不锈钢等级说明.docx

不锈钢等级说明.docx

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不锈钢等级说明

不锈钢等级说明

Inmetallurgy,stainlesssteelisdefinedasasteelalloywithaminimumof10%chromiumcontentbymass.[1]Stainlesssteeldoesnotstain,corrode,orrustaseasilyasordinarysteel（itstainsless）,butitisnotstain-proof.[2]Itisalsocalledcorrosion-resistantsteelorCRESwhenthealloytypeandgradearenotdetailed,particularlyintheaviationindustry.Therearedifferentgradesandsurfacefinishesofstainlesssteeltosuittheenvironmenttowhichthematerialwillbesubjectedinitslifetime.Commonusesofstainlesssteelarecutleryandwatchstraps.

Stainlesssteeldiffersfromcarbonsteelbyamountofchromiumpresent.Carbonsteelrustswhenexposedtoairandmoisture.Thisironoxidefilmisactiveandacceleratescorrosionbyformingmoreironoxide.Stainlesssteelshavesufficientamountofchromiumpresentsothatapassivefilmofchromiumoxideformswhichpreventsfurthercorrosion.

Contents[hide]

1History

2Properties

3Applications

3.1Usesinsculpture,buildingfacadesandbuildingstructures

4Recycling&reuse

5Typesofstainlesssteel

5.1Comparisonofstandardizedsteels

5.2Stainlesssteelgrades

6Stainlesssteelfinishes

7Seealso

8References

8.1Notes

8.2Bibliography

9Externallinks

notedtheirresistanceagainstattackbysomeacidsandsuggestedtheiruseincutlery.Metallurgistsofthe19thcentury,however,wereunabletoproducethecombinationoflowcarbonandhighchromiumfoundinmostmodernstainlesssteels,andthehigh-chromiumalloystheycouldproduceweretoobrittletobepractical.

Inthelate1890s,HansGoldschmidtofGermanydevelopedanaluminothermic（thermite）processforproducingcarbon-freechromium.Intheyears1904–1911severalresearchers,particularlyLeonGuilletofFrance,preparedalloysthatwouldtodaybeconsideredstainlesssteel.

FriedrichKruppGermaniawerftbuiltthe366-tonsailingyachtGermaniafeaturingachrome-nickelsteelhullinGermanyin1908.[4]In1911,PhilipMonnartzreportedontherelationshipbetweenthechromiumcontentandcorrosionresistance.OnOctober17,1912,KruppengineersBennoStraussandEduardMaurerpatentedausteniticstainlesssteel.[5]

SimilardevelopmentsweretakingplacecontemporaneouslyintheUnitedStates,whereChristianDantsizenandFrederickBecketwereindustrializingferriticstainless.

HarryBrearleyoftheBrown-FirthresearchlaboratoryinSheffield,Englandiscommonlycreditedastheinventorofstainlesssteel.In1913,whileseekinganerosion-resistantalloyforgunbarrels,hediscoveredandsubsequentlyindustrializedamartensiticstainlesssteelalloy.ThediscoverywasannouncedtwoyearslaterinaJanuary1915newspaperarticleinTheNewYorkTimes.[3]Thiswaslatermarketedunderthe"Staybrite"brandbyFirthVickersinEnglandandwasusedforthenewentrancecanopyfortheSavoyHotelin1929inLondon.[6]

[edit]Properties

Highoxidation-resistanceinairatambienttemperaturearenormallyachievedwithadditionsofaminimumof13%（byweight）chromium,andupto26%isusedforharshenvironments.[7]Thechromiumformsapassivationlayerofchromium（III）oxide（Cr2O3）whenexposedtooxygen.Thelayeristoothintobevisible,andthemetalremainslustrous.Itisimpervioustowaterandair,protectingthemetalbeneath.Also,thislayerquicklyreformswhenthesurfaceisscratched.Thisphenomenoniscalledpassivationandisseeninothermetals,suchasaluminiumandtitanium.Whenstainlesssteelpartssuchasnutsandboltsareforcedtogether,theoxidelayercanbescrapedoffcausingthepartstoweldtogether.Whendisassembled,theweldedmaterialmaybetornandpitted,aneffectthatisknownasgalling.Thisdestructivegallingcanbebestavoidedbytheuseofdissimilarmaterials,e.g.bronzetostainlesssteel,orevendifferenttypesofstainlesssteels（martensiticagainstaustenitic,etc.）,whenmetal-to-metalwearisaconcern.Inaddition,Nitronicalloys（trademarkofArmco,Inc.）reducethetendencytogallthroughselectivealloyingwithmanganeseandnitrogen.

Nickelalsocontributestopassivation,asdootherlesscommonlyusedingredientssuchasmolybdenumandvanadium.

[edit]Applications

ThepinnacleofNewYork'sChryslerBuildingiscladwithtype302stainlesssteel.[8]

AnartdecosculptureontheNiagara-MohawkPowerbuildinginSyracuse,NewYork

Pipesandfittingsmadeofstainlesssteel

Stainlesssteel’sresistancetocorrosionandstaining,lowmaintenance,relativelylowcost,andfamiliarlustermakeitanidealbasematerialforahostofcommercialapplications.Thereareover150gradesofstainlesssteel,ofwhichfifteenaremostcommon.Thealloyismilledintocoils,sheets,plates,bars,wire,andtubingtobeusedincookware,cutlery,hardware,surgicalinstruments,majorappliances,industrialequipment,andasanautomotiveandaerospacestructuralalloyandconstructionmaterialinlargebuildings.Orangejuiceandotherfoodtransportandstoragetankersareoftenmadeofstainlesssteel,duetoitscorrosionresistanceandantibacterialproperties.Thisalsoinfluencesitsuseincommercialcateringkitchensandfoodprocessingplants,asitcanbesteamcleaned,sterilized,anddoesnotneedpaintingorapplicationofothersurfacefinishes.

