Composite thermal insulation tin bath bottom brick and preparation method thereof

Abstract

The present invention belongs to the technical field of refractory materials, and specifically relates to a composite thermal insulation tin bath bottom brick and a preparation method thereof. A lightweight mixture is poured into a steel mold and mechanically vibrated for 10 to 20 minutes. A heavy mixture is then poured into the mold containing the vibrated lightweight mixture. After vibrating for 5 to 10 minutes, the mixture is allowed to stand and cure for 12 to 24 hours. The mixture is then demolded and cured for 12 to 15 hours to obtain a rough composite brick. The rough composite brick is then dried for 24 to 36 hours, sintered at high temperature, and then cooled to obtain the composite thermal insulation tin bath bottom brick. The present invention can improve the porosity and thermal insulation effect of the tin bath bottom brick while ensuring the mechanical strength and alkali corrosion resistance of the tin bath bottom brick.

Description

Technical Field

[0001] The invention belongs to the technical field of special refractory material application, and particularly relates to a composite thermal insulation tin bath bottom brick and a preparation method thereof. Background Art

[0002] The tin bath is a key thermal engineering component of the float glass furnace. During float glass production, the tin bath bottom bricks must simultaneously meet the following key performance requirements: resistance to molten tin (Sn) penetration, high temperature resistance (600-1050°C), thermal shock stability, good thermal insulation, and resistance to corrosion by alkaline volatiles (such as Na2O). The thermal insulation performance of the tin bath bottom bricks directly impacts the tin bath's temperature uniformity, energy consumption control, and glass forming quality.

[0003] Currently, existing tin bath bottom bricks are primarily single-layer clay bricks, resulting in poor insulation, low mechanical strength, and weak resistance to molten tin and gas corrosion. This inability to effectively control lateral temperature differences within the tin bath is particularly problematic during the production of ultra-thin and ultra-clear glass, requiring frequent activation of electric heating to adjust the temperature, increasing operational complexity and power consumption. Summary of the Invention

[0004] The object of the present invention is to provide a composite thermal insulation tin bath bottom brick and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0006] A method for preparing a composite thermal insulation tin bath bottom brick comprises the following steps:

[0007] S1. Add synthetic mullite into a ball mill, perform ball milling according to classification requirements, and then sieve to obtain synthetic mullite powder of different particle sizes;

[0008] Compounding synthetic mullite micropowders of different particle sizes to obtain composite mullite micropowder;

[0009] 38-45% of high-purity mullite, 48-55% of composite mullite powder, 3-8% of clay, 1-3% of additives and 0.5-2% of organic binder are weighed and pre-mixed for 3 minutes, and then water is added and mixing is continued for 3 minutes to obtain a heavy mixture;

[0010] S2. Weigh 18-22% of hierarchical porous alumina aggregate, 50-55% of sintered mullite, 5-8% of cement, 5-8% of dextrin, 3-5% of silica powder, and 8-10% of α-alumina powder by weight, and premix for 3 minutes. Then add water and continue mixing for 3 minutes to obtain a lightweight mixture.

[0011] S3. Pour the lightweight mixture into a steel mold and vibrate it mechanically for 10 to 20 minutes. Then pour the heavy mixture into the mold of the vibrated lightweight mixture, vibrate it for 5 to 10 minutes, let it stand and cure for 12 to 24 hours, then demold and cure it for 12 to 15 hours to obtain a rough composite brick. After drying the rough composite brick for 24 to 36 hours, sinter it at high temperature and then cool it down to obtain a composite insulation tin bath bottom brick.

[0012] As a further improvement, the preparation method of the multi-level porous alumina aggregate is:

[0013] S21, using hydraulic alumina and aluminum fluoride trihydrate as raw materials, preparing porous alumina by gel casting;

[0014] S22. The porous alumina is dispersed in diammonium hydrogen citrate, and needle-shaped nano-magnesium hydroxide pore-forming agent and methyl cellulose are added thereto. The mixture is evenly mixed to obtain a mixed slurry. The mixed slurry is injected into a mold, and after solidification and drying, it is placed in an alumina crucible with a lid, sintered at 1500° C. for 2 hours, and crushed into 3-5 mm particles to obtain a multi-level porous alumina aggregate.

