BiographyZHOUJian(１９８３mdash)MaleDoctorCandidate　EＧmailzhouＧjianＧ１６８１６３1049008com　ReceivedDateJune４２０１２

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JOURNALOFIRONANDSTEELRESEARCHINTERNATIONAL1049008２０１３２０(９)１１７Ｇ１２５10512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273105127310512731051273

MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD

ZHOUJian　MADangＧshen　CHIHongＧxiao　CHENZaiＧzhi　LIXiangＧyang(CentralIronandSteelResearchInstituteBeijing１０００８１China)

AbstractComparedwithH１３steeltheinfluencesofdifferentheattreatmentprocessonthemicrostructureandpropertiesofthenewtypeofhotworkingdiesteelH１３MODwerestudiedTheresultsshowthatthecompleteausＧtenitizingtemperatureofH１３MODisaround１０３０ andthequenchinghardnessachievesthemaximumvalueatthistemperatureWhileforH１３thecompleteaustenitizingtemperatureisabove１１００andthequenchinghardnessriseconstantlywiththequenchingtemperatureincreasingInquenchingprocesstheundissolvedMCcarbidescanpreventthecoarseningofgraininbothsteelsWiththeriseofquenchingtemperaturewhenMCcarbidesdissolvecompletelythegraingrowsquicklyThehardnessandstrengthofH１３MODathighertemperingtemperature(above５７０)arenearlythesameasthoseofH１３butitstoughnessishigherthanthatofH１３Mo２CcarbideisthemainstrengtheningphaseinH１３MODwhichisattributedtothehighercontentofMoThequantityofVCeutecticcarＧbidesisreducedbecauseoflowercontentofVinH１３MODwhichplaysanimportantroleinenhancingtheimpacttoughnessofH１３MODUnderacertainstrengthconditionH１３MODsteelcanbeusedintheenvironmentthathighertoughnessisrequiredandtheservicelifeofdiecastingmoldcanbeimprovedKeywordshotworkingdiesteelhardnessheattreatmentimpactductilitytensilestrength

　　DiecastingisaneconomicalwaytoproducelargequantitiesofcomplicatedshapedproductsoflightmetalswithhighprecisionandgoodsurfacefinishThemostimportantfailuremechanismsthatlimittheperformanceandservicelifeoftoolsinaluminＧiumandbrassdiecastingapplicationsarethermalfatiguecrackingerosioncorrosionsolderingandgrossfracture[１]Morethan８０failuresofthediesarecausedbythermalfatiguecheckingToincreasetheheatcheckingresistancethetoolsteel musthavegoodhighＧtemperaturestrengthhighＧtemperＧaturetoughnessandthermalconductivity[２]AISIH１３isthemostpopularsteelfordiecastingapplicaＧtionInthediecastingprocessthetoughnessshortＧageofH１３alwaysoccurswhichleadstothefailureofdieＧcastingmoldThereforetoimprovethemaＧterialtoughnessbecomesthe mainpurposeofenＧhancingtheservicelifeofdiesteelinacertaincondiＧtionofstrengthandhardnessInhotworkingdiesteeltheprecipitationofdifferenttypeofcarbideisanimportantfactortoaffectthestrengthandtoughＧnessofsteelandintroducingalloyingelementstomodifythesecondaryprecipitationseemstobea

morerelevantrouteforcasting dies orforgingtools[３]DieＧcastingsteelsoftencontainalloyingeleＧmentsofMoandVwhichcanimprovethestrengthofsteelbytheformationoffinecarbidesButtheexＧtraadditionofVinducestheheterogeneityofvanaＧdiumconcentrationwithinthematrixandtheforＧmationofsomeeutecticcarbides (VC)mayaffecttheimpacttoughnessofsteelThisisalsothereasonthatH１１steel(０1049008４Vmasspercent)hashighertoughnessthanthatofH１３steel(１1049008０VmassperＧcent)TheaustenitizationconditionscouldnotbemodifiedtoanextentbytheadditionofMo(２1049008７masspercent)wheresufficientdissolutionoccurredbecauseprimarycarbidesarefoundinquantitieswhichhaveadetrimentaleffectonthecharpyimpactenergy[３]Forthesereasonsmodified H１３steelwasdeveloped to meetthe aboverequirementsComparedwith H１３thenew H１３MODsteelhaslowercontentsofSiandVInadditiontothattoincreasethecontentofMoproperlycanensurethestrengthofsteelathightemperatureInthispaperthemicrostructureandmechanicalpropertiesoftheH１３MODarestudiedandcomparedwithH１３steel

１　ExperimentalMaterialsandMethods

　　Twokindsofexperimentalsteelsinthisstudywerepreparedbyvacuummeltingof２５kgingotfolＧlowedbyhotforgingtoproduceroundbarwithsizeofϕ１６mmtimes５００mmThechemicalcompositionoftestingsteelislistedinTable１Afterforging８７０－７６０isothermalannealingprocesswasadoptedforthefinalproductTheannealinghardnessesofH１３

andH１３MODareHB２０３andHB２００respectivelySpheroidalannealingstructuregradeof H１３andH１３MODbelongtotheratingofAS３andAS１reＧspectivelyaccordingtotheNADCA２０７Ｇ２００３annealedquality microstructurechartAfterannealingtheroundbar wascutintohardnesstestingsampleswithsizeof１２mmtimes１２mmtimes１６mmASTMstandardϕ５tensiletestpieceandCharpyUＧnotchedimpactspecimenswithsizeof１０mmtimes１０mmtimes５５mminlongitudinaldirectioninthecenteroftheroundbar

　　　　　　Table１　Chemicalcompositionofteststeel　　　　　　 　 (masspercent)

Steel C Si Mn S P Cr Mo V

H１３ ０1049008４４ ０1049008９４ ０1049008４１ ０1049008００６ ０1049008００９６ ４1049008６９ １1049008２２ ０1049008８４H１３MOD ０1049008３８ ０1049008３８ ０1049008４９ ０1049008００６ ０1049008００９７ ５1049008１３ １1049008８４ ０1049008４９

　　InordertodeterminethehardeningtreatmentprocessesoftestedsteelthehardnesstestingsamＧpleswerepreheatedat５００for３０minthenausＧtenitizedfor３０minatdifferenttemperaturesof９２０９５０９８０１０００１０３０１０６０and１１００inMufflefurnacewhichisfollowedbyoilquenching　　Inordertoresearchtheinfluenceoftemperingtemperatureonthemicrostructureandpropertiesoftestedsteeltensiletestpiecesandimpactspecimenswereaustenitizedfor３０minat１０３０quenchedinoilandthentemperedatdifferenttemperaturesof４５０４８０７１０５４０５７０６００and６５０for２htwice　 　 The annealed hardness was determined byHP２５０hardmeterwhilethequenchingandtempeＧringhardnessesweredeterminedbyTIME TH３００hardmeterTensilepropertiesweredeterminedonanLOS６００tensiletestmachineImpacttestonCharpyUＧnotchedsampleswasperformedfordeterminingimpacttoughnesswithaJB３０Bimpacttestmachineatroomtemperature　　MetallographicanalysiswasdonebyusinganLEICA MEF４opticalmicroscopeanHITACHISＧ４３００electronicscanningmicroscope(SEM)attachedanEDAXGENESIS６1049008０spectrumanalyzer(EDS)andanH８００transmissionelectronmicroscope(TEM)

