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46 5 Vol.46No.52010Æ5 547—553 ACTAMETALLURGICASINICAMay.2010pp.547–553 H2S L360MCS ∗ ( ( ) , 102249)! SEM EDS L360MCS (HAZ) H2S (SOHIC) . : # , , , . $ , % . & , , . MnS CaS , . , , .’() , (HAZ), (SOHIC),H2S, *+,-./TG172.801234A056/0412−1961(2010)05−0547−07STRESSORIENTEDHYDROGENINDUCEDCRACKINGBEHAVIOROFHEATAFFECTEDZONEOFL360MCSSTEELINWETH2SENVIRONMENTZHOUChengshuang,ZHENGShuqi,CHENChangfengMechanicalandElectricalEngineeringFaculty,ChinaUniversityofPetroleum,Beijing102249Correspondent:ZHENGShuqi,associateprofessor,Tel:(010)89733200,E-mail:zhengsq@cup.edu.cnSupportedbyNationalNaturalScienceFoundationofChina(No.50871122),SpecializedResearchFundfortheDoctoralProgramofHigherEducation(No.20070425021)Manuscriptreceived2009–10–10,inrevisedform2010–01–28ABSTRACTStressorientedhydrogeninducedcracking(SOHIC)behaviorofheataffectedzone(HAZ)ofL360MCSsteelinwetH2Senvironmentwasstudiedbyseparatingcrack,SEMandEDS.Thecracksareformedbyfour–pointbendingtestinwetH2Senvironment.ThemicrostructureofHAZisobviouslydifferentfromthebasemetal,andthehardnessofHAZislowerthanthoseofthebasemetalandweldingjoint.Thefracturesurfaceofthecrackswasseparatedandthehy-drogenblistersweretornoff.ThecrosssectionandfracturesurfaceofthecracksareanalyzedbySEMandEDS.ResultsshowthatthecracksofSOHICappearedasaxialcrackandverticalcrack,andtheformerispreferential.TheappearanceofcracksisassociatedwiththelowhardnessvalueofHAZ.Thedimensionofhydrogenblastersintensionstresszoneofbendedspecimenisbiggerthanthatinunstressedspecimen,whichisduetohydrogenconcentrationinbendedspecimenishigher.Bothaxialandverticalcracksnucleateindependentlyandpropagateinthequasi–cleavagemanner.Tensionstressnotonlyincreasesthesupersaturatedhydrogenconcentrationintensionstresszonebutdirectlypromotesverticalcrackpropagation.AxialcracknucleatesatMnS,CaSandprecipitatedphase,andpropagatesunderinternalhydrogenpressure.Verticalcrackmainlynu-cleatesonprecipitatedphaseandpropagatesunderbothinternalhydrogenpressureandtensilestress.KEYWORDSpipelinesteel,heataffectedzone(HAZ),stressorientedhydrogeninducecracking(SOHIC),H2S,tensionstress* 7 50871122 8 200704250219 :2009–10–10, :2010–01–28& : , ,1982 , DOI:10.3724/SP.J.1037.2009.00669 ! H2S ,! :# $ % & ’ ,# $ (). ** ; +,,H2S! # ! #%. ** () &’ - $%$( %(HAZ) .& )/!()(SCC), *()(HIC)5480& ! 