铝合金LB-VPPA复合焊接热源特性

以Al-Mn系铝合金LB-VPPA(laser beam-variable polarity plasma arc)复合焊接热源特性为研究对象,采用Y4-S2型高速摄像仪和汉诺威焊接质量分析仪分别研究了LB-VPPA复合热源焊接过程中的电弧形态的变化、焊接电流、电压的特征信息. 结果表明,激光对VPPA焊接电弧有吸引作用,并且与VPPA正、反极性作用机理不同. 正极性阶段发现激光被压缩于VPPA电弧内部且作用于电弧根部,而反极性阶段在VPPA电弧上方会出现一个等离子体柱. VPPA焊电弧根部等离子体对激光的逆轫致辐射吸收,电弧因温度升高而膨胀导致其横截面积变大;同时引入激光为VPPA焊接电弧提供了大量自由电子,电流密度增加、导电性增强、电导率提高、电阻减小,导致电弧电压下降了约3~4 V. 随着激光功率的增加,激光对VPPA电弧作用效果明显增强.

Characteristic of LB-VPPA hybrid heat source for welding process of aluminum alloy

Characteristic of laser beam-variable polarity plasma arc (LB-VPPA) hybrid heat source was studied for joining process of Al-Mn aluminum alloy. Arc shape was achieved by Y4-S2 high-speed camera, and welding current and arc voltage were obtained by Hannover welding quality analyzer. The results show that VPPA arc is attracted by laser and the mechanism which laser acts on arc is different for both positive polarity and negative polarity periods. Laser is concentrated on the roof of arc in positive polarity, while there is a protuberance-like plasma cylinder in negative polarity period. Roof plasma of VPPA arc absorbs laser by inverse bremsstroblung, and cross sectional area of arc becomes large as temperature increase. Meanwhile, laser provides plenty of free electrons to VPPA arc, thus current density and conductivity increase. Arc voltage decreases about 3-4 volts as resistance decreases. With the increasing of laser power, it obviously enhances the effects on VPPA arc.