High thermal shock resistance lip brick and preparation method and application thereof

Abstract

The application discloses a kind of high thermal shock resistance lip brick and preparation method and application, belong to refractory material technical field, first by gel-sintering process preparation porous corundum microsphere carrier, then by vacuum impregnation method rare earth-aluminum composite oxide precursor is pre-dispersed and loaded in its pore, composite oxide additive is prepared, subsequently the additive is mixed with alpha-Al2O3, rho-Al2O3 and the like raw materials, by three-phase electric arc furnace high-temperature melting, vibration casting forming, finally using traditional heating as main, microwave-assisted annealing treatment, high thermal shock resistance lip brick is prepared;The application reduces the thermal expansion coefficient of material, refines grain and pins grain boundary by the synergistic effect of rare earth additive grain boundary strengthening, rho-Al2O3 assisted dissolution and crystallization, sodium carbonate fluxing mineralization and microwave-assisted stress relief, inhibits crack initiation and propagation, significantly improves the thermal shock resistance stability of lip brick, reduces the risk of cracking and peeling under high temperature working condition, suitable for glass melting furnace lip high temperature alternating working condition.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically a high thermal shock resistant lip brick, its preparation method, and its application. Background Technology

[0002] Lid bricks are critical refractory components in the glass forming process of glass melting furnaces. Their working surfaces are in direct contact with high-temperature molten glass for extended periods, enduring erosion from the molten glass, alternating thermal shocks, and fluctuations in the furnace atmosphere—making their service environment extremely harsh. The performance of the lip brick directly affects the yield rate and production stability of glass products. Therefore, it must not only possess excellent resistance to molten glass erosion and low porosity, but also good thermal shock resistance to withstand the thermal stress impacts caused by rapid temperature changes, preventing cracking and spalling, thereby extending its service life.

[0003] Chinese patent application CN104129999A discloses a lip brick. The scheme uses tabular corundum, alumina, and zircon sand as the main aggregates, combined with a mixture containing phosphoric acid / phosphate, boron anhydride, and α-Al2O3 micro powder. The low porosity lip brick is prepared by vacuum slurry molding and high-temperature firing process, which improves the density and basic erosion resistance of the product to a certain extent.

[0004] However, this scheme uses a compound system of phosphate, boron anhydride, and zircon sand. Phosphate and boron anhydride, as low-temperature binding phases, are prone to softening, creep, and even decomposition in the high-temperature glass melt contact environment. This not only reduces the high-temperature strength and load softening temperature of the lip brick, but also introduces phosphorus and boron impurities into the glass melt, leading to defects such as nodules, discoloration, and bubbles in the glass. At the same time, zircon sand is prone to decomposition and phase transformation during long-term high-temperature service, generating internal stress with volume changes. Under frequent alternating hot and cold conditions, this can easily induce crack propagation, causing the lip brick to crack and peel off. This makes it difficult to meet the core requirements of high-end glass production lines for high-temperature stability, long service life, and high purity of glass products. Summary of the Invention

[0005] The purpose of this invention is to provide a high thermal shock resistant lip brick, its preparation method, and its application. Through the synergistic effect of rare earth additives strengthening grain boundaries, ρ-Al2O3 promoting crystallization, sodium carbonate aiding mineralization, and microwave-assisted stress relief, the thermal expansion coefficient of the material is reduced, the grains are refined and the grain boundaries are pinned, crack initiation and propagation are inhibited, the thermal shock resistance of the lip brick is significantly improved, and the risk of cracking and spalling under high temperature conditions is reduced. It is suitable for high-temperature alternating conditions at the lip of glass melting furnaces.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a high thermal shock resistant lip brick includes the following steps:

[0008] Step 1: Using high-purity α-Al2O3 as raw material, combined with PMMA pore-forming agent, porous corundum microspheres are prepared through gel molding and segmented sintering.

[0009] Step 2: The rare earth-aluminum precursor solution is loaded into porous corundum microspheres by vacuum impregnation, and then dried, decomposed and crystallized to obtain the composite oxide additive.

[0010] Step 3: Mix α-Al2O3 powder, ρ-Al2O3 powder, sodium carbonate, silicon dioxide, yttrium oxide and composite oxide additives, melt them to obtain a molten material, then vibrate and cast the molten material into shape, and then perform annealing with electric heating as the main method and microwave assisted method and cold working to obtain a lip brick with high thermal shock resistance.

