A method for manufacturing fused cast zirconia brick using waste zirconia products

Abstract

The present application belongs to the technical field of special refractory material, and particularly relates to a method for manufacturing fused cast zirconia brick by using waste zirconia product; the waste zirconia product is put into an electric arc furnace after being picked, crushed and de-ironed, and then is melted into a melt, and after being poured into a graphite mold in which 0.1-0.5mm zirconia hollow balls are previously placed, a method of pouring on one side and vibrating the graphite mold pouring platform on the other side is adopted in the mold pouring process, so that the zirconia hollow balls are dispersed in the melt; the tiny round holes generated by the zirconia hollow balls absorb the internal stress generated in the cooling process of the fused cast zirconia brick after pouring, prevent the micro-cracks generated by the internal stress from continuing to expand, and improve the fracture toughness of the fused cast zirconia brick. In the method for manufacturing the fused cast zirconia brick, no low-melting-point oxide is added, the fused cast zirconia brick manufactured has a high service temperature and strong corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of special refractory materials technology, specifically relating to a method for manufacturing fused cast zirconia bricks using waste zirconia products. Background Technology

[0002] As China has consistently ranked first in the world in steel production for many years, zirconia nozzles and slide gates are key functional refractory materials used in steelmaking operations to flow molten steel. The annual consumption of zirconia nozzles and slide gates is approximately 100,000 tons, with about 70,000 tons of waste zirconia nozzles and slide gates generated after dismantling. Recycling these waste zirconia ceramics, zirconia nozzles, and slide gates for the production of cast zirconia bricks is essential for the circular utilization of scarce zirconia resources.

[0003] Zirconia is the oxide with the strongest resistance to molten glass corrosion. When used in glass melting furnaces, cast zirconia bricks not only resist molten glass corrosion but also reduce contamination of the glass. Cast zirconia bricks can be used not only for flow channels and sidewalls in soda-lime glass melting furnaces but also for sidewalls, partitions, and flow channels in borosilicate and aluminosilicate glass melting furnaces. With the rapid development of technology and the electronics industry, displays are also rapidly being updated. To meet the requirements of high resolution and other high-quality requirements, thin-film transistor (TFT) liquid crystal displays were developed. The substrate glass used in TFT liquid crystal displays is a sodium-free borosilicate alkali-free glass. This type of glass severely corrodes the refractory materials of the melting furnace; therefore, high-quality cast zirconia bricks must be used for the refractory materials in the parts of the TFT glass melting furnace that come into contact with the molten glass.

[0004] The production process of fused cast zirconia bricks is basically the same as that of other fused cast bricks. However, when the ZrO2 content in the fused cast brick exceeds 41%, the fused cast block is prone to cracking and it is difficult to produce qualified products. The reason for the cracking is that during the cooling process after casting, the ZrO2 crystals transform from cubic phase to monoclinic phase, resulting in a phase transformation, volume expansion, and cracking.

[0005] To mitigate cracking in fused cast zirconia bricks, low-melting-point oxides are typically incorporated to create a glassy phase that absorbs or buffers the internal stress caused by volume expansion during the transformation of ZrO2 crystals from cubic to monoclinic phase. However, incorporating low-melting-point oxides lowers the service temperature of the fused cast zirconia bricks. For example, the existing patent CN201210222402.7, "A Component of a High Zirconia Brick for Glass Furnaces," uses the addition of 0.3–2.0% alumina, 0.45–8.0% silicon dioxide, 0.05–0.6% sodium oxide, 0.2–0.4% zinc oxide, and 0.5–1.0% boron trioxide to create a glassy phase to absorb or buffer internal stress. Similarly, the existing patent CN200480039608.X, "Fused Cast Zirconia Refractory Material with High Resistivity," uses the addition of 0.9–5% Al2O3 and 4.0–10.0% SiO2. 0.1–1.2% B2O3, up to 0.04% Na2O, up to 0.4% CaO, up to 0.1% Fe2O3 and up to 0.25% TiO2 are used to generate a glassy phase to absorb or buffer internal stress.

