254-654smo

CHARACTERISTICPROPERTIES•Austeniticstructure•Goodtoverygoodresistancetouniformcorrosion•Goodtoexceptionallygoodresistancetopittingandcrevicecorrosion•Verygoodresistancetovarioustypesofstresscorrosioncracking•GoodductilityandweldabilityAPPLICATIONS•Processequipmentinchemicalindustry•Bleachingequipmentinthepulpandpaperindustry•Fluegascleaning•Desalination•Seawaterhandling•HeatexchangersGENERALCHARACTERISTICSHigh-alloyedausteniticstainlesssteelshavesuchhighcontentsofchromium,nickel,molybdenumandnitrogenthattheydiffersubstantiallyfrommoreconventionalgradeswithregardtoresistancetocorrosionand,insomecases,alsomechanicalandphysicalproperties.Fromaworkshoppracticeviewpoint,i.e.,withregardtomanufacturingofcomponentsandequipment,theyaretosomeextentsimilartostandardausteniticgradessuchas1.4301and1.4401,buttheystillrequirespecialknow-howwithregardtoweldingandmachining.AvestaPolaritmanufacturesfoursteelsofthistype:904L,254SMO®and654SMO®,20-25-6canalsobedeliveredifspecified.Incertainapplicationsthegrades4439(austenitic)and2205(duplex)maybeusedasanalternativeto904L,whilstSAF2507®(duplex)maybeusedasanalternativeto254SMO®.Moreinformationconcerningduplexoptionsisavailableinthedatasheetforduplexsteels.CHEMICALCOMPOSITIONThechemicalcompositionofasteelgrademayvaryslightlybetweendifferentnationalstandards.Consequently,aspecifiedstandardshouldalwaysbestatedwhenordering.STEELGRADESHighAlloyedAusteniticStainlessSteel904L,254SMO®,654SMO®AvestaPolaritENASTM904L1.4539N08904254SMO®1.4547S31254654SMO®1.4652S32654AvestaPolaritInternationalTypicalcomposition,%Nationalsteeldesignations,steelnamesteelNosupersededbyENENASTMCNCrNiMoOthersBSDINNFSS44361.44363160.020.0516.910.72.6–316S331.4436Z7CND18-12-03234344391.4439S317260.020.1417.812.74.1––1.4439Z3CND18-14-05Az–20-25-61.4529N089260.010.2020256.4Cu–1.4529––904L1.4539N089040.010.0620254.31.5Cu904S131.4539Z2NCDU25-202562254SMO®1.4547S312540.010.2020186.1Cu–––2378654SMO®1.4652S326540.010.5024227.33,5Mn,Cu––––22051.4462S32205*0.020.17225.73.1–318S131.4462Z3CND22-05Az2377SAF2507®1.4410S327500.020.272574–––Z3CND25-06Az2328Ni-alloys**CmaxAlloy625–N066250.10–21609Nb2.4856AlloyC-276–N102760.02–156016W2.4819SAF2507®ismadeonlicencefromABSandvikSteel.*AlsoavailableasS31803**ThesealloysarenotproducedwithinAvestaPolaritTable1.ChemicalcompositionHighAlloyedAusteniticStainlessSteel2MECHANICALPROPERTIESThestrengthandelongationof904Laresimilartothoseforconventionalausteniticstainlesssteels.However,theadditionofnitrogenin254SMO®and654SMO®giveshigherandconsiderablyhigherstrengthrespectively,i.e.,proofstrengthandtensilestrength,seeTables3and4.Despitethegreaterstrengthofthesesteels,thepossibilitiesforcoldaswellashotformingareverygood.DataaccordingtoEN.MICROSTRUCTUREAllthreegradeshaveanausteniticmicrostructureinthequenchannealedcondition.Both254SMO®and654SMO®can,however,containtracesofintermetallicphases(chiandsigmaphase)atthecentreofthematerial.Normally,thisdoesnotaffecttheresistancetocorrosionormechanicalpropertiesofthesteel.Suchprecipitatescanalsooccurifthematerialisexposedtotemperaturesintherangeof600-1000°C.Providedthattherecommendationsgivenforhotforming,weldingandheattreatmentarefollowed,suchprecipitateshavenonegativeeffectinusability.Table2.Characteristictemperatures,°CTable3.Minimumvaluesat20°C904L254SMO®654SMO®ProofstrengthRp0.2MPa220300430Rp1.0MPa260340470TensilestrengthRmMPa520650750ElongationA5%353540HardnessHBmax.180210250ImpactvalueKVJ606060PHYSICALPROPERTIES904L254SMO®654SMO®Densitykg/dm38.08.08.0ModulusofelasticityGPa195195190Linearexpansionat(20100)°CX10-6/°C1616.515ThermalconductivityW/m°C121411ThermalcapacityJ/kg°C450500500ElectricresistivityµΩm1.00.850.78Table4.TensilePropertiesatelevatedtemperatures,minimumvalues,MPaTable5.TypicalvaluesaccordingtoEN10088904L254SMO®654SMO®Rp0.2Rp1.0RmRp0.2Rp1.0RmRp0.2Rp1.0Rm100°C205235500230270615350390680200°C175205460190225560315355620300°C145175440170205525300335585400°C125155160190510295330560904L254SMO®654SMO®Hotforming1200-9501200-10001200-1100Quenchannealing1080-11601150-1200*1150-1200*Pressurevesselapproval(-60)-400(-60)-400*Quenchingwithwateratathicknessabove2mm,below2mmanannealingtemperatureof1120-1150°Candcoolingwithair/watercanbeused.HighAlloyedAusteniticStainlessSteel3Fig.1.Isocorrosioncurves,0.1mm/y,inpuresulphuricacid.Fig.2.Isocorrosioncurves,0.1mm/y,insulphuricacidcontaining2000ppmchloride.Fig.3.Isocorrosioncurves,0.1mm/y,inpurehydrochloricacid.Fig.4.Isocorrosioncurves,0.1mm/y,inpurehydrofluoricacid.Fig.5.Isocorrosioncurves,0.1mm/y,inpurefluosilicicacid.CORROSIONRESISTANCEUniformcorrosionThehighcontentofalloyingmaterialsgivesthesteels904L,254SMO®and654SMO®exceptionallygoodresistancetouniformcorrosion.904Lwasoriginallydevelopedtowithstandenviron-mentsinvolvingdilutesulphuricacidanditisoneofthefewstainlesssteelsthatattemperaturesofupto35°Cprovidesfullcorrosionresistanceinsuchenvironmentswithintheentirerangeofconcentration,from0to100%,seeFigure1.Italsooffersgoodresistancetoanumberofotherinorganicacids,e.g.,phosphoricacid,aswellasmostorganicacids