Effect of reduced pressure atmosphere on weld geometry in partial penetration laser welding of stainless steel and aluminium alloy with high power and high brightness laser

This study investigated the effect of reduced pressure atmosphere (from ambient pressure of 101–0·1 kPa) on partial penetration welding. A 16 kW disc laser with a 1030 nm wavelength was employed to weld SUS304 stainless steel and A5052 aluminium alloy at a welding speed of 17 mm s^?1. Penetration depths in the stainless steel and the aluminium alloy reached 26 and 23 mm respectively at a reduced pressure of 10 kPa. These depths are >1·6 times deeper than those obtained at 101 kPa. The high speed video imagery showed that in SUS304 welding, the keyhole inlet size decreased and the welding process was stabilised at lower pressures. In A5052 welding, in contrast, the keyhole inlet size increased by a factor of >4 at pressures of 1 and 0·1 kPa compared with that at 101 kPa, resulting in instable welding process and shallow penetration.