The grade UNS S32205 (1.4462, F51) is the most commonly specified duplex stainless steel. Stainless steels using 22% chromium were developed in the 1930s for severe service applications in paper mills. The original specification was described under the UNS S31803 caption.
However, the content of chromium and molybdenum, which define resistance to pitting corrosion, was set at the higher end of the specification to form UNS S32205. Super duplex stainless steels were developed from the 1960s onwards, based around 25% chromium content. This gives them additional corrosion resistance and strength. Therefore, strictly speaking, 2205 super duplex is an inaccurate description of the 2205 duplex stainless steel.
Today, 2205 is most commonly made from 22% chromium, 3% molybdenum, and 5 to 6% nickel alloyed stainless steel.
Duplex stainless steels (such as grade UNS S32205) are extremely resistant to corrosion with their microstructures consisting of a mixture of austenite and ferrite phases. They display characteristics of both austenitic and ferritic stainless steels, with a combination of properties that mean some can compromise with pure austenitic and pure ferritic grades.
Duplex steels are also magnetic, which helps to differentiate them from common austenitic grades of stainless.
Langley Alloys carries an extensive stock of duplex stainless steel, up to 16″ (406.4mm) diameter solid bars, plate up to 3″ (76.2mm) thickness plus selected hollow bars, seamless tubes and fittings.
If you have any more questions about austenitic or duplex stainless steels, please contact us today. A member of our team will be more than happy to help and can also advise you on the best option for your application.