ELECTRIC ARC FURNACE APPARATUS HAVING A SHAPED MAGNETIC FIELD FOR INCREASING THE UTILIZED AREA OF THE ARCING SURFACE OF AN ELECTRODE AND IMPROVING THE HEATING EFFICIENCY

摘要

The unit heat flux to a fluid-cooled electrode and the heat flux to the material being heated by a diffused arc column operating at a given electric current level are controlled by a magnetic field coaxial with the electrode, part of the flux lines of which pass through both the arcing surface of the electrode and the molten bath. The magnetic field pattern at the electrode and near the electrode is shaped into desired configurations to accomplish the purposes of the invention by the use of high permeability material in the electrode in some embodiments, and permanent magnets in the electrode in other embodiments. Where high permeability material is employed, the material may form part of the electrode tip and be substantially symmetrical around the inside and outside diameter of the tip, or may be so proportioned as to provide an outside diameter biased electrode tip. The tip may be constructed of copper and high permeability material disposed within the tip either in the form of a short ring, or axially and radially extending material occupying a substantial portion of the volume of the tip and the supporting column. Where a permanent magnet is employed, it is disposed in the tip, and the north and south poles of the permanent magnet may be axially disposed with respect to each other with their axis parallel to the axis of the electrode. The poles of the permanent magnet are selectively in opposition to a field set up in the furnace by a solenoid, or selectively in polarity adding to the field set up in the furnace by the solenoid. Additionally, the permanent magnet may have its north and south poles lying perpendicular to the axis of the electrode. Selectively, the north pole of the permanent magnet may be on the side thereof adjacent the axis of the electrode, or may be on the side thereof farthest from the axis of the electrode, nearer to the wall of the furnace and nearer to the solenoid setting up a magnetic field within the furnace.