HARDENING AND TEMPERING WITH REESE:

When a steel in the austenitic phase (i.e. at temperatures over 723 °C) is suddenly cooled, the austenite transforms into martensite, a structure characterised by great hardness.

Tempering gives back the steel a certain toughness. The steel is tempered at temperatures as high as 700 °C for the optimal values of all mechanical properties.

This is particularly important for workpieces that are subjected to dynamic stress and therefore must exhibit high toughness.