. The arc melts a small pool in the, job and filler metal is added by using a separate rod., , The composition of the coating provides the flux, the, protective shield around the arc and a protective slag which, forms over the deposited weld metal during cooling., , Co, , Normally the carbon arc has very little use of welding. Its, main application is in cutting and gouging operations., , Bare electrodes are also used in some arc welding, processes (Fig 3). An inert gas is used to shield the molten, weld metal and prevent it from absorbing oxygen and, nitrogen. Filler metal is separately added through a filler, rod. Usually tungsten is used as one of the bare wire, electrode. In Co2 welding and submerged arc welding, processes the mild steel bare wire electrode is also used, as a filler wire., , 186, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46

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Chart, Types of Arc welding and cutting/gouging electrodes, Consumable electrode, Coated electrode, , Non consumable electrode, , Barewire electrode, , Carbon electrode, , Barewire metal electrode, , Copper coated mild steel, Factors, , Methods of flux, coating, , Solid, , Flux cored, , Tungsten, , Dipping process, Welding, , Cutting, , Extrusion process, Light coated, Medium coated, , Thoriated tungsten, , Zirconium based, tungsten, , Heavy coated, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Coating flux, , Pure tungsten, , Super heavy coated, Cellulosic coated, Rutile coated, Type of flux, coating, , Iron powder coated, Basic coated, , Shallow penetration, , Purpose of flux, coating, , Co, , Deep penetration, , All positive welding, , Flat/downhand position only, Hard facing, Gouging, , Mild steel, Ferrous, , Alloy steel, Stainless steel, Cast iron, , Core wire, material, , Non ferrous, , Phosphor bronze, Nickel alloy, , Hard facing, , Aluminium, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 187

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Coding of Electrodes as per BIS, AWS and BS, Objectives: At the end of this lesson you shall be able to, • explain the necessity of coding electrodes, • describe the electrode coding as per BIS, AWS and BS., Necessity of coding electrodes: Electrodes with different, flux covering gives different properties to the weld metal., Also electrodes are manufactured suitable for welding with, AC or DC machines and in different positions. These, conditions and properties of the weld metal can be, interpreted by the coding of electrodes as per Indian, Standards., The chart shown at the end of this lesson gives the, specification of a particular electrode and also shows what, each digit and letter in the code represents. By referring, to this chart any one can know whether an electrode with, a given specification can be used for welding a particular, job or not., , Different standards used in coding of electrodes, They are:, 1 I.S. (814 - 1991), 2 A.W.S., 3 B.S., INDIAN SYSTEM OF CODING OF ELECTRODES, ACCORDING TO IS: 814-1991, Type of covering: The type of covering shall be indicated, by the following letters., A, , -, , Acid, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Classification of electrodes shall be indicated by the IS:, 814-1991 coding system of letters and numerals to indicate, the specified properties or characteristics of the electrode., , c) letter 'X' indicating the radiographic quality., , Main coding: It consists of the following letters and, numerals and shall be followed in the order stated:, a) a prefix letter 'E' shall indicate a covered electrode for, manual metal arc welding, manufactured by extrusion, process;, , B, , -, , Basic, , C, , -, , Cellulosic, , R, , -, , Rutile, , RR, , -, , Rutile, heavy coated, , S, , -, , Any other type not mentioned above, , b) a letter indicating the type of covering;, , c) first digit indicating the ultimate tensile strength in, combination with the yield stress of the weld metal, deposit;, , Co, , d) second digit indicating the percentage elongation in, combination with the impact values of the weld metal, deposited;, e) third digit indicating welding position(s) in which the, electrode may be used and, , f) fourth digit indicating the current condition in which the, electrode is to be used., , Additional coding: The following letters indicating the, additional properties of the electrodes may be used, if, required:, a) letters H 1, H2, H 3 indicating hydrogen controlled, electrodes., b) letters J, K and L indicating increased metal recovery, as 'Effective Electrode Efficiency' as per IS: 13043:91., , Strength characteristics: The combination of the ultimate, tensile strength and the yield strength of the weld metal, deposited shall be indicated by the digits 4 and 5., (See Table 1), TABLE 1, , Designation of strength characteristics, (Clauses 5.2 and 5.3), , Designating, digit, , Ultimate tensile, strength, N/mm2, , Yield strength, Min, N/mm2, , 4, 5, , 410-510, 510-610, , 330, 360, , Elongation and impact properties: The combination of, percentage elongation and impact properties of all weld, metal deposited for the two tensile ranges (See Table 1), shall be as given in Table 2., , J = 110 - 129 percent;, K = 130 - 149 percent; and, L = 150 percent and above., , 188, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46

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TABLE 2, Combination of percentage elongation and impact, strength, (Clause 5.3), Designation, digit, , Percentage elongation (Min) on, 5.65/So, , Impact strength, in joules, (Min)/at °C, , (For tensile range 410-510 N/mm2), 0, 1, 2, 3, 4, , No elongation and impact requirements, 20, 47J/+27°C, 22, 47J/+0°C, 24, 47J/-20°C, 24, 27J/-30°C, , For the purpose of coating an electrode, for any of the, current conditions under 5.5 shall be size 4 mm or 5 mm, and shall be capable of being operated at the condition, satisfactorily within the current range recommended by, the manufacturer., Hydrogen controlled electrodes: The letters H1, H2 and, H3 shall be included in the classification as a suffix for, those electrodes which will give diffusible hydrogen per, 100 gm when determined in accordance with the reference, method given in IS:1806:1986 as given below., H1 - up to 15 ml diffusible hydrogen, H2 - up to 10 ml diffusible hydrogen, H3 - up to 5 ml diffusible hydrogen, TABLE 3, Welding current and voltage conditions, (Clause 5.5), , (For tensile range 510-610 N/mm2), , Digit, , No elongation and impact requirements, 18, 47J/+27°C, 18, 47J/+0°C, 20, 47J/-20°C, 20, 27J/-30°C, 20, 27J/-40°C, 20, 27J/-46°C, , Welding position: The welding position or positions on, which the electrodes can be used as recommended by, the manufacturer shall be indicated by the appropriate, designating digits as follows., 1 All positions, , Direct current: recommended Alternating, electrode polarity, current: open, circuit voltage,, V, Min, , 0, , –, , 1, 2, 3, 4, 5, 6, 7, 8, 9, , + or –, –, +, + or –, –, +, + or –, –, +, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , 0, 1, 2, 3, 4, 5, 6, , 2 All positions except vertical down, , Co, , 3 Flat butt weld, flat fillet weld and horizontal/vertical fillet, weld, 4 Flat butt weld and flat fillet weld, , 5 Vertical down, flat butt, flat fillet and horizontal and, vertical fillet weld, 6 Any other position or combination of positions nit, classified above, Where an electrode is coded as suitable for vertical and, overhead position it may be considered that sizes larger, than 4 mm are not normally used for welding in these, positions., An electrode shall not be coated as suitable for particular, welding position unless it is possible to use it satisfactorily, in the position to comply with test requirements of this, code., Welding current and voltage conditions: The welding, current and open circuit voltage conditions on which the, electrodes can be operated as recommended by the, manufacturer shall be indicated by the appropriate, designating digits as given in Table 3., , Not, recommended, 50, 50, 50, 70, 70, 70, 90, 90, 90, , 1 Symbol 0 reserved for electrodes used exclusively on, direct current,, 2 Positive polarity +, Negative polarity –., The frequency of the alternating current is, assumed to be 50 or 60 Hz. The open circuit, voltage necessary when electrode are used on, direct current is closely related to the dynamic, characteristics of the welding power source., Consequently no indication of the minimum, open circuit voltage for direct current is given., , Increased metal recovery: The letters J, K and L shall, be included in the classification as a suffix for those, electrodes which have appreciable quantities of metal, powder in their coating and give increased metal recovery, with respect to that of core wire melted, in accordance to, the range given in 5.0.2 (b)., The metal recovery shall be determined as 'Effective, Electrode Efficiency (EE) as per the method given in, IS 13043:1991., Radiographic quality electrodes: The letter 'X' shall be, included in the classification as a suffix for those electrodes, which deposit radiographic quality welds., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 189

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Example 1, The classification for the electrode EB 5426H1JX, E, , B, , 5, , 4, , 2, , 6, , H1, , Covered electrode, Type of covering (Basic), Strength characteristics (UTS = 510–610 N/mm2 and, YS = 360 N/mm2 min.), Elongation and impact properties (Elongation = 20% min. and, IMPACT = 27 J min. at – 30°C), Welding position (all positions except vertical down), Welding current and voltage condition (D + and A 70), Hydrogen controlled electrodes (15 ml max.), Increased metal recovery (110 – 129%), , Example 2, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Radiographic quality electrode, , The classification for the electrode ER 4211, E, , Covered electrode, Type of covering (Rutile), , R, , 4, , 2, , 1, , 1, , Co, , Strength characteristics (UTS = 410 – 510 N/mm2, and YS = 330 N/mm2 min.), , Elongation and impact properties (Eongation = 22% min. and, impact = 47 J min. at 0°C), Welding position (all positions), , Welding current and voltage conditions (D ± and A 50), , 190, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , J, , X

