蔡志强，林雪松，邓永龙，落志祯

(四川省电力工业调整试验所，四川 成都　610072)



高温再热器Super304H与T91异种钢接头开裂失效分析

蔡志强，林雪松，邓永龙，落志祯

(四川省电力工业调整试验所，四川 成都610072)

摘要：对国内首台600 MW循环流化床锅炉外置床内的高温再热器Super304H与T91异种钢接头开裂进行了失效分析。分析结果表明开裂原因为结构设计不当,该管段不能自由膨胀；加上该焊接接头熔合区存在界面突变，容易引起应力集中，在高温环境下长期运行后，抗高温蠕变性能较差T91侧出现蠕变孔洞，在熔合区形成蠕变裂纹：因此最终发展为宏观裂纹而失效。根据分析结果，提出将该异种钢接头布置在密封盒上方，且增加接头至联箱之间管程弯头数量的整改方案。

关键词：循环流化床;异种钢接头;失效分析; 设计不当；蠕变孔洞;应力集中

Abstract：Failure analysis for the cracking of Super304H and T91 dissimilar steels welded joint of high-temperature reheater in external heat exchanger is carried out in the first 600 MW circulating fluidized bed (CFB) boilers in China. The analysis results show that the cracking reason is the improper structure design, and the section cannot expand because of that wound. Coupled with the existing mutation interface in weld bead boundaries where exist stress concentration, the T91 with poorer high-temperature creep resistant properties would firstly generate creep cavity under high temperature after running for a long time, and then the creep crack is occurred, which finally leads to creep failure. According to the analysis result, the improved scheme is proposed, that is, the arrangement of dissimilar steels welded joint will be decorated above the seal box and the number of elbow between the joint and the header should be increased.

Key words：circulating fluidized bed (CFB); dissimilar steels welded joint; failures analysis; improper structure design; creep cavity; stress concentration

引言

随着火力发电站向超超临界机组发展，由于温度和压力等高参数的影响，锅炉受热面管对材质的要求越来越高，具有高热强性和高抗氧化性的铬镍奥氏体不锈钢(Super304H)及马氏体耐热钢(T91)便大量出现在锅炉受热面的高温高压段，因此就难免出现该两类钢种的异种焊接问题[1-2]。但由于这两类钢的化学成份、金相组织、机械性能及热膨胀系数存在较大差异，焊材的选择又通常是采用低匹配原则，容易导致在焊接接头两侧的熔合区产生较为复杂的金相组织及化学成分的不均匀性，使焊接接头在使用过程产生过早失效[3]。

国内……