Steels: Microstructure and Properties, Third Edition

357 Pages·2006·7.445 MB·English

by  Harry Bhadeshia, Robert Honeycombe

Steels
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Steels
Microstructure and Properties
Third edition
H. K. D. H. Bhadeshia
Professor of Physical Metallurgy
University of Cambridge
and
Adjunct Professor of Computational Metallurgy
Graduate lnstitute of FerrousTechnology,POSTECH
and
Sir Robert Honeycombe
Emeritus Goldsmiths’ Professor of Metallurgy
University of Cambridge
AMSTERDAM (cid:127) BOSTON (cid:127) HEIDELBERG (cid:127) LONDON (cid:127) NEW YORK (cid:127) OXFORD
PARIS (cid:127) SAN DIEGO (cid:127) SAN FRANCISCO (cid:127) SINGAPORE (cid:127) SYDNEY (cid:127) TOKYO
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Firstedition1981
Secondedition1995
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Inset:δ-TRIPsteel,S.Chatterjee
Background:magneticfieldduetoasmallparticleofiron,enclosedinacarbontube,
T.Kasama,R.Dunin–Borkowski,K.KoziolandA.H.Windle.
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CONTENTS
Prefacetothefirstedition ix
Prefacetothesecondedition x
Prefacetothethirdedition xi
1 Ironanditsinterstitialsolidsolutions 1
1.1 Introduction 1
1.2 Theallotropesofpureiron 2
1.3 Thephasetransformation:α-andγ-iron 4
1.4 Carbonandnitrogeninsolutioninα-andγ-iron 8
1.5 Somepracticalaspects 15
Furtherreading 16
2 Thestrengtheningofironanditsalloys 17
2.1 Introduction 17
2.2 Workhardening 18
2.3 Solidsolutionstrengtheningbyinterstitials 20
2.4 Substitutionalsolidsolutionstrengtheningofiron 27
2.5 Grainsize 27
2.6 Dispersionstrengthening 32
2.7 Anoverallview 33
2.8 Somepracticalaspects 34
2.9 Limitstostrength 35
Furtherreading 38
3 Theiron–carbonequilibriumdiagramandplaincarbonsteels 39
3.1 Theiron–carbonequilibriumdiagram 39
3.2 Theaustenite–ferritetransformation 42
3.3 Theaustenite–cementitetransformation 44
3.4 Thekineticsoftheγ αtransformation 45
→
3.5 Theaustenite–pearlitereaction 53
3.6 Ferrite–pearlitesteels 67
Furtherreading 69
4 Theeffectsofalloyingelementsoniron–carbonalloys 71
4.1 Theγ-andα-phasefields 71
4.2 Thedistributionofalloyingelementsinsteels 74
v
vi CONTENTS
4.3 Theeffectofalloyingelementsonthekineticsofthe
γ/αtransformation 77
4.4 Structuralchangesresultingfromalloyingadditions 84
4.5 Transformationdiagramsforalloysteels 91
Furtherreading 92
5 Formationofmartensite 95
5.1 Introduction 95
5.2 Generalcharacteristics 95
5.3 Thecrystalstructureofmartensite 100
5.4 Thecrystallographyofmartensitictransformations 103
5.5 Themorphologyofferrousmartensites 106
5.6 Kineticsoftransformationtomartensite 112
5.7 Thestrengthofmartensite 120
5.8 Shapememoryeffect 126
Furtherreading 127
6 Thebainitereaction 129
6.1 Introduction 129
6.2 Upperbainite(temperaturerange550–400 C) 129
◦
6.3 Lowerbainite(temperaturerange400–250 C) 132
◦
6.4 Theshapechange 135
6.5 Carboninbainite 135
6.6 Kinetics 139
6.7 Thetransitionfromuppertolowerbainite 143
6.8 Granularbainite 144
6.9 Temperingofbainite 145
6.10 Roleofalloyingelements 146
6.11 Useofbainiticsteels 147
6.12 Nanostructuredbainite 152
Furtherreading 154
7 Acicularferrite 155
7.1 Introduction 155
7.2 Microstructure 155
7.3 Mechanismoftransformation 157
7.4 Theinclusionsasheterogeneousnucleationsites 161
7.5 Nucleationofacicularferrite 162
7.6 Summary 164
Furtherreading 164
8 Theheattreatmentofsteels:hardenability 167
8.1 Introduction 167
8.2 UseofTTT andcontinuouscoolingdiagrams 168
CONTENTS vii
8.3 Hardenabilitytesting 170
8.4 Effectofgrainsizeandchemicalcomposition
onhardenability 176
