2009 Volume 27 Issue 2 Pages 4s-7s
In the present paper, a TIG arc in helium or argon is modeled taking into account the contamination of the plasma by the metal vapor from a stainless-steel weld pool. Iron, chromium and manganese are considered as the metal vapor species in this model. A viscosity approximation is used to express the diffusion coefficient in terms of the viscosities of the shielding gas and the metal vapor. The time-dependent two-dimensional distributions of temperature, velocity and metal vapor concentrations of iron, chromium and manganese are predicted, together with the weld penetration as a function of time for a 150 A arc at atmospheric pressure, for both helium and argon shielding gases. The distribution of the metal vapors depends on the diffusion term and the convection term. Due to the cathode jet, the convection term has a strong effect. Consequently, it is found that the metal vapors expand in the radial direction and are concentrated around the weld pool surface. The concentration of manganese vapor is larger than those of iron and chromium vapors, despite the fact that the proportion of manganese in stainless steel is significantly smaller.
