Effects of coupling between the laser plasma and two arcs on metal transfer in CO2 laser double-wire MIG hybrid welding

Abstract

CO2 laser double-wire MIG hybrid welding with direct current is a kind of process with high metal deposition rate and large weld penetration. Microscopic interaction model between the laser plasma and two arcs is proposed. Forces acting on the laser plasma and droplet were analyzed. A high speed camera system and an electrical signal acquisition system were used to investigate the coupling and metal transfer. The theoretical analysis and experimental results reveal that when the electromagnetic force of the leading arc on the laser plasma (FLP) is generally equal to the electromagnetic force of the trailing arc on the laser plasma (FTP), there is higher electron density in two lower sides of the laser plasma. Therefore, despite the great electromagnetic force, the two arcs do not deflect from the wire axis. A stable, spatter-free spray transfer can be achieved. When FLP > FTP, there is higher electron density in the upper left side and the lower right side of the laser plasma. Consequently, the trailing arc will deviate from the wire axis under the influence of the electromagnetic force, resulting in an unstable metal transfer with large spatter. Similarly, when FLP < FTP, there is an unstable welding process in the leading arc.