金属間化合物析出強化型9Cr-7Mo鋼の高温特性に及ぼすNiの影響
1996 年 82 巻 1 号 p. 87-91
詳細
1996 年 82 巻 1 号 p. 87-91
Since ferritic steels strengthened by intermetallic precipitates exhibited excellent creep strength compared with any other commercial steels, they are promising core materials for advanced fast breeder reactors. It is, however, worried that their ductile-brittle transition temperature (DBTT) increases markedly during service. Therefore, in order to improve the room temperature ductility of 9Cr-7Mo steels after aging with keeping high creep strength, influence of Ni addition on them were investigated.
The tensile properties of the specimens aged for 100h at 823K and 923K were markedly improved by Ni addition. And creep rupture strength at 923K was also improved with increasing amount of Ni addition. The α to γ transformation was partially observed in the specimens containing more than 6mass%Ni after creep testing. The formation of austenite would be effective to improve the long term creep strength, but it increases void swelling. The optimum Ni content in 9Cr-7Mo steel was approximately 3mass% for application of the fast breeder reactor core materials, considering the DBTT and the resistance to swelling.
