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1、焊接专业本科生用1WHATISWELDING?Weldingtechniqueshavebecomesoversatilethatitisdifficultnowadaystodefine“welding.Formerlyweldingwas"thejoiningofmetalsbyfusion^,thatis,bymelting,butthisdefinitionwillnolongerdo.Eventhoughfusionmethodsarcstillthemostcommon,theyarcnotalwaysused.Welding
2、wasnextdefinedasthe"joiningofmetalsbyheat'：butthisisnolongeraproperdefinitioneither.Notonlymetalscanbewelded,socanmanyoftheplastics.Furthermoreseveralweldingmethodsdonotrequireheat.Everymachinistisfamiliarwithheatlesswelding.Whenthechipslidesoverthecuttingtoolonalathe,ito
3、ftenleavesabuilt-upedgeofchipmaterialweldedtothetopofthecutterbit.Thisiscoldpressurewelding,whichunderothercircumstancesisproperproductionweldingmethod.Besidespressurewelding,wecanweldwithsoundandevenwithlightfromthefamouslaser.Facedwithadiversityofweldingmethodsthatincre
4、aseyearbyyear,wemusthereadoptthefollowingdefinitionofwelding,"weldingisthejoiningofmetalsandplasticsbymethodsthatdonotemployfasteningdevices二Thejoiningofmetalsbymethodsthatdonotemployfasteningdevicesisanartasoldasblacksmithing・Neverthelessweldingasamanufacturingprocessmus
5、tbeconsideredadevelopmentofthetwentiethcentury.Inthe1880'scarbonarclampswereusedforstreetlighting.Atthattimeitwasnotedthatthecarbonarclamp,likealllamps,producedmoreheatthanlight,andthefirstattemptsweremadetousethisheatforweldingmetals.Thusthefirstweldingmethodofthosestill
6、inusewascarbonarcwelding,perfectedabouttheturnofthecentury.Stickelectrodesandoxyacetyleneweldingalsoappearedabout1900.weldingwasgenerallyusedonlyforrepairandmaintenanceuntilthe1920's・X-rayexaminationofweldscamesoonafterwardanddidmuchtodevelopconfidenceinweldedjoints・Themi
7、ddleofthe20thcentuiysawgreatdevelopmentinweldingaswellasinothertechniques.Italsogaveus,amongotherthings,inertgaswelding.Sincethenweldinghasprogressedatatremendousrate.Ithelpsdevelopscienceandtechnology,includingtheelectronictechnique・Atthesametime,thetechnologyofweldingem
8、bracesawidearea.Manyelectroniccircuitsarerequiredtocontrolthemoreintricateweldingmachines・Evenra
