简介：Thecenterlinesegregationincontinuouscastingsteelisknowntobeformedbytheinterdendriticenrichedliquidflowatthesolidificationendinstrand.Atpresent,severalmethods,suchasthermalsoftreduction,electromagneticstirringanddynamicsoftreduction,areavailabletoreducethecentersegregationandtoimprovetheinternalquality.Althoughsomemethodscouldalleviatecentersegregationtosomeextent,theycanalsogiverisetonewproblems.Forinstance,thermalsoftreductioncanleadtosurfacecrackingduringcastingofsomesteelsandelectromagneticstirringcanresultinwhiteband.Dynamicsoftreductionisaneffectivetechnologyfortheimprovementofstrandqualityincontinuousslabcasting.Inthispaper,thekeyparametersofdynamicsoftreductiontechnology,suchassoftreductionregion,thetotalreductionamount,forlowcarbonsteelhavebeenstudiedbasedonexperimentalandtheoreticalanalysis.Thesoftreductionregionwasrelatedtothesegregationofchemicalcomposition,slabbulgingofnarrowsideandavoidinginternalcrackofslab.Thetotalreductionamountwascomposedofnaturalthermalshrinkageandactualreductionamountdependingoncriticalstrain.Forlowcarbonsteelwithslabdimensionof(950-1950)mm×170mm,thesolidfractionrangeinsoftreductionregionwasrecommendedfrom0.4to0.8,thetotalreductionamountwas2.0-2.8mm,andtheoptimizedreductionratewas0.4-1.2mm/min,respectively.Furthermore,adynamicsoftreductionsystemincontinuousslabcasting,VisualCast-Dynamic,hasbeendevelopedbymultithreadingmethod.Itdemonstratedthatthedynamicsoftreductionmodelinthisstudywascorrectwiththeabilityofonlinecontrol.

简介：Inthisstudy,theeffectsofstandoffdistance(SoD)onthesupersonicflowfields(includinggasandparticleflowfields)duringcoldgasdynamicspraying(CGDS)areinvestigatedbymeansofcomputationalfluiddynamics(CFD).Thevariationofvelocity,temperature,pressureanddensitywithdifferentSoDiselucidatedthroughtheanalysisofthedistributionpropertiesoftheflowfields.Itisfoundthattheshockwavesinfrontofthesubstrateremarkablyinfluencethegasandparticleflowfields.Thewavesystemofexpansionwavesandpressurewavescomeintobeingcontinuously.ThevelocityofgasreachesthesupersonicspeedatthepositionoftheMachdisc,whileitdecreasessharplywhenthegasflowcrossestheMachdisc.TheoptimalSoDsare40mmfor1μmparticlesand50mmforboth5μmand22μmparticles.

简介：A0.06%Clowcarbonsteelwasdeformedintorsionoverthetemperaturerange877-917℃ina2%H2-Argasatmosphere.Strainsof0.25-5.0wereappliedatstrainratesofε=0.04s-1andε=0.4s-1tostudytheformationofferritebydynamictransformation（DT）attemperaturesabovetheAe3.ThecriticalstrainforferriteformationbyDTwasaboutε=0.2anditsvolumefractionincreasedwithstrainanddecreasedwithtemperatureabovetheAe3.Averageferritegrainsizesof1.5μmto5μmwereproduced,whichdecreasedwithstrainrate.Atthelowerstrainrate(ε=0.04s-1)reversetransformation（RT）tookplaceduringdeformationonceanincubationtimeofabout40s,wasexceeded.Anincreaseinstrainratefromε=0.04s-1toε=0.4s-1arrestedRTduringtestingatalltemperaturesasthetotaltesttimesdidnotexceed13s.ThepresentworkshowsthatDTisfavoredathigherstrainratesbyincreasingthedrivingforce（i.e.storedenergy）andbysuppressingRT.