[0015] As a further improvement, in step S21, the preparation method of the porous alumina is as follows: use a ball mill to ball-mill hydraulic alumina, aluminum fluoride trihydrate and cerium oxide for 15 hours respectively, then use deionized water to magnetically stir and mix the ball-milled hydraulic alumina and aluminum fluoride trihydrate, add the ball-milled cerium oxide thereto to obtain a mixed slurry, inject the mixed slurry into a mold, and after curing and drying, place it in an alumina crucible with a lid, sinter at 1500°C for 2 hours, and crush it into 5-10mm particles to obtain porous alumina, the mass ratio of hydraulic alumina to aluminum fluoride trihydrate is 7:3, the mass of deionized water is the sum of the masses of hydraulic alumina and aluminum fluoride trihydrate, and the amount of cerium oxide is 3% of the mass of hydraulic alumina.

[0016] As a further improvement, 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 hydroxymethyl cellulose, titanium dioxide, and active α-Al2O3 micropowder.

[0017] 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-shaped 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.

[0018] As a further improvement, in step S1, the composite mullite micropowder comprises, by weight percentage: 50% synthetic mullite micropowder with an average particle size ≤1 mm, 30% synthetic mullite micropowder with an average particle size ≤800 mesh, and 20% synthetic mullite micropowder 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 is ≤4.3 μm.

[0019] As a further improvement, in step S3, the drying temperature of the rough composite brick is 40~60℃, and the cooling after high-temperature sintering is specifically as follows: heating to 580~600℃ at a rate of 10℃ / h and keeping warm for 5~6h, heating to 980~1050℃ at a rate of 8℃ / h and keeping warm for 7~8h, heating to 1350~1380℃ at a rate of 6℃ / h and keeping warm for 4~5h, heating to 1400~1450℃ at a rate of 5℃ / h and keeping warm for 17 days, and finally cooling to 105~110℃ within 36~72 hours, and then cooling naturally.

[0020] As a further improvement, in step S22, the preparation method of needle-shaped nano-magnesium hydroxide is as follows: magnesium chloride hexahydrate, potassium oleate and polyvinyl pyrrolidone are mixed and dissolved in deionized water, placed in a 10°C water bath, and 2 mol / L sodium hydroxide solution is added thereto while stirring. After the addition is completed, stirring is continued for 1 hour, and then the precipitate is filtered and washed with deionized water to obtain needle-shaped nano-magnesium hydroxide.

[0021] The invention also provides a composite thermal insulation tin bath bottom brick.

[0022] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0023] The present invention provides a composite thermal insulation tin bath bottom brick and a preparation method thereof. The porous alumina is prepared by a gel injection molding method, so that an interlocking structure of alumina wafers is formed inside the alumina, thereby reducing the thermal conductivity of the porous alumina. In addition, during the preparation of the porous alumina, the amount of cerium oxide used is 3% of the mass of the hydraulic alumina, which is conducive to the growth of alumina wafers inside the porous alumina, thereby improving the mechanical strength of the porous alumina without changing the porosity of the porous alumina.

[0024] Multi-level porous alumina is prepared using porous alumina as raw material, and needle-shaped nano-magnesium hydroxide is used as a pore-forming agent to form needle-shaped micropores, so that the multi-level porous alumina forms multi-level pores with different pore sizes and shapes, further reducing the thermal conductivity of the porous alumina aggregate and improving the thermal insulation effect of the porous alumina aggregate.

[0025] Composite thermal insulation tin bath bottom bricks are prepared by heavy mixture and light mixture. The heavy mixture can improve the mechanical strength of the bottom bricks, and adding multi-level porous alumina to the light mixture can improve the thermal insulation performance of the bottom bricks.

