Modeling of the thermal fluid flow and keyhole shape in stationary plasma arc welding

A three dimensional transient model has been developed to investigate the fluid flow and heat transfer in the weld pool with a dynamic-variation keyhole during stationary plasma arc welding (PAW). The level set method is used to track the moving boundary of the keyhole, and the evolution of both keyhole and weld pool in stationary keyhole PAW process are quantitatively analyzed. The thermal fluid flow of the molten metal surrounding the keyhole inside the weld pool is numerically simulated, and its effect on the keyhole shape is considered. The establishing time of an open keyhole is calculated for the stationary plasma arc welding of stainless steel plates with thickness 6 mm. The stationary keyhole PAW experiments are conducted to measure the keyhole shape, the fusion zone, and the establishment time of the keyhole. The predicted results, such as the keyhole length and width at bottom-side, the weld width at top- and bottom-side, and the establishment time of the keyhole, are in agreement with the experimental measurement.