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AWS codification of carbon and low alloy steel coated, electrodes, , The first two digit indicated tensile strength and yield stress., The next two digits indicate elongation and impact strength., , Chart - 1 shows details of AWS coding of an electrode., In the chart, E stands for electrode. It means that it is a, stick electrode., The first two digits are very important. They designate the, minimum tensile strength of the weld metal that the, electrode will produce., , The letter after the first 4 digits indicates the type of, covering., The first 3 digits after the letter indicating the type of covering, shows electrode efficiency., The fourth digit after the letter indicating type of covering, shows the welding position., , The third digit indicates the welding positions., The last digit the code indicates the kind of flux coating, used., BS codification of carbon steel and low alloy steel, covered electrodes (BS 639 : 1976 equivalent to ISO, 2560), , The fifth digit after the letter indicating type of covering, indicates current and voltage., In the case of rutile covered electrodes, the digits indicating, the electrode efficiency after the letter indicating type of, covering will not be given as shown in chart 1., Chart 2 shows an electrode coding with electrode efficiency., , As shown chart 2, E stands for covered MMA electrodes., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , CHART 1, , AWS CODIFICATION OF CARBON STEEL AND LOW-ALLOY STEEL COATED ELECTRODES, Electrode, , E, , First, digit, , Second, digit, , Co, , First two digits indicate, tensile strength of the, deposited weld metal, in 1000 PSI, , Third digit indicates, the welding, positions for electrodes., 1 All position, 2 Flat & horizontal, 3 Flat & down hand, , Third, digit, , Fourth, digit, , Fourth digit (0 to 8) indicate, the type of flux coating., 0 Cellulose sodium, or iron oxide mineral, 1 Cellulose potassium, 2 Titania sodium, 3 Titania potassium, 4 Iron powder titania, 5 Low hydrogen lime - sodium, 6 Low hydrogen lime - potassium, 7 Iron oxide plus iron powder, 8 Low hydrogen lime plus iron powder, 9 A number left over for peculiar coating., This number is rarely used., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 191

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FOUR DIGITS CODIFICATION, EXAMPLE : AWS – E 6013., , W, , E, , Tensile strength, 60,000 psi, , W, , 6, 0, , All position, electrode, , W, , 1, , Titania potassium, , W, , 3, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Electrode, , FIVE DIGITS CODIFICATION, , Electrode, , Co, , Tensile strength, 110,000 psi., , All position, electrode, , Low hydrogen lime, plus iron powder, , W, , W, , E, 1, 1, 0, , W, , 1, , W, , 8, , *To get the tensile strength of the weld in p.s.i., the number given, here should be multiplied by 1000., , 192, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46

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CHART 2 (BS 639 : 1976 equivalent to ISO 2560), COVERING 4, A, AR, B, C, O, R, RR, S, , STRENGTH 2, Electrode, designation, , Tensile, strength, N/mm2, , E43, E51, , Minimum yield, stress. N/mm2, , 430.550, 510.650, , Example (b), , Acid (iron oxide), Acid (rutile), Basic, Cellulosic, Oxidising, Rutile (medium coated), Rutile (heavy coated), Other types, , ELECTRODE, EFFICIENCY, 5, % recovery, to nearest, 10% (> 110), (H) 8, Indicates, hydrogen, controlled, (> 15mg/100g), , 330, 360, , E, , 51, , 33, , B, , 160, , 2, , 0, , (H), , 1, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , PROCESS, 1, Covered, MMA, electrode, , ELONGATION 3, First, Digit, , Minimum, elongation, %, , 0, 1, 2, 3, 4, 5, , Temperature for, impact value of, , CURRENT / VOLTAGE 7, , 28J, °C, , Co, , E43 E51, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , WELDING POSITION 6, 1, All positions, 2, All positions except vertical down, 3, Flat and, for fillet welds, horizontal vertical, 4, Flat, 5, Flat, vertical down and, flat fillet welds, horizontal, vertical, 6, Any position or combination of positions not, classified above., , Not specified, 20, 18, 22, 18, 24, 20, 24, 20, 24, 20, , Not specified, +20, 0, -20, -30, -40, , Code, , IMPACT 3, Second Minimum, Digit, , 0, 1, 2, 3, 4, 6, , Impact properties, , elongation, % Impact value, J, , Tempera-, , E43, , ture °C, , E51 E43, , Not specified, 22, 22, 22, 22, 22, 22, Not, 18, relevant 18, , E51, , Not specified, 47, 47, 47, 47, 47, 47, Not, 41, relevant 47, , +20, 0, -20, -30, -50, , Direct current, , Alternating current, , Recommended, electrode, polarity, , Minimum open, circuit voltage,, V., Not suitable, for use on A C, , 0, , Polarity as, recommended, by manufacturer, , 1, 2, 3, , + or +, , 50, 50, 50, , 4, 5, 6, , + or +, , 70, 70, 70, , 7, 8, 9, , + or +, , 90, 90, 90, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 193

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Example (1), , Covered electrode for manual metal arc welding having a rutile covering of medium thickness and depositing, weld metal with the following minimum mechanical properties. (BS 639), , Tensile Strength : 500 N/mm2, Elongation: 23 %, Impact strength: 71 J at + 20°C, 37 J at 0°C, 20 J at -20°C., It may be used for welding in all positions. It welds satisfactorily on alternating current with a minimum open-circuit, voltage of 50 V and on direct current with positive polarity., The complete classification for the electrode would therefore, , E, , 43, , 21, , R, , 1, , 3, , and the compulsory part would be E 43 21R 13., Covered electrode for manual metal arc welding, Tensile strength, Elongation and impact strength, Covering, Welding positions, , Example (2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Current and voltage, An electrode for manual metal arc welding having a basic covering, with a high efficiency and depositing, weld metal containing 8 ml of diffusible hydrogen per 100 g of deposited weld metal with the following, minimum mechanical properties., , Yield stress: 380 N/mm2, Tensile strength: 560 N/mm2, Elongation: 22%, Impact strength: 47 J at -20°C, Nominal efficiency: 158%, , }, , Also a minimum elongation of 20%, , with an impact value of 28 J at -20°C, , Co, , It may be used for welding in all positions except vertical down, direct current only., The complete classification for the electrode would, therefore, be, , E, , 51, , 33, , B, , 160, , and the compulsory part would be E 51 33 B 16020(H), Covered electrode for manual metal arc welding, Tensile strength and yield stress, Elongation and impact strength, Covering, Efficiency, Welding positions, Current and voltage, Hydrogen controlled, , 194, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.46, , 2, , 0, , (H)

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Fabrication, Related Theory for Exercise 1.3.47, Welder - Welding of Steel (OAW, 8mAW), Effects of moisture pick up storage and baking of electrodes, Objectives: At the end of this lesson you shall be able to, • explain about special purpose electrodes and their application, • state the necessity of baking a coated electrode, • store and handle the electrode properly for better weld quality., Storage of electrodes: The efficiency of an electrode is, affected if the covering becomes damp., , Electrode coating can pick up moisture if exposed to, atmosphere., , – Keep electrodes in unopened packets in a dry store., , Baking electrodes: Water in electrode covering is a, potential source of hydrogen in the deposited metal and, thus may cause:, , – Place packages on a duckboard or pallet, not directly, on the floor., – Store so that air can circulate around and through the, stack., – Do not allow packages to be in contact with walls or, other wet surfaces., , – Cracking in the weld., Indications of electrodes affected by moisture are:, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – The temperature of the store should be about 5°C higher, than the outside shade temperature to prevent, condensation of moisture., , – Porosity in the weld, , – Free air circulation in the store is as important as, heating. Avoid wide fluctuations in the store, temperature., − Where electrodes cannot be stored in ideal conditions, place a moisture-absorbent material (e.g. silica-gel), inside each storage container., Store and keep the electrodes (air tight) in a dry place., , Co, , Bake the moisture affected/prone electrodes in an electrode, drying oven at 110-150°C for one hour before using., (Fig 1)., , – White layer on covering., – Swelling of covering during welding., – Disintegration of covering during welding., – Excessive spatter, , – Excessive rusting of the core wire., Electrodes affected by moisture may be baked before use, by putting them in a controlled drying oven for approximately, one hour at a temperature around 110 - 150°C. This should, not be done without reference to the conditions laid down, by the manufacturer. It is important that hydrogen controlled, electrodes are stored in dry, heated conditions at all times., Warning: Special drying procedures apply to, hydrogen controlled electrodes. Follow the, manufacturer’s instructions., , Remember a moisture-affected electrode:, – has rusty stub end, – has white powder appearance in coating, – produces porous weld., Always pick up the right electrode that will, provide:, – good arc stability, , E, , – smooth weld bead, – fast deposition, – minimum spatters, – maximum weld strength, – easy slag removal., 195