[0011] Furthermore, the molten material is composed of α-Al2O3 powder, ρ-Al2O3 powder, sodium carbonate, silicon dioxide, yttrium oxide and composite oxide additives in a mass ratio of 85-90:5-10:3-3.5:0.5-0.7:0.15-0.25:1-1.5.

[0012] Furthermore, the frequency of vibration casting is 75-85Hz, and the amplitude is 0.15-0.25mm.

[0013] Furthermore, the microwave frequency for the electric heating-assisted annealing process is 2.45 GHz, the microwave power is 1-3 kW, the temperature is 1600-1700 ℃, and the heating time is 8-10 h.

[0014] Furthermore, the specific steps for using composite oxide additives are as follows:

[0015] Porous corundum microspheres were added to a vacuum impregnation apparatus, and a rare earth-aluminum mixed precursor solution was poured in until the liquid surface covered the carrier. The mixture was impregnated for 25-35 minutes under a vacuum of -0.09 MPa and 25°C, and then immersed for 50-70 minutes under normal pressure. After draining the surface solution, the mixture was dried at 110-130°C for 3.5-4.5 hours. Then, it was placed in a muffle furnace and heated to 800-900°C at a rate of 2°C / min and held for 1.5-2.5 hours to decompose nitrates. The impregnation, drying, and decomposition process was repeated 3-5 times. The mixture was then heated to 1300-1350°C and held for 0.8-1.2 hours to crystallize. After cooling in the furnace, the composite oxide additive was obtained.

[0016] Furthermore, the ratio of porous corundum microspheres to rare earth-aluminum mixed precursor solution is 14-16g:90-110mL.

[0017] Furthermore, the rare earth-aluminum mixed precursor solution is prepared by using yttrium nitrate hexahydrate, lanthanum nitrate hexahydrate, aluminum nitrate nonahydrate, and deionized water in a ratio of 3-3.4g:3.4-3.8g:18-19.5g:90-110mL.

[0018] Furthermore, the specific steps for producing porous corundum microspheres are as follows:

[0019] α-Al₂O₃ powder, polyisobutylene maleic anhydride dispersant, and deionized water were added to a polytetrafluoroethylene ball mill jar. Using zirconia beads as the grinding medium, the mixture was ball-milled for 5-7 hours at a speed of 180-220 r / min to obtain a uniform ceramic slurry. Subsequently, PMMA microspheres were added in batches at a speed of 50-70 r / min, and stirring was continued for 25-35 minutes to ensure uniform dispersion of the microspheres. The mixture was then subjected to vacuum degassing. The degassed slurry was poured into a mold and... The gel is formed, and then the gel preform is slowly dried at 35-45℃. The dried preform is crushed and sieved to obtain porous alumina green preform particles. The green preform particles are placed in a muffle furnace and heated to 480-520℃ at a rate of 2℃ / min in air atmosphere and held for 1.5-2.5h for pre-firing and debinding. Then, the temperature is further increased to 1300-1500℃ at a rate of 2℃ / min and held for 1.5-2.5h. After cooling in the furnace, porous corundum microspheres are obtained.

[0020] Furthermore, the ratio of α-Al2O3 powder, polyisobutylene maleic anhydride dispersant, deionized water, and PMMA microspheres is 95-99g: 0.8-1.2g: 90-110mL: 4-6g.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention improves the problems of traditional lip bricks being prone to cracking and spalling under alternating hot and cold conditions and having insufficient high-temperature strength by combining porous corundum microspheres loaded with rare earth-alumina composite oxide additives, multiphase alumina matrix, and an electrothermal-assisted microwave annealing process. It helps to improve the thermal shock resistance, mechanical strength, and density of lip bricks, and can be used in high-temperature alternating conditions such as glass melting furnace lips.

