Steel member and steel sheet

A steel member comprising, as a chemical composition, by mass %:

• C:
• 0.26% to 0.65%;
• Si:
• 0% to 2.00%;
• Mn:
• 0% to 3.00%;
• P:
• 0.100% or less;
• S:
• 0.0100% or less;
• N:
• 0.020% or less;
• O:
• 0.010% or less;
• W:
• 0.10% to 2.00%;
• Nb:
• 0% to 0.10%;
• Ti:
• 0% to 0.200%;
• Cu:
• 0% to 2.00%;
• Ni:
• 0% to 2.00%;
• Cr:
• 0% to 1.00%;
• B:
• 0% to 0.0200%;
• Mo:
• 0% to 1.00%;
• V:
• 0% to 1.00%;
• Ca:
• 0% to 0.020%;
• Mg:
• 0% to 0.010%;
• Al:
• 0% to 1.00%;
• Sn:
• 0% to 1.00%;
• Sb:
• 0% to 1.00%;
• Zr:
• 0% to 1.00%;
• Se:
• 0% to 1.00%;
• Bi:
• 0% to 1.00%;
• As:
• 0% to 1.00%;
• Ta:
• 0% to 1.00%;
• Re:
• 0% to 1.00%;
• Os:
• 0% to 1.00%;
• Ir:
• 0% to 1.00%;
• Tc:
• 0% to 1.00%;
• Co:
• 0% to 1.00%;
• REM:
• 0% to 0.30%;
• and
• a remainder:
• Fe and impurities,
• wherein, when a range of a ⅛ position to a ⅜ position of a thickness in a thickness direction from a surface of the steel member, with respect to a ¼ position of the thickness in the thickness direction from the surface as a center, is defined as a ¼ depth position,
• in a case where, at the ¼ depth position, with a <011> direction as a rotation axis, among grain boundaries of crystal grains having a body-centered structure, a length of a grain boundary having a rotation angle of 49° to 56° is denoted by L49-56°, a length of a grain boundary having a rotation angle of 64° to 72° is denoted by L64-72°, a length of a grain boundary having a rotation angle of 57° to 63° is denoted by L57-63°, and a length of a grain boundary having a rotation angle of 4° to 12° is denoted by L4-12°, (L49-56°+L64-72°)/(L57-63°+L4-12°) that is a ratio of a sum of the L49-56° and the L64-72° to a sum of the L57-63° and the L4-12° is 1.40 or more, and
• a tensile strength of the steel member is more than 1,500 MPa.