Non-equilibrium plasma property of ArGTA in low current range

Although the LTE assumption is effective to evaluate a high temperature region in the arc column in Gas Tungsten Arc (GTA) which is a kind of a transfer-type plasma torch, it is difficult to apply it to a low temperature region such as the fringe of the arc column or an electrical sheath due to the decrease of collision frequency. Especially, in order to consider the effect of chemical reaction between the arc plasma and the surface of the anode material, non-equilibrium property of the arc plasma should be considered without the LTE assumption, since it is required to understand the precise property of the arc plasma closed to the anode surface. Therefore, we have developed a non-equilibrium simulation model of GTA. In this paper, we will report simulation results of plasma property of argon GTA at atmospheric pressure. As a result it was found that the non-equilibrium property appears below the collision frequency of 3.8 ⁎ 1011/m3/s corresponding to the plasma temperature of 10,000 K in case of an arc current of 150 A.