Patent ID: 10060005

Abstract:
A high-strength hot-formed steel sheet member exhibiting both a consistent hardness and delayed-fracture resistance, and is characterized in that: the high-strength hot-formed steel sheet member has a prescribed chemical composition; the degree of Mn segregation α (=[maximum Mn concentration (mass %) at the sheet center in the thickness direction]/[average Mn concentration (mass %) at a depth of ¼ of the total thickness of the sheet from the surface]) is less than or equal to 1.6; the steel purity value as defined in JIS G 0555 (2003) is less than or equal to 0.08%; the average grain size for prior γ grains is less than or equal to 10 μm; and the number density of the residual carbides is less than or equal to 4×103 particles/mm2.