Roheisen

Roheisen, known in English as pig iron, is the crude iron produced directly from iron ore in a blast furnace. It is the primary product of commercial ironmaking and serves as the feedstock for subsequent steelmaking or for producing cast iron. The term Roheisen is the German name for this material.

Its composition is variable, but typical pig iron contains about 3.5 to 4.5 percent carbon, along with silicon, manganese, sulfur, and phosphorus as impurities. The carbon content and impurities give Roheisen a high hardness and brittleness, and in its as-cast state it is not suitable for most structural applications.

In a blast furnace, iron ore, coke, and limestone are charged from the top. Coke is burnt to generate heat and reducing gases (carbon monoxide and hydrogen) that reduce iron oxides to metallic iron. Limestone forms a slag with silicates and oxides, helping to remove impurities. The hot liquid iron and slag are tapped separately; the liquid iron is cast into molds to solidify as pigs or blocks.

As a raw material, Roheisen is refined in later steps to produce steel or cast iron. In steelmaking, it is converted to steel through processes such as basic oxygen fusion or electric arc furnace methods, which reduce carbon content and adjust alloying elements. Depending on refining and alloying, different end products can result, including various grades of cast iron and steel.