i Advanced welding processes ii Related titles: New developments in advanced welding (ISBN-13: 978-1 85573-970-3; ISBN-10: 1-85573-970-4) Recent developments in high-technology areas have significantly transformed the welding industry where automation, computers, process control, sophisticated scientific instruments and advanced processing methods are all common. Today’s engineers and technologists have to support complex systems and apply sophisticated welding technologies. This comprehensive book discusses the changes in advanced welding technologies, preparing the reader for the modern industry. MIG welding guide (ISBN-13: 978-1-85573-947-5; ISBN-10: 1-85573-947-X) Gas metal arc welding (GMAW), also referred to as MIG (metal inert gas) welding, is one of the key processes in industrial manufacturing. The MIG welding guide provides comprehensive, easy-to-understand coverage of this widely used process. The reader is presented with a variety of topics from the choice of shielding gases, filler materials, welding equipment and lots of practical advice. The book provides an overview of new developments in various processes such as: flux-cored arc welding; new high-productive methods; pulsed MIG welding; MIG-brazing; robotic welding applications and occupational health and safety. This will be essential reading for welding engineers, production engineers, designers and all those involved in industrial manufacturing. Cumulative damage of welded joints (ISBN-13: 978-85573-938-3; ISBN-10: 1-85573-938-0) Fatigue is a mechanism of failure that involves the formation of cracks under the action of different stresses. Fatigue cracks are exceedingly difficult to see, particularly in the early stages of crack growth. Cracks can progress to a significant extent before they are even discovered. To avoid fatigue it is essential to recognise at the design stage that the loading is such that fatigue may be a possibility and to design the structure with inherent fatigue strength. However, fatigue strength is not a constant material property. It may be assessed by fracture mechanics, but such characteristics are based on quantitative analysis and mere assumption. This book is primarily concerned with fatigue under variable amplitude loading, unlike most tests performed under constant loads. Details of these and other Woodhead Publishing materials books and journals, as well as materials books from Maney Publishing, can be obtained by: ∑ visiting our website at www.woodheadpublishing.com ∑ contacting Customer Services (e-mail: [email protected]; fax: +44 (0) 1223 893694; tel.: +44 (0) 1223 891358 ext. 30; address: Woodhead Publishing Ltd, Abington Hall, Abington, Cambridge CB1 6AH, England) Maney currently publishes 16 peer-reviewed materials science and engineering journals. For further information visit www.maney.co.uk/journals. iii Advanced welding processes Technologies and process control John Norrish Woodhead Publishing and Maney Publishing on behalf of The Institute of Materials, Minerals & Mining W OODHEAD PUBLISHING LIMITED Cambridge, England iv Woodhead Publishing Limited and Maney Publishing Limited on behalf of The Institute of Materials, Minerals & Mining Woodhead Publishing Limited, Abington Hall, Abington, Cambridge CB1 6AH, England www.woodheadpublishing.com First published 1992, IOP Publishing Ltd This edition 2006, Woodhead Publishing Limited © Institute of Materials, Minerals & Mining, 2006 The author has asserted his moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the author and the publishers cannot assume responsibility for the validity of all materials. Neither the author nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN-13: 978-1-84569-130-1 (book) ISBN-10: 1-84569-130-X (book) ISBN-13: 978-1-84569-170-7 (e-book) ISBN-10: 1-84569-170-9 (e-book) The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elementary chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. Typeset by Replika Press Pvt Ltd, India Printed by T J International Limited, Padstow, Cornwall, England v Contents Preface ix Acknowledgements xi 1 An introduction to welding processes 1 1.1 Introduction 1 1.2 Conventional welding processes 2 1.3 Summary 15 2 Advanced process development trends 16 2.1 Introduction 16 2.2 Safety and environmental factors 21 2.3 Skill and training requirements 21 2.4 Areas for development 21 2.5 Process application trends 22 2.6 