AISI 309 Stainless Steel Foil

AISI 309 Stainless Steel Foil (UNS S30900) is a high-chromium, high-nickel austenitic stainless steel foil engineered for elevated-temperature service, offering significantly superior oxidation resistance and strength retention compared with standard 18-8 grades. Its 22–24% chromium and 12–15% nickel composition forms a stable oxide scale under continuous and cyclic thermal exposure, while room-temperature mechanical properties of 621 MPa tensile strength and 49% elongation support good formability. Supplied in the annealed condition at 1.0 mm and 2.0 mm thicknesses in cut sizes up to 625 × 2500 mm, it is weldable by all common fusion processes and cold-formable by bending, roll forming, and drawing. Typical applications include furnace linings, heat-treatment retorts, and components exposed to hot acids, ammonia, and sulphur-bearing combustion gases. In research, it serves as a reproducible substrate for oxidation kinetics studies and thermal fatigue testing.