Abstract
Heat-to-heat variation of long-term creep strength property observed for 12Cr steel was investigated from viewpoints of creep deformation behaviour and stability of microstructure. Heat-to-heat variations of creep deformation behaviour and creep rupture strength properties were described by the differences in the parameter α in a modifiedθprojection method which indicates the acceleration in creep rate at the tertiary stage. It was shown that the magnitude of α and its change with creep depend on the morphology and stability of initial microstructure, and correlate with microstructural changes accompanied by recovery and recrystallization under tertiary creep. It is concluded therefore that the creep strength and rupture life can be controlled by the microstructure and its stability of 12Cr steels and expressed only by the rate constant α.
