Discussion of the Effect of Shielding Gas and Conductivity of Vapor Core on Metal Transfer Phenomena in Gas Metal Arc Welding by Numerical Simulation

Abstract

Gas metal arc welding is indispensable in many fields of industry. In this process, various kinds of shielding gas are used, and they significantly affect the behaviors of the arc plasma and metal transfer. In this study, these behaviors with various kinds of shielding gas are numerically investigated. In addition, the influence of the electrical conductivity of the metal vapor is discussed. Simulation results show that with Ar gas, spray transfer occurs at an arc current of more than 240 A, and with CO2 gas, the transfer mode is globular, even at an arc current of 300 A. The calculation results show that the current path near the wire tip critically determines droplet behavior. With Ar gas, the current path is spread out, covering the molten wire, whereas with CO2 gas, the current path is concentrated at the bottom of the molten wire. Therefore, to achieve spray transfer, the current path needs to be spread at the wire tip; however, if the spreading is excessive, the transfer mode becomes streaming transfer. To investigate the influence of the metal vapor, a numerical experiment using pseudo metal vapor was carried out. Even with CO2 gas, the electrical conductivity of the metal vapor was low, and thus the current path was not concentrated at the bottom of the molten wire, allowing spray transfer. The numerical results show that metal transfer phenomena can be regulated by controlling the electrical conductivity of the metal vapor.