Table Of ContentENGINEERING
METALLURGY
Parti
APPLIED PHYSICAL METALLURGY
Sixth Edition
RAYMOND A. HIGGINS
B.Sc (Birm.), C.Eng., F.I.M.
Formerly Senior Lecturer in Metallurgy, West Bromwich College of
Commerce and Technology; sometime Chief Metallurgist, Messrs
Aston Chain and Hook Co., Ltd., Birmingham; and Examiner in
Metallurgy to the Institution of Production Engineers, The City and
Guilds of London Institute, The Union of Lancashire and Cheshire
Institutes and The Union of Educational Institutes.
ARNOLD
A member of the Hodder Headline Group
LONDON • SYDNEY • AUCKLAND
First published in Great Britain 1957
Second edition 1968
Third edition 1971
Fourth edition 1973
Fifth edition 1983
Sixth edition 1993
Reprinted 1999 by Arnold
a member of the Hodder Headline Group
338 Euston Road, London NWl 3BH
98 Madison Avenue, New York, NY10016
© 1993 R A Higgins
All rights reserved. No part of this publication may be reproduced or
transmitted in any form or by any means, electronically or mechanically,
including photocopying, recording or any information storage or retrieval
system, without either prior permission in writing from the publisher or a
licence permitting restricted copying. In the United Kingdom such licences
are issued by the Copyright Licensing Agency: 90 Tottenham Court Road,
London WlP 9HE.
Whilst the advice and information in this book is believed to be true and
accurate at the date of going to press, neither the authors nor the publisher
can accept any legal responsibility for any errors or omissions that may be
made.
British Library Cataloguing in Publication Data
Higgins, Raymond A.
Engineering Metallurgy.—Vol. 1: Applied
Physical Metallurgy.—6 Rev. ed.
I. Title
669
ISBN 0 340 56830 5
14 15 16 17 18 19 20
Typeset in 10/1 lpt Linotron Times by Rowland Phototypesetting Ltd,
Bury St. Edmunds, Suffolk
Printed and bound in Great Britain by J W Arrowsmith Ltd, Bristol
PREFACE
To the First Edition
This text-book constitutes Part I of 'Engineering Metallurgy' and is
intended primarily for students taking metallurgy as an examination sub-
ject for a Higher National Certificate in Mechanical or Production Engin-
eering. The author hopes that it may also prove useful to undergraduates
studying metallurgy as an ancillary subject in an Engineering Degree
course. To students for whom metallurgy is a principal subject the book
can offer a helpful approach to certain sections of the work in preparation
for the Higher National Certificate and the City and Guilds Final Certifi-
cates in Metallurgy.
Comprehensive tables covering most of the alloys of importance to
engineers are given in the appropriate chapters. In these tables an attempt
has been made to relate British Standard Specifications to many commer-
cially produced alloys. The author hopes that these tables will remain of
use when the reader, no longer a student, finds it necessary to choose
alloys for specific engineering purposes.
A generation ago much of a student's time was spent in dealing with the
principles of extraction metallurgy. The widened scope of applied physical
metallurgy has, however, in recent years, established prior claims upon
the time available. Hence the brief survey in Chapter 2 of the production
of iron and steel has to serve as a sufficient introduction to the methods
of extraction metallurgy in general.
In the main, then, this book deals with the microstructural and mechan-
ical properties of metals and alloys. Processes such as heat-treatment,
surface hardening and welding are dealt with from the theoretical as well
as the practical aspect. The author trusts that the treatment in Chapter 1
of the basic principles of chemistry will enable readers to follow the study
of engineering metallurgy without being at a disadvantage if they have not
previously studied chemistry as an independent subject.
It has been considered desirable to provide a basis for practical metal-
lography; hence details of laboratory techniques are dealt with in
Chapter 10.
At the end of each chapter will be found a selection of questions and
exercises. Many of these have been taken from Higher National Certificate
examination papers, and the author is greatly indebted to those authorities
who have given permission for such questions to be used.
Although 'Engineering Metallurgy' Part II (Metallurgical Process Tech-
nology) is strictly speaking a sequel to the present volume, it may on
occasion be read with advantage as a companion book—particularly when
the approved syllabus for the Engineering Higher National Certificate is
more than usually ambitious, or when direct contacts of students with
metallurgical processes are limited by local circumstances.
In both Parts sections are numbered on the decimal system. In Part II
frequent references to appropriate sections of Part I make it easy for the
reader to look up the metallurgical principles governing any particular
process under study.
Except where otherwise stated, the photomicrographs in this book are
the work of the author or his students.
The author wishes to record his thanks to his wife for considerable help
in producing the line diagrams; and to his friends J. H. Parry, Esq., FIM,
of the School of Technology, Ipswich, and A. N. Wyers, Esq., AIM, of
the Chance Technical College, for reading the original MS and making
many helpful suggestions. He also wishes to record his appreciation of the
generous assistance given to him at all stages in the production of this book
by W. E. Fisher, Esq., OBE, DSc.
