CO2 laser welding of aluminum alloys at high speeds up to 20 m/min

CO2 laser welding of thin aluminum sheets was performed at welding speeds of up to 20 m/min to investigate the weldability, weld pool dynamics and mechanical properties of the weld bead of aluminum alloys. High-speed camera observation of weld areas showed that the thickness of the keyhole-front-face decreased to 100 μm under high-speed welding conditions and the weld pool became unstable. The focal length was optimized to increase the spot power density and thereby easily melt the aluminum sheets. Using a 76-mm focal length lens, which corresponds to 11 MW/cm2 power density, we obtained a keyhole mode weld bead with a depth of 1.3 mm at 20 m/min welding speed at 2 kW laser power. It was also possible to reduce the heat affected zone (HAZ) width to only 1.6 mm when the welding speed was 20 m/min. The HAZ width decreased as welding speed was increased. The tensile strength test of A6N01 weld beads showed that the fracture strength increased as the welding speed was increased up to 16 m/min, probably because the soft region of weld specimens was decreased. On the other hand, solidification cracks formed in the weld bead center at higher speeds, resulting in decreased strength.