铸钢轮装制动盘螺栓孔裂纹产生原因分析

Cause analysis of cracks in bolt holes of cast steel wheel-mounted brake disc

以存在螺栓孔裂纹的铸钢轮装制动盘为研究对象,通过裂纹断口宏微观形貌观察、显微组织分析、拉伸性能测试、冲击性能测试、布氏硬度测试等手段分析了制动盘摩擦面螺栓孔裂纹的性质和成因。结果表明:裂纹属于热疲劳裂纹,螺栓孔倒棱处及摩擦面附近存在缩孔、疏松等铸造缺陷是导致制动盘在制动过程中循环交变热应力驱动下产生裂纹的主要原因;粗大的沿枝晶状分布组织降低了制动盘的强度、韧性和热疲劳性能,加速了裂纹的扩展。

The nature and causes of the cracks in bolt holes of a cast steel wheel-mounted brake disc were investigated by means of fracture macro and micro morphology observation,metallographic examination,tensile property test,impact property test and Brinell hardness test.The results show that the cracks are thermal fatigue cracks,and the casting defects such as shrinkage and porosity at the chamfer of the bolt hole and near the friction surface are the main reasons that cause the crack formation under the cyclic alternating thermal stress during braking process.The coarse dendritic structure reduces the strength,toughness and thermal fatigue properties of the brake disc,and accelerates the crack propagation.