GB292997A - Improvements in the manufacture of solid bodies of high density - Google Patents

Abstract

292,997. General Electric Co., Ltd., (Assignees of Patent-Treuhand-Ges. fiir Elektrische Gl³hlampen). June 29, 1927, [Convention date]. Moulding processes. - Solid bodies of high density are obtained from material which do not yield such bodies by casting owing either to the refractory character of the material or the low density of the casting, by first. sintering pulverized raw material, preferably compressed, to form a porous body and then subjecting such body to a high pressure between members which offer little resistance to lateral expansion, the body being heated during or immediately before compression to a temperature above a red heat but below the temperature at which a previouslycompressed body attains a density not less than 85 per cent of that obtained by fusion. Heat treatment to equalize internal strain may be applied to the products. The following examples are given :-(1) Medium grain tungsten powder is subjected to a pressure of about 1,000 kg./cm.<2> and sintered at a temperature of not more than 2,400‹ C. ; the sintered body is subjected to a pressure of about 15,000 kg./cm.<2> between jaws in an atmosphere of reducing or inert gas at a temperature of 1,300‹ C. ; (2) calcium fluoride is. pressed at 800 kg./cm.<2> and sintered at 900‹ C., the resulting mass being compressed at a temperature of 1000‹ C. and a pressure of 1500 kg./cm.<2>. A press for carrying out the process comprises a furnace b lined with annular blocks e, f, g, of zirconium oxide and fitted with tungstem plungers i, k surrounded by a heating-coil m. The plungers i, k are furnished with jaw portions i<1>, k<1>, of a hard metal alloy containing more than 50 per cent of tungsten carbide, as described in Specification 213,524, [Class 82 (i), Metals, Extracting &c.]. The plunger i passes through a bush h. A base a supports the furnace b and also the plunger k through a block l. Reducing or inert gas is passed into the furnace through a tube q and passages r. To prevent welding of the body u to the jaws i<1>, k<1> they are covered by protective layers of paper &c. v.