GB809540A - Improvements in or relating to casting - Google Patents

Abstract

809,540. Induction heating of metals. BRENNAN, J. B. June 2, 1955, No. 15826/55. Class 39(3) [Also in Groups II and XXII] A method of casting in which molten metal is directed to a crucible 9, which is cooled so that a skull of metal 15 is formed and remains between a body of molten metal and the walls of the receptacle, consists in withdrawing molten metal to a casting zone from the body of molten metal only. The receptacle or copper crucible 9 is contained in a chamber 1 which may be evacuated or supplied with an inert gas through a line 3. The crucible is supplied from a metal rod 7 which is formed from 200 mesh metal powder e.g. of titanium fed past high frequency heating coils 39 which form a skin on, or sinter, or melt the powder. The surface of the rod is melted at its lower end by a high frequency coil 8. The metal passes to the crucible 9 and a passage 11, such as a copper die, both cooled by liquid in circulation. The metal in the crucible, except for the cooled skull 15 on the sides, is heated by parabolic coated graphite reflectors 16 heated by high frequency coils 18. These reflectors may also heat the rod 7 and the coils 8 be omitted. Alternatively, the coil 8 may so heat the metal that the reflectors 16 can be omitted. To ensure uniform heating the crucible is rotated by a gear 21 and the reflectors 16 may be oscillated or rotated. Alternatively, the reflectors 16 may be replaced by a single annular reflector. The solidified metal is withdrawn by fluid-cooled roolers 19 through a chamber 23 having a vacuum or gas connection 24. To avoid surface irregularities on the casting, the surface is fused by a coil 41 before being passed by the rollers 19 to a crucible 42 heated by a coil 43. In a modified apparatus, slugs of metal may be fed to a thorium oxide or zirconium oxide crucible 58, Fig. 3, heated by a high frequency coil 59, and the molten metal then passes to the crucible 9. The coil 59 consists of a copper tube disposed within a glass tube, cooling water being circulated within and around the inner tube. In further modifications, the heating may be by resistance filaments or by infra-red ray apparatus and may be concentrated on an annular portion of the metal pool. An argon atmosphere may be used; and chromium, cobalt or molybdenum may be melted.