高温高圧純水におけるSUS304鋼の応力腐食割れ

溶存酸素量およびひずみ速度の影響

抄録

This study was made to investigate the effects of dissolved oxygen, strain rate and solution treatment temperature on the stress corrosion cracking (SCC) of the sensitized SUS304 stainless steel. For the specimens solution-treated at 1373K, the high IGSCC susceptibility was attributed to Cr-depleated zone and the segregation of phosphorus in the water with dissolved oxygen. However, in the deaerated water, the IGSCC susceptibility decreased. As the solution treatment temperature increased, the degree of sensitization evaluated by Strauss test decreased owing to a narrow Cr-depleated zone. In a slow strain rate test (SSRT), IGSCC susceptibility increased with decrease in the strain rate independent of the solution treatment temperature. But, for the specimens solution-treated at 1573K, SSRT results were not correspondent with Strauss results, that is, SSRT was a severe test compared with corrosion tests such as Strauss test. It was found that the electrolytic conductivity of high temperature water in SSRT was higher on sensitized specimens than on solution-treated specimens. This increase in the electrolytic conductivity seems to be related to the pit formation at the grain boundaries of the sensitized specimens.