Abstract: A refractory of the invention is used in casting operation, which has good spalling resistance and corrosion resistance. The refractory includes: 0.0357-2.6548 wt % of amorphous silica particles having a specific surface area within a range of 15-30 m.sup.2 /g; 8.8495-28.5612 wt % of alumina particles having a particle diameter within a range of 10-50 mm; 1.3986-18.1715 wt % of at least one of fused magnesia and sintered magnesia, which contains 0.6993-10.9041 wt % of magnesia having a maximum particle diameter under 44 .mu.m; 0.6993-13.630 wt % of alumina cement; and 45.4545-88.1417 wt % of alumina. When the refractory is used, at lease one of fused magnesia and sintered magnesia surrounds the alumina particles, which react together to generate spinel to thereby form micro-crack layer around the alumina particles for preventing propagation of cracks in a refractory structure.

Abstract: A refractory for casting a basic substance comprises 100 parts by weight of a refractory aggregate having as main ingredients 3 to 40% by weight of zircon and 97 to 60% by weight of magnesia and a suitable amount of a binding agent. Another refractory for casting a basic substance comprises 100 parts by weight of a refractory aggregate having as main ingredients 3 to 40% by weight of zircon and 97 to 60% by weight of magnesia, not more than 7 parts by weight of metallic fibers, and a suitable amount of a binding agent. The refractories for casting a basic substance are used for ladles, tundishes, vacuum degasing furnaces, mixers, and the like.

Abstract: An alumina-spinel monolithic refractory consists essentially of 50-90 percent by weight of alumina clinker, 5-40 percent by weight of MgO--Al.sub.2 O.sub.3 spinel clinker not larger than 1 mm in size and 1-25 percent by weight of alumina cement. Another alumina-spinel monolithic refractory consists essentially of 50-90 percent by weight of alumina clinker, 5-40 percent by weight of MgO--Al.sub.2 O.sub.3 spinel clinker, 1-25 percent by weight of alumina cement and not more than 5 percent by weight of magnesia clinker. The alumina-spinel monolithic refractories are used for lining the inner walls of ladles, vacuum degassing vessels, hot-metal mixers, blast-furnace troughs and their covers, not-metal mixer cars, tundishes and the like.