Composite thermal insulation tin bath bottom brick and preparation method thereof

Abstract

The invention belongs to the technical field of refractory materials, and particularly relates to a composite heat preservation tin bath bottom brick and a preparation method thereof.The preparation method comprises the steps that a light mixture is poured into a steel mold, mechanical vibration is conducted for 10-20 min, then a heavy mixture is poured into the mold of the vibrated light mixture, vibration is conducted for 5-10 min, standing and curing are conducted for 12-24 h, then demolding and curing are conducted for 12-15 h, and a blank composite brick is obtained; and drying the blank composite brick for 24-36 hours, sintering at high temperature, and cooling to obtain the composite heat-preservation tin bath bottom brick. According to the invention, the mechanical strength and alkali corrosion resistance of the tin bath bottom brick can be ensured while the porosity of the tin bath bottom brick is improved and the heat preservation effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the application of special refractory materials, and particularly relates to a composite heat-insulating tin bath bottom brick and a preparation method thereof. Background Art

[0002] The tin bath is one of the key thermal equipment in the float glass furnace. During the production process of float glass, the tin bath bottom brick needs to simultaneously meet the following key properties: resistance to molten tin (Sn) penetration, high temperature resistance (600 - 1050 °C) and thermal shock stability, good heat-insulating performance, and resistance to erosion by alkaline volatile substances (such as Na2O, etc.). The heat-insulating performance of the tin bath bottom brick directly affects the temperature uniformity of the tin bath, energy consumption control, and glass forming quality.

[0003] Currently, the existing tin bath bottom bricks are mainly clay bricks, and they are single-layer materials, with poor heat-insulating effect, low mechanical strength, and weak resistance to tin liquid erosion and gas erosion. They cannot effectively control the horizontal temperature difference inside the tin bath, especially have a great impact during the production of ultra-thin glass and ultra-white glass, and it is necessary to frequently turn on the electric heating to adjust the temperature, increasing the production operation difficulty and power consumption. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite heat-insulating tin bath bottom brick and a preparation method thereof to solve the problems mentioned in the above background art.

[0005] To achieve the above technical purpose, the technical solution of the present invention is as follows: A preparation method of a composite heat-insulating tin bath bottom brick includes the following steps: S1. Add synthetic mullite to a ball mill, perform ball milling according to classification requirements, and then pass through a sieve to obtain synthetic mullite fine powders with different particle sizes; Compound the synthetic mullite fine powders with different particle sizes to obtain a compound synthetic mullite fine powder; Weigh 38 - 45% of high-purity mullite, 48 - 55% of the compound synthetic mullite fine powder, 3 - 8% of clay, 1 - 3% of an additive, and 0.5 - 2% of an organic binder by weight percentage, premix for 3 min, then add water and continue mixing for 3 min to obtain a heavy mixture; S2. Weigh 18 - 22% of multi-porous alumina aggregate, 50 - 55% of sintered mullite, 5 - 8% of cement, 5 - 8% of dextrin, 3 - 5% of silica fume, and 8 - 10% of α-alumina powder by weight percentage, premix for 3 min, add water and continue mixing for 3 min to obtain a light mixture; S3. Pour the light mixture into a steel mold, mechanically vibrate for 10 - 20 min, then pour the heavy mixture into the mold with the light mixture that has completed vibration, vibrate for 5 - 10 min and then let it stand for curing for 12 - 24 h, and then demold and cure for 12 - 15 h to obtain the blank composite brick. After drying the blank composite brick for 24 - 36 h, cool it down after high-temperature sintering to obtain the composite heat-insulating tin bath bottom brick.

[0006] As a further improvement, the preparation method of the multi-porous alumina aggregate is as follows: S21. Using hydraulic alumina and aluminum trifluoride trihydrate as raw materials, prepare porous alumina by the gel-casting method; S22. Disperse the porous alumina in diammonium hydrogen citrate, add needle-like nano magnesium hydroxide pore-forming agent and methyl cellulose to it, mix evenly to obtain a mixed slurry, inject the mixed slurry into a mold, after curing and drying, place it in a covered alumina crucible, sinter at 1500 °C for 2 h, and crush it into particles with a size of 3 - 5 mm to obtain the multi-porous alumina aggregate.

