Pig iron is a metal material that results when iron ore, low ash coke, and limestone are melted together under intense air pressure. When the combined material cools, it forms a high-carbon product known as pig iron. The cooled material is rarely used by itself, as the large amount of carbon makes the material brittle and unstable. This type of iron is further refined through additional melting and blending processes to create wrought iron, cast iron, or steel.