Cement-bonding-free high-aluminum castable and preparation method thereof
By using specific prepared binders in high alumina castables, the problems of poor fluidity, short construction time and low green strength of cementless high alumina castables are solved, and high flowability, long construction time and excellent high temperature strength are achieved, which improves the construction quality and service life.
Patent Information
- Application Number
- CN202510345404.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2025-05-27
AI Technical Summary
The existing high-aluminum castables have decreased their serviceability and life in high-temperature environments, and there are problems such as poor fluidity, short construction time, and low green strength, which affects their large-scale application.
The cementless bonded high alumina castable is prepared by mixing and heating reactions of specific prepared bonding agents, including modified silica powder, boehmite powder, hydrated alumina powder, bore acid powder, acrylamide powder and vanadium pentoxide powder.
It realizes high fluidity, long construction time, excellent green and high temperature strength of cementless combined with high alumina castable, and has good anti-explosion, thermal shock and corrosion resistance, which improves construction quality and service life.
Smart Images
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Figure BDA0005324493590000071
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of high-aluminum castables, and particularly relates to a cement-free bonded high-aluminum castable and a preparation method thereof. Background Art
[0002] High-aluminum castable is an amorphous refractory material with a relatively high aluminum content, and its raw materials generally consist of high-aluminum aggregates, fine powders, and binders. Due to the advantages of alumina such as stable structure, high strength, excellent resistance to scouring and wear, and excellent resistance to molten slag erosion at high temperatures, high-aluminum castables are widely used in working linings such as blast furnaces, torpedo ladles, steel ladles, and hot blast stoves.
[0003] Currently, the most widely used and largest amount of binder in high-aluminum castables is calcium aluminate cement. However, in the high-temperature environment where high-aluminum castables are applied, CaO contained in calcium aluminate cement reacts with Al 2 O 3 and SiO 2 and other components to form low-melting phases, including anorthite, gehlenite, and tricalcium aluminate, etc., resulting in a decrease in the high-temperature service performance and service life of the castable; at the same time, the addition of CaO to the castable components does not meet the current requirements for improving the cleanliness of steel; and the castable prepared with cement as the binder is prone to peeling or bursting during the initial heating (drying, dehydration) process, seriously affecting the construction progress and production safety. Therefore, it is necessary to develop a cement-free bonded high-aluminum castable. However, the existing cement-free bonded high-aluminum castables have problems such as poor fluidity, short workable time, and low green strength, which affect large-scale application and are the current technical difficulties to be solved. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a cement-free bonded high-aluminum castable and a preparation method thereof in view of the deficiencies of the existing technology. It has low water demand, good fluidity, long workable time, excellent green strength, medium-temperature strength, and high-temperature strength, and also has good anti-bursting, anti-thermal shock, and anti-erosion properties, thus ensuring its construction quality and service life.
[0005] To solve the technical problems proposed by the present invention, the present invention provides a cement-free bonded high-aluminum castable, which comprises raw materials with the following mass percentage contents: 63-74% of high-aluminum aggregate particles, 21-30% of fine powder, 4-8% of binder, and additionally 2-4% of water based on the total mass of the above raw materials.
[0006] In the above scheme, the high-aluminum aggregate particles are one or more of tabular corundum, bauxite, and fused white corundum.
[0007] In the above scheme, the Al 2 O 3The content is ≥94.0%, and the particle size is 0.1 - 8 mm.
[0008] Preferably, the grading of the high-aluminum aggregate particles is as follows: the mass ratio of particles with a particle size of 5 - 8 mm is 22 - 30%, the mass ratio of particles with a particle size of 3 - 5 mm (excluding 5 mm) is 24 - 28%, and the mass ratio of particles with a particle size of 1 - 3 mm (excluding 3 mm) is 42 - 54%.
[0009] In the above solution, the fine powder is a mixture of alumina fine powder and silica fine powder, and the particle size is ≤0.088 mm.
[0010] Preferably, the mass ratio of alumina fine powder to silica fine powder in the fine powder is (1.2 - 5):1.
[0011] Furthermore, the Al 2 O 3 content of the alumina fine powder in the fine powder is ≥98.5%, and the particle size is ≤0.088 mm.
