Micro-expansion high-alumina brick and preparation process thereof

Abstract

The invention relates to the technical field of micro-expansion high-alumina bricks, and discloses a micro-expansion high-alumina brick which comprises an anti-erosion layer, an expansion layer and a supporting layer which are sequentially arranged from top to bottom, each of the anti-erosion layer, the expansion layer and the supporting layer comprises a base material, a main expansion agent and a repairing capsule body, the repairing capsule body comprises a shell and a repairing material in the shell, and the repairing material comprises ZrSiO4 and silica sol. The preparation process comprises the following steps: respectively preparing materials of the anti-erosion layer, the expansion layer and the supporting layer; adding a repairing capsule body into the obtained materials of the anti-erosion layer, the expansion layer and the supporting layer, and uniformly mixing; the materials of the anti-erosion layer, the expansion layer and the supporting layer after mixing and repairing the capsule body are sequentially put into a mold in a layered mode to be pressed and formed, and a green brick is obtained; performing microwave pre-sintering; and finally burning the fuel gas. The invention provides a micro-expansion high-alumina brick and a preparation process thereof. The micro-expansion high-alumina brick can solve or at least alleviate the problems that an existing micro-expansion high-alumina brick is insufficient in corrosion resistance and does not have self-repairing capability.

Description

Technical Field

[0001] The invention relates to the technical field of micro-expansion high-alumina bricks, and in particular to a micro-expansion high-alumina brick and a preparation process thereof. Background Art

[0002] Traditional high alumina bricks are widely used in high-temperature industrial fields such as metallurgy, building materials, and chemical industries. However, some obvious problems have been exposed during actual use, which have promoted the development of micro-expansion high alumina brick technology.

[0003] Insufficient corrosion resistance: In high temperature environments, traditional high-alumina bricks are easily corroded by corrosive media such as slag and furnace gas, which damages the brick structure and shortens its service life. For example, in the steel smelting process, high-temperature slag will react chemically with high-alumina bricks, gradually corroding the bricks and affecting the normal operation and production efficiency of the furnace.

[0004] Poor thermal stability: drastic changes in temperature can cause thermal stress in traditional high-alumina bricks, resulting in cracks or even peeling of the bricks. In some high-temperature kilns, frequent heating and cooling processes will put the thermal stability of high-alumina bricks to a severe test, affecting their use effect and safety.

[0005] Lack of self-repairing ability: Traditional high-alumina bricks cannot repair themselves when defects occur in the brick body. Over time, these defects will continue to expand and eventually cause the brick body to fail. During long-term high-temperature use, tiny cracks may gradually expand, reducing the strength and performance of the brick body.

[0006] The current market demand for refractory materials has shifted to multifunctional integration. For example, the metallurgical industry requires the ladle lining to have the ability to resist corrosion, compensate for micro-expansion, and self-repair defects, but traditional processes make it difficult to achieve interlayer performance gradient design. In addition, the preparation of existing micro-expansion high-alumina bricks mostly relies on high-temperature calcination and simple pressing, lacking real-time monitoring and dynamic repair mechanisms for defects. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art, solve or at least alleviate the problem that the existing micro-expansion high-alumina bricks have insufficient corrosion resistance and no self-repairing ability, and provide a micro-expansion high-alumina brick and a preparation process thereof.

[0008] To achieve the above object, the present invention provides the following technical solutions: A micro-expansion high-alumina brick, comprising an erosion-resistant layer, an expansion layer, and a support layer arranged in sequence from top to bottom; the erosion-resistant layer, the expansion layer, and the support layer all comprise a base material, a main expansion agent, and a repair capsule. Among them, the main expansion agent accounts for 8-12% of the total formula mass. The base material includes third-grade high-alumina bauxite, nano-mullite, and sintered corundum micropowder. The main expansion agent includes kyanite, andalusite, sillimanite, and calcium zirconate nanoparticles. The repair capsule accounts for 1-5% of the total formula mass. The repair capsule includes a shell and a repair material therein. The repair material includes ZrSiO4 and silica sol. The volume ratio of ZrSiO4 to silica sol is 4:1. The particle size of ZrSiO4 is 40-60nm. After the repair capsule ruptures, the repair material reacts at high temperature to generate ZrO2 and mullite to enhance the strength of the repair area.

