Steel sheet for hot stamping and hot stamped part

Abstract

Provided is a steel sheet for hot stamping having a predetermined chemical composition and a metallographic structure comprising, by area ratio, ferrite: 10% or more and pearlite: 10% or more, wherein a total of ferrite and pearlite is 80% or more, and a dispersion index of pearlite is 0.50 or more. Further, provided is a hot stamped part having a predetermined chemical composition and a metallographic structure comprising, by area ratio, at least one of martensite, bainite, and tempered martensite in a total of 90% or more, wherein a standard deviation in a hardness distribution of prior austenite grains at a sheet thickness ¼ position is 150 Hv or less.

1 . A steel sheet for hot stamping having a chemical composition comprising, by mass %,
 C: 0.40 to 0.70%,   Si: 0.010 to 1.300%,   Mn: 0.60 to 3.00%,   P: 0.100% or less,   S: 0.0100% or less,   N: 0.0200% or less,   O: 0.0200% or less,   Al: 0.0010 to 0.5000%,   Nb: 0.0010 to 0.100%,   Ti: 0.010 to 0.200%,   B: 0.0005 to 0.0200%,   Cr: 0.010 to 0.80%,   Mo: 0.0010 to 1.000%,   Co: 0 to 2.00%,   Ni: 0 to 3.00%,   Cu: 0 to 1.00%,   V: 0 to 1.00%,   W: 0 to 1.000%,   Ca: 0 to 0.010%,   Mg: 0 to 1.000%,   REM: 0 to 1.000%,   Sb: 0 to 1.000%,   Zr: 0 to 1.000%,   Sn: 0 to 1.000%,   As: 0 to 0.100%, and   balance: Fe and impurities, and   a metallographic structure comprising, by area ratio,   ferrite: 10% or more and   pearlite: 10% or more, wherein   a total of ferrite and pearlite is 80% or more, and   a dispersion index of pearlite is 0.50 or more.   
     
     
         2 . The steel sheet for hot stamping according to  claim 1 , wherein the chemical composition contains, by mass %, one or more of
 Co: 0.001 to 2.00%,   Ni: 0.001 to 3.00%,   Cu: 0.001 to 1.00%,   V: 0.001 to 1.00%,   W: 0.001 to 1.000%,   Ca: 0.0001 to 0.010%,   Mg: 0.0001 to 1.000%,   REM: 0.0001 to 1.000%,   Sb: 0.001 to 1.000%,   Zr: 0.001 to 1.000%,   Sn: 0.001 to 1.000%, and   As: 0.001 to 0.100%.   
     
     
         3 . A hot stamped part having a chemical composition comprising, by mass %,
 C: 0.40 to 0.70%,   Si: 0.010 to 1.300%,   Mn: 0.60 to 3.00%,   P: 0.100% or less,   S: 0.0100% or less,   N: 0.0200% or less,   O: 0.0200% or less,   Al: 0.0010 to 0.5000%,   Nb: 0.0010 to 0.100%,   Ti: 0.010 to 0.200%,   B: 0.0005 to 0.0200%,   Cr: 0.010 to 0.80%,   Mo: 0.0010 to 1.000%,   Co: 0 to 2.00%,   Ni: 0 to 3.00%,   Cu: 0 to 1.00%,   V: 0 to 1.00%,   W: 0 to 1.000%,   Ca: 0 to 0.010%,   Mg: 0 to 1.000%,   REM: 0 to 1.000%,   Sb: 0 to 1.000%,   Zr: 0 to 1.000%,   Sn: 0 to 1.000%,   As: 0 to 0.100%, and   balance: Fe and impurities, and   a metallographic structure comprising, by area ratio, at least one of martensite, bainite, and tempered martensite in a total of 90% or more, wherein   a standard deviation in a hardness distribution of prior austenite grains at a sheet thickness ¼ position is 150 Hv or less.   
     
     
         4 . The hot stamped part according to  claim 3 , wherein the chemical composition contains, by mass %, one or more of
 Co: 0.001 to 2.00%,   Ni: 0.001 to 3.00%,   Cu: 0.001 to 1.00%,   V: 0.001 to 1.00%,   W: 0.001 to 1.000%,   Ca: 0.0001 to 0.010%,   Mg: 0.0001 to 1.000%,   REM: 0.0001 to 1.000%,   Sb: 0.001 to 1.000%,   Zr: 0.001 to 1.000%,   Sn: 0.001 to 1.000%, and   As: 0.001 to 0.100%.