NUMERICAL SIMULATION AND ORTHOGONAL ANALYSIS ON COUPLED ARC WITH MOLTEN POOL FOR KEYHOLING PLASMA ARC WELDING

A 2D axial symmetrical mathematical model was developed for stationary keyholing plasma arc welding (PAW), to describe the transport process in coupled high-temperature flow arc and molten pool in the workpiece. The evolutions of electric, magnetic, velocity and temperature fields were simulated. The simulated fu- sion line of the weld bead is in quite good agreement with the experimental results, validating the mathematical model. It turns out that, both the current density and the temperature reach the maximum values near the tip of the tungsten cathode. The arc displays a typical bell-shape above the workpiece, but becomes slim cone-shape near the central axis as the arc enters the keyhole. The argon plasma slows down sharply when it strikes the inner wall of the keyhole, so high pressure appears in the keyhole and some argon plasma flows back. The combination of fluid