Spheroidal Graphite Iron is sometimes referred to as Ductile Cast Iron, Nodular Cast Iron, and Spherulitic Graphite Cast Iron. Ductile iron rolls or S.G. iron (nodular) are offered in a variety of compositions and hardnesses for use in a wide range of tasks. In order to encourage the production of free graphite as nodules or spherulites, S G Iron is a variety of cast iron that has been processed with an element such as magnesium or cerium while it is still molten. The rolls are employed in the roughing, intermediate, and finishing stands of mills that produce both heavy and light section steel. Heat treatment is used to increase the strength of some important grades. This gives the cast metal a definite amount of ductility (easiness of manipulation). .