Multi-physics coupled Simulation of the Thermal-pressure Characteristics of Hybrid TIG-MIG Arc

Abstract A multi-physics coupled numerical model for the hybrid tungsten inert gas (TIG)-metal inert gas (MIG) arc (HTM arc) was established to investigate the arc behaviors in a simplified case without considering the droplet. The distribution of current density, temperature, electromagnetic force, velocity and pressure were analyzed in detail. The results indicated that a direct current path was established between the welding wire and the tungsten electrode, resulting in the merging of the original MIG and TIG arcs, which coupled to form the hybrid HTM arc. The electromagnetic repulsion force generated by the reverse current caused the original arcs to deflect along the welding direction, and the shape of the HTM arc was bimodal distribution. Compared with traditional single arc, the thermal influence range of the HTM arc on the workpiece surface expanded both along and perpendicular to the welding direction, reducing the temperature gradient and the cooling rate of molten metal behind the arc, which was beneficial to filling the weld toe. As the TIG current increased, the potential difference between the welding wire and tungsten electrode increased, which led to an augmentation in the current flux between them. This, in turn, diminished the electromagnetic force, thereby reducing the plasma velocity and weakening the arc pressure acting on the molten pool. The above thermal-pressure characteristics of HTM arc were beneficial to suppressing the occurrence of undercut and humping defects in high-speed welding, achieving high-quality and high-efficiency welding.