Numerical simulation of metal vapor behavior in arc plasma

A gas tungsten arc in helium is modeled taking into account the contamination of the plasma by the metal vapor from the weld pool surface. The whole region of gas tungsten arc welding, namely the tungsten cathode, arc plasma and weld pool, is treated using a unified numerical model. A viscosity approximation is used to express the diffusion coefficient in terms of the viscosities of the helium gas and the iron vapor. The time-dependent two-dimensional distributions of temperature, velocity and iron vapor concentration are predicted, together with the weld penetration as function of time for a 150 A arc current at atmospheric pressure. It is shown that the thermal plasma in gas tungsten arcs is markedly influenced by iron vapor from the weld pool surface and that the concentration of the iron vapor in the plasma is dependent on temperature of the weld pool surface.