Patent ID: 7833363

Claim:
A method for producing a high-strength forged part, the method comprising holding steel at a temperature of (Ae1 point—30° C.) to (Ae3 point—30° C.) for 10 seconds or more; allowing the steel to be forged at that temperature; thereafter cooling the steel to a temperature of 325° to 475° C. at an average cooling rate of 3° C./s or more; and holding the steel in that temperature range for 60 to 3600 seconds to produce the high-strength forged part, wherein the steel contains the following components in mass %: C: 0.1% to 0.5% Si + Al: 0.5% to 3% Mn: 0.5% to 3% P: 0.15% or less S: 0.02% or less, before holding the steel at the temperature of (Ae1 point—30° C.) to (Ae3 point—30° C.), the steel has untempered bainite structure, quenched bainite structure, untempered martensite structure, or quenched martensite structure; the high-strength forged part comprises a base phase structure and a second phase structure; the base phase structure contains 50% or more of tempered bainite or tempered martensite in terms of a space factor relative to the entire structure; the second phase structure contains retained austenite and martensite; the content of the retained austenite is 3% to 30% in terms of a space factor relative to the entire structure; and a portion of the retained austenite and martensite, which portion is 2 or less in an aspect ratio, is 25% or less in terms of a space factor.