[0023] 2. The composite oxide additive prepared by this invention has multiple functions: First, the additive uses porous corundum microspheres as a dispersion carrier, and achieves molecular-level pre-dispersion of rare earth-aluminum precursors through vacuum impregnation, effectively avoiding the agglomeration problem that easily occurs when directly mixing rare earth powders. Moreover, during the 2100℃ melting stage, the porous carrier melts with the high temperature of the melt, uniformly releasing rare earth ions, making the rare earth components more uniformly distributed in the melt and reducing local enrichment. Second, the uniformly distributed rare earth ions can refine corundum grains during cooling and annealing and enrich them at grain boundaries, which helps to form a relatively strong and tough grain boundary structure and has a certain positive effect on inhibiting crack propagation. Third, the additive and the solubilizing and crystallizing effects of ρ-Al2O3 work together to improve the melt processing performance and material toughness.

[0024] 3. In the matrix formulation of this invention, α-Al2O3 provides high refractoriness and structural stability. ρ-Al2O3 powder, as active alumina, can promote melt homogenization, reduce melt viscosity, and improve casting fluidity during the melting process. At the same time, it refines the corundum grains after cooling and increases density. The composite oxide additive further ensures the uniform distribution of rare earth components through a pre-dispersion-melting release mechanism, synergistically refining grains and purifying grain boundaries. Sodium carbonate rapidly decomposes at high temperatures to generate sodium oxide, which acts as a flux, reducing melt viscosity and improving fluidity. Its decomposition generates trace amounts of gas, which refines grains and increases density during vibration casting. After cooling, it forms trace amounts of low-melting-point phases, optimizing grain boundaries and enhancing thermal shock resistance. The introduction of silicon dioxide and yttrium oxide can adjust the liquid phase composition and grain boundary state, which helps to improve the density and high-temperature strength of the material.

[0025] 4. In the preparation process of this invention, the high-temperature melting of the three-phase electric arc furnace fully homogenizes the raw materials and reduces component segregation; vibration casting helps to improve the density of the billet and reduce the porosity; electric heating as the main method and microwave-assisted annealing can alleviate the residual internal stress inside the billet to a certain extent and stabilize the crystal phase structure through uniform heating, thereby improving the thermal shock resistance and service reliability of the lip brick. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: A high thermal shock resistant lip brick, prepared by the following steps:

[0028] S1: 97g of α-Al2O3 powder (purity ≥99.99%, D50 0.5-1.5μm), 1g of polyisobutylene maleic anhydride dispersant (PIBM), and 100mL of deionized water were added to a polytetrafluoroethylene ball mill jar. Using zirconia beads as the grinding medium, the mixture was ball-milled for 6 hours at 200r / min to obtain a uniform ceramic slurry. Subsequently, 5g of PMMA microspheres (60μm particle size) were added in batches at 60r / min, and stirring was continued for 30 minutes to ensure uniform dispersion of the microspheres. The mixture was then subjected to vacuum degassing. The degassed slurry was poured into a mold and stored in a constant temperature and humidity environment (temperature: [missing information - likely a temperature value]). The alumina green body was spontaneously gelled at 25℃ and 60% humidity. The gel green body was then slowly dried at 40℃. After drying, the green body was crushed and sieved to obtain porous alumina green body particles with a particle size of 50-100μm. The green body particles were placed in a muffle furnace and heated to 500℃ at a rate of 2℃ / min in air atmosphere and held for 2 hours for pre-firing and debinding. Then, the temperature was further increased to 1400℃ at a rate of 2℃ / min and held for 2 hours. After cooling in the furnace, porous corundum microspheres with a porosity of 30-40% were obtained.

[0029] S2: Add 3.19g of yttrium nitrate hexahydrate, 3.61g of lanthanum nitrate hexahydrate, 18.75g of aluminum nitrate nonahydrate and 100mL of deionized water to a reaction vessel, and stir and dissolve for 30min at a temperature of 25℃ and a speed of 300r / min to obtain a rare earth-aluminum mixed precursor solution.

[0030] 15g of porous corundum microspheres were added to a vacuum impregnation apparatus, and 100mL of rare earth-aluminum mixed precursor solution was poured in until the liquid surface covered the carrier. The mixture was impregnated for 30min under a vacuum of -0.09MPa and a temperature of 25℃, and then immersed for 1h under normal pressure. After draining the surface solution, the mixture was dried at 120℃ for 4h and then placed in a muffle furnace. The temperature was increased to 850℃ at a rate of 2℃ / min and held for 2h to decompose nitrates. This impregnation-drying-decomposition process was repeated 4 times. The temperature was then increased to 1300℃ and held for 1h to crystallize. After cooling in the furnace, the composite oxide additive was obtained.

