A Study on Adopting Λ-Shape Groove for Laser-Arc Hybrid Welding to Construct Thick Plate Butt Welded Joints

Most Japanese shipyards that build general merchant ships use arc welding, but they always have the problem that the accuracy of the hull construction is poor as a result of the thermal deformation caused by arc welding. As one method to overcome this problem, it is expected to adopt laser arc hybrid welding that can suppress the total heat input as a result of heat input concentration, but the initial introduction cost is high and this welding method has a poorer gap tolerance than conventional arc welding. In addition, few experiences to apply laser arc hybrid welding for constructing the joints at the plate thickness level used for hull members of general merchant ships. An improved procedure to fabricate a butt joint with a plate with a thickness of 15 to 20 mm, which is widely applied as a hull member of general merchant ships, is proposed in this study. Proposed procedure is that the Λ-shaped groove with a very small angle and one-pass welding by laser arc hybrid welding with CO₂ gas shielded arc welding to satisfy the weld reinforcement on the front side weld bead. The joint quality manufactured by using our proposed procedure was confirmed according to the Guidelines for Laser Arc Hybrid Welding by a classification society Nippon Kaiji Kyokai (ClassNK). It is expected to be introduced as an alternative method of plate joint welding for hull members, especially submerged arc welding with large heat input.