| 摘要 |
1,213,371. Isostatic hot pressing. E. I. DU PONT DE NEMOURS & CO. July 29, 1968 [July 31, 1967], No.36151/68. Heading C7D. Cemented carbide bodies are isostatically hot pressed by surrounding the bodies with a borosilicate glass essentially free of alkali and alkaline earth metals and consisting of 83-99À7% SiO2 and 0À3-17% B2O3, heating the glass to a temperature to make it plastic and applying sufficient pressure to increase the density of the carbide e.g. to at least 98% theoretical. The carbides are those of W, Ti, Ta and Nb bonded with 3-30% of Fe, Co, Ni or Mo and small amounts of oxides, borides nitrides and silicides may also be present. The cemented carbide bodies are formed by compacting at 200- 10,000 p.s.i. a mixture of the carbide and binder having a particle size less than 10 microns and sintering at 1300‹-1500‹C to a density of at least 60% theoretical. Alternatively the mixture may be isostatically pressed prior to sintering. The surface pores of the sintered bodies are less than 100 microns in diameter and the moulds used for the isostatic hot pressing in glass may be of graphite, W or Mo. The glass powder is first loaded into the mould and pressed, the cemented carbide body is then inserted and covered with more glass powder. The assembly is then heated to 1200‹-1700‹ C under vacuum or an inert gas, maintained at this temperature and hot pressed at 4000- 6000 p.s.i. The assembly is cooled quickly by removing from the furnace and the hot pressed billet is removed from the glass envelope. |
