P91末过出口导管硬度异常分析

Abnormal hardness analysis of exit pipe of P91 superheater

某电厂锅炉末级过热器出口导汽管弯头硬度值偏低,为查清原因,对试样进行化学成分分析、常温拉伸试验、高温拉伸试验、硬度测试、金相组织分析。结果表明:该弯头成分符合要求,常温和高温力学特性不符合要求,金相组织不是回火托氏体组织;判定P91弯管热处理工艺控制不严,回火温度偏高,得到回火索氏体组织,导致硬度降低,力学特性变差。

In a certain power plant,exit pipe elbows of final stage of superheater are at lower hardness. In order to find out the reason,chemical composition analysis,mechanical properties test at room temperature and high temperature,hardness test, microstructure observation were carried out. The results show that the composition is eligible,the mechanical properties fall short of request,The microstructures are not tempered troostite. The reasons of lower hardness and worse mechanical properties of P91 elbow are that the heat treatment process isn’t controlled strictly,the tempering temperature is on the high side,which results in tempered sorbite.