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Special purpose electrodes and their applications, Objectives: At the end of this lesson you shall be able to, • state the types of special purpose electrodes, • explain the applications of special purpose electrodes., – Deep penetration electrodes, – Contact electrodes or iron powder electrodes, – Cutting and gouging electrodes, – Underwater welding and cutting electrodes, – Low hydrogen electrodes, Deep penetration electrodes: These electrodes are used, to get deep penetration in the joints. Deep penetration, occurs because of the very strong stream of gas produced, by the burning of the cellulosic materials in the flux coating., Butt joints on heavy sections are welded without edge, preparation using these electrodes., , Underwater welding and cutting electrodes: These, electrodes are used to cut and weld metals under the, water. The coating having an external coating of varnish, by 'lacquer' polishing or 'celluloid' helps to insulate and, protect the electrode when immersed in water for welding, or cutting purpose., Low hydrogen electrodes: hydrogen controlled, electrodes shall be such that the diffusible hydrogen content, of the deposited metal will be low. This electrode is used, with DC reverse polarity and can be used in all welding, positions. These electrodes help to get a weld without, cracks., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The depth of the penetration will be more than to the core, wire diameter of the electrode used., , Cutting and gouging electrodes: The cutting electrodes, are of a tubular type. While cutting, air is sent through the, centre at high pressure to cut ferrous metals. The gouging, electrode can make 'U' grooves on the ferrous metals., , Co, , Contact electrodes (Iron powder): These electrodes, contain a large amount of iron powder in their coatings., Therefore the arc ignites very easily. These electrodes are, also called 'touch type' electrode. While using this type of, electrode a large amount of weld metal is deposited per, unit time., , 196, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.47

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Fabrication, Related Theory for Exercise 1.3.48, Welder - Welding of Steel (OAW, 8mAW), Weldability of metals, Objective: At the end of this lesson you shall be able to, • explain the effects of weldable quality on ferrous and non-ferrous metals., Weldability:, , Weldability of copper:, , •, , The ferrite and Martin site structure on carbon steels, are not suitable for welding. But, the crystal fine, structure enables brazing., , 99.9% pure copper with 0.01 to 0.08% oxygen in the form, of cuprous oxide is known as electrolyte copper and this, is not weldable., , •, , Austenitic steels are suitable for welding. In present, days all types of steels are welded using inert gas, shielded arc process., , A small quantity of phosphorous added to electrolyte, copper to de-oxidise, so as to make it weldable., , Weldability of cast Iron:, , Once the metal is cooled after welding, to reduce the grain, size and locked up stresses, the pressuring is done., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Cast Iron is welded after performing preheating to a, temperature of 200°C-210°C. On completion of first layer, of welding, the same preheating is repeated to maintain, the re-inforcement of weld. Next, the whole job is evenly, heated. This is called post-heating., , The surface of the base metal is preheated to a fairly high, temperature resulting in peacock neck blue colour; before, the actual welding started., , Co, , The job is cooled slowly, by covering under a heap of lime, or ash or dry sand., , 197

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Fabrication, Related Theory for Exercise 1.3.49, Welder - Welding of Steel (OAW, 8mAW), Importances of preheating, post-heating and maintenance of inter-pass, temperature, Objectives: At the end of this lesson you shall be able to, • state the purpose of preheating, • explain the method of preheating, • describe the types of preheating, • explain the purpose of post-heating a bigger job, • describe the maintenance of inter-pass temperature., Preheating: Heating the job before welding operation is, known as 'preheating'. The purpose of preheating of the, cast iron job is to reduce cracking due to distortion. The, rate of cooling, and gas consumption etc. are also reduced., , METHODS OF PREHEATING, , Local preheating: In this type, the preheating is done, only at the portion to be welded. This is usually done by, playing the blowpipe flame just before starting the welding., (Fig 2) In case of welding a cracked cast iron wheel, preheat, the area opposite to the area crack. (Fig 3), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Small casting jobs may be preheated by the application, of a blowpipe flame. But larger jobs should be preheated, in a 'gas-furnace' or by means of a temporary charcoal, furnace., , Full preheating: The process of heating the entire job, before commencing the welding operation is known as full, preheating. This is usually done in a furnace for heavy, jobs. In this type of preheating the heat of the job will be, retained during welding, and also it will cool down at a, uniform rate., , Co, , Preheating methods depend upon the size of the job and, the technique used for welding. Preheating can be done in, a temporarily built gas or charcoal furnace (Fig 1), blacksmith's forge and even by the oxy-acetylene flame., Heavy jobs can be preheated from the furnace and small, jobs by a flame from a blowpipe or from the forge., , TYPES OF PREHEATING, The type of preheating depends on the size and nature of, the job. There are three types of preheating., , – Full preheating, – Local preheating, – Indirect preheating, 198, , Indirect preheating: In this type, the preheating is being, done on the area which may be affected by the uneven, expansion and contracting due to the welding heat but not, on the portion to be welded. This also can be done by the, application of a blowpipe flame before commencing the, weld. (Fig 4)

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The slag and oxide on the surface of the finished weld can, be removed by scraping and brushing with a wire-brush, after cooling. The weld should not be hammered as cast, iron is brittle., Maintenance of inter-pass temperature: The, temperature of the preheated job can be checked by wax, crayons. Marks are made on the cold job pieces by these, crayons before preheating and after the job pieces reach, the preheating temperature the marks will disappear., This indicates that the job has been heated to the required, preheating temperature. Different wax crayons are available, for checking different temperatures. The temperature which, is checked by the crayon will be marked on it., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Purpose of post heating: If it is a bigger job, the welded, job should be post heated in the same preheating furnace, and allowed to cool slowly in the furnace itself so as to, avoid any crack or any other distortion due to rapid cooling., (Fig 5), , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.49, , 199

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Fabrication, Related Theory for Exercise 1.3.50, Welder - Welding of Steel (OAW, 8mAW), Classification of steels, Objectives: At the end of this lesson you shall be able to, • state the main classification of steels, • explain the effect of carbon content in steel, • describe the uses of various types of carbon steel., Classification of steel: The classification of steel is mainly, based on the chemical composition of various elements, like traces of sulphur, phosphorus, silicon, manganese, with a percentage of less than 1% carbon content in steel., Thus, the steel is classified as follows,, 1) Carbon steel, , Carbon: Carbon is a very important constituent of steel., The addition of carbon at varying proportions modifies the, characteristics of iron and makes it harder, stronger and, of greater use in the engineering industry. Slight variations, in the carbon content of steel lead to great differences in, the properties of steel. Depending upon the properties it is, put to different uses. (Table 1), , 2) Alloy steel, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Effects of carbon content in steel: Steel can be defined, as an alloy of carbon and iron, in which carbon is in a, combined state. The carbon content is a very important, factor to get the desired properties of steel., , TABLE 1, , Group, , Carbon content %, , Examples of uses, , Wrought iron, , Wrought iron, , Less than 0.05, , Chain for lifting tackle, crane hooks,, architectural iron work., , Dead mild steel, , Plain carbon steel, , 0.1 to 0.15, , Sheet for pressing out such shapes as motor car, body panels. Thin wire, rod, and drawn tubes., , Mild steel, , Plain carbon steel, , 0.15 to 0.3, , General purpose workshop bars, boiler plates,, girders., , Medium carbon, steel, , Plain carbon steel, , 0.3 to 0.5, 0.5 to 0.8, , Crankshaft forgings, axles., Leaf springs, cold chisels., , High carbon, steel, , Plain carbon, steel, , 0.8 to 1.0, 1.0 to 1.2, 1.2 to 1.4, , Coil springs, chisels used in woodwork., Files, drills, taps and dies., Fine edge tools (knives etc)., , 200, , Co, , Name

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Ferrite is a very weak solid solution of carbon and iron, with about 0.006% carbon. This is a very soft and ductile, constituent. (Fig 1) Pearlite contains alternate layers of, ferrite and cementite. This laminated structure makes, pearlite stronger. As the carbon content increases, the, pearlitic structure formation is also increased, and this, increases the tensile strength and hardness., , It may be noted from the figure that addition of carbon, beyond 0.83% cementite will not exist in the combined, form but appear around the crystal boundaries. Carbon,, existing in this form, reduces in tensile strength and ductility, but the hardness continues to increase even beyond 0.83%, of carbon., It may be said that plain steel will have a maximum strength, at 0.83% carbon - i.e. when the constituent of steel is fully, pearlite., Addition beyond 0.83% reduces its strength and ductility., Hardness of carbon of plain carbon steel increases, proportionately even beyond 0.83% carbon content., At room temperature in the annealed condition plain carbon, steel contains three main constituents., – Ferrite, – Cementite, , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Pearlite, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.50, , 201

