Abstract: A method of operating an electric arc furnace is disclosed by which an arc electrode provided in an electric arc furnace is supplied with electric power, an electric arc is extended from the arc electrode and raw material in the electric arc furnace is molten by the arc. Before operation of the electric arc furnace, an electric current I satisfying an equationd[Pi/(Pi-Pl-ql)]dI=0is first calculated where Pi is the secondary output of the used arc furnace transformer. Pl is the total ohmic loss of the secondary winding of the transformer and of an electric circuit connecting the secondary of the transformer with the arc electrode, ql is the heat loss of the used electric arc furnace and I is the electric current flowing from the secondary of the transformer to the arc electrode. Next, when electric power is really supplied to the arc electrode from the arc furnace transformer to operate the electric arc furnace, the beforehand obtained electric current is supplied to the arc electrode from the transformer.

Abstract: A method for controlling an arc furnace is disclosed. In first step, many V-curved correlations between a value of arc current and a specific electric power consumption are obtained with respect to each of a plurality of measuring melting materials of various different scrap blendings. Next, in factory operation of the arc furnace, a melting material is melt at an arc current value in the bottom of the curve or in the vicinity of the bottom where the specific electric power consumption is minimal in the pre-obtained V-curve correlation with respect to the measuring melting material of scrap blending corresponding to scrap blending of the melting material to be melted.

Abstract: Molten metal is pooled at the bottom of an electric arc furnace and a layer of slag is formed overlying the molten metal. Electric arcs are formed between the electrodes and molten metal, the arcs piercing through the slag layer to heat the molten metal and slag. Under this condition, reduced iron is charged into the slag layer, melted by the heat of slag and separated into slag component and iron component. The slag component is absorbed into the surrounding slag layer while the iron component passes through the slag layer and mixes in the molten metal. In case the temperatures of slag and molten metal have deviated from the setting values, the input power to the electrodes and the length of arcs formed between the electrodes and molten metal are so adjusted that the setting temperatures are restored.