激光-电弧复合焊接保护气体O2含量对焊缝均匀性和熔池流动的影响

Influence of Shielding Oxygen Content on Weld Homogeneity and Fluid Flow in Laser-Arc Hybrid Welding

研究了保护气体中O2含量对CO2激光-熔化极气体保护(GMA)复合焊焊缝合金元素均匀性和熔池流动行为分布的影响规律。结果表明,焊接方向为激光在前时,电弧保护气体中O2含量对复合焊焊缝均匀性具有明显的作用。保护气体中O2体积分数含量达到2%以上时,复合焊焊缝中合金元素的分布基本均匀。对于He-Ar惰性保护气体,在小孔后沿的熔池区域形成了外向流动;而当保护气体中O2含量达到2%以上时,熔池流动为内向流动。保护气体中O2含量对焊缝合金元素分布的影响规律主要取决于Marangoni对流。当电弧保护气体加入大于等于2%O2时,Marangoni对流方向由外向流动变为内向流动,促进了整个熔池的内向流动,获得了合金元素的均匀分布。

The effect of shielding gas compositions containing various oxygen contents on the weld homogeneity and fluid flow is investigated during CO： laser and gas metal arc （GMA） hybrid welding process. The results indicate that the shielding gas compositions show significant effect on the homogeneity of weld metal in leading laser. Almost homogeneous distribution of alloying elements can be attained if the oxygen content in the arc shielding gas is more than 2%. In He-Ar shielding, the fluid flow behind keyhole is outward, whereas it is inward as the shielding gas contains greater than or equal to 2% 02. These phenomena are mainly determined by Marangoni flow. The direction of Marangoni flow changes from outward to inward when the oxygen content in the shielding gas is over 2%. It promotes the inward flow of the entire molten pool, resulting in homogeneous distribution of alloying elements in hybrid welds.