RU2039026C1 - Fused cast high-zirconium refractory material - Google Patents

Abstract

FIELD: refractory industry. SUBSTANCE: fused cast high-zirconium refractory material contains, mass percent: SiO₂ 1.0 to 5.5; Al₂O₃ 0.3 to 1.2; SnO₂ 0.1 to 0.5; ZnO 0.1 to 0.4; P₂O₅ 0.1 to 0.3; at least one alkaline oxide from group Na₂O, K₂O, Zi₂O 0.1 to 0.3; at least one oxide from group MgO, CaO 0.4 to 7.0; at least one halogen from group F, Cl 0.1 to 0.3; Z₂O₂ the rest. EFFECT: enhanced refractories of refractory vitreous phase, enhanced degree of material penetration at a high corrosion resistance of refractory material to optical glass melts. 2 tbl

Description

 The invention relates to the refractory industry and can be used for the manufacture of fused-cast high-zirconia refractory materials for lining glass melting furnaces.

Known fused cast high zirconium refractory material [1] containing, by weight. ZrO ₂ 89.0-97.5; SiO ≅ 1.0; Al ₂ O ₃ ≅ 1.0; CaO or another stabilizing agent 2.5-8.0.

Also known is molten cast high zirconium refractory material [2] containing, by weight. ZrO ₂ 85.0-97.0; P ₂ O ₅ 0.05-3.0; SiO ₂ 2.0-10.0; B ₂ O ₃ 0.05-5.0; R ₂ O ≅ 1.0; Al ₂ O ₃ ≅ 1.0.

 The disadvantage of these materials is their low processability (low meltability of the material, fracture of the products) associated with a high content of zirconium dioxide and the irrational composition of the vitreous phase.

The closest technical solution to the proposed one is fused-cast refractory material [3] containing, by weight. SiO ₂ 1.2-8.0; Al ₂ O ₃ 0.3-2.0; P ₂ O ₅ 0.2-2.0; Na ₂ O 0.2-0.8; SnO ₂ 0.2-1.0; ZnO 0.2-0.6; ZrO _{2 the} rest.

 The specified refractory is characterized by low processability (low degree of meltability of the material in the furnace) and low refractoriness of the vitreous phase (low temperature of glass phase separation from the refractory), which reduces the quality of the manufactured optical glasses.

 The aim of the invention is to improve the manufacturability of the manufacture of refractory material, increase the refractoriness of its glassy phase, providing high corrosion resistance of the refractory material and the desired properties of the melted optical glasses.

This goal is achieved in that the fused-cast high-zirconium refractory material, including ZrO ₂ , SiO ₂ , Al ₂ O ₃ , SnO ₂ , ZnO, P ₂ O ₅ and R ₂ O as R ₂ O contains at least one oxide from group K ₂ O, Na ₂ O, Li ₂ O and additionally at least one oxide from the group MgO, CaO and at least one halogen from the group F, Cl in the following ratio of components, wt. SiO ₂ 1.0-5.5 Al ₂ O ₃ 0.3-1.2 SnO ₂ 0.1-0.5 ZnO 0.1-0.4 P ₂ O ₅ 0.1-0.3
At least one
oxide from the group Na ₂ O, K ₂ O, Li ₂ O 0.1-0.3
At least one
oxide from the group MgO, CaO 0.4-7.0
At least one
halogen from the group F, Cl 0.1-0.3 ZrO ₂ Else
According to experimental data, the high corrosion resistance of this refractory material is achieved by a high degree of crystallinity (92-94% vol.) And content in the crystalline phase in the amount of 98-99 wt. zirconium dioxide of various modifications. The ratio of zirconia modifications (ZrO ₂ monoclinic and ZrO ₂ cubic) at a given SiO ₂ content (1.0-5.5 wt.) Is determined by the amount of the RO component (MgO, CaO) in the material.

The content of the MgO, CaO component in an amount of 0.4-7.0% is determined by the need to form a ZrO ₂ cube phase in the refractory. which does not have bulk polymorphic transformations characteristic of the ZrO ₂ monocline phase. The content of MgO, CaO oxide in an amount of 7% is sufficient for complete stabilization of zirconia and the presence in the refractory phase of zirconia mainly in the form of ZrO ₂ cubic meters. In this case, the silica content is in the range of 1.0-4.0%. The content of the CaO component, MgO does not exert a stabilizing effect on zirconia less than 0.4%, and zirconia is present in the refractory in the form of a ZrO ₂ monocline phase. which requires achieving silica in the refractory composition in the range of 4.0-5.5% to achieve the manufacturability of refractory products. Improving the manufacturability of products (high meltability of the material in the furnace, low fracture of the products) is achieved by increasing the content of CaO, MgO oxide while reducing the silica content within the limits provided by the claims, and also vice versa.

