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No of Pages: 11
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Abstract:
Spheroidal Graphite (S.G) Iron is the name given to that cast –iron, where the graphite is present in the matrix in the form of spheroid or globules or nodules. Hence it is also called as Nodular Iron and because of its exceptionally high ductility (with elongation some times as high as 22%) is also referred to as ductile iron.
The rapid growth of S.G iron and its high consumption are testimonials to its outstanding mechanical properties. Heat treatments such as austempering have further enhanced its properties. S.G iron is hence finding extensive application in number of the fields. After having basically replaced a number of gray iron and malleable iron casting they have made penetrating in roads, the forging industry such as crank shafts and cam shafts originally made by the forging technology are now being cast in iron. S.G iron is produced by the treatment of gray-iron with either cerium or magnesium. The more commercial of the two is magnesium and is now almost universally used for production of S.G iron. Use of cerium is restricted as it is a carbide forming element beyond 0.01%.
Table of Content:
- DIFFERENT BETWEEN GREY IRON AND S.G IRON
- PRORERTIES OF S.G IRON
- PRODUCTION OF S.G. IRON
- SUBVERSIBLE ELEMENT AND ITS NEUTRALIZATION
Introduction:
The first announcement of successful production of Spheroidal Graphite structures in grey cast irons was made by H. Morragh of British cast iron Research Association in the year 1948 at the American Foundrymen”s society’s Annual convention in Phladelphia, U.S.A.The process involved a treatment of low sulphur hyper- eutectic cast iron with cerium, which was added as mish metal shortly before casting. In same convention, T.M Wickenden of the International Nickel Company, U.S.A disclosed that their researchers had also found out a method of production of Spheroidal Graphite structure in the as cast condition by the introduction in the iron, either hyper- eutectic, of a small but effective amount of magnesium or a magnesium containing addition such as a nickel-magnesium alloy. Since then the latter process has been found to be a commercially viable process and is now universally used for the production of Spheroidal cast-iron.
The mechanism of graphite nodule formation however is still a matter of great controversy. Various theories have been put forward by various researchers but none of them have gained universal acceptance.
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