[0007] As a further improvement, in step S21, the preparation method of the porous alumina is as follows: Ball-mill hydraulic alumina, aluminum trifluoride trihydrate and cerium oxide in a ball mill for 15 h respectively, then magnetically stir and mix the ball-milled hydraulic alumina and aluminum trifluoride trihydrate with deionized water, add the ball-milled cerium oxide to obtain a mixed slurry, inject the mixed slurry into a mold, after curing and drying, place it in a covered alumina crucible, sinter at 1500 °C for 2 h, and crush it into particles with a size of 5 - 10 mm to obtain the porous alumina. The mass ratio of hydraulic alumina to aluminum trifluoride trihydrate is 7:3, the mass of deionized water is the sum of the masses of hydraulic alumina and aluminum trifluoride trihydrate, and the dosage of cerium oxide is 3% of the mass of hydraulic alumina.

[0008] As a further improvement, the organic binder is one of phosphoric acid, industrial dextrin, peach gum, starch, polyvinyl alcohol, boron oxide, and the additive is one of sodium carboxymethyl cellulose, titanium dioxide, and active α - Al2O3 fine powder.

[0009] As a further improvement, in step S22, the mass of diammonium hydrogen citrate is 4% of the mass of the porous alumina, the mass of the pore-forming agent needle-like nano magnesium hydroxide is 10% of the mass of the porous alumina, and the mass of methyl cellulose is 1.25% of the mass of the porous alumina.

[0010] As a further improvement, in step S1, in the compound synthetic mullite fine powder, by weight percentage, it includes: 50% synthetic mullite fine powder with an average particle size ≤ 1 mm, 30% synthetic mullite fine powder with an average particle size ≤ 800 mesh, and 20% synthetic mullite fine powder with an average particle size ≤ 300 mesh; the high-purity mullite is polygonal particles with an average particle size ≤ 5 mm, and the average particle size of the clay ≤ 4.3 μm.

[0011] As a further improvement, in step S3, the drying temperature of the blank composite brick is 40 - 60°C. After high-temperature sintering, the cooling process is as follows: heating at a rate of 10°C / h to 580 - 600°C and holding for 5 - 6 h, then heating at a rate of 8°C / h to 980 - 1050°C and holding for 7 - 8 h, then heating at a rate of 6°C / h to 1350 - 1380°C and holding for 4 - 5 h, then heating at a rate of 5°C / h to 1400 - 1450°C and holding for 17 days, and finally cooling to 105 - 110°C within 36 - 72 hours, and then naturally cooling.

[0012] As a further improvement, in step S22, the preparation method of needle-like nano magnesium hydroxide is as follows: Mix magnesium chloride hexahydrate, potassium oleate, and polyvinylpyrrolidone, dissolve them with deionized water, place them in a water bath at 10°C, add a 2 mol / L sodium hydroxide solution thereto while stirring, continue stirring for 1 h after the addition is completed, then filter to obtain a precipitate, and wash it with deionized water to obtain needle-like nano magnesium hydroxide.

[0013] The present invention also provides a composite heat-insulating tin bath bottom brick.

[0014] Due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: For the composite heat-insulating tin bath bottom brick and its preparation method provided by the present invention, gel-casting is used to prepare porous alumina, forming an alumina wafer interlocking structure inside the alumina, reducing the thermal conductivity of the porous alumina. And during the preparation of the porous alumina, the dosage of cerium oxide is 3% of the mass of the hydraulic alumina, which helps the growth of alumina wafers inside the porous alumina, and improves the mechanical strength of the porous alumina without changing its porosity.

[0015] Using the porous alumina as a raw material to prepare hierarchical pore alumina, and using needle-like nano magnesium hydroxide as a pore-forming agent to form needle-like micropores, so that the hierarchical pore alumina forms hierarchical pores with different pore diameters and shapes, further reducing the thermal conductivity of the porous alumina aggregate and improving the heat-insulating effect of the porous alumina aggregate.

[0016] The composite heat-insulating tin bath bottom brick is prepared by a heavy mixture and a light mixture. The heavy mixture can improve the mechanical strength of the bottom brick, and adding hierarchical pore alumina to the light mixture can improve the heat-insulating performance of the bottom brick.