[0012] Furthermore, the SiO 2 content of the silica fine powder in the fine powder is ≥95.1%, and the particle size is ≤0.044 mm.
[0013] In the above solution, the preparation method of the binder includes the following steps:
[0014] 1) Add water and sodium tripolyphosphate to the silica fine powder, heat and react under stirring conditions, perform solid-liquid separation after the reaction ends, and dry the obtained solid to obtain modified silica fine powder;
[0015] 2) Mix the modified silica fine powder, boehmite fine powder, hydratable alumina fine powder, and boric acid fine powder to obtain a first mixed powder, and then externally add acrylamide fine powder and vanadium pentoxide fine powder and mix to obtain a second mixed powder;
[0016] 3) Add water to the second mixed powder, heat and react under stirring conditions, perform solid-liquid separation after the reaction ends, and dry the obtained solid to obtain the binder.
[0017] Furthermore, the SiO 2 content of the silica fine powder in step 1) is ≥95.1%, and the particle size is ≤30 μm.
[0018] Furthermore, the sodium tripolyphosphate is of analytical purity or higher, and the particle size is ≤30 μm.
[0019] Furthermore, the Al 2 O 3 content of the boehmite fine powder is ≥98.5%, and the particle size is ≤20 μm.
[0020] Furthermore, the Al of the hydratable alumina fine powder2 O 3 The content is ≥98.5%, and the particle size is ≤60 μm.
[0021] Furthermore, the boric acid micropowder is of analytical purity or higher, and the particle size is ≤40 μm.
[0022] Furthermore, the acrylamide micropowder is of analytical purity or higher, and the particle size is ≤60 μm.
[0023] Furthermore, the vanadium pentoxide micropowder is of analytical purity or higher, and the particle size is ≤40 μm.
[0024] Furthermore, in step 1), the mass ratio of silica micropowder, water and sodium tripolyphosphate is 1:(1 - 1.6):(0.001 - 0.005).
[0025] Furthermore, in step 1), the reaction temperature is 40 - 60 °C, and the reaction time is 30 - 60 min.
[0026] Furthermore, in step 1), the drying temperature is 80 - 100 °C, and the drying time is 12 - 24 h.
[0027] Furthermore, in step 2), the mass percentage content of each raw material in the first mixed powder is: modified silica micropowder 65 - 79%, boehmite micropowder 18 - 31%, hydratable alumina micropowder 1 - 3%, boric acid micropowder 1 - 3%.
[0028] Furthermore, in step 2), the addition amount of acrylamide micropowder is 0.2 - 0.6% of the mass of the first mixed powder.
[0029] Furthermore, in step 2), the addition amount of vanadium pentoxide micropowder is 0.1 - 0.4% of the mass of the first mixed powder.
[0030] Furthermore, in step 3), the mass ratio of the second mixed powder to water is 1:(1.2 - 1.8).
[0031] Furthermore, in step 3), the reaction temperature is 60 - 80 °C, and the reaction time is 6 - 12 h.
[0032] Furthermore, in step 3), the drying temperature is 80 - 100 °C, and the drying time is 12 - 24 h.
[0033] The present invention also provides a preparation method of a cement-free bonded high-alumina castable, comprising the following steps:
[0034] Mix the high-alumina aggregate particles, fine powder and binder evenly according to the ratio, and then add water and mix evenly to obtain a cement-free bonded high-alumina castable.
[0035] In the above solution, the flow value of the cement-free bonded high-alumina castable is 185-200 mm, the pourable time is 140-160 min, the room-temperature flexural strength at 110°C×24 h is 16-18.5 MPa, the room-temperature flexural strength at 1200°C×3 h is 36.5-38.5 MPa, the room-temperature flexural strength at 1550°C×3 h is 43-47 MPa, the anti-explosion temperature is 600-650°C, and the retention rate of the flexural strength after five thermal shock cycles at 1100°C is ≥85%.
