Ductile Iron (also known as Spheroidal Graphite Iron or Nodular Cast Iron) was invented in 1949. Ductile Iron retains the corrosion resistance of Cast Iron but has more than double the tensile strength [Cast Iron- 180 MPa (min), Ductile Iron - 420 MPa (min)]. The essential difference between Ductile and Cast Iron lies in the shape of the graphite in the microstructure of the metal. In Cast Iron, the graphite is present in plate-like flakes, which makes Cast Iron brittle. But in Ductile Iron, the shape of the graphite becomes a spheroidal nodule, which offers better mechanical properties and makes Ductile Iron sturdy, structurally stronger and shock-proof.
Ductile Iron is considered the most preferred pipe material for water supply and pressure sewerage application all over the world. It offers higher Tensile Strength than Mild Steel and retains the inherent corrosion resistance of Cast Iron. Pipes made from Ductile Cast Iron provide substantial benefits in terms of pressure bearing ability, impact resistance and capacity to sustain external static/ dynamic loading.