Review of allowable stress and new guideline of long-term creep strength assessment for high Cr ferritic creep resistant steels

Abstract

A large drop in creep rupture strength in the long-term is a noticeable phenomenon for high Cr ferritic creep resistant steels, since it may result in overestimation of 100,000 h creep rupture strength, and allowable stress. A program for assessment of long-term creep strength and review of current allowable stress of high Cr ferritic creep resistant steels has been conducted in Japan. Provisional rules for revised allowable stress and new life prediction method for those materials have been set up at the beginning of 2005. In this paper, the contents of those rules will be presented.

Keywords:

• creep
• allowable stress
• ferritic steel
• long-term creep strength
• Larson –Miller parameter