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Fabrication, Related Theory for Exercise 1.3.51, Welder - Welding of Steel (OAW, 8mAW), Welding of low carbon steel, medium and high carbon steel, Objectives: At the end of this lesson you shall be able to, • state the composition of carbon percentage in low carbon steel and medium carbon steel, • state the type of flame needed for welding low carbon steel, • describe the method of welding low carbon steel, • explain the procedure for the welding of medium carbon steel., A plain carbon steel is one in which carbon is the only, alloying element. The amount of carbon in the steel controls, its hardness, strength and ductility. The higher the carbon, the lesser the ductility of the steel., Carbon steels are classified according to the percentage, of carbon they contain. They are referred to as low, medium, and high carbon steels., , Application of flux: No flux is required, After treatment: Most of them do not respond to any heat, treatment process. Therefore except cleaning no post-heat, treatment is required., Medium carbon steel: These steel have a carbon range, from 0.30 to 0.6 percent. They are strong and hard but, cannot be welded as easily as low carbon steels due to, the higher carbon content. They can be heat treated. It, needs greater care to prevent formation of cracks around, the weld area, or gas pockets in the bead, all of which, weaken the weld., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Low carbon steels: Steels with a range of 0.05 to 0.30, per cent are called low carbon steel or mild steel. Steels, in this class are tough, ductile and easily machineable, and quite easy to weld., , Type of flame: Neutral flame to be used., , Welding technique: Up to 6 mm, leftward technique is a, suitable one. Above 6 mm rightward technique is preferable., Preparation: (Refer Fig 1 given below), , Welding procedure: Most medium carbon steels can, be welded in the same way as mild steel successfully, without too much difficulty but the metal should be, preheated slightly to 160°C to 320°C (to dull red hot). After, completion of welding, the metal requires post-heating to, the same preheating temperature, and allowed to cool, slowly., , Co, , After cooling, the weld is to be cleaned and inspected for, surface defects and alignment., Plate edge preparation: Fig 1 shows the plate edge, preparation depending on the thickness of the material to, be welded., High carbon steel: High carbon steels contain 0.6% to, 1.2% carbon. This type of steel is not weldable by gas, welding process because it is difficult to avoid cracking of, base metal and the weld., Welding procedure, The type of edge preparation, nozzle size, filler rod size,, pitch of tack for different thickness of sheets to be welded, are given in Table 1., Start welding from the right hand edge of the joint and, proceed in the leftward direction., , 202

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Table 1, Thickness, , Preparation, , Assembly, , Pitch of tacks (mm), , Nozzle size, , 1 mm, , Square edge, , No gap, , 20, , 1, , 1.2 mm, , 1.2 mm, , Square edge, , No gap, , 20, , 2, , 1.2 mm, , 1.5 mm, , Square edge, , No gap, , 25, , 2, , 1.6 mm, , No gap, , 45, , 5, , 3 mm, , 3 mm, , Filler rod, , Keep the tip of the inner cone of the flame within 1 to, 1.5 mm of the molten puddle, and hold the blowpipe at an, angle of 80-90° to the work. (Fig 2), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Add the filler rod by holding it close to the cone of the, flame. Upon withdrawing it from the puddle remove it, entirely from the flame until you are ready to dip it back, into the puddle., Care must be taken not to direct too much heat, on the end of the filler rod to avoid easy, melting and flowing., , Complete the weld in one pass on one side and avoid, multi-pass welding so as to reduce the effect of heat on, the weldment., , Co, , In this way the filler rod which melts at a lower temperature, than steel can flow forward and fill up the groove of the, metal as it fuses. Fig 3 shows the type of edge preparation, used for 3 mm thick metal., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.51, , 203

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Fabrication, Related Theory for Exercise 1.3.52, Welder - Welding of Steel (OAW, 8mAW), Alloying elements and their functions on steel, Objectives: At the end of this lesson you shall be able to, • state the necessity of alloying elements, • identify the common alloying elements, • describe the effects of each such element., Necessity of alloying elements: Certain elements are, added to increase the mechanical properties of metals., , Sulphur: Sulphur forms sulphide which makes steel vary, brittle at high temperatures and controls hot shortness., , Common alloying elements: The following are some, common alloying elements., , Phosphorus: The presence of phosphorus in steel vary, brittle at high temperature and controls hot shortness., , Carbon, , Silicon: This does not directly affect the mechanical, properties of the metal. It is generally present in small, quantities up to 0.4% and combines with oxygen in the, steel to form silicon dioxide. This floats to the top of the, molten pool during production, thereby removing oxygen, and other impurities from steel., , Manganese, Sulphur, , Silicon, Chromium, Nickel, Tungsten, Vanadium, Molybdenum, Effects:, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Phosphorus, , Chromium: Chromium is added to steel to increase, hardness and abrasion resistance. Increases resistance, to corrosion., Nickel: This metal is added for shock resistance and is, used with chromium to form a wide variety of stainless, steel groups., , Co, , Carbon: With the addition of a small amount of carbon to, pure iron, significant changes in the mechanical properties, of iron will take place. An increase in hardness and a, reduction in its melting point are the more significant of, the changes., , Manganese: This promotes soundness and eliminates, gas holes. It gives a higher tensile strength and hardness, to the metal without affecting the ductility. It controls the, sulphur content., , 204, , Tungsten: Tungsten increases hardness and toughness, and will not change even at high temperature., Vanadium: This increases hardness and toughness., Molybdenum: Molybdenum gives hardness, toughness, and anti-shock properties to steel.

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Fabrication, Related Theory for Exercise 1.3.53, Welder - Welding of Steel (OAW, 8mAW), Stainless steel properties types weld decay and weldability, Objectives: At the end of this lesson you shall be able to, • explain the classification of stainless steel, • state the physical properties of stainless steel, • explain the welding procedure, • describe the weldability test of stainless steel, • state the effect of weld decay., Classification of stainless steel: Stainless steel is an, alloy of iron, chromium, and nickel. There are many different, classification of stainless steel according to the percentage, of its alloying elements. Accordingly there are three main, classifications for stainless steel., , Method of controlling distortion: Since stainless steel, has a much higher coefficient of expansion with lower, thermal conductivity than mild steel, there are greater, possibilities of distortion and warping., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , One group is FERRITIC, which is non-hardenable and, magnetic. The other group is MARTENSITE, which is hardenable by heat treatment and is also magnetic. The third, group is 'AUSTENTIC' which is extremely tough and has, ductability. This is the most ideal for welding and requires, no annealing after welding. But it is mildly subjected to, corrosive actions. The other groups ferrite and martensite, are non-weldable. Usually the austentic type of stainless, steel is called 18/8 stainless steel which contain 18 percent, chromium 8% nickel apart from the iron percentage., To eliminate corrosive action in this type of stainless steel, stabilizing elements such as columbium, titanium,, molybdenum, zirconium etc. are added in a small, percentage. So, this weldable type of stainless steel is, called a 'stabilized type' stainless steel. These elements, also can be added to filler rods., , Flux: A special type powdered flux which contains zinc, chloride and potassium dichromate is available. During, welding powered flux is to be made into a paste form by, adding water and applied on the underside of the joint., , Co, , Physical properties of stainless steel: The coefficient, of expansion of stainless steel of ferrite and martensite, are approximately the same as carbon steel whereas the, austenitic type of stainless steel has about 50 to 60%, greater coefficient of expansion than carbon steel. So,, while welding this type of stainless steel, distortion will be, more. The heat conductivity is approximately 40 to 50%, less than that of carbon steel for austentic type., , Whenever possible clamps and jigs should be used to, keep the pieces in line until they have cooled. And also a, thick metal plate of copper should be used as a backing, bar during welding so as to reduce distortion in the parent, metal. Tacks at frequent intervals (i.e. pitch of tack is, 20 - 25 mm) will also reduce distortion., Welding procedure, , The type of edge preparation, nozzle size, filler rod size,, pitch of tack for different thickness of sheets to be welded, are given in Table 1., Start welding from the right edge of the joint and proceed, in the leftward direction., Keep the tip of the inner cone of the flame within 1 to, 1.5 mm of the molten puddle, and hold the blowpipe at an, angle of 80-90° to the work. (Fig 1), , All these types have a brighter colour without having any, stain in appearance., Types of stainless steel filler rods: Specially treated, stainless steel filler rods, which contain stabilizing, elements such as molybdenum, columbium, zirconium,, titanium etc., are available., The chromium percentage is also sometimes 1 to 1 1/2, percent more than in the base metal, so as to compensate, the losses that may occur during the welding operation, from the base metal. The melting point of the filler rod also, will be 10° to 20°C less than the base metal. Filler rods of, different sizes are available in the market., , 205

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Table 1, Thickness, , Preparation, , Assembly, , Pitch of tacks (mm), , Nozzle size, , 1 mm, , Square edge, , No gap, , 20, , 1, , 1.2 mm, , 1.2 mm, , Square edge, , No gap, , 20, , 2, , 1.2 mm, , 1.5 mm, , Square edge, , No gap, , 25, , 2, , 1.6 mm, , No gap, , 40, , 5, , 3 mm, , 3 mm, , In this way the filler rod which melts at a lower temperature, than steel can flow forward and fill up the groove of the, metal as it fuses. Fig 2 shows the type of edge preparation, used for 3 mm thick metal., , Filler rod, , The solution should be used at a temperature of about, 50°C., Always use a stainless steel wire brush for cleaning., Weld decay - its effects and remedy, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , When austenetic stainless steel is heated to above 1100°C, due to welding, the chromium and carbon will combine to, form chromium carbide during cooling; whenever this, happens chromium bases its resistance property to, corrosion. So stainless steel will start rusting gradually, near the weld area after welding is completed. This is called, "Weld decay"., , Add the filler rod by holding it close to the cone of the, flame. upon withdrawing it from the puddle remove it entirely, from the flame until you are ready to tip it back into the, puddle., Care must be taken not to direct too much heat, on the end of the filler rod to avoid easy, melting and flowing., , Co, , Complete the weld in one pass on one side and avoid, multi-pass welding so as to reduce the effect of heat on, the weldment., Success in welding stainless steel depends, upon keeping the heat to a minimum., Re-tracking a hot weld produce excessive heat, which is likely to increase the loss of the, corrosion-resistant property in the stainless, steel., , Weld decay can be eliminated by heat-treating the, weldment. For this purpose a welded part should e reheated, to 950° to 1100°C and quenched in water. Then the, precipitate chromium carbide will be descaled from the, boundaries of the welded part into the water., Weld decay can also be avoided by adding alloying, elements such as chromium, molybdenum, zirconium,, titanium, etc. (called stabilizing elements) either in the, parent metal or in the filler rod., Weldability of stainless steel: The ferrite martensitic, types of stainless steel are not a weldable quality, because, of their crystalline structure, but are brazable. Austentic, type stainless steel is a good weldable one. Nowadays, the inert gas shielded arc is used very widely for welding, all types of stainless steel., , Cleaning after welding, Scale and oxide must be removed from the finished weld, by grinding, polishing or by the use of a descaling of a, solution as given below., 50 parts of water, 50 parts of hydrochloric acid, 1/2 percent PICKLETTE or FERROCLEANOL, , 206, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.53

