Patent GB-375304-A (GB)
Title: Improvements relating to the fusion of substances in electric furnaces
IPC: F27B3/12
Filed: 1931-03-16
Abstract: 375,304. Electric furnaces. ELECTRIC FURNACE CO., Ltd., 17, Victoria Street, London.-(Assignees of Northrup, E. F. ; Ajax Park, Trenton, New Jersey, U.S.A.). March 16, 1931, No. 8026. Convention date, March 15,1930. [Class 39 (iii).] In an electric furnace to prevent contamination of the charge the furnace lining is formed of finely divided particles of the same material as the charge, loosely tamped, the lining being less highly compressed than the charge as supplied to the furnace. In a modification, the lining is in a less pure state than the charge or is a raw or intermediate material such as an ore, a matte or a rich slag. In one form, Fig. 3, the furnace consists of a casing 11 having a lining 17 formed of granules of the material to be treated loosely tamped, and is surrounded by an inductor coil 10. The coil may be of hollow tubing 10<1>, Fig. 9, through which water is circulated for cooling. The material 19 to be treated is added in large pieces or as compressed granules and is melted rapidly before sufficient heat is conducted to melt the lining. The molten material may be treated by slagging or otherwise to remove impurities or to change its composition, and may be poured off or allowed to solidify in the furnace. An indicating device is provided, consisting of a rod 24 which may be of the same material as the charge to prevent contamination and which carries a disc 25, the rod and disc falling when the charge melts. The disc may thereupon close the circuit of a lamp 28 or operate any other suitable indicator. In another form, the material is added as a compressed mass or as a solid block, bar, ingot or scrap to an induction furnace containing a mould of the same material as the charge but in lightly tamped granular form. The size of the crystals in the casting may be controlled by varying the rapidity of cooling, e.g. larger crystals are produced by cooling more slowly by discontinuing the inductive heating or continuing it at a reduced rate or at intervals. The method may be employed in melting, casting &c. high melting point metals and their alloys such as tungsten, molybdenum, tantalum, and tungsten-carbon-cobalt alloys known as " car. baloy." An air excluding atmosphere may be obtained by placing, preferably near the bottom of the charge, a trace of a highly volatile substance which will vaporize below the melting or sintering point of the charge, e.g. in the case of " carbaloy " a volatile metal such as zinc or cadmium may be employed. In a further form, Fig. 4, the furnace is heated by an electrical resistance 30 a heat reflector 31 being provided, or the resistance may be replaced by an electric arc. In another form, Fig. 7, heating is obtained by an electric current flowing through the charge between electrodes 33<2>, 34<2> arranged in the same vertical line. One of the electrodes, which is preferably of the same material as the charge, may be raised slightly above the charge to produce an arc. The electrodes may alternatively be arranged parallel to one another and at the same horizontal level.