[0026] In the heavy mixture, the density of the heavy mixture can be increased by compounding synthetic mullite powder of different particle sizes, and the heavy layer brick body of the obtained tin bath bottom brick is more compact, which improves the resistance to tin liquid flow erosion. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0028] Example 1 A method for preparing a composite thermal insulation tin bath bottom brick comprises the following steps:

[0029] S1, take 70g of hydraulic alumina, 30g of aluminum fluoride trihydrate and 2.1g of cerium oxide, use a ball mill to ball mill the hydraulic alumina, aluminum fluoride trihydrate and cerium oxide for 15h at a speed of 260r / min, then use 100g of deionized water to mix the ball-milled hydraulic alumina and aluminum fluoride trihydrate by magnetic stirring, add 2.1g of the ball-milled cerium oxide to obtain a mixed slurry, inject the mixed slurry into a mold, cure at room temperature for 24h, then dry the green body in a 40℃ oven for 5h, finally place the green body in a covered alumina crucible, sinter at 1500℃ for 2h, and then crush into 5mm particles to obtain porous alumina;

[0030] S2. Take 50g of porous alumina, disperse it in 2g of diammonium hydrogen citrate, and add 5g of needle-shaped nano-magnesium hydroxide pore-forming agent and 0.625g of methyl cellulose thereto, mix well to obtain a mixed slurry, inject the mixed slurry into a mold, cure at room temperature for 24h, then dry the green body in a 40°C oven for 5h, finally place the green body in a covered alumina crucible, sinter at 1500°C for 2h, and then crush into 3mm particles to obtain a multi-level porous alumina aggregate, the mass of diammonium hydrogen citrate is 4% of the mass of the porous alumina, the mass of the pore-forming agent needle-shaped nano-magnesium hydroxide is 10% of the mass of the porous alumina, and the mass of the methyl cellulose is 1.25% of the mass of the porous alumina;

[0031] S3, pour 20g of multi-level porous alumina aggregate, 53g of sintered mullite, 7g of cement, 7g of dextrin, 4g of silica powder and 9g of α-alumina powder into a cement mortar mixer and premix for 3min, add 7.4g of water and continue mixing for 3min to obtain a lightweight mixture;

[0032] S4, adding synthetic mullite into a ball mill, and ball-milling it into synthetic mullite micropowders of three levels of particle size, specifically, synthetic mullite micropowder with an average particle size ≤ 1 mm, synthetic mullite micropowder with an average particle size ≤ 800 mesh, and synthetic mullite micropowder with an average particle size ≤ 300 mesh;

[0033] 50 g of synthetic mullite micropowder with an average particle size of ≤1 mm, 30 g of synthetic mullite micropowder with an average particle size of ≤800 mesh, and 20 g of synthetic mullite micropowder with an average particle size of ≤300 mesh are compounded to obtain a composite mullite micropowder;

[0034] S5, weighing 40g of polygonal high-purity mullite with an average particle size of ≤5mm, 52g of mullite powder, 5g of clay, 2g of additives and 1g of organic binder, adding them into a cement mortar mixer and premixing for 3min, then adding 6.57g of water and continuing mixing for 3min to obtain a heavy mixture, wherein sodium hydroxymethyl cellulose is used as the additive and phosphoric acid is used as the organic binder;

[0035] The lightweight mixture is poured into a steel mold and mechanically vibrated for 10 minutes. The heavy mixture is then poured into the mold of the vibrated lightweight mixture. After vibrating for 10 minutes, it is allowed to stand and cured for 12 hours. Then, it is demolded and cured for 12 hours to obtain a rough composite brick. The rough composite brick is dried at 40°C for 24 hours and then sintered at high temperature to obtain a composite insulation tin bath bottom brick. During the high-temperature sintering process, the temperature is increased to 600°C at a rate of 10°C / h and kept warm for 5 hours, then increased to 1050°C at a rate of 8°C / h and kept warm for 7 hours, then increased to 1380°C at a rate of 6°C / h and kept warm for 4 hours, then increased to 1450°C at a rate of 5°C / h and kept warm for 17 days, and finally cooled to 105°C within 36 hours and then cooled naturally.

