Process of producing refractory,particularly unfired,magnesia-chrome and chrome-magnesia bricks

摘要

In a process for the production of refractory magnesia-chrome and chrome-magnesia bricks, from 3-9% tar, pitch, bitumen or a similar mixture of high molecular weight hydrocarbons is added to a mixture of substances containing Cr2O3 and substances yielding MgO (e.g. magnesite) which has been co-fired at 1700 DEG C. or more without fusion. Preferably at least 65% of the substances containing Cr2O3 (e.g. chromite) are present in a particle size above 0.12 mm., the magnesite has a particle size below 0.12 mm., the sintered mixture has a SiO2 content of at most 5.5% and a lime-silica ratio of at most 0.6. The sintered mixture may be mixed with sintered magnesia in amount up to 35% based on the refractory constituents in addition to the tar or pitch which preferably contains 80% hard pitch. The refractory bricks of the invention may be used in an unfired condition or they may be fired in a non-oxidizing atmosphere at 300-1000 DEG C. Al2O3 and Fe2O3 may also be present.