GB469978A - Improvements in or relating to quartz to metal joints - Google Patents

Abstract

469,978. Uniting metal to vitreous material by heat. GENERAL ELECTRIC CO., Ltd. (Patent-Treuhand-Ges. f³r Elektrische Gl³hlampen) May 15, 1936, No. 13821. [Class 36] In making a gas-tight seal between quartz and metal, as in the manufacture of a highpressure mercury vapour discharge device wherein the vapour pressure is above five atmospheres, part of the surface of the quartz member is coatetl by a sintering process with a firmly adherent layer or a finely divided refractory metal to which the metal member is soldered. The refractory metal employed is preferably tungsten. The quartz surface is covered with tungsten powder and heated in contact with the powder to a temperature of 1500 to 1600‹ C. for a period of ten to fifteen minutes, so that the quartz is softened sufficiently for the tungsten crystals to embed themselves. The sintering process is carried out in a neutral or slightly reducing gas, for example a mixture of nitrogen with 1 or 2 per cent hydrogen. In one form of the seal wherein a conductor 5, Fig. 1, is carried through a quartz member 1 which has a hole fitting the conductor closely, the part of the quartz member around the hole is coated with a layer of sintered tungsten 2 to which a metal cap 4 is soldered by solder 3, the lead 5 being soldered or welded to the end of the cap 4. In contracting, after soldering, the cap grips the quartz so that, to avoid breaking, the walls surrounding the hole must be relatively thick. In another construction a metal tube 6, Fig. 2, soldered at one end to a layer of sintered tungsten 2, upon a quartz member 1 is sealed at the other end, in known manner, to a glass tube 7. Alternatively the metal tube 6 may be replaced by two flanged or socketed metal tubes which are first attached to the respective members 1, 7 and then welded or soldered together. The glass member 7 may be replaced by a ceramic member which can be sealed to the metal tube 6 by a process similar to that for sealing the latter member to the quartz member 1, or by a sealing - glass or enamel in known manner. When the layer of sintered metal consists of tungsten, and the metal member soldered thereto is of iron or its alloys, the solder may be silver or copper, or an alloy of silver and copper.