4. Treatment deformations

During the conventional quenching and tempering process, deformations appear, the origin of which can be attributed to :

• on the one hand, to volume variations generated by structural transformations ( $\text{γ}\rightleftharpoons \text{α}$ , carbide precipitation, etc.) and the associated changes in material density;

• on the other hand, to variations in shape linked to mechanical stresses that may be imposed on steel, whose yield strength is greatly reduced by temperature: for example, untensioned machining stresses, the parts' own mass if they are poorly supported, thermal stresses generated by temperature gradients created during heating or cooling; as a first approximation,...