关键词: 铸钢制动盘, 螺栓孔裂纹, 热疲劳裂纹, 疏松, 缩孔

Abstract: 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.

Key words: cast steel brake disc, bolt hole crack, thermal fatigue crack, porosity, shrinkage