Development of high chromium steel for SFR in Japan and creep-fatigue assessment of the welded joint

液体金属炉用高クロム鋼の開発と溶接継手クリープ疲労強度評価法の開発

若井 隆純 ; 磯部 展宏*; 伊達 新吾*; 浅山 泰 ; 久保 重信* 

Wakai, Takashi; Isobe, Nobuhiro*; Date, Shingo*; Asayama, Tai; Kubo, Shigenobu*

This paper describes the provisional material specifications of the high chromium (Cr) ferritic steel for the Sodium cooled Fast Reactor (SFR) and development of creep-fatigue assessment procedure for the welded joint made of the steel. Based on the results of mechanical tests and metallurgical examinations, provisional specifications of the high Cr steel for SFR pipes and tubes were proposed. Creep-fatigue strength assessment procedure for the welded joints made of the steels was also investigated. An assessment procedure using 2-element model was proposed and verified by comparing with some creep-fatigue test results. The creep-fatigue lives observed in the experiments were well predicted by the proposed assessment procedure, but the failure point could not be predicted by the model. For more precise creep-fatigue strength assessment, the characteristics of the HAZ must be accounted for.