Hardening and tempering

According to DIN EN 10052, hardening and tempering is defined as a heat treatment resulting in high ductility at a certain tensile strength by hardening and subsequent tempering usually to higher temperatures. (at Ac1).

The desired high ductility is achieved by the formation of fine carbides with utmost even distribution. The rougher the hardening process, the finer the structure after tempering.

Tensile strength, yield strength and hardness are reduced with increasing tempering temperature while elongation, necking and notch impact strength increase.

The tempering process also changes mechanical properties at higher and lower temperatures (yield strength at temperature and notch impact strength).

In the steelheat treatment process, the martensite formed during quench hardening is transformed into dispersed carbides during the following tempering treatment. Depending on the type of hardener (water, oil, air), the process is referred to as water quenching and tempering, oil quenching and tempering or air quenching and tempering. Instead of the normal quench hardening of steel, it is also possible to cool down the steel in a hot bath (hot-bath hardening) to bainitic temperature and maintain it at this temperature (s. Austempering).

Additional references:

Hardening capacity
Hardness penetration capacity
Interrupted quenching
Flame hardening
Case hardening
Electron beam hardening
Torch hardening
Induction hardening
Laser hardening, Nitriding
Immersion hardening
Hot-bath hardening
Hardening and tempering and heat treatment, respectively, of hardenable aluminum alloys