Abstract
The combined addition of Si and Cu is effective in order to improve the stress corrosion cracking（SCC）resistance in hot water environment, and SUS315J1（18Cr-10Ni-1.5Si-1Mo-3Cu）has been developed and put in practical use. But, the preset temperature of equipments for supplying hot water in recent years has tended to become high（near 100℃）. Moreover, the influence of anion-species included in hot water on SCC has not been confirmed yet.
The SCC resistance of various stainless steels was examined by the immersion test using spot-welded specimens in 200 mg/L Cl－ solution at 60, 95 and 125℃. The materials used were SUS304, SUS315J1, SUS316 and SUS444 cold-rolled steel. SUS315J1 showed the good SCC resistance compared with SUS304 and SUS316 at a temperature under 95℃.
The influence of various anion-species（NO3－, SO42－, CO32－ and HCO3－）on SCC was considered by the immersion test or electrochemical measurement in 200 mgL－1 Cl－ solution. These anion-species that generally act as a corrosion inhibitor performed as accelerator on SCC initiation in addition of a small amount of anions. However, SCC tended not to occur in SUS315J1 in these solutions.
