Patent GB-471495-A (GB)
Title: Improvements in or relating to the treatment of alloys
IPC: C22F1/10
Filed: 1935-11-15
Abstract: 471,495. Alloys; coating with metals; furnaces; casting; magnets. PFANSTIEHL CHEMICAL CO. Nov. 15, 1935, No. 29851. Convention date, Nov. 15, 1934. [Classes 82 (i) and 82 (ii)] [Also in Groups XI, XII, XXII, and XXXV] Spheroids of the order of, for instance, one sixteenth or one eighth of an inch are'produced from alloys consisting essentially of cobalt, chromium, tungsten, and a small amount of carbon, for example, 35-50 parts of cobalt, 30-40 parts of chromium, 15-25 parts of tungsten, and 3-5 parts of carbon, particularly 46À7 per cent of cobalt, 30À8 per cent of chromium, 19À2 per cent of tungsten, and 3.3 per cent of carbon, by heating such a quantity of the alloy as will assume spheroidal form when molten to a temperature above the melting point, and cooling or solidifying the alloy so rapidly that the spheroid assumes a fine crystalline structure. The heating may occupy for example 5-15 seconds and the cooling 1 second or less. The alloys from which the spheroids are to be prepared are preferably made by melting in a crucible tungsten discs, chromium flakes, cobalt discs, and small particles of carbon in vacuo or an inert gas, the melt being held at a temperature several hundred degrees above its melting point for sufficient time to free it from gases and other volatile matter; and the solidified product may be again melted in vacuo and cast into slugs or ingots. Heating and cooling may be repeated one or more times before the final grinding and subsequent treatment. To make the spheroids, small measured charges of the powdered alloy are placed in series of moulds 42 which may be of lime, and heated in an electric furnace 44, Figs. 5 and 7, in which the moulds, admitted through a branch 47, pass over the lower of two electrically heated tungsten strips 55, 56 and then on to a watercooled copper block 57 by which they are rapidly cooled. A non-oxidizing gas such as hydrogen is fed to the furnace through a pipe 49. To supply the powdered alloy to the moulds 42 the required quantity may be picked up by means of an electromagnet, Fig. 2, comprising a soft iron wire 39 enclosed in a cylinder 40 surrounded by a winding 41, the amount picked up being varied by adjustment of the current through the winding 41. The spheroids may be welded to a metal base. for example, a pen nib, and in the case of a gold nib or other gold or gold-plated article, some gold may be mixed with the alloy powder before fusion, the gold being mainly expelled to the surface of the spheroid during fusion. A gold base alloy containing 10-15 per cent each of silver and copper is referred to. The spheroid may be welded to a base bv means of an electric are in an inert atmosphere. The Specification as open to inspection under Sect. 91 describes also the following subjectmatter. The alloy to be treated may be melted in a crucible in an evacuated high-frequency induction furnace, Fig. 1 (Cancelled, not shown), cooling being effected in the furnace and the product being preferably remelted and cooled ; or it may be melted in a furnace, Fig. 4 (Cancelled, not shown), having a movable bottom adapted to be lowered into a cooling zone ; or in an evacuated furnace 63, Fig. 6 (Cancelled), wherein the metal is heated in a crucible 5 surrounded by a resistance element 26, the metal when molten being poured through a graphite funnel 26 into a mould 34 mounted in a container 31 by tilting the furnace and container. The process of making the spheroids is applicable to other alloys than those of cobalt, chromium, tungsten, and carbon, and the spheroids may be applied to other purposes such as meter pivots. In a watt meter, for example, a pivot arm may carry a bearing resting in a jewel and made by grinding down one of the spheroids ; or a spheroid in the form of a ball may rest between two jewels. This subject-matter does not appear in the Specification as accepted.