Narrow Gap Welding of X80 Steel Using Laser-CMT Hybrid Welding with Misaligned Laser and Arc

Abstract

The feasibility of using laser-cold metal transfer (CMT) misaligned hybrid welding to join an X80 line-pipe steel in a narrow gap configuration was investigated. The laser beam interacted with the sidewall and its bottom at a small angle, while the CMT arc acted on the backside of the laser beam. The influence of the distance parameter between the laser spot and the tip of the welding wire on the formation and defects of the filled weld were investigated. Narrow gap bevel welds were performed, and the joints were tensile and had a satisfactory Charpy impact score. The tensile fracture is located in the base metal, and the impact fracture is a ductile fracture. Under this condition, the heat input could be efficiently reduced, preventing the formation of defects such as lack of fusion and reducing the number of pores. Additionally, welds with a narrow heat affect zone (HAZ) could be obtained. The results reveal that the hybrid process, as a low-heat input method, is suitable for narrow gap welding.

Keywords

• laser-CMT hybrid welding
• narrow gap
• misaligned laser and arc
• lack of fusion