高張力鋼の海水中 Zn 犠牲陽極下での疲れき裂伝播とその下限界値

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Fatigue crack growth rates, da/dN, and their thresholds, ⊿K_<th>, have been examined in sea water at zinc potential, sea water, and air, using seven kinds of 102-165kgf/mm^2 grade steels at the frequency of 0.167Hz and 20Hz and at the stress ratio of 0.10 and 0.70. The following results are mainly obtained. 1) At the zinc potential, the effect of corrosion control against fatigue crack growth of 100-120kgf/mm^2 grade steels is observed to be beneficial when ⊿K<55-60kgf/mm^<3/2> at the stress ratio of 0.10 and at the frequency of 0.167Hz. The value of ⊿K, however, decreases to 30kgf/mm^<3/2> for the 165kgf/mm^2 steel. 2) At the zinc potential, the effect of hydrogen on da/dN-⊿K curves is classified into two ; one is that for the plateau behavior (intergranular failure) which is sensitive to temper brittleness and the other is for the threshold ⊿K_<th> (trangranular failure) which is insensitive to that. 3) The value of ⊿K_<th> gradually decreases with increase of yield strength. At the zinc potential, the value decreases catastrophically at the yield strength of more than about 120kgf/mm^2 due to hydrogen.
社団法人日本鉄鋼協会の論文
1983-09-01