制造工程与技术专业英语阅读(一)教案

张新房专张新房专业英语阅读（一）教案PartII:Metal-CastingProcessesandEquipment金属铸造工艺与设备Inthispart,someimportantandfundamentalknowledgeaboutcastingmustbeunderstood.Forthischapter,weshouldknowthedifferencesofChinesemeaningsfortheseprofessionalEnglishwords,andIwilladdresstheseimportantparts.Forming:成型Molding:造型Powdermetallurgy:粉末冶金Pouring:浇注Ornament:装饰物Intricate:复杂的Hollow:中空的Fig.II.1Castpartsinatypicalautomobile图2.1一个典型的汽车中的铸造部件Waterpump:水泵Pulley:滑轮Grill:栅栏Intakeandexhaustmanifold:进气和排气管Diskbrake:刹车片SandSSandShellExpandablepatternPlasterCeramicInvestmentMetalcastingprocessesFoundriesExpandablemoldPermanentmoldSlushPressureDieCentrifugalSqueezeSemisolidSinglecrystalformicroelectronicsSingle-crystalturbinebladesDirectionalsolidificationCompositemoldSingle-crystalgrowingBrakecylinder:闸缸Lettering:编字码Differentialhousing:差速机壳Transmissionhousing:变速机壳Engineblock:汽缸体Carburetor:化油器Piston:阳模Alternatorhousing:同步发电机壳Fig.II.2.Outlineofmetal-castingprocessesdescribedinpartII.金属铸造工艺铸造金属铸造工艺铸造沙壳体消耗性的图形高聚物陶瓷围模料消耗性模永久性模凝壳压力锻压离心挤压半凝固单晶生长用于微电子的单晶单晶叶片定向凝固复合模具Chapter10FundamentalsofMetal-Casting金属铸造基础Forthischapter,itwasdividedintotheseparts:Introduction:简介Solidificationofmetals:金属的凝固Fluidflow:流体流动Fluidityofmoltenmetal:熔融金属的流动性Heattransfer:热传递Defects:缺陷First,1.IntroductionThecastingprocessbasicallyinvolvesthreesteps:pouringmoltenmetalintoamoldpatternedaftertheparttobemanufactured;(把熔融金属浇注到加工好的模具型腔)allowingittocoolandsolidify（冷却和凝固）removingthemetalfromthemold（从模具中取出金属）Asweknow,thecastingistheoldestprocesstomanufacturepartoftoolinthehumanbeing’shistory,becauseithasmanyadvantagescomparedwithothermanufacturedprocessesasfollows:complexshapes,suchasdifferentialhousing(差速机壳)usedintheautomobile,crankshaft（曲轴）andsoon;Verylargepart,suchasenginehousingusedintheshipmaking.Utilizetheworkpiecesthatothermanufacturedprocessescannotproduceofuneconomic,suchasturbineblade(涡轮机叶片).So,itisessentialforustounderstandthefundamentalsofmetalcastingbystudyingthisbookhard.Therearesomeimportantconsiderationsinthecastingoperationasfollows:Theflowofthemoltenmetalintothemoldcavity:熔融金属流入模具型腔,Fluidity.Thecoolingandsolidificationofmetalinthemold:金属在模具中的冷却和凝固:heattransfer:热传导.Theinfluenceofdifferenttypeofmoldmaterials,differentheattransferringability,不同的模具材料具有不同的热传导能力.Inthispart,wetalkedaboutsomeintroductionsofmetalcasting;inthenext,wewilltalkthesecondpart:solidificationofmetals.2.SolidificationofmetalsAsweknow,fordifferentmetals,suchaspuremetalsandalloys,thesolidificationprocessesaredifferent,sotheywillbedividedintopuremetalandalloytobediscusseddifferentsolidificationprocesses.1,PuremetalsForpuremetal,themeltingpointisconstant,so,thesolidificationislikethisone:ReleaseoflatentheatoffusionReleaseoflatentheatoffusion熔化潜热AfterreachingmeltingpointsolidificationfrominterfaceandthentocenterwithdifferentgraintypeandsizeFig.10.1Schematicillustrationofthreecasterstructureofmetalssolidifiedinasquaremold;a,puremetals;b,solid-solutionalloys;c,structuredobtainedbyusingnucleatingagents(孕育剂).Chillzone:极冷区，白口区，grainsizeduetoveryhighcoolingrate.Fig.10.1Schematicillustrationofthreecasterstructureofmetalssolidifiedinasquaremold;a,puremetals;b,solid-solutionalloys;c,structuredobtainedbyusingnucleatingagents(孕育剂).Columnarzone:柱状区，largegrainsizeduetolowercoolingrateandheterogeneousnucleation.Equiaxedzone:等轴晶区，homogeneousnucleation.Fig.10.2.Developmentofapreferredtexture(择优质构)atacoolmoldwall.Notethatonlyfavorablyorientedgrainsgrowawayfromthesurfaceofthemold.Fig.10.3.Schematicillustrationofalloysolidificationandtemperaturedistributioninthesolidifyingmetal.NFig.10.3.Schematicillustrationofalloysolidificationandtemperaturedistributioninthesolidifyingmetal.Notetheformationofdendritesinthemushyzone(多空隙的区域).10.2.2alloysThesolidificationprocessofalloyscanbeschematicallyillustratedfromFig.10.3.Fromthisfigure,wecansee,thesolidificationtakesplaceinatemperaturerange,TlandTs.Thesolidificationprocessofthistypealloycanbeillustratedasfollow:ChillzoneformationBelowTlBetweenChillzoneformationBelowTlBetweenTlandTsBelowTsCompleteDendriteformationSolidificationbeginCompleteDendriteformationSolidificationbeginForthistypedendrite,itcanbenamedascolumnardendrite,withthree-dimensionalarmsandbranches.Thestructureofdendriteinfluencesthepropertiesofcastingseriously,soitisessentialtofindandstudytheeffectorsonitsstructure.Asmentionedabove,thestructureofdendriteisaffectedbythemushyzone;inotherword,itcanbedescribedasdifferentmushyzoneduringsolidification,andthemushyzonecanbenamedasfreezingrange,asthis:Fig.10.4(a)Solidificationpatternsforgraycastironina180mmsquarecasting.Notethatafter11min.ofcooling,dendritesreacheachother,butthecastingisstillmushythroughout.(b)Solidificationofcarbonsteelinsandandchill(metal)molds.NotethedifferenceinsolidificationpatternsasthecarboncontentincreasesFreezingrange=Tl-Ts,thetemperaturedifferencebetweenTlandTsduringsolidification.Forexample:forpuremetalsandeutecticalloys,freezingrange=0,so,nomushyzone,nodendriteformation.Usually,theshortfreezingrange<50oC,forexample,Fe-basealloys.Thelongrangefreezingrang>110oC,example,AlandMg-basealloys,andthesealloysareinamushystatethroughoutmostofsolidificationprocess.EffectofcoolingrateThecastingstructureisaffectedseriouslybythecoolingrate:Usually,forslowcoolingrate(<102K/s),coarsedendriteformation;Fastercoolingrate(ontheorderof104K/s),finerdendriteformation;Highercoolingrate(106~108K/s),amorphousformation.Ascoolingrateincreases,thegrainsizedecreases,sostrengthandductilityenhanced,thatishall-petchformula.Forthesolidifiedstructure,itcanbecertifiedbytheratioofG/R,whereGisthermalgradientattheinterfaceofliquidandsolid,andRistherateatwhichtheliquid-solidinterfacemoves.TypicalvaluesforGrangefrom102to103K/mandforRfrom10-3to10-4m/s.Dendritictypestructures(Figs.5.5aandb)typicallyhaveanratiointherangeof105to107,whereasratiosof1010to1012Fig.10.6.Schematicofcaststructuresin(a)planefront,singlephase,and(b)planefront,twophases.Fig.10.5.Schematicillustrationofthreebasictypesofcaststructures:(a)columnardendritic;(b)equaiaxeddendritic;and(c)equiaxednondendritic.Fig.10.6.Schematicofcaststructuresin(a)planefront,singlephase,and(b)planefront,twophases.10.2.3.structure-propertyrelationshipAllcastingsarehopedtomeetdesignandservicerequirements.Usually,thepropertyisuptostructure.Thecompositionsofdendritesandtheliquidmetalaregivenbythephasediagramsofparticularalloys,usuallybinaryalloys.Ascoolingrateverylow,dendritewithuniformcompositiondevelops.Normal(fast)coolingrate,coredendritesdevelopwithdifferentcompositionatsurfaceandcenter,knownasconcentrationgradient(浓度梯度):highercontentofalloyingelementinthesurfacelayerthanthatofcenter.Thatisduetosoluterejectionduringsolidifiedprocess,resultinginmicrosegregation(微观偏析).Macrosegregation(宏观偏析)involvesdifferencesincompositionthroughoutthecasting.Normalsegregation(正常偏析),versesegeration(反向偏析),thereasonisthatliquidmetal(havingahigherconcentrationofalloyingelements)entersthecavitiesdevelopedfromsolidificationshrinkage(收缩)inthedendriticarmswhichsolidifiedsooner.Gravitysegregation(重力偏析)describestheprocesswherebyhigher-densityinclusions(夹杂)orcompositionssink(下沉)andlighterelements(suchasantimonyinantimony-leadalloy(锑-铅))float(上浮)tosurface.Inoculants(孕育剂)inducethenucleationofthegrainsthroughouttheliquidinducedheterogeneousnucleation.Convectionpromotestheformationofanouterchillzone,refinesgrainsizeandacceleratesthetransitionfromcolumnartoequiaxedgrains.Dendritemultiplication:枝晶增殖,rheocasting:流变铸造Inthispart,wetalkedaboutthesolidificationprocessfordifferentmetalsandtheproperty-structurerelation;next,thefluidflowwillbetalked.10.3.FluidflowThefluidflowismostimportantfactorincasting.Asshowninfig.10.7,thecastingprocessisdescribedas:themoltenmetalispouredthroughapouringbasin(转包，浇注槽)orcup.Itthenflowsthroughthegatingsystem(浇注系统)(sprue,runnersandgates,注流口,流道,内浇道)intothemoldcavity.Sprueisaverticalchannelthroughwhichmoltenmetalflowsdownwardinthemold.Runnersarethechannelsthatcarrythemoltenmetalfromthespruetothemoldcavity,orconnectthespruetothegate.Thegateisthatportionoftherunnerthroughwhichthemoltenmetalentersthemoldcavity.Risers(冒口)serveasreservoirs(储液槽)tosupplythemoltenmetalnecessarytopreventshrinkageduringsolidification,asshowninFig.10.7.Fig.10.7.Schematicillustrationofatypicalriser-gatedcasting.Risersserveasreservoirs,supplyingmoltenmetaltothecastingasitshrinksduringsolidification.Trapcontaminant:捕获杂质,prematurecooling:过早冷却,gasentrapment:夹气Fig.10.7.Schematicillustrationofatypicalriser-gatedcasting.Risersserveasreservoirs,supplyingmoltenmetaltothecastingasitshrinksduringsolidification.Gatingsystemdesignisthemostimportantparttogethighqualitycastings.Twobasicprinciplesoffluidflowarerelevanttogatingdesign:Bernoulli`stheoremandlawofmasscontinuity.Bernoulli`stheorem:百努利定律10.2Where