[0017] In the heavy mixture, by compounding synthetic mullite fine powders with different particle sizes, the density of the heavy mixture can be improved, and the heavy layer brick body of the obtained tin bath bottom brick is denser, improving the resistance to erosion by molten tin flow. Specific embodiments

[0018] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0019] Example 1 A preparation method of a composite heat-insulating tin bath bottom brick, comprising the following steps: S1. Take 70 g of hydraulic alumina, 30 g of aluminum fluoride trihydrate, and 2.1 g of cerium oxide. Use a ball mill to ball mill the hydraulic alumina, aluminum fluoride trihydrate, and cerium oxide at a rotation speed of 260 r / min for 15 h respectively. Then, use 100 g of deionized water to magnetically stir and mix the ball-milled hydraulic alumina and aluminum fluoride trihydrate, add 2.1 g of the ball-milled cerium oxide to obtain a mixed slurry. Inject the mixed slurry into a mold, cure it at room temperature for 24 h, then dry the green body in an oven at 40 °C for 5 h. Finally, place the green body in a covered alumina crucible, sinter it at 1500 °C for 2 h, and then crush it into 5 mm microparticles to obtain porous alumina. S2. Take 50 g of porous alumina, disperse it in 2 g of diammonium hydrogen citrate, and add 5 g of needle-like nano magnesium hydroxide pore-forming agent and 0.625 g of methyl cellulose thereto. After mixing evenly, obtain a mixed slurry. Inject the mixed slurry into a mold, cure it at room temperature for 24 h, then dry the green body in an oven at 40 °C for 5 h. Finally, place the green body in a covered alumina crucible, sinter it at 1500 °C for 2 h, and then crush it into 3 mm microparticles to obtain a multi-stage pore alumina aggregate. The mass of diammonium hydrogen citrate is 4% of the mass of porous alumina, the mass of the pore-forming agent needle-like nano magnesium hydroxide is 10% of the mass of porous alumina, and the mass of methyl cellulose is 1.25% of the mass of porous alumina. S3. Pour 20 g of the multi-stage pore alumina aggregate, 53 g of sintered mullite, 7 g of cement, 7 g of dextrin, 4 g of silica fume, and 9 g of α-alumina powder into a cement mortar mixer for premixing for 3 min, add 7.4 g of water and continue mixing for 3 min to obtain a lightweight mixture. S4. Add synthetic mullite to a ball mill and ball mill it into synthetic mullite micropowders with three levels of particle sizes, specifically, synthetic mullite micropowders with an average particle size ≤ 1 mm, synthetic mullite micropowders with an average particle size ≤ 800 mesh, and synthetic mullite micropowders with an average particle size ≤ 300 mesh. 50 g of synthetic mullite fine powder with an average particle size of ≤1 mm, 30 g of synthetic mullite fine powder with an average particle size of ≤800 mesh, and 20 g of synthetic mullite fine powder with an average particle size of ≤300 mesh are compounded to obtain a compound synthetic mullite fine powder; S5. Weigh 40 g of polygonal high-purity mullite with an average particle size of ≤5 mm, 52 g of compound synthetic mullite fine powder, 5 g of clay, 2 g of additive, and 1 g of organic binder, add them into a cement mortar mixer for premixing for 3 min, then add 6.57 g of water and continue mixing for 3 min to obtain a heavy mixture. Among them, sodium carboxymethyl cellulose is used as the additive, and phosphoric acid is used as the organic binder; Pour the light mixture into a steel mold, mechanically vibrate for 10 min, then pour the heavy mixture into the mold of the light mixture that has been vibrated, vibrate for 10 min, then stand for curing for 12 h, and then demold and cure for 12 h to obtain a blank composite brick. After drying the blank composite brick at 40 °C for 24 h, it is sintered at high temperature to obtain a composite heat-insulating tin bath bottom brick. During the high-temperature sintering process, it is heated at a rate of 10 °C / h to 600 °C and held for 5 h, heated at a rate of 8 °C / h to 1050 °C and held for 7 h, heated at a rate of 6 °C / h to 1380 °C and held for 4 h, heated at a rate of 5 °C / h to 1450 °C and held for 17 days, and finally cooled to 105 °C within 36 h, and then naturally cooled.

