2. Heat treatment

2.1 Relaxation treatment

The aim of this treatment is to significantly reduce residual casting stresses due to the complexity of the part's shape, which accentuates thermal heterogeneities during solidification and cooling in the mold.

These stresses can lead to deformation during machining or service and, in exceptional cases, to fracture. However, the majority of cast-iron parts do not require stress-relieving treatment, either because they contain no stresses, or because they are eliminated by another heat treatment.

In fact, stress relief is used for large parts that need to be dimensionally stable to a very high degree of accuracy (machine frames used in the watchmaking industry or in automatic control mechanisms), or for parts...