Application of a high-power CO laser in aluminum welding

Abstract

A multi-kW CO laser system with nearly diffraction limited beam quality has been developed. The performance data are presented. Experiments in laser welding of the aluminum alloy AlMgSil (6082) has been carried out using the CO laser and a commercial industrial carbon- dioxide laser. The welding performance of both laser systems has been compared with results of Nd-YAG laser welding from literature. It has been shown that the penetration depths with the CO laser are higher compared with the results of carbon-dioxide and Nd-YAG laser at the same power level. This is on the one hand a consequence of the better beam quality of the CO laser compared to the Nd-YAG laser and on the other hand the shorter 5 to 5.6 micrometer wavelength compared to the carbon-dioxide laser resulting in a reduced beam-plasma interaction. Owing to the shorter wavelength of the CO laser the absorption of the radiation by laser induced plasma -- one major problem in deep penetration welding with lasers -- is drastically reduced. The aluminum weld seams obtained with the CO laser are very homogeneous and regular at the surface in contrast to the weld seams obtained with the carbon-dioxide laser. The process parameters in CO laser aluminum welding can be changed in a wide range. This is not possible using the carbon-dioxide laser because of the low threshold intensity for a shielding plasma.