Handbook of mold, tool and die repair welding

211 Pages·1999·8.012 MB·English

by  Thompson, Steve

Handbook of mold, tool
and die repair welding
STEVE THOMPSON
W I L L I A MA N D R E WP U B L I S H I N G
Published by Abington Publishing
Woodhead Publishing Limited, Abington Hall,
Abington, Cambridge CBI 6AH, England
First published 1999, Abington Publishing
0 Woodhead Publishing Ltd, 1999
The author has asserted his moral rights.
Published in the United States of America by William Andrew Publishing
Information in this document is subject to change without notice and does not
represent a commitment on the part of William Andrew Publishing. No part of this
document may be reproduced or transmitted in any form or by any means,
electronic or mechanical, including photocopy, recording, or any information
retrieval and storage system, for any purpose without the written permission of
William Andrew Publishing.
Please note: Although the information in this volume has been obtained from
sources believed to be reliable, no warranty, expressed or implied, can be made
as to its completeness or accuracy. Design processing methods and equipment,
environment and other variables affect actual part and mechanical performance.
The manufacturers, suppliers, author and William Andrew Publishing have no
control over those variables or the use to which others may put the material and,
therefore, cannot assume responsibility for loss or damages suffered through
reliance on any information contained in this volume. No warranty is given or
implied as to application and to whether there is an infringement of patents is the
sole responsibility of the user. The information provided should not serve as a
substitute for careful testing of prototype parts in typical operating environments
before beginning commercial production.
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress.
ISBN 1-884207-82-0
Printed and bound in England.
Preface
My fascination with welding tool steels began when, as a novice, I tried
to weld two pieces of ground flat stock together with mild steel filler wire
and no pre-heat. The weld was neat and tidy (which was always my
trade mark), so I thought that I had done a good job. As I was welding
the two pieces of tool steel, I had heard funny noises like somebody
tapping two wrenches together several times! ‘Never mind’, I thought,
but as I moved the welded pieces to one side, they just fell apart!
I couldn’t believe my eyes - what had happened? It defied all the laws
of my logic that two pieces of metal should fall apart when they had
just been welded!
When the trauma of this subsided, I went to my boss to confess my
ignorance. He laughed and told me that you are supposed to pre-heat
tool steels before you weld them. I then asked him how much pre-heat
tool steel needed, but he said, ‘I don’t know, just heat it up’. I did as he
said and it worked! But I had to find out more information just in case
there was more than one type of tool steel and possibly a more accu-
rate method of choosing a pre-heat. The more I searched, the more I
realized how little anybody understood of this area. So the challenge was
on - who would I ask and where would I find this type of information?
I joined The Welding Institute and began regular visits to my city’s
central library. All I needed was a book on how to weld molds, tools and
dies but this did not exist. All I could find was general information on
how to weld tool steels.
So, slowly but surely, I started to build up my own bank of informa-
tion from trade literature, from welding and metallurgy books and from
x Preface
valuable advice from a close friend who is a metallurgist. This gradually
evolved into specific working practices which best suited my customers'
demands.
Eventually, it came to the point when I had so much general informa-
tion and enough years of practical knowledge that l decided to combine
them into the book that I could not find when I needed it. I had found
my niche, my project!
I hope what I have put together answers most of the questions that
you might have been asking yourself about the confusingly technical and
practically demanding but overlooked corner of industry that deals with
the repair of molds, tools and dies.
Steve Thompson
Introduction
This book is not a metallurgist’s definitive tool steel chemical composi-
tion handbook or a welding engineer’s definitive guide. It is a book
designed for the shop floor, written from the shop floor, using the 25
years of my experience to convey the most practical ways that I have
found for tackling the repair of molds, tools and dies.
Mold, tool and die repair welding is a very complicated process,
shrouded in mysteries, myths and closely guarded secrets! This is
because two very different trades have overlapped - welding and tool-
making. For many years, toolmakers and tool users have had to rely on
the small number of specialist welders who do understand exactly what
repair welding involves, and who have the hand skills to do it, especially
when it comes to welding mold tools.
Understanding the technical side of tool steels is a big problem for
welders and understanding the practical side of welding is a big
