Nitrogen Steels and High‐Nitrogen Steels: Industrial Technologies and Properties

Nitrogen pressure during melting can be a basis for the most general classification of steels alloyed by nitrogen. Nitrogen steels are made under normal pressure, and high‐nitrogen steels are made under pressure, being higher atmospheric in special units. Nitrogen, as well as carbon, strengthens and increases the thermal stability of austenite. The smaller size of the nitrogen ion compared with carbon results in smaller nitrides, lower surface energy and higher strengthening effect, and the ability to increase both the strength and corrosion resistance of austenite. Herein, the mechanisms of the influence of nitrogen on the properties of steel, the thermodynamics and kinetics of alloying with nitrogen, the critical concentration of nitrogen, and the influence of nitrogen on the properties of steels are considered. Examples of nitrogen and high‐nitrogen steels, including weld joints, steels with special properties, such as corrosion‐resistant steels in bioactive environments, bactericidal steel, and steels alloyed by C + N, are given.