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1、WuhanUniversityofTechnologyENGINEERINGMATERIALSTYPESOFMATERIALSMaterialsmaybegroupedinseveralways.Scientistsoftenclassifymaterialsbytheirstate:solid,liquid,orgas.Theyalsoseparatethemintoorganic(onceliving)andinorganic(neverliving)materials.Forindustrialpurposes,m
2、aterialsaredividedintoengineeringmaterialsornonengineeringmaterials.Engineeringmaterialsarethoseusedinmanufactureandbecomepartsofproducts.Nonengineeringmaterialsarethechemicals,fuels,lubricants,andothermaterialusedinthemanufacturingprocesswhichdonotbecomepartofth
3、eproduct.Thisgroupingisnotexact.Engineeringmaterialsmaybefurthersubdividedinto:1.Metals.2.Polymers3.Ceramics.Afourthtypeofmaterialsometimelistediscalledacomposite.Materialsinthisgrouparemadeupoftwoormorematerialfromtheengineeringgroups,Eachofthematerialsincomposi
4、teretainsitsoriginalcharacteristics.Examplesofcompositesincludewood-,concrete-,glass-reinforcedpolyester,andgraphitepolymeradvancedcomposites.COMMONMETALSPuremetalsareseldomusedincommonindustrialproducts.Purecopperisusedinelectricalapplications,inautomotiveradiat
5、ors,andgaskets.Purealuminumhasapplicationinthechemicalandelectricalindustries.However,mostmetalsarealloys(combinationsoftwoormoreelements).Thereareover25,000differentiron-carbonalloys(steel)andover200standardcopperalloysincludinganumberofbrasses,bronzes,andnickel
6、silvers.Eachofthesealloysareidentifiedbyacodenumber.Steelisanalloyofironandcarbonwithotherelementsaddedtoproducespecificproperties.Thevarioustypeofsteelcanbegroupedundertwomajorheading:(1)Carbonsteel.Asteelinwhichthemainalloyingelementiscarbon.Carbonsteelarefurth
7、erdividedintothreegroups.a.Lowcarbonsteel.Thissteelhasacarboncontentoflessthan0.30percent.Itisthemostcommontypeandisoftencalledmildsteel.Itisrelativelyinexpensive,ductile,soft,andiseasilymachinedandforged.Mildsteelcannotbeheat-treated(hardened).Lowcarbonsteelisag
8、eneralpurposesteel.b.Mediumcarbonsteel.Thissteelhasacarboncontentbetween0.30percentand0.80.Harderandstrongerthanmildsteel,itcanbehardenedbyheattreating.Mediumc
