Effects of Metal Vapor for Temperature Distribution of Transient Arc in Pulsed TIG Welding

Abstract

Pulsed arc welding is used for improvement of welding quality and stability. However, welding defects readily occur when welding is used under inappropriate parameters. Properties of arc and energy balance are very important for TIG welding. However, the theoretical elucidation of a transient arc has not been described quantitatively. As described in this paper, the temperature distribution is calculated under consideration of Fe vapor, which changes the energy balance of the arc and anode surface condition as a function of current. Consequently, expansion and contraction of the high-temperature area depends on the Fe vapor. During the peak current period, the increment of the high-temperature area slows when Fe vapor is a contaminant. During the base current period, decrement of the high-temperature area occurs rapidly when Fe vapor is a contaminant. The increment of radiation power and electrical conductivity alters properties such as the temperature and the axial flow velocity. Effects of the Fe vapor depend on its distribution because the temperature distribution depends on the current waveform. The relation between the current waveform and Fe vapor distribution was assessed. Three calculation conditions of the peak and base current were calculated as parameters. During the peak current period, the Fe vapor distribution differs in the case of current waveform. However, it is almost identical during the base current period. For pulsed TIG welding, metal vapor distribution changes instantaneously; its effects for properties of transient arc change as well.