[0009] To further implement the present invention, the following technical solutions can be preferentially selected: Preferably, the main expansion agent in the erosion-resistant layer accounts for 9-10% of the erosion-resistant layer formula mass. The erosion-resistant layer also contains 5% YSZ fibers and 2% SiCw of the erosion-resistant layer formula mass; the main expansion agent in the expansion layer accounts for 11-12% of the expansion layer formula mass; the main expansion agent in the support layer accounts for 8-9% of the support layer formula mass. The support layer also contains 15% sintered corundum particles.

[0010] Preferably, the mass ratio of the third-grade high-alumina bauxite, nano-mullite, and sintered corundum micropowder is 3:2:(0.5-1); the coarse particles with a particle size of 1-3mm in the third-grade high-alumina bauxite account for 40%, and the fine powder with a particle size less than 0.088mm accounts for 60%; the particle size of the nano-mullite is 50-100nm; the particle size of the sintered corundum micropowder is less than 5μm.

[0011] Preferably, the kyanite, andalusite, and sillimanite are proportioned in a gradient of 1:1.2:0.8, and the particle size distribution is bimodal with coarse particles of 0.088-0.5mm and ultrafine powder less than 10μm.

[0012] Preferably, the calcium zirconate nanoparticles are pretreated by three steps: yttrium doping pretreatment, yttrium oxide coating, and high-temperature in-situ reaction regulation. Specifically, it includes: yttrium nitrate and zirconia sol are mixed and calcined at 1:(5-10) to prepare Y³ + doped fibers, Y(CH3)3 is oxidized to form a Y2O3 coating layer, and a Y-Si-O liquid phase and a Zr-Si-O-C composite phase are formed at 1550-1650°C.

[0013] Preferably, the shell of the repair capsule is composed of an outer layer of Al2O3, a middle layer of Y2O3, and an inner layer of low-melting glass phase.

[0014] A preparation process for a micro-expansion high-alumina brick. The preparation process for preparing a micro-expansion high-alumina brick includes the following steps: Prepare the materials for the erosion-resistant layer, the expansion layer, and the support layer respectively; Add repair capsules to the obtained materials for the erosion-resistant layer, the expansion layer, and the support layer, and mix them evenly; Load the materials for the erosion-resistant layer, the expansion layer, and the support layer mixed with repair capsules into a mold layer by layer in sequence, and press and form them to obtain a brick blank; Pre-burn with microwaves, rapidly heat up to 1150 °C through a microwave field, and keep the temperature for 30 min to promote the reaction between nano-mullite and the matrix, and solidify the shell of the repair capsule; Final burn with gas, rise to 1550 °C at a rate of 5 °C / min in a gas kiln and keep the temperature for 4 h to form an interwoven corundum-mullite skeleton.

[0015] Preferably, the final burn with gas step includes: Capture internal defects in real time through terahertz wave non-destructive testing, and respectively count the defect rates in the erosion-resistant layer, the expansion layer, and the support layer before repair; Adjust the addition amount of the repair capsule, the pressing pressure, and the addition amount of the main expansion agent according to the defect rate before repair; Irradiate the defect area with a CO2 laser to make the heating rate of the defect area ≥ 50 °C / s, rupture the repair capsule, and repair the defect area; Respectively count the defect rates in the erosion-resistant layer, the expansion layer, and the support layer after repair, and adjust the addition amount of the repair capsule and the addition amount of the main expansion agent according to the defect rate after repair.

[0016] Preferably, the adjustment strategy according to the defect rate before repair is: when the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is less than the first threshold, reduce the addition amount of the repair capsule in the erosion-resistant layer, the expansion layer, or the support layer; when the defect rates of the erosion-resistant layer, the expansion layer, and the support layer are all greater than the second threshold and the difference rate is less than 10%, increase the pressing pressure; when the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is greater than the third threshold, increase the addition amount of the main expansion agent in the materials of the erosion-resistant layer, the expansion layer, and the support layer; The adjustment strategy according to the defect rate after repair is: when the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is greater than the fourth threshold and less than the fifth threshold, increase the addition amount of the repair capsule in the erosion-resistant layer, the expansion layer, or the support layer; when the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is greater than the fifth threshold, increase the addition amount of the repair capsule in the erosion-resistant layer, the expansion layer, or the support layer, and increase the addition amount of the main expansion agent in the materials of the erosion-resistant layer, the expansion layer, and the support layer.

