What’s 2205 steel?Duplex stainless steel S31803 or S32205?

Duplex stainless steel (UNS S31803, S32205, S32750, S32900) combines the advantages of Ferrite and Austenite steel. Its duplex structure is conducive to obtaining high strength and stress resistance. In addition, higher content of chromium, nitrogen and molybdenum increases corrosion performance and duplex steel also has good welding performance. Due to its excellent properties, duplex stainless steel is widely used in chemical industry, paper manufacturing, desalination equipment, firewalls, Bridges, pressure vessels, heat exchangers, turbine blades and transmission shafts of offshore systems.

Sometimes, UNS S31803 and UNS S32205 are referred to as duplex 2205. Generally, UNS2205 contains ASTM S31803 and S32205 duplex stainless steels. In other words, S31803 and S32205 are both called  2205 stainless steel, and S32205 is the upgraded series of S31803 by the adding of the lower limit content of Cr, Mo and N elements, which makes the little difference in mechanical properties. Their tiny differences in chemical elements and physical properties are showed below:

UNS2205C maxPSSi maxMn maxNMoNiCr









2.00 max0.14-0.23.0-3.54.5-6.522.0-23.0


UNS2205Tensile strength

min, Mpa

Yield strength

0.2% offset, min, Mpa

Elongation, A5%


According to the ASTM A182 Standard, Specification for forged or stainless steel pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service, UNS S31803 and UNS S32205 cannot be confused and they specified in different number, S31803 is marked by F51 and S32205 is F60.

When speaking of 2205 steel, it generally refers to S31803 or F51, while UNS S32205 or F60 conforms to ASTM 2205 adopts its higher corrosion resistance range, that is, UNS S32205 requires higher Chromium and Nitrogen content, thus guaranteeing better corrosion resistance. Generally, S32205 steel plate and S31803 are also called double standard steel plate, or 2205 steel plate for short. Our factory produce 2205 tubing and 2205 plates to make its chemical composition conform to two specifications of UNS 31803 and S30025. Our steel plate in stock can meet two kinds of standards at the same time.