| 摘要 |
According to the present invention, a starting mixture consisting of about 50 % by weight of refractory clay and about 50 % by weight of hydrated alumina is mixed before firing with a predetermined quantity, calculated on the clay content thereof, of a fluorine-containing compound. The mixture thus formed is then treated in a manner known per se, moulded and fired at a temperature required for dense-firing. Preferably, 5 to 20 % by weight of aluminium fluoride or 3 to 12 % by weight of hydrogen fluoride are mixed as a fluorine-containing compound with the starting mixture.
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