专业英语阅读(一)教案

专业英语阅读(一)教案 Part II:Metal-Casting Processesand Equipment金属铸造工艺与设备In thispart,some importantand fundamentalknowledge aboutcasting must be understood.For thischapter,we shouldknow thedifferences ofChinese meaningsfor theseprofessional Englishwords,and Iwill addressthese important parts.在本部分中,一些重要的和基本的知识必须明白。 铸造至于这一章,我们应该知道中国意义的差异这些专业的英语单词,我将解决这些重要的标准Forming:成型Molding:造型Powder metallurgy:粉末冶金Pouring:浇注Ornament:装饰物Intricate:复杂的Hollow:中空的Fig.II.1Cast partsin atypical automobile图2.1一个典型的汽车中的铸造部件Water pump:水泵Pulley:滑轮Grill:栅栏Intake andexhaust manifold:进气和排气管Disk brake:刹车片Brake drum:制动鼓Brake cylinder:闸缸Lettering:编字码Differential housing:差速机壳Transmission housing:变速机壳Engine block:汽缸体Carburetor:化油器Piston:阳模Alternator housing:同步发电机壳Fig.II.2.Outline ofmetal-casting processesdescribed inpart II.Sand ShellExpandable patternPlaster CeramicInvestment Metalcasting processesFoundries Expandablemold Permanentmold SlushPressure DieCentrifugal SqueezeSemisolid Singlecrystal formicroelectronics Single-crystal turbine blades Directionalsolidification Compositemold Single-crystal growing图II.2.在第二章中所描述的金属铸造工艺概要Chapter10Fundamentals ofMetal-Casting金属铸造基础For thischapter,it wasdivided into these parts:1.Introduction:简介2.Solidification of metals:金属的凝固3.Fluid flow:流体流动4.Fluidity ofmolten metal:熔融金属的流动性5.Heat transfer:热传递6.Defects:缺陷As weknow,the casting is theoldest processto manufacturepart oftool in the humanbeings history,because ithas manyadvantages paredwith othermanufactured processesas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follows:正如我们所知道的,是最古老的铸造工艺到生产制造工具的一部分在人类的历史,因为它具有许多优点,相较于其他生产过程如下?plex shapes,such as differential housing(差速机壳)used in the automobile,crankshaft（曲轴）and soon;复杂的形状,例如不同的外壳，用于汽车、曲轴等?Very largepart,such asengine housingused in the shipmaking.非常大的部分,如发动机房屋用于船舶制造?Utilize thework piecesthat othermanufactured processescan notproduce ofuneconomic,such asturbine blade(涡轮机叶片).利用其他制造过程工件不会产生的不赚钱的,如涡轮叶片1,Pure metalsFor puremetal,the melting point is constant,so,the solidificationis likethis one对纯金属、熔点是不变的,所以,凝固就是熔化潜热After reachingmeltingpointsolidification frominterface and then tocenter withdifferent graintype andsize凝固界面,然后从中心对不同晶粒类型和大小Release oflatent heatof fusioheatChill zone:极冷区，白口区，grain sizedue tovery highcooling rate.Columnar zone:柱状区，由于节省了大粒度的降温速率和异质形核。 Equiaxed zone:等轴晶区，homogeneous nucleation.Fig.10.2.Development of a preferred texture(择优质构)at acool mold wall.Note thatonly favorablyoriented grainsgrow awayfrom thesurface of the mold.Fig.10.1Schematic illustrationof threecaster structure ofmetalssolidified in a squaremold;a,pure metals;b,solid-solution alloys;c,structured obtainedby usingnucleating agents(孕育剂).图解We cansee,different metalshave differentsolidified structures,and thenucleation agentsaffect it.发展较佳的纹理(择优质构)在一个凉爽的模具的墙。 注意,只有以优惠的谷物种植远离表面的模具。 