Steel sheet for hot stamping and hot-stamping formed body

Abstract

This hot-stamping formed body has a predetermined chemical composition and has a microstructure in which an average grain size of prior austenite grains is 5 to 25 μm, and a standard deviation of grain sizes of the prior austenite grains is 0.1 to 2.0 μm. In addition, this steel sheet for hot stamping has a predetermined chemical composition and has a microstructure in which an average value of the pole densities of ferrite in the orientation group consisting of {100}<011> to {223}<110> is 10.0 or less, in entire ferrite, a number proportion of ferrite containing a carbide having an equivalent circle diameter of 0.2 μm or more in grains is 20% or more, and the steel sheet for hot stamping has a microstructure in which an area ratio of pearlite is 10% to 90% and an ratio of ferrite is 10% to 90%.

1 . A steel sheet for hot stamping consisting of, as a chemical composition, by mass %:
 C: more than 0.40% and 0.70% or less;   Si: 0.010% to 1.30%;   Mn: 0.10% to 0.60%;   P: 0.100% or less;   S: 0.0100% or less;   N: 0.0140% or less;   O: 0.0200% or less:   Al: 0.0010% to 0.500%;   Cr: 0.010% to 0.80%;   Nb: 0% to 0.100%;   Ti: 0% to 0.100%;   B: 0% to 0.0100%;   Mo: 0% to 1.00%;   Co: 0% to 2.00%;   Ni: 0% or more and less than 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   a remainder of Fe and impurities,   wherein the steel sheet for hot stamping has a microstructure in which an average value of pole densities of ferrite in an orientation group consisting of {100}<011> to {223}<110> is 10.0 or less,   in entire ferrite, a number proportion of ferrite containing a carbide having an equivalent circle diameter of 0.2 μm or more in grains is 20% or more, and an area ratio of pearlite is 10% to 90% and an area ratio of ferrite is 10% to 90%.   
     
     
         2 . The steel sheet for hot stamping according to  claim 1 , wherein the steel sheet for hot stamping contains, as the chemical composition, by mass %, one or more of:
 Nb: 0.001% to 0.100%,   Ti: 0.010% to 0.100%,   B: 0.0015% to 0.0100%,   Mo: 0.05% to 1.00%,   Co: 0.05% to 2.00%,   Ni: 0.01% or more and less than 3.00%,   Cu: 0.01% to 1.00%,   V: 0.01% to 1.00%,   W: 0.001% to 1.000%,   Ca: 0.001% to 0.010%,   Mg: 0.001% to 1.000%,   REM: 0.001% to 1.000%,   Sb: 0.005% 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-stamping formed body consisting of, as a chemical composition, by mass %:
 C: more than 0.40% and 0.70% or less;   Si: 0.010% to 1.30%;   Mn: 0.10% to 0.60%;   P: 0.100% or less;   S: 0.0100% or less;   N: 0.0140% or less;   O: 0.0200% or less;   Al: 0.0010% to 0.500%;   Cr: 0.010% to 0.80%;   Nb: 0% to 0.100%;   Ti: 0% to 0.100%;   B: 0% to 0.0100%;   Mo: 0% to 1.00%;   Co: 0% to 2.00%;   Ni: 0% or more and less than 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   a remainder of Fe and impurities,   wherein the hot-stamping formed body has a microstructure in which an average grain size of prior austenite grains is 5 to 25 μm,   a standard deviation of grain sizes of the prior austenite grains is 0.1 to 2.0 μm, and   a tensile strength of the hot-stamping formed body is 2,200 MPa or more.   
     
     
         4 . The hot-stamping formed body according to  claim 3 ,
 wherein the hot-stamping formed body contains, as the chemical composition, by mass %, one or more of:   Nb: 0.001% to 0.100%,   Ti: 0.010% to 0.100%,   B: 0.0015% to 0.0100%,   Mo: 0.05% to 1.00%,   Co: 0.05% to 2.00%,   Ni: 0.01% or more and less than 3.00%,   Cu: 0.01% to 1.00%,   V: 0.01% to 1.00%,   W: 0.001% to 1.000%,   Ca: 0.001% to 0.010%,   Mg: 0.001% to 1.000%,   REM: 0.001% to 1.000%,   Sb: 0.005% to 1.000%,   Zr: 0.001% to 1.000%,   Sn: 0.001% to 1.000%, and   As: 0.001% to 0.100%.   
     
     
         5 . The hot-stamping formed body according to  claim 3 , wherein an area ratio of the prior austenite grains having an average grain size of 0.5 to 3.0 μm is 60% or less. 
     
     
         6 . The hot-stamping formed body according to  claim 4 , wherein an area ratio of the prior austenite grains having an average grain size of 0.5 to 3.0 μm is 60% or less. 
     
     
         7 . A steel sheet for hot stamping comprising, as a chemical composition, by mass %:
 C: more than 0.40% and 0.70% or less;   Si: 0.010% to 1.30%;   Mn: 0.10% to 0.60%;   P: 0.100% or less;   S: 0.0100% or less;   N: 0.0140% or less;   O: 0.0200% or less;   Al: 0.0010% to 0.500%;   Cr: 0.010% to 0.80%;   Nb: 0% to 0.100%;   Ti: 0% to 0.100%:   B: 0% to 0.0100%;   Mo: 0% to 1.00%;   Co: 0% to 2.00%;   Ni: 0% or more and less than 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   a remainder of Fe and impurities,   wherein the steel sheet for hot stamping has a microstructure in which an average value of pole densities of ferrite in an orientation group comprising {100}<011> to {223}<110> is 10.0 or less,   in entire ferrite, a number proportion of ferrite containing a carbide having an equivalent circle diameter of 0.2 μm or more in grains is 20% or more, and   an area ratio of pearlite is 10% to 90% and an area ratio of ferrite is 10% to 90%.