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TheDevelopmentandSummaryofCasting铸造的发展与摘要Castingisoneoftheoldestofallindustries,bothancientandmedievalhistoryofferingexamplesofthemanufactureanduseofcasting.Fromsimpleaxeheadspouredfromcopperinopenmouldssome5000yearsage,castinginthepre-Christianworlddevelopedtoapointatwhichelaboratebronzestatuarycouldbeproducedintwo-pieceandcoredmoulds.Bytheendofthemedievalperiod,decoratedbronzeandpewtercastinghadbeguntobeusedinEuropeanchurchanddomesticlife.金属铸造是最古老的产业之一，远古时期和中世纪就有人使用和制造铸件了。5000年前人们只能用铜在开式模具中浇注简单的斧头，二公元前已经能够用分体式模具和型芯制造复杂的青铜雕塑了。中世纪末期，欧洲的交通那个和家庭开始使用青铜和锡铅合金铸件制造器皿进行装饰。ThewidespreadadoptionofcastironasengineeringmaterialawaitedthesuccessofAbrahamDarbyin1790insmeltinginthecokeblastfurnace;thispavedthewayforthemassiveuseofcastironinconstructionduringtheyearsfollowingtheindustrialrevolution.工程材料广泛只用铸铁得益于1709年希伯来用鼓风炼焦炉融化金属，这为工业革命时期在建设中大量使用铸铁铺平了带路。Manyfoundriessprangupaftertheindustrialrevolution,thevastmajoritybeingforthemanufactureofthecastironthenbeingusedasastructuralmaterial.Thequantityproductionofironcastingsinthenineteenthcenturywasnotmatchedbyauniversaladvanceinqualityandtheengineeringuseoftheproductsencounteredmoreseriousrisksinanon-ductilematerial.工业革命以后铸铁作坊纷纷兴起，生产的铸件主要用作建筑材料。19世纪铸件的产量虽然很大，但质量的提高并不普遍，工程中使用这些延展性很差的材料要冒极大的风险。Despitetheskillofthemolderinproducingcomplexforms,therewaslittlechangeinthemetallurgicalandengineeringsituationuntilthemodernerabroughtabetterunderstandingofthefactorsdeterminingquality.Withmoderntechniquesofprocesscontroltherudimentaryjudgmentoftheoperatorcouldgivewaytoobjectivemeasurementsofmetaltemperature,moldingmaterialpropertiesandotherproductionvariables.Theseimprovementshavebeenappliednotonlytocastironbuttoawiderangeofcastalloys.尽管铸件工人已经可以制造比较复杂的模型，但整个行业的情况几乎没有什么变化，直到现代人们才逐渐了解那些影响铸件质量的各种因素。现代加工技术不再使用那些粗略的判断，而是对金属温度、材料特性以及生产过程中的其他因素进行客观的测量。这些改进不仅应用到铸铁，而且应用于各种浇注合金。Therearefourbasiccastingmethods:sand-casting,die-casting,investment-casting,andcentrifugalcasting.铸造方法基本有四种：砂型铸造、金属模铸造、熔模铸造和离心铸造。Sand-castingisthemostwidelyusedmethodemployedinfoundry.Inthisprocess,sandmouldsarecontainedinmetalmoldingboxesthathavefoursidesbutnotoporbottom.Duringthemoldingoperationtheboxesarelocatedtogetherbypinssothattheycanbeseparatedtoremovethepattern,andreplacedinthecorrectpositionbeforethemetalispouredin.Theboxesareclampedtogether,orthecope(topsection)weighteddownwhenpouringtopreventthecopefrom“floatingaway”fromthedrag(lowersection)whenthemouldisfullofmoltenmetal.Thesequencewhenmoldingthesimpletwo-partmouldtocastabracketisillustratedasfollows.