CASTABLE-REFRACTORY DIE COMPOSITION ESSENTIALLY FREE OF CALCIUM ALUMINATE AND METHOD OF USING

摘要

1333750 Refractory compositions CERAMCO Inc 2 Oct 1970 [28 Oct 1969] 47049/70 Heading C3N [Also in Division C1] A castable-refractory composition, substantially free of calcium aluminate, comprises one part by weight of a colloidal silica sol of 40% by weight solids, and 2À5 to 5 parts by weight of a dry blend of ingredients. These comprise 140 to 100 parts by weight of magnesia and 15 to 25 parts of an alkali-metal phosphate or ammonium dihydrogen phosphate, and the proportions are so selected that the composition is dimensionally stable when fired at 1800‹ to 3000‹ F., that is its dimensions change by between 0À0 and +0À2%. The dry blend may also include not more than 40 parts by weight of alumina or zirconia. In a modification, a soda-lime-silica glass having a coefficient of thermal expansion in the range of 10 to 12 x 10SP-6/SP in./in./‹ C. is added to the extent of not more than 18 weight per cent and the dimensional stability goes up to 2000‹ F. A preferred glass is one modified by the addition of lithia and magnesia and is used in amount 14 to 18% together with one part of silica solution to four parts of dry blend. These compositions harden to a green compact in about 30 minutes and can then be fired.