Martensitic Stainless Steel

Abstract

Martensitic stainless steel according to the invention contains, by mass, 0.001% to 0.01% C, at most 0.5% Si, 0.1% to 3.0% Mn, at most 0.04% P, at most 0.01% S, 10% to 15% Cr, 4% to 8% Ni, 2.8% to 5.0% Mo, 0.001% to 0.10% Al, at most 0.07% N, 0% to 0.25% Ti, 0% to 0.25% V, 0% to 0.25% Nb, 0% to 0.25% Zr, 0% to 1.0% Cu, 0% to 0.005% Ca, 0% to 0.005% Mg, 0% to 0.005% La, and 0% to 0.005% Ce, with the balance being Fe and impurities, and the steel satisfies Expressions (1) and (2) and has a yield stress in the range from 758 MPa to 860 MPa. In this way, in the martensitic stainless steel according to the invention, the tempering temperature range at which a yield stress in the range from 758 MPa to 860 MPa can be obtained is increased. 922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600   (1) 30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0   (2)

1 . Martensitic stainless steel, comprising, by mass, 0.001% to 0.01% C, at most 0.5% Si, 0.1% to 3.0% Mn, at most 0.04% P, at most 0.01% S, 10% to 15% Cr, 4% to 8% Ni, 2.8% to 5.0% Mo, 0.001% to 0.10% Al, at most 0.07% N, 0% to 0.25% Ti, 0% to 0.25% V, 0% to 0.25% Nb, 0% to 0.25% Zr, 0% to 1.0% Cu, 0% to 0.005% Ca, 0% to 0.005% Mg, 0% to 0.005% La, and 0% to 0.005% Ce, the balance being Fe and impurities, said steel satisfying Expressions (1) and (2) and having a yield stress in the range from 758 MPa to 860 MPa.
   922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600  (1)     30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0  (2)   
       where the contents of the elements in percentage by mass are substituted for the characters representing the elements. 
     
     
         2 . The martensitic stainless steel according to  claim 1 , further comprising at least one of 0.005% to 0.25% Ti, 0.005% to 0.25% V, 0.005% to 0.25% Nb, and 0.005% to 0.25% Zr. 
     
     
         3 . The martensitic stainless steel according to  claim 1 , further comprising 0.05% to 1.0% Cu. 
     
     
         4 . The martensitic stainless steel according to  claim 2 , further comprising 0.05% to 1.0% Cu. 
     
     
         5 . The martensitic stainless steel according to  claim 1 , further comprising at least one of 0.0002% to 0.005% Ca, 0.0002% to 0.005% Mg, 0.0002% to 0.005% La, and 0.0002% to 0.005% Ce. 
     
     
         6 . The martensitic stainless steel according to  claim 2 , further comprising at least one of 0.0002% to 0.005% Ca, 0.0002% to 0.005% Mg, 0.0002% to 0.005% La, and 0.0002% to 0.005% Ce. 
     
     
         7 . The martensitic stainless steel according to  claim 3 , further comprising at least one of 0.0002% to 0.005% Ca, 0.0002% to 0.005% Mg, 0.0002% to 0.005% La, and 0.0002% to 0.005% Ce. 
     
     
         8 . The martensitic stainless steel according to  claim 4 , further comprising at least one of 0.0002% to 0.005% Ca, 0.0002% to 0.005% Mg, 0.0002% to 0.005% La, and 0.0002% to 0.005% Ce.