omsättningshärdning

Omsättningshärdning, also known as tempering or case hardening, is a surface heat treatment process used to harden the outer layer of steel while leaving the core relatively soft and ductile. This is achieved by heating the steel to a specific temperature, typically above its critical transformation temperature, and then rapidly cooling it in a quenching medium such as oil or water. The rapid cooling causes the surface layer to transform into a hard, brittle structure called martensite.

Following the quenching process, the steel is subjected to a tempering heat treatment. This involves reheating the steel to a lower temperature, below its critical transformation temperature, and holding it there for a period before cooling it again. The tempering process reduces the hardness and brittleness of the martensitic surface layer, increasing its toughness and ductility. The specific tempering temperature and time are carefully controlled to achieve the desired balance of hardness, strength, and toughness in the surface layer.

Omsättningshärdning is commonly applied to components that require a hard, wear-resistant surface, such as gears, shafts, and cutting tools, while also needing a tough core to withstand impact and bending loads. The depth of the hardened layer, known as the case depth, can be controlled by varying the heating and cooling rates, as well as the composition of the steel. The process is essential in extending the service life and improving the performance of many mechanical components.