A novel welding method for extra-thick high-strength steel: Double-sided narrow gap oscillating laser and oscillating laser-TIG hybrid welding

This paper developed a novel welding method for extra-thick high-strength steel, namely double-sided narrow gap oscillating laser autogenous backing welding and oscillating laser-TIG hybrid filling welding in horizontal position. The penetration and formation performance of double-sided oscillating laser autogenous backing welding under different laser beam spacings were performed. Meanwhile, the fusion and formation performance of oscillating laser-TIG hybrid filling welding under different welding currents were studied deeply. Under the optimal process parameters of the backing welding and filling welding, the sound welded joints of 80 mm thick SA-738Gr.B steel in the horizontal position are produced, emerging symmetrically two-fingers morphology. The microstructure and mechanical properties of the welded joints were tested and analyzed. The weld metal and heat-affected zone (HAZ) of the backing layerare composed of bainite with fine equiaxed grains, and that of the filling layer mainly consists of bainite and martensite. The average grain diameter in the weld is much smaller than that of the base material (BM). The mechanical properties of the welded joint meet the design requirements, and the strength and toughness of the welded joints are sufficient. High quality and efficient welding of 80 mm thick SA-738Gr.B steel was achieved with the novel method under the optimal process parameters.

Automated summary

This paper presents a novel welding method for extra-thick high-strength steel, involving double-sided narrow gap oscillating laser autogenous backing welding and oscillating laser-TIG hybrid filling welding. The performance of penetration and formation of the backing welding and fusion and formation of the filling welding were studied under different process parameters. Under the optimal conditions, sound and symmetric welded joints were achieved for 80 mm thick SA-738Gr.B steel in the horizontal position. The microstructure and mechanical properties of the welded joints were analyzed, showing fine equiaxed grains in the weld metal and heat-affected zone. The mechanical properties of the welded joint met the design requirements, indicating sufficient strength and toughness.