简介：DynamicmodelcontroltechnologiesofsecondarycoolingandsoftreductionofBaosteelareintroduced.Modelprincipleandcontrolsystemarchitecturearesummarized,aswellasfunctionsandfeatures.Finally,applicationsofmodeltechnologiesarediscussed.Theself-developeddynamicsecondarycoolingmodelandthedynamicsoftreductionmodelhavebeenappliedonseveralcastingmachinesinsideandoutsideBaosteel,desiredcontroleffectswereachievedwithgoodstabilityandreliability.Temperaturemeasurementresultsverifiedthecorrectnessofmodel.

简介：316Lstainlesssteelcoatingswerepreparedbycoldgasdynamicspraying(CGDS)onacarbonsteel.Anewheaterofsprayedpowderswasaddedtothetraditionalfacility.Theresultsshowthatthecoatingqualityisobviouslyimproved,duetobetterinterfacebondingandreducedporosity.

简介：Animprovedthree-dimensional(3-D)experimentalvisualizationmethodologyispresentedforevaluatingthefracturemechanismsofferriticstainlesssteelsbyin-situtensiletestingwithanenvironmentalscanningelectronmicroscope(ESEM).Thesamplesweremachinedwitharadialnotchedshapeandaslopedsurface.Bothplanarsurfacedeformationandslopingsurfacedeformation-inducedmicrovoidswereobservedduringdynamictensionexperiments,whereagreateramountofinformationcouldbeobtainedfromtheslopingsurface.Theresultsshowedthatmicrovoidsformedatthegrainboundariesofhighlyelongatedlargegrains.Themicrovoidsnucleatedintheseverelydeformedregionsgrewnearlyparalleltothetensileaxis,predominantlyalongthegrainboundaries.Themicrovoidsnucleatedattheinterfaceofparticlesandthematrixdidnotpropagateduetothehighplasticityofthematrix.Thelargemicrovoidspropagatedandshowedazigzagshapealongthegrainboundanes,seeminglyaconsequenceofthefractureoftheslipbandscausedbydislocationpile-ups.Thefinalfailuretookplaceduetothereductionoftheload-bearingarea

简介：Inconel718superalloycoatingwaspreparedonamartensiticsteelsubstratebycoldgasdynamicspraying(CGDS).Microstructureandmicro-hardnessofthecoatingwerecharacterizedbymeansofscanningelectronicmicroscope(SEM),energydispersivespectrometer(EDS),andmicro-hardnessandnano-indentationtests.Theresultshaveindicatedthatthecoating’sthicknesscanreachmorethan300μm,andthereexistsagoodinterfacialcohesionbetweenthecoatingandthesubstrate.Thequantityandsizeofthedefectsatthebottom,middleandtopareasincreasegradually.ThereisnosignificantchangetotheoriginalmicrostructureoftheInconel718superalloyparticleaftertheprocessofCGDS;andanobvioustorsionaldeformationontheparticle’sprofileisproducedwhilelittledeformationatthecenterpartoccurs.Themicro-hardnessofthecoatingatthebottom,middleandtopareasdecreasesinturn.Comparedwiththebottomarea,themicro-hardnessofthemiddleandtopareasdecreasesbyabout10%and21%,respectively.Thenano-hardnessofthecoatingismuchlowerthantheoriginalparticle,whichdecreasesbyabout13.5%atthebottomareaand28%atthetoparea,respectively.Thedistributionofmicro-defectsisanimportantfactortothemicro-hardnessofthecoating.

简介：Theeffectsofthesubstratetemperatureonthedepositionandmicrostructureofthe304stainlesssteel(SS)coldgasdynamicspraying(CGDS)coatingswereinvestigated.Itwasfoundthatthehighersubstratetemperaturecouldincreasethedepositionrateofthe304SSparticles,eventheoxidefilmsexistedattheinterface.Therewasacriticaloxidefilmwithathicknessof3-4μmwhichcouldbedestroyedbytheimpactedparticles.Themicro-hardnessandmicrostructureofthe304SScoatingsunderdifferentsubstratepreheatingtemperatureswerealmostthesame.