Numerical simulation of the plasma-MIG process-interactions of the arcs, droplet detachment and weld pool formation

The plasma-metal inert gas (MIG) process is characterized by a variety of process parameters. Numerical simulation can be used to investigate the influence of these process parameters and thus helps to improve the properties of the weld. In this paper we discuss a procedure to describe the plasma-MIG process by coupling numerical models of the arc and the droplet detachment with a three-dimensional model for the plasma-MIG weld pool. Using the magnetohydrodynamic (MHD) arc model, the effects of process parameters on the arc pressure profile and the energy input profile on the workpiece can be analyzed. The volume-of-fluid (VoF)-MHD model of the droplet detachment describes the properties of the resulting droplet in terms of its size, temperature and speed. In the three-dimensional VoF model of the weld pool, the influences of the arc and the droplet are simplified by source terms in the mass, momentum and energy equations. Due to these simplifications in the physical complexity, the process and the seam shape can be described with reasonable computational effort.