Weld formation mechanism of fiber laser oscillating welding of austenitic stainless steel

The effects of beam oscillating parameters on weld morphologies are investigated. Weld geometrical sizes were counted statistically. The results showed that the difference in cross-section width from the top to the lower gradually reduced to disappear with the increase of oscillating frequency. Weld cross-section was featured by slender nail when the frequency was 10 Hz or so, which was similar with conventional laser keyhole weld. It changed to dumpy nail, V-shape and U-shape in sequence with the increase of the frequency within the range from 20 Hz to 1000 Hz. The welding speed thresholds transforming the welding from keyhole mode to unstable mode and from unstable mode to heat conduction mode were confirmed as 24 m/min and 48 m/min, respectively. Weld formation mechanisms were summarized by weld overlapping ratio and the transformation of welding mode.