Skip to main content
The Natural Composite: spheroidal Graphite Iron
  • Ajit Behera, Indian Institute of Technology - Kharagpur

The conventional materials are nowadays not sufficient to cater to the variety of uses and exposure to various environments that may take place while they are put into use. Hence this leads to the development of composites, which nearly suffice the above two conditions. Composite material is a material composed of two or more distinct phases (matrix phase and reinforcing phase) and having bulk properties significantly different from those of any of the constituents. In this developing age for iron industry there is large demand for spherodial Graphite iron (S.G. Iron). S.G. Iron also known as a composite in which the matrix consists of ferrite and/or pearlite and reinforcing component is graphite nodules which present in it. SG Iron also referred to as nodular cast iron or ductile cast Iron or spherulitic graphite cast iron. The scientist discovered the S.G. Iron in 1948. It is a special variety of cast iron having carbon content more than 3% and has graphite present in compact, spherical shapes. These compact spheroids hamper the continuity of the matrix much less than graphite flakes which results in higher strength and toughness which imparting superior mechanical properties i.e. much higher than all other cast irons and which can be compared to steels. This unique property enables S.G. irons to be used for numerous industrial applications. Tensile strength of S.G. Iron will be about 47-55 kg/sq. mm with an elongation of 10-25%. The excellent combination of mechanical properties obtained in S.G. iron can further be informed by the heat treatment. The use of this type of cast iron as an engineering material has been increasing day by day ever since its discovery. It is now replacing steel in many important engineering applications. The production of S.G Iron increased to a large extent during last two decades.

  • Spherodial Graphite irons (S.G. Iron); Morphology; Nodularity.
Publication Date
Citation Information
Ajit Behera. "The Natural Composite: spheroidal Graphite Iron" (2011)
Available at: