Patent ID: 7314532

Claim:
A high-strength forged part comprising a base phase structure and a second phase structure and containing the following components in mass % (also in the following): C: 0.41% to 0.6% Si+Al: 0.5% to 3% Mn: 0.5% to 3% P: 0.15% or less (not including 0%) S: 0.02% or less (including 0%), wherein the base phase structure contains 30% or more of ferrite in terms of a space factor relative to the entire structure, the second phase structure comprises retained austenite, as well as bainite and/or martensite, the content of the retained austenite is represented by the following expression (1) relative to the entire structure, an average grain diameter, d, of the second phase structure is 5 μm or less, and a space factor of a coarse portion of (1.5×d) or more in an average grain diameter contained in the second phase structure is 15% or less: 50×[C]<[V γR ]<150×[C] (1) where [V γR ] stands for a space factor of the retained austenite relative to the entire structure and [C] stands for the content (mass %) of C in the forged part.