:h:theelevationaboveacertainplane,p:pressureatthatelevation,v:velocityoftheliquidatatelevation,ρ:thedensityofthefluid,g:gravitationalconstant.Conservationofenergyrequiresthat,ataparticularlocation,inthissystem,therelationshipissatisfied:10.3Where,subscripts(下标)1and2representtwodifferentelevations,andfrepresentsthefrictionallossintheliquidasittravelsdownwardthroughthesystem.Continuity(连续性)Thelawofmasscontinuity(质量连续性)statesthatforincompressible(不可压缩的)liquidandinasystemwithimpermeable(不可渗透的)wall,therateofflowisconstant:10.4WhereQ:therateofflow,A:thecross-sectionalareaoftheliquid,andv:theaveragevelocityoftheliquidinthatcross-sectionallocation.Thedescription1and2refertotwodifferentlocationsinthesystem.Forexample,forspruedesign:10.5so,theareaofthebottominthesprueissmallerthanthatoftop,thatmeanstaperedsprue(圆锥型铸道).Aspiration:吸出,choke:节流口，缩颈Recallthatinafree-fallingliquid(suchaswaterfromafaucet:水龙头)thecross-sectionareaofthestreamdecreasesasitgainsvelocitydownward.Ifwedesignaspruewithaconstantcross-sectionareaandpourthemoltenmetalintoit,regionsmaydevelopwheretheliquidlosscontactwiththespruewalls.Asaresultaspiration,aprocesswherebyairissuckedinorentrappedintheliquid,maytakeplace.Ontheotherhand,taperedspruesarenowreplacedinmanysystemsbystraight-sidedsprureswithachoketoallowthemetaltoflowsmoothly.回想自由落下的水流(例如从水龙头流下的水)，其横截面积随其获得的向下的速度而减小。如果我们设计一个截面积不变的直浇道并向其浇注金属液，可能会出现液流接触不到浇道壁的区域。由于有吸气作用，在浇注过程中可能卷入空气。另一方面，锥形的直浇道现在在许多系统中被带节流口的平直直浇道所取代，以使金属液平稳地流动。Flowcharacteristics:Animportantconsiderationinthefluidflowingatingsystemsisthepresenceofturbulence(湍流)asopposedtothelaminarflow(层流).WeusetheReynoldsnumber(雷诺系数),Re,toquantify(定量)thisaspect(方面)offluidflow;Itrepresentstherationtheinertia(惯性)totheviscousforces(粘滞力)influidflow,andisdefinedas:10.6Where,v:velocity,D:diameterofthechannel;ρandηdensityandviscosity(粘度).Re<2000,laminarflow,good;2000~20000,mixtureoflaminarandturbulentflow,butnoharmless.>200000,severeturbulentflow,resultinginairentrainmentandtheformationdross(熔渣)(thescum(浮渣)thatformsonthesurfaceofthemoltenmetal)fromthereactionoftheliquidmetalwithairandothergases.Techniquesforminimizingturbulencegenerallyinvolveavoidanceofsuddenchangesinflowdirectionandinthegeometryofchannelcross-sectionsingatingsystemdesign.Mitigate:缓和，减小Skimming:挡渣10.4FluidityofmoltenmetalThecapability(能力，本领)ofthemoltenmetaltofillmoldcavitiesiscalledfluidity(流动性);itconsists(包括)oftwobasicfactors:(1)characteristicsofthemoltenmetal,and(2)castingparameters.Thefollowingcharacteristicsofmoltenmetalinfluencefluidity:a,viscosityincreasing,fluiditydecreasing;b,surfacetension(表面张力)increasing,fluiditydecreasing;c,inclusion(夹杂)increasing,fluiditydecreasing;d,solidificationpatternofthealloy,freezingrangeincreasing,fluiditydecreasing.Thefollowingcastingparametersinfluencefluidityandalsoinfluencethefluidflowandthermalcharacteristicsofthesystem:Molddesign,thedesignanddimensionsofsprue,runnerandrisersallinfluencefluidity;Moldmaterialsanditssurfacecharacteristics:thermalconductivityandsurfaceroughincreasing,fluiditydecreasing;Degreeofsuperheat(过热)increasing,fluidityincreasing;Rateofpouringdecreasing,fluiditydecreasing;Heattransfer.Thisfactordirectlyaffectstheviscosityoftheliquidmetal.Castabilty(可铸性):theeasewithwhichametalcanbecasttoobtainapartwithgoodquality,includesnotonlyfluiditybutalsocastingparametersaswell.Fig.10.8Atestmethodforfluidityusingaspiralmold(螺旋模).Fig.10.8Atestmethodforfluidityusingaspiralmold(螺旋模).Thefluidityindex(流动性指数)isthelengthofthesolidifiedmetalinthespiralpassage(通道，通路).Thegreaterthelengthofthesolidifiedmetal,thegreaterisitsfluidity.10.5HeattransferAnimportantconsiderationincastingistheheattransferduringthecompletecyclefrompouringtosolidificationandcoolingtoroomtemperature.Forinstance,incastingthinsections,themetalflowratesmustbehighenoughtoavoidpremature(早期的)chillingandsolidification.However,theflowratemustnotbesohighastocauseexcessive(过多的)turbulencewithitsdetrimental(有害的)effectsonthecastingprocess.Fig.10.9Temperaturedistributionattheinterfaceofthemoldwallandtheliquidmetalduringsolidificationofmetalsincasting.Theshapeofthecurvedependsonthethermalpropertiesofthemoltenmetalandthemold.Fig.10.9Temperaturedistributionattheinterfaceofthemoldwallandtheliquidmetalduringsolidificationofmetalsincasting.10.5.1.SolidificationtimeDuringearlystagesofsolidification,athin,solidifiedskinbeginstoformatthecoolmoldwallsand,astimepasses,theskinthickens.Withflatmoldwall,thisthicknessisproportionaltothesquarerootoftime.Thesolidificationtimeisafunctionofthevolumeofacastinganditssurfacearea(Chvorinov’srule);thatis,Solidificationtime=10.7Where,C:aconstantthatreflectsmoldmaterial,metalproperties(includelatentheat),andtemperature.Thatmeans,thesolidificationtimeisinverseproportionaltospecificarea.Notethattheskinthicknessincreaseswithelapsedtime,butthattheskinisthinneratinternalangel(内切角)thanatexternalangels(外切角).Thislatterconditioniscausedbyslowercoolingatinternalangelsthanatexternalangels.Fig.10.10SolidifiedskinonasteelcastingForexample,samevolumeforsphere,cubeandcylinder,thesequenceofsurfaceareais:sphere<cylinder<cube,sospherehasfastestsolidificationrate.Fig.10.10Solidifiedskinonasteelcasting10.5.2.Shrinkage(收缩)Shrinkageistheresultofthefollowingthreeevents:contraction(收缩)ofthemoltenmetalasitcoolspriortoitssolidification;contractionofthemetalduringphasechangefromliquidtosolid(latentheatoffusion);Contractionofthesolidifiedmetal(thecasting)asitstemperaturedropstoambienttemperature.TABLE10.1SolidificationContractionforvariousCastMetalsMetaloralloyVolumetricsolidificationcontraction(%)MetaloralloyVolumetricsolidificationcontraction(%)Aluminum6.670%Cu-30%Zn4.5Al-4.5%Cu6.390%Cu-10%Al4Al-12%Si3.8GrayironExpansionto2.5Carbonsteel2.5~3Magnesium4.21%carbonsteel4Whiteiron4~5.5copper4.9zinc6.5Thelargestamountofshrinkageoccursduringcoolingofthecasting.Notethatgraycastironexpands,duetothatgraphitehasarelativelyhighspecificvolume,andwhenitprecipitatesasgraphiteflakes(薄片，片状的)duringsolidification,itcausesanetexpansionofthemetal.10.6DefectsSevenbasiccategoriesofcastingdefectsnamedbytheInternationalcommitteeofFoundryTechnicalAssociationsareshownasfollows:Metallicprojection(突出，隆起),consistingoffins(毛刺),flash(飞刺),ormassiveprojectionsasswells(隆起)androughsurface(粗燥表面，铸疵);Cavities(空洞，凹起),consistingofrounded(滚圆的)orrough(粗燥的)orexposed(外露的)cavities,includingblow-holes(砂眼),pinholes(引孔线,针孔，气孔),andshrinkagecavities(收缩孔),hottear(热撕裂),exothermicpadding(发热贴片).Discontinuities(不连续性，间断),suchascracks,coldorhottearing,andcoldshuts(冷疤);Defectivesurface,suchassurfacefolds(表面褶皱),laps(褶皮),scars(冻结物),adheringsandlayers,andoxidescale(氧化皮);Incompletecasting,suchasmisruns(铸件不满),insufficientvolumeofthemetalpouredandrunout,reason:moltenmetalwithlowtemperatureorlowspeedofpour;Incorrectdimensionsorshape,owingtofactorssuchasimpropershrinkageallowance,patternmountingerror,irregularcontraction,definedpattern,orwarpedcasting(翅曲，凹凸);Inclusion(夹杂),whichformduringmelting,solidificationandmolding,spalling(涨裂，剥落).Fig.10.11Examplesofhottears.Thesedefectsoccurbecausethecastingcannotshrinkfreelyduringcooling,owingtoconstraintsinvariousportionsofthemoldsandcores.Exothermic(heatproduction)compoundsmaybeused(asexothermicpadding)tocontrolcoolingatcriticalsectiontoavoidhottearing.Fig.10.12Examplesofcommondefectsincastings.Thesedefectscanbeminimizedoreliminatedbyproperdesignandpreparationofmoldsandcontrolofpouringprocedures.Fig.10.12Examplesofcommondefectsincastings.Thesedefectscanbeminimizedoreliminatedbyproperdesignandpreparationofmoldsandcontrolofpouringprocedures.Fig.10.13Varioustypesof(a)internaland(b)externalchills,usedincastingstoeliminateporositycausedbyshrinkage.Chillsareplacedinregionswherethereisalargervolumeofmetal,asshownin(c).10.6.1Fig.10.13Varioustypesof(a)internaland(b)externalchills,usedincastingstoeliminateporositycausedbyshrinkage.Chillsareplacedinregionswherethereisalargervolumeofmetal,asshownin(c).Porosityinacastingmaybecausedbyshrinkageorgasesorboth,itdeducesthestrengthandductilityofthecastingorevenfailed.Porositycausedbyshrinkagecanbereducedoreliminatedbyvariousmeans.Adequateliquidmetalshouldbeprovidedtoavoidcavitiescausedbyshrinkage.Internalorexternalchills(冷铁，冷模,冷却片),arealsoeffectivemeanstoreduceshrinkageporosity.Thefunctionofchillsistoincreasetherateofsolidificationincriticalregions.Fig.10.14Solubilityofhydrogen(H)inaluminum(Al).Notethesharpdecreaseinsolubilityasthemoltenmetalbeginstosolidify.Liquidmetalshavemuchgreatersolubility(溶解度)forgasesthandosolidmetals,asshowninFig.10.14.Whenametalbeginstosolidify,thedissolved(溶入的)gasesareexpelled(挤出)fromthesolution.Gasesmayalsoresultfromreactionsofthemoltenmetalwiththemoldmaterials.Gaseseitheraccumulate(聚集)inregionsofexistingporosity(suchasininterdendriticregions)ortheycasemicroporosityinthecasting,particularlyincastiron,AlandCu.Fig.10.14Solubilityofhydrogen(H)inaluminum(Al).Notethesharpdecreaseinsolubilityasthemoltenmetalbeginstosolidify.Dissolvedgasesmayberemovedfromthemoltenmetalbyflushing(吹)orpurging(吹洗)withaninertgas(惰性气体),orbymeltingandpouringthemetalinavacuum.Ifthedissolvedgasisoxygen(O),themoltenmetalcanbedeoxidized(脱氧).SteelisusuallydeoxidizedwithAl,Cu-basedalloyswithphosphoruscopper(磷铜),titanium(Ti),andzirconium-bearingmaterials.Whethermicroposityisaresultofshrinkageoriscausedbygasesmaybedifficulttodetermine.Iftheporosityissphericalandhassmoothwalls,itisgenerallyfromgases.Ifthewallsareroughandangular.Porosityislikelyfromshrinkagebetweendendrites.Gross(粗的、大的)porosity(isfromshrinkageandisusuallycalledshrinkagecavity(收缩孔).SUMMARYCastingisasolidificationprocessinwhichmoltenmetalispouredintoamoldandallowedtocool.Themetalmayflowthroughavarietyofpassages(includingpouringbasins,sprues,risers,andgatingsystem)beforereachingthefinalmoldcavity.Bernoulli’stheorem,thecontinuitylaw,andtheReynoldsnumberaretheanalyticaltoolsusedindesign,withthegoalsofanappropriateflowrateandtheeliminationofdefectsassociatedwithfluidflow.铸造是一种凝固工艺方法。这种工艺方法是将熔化的金属浇注到铸型中并使之冷却。金属液可能流经各种通道（包括浇口池，直流道，横流道，冒口和内浇口）才达到最终型腔。利用百努利定律，连续性定理和雷诺系数作为设计中的分析工具，以达到适当的流速流量，消除因流体流动性不足而引起的缺陷。Solidificationofpuremetalstakesplaceataconstanttemperature;solidificationofalloysoccursoverarangeoftemperature,dependingoncomposition.Phasediagramsareimportanttoolsforidentifyingthesolidificationpointorpointsfortechnologicallyimportantmaterials.纯金属在确定的温度凝固；依赖其成分，合金的凝固是在一个温度区间进行的。相图示用于取代工艺材料凝固点的重要工具。Compositionandcoolingratesofthemeltaffectthesizeandtheshapeofgrainsanddendritesinthesolidifiedcasting.Solidificationtimeisafunctionofvolumeofacastinganditssurfacearea(Chvorinov’srule).金属的成分和冷却速率影响铸件凝固后的晶粒和枝晶的尺寸和形状。凝固时间是铸件体积和表面积的函数（契维瑞诺夫定则）。Thegrainstructureofcastingscanbecontrolledbyvariousmeanstoobtainthedesiredproperties.Becausemetalscontractduringsolidificationandcooling,cavitiescanforminthecasting.Porositycausedbygasesevolvedduringsolidificationcanbeasignificantproblem,particularlybecauseofitsadverseeffectonthemechanicalpropertiesofthecastings.Variousdefectscandevelopincastingsfromlackofcontrolofmaterialandprocessvariables.可以通过各种方法来对铸件的晶粒组织进行控制以获得所期望的性能。由于金属在凝固和冷却期间与型腔接触，所以型腔能够形成铸件。凝固期间析出的气体引起的气孔施工严重的问题，特别是对铸件的机械性能有负面的影响。由于缺乏对材料和工艺变量的控制，而在铸件中形成各种缺陷。Althoughmostmetalsshrinkduringsolidification,graycastironandaluminumalloysactuallyexpand.Dimensionalchangesandcracking(hottearing)anddifficultieswhichcanariseduringsolidificationandcooling.Sevenbasiccategoriesofcastingdefectshavebeenidentified.虽然大多数金属在凝固期间产生收缩，但灰铸铁和一些铝合金却发生膨胀。在凝固和冷却期间可能发生尺寸变化和裂纹（热撕裂）以及其它问题。已鉴别出的铸件缺陷有7类。Meltingpracticeshaveddirecteffectonthequalityofcasting,asdofoundryoperationssuchaspatternandmoldmaking,pouringofthemelt,removalofcastpartsfrommolds,cleaning,heattreatment,andinspection.熔炼操作对铸件质量有直接的影响，铸造操作也是这样，例如模样和铸型制作，金属液浇注，铸件出型和清理，热处理，检验等环节。