Steel for carburising is a group of machine alloy structural steels for thermo-chemical treatment, in which, after carburizing or cyaniding and heat treatment, it is expected to obtain a hard and wear-resistant surface of the product while maintaining sufficiently high ductility of the core. For this reason, steel for carburising is the most widely used and referred to as gear steel.

The hardness and abrasion-resistant surface are obtained by saturating it with carbon to a depth in the range of 0.8 – 1.5 mm and heat treatment, the subsequent stages of which are hardening and tempering. Steels from this subgroup are characterized by a relatively low carbon content in the chemical composition – max. 0.25% compared to other structural alloy steels (eg steel for improvement).

Compared to other surface hardening methods, such as nitriding, cyanidation or surface hardening, with the carburized surface of the product, the properties and hardness of the material deep into the core are tested and the parameters decrease not suddenly, but gradually. it is recommended to use mild carburizing agents for the surface of the material.

The carburizing process, depending on the steel grade, is carried out in the temperature range from approx. 880 – 1050 ℃. The subsequent quenching process for the core is 880-920 ℃, which can be entered immediately after the carburizing treatment. Hardening of carburized layers is in the range of 780-820 ℃. Tempering is carried out at temperatures of about 150-200 ℃.