duplex stainless steel's Classification

Duplex stainless steel is classified according to the level of PRE:

PRE =( Cr%+3.3×(Mo+1/2W)%+16×N% in steel)

1. Low-alloy duplex stainless steel: Representative grade: UNS S32304 (23Cr-4Ni-0.1N),  does't contain molybdenum, pitting resistance equivalent, PRE value is 24-25, It can be used in place of AISI304 (0Cr18Ni9) or 316L (00Cr17Ni12Mo2) in terms of stress corrosion resistance.

2. Medium dulex stainless steel: Representative grade: UNS S31803 duplex stainless steel（22Cr-5Ni-3Mo-0.15N)，(SAF 2505 duplex stainless steel)  PRE value is 32-33. its corrosion resistance is between AISI316L (00Cr17Ni12Mo2) and 6%Mo+N  stainless steel.

3, high alloy dulex stainless steel:  The Cr of this type of duplex stainless steel is up to 25% chromium and it is the earliest duplex stainless steel.Representative grade: United States 329 .Subsequently, all major industrial countries have developed, with more brands and applications.

4, super dulex stainless steel: refers to PREN> 40, containing 25% Cr and high molybdenum (>3.5%), high nitrogen (0.22% ~ 0.30%) of dulex stainless steel, the main brands are UNS S32550 (UR52N +), S32750 duplex stainless steel (SAF 2507 duplex stainless steel) and S32760 (Zeron 100),They were developed by French CLI, Swedish SANDVIK and British MATER+PLATT.