[0017] Preferably, the defect rate is the ratio of the volume of the space where the defect area is located to the total volume of the erosion-resistant layer, the expansion layer, or the support layer.

[0018] The beneficial effects of the present invention are: The micro-expansion high-alumina brick of the present invention has excellent erosion resistance. YSZ fibers and SiCw are added to the erosion-resistant layer, which can effectively resist the erosion of erosion media such as slag and furnace gas, and improve the erosion resistance of the brick body. YSZ fibers have good chemical stability and high-temperature performance, while SiCw has high hardness, high strength and good oxidation resistance. The two work synergistically to enhance the protection effect of the erosion-resistant layer.

[0019] The micro-expansion high-alumina brick of the present invention also has good micro-expansion performance. The main expansion agent expands at high temperature, which can compensate for the shrinkage of the brick body during use and reduce the generation of cracks. At the same time, the addition amount of the main expansion agent in different layers is different, which can be adjusted according to the functional requirements of each layer to optimize the performance of the brick body. For example, the content of the main expansion agent in the expansion layer is relatively high, which can provide greater expansion force and enhance the integrity and stability of the brick body.

[0020] The micro-expansion high-alumina brick of the present invention has a self-healing function. The design of the repair capsule is a major innovation of the present invention. When defects occur in the brick body, the repair capsule ruptures at high temperature, and the repair materials (ZrSiO4 and silica sol) react to generate ZrO2 and mullite, improving the strength of the repair area and realizing the self-healing function of the brick body. This self-healing mechanism can timely repair the minor defects of the brick body and extend the service life of the brick body.

[0021] The preparation process of the present invention adopts a preparation process combining microwave pre-sintering and gas final sintering, which can promote the reaction between nano-mullite and the matrix, solidify the shell of the repair capsule, form an interwoven corundum-mullite skeleton, and improve the strength and stability of the brick body. During the gas final sintering process, through technologies such as terahertz wave non-destructive testing and laser irradiation, internal defects can be captured in real time and repaired. At the same time, the addition amounts of the repair capsule and the main expansion agent are adjusted according to the defect rate to further optimize the performance of the brick body.

[0022] The repair capsule not only enables the micro-expansion high-alumina brick to have a self-healing function during use, but also can fix-point repair the defects during preparation to ensure the quality of the micro-expansion high-alumina brick when it leaves the factory. Detailed implementation mode

[0023] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Embodiment 1 This embodiment discloses a slightly expanded high-alumina brick, which includes an erosion-resistant layer, an expansion layer, and a support layer arranged in sequence from top to bottom; The erosion-resistant layer, the expansion layer, and the support layer all include a base material, a main expansion agent, and a repair capsule. Among them, the main expansion agent accounts for 8-12% of the total formula mass. The base material includes third-grade high-alumina bauxite, nano-mullite, and sintered corundum micropowder. The main expansion agent includes kyanite, andalusite, sillimanite, and calcium zirconate nanoparticles. The repair capsule accounts for 1-5% of the total formula mass. The repair capsule includes a shell and a repair material inside. The repair material includes ZrSiO4 and silica sol. The volume ratio of ZrSiO4 to silica sol is 4:1, and the particle size of ZrSiO4 is 40-60nm. After the repair capsule ruptures, the repair material reacts at high temperature to generate ZrO2 and mullite, improving the strength of the repair area.

[0026] In the erosion-resistant layer, the main expansion agent accounts for 9-10% of the erosion-resistant layer formula mass. The erosion-resistant layer also contains 5% YSZ fiber and 2% SiCw of the erosion-resistant layer formula mass; In the expansion layer, the main expansion agent accounts for 11-12% of the expansion layer formula mass; In the support layer, the main expansion agent accounts for 8-9% of the support layer formula mass. The support layer also contains 15% sintered corundum particles.

