Al2O3-SiC-C refractory castable and preparation method thereof
In-situ synthesis of Al4Si2C5 crystals in Al2O3-SiC-C refractory castables addresses carbon oxidation and mechanical strength issues, enhancing high-temperature performance and durability.
Patent Information
- Application Number
- CN202510586740.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-08
- Publication Date
- 2025-07-15
AI Technical Summary
Traditional Al2O3-SiC-C refractory castables are prone to oxidation and loss of carbon components in high-temperature oxidation environments, and the material's flexural strength is limited by the distribution of aggregate particles and weak matrix bonding, which is difficult to meet the mechanical performance requirements of complex working conditions.
By synthesizing Al4Si2C5 wafers in situ in the Al2O3-SiC-C castable matrix, the high temperature and flexural strength of the material are employed to block oxygen penetration and improve the material's oxidation resistance. At the same time, the directional growth and uniform distribution of the wafer are achieved by controlling the raw material ratio and reaction conditions, thereby enhancing the high temperature and flexural strength of the material.
It significantly improves the high-temperature oxidation resistance and thermal shock resistance of the material, solves the structural failure problems caused by high-temperature softening or volume expansion of traditional materials, reduces energy consumption and reduces maintenance costs, and provides a high-performance fire resistance solution.
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Figure CN120309324A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of unshaped refractory castables, and particularly to an Al2O3-SiC-C refractory castable and a preparation method thereof. Background Art
[0002] In the field of refractory materials for blast furnace tapping troughs, Al2O3-SiC-C refractory castables are widely used in industries such as metallurgy, ceramics, and glass manufacturing due to their excellent high-temperature strength, thermal shock stability, and slag erosion resistance. However, traditional Al2O3-SiC-C materials still face two core challenges during long-term service: firstly, the carbon components (such as carbon black and graphite) are prone to oxidative loss in a high-temperature oxidation environment, leading to the deterioration of the material structure and significantly reducing its service life; secondly, the flexural strength of the overall material is limited by the random distribution of aggregate particles and the weak bonding with the matrix, making it difficult to meet the stringent requirements of mechanical properties under complex working conditions.
[0003] To address the above problems, researchers have attempted to enhance the antioxidant and mechanical properties by introducing external ceramic fibers or nanoparticles, but there are problems such as complex processes, high costs, and poor interfacial compatibility. In recent years, in-situ synthesis technology has gradually become a research hotspot in refractory material modification due to its strong controllability and the ability to achieve chemical bonding between the reinforcing phase and the matrix. Among them, Al4Si2C5, as a new type of silicon aluminum carbide wafer, exhibits excellent antioxidant potential due to its unique layered crystal structure and chemical stability - its densely arranged hexagonal lattice can effectively block oxygen penetration and inhibit the oxidation reaction of carbon components; at the same time, its high hardness and directional growth characteristics can significantly improve the flexural strength of the material.
[0004] However, the synthesis of existing Al4Si2C5 wafers mostly relies on complex processes such as high-temperature hot pressing sintering, making it difficult to achieve in-situ controllable synthesis during the preparation of castables, and the synergistic mechanism between the wafers and the matrix has not been clarified.
[0005] Therefore, a method capable of in-situ synthesizing Al4Si2C5 wafers in the matrix of Al2O3-SiC-C castables is developed to achieve high antioxidant properties at high temperatures and improve its mechanical properties. Summary of the Invention
[0006] The purpose of the present invention is to propose an Al2O3-SiC-C refractory castable and a preparation method thereof to address the above deficiencies. Through synchronous improvement of the formula and process, in-situ controlled synthesis of Al4Si2C5 wafers is achieved, enabling the Al2O3-SiC-C refractory castable to have high antioxidant properties and simultaneously improving the conventional mechanical properties and thermal shock resistance of the material, with broad application prospects.