２　ResultsandDiscussion２1049008１　Effectofquenchingtemperatureonhardnessandmicrostructure　 　 The variations of hardness with differentquenchingtemperatureforH１３andH１３MODsteelsareshowninFig1049008１ThehardnessesofthesetwosteelsrisewiththeincreaseofquenchingtemperaＧturewhenthetemperatureisbelow１０３０andthe

Fig1049008１　HardnessandgraingradecurvesofH１３andH１３MODatdifferentquenchingtemperatures

hardnessofH１３MODishigherthanthatofH１３Thehardnessof H１３MODreachesthe maximumvalueat１０３０ andhasnofurtherincreasewiththeriseofquenchingtemperaturewhilefor H１３steelitstillkeepsonincreasingThehardnessofH１３steelisHRC２1049008７higherthanthatofH１３MODsteelwhenquenchedat１１００Theaustenitizationconditionsofbothsteelsarecalculated by usingThermoＧCalcsoftware(Fig1049008２)Theresultsshowthatinthetemperaturerangeof５００－１２００ thecarＧbidesofM２３C６MCandM７C３existinH１３steelaswellas M２３C６MCand M６Cexistin H１３MODsteelExceptMCcarbidesnoM２３C６M６CM７C３

carbidesleftinH１３andH１３MODwhenthequenchＧingtemperatureisabove９００ThedissolvingtemＧperatureofMCcarbidesforH１３is１１４１whichis１０１higherthanthatofH１３MODItisremarkＧablethatthedissolvingtemperatureofMCcarbidesisjustthecompleteaustenitizingtemperatureofthetwosteelsWhensolutiontemperatureisbelow１０３０carbonisnotcompletelydissolvedintotheaustenite

1048944８１１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

(a)H１３　 (b)H１３MODFig1049008２　Effectoftemperatureontransformedamountofcarbides

butexistsintheformofundissolvedMC(VＧrich)inH１３ItisclearthattheasＧquenchedhardnessisgreatlyaffectedbytheextentofsolidsolutionhardＧeningbycarbonandalloyingelementsAsthetemＧperatureincreasesmoreand morecarbidesdisＧsolvethusenrichingtheausteniteincarbonandalＧloyingelementsHighercarbonandalloyingeleＧmentsintheaustenite(uptoalimit)willleadtohigherhardnessofthemartensiteproducedfromthisaustenite[４]ThecarbidesinH１３MODaredissolvedat１０３０ completelywhilein H１３itneedsahigheraustenitizingtemperaturetobringthemintosolidstatesolutionentirelysothehardnessofH１３islowerthanthatofH１３MODwhensolutiontemＧperatureisbelow１０３０WhenquenchingtemperＧatureishigherthan１０３０ H１３MODhasbeencompletelyaustenizitingThereforewiththeriseofquenchingtemperaturethehardnessofH１３MODhasnofurtherincreasewhileforH１３MCcarbides(VＧrich)dissolveintoaustenitematrixcontinuouslywhichleadstothecontentofcarboninquenchingmartensiteincreasesgraduallyandthehardnessinＧcreasescorrespondingly　　Fig1049008３showsthemetallographicstructuresofbothH１３andH１３MODquenchedat１０００and１０３０ TherearealotofundissolvedsmallcarbidesinmarＧtensiticmatrixofbothsteelswhenquenchedat１０００[Fig1049008３(a)and(b)]butat１０３０ undissolvedcarbidescanonlybefoundinH１３[Fig1049008３(c)]Itiscleartoseethattheundissolved MCparticles(VＧrich)existinH１３whenquenchedat１０３０ [Fig1049008４(a)]whileinH１３MODnearlyallcarbidesaredisＧ

solvedandthemicrostructureismartensite[Fig1049008４(b)]atthistemperatureFromtheaboveresultsitcanbeseenthattheresultscalculatedbyThermoＧCalcoftheteststeelsareingoodagreementwiththeexperimentalones　　AccompanyingwiththedissolutionofthealloycarbidesandtheincreasingofaustenitizingtemperaＧtureausteniticgrainsizeincreasesasindicatedinFig1049008１ButforH１３MODcoarseningofthegrainsizeismuch moreobviousthanthatof H１３especiallywhenthequenchingtemperatureisabove１０３０ ThisisattributedtotheundissolvedcarbidesthatinhibitgraingrowthinH１３steelthusthegrainsizestillretains９gradesuntilthequenchingtemperaturereaches１０６０ButitiseasytorecognizethatthebrittlenessofsteelriseswiththehardnessincreasＧingespeciallythelargesizeworkpiecewhichisveryeasytocrackwhenquenchingat１０６０Soitismuchbettertochoose１０３０ asthereasonablequenchingtemperaturewhichisestablishedempiriＧcallyforeachsteelonthebasisofattainablehardＧnessandgraincoarsening

２1049008２　EffectoftemperingtemperatureonmicrostrucＧtureandmechanicalproperties　　Fig1049008５showstheplotsoftemperedhardnesstenＧsilestrengthreductionofarea(Z)andelongationafterfracture(A)asfunctionsoftemperingtemperatureforH１３and H１３MODAstemperingtemperatureincreasesthehardnessfirstincreasestoamaximumandthengraduallydecreasesBothofthetwosteelsundergosecondaryhardeningassociatedwiththeprecＧ

1048944９１１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)H１３１０００　 (b)H１３MOD１０００　 (c)H１３１０３０　 (d)H１３MOD１０３０Fig1049008３　Metallographicstructuresofteststeelsquenchedat１０００and１０３０

(a)H１３　 (b)H１３MODFig1049008４　SEM microstructuresofteststeelsquenchedat１０３０

ipitationofalloycarbidesintempered martensiteTheprecipitationofsecondarycarbidesretardssofＧteningandincreasesthehardnessesofthetwosteelsH１３hasasecondaryhardeningpeakat５１０ whileforH１３MODitisat４８０ AndthetemperedhardnessofH１３MODisslightlylowerthanthatofH１３whenthetemperatureisbelow５４０ Whenthetemperatureisabove５４０H１３andH１３MODsteelshavenearlythesamehardness　　ThevariationoftensilestrengthwithtemperingtemperatureinFig1049008５showsnearlythesametrendashardnessThetensilestrengthofH１３ishigherthan

thatofH１３MODwhenthetemperingtemperatureisbelow５４０andreachesitsmaximumat５１０whichisalsotheminimumvalueofreductionofareaThemixＧclusterwhichiscalled [MＧC]segregationgroupdevelopedby MoCrandCatomsonαＧphaseinduceslatticedistortion[５]andthesmallVCparticlesprecipitatedwhiletemperinggeneratesigＧnificantsecondaryphasestrengthening[６]whichinＧducesatensilestrengthincrementofH１３comparedwithH１３MODinthistemperaturerangeWiththeincreaseoftemperingtemperaturethedifferenceofreductionofareabetweenthetwosteelstendstobe

