Numerical investigation for dominant factors in slag transfer and deposition process during metal active gas welding using incompressible smoothed particle hydrodynamics method

Numerical simulation based on an incompressible smoothed particle hydrodynamics method was performed to clarify dominant factors of slag transfer and deposition processes in a metal active gas welding. The computational model considered the effects of a shielding gas flow on a slag floating on a weld pool surface. The computational result showed that the slags were generated on the weld pool surface near the centre of a heat source and were transferred to the edge of the pool. Those tendencies were similar to those observed in an experiment. The slags stayed at the trailing region of the pool and then deposited on a weld bead. These behaviours supported the validity of the present computational result. To identify the dominant factors of the slag behaviour on the weld pool, numerical experiments were conducted with individually acting forces due to the Marangoni effect, the shearing force, the Lorentz force, and the drag by the shielding gas flow. The computational results suggested that the shearing force and the drag due to the shielding gas were dominant near the centre of the heat source, and the slag was transferred from the vicinity of the heat source to the end of the weld pool. On the other hand, the force due to the Marangoni effect was dominant in the trailing region of the weld pool, and consequently, the slag was transferred from there to the front region in the welding direction.