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Fabrication, Related Theory for Exercise 1.3.54, Welder - Welding of Steel (OAW, 8mAW), Welding of brass, Objectives: At the end of this lesson you shall be able to, • state the composition of brass, • state the selection of nozzle, flame and flux, • explain the necessity of oxidising flame and welding technique., Composition of brass: Brass is an alloy of copper and, zinc in various proportion, possibly with the addition of, other elements in very less percentage., The percentage of zinc various from 1 to 50% which makes, available 15 individual commercial brasses. These brasses, containing 20 to 40% zinc have a variety of uses., , It is difficult to weld brass by electric arc process., Flux is very important in welding brass. A fresh mixture of, borax paste makes a good flux for brass welding., The flux should be applied on the underside of the joint, area and to the filler rod., Edge preparation is as shown in Table 1., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Melting temperature of brass: The melting point of, copper is 1083°C and that of zinc is 419°C. Brass melts, at intermediate temperatures. The greater the amount of, copper the higher the melting point. The melting point of, brass is generally around 950°C., , for welding mild steel plate of the same thickness. This, will give a soft oxidising flame., , Selection of nozzle, flame and flux: The main difficulty, in welding of brass is the vapourisation of zinc, because, the melting point of zinc is lower than that of brass. Due to, the loss of zinc, below holes or porosity is produced in the, weld and only copper is left over., , Welding technique: Adopt leftward technique and keep, the angle of the blowpipe at 60°-70° and the filler rod at, 30°-40°. At the end of the joint reduce the blowpipe angle, and withdraw entirely to reduce the heat input at the crater., (Fig 1), , The strength is thereby reduced, and the weld gives a, pitted appearance when polished., Therefore excess burning of zinc should be controlled., , Co, , These 'zinc' problems are minimized by excess oxygen in, the oxidising flame. The excess oxygen in the oxidising, flame will convert zinc into zinc oxide whose melting point, is more than that of zinc. So use of oxidising flame, prevents evaporation of zinc. The flux helps to retain the, zinc while solidification of weld metal occurs. The copperzinc alloys, most of which are called BRASS, are more, difficult to weld than copper. The zinc in the alloy produces, irritating and destructive fumes or vapours during the, welding process. Be sure to provide adequate ventilation, and avoid inhaling zinc fumes., , Ensure complete removal of all traces of flux because the, residual flux will react and reduce the strength of the joint., Use a respirator and avoid inhaling zinc fumes, during welding., , For oxy-acetylene welding of brass, an oxidising flame is, used and the nozzle is one size larger than the one used, Table 1, Thickness, , Preparation, , Assembly, , 1 mm, , Square edge, , No gap, , 1.2 mm, , Square edge, , 1.5 mm, 3 mm, , Pitch of tacks (mm), , Nozzle size, , Filler rod, , 25, , 2, , 1.6 mm, , 0.8 mm gap, , 38, , 3, , 2 mm, , Square edge, , 0.8 mm gap, , 38, , 3, , 2 mm, , Single V, , 1.5 mm gap, , 75, , 5 to 7, , 3 mm, 207

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Fabrication, Related Theory for Exercise 1.3.55, Welder - Welding of Steel (OAW, 8mAW), Copper-Properties-Types and Weldability, Objectives: At the end of this lesson you shall be able to, • describe the various types of copper, • state the physical properties of copper, • explain the welding procedure., Electrolyte copper: This type contains 99.9% pure copper, with 0.01 to 0.08% oxygen in the form of cuprous oxide., (Cu2O). This type of copper is not weldable., De-oxidized copper: In this type a small quantity of, phosphorous, a de-oxidising element is added to the, electrolyte copper. This type of copper is weldable., , Up to 1.2 mm - edge or flange point., Over 1.5 mm up to 2.5 mm - square butt with 50% of, sheet thickness as root gap., 2.5 mm to 16 mm - a angle 'V' of 80°-90°., Over 16 mm - Double 'V' preparation of 90°., , Characteristics of copper, Types of cleaning, Reddish in colour., Mechanical cleaning is done to remove dirt and any other, foreign material. Chemical cleaning is done by applying, solutions to remove oil, grease, paint etc., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , High thermal and electrical conductivity., Excellent resistance to corrosion., , Excellent workability in either hot or cold condition and in, forming wires, sheets, rods, tubes and castings., Melting point: 1083°C., , Filler rod and flux: A completely de-oxidized copper rod, (copper-silver alloy filler rod) having a lower melting point, than the base metal is used., Flux: Copper-silver alloy flux is applied on the edges to, be joined in paste form., , Density: 8.98 g/cm3, , Nozzle size: Use a nozzle which is one size larger than, that used for mild steel., , Edges preparation (Fig 1), , Flame: Adjust a strictly neutral flame., , Co, , Coefficient of linear expansion (ic): 0.000017 mm/mm/°C, , Effects of setting 'carburizing' or 'oxidising' flame, Too much oxygen will cause the formation of copper oxide, and the weld will be brittle., Too much acetylene will cause steam to form a porous, weld., Setting: 1.6 mm root gap between the sheets with a, divergence allowance at the rate of 3-4 mm per 300 mm, run. (Fig 2) Use wedge for welding long seam in copper., (Fig 3) No tacking is done., Preheat: Surface of the base metal is raised to a fairly, high temperature 750°C (peacock neck blue colour) before, the actual welding is started., , 208

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Welding technique: Adopt leftward technique up to, 3.5 mm thickness and rightward technique for 4 mm, thickness and above. Usually the welding starts from a, point 40 to 50 mm away from the right end of the job and, after welding till the left end turn the job by 180° and weld, the balance unwelded portion. Always welding is done, towards the open end of the joint. (Fig 4), , Control of distortion, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Divergence allowance (as already stated in job setting), acts as an effective controlling distortion., Chill plates or backing bar also prevents distortion., After treatment, , Co, , Peening is done in order to reduce the grain size and the, locked up stresses. This is done when the metal is in hot, condition., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.55, , 209

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Fabrication, Related Theory for Exercise 1.3.56, Welder - Welding of Steel (OAW, 8mAW), Bronze welding of copper, Objectives: At the end of this lesson you shall be able to, • explain the principle of bronze welding of copper, • describe the welding technique, • explain the advantages of bronze welding of copper, • describe the brazing problems and their remedies., Principle of bronze welding of copper: Brazing is also, a process of joining of similar or dissimilar metals together, in a solid state by means of alloys (hard solder) which, have a lower melting point than the metals to be joined., This process is used at a temperature above 452°C to, 800°C depending upon the type of metal., , Filler rod: The silicon-bronze filler rod should be melted, by the heated members, as the filler rod is made to touch, the edge of the member, and never melted directly by the, flame. The method of depositing multiple pass on a fillet, lap weld is shown in Fig 2. After the joint is completed, the, bronze weld and the base metal should be allowed to cool, slowly. Non-ferrous metals may be cooled in water also., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , In bronze welding the base metal are not melted. Instead,, they have been raised to a point which is above the melting, point of the hard solder. The molten filler wets the surfaces, to be joined, spreads over them, and solidifies, thereby, forming the joint., , Technique: After the joint surfaces are perfectly cleaned, the members of the joint should be clamped in a jig or in a, fixture giving easy access for brazing the joint from all, sides. The clearance should be set in advance., , Heating: Set a suitable oxidising flame. Heating should, be done with the broad part of the flame. (Fig 1) When, joining unequal sections of unequal thickness, the flame, should be made to play on the thicker section., , Advantages, , Dissimilar metals can be joined., , Co, , Assemblies can be 'bronzed' in a stress-free condition., Complex assemblies can be bronzed in several steps by, using filler metals at progressively lower melting, temperatures., Materials of different thickness can be joined., Cast and wrought metals can be joined., Metallurgical properties of the base materials are not, seriously disturbed., , Flux: Brazing flux should be applied to the heated joint, surfaces just before brazing. Some flux should also be, applied to the filler rod which should be slightly heated., , 210, , Brazed joints require little or no finishing.

