冷間加工を施したオーステナイト質ステンレス鋼のMgCl₂水溶液中における応力腐食割れ

抄録

The effect of cold-working on the stress corrosion cracking sensitivity of five austenitic stainless steels in boiling 42%MgCl₂ solution was studied using beam type specimens. On 18-8, 18-8Nb and 25-20, the apparent threshold stress, below which any crack did not appear in the specimen within the maximum period of experiment,rose with the cold-reduction. Of these steels, 18-8 and 18-8Nb were partially transformed from austenite to ferrite by cold-rolling, and this ferritic phase was preferentially attacked in the solution. As to 25-20, the annealed austenitic structure was still stable after cold-rolling. All these three steels, however, suffered from general corrosion in their hardened state. But in the other two steels, 18-12Mo and 18-20MoCu, both of which contain Mo, the apparent thereshold stress scarecely rose with cold-reduction. In these two steels, the general corrosion rate in the solution was very low even in their hardened condition.