SUS304鋼の高温流動ナトリウム中における低サイクル疲労特性

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Fatigue tests in sodium fluid at elevated temperatures were conducted to investigate the effect of sodium on low-cycle fatigue properties of SUS 304 stainless steel, which is the main structural material in FBRs. The tests were conducted at 500℃, 550℃ and 600℃ under the following condition; the sodium flow rate of 1m/sec, the cold trap temperature of 120℃, the strain rate of 1×10^<-3>/sec, and the total strain range from 0.3 to 1.9 % with triangular wave form. It was found that the fatigue lives in sodium were equal to or greater than those in air. Secondary cyclic hardening, which is considered to be caused by precipitation, was observed at 500℃ and 550℃ in the low strain range. This phenomenon was evident in sodium at 500℃ and was restrained by pre-precipitation which occurred during aging. Crack propagation was transgranular and striations were observed on the fracture surfaces. From the qualitative crack propagation analysis based on the measured striation spacing, it was shown that the propagation rate in sodium was almost the same as that in air. It was presumed that the difference in fatigue life was mainly caused by the difference in crack initiation time. Surface cracks found in sodium were fewer than those found in air. This observation shows that cracks are more difficult to initiate in sodium than in air. The reduction in crack formation was considered to be caused by the suppression of oxidation by the reducing atmosphere. It was presumed that the oxidation suppression caused the increase in crack initiation time.
社団法人日本材料学会の論文
1988-03-15

SUS304鋼の高温流動ナトリウム中における低サイクル疲労特性

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