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Welding processes handbook

© 2003, Woodhead Publishing Ltd

Welding processes handbook

Klas Weman

CRC Press Boca Raton Boston New York Washington, DC

W O O D H E A D P U B L I S H I N G L I M I T E D Cambridge, England


Published by Woodhead Publishing Ltd, Abington Hall, Abington Cambridge CB 1 6AH, England www.woodhead-publishing.com

Published in North America by CRC Press LLC, 2000 Corporate Blvd, NW Boca Raton FL 3343 1, USA

First published 2003, Woodhead Publishing Ltd and CRC Press LLC

O 2003, Woodhead Publishing Ltd 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 the publishers.

The consent of Woodhead Publishing and CRC Press 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 or CRC Press 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.

Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress.

Woodhead Publishing ISBN 1 85573 689 6 CRC Press ISBN 0-8493-1773-8 CRC Press order number: WPI 773

Printed by TJ International, Padstow. Cornwall


www.woodhead-publishing.com

Contents

Preface ............................................................................................................... ix

ARC WELDING . AN OVERVIEW ............................................................ 1 History of welding .................................................................................. 1 Terminology ............................................................................................ 3 Distortion .................................................................................................... 7 The welding arc .......................... ........... ........................................... 8 Shielding gases ..................... .. ....... ..... ............................................. 12 Power sources ............................................................................... 13

GAS WELDING ...................................................................................... 26 Equipment ................................................................................................ 26

TIG WELDING ......................................................................................... 31 A description of the method ..................................................................... 31

................................................................................................ Equipment 31 Consumables ........................................................................................... 35

PLASMA WELDING ............................................................................... 37 ..................................................................... A description of the method 37

Equipment ................................................................................................ 39 Gases for plasma welding ........................................................................ 40 The advantages of the plasma method .................................................... 40

MIGIMAG WELDING ............................................................................... 41 Equipment ................................................................................................ 41 Setting of welding parameters ............................................................... 44

........................................................................................... Consumables 47 Weld quality ............................................................................................. 60

METAL ARC WELDING WITH COATED ELECTRODES ...................... 63 Description of the method ........................................................................ 63 Equipment ................................................................................................ 63 Electrodes ................................................................................................ 64 Weld defects ............................................................................................ 67

SUBMERGED ARC WELDING ............................................................... 68 Description ............................................................................................... 68 Equipment ................................................................................................ 69 Filler material ............................................................................................ 71 The effect of the welding parameters ....................................................... 73

....................................................................... Productivity improvements 75 Joint preparation ...................................................................................... 77 Risks of weld defects ............................................................................... 77


CONTENTS

PRESSURE WELDING METHODS ......................................................... 80 Resistance welding .................................................................................. 80 Friction welding ........................................................................................ 86 High-frequency welding ............................................................................ 89 Ultrasonic welding .................................................................................... 89 Explosion welding .................................................................................... 90

............................................................................ Magnetic pulse welding 91 Cold pressure welding .............................................................................. 92

...................................................................................... Diffusion welding 92

.......................................................... OTHER METHODS OF WELDING 93 ................................................. ............................ Electroslag welding .. 93

Electrogas welding ................................................................................... 94 ......................................................................................... Stud welding 94 ........................................................................................... Laser welding 95

............................................................................. Electron beam welding 99 .................................................................................... Thermite welding 101

............................................................................ CUTTING METHODS 102 Thermal cutting ...................................................................................... 102

..................................................................................... Water jet cutting 105 Thermal gouging .................................................................................... 106

SURFACE CLADDING METHODS ....................................................... 108 Cladding to provide a corrosion-resistant layer ...................................... 108 Hardfacing ............... ... ...................................................................... 108 Thermal spraying ................................................................................... 110

MECHANISATION AND ROBOT WELDING ........................................ 114 .......................... .............................................. Narrow-gap welding .. 114

Arc welding using robots ........................................................................ 116 Mechanised TIG welding ........................................................................ 120 Quality requirements for mechanised welding ....................................... 122

SOLDERING AND BRAZING ................................................................ 124 General .................................................................................................. 124 Soft soldering ...................................................................................... 127 Brazing ................................................................................................... 129

THE WELDABILITY OF STEEL ............................................................ 132 Carbon steels ....................................................................................... 132 High-strength and extra high-strength steels ......................................... 136 Austenitic steels ..................................................................................... 139

DESIGN OF WELDED COMPONENTS ................................................ 148 Introduction ................... .. ................................................................... 148 Symbolic representation of welds on drawings ...................................... 148 Welding classes ..................................................................................... 151 Residual stresses in welds. weld distortions ..................... .. ............. 152


CONTENTS

......................................................... .............. Design consideration ... 153 Strength considerations of welded joints ................................................ 163 Analysis of statically loaded welded joints .............................................. 163 Welded structures subjected to fatigue loads .................................... 166 References ............................................................................................. 170

16 QUALITY ASSURANCE AND QUALITY MANAGEMENT ................... 171 Quality requirements for welding (EN 729) ........................................ 172

.......................................................... Welding coordination (EN 71 9) 173 .................. Specification and approval of welding procedures (EN 288) 175

Approval testing of welders (EN 287) ..................................................... 180 Non-destructive testing .......................................................................... 182

17 WELDING COSTS ................................................................................ 184 ....................................................................... Welding cost calculations 184

Some welding cost concepts .................................................................. 184 Cost calculation ...................................................................................... 186

............................................. Mechanisation. automation. robot welding 189

vii


Preface

Production of this guide to welding was prompted originally by a wish for an up-to-date reference on applications in the field. The content has been chosen so that it can be used as a textbook for European welding courses in accordance with guidelines from the European Welding Federation. Over the last few years, an equivalent Swedish guide has been used for courses on welding processes and equipment. The author hopes that this guide will serve as a useful reference book for those involved in welding.

In writing the book, there has been a conscious effort to ensure that both text and illustrative material is clear, concentrating particularly on interesting and important aspects.

Although the book has been written in Sweden, with input from Swedish experts, it reflects technology and methods that are internationally accepted and used. My thanks are due to all those who have been involved in the work, with particular mention to:

Clues Olsson, HighTech Engineering, who wrote the chapter on design of welded components. Clues-Ove Pettersson, Sandvik, who edited the section on stainless steel. Curt Johansson, SAQ, who wrote the chapter on quality management. Gunnar LindLn, Air Liquide, who edited the chapter on welding costs.

Klas Weman


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