Some Basic Aspects of Geometrical Characteristics of Pulsed Current Vertical-up GMA Weld.

Abstract

The performance of pulsed current gas metal arc welding (GMAW) in vertical-up position has been studied in reference to thermal behaviour of the droplet at the time of deposition affecting the geometrical characteristics of weld deposit. A more realistic estimation of heat generation at tip of the filler wire has been worked out by modifying its resistive heating component using effective current (RMS value) of the pulse current wave. The estimated rate of heat generation and measured burnoff rate of the filler wire are correlated to a factor o defined as summarised influence of pulse parameter such as peak current, base current, pulse duration and pulse frequency. Analysis of heat balance in between the heat generated at tip of the filler wire and heat consumed in melting the volume of filler wire fed to the arc indicates that the temperature of droplet decreases with the increase of both o and mean current. The variation in pulse parameters affects the weld geometry by maintaining a good correlation with factor o. In consideration of these correlations, a qualitative understanding over the control of pulse current G MAW process in vertical-up position, affecting weld geometry has been developed.