砂型铸造是铸造厂最普遍使用的方法。铸造时，砂模装在没有上、下底的金属砂箱里。制模时砂箱使用销子连在一起，这样取模时可以把砂箱拆开，并在浇注前作必要的校正。砂箱被夹在一起，为了防止浇注的金属在充满砂箱时把上砂箱和下砂箱顶开，有时也把上砂箱放在底部。分离式简单模具的制造过程可以用托架的铸造，说明如下：Atthefirststagethepatternisseatedonthemouldingboard.Thepatterniscoveredwithfacingsand,whichisaspeciallypreparedsandofgoodquality,whichcantakeacleanandsmoothimpression,andcanresisttheheatfromthemoltenmetalthatwillbeincontactwithit.Thefacingsandisbackedupwithmoldingsand,whichisoldfacingsandfrompreviousmoulds.Themoldingsandiscarefullyrammedupsothatitisfairlytightaroundthepatterntoproduceagoodsolidmould,yetpermeableenoughtoallowthegasesproducedduringcastingtoescape.Thesandisfinallyleveledoff.第一步先把托架模型放在横板上，模型上覆盖面砂。面砂经过专门制造，质量很高，能够生成干净光滑的模型印痕表面，抵抗熔融金属接触时的高温。面砂外面用型砂填充，型砂包括用过的面砂，经过仔细压紧，形成坚固的模腔，并具有良好的透气性，排放铸造时产生的气体。最后经过整型，平整砂模表面。Atthesecondstagethemouldwiththepatternstillinpositionisinverted;theexposedsandlightlycoveredwithpartingsand,andtheexposedpatternwithfacingsand.(Thepartingsandhasnocohesion,andisintroducedtopermitacleanseparationwhenthemouldisopeneduptoremovethepattern.)Thesecondmoldingboxislocatedinpositiononthefirstboxandfilledwithmoldingsand.Twoormoreplugsareintroducedwhenthesecondboxisbeingfilled(theseareremovedlater,leavingchannelsinthesand).Oneoftheseplugsispositionedtoonesideofthepattern.Thesandisrammedupandleveledoff.第二步吧砂箱连同内部的模型就地倒置安放，在暴露的型砂上轻轻地覆盖一层分型砂，暴露的模型外覆盖面砂。（分型砂内没有粘结剂，这样在开箱取出模型时达到完全、清晰地分离。）第二个砂箱放在刚才第一个砂箱的上面，填满型砂。第二个砂箱填充时要插入两个或更多塞子，以便塞子拔出时在砂子中间留下通孔。其中的一个塞子放置在模型的一侧。最后把砂子夯实、平整。Now,atstage3,toallowthepatterntoberemoved.Thisisdonebyscrewingabarwithathreadedendintoasuitableinsertinthepattern,dampingthesandaroundthepattern,andgentlyrappingthebarinalldirectionssothatthepatterncanbecarefullywithdrawn.Tofacilitatetheremovalofthepatternwithoutscuffingthesidesoftheimpression,allsurfacesthatlieinthedirectionofpatternremovalareinclinedslightlybyasmallamount(thedrawangle).第三步是取模。把一根端部刻有螺纹的起模棒旋拧进模型，把模型周围的砂子弄湿，然后轻轻在各个方向晃动起模棒并仔细地取出模型。为了便于取模而不划伤模腔四周的印痕，沿取模方向的表面都应该稍倾斜一个角度（拔模斜度）。Agroovecalledagateiscutinthesandfacetoallowthechannelproducedbytheplugthatisoutsidethepatterntoconnectwiththeimpression.Themetalispouredthroughthischannel(calledtherunner),andthegatepreventsitfromdroppingstraightintotheimpressionanddamagingit.Thecross-sectionofthegateisslightlysmallerthanthatofchannelsothatafullrunnerwillalwayssupplymetaltothegateataslightpressure.型砂中间要开一个沟槽，叫做内浇口或横浇口。内浇口可以使前面塞子拔出时形成的不与模型相连的通孔与模腔相连。当向这个称为浇口的通孔内浇注金属时，内浇口可以避免金属直接冲入模腔而把表面的印痕冲坏。内浇口的横截面积要稍微小于浇口，这样金属是经过内浇口时能保持一定的压力。Finally,themouldisreassembled,carefullylocatingandsecurin