Duplex is a stainless steel designed to combine improved resistance to stress corrosion cracking, pitting, crevice corrosion and high strength when compared with other stainless alloys. With its austenitic ferritic chromium, nickel, molybdenum composition duplex stainless steel alloy resists chloride environments and sulphide stress corrosion. Duplex stainless steel is designed to combine improved resistance to stress corrosion cracking, pitting, crevice corrosion and high strength when compared with other stainless alloys. Duplex resists chloride environments and sulphide stress corrosion. Duplex steel has a ductile/brittle transition at approximately -50°C. Duplex is also roughly double the strength of standard austenitic stainless steels.
Duplex stainless steels have a mixed microstructure of ferrite and austenite , the aim of this being to produce a 50/50 mix, although in commercial alloys, the mix may be 40/60 respectively. Duplex stainless steel has improved strength over austenitic stainless steel and also improved resistance to localised corrosion, particularly pitting, crevice corrosion and stress corrosion cracking. Duplex stainless is characterised by high chromium (19–28%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. The most used Duplex Stainless Steel are the 2205 (22% Chromium, 5% Nickel) and 2507 (25% Chromium, 7% Nickel) sometimes the 2507 is also called Super Duplex due to the higher corrosion resistance.
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