Lean Duplex UR2202: an alternative to 304L with increased corrosion resistance and mechanical properties

Due to their lower Ni content, duplex stainless steels are less sensitive to raw materials fluctuations compared to austenitics. In numerous applications, a very cost effective duplex solution can be proposed as an alternative to austenitic material with at least similar corrosion resistance and better mechanical properties. For instance, UNS S32304 (EN 1.4362) replaced 316L (EN 1.4404) material in evaporators for sea water desalination units and UNS S32205 (EN 1.4462) is used instead of 317LMN (EN 1.4439) in the absorbers of wet flue gas desulphurization systems. This paper presents the new Mo free duplex stainless steel UR2202 (EN 1.4062-X2 CrNiN 22-2, UNS S32202) developed to provide a cost effective alternative to 304L (EN 1.4307), concrete, organic materials or galvanized carbon steel in potable water systems, pulp & paper industry and construction applications. The reduction of Ni is balanced by a nitrogen addition in order to obtain a microstructure containing approximately 50% ferrite and 50% austenite. After a preliminary study performed with laboratory heats, several industrial heats were produced with 22Cr%, 2Ni% and 0.2% as the typical compositions.In this paper, the results of an investigation performed on hot rolled plates are presented and discussed. Both, general corrosion properties and corrosion resistance in media representative of specific applications are shown to compare the behavior of UR2202 with that of other stainless steel grades. It appears that this new lean duplex grade UR2202 has a localized and uniform corrosion better than 304L material and about twice the yield strength.