Steel material

Abstract

The steel material of the present disclosure includes a chemical composition consisting of, in mass %, C: 0.035% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.030% or less, S: 0.0050% or less, sol. Al: 0.005 to 0.100%, N: 0.001 to 0.020%, Ni: 5.00 to 7.00%, Cr: 10.00 to 14.00%, Cu: 1.50 to 3.50%, Mo: 1.00 to 4.00%, V: 0.01 to 1.00%, Ti: 0.02 to 0.30%, Co: 0.01 to 0.50%, Ca: 0.0003 to 0.0030%, O: 0.0050% or less, W: 0 to 1.50%, Nb: 0 to 0.50%, B: 0 to 0.0050%, Mg: 0 to 0.0050%, and rare earth metals (REM): 0 to 0.020%, with the balance being Fe and impurities, in which a total number density of Mn sulfide having an equivalent circular diameter of 1.0 μm or more and Ca sulfide having an equivalent circular diameter of 2.0 μm or more is 0.50 pieces/mm2 or less.

1 - 5 . (canceled) 
     
     
         6 . A steel material, comprising
 a chemical composition consisting of, in mass %,   C: 0.035% or less;   Si: 1.00% or less;   Mn: 1.00% or less;   P: 0.030% or less;   S: 0.0050% or less;   sol. Al: 0.005 to 0.100%;   N: 0.001 to 0.020%;   Ni: 5.00 to 7.00%;   Cr: 10.00 to 14.00%;   Cu: 1.50 to 3.50%;   Mo: 1.00 to 4.00%;   V: 0.01 to 1.00%;   Ti: 0.02 to 0.30%;   Co: 0.01 to 0.50%;   Ca: 0.0003 to 0.0030%;   O: 0.0050% or less;   W: 0 to 1.50%;   Nb: 0 to 0.50%;   B: 0 to 0.0050%;   Mg: 0 to 0.0050%; and   rare earth metals (REM): 0 to 0.020%,   with the balance being Fe and impurities, wherein   among inclusions in the steel material, a total number density of Mn sulfide having a Mn content of 10% or more and a S content of 10% or more, and having an equivalent circular diameter of 1.0 μm or more, and Ca sulfide having a Ca content of 20% or more and a S content of 10% or more, and having an equivalent circular diameter of 2.0 μm or more is 0.50 pieces/mm 2  or less.   
     
     
         7 . The steel material according to  claim 6 , wherein
 the chemical composition contains   W: 0.01 to 1.50%.   
     
     
         8 . The steel material according to  claim 6 , wherein
 the chemical composition contains   Nb: 0.01 to 0.50%.   
     
     
         9 . The steel material according to  claim 7 , wherein
 the chemical composition contains   Nb: 0.01 to 0.50%.   
     
     
         10 . The steel material according to  claim 6 , wherein
 the chemical composition contains one or more types of element selected from the group consisting of:   B: 0.0001 to 0.0050%,   Mg: 0.0001 to 0.0050%, and   rare earth metals (REM): 0.001 to 0.020%.   
     
     
         11 . The steel material according to  claim 7 , wherein
 the chemical composition contains one or more types of element selected from the group consisting of:   B: 0.0001 to 0.0050%,   Mg: 0.0001 to 0.0050%, and   rare earth metals (REM): 0.001 to 0.020%.   
     
     
         12 . The steel material according to  claim 8 , wherein
 the chemical composition contains one or more types of element selected from the group consisting of:   B: 0.0001 to 0.0050%,   Mg: 0.0001 to 0.0050%, and   rare earth metals (REM): 0.001 to 0.020%.   
     
     
         13 . The steel material according to  claim 9 , wherein
 the chemical composition contains one or more types of element selected from the group consisting of:   B: 0.0001 to 0.0050%,   Mg: 0.0001 to 0.0050%, and   rare earth metals (REM): 0.001 to 0.020%.   
     
     
         14 . The steel material according to claim  1 , wherein
 the steel material is a seamless steel pipe for oil country tubular goods.