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《机械制造专业英语第7章SANDCASTING(砂型铸造)》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。
1、SANDCASTINGMostmetalcastingsaremadebypouringmoltenmetalintoapreparedcavityandallowingittosolidify.Theprocessdatesfromantiquity.ThelargestbronzestatueinexistencetodayisthegreatSunBuddhainNara,Japan.Castintheeighthcentury,itweighs551tons(500metrictons)andismorethan71ft(21m)high.ArtisansoftheShan
2、gDynastyinChina(1766-1222B.C.)createdartworksofbronzewithdelicatefiligreeassophisticatedasanythingthatisdesignedandproducedtoday.Therearemanycastingprocessesavailabletoday,andselectingthebestonetoproduceaparticularpartdependsonseveralbasicfactors,suchascost,size,productionrate,finishtolerance,
3、sectionthickness,physical-mechanicalproperties,intricacyofdesign,machinability,andweldability.Sandcasting,theoldestandstillthemostwidelyusedcastingprocess,willbepresentedinmoredetailthantheotherprocessessincemanyoftheconceptscarryoverintothoseprocessesaswell.GreenSandGreensandgenerallyconsists
4、ofsilicasandandadditivescoatedbyrubbingthesandgrainstogetherwithclayuniformlywettedwithwate匚Morestableandrefractorysandshavebeendeveloped,suchasfusedsilica,zircon,andmullite,whichreplacelower-costsilicasandandhaveonly2%linearexpansionatferrousmetaltemperatures.Also,relativelyunstablewaterandcl
5、aybondsarebeingreplacedwithsyntheticresins,whicharemuchmorestableatelevatedtemperatures.Greensandmoldingisusedtoproduceawidevarietyofcastingsinsizesoflessthanapoundtoaslargeasseveraltons-Thisversatileprocessisapplicabletobothferrousandnonferrousmaterials.Greensandcanbeusedtoproduceintricatemol
6、dssinceitprovidesforrapidcollapsibility;thatis,themoldismuchlessresistanttothecontractionofthecastingasitsolidifiesthanareothermoldingprocesses.Thisresultsinlessstressandstraininthecasting・Thesandisrammedorcompactedaroundthepatternbyavarietyofmethods,includinghandorpneumatic-toolramming,joltin
7、g(abruptmechanicalshaking),squeezing(compressingthetopandbottommoldsurfaces),anddrivingthesandintothemoldathighvelocities(sandslinging).Sandslingersareusuallyreservedforuseinmakingverylargestingswheregreatvolumesofsandarehandled.Forsmal
