Comparison of joining efficiency and residual stresses in laser and laser hybrid welding

Laser welding is a high energy density process, which can produce welds with less energy input and thereby lower residual stress generation compared to arc welding processes. However, the narrow beam dimension makes it extremely sensitive in terms of fit up tolerance. This causes a problem in achieving high quality welds. Laser with arc hybrid process overcomes such issues. In this paper, longitudinal residual strains were compared for autogenous laser welding and laser/TIG hybrid processes. Joining efficiency, which is defined by the penetration depth achieved per unit of energy input, was correlated with the residual strain generation. It has been shown that to achieve a specific penetration depth, there is an optimum welding condition for each of the welding processes, which will give minimum tensile residual stress generation. The results imply that for the same penetration depth, hybrid process resulted in similar to 50% higher tensile longitudinal domain compared to autogenous laser.