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Duplex stainless steel pipes, plates, fittings, and forgings exhibit a microstructure comprising approximately equal parts of austenite and a ferrite matrix. This composition, in tandem with a general alloying level, imparts notable characteristics. These alloys exhibit high strength compared to standard austenitic steels like type 316L, ensuring robustness in various applications. Their corrosion resistance extends across diverse environments, making them well-suited for challenging conditions. Notably, they demonstrate elevated resistance to chloride-induced stress corrosion cracking (CSCC) and pitting attacks in chloride-rich environments, such as seawater. In the offshore oil/gas, chemical, and petrochemical process industries, these alloys find expanding applications, encompassing pipework systems, flowlines, risers, manifolds, and more. Additionally, the filler metal derived from these alloys is utilized for welding stainless structures requiring exceptionally high strength.

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).

Preheating is typically considered unnecessary in welding processes, and adherence to a maximum interpass temperature of 150°C is recommended. The acceptable range for heat input falls within 1.0–2.5 kJ/mm, contingent on material thickness, though certain codes impose more stringent limits, often capping it at 1.75 or 2.0 kJ/mm. While welds in wrought duplex stainless steels are commonly left in the as-welded condition, substantial repairs to castings are typically specified in the solution-treated state. Experience in the field has consistently demonstrated favorable material properties when employing a treatment regimen involving exposure to 1120°C for 3-6 hours, followed by a water quenching process. In some instances, incorporating an additional cooling step to 1060°C before quenching has shown promising results in further enhancing the structural characteristics and overall performance of the welded components.