日本金属学会誌

J. Japan Inst. Metals, Vol. 51, No. 4 (1987),
pp. 350-355

Effects of Chromium Content and Sodium Velocity on the Compatibility of High-Cr Ferritic Steels in a Sodium Environment

Isao Mutoh1 and Tadashi Suzuki1

1National Research Institute for Metals. Tsukuba Laboratories, Sakura-mura, Ibaraki

Abstract:

To obtain fundamental data on the compatibility of high-chromium ferritic steels in sodium, high-purity Fe-0.1C-1Mo-5, 9 or 13Cr ferritic steels were prepared by vacuum melting. Test specimens of these steels which were normalized and tempered and a reference type 316 stainless steel (316 ss) were exposed to two sodium-velocity regions for periods up to 10.8 Ms in a sodium loop system which had a direct resistance main heater and was made of SUS 316. The test temperature, the maximum temperature, of the loop system in this work was 873 K, the oxygen content of sodium was 1--2 ppm, and the sodium velocities were about 4.0 and 0.02 m/s. The specimens exposed to the high sodium-velocity region revealed that corrosion loss at a zero downstream position of the three kinds of ferritic steels was smaller than that of the reference 316 ss; about one fifth for the 5 and 9%Cr steels and one half for the 13%Cr steel. The surface analysis showed deposition of Ni that dissolved at upstream for all the ferritic steels, deposition of Cr for the 5%Cr steel, and selective dissolution of Cr for the 9 and 13%Cr steels. The ferritic steels without Ni and with less amounts of Cr than the reference 316 ss would result in their smaller corrosion loss than the 316 ss. Transfer of carbon, nitrogen and oxygen was not remarkable, except the carburization of the 5%Cr steel. The specimens of the three kinds of ferritic steels which were exposed to the low sodium-velocity region revealed much smaller corrosion loss than that in the high velocity region, deposition of both Ni and Cr, and no transfer of carbon, nitrogen and oxygen except for slight carburization of the 13%Cr steel.


(Received 1986/11/5)

Keywords:

liquid metal fast breeder reactor, sodium, high-chromium ferritic steel, type 316 stainless steel, sodium, compatibility, sodium velocity, sodium loop system, corrosion loss, nickel, chromium, carbon, deposition, selective dissolution, transfer


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