1. Austenitization

The purpose of austenitizing is to bring the carbon and any alloying elements precipitated in the form of carbides into solution. To achieve this, it is necessary to set the conditions under which carbon is soluble in iron, i.e. to cause, by heating, the transformation of iron α into iron γ.

It should be remembered that the examination of equilibrium diagrams (cf. ) shows that carbides precipitated after solidification or hot forming can be cementite (in non-alloy steels), substituted cementite (in low-alloy steels) or formed from carburigenic elements (in alloy steels), and that their solution conditions are therefore generally very different.

In the case of heat treatment in the mass, austenitization involves two stages:

• heating to a temperature known as the austenitizing...