Steel Member And Steel Sheet

Abstract: A steel member according to the present invention has a specific chemical composition, and if a position corresponding to 1/4 the thickness from the surface in the thickness direction is taken as the 1/4 depth position, the metal structure at the 1/4 depth position contains, in volume fractions, 90% or more of martensite. With respect to the metal structure at the 1/4 depth position, among the crystal grains each having a body-centered structure, the ratio (L49-56°)/(L4-12°) of the length L49-56° of a grain boundary having a rotation angle of 49° to 56° to the length L4-12° of a grain boundary having a rotation angle of 4° to 12° is 1.10 or more as measured using the <011> direction as the rotation axis; and the tensile strength is more than 1,500 MPa.

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