The comparison of the effects of welding parameters on weld quality and hardness of T-butt joints welded with CO2 laser, Nd:YAG laser and CO2 laser-GMA hybrid welding

Abstract

Autogenous laser welding is nowadays widely spread welding process especially in thin sheet welding. It is an efficient process, which unfortunately has a major drawback: the tolerances for beam alignment and groove preparation are quite strict. The laser hybrid welding, combination of laser and arc welding has during the recent years become a popular process due to less severe joint requirements.This study is concentrated on the effects of beam alignment, welding speed, focal position, beam impingement angle and airgap on weld quality and hardness of the weld areas of T-butt joints. The processes used were autogenous CO2 and Nd:YAG laser welding as well as CO2-laser-GMA hybrid welding. The results indicated that the requirements of groove preparation can be relaxed with hybrid welding in comparison to autogenous laser welding but the requirements of laser beam alignment are similar in all processes. If there is no airgap the maximum welding speed achieving full penetration for CO2-GMA hybrid welding is lower than for autogenous CO2 laser welding. The welding speed can, however, be increased with increase in air gap width. Airgaps can be bridged up to width of 1.5 mm, but at this maximum width the process is quite unstable producing spatter. The welds produced by hybrid welding have also lower hardness in comparison to autogenous welding.Autogenous laser welding is nowadays widely spread welding process especially in thin sheet welding. It is an efficient process, which unfortunately has a major drawback: the tolerances for beam alignment and groove preparation are quite strict. The laser hybrid welding, combination of laser and arc welding has during the recent years become a popular process due to less severe joint requirements.This study is concentrated on the effects of beam alignment, welding speed, focal position, beam impingement angle and airgap on weld quality and hardness of the weld areas of T-butt joints. The processes used were autogenous CO2 and Nd:YAG laser welding as well as CO2-laser-GMA hybrid welding. The results indicated that the requirements of groove preparation can be relaxed with hybrid welding in comparison to autogenous laser welding but the requirements of laser beam alignment are similar in all processes. If there is no airgap the maximum welding speed achieving full penetration for CO2-GMA hybrid welding is l...