A novel high efficiency narrow-gap laser welding technology of 120 mm high-strength steel

Porosity, incomplete fusion, and solidification cracks are frequently encountered defects in narrow gap laser welding. How to effectively inhibit welding defects while significantly improving welding efficiency has become the key technical challenge of narrow gap laser welding. In this paper, a new method of high-efficiency narrow gap dual-beam laser welding utilizing laser plume energy radiation to achieve "quasi-hot wire" filling is proposed. The solidification behavior of the molten pool was controlled by dual-beam to realize the reliable suppression of welding solidification cracks. The wire feeding speed and stability of the filler wire were improved by developing a high temperature resistant tungsten wire feeding nozzle. The "quasi-hot wire" filling was realized by the heating effect of laser plume energy radiation on the tungsten wire feeding nozzle. The wire feeding stability, thermal radiation characteristics, laser plume characteristics and weld formation during the welding process were studied. The high-efficiency welding of 120 mm high-strength steel was realized and the micro-structure and mechanical properties of the joints were tested and analyzed. The results showed that the method could effectively suppress the defects of porosity, incomplete fusion and solidification cracks in narrow gap laser welding. Compared with the traditional narrow gap laser welding (NGLW), the laser power was reduced by 10%. The welding speed was doubled, and the wire filling efficiency was increased by more than 1 time. The mechanical properties of the welded joint were comparable to those of the traditional narrow gap welded joints, which solved the prominent contradiction between the quality and efficiency of narrow gap laser welding of thick-wall components.