Stabilization mechanism and weld morphological features of fiber laser-arc hybrid welding of pure copper

Process characterization of laser-arc hybrid welding of pure copper was studied. The morphological features and the porosity of the welds were measured by optical microscope and X-ray non-destructive test, respectively. Process stability was characterized by the numbers in interruption and short circuit of the arc, which were counted from the waveform of arc current. The dynamic behaviors of molten pool, keyhole and droplet transfer were observed by high speed video camera. The results showed that the process was unstable in single laser welding and single arc welding, but could be easily stabilized by hybrid welding. Accepted weld and stable process could be obtained under the optimized parameters, which were the laser power around 4 kW, the arc current higher than 120 A and the welding speed lower than 1.5 m/min. The process stabilization was attributed to two reasons. Firstly, laser keyhole was stabilized by homogenizing and decreasing of dynamic vapor pressure on keyhole rear wall. Secondly, the arc wandering was avoided by keyhole fixation. Both of the reasons prevented the fast heat loss caused by the high heat conductivity of pure copper.