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采用富Ar混合气体TIG焊焊接了镁合金板材,分析了Ar、He、CO2和N2不同配比混合气体的电弧特性及其对焊缝成形、熔深、显微硬度和抗拉强度的影响。结果表明:富Ar混合气体加入一定比例CO2会造成镁元素蒸发,焊接过程中有飞溅现象,加入一定比例N2会在焊缝表面生成Mg3N2膜,影响焊缝质量。He-Ar混合气体随着氦气体积分数的增大,电弧稳定性增强,阴极热功率所占电弧总功率的比例减少。当He体积比等于50%时,电弧阴极区域明显收缩而阳极区域发散扩展,可获得外形美观、熔透率高、焊缝区组织均匀细小的镁合金焊接接头。焊缝的平均显微硬度为60HV,达到母材的82.6%,抗拉强度为186MPa,是母材的76%,断裂发生在热影响区,属于韧-脆混合断裂。
The arc welding of Ar, He, CO2 and N2 mixed gases with different ratios of Ar, He, CO2 and N2 and their effects on the forming, penetration depth, microhardness and tensile strength of the weld were analyzed. The results show that the addition of a certain proportion of Ar2 rich gas will cause the evaporation of magnesium element and the splashing during the welding process. Adding a certain proportion of N2 will result in the formation of Mg3N2 film on the weld surface, which will affect the weld quality. He-Ar mixed gas with the helium gas volume fraction increases, the arc stability increases, the proportion of the total cathode arc power of the total power of the cathode heat decreases. When the volume ratio of He is equal to 50%, the arc cathode area shrinks conspicuously and the anode area diverges and expands, and the magnesium alloy welded joint with good appearance, high penetration rate and uniform microstructure of weld zone can be obtained. The average microhardness of the weld is 60HV, reaching 82.6% of the base metal, the tensile strength of 186MPa, 76% of the base metal, the fracture occurred in the heat affected zone, which belongs to the ductile-brittle mixed fracture.