Patent ID: 7166551

Claim:
An unshaped refractory composition comprising: 20 to 70% by weight of (i) raw spinel material comprising an MgO—Al 2 O 3 spinel phase and containing from 2 to 20% by weight of magnesia based on the total weight of the raw spinel material and/or (ii) raw spinet/corundum material comprising an MgO—Al 2 O 3 spinel phase and a corundum phase and containing from 2 to 20% by weight of magnesia based on the total weight of the raw spinel/corundum material; 3 to 12% by weight of raw magnesia material having a particle diameter of 0.3 mm or smaller, containing particle sizes of 75 μm or smaller in an amount of from 55 to 85% by weight, and having a magnesia purity of 90% by weight or higher; 3 to 10% by weight of alumina cement having a calcia content of lower than 20% by weight; 0.3 to 1.5% by weight of ultrafine powder consisting mainly of silica; and a raw alumina material as a remainder.