Numerical Investigation of the Iron and Oxygen Transport in Arc Plasma During an Activated Tungsten Inert Gas Welding Process

This study presents a numerical investigation of the iron vapour and oxygen transport in activated tungsten inert gas (A-TIG) welding, in which 0.5% oxygen was added to the shielding gas to improve weld penetration. The influence of the iron vapour on the arc properties is examined. The combined diffusion coefficient method was employed to treat the diffusion of the iron in the iron-argon system in the arc, and the diffusion of the oxygen in the oxygen-argon system. It is found that, compared with TIG welding, the iron vapour concentration near the weld pool in A-TIG welding increases significantly. This increased iron vapour concentration originates from the higher temperature and thus intensified evaporation of the weld pool in A-TIG welding. Both the effects of the applied electric strength and the temperature gradient are minimal. In addition, the presence of iron vapour causes the current density and heat flux at the weld pool surface to decrease on axis and expand radially for conventional TIG welding, and to increase on axis and constrict for A-TIG welding. The oxygen distribution is heterogeneous both in the arc plasma bulk and immediately adjacent to the weld pool, and the influence of the presence of the iron vapour needs to be considered when determining oxygen transfer to the weld pool. The numerical results are reasonably consistent with the available experimental data.