某超超临界直流锅炉高温再热器进口管异种钢（T91/HR3C）焊接接头在试运行168 h后出现开裂泄漏现象，通过宏观检验、化学成分分析、硬度测试、金相检验、断口分析等方法分析了该焊接接头开裂的原因。结果表明：不当的焊接工艺导致接头T91钢管侧热影响区晶粒粗化和过大的残余应力，在过大残余应力的作用下热影响区产生了IV型裂纹，并导致焊接接头的开裂泄漏。最后提出相应的防控措施。

Cracking leakage occurred to the T91/HR3C dissimilar steel welded joint used on high temperature reheater of an ultra-supercritical concurrent boiler after 168 h of service. The cracking causes of the welded joint were analyzed by means of macroscopic examination, chemical composition analysis, hardness test, metallographic examination, fracture analysis and so on. The results show that the improper welding process led to the coarsening and excessively large residual stress in the heat affected zone (HAZ) of T91 steel pipe side, and type IV cracks produced in the HAZ under the effect of excessive residual stress, which resulted in the cracking leakage of the welded joint. Corresponding suggestions were put forward at last.