研究了氦-氩混合保护气体对铝合金激光- MIG复合焊熔滴过渡行为及焊缝气孔缺陷的影响,结合焊接过程中匙孔的动态特征,分析了气孔缺陷得到抑制的原因。结果表明,采用氦-氩混合保护气体时,焊接过程匙孔更加稳定,焊缝气孔率得到有效降低。当氦-氩混合保护气体中氦气体积分数为50%时,熔滴过渡形式由射滴过渡转变为短路过渡,焊缝气孔率约为1.0%,相比于纯氩气保护时降低了80%;继续增加氦气,对气孔的抑制并无显著效果。纯氦气时,焊接过程中产生大量飞溅,焊缝表面成形差。

The influences of the He-Ar mixed shielding gas on the droplet transition behaviors and the weld porosity defects are investigated in the laser-MIG hybrid welding of aluminum alloys. According to the dynamic characteristics of the keyholes in the welding process, the reason for the suppression of porosity defects is analyzed. The results show that, the He-Ar mixed shielding gas can enhance the stability of the keyholes and reduce the weld porosity effectively. When the volume fraction of He in the He-Ar mixed shielding gas is 50%, the droplet transition mode changes from “one drop per pulse” to “short-circuit” transition and the weld porosity is about 1.0%, reduced by 80% if compared with that for the pure argon shielding gas. The further increase of the He content is not helpful to the suppression of the porosity. When the shielding gas is the pure He gas, the big spatter and the bad welding seam occur.