Analysis of welding solidification crack in narrow gap laser welding of high-strength steel.

The welding solidification crack is a common welding defect occurring in the narrow gap laser welded high-strength steel joint, which poses a detrimental effect in reducing the weld quality. However, the relationship between the weld geometric characteristics and the metallurgical characteristics with the solidification crack of the narrow gap laser weld is still unclear. In this study, a 20-mm-thick 10Ni5CrMoV high-strength steel with a root gap of 3 mm and groove angle of 1º was used to analyze the single-pass welding process of narrow gap laser welding using high-frequency beam oscillation. The correlation between the weld form factor and the welding solidification crack was discussed, alongside with the clarification on the influence of the welding process parameter on the welding solidification crack, the aim of which was to analyze the causes for the formation of welding solidification crack and explore the effective ways to suppress it. The results showed that the influence of welding process parameters on welding solidification crack could be attributed to change in the form factor of the weld and weld metal solidification crystallization characteristics. The smaller the weld form factor, the larger the area of the opposite crystal growth in the upper part of the weld cross section, and the higher the tendency toward solidification crack formation. Furthermore, the higher welding speed was also likely to have columnar grains with a larger angle of crystallization direction with the centerline. This resulted in a higher tendency of solidification crack formation. Under the test conditions used in this study, a weld form factor φ = 0.8 was considered effective for controlling welding solidification crack. [ABSTRACT FROM AUTHOR]