[0006] However, the substrate glass used in TFT LCD displays is a sodium-free borosilicate alkali-free glass. Since TFT glass does not contain flux alkali, its melting temperature is very high, which places high demands on the heat resistance of the cast high zirconia bricks in the part of the TFT glass melting furnace that comes into contact with the molten glass. Increasing the glass phase through existing technology to absorb or buffer the internal stress of ZrO2 crystallization will reduce the corrosion resistance of the cast zirconia bricks. Summary of the Invention

[0007] This invention solves the technical problem in the conventional method for producing fused cast zirconia bricks, which uses the addition of low-melting-point oxides to generate a glassy phase to absorb or buffer the internal stress of ZrO2 crystallization. However, the addition of low-melting-point oxides lowers the operating temperature of the fused cast zirconia bricks and reduces their corrosion resistance, making them unsuitable for producing fused high zirconia bricks in the contact area with molten glass in TFT glass melting furnaces.

[0008] To solve the above technical problems, the present invention adopts the following technical solution:

[0009] A method for manufacturing fused cast zirconia bricks using waste zirconia products includes the following steps:

[0010] Step 1: Manually sort the recovered waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain powdered material.

[0011] Step 2: The powdered materials that have been artificially processed are thoroughly mixed to obtain a mixture. The mixture is then put into an electric arc furnace for melting at a temperature of 2600-3000℃, so that the materials are fully melted into a molten state.

[0012] Step 3: Assemble the mold required for casting zirconia bricks using graphite plates, and evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold;

[0013] Step four: Pour the high-temperature molten liquid into a vibrating graphite mold, while simultaneously vibrating the mold to cause the zirconium oxide hollow spheres to rise, disperse, and mix.

[0014] Step 5: After casting, wait at least 3 minutes before removing the mold;

[0015] Step six: The high-temperature cast zirconia bricks, after the mold has been removed, are subjected to forced or natural heat preservation and annealing.

[0016] Step 7: The heat-insulated and annealed fused cast zirconia bricks are cut and ground into the desired finished products.

[0017] Furthermore, the mixture in step two is a mixture of yttrium, calcium, magnesium, and cerium-stabilized zirconium oxide, and its main components are: Zr(Hf)O2 content greater than 87%, yttrium oxide content of 0-8%, calcium oxide content of 0-4.5%, magnesium oxide content of 0-4%, and cerium oxide content of 0-14%.

[0018] Furthermore, the 0.1-0.5 mm zirconia hollow spheres in step three are monoclinic zirconia, whose main components are: Zr(Hf)O2 content greater than 97%, silicon dioxide content of 0-2%, and aluminum oxide content of 0-1%.

[0019] Furthermore, in step three, the 0.1-0.5 mm zirconia hollow spheres are baked and dried in an oven at 150-500°C.

[0020] Furthermore, in step three, the amount of 0.1-0.5mm zirconia hollow spheres added is controlled according to the porosity of the cast zirconia bricks. The amount added is 8-30% of the total amount of molten casting, and the porosity of the cast zirconia bricks is controlled between 5-20%.

[0021] This invention involves sorting, crushing, and removing iron from recycled waste zirconia products before melting them in an electric arc furnace. The molten material is then poured into a graphite mold containing a pre-placed amount of 0.1–0.5 mm hollow zirconia spheres. The casting process employs a method of simultaneously pouring and vibrating the graphite mold casting platform to disperse the 0.1–0.5 mm hollow zirconia spheres in the molten material. The technical principle lies in the fact that the 0.1–0.5 mm hollow zirconia spheres are monoclinic zirconia hollow spheres, with a melting point approximately 300°C higher than that of the waste zirconia products, which are typically yttrium-stabilized zirconia or calcium oxide. Stabilized zirconia, magnesium-stabilized zirconia, and cerium-stabilized zirconia, etc., are mixtures of waste zirconia products after sorting and crushing. These mixtures are yttrium, calcium, magnesium, and cerium-stabilized zirconia. The melting point of this mixture is lower than that of monoclinic zirconia. Therefore, the 0.1-0.5 mm hollow zirconia spheres cast and dispersed in the molten material will not melt away and will remain in the form of tiny pores. These tiny pores can absorb the internal stress generated during the cooling process of the cast zirconia bricks, prevent the microcracks caused by the internal stress from continuing to propagate, and improve the fracture toughness of the cast zirconia bricks.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention disperses 0.1-0.5mm hollow zirconia spheres in the molten mixture of waste zirconia products that have been sorted, crushed, and melted. The tiny pores created by the hollow zirconia spheres absorb the internal stress generated during the cooling process of the cast zirconia bricks, preventing the microcracks caused by the internal stress from continuing to propagate and improving the fracture toughness of the cast zirconia bricks. This invention innovates the existing technology and conventional production methods that use the addition of low-melting-point substances to generate a glassy phase to absorb or buffer internal stress.

