Composition & metallurgy

Typical duplex 2205 uses about 22% chromium with nickel, molybdenum and nitrogen. Super duplex 2507 raises chromium, molybdenum and nitrogen for more severe chloride environments.

Common grades

Lean duplex 2101/2304, duplex 2205 (UNS S31803/S32205) and super duplex 2507 (UNS S32750), plus other super/lean duplex grades.

Applications

Desalination, offshore and marine systems, chemical processing, pulp and paper, pressure vessels, heat exchangers and high-chloride water service.

Engineering characteristics

Roughly twice the yield strength of common 300-series stainless in many product forms. Welding heat input and interpass temperature must be controlled to maintain phase balance and avoid harmful intermetallic phases.

Known manufacturers

Outokumpu, Alleima, Acerinox, Aperam, Jindal Stainless, POSCO, Tsingshan and other qualified duplex plate/tube producers.

Specification checks

Confirm the current standard revision, exact product form, heat-treatment condition, mechanical properties, impact requirements where applicable, corrosion environment, welding procedure, dimensions, tolerances, NDT and mill test certification. Similar designations across standards are not automatically equivalent.

Element Folio engineering reference. Manufacturer examples are indicative and product availability changes by plant, region and year.