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1、料的溶解和元素的扩散。当液态钎料过饱和时，会在局部形核，形成镍基固溶体。在岛状镍基固溶体连成一片时，溶解停止，母材与镍基固溶体相发生固态扩散，在界面处形成很薄的一层磷化物层。随着温度的降低，在钎缝中心的液相会析出Ni（Fe，Cr，Cu）相，由于形状比较大的Ni（Fe，Cr，Cu）相周围的液相成分偏离了原始成分，此时，在Ni（Fe，Cr，Cu）相周围形成了CrNiP化合物，最后，剩余的液相凝固结晶，达到共晶点时形成Ni3P-Ni（Fe,Cr,Cu）的共晶相。接头断裂在钎缝中心处，钎缝中心含有脆性的Ni3P相，断裂形式为准解
2、理断裂。裂纹在脆性相Ni3P处萌生并扩展，在遇到镍基固溶体时停止扩展，经过一段时间之后，在剪切应力的作用下裂纹会在镍基固溶体周围再次形成并继续沿着脆性相扩展。关键词：316L不锈钢，合金元素Cu，微观组织，抗剪强度，钎焊机理II万方数据STUDYONTHEPROCESSANDMECHANISMOFBRAZINGSTAINLESSSTEELUSINGMODIFIEDNICKEL-BASEDBRAZINGALLOYABSTRACTWiththequalityoflifeofpeopleimprove,demandforcar
3、sisalsomoreandmorehigh,however,effectsofautomobileexhaustpollutionofourenvironment,especiallypresentsasignificantchallengetolargeandmedium-sizedcitylivingenvironment.EGRcoolercanimprovetheenvironment,reducingemissionsofpollutants.Manufacturingcoolerpartsofthemate
4、rialusuallychoose304、306、316and316Lstainlesssteelprecisioncastingsorprofile,the316Lstainlesssteelwithgoodresistancetointergranularcorrosionandbecomethepreferredmaterial.Intheweldingprocessofstainlesssteel,stainlesssteelwithnickelbasebrazingfillerismostcommon,howe
5、ver,duringbrazingalloying,brazingseamcentergeneratesbrittleintermetalliccompoundphase,whichmakesthemechanicalpropertiesoftheweldedjointisreduced,therefore,needtostudytheinteractionbetweenbasemetalandfillermetalandhowtoreducethebrittlecompoundbrazingseamcenter.Bas
6、edontheBNi-7brazingalloy,addingalloyingelementsCu,throughthebrazingalloyformulamorereasonabledesigntooptimizetheweldingjoint.Theresearchresultsshowthat:themeltingpointofthebrazingalloyalloyelementsaddeddecreasedafterCu,butthesolid-liquidphaselinetemperatureslight
7、lyincreased.Improvedwettingfrontaretheprecursorfilmexists,theprecursorfilmplaysanimportantroleinbrazingalloywettabilitycontactangledecreaseandincrease.WiththeincreaseofCucontent,thebrazingtemperatureandholdingtime,theprecursorfilmbrazingalloywettingfrontwidens,br
8、azingalloyspreadingareaincreases,thewettabilityimprovement.TheadditionofCuorganizationisNi(Cr,Cu)solidsolution,Ni3P-Ni(Cr,Cu)eutecticstructureandasmallamountof
