Ductile iron pipes and ordinary cast iron contain graphite monomer, which means that cast iron is a mixture of iron and graphite. The graphite in ordinary cast iron is flake, the strength of graphite is very low, so there are many flake voids in cast iron, so the strength of ordinary cast iron is lower and brittle.
The properties of ductile iron are close to that of carbon steel. Graphite in graphite cast iron is spherical, which is equivalent to many spherical voids in cast iron. The effect of spherical voids on the strength of cast iron is much smaller than that of flake, so the strength of ductile iron is much higher than that of ordinary cast iron. High-strength ductile iron pipes are welcomed by users.