Influence of surface-active elements on GTA welds with respect to metallographic analysis and temperature distribution

Welding is one of the most formidable joining procedures used in manufacturing and assembly industry. Gas tungsten arc (GTA) welding method is the most feasible and liable joining procedure to weld stainless steel alloys at industrial perspective in terms of weld joint attributes and manufacturing cost. Moreover, the weld section undergoes severe microstructural and structural transformation with respect to differential temperature gradient attained across and along the weld joint. The temperature transition governs the thermal transmission and fluid flow direction within the melt pool which in effect influences the final weld morphology. Therefore, the present work is aimed at improvement of SS 316 weld morphology by using different activating fluxes during GTA welding process for the same operating conditions. Also, the temperature distribution in the melt pool is examined corresponding to GTA weldments processed with and without activating fluxes. The activating oxide fluxes which are used during GTA welding procedures are TiO2, SiO2 and Al2O3 and combination of these fluxes. Based on results, it is observed that the weld penetration is enhanced due to incorporation of TiO2 flux during welding procedure when compared with other activating fluxes. While, a wider width and shallower penetration is obtained when GTA welding is performed with Al2O3 flux. In this research article, the weld penetration is assessed with respect to Marangoni convection and temperature distribution. From the results, it was determined that a higher Marangoni convection forces and temperature is induced at the weld region due to incorporation of activating flux. And, this phenomenon is on account of surface tension forces which established higher Marangoni convection and enhanced the thermal transmission rate.