Ferromanganese plant in Brens (Cee), Spain
Ferromanganese, a ferroalloy with high content of manganese, is made by heating a mixture of the oxides MnO2 and Fe2O3, with carbon, usually as coal and coke, in either a blast furnace or an electric arc furnace-type system, called a submerged arc furnace. The oxides undergo carbothermal reduction in the furnaces, producing the ferromanganese. Ferromanganese is used as a deoxidizer for steel.
Henry Bessemer invented the use of ferromanganese as a method of introducing manganese in controlled proportions during the production of steel. The advantage of combining powdered iron oxide and manganese oxide together is the lower melting point of the combined alloy compared to pure manganese oxide.
A North American standard specification is ASTM A99. The ten grades covered under this specification includes;
- Standard ferromanganese
- Medium-carbon ferromanganese
- Low-carbon ferromanganese
A similar material is a pig iron with high content of manganese, is called spiegeleisen.