(A) study on numerical analysis of welding arc and molten pool considering electrode angle in stationary TIG welding

Abstract

The characteristics of argon arc in TIG welding have been studied by considering the electrode shape which has an effect on the current density distribution near the electrode tip. For including the electrode surface configuration into the solution domain, the boundary-fitted coordinates system was employed. Then, a non-rectangular computational region in the physical domain was transformed into a rectangular area with uniformly spaced grids in the computational domain using the second order central difference method. With the geometric transformation coefficients, the finite difference equations were derived in the transformed domain. The influences of the parameters such as electrode angle, welding current and arc length on the TIG welding arc using Ar shielding gas have been studied by assuming the current density distribution along the cathode surface. Its distribution was assumed to have a Gaussian form which is characterized by the maximum current density at the electrode tip or the distribution parameter. For determining these two characteristic values according to the electrode angle and welding current, the temperature distributions of the 60 deg. angle electrode were calculated for 100, 200 and 300 A welding currents and compared with experimental measurements obtained by the previous researcher. As a result, the distribution parameter for the 60 deg. angle electrode was determined such that the maximum current density at the electrode tip have 136.5 A/mm2 irrespective of welding current. With this reference value, for electrodes below 60 deg. angle the distribution parameter was increased to maintain the maximum current density to be 136.5 A/mm2, on the other hand, for electrodes above 60 deg. angle the distribution parameter was set to be the same as the 60 deg. angle electrode. Using these assumed current density distributions as the boundary condition for the current continuity equation, the heat flux and current density on the base plate were c...