Weld shape variation in Ar-O2 and Ar-CO2 shielded GTA welding

Abstract

The effect of the welding parameters on the GTA weld shape is systematically investigated using SUS304 stainless steel in Ar-O2 and Ar-CO2 mixed shielding gases. The results showed that the GTA weld shape depends to a large extent on the pattern and magnitude of the Marangoni convection on the liquid pool surface, which is controlled by the combination of the oxygen content in the weld pool and the temperature distribution on the pool surface. An outward Marangoni convection pattern will change to the inward convection mode when the oxygen content in the weld pool is over the critical value of 100 ppm. Different welding parameters will change the temperature distribution and gradient on the pool surface, and therefore affect the strength of the Marangoni convection and the weld shape. A slight difference in the weld metal oxygen content from different shielding gases introduces a significantly different response in the weld depth/width ratio to the various welding parameters.