[0024] 2. In the method for producing fused cast zirconia bricks of the present invention, no low-melting-point oxides are added. The resulting fused cast zirconia bricks have a service temperature more than 300°C higher than those produced with added low-melting-point oxides, and exhibit strong corrosion resistance. They are suitable for use as substrate glass in TFT liquid crystal displays made of sodium oxide-free borosilicate alkali-free glass. Since TFT glass does not contain flux alkali and has a very high melting temperature, the tiny pores created by the hollow zirconia spheres absorb the internal stress generated during the cooling process of the cast fused cast zirconia bricks. This does not affect the service temperature or performance of the fused cast zirconia bricks, and solves the problem of reduced corrosion resistance and lower service temperature caused by adding a glass phase to absorb or buffer the internal stress of ZrO2 crystallization.

[0025] 3. This invention utilizes recycled waste zirconia products and processes them into cast zirconia bricks through high-temperature smelting in an electric arc furnace. The production cost is low and it has strong market competitiveness. In the case of limited zirconia resources, it also realizes the recycling of zirconia resources and protects the ecological environment.

[0026] 4. The casting process of this invention employs a method of simultaneous casting and vibration of the graphite mold casting platform, which disperses 0.1-0.5mm zirconia hollow spheres in the molten liquid. Compared with existing technologies in the market that use recycled zirconia to form blanks through pressure vibration and then fire them, this method reduces the steps of mixing materials for blanks, simplifies the production process and preparation method, and solves the technical problem of mixing materials with zirconia hollow spheres in a high-temperature molten state by using a vibrating graphite mold casting platform. This allows the zirconia hollow spheres to be dispersed in the high-temperature molten material, and the resulting micro-pores absorb the internal stress generated during the cooling process of the cast zirconia bricks. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the present invention for manufacturing fused cast zirconia bricks using waste zirconia products. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a method for manufacturing fused cast zirconia bricks using waste zirconia products, such as... Figure 1 As shown, the recycled waste zirconia products undergo sorting, crushing, melting, ingot casting, cooling, and processing to manufacture fused cast zirconia bricks. The specific method includes the following steps:

[0030] Step 1: Manually sort the recovered waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain granular material.

[0031] Step 2: The powdered materials that have been artificially processed are thoroughly mixed to obtain a mixture. The mixture is then put into an electric arc furnace for melting at a temperature of 2600-3000℃, so that the materials are fully melted into a molten state.

[0032] The mixture is a mixture of yttrium, calcium, magnesium and cerium stabilized zirconium oxide, and its main components are: Zr(Hf)O2 content greater than 87%, yttrium oxide content of 0-8%, calcium oxide content of 0-4.5%, magnesium oxide content of 0-4%, and cerium oxide content of 0-14%.

[0033] Step 3: Assemble the mold required for casting zirconia bricks using graphite plates, and evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold;

[0034] The aforementioned hollow zirconia spheres are monoclinic zirconia, i.e., desilicationized zirconia, whose main components are: Zr(Hf)O2 content greater than 97%, silicon oxide content of 0-2%, and aluminum oxide content of 0-1%;

[0035] The zirconium oxide hollow spheres are baked and dried in an oven at 150-500℃;

[0036] The amount of zirconia hollow spheres added is controlled according to the porosity of the cast zirconia bricks. The amount added is 8% to 30% of the total amount of molten casting. The porosity of the cast zirconia bricks is generally controlled between 5% and 20%.

[0037] Step four: Pour the high-temperature molten liquid into a vibrating graphite mold, while simultaneously vibrating the mold to cause the zirconium oxide hollow spheres to rise and disperse, mixing into the high-temperature molten liquid.