[0007] To achieve the above object, the present invention provides the following technical solutions: A preparation method of an Al2O3-SiC-C refractory castable, comprising the following steps: S1: Prepare the wafer micropowder raw materials in proportion Weigh the wafer micropowder raw materials according to the mass fraction ratio, 5-15 wt.% of silicon carbide, 2-5 wt.% of aluminum powder, 2-5 wt.% of silicon powder, 2-5 wt.% of carbonaceous raw materials, and 2-10 wt.% of aluminum fluoride, and mix them evenly to obtain the wafer micropowder raw materials; S2: Prepare the composite micropowder raw materials in proportion Prepare brown fused alumina particles, silicon carbide particles, dense corundum, calcium aluminate cement, ɑ-Al2O3 micropowder, pitch coke, boron carbide, and sodium tripolyphosphate in proportion, and mix them evenly to obtain the refractory castable raw materials; Among them, 50-55 wt.% of brown fused alumina particles, 12-16 wt.% of silicon carbide particles, 6-9 wt.% of dense corundum, 2-3 wt.% of calcium aluminate cement, 2-4 wt.% of ɑ-Al2O3 micropowder, 2-3 wt.% of pitch coke, 0.2-0.3 wt.% of boron carbide, and 0.1-0.2 wt.% of sodium tripolyphosphate; S3: Mix the raw materials again Mix the wafer micropowder raw materials and the composite micropowder raw materials evenly to obtain the final mixed raw materials; S4: Molding of the refractory castable block Add water accounting for 3.5-8 wt% of the total weight of the final mixed raw materials to the final mixed raw materials, mechanically stir and then pour them into a mold, and vibrate to form a refractory castable block matrix; S5: High-temperature internal strengthening Heat the dried refractory castable block matrix to 1400°C - 1600°C under the protection of reducing gas. After the components in the matrix react for 0.5-1 h, uniformly dispersed hexagonal plate-like Al4Si2C5 wafers grow in-situ between the pores of the raw material particles inside the refractory castable block, filling the microscopic pore defects existing in the castable block matrix to form a rigid phase; at the same time, during the formation of Al4Si2C5 wafers, the dispersion distribution of silicon carbide particles is promoted to reduce the local stress concentration of the refractory castable block.
[0008] In step S1, the purity of silicon carbide is greater than 97 wt%, and the particle size is less than 75 μm; the purity of aluminum powder is greater than 95 wt%, and the particle size is less than 75 μm; the purity of silicon powder is greater than 95 wt%, and the particle size is less than 75 μm; the carbonaceous raw material is one or a mixture of carbon black, pitch coke, graphite, activated carbon, and coke, and the particle size is less than 3 mm.
[0009] In step S2, the brown fused alumina particles have Al2O3 > 96%, and the particle sizes include 8 - 5 mm, 5 - 3 mm, 3 - 1 mm, and 1 - 0 mm; the silicon carbide particles have SiC3 > 98%, and the particle sizes include 3 - 1 mm and 1 - 0 mm; the dense fused alumina has Al2O3 > 99%, and the particle size is 325 mesh; the calcium aluminate cement has Al2O3 > 70%, and the particle size < 40 μm; the α-Al2O3 micropowder has Al2O3 > 99%, and the particle size is 2 - 5 μm; the spherical pitch has a fixed carbon content > 50%, and the particle size is 0.2 - 0.7 mm; the boron carbide has B4C > 99%, and the particle size is 200 mesh; the sodium tripolyphosphate has a purity greater than 95%, and the particle size is 100 mesh.
[0010] In step S3, a horizontal mixer is used for mechanical mixing for 2 hours at a rotation speed of 50 revolutions per minute.
