A533B圧力容器用鋼の高温水中における疲労き裂進展挙動に及ぼす熱時効の影響

概要

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The fatigue crack growth behavior of A 533 B steel which was subjected to PWHT and stepcooling heat treatments was examined in a simulated BWR water environment and in air. The test variables investigated included thermal aging effect, frequency variation over the range 0.05 to 0.5 Hz, and R-ratios of 0.1 and 0.5. The physical and metallographic examinations were carried out using transmission and scanning electron microscopes, and Auger spectroscopy. The results show that the thermal aging such as the step-cooling has no noticeable effect on the fatigue crack growth behavior both in air and 288℃ water environment. The crack growth rate in 288℃ water environment is accelerated when frequency decreased and stress ratio increased. The acceleration of the crack growth rate may be due to occurrence of quasi cleavage associated with hydrogen embrittlement.
1999-02-25