Pig iron

Pig iron is iron in an ingot form. It is the immediate product of heating iron ore, coke, and limestone in a blast furnace - a hard but brittle mix of iron (90% or more) and carbon (roughly 4%), manganese, sulfur, phosphorus, and silicon (roughly 3% in total). It requires further treatment to produce steel or wrought iron.

The name is derived from the time when the iron ran into molds in sand beds fed from a common runner. The row of molds was said to resemble a litter of suckling pigs, hence the individual ingots were referred to as pigs and the runner was called the sow.

This same material is called cast iron when cast into objects. The salient feature of its manufacture is that the mix of about 3.5 percent carbon with iron makes an alloy that has a minimum melting point (ca 1420-1470 K), and therefore can be created at temperatures at least 300 K lower than the melting point of pure iron.

The Chinese were making pig iron by the later Zhou Dynasty (1122 BC - 256 BC). In Europe, the process did not become common until the 14th century.