Cold-rolled steel sheet and steel member

A steel member comprising:

• a processed portion;
• and
• a non-processed portion,
• wherein at least the non-processed portion contains, as a chemical composition, by mass %,
• C:
• 0.180% or more and 0.400% or less,
• Si:
• 0.050% or more and 1.000% or less,
• Mn:
• 2.00% or more and 4.00% or less,
• Al:
• 0.10% or more and 2.00% or less,
• Ti:
• 0.010% or more and 0.200% or less,
• B:
• 0.0010% or more and 0.0100% or less,
• N:
• 0.0010% or more and 0.0100% or less,
• P:
• 0% or more and 0.0400% or less,
• S:
• 0% or more and 0.0100% or less,
• O:
• 0% or more and 0.0060% or less,
• Cr:
• 0% or more and 0.50% or less,
• Ni:
• 0% or more and 1.00% or less,
• Cu:
• 0% or more and 1.00% or less,
• Mo:
• 0% or more and 0.500% or less,
• Nb:
• 0% or more and 0.200% or less,
• V:
• 0% or more and 0.500% or less,
• W:
• 0% or more and 0.100% or less,
• Ta:
• 0% or more and 0.100% or less,
• Sn:
• 0% or more and 0.050% or less,
• Co:
• 0% or more and 0.500% or less,
• Sb:
• 0% or more and 0.050% or less,
• As:
• 0% or more and 0.050% or less,
• Mg:
• 0% or more and 0.050% or less,
• Ca:
• 0% or more and 0.040% or less,
• REM:
• 0% or more and 0.050% or less,
• Bi:
• 0% or more and 0.050% or less,
• Zr:
• 0% or more and 0.050% or less,
• Sr:
• 0% or more and 0.050% or less, and
• a remainder including Fe and impurities,
• when a thickness in units of mm is denoted by t, and a range from a t/8 position to a 3t/8 position in a thickness direction from a surface of the steel member is denoted by a t/4 position,
• at the t/4 position,
• a microstructure contains, by volume percentage, martensite:
• 95% or more, in which a volume percentage of tempered martensite is 95% or less,
• a prior austenite grain size is 7.0 μm or less, and
• a grain boundary segregation degree of Mn is 2.0 or less.