Improving weld forming quality and process adaptability by using a copper liner in laser-MAG hybrid overhead welding

During overhead welding, gravity inevitably drives the molten pool downward, resulting in poor adaptability and concave defect. To address this issue, this paper proposed a novel laser-MAG hybrid overhead welding technique utilising a copper liner (COL). Compared to single-arc welding, laser-MAG hybrid welding can reduce the volume of the molten pool, while the laser increases its support force. The COL can accelerate the molten pool's solidification rate. Additionally, the adhesion force between the molten pool and the COL can partially counterbalance gravity. As a result, good weld formation still was achieved even when the misalignment was 0–1 mm and the butt gap was 0–2 mm. Moreover, the back reinforcement height and width were not less than 0.71 and 3.66 mm, respectively.