Austenitic Stainless Steel

Abstract

Provided is an austenitic stainless steel having excellent anti-carburizing properties even in a high temperature carburizing environment, and an excellent hot workability in its production. The austenitic stainless steel according to the present embodiment includes a chemical composition consisting of, in mass percent, C: 0.03 to less than 0.25%, Si: 0.01 to 2.0%, Mn: 2.0% or less, Cr: 10 to less than 22%, Ni: more than 30.0% to 40.0%, Al: more than 2.5% to less than 4.5%, Nb: 0.01 to 3.5%, Ca: 0.0005 to 0.05%, Mg: 0.0005 to 0.05%, and N: 0.03% or less, with the balance being Fe and impurities. In the austenitic stainless steel, a Cr concentration C Cr z,23 n its outer layer and an Al concentration C Al n the outer layer satisfy Formula (1) for a Cr concentration C Cr in an other-than-outer-layer region and an Al concentration C Al in the other-than-outer-layer region. 0.40≤( C Cr C Cr /C Al )≤0.80  (1)

1 . An austenitic stainless steel comprising a chemical composition consisting of, in mass percent:
 C: 0.03 to less than 0.25%;   Si: 0.01 to 2.0%;   Mn: 2.0% or less;   P: 0.04% or less;   S: 0.01% or less;   Cr: 10 to less than 22%;   Ni: more than 30.0% to 40.0%;   Al: more than 2.5% to less than 4.5%;   Nb: 0.01 to 3.5%;   N: 0.03% or less;   Ca: 0.0005 to 0.05%;   Mg: 0.0005 to 0.05%;   Ti: 0 to less than 0.2%;   Mo: 0 to 0.5%;   W: 0 to 0.5%;   Cu: 0 to 0.5%;   V: 0 to 0.2%; and   B: 0 to 0.01%,   with the balance being Fe and impurities, and satisfying Formula (1):
   0.40≤( C   Cr     C   Cr   /C   Al )≤0.80  (1)
 
   where, a Cr concentration (mass percent) in an outer layer of the austenitic stainless steel is substituted for C Cr   n Formula (1), an Al concentration (mass percent) in the outer layer of the austenitic stainless steel is substituted for C Al    a Cr concentration (mass percent) in an other-than-outer-layer region of the austenitic stainless steel is substituted for C Cr , and an Al concentration (mass percent) in the other-than-outer-layer region of the austenitic stainless steel is substituted for C Al .   
     
     
         2 . The austenitic stainless steel according to  claim 1 , wherein
 the chemical composition contains one or two or more elements selected from the group consisting of:   Ti: 0.005 to less than 0.2%;   Mo: 0.01 to 0.5%;   W: 0.01 to 0.5%;   Cu: 0.005 to 0.5%;   V: 0.005 to 0.2%; and   B: 0.0001 to 0.01%.