Combination of two Nd:YAG laser beams and their welding characteristics

Nd:YAG laser oscillators of two different types were used simultaneously in order to enhance welding ability. A pulse beam emitted from a pulse pumped oscillator was irradiated onto stainless steel (304) together with a rectangularly modulated pulse beam emitted from a cw pumped laser oscillator. The deepest penetration of 7.3 mm was obtained at the total average power of 2.9 kW at a welding speed of 5 mm/s in a bead-on-plate test. It is nearly equal to the penetration depth of 7.7 mm produced by two modulated pulse beams at a total average power of 4 kW. From these results, it can be certified that the pulse beam of high peak power is effective in increasing the penetration depth in two laser beam welding. The plume is extinct after the pulse beam irradiation, although the modulated pulse beam is still irradiated. This phenomenon suggests that the pulse beam effectively enlarges a keyhole, and consequently deepens penetration.