1048944０２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008５　Influencesofhardnesstensilestrengthreductionofarea(Z)andelongationafterfracture(A)ondifferenttemperingtemperaturesofH１３steelandH１３MODsteel

smallerH１３MODhasabetterductilitycomparedwithH１３AtthehighertemperingtemperatureesＧpeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　　Thethin martensitelathsanddispersedcarＧbidesarefoundinthetemperedmicrostructuresofH１３andH１３MOD (quenchedat１０３０ andtemＧperedat６００ )therearemuch morelargesizeM２３C６ (CrＧrich)M６C (MoＧrich)andMC (VＧrich)carbides(distinguishedbyEDS)existinH１３steelcompared with H１３MOD steel (Fig1049008６)In H１３steelarapidcarbidetransitionwhichnegativelyinfluencestheprecipitationstrengtheningoccursatmoderatelyhightemperatures(６００)ThedistriＧbutionofundissolvedVＧrichcarbides(MC)transＧformstoacoarserdistributionofCrＧrichcarbides(M２３C６)whicharelesseffectivefromaprecipitatiＧonstrengthening perspective[７]Fig1049008７ showstheTEMimagesofpartcarbidesinH１３steelunderdifＧ

ferentheattreatmentconditionsTheTEMinvestiＧgationsrevealedundissolved MCcarbides(VＧrich)andthecoarseningofM６CandM２３C６carbidepartiＧclesinmatrix [Fig1049008７ (a)]whichmayleadtothedecreaseofstrengtheningeffect　　Fig1049008８showstheTEMimagesofcarbidesinH１３MODsteelaftertemperingat５４０and６００ItcanbeseenthatanumberofsmallrodＧlikecarbideparticlesarethemainmicrostructuralfeaturewhentemperedat５４０ [Fig1049008８(a)]Diffractionpatternofcarbidestemperedat６００ [Fig1049008８(c)]showsthattherodＧlikecarbideparticlesarealloycementites(M３C)precipitatedfrom martensiteIncreasingthetempeＧringtemperatureabove６００ causescoarseningofalloycementites[Fig1049008８ (b)]andrecoveryofmarＧtensitewhicharethereasonsforconsiderablehardＧnessandstrengthdropItcanbeseenthattheextentofhardnessandtensilestrengthdropofH１３MODislowerthanthatofH１３ForthehighercontentofMoinH１３MODMoprovidessecondaryhardeningandredhardnessbytheformationoftheMo２Ctype

Fig1049008６　SEM microstructuresofH１３(a)andH１３MOD(b)temperedtwiceat６００ (quenchedat１０３０)

1048944１２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

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[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

１　ExperimentalMaterialsandMethods

　　Twokindsofexperimentalsteelsinthisstudywerepreparedbyvacuummeltingof２５kgingotfolＧlowedbyhotforgingtoproduceroundbarwithsizeofϕ１６mmtimes５００mmThechemicalcompositionoftestingsteelislistedinTable１Afterforging８７０－７６０isothermalannealingprocesswasadoptedforthefinalproductTheannealinghardnessesofH１３

andH１３MODareHB２０３andHB２００respectivelySpheroidalannealingstructuregradeof H１３andH１３MODbelongtotheratingofAS３andAS１reＧspectivelyaccordingtotheNADCA２０７Ｇ２００３annealedquality microstructurechartAfterannealingtheroundbar wascutintohardnesstestingsampleswithsizeof１２mmtimes１２mmtimes１６mmASTMstandardϕ５tensiletestpieceandCharpyUＧnotchedimpactspecimenswithsizeof１０mmtimes１０mmtimes５５mminlongitudinaldirectioninthecenteroftheroundbar

　　　　　　Table１　Chemicalcompositionofteststeel　　　　　　 　 (masspercent)

Steel C Si Mn S P Cr Mo V

H１３ ０1049008４４ ０1049008９４ ０1049008４１ ０1049008００６ ０1049008００９６ ４1049008６９ １1049008２２ ０1049008８４H１３MOD ０1049008３８ ０1049008３８ ０1049008４９ ０1049008００６ ０1049008００９７ ５1049008１３ １1049008８４ ０1049008４９

　　InordertodeterminethehardeningtreatmentprocessesoftestedsteelthehardnesstestingsamＧpleswerepreheatedat５００for３０minthenausＧtenitizedfor３０minatdifferenttemperaturesof９２０９５０９８０１０００１０３０１０６０and１１００inMufflefurnacewhichisfollowedbyoilquenching　　Inordertoresearchtheinfluenceoftemperingtemperatureonthemicrostructureandpropertiesoftestedsteeltensiletestpiecesandimpactspecimenswereaustenitizedfor３０minat１０３０quenchedinoilandthentemperedatdifferenttemperaturesof４５０４８０７１０５４０５７０６００and６５０for２htwice　 　 The annealed hardness was determined byHP２５０hardmeterwhilethequenchingandtempeＧringhardnessesweredeterminedbyTIME TH３００hardmeterTensilepropertiesweredeterminedonanLOS６００tensiletestmachineImpacttestonCharpyUＧnotchedsampleswasperformedfordeterminingimpacttoughnesswithaJB３０Bimpacttestmachineatroomtemperature　　MetallographicanalysiswasdonebyusinganLEICA MEF４opticalmicroscopeanHITACHISＧ４３００electronicscanningmicroscope(SEM)attachedanEDAXGENESIS６1049008０spectrumanalyzer(EDS)andanH８００transmissionelectronmicroscope(TEM)

２　ResultsandDiscussion２1049008１　Effectofquenchingtemperatureonhardnessandmicrostructure　 　 The variations of hardness with differentquenchingtemperatureforH１３andH１３MODsteelsareshowninFig1049008１ThehardnessesofthesetwosteelsrisewiththeincreaseofquenchingtemperaＧturewhenthetemperatureisbelow１０３０andthe

