4. Two important concepts: hardenability and hardenability of steel

The conditions under which the γ → α transformation takes place enable the formation of different constituents that confer properties on the steel that can vary over very wide ranges. By modifying these conditions, it is therefore possible to change the mechanical strength characteristics of the steel as required, by influencing its hardening.

The upper limit of a steel's hardenability is defined by its hardenability, the maximum value of hardenability that can be achieved in the martensitic state. It is directly related to the amount of carbon dissolved in the austenite prior to transformation (figure ). This is an intrinsic characteristic of steel.

In practice, however, we have to take into account a feasibility criterion...