INHERENT CREEP STRENGTH AND LONG-TERM CREEP STRENGTH PROPERTIES OF FERRITIC STEELS

Inherent creep strength is defined as a constant creep strength indepe ndent of time and microstructure. Sigmoidal inflection of a relation b etween stress and time to rupture is explainable in terms of a loss of creep strength followed by the advent of inherent creep strength. Alt hough a large variation of short term creep rupture strength is observ ed, inherent creep strength is evaluated to be almost the same for sev eral low alloy Cr-Mo steels. Creep rupture strength of the 12Cr-1Mo-1W -0.3V steel is higher than the other steels investigated in the short term region, however, it decreases with decrease in stress abruptly an d it is almost the same as common inherent creep strength for low allo y Cr-Mo steels. On the other hand, creep rupture strength of the modif ied 9Cr-1Mo steel is higher than the other steels even at low stresses . (C) 1997 Elsevier Science S.A.