[0011] The method for preparing the Al2O3-SiC-C refractory castable is characterized in that step S5 includes the following steps: S5-1 By adjusting the temperature range in the reaction conditions (including the temperature rise rate, heating duration, etc.), the wafer size, morphology, and distribution are precisely controlled: when slowly heating (5°C / min), at a lower heating temperature (1450°C), and for a shorter duration (1 h), the wafer thickness size is smaller (100 nm - 300 nm) and the distribution is uniform; when rapidly heating (10°C / min), at a higher heating temperature (1600°C), and for a longer duration (3 h), the wafer thickness size is larger (300 nm - 500 nm) and there is local agglomeration. S5-2 By adjusting the raw material ratio in step S1, the wafer size, morphology, and distribution are precisely controlled: While keeping other raw materials unchanged, when increasing the proportion of aluminum fluoride (range 2 - 10 wt.%), the number of wafers increases, and the size and morphology do not change significantly; while keeping the aluminum fluoride unchanged, when synchronously increasing the proportions of aluminum powder, silicon powder, and carbonaceous raw materials (range for all is 2 - 5 wt.%), the number of wafers increases, and the size and morphology do not change significantly; while keeping other raw materials unchanged, when increasing the proportion of silicon carbide (range 5 - 15 wt.%), the distribution can be promoted to be uniform, and the size and morphology do not change significantly.
[0012] An Al2O3-SiC-C refractory castable is prepared by the foregoing method. Beneficial effects
[0013] 1. The present invention realizes the directional growth of Al4Si2C5 wafers by controlling the raw material ratio and reaction conditions, and the obtained wafers have the characteristics of high purity, controllable size and good thermal stability. When the castable prepared by the raw material system is applied to a high-temperature reducing environment such as the iron outlet of a blast furnace, the Al4Si2C5 wafers are continuously generated in situ during service, which significantly improves the high-temperature strength, oxidation resistance and thermal shock resistance of the material, and effectively solves the structural failure problem of traditional refractory materials caused by high-temperature softening or volume expansion. The present invention uses industrial-grade raw materials to achieve low-cost in-situ synthesis, the process flow is simple and controllable, and the synergistic effect of the wafer and the matrix effectively improves the comprehensive performance of the composite material, providing a high-performance refractory solution for the high-temperature field of metallurgy. The process parameters of the synthesis process are easy to control, and the cost advantage is significant. It has broad application prospects in high-temperature engineering such as steel smelting and non-ferrous metal smelting.
[0014] 2. The present invention directly synthesizes Al4Si2C5 wafers in Al2O3-SiC-C refractory castables by in-situ growth method. The process is simple and controllable. The wafers are directly generated by the reaction of matrix components to form a uniformly dispersed microstructure. This method avoids the interface bonding problem caused by traditional external wafers, significantly reduces energy consumption, and can accurately control the wafer size, morphology and distribution by adjusting the reaction conditions (such as temperature and raw material ratio), providing a technical path for the large-scale production of highly dispersed and highly bonded Al4Si2C5 wafers.
[0015] 3. The Al4Si2C5 wafer synthesized in situ in the Al2O3-SiC-C castable matrix of the present invention has a regular hexagonal sheet structure (the side length of the regular hexagon of the wafer is about 2~3μm, and the thickness of the wafer is about 200~500μm), which is mainly distributed in the macro / micro pores and the matrix. The in-situ generation of the Al4Si2C5 wafer in the Al2O3-SiC-C castable matrix fills the microscopic pore defects in the castable, effectively inhibiting the diffusion of external air into the material, thereby improving the overall antioxidant capacity of the material; at the same time, the presence of the wafer requires the crack to repeatedly bypass or pass through these rigid phases when expanding, which can significantly increase the fracture work, thereby improving the toughness of the material.
[0016] 4. After the in-situ grown Al4Si2C5 wafer is introduced into the present invention, the mechanical properties (such as bending strength and compressive strength) of the Al2O3-SiC-C castable are significantly improved, the high temperature stability is enhanced, and a strong chemical bond is formed between the wafer and the matrix, which effectively inhibits the volume shrinkage and crack initiation at high temperature. In addition, the Al4Si2C5 wafer generation process can promote the dispersion distribution of SiC particles, reduce local stress concentration, improve the material's ability to resist slag erosion and oxidation, extend the service life of the refractory material, and reduce maintenance costs.
