Duplex Stainless Steel

Duplex stainless steel grade 2205 (also known as UNS S31803/S32205, ASTM A240 Type 2205, Inox 2205, AISI 318LN, SUS 329J3L, or EN 1.4462) is a two-phase (ferritic-austenitic) alloy containing about 22–23% chromium, 2.5–3.5% molybdenum, 4.5–6.5% nickel, and roughly 0.15% nitrogen. Its balanced microstructure provides a unique combination of high strength and excellent corrosion resistance. For example, grade 2205 typically has about twice the yield strength of 316L stainless steel, allowing designers to use much thinner, lighter sections without sacrificing performance.

The alloy is normally supplied in the solution-annealed condition (per ASTM A240/A240M) to retain an ideal duplex structure. Grade 2205 remains tough from cryogenic temperatures (around –50°C) up to about +300°C; beyond this range, brittle sigma phase can form in welds. These properties make duplex 2205 an excellent choice for demanding applications such as chemical processing, offshore oil & gas, and marine environments where both high strength and chloride corrosion resistance are required.