两阶段控制冷却工艺对含钼X80抗大变形管线钢组织与性能的影响

33720117JournalofUniversityofScienceandTechnologyBeijingVol．33No．7Jul．2011X801112211000832250101[e-mail]80－M/A．M/AM/A．690℃、450℃23%、5μmM/A1μm．TG142.4TG335.1Effectoftwo-stagecontrolledcoolingonthemicrostructureandpropertiesofMo-containingX80high-deformabilitypipelinesteelMENGDe-liang1KANGYong-lin1ZHENGXiao-fei1ANShou-yong2XIADian-xiu21SchoolofMaterialsScienceandEngineeringUniversityofScienceandTechnologyBeijingBeijing100083China2TechnologyCenterJinanIron＆SteelCo．Ltd．Jinan250101China[e-mail]-containingX80high-deformabilitypipelinesteelwasprocessedbyTMCProllingandtwo-stagecontrolledcoolinginlaboratory．TheeffectsofcoolingconditionsonthemicrostructureandpropertiesofthesteelwereinvestigatedbyscanningelectronmicroscopySEMandtransmissionelectronmicroscopyTEM．Itisfoundthatthemicrostructureofthesteelprocessedbytwo-stagecontrolledcoolingisferrite-bainitedualphase．AsthestarttemperatureinacceleratedcoolingcomesdownboththestrengthandyieldratiodecreaseandtheuniformelongationuElincreaseswiththeferriticvolumefractionincreasing．Asthefinishtemperatureinacceleratedcoolingbecomeslowertheamountofmartensite-austeniteM/AconstituentsinbainitedecreasesandtheM/Aislandsaremuchfinerandmoreuniformlydispersed．ThestrengthchangeslittlebuttheuElincreasessignificantly．ItisconsideredthatuEliscloselyrelatedtoM/Aconstituentsinbainitewhentheferriticvolumefractionisconstant．FinelyanduniformlydispersedM/AislandscanincreasethevalueofuElbyincreasingtheworkhardeningrateanddelayingtheonsetofnecking．Whentheacceleratedcoolingstartsat690℃andfinishesat450℃theferriticvolumefractionisabout23%thegrainsizeisapproximately5μmandtheaveragegrainsizeofM/Aislandsisapproximately1μm．Theuniformmicrostructureprovidesgoodcombinationofstrength-ductilityproperties．KEYWORDSpipelinesteelmolybdenumcontrolledcoolingmicrostructuremechanicalproperties2010--07--09No．2009AA03Z518、、7X80．1．、．．Rt0.5/Rm≤0.85、n＞0.10、uEl≥10%--2．--、13--5．Ishikawa3－．6Mo．--Mo．CMoTMCP--X80--．1CMo1Nb、Ti、CuNi．50kg95mm×100mm．1Table1Chemicalcompositionoftheexperimentalsteel%CSiMnMoPS0.060.161.850.260.0070.0051200℃2h350mm11mm．1150℃1050℃＞60%950℃800℃＞70%．--1Ar3ACC．．2．1Fig．1Schematicdiagramofthetwo-stagecontrolledcoolingprocess2Table2Controlledcoolingscheduleofthehotrolledsamples/℃/℃/℃·s－1172050020～30269050020～30369045020～30466050020～301/4．、4%Leica--S440iSEMJEMS2000TEM．API5LCMT--4305．·538·3322.1SEM2．1～4--．PFQFM/AGB．1、24．720℃5μm2a690℃5μm2b660℃10μm2d．720℃690℃690℃660℃．233450℃．SEM22b32c．3M/A1μm23～4μm．2SEM．