Radiation Loss of Gas Tungsten Arc Welding Affected by Current Increment

Abstract

Gas tungsten arc welding (GTAW) is a high quality and productive joining technology. The tungsten inert gas (TIG) welding which is one of the GTAW has been used as a high quality joining case. Because the inert gas is used as a shielding gas, the arc is not contaminated by surrounding gas. Therefore, this joining process is very clean to join the materials. However, the weld defects are occurred, such as lack of penetration and overlap because of low heat transfer to the anode. Some researchers have researched the weld defect. However, the view point of radiation loss has not been researched. Especially, the TIG welding is contaminated with metal vapor from anode material. In this case, the heat transfer to anode is affected by radiation emitted from metal vapor, because of the net emission coefficient emitted from metal vapor is very high. In this paper, the radiation loss of gas tungsten arc welding affected by current increment is elucidated. When the current increases, the heat transfer to the anode increases, and then the contamination ratio of metal vapor increases. When the contamination ratio of metal vapor increases, the arc temperature changes, and then the heat transfer to the anode changes. Therefore, that energy balance of heat transfer to anode and radiation loss should be considered in the TIG welding. As a result, the radiation loss increases with increasing the current. When the metal contamination ratio and its distribution change, the radiation loss changes. In addition, the current increase to 300A, the radiation loss is saturated. Therefore, the radiation loss is obtained by the complex condition between the current, temperature, metal contamination distribution. And the heat transfer to the anode is affected by this radiation loss.