| 配方类型： |
METALS AND THEIR TREATMENT |
| 配方说明： |
Metal-Casting Mold (U.S. Patent 2,681,860) |
| 配制方法： |
Use silica powder of at least 99% silicon oxide content and grind it to such a fineness that 99% will pass through a 250-mesh sieve, the average particle size being 3 to 5 microns. Mix this powder with an aqueous solution of sodium hexametaphosphate by weight, in the proportion of 100 g. of powder to 34 ml. of solution. Thus, the sodium hexametaphosphate amounts to 0.085% of the silica. Mixing mechanically for at least 10 minutes, the fluidity increases as the mixing continues.
Pour the resultant slurry around one or more wax patterns mounted on absorbent asbestos board within a ring of heat-resisting metal. This ring is prolonged upward by a paper extension and the ring and extension are filled with the slurry. Liquid will separate from the slurry as a supernatant layer within the paper extension. After about 2 hours, decant this liquid and, 30 minutes later, cut off the extension level with the top of the metal ring. Dry the investment mold so preduced in the usual way, e.g., by heating for 0.5 hour pe |
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