X20CrMoV121钢长时间时效后材质状态试验分析

开展在役高温部件的材质状态检验,掌握设备的安全状态和寿命损耗,对保障设备的安全运行.合理地安排机组检修周期,降低检修成本等,具有重要意义.为了解设备的安全状态和寿命损耗,对某电厂经12万h长期运行后的X20CrMoV121钢制末级过热器管及高温再热器管进行了拉伸试验、显微组织分析及高温持久断裂试验.结果表明,运行管与原始管相比强度有所下降;沉淀相发生熟化,同时还出现了局部板条特征减弱,板条内出现亚结构,位错密度明显降低;高温持久强度仍然高于设计值.综合分析表明,经12万h长期运行后的X20CrMoV121管发生了一定程度的老化,但仍可满足设计工况下安全运行要求.

Analysis on X20CrMoV121 Steel After Long-Time Aging

It is of great significance to analyze the material status of high-temperature parts in service as well as its security status and life loss.It is good to the safety operation,reasonable arrangements for unit maintenance cycle and maintenance cost reduction,etc.In order to investigate the safety status and service life of equipment,elongation tests,microstructure analysis and high-temperature lasting strength tests on the final superheater and final reheater tubes made of X20CrMoV121 steel were conducted in one thermal power plant after 12 000-h service.The results show that compared with the original tubes,the strength of the tubes in service is getting lower and the crystal grain of precipitation phases is becoming larger and rounder.In addition the substructure appears in martensite laths and the dislocation density declines apparently.However the high-temperature permanent strength is still higher than the designed value.Comprehensive analysis concludes that although certain aging occurs to some extents after 12 000-h operation,the tubes can still satisfy the requirements of safe operation under the designed working conditions.