Laser narrow gap welding of thick carbon steels using high brightness laser with beam oscillation

Laser narrow gap welding with beam oscillation was developed to prevent lack of fusion and hot cracking in the welding of thick steel plates. The weld qualities of carbon steel joints with a thickness of 60 and 150mm were examined in this work. The results show that beam oscillation condition, especially oscillation amplitude affects soundness of the weld, and must be adjusted by considering the change in groove width to avoid lack of fusion on the side wall of the groove. In addition, geometry control of each weld bead in build-up welding is required to avoid solidification cracking of weld metal. Mechanical properties of the joints such as tensile strength, ductility, hardness distribution and toughness were also evaluated, and confirmed to meet product requirements. Beam oscillation in narrow gap welding with high power laser has a great potential to improve weld qualities of large scale weld structure.