重型汽车的制动鼓材料为灰口铸铁,在使用中容易开裂。为此,对开裂的制动鼓进行了宏观检查、金相检验、化学成分分析、硬度测试及断口分析,以揭示制动鼓开裂的原因。结果表明,由于石墨与基体的结合强度弱,且石墨的强度、膨胀系数等与基体存在明显差异,导致裂纹起源于石墨片,并在拉应力、摩擦力的作用下沿制动鼓轴向扩展。 Brake drums for heavy duty vehicles are gray cast iron, which is easily cracked in service. To this end, the cracked drum brake macro examination, metallographic examination, chemical composition analysis, hardness test and fracture analysis to reveal the reasons drum brake cracking. The results show that due to the weak bonding strength between graphite and matrix, and graphite strength, expansion coefficient and other significant differences with the matrix, resulting in cracks originated in the graphite sheet, and in the tensile stress, friction along the drum axial expansion .