我们可以看出,不同的金属有不同凝固结构,以及成核剂影响它10.2.2alloys The solidification process of alloyscan beschematically illustratedfrom Fig.10.3.From thisfigure,we cansee,the solidificationtakes placein atemperature range,Tl andTs.The solidification processofthis typealloy can be illustratedas follow:合金凝固过程可以从图10.3schematically说明。 从这个图,我们可以看出,凝固发生在一个温度范围、Tl和Ts。 这种类型的合金凝固过程可以被描述为Below TlChill zoneformation BetweenTl andTs BelowTs Fig.10.3.Schematic illustrationof alloysolidification and temperature distributionin thesolidifying metal.Note the formation of dendrites in the mushy zone(多空隙的区域).For thistype dendrite,it can be named as columnardendrite,with three-dimensional armsand branches.该类型的枝晶,它可以称为柱状枝晶,与三维武器和枝条。 The structureof dendriteinfluences theproperties of casting seriously,so it is essentialto findand studythe effectorson itsstructure.枝晶结构的性能严重影响铸件,所以它必须找到并研究其结构对比。 As mentionedabove,the structureofdendriteis affectedby themushy zone;in otherword,it can be described asdifferentmushy zoneduring solidification,and themushy zonecan benamedasfreezing range,as this:如上所述,枝晶的结构受糊状区;换句话说,可以把它称为不同的糊状区凝固、糊状区可以称为冰冷的范围Solidification beginDendrite formationComplete Fig.10.4(a)Solidification patternsfor gray cast ironin a180mm squarecasting.Note that after11min.of cooling,dendrites reacheach other,but the casting isstill mushythroughout.球墨铸铁凝固模式在180毫米的平方的铸件。 注意:当11分钟。 对冷却,树突到对方,但仍在铸造糊状。 (b)Solidification ofcarbon steelin sandand chill(metal)molds.Note thedifference insolidification patternsas thecarbon contentincreases Freezingrange=Tl碳钢凝固在沙子里放松(金属)模具。 注意不同的凝固模式中的碳含量增加=Tl-Ts冻结范围温差及Ts凝固过程中,组合成的Tl。 -Ts,the temperaturedifference betweenTl andTs during solidification.For example:for pure metals andeutectic alloys,freezing range=0,so,no mushyzone没有糊状区,no dendriteformation.没有枝晶的形成。 Usually,the shortfreezing range110o C,example,Al andMg-base alloys,and thesealloys arein amushy statethroughout mostof solidificationprocess.这些合金在一个国家在大部分糊状凝固过程Effect ofcooling rateThe castingstructure is affected seriouslyby the cooling rate:Usually,for slowcooling rate(102K/s),coarse dendriteformation;Faster coolingrate(on theorder of104K/s),finer dendriteformation;Higher coolingrate(106108K/s),amorphous formation.As coolingrate increases,the grain size decreases,so strengthand ductilityenhanced,that ishall-petch formula.作为冷却速率的增加,晶粒尺寸减小,强度和优良的延性提高,这是hall-petch公式。 For the solidified structure,it canbe certifiedby theratio ofG/R,where Gis thermalgradient at the interface of liquid and solid,and Ris the rate atwhich the liquid-solid interfacemoves.Typical valuesfor Grange from102to103K/m and for Rfrom10-3to10-4m/s.Dendritic typestructures(Figs.5.5a andb)typically havean ratioin therange of105to107,whereas ratiosof1010to1012produce aplane-front,nondendritic liquid-solid interface(Fig.10.6).为凝固结构,它可以认可G/R比,在G的界面温度梯度在液体和固体,R是固液界面速度移动。 典型值G范围为102到103K/m和R/s,从10-4m球。 树突式结构(无花果。 