Heat and fluid flow in pulsed current GTA weld pool

In this study the heat transfer, fluid flow and phase change of the weld pool in pulsed current gas tungsten arc (GTA) welding were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, namely self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc force. Furthermore, the effect of deformed free surface due to the arc pressure acting on the weld pool surface was considered. Heat and mass transfer equations, including the generalized Navier-Stokes equation and electric transport equation, were solved by a finite difference method. Because the fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model for pulsed current welding was applied to AISI 304 stainless steel and compared with the results of the constant current.