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1、B级要求10REVIEWQUESTIONS10.1Whyiscastinganimportantmanufacturingprocess?Aswithallothermanufacturingprocesses,anunderstandingofthefundamentalsisessential-bothfortheproductionofgoodqualityandeconomicalcastings,andtoestablishpropertechniquesformolddesignandcastingpractice.10.2What
2、isthedifferencebetweenthesolidificationofpuremetalsandmetalalloys?Theflowofmoltenmetalsintothemoldcavityisdiscussedintermsofmolddesignandfluidflowcharacteristics.10.3Whataredendrites?Notetheformationofdendritesinthemushyzone.10.4Statethedifferencebetweenshortandlongfreezingr
3、anges.Howisrangedetermined?Theshortertherange(asinpuremetalsandeutectics),thehigherthefluidity.Conversely,alloyswithlongfreezingranges(suchassolid-solutionalloys)havelowerfluidity.1Molddesign.2Moldmaterialanditssurfacecharacteristics.3Degreeofsuperheat.R4ateofpouring,5Heattr
4、ansfer.10.5Describetheparametersonwhichsolidificationtimedepends.Thislackofconvectionaffectssolidificationstructureanddistributionofimpurities.Recentexperimentsinvolvethegrowthofcrystalsforproductionofcadmium-zinctelluride,mercury-zinctelluride,andselenium-dopedgalliumarseni
5、desemiconductorsamples.10.6Defineshrinkageandporosity.Howcanyoutellwhethercavitiesinacastingareduetoporosityortoshrinkage?Porositycausedbygasesevolvedduringsolidificationcanbeasignificantproblem,particularlybecauseofitsadverseeffectonthemechanicalpropertiesofthecastings.Vari
6、ousdefectscandevelopincastingsfromlackofcontrolofmaterialandprocessvariables.10.7Whatisthefunctionofchills?Internalchillsareusuallymadeofthesamematerialasthecastingandareleftinthecasting10.8Howaredissolvedgasesremovedfrommoltenmetal?Dissolvedgasesmayberemovedfromthemoltenmet
7、albyflushingorpurgingwithaninertgas,orbymeltingandpouringthemetalinavacuum.Ifthedissolvedgasisoxygen,themoltenmetalcanbedeoxidized.10.9Describethefeaturesofagatingsystem.Themetalmay[lowthroughavarietyofpassages(includingpouringbasins,sprues,runners,risers,andgatingsystems)be
8、forereachingthefinalmoldcavity.Bernoulli'sthcorcm,thecontinuitylaw,andtheRe
