抄録
As one of techniques to improve a penetration depth in a gas tungsten arc welding, it has been proposed that carbon dioxide gas is applied as a shielding gas using a double shielding torch. Two types of gases can flow independently in the double shielding torch: inner gas and outer gas. The purpose of this study was clarification of the carbon dioxide behavior to establish a guideline for controlling oxygen contamination which affects the toughness of welded part formed by this welding process. As a result, it was revealed that carbon dioxide in the outer gas was transported to the vicinity of central axis of a tungsten electrode by the vortex generated near the electrode. Then, oxygen was produced by dissociation of carbon dioxide. It was suggested that the dissociated oxygen increased the oxygen concentration in the gas flowing on a base metal surface.
