蠕变历程中电厂承压材料SA508-Ⅲ钢的细观应力研究

长期服役温度下(300℃以上)的承压容器及管道极易发生热老化和高温蠕变,微观组织表征为晶内粗大第二相粒子、晶界粗化和蠕变空洞,因而材料的细观非均匀性也使得细观应力分析变得更加复杂。首先详细阐述了Eshelby等效夹杂理论,针对电厂服役承压材料SA508-III钢的微观组织变化,当基体中夹杂一种掺入体时,即稀疏材料系统(夹杂数量少)结合蠕变第一阶段和第二阶段初期,非稀疏材料系统则结合蠕变第二阶段中期,分别进行掺入体的细观应力应变分析,并计算在温度变化或有外载荷作用时的应力和转变应变。在此基础上,进一步结合承压材料在蠕变第二阶段后期和第三阶段微观组织特征,推导了基体中夹杂两种不同掺入体的转变应变及弹性模量。

THE MICRO-STRESS IN PRESSURE BEARING STEEL SA508-Ⅲ IN POWER PLANT DURING CREEP PROCESS

At the long-term service temperature(above 300 ℃), the pressure vessels and the pipelines are prone to thermal aging and high-temperature creep. The microstructure is characterized by the coarse second phase particles, the grain boundary coarsening and the creep cavities, so the microstructure heterogeneity of the material makes the micro-stress analysis very complicated. Firstly, the Eshelby’s equivalent inclusion theory is elaborated in detail. In view of the microstructure change of the pressure bearing Steel SA508-III in service in the power plant, when an inclusion is contained in the matrix, the sparse material system(with a small number of inclusions) combines the first and in the early of the second stage of creep, and the non-sparse material system combines in the middle period of the second stage of creep. The microscopic stress and strain analysis of the inclusions is performed, and the stress and the transition strain are calculated when the temperature changes or an external load is applied. On this basis, combining the microstructure characteristics of the pressure bearing materials in the final period of the second stage and the third stage of creep, the transformation strain and elastic modulus of the two different inclusions in the matrix are obtained.