Saint-gobain Tm K.k.

Toshimitsu Kuboki

Hiroshi Sugiyama

Yasuo Misu

Itaru Hashimoto

A high zirconia electrically fused cast refractory having long time durability with less cracking during production and in the course of temperature rising, excellent in productivity, less forming zircon crystals in the refractory itself and even in contact with molten glass, excellent in bubble foamability to molten glass, less generating cracks even undergoing heat cycles during operation of a glass melting furnace. A high zirconia electrically fused cast refractory comprises, as chemical component, 85 to 95% by weight of ZrO, 0.4 to 2.5% by weight of AlO, 3.5 to 10.0% by weight of SiO, 0.05% by weight or more of NaO, 0.05 to 0.7% by weight of NaO and KO in total, 0.01 to 0.04% by weight of BO, 0.1 to 3.0% by weight of SrO or BaO when one of BaO and SrO is contained, 0.1% by weight or more of SrO and 0.1 to 3.0% by weight of SrO and BaO in total when both of BaO and SrO are contained, 0.01 to 0.2% by weight of CaO, 0.1% by weight or less of MgO, 0.01 to 0.7% by weight of SnO, 0.3% by weight or less of FeOand TiOin total, less than 0.01% by weight of PO, and less than 0.01% by weight of CuO.

High zirconia electrically fused cast refractory

A high zirconia electrically fused cast refractory of high electric resistance having long time durability, less suffering from cracking during production and upon temperature rising, excellent in productivity, less forming zircon crystals even upon heating the refractory in itself and when the refractory is in contact with molten glass, generating less cracks even when undergoing heat cycles during operation of a glass melting furnace is provided. A high zirconia electrically fused cast refractory has, as chemical components, 85 to 95% by weight of ZrO, 0.1 to less than 0.8% by weight of AlO, 3.5 to 10.0% by weight of SiO, less than 0.05% by weight of NaO and KO in total, 0.1 to 1.5% by weight of BO, 0.1% by weight or less of MgO, 0.01 to 0.2% by weight of CaO, in the case where any one of BaO and SrO is contained, from 0.05 to 3.0% by weight of BaO or 0.01 to 3.0% by weight of SrO, or in the case where both of them are contained, 0.01% by weight or more of SrO and from 0.01% to 3.0% by weight in total of SrO and BaO, 0.1 to 0.7% by weight of SnO, 0.3% by weight or less of FeOand TiOin total, less than 0.01% by weight of PO, and less than 0.01% by weight of CuO.

[Problems] To provide a high zirconia fused cast refractory that suffers less cracks in production and on heating, has excellent productivity, is hard to form zircon crystals with the refractory solely and under conditions where the refractory is in contact with molten glass, is hard to suffer cracks on receiving heat cycles in operation of a glass melting furnace, and has durability for a prolonged period of time. [Solution to Problems] A high zirconia fused cast refractory containing, as chemical components, from 85 to 95% by weight of ZrO, from 0.4 to 2.5% by weight of AlO, from 3.5 to 10% by weight of SiO, from 0.05 to 1% by weight in total of NaO and KO, more than 0.04% by weight and 1% by weight or less of BO, 0.02% by weight or less of PO, 0.05% by weight or less of MgO, from 0.01 to 0.2% by weight of CaO, in the case where any one of SrO and BaO is contained, from 0.3 to 3% by weight of SrO or more than 0.5% by weight and 3% by weight or less of BaO, and in the case where both of them are contained, 0.3% by weight or more of SrO and from 0.3 to 3% by weight in total of SrO and BaO, from 0.01 to 0.7% by weight of SnO, and 0.3% by weight or less in total of FeOand TiO.

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Tokyo, Japan

Toshimitsu Kuboki