Patent GB-811917-A (GB)
Title: Improvements in or relating to apparatus for forming ingots by electric heating
Inventor: GARMY ROBERT JAMES
IPC: C22B34/12
Filed: 1955-07-19
Abstract: 811,917. Arc melting furnaces. REPUBLIC STEEL CORPORATION, July 19, 1955, No. 20905/55. Class 39(3) [Also in Groups XII and XXXV] Metal ingots are formed from metal particles especially of titartum or zirconium or to form alloys of these metals with vanadium, aluminium, chromium or iron by feeding the particles continuously into the centre of a crucible 4, while moving at least one electrode 22 continuously over the periphery of the charge. T h e cylindrical water-cooled crucible 4 of copper or molybdenum is mounted on springs 131 on jacks 128 on a trolley 5, whereby the crucible may be raised so that an outer flange 109 near its top engages a circular ring 102 at the base of a cylindrical shell 1 open at its lower end through which project the lower ends 50 of the electrodes 22. The electrodes may be oscillated radially and circularly about the of the crucible to move over an annular surface of the charge. The particles are fed through a vibrated lateral pipe 52 into a hopper 59 mounted on a central hollow pipe 58 in the shell and pass through an opening 58a into the pipe 58 through which they then fall. The electrodes 22 project down into the crucible from supporting masts 10 on a frame 8 which may be rotated or oscillated. The D.C. arc passes to and through the charge, the other current terminal being connected to the base of the crucible. The water-cooled electrodes 22 have each an offset tip 50 of graphite, tungsten or of the material to be melted, so that on rotation of each electrode on its main axis by a motor 23, the electrode tip moves over a circle. The electrodes and their support masts 10 are mounted away from the centre line of the crucible so that the electrodes can rotate about the centre of the crucible and about their own main axes. The amplitude of the oscillations may be controlled by limit switches. Four electrodes may be spaced at equal angles about the crucible axis, and the shell 8 may oscillate through this angle (90 degrees). Each electrode may be automatically moved vertically to maintain a constant arc length (see Group XXXV). The electrodes are assembled as shown in Fig. 10 with water inlet 43a and outlet 43b and are mounted with their motors 23 on carriages 17 carrying springs to protect the electrodes against shock and carrying wheels running in grooved rails on the masts 10. D.C. is fed to the electrodes, which are counterbalanced, from bus-bars 166 through flexible water-cooled cables 167. Cooling water for the electrodes, which are maintained at a negative potential relatively to the crucible, is separately supplied from a manifold 160 through flexible pipes 161. The electrodes may all move inwardly together or two may move inwards and two outwards, but after a time they may all move at an equal distance from the crucible axis. One electrode 22 passes through the hopper 59, from which it is spaced by a sleeve. Inert gas e.g. helium or argon is fed at regulated pressure from a lateral pipe 61 to a space between the hopper and a shield 60 around it, whence the gas passes through a sleeve 62 around the central pipe 58 for cooling purposes. The gas is collected, cooled in a condenser to remove impurities and recirculated. Three sight tubes 74 extend through the upper end plate 65 of the shell 1, each comprising a window in a frame 76 and a lower hinged cover 77. The central tube 58 has at the top a prismatic viewer 74a. Inert gas admitted by tubes 81, 82 to the sight tubes keep them free from dust, and the windows carry centrally mounted rotatable wipers. D.C. is passed through a heavy coil 150 round the crucible 4 to provide a magnetic field extending vertically therethrough, in order to stabilize the arcs and to stir the molten part of the ingot. The water-cooled shell is preferably of steel, which must be magnetically saturated, but may be of non-magnetic stainless steel. Specification 811,918 is referred to.