[0031] S3: Add 87g α-Al2O3 powder, 8g ρ-Al2O3 powder, 3g sodium carbonate, 0.6g silicon dioxide, 0.2g yttrium trioxide, and 1.5g composite oxide additive to a ball mill jar. Use deionized water as the medium and ball mill for 2 hours at a speed of 250 r / min to mix evenly and obtain a homogeneous mixture. Put the mixture into a three-phase electric arc furnace and heat it at a rate of 5℃ / min to 2100℃ and hold it for 1.5 hours to fully melt and homogenize the material to form a molten material.

[0032] S4: The molten material is vertically poured into a mold preheated to 900℃. During the casting process, a small amplitude vibration with a frequency of 80Hz and an amplitude of 0.2mm is applied. The material is then naturally cooled and shaped to obtain a lip brick blank. The blank is placed in an annealing furnace and heated mainly by electric heating, supplemented by a microwave field with a power of 2.45GHz and a power of 2kW. The temperature is increased to 1650℃ at a rate of 2℃ / min and held for 9 hours. The blank is then slowly cooled to room temperature in the furnace to eliminate internal stress and stabilize the crystal phase. Subsequently, the blank is cut, ground, polished, and cold-worked to adjust the size and surface, thus obtaining a lip brick with high thermal shock resistance.

[0033] Example 2: A high thermal shock resistant lip brick, its preparation method and application, prepared through the following steps:

[0034] S1: 95g of α-Al2O3 powder (purity ≥99.99%, D50 0.5-1.5μm), 0.8g of polyisobutylene maleic anhydride dispersant (PIBM), and 90mL of deionized water were added to a polytetrafluoroethylene ball mill jar. Using zirconia beads as the grinding medium, the mixture was ball-milled for 5 hours at 180r / min to obtain a uniform ceramic slurry. Subsequently, 4g of PMMA microspheres (60μm particle size) were added in batches at 50r / min, and stirring was continued for 25 minutes to ensure uniform dispersion of the microspheres. The mixture was then subjected to vacuum degassing. The degassed slurry was poured into a mold and stored in a constant temperature and humidity environment (temperature 2...). The alumina green body was spontaneously gelled at 5℃ and 60% humidity. The gel green body was then slowly dried at 35℃. After drying, the green body was crushed and sieved to obtain porous alumina green body particles with a particle size of 50μm. The green body particles were placed in a muffle furnace and heated to 480℃ at a rate of 2℃ / min in air atmosphere and held for 1.5h for pre-firing and debinding. Then, the temperature was further increased to 1300℃ at a rate of 2℃ / min and held for 1.5h. After cooling in the furnace, porous corundum microspheres with a porosity of 30-40% were obtained.

[0035] S2: Add 3g of yttrium nitrate hexahydrate, 3.4g of lanthanum nitrate hexahydrate, 18g of aluminum nitrate nonahydrate and 90mL of deionized water to a reaction vessel, and stir and dissolve for 25min at a temperature of 20℃ and a speed of 250r / min to obtain a rare earth-aluminum mixed precursor solution.

[0036] 14g of porous corundum microspheres were added to a vacuum impregnation apparatus, and 90mL of rare earth-aluminum mixed precursor solution was poured in until the liquid surface covered the carrier. The mixture was impregnated for 25min under a vacuum of -0.09MPa and a temperature of 25℃, and then immersed for 50min under normal pressure. After draining the surface solution, the mixture was dried at 110℃ for 3.5h and then placed in a muffle furnace. The temperature was increased to 800℃ at a rate of 2℃ / min and held for 1.5h to decompose nitrates. This impregnation-drying-decomposition process was repeated 3 times. The temperature was then increased to 1300℃ and held for 0.8h to crystallize. After cooling in the furnace, the composite oxide additive was obtained.

