对火力发电厂中在571 ℃使用约26万h后的2.25Cr-1Mo钢管焊接接头不同区域的显微组织进行了观察, 重点对热影响区的蠕变损伤程度进行了分析。结果表明: 该钢弯管焊接接头腹侧的热影响区主要为细晶组织, 接近设计寿命时细晶区内蠕变孔洞面积占比约为0.8%, 这可作为同种材料管道焊接接头蠕变失效的判据; 细晶区内部还存在大量的MnS夹杂物, 其附近多伴有孔洞和微裂纹, 是影响焊接接头蠕变寿命的一个因素。

In the current work, observation was performed on the microstructure of different regions on the welded joint of a 2.25Cr-1Mo steel pipe that had been operating at 571 ℃ for about 260 000 h in a power plant. The creep damge in heat affected zone(HAZ) was mainly analyzed. The results show that the HAZ of welded joint intrades was mainly fine-grained structure. The creep cavity area in fine-grained zone was about 0.8% when steel pipe approached the design life, which could be a criterion for the creep failure of welded joints made of the same material. There were many MnS inclusions inside the fine-grained zone accompanied by cavities and microcracks, which was a factor of affecting the creep life of the welded joint.