Abstract: Based on the magnetohydrodynamic (MHD) model， the dynamic mesh method (DMM) was used to track arc-molten pool interface， and a mathematical model for coupled fluid flow， heat transfer， solidification/melting and dynamic interface tracking during TIG welding process was established. Firstly， a free-burning arc was simulated to obtain the accurate arc parameters， such as the speed， temperature and pressure. Then， the four driving forces of electromagnetic， thermal buoyancy， drag and Marangoni were validated respectively. Considering the arc-molten pool interaction and tracking the interface from pressure balance， the TIG welding process for the 304 stainless steel was simulated and the depression in the pool center and the lifting on the pool periphery caused by plasma shock were obtained. It is shown that the proposed model can simulate the arc-pool interface and molten pool shape more accurately in comparison with the experimental data.

Key words: numerical simulation, arc plasma, magnetohydrodynamics, interface tracking, dynamic mesh