Fig1049008１　HardnessandgraingradecurvesofH１３andH１３MODatdifferentquenchingtemperatures

hardnessofH１３MODishigherthanthatofH１３Thehardnessof H１３MODreachesthe maximumvalueat１０３０ andhasnofurtherincreasewiththeriseofquenchingtemperaturewhilefor H１３steelitstillkeepsonincreasingThehardnessofH１３steelisHRC２1049008７higherthanthatofH１３MODsteelwhenquenchedat１１００Theaustenitizationconditionsofbothsteelsarecalculated by usingThermoＧCalcsoftware(Fig1049008２)Theresultsshowthatinthetemperaturerangeof５００－１２００ thecarＧbidesofM２３C６MCandM７C３existinH１３steelaswellas M２３C６MCand M６Cexistin H１３MODsteelExceptMCcarbidesnoM２３C６M６CM７C３

carbidesleftinH１３andH１３MODwhenthequenchＧingtemperatureisabove９００ThedissolvingtemＧperatureofMCcarbidesforH１３is１１４１whichis１０１higherthanthatofH１３MODItisremarkＧablethatthedissolvingtemperatureofMCcarbidesisjustthecompleteaustenitizingtemperatureofthetwosteelsWhensolutiontemperatureisbelow１０３０carbonisnotcompletelydissolvedintotheaustenite

1048944８１１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

(a)H１３　 (b)H１３MODFig1049008２　Effectoftemperatureontransformedamountofcarbides

butexistsintheformofundissolvedMC(VＧrich)inH１３ItisclearthattheasＧquenchedhardnessisgreatlyaffectedbytheextentofsolidsolutionhardＧeningbycarbonandalloyingelementsAsthetemＧperatureincreasesmoreand morecarbidesdisＧsolvethusenrichingtheausteniteincarbonandalＧloyingelementsHighercarbonandalloyingeleＧmentsintheaustenite(uptoalimit)willleadtohigherhardnessofthemartensiteproducedfromthisaustenite[４]ThecarbidesinH１３MODaredissolvedat１０３０ completelywhilein H１３itneedsahigheraustenitizingtemperaturetobringthemintosolidstatesolutionentirelysothehardnessofH１３islowerthanthatofH１３MODwhensolutiontemＧperatureisbelow１０３０WhenquenchingtemperＧatureishigherthan１０３０ H１３MODhasbeencompletelyaustenizitingThereforewiththeriseofquenchingtemperaturethehardnessofH１３MODhasnofurtherincreasewhileforH１３MCcarbides(VＧrich)dissolveintoaustenitematrixcontinuouslywhichleadstothecontentofcarboninquenchingmartensiteincreasesgraduallyandthehardnessinＧcreasescorrespondingly　　Fig1049008３showsthemetallographicstructuresofbothH１３andH１３MODquenchedat１０００and１０３０ TherearealotofundissolvedsmallcarbidesinmarＧtensiticmatrixofbothsteelswhenquenchedat１０００[Fig1049008３(a)and(b)]butat１０３０ undissolvedcarbidescanonlybefoundinH１３[Fig1049008３(c)]Itiscleartoseethattheundissolved MCparticles(VＧrich)existinH１３whenquenchedat１０３０ [Fig1049008４(a)]whileinH１３MODnearlyallcarbidesaredisＧ

solvedandthemicrostructureismartensite[Fig1049008４(b)]atthistemperatureFromtheaboveresultsitcanbeseenthattheresultscalculatedbyThermoＧCalcoftheteststeelsareingoodagreementwiththeexperimentalones　　AccompanyingwiththedissolutionofthealloycarbidesandtheincreasingofaustenitizingtemperaＧtureausteniticgrainsizeincreasesasindicatedinFig1049008１ButforH１３MODcoarseningofthegrainsizeismuch moreobviousthanthatof H１３especiallywhenthequenchingtemperatureisabove１０３０ ThisisattributedtotheundissolvedcarbidesthatinhibitgraingrowthinH１３steelthusthegrainsizestillretains９gradesuntilthequenchingtemperaturereaches１０６０ButitiseasytorecognizethatthebrittlenessofsteelriseswiththehardnessincreasＧingespeciallythelargesizeworkpiecewhichisveryeasytocrackwhenquenchingat１０６０Soitismuchbettertochoose１０３０ asthereasonablequenchingtemperaturewhichisestablishedempiriＧcallyforeachsteelonthebasisofattainablehardＧnessandgraincoarsening

２1049008２　EffectoftemperingtemperatureonmicrostrucＧtureandmechanicalproperties　　Fig1049008５showstheplotsoftemperedhardnesstenＧsilestrengthreductionofarea(Z)andelongationafterfracture(A)asfunctionsoftemperingtemperatureforH１３and H１３MODAstemperingtemperatureincreasesthehardnessfirstincreasestoamaximumandthengraduallydecreasesBothofthetwosteelsundergosecondaryhardeningassociatedwiththeprecＧ

1048944９１１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)H１３１０００　 (b)H１３MOD１０００　 (c)H１３１０３０　 (d)H１３MOD１０３０Fig1049008３　Metallographicstructuresofteststeelsquenchedat１０００and１０３０

(a)H１３　 (b)H１３MODFig1049008４　SEM microstructuresofteststeelsquenchedat１０３０

ipitationofalloycarbidesintempered martensiteTheprecipitationofsecondarycarbidesretardssofＧteningandincreasesthehardnessesofthetwosteelsH１３hasasecondaryhardeningpeakat５１０ whileforH１３MODitisat４８０ AndthetemperedhardnessofH１３MODisslightlylowerthanthatofH１３whenthetemperatureisbelow５４０ Whenthetemperatureisabove５４０H１３andH１３MODsteelshavenearlythesamehardness　　ThevariationoftensilestrengthwithtemperingtemperatureinFig1049008５showsnearlythesametrendashardnessThetensilestrengthofH１３ishigherthan

thatofH１３MODwhenthetemperingtemperatureisbelow５４０andreachesitsmaximumat５１０whichisalsotheminimumvalueofreductionofareaThemixＧclusterwhichiscalled [MＧC]segregationgroupdevelopedby MoCrandCatomsonαＧphaseinduceslatticedistortion[５]andthesmallVCparticlesprecipitatedwhiletemperinggeneratesigＧnificantsecondaryphasestrengthening[６]whichinＧducesatensilestrengthincrementofH１３comparedwithH１３MODinthistemperaturerangeWiththeincreaseoftemperingtemperaturethedifferenceofreductionofareabetweenthetwosteelstendstobe

