GB1061643A - Melting of metals in a furnace by means of a stabilized alternating current arc - Google Patents

Abstract

1,061,643. Supply systems for arc furnaces. BRITISH OXYGEN CO. Ltd. April 6, 1964 [April 11, 1963], No. 14653/63. Heading H2H. [Also in Division H5] Apparatus for melting metals includes at least one plasma torch operated to provide both a main arc, which is sustained between the torch and the metal to be melted by an A.C. supply, and a plasma jet sustained by a D.C. supply. As shown, a plasma torch comprises a cylindrical housing 1 formed with an axial cylindrical passage 2 having a nozzle 5 which constitutes an annular electrode and which may have a coating of alumina, a rod electrode 3 disposed axially within the passage 2, conduits 7 and 8 for the supply and exhaust of liquid coolant, and a conduit 6 for the supply of working gas. In use, the torch extends through the roof 10 of a furnace 11 containing a charge 14 of metal to be melted. Electrodes 3 and 5 are connected respectively to the negative and positive terminals of a D.C. power supply 20, whilst an A.C. supply 16 is connected between electrode 5 and a return electrode 13 in contact with the charge 14. In operation, an inert gas such as argon or helium is supplied through the conduit 6; an auxiliary D.C. arc is then struck between electrodes 3 and 5 so that the gas flowing out of the torch on to the metal charge 14 is heated and ionized; and the main A.C. arc is established between electrode 5 and the surface of the charge 14, its position tending to remain stable since it keeps to the ionized path provided by the gas stream. The electrode 13 may be replaced by an electrode 13A introduced into the furnace through a pouring spout 15, or by an electrode 23 disposed in the bottom wall of the furnace. A plurality of torches may be provided, and a three-phase embodiment is described with reference to Fig. 3 (not shown). The metal to be melted may be in the form of a bar which is fed continuously into the furnace (Fig. 4, not shown).