54 research outputs found
Proceedings of CREEP8 Eighth International Conference on Creep and Fatigue at Elevated Temperatures PVP2007-26406 REGION SPLITTING ANALYSIS ON CREEP STRENGTH ENHANCED FERRITIC STEELS
ABSTRACT Overestimation of long-term creep strength of creep strength enhanced ferritic steels is caused by inflection of a relation between stress and time to rupture. Creep rupture strength of those steels has been re-evaluated by a region splitting analysis and allowable tensile stress of some steels regulated in METI (Ministry of Economy, Trade and Industry) Thermal Power Standard Code in Japan has been reduced. A region splitting analysis method evaluates creep rupture strength in the short-and the long-term individually, which is separated by 50% of 0.2% offset yield stress. Inflection of stress vs. time to rupture curve is attributable to longer creep rupture life with a stabilized microstructure of creep strength enhanced ferritic steels, since tensile strength property, which determines short-term creep rupture strength, remains the same level. Accuracy of creep rupture strength evaluation is improved by region splitting analysis. Delta ferrite produces concentration gap due to difference in equilibrium composition of austenite and ferrite at the normalizing temperature. It increases driving force for diffusion and promotes recovery of tempered martensite adjacent to delta-ferrite. Concentration gap may be produced also in heat affected zone (HAZ), especially in fine grain HAZ similar to that in dual phase steel, and it has possibilities to promote recovery and, therefore, to decrease creep strength
Heterogeneous Recovery and Precipitation of Z Phase during Long Term Creep Deformation of Modified 9Cr-1Mo Steel
Precipitation of Z-phase and Precipitation Sequence during Creep Deformation of Mod.9Cr-1Mo Steel
Beneficial Effect of Re on the Long-term Creep Strength of High Cr Ferritic Heat Resistant Steels
Influence of Chemical Composition and Heat Treatment Condition on Impact Toughness of 15Cr Ferritic Creep Resistant Steel
Effect of Initial Microstructure on Long-term Creep Strength Properties of 2.25Cr-1Mo Steel
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