钼对低碳微合金钢组织和性能的影响英文版

ShortCommunicationInfluenceofMocontentonmicrostructureandmechanicalpropertiesofhighstrengthpipelinesteelKongJunhuaa,b,*,ZhenLinb,GuoBinb,LiPingheb,WangAihuaa,XieChangshengaaDepartmentofMaterialsScienceandEngineering,HuazhongUniversityofScienceandTechnology,Wuhan430074,ChinabTechnologyCentre,IronandSteelResearchInstitute,WuhanIronandSteel(Group)Company,Wuhan430080,ChinaReceived12November2003;accepted22March2004Availableonline22April2004AbstractTheeffecttheMocontentonthemicrostructureandmechanicalpropertiesofhighstrengthpipelinesteelX80wasinvestigatedinthepresentstudy.Opticalmicroscopy,scanningelectronmicroscopyandtransmissionelectronmicroscopywereusedtoinvestigatethemicrostructureofthesteel.Itwasconcludedthat,theproportionofacicularferriteincreasedastheamountofMocontentincreased,whichresultedintheenhancementofyieldandtensilestrength;ontheotherhand,theyieldratiodecreasedandthetoughnessdeterioratedasthequantityofM–Aincreased.
2004ElsevierLtd.Allrightsreserved.Keywords:Pipelinesteel;Molybdenum;Mechanicalproperties;Microstructure1.IntroductionAfterWorldWarII,transportingpipelineshavebeendevelopedrapidlytohighgradesteelasthepressureoftransportednaturalgascontinuouslyincreased.Sincetheendof1980s,thermo-mechanicalprocessing(TMP)andacceleratedcooling(ACC)havebeenappliedtotheproductionasthedevelopmentofhotrollingtechnologyandimprovementofitsequipment.Carboncontentofpipelinesteelswasallowedtodecrease,butthestrengthandtoughnessincreased,somealloyelements,suchasMo,Ni,Cu,wereaddedtothesteelsinordertoimprovethestrength.Improvingcoolingrateandreducingcoolinginterrupttemperatureledtothecompletechangeofitsfinalmicrostructurefromatraditionalferrite–pearlitestructuretoanacicularferritestructure.Basingonthisprinciple,alowcarbonbainiticpipelinesteelX80hasbeendevelopedinrecentyears.Asanhighstrengthlowalloy(HSLA)steel,manystudieshavebeendoneconcerningtheeffectsofmicroalloys[1],TMP[2]andACC[3]processingonthepropertiesofthesteels.Itwasreported[4]thatMoinsmallproportionexertedavigorouseffectonhardenabilitywhenitwasdis-solvedinaustenite.Somework[5]hasjustifiedthatmolybdenumenhancedtheeffectofprecipitationhard-eninginHSLAsteelscontainingNb.ButtheeffectofMocontentonmicrostructureandmechanicalproper-tiesofhighstrengthpipelinesteelhasnotbeenwellrecognized.Fromtheaustenitethermo-transformationcurveoftheMo-containedsteel,itwasknownthat,theadditionofelementMocouldshifttheferritetransformationstartinglinetotherightobviously,butdidnotinfluencebainitetransformationstartinglinedistinctly,sothecooledaustenitetransformedtobainitedirectlywithnoorfewprecipitationofthepolygonalferrite.Therefore,thispaperaimedattheeffectofMocontentonthemicrostructureandmechanicalpropertiesofanHSLApipelinesteel-X80.*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](K.Junhua).0261-3069/$-seefrontmatter
2004ElsevierLtd.Allrightsreserved.doi:10.1016/j.matdes.2004.03.009MaterialsandDesign25(2004)723–728)20C.AnOLYMPUSGX71typeopticalmicroscope,anFEIXL30typescanningelectronmicroscopeandaJEM-2000FXIItypetransmissionelectronmicro-scopewereemployedtoinvestigatethemicrostructuresofthesteels.3.Results3.1.EffectofMoonmechanicalpropertiesFig.1showedtheeffectofMocontentontheme-chanicalpropertiesofthesteels.TheyieldandtensilestrengthswereenhancedwithanincreaseintheamountofMoaddedtothesteels,buttheenhancedrangeofthetensilestrengthwashigherthanthatoftheyieldstrength(seeFig.1(a)),sotheyieldratiowasdecreasedaccord-ingly(Fig.1b).WhentheamountofMoincreasedfrom0to0.20wt%,theenhancedrangeofyieldstrengthandtensilestrengthwas12and47MPa,respectively.MorecontentofelementMoaddedtothesteelsledtothesmallerenhancedrangeofbothyieldandtensilestrengthswhiletheyieldratiowaskeptconstant.Fig.1(c)illustratedtheimpactenergyaffectedbytheamountofMocontent.AtotaldecreasingtrendoftheimpactenergywasrevealedwiththeincreaseoftheMocontentalthoughthereweresomefluctuationsinthevalueoftheimpactenergy.Therefore,if0.20wt%MoalloywasaddedtothehighstrengthX80pipelinesteels,thetensilestrengthwouldimprovedistinctly,whileyieldstrengthimprovedalittle,onthecontrast,theimpacttoughnesswouldhavesomeloss.ThemoretheincreaseinMocontent,thesmallertheimprovedstrengthrange,andthelargerthelosingvalueofthetoughness.0.00.10.20.30.40.00.10.20.30.40.00.10.20.30.4520540560580600620640660(a)Strength,MPaMocontent,wt%Rt0.5Rm0.820.830.840.850.860.87(b)Rt0.5/RmMocontent,wt%120130140150160170180190(c)Akv,JMocontent,wt%Fig.1.Mechanicalpropertiesofthesteels:(a)theyieldandtensilestrengthofthesteelswithdiffe