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Brazing problems and remedies, Remedy, , The filler metal 'balls up', does not melt and flow into, the joint., , Add more flux. Ensure pickling or additional mechanical, cleaning to remove oxides, oils, or other surface coatings., Use fresh flux. Also check for contaminated pickling acid of, 'dirty' grinder wheels that could spread impurities instead of, removing them., , The filler metal melts but, does not flow completely, through the joint., , Increase the preheating period. The base metal may not be hot, enough. Ensure thorough cleaning. Try a wider or narrower joint, gap. Joint must not be too tight or too loose. Also check for gaps, or spaces where capillarity is interrupted. Apply more flux to both, filler rod and base metal. If not successful use a different flux, compound. Improper flux may be breaking down due to too much heat., , The filler metal runs out, instead of into the joint., , Reposition (tilt) the joint, so that gravity helps the filler joint., Make a small reservoir in the joint to start the capillary action., Feed the filler metal into the joint from above rather than, horizontally or from below., , The filler metal melts but, does not flow., , Ensure additional cleaning of the filler metal to remove the oxides., Use more flux on both the filler rod and the base metals., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Problem, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.56, , 211

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Fabrication, Related Theory for Exercise 1.3.57, Welder - Welding of Steel (OAW, 8mAW), Welding of aluminium and its alloys, Objectives: At the end of this lesson you shall be able to, • explain the properties of aluminium and its alloys, • state the difficulties in welding of aluminium by oxy-acetylene process, • describe the joint design, importance of flux and welding procedure, • state the various process of welding aluminium, • explain the advantages and disadvantages of welding of aluminium by oxy-acetylene process., , Silvery white in colour., , Joint design: Up to 1.6 mm, the edges should be formed, to a 90° flange at a height equal to the thickness of the, material., , Weighs only about one third as much as the commonly, used low carbon steel., , From 1.6 to 4 mm it can be butt-welded provided the edges, are notched with a saw or cold chisel. (Fig 1), , Properties of aluminium and its alloys, , Highly resistant to corrosion., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Possesses great electrical and thermal conductivity., Very ductile, adaptable for forming and pressing operations., Non-magnetic., , Melting point of pure aluminium is 659°C, , Aluminium oxide has a higher melting point (1930°C) than, aluminium., Types, , Aluminium is classified into three main groups., , For welding heavy aluminium plates, 4 mm or more in, thickness, the edges should be bevelled to form 90°, included angle with a root gap of 1.6 mm to 3 mm. (Fig 2), , – Wrought alloys, , Co, , – Commercially pure aluminium, , – Aluminium cast alloys, , Commercially pure aluminium has a purity of atleast 99%, the remaining 1% consisting of iron and silicon., , Difficulties in welding of aluminium by gas: Aluminium, does not change in colour before it reaches the melting, temperature. When the metal begins to melt, it collapses, suddenly., Molten aluminium oxidizes very rapidly form a heavy coating, of aluminium oxide on the surface of the seam which has, a higher melting point - 1930°C. This oxide must be, thoroughly removed by using a good quality flux., Aluminium, when hot, is very flimsy and weak. Care must, be taken to support it adequately during the welding, operation., , 212, , Preparation, pitch of tack, nozzle, size, filler rod etc. are, given in Table 1 for butt joints., Importance of flux: Since aluminium oxidizes very rapidly,, a layer of flux must be used to ensure a sound weld.

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Aluminium flux powder is to be mixed with water (two parts, of flux to one part of water)., , – TIG welding, , The flux is applied to the joint by means of a brush. When, a filler rod is used, the rod is also coated with flux., , – Resistance welding, , On heavy sections, it is advisable to coat the metal as, well as the rod for greater ease in securing better fusion., , – Solid state welding:, , Necessity of preheat: Aluminium and its alloys possess, high thermal conductivity and high specific and latent heat., For this reason, a large amount of heat is required for, fusion welding., , – diffusion welding, , – MIG welding, , – Carbon arc welding, , – cold welding, , – explosive welding, – ultrasonic welding., , To ensure fusion and complete penetration to avoid, cracking, and to reduce gas consumption, aluminium, castings and assemblies in wrought alloys of above, 0.8 mm are to be preheated., , Advantages of adopting oxy-acetylene process for, welding of aluminium, , Preheating temperature varies from 250°C to 400°C, according to the size of the work, and can be done by, using a torch or by keeping the job in the furnace where, preheating is done., , For welding thinner sheets, gas welding may prove to be, economical., , Simple and low cost equipment, , Disadvantages, The flux residue, if not properly removed, may result in, corrosion., , Various processes of welding of aluminium, , Distortion is greater than in arc welding., , – Oxy-acetylene welding, , Heat-affected zone is wider than in arc welding., , – Manual metal arc welding, , Welding speed is lower., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Welding procedure: Please refer to Working Steps and, Skill Information of Ex. No. 2.28/G-55., , Table 1, , 1, 1.2, 1.5, , 3, , Preparation, , Joint assembly, , Pitch of tacks (mm), , Nozzle size, , Filler rod, , Square, , No gap, , 25, , 1, , 2.5 mm, , Square, , No gap, , 40, , 2, , 2.5 mm, , Square, , No gap, , 40, , 2, , 2.5 mm, , 1.5 - 3 mm gap, , 75, , 5, , 3.15 mm, , Co, , Metal thickness, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.57, , 213

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Fabrication, Welder - Welding of Steel (OAW, 8mAW), , Related Theory for Exercise 1.3.58, , Metallic arc cutting and gouging, Objectives: At the end of this lesson you shall be able to, • state the different arc cutting and gouging processes, • state the equipments and accessories, • explain the different electrodes and their properties, • describe the current setting for different size electrodes, • describe the arc cutting and gouging procedures, • explain the advantages and applications., Different arc cutting and gouging processes, , ELECTRODES AND THEIR PROPERTIES, , – Metallic arc cutting gouging process, , Oxy-arc cutting electrode: This electrode is similar to, the manual arc welding electrode and is coated with a, flux, whose function is to provide an insulated sleeve to, stabilise the arc and to make the products of combustion, more fluid. The core wire, however, is in the form of a hollow, tube through which a stream of oxygen is passed and, designed holder, capable of conveying electric current to, the electrode as well as oxygen to the arc, is used. (Fig 1), , – Carbon arc cutting process, – Air arc cutting process, – Plasma arc cutting process, – Oxy-arc cutting process, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Carbon arc gouging process, , Metallic arc cutting - equipment and accessories, They are:, – AC or DC machines, , – cables with lugs and earth clamp, – electrode holders, , – shield or helmet with suitable glasses (Shade No. 14), – chipper or chipping hammer, , Metallic arc cutting and gouging electrodes: These, electrodes are normally the same as welding electrodes, or are sometime specially designed as cutting electrodes, (Fig 2) at a current setting which is 20 to 50% higher than, that normally used for a given size for welding. Although, AC can be used, DC with electrode negative is preferred., Sometimes it helps to make the electrode slightly wet., Water in the coating reduces overheating of the electrode, to some extent and disassociates in the arc to render it, more penetrating., , Co, , – apron, gloves, safety boots and white goggles., , Tungsten arc cutting electrode: This is an arc cutting, electrode, which is used in TIG and plasma arc cutting, processes., , 214

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CURRENT SETTING FOR DIFFERENT SIZE ELECTRODES, Metal thickness, , Electrode, diameter, , AC Range, amps, , DC (DCEN), amps, , in., , mm, , in., , mm, , 1/8, , 3.2, , 3/32, , 2.4, , 40-150, , 75 - 115, , 1/8 - 1, , 3.2 - 25.4, , 1/8, , 3.2, , 125-300, , 150 - 175, , 3/4 - 2, , 19.1 - 50.8, , 5/32, , 4.00, , 250-375, , 170 - 500, , 1-3, , 25.8 - 76.2, , 3/16, , 4.8, , 300-450, , —, , 3 and over, , 76.2 and over, , 1/4, , 6.4, , 400-650, , —, , ARC CUTTING AND GOUGING PROCEDURE, Arc cutting procedure: Prepare the piece as per the, requirements. Clean the surface to be cut. Mark and punch, the line. Position the job in flat., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Choose the welding machine and set the polarity DCEN,, if DC is used., Select the electrode size according to the thickness of, the material., , Set the current as per the requirements for the selected, electrodes., , and the rate of travel uniform to obtain a groove of uniform, width and depth., , Check the cut surface for its smoothness and uniformity., , Advantages: Arc gouging procedure can be used when, other cutting and gouging processes are not available., , Co, , Strike the arc and move the electrodes up and down on, the edge of the plate. As the metal melts brush it, downwards with the arc. Feed the electrodes into the slot, and make the molten metal to run away underneath. Use, only half the electrode and keep it away to cool for use, again., , Arc gouging procedure: Prepare the piece as per the, requirements. Clean the surface to be gouged. Mark and, punch the line. Position the job in flat., Choose the machine and set the polarity DCEN if DC is, used., , Select suitable sizes of electrodes and set the required, current., Strike the arc and as a molten pools is established, lower, the electrode holder and reduce the angle between 5°-15°, from 20°-30°. (Fig 3), Move the electrode along the line of marking from the right, to the left side of the plates and push the molten pool and, slag away from the gouged groove., Because of the rapid fusion due to the arc heat, move the, electrode fast and control the gouging operation. Ensure, that the angle of slope is not too steep, and avoid grooving, too deeply. Maintain the angle of the electrode constant, , Clean the surfaces., , Check the smoothness, depth and uniformity., , In emergency it is more useful., It can be used on metals which are difficult to cut by the, oxy-acetylene cutting process., (Cast iron, stainless steel, wrought iron, manganese steel, and non-ferrous metals etc.), Applications: Metallic arc cutting and gouging are used:, – to remove weld defects, – to make the groove on the root penetration for, depositing sealing run, – to cut the scarp, – to remove rivets, – to pierce holes, – to remove casting defects and make grooves., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.58, , 215

