高温水中における低合金鋼の応力腐食割れに及ぼす溶存酸素及び温度の影響

抄録

The effects of dissolved oxygen concentration and temperature on the susceptibility to SCC of low alloy steels in pure water have been studied by means of slow strain rate tensile test (SSRT). The results obtained are summarized as follows: 1) The effect of dissolved oxygen on the susceptibility to SCC appears more clearly at the high temperature range from 200 to 288°C, and the susceptibility to SCC decreases with decreasing dissolved oxygen concentration. On the other hand, the susceptibility to SCC in water containing dissolved oxygen concentration from 0.2 to 8ppm becomes almost the same at the low temperature range belows 150°C. 2) The susceptibility to SCC increases with rising temperature in the case of high dissolved oxygen of 8ppm, but passes through a maximum at the temperatures below 288°C in the case of low dissolved oxygen of 0.2 and 2ppm. 3) Pitting corrosion occurs in water containing 0.2, 2 and 8ppm of dissolved oxygen at temperatures ranging from 50 to 288°C. SCC nucleates at corrosion pits, and correlation is found between the susceptibility to SCC and the number of corrosion pits.