1048944０２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008５　Influencesofhardnesstensilestrengthreductionofarea(Z)andelongationafterfracture(A)ondifferenttemperingtemperaturesofH１３steelandH１３MODsteel

smallerH１３MODhasabetterductilitycomparedwithH１３AtthehighertemperingtemperatureesＧpeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　　Thethin martensitelathsanddispersedcarＧbidesarefoundinthetemperedmicrostructuresofH１３andH１３MOD (quenchedat１０３０ andtemＧperedat６００ )therearemuch morelargesizeM２３C６ (CrＧrich)M６C (MoＧrich)andMC (VＧrich)carbides(distinguishedbyEDS)existinH１３steelcompared with H１３MOD steel (Fig1049008６)In H１３steelarapidcarbidetransitionwhichnegativelyinfluencestheprecipitationstrengtheningoccursatmoderatelyhightemperatures(６００)ThedistriＧbutionofundissolvedVＧrichcarbides(MC)transＧformstoacoarserdistributionofCrＧrichcarbides(M２３C６)whicharelesseffectivefromaprecipitatiＧonstrengthening perspective[７]Fig1049008７ showstheTEMimagesofpartcarbidesinH１３steelunderdifＧ

ferentheattreatmentconditionsTheTEMinvestiＧgationsrevealedundissolved MCcarbides(VＧrich)andthecoarseningofM６CandM２３C６carbidepartiＧclesinmatrix [Fig1049008７ (a)]whichmayleadtothedecreaseofstrengtheningeffect　　Fig1049008８showstheTEMimagesofcarbidesinH１３MODsteelaftertemperingat５４０and６００ItcanbeseenthatanumberofsmallrodＧlikecarbideparticlesarethemainmicrostructuralfeaturewhentemperedat５４０ [Fig1049008８(a)]Diffractionpatternofcarbidestemperedat６００ [Fig1049008８(c)]showsthattherodＧlikecarbideparticlesarealloycementites(M３C)precipitatedfrom martensiteIncreasingthetempeＧringtemperatureabove６００ causescoarseningofalloycementites[Fig1049008８ (b)]andrecoveryofmarＧtensitewhicharethereasonsforconsiderablehardＧnessandstrengthdropItcanbeseenthattheextentofhardnessandtensilestrengthdropofH１３MODislowerthanthatofH１３ForthehighercontentofMoinH１３MODMoprovidessecondaryhardeningandredhardnessbytheformationoftheMo２Ctype

Fig1049008６　SEM microstructuresofH１３(a)andH１３MOD(b)temperedtwiceat６００ (quenchedat１０３０)

1048944１２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

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[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)H１３　 (b)H１３MODFig1049008２　Effectoftemperatureontransformedamountofcarbides

butexistsintheformofundissolvedMC(VＧrich)inH１３ItisclearthattheasＧquenchedhardnessisgreatlyaffectedbytheextentofsolidsolutionhardＧeningbycarbonandalloyingelementsAsthetemＧperatureincreasesmoreand morecarbidesdisＧsolvethusenrichingtheausteniteincarbonandalＧloyingelementsHighercarbonandalloyingeleＧmentsintheaustenite(uptoalimit)willleadtohigherhardnessofthemartensiteproducedfromthisaustenite[４]ThecarbidesinH１３MODaredissolvedat１０３０ completelywhilein H１３itneedsahigheraustenitizingtemperaturetobringthemintosolidstatesolutionentirelysothehardnessofH１３islowerthanthatofH１３MODwhensolutiontemＧperatureisbelow１０３０WhenquenchingtemperＧatureishigherthan１０３０ H１３MODhasbeencompletelyaustenizitingThereforewiththeriseofquenchingtemperaturethehardnessofH１３MODhasnofurtherincreasewhileforH１３MCcarbides(VＧrich)dissolveintoaustenitematrixcontinuouslywhichleadstothecontentofcarboninquenchingmartensiteincreasesgraduallyandthehardnessinＧcreasescorrespondingly　　Fig1049008３showsthemetallographicstructuresofbothH１３andH１３MODquenchedat１０００and１０３０ TherearealotofundissolvedsmallcarbidesinmarＧtensiticmatrixofbothsteelswhenquenchedat１０００[Fig1049008３(a)and(b)]butat１０３０ undissolvedcarbidescanonlybefoundinH１３[Fig1049008３(c)]Itiscleartoseethattheundissolved MCparticles(VＧrich)existinH１３whenquenchedat１０３０ [Fig1049008４(a)]whileinH１３MODnearlyallcarbidesaredisＧ

solvedandthemicrostructureismartensite[Fig1049008４(b)]atthistemperatureFromtheaboveresultsitcanbeseenthattheresultscalculatedbyThermoＧCalcoftheteststeelsareingoodagreementwiththeexperimentalones　　AccompanyingwiththedissolutionofthealloycarbidesandtheincreasingofaustenitizingtemperaＧtureausteniticgrainsizeincreasesasindicatedinFig1049008１ButforH１３MODcoarseningofthegrainsizeismuch moreobviousthanthatof H１３especiallywhenthequenchingtemperatureisabove１０３０ ThisisattributedtotheundissolvedcarbidesthatinhibitgraingrowthinH１３steelthusthegrainsizestillretains９gradesuntilthequenchingtemperaturereaches１０６０ButitiseasytorecognizethatthebrittlenessofsteelriseswiththehardnessincreasＧingespeciallythelargesizeworkpiecewhichisveryeasytocrackwhenquenchingat１０６０Soitismuchbettertochoose１０３０ asthereasonablequenchingtemperaturewhichisestablishedempiriＧcallyforeachsteelonthebasisofattainablehardＧnessandgraincoarsening

２1049008２　EffectoftemperingtemperatureonmicrostrucＧtureandmechanicalproperties　　Fig1049008５showstheplotsoftemperedhardnesstenＧsilestrengthreductionofarea(Z)andelongationafterfracture(A)asfunctionsoftemperingtemperatureforH１３and H１３MODAstemperingtemperatureincreasesthehardnessfirstincreasestoamaximumandthengraduallydecreasesBothofthetwosteelsundergosecondaryhardeningassociatedwiththeprecＧ

1048944９１１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)H１３１０００　 (b)H１３MOD１０００　 (c)H１３１０３０　 (d)H１３MOD１０３０Fig1049008３　Metallographicstructuresofteststeelsquenchedat１０００and１０３０

(a)H１３　 (b)H１３MODFig1049008４　SEM microstructuresofteststeelsquenchedat１０３０

ipitationofalloycarbidesintempered martensiteTheprecipitationofsecondarycarbidesretardssofＧteningandincreasesthehardnessesofthetwosteelsH１３hasasecondaryhardeningpeakat５１０ whileforH１３MODitisat４８０ AndthetemperedhardnessofH１３MODisslightlylowerthanthatofH１３whenthetemperatureisbelow５４０ Whenthetemperatureisabove５４０H１３andH１３MODsteelshavenearlythesamehardness　　ThevariationoftensilestrengthwithtemperingtemperatureinFig1049008５showsnearlythesametrendashardnessThetensilestrengthofH１３ishigherthan

thatofH１３MODwhenthetemperingtemperatureisbelow５４０andreachesitsmaximumat５１０whichisalsotheminimumvalueofreductionofareaThemixＧclusterwhichiscalled [MＧC]segregationgroupdevelopedby MoCrandCatomsonαＧphaseinduceslatticedistortion[５]andthesmallVCparticlesprecipitatedwhiletemperinggeneratesigＧnificantsecondaryphasestrengthening[６]whichinＧducesatensilestrengthincrementofH１３comparedwithH１３MODinthistemperaturerangeWiththeincreaseoftemperingtemperaturethedifferenceofreductionofareabetweenthetwosteelstendstobe