[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0037] The present invention provides a cement-free bonded high-alumina castable, which selects high-alumina aggregate and silica-alumina fine powder, and introduces a specifically developed binder into the system. The binder is prepared by mixing modified silica powder, boehmite powder, hydratable alumina powder, boric acid powder, acrylamide powder and vanadium pentoxide powder and then heating and reacting; First, the silica powder is modified by sodium tripolyphosphate. Due to the negative charge on the surface of the silica powder, during the heating process, the hydrolysis of sodium tripolyphosphate promotes the mutual repulsion and more uniform dispersion of the silica powder by the tripolyphosphate ions, which is beneficial to improving the fluidity of the castable; the modified silica powder forms a bridge with the boehmite powder and Al in the hydratable alumina during the heating process. 3+ Adding acrylamide to the adsorbed traction effect of the combined silica powder and Al 3+ can promote the more uniform and rapid mullitization reaction during the heating process of the castable, reduce the baking time of the castable, and improve the medium- and high-temperature strength, erosion resistance and anti-explosion performance of the castable; in the above process, the reaction temperature and time play a key role. Too high a temperature and too long a time will cause the connection bonds and bridges to break, and too low a temperature and too short a time will result in fewer and weaker binding bonds and bridges; in the above process, due to the large specific surface area and pore volume of boehmite, it can adhere to and infiltrate silicon ions, which is beneficial to the progress of the mullitization reaction. The addition of vanadium pentoxide can cause the mullitization reaction of the combined silica powder and Al 3+ at a temperature below 1200°C, and develop into long-columnar mullite with an interlaced structure at a temperature above 1450°C, which can effectively improve the densification and internal bonding force of the castable, making the castable have excellent medium- and high-temperature strength and erosion resistance; the addition of boric acid can, on the one hand, improve the pH value of the solution, realize the effect of acrylamide dispersing the silica powder, and promote the combination of the silica powder and Al 3+On the other hand, borate can react with boehmite micropowder and hydratable alumina micropowder at a relatively low temperature to generate aluminum borate whiskers, filling the pores while enhancing toughening, improving the strength and erosion resistance of the castable. In addition, the crystal water carried by hydratable alumina, acrylamide, boric acid, etc. makes the dehydration rate of the castable relatively slow during the drying, baking and first heating processes. And due to the small intermolecular force and water absorption rate inside the binder, compared with traditional castables, the water addition can be reduced to achieve casting molding. The prepared castable is not prone to peeling, cracking and bursting phenomena, significantly improving the anti-burst performance of the castable. Through the above synergistic effects, the preparation of high-performance cement-free bonded high-aluminum castables is finally realized. Detailed implementation mode
[0038] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.
[0039] In the following embodiments, the alumina micropowder used has an Al 2 O 3 content ≥ 98.5%, and the particle size ≤ 0.088 mm; the silica micropowder used for the fine powder has an SiO 2 content ≥ 95.1%, and the particle size ≤ 0.044 mm; the silica micropowder used in the preparation process of the binder has an SiO 2 content ≥ 95.1%, and the particle size ≤ 30 μm; the sodium tripolyphosphate is of analytical purity, and the particle size ≤ 30 μm; the boehmite micropowder has an Al 2 O 3 content ≥ 98.5%, and the particle size ≤ 20 μm; the hydratable alumina micropowder has an Al 2 O 3 content ≥ 98.5%, and the particle size ≤ 60 μm; the boric acid micropowder is of analytical purity, and the particle size ≤ 40 μm; the acrylamide micropowder is of analytical purity, and the particle size ≤ 60 μm; the vanadium pentoxide micropowder is of analytical purity, and the particle size ≤ 40 μm.
[0040] Example 1
[0041] The cement-free bonded high-aluminum castable in this example is prepared by the following steps: After mixing 63 wt% of high-aluminum aggregate particles, 30 wt% of fine powder, and 7 wt% of binder evenly, then adding 3.5% of the total mass of the above raw materials of water and mixing evenly to obtain a cement-free bonded high-aluminum castable. Among them:
[0042] The high-aluminum aggregate particles are tabular corundum, with an Al 2 O 3 content ≥ 94.0%, and the particle size grading is: the mass ratio of particle size 5 - 8 mm is 22%, the mass ratio of particle size 3 - 5 mm is 24%, and the mass ratio of particle size 1 - 3 mm is 54%.
[0043] The fine powder is composed of alumina fine powder and silica fine powder mixed in a mass ratio of 1.2:1.
