Table Of Content

Steels This page intentionally left blank 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 Butterworth-Heinemann is an imprint of Elsevier Butterworth-HeinemannisanimprintofElsevier LinacreHouse,JordanHill,OxfordOX28DP,UK 30CorporateDrive,Suite400,Burlington,MA01803,USA Firstedition1981 Secondedition1995 Reprinted1976,2000 Transferredtodigitalprinting2003 Thirdedition2006 Copyright©2006,R.W.K.HoneycombeandH.K.D.H.Bhadeshia.PublishedbyElsevierLtd. Allrightsreserved Nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmittedinany formorbyanymeanselectronic,mechanical,photocopying,recordingorotherwisewithout thepriorwrittenpermissionofthepublisher PermissionsmaybesoughtdirectlyfromElsevier’sScience&TechnologyRights DepartmentinOxford,UK:phone( 44)(0)1865843830;fax( 44)(0)1865853333; + + email:permissions@elsevier.com.Alternativelyyoucansubmityourrequestonlineby visitingtheElsevierwebsiteathttp://elsevier.com/locate/permissions,andselecting ObtainingpermissiontouseElseviermaterial Notice Noresponsibilityisassumedbythepublisherforanyinjuryand/ordamagetopersonsorpropertyasa matterofproductsliability,negligenceorotherwise,orfromanyuseoroperationofanymethods,products, instructionsorideascontainedinthematerialherein.Becauseofrapidadvancesinthemedicalsciences, inparticular,independentverificationofdiagnosesanddrugdosagesshouldbemade BritishLibraryCataloguinginPublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary LibraryofCongressCataloginginPublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress ISBN-13:978-0-750-68084-4 ISBN-10:0-7506-8084-9 For information on all Butterworth-Heinemann publications visitourwebsiteathttp://books.elsevier.com CoverImages,usedwithpermission Inset:δ-TRIPsteel,S.Chatterjee Background:magneticfieldduetoasmallparticleofiron,enclosedinacarbontube, T.Kasama,R.Dunin–Borkowski,K.KoziolandA.H.Windle. TypesetbyCharonTecLtd,Chennai,India www.charontec.com PrintedandboundinGreatBritain 0607080910 10987654321 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