Fatigue limit ratio to excellent high-strength hot forging non-heat treated steel parts

摘要

PROBLEM TO BE SOLVED: To provide a hot forged non-heat treated steel component having excellent tensile strength and fatigue limit ratio even as-hot forged.;SOLUTION: (1) The high strength hot forged non-heat treated steel component has a composition comprising 0.10 to 0.50% C, 0.05 to 2% Si, 0.3 to 3% Mn, 0.005 to 0.1% Al, ≤0.05% P, ≤0.5% S, ≤0.003% O, ≤0.02% N, and at least Nb and/or Ti among Nb, Ti and V, and in which V may be comprised, where, in the case Nb is comprised, ≤0.2% Nb is satisfied, in the case Ti is comprised, ≤0.20% Ti, 0.010% N and Ti/N≥3.4 are all satisfied, in the case V is comprised, ≤0.6% V is satisfied, and the balance Fe with inevitable impurities. (2) In ferrite, Nb and/or Ti-containing precipitates (wherein, V may be comprised as well) are comprised, and the above precipitates with the average particle diameter of ≤15 μm in which prescribed MP value satisfies MP≥0.05 are comprised by ≥50 pieces/μm².;COPYRIGHT: (C)2008,JPO&INPIT