Stainless steel used for oil country tubular goods

Abstract

A stainless steel for an oil country tubular good according to the invention includes, in percent by mass, 0.001% to 0.05% C, 0.05% to 1% Si, at most 2% Mn, at most 0.03% P, less than 0.002% S, 16% to 18% Cr, 3.5% to 7% Ni, more than 2% and at most 4% Mo, 1.5% to 4% Cu, 0.001% to 0.3% rare earth metal, 0.001% to 0.1% sol. Al, 0.0001% to 0.01% Ca, at most 0.05% O, and at most 0.05% N, and the balance consists of Fe and impurities. The stainless steel according to the invention includes REM and therefore has high SCC resistance in a high temperature chloride aqueous solution environment.

1 . Stainless steel used for oil country tubular goods, comprising, in percent by mass, 0.001% to 0.05% C, 0.05% to 1% Si, at most 2% Mn, at most 0.03% P, less than 0.002% S, 16% to 18% Cr, 3.5% to 7% Ni, more than 2% and at most 4% Mo, 1.5% to 4% Cu, 0.001% to 0.3% rare earth metal, 0.001% to 0.1% sol. Al, 0.0001% to 0.01% Ca, at most 0.05% O, and at most 0.05% N, the balance consisting of Fe and impurities. 
     
     
         2 . The stainless steel according to  claim 1 , further comprising, in place of a part of Fe, at least one selected from the group consisting of at most 0.5% Ti, at most 0.5% Zr, at most 0.5% Hf, at most 0.5% V, and at most 0.5% Nb. 
     
     
         3 . The stainless steel according to  claim 1 , having a structure including, in percent by volume, 10% to 60% ferrite phase and 2% to 10% residual austenite phase. 
     
     
         4 . The stainless steel according to  claim 2 , having a structure including, in percent by volume, 10% to 60% ferrite phase and 2% to 10% residual austenite phase. 
     
     
         5 . The stainless steel according to  claim 1 , having a yield stress of at least 654 MPa. 
     
     
         6 . The stainless steel according to  claim 2 , having a yield stress of at least 654 MPa. 
     
     
         7 . The stainless steel according to  claim 3 , having a yield stress of at least 654 MPa. 
     
     
         8 . The stainless steel according to  claim 4 , having a yield stress of at least 654 MPa.