Duplex Stainless Steel refers to stainless steel with ferrite and austenite each accounting for about 50%. Generally, the content of less phases needs to be at least 30%. In the case of low C content, the Cr content is 18% to 28%, and the Ni content is 3% to 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N.
Classification of duplex stainless steel
1. Low alloy type, representative grade UNS S32304 (23Cr-4Ni-0.1N), no molybdenum in the steel, PREN value 24-25, can be used instead of AISI304 or 316 in terms of stress corrosion resistance.
2. Medium alloy type, representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N), PREN value is 32-33, and its corrosion resistance is between AISI 316L and 6%Mo+N austenitic stainless steel.
3. High alloy type, generally containing 25% Cr, also containing molybdenum and nitrogen, and some also containing copper and tungsten, standard grade UNSS32550 (25Cr-6Ni-3Mo-2Cu-0.2N), PREN value is 38-39, this The corrosion resistance of similar steel is higher than that of 22%Cr duplex stainless steel.
4. Super duplex stainless steel type, containing high molybdenum and nitrogen, standard grade UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), and some also containing tungsten and copper, PREN value greater than 40, suitable for harsh media conditions , It has good corrosion resistance and comprehensive mechanical properties, comparable to super austenitic stainless steel.
Duplex stainless steel is a versatile material whether it is in highly corrosive environments or engineering materials for stainless steel structures. Its uses include:
● Paper industry;
● Chemical and petrochemical industry;
● Organic acid and caustic alkali medium;
● Pollution control equipment;
● Chemical storage tank;
● Offshore and coastal applications;
● Piping installations in wineries;
Application of Duplex Stainless Steel in chemical transportation
Application of Duplex stainless steel in Marine Engineering
Duplex stainless steel is a type of steel that combines excellent corrosion resistance, high strength, and easy manufacturing and processing. Its physical properties are between austenitic stainless steel and ferritic stainless steel, but closer to ferritic stainless steel and carbon steel.
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