a1b2c3d4Fig．2SEMmicrostructuresofsamplesunderdifferentcoolingconditionsasampleNo．1bsampleNo．2csampleNo．3dsampleNo．4323PF、QF、GBM/A．PFQFPFQF3adGB、3cd．100nmNbTiCN3b．QFGBM/A3abcGBM/A3c．23M/A2M/A3M/A．2.231～4．Rt1.5/Rt0.5ε=1.5%ε=0.5%．n3．3X80·638·7X803TEM．ab2M/A、QFcd3M/A、GB、QFPFFig．3TEMmicrographsofsamplesatdifferentACCfinishtempera-turesabM/AQFandprecipitatesinsampleNo．2cdM/AGBQFandPFinsampleNo．3、．3Table3LongitudinaltensilepropertiesofthesamplesRt0.5/MPaRm/MPaRt0.5/RmEl/%uEl/%Rt1.5/Rt0.5530～630625～770≤0.80≥20≥10≥1.1515807700.75288.31.1625657800.72288.71.1835657500.752910.51.1545407600.71309.01.17El．--4．--“”．．3GBQF．C、N．54--Fig．4Longitudinalstrain-stresscurvesofthesamplesImageToolLepra7．720℃660℃15%32%580MPa540MPa0.750.718.3%9.0%5ab690℃5a．500℃450℃780MPa750MPa8.7%10.5%0.720.755c．3．－、M/A．、．3.11Ar3PF2QF·738·335．abcFig．5EffectsofcoolingconditionsonthetensilepropertiesofthesamplesduringaccelerationcoolingaeffectofstarttemperatureonstrengthbeffectofstarttemperatureonferriticvolumefractionanduElceffectoffinishtemperatureonuElandyieldratio--．PF、QF、、M/A、8--9．PFQF、．11．35、、．Mo．Mo6700℃70%680℃80%．Mo0.26%690℃23%660℃32%2、5．Mo．MoMoC、γ→α10．Mo．50%--420%～30%X8010%511．Mo．690℃Mo23%5μm530MPa10%．5a．720℃660℃．M/AM/AACC2ab．M/A．3.223690℃、2、3．2·838·7X80．M/A．、--．、8．．Ishikawa1560℃305℃M/A．Wang12、M/A．2b、c3500℃2M/A、2b8.7%450℃3M/A1μm0.720.7510%．．dσdε≤(σ1σ×dσdε≤)11、dσ/dε．1/σdσ/dε1/σdσ/dε＞1．23--6．232332．23623Fig．6RelationshipbetweeninstantaneousworkhardeningrateandtruestrainofsampleNo．2andNo．3M/A．AshbyBalligerfd7dσdε=KGb1/2ε1/2f槡d2GG=82400MN·m－2bb≈0.247nmK1．2．7．2M/A、．3M/AM/A．M/A、M/Adσ/dε．M/A、．dσ/dεM/AM/A．M/A·938·33、．、M/A、－．41Mo--．2720℃660℃Mo15%32%．500℃M/A3～4μm450℃M/A1μm．3Mo．M/A．M/AM/A．4690℃、450℃Mo23%、5μmM/A1μm565MPa0.7510.5%．1IshikawaNOkatsuMEndoSetal．Designconceptandpro-ductionofhighdeformabilitylinepipe//ProceedingsofIPC20066thInternationalPipelineConference．Calgary20062152JiLKChenHYHuoCYetal．Keyissuesinthespecifica-tionofhighstrainlinepipeusedinstrain-baseddesigneddistrictsofthe2ndwesttoeastpipeline//ProceedingsofIPC20087thIn-ternationalPipelineConference．Calgary200813IshikawaNOkatsuMEndoSetal．Materialdesignconceptandproductionofhighstrengthlinepipeforstrain-baseddesignap-plications//Strain-BasedDesignofPipelinesSeminarForum．Beijing2007604IshikawaNShikanaiNKondoJ．Developmentofultra-highstrengthlinepipeswithdual-phasemicrostructureforhighstrainapplication．JFETechRep200812155ShinoharaYTsuruEAsahiHetal．Developmentofhigh-strengthsteellinepipeforSBDapplications．IntJOffshorePolarEng2