Research status of solidification cracks in laser welding of high-strength steel

Hot cracks,mainly solidification cracks,occurred when laser welding,laser wire filling and laser-arc hybrid welding were used in high strength steel welding. For the problem in the paper,the research status of solidification crack in high-strength steel by laser welding and laser-arc hybrid welding in recent years was comprehensively discussed,characteristics,formation mechanism and preventive measures of solidification cracks were introduced. According to the current research results,the solidification cracks in laser welding of high-strength steel were mainly longitudinal cracks in the weld. The formation of solidification cracks was mainly studied at home and abroad from four influence factors of chemical composition,molten pool geometry,welding parameters,and restraint intensity. The focus was on the influence of convex part and depth-to-width ratio of the molten pool on the formation of solidification crack. The convex part would cause solidification delay,generate large tensile stress,and promote the segregation of S and P impurity elements. Larger depth-to-width ratio would cause local stress concentration and then cause cracks. Changing the weld geometry by different techniques was an important direction to solve the solidification cracks in laser welding.