Effect of laser on the plasma arc in laser-plasma hybrid welding

This paper investigates the influence of laser on the plasma arc in laser-plasma hybrid welding. First, the external characteristics of the welding power supply were measured, the arc morphology was captured, and the weld bead morphology was analyzed. Then, a three-dimensional mathematical model was established to describe the interaction between the laser-plasma hybrid welding arc and the molten pool based on the assumption of local thermal equilibrium and by considering metal vapor. Important results such as the temperature field, velocity field, and current density distribution of the arc and molten pool were obtained by solving the coupled Maxwell equations, continuity equation, momentum conservation equation, energy conservation equation, and species transport equation. The results show that an approximately perfect bell-shaped plasma arc can be achieved, compressed through a nozzle, when the laser and the tungsten electrode are arranged at a certain angle. The plasma discharge potential gradient increases with the increase in laser power when the welding current is low; the plasma discharge potential gradient decreases with increasing laser power when the welding current is high. A welding current of 15 A is the threshold for the change in voltage. The maximum temperature in the arc gradually shifts from the tungsten electrode tip to the anode workpiece as the laser power increases, and the higher the welding current, the greater the laser power required for this shift.