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Fabrication, Welder - Welding of Steel (OAW, 8mAW), , Related Theory for Exercise 1.3.59, , Carbon Arc Cutting and Gouging, Objectives: At the end of this lesson you shall be able to, • describe the machine used for carbon arc cutting, • explain the different sizes of electrodes and current setting, • describe the method of carbon arc cutting, • state the applications of this process, • explain the method of gouging by air carbon arc process, • explain the safety points to be observed while cutting., Carbon arc cutting is a process of cutting metals by melting, with the heat of a carbon arc. It is melting process and as, such does not produce smooth even edges. The actual, cutting process is similar to that of metallic arc cutting., The equipment consists of:, – an AC, DC or AC/DC (rectifier) welding machine (Fig 1), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – a special carbon electrode holder (Fig 2), – heavy duty gloves (asbestos)., Two types of electrodes are available i.e. AC electrodes, (copper added electrodes) and DC electrodes. An AC, machine is used when AC electrodes are used, and the, DC electrodes (plain carbon electrodes) are connected to, the negative side of the DC machine., Carbon electrodes, used for cutting, come in sizes ranging, from 12.2 mm to 25.4 mm. Rods are available in different, lengths i.e. 305,457 and 610 mm (12, 18 and 24 inches)., , Co, , A table of recommended electrode sizes, current settings,, and speeds for carbon arc cutting various thickness of, steel is given. (Table 1), , TABLE 1, , Recommended electrode sizes, current settings, and speeds for, carbon arc cutting of various thickness of steel, Thickness of plate, , in., , mm, , Current setting and carbon electrode diameter, 300 amps, 1/2 in. dia., (12.2 mm), , 500 amps, 5/8 in. dia., (15.9 mm), , 700 amps, 3/4 in. dia., (19.1 mm), , 1000 amps, 1 in. dia., (25.4 mm), , SPEED OF CUTTING IN MINUTES PER FOOT, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4, 2, , 216, , 12.7, 19.1, 25.4, 31.8, 38.1, 44.5, 50.8, , 3.5, 4.7, 6.8, 9.8, -, , 3.5, 4.7, 6.8, 9.8, -, , 1.5, 2.0, 2.9, 4.0, 5.8, 8.0, -, , 1.0, 1.4, 2.0, 2.9, 4.0, 5.3, 7.0

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Prior to cutting, the carbon electrodes should be ground, to a very sharp point. The length of taper should be 6-8, times the electrode diameter. (Fig 3), , The electrode should stick out from the electrode holder, to a distance equal to 10 times the electrode diameter., (This is necessary to reduce electrical resistance and the, heating effect on the electrodes. If carbon wears away too, fast, shorten the electrode extension out of the electrode, holder to as little as 7 cms.), , – almost all types of steels, – light gauge to heavy gauges of metals., – non-ferrous metals., Safety precautions: In cutting operations a large amount, of metal always falls on the floor. Therefore be sure there, are no combustible materials nearby when excessive, amount of cutting is to be done. It is a good idea to sprinkle, sand over the concrete floor. This prevents the molten metal, from heating the concrete and thus avoid cracks and, particles to fly upward. Alternatively provide water/sand, tray on the floor where cutting is to be done., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Carbon electrodes holders are designed for: A-3.2 mm (1/8, in.) carbon electrode B - 6.4 - 9.5 mm carbon electrode, C 12.7 - 15.9 mm carbon electrode and D - 19.1 mm carbon, electrode. (Fig 4), , This method is used to cut:, , DIFFERENCES BETWEEN METAL ARC CUTTING AND, CARBON ARC CUTTING, Metal arc cutting: The arc is struck between the, consumable steel electrode and base., , Co, , AC and DC machines can be used., The electrode used are of smaller diameters, say 4 mm ø., Sheets and plates can be cut., The cut face is not as fine when compared to the face, produced by carbon arc cutting., , Procedure: Start the cutting at the bottom right hand edge, of the plate and proceed towards the left end of the plate., During the actual cutting, the carbon electrode should be, manipulated in a vertical elliptical movement to cut the, metal. This motion facilitates the removal of the molten, metal. In addition to the vertical motion, a side-to-side, crescent motion is recommended along the line of cut., For heavy plates the electrode angle is about 20° off from, the vertical. (Fig 5), Applications: The carbon arc method of cutting may be, used successfully on cast iron because the temperature, of the arc is sufficient to melt the iron oxides formed., , This process is more suitable for cutting scarps, rivets, and for piercing holes., Ordinary electrode holder is used., Carbon arc cutting: A carbon arc is struck between the, consumable carbon electrode and base metal., Generally a DC machine is used., A special type of holder is used., The electrodes used are of a bigger diameter i.e. above, 12 mm, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.59, , 217

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A water cooling type holder is used when cutting with a, higher current., Generally heavy sections are cut by this process., The cut face is more hard., Good for cast iron and non-ferrous metal cuttings., Gouging: Air-carbon arc method, Equipment: The equipment used for air-carbon arc cutting, (ARC) consists of the following., AC, DC or AC/DC welding machine., An air compressor or compressed air cylinders., A compressed air hose., , Electrode, diameter, in., mm, 5/32, 4.0, 3/16, 4.8, 1/4, 6.4, 5/16, 7.9, 3/8, 9.5, 1/2, 12.7, 5/8, 15.9, 3/4, 19.1, 1, 25.4, , Amperage, with DCEP (DCRP), electrode, Min., Max., 90, 150, 150, 200, 200, 400, 250, 450, 350, 600, 600, 1000, 800, 1200, 1200 1600, 1800 2200, , Amperage, with Ac, electrode, Min., Max., —, —, 150, 200, 200, 300, —, —, 300, 500, 400, 600, -, , When gouging, the air stream must be turned on prior to, striking the arc. The air stream must be directed from, behind the carbon electrode. (Fig 7), , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , An air carbon arc torch equipment with an air jet device., (Fig 6), , TABLE 2, Suggested current setting for various diameters, and types of air carbon arc electrodes, , Co, , Electrodes: Electrodes may be of carbon form or graphite, form or a mixture of carbon and graphite., , This permits the metal to be blown out of the arc pool as, shown in the Fig 8., , There are 3 basic types of air-carbon arc cutting electrodes., They are:, – CDEP, plain, – DCEP, copper coated, – AC, copper coated, The copper coating helps to reduce the oxidation of the, electrode body. It also helps to keep the electrode cool., , Carbon electrodes for gouging come in sizes from 4 mm, to 25.4 mm., A table suggesting current settings for various diameters, and types of air carbon arc electrodes is given. (Table 2), , In the vertical position, gouging should be done from the, top to downwards. This permits gravity to help remove the, molten metal from the arc groove. Gouging in horizontal, position may be done from the right to the left., When gouging overhead, the electrode should be placed, in the electrode holder so that it is nearly parallel to the, centre line of the holder., , Gouging procedure: In gouging, the amperage and, electrode diameter are selected according to the width, and depth of the desired groove., , 218, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.59

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Fabrication, Related Theory for Exercise 1.3.60, Welder - Welding of Steel (OAW, 8mAW), Cast Iron-Properties-Types and Weldability, Objectives: At the end of this lesson you shall be able to, • explain the properties of cast iron and its types, • explain the method of edge preparation, • describe the cast iron welding technique, • select filler rods for the jobs to be welded by gas., Cast iron is widely used in the manufacture of machine, parts, since it has a good compressive strength and easy, to make the castings. There are different problems in the, welding of cast iron in comparison to mild steel, even, though this is also in the group of ferrous metals., Types of cast iron, There are four basic types of cast iron available., , – White cast iron, – Malleable cast iron, , Method and types edge preparation: The edges of grey, cast iron can be prepared by different methods such as, chipping, grinding, machine and filing. The above methods, are used according to the condition and type of the job., Usually it is required to weld, a cracked casting or a butt, joint. Also the thickness of the casting to be welded or, repaired will be 6 mm and above. So usually a single V, butt joint is prepared as shown in Fig 1., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , – Grey cast iron, , Since the carbon is in free graphite form it gives a grey, colour to the fractured structure., , – Nodular cast iron (or) spheroidal graphite iron, , Grey cast iron: Grey cast iron is soft and tougher than, the white cast iron which is hard and brittle. The good, mechanical properties of grey cast iron are due to the, presence of particles of free state carbon or graphite, which, separate out during slow cooling. Grey cast iron is of a, weldable type. It contains 3 to 4% of carbon., , Co, , White cast iron: White cast iron is produced from pig, iron by causing the casting to cool very rapidly. The rate of, cooling is too rapid and this does not allow the carbon to, separate from the iron carbide compound. Consequently, the carbon found in white cast iron exists in the combined, form. This type of cast iron is very hard and brittle and is, not weldable and also not easily machinable., , Malleable cast iron: Malleable cast iron is obtained by, annealing white cast iron over a prolonged period of time,, and then allowing it to cool slowly. This heat treatment, results in greater resistance to impact and shock., Nodular cast iron: It is also known as spheroidal graphite, iron (SG iron). It is obtained by adding magnesium to the, molten grey cast iron. The tensile strength and elongation, of nodular iron is similar to that of steels which makes this, iron a ductile material., Properties of grey cast iron: Grey cast iron is mostly, used in the manufacture of machine components. It has, got good mechanical properties due to the free state, carbon/graphite. The other constituents are silicon, sulphur,, manganese and phosphorous. The grey cast iron has a, much higher compressive strength than steel but has low, ductility and tensile strength., , Method of cleaning, , There are two methods used for cleaning cast iron jobs., – Mechanical cleaning, – Chemical cleaning, , Mechanical cleaning is mostly used to clean the surface, of the cast iron jobs., In this method grinding, filing and wire brushing tec. are, done., The chemical cleaning process is applied to remove oil,, grease and any other substances which cannot be, removed by mechanical cleaning., Flame (strict neutral flame): Nozzle no. 10 is used in, the blow pipe and a strict neutral flame should be adjusted., Care should be taken that there is not even the slightest, trace of oxygen which would cause a weak weld through, oxidation., Filler rod: A 5 mm size round or square high (super) silicon, cast iron filler rods containing 2.8 - 3.5 percentage silicon, are used for cast iron welding. The weld metal by this rod, is easily machinable. (The S-CI 1 as per IS 1278 - 1972)., 219

