Fundamental phenomena during vacuum laser welding

Abstract

Laser welding under vacuum conditions (760 Torr - 10−5 Torr) was performed and the fundamental phenomena during Vacuum Laser Welding were dynamically observed, including the behavior of laser plasma, the molten pool and the beam hole. Observation was performed with a high speed camera and by the transmission X-ray method. It was found that Vacuum Laser Welding can almost completely suppress laser plasma and that this allows deep penetration at a very slow welding speed. Under these conditions, the shape and behavior of the beam hole during welding were very similar to electron beam welding. The Fundamental characteristics of Vacuum Laser Welding were also studied, including the effect of gas pressure and the welding speed on the penetration depth. The penetration depth increased with decreasing pressure and also as the welding speed decreased. A penetration depth of over 40 mm was achieved at a power of 11 kW, a pressure of 10−3 Torr, and a speed of 10 cm/min. Vacuum laser welding using an aerodynamic window was proposed for practical applications, and a penetration of over 25 mm was subsequently achieved, even at a pressure of 50 Torr.