[0037] S3: Add 85g α-Al2O3 powder, 5g ρ-Al2O3 powder, 3g sodium carbonate, 0.5g silicon dioxide, 0.15g yttrium trioxide, and 1g composite oxide additive to a ball mill jar. Use deionized water as the medium and ball mill for 1.5h at a speed of 200r / min to mix evenly and obtain a homogeneous mixture. Put the mixture into a three-phase electric arc furnace and heat it at a rate of 5℃ / min to 2100℃ and hold it for 1.2h to fully melt and homogenize the material to form a molten material.

[0038] S4: The molten material is vertically poured into a mold preheated to 800℃. During the casting process, a small amplitude vibration with a frequency of 75Hz and an amplitude of 0.15mm is applied. The material is naturally cooled and shaped to obtain a lip brick blank. The blank is placed in an annealing furnace and heated mainly by electric heating, supplemented by a microwave field with a power of 2.45GHz and a power of 2kW. The temperature is raised to 1600℃ at a rate of 2℃ / min and held for 8 hours. The blank is then slowly cooled to room temperature in the furnace to eliminate internal stress and stabilize the crystal phase. Subsequently, the blank is cut, ground, polished, and cold-worked to adjust the size and surface, thus obtaining a lip brick with high thermal shock resistance.

[0039] Example 3: A high thermal shock resistant lip brick, its preparation method and application, prepared through the following steps:

[0040] S1: 99g of α-Al2O3 powder (purity ≥99.99%, D50 0.5-1.5μm), 1.2g of polyisobutylene maleic anhydride dispersant (PIBM), and 110mL of deionized water were added to a polytetrafluoroethylene ball mill jar. Using zirconia beads as the grinding medium, the mixture was ball-milled for 7 hours at 220r / min to obtain a uniform ceramic slurry. Subsequently, 6g of PMMA microspheres (60μm particle size) were added in batches at 70r / min, and stirring was continued for 35 minutes to ensure uniform dispersion of the microspheres. The mixture was then subjected to vacuum degassing. The degassed slurry was poured into a mold and stored in a constant temperature and humidity environment (temperature 25°C). The alumina green body was spontaneously gelled at 45°C and 60% humidity. The gel green body was then slowly dried at 45°C. After drying, the green body was crushed and sieved to obtain porous alumina green body particles with a particle size of 50-100 μm. The green body particles were placed in a muffle furnace and heated to 520°C at a rate of 2°C / min in air atmosphere and held for 2.5 h for pre-firing and debinding. Then, the temperature was further increased to 1500°C at a rate of 2°C / min and held for 2.5 h. After cooling in the furnace, porous corundum microspheres with a porosity of 30-40% were obtained.

[0041] S2: Add 3.4g of yttrium nitrate hexahydrate, 3.8g of lanthanum nitrate hexahydrate, 19.5g of aluminum nitrate nonahydrate and 110mL of deionized water to a reaction vessel, and stir and dissolve for 35min at a temperature of 30℃ and a speed of 350r / min to obtain a rare earth-aluminum mixed precursor solution.

[0042] 16g of porous corundum microspheres were added to a vacuum impregnation apparatus, and 110mL of rare earth-aluminum mixed precursor solution was poured in until the liquid surface covered the carrier. The mixture was impregnated for 35min under a vacuum of -0.09MPa and a temperature of 25℃, and then immersed for 70min under normal pressure. After draining the surface solution, the mixture was dried at 130℃ for 4.5h and then placed in a muffle furnace. The temperature was increased to 900℃ at a rate of 2℃ / min and held for 2.5h to decompose nitrates. This impregnation-drying-decomposition process was repeated 5 times. The temperature was then increased to 1350℃ and held for 1.2h to crystallize. After cooling in the furnace, the composite oxide additive was obtained.

[0043] S3: Add 90g α-Al2O3 powder, 10g ρ-Al2O3 powder, 3.5g sodium carbonate, 0.7g silicon dioxide, 0.25g yttrium trioxide, and 1.5g composite oxide additive to a ball mill jar. Use deionized water as the medium and ball mill at 300r / min for 2.5h to mix evenly and obtain a homogeneous mixture. Put the mixture into a three-phase electric arc furnace and heat it at a rate of 5℃ / min to 2100℃ and hold it for 1.8h to fully melt and homogenize the material to form a molten material.