[0044] The binder is prepared by the following steps:
[0045] 1) Add water and sodium tripolyphosphate to the silica fine powder. The mass ratio of the silica fine powder, water and sodium tripolyphosphate is 1:1:0.005. Heat it in a water bath to 60 °C and react for 60 min under stirring conditions. After the reaction, centrifuge, and dry the precipitate at 80 °C for 24 h to obtain modified silica fine powder;
[0046] 2) Mix four raw materials according to 79 wt% of modified silica fine powder, 18 wt% of boehmite fine powder, 1 wt% of hydratable alumina fine powder, and 2 wt% of boric acid fine powder to obtain the first mixed powder. Then, add 0.6% of acrylamide fine powder and 0.4% of vanadium pentoxide fine powder based on the mass of the first mixed powder and mix to obtain the second mixed powder;
[0047] 3) Add water to the second mixed powder. The mass ratio of the second mixed powder to water is 1:1.8. Heat it in a water bath to 80 °C and react for 12 h under stirring conditions. After the reaction, centrifuge, and dry the precipitate at 100 °C for 24 h to obtain the binder.
[0048] Example 2
[0049] The cement-free bonded high-alumina castable of this example is prepared by the following steps: Mix 74 wt% of high-alumina aggregate particles, 21 wt% of fine powder, and 5 wt% of binder evenly, and then add 2.5% of water based on the total mass of the above raw materials and mix evenly to obtain the cement-free bonded high-alumina castable. Among them:
[0050] The high-alumina aggregate particles are fused white corundum, with an Al 2 O 3 content ≥ 94.0%, and the particle size distribution is: the mass ratio of particle size 5 - 8 mm is 24%, the mass ratio of particle size 3 - 5 mm is 26%, and the mass ratio of particle size 1 - 3 mm is 50%.
[0051] The fine powder is composed of alumina fine powder and silica fine powder mixed in a mass ratio of 5:1.
[0052] The binder is prepared by the following steps:
[0053] 1) Add water and sodium tripolyphosphate to the silica fine powder. The mass ratio of the silica fine powder, water and sodium tripolyphosphate is 1:1.6:0.001. Heat it in a water bath to 40 °C and react for 30 min under stirring conditions. After the reaction, centrifuge, and dry the precipitate at 100 °C for 24 h to obtain modified silica fine powder;
[0054] 2) Mix the four raw materials according to 65 wt% of modified silica powder, 31 wt% of boehmite powder, 3 wt% of hydratable alumina powder, and 1 wt% of boric acid powder to obtain the first mixed powder. Then, add 0.2% acrylamide powder and 0.1% vanadium pentoxide powder based on the mass of the first mixed powder and mix them to obtain the second mixed powder;
[0055] 3) Add water to the second mixed powder. The mass ratio of the second mixed powder to water is 1:1.2. Heat it in a water bath to 60 °C and react for 6 h under stirring conditions. After the reaction, centrifuge it, and dry the precipitate at 90 °C for 18 h to obtain the binder.
[0056] Example 3
[0057] The cement-free bonded high-alumina castable of this example is prepared by the following steps: Mix 70 wt% of high-alumina aggregate particles, 22 wt% of fine powder, and 8 wt% of binder evenly, and then add 2% water based on the total mass of the above raw materials and mix evenly to obtain the cement-free bonded high-alumina castable. Among them:
[0058] The high-alumina aggregate particles are composed of tabular corundum and bauxite mixed according to a mass ratio of 1.5:1, with an Al 2 O 3 content ≥ 94.0%, and the particle size distribution is: the mass ratio of particle size 5 - 8 mm is 30%, the mass ratio of particle size 3 - 5 mm is 28%, and the mass ratio of particle size 1 - 3 mm is 42%.
[0059] The fine powder is composed of alumina powder and silica powder mixed according to a mass ratio of 3:1.