[0027] The mass ratio of third-grade high-alumina bauxite, nano-mullite, and sintered corundum micropowder is 3:2:0.5-1. Among them, third-grade high-alumina bauxite is selected from medium and low-grade bauxite ore (Al2O3 content is about 70-75%) to reduce costs. Coarse particles with a particle size of 1-3mm account for 40%, and fine powder with a particle size less than 0.088mm accounts for 60%. The particle size of nano-mullite is 50-100nm, which is synthesized by the sol-gel method to enhance the matrix densification and thermal shock stability. The particle size of sintered corundum micropowder is less than 5μm, which fills the pores as a binding phase to improve the high-temperature strength.

[0028] Kyanite, andalusite, and sillimanite are proportioned in a gradient of 1:1.2:0.8. The particle size adopts a bimodal distribution of coarse particles with a particle size of 0.088-0.5mm and ultrafine powder with a particle size less than 10μm. The coarse particles delay the reaction rate, and the ultrafine powder quickly generates a mullite skeleton to achieve step-by-step expansion.

[0029] Calcium zirconate nanoparticles undergo a solid-phase reaction with the Al2O3 matrix at temperatures above 1200°C: CaZrO3 + Al2O3 → CaAl2O4 This reaction is accompanied by a volume expansion of 6 - 8%, and the phase transformation of ZrO2 (monoclinic → tetragonal) further contributes an expansion of about 3 - 5%.

[0030] In the temperature range of 1300 - 1400 °C, CaZrO3 reacts with free SiO2 in the matrix to form a high-viscosity Ca-Zr-Si-O liquid phase, which not only buffers stress concentration but also promotes particle rearrangement to achieve controllable expansion.

[0031] CaZrO3 starts to react with Al2O3 at 1200 °C and reaches the peak expansion rate at 1400 °C. By adjusting the content of nanoparticles (3 - 5%), the expansion amount can be precisely controlled (0.45 - 0.6%). Nanoparticles shorten the ion diffusion distance, increasing the reaction rate by 3 - 5 times and avoiding the hysteresis effect of traditional coarse particles.

[0032] The CaAl2O4 (melting point 1600 °C) and ZrO2 (high hardness) formed by the reaction form a rigid skeleton, and the high-temperature flexural strength is increased to 18 - 22 MPa. The Ca-Zr-Si-O liquid phase wraps the unreacted particles, inhibiting excessive expansion and ensuring volume stability.

[0033] Example Two The calcium zirconate nanoparticles are pretreated before mixing, and the pretreatment method includes the following steps: Sa. Yttrium doping pretreatment: Yttrium nitrate and zirconia sol are mixed at a molar ratio of 1:10 - 1:5, stirred at a constant temperature of 80 - 120 °C for 2 - 4 hours to form a Y-Zr-O gel, and calcined at 600 - 800 °C for 2 hours to obtain a Y³ + doped zirconia fiber precursor; Sb. Yttrium oxide coating: Y(CH3)3 reacts with O2 at 400 - 500 °C to form a Y2O3 coating layer, and annealed at 600 °C for 1 hour under argon protection to eliminate the internal stress in the coating layer; Sc. High-temperature in-situ reaction regulation: Keep at 1550 - 1650 °C for 2 - 4 hours, and control the oxygen partial pressure at 10 -3 -10 -5 atm, Y2O3 reacts with SiO2 to form a Y-Si-O liquid phase, and at the same time combines with C to form a Zr-Si-O-C composite phase, with a coverage rate of over 90%.

[0034] Utilizing the migration characteristics of yttrium oxide-coated calcium zirconate nanoparticles, microcracks in the range of 0.1 - 5 μm can be automatically filled during sintering at 1400 °C, reducing the fluctuation of the flexural strength to ±3%.

[0035] Example Three The outer shell of the repair capsule includes an outer layer, a middle layer and an inner layer. Among them, the outer layer is Al2O3, which can withstand high temperatures of 1500 °C. The middle layer is Y2O3, which is used to inhibit the phase change of ZrO2. The inner layer is made of a low-melting glass phase material, and the triggering temperature is 1300 °C.

