3. Income

Applied to alloyed or unalloyed carbon steels after martensitic and/or martensitic-bainitic hardening, tempering (cf. ) is designed to precipitate carbon in a controlled form and under controlled conditions in order to achieve optimum hardening. This operation generates a structural evolution from the metastable state obtained after quenching to a state closer to physico-chemical equilibrium.

Eventually, this tempering may cause residual austenite to transform into bainite during holding, or into secondary martensite during final cooling.