Dynamically Plasma Diagnostics in MIG Welding of Aluminum

In this study, plasma diagnostics in MIG welding of aluminum is performed. In MIG welding, the metal vapor has the large influences on the welding process since the content of the metal vapor in the arc plasma is large. The distribution of metal vapor varies dynamically by a metal transfer. Therefore, the dynamical distributions of temperature and concentration of metal vapor are obtained by the spectral images pictured by high-speed video cameras. Consequently, the metal vapor is distributed near the center axis and the temperature of the arc plasma decreases. Finally, we discuss plasma physics in the welding arc through numerical simulations, using the basic conservation equations of mass, energy, momentum, current and electron density of plasma physics. There is close interaction between the electrode, the arc plasma, the weld pool, and also the metal vapor, which constitute the welding process, and must be considered as a unified system. The simulation results also show the temperature of the arc plasma decreases near the center axis. This is caused by the fact that the energy loss by the radiation increases with increases with the metal content.