Numerical Analysis of Heat Transfer from Plasma to Base Metal Surface in Gas Tungsten Arc Welding with Metal Vapor

In order to clarify the mechanism of metal vapor generation in helium (He) gas tungsten arc plasma, the phenomenon of heat transfer between the plasma and the base metal was examined. In addition to the argon (Ar) arc and He arc, the numerical analyses of imaginary arcs changing the thermal conductivities of respective arcs were conducted, and the plasma temperatures, molten pool temperatures, and the concentrations of metal vapor were compared. As a result, with the increase of the thermal conductivity of the plasma, the maximum temperature of the molten pool surface and the maximum iron (Fe) vapor concentration went up while the plasma temperature in the vicinity of the molten pool dropped. Therefore it is assumed that the phenomenon of Fe vapor generation in the He arc and the phenomenon of the plasma temperature drop near the molten pool are influenced greatly by the high thermal conductivity of the He plasma.