Study on the alternative burning behavior of arcs in hybrid laser–double-arc welding

Hybrid laser–double-arc welding (HLDAW) is a perspective welding technology with high-deposition quantity, deep penetration, superior gap-bridging ability, and is simply equipped and flexibly adjusted. Either double-power supply system or single-power supply system can be used in this welding system. In the single-power supply mode, there is a particular phenomenon called “alternative burning” presented under certain welding conditions. The frequency of alternative burning is the key to the welding stability. However, the mechanism of this phenomenon and its change rules are not clear. This research mainly aims at the change laws of alternative burning and its essential mechanism. It was found that the alternating period is inversely proportional to laser power and wire-feeding speed, and is proportional to wire spacing and arc voltage. The essence of alternative burning is the regularly repetitive transfer of arc from one wire tip to the other in the condition of relatively low electron density in arc zone which is hard to maintain two arcs burning simultaneously. This phenomenon will disappear when the electron density is greater than 5.54 × 1016 cm−1. Results are meaningful for understanding the interaction mechanism of heat source and its influence on welding stability of HLDAW process in this kind of power supply.