GB866106A - Improved arc working process and apparatus - Google Patents

Abstract

866,106. Arc melting furnaces. UNION CARBIDE CORPORATION. June 28, 1957 [June 29, 1956], No. 20417/57. Class 39(3). An arc furnace comprises a chamber 44 enclosing a -crucible 40 for holding the material 52, e.g. titanium sponge to be melted and means for producing an electric discharge between an electrode 60 and the material 52, the means forming one or more arc torches producing a stable beam of ionised gas directed to the material 52. A non-consumable tungsten electrode 60 is mounted within a metal nozzle 54 having an orifice 56 through which the arc is directed; and an inert gas, e.g. argon supplied under pressure from a pipe 66 to the nozzle fills the chamber. The arc torch is mounted in a ball and socket joint 50 on a cover 51 of the water-cooled chamber, so that the arc may be directed to any part of the surface of the material 52. The electrode 60 is connected to the negative side of a D.C. source having its positive side connected to the crucible 40 and for starting the arc through a ballast resistor 64 to the nozzle 54. The orifice 56 of the nozzle shapes the cross-section of the arc and is water-cooled. Several arc torches may be mounted in the cover 51; and if material to be melted is non-conductive when cold, a pair of stabilised beams of ionised gas is arranged to impinge on one another just above the material. The electrodes may be of the same or opposite potential and the crucible is of opposite potential to at least one of the electrodes. If the material becomes conductive when hot, the arc torches are then directed on to it so that it forms a resistance in series with the arcs. The titanium sponge is fed to the crucible through a pipe 68. The arc torch impinges on the molten material, e.g. an alloy so as to cause stirring thereof. The crucible 40 is of copper and is cooled by water. A 3 phase A.C. may be used in star connection with three electrodes. In a modification a protective gas, e.g. argon or nitrogen is fed to the electrode to make the arc torch and another gas either cheaper or more reactive is fed into the arc downstream of the arc. Thus preheated oxygen may be added to the arc in making steel by an oxygen gas process. An annular consumable carbon electrode may surround the nozzle and may be fed automatically so that its lower end projects just below the nozzle. A larger current is supplied to the carbon electrode than to the central arc torch which it surrounds and supplies energy to the arc torch. Specifications 845,410 and 845,411 are referred to.