Hardening and annealing

Hardening

The hardening process consists of heating the steel parts to the austenitizing temperature, followed by a controlled quenching, in order to obtain the martensite structure. The austenitizing temperature, the hardenability, and the quenching speed are determined according to the steel composition, and can be obtained from steel manufacturers catalogues and from their respective TTT (Time Temperature Transformation) diagrams. Hardening is usually followed by a complementary heat treatment called tempering.

The hardening salt baths (austenizing) can be divided in 2 groups: with cyanide and without cyanide.

The hardening salts without cyanide are recommended for heat treatment of tool steels with medium and high chrome levels, martensitic stainless steels and also high speed steels. Durferrit has proper salts for several hardening needs.

Annealing is a heat treatment used in order to reach some of the following goals: to remove tensions due to hot or cold mechanical treatment, to reduce hardness to improve machinability, to alter mechanical properties such as resistance, ductility, etc., to adjust grain size, etc. Depending on the necessary temperature and the parts specifications, some hardening baths can also be used for annealing.