Sponge Iron

Sponge iron, also called direct reduced iron, is the product created when iron ore is reduced to metallic iron, usually with some kind of carbon (charcoal, etc), at temperatures below the melting point of iron. This results in a spongy mass, sometimes called a bloom, consisting of a mix of incandescent wrought iron and slag.

Sponge iron is not useful in it, but can be processed to create wrought iron. The sponge is removed from the furnace, called abloomery, and repeatedly beaten with heavy hammers and folded over to remove the slag, oxidize any carbon or carbide and weld the iron together. This treatment usually creates wrought iron with about three percent slag and a fraction of a percent of other impurities. Further treatment may add controlled amounts of carbon, allowing various kinds of heat treatment (e.g. "steeling").Today, sponge iron is created by reducing iron ore without melting it. This makes for an energy-efficient feedstock for specialty steel manufacturers which used to rely upon scrap metal.