[0036] In this embodiment, the preparation method of needle-shaped nano-magnesium hydroxide is as follows: 20g of magnesium chloride hexahydrate, 1g of potassium oleate and 0.25g of polyvinyl pyrrolidone are mixed and dissolved with 30mL of deionized water, placed in a 10°C water bath, and 100mL of 2mol / L sodium hydroxide solution is added thereto at a dropwise addition rate of 2mL / min while stirring at a stirring speed of 1200rpm. After the dropwise addition is completed, stirring is continued for 1h, and then the precipitate is filtered and washed with deionized water to obtain needle-shaped nano-magnesium hydroxide.

[0037] Example 2 This example provides a method for preparing a composite thermal insulation tin bath bottom brick, comprising the following steps:

[0038] S1. Preparation of porous alumina. The specific preparation method is the same as that in Example 1, except that the alumina is crushed into 10 mm particles after sintering.

[0039] S2. The preparation method of the multi-level porous alumina aggregate is the same as that of Example 1, except that the aggregate is crushed into 5 mm particles after sintering;

[0040] S3, 18g of multi-level porous alumina aggregate, 55g of sintered mullite, 5g of cement, 8g of dextrin, 5g of silica powder and 9g of α-alumina powder were poured into a cement mortar mixer and premixed for 3min, 6.57g of water was added and mixing was continued for 3min to obtain a lightweight mixture;

[0041] S4, weighing 38g of polygonal high-purity mullite with an average particle size of ≤5mm, 55g of compounded mullite powder, 4g of clay, 1g of sodium hydroxymethyl cellulose and 2g of phosphoric acid, adding them into a cement mortar mixer and premixing for 3min, then adding 8.37g of water and continuing mixing for 3min to obtain a heavy mixture;

[0042] The lightweight mixture is poured into a steel mold and mechanically vibrated for 20 minutes. The heavy mixture is then poured into the mold of the vibrated lightweight mixture. After vibrating for 5 minutes, it is allowed to stand and cured for 24 hours. It is then demolded and cured for 15 hours to obtain a rough composite brick. The rough composite brick is dried at 40°C for 36 hours and then sintered at high temperature to obtain a composite insulation tin bath bottom brick. During the high-temperature sintering process, the temperature is increased to 580°C at a rate of 10°C / h and kept warm for 5 hours, then increased to 980°C at a rate of 8°C / h and kept warm for 7 hours, then increased to 1350°C at a rate of 6°C / h and kept warm for 4 hours, then increased to 1400°C at a rate of 5°C / h and kept warm for 17 days, and finally cooled to 110°C within 72 hours and then cooled naturally.

[0043] Example 3 This example provides a method for preparing a composite thermal insulation tin bath bottom brick, comprising the following steps:

[0044] S1. Preparation of porous alumina. The specific preparation method is the same as that in Example 1, except that the porous alumina is crushed into 8 mm particles after sintering.

[0045] S2. The preparation method of hierarchical porous alumina is the same as that of Example 1, except that it is crushed into 4 mm particles after sintering;

[0046] S3, 22g of multi-level porous alumina aggregate, 50g of sintered mullite, 8g of cement, 5g of dextrin, 5g of silica powder and 10g of α-alumina powder were premixed for 3min, then poured into a cement mortar mixer and premixed for 3min, 6.48g of water was added and mixing continued for 3min to obtain a lightweight mixture;

[0047] S4, weighing 45g of polygonal high-purity mullite with an average particle size of ≤5mm, 48g of composite mullite powder, 3.5g of clay, 3g of sodium hydroxymethyl cellulose and 0.5g of phosphoric acid, adding them into a cement mortar mixer and premixing for 3min, then adding 8.37g of water and continuing mixing for 3min to obtain a heavy mixture;

[0048] The lightweight mixture is poured into a steel mold and mechanically vibrated for 15 minutes. The heavy mixture is then poured into the mold of the vibrated lightweight mixture. After vibrating for 8 minutes, it is allowed to stand and cured for 20 hours. Then, it is demolded and cured for 13 hours to obtain a rough composite brick. The rough composite brick is dried at 40°C for 30 hours and sintered at high temperature to obtain a composite insulation tin bath bottom brick. During the high-temperature sintering process, the temperature is increased to 590°C at a rate of 10°C / h and kept warm for 5 hours, then increased to 1000°C at a rate of 8°C / h and kept warm for 7 hours, then increased to 1360°C at a rate of 6°C / h and kept warm for 4 hours, then increased to 1430°C at a rate of 5°C / h and kept warm for 17 days, and finally cooled to 108°C within 54 hours, and then cooled naturally.

