Steel sheet for hot stamping and method for producing steel sheet for hot stamping, and hot stamp formed body

Abstract

A steel sheet for hot stamping includes a composition including at least, in mass %, C: 0.100% to 0.600%, Si: 0.50% to 3.00%, Mn: 1.20% to 4.00%, Ti: 0.005% to 0.100%, B: 0.0005% to 0.0100%, P: 0.100% or less, S: 0.0001% to 0.0100%, Al: 0.005% to 1.000%, and N: 0.0100% or less, with a balance of Fe and impurities, surface roughness of the steel sheet satisfies Rz>2.5 μm, and 50 mg/m 2 to 1500 mg/m 2 of coating oil is applied to a surface.

1 . A steel sheet for hot stamping, comprising a composition containing:
 in mass %,   C: 0.100% to 0.600%;   Si: 0.50% to 3.00%;   Mn: 1.20% to 4.00%;   Ti: 0.005% to 0.100%;   B: 0.0005% to 0.0100%;   P: 0.100% or less;   S: 0.0001% to 0.0100%;   Al: 0.005% to 1.000%;   N: 0.0100% or less;   Ni: 0% to 2.00%;   Cu: 0% to 2.00%;   Cr: 0% to 2.00%;   Mo: 0% to 2.00%;   Nb: 0% to 0.100%;   V: 0% to 0.100%;   W: 0% to 0.100%, and   a total of one kind or two or more kinds selected from a group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%,   with a balance being Fe and impurities,   wherein surface roughness of the steel sheet satisfies Rz>2.5 μm, and coating oil in an amount of 50 mg/m 2  to 1500 mg/m 2  is applied onto a surface.   
     
     
         2 . The steel sheet for hot stamping according to  claim 1 ,
 wherein an amount of S contained in the coating oil which is applied onto the steel sheet is 5% or less in mass %.   
     
     
         3 . The steel sheet for hot stamping according to  claim 1 ,
 wherein the composition of the steel sheet contains, in mass %,   one kind or two or more kinds selected from a group consisting of   Ni: 0.01% to 2.00%,   Cu: 0.01% to 2.00%,   Cr: 0.01% to 2.00%,   Mo: 0.01% to 2.00%,   Nb: 0.005% to 0.100%,   V: 0.005% to 0.100%, and   W: 0.005% to 0.100%.   
     
     
         4 . The steel sheet for hot stamping according to  claim 1 ,
 wherein the composition of the steel sheet contains, in mass %,   a total of 0.0003% to 0.0300% of one kind or two or more kinds selected from the group consisting of REM, Ca, Ce and Mg.   
     
     
         5 . A method for producing a steel sheet for hot stamping, comprising:
 a step of casting a slab containing,   in mass %,   C: 0.100% to 0.600%;   Si: 0.50% to 3.00%;   Mn: 1.20% to 4.00%;   Ti: 0.005% to 0.100%;   B: 0.0005% to 0.0100%;   P: 0.100% or less;   S: 0.0001% to 0.0100%;   Al: 0.005% to 1.000%;   N: 0.0100% or less;   Ni: 0% to 2.00%;   Cu: 0% to 2.00%;   Cr: 0% to 2.00%;   Mo: 0% to 2.00%;   Nb: 0% to 0.100%;   V: 0% to 0.100%;   W: 0% to 0.100%, and   a total of one kind or two or more kinds selected from a group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%,   with a balance being Fe and impurities, and hot rolling the slab directly or by allowing the slab to cool and heating the slab to obtain a hot-rolled steel sheet;   a step of pickling the hot-rolled steel sheet for 30 seconds or more in an aqueous solution having a temperature of 80° C. to lower than 100° C. and including an inhibitor with a concentration of an acid being 3 mass % to 20 mass %; and   a step of applying a rust inhibiting oil to the steel sheet after carrying out the pickling,   wherein a rust inhibiting oil remaining amount on a steel sheet surface is limited to 50 mg/m 2  to 1500 mg/m 2 .   
     
