Analysis of dynamic characteristics of vapor plume of oscillating laser welding of SUS301L-HT stainless steel

Abstract

Investigations had made much efforts on the vapor plume dynamic characteristics of laser beam welding (LBW) but only showed a little knowledge about the oscillating laser beam welding (OLBW). The velocity magnitude and direction of OLBW varied abidingly, resulting in complicated evolution process of vapor plume. Present research attempted to elucidate the effect of oscillation frequency on the dynamic behavior of vapor plume. The vapor plume morphology was uniform at 50 Hz and 100 Hz. The abrupt change in velocity direction easily led to the occurrence of attenuation and even annihilation of the vapor plume at the frequency less than 20 Hz or greater than 150 Hz. The vapor plume area less than 31.44 mm2 or the vapor plume orientation greater than −40° could be used as the judgment criterion of keyhole instability. The coefficient of variation of vapor plume area or orientation and the proportion of keyhole instability time showed similar trends of first decreasing and then increasing with the increase of oscillation frequency. The stability of vapor plume or keyhole was the best at 50 Hz.