[0038] Step 5: After casting, wait for at least 3 minutes before removing the mold.

[0039] Step six involves subjecting the high-temperature cast zirconia bricks, after removing the mold, to forced or natural heat preservation and annealing.

[0040] Step 7: The heat-insulated and annealed fused cast zirconia bricks are cut and ground into the desired finished products.

[0041] The above describes a method for manufacturing fused cast zirconia bricks using waste zirconia products. The recycled waste zirconia products undergo a manufacturing process of manual sorting, crushing, melting in a furnace, casting into a mold, cooling, and processing to obtain fused cast zirconia bricks with high operating temperature, strong corrosion resistance, and good thermal shock resistance. The fused cast zirconia bricks manufactured using this invention do not contain any low-melting-point oxides and are suitable for producing substrate glass for TFT liquid crystal displays using sodium oxide-free borosilicate alkali-free glass.

[0042] Example 1

[0043] This embodiment provides a method for manufacturing fused cast zirconia bricks using waste zirconia products. The specific steps are as follows:

[0044] Step 1: Manually sort the recovered waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain powdery materials.

[0045] Step 2: Thoroughly mix the artificially processed powdered materials and put them into an electric arc furnace for melting. The melting temperature is 2600-3000℃, so that the materials are fully melted into a molten state.

[0046] Step 3: Assemble the mold required for casting zirconia bricks using graphite plates. Evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold. The amount of hollow spheres added is 8% of the total amount of molten casting.

[0047] Step 4: Pour the high-temperature molten liquid into a vibrating graphite mold. Vibrate the mold while pouring to make the zirconia hollow spheres rise, disperse, and mix.

[0048] Step 5: After casting, wait at least 3 minutes before removing the mold;

[0049] Step Six: Force or natural heat treatment and annealing of the high-temperature cast zirconia bricks after removing the mold;

[0050] Step 7: Cut and grind the heat-insulating and annealed cast zirconia bricks into the desired finished products.

[0051] The chemical composition of the fused cast zirconia brick obtained in Example 1 includes: 0.85% SiO2, 0.45% Al2O3, 0.09% Fe2O3, 0.15% TiO2, 92.14% Zr(Hf)O2, 2.12% CaO, 1.31% MgO, 2.13% Y2O3, and 0.56% CeO2. The fused cast zirconia brick has a bulk density of 5.2 g / cm3, a porosity of 5.4%, and thermal shock resistance of 6 to 10 cycles from room temperature to 1400℃ (15-minute intervals). The service temperature can reach 2150℃.

[0052] Example 2

[0053] This embodiment provides a method for manufacturing fused cast zirconia bricks using waste zirconia products. The specific steps are as follows:

[0054] Step 1: Manually sort the recovered waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain powdery materials.

[0055] Step 2: Thoroughly mix the artificially processed powdered materials and put them into an electric arc furnace for melting. The melting temperature is 2600-3000℃, so that the materials are fully melted into a molten state.

[0056] Step 3: Assemble the mold required for casting zirconia bricks using graphite plates. Evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold. The amount of hollow spheres added should be 19% of the total amount of molten casting.

[0057] Step 4: Pour the high-temperature molten liquid into a vibrating graphite mold. Vibrate the mold while pouring to make the zirconia hollow spheres rise, disperse, and mix.

[0058] Step 5: After casting, wait at least 3 minutes before removing the mold;

[0059] Step Six: Force or natural heat treatment and annealing of the high-temperature cast zirconia bricks after removing the mold;

[0060] Step 7: Cut and grind the heat-insulating and annealed cast zirconia bricks into the desired finished products.

[0061] The chemical composition of the fused cast zirconia brick obtained in Example 2 includes: 1.25% SiO2, 0.45% Al2O3, 0.12% Fe2O3, 0.19% TiO2, 90.38% Zr(Hf)O2, 1.52% CaO, 1.01% MgO, 4.13% Y2O3, and 0.76% CeO2. The fused cast zirconia brick has a bulk density of 4.9 g / cm3, a porosity of 12.3%, and thermal shock resistance of 12-16 cycles from room temperature to 1400℃ (15-minute intervals). The service temperature can reach 2100℃.

