溴化锂机组不锈钢焊接管腐蚀失效的原因

Corrosion Failure Reasons for Stainless Steel Welded Tube in Lithium Bromide Units

通过外观、显微组织、化学成分、扫描电镜和能谱分析等检测方法,对溴化锂机组发生器436L不锈钢焊接管和吸收器304不锈钢焊接管焊缝附近的腐蚀失效进行了分析。结果表明:436L焊管内有氯化物和盐粒,其腐蚀泄漏主要是由氯化物点蚀引起的;304不锈钢管点蚀坑及其附近富集硫元素,该处发生了由硫或硫酸盐引起的微生物腐蚀;建议采用等轴晶化处理,激光焊接铁素体不锈钢管等措施提高焊缝质量;管子安装时焊缝应置于上方,试车时用纯净的水,长期停机应保持干燥。

The corrosion failure reasons for 436 Lstainless steel welded tube of generator and 304 stainless steel welded tubes of absorber in lithium bromide units were analyzed by detection methods of macrograph,microstructure,chemical composition,SEM and EDS analysis.The results show that there were chloride and salt in the 436 Lwelded tubes.The pitting corrosion caused by chloride was the main reason for corrosion and leak of the tubes.The sulfur element near the pits of 304 stainless steel tubes was elevated abnormally,where microbiological corrosion because of sulfur and sulfate happened.The equiaxed grain crystallization processing and laser welding of ferritic stainless steel tube were suggested to improve the quality of weld.Moreover,the welds should be put on the top during installing,and pure water should be used during the test and the tubes should be kept dry during the long-term shutdown.