This group includes all types of  structural steels that are to be quenched and tempered, i.e. which will undergo massive hardening followed by adequate tempering.

When the steel has only been hardened, it takes on an extreme toughness with very low tenacity:  it is therefore necessary to temper the steel in order to  eliminate all the fragility and tension.  Indeed, this process gives the pieces a particular toughness and tenacity, making them suitable for use in even the most severe conditions and reaching a compromise between tenacity/toughness and resilience.

The tempering process is generally carried out on pieces that have reached the final stage of production, after most of the mechanical treatments. In this case, the semi-finished raw material can be supplied in its natural state of being workable as rolled or annealed, depending on the type of steel.