Numerical simulation of heat source properties of pulsed tungsten inert gas arc

Abstract

The heat source properties of TIG arc strongly depend on composition of shielding gas. For example, since the arc column is constricted due to low electrical conductivity of the helium arc, heat flux onto a base metal in case of helium TIG arc is higher than that of argon TIG arc. The heat source properties can be controlled also by current waveform. Pulsed TIG welding is suitable for back-bead welding and thin plate welding, because the heat flux onto the base metal can be controlled by adjusting peak / base current ratio and frequency. A number of results on experimental and theoretical investigations of the heat source properties of DC TIG arc have been reported. However, those of pulsed TIG arc are still not fully understood because of the complexity of the phenomenon. In this paper, numerical simulation result of the heat source properties of pulsed TIG arc for various shielding gas composition will be reported. As a result, it was found that the heat flux increased immediately after transition from base current to peak current because of the thermal pinch effect. Furthermore, temperature distribution of helium arc changes following change in current immediately due to high thermal conductivity