Some effects of Alloying elements in.docx
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Some effects of Alloying elements in.docx
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SomeeffectsofAlloyingelementsin
SomeeffectsofAlloyingelementsin Steel
ByMathew
Alloyingadditionsarecommonlyaddedtosteelsto;
∙increasehardenability,
∙improvestrength,
∙improvemechanicalproperties(atoperatingtemperature),
∙improvetoughnessforagivenstrengthorhardness,
∙increasewearresitance,
∙improvemagneticproperties.
Increasingthehardenabilitymeansthatpearlitetransformationwillbedelayedtolongertimes.Thismeansitiseasiertoobtainmartensiteorbainiteoncooling,orbyisothermalholdingaftercoolingpastthepearlitestarttemperature.
ClassificationofalloyingelementsbyBaininTheAlloyingElementsinSteel
DissolvedinFerrite
Ni,Si,Al,Zr,Mn,Cr,W,Mo,V,Ti,P,S(?
)Cu.
Nickel,silicon,aluminium,zirconia,manganese,chromium,tungsten,molybdenum,vanadium,titanium,phoshorous,sulphurandcopper.
CombinedinCarbide
Mn,Cr,W,Mo,V,Ti.
Manganese,chromium,tungsten,molybdenum,vanadium,titanium.
InNonmetallicInclusions
SiO2,MxOy,Al202,etc
ZrO,MnS,MnFeO,MnO,SiO2,CrxOy
VxOy,TixOy,MnFeS,ZrS
SpecialIntermetallicCompounds
Ni-SiCompound(?
),AlxNy,ZrxNy
VxNy,TixNyC2,TixNy
Elementalstate
Cuabove0.8%
Pb(?
)
Theeffectsofcommonalloyingelementsinsteelwassummarisedasfollows(datafrom‘MetalsHandbook’1948,AmericanSocietyforMetals,MetalsPark,Ohio.
Al–Aluminium
SolidSolubility
InGammaIron(austenite)
1.1%(increasedbyC)
InAlphaIron(ferrite)
36%
Influenceonferrite
Hardensconsiderablybysolidsolution.
Influenceonaustenite(hardenability)
Increaseshardenabilitymildly,ifdissolvedinaustenite.
Influenceexertedthroughcarbide
Carbideformingtendency
Negative(graphitizes).
Actionduringtempering
-
Principalfunctions
∙Dexodisesefficiently.
∙Restrictsgraingrowth(byformingdispersedoxidesornitrides).
∙Alloyingelementinnitridingsteel.
Cr–Chromium
SolidSolubility
InGammaIron(austenite)
12.8%(20%with0.5C)
InAlphaIron(ferrite)
Unlimited
Influenceonferrite
Hardensslightly;increasescorrosionresistance.
Influenceonaustenite(hardenability)
Increaseshardenabilitymoderately.
Influenceexertedthroughcarbide
Carbideformingtendency
GreaterthanMn;lessthanW.
Actionduringtempering
Mildlyresistssoftening.
Principalfunctions
∙Increasesresistancetocorrosionandoxidation.
∙Increaseshardenability.
∙Addssomestrengthathightemperatures.
∙Resistsabrasionandwear(withhighcarbon).
Co–Cobalt
SolidSolubility
InGammaIron(austenite)
Unlimited
InAlphaIron(ferrite)
75%
Influenceonferrite
Hardensconsiderablybysolidsolution.
Influenceonaustenite(hardenability)
Decreaseshardenabilityasdissolved.
Influenceexertedthroughcarbide
Carbideformingtendency
SimilartoFe.
Actionduringtempering
Sustainshardnessbysolidsolution.
Principalfunctions
∙Contributedtored-hardnessbyhardeningtheferrite.
Mn–Manganese
SolidSolubility
InGammaIron(austenite)
Unlimited
InAlphaIron(ferrite)
3%
Influenceonferrite
Hardensmarkedly;reducesplasticitysomewhat.
Influenceonaustenite(hardenability)
Increaseshardenabilitymoderately.
Influenceexertedthroughcarbide
Carbideformingtendency
GreaterthanFe;lessthanCr.
Actionduringtempering
Verylittleinusualquantities.
Principalfunctions
∙Counteractsbrittlenessfromsulphur[byformingMnSsulphides).
∙Increaseshardenabilityinexpensively.
Mo–Molybdenum
SolidSolubility
InGammaIron(austenite)
~3%(8%with0.3%C)
InAlphaIron(ferrite)
37.5%(lesswithloweredtemperature)
Influenceonferrite
ProvidesagehardeningsysteminhighMo-Fealloys.
Influenceonaustenite(hardenability)
Increaseshardenabilitystrongly(Mo>Cr).
Influenceexertedthroughcarbide
Carbideformingtendency
Strong;greaterthanCr.
