Numerical analysis of molten pool convection considering geometric parameters of cathode and anode

The heat transfer and fluid flow in the molten pool during stationary gas tungsten arc welding (GTAW) using Ar shielding gas have been studied with an emphasis on the impact of geometric parameters on the welding arc, such as electrode bevel angle, arc length and surface depression due to arc pressure acting on the molten pool surface. Driving forces responsible for weld pool convection, i.e., self-induced electromagnetic force, surface tension due to the temperature gradient at the surface of the molten pool and shear stress acting on the molten pool surface by the arc plasma flow, were considered. The numerical model was applied to type 304L stainless steel plate with 30 ppm sulfur. As the welding current increased, the discrepancy of penetration at the weld center between the calculation and experiment increased because of the strong flow along the molten pool surface. As the electrode bevel angle decreased, the shear stress acting on the molten pool surface increased. Therefore, the fusion width increased and the fusion depth decreased. Changing the arc length did not influence the fusion shape because variation in shear stress, which determined the surface flow along the molten pool surface, was minor. From the simulation, considering the depression of the molten pool surface, the effects of the increased arc length and elevated anode temperature resulted in a more accurate fusion width.