文献翻译-钢制压力容器在高温腐蚀性铝酸溶液中的应力腐蚀裂纹研究

英文文献1英文原文StressCorrosionCrackingofPressureVesselSteelsinHigh-TemperatureCausticAluminateSolutionsSUELIU,ZIYONGZHU,HUIGUAN,andWEIKEStresscorrosioncracking(SCC)behaviorofthreekindsoflowalloypressurevesselsteelsinhightemperature(200to300)causticaluminate(AlO2-)solutionshasbeenstudiedbyslowstrainratetests(SSRT).TheresultsindicatethatthesepressurevesselsteelsaresusceptibletoSCCincausticalnminatesolutionandthattheSCCsusceptibilityincreaseswithincreasingtemperaturebetween200to300SulfidecontentandstringeredsulfideinclusionsseverelyandanisotropicallyaffectthecausticSCCoftheselowalloysteels.Theinclusionsintherare-earth-treatedsteelarepredominantlyglobularrare-earthsulfidesoroxysulfides,resultinginimprovedtransverseproperties.TheeffectofinclusionsonSCCbehaviorcorrelateswiththeprojectedareaofinclusionsperunitvolumeatthecracktip,Av,ontheplaneperpendiculartothetensiledirection.ThesusceptibilitytoSCCincreaseswithincreasingAv.I.INTRODUCTIONLOWalloypressurevesselsteelsarethecommonstructuralmaterialsforweldedreactionvessels(e.g.,digesters,precipitators,andevaporators)intheBayerprocessforextractionofaluminafromhydratedoxideores(e.g.,bauxite).Theselowalloyreactionvesselsareincontactwithhightemperatureconcentratedcausticalnminatesolutionsandfrequentlysufferfromstresscorrosioncracking(SCC)duringservice.1,2AlthoughSCCofsteelsinsimpleNaOHsolutionshasbeenthesubjectofnumerousstudies,f3,41littleworkhasbeendoneincausticaluminatesolutionsat92oc.t5,61Topurifyaluminafromlowerqualityores,theextractingtemperaturehasbeenelevated.However,therearenodataonSCCsusceptibilityofsteelsusedinthealuminaindustryathighertemperatures.TheobjectiveofthepresentworkistostudytheSCCbehavioroflowalloypressurevesselsteelswithdifferentsulfurcontentsinanimitativeBayerprocessat200to300Overthepastfewyears,anumberofresearchworks7,8,9haveshownthatnonmetallicsulfideinclusionscancauseenvironmentallyassistedcrackingtooccurinhigh-temperaturewaterrelatedprimarilytoBoilingWaterReactor(BWR)andPressurizedWaterReactor(PWR)environments.TheeffectofMnSinclusionsoncausticSCCpropertyisalsodiscussedinthisarticletogiverecommendationsforimprovingSCCresistanceofmaterialsusedinthealuminaindustry.II.EXPERIMENTALPROCEDUREStudieswereconductedonthreekindsoflowalloysteels:16MnR,A48CPR,andrare-earth-treated16MnRE.Thepressurevesselqualityrollingsteelplatesusedinthisworkwere50-mmthickandwereannealedat650Thechemicalcompositionsandmechanicalpropertiesofthesesteelsweresimilar(TablesIandII),althoughthesulfurcontentswereverydifferent.Thecylindricaltensilespecimenswere24mmingagelengthand5mmindiameterwiththreadsateachendtofittensilegrips.Twokindsoftensiletestpiecesweresectionedfromthesteelplatesparallel(Lspecimen)andperpendicular(Tspecimen)totherollingdirectiontoinvestigatespecimenorientationeffects.Allspecimenswerepolishedwitha1000gritemerypaperandthencleanedwithalcoholandacetonebeforetesting.ThetestenvironmentimitatedtheindustrialBayerprocess,andthetemperaturewasvariedfrom200to300Theinitialmolal(M)concentration(TableIII)inimitativeBayersolutions(IBS)was7.42MNaOH,1.32MA12033H20,andsomeimpurities:carbonate,sulfate,andchloride.Thetestsolutionwaspreparedfromdistilledwaterandanalyticalgradechemicals.Theresultingconcentrationsofanionsarebasedonstoichiometricformationofaluminatespecies(AlOe-)accordingtoEq.1:OHAIOAIH222324TheslowstrainratetestswereperformedonanSERT-5000DP-9Lmachineinastaticautoclaveataninitialstrainrateof3.3*10-6/s.Toprotecttheautoclavefromcausticsolution,aloose-fittingnickelliner,whichheldthecorrosivemedia,wasplacedwithinit.Asmallamountofwaterwasinjectedintothecrevicebetweentheautoclaveandthelinertoimproveheattransferandtopreventtheformationofaconcentratedcausticsolutioninthiscrevice.Aftersealing,thesystemwasoverpressuredwith2.0MPanitrogentopreventboilingandtominimizethetransferofcorrosivemediatothecrevice.Atthestartofeachtest,specimenswereinitiallyloadedto50MPaandthenstrainedtofracture.Thetensilespecimenswereatthenaturalcorrosionpotentialduringstraining.TheresultsobtainedinIBSwerecomparedwiththoseinaninertenvironmentof2.0MPanitrogen.Thetimetofailure(TTF),thepercentreductionofcrosssectionalarea(petROA),andtheelongation(E)werethemainparametersusedtoevaluateSCCsusceptibility.One-halfofthespecimenwasmountedwithepoxyresin,ground,andgivenafinalmetallographicpolishtoobservethesecondarycracksalongthegagelengthbyopticalmicroscopy.TableI.AnalysesofComposition(WeightPercent)SteelsCSiMnPSAlCuMoNiRE16MnR0.160.471.530.0140.018-0.055-A48CPR0.1750.341.350.0120.006-0.0450.058-16MnRE0.160.401.380.0180.009-0.020TableII.MechanicalPropertiesofSteelsImpactStrength（J/cm,byCharpyTest）25260SteelsUltimateStrengt（MPA）YieldStrength（MPA）Elongation（Pct）LSpecimenTSpecimenLSpecimenTSpecimen16MnR530.0350.032.0159172777597142169858176A48CPR528.9316.131.620924018723329831723125827216MnRE535.0338.032.5169172172156129122TableIII.CompositionofIBS(M)NaOHAl2O33H2ONa2CO3Na2SO4NaCl7.421.34Ill.RESULTSA.TheEffectofTemperatureonCausticSCCBehaviorFigure1showstheeffectoftemperatureonSCCbehaviorforLspecimensof16MnRsteelinIBSat260ThepctROAisreducedbythecorrosivesolutionascomparedwiththatinnitrogen.AlsotheTTF,pctROA,andEofspecimensinIBSdecreasewithincreasingtesttemperature