95-paper-HOW TO SPECIFY STAINLESS STEELS COST EFFE

HOWTOSPECIFYSTAINLESSSTEELSCOSTEFFECTIVELYCHARLESJacquesArcelorStainless,Innovationvice-president.Abstract:StainlesssteelsareofmainconcernswhenconsideringCRA'Smaterials.Thepaperoutlinesthetremendousgrowthrateofstainlesssteelproduction(morethan5%peryearthislatestdecade).Integratedstainlesssteelplantswithmorethanonemillionoftonsarenowconsidered.Themovefromspecialtymarkettovolumemarketisnowveryclear.Thisconcernsmorethan80%oftheworldproductionofstainlesssteels.Nevertheless,evenifstainlesssteelsareconsideredasreliablematerials,theuseofCRAmaterialsinnewapplicationsand/orinthemostsevereconditionsneedsalwaysunderstandingandknowledge.ThepaperpresentsthedifferentStainlessSteelgradesandproperties.Thisincludesthe300,200,400seriesandso-calledduplexgrades.Chemicalcompositions,mechanicalandcorrosionresistancepropertieswillbepresented.Typicalindustrialapplicationswillillustratetheversatilepropertiesofstainlessgradesandwiderangeofuses.Wrongspecificationsresultintremendousunexpectedexpenses.Thisconcernsparticularlythespecificationsofalloysforequipmentsperforminginprocessindustrieswherereliabilityisoffirstconcern.Materialselectionguidelines,data,fieldexperienceandtechnicalknowledgearethenneeded.Theproductor-customercontactsmaythanbedrasticallymodifiedfromvolumemarketdrivennegotiationtoapartnershipandmutualinterestrelation.Globalsolutionsandrealinnovativesolutionsmaythantakeplace:thoseaspectswillbefurtherdiscussedinthepaper.Keywords:Stainlesssteels,properties,specification,serviceexperience,applications.0.IntroductionStainlesssteelshavenumerousadvantagesincludingtheirtailor-madepropertiesobtainedbyaspecificchemistrybalanceinchromium,nickel,molybdenum,manganese,carbon,copper,silicon,tungsten…carbonandnitrogen.Thisdeterminesthecorrosionresistancepropertiesbutalsotheirmicrostructure-ferritic,martensitic,andausteniticormixedphasemicrostructuresincludinga50/50%ferritic/austeniticbalance–theso-calledduplexgrades.Thisgivesauniqueopportunitytodesignwithstainlesssteelsgradesandtakeadvantageofoneormoreoftheircombinationofproperties.Thisincludes:WetcorrosionresistanceinacidicorbasicliquidsCorrosionresistanceinoxidizing,neutralorreducingenvironmentHeatresistancepropertiesHighductilityprovidedbytheausteniticstructureHighstrengthprovidedbythemartensiticgradesAppearanceincludingbrightannealingsurfacesEasyweldabilityandformingcharacteristicsReliabilityandimprovedlifecyclecostRecyclability…Moreoveroptimumselectionofstainlesssteelgradesmakesitpossibletoreducethecostlyalloyingelementsadditionslikenickel,molybdenum.Besidethewellknow304and316gradesothergradesincludingtheferriticsgrades–400series-,Mncontainingausteniticgrades-the200series-andtheduplexgradespresentalternativesolutionswhichadvantageswillbediscussed1.Somedateconcerningstainlesssteelmarket.Figure1presentsthevolumepercentagesofNi-austenitic,Mn-austeniticandferriticstainlesssteelworldwideproduced.Ni-Austeniticgrades–particularlythe304(L)typegrade–isthemostcommonfamily.MorerecentlyMn-AusteniticgradesduetoNisurchargehavegrowth.Ferriticstainlesssteelsrepresentapproximately23%ofthetotalmarket.Mostofthevolumeismadebyonlyfewalloysincluding304(L),316,430,and409typegrades.Mostoftheproductionisalsoissuedfromcoldrolledproducts.Hotrolledplatesrepresentlessthan10%ofthetotalflatstainlessmarket.Specialties,includingsupermartensiticgrades,duplexstainlesssteels,nitrogencontainingausteniticgrades,superausteniticgradesconcernlessthan10%oftheworldproductionofstainlesssteel!Specialties,nowadaysmainlyinvolvedinprocessindustries,havenottobeassociatedwithstainlesssteelvolumemarkets.Theymaytakeadvantageofproductivityaspectsgeneratedbyequipmentdealingwithvolumemarketsbuttheyintroducespecificcomplexityduetotheirspecificproductionroute.Higherproductivityforvolumemarketmay,inthefuture,requestlesscomplexity.Theworktoproducespecialties(includingR&DandMKT)musthaveapaid-backadvantage!Figure1:StainlessSteelCrudeProductionbycategoriesin%.Figure2:Schaeffler/Delongdiagram.2.Thestainlesssteelsgrades:phasestability/microstructures/mechanicalproperties.Inordertopresentthecloserelationbetweenmicrostructureandchemicalcompositionofstainlesssteelgrades,theSchaeffler-Delongdiagramisveryuseful(normallyusedforweldedstructures).Stainlessgradesmaybedividedinseveralfamilies:ferritic,martensitic,austeniticormulti-phases(ex:duplexgrades)(figure2).Typicalmechanicalpropertiesofthedifferentstainlesssteelgradesarepresentedfigure3.Itisobservedthat:oFerriticstructurehashigheryieldstrengththanausteniticmicrostructure(forlowC/Ncontents).oInterstitialelements(C/N)haveastronghardeningeffect.oDuplexgradesthanks’tograinrefiningeffectsandmixedferrite/austenitestructureshavehighMP.Figure3:MechanicalpropertiesofseveralS.S.grades71.55.323.272.25.722.170.87.421.865.69.323.101020304050607080%2001200220032004(p)DataprovidedbyISSFCrNiCrMnCr71.55.323.272.25.722.170.87.421.865.69.323.101020304050607080%2001200220032004(p)DataprovidedbyISSFCrNiCrMnCr0.6C+N(%)YS/0.2%ProofStrength(MPa)AL201LP300A16-7Mn16-4MnD10Posco204MAL219H400P202ANitronic19DAF2020-7