While ductile iron can be produced from steel or iron scrap, pig iron is the primary source of infeed for most modern ductile iron foundries. Pig iron refers to the primary iron production of a blast furnace that contains over ninety percent iron.
The term “pig iron” arose from the old-fashioned method of casting blast furnace iron into molds arranged in sand beds in such a manner that they could be fed from a common runner. Because the groups of molds resembled a litter of suckling pigs, the individual pieces of iron were referred to as “pigs” and the runner was referred to as a sow. Modern pigs are produced by a continuous pig casting machines.
Pig iron is used in ductile iron production as a primary source of pure iron. It offers a number of unique advantages: pig iron contains low residual or harmful elements, has a consistent chemistry, promotes optimal slag conditions, and improves process control by providing consistent charge properties. Demand for pig iron has increased in recent years as ductile iron foundries utilize its advantages over alternate iron sources such as iron scrap, or melting steel scrap and adding carbon.