[0020] In this example, the preparation method of needle-like nano magnesium hydroxide is as follows: 20 g of magnesium chloride hexahydrate, 1 g of potassium oleate, and 0.25 g of polyvinylpyrrolidone are mixed and dissolved in 30 mL of deionized water, placed in a water bath at 10 °C, 100 mL of 2 mol / L sodium hydroxide solution is added thereto, the dropping rate is 2 mL / min, stirring is carried out while adding, the stirring speed is 1200 rpm. After the dropping is completed, stirring is continued for 1 h, then the precipitate is filtered and washed with deionized water to obtain needle-like nano magnesium hydroxide.

[0021] Example 2. This example provides a preparation method of a composite heat-insulating tin bath bottom brick, including the following steps: S1. Preparation of porous alumina. The specific preparation method is the same as that in Example 1, the difference is that it is crushed into 10 mm fine particles after sintering; S2. The preparation method of the multi-stage pore alumina aggregate is the same as that in Example 1, the difference is that it is crushed into 5 mm fine particles after sintering; S3. Pour 18 g of multi-stage pore alumina aggregate, 55 g of sintered mullite, 5 g of cement, 8 g of dextrin, 5 g of silica powder, and 9 g of α-alumina powder into a cement mortar mixer for premixing for 3 min, add 6.57 g of water and continue mixing for 3 min to obtain a light mixture; S4. Weigh 38 g of polygonal high-purity mullite with an average particle size of ≤5 mm, 55 g of compound synthesized mullite fine powder, 4 g of clay, 1 g of sodium carboxymethyl cellulose, and 2 g of phosphoric acid, add them to a cement mortar mixer for premixing for 3 min, then add 8.37 g of water and continue mixing for 3 min to obtain a heavy mixture; Pour the light mixture into a steel mold, mechanically vibrate for 20 min, then pour the heavy mixture into the mold of the light mixture that has been vibrated, vibrate for 5 min, then let it stand for curing for 24 h, and then demold and cure for 15 h to obtain a blank composite brick. After drying the blank composite brick at 40°C for 36 h, it is sintered at high temperature to obtain a composite heat-insulating tin bath bottom brick. During the high-temperature sintering process, it is heated at a rate of 10°C / h to 580°C and held for 5 h, heated at a rate of 8°C / h to 980°C and held for 7 h, heated at a rate of 6°C / h to 1350°C and held for 4 h, heated at a rate of 5°C / h to 1400°C and held for 17 days, and finally cooled to 110°C within 72 h, and then naturally cooled.

[0022] Example 3. This example provides a method for preparing a composite heat-insulating tin bath bottom brick, including the following steps: S1. Preparation of porous alumina. The specific preparation method is the same as that in Example 1, except that after sintering, it is crushed into 8 mm fine particles; S2. The preparation method of hierarchical porous alumina is the same as that in Example 1, except that after sintering, it is crushed into 4 mm fine particles; S3. Premix 22 g of hierarchical porous alumina aggregate, 50 g of sintered mullite, 8 g of cement, 5 g of dextrin, 5 g of silica fume, and 10 g of α-alumina powder for 3 min, then pour them into a cement mortar mixer for premixing for 3 min, add 6.48 g of water and continue mixing for 3 min to obtain a light mixture; S4. Weigh 45 g of polygonal high-purity mullite with an average particle size of ≤5 mm, 48 g of compound synthesized mullite fine powder, 3.5 g of clay, 3 g of sodium carboxymethyl cellulose, and 0.5 g of phosphoric acid, add them to a cement mortar mixer for premixing for 3 min, then add 8.37 g of water and continue mixing for 3 min to obtain a heavy mixture; Pour the light mixture into a steel mold, mechanically vibrate for 15 min, then pour the heavy mixture into the mold of the light mixture that has been vibrated, vibrate for 8 min, then let it stand for curing for 20 h, and then demold and cure for 13 h to obtain a blank composite brick. After drying the blank composite brick at 40°C for 30 h, it is sintered at high temperature to obtain a composite heat-insulating tin bath bottom brick. During the high-temperature sintering process, it is heated at a rate of 10°C / h to 590°C and held for 5 h, heated at a rate of 8°C / h to 1000°C and held for 7 h, heated at a rate of 6°C / h to 1360°C and held for 4 h, heated at a rate of 5°C / h to 1430°C and held for 17 days, and finally cooled to 108°C within 54 h, and then naturally cooled.

