Pig iron

Pig iron has a high carbon content, typically 3.8–4.7%,[1] along with silica and other dross, which makes it brittle and not useful directly as a material except for limited applications.

[4] As pig iron is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling.

Alternatively, decarburizing the pig iron into steel was an extremely tedious process using medieval technology, so in Europe before the Middle Ages the prills were discarded with the slag.

[9] In these processes, pig iron is melted and a strong current of air is directed over it while it is stirred or agitated.

Pig iron was historically poured directly out of the bottom of the blast furnace through a trough into a ladle car for transfer to the steel mill in mostly liquid form; in this state, the pig iron was referred to as hot metal.