The author wishes to acknowledge the considerable help given by those
connected with various industrial organisations, but in particular W. E.
Bardgett, Esq., BSc, FIM (Messrs. United Steel Companies Ltd., Shef-
field); J. F. Hinsley, Esq. (Messrs. Edgar Allen and Co. Ltd., Sheffield);
Dr. J. R. Rait (Messrs. Hadfields Ltd., Sheffield); Dr. R. T. Parker and
Dr. A. N. Turner (Messrs. Aluminium Laboratories Ltd., Banbury);
Messrs. Samuel Osborn & Co. Ltd., and Prof. Dr. Fritz Gabler and
Messrs. C. Reichert of Vienna.
R. A. HIGGINS
Department of Science,
The Technical College,
West Bromwich, Staffs.
PREFACE
To the Sixth Edition
In 1937 I was a fledgling graduate with slim expectations of making a
decent living as a scientist in British industry. The most exciting job the
University Appointments Board was able to suggest for me involved the
routine testing of aircraft carburettors on a twelve-hour shift basis (days
and nights turn about) for the princely pittance of two guineas (£2.10)
per week. Not unnaturally I spurned the offer and my name was summarily
expunged from the files of the Appointments Board lest my 'unhelpful
attitude' upset the delicate susceptibilities of their 'important clients' were
I to be let loose near them.
There followed a dismal period when I eked out a precarious existence
by twanging a Hawaiian steel guitar in a hula-hula band, performing in
some of the more malodorous fleapits which served as variety theatres in
those days of the nineteen-thirties. My lingering memory of that period of
my life is not of the alleged glamour of showbiz but of the acrid smell of
soft soap trapped in the wide cracks between the floorboards of the grubby
little dressing rooms.
As war clouds gathered late in 1938 and the more enlightened sections of
the metals industry anticipated the future need of scientists, I was offered a
job at the then quite reasonable weekly wage of £3.10s (£3.50). This I
grabbed with alacrity—after all it was a wage equal to that of a general
shop-floor worker and slightly more than half that paid to the semi-skilled
brass casters who were placed under my care, so who was I to grumble?
It will come as no surprise to the reader to learn that as soon as was
possible I quit British industry for ever and sought employment in technical
education, an occupation which for the next thirty-five years provided
intellectual freedom, a decent standard of life, time to become a mountain-
eer—and to write text books.
During the days which have followed the Second World War the func-
tions of the scientist and engineer in industry have reputedly become
increasingly important. But has status and remuneration improved pro-
portionally? I suspect not. An examination of recent job advertisements
leads me to believe that, allowing for some fifty years of inflation coupled
with a higher proportion of salary lost to taxation as compared with pre-war
days, real remuneration has changed little for the young graduate. Only
the jargon of the advertisement is different. Now, instead of 'qualifications
and experience', your 4CV is required and the salary is quoted in £K—
meant to impress I suppose. One advertisement I noticed recently pre-
ferred a 'Chartered Engineer or equivalent'. What, I wondered, would
be regarded as an 'equivalent'? Applicants were asked to write to the
'Human Resources Department' which suggested to me that a prospective
employee would be equated with so many tons of coal or some other
expendable commodity. What's wrong with the old title 'Personnel Office'
for God's sake? One wonders whether such an organisation has recruited
Monty Python as its managing director.
It is now almost forty years since the late Dr W. E. Fisher, OBE, bullied
me into producing the manuscript which became the First Edition of this
book. Then in his late seventies and the dynamic Technical Editor of the
then English Universities Press, he remains a great inspiration to me now
that I in turn find myself at a similar age. Originally the book was written
as a text for those student engineers taking metallurgy as a subject in
the Higher National Certificate (Engineering) Courses. At the temporary
demise of the Higher National Certificate some ten years ago this volume
was largely rewritten to provide a treatment of general physical metallurgy
at the elementary and intermediate levels.
When some years previously, 'metallurgy' had been replaced by
'materials science' in engineering syllabuses, many authors—attempting
an adroit vault on to the bandwaggon—added a hurried chapter on 'plas-
tics' to their existing texts. In many cases this served only to display a
rather nebulous understanding of the true nature of the covalent bond. No
mention was made of other non-metallic engineering materials. Obviously
in almost forty years many new sophisticated metallic alloys have been
developed whilst other metals, hitherto known only as symbols in the
Periodic Classification of the Elements, have been drawn into the technol-
ogy of the late twentieth century. Thus lithium, scandium, gallium, yttrium,
indium, lanthanum, praseodymium, neodynium, samarium, gadolinium,
dysprosium, erbium, thulium and ytterbium have all found uses during
recent years in commercial alloys. They join boron, titanium, germanium,
zirconium, niobium, cerium, hafnium and tantalum which had become
metallurgically valuable during the immediately previous decades. Conse-
quently this book has grown over the years so that it contains some 40%
more pages than the first edition. Nevertheless it is still confined to a study
of metallurgy and those who wish to study materials science for HNC or
on a more general level should consult other titles.
