某石化装置上使用的异径三通管件在水压试验过程中出现了泄漏。采用宏观观察、化学成分分析、金相检验、断口及能谱分析、力学性能试验等方法对该异径三通管件的泄漏原因进行了分析。结果表明：该异径三通管件本身存在铸造夹杂(渣)和制管过程中产生的折叠缺陷，在冷挤压过程中沿原始缺陷在变形量最大的过渡径部位产生裂纹，因而在后续水压试验时发生泄漏。

The reducing tee pipe fitting used in a petrochemical plant leaked during the hydrostatic test. The leakage causes of the reducing tee pipe fitting were analyzed by means of macro observation, chemical composition analysis, metallographic examination, fracture and energy spectrum analysis, mechanical property test. The results show that there were casting inclusions (slag) and folding defects in the process of pipe making. In the process of cold extrusion, cracks occurred along the original defects at the transition diameter part with the largest deformation, so leakage occurred in the subsequent hydrostatic test.