[0044] S4: The molten material is vertically poured into a mold preheated to 1000℃. During the casting process, a small amplitude vibration with a frequency of 85Hz and an amplitude of 0.25mm is applied. The material is naturally cooled and shaped to obtain a lip brick blank. The blank is placed in an annealing furnace and heated mainly by electric heating, supplemented by a microwave field with a power of 2.45GHz and a power of 2kW. The temperature is raised to 1700℃ at a rate of 2℃ / min and held for 10 hours. The blank is then slowly cooled to room temperature in the furnace to eliminate internal stress and stabilize the crystal phase. Subsequently, the blank is cut, ground, polished, and cold-worked to adjust the size and surface, thus obtaining a lip brick with high thermal shock resistance.

[0045] Comparative Example 1: Based on Example 1, steps S1 and S2 for the preparation of the composite oxide additive were omitted, and no composite oxide additive was added in step S3. Other steps and parameters remained unchanged, and a lip brick was obtained.

[0046] Comparative Example 2: Based on Example 1, step S1, the preparation of porous corundum microspheres was omitted, and commercially available ordinary porous alumina powder was used directly to replace the porous corundum microspheres as the carrier material. In step S2, the additives were prepared by impregnation, while other steps and parameters remained unchanged, and lip bricks were obtained.

[0047] Comparative Example 3: Based on Example 1, step S2, the preparation of the composite oxide additive, was omitted. In step S3, an equal amount of unloaded rare earth-aluminum oxide powder was directly added, while other steps and parameters remained unchanged, resulting in a lip brick.

[0048] Comparative Example 4: Based on Example 1, the electric heating-microwave assisted annealing process in step S4 was replaced with conventional annealing, and the process was kept at 1650℃ for 9 hours. Other steps and parameters remained unchanged, and a lip brick was obtained.

[0049] The high thermal shock resistant lip bricks prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests:

[0050] Thermal shock stability test: The test was conducted in accordance with GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractory Materials" (Water Quenching Method). The lip brick was cut into standard specimens (size: 114mm×64mm×25mm), placed in an electric furnace, heated to 1100℃ at a rate of 10℃ / min and held for 30min. Then the specimens were quickly removed and quenched in room temperature water for 5min. This process was repeated until visible cracks or spalling appeared on the specimens. The number of cycles (N) before the first crack appeared was recorded. The higher the number of thermal shock cycles, the stronger the material's ability to resist drastic temperature changes and prevent cracking and spalling.

[0051] Thermal expansion coefficient test: The test was conducted according to GB / T 7320-2018 "Test Method for Thermal Expansion of Refractory Materials". A thermal expansion apparatus was used, and the temperature was increased from room temperature to 1000℃ at a rate of 5℃ / min in air atmosphere. The linear expansion was recorded, and the average thermal expansion coefficient (×10) was calculated. -6 / K); the lower the coefficient of thermal expansion, the less thermal stress the material generates when the temperature changes, and the better its thermal shock resistance.

[0052] Room temperature compressive strength test: The test is conducted in accordance with GB / T 5072-2008 "Test Method for Room Temperature Compressive Strength of Refractory Materials". The lip brick is processed into a standard cylindrical specimen with a diameter of 50mm and a diameter of 50mm. The specimen is pressurized on a universal testing machine at a loading rate of 0.5MPa / s. The maximum pressure at which the specimen fails is recorded, and the room temperature compressive strength (MPa) is calculated. The higher the compressive strength, the stronger the material's ability to withstand mechanical loads during service.

[0053] Porosity and bulk density testing: The tests were conducted according to GB / T 2997-2015 "Test Methods for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products". The Archimedes displacement method was used. The samples were dried at 110℃ to constant weight, and their dry weight (m1) and saturated weight (m2) were measured. The buoyancy in water (m3) was also determined. The apparent porosity (%) and bulk density (g / cm³) were calculated. 3 The lower the apparent porosity and the higher the bulk density, the higher the material density and the stronger its resistance to erosion and permeation.