.Theresultsindicatethat16MnRsteelissusceptibletoSCCinIBSandthatthesusceptibilityincreaseswithanincreaseintemperaturefrom200to300B.ComparisonofSCCSusceptibilitybetween16MnR,A48CPR,and16MnRESteelsThepetROAdataofLspecimensforbothsteelsshowninFigure2aretheaveragevaluesofduplicatespecimensineachtestcondition,andtheresultscanbereproducedasfollows.ForA48CPRsteel,thepctROAdataare66.0and64.2at260and63.6and61.1at280For16MnRsteel,thepctROAdata(asshowninFigure1)are57.2and55.0at260and49.6and47.0at280Theresults(Figure2)ofLspecimensforbothsteelsindicatethatA48CPRsteelisalsosusceptibletoSCCunderthetestconditionsandthatthesusceptibilitymayincreaseslightlywithincreasingtemperaturefrom260to280TheLspecimensof16MnRsteelareinferiortothoseofA48CPRsteel.TheeffectsofspecimenorientationonSCCbehaviorarshowninFigure3.TheTspecimensof16MnRsteelarobviouslymoresusceptibletoSCCthanitsLspecimensHowever,theSCCbehaviorforA48CPRsteelofTspecmensissimilartotheLspecimens.TheSCCresistancfortheTspecimenofrare-earth-treatedsteel16MnREimproved,andtheextentofanisotropyof16MnREdecreasesascomparedwith16MnR.ThelargenumberofcracksobservedonanLspecimenof16MnRsteelaftertestinginIBSat280isshowninFigure4.ThecrackingpathofatypicalspecimenisshowninFigure5.Thecrackspredominantlypropagatedinintergranularpath,buttherearealsosometransgranularcracks.IV.DISCUSSIONCausticSCCoflowalloypressurevesselsteelsinIBSatelevatedtemperaturesispredominatelyintergranular(Figure5)asat92TheSCCsusceptibilityincreasesathightemperaturesbetween200and300(Figures1and2).Incomparisontotheconventional(25Pourbaixdiagram,themostnoticeablechangeathighertemperaturediagramsisthelargerareaofstabilityfortheHFeOiion.AnassociationbetweencausticcrackingandtheformationofHFeO2ionhasbeenpreviouslysuggested,vqSimultaneously,thereactionrateoftheanodicandcathodicreactionsincreasesattheelevatedtemperature.TheorientationeffectonSCCbehavior(Figure3)isconsideredtoberelatedtoinclusionsinthesteels.Thevolumefraction,shape,anddistributionofmanganesesulfideinclusionsin16MnRandA48CPRsteelsareverydifferent,asshowninFigures6(a)and(b).Thevolumefractionofinclusionsin16MnRsteelisgreaterthaninA48CPRsteelbecausethesulfurcontentishigher.TheinclusionsinA48CPRsteelareglobularandwelldistributed,whereasthosein16MnRsteelarepredominantlyelongatedandinbandsparalleltotherollingdirection.TheSCCprocessisthebrittleorquasibrittlefractureofamaterialundertheconjointactionsofstressandcorrosiveenvironments.Thedetrimentaleffectsofnonmetallicinclusionsonthemechanicalpropertiesofsteelsarenowwellestablished,tgConsideringthemechanicalfractureaspectduringtheSCCprocess,theeffectofinclusiononSCCbehaviorcorrelateswiththetotalprojectedarea,Aw,ofinclusionsperunitvolumeatthecracktipontheplaneperpendiculartothetensiledirection,i.ThecrackpropagationrateisacceleratedbycrackinginoraroundtheinclusionsnearthecracktipandismoreseverewithincreasingAw.Iftheshapeofinclusionisassumedtobetriaxialellipsoids(Figure7),itispossibletocalculatethemagnitudeofAviinthefollowingequation:Avi=6Vv/(di)2whereVvisthevolumefractionofinclusionanddiistheaveragedimensionsofinclusioninthetensiledirection,i.Therearemoreinclusionsin16MnRsteelthaninA48CPRsteel.ThevalueofVvfor16MnRsteelisthereforelarger.Buttheaveragedimensionoftheelongatedinclusionsonthelongitudinalsection,forLspecimensof16MnRsteelisalsolarger.However,thevalueofAwontheplaneperpendiculartothetensiledirection,fortheLspecimen,issimilarforbothsteels.SothedifferenceinSCCsusceptibilityofLspecimensbetween16MnRandA48CPRsteelsisslight(Figure2).TheresultsindicatethattheamountandshapeofinclusionhavenosignificanteffectontheSCCbehaviorforLspecimens.However,theshapeanddistributionofinclusioninsteelsseverelyaffectthetransversepropertiessuchastheimpactstrengthofCharpytests(TableII)andSCCsusceptibility(Figure3).Eventhoughasteelcontainsthesameamountofinclusion,inagivensteel,thevolumefractureofinclusionshouldbethesame,buttheinclusionlengthdimensiondiandAwonthedifferentfractureplanemaybedifferentaccordingtotheshapeofinclusion.Becauseinclusionsin16MnRsteelarestringeredbandsparalleltotherollingdirection,theaveragelengthdimensionofinclusionsinthelongitudinaldirection,ismuchlargerthanthatinthetransversedirection,d2,andtheaverageprojectedareaonthetransverseplaneforthelongitudinalspecimen,Aw,iscorrespondinglysmallerthanthatonthelongitudinalplaneforthetransversespecimen,Av2.Theelongatedinclusionsinthe16MnRsteelcauseanisotropyinitsSCCresistance(Figure3).Incomparisonwiththe16MnRsteel,thevalueofArtisequaltothatofAt2forglobularinclusionsintheA48CPRsteel,sotheSCCbehaviorisisotropic.Ontheotherhand,SCCisalsoanelectrochemicalprocess.Thepre-existingactive-paththeoriestl31havebeenappliedprimarilytointergranularcrackingofductilealloysinaqueousenvironmentsandrelatethepropagationprocesstothepreferentialdissolutionofchemicallyactiveregionsinthegrainboundaries.TherecentinvestigationsindicatethattheMnSinclusionsdissolvereadilyinhigh-temperaturewater,presumablyformingHS-andH2S.ThesespeciesstronglyaffectthecrackgrowthrateduringSCCorcorrosionfatigueprocessesYlInareascontainingadensedistributionofelongatedMnSinclusions,thecracktipcanpropagatemuchfasterthaninthesurroundingarea.SoinclusionsinsteelshaveaninfluenceonSCCbehavior.Theresultsofrare-earth-treatedsteel16MnREunderthesametestconditionsfurtherconfirmedtheinclusioneffect.Theinclusionsin16MnREsteelsarepredominatelyglobularrare-earthsulfidesoroxysulfides(Figure6(c)whicharehardparticlesanddifficulttobedeformedandelon-gated.TheSCCresultsshowninFigures3and8indicatethattheratioofpctROAforTspecimens,ROA(T),tothatforLspecimens,ROA(L),increasesincomparisonwiththatfor16MnRsteel.ThetransverseSCCresistanceobviouslyimproveswithinclusionshape,controlledbyaddingrare-earthelementsinthelowalloysteel16MnR.Buttherearestillafewstringeredinclusions(Figure6(c)in16MnRE,sothetransverseSCCresistanceof16MnREisnotasgoodasthatofA48CPR.Nevertheless,itishopedthat16MnREsteelcanhavethesameSCCresistanceasthatofA48CPRusedinthealuminaindustrybycontrollingtheamountofrare-earthelementsaddedandtherollingprocess.V.CONCLUSIONS1.Both16MnRandA48CPRsteelsexhibitcausticSCCsusceptibilityintheIBS.TheSCCsusceptibilityof16MnRsteelincreaseswithincreasingtemperaturefrom200to3002.Thevolumefraction,shape,anddistributionofinclusionsinsteelsaffectthecausticSCCoflowalloypressurevesselsteels,especiallyinsteelswithstringeredsulfideinclusionswherethetransverseSCCresistanceisseverelyreduced.Addingrare-earthelementstothesteelimprovestransverseSCCresistancebycontrollingtheshapeanddistributionofinclusions.3.TheeffectsofinclusiononSCCbehaviorcorrelatewiththeprojectedareaofinclusionsatthecracktip,Av,ontheplaneperpendiculartothetensiledirection.TheSCCsusceptibilityincreaseswithAv.ACKNOWLEDGMENTSThisworkwassupportedbytheNationalNaturalScienceFoundationofChina(ContractNo.59271049)andtheStateKeyLaboratoryofCorrosionandProtection,AcademiaSinica.REFERENCES1.CausticStressCorrosionSymposium,AlcanJamaicaCompany(Aljam),Mandeville,Jamaica,Mar.1982.2.V.I.Artemev,V.I.Seregin,E.P.Zholoboya,andV.P.Belyaev:Zashch.Met.,1979,vol.15,p.62-65.3.M.F.Maday,A.Mignone,andA.Borello:Corrosion,1989,vol.45,pp.273-82.4.D.SingbeilandD.Tromans:Metall.Trans.A,1982,vol.13A,pp.1091-98.5.HuyHaLeandEdwardGhali:Corros.Sci.,1990,vol.30,pp.117-34.6.R.SriramandD.Tromans:Corrosion,1985,vol.41,pp.381-85.7.F.P.Ford:Proc.2ndInt.AtomicEnergyAgencySpecialistsMeetingonSubcriticalCrackGrowth,Sendai,Japan,May15-17,1985,W.H.Cullen,ed.,NUREGCP-0067,vol.2,pp.3-72.8.H.Hanninen,K.Torronen,M.Kemppainen,andS.Salonen:Corros.Sci.,1983,vol.23(6),pp.663-79.9.J.H.Bulloch:Proc.3rdlnt.Symp.onEnvironmentalDegradationofMaterialsinNuclearPowerSystems-WaterReactors,TMS,Warrendale,PA,1988,pp.261-68.10.H.E.Townsend:Corros.Sci.,1970,vol.10,pp.343-58.11.M.J.HumphriesandR.N.Parkins:Syrup.FundamentalAspectsofStress-CorrosionCracking,TheOhioStateUniversity