[0036] Example 4 A preparation process of a slightly expanded high-alumina brick includes the following steps: S1. Prepare the materials for the erosion-resistant layer, the expansion layer and the support layer respectively; S2. Add the repair capsule to the materials of the erosion-resistant layer, the expansion layer and the support layer obtained in step S1 and mix them evenly; S3. Layer the materials of the erosion-resistant layer, the expansion layer and the support layer mixed with the repair capsule in sequence into a mold and press them into shape to obtain a brick blank; S4. Microwave pre-firing, rapidly heating to 1150 °C through a microwave field (2.45 GHz, power density 3 W / cm³) and holding for 30 min to promote the reaction between nano-mullite and the matrix and solidify the outer shell of the repair capsule; S5. Final firing with gas, heating to 1550 °C at a rate of 5 °C / min in a gas kiln and holding for 4 h to form an interwoven corundum-mullite skeleton.

[0037] Among them, step S5 includes the following steps: S51. Use terahertz wave non-destructive testing to capture internal defects in real time. When defects appear, enter step S52, respectively count the defect rates in the erosion-resistant layer, the expansion layer and the support layer and enter step S53; S52. Use a CO2 laser to irradiate the defect area to make the heating rate of the defect area ≥ 50 °C / s, rupture the repair capsule, repair the defect area, and then enter step S54; S53. When the defect rate of the erosion-resistant layer, the expansion layer or the support layer is less than the first threshold, reduce the addition amount of the repair capsule in the erosion-resistant layer, the expansion layer or the support layer. When the defect rates of the erosion-resistant layer, the expansion layer and the support layer are all greater than the second threshold and the difference rate is less than 10%, increase the pressure during pressing in step S3. When the defect rate of the erosion-resistant layer, the expansion layer or the support layer is greater than the third threshold, increase the addition amount of the main expansion agent of the materials of the erosion-resistant layer, the expansion layer and the support layer in step S1; S54. Nondestructively detect internal defects in real time through terahertz waves, and separately count the defect rates in the erosion-resistant layer, the expansion layer, and the support layer. When the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is greater than the fourth threshold and less than the fifth threshold, increase the addition amount of the repair capsules in the erosion-resistant layer, the expansion layer, or the support layer in step S2. When the defect rate of the erosion-resistant layer, the expansion layer, or the support layer is greater than the fifth threshold, increase the addition amount of the repair capsules in the erosion-resistant layer, the expansion layer, or the support layer in step S2, and increase the addition amount of the main expansion agent of the materials of the erosion-resistant layer, the expansion layer, and the support layer in step S1. The defect rate in step S51 is the ratio of the volume of the space where the defect area is located to the total volume of the erosion-resistant layer, the expansion layer, or the support layer.

[0038] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A kind of slightly expanded high-alumina brick, characterized in that, It includes an erosion-resistant layer, an expansion layer, and a support layer arranged successively from top to bottom; the erosion-resistant layer, expansion layer, and support layer all include a substrate, a main expander, and repair capsules. Among them, the main expander accounts for 8-12% of the total formula mass. The substrate includes tertiary bauxite, nano-mullite, and sintered corundum micropowder. The main expander includes kyanite, andalusite, sillimanite, and calcium zirconate nanoparticles. The repair capsules account for 1-5% of the total formula mass. The repair capsules include a shell and a repair material inside. The repair material includes ZrSiO4 and silica sol. The volume ratio of ZrSiO4 to silica sol is 4:

1. The particle size of ZrSiO4 is 40-60nm. After the repair capsules rupture, the repair material reacts at high temperature to generate ZrO2 and mullite to enhance the strength of the repair area.

2. The micro-expanding high-alumina brick according to claim 1, characterized in that In the erosion-resistant layer, the main expander accounts for 9-10% of the erosion-resistant layer formula mass. The erosion-resistant layer also contains 5% YSZ fibers and 2% SiCw of the erosion-resistant layer formula mass; in the expansion layer, the main expander accounts for 11-12% of the expansion layer formula mass; in the support layer, the main expander accounts for 8-9% of the support layer formula mass, and the support layer also contains 15% sintered corundum particles.

3. A kind of slightly expanded high-alumina brick according to claim 1, characterized in that, The mass ratio of the tertiary bauxite, nano-mullite, and sintered corundum micropowder is 3:2:(0.5-1); in the tertiary bauxite, the coarse particles with a particle size of 1-3mm account for 40%, and the fine powder with a particle size less than 0.088mm accounts for 60%; the particle size of the nano-mullite is 50-100nm; the particle size of the sintered corundum micropowder is less than 5μm.

