蠕变抗力恢复热处理对21/4Cr-1Mo钢焊接接头蠕变空洞形态及其分布的影响

Effects of Creep Strength Recovery Heat-treatment on Morphology and Distribution of Creep Voids for a 21/4 Cr-1Mo Steel Welding Joints

本文用光镜(OLM)、扫描电镜(SEM)分析了一段已服役约210000h 的电厂再热蒸汽管道焊接接头蠕变空洞的分布形态;分析了两种恢复热处理工艺(亚临界温度热处理和正回火热处理)对蠕变空洞形态及其分布的影响.试验结果表明,两种恢复热处理工艺都能减少蠕变空洞的数量,改善蠕变空洞的形态及其分布,使蠕变空洞由原来不规则的形状变成球形,使原来主要分布在晶界处的蠕变空洞部分“迁移”到晶内,从而改善了晶界处的应力状态,提高了蠕变抗力.比较两种恢复热处理工艺对减少蠕变空洞的数量,以及对改善螭变空洞的形态及其分布的作用后发现,正回火工艺优于亚临界温度热处理工艺.

The morphology and distribution of creep voids for a service exposed (about 210000h.) 2(1/4)Cr-1Mo steel reheat steam piping weldment are examined before and after creep strength recovery beat-treatment.Effects of both the subcritical reheat-treatment and normalizing reheat-treatment on the morpholgy and distribution of crcep voids are evaluated.The results show that both of the reheat-treatments could reduce the number of voids,improve the morphology and distribution of voids,which became spherical from irregular forms,migrated to grain boundaries from the inside of grain.As compared with the subcritical reheat-treatment,the normalizing reheat-treatment has better effect on the morphology and distribution of creep voids.