摘要 |
1,158,299. Electrically insulating magnesia refractories. NORTON CO. 19 Oct., 1967 [25 Oct., 1966], No. 47656/67. Heading C1A and C1J. [Also in Division H5] An electrically insulating refractory material comprises a mixture of particulate fused MgO with from 0À5 to 8% by weight of a particulate mixture of crystalline zirconia and glassy silica, the zirconia and silica preferably being approximately equimolar. The. zirconia and silica may be produced by fusing zircon ZrSiO 4 then cooling. The fused zircon preferably passes through a 100 mesh sieve (U.S. Series) with preferably at least 20% passing through a 325 mesh sieve. It is preferred that the particle size of the fused zircon is no larger than the maximum particle size of the MgO. The insulating material is typically heated to 900‹ C. |