Cast iron is produced by smelting iron-carbon alloys that have a carbon content greater than 2%. After smelting, the metal is poured into a mold. cast iron contains 2–4% carbon and other alloys, and 1–3% of silicon, which improves the casting performance of the molten metal. It is the combination of high carbon content, and the presence of silicon, that gives cast iron its excellent castability. Various types of cast irons are produced using different heat treatment and processing techniques, including gray iron, white iron, malleable iron, ductile iron, and compacted graphite iron.