RoleofLadleRefiningandVacuumDegassinginRailroadWheelSteel

Cleanliness

Cameron Lonsdale & Jay Galbraith Standard Steel, LLC Burnham, PA, USA

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RecentCapitalProjects•  Projectstotalingmorethan$60MUSD

•  Steelmaking

–  Newbasicelectricarcfurnace

–  Twin-tankladlerefiningandvacuumdegassingstaCon

•  SynchronizedInclinedRotaryDishingPress(SIRD)InstallaCon

•  Goals:Produceultra-clean,low-stress,high-precisionwheels

2

MeltShopInstallaAonUpdatePhase1ofprojectcompletedattheendofDec2013:

•  RevampedElectricArcFurnace(conCnuedacidpracCce)

•  Replaced30MVAtransformerwitha50MVA

•  Installednewwatercoolingsystem&baghousewasupgraded

•  Installednew110-toncrane

Phase2completedJan2014-2015:

•  Twintankladlerefining/vacuumdegassingfacility

•  Slagrakesystem

•  Change-overtobasicsteelmakingpracCce–January2015

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ElectricArcFurnaceRevamp

Before

AIer

During

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LadleTiltStand/SlagRakeSystemForRemovingEAFSlag

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NewTwin-Tank,LadleRefining/VacuumDegassing(LFVD)StaAon

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OverviewofLadleRefining&VacuumDegassingStaAon

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Twin-TankLFVDStaAon

TwostaConaryvacuumtanks

Ladlefurnaceroof(forheaCng)swingsbetweentanks

Twogantrycarvacuumcoverlids

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LFVDStaAonswithladlebeingheatedVacuumcoverlidmovesintoposiCononrails

Chuteforaddingalloysviaconveyorsystem

Ladlefurnaceroof(heaCng)

Pulpit

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MaterialHandlingSystem-PreciseAlloyAddiAons

Alloystoragebins

Weighinghoppers

UpperconveyorsystemfortransporCngalloystoladle

Lowerconveyorsystem

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Guidetubesystemsdirectswireintoeachtank

WireFeedingSystems–PreciseAlloyAddiCons

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SteelCleanlinessImprovements:ImplicaAonsforHeavyHaulWheels

•  Wheelsaresubjecttoadynamicloadingenvironment-impacts

•  Forsteelswithsimilarstrength(i.e.,hardness),dynamicfracturetoughnessisastrongfuncConofthesteel’scleanliness,micro-porosity,andmicrostructure

•  Underheavyaxleloads,rimfaCguecrackscaniniCateinternallyatstressconcentraCons(i.e.,voidsandinclusions)

–  Hardoxideinclusions,primarilyalumina,arelikelysourcesofiniCaCon–  InterdendriCcsulfidesreduceducClityandtoughness

•  EvidencesuggeststhatsteelswithahighdegreeofcleanlinessarelesssuscepCbletoshaberedrims&rollingcontactfaCgue(i.e.,shelling)

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SteelCleanlinessImprovements•  VerificaConbytwomethods:

–  ASTMStandardPracCceE1245(average&worstfieldarea%’sofoxides,voids,&sulfides)BasisforAARspecificaCon.

MeanVolume%Voids+Oxides

MaximumVolume%

Voids+Oxides

MeanVolume%Sulfides

MaximumVolume%Sulfides

0.0095% 0.150% 0.137% 0.365%

0.0073% 0.045% 0.120% 0.224%

23% 70% 12% 39%

OldSteelmakingProcess

NewSteelmakingProcess

%ImprovementwithNewProcess

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SteelCleanlinessImprovements– AutomatedSteelCleanlinessAnalysisTool(ASCAT)

•  Basedoncomputer-controlledscanningelectronmicroscopy•  ProvidesdetailedsizedistribuConandchemistryinformaConofinclusionsinsteel

•  HasbeenshowntoprovidegoodcorrelaConwithultrasonictestdata

•  DevelopedbyUSSteel,CarnegieMellonUniversity&RJLeeGroup

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ASCAT•  Samplesaretakenfromtheladle•  GivesinformaAononnumberofinclusions&areafracAonofinclusionsinthesamples

•  ProvidesinformaAononspecificinclusiontypesandchemistry

•  Notjust–“Oxide”butspecifictypeofoxide

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ASCAT•  NumberDensity–Thecount(number)ofinclusionsseenbythecomputeronapolishedsteelsamplesurfaceintheareascanned.

