Duplex stainless steels are extremely corrosion resistant, work hardenable alloys. Their microstructures consist of a mixture of austenite and ferrite phases. As a result, duplex stainless steels display properties characteristic of both austenitic and ferritic stainless steels. This combination of properties can mean some compromise when compared with pure austenitic and pure ferritic grades.
Duplex stainless steels are in most cases, tougher than ferritic stainless steels. Strengths of duplex stainless steels can in some cases be double that for austenitic stainless steels.
Whilst duplex stainless steels are considered resistant to stress corrosion cracking, they are not as resistant to this form of attack as ferritic stainless steels. However, the corrosion resistance of the least resistant duplex stainless steels is greater than that for the most commonly used grades of stainless steels, i.e. 304 and 316.
Duplex steels are also magnetic, a property that can be used to easily differentiate them from common austenitic grades of stainless.
S32205 composition % according to ASTM A789 ASTM A790:
S31803 composition % according to ASTM A789 ASTM A790:
Tensile Strength (MPa/ksi)
Yield Strength 0.2% Proof (MPA/ksi) min
Elongation (% in 50mm) min
· Heat exchangers, tubes and pipe for production and handling of gas and oil
· Heat exchangers and pipes in desalination plants
· Pressure vessels, pipes, tanks and heat exchangers for processing and transport of various chemicals
· Pressure vessels, tanks and pipes in process industries handling chlorides
· Rotors, fans, shafts and press rolls where the high corrosion fatigue strength can be utilized
· Cargo tanks, piping and welding consumables for chemical tankers