ON THE CALCULATION OF THE FREE-SURFACE TEMPERATURE OF GAS-TUNGSTEN-ARC WELD POOLS FROM 1ST PRINCIPLES .2. MODELING THE WELD POOL AND COMPARISON WITH EXPERIMENTS

By combining a mathematical model of the welding arc and of the weld pool, calculations are presented to describe the free surface temperature of weld pools for spot welding operations. The novel aspects of the treatment include the calculation of the heat and current fluxes falling on the free weld pool surface from first principles, a realistic allowance for heat losses due to vaporization, and a realistic allowance for the temperature dependence of the surface tension. The most important finding reported in this article is that the free surface temperature of weld pools appears to be limited by Marangoni convection, rather than heat losses due to vaporization. Furthermore. it was found that once thermocapillary flow can produce high enough surface velocities (> 25 cm/s), the precise nature of the relationship between temperature and surface tension will become less important.