,Columbus,OH,Sept.1115,1967,R.W.Stache,A.J.Forty,andD.VanRooyen,eds.,NACE,Houston,TX,1969,pp.384-95.12.W.A.Spitzig:Metall.Trans.A,1984,vol.15A,pp.1259-64.13.ShinobuMatsushima,YasuyukiKatada,ShunjiSato,andNorioNagata:CorrosionControl,Proc.7thAsian-PacificCorrosionControlConf.,InternationalAcademicPublisher,Beijing,1991,pp.112-172译文钢制压力容器在高温腐蚀性铝酸溶液中的应力腐蚀裂纹研究刘舒朱自勇关慧魏柯通过慢应变速率（SSRT）的测试，对三种低合金压力容器用钢在高温（200-300）腐蚀性铝酸（AlO2-）溶液中的应力腐蚀开裂（SCC）情况进行了研究。结果表明，这类压力容器钢在该类溶液中SCC较敏感，并随温度升高SCC会加剧。另外，硫化物及其它杂质的混入也会引起钢的腐蚀。稀土处理过的钢中主要含球状的硫化稀土和硫氧化合稀土，这就导致其加大了横向断裂特性，包括在延伸区域应力腐蚀断裂点Av，也就是在垂直与平面的伸长方向，随着Av值的变大，应力腐蚀特性较为明显。一引言低合金钢是比较常见的焊接反应容器的材料（例如沼气池，除尘器，蒸发器等），通过贝尔反应从含氧的水合物中将AlO2-提取出来。这类低合金反应容器与具腐蚀性的高温铝酸溶液接触并立刻出现腐蚀现象。在此期间，钢材在纯NaOH溶液中的应力腐蚀已经有过大量的研究，在92腐蚀性铝酸溶液中也做了小规模的实验。为了将氧化铝从杂质矿石中提取出来，提取时的温度大大高于92。然而，很难预知SCC的敏感性在更高温度下的铝酸盐工业中的情况。目前的主要工作就是研究低合金压力容器用钢与不同硫化物模拟在200-300时的贝尔反应情形下的应力腐蚀断裂。在过去的几年里，大量的研究工作表明，能引起非金属硫化物在沸水中对容器的腐蚀，主要与反应器和压水器的环境有关，包括含腐蚀性的MnS的影响，这一点在本文也将提到，并介绍抗SCC材料在铝酸盐工业中的应用。二实验步骤三种低合金钢处理方式的研究:16MnR钢，A48CPR，稀土处理过的16MnRE。进行试验的压力容器轧制钢板厚50毫米，650退火处理。这类钢材的化学成分和力学性能（表一和表二）较为相似，但硫的含量大不相同。取可伸长的圆柱形样本原长24毫米，直径5毫米，且均带螺纹便于装紧。从钢材的横断面和纵断面方向分别切割，这种张力实验研究样本的向性能力，所有样本用硬度为1000的砂轮抛光并且测试前用酒精和丙酮液清洗。测试环境模仿工业上的贝尔过程，温度持续在200到300之间。初始摩尔（M）浓度（表三）类似贝尔溶液：7.42M的NaOH，1.32M的Al2O33H2O，并含有杂质碳酸盐、硫酸盐、氯化物。待测液由蒸馏水和分析化学药物组成。此化学反应根据反应前后负离子（AlO2-）浓度相等得到公式：1OHAIOAIH2324在一个SERT-5000DP-9L型机器中进行试验，应变速率为3.3*10-6/秒。为避免腐蚀性溶液腐蚀反应容器，内置一个装有抗腐蚀介质的密合式镍垫片。将少量的水注入反应容器和垫片之间的缝隙，以提高传热和防止缝隙中形成腐蚀性的浓碱溶液。密封后，该系统充入2.0MPa氮，以防止沸腾并最大限度地减小缝隙的腐蚀。在每次试验之前，样本先被加压到50MPa，然后将裂缝张紧。受拉样本在被拉时处于自然腐蚀的状态。在IBS情况下获得的结果与在2.0MPa氮的情况下作比较。其失效期（TTF），伸缩率（pctROA），伸长率（E）是用来评价SCC敏感性的主要参数。其中一半的样本加上环氧树脂，并做最后的磨光处理，使其有金属光泽，观察沿断面方向的二次断裂。表一分析成分（重量百分比）钢材CSiMnPSAlCuMoNiRE16MnR0.160.471.530.0140.018-0.055-A48CPR0.1750.341.350.0120.006-0.0450.058-16MnRE0.160.401.380.0180.009-0.020表二钢的力学性能冲击强度（焦耳/厘米2，贝尔试验）25260钢材极限强度（MPA）屈服强度（MPA）伸缩率（Pct）L样本T样本L样本T样本16MnR530.0350.032.0159172777597142169858176A48CPR528.9316.131.620924018723329831723125827216MnRE535.0338.032.5169172172156129122表三.组成IBS的成分（摩尔）NaOHAl2O33H2ONa2CO3Na2SO4NaCl7.421.34三实验结果A.温度对SCC性能的影响。图1表明温度为260时，在IBS中16MnR钢的SCC状况。在腐蚀性溶液中其收缩率与在氮气中相比较而言变小了。样本在IBS中，其失效率、伸缩率、伸长率随测试温度的升高也减小了。结果表明，在IBS中，16MnR钢极易发生应力腐蚀断裂，而且随着温度的升高，SCC也变的更为明显。图1图2B.16MnR、A48CPR、16MnRE之间SCC敏感性对比。图2表示同种钢材L样本的伸缩率在同一条件下其数据的平均值，以下可重复利用此结果。对于A48CPR钢材，伸缩率在260时是66.0和64.2，在280时是63.6和61.1。对于16MnR钢材，伸缩率在260时是（如图1所示）57.2和55.0，在280时是49.6和47.0,其结果和图2相吻合。表明A48CPR钢材在测试条件下也极易发生SCC现象。随着温度的升高，从260到280，其SCC现象更为明显，不难看出,16MnR钢的L样本性能比A48CPR钢的性能差。图3表示样本对SCC特性的影响。由图可知，16MnR钢材的T样本比L样本更易出现SCC现象。然而，A48CPR钢材的T样本与L样本SCC程度是一样的。稀土处理过的16MnRE钢材的T样本抗SCC能力强些，同16MnR钢材相比，16MnRE的性能较低。图4表