某电厂亚临界机组锅炉末级过热器钢管在原定位滑块焊接处发生泄漏。采用宏观检验、力学性能试验、金相检验、扫描电镜以及能谱分析等方法对钢管泄漏原因进行了分析。结果表明：焊接工艺执行不当造成钢管在焊接定位滑块时局部管壁组织发生相变，钢管热影响区在长期运行后抗蠕变性能下降是导致钢管在运行时发生泄漏的主要原因。

Leakage occurred in the weld on the original positioning slider of steel pipe of boiler final superheater of subcritical unit in a power plant. The leakage causes of steel pipe were analyzed by macroscopic inspection, mechanical property test, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that phase transformation in the local pipe wall was caused by improper welding process during welding positioning slider of steel pipe. The creep resistance of steel pipe in heat-affected zone decreased after long-term operation, which was the main cause for leakage of steel pipe in operation.