Numerical analysis of arc welding phenomena from a unified arc-electrodes model

点击翻译按钮获取中文摘要

The development of a numerical model of the process is quite useful for understanding quantitative values of the balances of mass, energy and force in the welding phenomena, because there is still luck of experimentally understanding the quantitative values of them due to the existence of complicated interactive phenomena between the arc plasma and the weld pool. This study was focused on a stationary tungsten inert gas (TIG) welding process for simplification, but the whole region of TIG arc welding, namely, tungsten cathode, arc plasma, work-piece and weld pool was treated in a unified numerical model because of taking the close interaction between the arc plasma and the weld pool into account. Calculations were made for stationary TIG welding at a current of 150 A. The anode was assumed to be a stainless steel, SUS304. The two-dimensional distributions of temperature and velocity in the whole region of TIG welding process were predicted. The weld penetration geometry was also predicted. Furthermore, quantitative values of the energy balance for the various plasma and electrode regions were given. The predicted temperatures of the arc plasma and the tungsten cathode surface were in good agreement with the experiments. There was also approximate agreement of the weld shape with experiment. The calculated convective flow in the weld pool was mainly dominated by the drag force of the cathode jet and the Marangoni force as compared with other two driving forces, namely, the buoyancy force and the electromagnetic force. It was shown that change in the direction of re-circulatory flow in the weld pool led to dramatically different weld penetration geometry.