8.5 Hardenabilityandheattreatment 177
8.6 Quenchingstressesandquenchcracking 179
Furtherreading 181
9 Thetemperingofmartensite 183
9.1 Introduction 183
9.2 Temperingofplaincarbonsteels 184
9.3 Mechanicalpropertiesoftemperedplaincarbonsteels 190
9.4 Temperingofalloysteels 191
9.5 Maragingsteels 207
Furtherreading 207
10 Thermomechanicaltreatmentofsteels 209
10.1 Introduction 209
10.2 Controlledrollingoflow-alloysteels 210
10.3 Dual-phasesteels 220
10.4 TRIP-assistedsteels 223
10.5 TWIPsteels 229
10.6 Industrialsteelssubjectedtothermomechanicaltreatments 231
Furtherreading 233
11 Theembrittlementandfractureofsteels 235
11.1 Introduction 235
11.2 Cleavagefractureinironandsteel 235
11.3 Factorsinfluencingtheonsetofcleavagefracture 237
11.4 Criterionfortheductile/brittletransition 240
11.5 Practicalaspectsofbrittlefracture 243
11.6 Ductileorfibrousfracture 245
11.7 Intergranularembrittlement 252
Furtherreading 258
12 Stainlesssteel 259
12.1 Introduction 259
12.2 Theiron–chromium–nickelsystem 259
12.3 ChromiumcarbideinCr–Niausteniticsteels 264
12.4 Precipitationofniobiumandtitaniumcarbides 267
12.5 Nitridesinausteniticsteels 270
12.6 Intermetallicprecipitationinaustenite 270
12.7 Austeniticsteelsinpracticalapplications 273
viii CONTENTS
12.8 Duplexandferriticstainlesssteels 274
12.9 Mechanicallyalloyedstainlesssteels 278
12.10 Thetransformationofmetastableaustenite 281
Furtherreading 286
13 Weldmicrostructures 287
13.1 Introduction 287
13.2 Thefusionzone 287
13.3 TheHAZ 298
Furtherreading 306
14 Modellingofmicrostructureandproperties 307
14.1 Introduction 307
14.2 Example1:alloydesign–high-strengthbainiticsteel 309
14.3 Example2:mechanicalpropertiesofmixedmicrostructures 315
14.4 Methods 321
14.5 Kinetics 326
14.6 Finiteelementmethod 329
14.7 Neuralnetworks 330
14.8 Definingcharacteristicsofmodels 333
Furtherreading 334
Index 335
PREFACETOTHE FIRST EDITION
In this book, I have attempted to outline the principles which determine the
microstructures of steels and through these the mechanical properties. At a
timewhenourmetallographictechniquesarereachingalmosttoatomicresolu-
tion,itisessentialtoemphasizestructureonthefinestscale,especiallybecause
mechanicalpropertiesaresensitivetochangesatthislevel.Whilethisisnota
bookontheselectionofsteelsfordifferentuses,Ihavetriedtoincludesufficient
informationtodescribehowbroadcategoriesofsteelsfulfilpracticalrequire-
ments. However, the main thrust of the book is to examine analytically how
the γ/α phase transformation is utilized, and to explain the many effects that
non-metallicandmetallicalloyingelementshave,bothonthistransformation
andonotherphenomena.
Thisbookiswrittenwiththeneedsofmetallurgists,materialsscientistsand
engineersinmind,andshouldbeusefulnotonlyinthelateryearsofthefirst
degree and diploma courses but also in postgraduate courses.An elementary
knowledge of materials science,metallography,crystallography and physics is
assumed.
Iamindebtedtoseveralcolleaguesfortheirinterestinthisbook,particularly
Dr D.V. Edmonds, who kindly read the manuscript, Dr P. R. Howell, Dr B.
MuddleandDrH.K.D.H.Bhadeshia,whomadehelpfulcommentsonvarious
sections,andnumerousothernumbersofmyresearchgroupwhohaveprovided
illustrations.Iwishalsotothankmycolleaguesindifferentcountriesfortheir
kind permission to use diagrams from their work. I am also very grateful to
Mr S. D. Charter for his careful preparation of the line diagrams. Finally, my
warmest thanks go to Mrs DianaWalker and Miss Rosemary Leach for their
carefulanddedicatedtypingofthemanuscript.
RWKH
Cambridge
1980
ix