[0023] Example 4. This example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific preparation method is the same as that in Example 1, except that in step S4, for the light mixture, 18 g of multi-stage pore alumina aggregate, 55 g of sintered mullite, 8 g of cement, 8 g of dextrin, 3 g of silica fume, and 8 g of α-alumina powder are poured into a cement mortar mixer and premixed for 3 min, then 6.57 g of water is added and mixing continues for 3 min to obtain the light mixture; Weigh 38 g of polygonal high-purity mullite with an average particle size ≤ 5 mm, 50 g of composite synthetic mullite fine powder, 8 g of clay, 3 g of sodium carboxymethyl cellulose, and 1 g of phosphoric acid, add them to a cement mortar mixer and premix for 3 min, then add 7.92 g of water and continue mixing for 3 min to obtain the heavy mixture.

[0024] Example 5. This example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific preparation method is the same as that in Example 1, except that in step S4, weigh 44 g of polygonal high-purity mullite with an average particle size ≤ 5 mm, 48 g of composite synthetic mullite fine powder, 3 g of clay, 3 g of sodium carboxymethyl cellulose, and 2 g of phosphoric acid, add them to a cement mortar mixer and premix for 3 min, then add 8.28 g of water and continue mixing for 3 min to obtain the heavy mixture.

[0025] Examples 6 - 10 provide a method for preparing a composite heat-insulating tin bath bottom brick. The specific preparation method is the same as that in Example 1, except that different organic binders and additives are used, as shown in Table 1 specifically.

[0026] Table 1 Organic binders and additives used in the preparation of the composite heat-insulating tin bath bottom brick in Examples 6 - 10

[0027] Comparative Example 1. This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S1, the dosage of cerium oxide is 4% of the mass of hydraulic alumina.

[0028] Comparative Example 2. This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S1, the dosage of cerium oxide is 2% of the mass of hydraulic alumina.

[0029] Comparative Example 3. This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S1, after sintering, it is crushed into 3-mm fine particles; in step S3, the multi-stage pore alumina is replaced with the above-mentioned crushed 3-mm porous alumina to obtain the porous alumina aggregate; in step S4, when preparing the light mixture, the multi-stage pore alumina aggregate is replaced with the above-prepared porous alumina aggregate.

[0030] Comparative Example 4 This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the compound synthesized mullite fine powder is replaced with a synthesized mullite fine powder with an average particle size ≤ 1 mm.

[0031] Comparative Example 5 This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the compound synthesized mullite fine powder is replaced with a synthesized mullite fine powder with an average particle size ≤ 800 mesh.

[0032] Comparative Example 6 This comparative example provides a method for preparing a composite heat-insulating tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the compound synthesized mullite fine powder is replaced with a synthesized mullite fine powder with an average particle size ≤ 300 mesh.

[0033] The porous alumina used in the lightweight mixture in Example 1, Comparative Example 1, and Comparative Example 2 was tested for bulk density, porosity, and compressive strength.

[0034] The porosity and bulk density of the porous alumina were measured by the Archimedes drainage method. The specific testing steps are as follows: After drying the sample, use a balance to measure the dry weight of the sample in air and record it as m1; place the sample in a beaker, evacuate it, then add deionized water to completely immerse the sample so that the pores of the sample are filled with deionized water. Subsequently, place the saturated sample in a densitometer and measure its mass m2 in water; take out the sample and gently wipe the water droplets on the surface of the saturated sample with a wet paper towel, and weigh the mass m3 of the sample in air. Calculate the porosity and bulk density, and the results are shown in Table 1.

[0035] The surface of the sample was ground flat, and the area of the compressed surface of the sample was measured. The pressing head speed of the universal testing machine was 0.2 mm / min, and the maximum load when the sample was damaged was measured. The maximum load value divided by the area of the compressed surface is the compressive strength, and the results are shown in Table 2.