[0017] 5. The present invention realizes low-cost in-situ synthesis using industrial-grade raw materials. The process flow is simple and controllable. The synergistic effect between the wafer and the matrix effectively improves the comprehensive performance of the composite material, providing a high-performance refractory solution for the metallurgical high-temperature field. The process parameters in the synthesis process are easy to control, and the cost advantage is significant. It has broad application prospects in high-temperature engineering such as steel smelting and non-ferrous metal melting. Description of the Drawings
[0018] Figure 1 SEM image (1μm scale) of the hexagonal Al4Si2C5 wafers in-situ grown in the refractory castable prepared in Example 1 of the present invention.
[0019] Figure 2 SEM image (2μm scale) of the hexagonal Al4Si2C5 wafers in-situ grown in the refractory castable prepared in Example 1 of the present invention.
[0020] Figure 3 XRD pattern of the hexagonal Al4Si2C5 wafers in-situ grown in the refractory castable prepared in Example 1 of the present invention.
[0021] Figure 4 Comparison chart of the antioxidant effect of the refractory castable with in-situ grown hexagonal Al4Si2C5 wafers in Example 2 of the present invention. Detailed Embodiments
[0022] The following combines multiple embodiments and the attached Figures 1-4 to further describe the technical solutions of the present invention.
[0023] Basic Embodiment This embodiment provides a preparation method for Al2O3-SiC-C refractory castable, which includes the following steps: S1: Prepare the wafer micro-powder raw materials in proportion Weigh the wafer micro-powder raw materials according to the mass fraction ratio. Silicon carbide is 5-10wt.%, aluminum powder is 2-4wt.%, silicon powder is 2-4wt.%, carbonaceous raw material is 2-4wt.%, and aluminum fluoride is 2-10wt.%, and mix them evenly to obtain the wafer micro-powder raw materials; Among them, the purity of silicon carbide is greater than 97wt%, and the particle size is less than 75μm; the purity of aluminum powder is greater than 95wt%, and the particle size is less than 75μm; the purity of silicon powder is greater than 95wt%, and the particle size is less than 75μm; the carbonaceous raw material is one or a mixture of carbon black, pitch coke, graphite, activated carbon, coke, and the particle size is less than 3 mm; S2: Prepare the composite micro-powder raw materials in proportion Prepare brown fused alumina particles, silicon carbide particles, dense fused alumina, calcium aluminate cement, ɑ-Al2O3 micro-powder, pitch coke, boron carbide, and sodium tripolyphosphate in proportion, and mix them evenly to obtain the refractory castable raw materials; Among them, brown fused alumina particles are 50 - 55 wt.%, silicon carbide particles are 12 - 16 wt.%, dense fused alumina is 6 - 9 wt.%, calcium aluminate cement is 2 - 3 wt.%, ɑ - Al2O3 micropowder is 2 - 4 wt.%, spherical pitch is 2 - 3 wt.%, boron carbide is 0.2 - 0.3 wt.%, and sodium tripolyphosphate is 0.1 - 0.2 wt.%, and they are mixed evenly; In the brown fused alumina particles, Al2O3 > 96%, and the particle sizes include 8 - 5 mm, 5 - 3 mm, 3 - 1 mm, and 1 - 0 mm; in the silicon carbide particles, SiC3 > 98%, and the particle sizes include 3 - 1 mm and 1 - 0 mm; in the dense fused alumina, Al2O3 > 99%, and the particle size is 325 mesh; in the calcium aluminate cement, Al2O3 > 70%, and the particle size < 40 μm; in the ɑ - Al2O3 micropowder, Al2O3 > 99%, and the particle size is 2 - 5 μm; in the spherical pitch, the fixed carbon content > 50%, and the particle size is 0.2 - 0.7 mm; in the boron carbide, B4C > 99%, and the particle size is 200 mesh; the purity of sodium tripolyphosphate is greater than 95%, and the particle size is 100 mesh; S3: Re - mixing of raw materials Using a horizontal mixer, mechanically mixing for 2 hours at a rotation speed of 50 revolutions per minute, mixing the wafer micropowder raw material and the composite micropowder raw material evenly to obtain the final mixed raw material; S4: Shaping of refractory castable blocks Adding water accounting for 3.5 - 8 wt% of the total weight of the final mixed raw material to the final mixed raw material, mechanically stirring and then pouring it into a mold, and vibrating to form a refractory castable block matrix; S5: High - temperature internal strengthening Heating the dried refractory castable block matrix to 1400℃ - 1600℃ under the protection of a reducing gas. After the components in the matrix react for 0.5 - 1 h, regular hexagonal flake - shaped Al4Si2C5 wafers grow in - situ and are evenly dispersed among the pores between the raw material particles inside the refractory castable block, filling the microscopic pore defects existing in the refractory castable block matrix to form a rigid phase; at the same time, during the formation of Al4Si2C5 wafers, the dispersion distribution of silicon carbide particles is promoted to reduce local stress concentration in the refractory castable block.