5.5a组和b组)通常有一个比在105至107之间,而比1010年到1012年生产plane-front,nondendritic液-固界面Fig.10.5.Schematic illustrationof threebasic typesofcast structures:(a)columnar dendritic;(b)equaiaxed dendritic;and(c)equiaxed nondendritic.10.2.3.structure-property relationship希望所有铸件符合设计和服务的要求。 通常,财产是结构。 晶体的成分组成和液态金属作了特别的合金相图,通常是二元合金。 作为冷却率很低,枝晶成分均匀的发展。 正常(快)冷却速度,发展核心树突不同成分的表面和中心,称为浓度梯度(浓度梯度):中各金属元素含量更高的表层的中心。 这是由于在凝固过程中溶质排斥反应,导致microsegregation(微观偏析)Macrosegregation(宏观偏析)involves differencesin positionthroughout the casting.Normal segregation(正常偏析),verse segeration(反向偏析),Fig.10.6.Schematic ofcaststructuresin(a)plane front,single phase,and(b)plane front,two phases.the reasonis thatliquid metal(having ahigher concentrationof alloyingelements)enters thecavities developedfrom solidificationshrinkage(收缩)in thedendritic armswhich solidifiedsooner.正常的隔离(正常偏析),诗歌segeration(反向偏析),原因是液态金属(具有较高含量的合金元素)进入腔凝固收缩产生(收缩)在树突武器,凝固得更快Gravity segregation(重力偏析)describes theprocess wherebyhigher-density inclusions(夹杂)or positionssink(下沉)and lighterelements(such asantimony in antimony-lead alloy(锑-铅)float(上浮)to surface.重力隔离(重力偏析)描述了过程,higher-density物(夹杂)或成分(下沉)和轻沉要素(如在antimony-lead锑合金(锑-铅)浮子(上浮)表面Inoculants(孕育剂)induce thenucleation of the grainsthroughout the liquid inducedheterogeneous nucleation.孕育剂(孕育剂)诱导成核颗粒在液体的成核诱导异质性Convection promotestheformationof anouter chillzone,refines grainsize andaelerates thetransition fromcolumnar toequiaxed grains.促进形成对流外部寒冷地带,改良粒度和加速的转变,晶粒粗粒Dendrite multiplication:枝晶增殖,rheocasting:流变铸造In thispart,we talkedabout the solidificationprocessfor differentmetals and the property-structure relation;next,the fluid flow willbe talked.在这一部分,我们谈论了不同金属凝固过程和property-structure关系;其次,流体流动会说话10.3.Fluid flowThe fluid flow ismost importantfactor in casting.As shownin fig.10.7,the castingprocess isdescribedas:the molten metal ispoured through a pouring basin(转包，浇注槽)or cup.It thenflows throughthe gating system(浇注系统)(sprue,runners andgates,注流口,流道,内浇道)into the mold cavity.Sprue is a verticalchannel through which molten metal flowsdownward inthe mold.Runners are the channelsthat carrythe molten metal from the sprueto the mold cavity,or connectthe sprueto thegate.The gateis thatportion of the runnerthroughwhichthe molten metal entersthe mold cavity.Risers(冒口)serve as reservoirs(储液槽)to supplythe molten metal necessaryto preventshrinkage during solidification,as shownin Fig.10.7.流动中最重要的因素是铸件。 ,如图10.7,铸造是描述为:通过熔化的金属浇一浇盆地,浇注槽转包)或量杯。 然后流经浇注系统(浇注系统)(浇道截面积、注流口流道和盖茨,流道,内浇道)进入模具腔。 浇口是一种垂直通道,通过这一往低处流熔融金属在模具。 跑者们的频道,把熔化的金属从物料对模具型腔、流道连接到大门口。 大门的那一部分,通过转轮熔化的金属进入型腔的。 近期(冒口)作为储层(储液槽提供熔化的金属凝固过程中,为了防止收缩,如图所示图Trap contaminant:捕获杂质,premature cooling:过早冷却,gas entrapment:夹气Gating systemdesign is the mostimportantpartto gethigh qualitycastings.浇注系统的设计是最重要的部分,得到高质量的铸件wo basicprinciples of fluidfloware relevantto gatingdesign:Bernoullis theoremand lawof mass continuity.我们基本原则的相关流体浇注设计:伯努利定理和法律的大规模的连续性TBernoullis theorem:百努利定律t consgvgphtan22?10.2Fig.10.7.Schematic illustrationofatypical riser-gated casting.Risers serveasreservoirs,supplying molten metal to the castingas itshrinks during solidification.