| 摘要 |
Refractory articles are made by baking a mixture of silicon carbide, graphite, and a metal or alloy, or a metal oxide capable of combining with the silicon of the carbide to form a metallic silicide, in quantity insufficient to combine with the whole of the silicon of the silicon carbide. Examples of metals employed are iron, nickel chromium and manganese, either as such or in the form of alloys or oxide. The raw mixture may also contain an organic binder. When the mixture is heated to 1100-1300 DEG C. it matures to a refractory substance comprising particles of silicon carbide and graphite bonded by a metallic silicide. The baking however may be at a lower temperature 800-900 DEG C. to form products which can be handled, the maturing of the bond then taking place during a second heating to a higher temperature 1100-1300 DEG C. When the metals are added as oxides, a fluoride, e.g. fluorspar or cryolite is added. In an example, a raw mix comprises 36 kgs. of graphite in flakes, 60 kgs. of silicon carbide, 12 kgs. of white sand 16 kgs. of ferromanganese alloy and 50 kgs. of organic binder, e.g. tar. This is shaped, e.g. as a crucible, and baked at 800-900 DEG C. for about 8 hours. A protective glaze is developed when the article is heated to a higher temperature, about 1200 DEG C. either in use or by a special baking. In another example the metal is in the form of iron oxide and chromium oxide, and a double fluoride, physalite, is added. |