[0060] The binder is prepared by the following steps:
[0061] 1) Add water and sodium tripolyphosphate to the silica powder. The mass ratio of silica powder, water, and sodium tripolyphosphate is 1:1.3:0.003. Heat it in a water bath to 50 °C and react for 50 min under stirring conditions. After the reaction, centrifuge it, and dry the precipitate at 90 °C for 18 h to obtain the modified silica powder;
[0062] 2) Mix the four raw materials according to 75 wt% of modified silica powder, 20 wt% of boehmite powder, 2 wt% of hydratable alumina powder, and 3 wt% of boric acid powder to obtain the first mixed powder. Then, add 0.4% acrylamide powder and 0.2% vanadium pentoxide powder based on the mass of the first mixed powder and mix them to obtain the second mixed powder;
[0063] 3) Add water to the second mixed powder. The mass ratio of the second mixed powder to water is 1:1.5. Heat it in a water bath to 70 °C and react for 10 h under stirring conditions. After the reaction, centrifuge it, and dry the precipitate at 80 °C for 12 h to obtain the binder.
[0064] Example 4
[0065] The cement-free high-alumina castable of this example is made by the following steps: After mixing 67 wt% of high-alumina aggregate particles, 29 wt% of fine powder, and 4 wt% of binder evenly, then adding 4% of the total mass of the above raw materials of water and mixing evenly, the cement-free high-alumina castable is obtained. Among them:
[0066] The high-alumina aggregate particles are composed of tabular corundum, bauxite, and fused white corundum mixed in a mass ratio of 1:1:1.2, with an Al 2 O 3 content ≥ 94.0%, and the particle size distribution is: the mass ratio of particle size 5 - 8 mm is 26%, the mass ratio of particle size 3 - 5 mm is 28%, and the mass ratio of particle size 1 - 3 mm is 46%.
[0067] The fine powder is composed of alumina fine powder and silica fine powder mixed in a mass ratio of 2:1.
[0068] The binder is made by the following steps:
[0069] 1) Add water and sodium tripolyphosphate to silica fine powder. The mass ratio of silica fine powder, water, and sodium tripolyphosphate is 1:1.5:0.004. Under stirring conditions, heat in a water bath to 55 °C and react for 45 min. After the reaction, centrifuge, and dry the precipitate at 100 °C for 18 h to obtain modified silica fine powder;
[0070] 2) Mix four raw materials of 72 wt% of modified silica fine powder, 24 wt% of boehmite fine powder, 2 wt% of hydratable alumina fine powder, and 2 wt% of boric acid fine powder to obtain the first mixed powder, and then mix with 0.5% of acrylamide fine powder and 0.3% of vanadium pentoxide fine powder based on the mass of the first mixed powder to obtain the second mixed powder;
[0071] 3) Add water to the second mixed powder. The mass ratio of the second mixed powder to water is 1:1.6. Under stirring conditions, heat in a water bath to 75 °C and react for 11 h. After the reaction, centrifuge, and dry the precipitate at 80 °C for 24 h to obtain the binder.
[0072] Comparative Example 1
[0073] The binder of Comparative Example 1 is CA71 calcium aluminate cement.
[0074] Comparative Example 2
[0075] The difference between Comparative Example 2 and Example 2 is only that: step 1) is not carried out, that is, the silica fine powder is not modified, and the modified silica fine powder in step 2) is replaced with unmodified silica fine powder.
[0076] Comparative Example 3
[0077] The difference between Comparative Example 3 and Example 3 is only that steps 2) and 3) are not carried out, and the modified silica micro powder obtained in step 1) is used as the binder.
[0078] Comparative Example 4
[0079] The difference between Comparative Example 4 and Example 1 is only that step 3) is not carried out, and the second mixed powder obtained in step 2) is used as the binder.
[0080] Comparative Example 5
[0081] The difference between Comparative Example 5 and Example 1 is only that boehmite micro powder, hydratable alumina micro powder and acrylamide are not added in step 2).
[0082] The properties of the castables prepared in the above examples and comparative examples were tested. Among them, the flow value and the pourable time were measured by the slump method, the room temperature flexural strength was measured with reference to GB / T 3001-2017 "Test Method for Room Temperature Flexural Strength of Refractories", the anti-explosion temperature was measured with reference to YB / T 4117-2003 "Test Method for Anti-explosion Property of Dense Refractory Castables", and the strength retention rate after thermal shock was measured with reference to GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractories".
[0083] Table 1 Performance test results
[0084]
[0085]
[0086] The above examples are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.