[0036] Table 2 Results of porosity, bulk density, and compressive strength of porous alumina in each lightweight mixture

[0037] It can be seen from Table 1 that when the addition amount of cerium oxide is 4% of the mass of hydraulic alumina, the porosity of the obtained porous alumina is similar to that of the porous alumina obtained in Example 1, but its compressive strength is poor. When the addition amount of cerium oxide is 2% of the mass of hydraulic alumina, although the compressive strength of the obtained porous alumina is slightly better than that in Example 1, its porosity decreases. Therefore, in the present invention, the addition amount of cerium oxide is selected to be 3% of the mass of hydraulic alumina, and the obtained porous alumina has a relatively high porosity and relatively high mechanical strength.

[0038] The composite heat-insulating tin bath bottom bricks obtained in Example 1 and Comparative Examples 1-6 were tested for porosity, bulk density, mechanical strength, tin corrosion resistance and heat-insulating effect, and the data of the heavy layer and the light layer of the composite tin bath bottom bricks were measured respectively. The specific test methods are as follows: According to GB / T 2997-2015, the apparent porosity and bulk density were tested by the Archimedes method (drainage method); according to GB / T 5072-2023, the compressive strength of the sample was tested by a WE-30B hydraulic universal testing machine with a loading rate of 1 MPa / s; according to GB / T 3002-2017, the high-temperature flexural strength was measured at 1300 °C with a loading rate of 0.15 MPa / s; according to GB / T5990-2021, the thermal conductivity was measured by the flat plate steady-state method at 1300 °C.

[0039] The tin corrosion resistance was tested by the following method: The heavy layer of the tin bath bottom brick was cut into a specimen of 50 mm×50 mm×50 mm, the surface was polished to remove burrs, and then it was immersed in molten tin at 1300 °C for 24 h. Nitrogen was introduced during the immersion process to protect against oxidation interference, and then the mass change rate and erosion depth of the specimen were measured.

[0040] The measurement results of the above test methods are shown in Tables 3 and 4.

[0041] Table 3 Test results of each group of composite heat-insulating tin bath bottom bricks

[0042] Table 4 Test results of the heavy layer of each group of composite heat-insulating tin bath bottom bricks against molten tin corrosion

[0043] As can be seen from Tables 3 and 4, compared with Example 1 and Comparative Examples 1 and 2, when the porosity of the tin bath bottom brick in Example 1 was better, its mechanical strength was also better, indicating that the addition amount of cerium oxide had a significant effect on balancing the porosity and mechanical strength. Therefore, in the present invention, the addition amount of cerium oxide was selected to be 3% of the mass of hydraulic alumina; compared with Example 1 and Comparative Example 3, in Comparative Example 3, the porous alumina was not prepared into hierarchical porous alumina, which had a greater impact on both the porosity and thermal conductivity of the tin bath bottom brick. This was because in Example 1 of the present invention, the porous alumina was further prepared into hierarchical porous alumina, and needle-shaped micropores formed after sintering of needle-shaped nano-magnesium oxide existed in the hierarchical porous alumina, which increased the porosity and significantly improved the heat-insulating performance; compared with Example 1 and Comparative Examples 4-6, the tin corrosion resistance of the heavy layer was significantly improved, which was because a composite of synthetic mullite micropowders with multiple particle sizes was used in the heavy mixture, increasing the density of the heavy layer in the tin bath bottom brick and effectively reducing the erosion of molten tin.

[0044] The specific embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A preparation method of a composite heat-insulating tin bath bottom brick, characterized in that It includes the following steps: S1. Add synthetic mullite into a ball mill, perform ball milling according to classification requirements, and then screen to obtain synthetic mullite micropowders with different particle sizes; Compound the synthetic mullite micropowders with different particle sizes to obtain a compound synthetic mullite micropowder; Weigh 38 - 45% of high-purity mullite, 48 - 55% of the compound synthetic mullite micropowder, 3 - 8% of clay, 1 - 3% of an additive, and 0.5 - 2% of an organic binder by weight percentage, premix for 3 min, then add water and continue mixing for 3 min to obtain a heavy mixture; S2. Weigh 18 - 22% of multi-porous alumina aggregate, 50 - 55% of sintered mullite, 5 - 8% of cement, 5 - 8% of dextrin, 3 - 5% of silica fume, and 8 - 10% of α-alumina powder by weight percentage, premix for 3 min, add water and continue mixing for 3 min to obtain a light mixture; S3. Pour the light mixture into a steel mold, mechanically vibrate for 10 - 20 min, then pour the heavy mixture into the mold of the light mixture after vibration is completed, vibrate for 5 - 10 min and then statically cure for 12 - 24 h, and then demold and cure for 12 - 15 h to obtain a blank composite brick. After drying the blank composite brick for 24 - 36 h, cool down after high-temperature sintering to obtain a composite heat-insulating tin bath bottom brick.

2. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 1, characterized in that, The preparation method of the multi-porous alumina aggregate is as follows: S21. Use hydraulic alumina and aluminum trifluoride trihydrate as raw materials, and prepare porous alumina by gel casting; S22. Disperse the porous alumina in diammonium hydrogen citrate, add a needle-like nano magnesium hydroxide pore-forming agent and methyl cellulose thereto, mix evenly to obtain a mixed slurry, inject the mixed slurry into a mold, cure and dry it, then place it in a covered alumina crucible, sinter at 1500 °C for 2 h, and crush it into 3 - 5 mm fine particles to obtain the multi-porous alumina aggregate.

3. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 2, characterized in that, In step S21, the preparation method of the porous alumina is as follows: Use a ball mill to ball mill hydraulic alumina, aluminum trifluoride trihydrate, and cerium oxide for 15 h respectively, then magnetically stir and mix the ball-milled hydraulic alumina and aluminum trifluoride trihydrate with deionized water, add the ball-milled cerium oxide thereto to obtain a mixed slurry, inject the mixed slurry into a mold, cure and dry it, then place it in a covered alumina crucible, sinter at 1500 °C for 2 h, and crush it into 5 - 10 mm fine particles to obtain the porous alumina. The mass ratio of hydraulic alumina to aluminum trifluoride trihydrate is 7:3, the mass of deionized water is the sum of the masses of hydraulic alumina and aluminum trifluoride trihydrate, and the dosage of cerium oxide is 3% of the mass of hydraulic alumina.

4. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 1, characterized in that, The organic binder is one of phosphoric acid, industrial dextrin, peach gum, starch, polyvinyl alcohol, and boron oxide, and the additive is one of sodium carboxymethyl cellulose, titanium dioxide, and active α-Al2O3 micropowder.

5. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 2, wherein, In step S22, the mass of diammonium hydrogen citrate is 4% of the mass of the porous alumina, the mass of the pore-forming agent needle-like nano magnesium hydroxide is 10% of the mass of the porous alumina, and the mass of methyl cellulose is 1.25% of the mass of the porous alumina.

6. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 1, characterized in that In step S1, in the compound synthetic mullite fine powder, by weight percentage, it includes: 50% of synthetic mullite fine powder with an average particle size ≤ 1 mm, 30% of synthetic mullite fine powder with an average particle size ≤ 800 mesh, and 20% of synthetic mullite fine powder with an average particle size ≤ 300 mesh; the high-purity mullite is polygonal particles with an average particle size ≤ 5 mm, and the average particle size of the clay ≤ 4.3 μm.

7. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 1, characterized in that, In step S3, the drying temperature of the blank composite brick is 40 - 60 °C. After high-temperature sintering, the cooling is specifically as follows: heating at a rate of 10 °C / h to 580 - 600 °C and holding for 5 - 6 h, heating at a rate of 8 °C / h to 980 - 1050 °C and holding for 7 - 8 h, heating at a rate of 6 °C / h to 1350 - 1380 °C and holding for 4 - 5 h, heating at a rate of 5 °C / h to 1400 - 1450 °C and holding for 17 days, and finally cooling to 105 - 110 °C within 36 - 72 hours, and then naturally cooling.

8. The preparation method of the composite heat-insulating tin bath bottom brick according to claim 2, characterized in that, In step S22, the preparation method of needle-like nano magnesium hydroxide is: mixing magnesium chloride hexahydrate, potassium oleate and polyvinylpyrrolidone and dissolving them with deionized water, placing them in a water bath at 10 °C, adding 2 mol / L sodium hydroxide solution to it while stirring, continuing to stir for 1 h after the addition is completed, then filtering to obtain a precipitate, and washing it with deionized water to obtain needle-like nano magnesium hydroxide.

9. The composite heat-insulating tin bath bottom brick prepared by the preparation method of the composite heat-insulating tin bath bottom brick according to claim 1.

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