T91/HR3C异种钢焊接接头裂纹原因分析

Reason analysis on crack appeared in welded joints of dissimilar heat-resistant steel T91/HR3C

对某台1 000MW机组锅炉高温过热器管的T91/HR3C异种钢焊接接头裂纹进行了宏观检验、材质检验及焊接、热处理工艺分析,认为接头裂纹为淬硬脆化焊接冷裂纹,开裂主要由未严格执行焊接工艺,焊缝错口量大引起高拘束应力所致。T91属于马氏体耐热钢,在空冷状态下会形成马氏体,而焊接时其T91侧更易形成淬硬倾向更大的马氏体,发生冷裂。

Aiming at finding the cause of cracks at welded point of T91/HR3C dissimilar heat-resistant steels for high temperature superheater in 1 000 MW unit of a power plant,various tests such as macroscopic examination,material evaluation and welding,heat treatment process analysis were conducted.Results showed that,the cracks are cold crack,and large restraint stress caused by no weld preheating was considered as the main reason.Because the T91 steel is martensitic heat resistant steel,it will form martensite at air cooling condition,while during welding,martensite with high harden quenching tendency will be formed more easily,so the cold crack happens.