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Ti(,250061)()Ti,,TiN,,,t8P5(800500),TiNEffectofTionStructureandToughnessofCoarseGrainHeatAffectedZoneofHighStrengthLowAlloySteelChenMaoai(CollegeofMaterialScienceandEngineering,ShandongUniversity,Jinan250061)TangYiminandLouSongnian(CollegeofMaterialScienceandEngineering,ShanghaiJiaoTongUniversity)AbstractTheresultsofstudyonstructureandtoughnessofweldcoarsegrainheataffectedzone(CGHAZ)ofTimi2croalloyedsteelshowthatduringweldthermalcycling,theoriginalaustenitegraincoarseningisprohibitedandtheformationofacicularferriteispromotedbydispersedTiNparticlesinTimicroalloyedsteel.ThetoughnessofCGHAZinHSLAsteelisim2provedremarkablybyadditionofTi.Andthelongerthecoolingtimefrom800to500(t8P5),thebetterthetoughnessofTimicroalloyedsteel.MaterialIndexTiN,AusteniteGrain,AcicularFerrite,,+,TiNbV,TiNNbNVN,[12]Ti,,Ti1,,1ATi,BTi()TiN,,11mm11mm56mm,Thermorestor2W:Tm=1350,t8P5=16s60s120s1P%Table1CompositionsofmaterialtestedP%CMnSiSPTiAlNA0.131.260.380.0050.0160.0180.0450.0067B0.121.350.270.0020.009-0.0310.00225225Vol.22.No.5200110SPECIALSTEELOctober2001©1994-2010ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.:2%(2mm2mm)(3%,20V),,500Neophto220H2800STEM,70m,Atan6002TMP22.1Ti1(a)(b)Ti,,,TiN2TiN(,1000100),L,N(Pm2)2(a),Ti30nm,,:F=Kfr(1)KPNm-2;fPm3;rPm(1),,,2(a)2(b),,TiNf,r,,,TiN,t8P5=120s,,,,TiN3t8P5AB,(t8P5),TiTiB,t8P5,TiN1TiN(a);(b)(t8P5=60s)Fgi.1MorphologyofTiNParticlesinparentmetal(a)andCGHAZ,t8P5=60s(b)622©1994-2010ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(a);(b)Fig.2SizedistributionofTiNparticlebeforeandafterweldthermalcycling:(a)parentmetal;(b)CGHAZ3A(Ti)B(Ti)Fig.3AustenitegrainsizeinCGHAZofsteelA(Timi2croalloyed)andSteelB(Without)Tiadded2.2TiN4(a)(c)Ti,t8P5=16s,,,4(a)t8P5=60s,,,,4(b)t8P5120s,,,,4(c)t8P5,TiCGHAZTiB,t8P516120s,CGHAZ,4(d),t8P5=120sBCGHAZTiN,M2A,[3],,,N2WK2S[4];,,,2.3CGHAZt8P516s60s120sABvTr2,t8P5,TiTiTiNt8P5,TiTi,(4(a)),,t8P5,,Ti,Ti,t8P5,t8P5,75:Ti©1994-2010ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(4(d))Ti,t8P5t8P5,CGHAZ(3),,2TiTi(CGHAZ)vTr(27J)PTable2BrittlenesstransformationtemperaturevTr(27J)ofCGHAZinsteelTi2microalloyedandwithoutTiaddedPvTrP16s60s120sA(Ti)-27-30-37B(Ti)-21-974A(Ti):t8P5=16s(a),60s(b),120s(c);B(Ti):t8P5=120s(d)Fig.4OpticalstructureinCGHAZofsteelA(Timicroalloyed):t8P5=16s(a),60s(b)and120s(c);steelB(WithoutTiadded):t8P5=120s(d)3(1)TiTiN,,(2),Ti;t8P5,(3)t8P516s120s,Ti();,1,.TiN¼Ó©.,1975,61(11):652LeeJL,etal.MicrostructureandToughnessoftheSimulatedHAZinTiandAlKilledSteels.Mater.Sci.Enger.,1991,136A:1093BhadeshiaH,etal.TheMechanismofBaniteTormationinSteel,ActaMetall.1980,28(3):12654LeeJL,etal.TransformationProcessesandProductsforC2MnSt2eeslsduringContinuousCooling.Mater.Sci.Tech.,1989,5(7):674,,35,1997,:2001206222822©1994-2010ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.