某苯乙烯装置中氢压机四级气缸东侧吸气阀在运行中发现其阀座密封面有部分区域断裂。通过宏观分析、低倍分析、化学成分分析、金相检验、硬度测试和扫描电镜分析等方法，对阀座密封面断裂的原因进行了分析，并提出了相应的措施。结果表明：阀座因热处理工艺不当，在阀座上表面外圈台阶部分金属损伤处形成疲劳裂纹，并在工作过程中向两端不断扩展，在交变载荷的作用下阀片内的弹簧断裂，导致裂纹处应力更加集中和阀座承载能力下降，加快阀座疲劳裂纹的扩展，最终导致阀座密封面部分区域断裂损伤。

Some area on the sealing surface of valve seat of suction valve on the east side of the four-stage cylinder of hydrogen compressor in a styrene plant fractured in operation. The fracture causes of the sealing surface of valve seat were analyzed by means of macro analysis, low power analysis, chemical composition analysis, metallographic examination, hardness test and scanning electron microscope analysis, and the corresponding measures were put forward. The results show that due to the improper heat treatment process, the fatigue crack was produced by the metal damage of the outer ring step on the upper surface of the valve seat and extended to both ends continuously in working process. Under the action of alternating load, the springs in valve broke, which resulted in more concentrated stress at the crack and decreased bearing capacity of the valve seat, accelerated the fatigue crack growth of the valve seat, and finally led to the fracture of some area on the sealing surface of valve seat.