[0054] The results are shown in Table 1:

[0055] Table 1 Performance test results of each lip brick

[0056] Project Group Number of thermal shock cycles (times) <![CDATA[Average coefficient of thermal expansion (×10 -6 / K)]]> room temperature compressive strength (MPa) Apparent porosity (%) <![CDATA[Bulk density (g / cm 3 )]]> Example 1 48 7.0 126 8.1 3.12 Example 2 45 7.1 121 8.5 3.08 Example 3 50 6.8 129 7.9 3.15 Comparative Example 1 35 7.9 105 9.6 2.98 Comparative Example 2 30 7.7 96 10.7 2.89 Comparative Example 3 40 7.4 98 10.2 2.95 Comparative Example 4 38 7.2 105 9.0 3.05

[0057] The performance test results show that the high thermal shock resistant lip bricks prepared in Examples 1-3 of this invention achieve uniform distribution of rare earth elements through pre-dispersion of porous corundum microspheres loaded with rare earth-aluminum precursors, melting and decomposition release, ρ-Al2O3 as a solvent and crystallizer, sodium carbonate as a flux for mineralization and micro-grain boundary regulation, combined with an electrothermal-based and microwave-assisted annealing process, thus constructing a multi-synergistic strengthening system. This system simultaneously optimizes the material's thermal shock resistance, room temperature mechanical strength, and density. While ensuring high refractoriness and low impurity precipitation in the matrix, this system helps to refine grains, pin grain boundaries, prevent crack propagation, and effectively alleviate residual internal stress generated during the molding process. It plays a positive role in improving the cracking and spalling problem of lip bricks under alternating hot and cold conditions.

[0058] Comparative Example 1 omits the preparation steps of the composite oxide additive and does not add functional additives to the matrix. Its thermal shock cycle count and room temperature compressive strength are lower than those of the embodiments of the present invention, while its coefficient of thermal expansion and apparent porosity are higher. This may be related to the lack of rare earth components to refine the grains and strengthen the grain boundaries. Insufficient grain boundary strength will make the material more prone to crack initiation during temperature alternation, and the density will decrease slightly, thus affecting the mechanical properties and thermal shock resistance. This result shows that the rare earth-aluminum composite oxide additive used in the present invention has a certain effect on improving the comprehensive performance of the lip brick.

[0059] Comparative Example 2 used commercially available ordinary porous alumina powder instead of self-made porous corundum microspheres. Its thermal shock stability, mechanical strength and density were weaker than those of the example. This result indicates that the pore structure of the self-made porous corundum microspheres is more suitable for the pre-dispersion of the precursor, which can more effectively avoid the agglomeration of rare earth components and ensure the uniform distribution of rare earth after melting. The pore structure of ordinary porous alumina powder may lead to poor loading effect and fail to give full play to the reinforcing effect of rare earth components, thereby affecting the thermal shock resistance of the lip brick.

[0060] Comparative Example 3 omitted the porous carrier impregnation and loading step, and directly used an equal amount of unloaded rare earth-aluminum oxide powder to replace the composite oxide additive. Its thermal shock stability and mechanical properties were lower than those of the Example. This indicates that the porous carrier pre-dispersion-melting release mechanism can effectively avoid rare earth powder agglomeration, improve the uniformity of rare earth component distribution, and better play the role of refining grains and preventing cracks. It is of certain significance for improving the long-term thermal shock resistance of the lip brick.

[0061] Comparative Example 4 omitted the electric heating-microwave assisted annealing process and used conventional annealing to treat the lip brick blank. Its thermal shock cycle count and room temperature compressive strength were lower than those of the Example, while its thermal expansion coefficient and apparent porosity were higher. This may be due to the insufficient heating uniformity of conventional tunnel kiln annealing, making it difficult to effectively eliminate residual internal stress in the blank. Under alternating temperature conditions, crack initiation and propagation are easily induced, leading to a decrease in the thermal shock resistance of the lip brick. This result shows that the electric heating-microwave assisted annealing process plays an important role in relieving internal stress in the blank, stabilizing the crystal structure, and ensuring the service performance of the lip brick.

[0062] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a high thermal shock resistant lip brick, characterized in that, Includes the following steps: Step 1: Using high-purity α-Al2O3 as raw material, combined with PMMA pore-forming agent, porous corundum microspheres are prepared through gel molding and segmented sintering. Step 2: The rare earth-aluminum precursor solution is loaded into porous corundum microspheres by vacuum impregnation, and then dried, decomposed and crystallized to obtain the composite oxide additive. Step 3: Mix α-Al2O3 powder, ρ-Al2O3 powder, sodium carbonate, silicon dioxide, yttrium oxide and composite oxide additives, melt them to obtain a molten material, then vibrate and cast the molten material into shape, and then perform annealing with electric heating as the main method and microwave assisted method and cold working to obtain a lip brick with high thermal shock resistance.