Stainlesssteelisalsousedforjewelleryandwatches.Themostcommonstainlesssteelalloyusedforthisis316L.Itcanbere-finishedbyanyjewellerandwillnotoxidizeorturnblack.Notallmanufacturersusethistype;Rolexforinstanceusetype904Lfortheirstainlesssteelwatches.[9]

[edit]Usesinsculpture,buildingfacadesandbuildingstructures

Stainlesssteelwasinvogueduringtheartdecoperiod.ThemostfamousexampleofthisistheupperportionoftheChryslerBuilding（illustratedtotheright）.Dinersandfastfoodrestaurantsfeaturelargeornamentalpanels,stainlessfixturesandfurniture.Owingtothedurabilityofthematerial,manyofthesebuildingsretaintheiroriginalappearance.

Theforgingofstainlesssteelhasgivenrisetoafreshapproachtoarchitecturalblacksmithinginrecentyears.

TheGatewayArch（pictureabove）iscladentirelyinstainlesssteel:

886tons（804metrictonnes）of0.25in（6.4mm）plate,#3finish,type304stainlesssteel.[1]

Type316stainlessisusedontheexteriorofboththePetronasTwinTowersandtheJinMaoBuilding,twooftheworld'stallestskyscrapers.[2]

TheParliamentHouseofAustraliainCanberrahasastainlesssteelflagpoleweighingover220tons.

TheaerationbuildingintheEdmontonCompostingFacility,thesizeof14hockeyrinks,isthelargeststainlesssteelbuildinginNorthAmerica.[3]

TheUnitedStatesAirForceMemorialhasanausteniticstainlesssteelstructuralskin.

[edit]Recycling&reuse

Stainlesssteelis100%recyclable.Infact,anaveragestainlesssteelobjectiscomposedofabout60%recycledmaterial,25%originatingfromend-of-lifeproductsand35%comingfrommanufacturingprocesses.[10]

[edit]Typesofstainlesssteel

Therearedifferenttypesofstainlesssteels:

whennickelisadded,forinstance,theaustenitestructureofironisstabilized.Thiscrystalstructuremakessuchsteelsnon-magneticandlessbrittleatlowtemperatures.Forgreaterhardnessandstrength,carbonisadded.Whensubjectedtoadequateheattreatment,thesesteelsareusedasrazorblades,cutlery,tools,etc.

Significantquantitiesofmanganesehavebeenusedinmanystainlesssteelcompositions.Manganesepreservesanausteniticstructureinthesteelasdoesnickel,butatalowercost.

Stainlesssteelsarealsoclassifiedbytheircrystallinestructure:

Austenitic,or300series,stainlesssteelscompriseover70%oftotalstainlesssteelproduction.Theycontainamaximumof0.15%carbon,aminimumof16%chromiumandsufficientnickeland/ormanganesetoretainanausteniticstructureatalltemperaturesfromthecryogenicregiontothemeltingpointofthealloy.Atypicalcompositionof18%chromiumand10%nickel,commonlyknownas18/10stainless,isoftenusedinflatware.Similarly,18/0and18/8arealsoavailable.Superausteniticstainlesssteels,suchasalloyAL-6XNand254SMO,exhibitgreatresistancetochloridepittingandcrevicecorrosionduetohighmolybdenumcontent（>6%）andnitrogenadditions,andthehighernickelcontentensuresbetterresistancetostress-corrosioncrackingversusthe300series.Thehigheralloycontentofsuperausteniticsteelsmakesthemmoreexpensive.Othersteelscanoffersimilarperformanceatlowercostandarepreferredincertainapplications.[citationneeded]

ThelowcarbonversionoftheAusteniticStainlessSteel,forexample316Lor304L,areusedtoavoidcorrosionproblemcausedbywelding.The"L"meansthatthecarboncontentoftheStainlessSteelisbelow0.03%,thiswillreducethesensitizationeffect,precipitationofChromiumCarbides,duetothehightemperatureproducedbyweldingoperation.

Ferriticstainlesssteelsarehighlycorrosion-resistant,butlessdurablethanausteniticgrades.Theycontainbetween10.5%and27%chromiumandverylittlenickel,ifany,butsometypescancontainlead.Mostcompositionsincludemolybdenum;some,aluminiumortitanium.Commonferriticgradesinclude18Cr-2Mo,26Cr-1Mo,29Cr-4Mo,and29Cr-4Mo-2Ni.

Martensiticstainlesssteelsarenotascorrosion-resistantastheothertwoclassesbutareextremelystrongandtough,aswellashighlymachineable,andcanbehardenedbyheattreatment.Martensiticstainlesssteelcontainschromium（12-14%）,molybdenum（0.2-1%）,nickel（0-<2%）,andcarbon（about0.1-1%）（givingitmorehardnessbutmakingthematerialabitmorebrittle）.Itisquencheda