Stainless Steel: Families, Grades & Selection
Stainless steels use chromium to form a passive surface film and are selected for corrosion resistance, hygiene, appearance, oxidation resistance and combinations of strength and toughness.
Composition & metallurgy
Most stainless steels contain at least about 10.5% chromium. Nickel, molybdenum, nitrogen, manganese, copper and other elements are added to tailor corrosion resistance, formability, strength and phase balance.
Common grades
Common families include 304/304L, 316/316L, 321, 347, 430, 409, 410, 420, 440C, duplex 2205, super duplex 2507 and precipitation-hardening 17-4PH.
Applications
Food and pharmaceutical equipment, architectural cladding, water systems, chemical plants, heat exchangers, marine equipment, exhausts, pressure piping, fasteners and medical devices.
Engineering characteristics
Corrosion performance depends on grade, surface finish, fabrication quality, chloride exposure, temperature and crevice conditions. Stainless does not mean corrosion-proof.
Known manufacturers
China — Tsingshan, TISCO/Baowu, Delong; India — Jindal Stainless; South Korea — POSCO; Finland/United States — Outokumpu; Spain/United States — Acerinox; Europe/Brazil — Aperam; Japan — Nippon Steel and specialty stainless 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.
