Preparation of highly impervious refractories

Claim 1

A PROCESS FOR PREPARING HIGHLY IMPERVIOUS REFRACTORIES COMPRISING MIXING (1) FROM 11-35% BY WEIGHT OF METAL PARTICLES OF THE GROUP CONSISTING OF ALUMINUM AND ALLOYS HAVING A MAJOR AMOUNT OF ALUMINUM, SAID PARTICLES HAVING A BULK DENSITY GREATER THAN 0.6 GRAM/ CC. AND HAVING ALL THREE DIMENSIONS BETWEEN 0.005 INCH AND 0.250 INCH, THE GREATEST DIMENSION OF SAID PARTICLES BEING LESS THAN TEN TIMES THAT OF THE LEAST DIMENSION, WITH (2) AT LEAST ABOUT 0.02% BY WEIGHT OF A FLUXING AGENT BASED ON THE WEIGHT OF THE ALUMINUM AND (3) FROM ABOUT 65-89% BY WEIGHT OF FILLER REFRACTORY PARTICLES, AT LEAST 25% OF WHICH ARE MAGNESIA, SAID REFRACTORY PARTICLES BEING OF A SIZE WHICH WILL PASXS THROUGH A 4-MESH SIEVE, SHAPING THE MIXTURE UNDER SUFFICIENT PRESSURE TO GIVE A POROSITY OF BETWEEN (0.27XPERCENT ALUMINUM+17) PERCENT AND (0.38XPERCENT ALUMINUM+27.5) PERCENT AFTER REMOVAL OF VOLATILE MATERIALS AND FIRING THE SHAPED BODY TO OXIDIZE THE ALUMINUM AT A TEMPERATURE OF AT LEAST ABOUT 600*C. AND AT A RATE SO THAT THE TEMPERATURE OF THE MOLDED OBJECT DOES NOT EXCEED THE AMBIENT TEMPERATURE BY MORE THAN 100*C.