Summary 25 3Welding power source technology 26 3.1 Introduction 26 3.2 Basic power source requirements 26 3.3 Conventional power source designs 27 3.4 Electronic power regulation systems 31 3.5 Output level, sequence and function control 39 3.6 Practical implications of electronic power regulation and control 42 3.7 Summary 43 4 Filler materials for arc welding 44 4.1 Introduction 44 4.2 MMAW consumables 44 4.3 Submerged arc welding consumables 46 vi Contents 4.4 Filler wires for GMAW and FCAW 47 4.5 Summary 57 5 Gases for advanced welding processes 58 5.1 Introduction 58 5.2 Shielding gases for arc welding processes 58 5.3 Gases for laser welding 71 5.4 Summary 72 6 Advanced gas tungsten arc welding 74 6.1 Introduction 74 6.2 Process developments 74 6.3 Process variants 79 6.4 Control of GTAW and related processes 91 6.5 Summary 98 7 Gas metal arc welding 100 7.1 Introduction 100 7.2 Metal transfer in GMAW 100 7.3 The physics of metal transfer 110 7.4 Summary: metal transfer phenomena 113 7.5 Control of conventional GMAW 113 7.6 Summary: process control 120 7.7 Recent developments in the GMAW process 120 7.8 Summary 134 8 High-energy density processes 136 8.1 Introduction 136 8.2 Plasma keyhole welding 138 8.3 Laser welding 144 8.4 Electron beam welding 157 8.5 Summary 164 9 Narrow-gap welding techniques 165 9.1 Introduction 165 9.2 Principles and features of narrow-gap welding 165 9.3 Narrow-gap welding processes 166 9.4 Summary and implications 177 10 Monitoring and control of welding processes 179 10.1 Introduction 179 10.2 Manual control techniques 180 10.3 Monitoring 188 Contents vii 10.4 Automated control techniques 203 10.5 Summary and implications 216 11 Welding automation and robotics 218 11.1 Introduction 218 11.2 Automation options 219 11.3 Simple mechanization 219 11.4 Dedicated and special-purpose automation 223 11.5 Robotic welding 225 11.6 Modular automation 236 11.7 Programmable control 236 11.8 Remote-control slave and automated systems 237 11.9 Advances in welding automation 238 11.10 Evaluation of and justification for automated welding 242 11.11 Summary 246 Appendices 247 Appendix 1: Welding processes classification 249 Appendix 2: Shielded metal arc welding (SMAW) electrode classification 250 Appendix 3: Burn-off characteristics 254 Appendix 4: American, Australian and European FCAW classification systems 257 Appendix 5: Flux-cored wire for surfacing and wear resistance 260 Appendix 6: Plasma keyhole welding parameters 262 Appendix 7: Plasma keyhole welding of titanium 263 References 265 Index 279 This page intentionally left blank ix Preface Welding has traditionally been regarded as a craft rather than a technological manufacturing process. This reputation has not been helped by the dependence of conventional joining techniques on highly skilled manual operators and the relatively high cost and poor reproducibility associated with many welding processes. These attributes led to the ‘Special Process’ classification of welding in international quality standards. In fact, although it may be a complex multi- disciplinary subject, a great deal of high-quality research has been conducted into the fundamentals of welding processes and the basic principles are now well understood. This research has provided a scientific basis for significant developments in the technology. Early developments in welding technology were focused largely on weldability and metallurgical research, which enabled a wide range of materials to be joined, adequate joint properties to be maintained and the integrity of welded joints to be controlled. Whilst further work is still required in the materials research area, in particular to enable advanced materials to be joined effectively, much of the recent effort has been devoted to improved understanding of the basic processes, consumable and equipment development and control and automation. John Norrish University of Wollongong This page intentionally left blank xi Acknowledgements I would like to acknowledge the continued help, advice, encouragement and goading which have been generously provided by many friends and colleagues in the welding industry around the world, also my students, who have taught me much and whose work is reported widely in the following pages. Last, but by no means least, I would like to thank my long-suffering family for their forbearance during the protracted gestation of this work.