Development of 14Cr-25Ni advanced austenitic steels(III); Out of piles tensile and thermal creep properties evaluation

Otsuka, Satoshi   ; Uwaba, Tomoyuki ; not registered  ; Mizuta, Shunji 

14Cr-25Ni advanced austenitic steels (14Cr-25Ni steel) was developed in order to improve the swelling resistance of modified 15Cr-20Ni base austenitic steels(PNC1520). This steel is planned to be utilized as back-up material for Monju advanced core component. Seven types of cladding tubes with different amounts of alloying elements of Ti, Nb, V and P had been fabricated and the out-of-pile testing of these cladding tubes has been conducted. Among out of piles properties, tensile property and creep property of 14Cr-25Ni steels were evaluated in this study. The results can be summarized as follows. (1)Tensile properties (0.2% yield stress, ultimate tensile strength, uniform elongation, ultimate elongation) of 14Cr-25Ni steels were almost equivalent to those of PNC316 steel and PNC1520 steel in the temperature range from room temp. to 900C. (2)The creep strength of 14Cr-25Ni steels was between PNC316 and PNC1520. It was shown that the long term creep strength at 750C was remarkably improved by the Ti, Nb and V addition. (3)It is suspected that the improvement of creep strength of V-added-steel would be caused by stabilization of dislocation microstructure due to finely distributed carbo-nitride [Ti, Nb, V(C, N)] precipitates.