problem for machinists. I have tried to write this book so that either will
understand it and learn something from it.
Tool steels should be pre-heated or even annealed before welding and
then cooled carefully or even post-heat treated. But in all my years of
welding tool steels, I have never been allowed to anneal a tool before
welding because the customer would never accept the increased down
time and cost! This book, therefore, tells the repair welder how to com-
promise between what the customer wants and how best to give him
that within the constraints of good welding practice.
Purchasing and safely setting up suitable equipment is an essential
part of mold tool and die repair welding. If you do not have suitable
xiv Introduction
equipment, it will be like trying to play classical guitar music on a
banjo inappropriate and not always possible. Unfortunately, welding
-
suppliers are not always as expert as they should be in selling
toolmakers the most appropriate welding equipment for the kind of work
they have in hand.
It is not always necessary to spend a lot of money to get the equip-
ment that lets you do your job properly. Learning how to choose your
equipment well is something that comes with experience. If more of us
shopped around and insisted on borrowing equipment on approval
before purchasing, fewer expensive mistakes would be made. Purchas-
ing and safely setting up suitable equipment is discussed in Chapter 7.
The chemical compositions in this book come from many different
sources, old and naw. Some may, therefore, be incomplete or slightly
inaccurate but I have still used them because they contain sufficient
information for welding purposes.
All the technical and practical information in this book is based on the
way that I approach mold, tool and die repair welding, and should not
be confused with official tool steel welding procedures.
Contents
Preface ix
Acknowledgements xi
Introduction xiii
1 How to use this book
Can you TIG weld?
Weld procedure
Review
2 Writing your weld procedure 3
Why you may need a weld procedure 3
Collecting your information 4
Weld procedure 1 6
Weld procedure 2 9
Weld procedure 3 13
Weld procedure 4 17
3 Identification of material 22
Tool steels 22
HRC file check 23
Tool coppers 35
Tool aluminum 36
vi Contents
4 Choosing your filler wire 37
Buying filler wires 37
Choosing filler wires 38
General color match 44
Photo/acid etch 45
Cheapest filler 45
Hardness (HRC) 46
Butter/crack repair 46
Filler wires for tool coppers 47
Tab testing on aluminum and copper tools 47
5 Heat control 49
Pre-h eats 49
Cooling 50
Heat sources 52
Pre-heating 52
Oven heating 52
Heating larger tools 53
Post-heat treatment 55
Pre-heating aluminum and copper 55
Minimizing pre-heats on aluminum and copper 56
6 Weld techniques 57
Weld procedures 57
Cracking 63
70
Previous bad weld repairs
71
Sink
Under cut (notches) 73
Building pads of weld 74
Preparing a tool for a pedestal pad 78
80
Porosity (pin/blow holes)
Arc marks (earthing and protecting sensitive areas) 83
86
Using heat soaks and flood supports
90
Getting around bad access
92
Bending tungsten
94
Controlling distortion
96
Welding without full pre-heat
Contents vii
Welding case-hardened tools 97
Welding photo/acid etched and polished tools 98
Using base metal as filler wire 101
Welding fine details 101
Filler wire 102
7 Equipment 105
Safety 105
Safety wear 107
Keeping your work place tidy 110
Power tools 111
Welding equipment 111
Setting up your equipment 115
Control panels 120
Other equipment 123
8 Basic TIG welding for beginners 129
Holding your torch 131
Torch angles 132
Striking your arc 133
Using your filler wire 134
Welding exercises 136
Appendix I Other steels and tool steels 144
Appendix II Elements and their symbols 193
Appendix Ill Millimeters to inches conversion table 195
Appendix IV Temperature conversion table 196
Appendix V Hardness conversion chart 197
Weld procedure sheet 199
Index 20 1
How to use this book
This book covers most of the aspects of mold, tool and die repair
TIG (tungsten inert gas) welding at shop floor level as well as the
relative technical areas. In time, it will help you to understand the dif-
ference between tool steels and why they need to be repaired dif-
ferently, and aspects such as what your tool is made of, whether you
need to pre-heat and what type of welding rods you should
use, or even how do you weld and what should you weld with! Hope-
fully this book will answer most, if not all, of these questions. So,
whatever stage of welding competence you are at, this is your
starting point.
Can you TIG weld?
No: if you cannot TIG weld, Chapter 7 discusses welding equipment,
the types of accessory you will need and how to set them up. Chapter
7 also discusses safety, which is essential when dealing with welding.
Chapter 8 goes on to tell you how to use your equipment and it also
gives you welding exercises to help you develop your hand skills. Go
to Chapter 7 then carry on to Chapter 8.
Yes: read through Chapters 7 and 8 to make sure that you have
suitable equipment and that it is set up correctly, and that you fully
understand the weld techniques you may need to master before you
undertake tool repairs. Go to Chapters 7 and 8.