1048944０２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008５　Influencesofhardnesstensilestrengthreductionofarea(Z)andelongationafterfracture(A)ondifferenttemperingtemperaturesofH１３steelandH１３MODsteel

smallerH１３MODhasabetterductilitycomparedwithH１３AtthehighertemperingtemperatureesＧpeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　　Thethin martensitelathsanddispersedcarＧbidesarefoundinthetemperedmicrostructuresofH１３andH１３MOD (quenchedat１０３０ andtemＧperedat６００ )therearemuch morelargesizeM２３C６ (CrＧrich)M６C (MoＧrich)andMC (VＧrich)carbides(distinguishedbyEDS)existinH１３steelcompared with H１３MOD steel (Fig1049008６)In H１３steelarapidcarbidetransitionwhichnegativelyinfluencestheprecipitationstrengtheningoccursatmoderatelyhightemperatures(６００)ThedistriＧbutionofundissolvedVＧrichcarbides(MC)transＧformstoacoarserdistributionofCrＧrichcarbides(M２３C６)whicharelesseffectivefromaprecipitatiＧonstrengthening perspective[７]Fig1049008７ showstheTEMimagesofpartcarbidesinH１３steelunderdifＧ

ferentheattreatmentconditionsTheTEMinvestiＧgationsrevealedundissolved MCcarbides(VＧrich)andthecoarseningofM６CandM２３C６carbidepartiＧclesinmatrix [Fig1049008７ (a)]whichmayleadtothedecreaseofstrengtheningeffect　　Fig1049008８showstheTEMimagesofcarbidesinH１３MODsteelaftertemperingat５４０and６００ItcanbeseenthatanumberofsmallrodＧlikecarbideparticlesarethemainmicrostructuralfeaturewhentemperedat５４０ [Fig1049008８(a)]Diffractionpatternofcarbidestemperedat６００ [Fig1049008８(c)]showsthattherodＧlikecarbideparticlesarealloycementites(M３C)precipitatedfrom martensiteIncreasingthetempeＧringtemperatureabove６００ causescoarseningofalloycementites[Fig1049008８ (b)]andrecoveryofmarＧtensitewhicharethereasonsforconsiderablehardＧnessandstrengthdropItcanbeseenthattheextentofhardnessandtensilestrengthdropofH１３MODislowerthanthatofH１３ForthehighercontentofMoinH１３MODMoprovidessecondaryhardeningandredhardnessbytheformationoftheMo２Ctype

Fig1049008６　SEM microstructuresofH１３(a)andH１３MOD(b)temperedtwiceat６００ (quenchedat１０３０)

1048944１２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

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[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)H１３１０００　 (b)H１３MOD１０００　 (c)H１３１０３０　 (d)H１３MOD１０３０Fig1049008３　Metallographicstructuresofteststeelsquenchedat１０００and１０３０

(a)H１３　 (b)H１３MODFig1049008４　SEM microstructuresofteststeelsquenchedat１０３０

ipitationofalloycarbidesintempered martensiteTheprecipitationofsecondarycarbidesretardssofＧteningandincreasesthehardnessesofthetwosteelsH１３hasasecondaryhardeningpeakat５１０ whileforH１３MODitisat４８０ AndthetemperedhardnessofH１３MODisslightlylowerthanthatofH１３whenthetemperatureisbelow５４０ Whenthetemperatureisabove５４０H１３andH１３MODsteelshavenearlythesamehardness　　ThevariationoftensilestrengthwithtemperingtemperatureinFig1049008５showsnearlythesametrendashardnessThetensilestrengthofH１３ishigherthan

thatofH１３MODwhenthetemperingtemperatureisbelow５４０andreachesitsmaximumat５１０whichisalsotheminimumvalueofreductionofareaThemixＧclusterwhichiscalled [MＧC]segregationgroupdevelopedby MoCrandCatomsonαＧphaseinduceslatticedistortion[５]andthesmallVCparticlesprecipitatedwhiletemperinggeneratesigＧnificantsecondaryphasestrengthening[６]whichinＧducesatensilestrengthincrementofH１３comparedwithH１３MODinthistemperaturerangeWiththeincreaseoftemperingtemperaturethedifferenceofreductionofareabetweenthetwosteelstendstobe

1048944０２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008５　Influencesofhardnesstensilestrengthreductionofarea(Z)andelongationafterfracture(A)ondifferenttemperingtemperaturesofH１３steelandH１３MODsteel

smallerH１３MODhasabetterductilitycomparedwithH１３AtthehighertemperingtemperatureesＧpeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　　Thethin martensitelathsanddispersedcarＧbidesarefoundinthetemperedmicrostructuresofH１３andH１３MOD (quenchedat１０３０ andtemＧperedat６００ )therearemuch morelargesizeM２３C６ (CrＧrich)M６C (MoＧrich)andMC (VＧrich)carbides(distinguishedbyEDS)existinH１３steelcompared with H１３MOD steel (Fig1049008６)In H１３steelarapidcarbidetransitionwhichnegativelyinfluencestheprecipitationstrengtheningoccursatmoderatelyhightemperatures(６００)ThedistriＧbutionofundissolvedVＧrichcarbides(MC)transＧformstoacoarserdistributionofCrＧrichcarbides(M２３C６)whicharelesseffectivefromaprecipitatiＧonstrengthening perspective[７]Fig1049008７ showstheTEMimagesofpartcarbidesinH１３steelunderdifＧ

ferentheattreatmentconditionsTheTEMinvestiＧgationsrevealedundissolved MCcarbides(VＧrich)andthecoarseningofM６CandM２３C６carbidepartiＧclesinmatrix [Fig1049008７ (a)]whichmayleadtothedecreaseofstrengtheningeffect　　Fig1049008８showstheTEMimagesofcarbidesinH１３MODsteelaftertemperingat５４０and６００ItcanbeseenthatanumberofsmallrodＧlikecarbideparticlesarethemainmicrostructuralfeaturewhentemperedat５４０ [Fig1049008８(a)]Diffractionpatternofcarbidestemperedat６００ [Fig1049008８(c)]showsthattherodＧlikecarbideparticlesarealloycementites(M３C)precipitatedfrom martensiteIncreasingthetempeＧringtemperatureabove６００ causescoarseningofalloycementites[Fig1049008８ (b)]andrecoveryofmarＧtensitewhicharethereasonsforconsiderablehardＧnessandstrengthdropItcanbeseenthattheextentofhardnessandtensilestrengthdropofH１３MODislowerthanthatofH１３ForthehighercontentofMoinH１３MODMoprovidessecondaryhardeningandredhardnessbytheformationoftheMo２Ctype

