Patent ID: 10988819

Abstract:
A high-strength steel material that has a chemical composition containing, by mass %, C: 0.30 to 1.0%, Si: 0.05 to 1.0%, Mn: 16.0 to 35.0%, P: 0.030% or less, S: 0.030% or less, Al: 0.003 to 0.06%, N: 0.1% or less, V: 0 to 3.0%, Ti: 0 to 1.5%, Nb: 0 to 1.5%, Cr: 0 to 5.0%, Mo: 0 to 3.0%, Cu: 0 to 1.0%, Ni: 0 to 1.0%, B: 0 to 0.02%, Zr: 0 to 0.5%, Ta: 0 to 0.5%, Ca: 0 to 0.005%, Mg: 0 to 0.005%, and the balance: Fe and impurities, and that satisfies [V+Ti+Nb>2.0], in which: a number density of carbides/carbo-nitrides having a circle-equivalent diameter of 5 to 30 nm precipitating in the steel is 50 to 700/μm2, and a number density of carbides/carbo-nitrides having a circle-equivalent diameter of more than 100 nm precipitating in the steel is less than 10/μm2; a yield stress is 758 MPa or more; and a KISSC value obtained in a DCB test is 33.7 MPa·m0.5 or more.