Production of Silico-Manganese in a Submerged Arc Furnace Jun09

Production of Silico-Manganese in a Submerged Arc Furnace...

Production of Silico-Manganese in a Submerged Arc Furnace Silico-manganese (Si-Mn) is an alloy used for adding both silicon (Si) and manganese (Mn) to liquid steel during steelmaking at low carbon (C) content. A standard Si-Mn alloy contains 65 % to 70 % Mn, 15 % to 20 % Si and 1.5 % to 2 % C. Si-Mn alloy grades are medium carbon (MC) and low carbon (LC). The steelmaking industry is the only consumer of this alloy. Use of Si-Mn during steelmaking in place of a mix of high carbon ferro-manganese (Fe-Mn) alloy and ferro-silicon (Fe-Si) alloy is driven by economic considerations. Both Mn and Si are crucial constituents in steelmaking. They are used as deoxidizers, desulphurizers and alloying elements. Si is the primary deoxidizer. Mn is a milder deoxidizer than Si but enhances the effectiveness due to the formation of stable manganese silicates and aluminates. It also serves as desulphurizer. Manganese is used as an alloying element in almost all types of steel. Of particular interest is its modifying effect on the iron-carbon (Fe-C) system by increasing the hardenability of the steel. Si-Mn is produced by carbo-thermic reduction of oxidic raw materials in a three-phase, alternating current (AC), submerged arc furnace (SAF) which is also being used for the production of Fe-Mn. Operation of the process for the Si-Mn production is often more difficult than the Fe-Mn production process since higher process temperature is needed. The common sizes of the SAF used for the production of Si-Mn are normally in the range 9 MVA to 40 MVA producing 45 tons to 220 tons of Si-Mn per day. In the carbo-thermic reduction of oxidic raw materials, heat is just as essential for reduction as C is, due to the endothermic reduction reactions and a...