Patent ID: 9637813
Date: 2017-05-02
CPC Classifications: C21D,C22C

Claim:
1. A duplex ferritic austenitic stainless steel for use in the chemical industry for nitric acid environments wherein good uniform corrosion resistance and high strength are required, wherein the microstructure of the stainless steel has 35-65 volume % of ferrite, the balance being austenite, and the chemical composition contains less than 0.03 weight % carbon, less than 1 weight % silicon, less than 3 weight % manganese, 26-29.5 weight % chromium, 5-8.5 weight % nickel, 1-3 weight % molybdenum, 0.25-0.35 weight % nitrogen, 1-3 weight % copper, up to 1 weight % tungsten, the rest being iron and inevitable impurities occurring in stainless steels, and wherein the sigma equivalent SGR (Cr+2×Mo−40×N+0.5×Mn−2×Cu) is less than 18, and the pitting resistance equivalent value PRE (Cr+3.3×Mo+30×N—Mn) is at the range of more than 41.