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Flux: The flux should be of good quality to dissolve the, oxides and prevent oxidation., , Selection of filler rod, Filler rod should be selected according to the:, , Cast iron flux is composed of borax, sodium carbonate,, potassium carbonate, sodium nitrate and sodium, bicarbonate. This is in a powder form., Technique of cast iron welding: The welding operations, should be performed on the preheated, dull red hot, cast, iron piece. The preheating temperature for C.I welding varies, from 200°C to 310°C., , thickness of metal to be welded (including joint edge, preparation) (Table 2), – nature of joint to be made (i.e.), fusion welding or braze, welding (non-fusion), – welding technique to be used (leftward or rightward)., Table 1, Metals, , Filler rods, , Mild steel and, wrought iron, , Copper coated mild steel, (C.C.M.S), , High carbon and, alloy steel, , High Carbon steel, Silicon-manganese steel, Wear-resisting alloy steel, 3.5% Nickel steel, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The blowpipe angle should be 60° to 70° and the filler rod, angle 40° to 50° to the line of weld. (Fig 2), , – kind or type of metal to be welded, i.e. ferrous, nonferrous, hard facing (Table 1)., , Using the leftward or forehead technique, the first layer, should be complete by giving a slight weaving motion to, the blowpipe but not to the filler rod. The hot rod end should, be dipped into the powdered flux at intervals., , Columbium stainless steel, , Cast iron, , Super silicon cast iron, Ferrotectic cast iron, Nicotectic cast iron, , Copper and its, alloys (brass,, bronze), , Copper-silver alloy, Silicon-brass, silicon-bronze, Nickel bronze, Manganese bronze, , Aluminium and, its alloys, , Pure aluminium, 5% Silicon aluminium alloy, 10-13% Silicon aluminium alloy, , Co, , After the completion of the first layer, play the flame on, the job so as to heat evenly and then deposit the second, layer with a slight reinforcement of weld metal from the, surface of the job. (Fig 3), , Stainless steel, , Table 2, , The technique of welding the second layer is the same as, that for the first layer., After completion of the second layer, play the flame again, on the whole job for getting an even heat. This is called, 'post heating'., Then allow the job to cool slowly by covering with a heap, of lime or ash or dry sand., , 220, , Thickness, mm, , Edge, preparation, mm, , Root, gap, , Dia. of, filler rod, mm, , 0.8, 1.6, 2.4, 3.2, 4.0, 5.0, , Square, Square, Square, 80° Vee, 80° Vee, 80° Vee, , 2.4, 3.2, 3.2, 3.2, 3.2, , 1.6, 1.6, 1.6, 2.4, 3.2, 4.0, , More the thickness of the metal welded, more, the diameter of the filler rod used. Less the, number of weld runs deposited, less the, distortion and faster the welding., , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.60

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Fabrication, Related Theory for Exercise 1.3.61, Welder - Welding of Steel (OAW, 8mAW), Bronze welding of cast iron, Objectives: At the end of this lesson you shall be able to, • describe the principle of bronze welding and its application, • explain the functions of bronze filler rods and flux, • describe the advantage and limitations of bronze welds of C.I, • state the various types and composition of bronze welding filler rods and function of each element in it., Bronze welding, Bronze welding is a process in which the joint is produced, by heating the metal to suitable temperatures above 425°C, (800°F) and depositing filler metal into a groove of the joint, by using a non-ferrous filler rod having a melting point below, that of the base metal., When the filler metal is made of copper-zinc alloy, the, process is referred to as bronze welding., , Co, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Applications of bronze welding: Bronze welding is, particularly adoptable for joining or repairing such metals, as cast iron, malleable iron, copper, brass and various, dissimilar sections such as worn out of gear teeth., (Figs 1, 2, 3 & 4), , The elements like tin, manganese and silicon contained, in the filler rod help to deoxidize the weld metal, decrease, the tendency of zinc to fume, and increase the free-flowing, action of the molten metal., Hardness and wear-resistance is improved., Flowing and wetting properties are improved., A bronze filler rod generally contains 60% copper and 40%, zinc. A small percentage of other metals such as, manganese, tin, nickel and silicon is added in the filler, rod., , Characteristics of bronze filler rod: The main elements, of a bronze filler rod used in bronze welding are copper, and zinc which produce high tensile strength and ductility., , Importance of flux for bronze welding: Adhesion of, the molten bronze to the base metal will take place only if, the surface is chemically clean. Good surface cleaning, action will be obtained by applying good quality flux which, also prevents oxidation during welding., , 221

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Type of flame: A slightly oxidising flame is a suitable, one. Since the melting point of zinc is 540°C and that of, copper is 1083°C, before copper starts melting the zinc, will evaporate as white fumes. Excess oxygen in the, oxidising flame will convert zinc into zinc oxide and arrest, the evaporation of zinc due to the higher melting pint of, zinc oxide. While solidifying the flux will remove the oxide, and maintain the bronze deposit., Welding technique: The edges are prepared as shown, in Fig 5. All the edges of the joint are to be rounded off to, avoid sharp edges., , Advantages of bronze welding, Bronze welding is done at low temperature, Bronze welding can be done faster than fusion welding., , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , The base metal need not be heated to a molten condition., So there is less possibility of destroying the main, characteristics of the base metal. This results in lower, fuel consumption., , Use leftward welding technique and keep the joint inclined, at 30°. (Fig 6), , The low degree of heat in bronze welding reduces to a, minimum the expansion and contraction forces and thereby, reduces distortion., Machining the welded portion is possible., Limitations of bronze welding, , Co, , Bronze welding is not useful to weld a metal that will be, subjected to a high temperature in service, since bronze, loses its strength when heated to (500°F) 260°C or more., Bronze welding should not be used on steel parts that, must withstand unusually high stresses., Colour match will not be there with ferrous metals., The filler metal costs more than the super silicon cast iron, or steel filler metals used for full fusion welding., In certain chemical processes, some materials that have, almost no effect on cast iron but will react with the bronze, filler metal., , Ensure the job is preheated to 200°C to 300°C and the, weld face is properly wetted/tinned before depositing the, bronze filler metal. (Fig 7), , Filler rods for bronze welding of cast iron, Types of filler rods, , Use No. 10 nozzle on the blowpipe and 3 mm bronze filler, rod dipped in powdered flux., , S-C4, , Cool the joint slowly by covering the job with asbestos, powder or dry sand., , S-C6, , Remove the flux residue from the joint and clean the joint., , S-C9, , S-C5, , S-C8, , S-C10, , 222, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.61

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COMPOSITION OF EACH TYPE, , Manganese bronze or high tensile brass., , S-C4, , S-C9, Copper 57 to 63%, Silicon 0.15 to 0.3%, Manganese 0.05 to 0.25%, Iron 0.1 to 0.5 %, Balance % zinc, , High nickel bronze (High tensile nickel brass), S-C10, High nickel bronze (High tensile nickel brass), , Melting point of this filler rod is 870° to 900°C, , FUNCTIONS OF EACH ELEMENT, , S-C, Fabrication : Welder - Exercise 1.1.01, Fabrication : Welder - Exercise 1.1.015, , Phosphorus, De-oxidiser, , Tin 0.5% max, Manganese 0.5% max, Iron 0.5% max, Copper 45 to 53%, Melting point 970° to 980°C, Silicon 0.15 to 0.5%, Nickel 8 to 11%, , Improves the strength and corrosion resistance and wear, resistance., Nickel, , No py, t t rig, o ht, be @, Re NI, pu M, bl I, ish, ed, , Improves corrosion resistance, ductility., , S-C6, , Copper 41 to 45%, Silicon 0.2 to 0.5%, Nickel 14 to 16%, Tin 1.00% max, Manganese 0.2 % max, , Manganese, , De-oxidiser, improves wear resistance., , }, }, }, , Silicon, , Optional, , Improves fluidity., , Removes impurities., , Co, , Iron - 0.3% max, Zinc balance, S-C8, , Tin, , Fabrication : Welder (NSQF LEVEL - 4) - Related Theory for Exercise 1.3.61, , 223