Claims
1. A cement-free high-alumina castable, characterized in that: The invention comprises the following raw materials in percentage by weight: 63-74% of high-aluminum aggregate particles, 21-30% of fine powder, 4-8% of binder, and 2-4% of water based on the total weight of the above raw materials; wherein the fine powder is a mixture of alumina micropowder and silicon dioxide micropowder; and the preparation method of the binder comprises the following steps: 1) adding water and sodium tripolyphosphate to silica powder, heating to react under stirring conditions, separating the solid and the liquid after the reaction, and drying the obtained solid to obtain modified silica powder; 2) mixing modified silica powder, boehmite powder, hydrated alumina powder and boric acid powder to obtain a first mixed powder, and then adding acrylamide powder and vanadium pentoxide powder to obtain a second mixed powder; 3) adding water to the second mixed powder, heating the mixture under stirring conditions for reaction, separating the solid and the liquid after the reaction is completed, and drying the obtained solid to obtain a binder.
2. The cement-free high-alumina castable according to claim 1, characterized in that: The high-aluminum aggregate particles are one or more of plate-shaped corundum, high-aluminum bauxite, and fused white corundum; the Al2O3 content of the high-aluminum aggregate particles is ≥94.0%, and the particle size is 0.1-8 mm.
3. The cement-free high-alumina castable according to claim 1, characterized in that: The gradation of the high-alumina aggregate particles is as follows: the particle size of 5-8 mm accounts for 22-30% by weight, the particle size of 3-5 mm accounts for 24-28% by weight, and the particle size of 1-3 mm accounts for 42-54% by weight.
4. The cement-free high-alumina castable according to claim 1, characterized in that: The mass ratio of alumina micropowder to silica micropowder in the fine powder is (1.2-5):1; the Al2O3 content of the alumina micropowder in the fine powder is ≥98.5%, and the particle size is ≤0.088mm; the SiO2 content of the silica micropowder in the fine powder is ≥95.1%, and the particle size is ≤0.044mm.
5. The cement-free high-alumina castable according to claim 1, characterized in that: In step 1), the mass ratio of silicon dioxide powder, water and sodium tripolyphosphate is 1:(1-1.6):(0.001-0.005), the reaction temperature is 40-60° C., and the reaction time is 30-60 min.
6. The cement-free high-alumina castable according to claim 1, characterized in that: In step 2), the mass percentage content of each raw material in the first mixed powder is: modified silica powder 65-79%, boehmite powder 18-31%, hydrated alumina powder 1-3%, boric acid powder 1-3%, acrylamide powder added in an amount of 0.2-0.6% of the mass of the first mixed powder, and vanadium pentoxide powder added in an amount of 0.1-0.4% of the mass of the first mixed powder.
7. The cement-free high-alumina castable according to claim 1, characterized in that: In step 3), the mass ratio of the second mixed powder to water is 1:(1.2-1.8), the reaction temperature is 60-80°C, and the reaction time is 6-12h; in step 1) and step 3), the drying temperature is 80-100°C, and the drying time is 12-24h.
8. The cement-free high-alumina castable according to claim 1, characterized in that: In step 1), the SiO2 content of the silicon dioxide micropowder is ≥95.1%, and the particle size is ≤30μm; the Al2O3 content of the boehmite micropowder is ≥98.5%, and the particle size is ≤20μm; the Al2O3 content of the hydratable alumina micropowder is ≥98.5%, and the particle size is ≤60μm; the particle size of the sodium tripolyphosphate is ≤30μm; the particle size of the boric acid micropowder is ≤40μm; the particle size of the acrylamide micropowder is ≤60μm; and the particle size of the vanadium pentoxide micropowder is ≤40μm.
9. The cement-free high-alumina castable according to claim 1, characterized in that: The flow value of the cement-free high-alumina castable is 185-200 mm, the pouring time is 140-160 min, the flexural strength at room temperature of 110°C×24 h is 16-18.5 MPa, the flexural strength at room temperature of 1200°C×3 h is 36.5-38.5 MPa, the flexural strength at room temperature of 1550°C×3 h is 43-47 MPa, the anti-burst temperature is 600-650°C, and the flexural strength retention rate after five thermal shock cycles at 1100°C is ≥85%.
10. A method for preparing a cement-free high-alumina castable according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing high-aluminum aggregate particles, fine powder and a binder evenly according to a proportion, and then adding water and mixing evenly to obtain a cement-free high-aluminum castable.