[0024] Based on the above steps, step S5 also includes the following targeted adjustment steps: S5-1. By adjusting the temperature range in the reaction conditions (including temperature rise rate, heating time, etc.), the chip size, morphology and distribution can be precisely controlled: when the temperature is slowly increased (5℃ / min), the heating temperature is relatively low (1450℃) and the heating time is relatively short (1h), the chip thickness is relatively small (100nm~300nm) and the distribution is uniform; when the temperature is quickly increased (10℃ / min), the heating temperature is relatively high (1600℃) and the heating time is relatively long (3h), the chip thickness is relatively large (300nm~500nm) and local agglomeration occurs; S5-2, by adjusting the raw material ratio in step S1, the chip size, morphology and distribution can be precisely controlled: When keeping other raw materials unchanged and increasing the proportion of aluminum fluoride (ranging from 2 to 10wt.%), the number of chips increases, and the size and morphology do not change significantly; when keeping aluminum fluoride unchanged and simultaneously increasing the proportions of aluminum powder, silicon powder and carbon raw materials (all ranging from 2 to 5wt.%), the number of chips increases, and the size and morphology do not change significantly; when keeping other raw materials unchanged and increasing the proportion of silicon carbide (ranging from 5 to 15wt.%), it can promote uniform distribution, and the size and morphology do not change significantly.
[0025] An Al2O3-SiC-C refractory castable is prepared by the aforementioned method, and the physical and chemical characteristics of the wafer therein can be specifically adjusted according to steps S5-1 and / or S5-2.
[0026] Example 1 The Al2O3-SiC-C refractory castable and preparation method thereof provided in this embodiment are specific selections based on the basic embodiment, and provide a preparation method for high-temperature in-situ synthesized Al4Si2C5 wafers, which are then applied to Al2O3-SiC-C refractory castables, comprising the following steps: First, prepare the chip micro powder raw materials according to the proportion, weigh 13g of silicon carbide powder, 5g of aluminum powder, 5g of silicon powder, 5g of carbon black and 2.5g of aluminum fluoride; Among them, the purity of silicon carbide is 98wt%, and the particle size is less than 75μm; the purity of aluminum powder is 96wt%, and the particle size is less than 75μm; the purity of silicon powder is 96wt%, and the particle size is less than 75μm; the carbon raw material is a mixture of carbon black and ball pitch in a mass ratio of 1:1, and the particle size is less than 3 mm; Then, all the raw materials were placed in a mixing and grinding tank and mixed for 6 hours to obtain a mixed material; Next, 1.5 g of water was added to the mixture and mixed thoroughly, and then poured into a silicone mold and vibrated to form a test block; finally, the test block was buried in a graphite crucible with graphite powder and heated to 1450°C and kept warm for 3 hours; The SEM image of the Al4Si2C5 wafer obtained in this embodiment is as follows: Figure 1 and Figure 2As shown, Al4Si2C5 is in the shape of hexagonal wafers. The side length of the wafers is about 2 - 3 μm, and the thickness is about 200 - 500 μm. At high temperatures, an interlocking network structure similar to whiskers can be formed. This structure can effectively disperse stress, inhibit crack propagation, thereby enhancing the flexural strength of the castable, and can also block the pore channels and inhibit slag penetration.
