The first type of low alloy duplex stainless steel. The representative grade is UNS S32304 (23Cr-4Ni-0.1N), the steel does not contain molybdenum, the PREN value is 24-25, and it can replace AISI304 or 316 in terms of stress corrosion resistance.
The second type of alloy type duplex stainless steel. The representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N), the PREN value is 32-33, and its corrosion resistance is between AISI 316L and 6%Mo+N austenitic stainless steel.
The third type of high-alloy duplex stainless steel. It generally contains 25% Cr, molybdenum and nitrogen, and some also contains copper and tungsten. The standard grade is UNSS32550 (25Cr-6Ni-3Mo-2Cu-0.2N), and the PREN value is 38-39. The corrosion resistance of this type of steel Duplex stainless steel with more than 22%Cr.
The fourth type of super duplex stainless steel. Contains high molybdenum and nitrogen, standard grade UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), some also contain tungsten and copper, PREN value is greater than 40, suitable for harsh medium conditions, with good corrosion resistance and mechanical properties The overall performance is comparable to that of super austenitic stainless steel.