46 ’)/ *()(SOHIC)[1].SOHIC; Æ$!’ () , ( )(/#)#= *+ $*+%.+,,$- SCC’HIC,. %/-1$&2! ’3[2−6].&,SOHIC; Æ$)(/0( -( + ’31..#2,.3./01/4’(.Ca-yard)[7,8])4*502*+,.,$ ,SOHIC 5,1),$-,2 34+,51#,,-)-?66.+SOHIC)/( +7,&,8,39.4:;)/,( 2/ )/ =56,! ,077 0’3SOHIC 186.Orie’Fletcher[9] 278)/!02 12SOHIC)/,,-3HIC)/’SOHIC)/,#294,&,8123 (): ,9;49,0+5= ?:?:3Æ6.75Æ)4667;.& )/!027 ’3L360 *HAZ SOHIC& ,,)4 ?..48;9 :84=99SEM’EDS,+SOHIC 14:9( !:’)/!@)$&7 ’3’=9.1@ABC02;AL360MCS; $6C@,.,$-% ** $&02. &1=(B4==,%) :C0.13,Si0.40,Mn1.50,P0.02,S0.003,FeC4. / :=A(B360MPa,780460MPa,=(=0.90,?8=25.2%,VickersDBHV206.02@A39 9?A1@@,E 9, $?.02A39.4ABBF?CG400C,1@CA D,DBHBDE.SCC02CINACETM0177[10]$&.02;A667;@JEE@%JF.CIDDASTMG39–99[11]7;5)/!39 K :EK 39,39EF 115mm×15mm×5mm.7G02! HANACEDDAFL(5%NaCl+0.5%CH3COOH I’H2SFL),FB (24±3)J,@J)/ 90%G=A(B(SMYS),02MG 720h,H2SH.HAAH) : .HIC02CINACETM0284[12],39EF 100mm×20mm×8mm.! I9HANACEDDAFL,FB (25±3)J,02MG 96h,H2SH.HAAH) : .02J1D,A3.7%HCl+10g/LC6H12N4EKIA39.4 !% J.Æ%239?CG2000CBF,A%G ’CH$&K6DA4%KLBCD!.EAOlympusCK40MM%2+,F(OM)LL 9 $’HAZ+,5.EAHXS–1000AMMEN+,DBI+L 9 $’HAZ+,DBO.DGB/T9711.3;#I6,34DBNGJ#I 8MHO.EAÆ ?44NP&O DQA%/=; :E8;HIC02D%+ ?,EAP6$PK :E+R)/$&=;.EAF1L360MCS LQRSSTNFig.1SamplingschematicofL360MCSsteelspecimensusedinstresscorrosioncracking(SSC)test(a)samplingpositionfromweldedL360MCSpipelinesteel,perpendiculartoweldingjoint,weldingjointinthemiddle,length115mm,width15mm(b)magnifiedimageofspecimen(c)samplingpositionofspecimenwith5mmthick-nessFEIquanta200FMTUQ:+,F(SEM)L ?’SOHIC)/ I,AEDAXA10MVU(EDS)=9 ?’SOHIC)/ M%V:.2@AGHIJK2.1LMNOPQRL360MCSL 9HAZ’ $ +,5?A2@@.8A8J,L +,5 K?O:.+RPO:.+W?O:.+/466.(A2a). *HAZ8,# *$4( ,SXQTW.&, 5; O:.+66.+/49+ %XGYR.(A2b). $% 5 U SN9O:.+W?O:.+/4TW.(A2c).DB33GJ.:,L 9HAZ’ $ HV=V 206,164’199.8 8JYO:.+66. & HAZDB:+W,L ’ $.L +,54 4W?O:., 1(LM,29NK UGPZ,,[4 48OZ8X,3\ (B4V /PQ[13].;LMU HAZ8,SXQTW.&,LMXQS; )RLY%8OZ8XW-,\ (B:+OW[14].2.2TUVWPXYZ[SCC02D,L360MCS39.4 1ÆY]X !% J.IA!% D, 784HAZ%+1: 5 [ZY[:^H2SRP L360MCSSTQ_\Z‘\]R][a^ST\]549F2L360MCSb^ ^#_Fig.2OMimagesofthetestedsteelL360MCSafter4%nitaletching(a)basemetal,ferrite(F)+lathferrite(LF)+aci-cularferrite(AF)+pearlite(P)(b)HAZ,ferrite+pearlite+tertiarycementite(TC)+precipitate(c)weldingjoint,pro–eutectoidferrite(PF)+Wid-manstattenferrite(W)+acicularferrite+ ?,1_I $\_ ? MHEU‘ 890µm,a_+1U‘39VB: )/(?A3@@).; 39‘Æ4.D ?’)/+1.)4+ )/4=9 1,L360MCSHAZ)/8a784 )/’U‘