2. The method for preparing a high thermal shock resistant lip brick according to claim 1, characterized in that, The molten material is composed of α-Al2O3 powder, ρ-Al2O3 powder, sodium carbonate, silicon dioxide, yttrium oxide and composite oxide additives in a mass ratio of 85-90:5-10:3-3.5:0.5-0.7:0.15-0.25:1-1.

5.

3. The method for preparing a high thermal shock resistant lip brick according to claim 1, characterized in that, The vibration casting frequency is 75-85Hz, and the amplitude is 0.15-0.25mm.

4. The method for preparing a high thermal shock resistant lip brick according to claim 1, characterized in that, The microwave frequency for the electric heating-assisted annealing process is 2.45 GHz, the microwave power is 1-3 kW, the temperature is 1600-1700 ℃, and the heating time is 8-10 h.

5. The method for preparing a high thermal shock resistant lip brick according to claim 1, characterized in that, The specific steps for obtaining the composite oxide additive are as follows: Porous corundum microspheres were added to a vacuum impregnation device, and a rare earth-aluminum mixed precursor solution was poured in until the liquid surface covered the carrier. The microspheres were impregnated for 25-35 minutes under a vacuum of -0.09 MPa and 25°C, and then immersed for 50-70 minutes under normal pressure. After draining the surface solution, the microspheres were dried at 110-130°C for 3.5-4.5 hours. The microspheres were then placed in a muffle furnace and heated to 800-900°C at a rate of 2°C / min and held for 1.5-2.5 hours to decompose nitrates. The impregnation, drying and decomposition process was repeated 3-5 times. The microspheres were then heated to 1300-1350°C and held for 0.8-1.2 hours to crystallize. After cooling in the furnace, the composite oxide additive was obtained. The ratio of the porous corundum microspheres to the rare earth-aluminum mixed precursor solution is 14-16g:90-110mL.

6. The method for preparing a high thermal shock resistant lip brick according to claim 5, characterized in that, The rare earth-aluminum mixed precursor solution was prepared by using yttrium nitrate hexahydrate, lanthanum nitrate hexahydrate, aluminum nitrate nonahydrate, and deionized water in a ratio of 3-3.4g:3.4-3.8g:18-19.5g:90-110mL.

7. The method for preparing a high thermal shock resistant lip brick according to claim 5, characterized in that, The specific steps for producing the porous corundum microspheres are as follows: α-Al₂O₃ powder, polyisobutylene maleic anhydride dispersant, and deionized water were added to a polytetrafluoroethylene ball mill jar. Using zirconia beads as the grinding medium, the mixture was ball-milled at 180-220 r / min for 5-7 h to obtain a uniform ceramic slurry. Subsequently, PMMA microspheres were added in batches at 50-70 r / min, and stirring was continued for 25-35 min to ensure uniform dispersion of the microspheres. The mixture was then subjected to vacuum degassing. The degassed slurry was poured into a mold to spontaneously gel. The gel preform was then slowly dried at 35-45℃. After drying, the preform was crushed and sieved to obtain porous alumina green preform particles. The green preform particles were placed in a muffle furnace and heated to 480-520℃ at a rate of 2℃ / min in air atmosphere and held for 1.5-2.5h for pre-firing and debinding. Then, the temperature was further increased to 1300-1500℃ at a rate of 2℃ / min and held for 1.5-2.5h. After cooling in the furnace, porous corundum microspheres were obtained.

8. The method for preparing a high thermal shock resistant lip brick according to claim 1, characterized in that, The ratio of α-Al2O3 powder, polyisobutylene maleic anhydride dispersant, deionized water and PMMA microspheres is 95-99g: 0.8-1.2g: 90-110mL: 4-6g.

9. A lip brick with high thermal shock resistance, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The application of a high thermal shock resistant lip brick in a glass melting furnace, characterized in that, The high thermal shock resistant lip brick is prepared by the preparation method described in any one of claims 1-8.