This range of cast irons is known under a variety of names - Nodular, SG iron, Ductile or Spheroidal Graphite iron. These materials possess strength and ductile properties of a different type to flake or grey cast irons, whilst maintaining comparable machining characteristics.

While providing mechanical properties similar to cast steel or malleable iron, nodular iron presents few of the problems met with either (founding, high heat treatment and distortion, seize and section limitations etc).

As nodular iron can be poured at temperatures much lower than for cast steel, cast finish and dimensional accuracy are improved.