某公司生产的材料为具有铝硅镀层的22MnB5热冲压成形钢的汽车加强板在总装前发生开裂，采用断口形貌、显微组织观察以及化学成分、硬度测试等方法对其失效原因进行了分析。结果表明：该失效加强板的断裂方式为韧性加脆性的混合断裂；激光剪边落料时拐角半径较小，导致裂纹在剪边边缘萌生，运输过程中在冲击载荷作用下，裂纹沿未进行激光剪边的弯曲变形区域快速扩展；增大拐角处的半径，同时冲压成形后对加强板进行全面的激光剪边，发现总装前加强板镀层上的压痕变浅，未发生开裂。

The automobile reinforcement plate produced by a company cracked before final assembly, whose material was 22MnB5 hot stamping steel with Al-Si coating. The failure reason was analyzed by fracture morphology and microstructure observation, and chemical composition and hardness tests. The results show that the fracture mode of the failed reinforcement plate was a mixture fracture of ductile and brittle. The corner radius was relatively small during laser trimming blanking, leading to the crack initiation at the edge of trimming. The cracks propagated rapidly along the bending deformation region without laser trimming under the impact load during transport. By increasing radius at the corner and all-round laser trimming of the reinforcement plate after stamping, the indentation on the coating of the reinforcement plate became shallow before final assembly, and no cracking occurred.