Patent GB-769502-A (GB)
Title: Improvements in or relating to the arc-melting of high melting point metals or alloys
Inventor: PRESTON JACK
IPC: H05K7/18
Filed: 1954-04-02
Abstract: 769,502. Arc - melting furnaces. IMPERIAL CHEMICAL INDUSTRIES, Ltd. March 28, 1955 [April 2, 1954], No. 9695/54. Class 39(3) An arc-melting furnace for high M.P. metals such as titanium, zirconium, molybdenum, thorium, hafnium, tantalum, chromium and their alloys comprise a water-cooled arc-melting crucible 1 superimposed on a water-cooled arc melting crucible 2 of larger cross section, a watercooled base member 3 longitudinally adjustable between an upper position where it closes the base of the upper crucible and a lower position where it closes the base if the lower crucible, a pipe 9 for avacuating apparatus and if desired supplying an inert gas e.g. helium or argon thereto, and a longitudinally adjustable consumable electrode 12 for the upper crucible, said electrode being lowered into the top part of the molten mass 24 in the upper crucible so that on cooling it forms a stem for the electrode 24 formed in the upper crucible; and on lowering the base 3. the electrode 24 is lowered into the crucible 2 and is arc-melted therein. The upper electrode 12 is a forged bar e.g. of titanium or several units consolidated from the divided metal and welded or otherwise joined together. The divided metal to be melted is fed from a hopper 7 having a vibrator 8 into a water-cooled cone and hence into the crucible 1. The electrode 12 is vertically adjusted by feed rollers 13 and carries a contact 14. The other contact 22 is attached to a watercooled stem 19 of the base plate 3, which is vertically moved by a rack and pinion 21. When the molten mass 24 has been built up in the crucible 1 to the desired height, the electrode 12 is lowered into the molten top surface of the mass 24 and allowed to set therein. The base 2 is then lowered to form the base of the lower crucible 2 and rests on a copper seating 17, from which any metal powder is removed by a brush 23 on the stem 19 to ensure accurate seating. The electrode 24 is then lowered into the larger lower crucible 2 into which a charge of metal powder from the hopper 7 is fed, so that on striking an arc between the electrode 24 and this added metal, the mass 24 is melted. The ingot so formed is allowed to set and is removed by lowering the base 3. the seating member 17 and a box 18 on which the latter rests. The upper electrode 12 may be supported by a watercooled copper stem and may be enclosed with the feed roller 13 in a gas-tight extension from the furnace lid. Several upper crucibles 1 may be mounted on a single lower crucible 2 so that three electrodes 24 may be simultaneously lowered into the crucible 2. The upper crucible 1 may be slightly conical to facilitate removal of the mass 24. The cone 4 and crucibles 1 and 2 are insulated from one another bv insulating rings 15. 16. The divided metal is preferably fed to a upper crucible 1 at a higher rate than is consistent with the complete melting of the metal, but allowing a coherent though incompletely melted mass 24 to be built up, as described in Specification 767,721 [Group XXII].