| 摘要 |
PROBLEM TO BE SOLVED: To obtain a purified material for an electric furnace for heat treatment mainly comprising alumina and silica by purifying the material in a gaseous atmosphere containing a specific gas such as hydrogen chloride, etc., at a prescribed temperature allowing to decrease the evaporation of impure metal elements. SOLUTION: The material for electric furnace for heat treatment mainly comprising 70 to 99wt.% of alumina and 30 to 1wt.% of silica is purified in the gaseous atmosphere containing at least one kind of gas selected from hydrogen chloride gas, chlorine gas, fluorine gas and hydrogen fluoride gas, at 400 to 1400 deg.C. If required, the material is washed and purified using aqueous solution of at least one kind of acid selected from nitric acid, hydrochloric acid, sulfuric acid and hydrofluoric acid at 20 to 80 deg.C. This material for furnace contains 1 to 100wt.ppm of Na, 50wt.ppm of Cu, 50wt.ppm of Ni, 1000wt.ppm of Fe. This material for furnace has 0.1 to 1g/cm<3> of bulk density, 0.1 to 1kcal/mh deg.C of thermal conductivity at 1000 deg.C. Alumina powder and silica powder having 1 to 500μm of particle size. 99.99wt.% of purity are used as the raw material powder of the material for furnace.
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