Effect of Tensile Direction on HAZ Softening Fracture of Laser Welded Martensite Steel Sheet.

In recent years, demand for high-tensile strength steel sheets has been increasing from the viewpoints of energy conservation through weight reduction and the upgrading of product functions. However, since such high tensile strength steel sheets contain martensite, it has been reported that material strength is greatly reduced in the Heat Affected Zone (HAZ) due to tempering during laser welding. In other words, when laser welding is applied to high-strength materials, there is a possibility that rupture will be apparent in the HAZ softened zone. In this study, we evaluate the strength of a 1500 MPa steel sheet, which is subject to HAZ softening, by applying tension in any direction to the laser weld line and rupturing it. The results show that a welding angle of 20 ° significantly improves elongation and strength. If it is possible to minimize the strength loss due to HAZ softening by using these results, the welding portion of high-strength materials can be located where tensile deformation occurs during forming or collision, thereby increasing design flexibility. [ABSTRACT FROM AUTHOR]