[0049] Example 4 This example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific preparation method is the same as that of Example 1, except that, in step S4, 18 g of multi-level porous alumina aggregate, 55 g of sintered mullite, 8 g of cement, 8 g of dextrin, 3 g of silica powder and 8 g of α-alumina powder are poured into a cement mortar mixer and premixed for 3 min. 6.57 g of water is added and mixing is continued for 3 min to obtain a lightweight mixture;

[0050] 38 g of polygonal high-purity mullite with an average particle size of ≤5 mm, 50 g of composite mullite micropowder, 8 g of clay, 3 g of sodium hydroxymethyl cellulose and 1 g of phosphoric acid were weighed and added into a cement mortar mixer and premixed for 3 minutes. Then, 7.92 g of water was added and mixing was continued for 3 minutes to obtain a heavy mixture.

[0051] Example 5 This example provides a preparation method for a composite thermal insulation tin bath bottom brick. The specific preparation method is the same as that in Example 1, except that, in step S4, 44 g of polygonal high-purity mullite with an average particle size ≤ 5 mm, 48 g of composite mullite micropowder, 3 g of clay, 3 g of sodium hydroxymethyl cellulose and 2 g of phosphoric acid are weighed and added into a cement mortar mixer and premixed for 3 minutes, and then 8.28 g of water is added and mixing is continued for 3 minutes to obtain a heavy mixture.

[0052] Examples 6-10 provide a method for preparing a composite thermal insulation tin bath bottom brick. The specific preparation method is the same as that of Example 1, except that different organic binders and additives are used, as shown in Table 1.

[0053] Table 1 Organic binders and additives used in the preparation of composite thermal insulation tin bath bottom bricks in Examples 6-10

[0054]

[0055] Comparative Example 1 This comparative example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S1, the amount of cerium oxide used is 4% of the mass of hydraulic alumina.

[0056] Comparative Example 2 This comparative example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S1, the amount of cerium oxide used is 2% of the mass of hydraulic alumina.

[0057] Comparative Example 3 This comparative example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that, in step S1, the bricks are crushed into 3 mm particles after sintering is completed; in step S3, the multi-level porous alumina is replaced with the above-mentioned crushed 3 mm porous alumina to obtain porous alumina aggregate; in step S4, when preparing a lightweight mixture, the multi-level porous alumina aggregate is replaced with the above-prepared porous alumina aggregate.

[0058] Comparative Example 4 This comparative example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the composite mullite powder is replaced with synthetic mullite powder with an average particle size of ≤1 mm.

[0059] Comparative Example 5 This comparative example provides a method for preparing a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the composite mullite powder is replaced with synthetic mullite powder with an average particle size of ≤800 mesh.

[0060] Comparative Example 6 This comparative example provides a preparation method of a composite thermal insulation tin bath bottom brick. The specific steps are the same as those in Example 1, except that in step S5, the composite synthetic mullite powder is replaced with synthetic mullite powder with an average particle size of ≤300 mesh.

[0061] The porous alumina used in the lightweight mixtures in Example 1, Comparative Example 1 and Comparative Example 2 were tested for bulk density, porosity and compressive strength.

[0062] The porosity and bulk density of porous alumina were measured using the Archimedean drainage method. The test steps are as follows: After drying the sample, use a balance to measure the sample's dry weight in air (m1). The sample is placed in a beaker, evacuated, and then deionized water is added to completely submerge the sample, filling the sample's pores with deionized water. The saturated sample is then placed in a densitometer, and its mass in water (m2) is measured. The sample is removed and water droplets on the saturated sample surface are gently wiped with a moistened paper towel. The sample's mass in air (m3) is then weighed. The porosity and bulk density are calculated, and the results are shown in Table 1.

