某动力站碱液输送泵泵轴在运行期间发生断裂，通过断口分析、化学成分分析、金相检验、硬度测试、拉伸试验和垢样分析等方法对泵轴断裂原因进行了分析。结果表明：泵轴断裂一方面是因为泵轴材料没有进行调质处理，疲劳强度降低；另一方面是因为输送泵机械密封不良造成碱液泄漏，生成的结晶物使轴套间的间隙阻塞，导致泵轴动作不灵甚至卡死，增加了泵启动的阻力和轴的扭矩，从而使泵轴发生了疲劳脆性断裂。

The pump shaft of a power station lye transportation pump fractured during operation, and the fracture reasons of the pump shaft were analyzed by means of fracture analysis, chemical composition analysis, metallographic examination, hardness test, tensile test, scale analysis and so on. The results show that the fracture of the pump shaft was partly because the shaft material was not quenched and tempered, which decreased its fatigue strength. On the other hand, the leakage of lye due to poor mechanical seal of the transportation pump resulted in the blockage of the clearance between the shaft sleeves by the resulting crystals, which made the pump shaft movement ineffective or even stuck. So the resistance of the pump and the torque of the shaft were increased, and fatigue brittle fracture occurred to the pump shaft.