一个典型的riser-gated原理说明铸件。 作为储层隔,供应熔融金属铸件凝固过程中,它缩短了Where:h:the elevation above acertain plane海拔超过一定的飞机,p:pressure atthat elevati压力在那个海拔,v:velocity of the liquidat atelevation液体的速度就在海拔高度,:the densityof the fluid液体的密度,g:gravitational constant.重力不变Conservation ofenergy requiresthat能量守恒定律要求,at aparticular location在某个特定的位置发,in thissystem,the relationshipis satisfied:fgvgphgvgph?2222222111?10.3Where,subscripts(下标)1and2represent two different elevations,andfrepresents thefrictional lossinthe liquid as it travelsdownward throughthe system.Continuity(连续性)The lawof masscontinuity(质量连续性)states thatfor inpressible(不可压缩的)liquidandinasystem withimpermeable(不可渗透的)wall,the rate of flowisconstant:2211v Av AQ?10.4Where Q:therateof flow,A:the cross-sectional areaof the liquid,and v:the averagevelocity of the liquidin thatcross-sectional location.The description1and2refer totwodifferentlocations inthe system.For example,for spruedesign:2121hhAA?10.5so,the areaof thebottom inthe sprueis smallerthan thatof top,that meanstapered sprue(圆锥型铸道).Aspiration:吸出,choke:节流口，缩颈Recall thatinafree-falling liquid(such aswater froma faucet:水龙头)the cross-section areaof thestream decreasesas itgains velocitydownward.If wedesign asprue with a constantcross-section areaand pourthe molten metal intoit,regions maydevelop wheretheliquidloss contactwith thesprue walls.As aresult aspiration,a processwhereby airis suckedin orentrapped intheliquid,may takeplace.On theother hand,tapered spruesare nowreplaced inmany systemsby straight-sided sprureswithachoke toallow the metal toflow smoothly.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。 Flow characteristics:An importantconsideration inthefluidflow ingating systemsis thepresence ofturbulence(湍流)as opposedto thelaminar flow(层流).We usethe Reynolds number(雷诺系数),Re,to quantify(定量)this aspect(方面)offluidflow;It representsthe ration the inertia(惯性)totheviscous forces(粘滞力)in fluidflow,and isdefined as:?vD?Re10.6Where,v:velocity,D:diameter of the channel;anddensity andviscosity(粘度).Re200000,severe turbulentflow,resulting inair entrainmentand theformation dross(熔渣)(the scum(浮渣)that formson thesurface of the molten metal)from thereaction of theliquid metal withair andother gases.Techniques forminimizing turbulencegenerally involveavoidance ofsudden changesin flowdirection andinthegeometry ofchannel cross-sections ingating systemdesign.严重的湍流,导致空气诱导作用、形成糟粕(熔渣)(人渣(浮渣)的表面形成熔融金属)从反应为液态金属对空气和其它气体。 技术,降低湍流通常包括避免突然改变方向并在流动通道的几何在浇注系统设计的横切面。 Mitigate:缓和，减小Skimming:挡渣10.4Fluidity ofmolten metalThe capability(能力，本领)of the molten metalto fillmold cavitiesis calledfluidity(流动性);it consists(包括)of twobasic factors: (1)characteristics of the moltenmetal,and (2)casting parameters.The followingcharacteristics ofmoltenmetal influence fluidity:a,viscosity increasing,fluidity decreasing;b,surface tension(表面张力)increasing,fluidity decreasing;c,inclusion(夹杂)increasing,fluidity decreasing;d,solidification patternof thealloy,freezing rangeincreasing,fluidity decreasing.The followingcasting parametersinfluence fluidityand alsoinfluence thefluidflowand thermalcharacteristics of the system:合金的凝固模式、冷冻范围增大,流动性减少。 