Composition Of Ductile Iron Castings

Cast iron is an iron-carbon alloy with a carbon content exceeding 2.11%, produced by melting and casting industrial pig iron, scrap steel, and other ferrous materials. In addition to iron, the carbon within the alloy precipitates in the form of graphite. Depending on the shape of the precipitated graphite, the material is classified as follows: flake graphite indicates gray cast iron; vermicular (worm-like) graphite indicates compacted graphite iron; flocculent (clump-like) graphite indicates malleable iron; and spheroidal (spherical) graphite indicates ductile iron (also known as nodular cast iron or spheroidal graphite iron).
Apart from iron, the typical chemical composition of ductile iron includes 3.0–4.0% carbon, 1.8–3.2% silicon, a combined manganese, phosphorus, and sulfur content not exceeding 3.0%, and appropriate amounts of spheroidizing elements such as rare earth metals and magnesium.