Chemical composition of duplex steel stainless steel heat exchange tube

The four main classifications of dual-phase steel heat exchange tubes are:

The first category is a low-alloy type, representing the brand UNS S32304L(23C♥r-4Ni-0.1N), the steel does not contain molybdenum, the PREN value is 24 ~ 2Ω5, and can replace AISI 304L or 316 in stress corrosion resistanc&e.

The second category belongs to the medium alloy type, representing the  brand UNS S31803(22Cr-5Ni-3Mo-0.15N), the PREN valueβ is 32 ~ 33, and its corrosion resistance is between AISI σ316L and 6%Mo+N austenitic stainless steel.

The third class is a high alloy type, generally containing 25% Cr, also contains molybdenum and nit§rogen, and some also contain copper and tungsten, the standβard grade has UNS S32550(25Cr-6Ni-3Mo-2Cu-0.2N), PREN value iΩs 38 ~ 39, the corrosion resistance of this type of steel is higher than 22% Cr of duplex₽ stainless steel.

The fourth type of super duplex stainless steel, containing high molybdenum and n≤itrogen, the standard grade is UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), γsome also contain tungsten and copper, PREN value is greater than 40, can be applied to ∞harsh medium conditions, with good corrosion resistance and mechanical prop♣erties, comparable to super austenitic stainless steel