Abstract
High-power CO2 laser welding of A5083 and A6N01 aluminum alloys was performed with filler wires, and the optimum laser wire welding conditions were estimated by comparing surface appearances and fusion zone geometries of weld beads made at different wire feeding rates, welding speeds, shielding gas types and feeding directions. The high-speed shadowgraph imaging technique was applied to ascertain filler wire melting dynamics during laser welding under different conditions. A comparison of the surface appearances of weld beads produced in two wire feeding directions, i.e., leading-wire-feed and lagging-wire-feed, shows that a smooth surface can be obtained with the former. Sound beads were also attained at a relatively long defocusing distance and a high wire feeding rate, under the conditions in which the frequency of weld pool boiling decreased. Parametric experiments revealed that adding filler wire to the weld pool made A6N01 aluminum alloy more weldable than no use of a filler wire. Shadowgraphic observation of wire melting showed that humping beads were formed when large metal droplets were periodically supplied to the weld pool. It was also found that a shielding gas exerted a great influence on the melting dynamics. Especially, the type of the shielding gas affected weldability in terms of the maximum feeding rate and location tolerance of a wire. The highest weldability was obtained using N2 gas, which is attributed to the higher surface absorption of AlN film produced on the molten pool surface. When Ar or He shielding gas was used, a wine-cup-shaped fusion zone was produced, but when N2 shielding gas was used a bobbin-shaped fusion zone was formed. These results suggest that from the viewpoint of melting ability, N2 shielding gas is preferable in the case of CO2 laser welding of aluminum alloys using a filler wire.
