Improvement of Creep Life Prediction of High Cr Ferritic Creep Resistant Steels by Region Partitioning Method of Stress vs.Time to Rupture Diagram
Kazuhiro KIMURA, Hideaki KUSHIMA and Fujio ABE
Abstract:Creep life prediction method has been investigated on 9-12Cr ferritic creep resistant steels in conjunction with region partitioning method of stress vs. time to rupture diagram. Region partitioning method of creep vs. time to rupture diagram has been discussed from a viewpoint of correspondence of breakdown observed in stress vs. time to rupture curves with both change in creep deformation behaviour and 0.2% proof stress. Good correspondence have been observed between breakdown in stress vs. time to rupture curve and the stress condition where the onset strain of tertiary creep stage is 0.012 and 1/2 of the 0.2% proof stress. It has been concluded that creep rupture data in the stress region less than 1/2 of the 0.2% proof stress should be used for a long-term creep life prediction by Larson-Miller parameter with a constant of 20. Key Words:Long-term creep strength, Prediction, High Cr ferritic creep resistant steel, Region partitioning method