オーステナイト鋼の疲労限改善に高濃度炭素は必要か：

ひずみ時効とひずみ集中

抄録

Carbon concentration dependence of fatigue limit in Fe-33Mn-xC (mass%) steels was investigated using rotating bending fatigue test at ambient temperature. The hardness increased with increasing carbon concentration, accordingly, the fatigue limit also increased. A factor increasing the fatigue limit by carbon is solution hardening. In addition, I noted the carbon concentration dependence of the fatigue limit normalized by hardness. The fatigue limit normalized by hardness increased with increasing carbon concentration up to 0.6%, but did not change with further increase of carbon content from 0.6% to 1.1%. The extraordinary increase in fatigue limit normalized by hardness in the Fe-33Mn-0.3C and Fe-33Mn-0.6C steels cannot be explained by hardness increase due to solution hardening. This fact implies that dynamic strain aging that occurs in the alloy system contributes to increase the fatigue limit. More interestingly, the effect of dynamic strain aging is not monotonically enhanced by increasing carbon concentration, namely, the optimal carbon concentration in the alloy system is 0.6% regarding fatigue limit improvement by the dynamic strain aging.