Patent ID: 10253398

Abstract:
The high-strength steel for steel forgings according to the present invention has a composition that includes, as basic components, C: 0.35 mass % to 0.47 mass %; Si: 0 mass % to 0.4 mass %; Mn: 0.6 mass % to 1.5 mass %; Ni: more than 0 mass % up to 2.0 mass %; Cr: 0.8 mass % to 2.5 mass %; Mo: 0.10 mass % to 0.7 mass %; V: 0.035 mass % to 0.20 mass %; Al: 0.015 mass % to 0.050 mass %; N: 30 ppm to 100 ppm, and O: more than 0 ppm up to 30 ppm, the balance being Fe and inevitable impurities. The metal structure is mainly bainite, martensite or a mixed structure of bainite and martensite. Among cubic B1-type precipitates, the number of coherent precipitates having a diameter equal to or smaller than 30 nm is equal to or smaller than 50/μm2.