Austenitic fe-ni-cr alloy

Abstract

An austenitic Fe—Ni—Cr alloy comprises C: 0.005˜0.03 mass %, Si: 0.15˜1.0 mass %, Mn: not more than 2.0 mass %, P: not more than 0.030 mass %, S: not more than 0.002 mass %, Cr: 18˜28 mass %, Ni: 20˜38 mass %, Mo: 0.10˜3 mass %, Co: 0.05˜2.0 mass %, Cu: less than 0.25 mass %, N: not more than 0.02 mass %, provided that PRE=Cr+3.3×Mo+16×N≧20.0 and PREH=411−13.2×Cr−5.8×Mo+0.1×Mo 2 +1.2×Cu≦145.0 (wherein each element symbol represents a content (mass %) of each element) and has an excellent corrosion resistance in air or under a wet environment even at a surface state having an oxide film formed by a intermediate heat treatment on the way of the production process.

1 . An austenitic Fe—Ni—Cr alloy having a chemical composition comprising C: 0.005˜0.03 mass %, Si: 0.15˜1.0 mass %, Mn: not more than 2.0 mass %, P: not more than 0.030 mass %, S: not more than 0.002 mass %, Cr: 18˜28 mass %, Ni: 20˜38 mass %, Mo: 0.10˜3 mass %, Co: 0.05˜2.0 mass %, Cu: less than 0.25 mass %, N: not more than 0.02 mass %, provided that Cr, Mo, N and Cu satisfy the following equations (1) and (2):
   PRE=Cr+3.3×Mo+16×N≧20.0   (1)
 
   PREH=411−13.2×Cr−5.8×Mo+0.1×Mo 2 +1.2×Cu≦145.0   (2)
 
 
       (wherein each element symbol in the above equations represents a content (mass %) of each element), and the balance being Fe and inevitable impurities. 
     
     
         2 . An austenitic Fe—Ni—Cr alloy according to  claim 1 , which further contains in addition to the above chemical composition one or more selected from Al: 0.10˜1.0 mass %, Ti: 0.10˜1.0 mass % and Zr: 0.01˜0.5 mass % and satisfying the following equation (3):
   Al+Ti+1.5×Zr: 0.5˜1.5   (3)
 
 
       (wherein each element symbol in the above equation represents a content (mass %) of each element).