•  AreaFracAon–Theareapercentageofthepolishedsteelsamplesurfacethatisinclusions,andnotsteel

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NewSteelmakingPracCceResults:ReducConinOxideInclusions

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NewSteelmakingPracCceResults:ReducConinOxideInclusions

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RemovalofOxideInclusionsDuringVacuumDegassing

GraphShowsNumber/squarecm

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RemovalofOxideInclusionsDuringVacuumDegassing

GraphShowsAreaFracCon

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SteelCleanliness•  Removalofoxidesthataredeleterioustodynamicfracture

toughnessandrollingcontactfaCguerequiretherightcombinaConofslagchemistryandslag/metalinteracCon

•  MostnotableisthepresenceofsmallerandfeweraluminainclusionswhichresultsingreaterresistancetofaCgue&fracture

•  ReducedareafracConandnumberdensityofinclusions•  Hydrogenismeasured,andcontrolledwithdegassing

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NewSteelmakingPracCceResults:ImpactonSulfideInclusions

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NewSteelmakingPracCceResults:ImpactonSulfideInclusions

•  SimilarareafracConofsulfides,buthighernumberdensity→sulfidesaresmaller.

•  Wearenowre-sulfurizingtohelpinsuremachinability–Sulfurassistsmachining

•  Finishboring&treadturningdownstream•  Sulfidecontentcouldbemademuchlower

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NewSteelmakingPracCceResults:ImpactonSulfideInclusions

•  17%moresulfideinclusionsinthe1to2.5micron(SMALL)rangeforsteelproducedusingthenewpracCce.

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ImprovementinSulfideMorphology

•  Evenatthesamesulfurlevels(tomaintainacceptablemachinability),thenewsteelmakingpracCceresultsinsmall,globularsulfideswithacompletelackoflarge,eutecCcsulfides.EutecCcsulfidestendtoreducetensileducClityandtoughness.

OldPracAceNewPracAce

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NewSteelmakingPracAceResults:ImprovementinMechanicalProperAes

•  RoomtemperaturetensiletestdataofAARGradeFaxles

•  CleansteelmakingpracCceswithimproveddeoxidaConpracCcesresultsin:

–  Finer-grained–  Slightlyhigherstrength–  HigherducClity

Tensile Strength

(ksi)

Yield Strength

(ksi) %

Elongation %

Reduction in Area

ASTM Grain Size #

Old Steelmaking

Process 98.1 56.9 22.9 44.9 7.0

New Steelmaking

Process 98.7 57.9 24.8 48.8 7.8

Improvement: 1% 2% 8% 9% 12%

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UpcomingTechnicalPaperatWCRR,Milan,Italy

•  Kato,etal.,tobepresentedMay30–June2•  Failuredata(brokenrim,AARWhyMadeCode68)of

“cleansteel”ClassCvsconvenAonalwheelsexamined•  “Higherfracturetoughnesswheelswerepredictedtohave

muchlowerVSRratesthanconvenAonalwheels.”•  “Higherfracturetoughnesswheelsteelsmakeitpossible

toreducetherateofVSRfailuresinwheels.”

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SynchronizedInclinedRotaryDishingPress(SIRD)InstallaAon:HigherPrecision-ForgedWheels

•  Principle:IncrementaldeformaConusinganinclinedtopforgingdiethatmaintainsconstantcontactwhileboththetop&bobomdiesrotatetomaintainworkpiecestability

•  Advantages:

–  Closertonet-shapepriortomachining–  Tighteroveralldimensionaltolerances–  Rotundityandeccentricitybetweenroughboreandtread

significantlyimproved→ReducConinoverallstressstateoftherailroad

–  Expectedtoresultinconsistentlylargertapesizeswithmoreuseablewearmetalintherim

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SynchronizedInclinedRotaryDishingPress(SIRD)PreliminaryResults

•  Radialrun-outcontourplotsshowimprovementintheconcentricityofthehubandrimwithSIRDprocess

•  Rimthicknessismoreconsistentaroundthecircumference

•  Tapesizeismoreuniform

•  MinimalvariaConinfrontface/backfacerimthickness&hubwallthickness

Before

Aier

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QuesAons?

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