Effects of surface depression on pool convection and geometry in stationary GTAW

Abstract

The effects of surface depression on pool convection and geometry in stationary GTAW are simulated numerically under DC and pulsed-current conditions. Welding current and Marangoni flow affect surface depression and velocity such that inward flow by the current and positive surface-tension gradient acts to decrease surface depression. Arc pressure is found to be a major factor in surface depression and in fluctuations of free surface and flow velocity. While arc pressure at the low current range has negligible effects on surface depression and pool geometry, it should be considered in the high current range. Under the pulsed current condition, deep penetration is produced mainly by arc pressure at peak duration. The solid-liquid interface profile at the pool center and periphery becomes similar to that of peak and base current, respectively, and penetration is closely correlated to surface depression.