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Stainless steel according to the AISI standard (American Iron and Steel Institute) is marked with three digits and in some cases with Latin letters following them. The first digit indicates the steel class (2,3 for austenitic steels and 4 for ferritic and martensitic steels), the other two are the serial number within the class. The letters indicate the content of certain additives in the alloy: L stands for reduced carbon content, N - nitrogen addition, F - increased sulfur and phosphorus content, etc.

The most common are Class 3 alloys, which include:

  • AISI 304. The composition includes chromium 18%, nickel 10%, carbon 0.08%, copper, titanium and silicon in small quantities. It is used in the chemical and food industry, construction, housing and communal services, for the manufacture of bulk products of complex configuration for various purposes in the fields of mechanical engineering, furniture manufacturing, design;
  • AISI 316. Contains, in addition to chromium and nickel, molybdenum (2.5%). This additive provides maximum corrosion resistance of steel of this brand among massively used stainless steels. Environmentally friendly material used in the food and pharmaceutical industry. Resistance to aggressive environments allows it to be used in pipelines and other structures operating in environments with a high content of alkalis, salt and acid solutions, in the chemical and petrochemical industries, shipbuilding;
  • AISI 321. Contains 1.0% titanium. Durable heat-resistant steel (withstands temperatures up to 800 °C) with increased corrosion resistance. It is used in the chemical and oil refining industries, in pipelines operating under pressure.