[0062] Example 3

[0063] This embodiment provides a method for manufacturing fused cast zirconia bricks using waste zirconia products. The specific steps are as follows:

[0064] Step 1: Manually sort the recovered waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain powdery materials.

[0065] Step 2: Thoroughly mix the artificially processed powdered materials and put them into an electric arc furnace for melting. The melting temperature is 2600-3000℃, so that the materials are fully melted into a molten state.

[0066] Step 3: Assemble the mold required for casting zirconia bricks using graphite plates. Evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold. The amount of hollow spheres added should be 30% of the total amount of molten casting.

[0067] Step 4: Pour the high-temperature molten liquid into a vibrating graphite mold. Vibrate the mold while pouring to make the zirconia hollow spheres rise, disperse, and mix.

[0068] Step 5: After casting, wait at least 3 minutes before removing the mold;

[0069] Step Six: Force or natural heat treatment and annealing of the high-temperature cast zirconia bricks after removing the mold;

[0070] Step 7: Cut and grind the heat-insulating and annealed cast zirconia bricks into the desired finished products.

[0071] The chemical composition of the fused cast zirconia brick obtained in Example 3 is as follows: 0.78% SiO2, 0.63% Al2O3, 0.07% Fe2O3, 0.18% TiO2, 92.55% Zr(Hf)O2, 3.12% CaO, 0.81% MgO, 1.13% Y2O3, and 0.53% CeO2. The fused cast zirconia brick has a bulk density of 4.6 g / cm3, a porosity of 19.3%, and thermal shock resistance of 18-22 cycles from room temperature to 1400℃ (15-minute intervals). The service temperature can reach 2200℃.

Claims

1. A method for manufacturing fused cast zirconia bricks using waste zirconia products, characterized in that, Includes the following steps: Step 1: Manually sort the recycled waste zirconium oxide products to remove foreign objects, scrape off the surface adhering substances, then crush and pulverize them and remove iron by magnetic separation to obtain powdered material. Step 2: The powdered materials that have been artificially processed are thoroughly mixed to obtain a mixture. The mixture is then put into an electric arc furnace for melting at a temperature of 2600-3000℃, so that the materials are fully melted into a molten state. Step 3: Assemble the mold required for casting zirconia bricks using graphite plates, and evenly sprinkle a layer of baked and dried 0.1-0.5mm zirconia hollow spheres on the bottom of the mold; Step four: Pour the high-temperature molten liquid into a vibrating graphite mold, while simultaneously vibrating the mold to cause the zirconium oxide hollow spheres to rise, disperse, and mix. Step 5: After casting, wait at least 3 minutes before removing the mold; Step six: The high-temperature cast zirconia bricks, after the mold has been removed, are subjected to forced or natural heat preservation and annealing. Step 7: The heat-insulated and annealed fused cast zirconia bricks are cut and ground into the desired finished products.

2. The method for manufacturing fused cast zirconia bricks using waste zirconia products according to claim 1, characterized in that, The mixture in step two is a mixture of yttrium, calcium, magnesium and cerium stabilized zirconium oxide, and its main components are: Zr(Hf)O2 content greater than 87%, yttrium oxide content of 0-8%, calcium oxide content of 0-4.5%, magnesium oxide content of 0-4%, and cerium oxide content of 0-14%.

3. The method for manufacturing fused cast zirconia bricks using waste zirconia products according to claim 1, characterized in that, In step three, the 0.1-0.5 mm zirconia hollow spheres are monoclinic zirconia, whose main components are: Zr(Hf)O2 content greater than 97%, silicon dioxide content of 0-2%, and aluminum oxide content of 0-1%.

4. The method for manufacturing fused cast zirconia bricks using waste zirconia products according to claim 1, characterized in that, In step three, the 0.1-0.5 mm zirconia hollow spheres are baked and dried in an oven at 150-500℃.

5. The method for manufacturing fused cast zirconia bricks using waste zirconia products according to claim 1, characterized in that, In step three, the amount of 0.1-0.5mm zirconia hollow spheres added is controlled according to the porosity of the cast zirconia bricks. The amount added is 8-30% of the total amount of molten casting, and the porosity of the cast zirconia bricks is controlled between 5-20%.

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