[0063] The sample surface was ground flat, and the area of ​​the compressive surface of the sample was measured. The indenter speed of the universal testing machine was 0.2 mm / min. The maximum load when the sample was destroyed was measured. The maximum load value divided by the area of ​​the compressive surface was the compressive strength. The results are shown in Table 2.

[0064] Table 2 Porosity, bulk density and compressive strength of porous alumina in each group of lightweight mixtures

[0065]

[0066] It can be seen from Table 1 that when the amount of cerium oxide added is 4% of the mass of the 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 amount of cerium oxide added is 2% of the mass of the hydraulic alumina, although the compressive strength of the obtained porous alumina is slightly better than that of Example 1, its porosity decreases. Therefore, the present invention selects an amount of cerium oxide added of 3% of the mass of the hydraulic alumina. When the porosity of the obtained porous alumina is higher, its mechanical strength is also higher.

[0067] The composite 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 thermal insulation effect. The data of the heavy layer and the light layer of the composite tin bath bottom bricks were measured respectively. The specific test method is as follows:

[0068] According to GB / T 2997-2015, the apparent porosity and bulk density were tested using the Archimedes method (water displacement method). According to GB / T 5072-2023, the compressive strength of the samples was tested using a WE-30B hydraulic universal testing machine at a loading rate of 1 MPa / s. According to GB / T 3002-2017, the high-temperature flexural strength was measured at 1300°C at a loading rate of 0.15 MPa / s. According to GB / T 5990-2021, the thermal conductivity was measured at 1300°C using the flat plate steady-state method.

[0069] The ability to resist tin corrosion is tested using the following methods:

[0070] The heavy layer of the tin bath bottom brick was cut into 50mm×50mm×50mm specimens, the surface was polished to remove burrs, and then immersed in tin liquid at 1300℃ for 24h. Nitrogen protection was introduced during the immersion process to prevent oxidation interference, and then the mass change rate and corrosion depth of the specimens were measured.

[0071] The test results are shown in Tables 3 and 4.

[0072] Table 3 Test results of each group of composite insulation tin bath bottom bricks

[0073]

[0074] Table 4 Test results of the heavy layer of each group of composite insulation tin bath bottom bricks against tin liquid corrosion

[0075]

[0076] It can be seen from Table 3 and Table 4 that, compared with Example 1 and Comparative Examples 1 and 2, the tin bath bottom brick of Example 1 has better porosity and better mechanical strength, indicating that the amount of cerium oxide added has a significant effect on the balance of porosity and mechanical strength. Therefore, the present invention selects the addition of cerium oxide as 3% of the mass of hydraulic alumina; compared with Example 1 and Comparative Example 3, the porous alumina is not prepared into multi-level porous alumina in Comparative Example 3, which has a greater impact on the porosity and thermal conductivity of the tin bath bottom brick. This is because in Example 1 of the present invention, the porous alumina is further prepared into multi-level porous alumina, and the multi-level porous alumina contains needle-shaped micropores formed after sintering of needle-shaped nano-magnesium oxide, which increases the porosity and significantly improves the thermal insulation performance; compared with Comparative Examples 4-6, the heavy layer's ability to resist tin liquid corrosion is significantly improved. This is because the heavy mixture uses a compound of synthetic mullite micropowder with multi-level particle size to increase the density of the heavy layer in the tin bath bottom brick, which can effectively reduce the corrosion of tin liquid.