下面的铸造工艺也影响的流动性和影响流体流动和热特性的系统a.Mold design,the designand dimensionsof sprue,runner andrisers allinfluence fluidity;模具设计、设计和浇口尺寸,奔跑的人,都会影响近期的流动性b.Mold materialsand itssurface characteristics:thermal conductivityand surfacerough increasing,fluidity decreasing;模具材料及其表面特征:导热系数和表面粗糙的增加、流动性减小;c.Degree ofsuperheat(过热)increasing,fluidity increasing;过热程度(过热)增大,流动性增Rate of pouring decreasing,fluidity decreasing;降低利率灌装、流动性减小d.Heat transfer.This factordirectly affectsthe viscosityof theliquidmetal.热传递。 这个因素直接影响液体的黏滞性的金属。 Castabilty(可铸性):the easewith whicha metal canbecast to obtain apart withgood quality,includes notonly fluiditybut alsocasting parametersas well.(可铸性):指一个金属将获得部分的质量、良好的流动性也不仅包括铸造工艺10.4.1Tests forfluidity Fig.10.8A testmethod forfluidity usinga spiral mold(螺旋模).The fluidity index(流动性指数)isthe length of the solidified metal inthe spiralpassage(通道，通路).The greaterthelengthof the solidifiedmetal,the greateris itsfluidity.更大的长度的金属凝固,但更大的是其流动性10.5Heat transferAn importantconsideration incastingisthe heattransfer during the pletecycle frompouring tosolidification andcooling toroom temperature.For instance,incastingthin sections,the metalflow ratesmustbehigh enoughto avoidpremature(早期的)chilling andsolidification.However,the flow rate mustnot beso highas tocause excessive(过多的)turbulence withits detrimental(有害的)effects on the castingprocess.在铸造是一个重要的考虑传热在完整的周期从浇到凝固和冷却到室温。 例如,在铸体薄片、金属流动速率必须足够高(早期的)避免过早寒蝉和凝固。 然而,流量不能这么高,否则可能会导致过度过多的)湍流以其不利影响(有害的)铸件的过程。 The shape of thecurve dependson thethermal propertiesof the moltenmetaland themold曲线的变化取决于热性能和熔化的金属模具10.5.1.Solidification timeDuring earlystages ofsolidification,a thin,solidified skinbegins toform atthecoolmold wallsand,as timepasses,the skinthickens.With flatmoldwall,this thicknessis proportionaltothesquare rootof time.在早期的固化、一种薄的,皮肤开始凝固形成模具冷却壁和,随着时间的流逝,皮肤变厚。 平模壁,该厚度成正比的平方根的时间。 Thesolidificationtime isa function ofthevolume ofa castingand itssurface area(Chvorinovs rule);that is,Solidification time=2)(a surfacearevolumeC10.7Where,C:a constantthat reflectsmold material,metal Fig.10.9Temperature distributionattheinterfaceofthemoldwall and theliquidmetal duringsolidification ofmetals incasting.在界面温度分布的模具墙和液态金属在凝固过程中重金属的铸件properties(include latent heat),andtemperature.That means,thesolidificationtime isinverse proportionalto specificarea.一个常数,反映模具材料、金属性能(包括潜热)、温度。 这句话的意思是,凝固时间是逆比例的特定的区域。 Note thatthe skinthickness increaseswith elapsedtime,but thatthe skinis thinnerat internalangel(内切角)than at external angels(外切角).This lattercondition is caused byslower cooling at internalangels thanatexternalangels.