TRENDS发展趋势Argon-oxygendecarburizationanddeoxidation,aswellaselectroslagremelting,ladlemetallurgy,plasmarefining,andcalciumwireinjectionfortheproductionofhigh-qualitysteels,arenowbeingpracticedbymodernfoundries.氩-氧脱碳和还原，以及电渣重熔，浇包冶金，等离子精炼和钙丝注入等，正在现代铸造厂用于优质钢生产。Investigationofthefollowingisunderway:electromagneticstirringofthemoltenmetalinthemoldandvibrationofthemoldtoobtainsmallerandmoreuniformgrainsizeduringsolidification;counter-gravitypouring;andshroudingthepouringstream.以下调查正在进行中：凝固期间电磁搅拌铸型中的金属液和振动铸型以获得小的和更均匀的晶粒；反重力浇注，屏蔽浇注液流。Computer-aideddesignandmanufacturingtechniquesarebeingusedtopredictsolidificationpatterns,preventcastingdefects,andcalculateweights,volumes,anddimensionsforpropermolddesignandeconomicalproduction.为获得正确的铸型设计和更经济地生产铸件，计算机辅助设计和制作技术正被用于预测凝固模式，防止铸件缺陷，计算重量，体积和尺寸等。Improvementsintheefficiencyoffurnaces,moltenmetalquality,andpurifyingandfilteringtechniquesarebeingmade.正在开发应用提高熔炉效率和金属液质量，净化和过滤等技术工艺。Keywords:Forming:成型Molding:造型Powdermetallurgy:粉末冶金Pouring:浇注Ornament:装饰物Intricate:复杂的Hollow:中空的Waterpump:水泵Pulley:滑轮Grill:栅栏Intakeandexhaustmanifold:进气和排气管Diskbrake:刹车片Brakedrum:制动鼓Brakecylinder:闸缸Lettering:编字码Differentialhousing:差速机壳Transmissionhousing:变速机壳Engineblock:汽缸体Carburetor:化油器Piston:阳模Alternatorhousing:同步发电机壳Crankshaft:曲轴turbineblade:涡轮机叶片latentheatoffusion:熔化潜热nucleatingagents:孕育剂Chillzone:极冷区，白口区Columnarzone:柱状区Equiaxedzone:等轴晶区preferredtexture:择优质构mushyzone:多空隙的区域concentrationgradient:浓度梯度microsegregation:微观偏析Macrosegregation:宏观偏析Normalsegregation:正常偏析versesegeration:反向偏析shrinkage:收缩Gravitysegregation:重力偏析Inclusion:夹杂Inoculants:孕育剂Dendritemultiplication:枝晶增殖rheocasting:流变铸造pouringbasin:转包，浇注槽gatingsystem(浇注系统)(sprue,runnersandgates,注流口,流道,内浇道)Risers:冒口Reservoirs:储液槽Trapcontaminant:捕获杂质,prematurecooling:过早冷却,gasentrapment:夹气masscontinuity:质量连续性incompressible:不可压缩的impermeable:不可渗透的Aspiration:吸出,choke:节流口，缩颈Turbulence:湍流,laminarflow:层流Inertia:惯性,viscousforce:粘滞力,viscosity:粘度dross(熔渣)(thescum(浮渣)Mitigate:缓和，减小Skimming:挡渣Thecapability(能力，本领)Fluidity:流动性surfacetension:表面张力Castabilty:可铸性spiralmold:螺旋模fluidityindex:流动性指数passage:通道，通路premature:早期的excessive:过多的contraction:收缩flake:薄片，片状的projection(突出，隆起),consistingoffins(毛刺),flash(飞刺),ormassiveprojectionsasswells(隆起)androughsurface(粗燥表面，铸疵)Cavities(空洞，凹起),consistingofrounded(滚圆的)orrough(粗燥的)orexposed(外露的blow-holes(砂眼),pinholes(引孔线,针孔，气孔),andshrinkagecavities(收缩孔),hottear(热撕裂),exothermicpadding(发热贴片)Discontinuity:不连续性，间断coldshut:冷疤surfacefolds(表面褶皱),laps(褶皮),scars(冻结物),andoxidescale(氧化皮)misrun:铸件不满warped:翅曲，凹凸spalling:涨裂，剥落Porosity:气孔，孔隙Chill:冷铁，冷模,冷却片Chapter11Metal-CastingProcesses第11章金属铸造工艺11.1Introduction简介11.2SandCasting砂型铸造11.3Shell-moldCasting壳型铸造11.4Expendable-PatternCasting(LostFoam)一次模铸造（消失泡沫）11.5Plaster-MoldCasting石膏型铸造11.6Ceramic-MoldCasting陶瓷型铸造11.7InvestmentCasting熔模铸造11.8VacuumCasting真空铸造11.9Permanent-MoldCasting永久型铸造11.10SlushCasting凝壳铸造11.11Pressu