某亚临界电站锅炉屏式过热器异种钢焊接接头在运行过程中发生断裂。通过宏观观察、化学成分分析、力学性能试验、金相检验、微观分析等方法，对该异种钢焊接接头的断裂原因进行了分析。结果表明：屏式过热器接头两边母材蠕变强度差较大引起了该异种钢焊接接头的早期失效，同时焊接质量及成形不佳，焊接接头受到膨胀热应力、焊接残余应力、温度波动热疲劳等因素影响加速了此过程，最终导致该异种钢焊接接头断裂。

The dissimilar steel welded joint of platen superheater of a subcritical power plant boiler fractured during operation. The fracture causes of the dissimilar steel welded joint were analyzed by means of macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination and microscopic analysis. The results show that the difference of creep strength between the base metal on both sides of the platen superheater joint was large, which caused the early failure of the dissimilar steel welded joint. At the same time, the welding quality and forming were poor, and the welding joint was affected by expansion thermal stress, welding residual stress and temperature fluctuation thermal fatigue accelerated the process, which eventually led to the fracture of the dissimilar steel welded joint.