Ferritic stainless steel

Abstract

A ferritic stainless steel having excellent creep resistance and thermal fatigue resistance. The ferritic stainless steel has a chemical composition comprising, by mass %, C: 0.020% or less, Si: 0.1 to 1.0%, Mn: 0.05 to 0.60%, P: 0.050% or less, S: 0.008% or less, Ni: 0.02 to 0.60%, Al: 0.001 to 0.25%, Cr: 18.0 to 20.0%, Nb: 0.30 to 0.80%, Mo: 1.80 to 2.50%, N: 0.015% or less, Sb: 0.002 to 0.50%, and the balance being Fe and inevitable impurities. The expression Nb+Mo: 2.3 to 3.0% is satisfied, where Nb and Mo in the expression represent the contents, by mass %, of the respective elements.

1 . A ferritic stainless steel having a chemical composition comprising, by mass %:
 C: 0.020% or less;   Si: 0.1 to 1.0%;   Mn: 0.05 to 0.60%;   P: 0.050% or less;   S: 0.008% or less;   Ni: 0.02 to 0.60%;   Al: 0.001 to 0.25%;   Cr: 18.0 to 20.0%;   Nb: 0.30 to 0.80%;   Mo: 1.80 to 2.50%;   N: 0.015% or less;   Sb: 0.002 to 0.50%; and   the balance being Fe and inevitable impurities,   wherein the following expression (1) is satisfied:
   Nb+Mo: 2.3 to 3.0%  (1)
 
   where Nb and Mo in expression (1) represent the contents, by mass %, of the respective elements.   
     
     
         2 . The ferritic stainless steel according to  claim 1 , wherein the chemical composition further comprises, by mass %, at least one selected from the group consisting of Ti: 0.01 to 0.16%, Zr: 0.01 to 0.50%, Co: 0.01 to 0.50%, B: 0.0002 to 0.0050%, V: 0.01 to 1.0%, W: 0.01 to 5.0%, Cu: 0.01 to 0.40%, and Sn: 0.001 to 0.005%. 
     
     
         3 . The ferritic stainless steel according to  claim 1 , wherein the chemical composition further comprises, by mass %, at least one selected from the group consisting of Ca: 0.0002 to 0.0050% and Mg: 0.0002 to 0.0050%. 
     
     
         4 . The ferritic stainless steel according to  claim 1 , wherein the ferritic stainless steel is used for an exhaust manifold whose temperature is elevated to 700° C. or higher by an exhaust gas from an engine. 
     
     
         5 . The ferritic stainless steel according to  claim 2 , wherein the chemical composition further comprises, by mass %, at least one selected from the group consisting of Ca: 0.0002 to 0.0050% and Mg: 0.0002 to 0.0050%. 
     
     
         6 . The ferritic stainless steel according to  claim 2 , wherein the ferritic stainless steel is used for an exhaust manifold whose temperature is elevated to 700° C. or higher by an exhaust gas from an engine. 
     
     
         7 . The ferritic stainless steel according to  claim 3 , wherein the ferritic stainless steel is used for an exhaust manifold whose temperature is elevated to 700° C. or higher by an exhaust gas from an engine. 
     
     
         8 . The ferritic stainless steel according to  claim 5 , wherein the ferritic stainless steel is used for an exhaust manifold whose temperature is elevated to 700° C. or higher by an exhaust gas from an engine. 
     
     
         9 . An exhaust manifold whose temperature is elevated to 700° C. or higher by an exhaust gas from an engine, the exhaust manifold comprising the ferritic stainless steel according to  claim 1 .