The earliest casting of iron dates back to the fifth century. Through the eras, cast iron has been put into use for various purposes from architectural to engineering and textile to agricultural purposes. The re-melting of pig iron to make iron casting in a furnace involves an elaborate process that includes removal of impurities and addition of other elements and regulation and replacement of a few substances. After the melting is complete, the molten iron is poured into suitable casts depending upon its application.
Based on the type of alloy added, cast iron is classified as gray, white and malleable cast iron. While gray cast iron is characterized by its graphitic microstructure and is the most widely used cast iron, the white cast iron exhibits white fractured surface due to the presence of cementite. When the white iron is given heat treatment, they turn into malleable cast iron that does not have stress concentration problems because of their blunt boundaries as opposed to white iron that exhibit flakes.