Investigation of heat transfer and fluid flow in high current GTA welding by a unified model

Abstract

This research is aimed to understand the heat transfer and fluid flow of the arc plasma and weld pool with a significant deformation of the weld pool surface during high current gas tungsten arc welding (GTAW). A unified model including the tungsten electrode, arc plasma and the weld pool of low carbon steel is developed by presetting a free surface deformation from the experimental observations. Buoyance, Lorentz force, plasma drag force and Marangoni force are taken into account to investigate the weld pool dynamics with a great depressed free surface. Heat flux, current density, Marangoni force and plasma drag force at the weld pool surface are presented to understand the heat and momentum transfer from the arc plasma to the weld pool. It is found that the distributions of the heat flux and current density as well as temperature at the depressed weld pool surface are double-peak profiles; the molten metal flow of the weld pool with severe surface depression are determined by the plasma drag force rather than the Marangoni force. The effect of the Lorentz force is more important than that of the buoyance, but weaker than the Marangoni force. The results are consistent with the existing results of both the experiment and the theory.