Cast iron, an alloy of iron containing 2% to 4% carbon, with varying amounts of silicon and manganese and trace impurities such as sulfur and phosphorus. It is a blast furnace made by reducing iron ore. The liquid iron is cast or poured and hardened into coarse ingots called ingots, which are then remelted in cupola furnaces along with scrap and alloying elements, and recast into molds used to produce various products.