Stainlesssteel

Stainless steel is a family of iron-based alloys characterized by high corrosion resistance due to a minimum chromium content of about 10.5% by mass. When chromium is present, it forms a thin, adherent chromium oxide layer on the surface that self-repairs in oxidizing environments, giving stainless steel its characteristic durability.

Stainless steels are grouped into several families, based on their crystal structure and alloying. The main types are austenitic (for example, 304 and 316), ferritic (such as 430), martensitic (such as 410 and 420), duplex (e.g., 2205), and precipitation-hardening grades (such as 17-4 PH). Austenitic steels are generally non-magnetic and offer good formability and corrosion resistance; ferritic and martensitic grades are often cheaper and stronger, with varying weldability; duplex grades balance strength and corrosion resistance; precipitation-hardening grades achieve high strength via ageing treatments.

Typical composition also includes elements like nickel, molybdenum, vanadium, titanium, and niobium, added to enhance specific properties. Stainless steel is produced by melting and refining iron with alloying elements, then forming by hot rolling or forging, followed by annealing, pickling, and sometimes passivation to restore the protective oxide film. Standards for grades are defined by organizations such as ASTM, EN, and JIS.

Applications span kitchenware, architecture, medical devices, chemical processing, oil and gas, and transportation. While stainless steel offers high corrosion resistance and strength, it may be sensitive to pitting or crevice corrosion in chloride-rich environments, and welding or heat treatment requires appropriate specifications to avoid sensitization or loss of corrosion resistance. Cost is generally higher than for carbon steel.