Behavior of laser induced plasma, keyhole and reflected light during laser welding with superimposed beams of different wavelengths

Abstract

This paper deals with the behavior of a keyhole and a laser-induced plasma observed during laser welding of several metals with a single YAG laser or superimposed two beams through the ultra high-speed video camera, with the objective of understanding enhanced beam absorption due to two different wavelength laser beams. Moreover, reflected YAG laser beams were measured by photodiodes, and the relationship between the keyhole behavior and the reflected-laser photodiode signal was investigated to clarify rapid welding phenomena. It was observed that the behavior of a keyhole and a laser-induced plasma during laser welding was considerably different between a single beam and combined two different beams. And the reflected light intensity during welding with the superimposed two different laser beams lowered in the earlier stage than that with a single pulsed YAG laser beam.