Steel plate for hot stamping

Abstract

A steel plate for hot stamping contains, in % by mass, C: 0.25% or more and 0.4% or less, Si: 1.05% or more and 1.4% or less, Mn: 0% or more and 1.4% or less, Cr: 0.6% or more and 3.0% or less, P: 0% or more and 0.03% or less, S: 0% or more and 0.02% or less, Al: 0.01% or more and 1% or less, N: 0% or more and 0.01% or less, B: 0.0005% or more and 0.005% or less, Ti: 0.005% or more and 0.1% or less, and iron and inevitable impurities as remainder. This steel plate for hot stamping exhibits excellent hardness stability in addition to a balance between strength and toughness as a relational expression of [C]2/9[Si]+7/9[Mn]+8/9[Cr]−7/4>0 is satisfied.

1 . A steel plate, comprising:
 in % by mass,   C: 0.25% or more and 0.4% or less,   Si: 1.05% or more and 1.4% or less,   Mn: 0% or more and 1.4% or less,   Cr: 0.6% or more and 3.0% or less,   P: 0% or more and 0.03% or less,   S: 0% or more and 0.02% or less,   Al: 0.01% or more and 1% or less,   N: 0% or more and 0.01% or less,   B: 0.0005% or more and 0.005% or less, and   Ti: 0.005% or more and 0.1% or less,   wherein the following relational expression (1) is satisfied   
       
         
           
             
               
                 
                   
                     
                       
                         [ 
                         C 
                         ] 
                       
                       + 
                       
                         
                           2 
                           9 
                         
                          
                         
                           [ 
                           Si 
                           ] 
                         
                       
                       + 
                       
                         
                           7 
                           9 
                         
                          
                         
                           [ 
                           Mn 
                           ] 
                         
                       
                       + 
                       
                         
                           8 
                           9 
                         
                          
                         
                           [ 
                           Cr 
                           ] 
                         
                       
                       - 
                       
                         7 
                         4 
                       
                     
                     > 
                     0 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         where [C] denotes the C content, [Si] denotes the Si content, [Mn] denotes the Mn content, and [Cr] denotes the Cr content. 
       
     
     
         2 . The steel plate of  claim 1 , comprising, in % by mass, one or more selected from the group consisting of
 Mo: 0% or more and 1.0% or less,   Nb: 0% or more and 0.1% or less, and   V: 0% or more and 0.1% or less.   
     
     
         3 . The steel plate of  claim 1 , comprising, in % by mass, one or more selected from the group consisting of
 Cu: 0% or more and 0.5% or less, and   Ni: 0% or more and 0.5% or less.   
     
     
         4 . The steel plate of  claim 2 , comprising, in % by mass, one or more selected from the group consisting of
 Cu: 0% or more and 0.5% or less, and   Ni: 0% or more and 0.5% or less.