Cast iron is a generic term for a family of high carbon,high silicon iron alloys.All cast irons contain at least 2%carbon which exceeds the solubility limit in iron.During solidification,carbon precipitates out of solution to form a solid particle of graphite.Gray cast irons contain graphite in the form of flakes.Ductile cast irons contain graphite in the form of spheres or nodules.Gray irons tend to be relatively weak and brittle while ductile iron is much stronger and has properties similar to carbon steel.The graphite nodules also enhance machinability,acting as a chip breaker and providing a lubricating surface between the workpiece and tool.This paper explains the metallurgical characteristics of ductile iron,engineering properties and opportunities for cost reduction by converting from carbon steel to ductile iron.