Effect of Laser Power and Defocus on the Stability of Laser Welding 5083 Al Alloy with 5183 Al Alloy Filler Wire
S-H. Han, B. Yi, Y-Q. Yang, Z-Y. Luo, D-T. Cai, Y-F. Xue and X-H. Ren
To clarify the influence of laser power density on the stability of laser welding 5083 Al alloy with 5183 Al alloy filler wire, experiments with different laser powers and levels of defocus, which are related to laser density, were carried out. A high speed camera, appearance inspection and macroscopic metallography were used to analyse the effects of laser power and defocus on the stability of welding wire melting, droplet transfer, molten pool fluctuation and weld solidification. The results showed that a small curvature curl would appear at the end of the wire if the laser power could evaporate the wire instantly. A large curvature curl would occur in the low power of the laser beam, which is too small to melt the wire. The droplet transition mode has gone through three stages of droplet transition liquid bridge transition→droplet transition, as the laser power was changed from 1600 to 2000 W, or the focus changed from -9 to +15 mm. Compared to the defocus, the laser power has a greater effect on the power density and the stability of the laser welding with filler wire. The droplet transition would occur when the diameter of the droplet exceeded the diameter of the wire. The weld metal surface had irregular flat areas periodically, while it was smooth during the liquid bridge transition. The violently fluctuating molten pool, splashes and holes would be appeared in the weld seam, when the molten pool had a high power density; however, when the molten pool had a low power density, asymmetric weld reinforcement would be found due to the small volume pool.
Keywords: Disk laser, 5083 Al alloy, 5183 Al alloy, filler wire, laser welding, stability, power density, defocus, droplet transfer, weld formation