Creep-fatigue life evaluation for welding of modified 9Cr-1Mo steel

摘要

Modified 9Cr-1Mo steels have been used in boiler headers and pipes. To confirm the structuralintegrity of these components in further long-term operation, a series of basic creep-fatigue tests ofwelded joints was conducted. Welded joints were inclined to fracture at the heat-affected zone (HAZ)and the fatigue life was reduced by strain holding, mainly due to the creep strain concentration at theHAZ during holding and creep void occurrence at the HAZ due to plastic restraint. A life evaluationmethod is proposed based on the fracture mechanism. Prediction of experimental life times by thismethod proved that lives could be predicted within a factor of two.