MODELLING OF WELD POOL PHENOMENA IN TIG, CO_2 LASER AND HYBRID (TIG + CO_2 LASER) WELDING

摘要

The efficiency of the welding process in terms of weld penetration and weld width is greatly determined by the heat, mass and charge transfer phenomena in the weld pool. These phenomena, in turn, depend on the thermal and electromagnetic interaction of the heat source used with the metal being welded. The most adequate models of the welding processes should consider the interaction of the phenomena in the heat source, on the base metal surface and inside its volume by a self-consistent way. This paper is devoted to the development of a self-consistent model of weld pool dynamics in TIG, laser and hybrid (laser + TIG) spot welding without a keyhole formation. The proposed model allows simulation of processes taking place in the weld pool and on its surface. The model takes into account free surface deformation, influence of plasma shear stress, thermocapillary Marangoni effect and Lorentz forces on the weld pool, as well as of the processes in the arc plasma including laser-arc interaction. For this purpose the model of the weld pool is combined with a model of arc plasma column where the interaction processes between Gaussian beam radiation emitted by a continuous-wave CO_2 laser and the argon arc plasma are described. The equations of the model proposed are solved numerically by means of FEM. The simulation results are compared with real welding experiments performed with steel S-235JR. A good accordance between simulation and experimental results is observed.