2209

The 2209 subfamily is used in pipes, plates, fittings, and forgings made from duplex stainless steel. This type of steel has a microstructure composed of about 50% austenite with a ferritic matrix. This composition, together with the general level of alloying, ensures superior strength compared to conventional austenitic steels, such as type 316L. It also offers excellent corrosion resistance in a wide range of environments, along with notable resistance to chloride-induced stress corrosion cracking (CSCC) and pitting attack in chlorinated environments, such as seawater. These characteristics make the alloys particularly appreciated in offshore applications in the oil, gas, chemical, and petrochemical sectors, including piping systems, flow lines, risers, and manifolds.

22%Cr standard ferritic-austenitic duplex stainless steels.

Multipass welds in the as-welded condition contain about 25–50% ferrite depending on dilution and heat input/cooling rate conditions.

• EN W.Nr.: 1.4462 (X2CrNiMoN22-5-3), 1.4362 (X2CrNiN23-4)
• ASTM: A182 Gr F51, A890 Gr 4A (cast)
• UNS: S31803, S32205, S32101, S32304, S32001, J92205
• PROPRIETARY: SAF2205, SAF 2304 (Sandvik), Uranus® 45N, 35N (Industeel), A903 (voestalpine), Cronifer 2205LCN (VDM), Maresist F51 (Schmidt + Clemens), SM22Cr (Nippon Steel Corporation), LDX 2101 (Outokumpu)

Generally, preheating is not necessary for welding. It is advisable to maintain a maximum interpass temperature of 150 °C. The heat input should be between 1.0 and 2.5 kJ/mm, depending on the material thickness; however, some codes limit the value to a maximum of 1.75 or 2.0 kJ/mm. Although welds on duplex stainless steels are almost always left as-welded, solution treatment is generally required for major repairs on castings. Studies and experience have shown that a water quench treatment at 1120 °C for 3-6 hours, with or without a cooling step at 1060 °C before quenching, imparts excellent metallurgical properties.