[0077] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a composite thermal insulation tin bath bottom brick, characterized in that: The following steps are involved: S1. Add synthetic mullite into a ball mill, perform ball milling according to classification requirements, and then sieve to obtain synthetic mullite powder of different particle sizes; Compounding synthetic mullite micropowders of different particle sizes to obtain composite mullite micropowder; 38-45% of high-purity mullite, 48-55% of composite mullite powder, 3-8% of clay, 1-3% of additives and 0.5-2% of organic binder are weighed and pre-mixed for 3 minutes, and then water is added and mixing is continued for 3 minutes to obtain a heavy mixture; The additive is one of sodium hydroxymethyl cellulose, titanium dioxide, and active α-Al2O3 micropowder; S2. Weigh 18-22% of hierarchical porous alumina aggregate, 50-55% of sintered mullite, 5-8% of cement, 5-8% of dextrin, 3-5% of silica powder, and 8-10% of α-alumina powder by weight, and premix for 3 minutes. Then add water and continue mixing for 3 minutes to obtain a lightweight mixture. S3, pouring the lightweight mixture into a steel mold, mechanically vibrating for 10 to 20 minutes, then pouring the heavy mixture into the mold of the vibrated lightweight mixture, vibrating for 5 to 10 minutes, standing and curing for 12 to 24 hours, and then demolding and curing for 12 to 15 hours to obtain a rough composite brick, drying the rough composite brick for 24 to 36 hours, sintering at high temperature and then cooling to obtain a composite insulation tin bath bottom brick; The preparation method of the multi-level porous alumina aggregate is: S21. Using hydraulic alumina and aluminum fluoride trihydrate as raw materials, porous alumina was prepared by gel casting. Specifically, the hydraulic alumina, aluminum fluoride trihydrate, and cerium oxide were ball-milled for 15 hours in a ball mill. The ball-milled hydraulic alumina and aluminum fluoride trihydrate were then magnetically stirred and mixed with deionized water. The ball-milled cerium oxide was added to the mixed slurry to obtain a mixed slurry. The mixed slurry was injected into a mold, cured and dried, and then placed in an alumina crucible with a lid. The crucible was sintered at 1500° C. for 2 hours and crushed into 5-10 mm particles to obtain porous alumina. S22, dispersing porous alumina in diammonium hydrogen citrate, adding needle-shaped nano-magnesium hydroxide pore-forming agent and methyl cellulose thereto, mixing evenly to obtain a mixed slurry, injecting the mixed slurry into a mold, curing and drying, placing it in an alumina crucible with a lid, sintering it at 1500° C. for 2 hours, and crushing it into 3-5 mm particles to obtain a multi-level porous alumina aggregate; The preparation method of the needle-shaped nano-magnesium hydroxide comprises: mixing magnesium chloride hexahydrate, potassium oleate and polyvinyl pyrrolidone, dissolving the mixture in deionized water, placing the mixture in a 10° C. water bath, adding a 2 mol / L sodium hydroxide solution, and stirring the mixture while adding. After the dropwise addition is completed, stirring is continued for 1 hour, and then filtering the precipitate, washing the mixture with deionized water to obtain the needle-shaped nano-magnesium hydroxide.

2. The method for preparing the composite thermal insulation tin bath bottom brick according to claim 1, characterized in that: In step S21, the mass ratio of hydraulic alumina to aluminum fluoride trihydrate is 7:3, the mass of deionized water is the sum of the masses of hydraulic alumina and aluminum fluoride trihydrate, and the amount of cerium oxide is 3% of the mass of hydraulic alumina.

3. The method for preparing the composite thermal insulation tin bath bottom brick according to claim 1, characterized in that: The organic binder is one of industrial dextrin, peach gum, starch or polyvinyl alcohol.

4. The method for preparing the composite thermal insulation tin bath bottom brick according to claim 1, characterized in that: 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-shaped 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.

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

6. The method for preparing the composite thermal insulation tin bath bottom brick according to claim 1, characterized in that: In step S3, the drying temperature of the rough composite brick is 40~60℃, and the cooling after high-temperature sintering is specifically as follows: heating to 580~600℃ at a rate of 10℃ / h and keeping warm for 5~6h, heating to 980~1050℃ at a rate of 8℃ / h and keeping warm for 7~8h, heating to 1350~1380℃ at a rate of 6℃ / h and keeping warm for 4~5h, heating to 1400~1450℃ at a rate of 5℃ / h and keeping warm for 17 days, and finally cooling to 105~110℃ within 36~72 hours, and then cooling naturally.

7. The composite thermal insulation tin bath bottom brick prepared by the preparation method of the composite thermal insulation tin bath bottom brick according to claim 1.

Images