Isothermal annealing is a heat treatment that completely eliminates the tensions deriving from hot and cold plastic processing, considerably reduces the hardness of the material and homogenises the metallographic structure.
On an industrial level, it is preferred to complete annealing because it is more convenient both in terms of time and means.
Isothermal annealing is composed of several stages:
The scope is to obtain maximum workability of the tool and excellent dimensional stability which can be found even after the final heat treatments such as carburizing, hardening and tempering or hardening
The steels particularly suitable for this type of treatment are case-hardening steels, special mold steels, hypereutectoid steels.
Permanence until the complete transformation of the austenite; cooling in air or other, since the cooling rate no longer influences the transformation.
Structurally very uniform lamellar ferrite and / or perlite are thus obtained, thanks to the constant temperature stop.