某电厂锅炉高温过热器管在运行过程中发生了泄漏。通过宏观观察、化学成分分析、金相检验及拉伸试验等方法对高温过热器管的泄漏原因进行了分析。结果表明：异物堵塞使冷却介质流量过低，管壁温度在短时间内突然上升，超过了12Cr2MoWVTiB钢的相变温度，管壁强度大幅降低。在内部蒸汽压力的作用下，管壁发生塑性变形，管径胀粗、管壁减薄，随后管壁发生剪切断裂而泄漏。

The high temperature superheater tube of a power plant boiler leaked during operation. The leakage causes of the high temperature superheater tube were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination and tensile test. The results show that the flow rate of cooling medium was too low due to the blockage of foreign matters. The temperature of tube wall rose suddenly in a short time, which exceeded the phase transformation temperature of 12Cr2MoWVTiB steel, and the strength of tube wall was greatly reduced. Under the action of internal steam pressure, the tube wall plastic deformation occurred, the tube diameter expanded and the tube wall thinned. Then the tube wall was shear fractured and leaked.