Fig1049008６　SEM microstructuresofH１３(a)andH１３MOD(b)temperedtwiceat６００ (quenchedat１０３０)

1048944１２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

Fig1049008５　Influencesofhardnesstensilestrengthreductionofarea(Z)andelongationafterfracture(A)ondifferenttemperingtemperaturesofH１３steelandH１３MODsteel

smallerH１３MODhasabetterductilitycomparedwithH１３AtthehighertemperingtemperatureesＧpeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　　Thethin martensitelathsanddispersedcarＧbidesarefoundinthetemperedmicrostructuresofH１３andH１３MOD (quenchedat１０３０ andtemＧperedat６００ )therearemuch morelargesizeM２３C６ (CrＧrich)M６C (MoＧrich)andMC (VＧrich)carbides(distinguishedbyEDS)existinH１３steelcompared with H１３MOD steel (Fig1049008６)In H１３steelarapidcarbidetransitionwhichnegativelyinfluencestheprecipitationstrengtheningoccursatmoderatelyhightemperatures(６００)ThedistriＧbutionofundissolvedVＧrichcarbides(MC)transＧformstoacoarserdistributionofCrＧrichcarbides(M２３C６)whicharelesseffectivefromaprecipitatiＧonstrengthening perspective[７]Fig1049008７ showstheTEMimagesofpartcarbidesinH１３steelunderdifＧ

ferentheattreatmentconditionsTheTEMinvestiＧgationsrevealedundissolved MCcarbides(VＧrich)andthecoarseningofM６CandM２３C６carbidepartiＧclesinmatrix [Fig1049008７ (a)]whichmayleadtothedecreaseofstrengtheningeffect　　Fig1049008８showstheTEMimagesofcarbidesinH１３MODsteelaftertemperingat５４０and６００ItcanbeseenthatanumberofsmallrodＧlikecarbideparticlesarethemainmicrostructuralfeaturewhentemperedat５４０ [Fig1049008８(a)]Diffractionpatternofcarbidestemperedat６００ [Fig1049008８(c)]showsthattherodＧlikecarbideparticlesarealloycementites(M３C)precipitatedfrom martensiteIncreasingthetempeＧringtemperatureabove６００ causescoarseningofalloycementites[Fig1049008８ (b)]andrecoveryofmarＧtensitewhicharethereasonsforconsiderablehardＧnessandstrengthdropItcanbeseenthattheextentofhardnessandtensilestrengthdropofH１３MODislowerthanthatofH１３ForthehighercontentofMoinH１３MODMoprovidessecondaryhardeningandredhardnessbytheformationoftheMo２Ctype

Fig1049008６　SEM microstructuresofH１３(a)andH１３MOD(b)temperedtwiceat６００ (quenchedat１０３０)

1048944１２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

(a)MCcarbideat５７０ (TEMdarkＧfieldimage)　 (b)M２３C６carbideat６００ (TEMdarkＧfieldimage)(c)M６Ccarbideat６００ (TEMbrightＧfieldimage)

Fig1049008７　CarbidesandselectedareaelectrondiffractionimagesofH１３steelatdifferenttemperingtemperatures(quenchedat１０３０)

(a)Temperedtwiceat５４０　 (b)Temperedtwiceat６００　 (c)Diffractionpatternofcarbidesof(b)Fig1049008８　TEMdarkＧfieldimagesoftemperedH１３MODsteel(quenchedat１０３０)

ofcarbide[８]Mo２CkeepscoherentwithmatrixacＧcumulatingandcoarseningslowlywhichmayalsoleadtosecondaryhardeningFortheinterferenceofthealloycementitenoM２CcarbidediffractionpatＧternisobtainedfromthethinfoilat６００orlowertemperingtemperatureButforH１３MODtestsamＧplewhichhasbeenquenchedat１０３０ andtemＧperedat６００ twicefurthertemperingonthissampleat６２０for２hitisfoundthatM２C (forH１３MODitmaywellbeMo２C)carbidehasastrongdiffractionpatternFurthermorethecarbidesstillkeepverysmallsize(Fig1049008９)ThereforeM２CisthemainstrengtheningphaseinH１３MODwhichisalＧsotheimportantreasonthathigherhardnessandstrengthcanbekeptinH１３MODathightemperingtemperature

　　TheresultsofCharpyimpacttestperformedatroomtemperaturetoevaluatetoughnessofthetwosteelsarepresentedinFig1049008１０Itisnoticedthattheminimaintheimpactenergycurvesoccursatthetemperingtemperatureof５１０ forH１３steeland４８０forH１３MODsteelwhichiscorrespondingtothetemperedhardnesscurves(Fig1049008５)ThisatＧtendantlossofimpacttoughnessisknownasreversＧibletemperedembrittlementTheembrittlementisfoundtobeconcurrentwiththeinterlathprecipitatiＧonofalloycementitesduringtemperingandtheconＧsequentmechanicalinstabilityofinterlathfilmsofretainedausteniteduringsubsequentloading[９－１０]TheincreaseofimpactenergyabovethebrittletemＧperatureisassociatedwiththematrixsofteningandcoarseningofcarbidesparticles[１１]

1048944２２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

Fig1049008９　TEMdarkＧfieldimageofH１３MODtemperedat６２０for２h(afterquenchingat１０３０andtemperingat６００twice)(a)anddiffractionpatternofcarbides(b)

Fig1049008１０　ImpactenergiesofH１３andH１３MODsteels

　　AscanbeseenfromFig1049008１０theimpacttoughＧnessofH１３MODismuchhigherthanthatofH１３steelevenunderthesametemperinghardnesswhentemperingtemperatureisabove５４０ (Fig1049008５)ThatistosayH１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredthusenhancethermalfatigueresistanceandservicelifeofmouldTheSEManalysisonfracＧturesurfaceindicatesthatthefracturecharacterisＧticofH１３isquasiＧcleavage[Fig1049008１１(a)]aftertemＧperingat６００whileforH１３MODsteelitisquasiＧcleavagefracturewithmasssmalldimples[Fig1049008１１(b)]

Fig1049008１１　SEMfractographsoftemperedimpactsampleofH１３(a)andH１３MOD(b)steels(quenchingat１０３０andtemperingtwiceat６００)

ThebasiccharacteristicsofquasiＧcleavagefracturearesmallcrackedgrainandtearridgesThecrackgivebirthtonuclearinthestresshighlyconcentratＧedlocation(suchasinclusionsandcarbides)ThenthecrackoriginextendsrespectivelyalongtheeasiＧestexpending wayfuseintoeachotherbystrongplasticdeformationinlocalareaandform quasiＧcleavagefracturefinallyInsmallcracksurfacemanycurvingtearridgesspreadwhichareobviousＧ

lydifferentfromthecleavagefractureofldquoriverpatＧternrdquoTheformerisdevelopedbystrongplasticdeＧformationconnectioninthe matrix micro zonewhilethelatterisjoinedbyeachcleavagestepandtheplasticdeformationisrarelyseenQuasiＧcleavageisadiscontinuousfractureprocesswheneveryhidＧdencrackconnectswitheachotherlargerplasticdeformationcalledtearridgealwaysoccursForH１３MODitiseasytofindoutthedomainofplastic

