Numerical study and comparisons of gas tungsten arc properties between argon and nitrogen

In this paper, nitrogen was used as an alternative gas for its fine protection to weld pool and relatively low cost, in contrast to widely used argon and helium shielding gases in gas tungsten arc welding (GTAW). A two-dimensional axisymmetric numerical model from McKelliget et al. was adopted to describe the heat transfer and fluid flow in the gas tungsten arc (GTA) to predict the basic energy source properties of nitrogen GTA. Simulation results showed that the arc temperature contours, the distribution of heat flux and current density at the anode agree well with experimental results in literature for both argon-shielded arc and nitrogen-shielded arc. To solve the model, the nitrogen arc plasma properties, i.e. temperature, voltage drop and flow fields have been derived. And the distribution of the heat flux, current density and gas shear stress at the anode with the different arc lengths and welding currents has been studied. Moreover, by comparing with the properties between the argon and nitrogen arc, the results indicate that the nitrogen arc is more contraction than that of argon arc under the same arc length and welding current. Especially, the increasing of the maximum of heat flux and current density at the anode shows that the nitrogen GTA possessed excellent energy source properties for GTAW in contrast to the argon arc.