采用通道式合金分析仪、光学显微镜、拉伸和冲击试验机、扫描电子显微镜等分析了预启阀阀碟的化学成分、显微组织、力学性能以及断口宏观和微观形貌，并结合预启阀阀碟现场工况条件对其开裂原因进行了分析。结果表明：由于该预启阀阀碟韧性和塑性较差，从而导致其在与止转销接触面承受较大胀紧力处发生脆性开裂；裂纹起源于阀碟与止转销接触的内表面中心处，材料内部的密集孔洞连接形成最初的微裂纹，晶界析出的碳化物使得材料整体抗裂纹扩展能力变差，裂纹随后发生快速扩展并彼此连接成大裂纹，最终导致阀碟开裂失效。

The chemical compositions, microstructure, mechanical properties, and macroscopic and microscopic fracture morphology of an equalizing valve disc were analyzed by using channel alloy analyzer, optical microscope, tensile and impact testing machines, and scanning electron microscope. And the cracking causes of the equalizing valve disc were analyzed in combination with the site conditions. The results show that due to the poor toughness and plasticity of the equalizing valve disc, brittle cracking happened at the contact position with the anti-rotating pin where there was a large expansion force. Cracks originated from the center of the inner surface of the valve disc in contact with the anti-rotating pin, and the dense cavities in the material connected to form the initial micro-cracks. The carbides precipitating at the grain boundaries deteriorated the overall crack propagation resistance of the material, so the cracks expanded rapidly and connected to each other to form large cracks, which eventually caused the valve disc to crack.