Electrical Design for Modern Arc Furnace Operating Modes.

Compared with conventional units, the design of modern arc melting furnaces focuses largely on the melting process because, except for the removal of phosphorus, metallurgical treatment of the molten bath is increasingly effected outside the furnace vessel. Following some considerations on process power input, the strategies for furnaces equipped with water-cooled furnace linings and/or operating with a foamy slag are discussed. It is found that conditions favor the use of an arc of shorter length and lower current density. This offers three advantages: electrode consumption is reduced, process efficiency increased and tap-to-tap time shortened. An analysis of the possibilities for substituting other sources of energy for electric power shows that this loses attractiveness as furnace size and/or output increase. Moreover, the rising costs of primary energy impose limitations beyond those originally anticipated. Oxygen, oil-oxygen or gas-oxygen burners will in future be increasingly used to achieve a uniform rate of melt-down.