The content of SiO ₂ in the range of 1.0-5.5% in combination with alkaline oxide Na ₂ O, K ₂ O, Li ₂ O (0.1-0.3%), alumina (0.3-1.2 %), phosphoric anhydride (0.1-0.3%), as well as halogen F, Cl (0.1-0.3%), allows the formation of a refractory glassy phase in the refractory (with a high temperature at which the glass phase precipitates from the refractory) , which is characterized by sufficient fluidity, which allows to increase the degree of meltability of the refractory, as well as to reduce the fracture of the obtained refractory castings.

An increase in the content of these components of the glass phase, especially alkaline oxide Na ₂ O, K ₂ O, Li ₂ O and phosphoric anhydride P ₂ O ₅ , leads to a decrease in its refractoriness.

The component that increases the refractoriness of the glass phase is SnO ₂ , the content of which with respect to SiO ₂ must correspond to SiO ₂ : SnO ₂ ≥ 10 (mass ratio). However, an increase in the content of SnO _{2 in} excess of 0.5% may cause the formation of defects (stone, schliere) in optical glass and changes in its properties.

Zinc oxide is a component of the glass phase, increasing its oxidation state (minimal carburization during melting). When the content of zinc oxide in an amount of 0.4%, the carbon content in the glass phase of the refractory does not exceed 0.005%, which is sufficient for use in melting electrovacuum and optical glasses. This level of zinc oxide also provides high temperature (> 1450 ° ^C) from the refractory vitreous allocation.

 The presence in the refractory of halogen F, Cl in an amount of 0.1-0.3% in combination with alkaline oxide provides high mobility of the melt ions, which determines its fluidity and a high degree of meltability of the material. An increase in the halogen content in excess of 0.3%, although it increases the fluidity of the melt, but also leads to a decrease in its operational characteristics.

 To obtain refractory material, batch was prepared consisting of zirconium dioxide, quartz sand, alumina, zinc oxide, tin oxide, sodium phosphate, lithium and potassium carbonates, cryolite, fluorspar, carnallite, limestone. The mixture was melted in an electric arc furnace with a furnace body diameter of 1200 mm at a voltage of 110-160 V and a current of 1-1.5 kA. The melt was poured into graphite casting molds, after which castings measuring 155x155x240 mm in size were annealed in natural conditions in thermal boxes with heat-insulating backfill for 3-4 days.

 Specific compositions of the proposed refractory material are presented in table 1.

100 где S_n площадь внутреннего сечения корпуса печи (S_n π R², R 600 мм);
S_р площадь поверхности расплава огнеупорного материала внутри печи после плавления материала (шихты) в течение 60 мин.The degree of meltability (K _av. %) Of the material was determined by the formula:
K _ol

100 where S _{n is} the internal sectional area of the furnace body (S _n π R ² , R 600 mm);
S _p the surface area of the melt of the refractory material inside the furnace after melting the material (charge) for 60 minutes

 The temperature of the onset of the release of the vitreous phase from the refractory was determined using a MNO-2 high-temperature microscope (Karl Zeiss) according to the STP 38-14-79 method, GIS.

The determination of the corrosion resistance of refractory materials was carried out in a melt of borosilicate optical glass of the composition, wt. SiO ₂ 68.8; B ₂ O ₃ 11.2; As ₂ O ₃ 0.36; BaO 2.7; K ₂ O 6.7; Na ₂ O 10.4; under static conditions at 1450 ^C for 24 hours.

 Corrosion resistance (corrosion rate) of refractory samples was determined by the change in linear dimensions (sample cross-section 10x10 mm) at the glass level after corrosion tests.

 Technological indicators and results of operational tests of refractories are given in table.2.

From the table. 2 that the refractory material of the proposed composition (formulations 1-4) has a higher (65-80 ° ^C) temperature selection start glassy phase of the refractory, and also characterized by a high degree proplavlyaemosti material and higher corrosion resistance compared with known refractory (compositions 5-6).

 The use of the present invention allows it to be implemented in the organization of the production of fused-cast high-zirconium refractory, characterized by high manufacturability of products and high performance characteristics to the action of the melt of optical glass.

Claims (1)

PLAVLENOLITOY VYSOKOTSIRKONIEVY refractory material comprising ZrO _2, SiO _2, Al ₂ O _3, SnO _2, ZnO, P ₂ O ₅ and R ₂ O, characterized in that the R ₂ O it contains at least one oxide from the group of: Na ₂ O, K ₂ O, Li ₂ O and additionally at least one oxide from the group: MgO, CaO and at least one halogen from the group: F, Cl in the following ratio of components, wt. SiO ₂ 1.0 5.5
Al ₂ O ₃ 0.3 1.2
SnO ₂ 0.1 0.5
ZnO 0.1 0.4
P ₂ O ₅ 0.1 0.3
At least one oxide from the group: Na ₂ O, K ₂ O, Li ₂ O 0.1 0.3
At least one oxide from the group MgO, CaO 0.4 7.0
At least one halogen from group F, Cl 0.1 0.3
ZrO ₂ Else

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