Hot-pressed member, cold-rolled steel sheet for hot pressing, and manufacturing methods therefor

A hot-pressed member, comprising:

• a chemical composition consisting of, in mass %,
• C:
• 0.31% or more and less than 0.55%,
• Si:
• 0.01% or more and 1.0% or less,
• Mn:
• 1.0% or more and 2.5% or less,
• P:
• 0.05% or less,
• S:
• 0.005% or less,
• Al:
• 0.01% or more and 0.50% or less,
• N:
• 0.01% or less, and
• Cu:
• 0.002% or more and 0.25% or less,
• and optionally one or more one or more selected from the group consisting of
• Mo:
• 0.005% or more and 0.35% or less,
• Cr:
• 0.005% or more and 0.35% or less,
• Nb:
• 0.001% or more and 0.05% or less,
• Ti:
• 0.001% or more and 0.050% or less,
• B:
• 0.0002% or more and 0.0050% or less,
• Ca:
• 0.005% or less,
• V:
• 0.05% or less,
• Sb:
• 0.001% or more and 0.020% or less,
• Ni:
• 0.50% or less, and
• Sn:
• 0.50% or less,
• with a balance consisting of Fe and inevitable impurities;
• a microstructure in which a prior austenite average grain size is 8 μm or less, a volume fraction of martensite is 95% or more, and a volume fraction of granular carbide of 0.1 μm or more in grain size is 0.10% or more and 4.0% or less;
• a Ni diffusion region of 2.0 μm or more in a depth direction in a surface layer;
• and
• a tensile strength of 1850 MPa or more.