1048944３２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

deformation[Fig1049008１１(b)]whichshowshigherimＧpacttoughnessofH１３MOD　　ItwassuggestedthatsuperiortoughnessisasＧsociated with minimization oflargeprimarycarＧbidesTheundissolvedprimarycarbideshaveagreaＧtereffectontoughnessthanthatofcarbidesprecipiＧtatedupontemperingDuringsolidificationofvanaＧdiumsteelsthelastsectionsofliquidbetweenausＧtenitedendritesareenrichedinvanadiumandcarbonuptotheeutecticcompositionandeutecticsolidificaＧtionoccursLrarrγ＋VC[１２]AsmentionedabovebeＧcauseofthehighercontentofVinH１３steelitiseasytoformlargepseudoprimaryMCＧtype(VＧrich)carbides (primary carbides)during solidificationcomparedwithH１３MODVCisanexothermictype

compoundcombiningwithhighhardnessandintenＧsityItisundissolvedinausteniteunderhightemＧperaturethusin H１３steelitiseasytofindouttheselargeundissolvedprimarycarbidesin SEMfractograph[Fig1049008１２ (a)]BytheanalysisofEDStheblockeutecticcarbidesareidentifiedas(VTi)CThesecarbidesinH１３steelleadtodeteriorationintoughnessAscanbeseenfromFig1049008１３(a)mostoftheseprimaryundissolvedcarbidesappearirregularshapewhicharedifferentfromthesecondarycarＧbidesprecipitatedinthetemperingprocessThesecarbidesdamagethecontinuityofthematrixhavＧingadirectinfluenceontheimpacttoughnessThelargeundissolvedcarbidesreduceboththefracturetoughnessandtheimpacttoughnessatthesamestrＧ

(a)Largeblockeutecticcarbide　 (b)EDXofcarbideFig1049008１２　SEMfractographofimpactsampleofH１３steeltemperedtwiceat６００

(a)Largeblockeutecticcarbide　 (b)EDXofeutecticcarbideFig1049008１３　SEMofmicrostructureofH１３steeltemperedtwiceat６００

engthlevel[１３]

３　Conclusions　　１)H１３hashigherhardnesswhenquenchingtemperatureisabove１０３０H１３MODreachesthemaximumvalueofhardnessat１０３０andhasnofurtherincreasewiththeriseofquenchingtemperaＧtureCoarseningofthegrainsizein H１３MODismuch moreobviousthanthatin H１３especially

whenthequenchingtemperatureisabove１０３０ Bothofthetwosteelshaveareasonablequenchingtemperatureat１０３０　　２)H１３andH１３MODhavesecondaryhardeningpeaksat５１０and４８０respectivelyafterquenchingat１０３０ Thevariationoftensilestrength withtemperingtemperatureshowsnearlythesametrendashardnessThehardnessandtensilestrengthofH１３arehigherthanthoseofH１３MODwhentemＧ

1048944４２１1048944 　　　　　　JournalofIronandSteelResearchInternational　　　　　　　　　　　　　　Vol1049008２０　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD　

peringtemperatureisbelow５４０butatahighertemperingtemperatureespeciallyintherangefrom５８０to６００ whichisgenerallyappliedformosthotworkingapplicationsbothofthetwosteelshavealmostthesamestrengthproperties　 　３)Theimpacttoughnessand ductility ofH１３MODaremuchhigherthanthoseofH１３steelevenunderthesametemperinghardness(temperingtemperatureabove５４０)H１３MODcanbeusedinthesamehardnessenvironmentasH１３buthighertoughnessisrequiredThenewdevelopedH１３MODsteelhaveabetterthermalfatigueresistanceandservicelifecomparedwithH１３

References

[１]　PerssonAOnToolFailureinDieCasting[D]UppsalaSweＧdenUppsalaUniversity２００３

[２]　LarsＧAkeNorstromLennartJonsonBengtKlarenfjordDeＧvelopmentofPremiumDieSteelforDieCasting[J]DieCastＧingManagement１９９０１２２４

[３]　MichaudPDelagnesaDLamesleaPTheEffectoftheAddiＧtionofAlloyingElementsonCarbidePrecipitationandMechanＧicalPropertiesin５ Chromium MartensiticSteels[J]ActaMaterialia２００７５５(１４)４８７７

[４]　PaysonPTheMetallurgyofToolSteels[M]New YorkJohn

WileyandSonsInc１９６２[５]　LIUZongＧchangDUZhiＧweiZHUWenＧfangSecondaryHardenＧ

ingofH１３SteelDuringTemering[J]OrdnanceMaterialSciＧenceandEngineering２００１２４(３)１１(inChinese)

[６]　CHENYingCHENZaiＧzhiDONGHanAdvanceinResearchofTemperingSecondary HardeningofAlloyToolandDieSteelFeＧMＧCQuenchedMartensite[J]JIronSteelRes２００６１８(５)２９(inChinese)

[７]　SandbergOMillerPKlarenfjordBPropertiesProfileComＧparisonofPremium QualityH１３and ModifiedHotWorkDieSteel[J]DieCastingEngineer(USA)２００２４６(３)４０

[８]　NehrenbergAEHeatandTemperResistantAlloySteelUS３６００１６０[P]１９７１Ｇ８Ｇ１７

[９]　SarmaDSTemperedMartensiteEmbrittlement[J]ToolAlＧloySteels１９８４１８(１２)３６３

[１０]　Nam WJKim DSAhnSTEffectsofAlloyingElementsonMicrostructuralEvolutionandMechanicalPropertiesofInＧductionQuenchedＧandＧTemperedSteels[J]JournalofMateＧrialsScience２００３３８(１７)３６１１

[１１]　HornRMRitchieROMechanismsofTemperedMartensiteEmbrittlementinLowAlloySteels[J]MetallurgicalTransＧactions１９７８９A(８)１０３９

[１２]　MalinochkaY NOlikhovaM AMakogonovaTICarbideEutecticin Vanadium Steels [J]MetalScienceand HeatTreatment１９７９２１(３)１７１

[１３]　LechtenbergTATheMicrostructureMechanicalPropertiesandAbrasiveWearResistanceofModifiedSecondaryHardenＧingSteels[D]BerkeleyUniversityofCaliforniaBerkeleyCA１９７９

1048944５２１1048944Issue９　　　　　　　　　MicrostructureandPropertiesofHotWorkingDieSteelH１３MOD