R. A. HIGGINS
Walsall,
West Midlands.
Dedicated to My Wife, Helen,
Who helped with the First Edition almost forty years ago—
and who still provides cups of tea whilst I scribble.
'The smith also sitting by the anvil, and considering the iron work, the
vapour of the fire wasteth his flesh, and he fighteth with the heat of the
furnace: the noise of the hammer and the anvil is ever in his ears and his
eyes look still upon the pattern of the thing that he maketh; he setteth his
mind to finish his work, and watcheth to polish it perfectly . . .'
Ecclesiasticus, c. 38; v. 28.
Contents
Preface to the First Edition .................................................. v
Preface to the Sixth Edition ................................................. vii
1. Some Fundamental Chemistry .................................. 1
1.1 Atoms, Elements and Compounds ............................... 2
1.2 Chemical Reactions and Equations .............................. 7
1.3 Oxidation and Reduction ............................................... 9
1.4 Acids, Bases and Salts .................................................. 11
1.5 Atomic Structure ............................................................ 12
1.6 Chemical Combination and Valence ............................. 18
1.7 Secondary Bonding Forces ........................................... 26
1.8 Isotopes ......................................................................... 27
1.9 Exercises ....................................................................... 29
1.10 Bibliography ................................................................... 30
2. The Physical and Mechanical Properties of
Metals and Alloys ....................................................... 31
2.1 Fundamental Mechanical Properties ............................ 34
2.2 Tenacity or Tensile Strength ......................................... 35
2.3 Hardness Tests .............................................................. 42
2.4 Impact Tests .................................................................. 48
2.5 Other Destructive Tests ................................................. 49
2.6 Non-destructive Tests .................................................... 50
2.7 The Detection of Surface Faults .................................... 50
2.8 The Detection of Internal Defects .................................. 51
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xii Contents
2.9 Exercises ....................................................................... 56
2.10 Bibliography ................................................................... 57
3. The Crystalline Structure of Metals ........................... 58
3.1 Blow-holes ..................................................................... 71
3.2 Shrinkage ....................................................................... 72
3.3 Segregation of Impurities .............................................. 73
3.4 Line and Points Defects in Crystals .............................. 75
3.5 Exercises ....................................................................... 76
3.6 Bibliography ................................................................... 78
4. Mechanical Deformation and Recovery .................... 79
4.1 Energy of Mechanical Deformation ............................... 89
4.2 Annealing and Recrystallisation .................................... 90
4.3 Superplasticity ............................................................... 96
4.4 Exercises ....................................................................... 99
4.5 Bibliography ................................................................... 99
5. Fracture of Metals ....................................................... 101
5.1 Brittle Fracture ............................................................... 102
5.2 Ductile Fracture ............................................................. 104
5.3 Factors Leading to Crack Formation ............................. 105
5.4 Ductile-brittle Transition in Steels .................................. 108
5.5 Fatigue ........................................................................... 109
5.6 Creep ............................................................................. 114
5.7 Exercises ....................................................................... 117
5.8 Bibliography ................................................................... 118
6. The Industrial Shaping of Metals ............................... 119
6.1 Sand Casting, Die Casting and Allied Processes ......... 120
6.2 Hot-working Processes ................................................. 124
6.3 Cold-working Processes ................................................ 128
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Contents xiii
6.4 Sintering from a Powder ................................................ 133
6.5 The Machinability of Metals and Alloys ......................... 134
6.6 Exercises ....................................................................... 139
6.7 Bibliography ................................................................... 139
7. An Introduction to Steel ............................................. 140
7.1 Pig Iron Production ........................................................ 141
7.2 The Manufacture of Steel .............................................. 145
7.3 Basic Oxygen Steelmaking (BOS) ................................ 147
7.4 Electric Arc Steelmaking ................................................ 149
7.5 The Microstructural Nature of Carbon Steels ................ 150
7.6 The Uses of Plain Carbon Steels .................................. 156
7.7 Exercises ....................................................................... 158
7.8 Bibliography ................................................................... 159
8. The Formation of Alloys ............................................. 160
8.1 The Solid Solution ......................................................... 162
8.2 Intermediate Phases ...................................................... 169
8.3 Eutectics and Eutectoids ............................................... 172
8.4 Strengthening Mechanisms in Alloys ............................ 175
8.5 Exercises ....................................................................... 177
8.6 Bibliography ................................................................... 178
9. Thermal Equilibrium Diagrams .................................. 179
9.1 The Phase Rule ............................................................. 182
9.2 Case I – Two Metals Which Are Only Partially
Soluble in Each Other in the Liquid State ..................... 187
9.3 Case II – Two Metals Mutually Soluble in All
Proportions in the Liquid State Becoming
Completely Insoluble in the Solid State ........................ 189
9.4 Case III – Two Metals, Mutually Soluble in All
Proportions in the Liquid State, Remain Mutually
Soluble in All Proportions in the Solid State .................. 191
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