az31镁合金非熔化极气体保护焊工艺及性能研究

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1、硕士论文AZ31镁合金非熔化极气体保护焊工艺及性能研究摘要针对5mm厚AZ31镁合金对接接头，进行TIG焊和等离子弧焊接工艺试验，通过对焊接接头的抗拉强度、HV硬度、X射线探伤进行检测，分析研究了接头各区域的显微组织和力学性能。对比两种焊接方法接头组织与性能，探讨镁合金非熔化极气保焊的焊接工艺。研究结果表明：采用TIG焊焊接AZ31镁合金薄板时，焊缝成型美观、无缺陷，最佳规范为焊接电流140A、焊速100mm／min。母材硬度为60，焊缝区组织细小，硬度较母材高，HV达到68，热影响区组织粗大，硬度较母材有所下降，HV为50；接头的抗拉强度达

2、到母材强度的83％以上，拉伸断裂多发生在热影响区，说明热影响区是焊接接头的薄弱区域，断口呈韧．脆混合断裂形貌，即为韧窝和解理断裂的混合形貌。采用等离子弧焊接AZ3l镁合金薄板时，焊缝连续、狭窄，表面熔透均匀，接头变形小。最佳规范为焊接电流100A、焊速100mm／min、离子气流量为O．6L／min。焊缝区组织细小，硬度较TIG焊焊缝区高，HV达到74，热影响区狭小，硬度较母材略有下降，HV为54；接头的抗拉强度达到母材强度的89％，拉伸断裂多发生在焊缝区，断口仍然呈韧．脆混合断裂形貌。试验过程发现：AZ31镁合金TIG焊和等离子弧焊接时存在

3、的主要缺陷都是气孔和热裂纹，对工件表面的氧化膜和油污进行处理，加强对焊接熔池的保护等工艺措施，可以有效减少焊接气孔和焊缝裂纹的产生。关键词：镁合金，TIG焊，等离子弧焊，接头性能Abstract硕．L论文Inthisthesis，theprocessingofgastungstenarc(TIG)weldingandPlasmaarcweldingofmagnesiumalloyAZ31plateswith5．0thicknesswerestudied．Themicrostructureandmechanicalpropertiesofjoi

4、ntregionalwasinvestigatedthroughdetectionoftensilestrength、HVhardness、X-rayinspectiononthejoints．Meanwhile，thecharacteristicsofmagnesiumalloyAZ31weldingwerefurtheranalyzedthroughthedifferencesbetweenthejointsofTIGweldingandPlasmaarcwelding．Theresultsshowthat：thebeststandard

5、ofjointswithgoodsurfaceandhavenodefectwaswhenthecurrentwas140Aandthespeedwas100mm／min．TheHVhardnessofbasemetalwas60，grainsintheheat—affectedzonearecoarse，theHVhardnesswashigherthanbasemetal，canreachto66，whilethegrainsintheweldedzonearefiner,HVhardnessWas50，lowerthanbasemeta

6、l．Thetensilestrengthofweldedjointscanreachupto83％ofthestrengthofbasemetal．TensilefractureofjointsusuallyoccursintheHAZ，whichshowsthatHAZistheweakzoneinthejoints．Themorphologyoffractureisductileandbrittlemode．It’SfoundthatMg—AZ315．0mm-thickplatescanbesuccessfullyweldedbyPlas

7、maarcwelding．thebeststandardofjointswithgoodsurfaceandhavenodefectwaswhenthecurrentwasIOOAandthespeedwas100mm／min．TheHVhardnessofbasemetalwas60，grainsintheheat—affectedzonearecoarse，theHVhardnesswashigherthanbasemetal，Callreachto74，whilethegrainsintheweldedzonearefiner，HVha

8、rdnesswas54．Thetensilestrengthofweldedjointscanreachupto89％ofthestrengthofbasemeta