Hot stamped steel and method for producing hot stamped steel

A hot stamped steel comprising, by mass %:

• C:
• 0.030% to 0.150%;
• Si:
• 0.010% to 1.00%;
• Mn:
• 1.50% to 2.70%;
• P:
• 0.001% to 0.060%;
• S:
• 0.001% to 0.010%;
• N:
• 0.0005% to 0.0100%;
• Al:
• 0.010% to 0.050%, and
• optionally one or more of
• B:
• 0.0005% to 0.0020%;
• Mo:
• 0.01% to 0.50%;
• Cr:
• 0.01% to 0.50%;
• V:
• 0.001% to 0.100%;
• Ti:
• 0.001% to 0.100%;
• Nb:
• 0.001% to 0.050%;
• Ni:
• 0.01% to 1.00%;
• Cu:
• 0.01% to 1.00%;
• Ca:
• 0.0005% to 0.0050%;
• REM:
• 0.0005% to 0.0050%, and
• a balance including Fe and unavoidable impurities, wherein
• when [C] represents an amount of C by mass %, [Si] represents an amount of Si by mass %, and [Mn] represents an amount of Mn by mass %, a following expression (A) is satisfied,
• a metallographic structure after a hot stamping includes 40% to 90% of a ferrite and 10% to 60% of a martensite in an area fraction,
• a total of an area fraction of the ferrite and an area fraction of the martensite is 60% or more,
• the metallographic structure optionally further includes one or more of 10% or less of a pearlite in an area fraction, 5% or less of a retained austenite in a volume ratio, and less than 40% of a bainite as a remainder in an area fraction,
• a hardness of the martensite measured with a nanoindenter satisfies a following expression (B) and a following expression (C),
• TS×λ which is a product of a tensile strength TS and a hole expansion ratio λ is 50000 MPa·% or more,
• (5×[Si]+[Mn])/[C]>11 (A),
• H2/H1<1.10 (B),
• σHM<20 (C), and
• the H1 is an average hardness of the martensite in a surface part of a sheet thickness after the hot stamping, the H2 is an average hardness of the martensite in a central part of the sheet thickness which is an area having a width of 200 μm in a thickness direction at a center of the sheet thickness after the hot stamping, and the σHM is a variance of the average hardness of the martensite in the central part of the sheet thickness after the hot stamping.