4. A kind of slightly expanded high-alumina brick according to claim 1, characterized in that, The kyanite, andalusite, and sillimanite are proportioned in a gradient of 1:1.2:0.8, and the particle size adopts a bimodal distribution of coarse particles of 0.088-0.5mm and ultrafine powder less than 10μm.

5. A kind of slightly expanding high-alumina brick according to claim 1, characterized in that, The calcium zirconate nanoparticles are pretreated by three steps: yttrium doping pretreatment, yttrium oxide coating, and high-temperature in-situ reaction regulation, which specifically include: mixing yttrium nitrate and zirconia sol at a ratio of 1:(5-10) and calcining to obtain Y 3+ doped fibers, oxidizing Y(CH3)3 to form a Y2O3 coating layer, and forming a Y-Si-O liquid phase and a Zr-Si-O-C composite phase at 1550-1650 °C.

6. A kind of slightly expanding high-alumina brick according to claim 1, characterized in that, The shell of the repair capsules is composed of an outer layer of Al2O3, a middle layer of Y2O3, and an inner layer of low-melting glass phase.

7. A preparation process of a slightly expanded high-alumina brick, the preparation process being used to prepare a slightly expanded high-alumina brick as described in any one of claims 1-6, characterized in that, It includes the following steps: Prepare the materials for the erosion-resistant layer, expansion layer, and support layer respectively; Add the repair capsules to the materials of the erosion-resistant layer, expansion layer, and support layer obtained above and mix evenly; Load the materials of the erosion-resistant layer, expansion layer, and support layer mixed with the repair capsules into a mold layer by layer and press them into shape to obtain a brick blank; Microwave pre-sintering, rapidly heating to 1150°C through a microwave field and holding for 30min to promote the reaction between nano-mullite and the matrix and solidify the shell of the repair capsules; Gas final sintering, heating to 1550°C at 5°C / min in a gas kiln and holding for 4h to form an interwoven corundum-mullite skeleton.

8. The preparation process of a slightly expanded high-alumina brick according to claim 7, characterized in that, The gas final sintering step includes: Use terahertz wave non-destructive testing to capture internal defects in real time, and separately count the defect rates in the erosion-resistant layer, expansion layer, and support layer before repair; Adjust the addition amount of the repair capsules, the pressing pressure, and the addition amount of the main expander according to the defect rate before repair; Irradiate the defect area with a CO2 laser to make the heating rate of the defect area ≥50°C / s, rupture the repair capsules, and repair the defect area; Separate the defect rates in the erosion-resistant layer, expansion layer, and support layer after repair, and adjust the addition amount of the repair capsules and the addition amount of the main expander according to the defect rate after repair.

9. The preparation process of a slightly expanded high-alumina brick according to claim 8, characterized in that, The adjustment strategy based on the defect rate before repair is as follows: when the defect rate of the erosion-resistant layer, expansion layer or support layer is less than the first threshold, reduce the addition amount of the repair capsule in the erosion-resistant layer, expansion layer or support layer; when the defect rates of the erosion-resistant layer, expansion layer and support layer are all greater than the second threshold and the difference rate is less than 10%, increase the pressure of pressing and forming; when the defect rate of the erosion-resistant layer, expansion layer or support layer is greater than the third threshold, increase the addition amount of the main expansion agent of the materials of the erosion-resistant layer, expansion layer and support layer; The adjustment strategy based on the defect rate after repair is as follows: when the defect rate of the erosion-resistant layer, expansion layer or support layer is greater than the fourth threshold and less than the fifth threshold, increase the addition amount of the repair capsule in the erosion-resistant layer, expansion layer or support layer; when the defect rate of the erosion-resistant layer, expansion layer or support layer is greater than the fifth threshold, increase the addition amount of the repair capsule in the erosion-resistant layer, expansion layer or support layer, and increase the addition amount of the main expansion agent of the materials of the erosion-resistant layer, expansion layer and support layer.

10. The preparation process of a slightly expanded high-alumina brick according to claim 8, characterized in that, The defect rate is the ratio of the volume of the space where the defect area is located to the total volume of the erosion-resistant layer, expansion layer or support layer.