GB1225966A - - Google Patents

Abstract

1,225,966. Magnesia - based refractories. STEETLEY REFRACTORY BRICK CO. Ltd 22 March, 1968 [22 March, 1967], No. 13517/67. Addition to 1,085,841. Heading C1A. [Also in Division F4] Basic refractory bricks are made by mixing a coarse fraction and a fine fraction of a deadburnt magnesia with at least one oxide of lithium, sodium or potassium, or a compound which yields one of these on heating, and with calcium oxide or a calcium oxide precursor (as defined below), thereafter adding a temporary liquid binder, forming the mixture into bricks and firing so that the bricks have a modulus of rupture of at least 600 p.s.i. at 1260‹ C. The " calcium oxide precursor " is a material which will yield calcium oxide for reaction with less basic constituents under the normal conditions of firing, or will provide calcium oxide already in combination with silica, e.g. as silicates. A mixture suitable for use in this method comprises the magnesia, the alkali metal oxide or compound and the calcium oxide or precursor such that if a liquid temporary binder is added and the bricks fired, the resulting bricks will have a modulus of rupture of at least 600 p.s.i. at 1260‹ C. The fine fraction of magnesia may pass a 72 B.S. sieve, and the coarse fraction be held by such a sieve. In this case, the ratio fine : coarse may be from 90 : 10 to 20 : 80. The alkali metal oxides or compounds may be added to the extent of from 0.1-3À0% by wt. The calcium oxide or oxide precursor may be added to the fine fraction, and have the same particle size thereof. The molar ratio lime : silica in the fine fraction after addition of oxides or oxide precursors, but before addition of the coarse fraction may be at least 2 : 1 and, after addition of the coarse fraction, 1 : 1 to 4 : 1