• Tanaka, Manabu
• Tashiro, Shinichi
• Yuji, Toshifumi
• Bin Mamat, Sarizam

Abstract

In plasma MIG welding, inert gas introduced from the torch nozzle is ionized in upstream region of the MIG arc, which is termed as “plasma”. This study aims to clarify effect of the plasma on metal transfer process in the plasma MIG welding through numerical analysis. As a result, the plasma with temperature of approximately 10,000 K was found to be formed around the wire tip. The MIG arc temperature around the wire tip was 11,000 K at the maximum, which was lower than that of the conventional MIG welding by approximately 1,000 K. This difference was caused by the decreased current density around the wire tip due to influence of the plasma. The droplet temperature was also decreased by 400 K due to this lower current density. The amount of the metal vapor evaporated from the droplet was decreased than that of the conventional MIG welding due to the lower droplet temperature. It might lead to smaller amount of fume formation generally known in the plasma MIG welding. In the conventional MIG welding, the arc attachment was concentrated around the wire tip, leading to the higher current density. However, in the plasma MIG welding, the plasma transported to the surrounding of the wire tip increases the electric conductivity in that region also due to the influence of the metal vapor mixture. It leads to dispersion of the arc attachment toward the wire root. Consequently, the current density in the plasma MIG welding was found to decrease compared with that of the conventional MIG welding. The lower current density in plasma MIG welding decreases the Lorenz force acting on the wire neck, thus delaying droplet detachment to make the droplet diameter larger and the metal transfer frequency smaller. The latter was about 20 % of that in the conventional MIG welding.

Topics

• density
• impedance spectroscopy
• dispersion
• current density
• wire