Abstract
The instability of the arc in the $CO_2$ arc welding affects the quality of the weld in the automotive industry. This paper evaluates the effects of the arc stability in $CO_2$ arc welding with respect to vertical welding positions. In this experiment, galva-annealed steel sheets(CA) were used as specimens, and these materials were welded by adopting new Cold Metal Transfer (CMT) process. For each sample, fillet joint welding trials were carried out using the same conditions. Each part of welding joints was welded with vertical-up, vertical-down position at $45^{\circ},\;90^{\circ}\;and\;135^{\circ}$ degrees. A high speed camera and a welding signal monitoring system were used for monitoring fluid-flow phenomena in weld pools and frequency measurements, respectively. Through this study, the welding position were found to be key factors mainly to influence the arc stability in $CO_2$ welding moreover and that the arc stability in the vertical-up welding position was observed to be more stable than the vertical-down welding position below $90^{\circ}$.
