超超临界锅炉Super304H过热器失效分析

Analysis on Failure of Super304H Steel Superheater in Ultra Supercritical Boiler

某电厂超超临界锅炉Super304H过热器发生泄漏,采用宏观形貌、化学成分分析、硬度试验、金相组织、扫描电镜及强度校核等方法对泄漏管段进行分析。结果表明:后屏过热器水平管段内部介质流动不畅,介质的冷却作用降低,管壁直接被外部烟气加热,超过了材料许用温度,当管内最大应力达到该温度下的抗拉强度时发生短时过热爆管。。

A leakage accident of Super304H steel superheater in ultra supercritical boiler of a power plant occured. The failure analysis for the leakage pipe was carried out by macro morphology, chemical composition analysis, hardness test, metallography, scanning electron microscopy and intensity.The results show that the flow of internal meditm behind screen superheater in horizontal section is not fluent, so the cooling effect reduces greatly, and the tube is directly heated by external flue gas, then ,the temperature is significantly higher than the material allowing temperature range. The short-term overheating explosion for tube occurs when the maximum stress reaches the tensile strength which is at allowed temperature.