HEAT AND FLUID-FLOW IN PULSED CURRENT GTA WELD POOL

In this study the heat transfer, fluid flow and phase change of the we ld pool in pulsed current gas tungsten are (GTA) welding were investig ated. Transporting phenomena from the welding are to the base material surface, such as current density, heat flux, are pressure and shear s tress acting on the weld pool surface, were taken from the simulation results of the corresponding welding are. Various driving forces for t he weld pool convection were considered, namely self-induced electroma gnetic, surface tension, buoyancy, and impinging plasma are force. Fur thermore, the effect of deformed free surface due to the are pressure acting on the weld pool surface was considered. Heat and mass transfer equations, including the generalized Navier-Stokes equation and elect ric transport equation, were solved by a finite difference method. Bec ause the fusion boundary has a curved and unknown shape during welding , a boundary-fitted coordinate system was adopted to precisely describ e the boundary for the momentum equation. The numerical model for puls ed: current welding was applied to AISI 304 stainless steel and compar ed with the results of the constant current. (C) 1998 Elsevier Science Ltd. All rights reserved.