某电厂低温过热器管泄漏原因分析

Failure Analysis Report on Leakage of Low-Temperature Superheater

摘要: 以某630 MW亚临界燃煤发电机组低温过热器泄漏管段为研究对象，开展系统性失效分析研究。通过对原始泄漏管段及相邻吹损管段进行宏观检验、室温拉伸试验、布氏硬度测试与金相组织分析等综合表征，深入揭示了其失效的根本原因及演化机制。分析表明：失效直接源于低温过热器管屏弯头外弧面发生严重局部壁厚减薄，最薄处壁厚不足3 mm，显著低于设计要求(公称壁厚6 mm)，致使该处有效承载截面显著缩减，最终在正常运行应力作用下发生韧性过载断裂。材料基础力学性能及基体显微组织均满足SA-210C标准技术要求，未发现因长期过热、组织老化或严重腐蚀导致的显微组织劣化。

Abstract: Based on the leakage section of a low-temperature superheater in a 630 MW subcritical coal-fired power generation unit, a systematic failure analysis study was conducted. Through comprehensive characterization methods including macroscopic inspection, room-temperature tensile testing, Brinell hardness testing, and metallographic analysis of the original leakage section and adjacent erosion-damaged sections, the root cause and evolution mechanism of the failure were thoroughly revealed. The analysis shows that the failure was directly caused by severe local wall thinning on the outer arc surface of the low-temperature superheater tube panel bend, with the minimum wall thickness less than 3 mm, significantly below the design requirement (nominal wall thickness 6 mm). This resulted in a substantial reduction in the effective load-bearing cross-section, ultimately leading to ductile overload fracture under normal operating stress. Both the basic mechanical properties and the matrix microstructure of the material met the technical requirements of the SA-210C standard, with no evidence of microstructural degradation due to long-term overheating, aging, or severe corrosion.