注意皮肤厚度随时间过去,但是,皮肤较薄的内部天使(内切角)比在外部的天使(外切角)。 这第二种情况是由于缓慢冷却的内部外部天使比天使。 For example,same volumefor sphere,cube andcylinder,the sequenceof surface area is:sphere TABLE10.1Solidification Contractionfor variousCast MetalsMetal oralloy Volumetricsolidification contraction(%)Metal oralloy Volumetricsolidification contraction(%)Aluminum6.670%Cu-30%Zn4.5Al-4.5%Cu6.390%Cu-10%Al4Al-12%Si3.8Gray ironExpansion to2.5Carbon steel2.53Magnesium4.21%carbon steel4White iron45.5copper4.9zinc6.5The largestamount ofshrinkage oursduring coolingofthecasting.Note thatgray cast iron expands,due tothat graphitehas arelatively highspecific volume,and whenit precipitatesas graphiteflakes(薄片，片状的)duringsolidification,it causesa expansion ofthemetal.最多的收缩发生在冷却过程中铸件。 注意,球墨铸铁膨胀时,由于石墨具有较高的特定流量,当它沉淀石墨薄片(薄片,片状的)在凝固过程,它使网络扩展的金属。 10.6Defects Seven basic categories of casting defects namedby theInternational mitteeof FoundryTechnical Associationsare shownas follows:七个基本类别的铸造缺陷命名的国际委员会铸造技术协会显示如下:A.Metallic projection(突出，隆起),consisting offins(毛刺),flash(飞刺),or massiveprojections asswells(隆起)and roughsurface(粗燥表面，铸疵);B.Cavities(空洞，凹起),consisting ofrounded(滚圆的)or rough(粗燥的)or exposed(外露的)cavities,including blow-holes(砂眼),pinholes(引孔线,针孔，气孔),and shrinkagecavities(收缩孔),hot tear(热撕裂),exothermic padding(发热贴片).C.Discontinuities(不连续性，间断),such ascracks,cold orhot tearing,and cold shuts(冷疤);D.Defective surface,such assurface folds(表面褶皱),laps(褶皮),scars(冻结物),adhering sandlayers,and oxidescale(氧化皮);E.Inplete casting,such asmisruns(铸件不满),insufficient volume ofthemetal pouredand runout,reason:moltenmetalwith lowtemperature orlow speedofpour;F.Incorrect dimensionsor shape,owing tofactors such as impropershrinkage allowance,pattern mountingerror,irregular contraction,defined pattern,定义模式or warpedcasting(翅曲，凹凸);G.Inclusion(夹杂),which formduring melting,solidification andmolding,spalling(涨裂，剥落).Fig.10.11Examples ofhot tears.These defectsour becausethecastingcannot shrinkfreely duringcooling,owing toconstraints invarious portionsofthemolds andcores.Exothermic(heat production)pounds may be used(as exothermic padding)to controlcoolingatcritical sectionto avoidhot tearing.热撕裂的例子。 这些缺陷发生的,因为在冷却过程中不能自由收缩铸造,由于在不同的部分约束模具和核心。 放热(产热)化合物可用于(如放热填充物)控制关键部分冷却,避免热裂。 10.6.1.Porosity(气孔，孔隙)Fig.10.12Examples ofmon defectsin castings.These defectscanbeminimized oreliminated byproper designand preparationof moldsand controlof pouringprocedures.Fig.10.13Various typesof(a)internal and(b)external chills,used in castings toeliminate porositycaused by shrinkage.Chills arePorosity ina castingmay becaused by shrinkage orgases orboth,it deducesthe strengthand ductilityofthecasting oreven failed.在铸件气孔可能由于收缩或气体或两者兼而有之,推导出了铸件强度和优良的延性甚至失败了。 Porosity causedbyshrinkagecanbereduced oreliminated by various means.Adequate liquidmetal shouldbe providedto avoidcavities causedbyshrinkage.Internal orexternal chills(冷铁，冷模,冷却片),are alsoeffective means to reduceshrinkag