     
         6 . The method for producing a steel sheet for hot stamping according to  claim 5 ,
 wherein the rust inhibiting oil is applied to the hot-rolled steel sheet which has been pickled.   
     
     
         7 . The method for producing a steel sheet for hot stamping according to  claim 5 , further comprising:
 a step of cold rolling the hot-rolled steel sheet which has been pickled to obtain a cold-rolled steel sheet,   wherein the rust inhibiting oil is applied to the cold-rolled steel sheet.   
     
     
         8 . The method for producing a steel sheet for hot stamping according to  claim 5 , further comprising:
 a step of cold rolling the hot-rolled steel sheet which has been pickled, and further performing thermal treatment in a continuous annealing facility or a box type annealing furnace to obtain a cold-rolled steel sheet,   wherein the rust inhibiting oil is applied to the cold-rolled steel sheet.   
     
     
         9 . The method for producing a steel sheet for hot stamping according to  claim 5 ,
 wherein an amount of S in the rust inhibiting oil that is applied to the steel sheet is 5% or less in mass %.   
     
     
         10 . The method for producing a steel sheet for hot stamping according to  claim 5 ,
 wherein a composition of the slab contains, in mass %,   one kind or two or more kinds selected from a group consisting of   Ni: 0.01% to 2.00%,   Cu: 0.01% to 2.00%,   Cr: 0.01% to 2.00%,   Mo: 0.01% to 2.00%,   Nb: 0.005% to 0.100%,   V: 0.005% to 0.100%, and   W: 0.005% to 0.100%.   
     
     
         11 . The method for producing a steel sheet for hot stamping according to  claim 5 ,
 wherein a composition of the slab contains, in mass %,   a:total of 0.0003% to 0.0300% of one kind or two or more kinds selected from the group consisting of REM, Ca, Ce and Mg.   
     
     
         12 . A hot stamp formed body, comprising a composition containing:
 in mass %,   C: 0.100% to 0.600%;   Si: 0.50% to 3.00%;   Mn: 1.20% to 4.00%;   Ti: 0.005% to 0.100%;   B: 0.0005% to 0.0100%;   P: 0.100% or less;   S: 0.0001% to 0.0100%;   Al: 0.005% to 1.000%;   N: 0.0100% or less;   Ni: 0% to 2.00%;   Cu: 0% to 2.00%;   Cr: 0% to 2.00%;   Mo: 0% to 2.00%;   Nb: 0% to 0.100%;   V: 0% to 0.100%;   W: 0% to 0.100%, and   a total of one kind or two or more kinds selected from a group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%,   with a balance being Fe and impurities,   wherein three or more irregularities in a range of 0.2 μm to 8.0 μm in depth are present per 100 μm in an interface between scale and a base iron, and tensile strength is 1180 MPa or more.   
     
     
         13 . The hot stamp fonned body according to  claim 12 ,
 wherein an Si oxide, FeO, Fe 3 O 4  and Fe 2 O 3  are included in a surface of the hot stamp formed body, and a thickness of the scale is 10 μm or less.   
     
     
         14 . The hot stamp formed body according to  claim 12 ,
 wherein the composition of the hot stamp formed body contains, in mass %,   one kind or two or more kinds selected from a group consisting of   Ni: 0.01% to 2.00%,   Cu: 0.01% to 2.00%,   Cr: 0.01% to 2.00%,   Mo: 0.01% to 2.00%,   Nb: 0.005% to 0.100%,   V: 0.005% to 0.100%, and   W: 0.005% to 0.100%.   
     
     
         15 . The hot stamp formed body according to  claim 12 ,
 wherein the composition of the hot stamp formed body contains, in mass %,   a total of 0.0003% to 0.0300% of one kind or two or more kinds selected from the group consisting of REM, Ca, Ce and Mg.