Study on Attraction of Laser to Arc Plasma in Laser-TIG Hybrid Welding on Magnesium Alloy

This paper presents the results of investigation on the attraction of laser to the electric arc plasma in laser-tungsten inert gas (TIG) hybrid welding of magnesium alloy AZ31B plates. By comparably estimating the characteristics of arc plasma, including the shape, the electron temperature, and density of the arc plasmas in hybrid welding and single TIG welding, three interactions between laser and arc plasma in hybrid welding are managed to be distinguished. The influences of laser power, intensity of arc current, and the distance between laser beam axis and tungsten electrode tip (D_la) on the attraction are analyzed. Moreover, a new mechanism for attraction is proposed by a physical model in the viewpoint of electromagnetic interaction between the currents. It is thought that there exists a current in the welding keyhole in hybrid welding, and the electromagnetic force between this current and arc plasma current is the driving force of the attraction. Attraction happens when the driving force overcomes the stiffness of the electric arc.