Actionduringtempering
Opposessoftening,bysecondaryhardening.
Principalfunctions
∙Raisesgrain-coarseningtemperatureofaustenite.
∙Deepenshardening.
∙Counteractstendencytowardtemperbrittleness.
∙Raiseshotandcreepstrength,red-hardness.
∙Enhancescorrosionresistanceinstainlesssteel.
∙Formsabrasionresistingparticles.
Ni–Nickel
SolidSolubility
InGammaIron(austenite)
Unlimited
InAlphaIron(ferrite)
10%(irrespectiveofcarboncontent)
Influenceonferrite
Strengthensandtoughensbysolidsolution.
Influenceonaustenite(hardenability)
Increaseshardenabilitymildly,buttendstoretainausteniteathighercarboncontents.
Influenceexertedthroughcarbide
Carbideformingtendency
Negative(graphitizes).
Actionduringtempering
Verylittleinsmallpercentages.
Principalfunctions
∙Strengthensunquenchedorannealedsteels.
∙Toughenspearlitic-ferriticsteels(especiallyatlowtemperature).
∙Rendershigh-chromiumironalloysaustenitic.
P–Phosphorus
SolidSolubility
InGammaIron(austenite)
0.5%
InAlphaIron(ferrite)
2.8%(irrespectiveofcarboncontent)
Influenceonferrite
Hardensstronglybysolidsolution.
Influenceonaustenite(hardenability)
Increaseshardenability.
Influenceexertedthroughcarbide
Carbideformingtendency
.
Nil
Actionduringtempering
-
Principalfunctions
∙Strengthenslow-carbonsteel.
∙Increasesresistancetocorrosion.
∙Improvesmachinabilityinfree-cuttingsteels.
Si–Silicon
SolidSolubility
InGammaIron(austenite)
~2%(9%with0.35%C)
InAlphaIron(ferrite)
18.5%(notmuchchangedbycarbon).
Influenceonferrite
Hardenswithlossinplasticity(MnInfluenceonaustenite(hardenability)
Increaseshardenabilitymoderately.
Influenceexertedthroughcarbide
Carbideformingtendency
Negative(graphitizes).
Actionduringtempering
Sustainshardnessbysolidsolution.
Principalfunctions
∙Usedasageneralpurposedeoxidiser.
∙Alloyingelementforelectricalandmagneticsheet.
∙Improveoxidationresistance.
∙Increasehardenabilityofsteelscarryingnon-graphitisingelements.
∙Strengthenslow-alloysteels.
Ti–Titanium
SolidSolubility
InGammaIron(austenite)
0.75%(1%with0.2%C)
InAlphaIron(ferrite)
~6%(lesswithloweredtemperature)
Influenceonferrite
ProvidesagehardeningsysteminhighTi-Fealloys.
Influenceonaustenite(hardenability)
Probablyincreaseshardenabilityverystronglyasdissolved,thecarbideeffectsreducehardenability.
Influenceexertedthroughcarbide
Carbideformingtendency
Greatestknown(2%Tirenders0.5%carbonsteelunhardenable).
Actionduringtempering
Persistentcarbidesprobablyunaffected.Somesecondaryhardening.
Principalfunctions
∙Fixescarbonininertparticles;
∙reducesmartensitichardnessandhardenabilityinmediumCrsteels.
∙preventsformationofausteniteinhighCrsteels.
∙preventslocaliseddepletionofchromiuminstainlesssteelduringlongheating.
W–Tungsten
SolidSolubility
InGammaIron(austenite)
6%(11%with0.25C)
InAlphaIron(ferrite)
33%(lesswithloweredtemperature)
Influenceonferrite
ProvidesagehardeningsysteminhighW-Fealloys.
Influenceonaustenite(hardenability)
Increaseshardenabilitystronglyinsmallamounts.
Influenceexertedthroughcarbide
Carbideformingtendency
Strong.
Actionduringtempering
Opposessofteningbysecondaryhardening.
Principalfunctions
.
∙Formshard,abrasionresistantparticlesintoolsteels.
∙Promoteshardnessandstrengthatelevatedtemperature.
V–Vanadium
1(4%with0.2%C)
SolidSolubility
InGammaIron(austenite)
Unlimited.
InAlphaIron(ferrite)
Hardensmoderatelybysolidsolution.
Influenceonferrite
Unlimited.
Influenceonaustenite(hardenability)
Increaseshardenabilityverystronglyasdissolved.
Influenceexertedthroughcarbide
Carbideformingtendency
Verystrong
Actionduringtempering
Maximumforsecondaryhardening.
Principalfunctions
∙Elevatescoarseningtemperatureofaustenite(promotesfinegrain).
∙Increaseshardenability(whendissolved).
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