Abstract
In previous evaluations of GTA welding on stainless steel plates the surfactant content in the workpiece has been assumed to be in a state of equilibrium. However, surfactant concentration usually had to be adjusted in order to achieve agreement between the weld pool shapes in experiments and those in simulations. In this study a physicochemical approach to the redistribution of surfactant at the surface and in the bulk is presented for the first time. Sulphur was considered as a representative surfactant. The model allows surfactant molecular transport via convection, diffusion, and sorption. It is shown that sulphur atoms accumulate at the surface at stagnation points, affecting the coefficient of surface tension and thus the final weld pool shape. Thus, the sulphur content in the simulation approaches the nominal sulphur content in the steel plate. The theory is strengthened by both electron probe microanalysis and Auger electron spectroscopy.
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