Ductile Cast Iron
Ductile cast iron is an alloy of iron, carbon and silicon, in which the carbon is in the pure state, in the form of spheroidal graphite. This spheroidal form of graphite, added to the known advantages of gray cast iron, such as tensile strength, impact resistance, high yield strength and high elongation, differentiate ductile iron from other types of cast iron.
The influence of graphite shape
In gray cast iron, graphite presents itself in the form of lamellae, from which derives its metallurgical name: cast iron with lamellar graphite. Each of these graphite lamellae may, under a concentration of abnormal stress at certain points, cause a fracture to begin. Metallurgists sought a way to lessen or even eliminate these effects by changing the size or shape of these coverslips. The centrifugation allowed to obtain very thin spheroidal lamellae that significantly increase the mechanical qualities of the iron, as can be seen in the scheme below:
Mechanical properties of ductile iron
- Elasticity (Re ≥ 270 MPa);
- Breaking strength (Rm ≥ 420 MPa);
- Brin Brinell hardness (≤ 230 HB);
- Resistance against shocks;
- Large stretchability (> 10%).