P91钢管道异常低硬度部位的组织和性能

对电厂运行过程中发现的P91钢主蒸汽管道的低硬度部位进行了微观组织观察、短时力学性能试验和高温持久强度试验,分析了其硬度偏低的原因。结果表明,低硬度区域P91钢组织为铁素体+析出物,位错密度较低,M₂₃C₆相在晶界处粗化聚集,同时析出新相Laves相,使得P91钢的短时力学性能和高温持久强度下降严重。

Microstructure and properties of P91 steel pipeline in abnormal low hardness parts

The causes of abnormal low hardness found in some parts of P91 steel main steam pipeline during operation of power plant were analyzed by microstructure observation,short-term mechanical properties test and high temperature creep rupture strength test.The results show that the microstructure in low hardness parts of the P91 steel is composed of ferrite and precipitates.The ferrite has a relatively low dislocation density,while the precipitate phases include coarsened M23 C6 phase aggregating at grain boundary,as well as a new precipitated phase of Laves type.Such a microstructure leads to serious reduction of the short-term mechanical properties and high-temperature durability of the P91 steel.