Study of arc shape and voltage-current characteristics in variable polarity plasma arc-MIG hybrid welding of aluminum alloys

Butt weld experiments were performed on aluminum alloys plates using VPPA-MIG hybrid welding method. Arc shape and voltage-current characteristics were obtained by high-speed camera and data acquisition system. The results show that arcs are repellent during VPPA direct current electrode negative period and attractive during direct current electrode positive period as the effect of magnetic field coupling. By applying external transverse alternative magnetic field, arc swing amplitude can be reduced apparently. Due to the existence of MIG arc, voltage-current characteristics of VPPA are changed. Atmosphere is easily ionized in arc column, and the voltage of VPPA decreases. VPPA voltage decreases with increasing MIG current when VPPA current value in low level, and VPPA voltage slightly decreases with increasing MIG current when VPPA current value in high level. Experiments provide theoretical support for high efficiency welding of thick plate aluminum alloys and arc coupling mechanism.