[0027] After the test block prepared from it was broken, the XRD pattern of the powder was as Figure 3 shown. The phase composition of the raw material of the wafer micropowder after calcination is SiC, Al2O3, C, and Al4Si2C5, all of which are the main components of the Al2O3 - SiC - C refractory castable.
[0028] In this embodiment, the temperature range in the reaction conditions (including the temperature rise rate, heating duration, etc.) can be further adjusted to precisely control the wafer size, morphology, and distribution: when the temperature is raised slowly (5 °C / min), the heating temperature is relatively low (1450 °C), and the duration is short (1 h), the thickness size of the wafers is small (100 nm - 300 nm) and the distribution is uniform.
[0029] Example 2 The Al2O3 - SiC - C refractory castable and its preparation method provided in this embodiment are specific selections within the scope recorded in the basic embodiment, and it includes the following steps: First, prepare the raw material of the wafer micropowder in proportion. Weigh 7.5 wt% of silicon carbide powder, 2 wt% of aluminum powder, 2 wt% of silicon powder, 2 wt% of carbon black, and 2 wt% of aluminum fluoride as the composite micropowder raw material of the wafer and mix them for 6 hours to obtain the wafer micropowder; Secondly, prepare the raw materials of the refractory castable. Weigh 54 wt% of brown fused alumina particles, 16 wt% of silicon carbide particles, 9 wt% of dense corundum, 2 wt% of calcium aluminate cement, 2 wt% of α - Al2O3 micropowder, 2 wt% of spherical pitch, 0.2 wt% of boron carbide, and 0.1 wt% of sodium tripolyphosphate, and mix them for 3 hours to obtain the raw materials of the refractory castable; Thirdly, mix the raw materials of the refractory castable with the raw material of the wafer micropowder for 2 hours to obtain the final mixed raw material; Then, add 6 wt% of water to the final mixed raw material, then mechanically stir for 3 minutes, pour it into a mold and vibrate it to form a casting test block; Finally, perform high-temperature internal strengthening: Heat the dried refractory castable block matrix to 1500°C under argon protection (or bury it in a graphite crucible with graphite powder). After the components in the matrix react for 0.5 h, keep it warm for 3 hours. Uniformly dispersed hexagonal plate-like Al4Si2C5 wafers grow in-situ in the pores between the raw material particles inside the refractory castable block, filling the microscopic pore defects existing in the castable block matrix to form a rigid phase; at the same time, the dispersion distribution of silicon carbide particles is promoted during the formation of Al4Si2C5 wafers to reduce local stress concentration in the refractory castable block.
[0030] In this embodiment, the temperature range in the reaction conditions (including the temperature rise rate, heating duration, etc.) can be further adjusted to precisely control the wafer size, morphology, and distribution: Rapid heating (10°C / min), a relatively high heating temperature (1600°C), and a relatively long duration (3 h) result in a relatively large wafer thickness size (300 nm - 500 nm) and local agglomeration.
[0031] Example 3 The Al2O3 - SiC - C refractory castable and its preparation method provided in this embodiment are specific selections within the scope recorded in the basic embodiment. It is basically the same as Example 2, and the differences are as follows: The weighed wafer micropowder raw materials are: 5 wt% silicon carbide powder, 3 wt% aluminum powder, 3 wt% silicon powder, 3 wt% carbon black, and 6 wt% aluminum fluoride, and they are mixed for 6 hours.
[0032] In this embodiment, the wafer size, morphology, and distribution can be precisely controlled by further adjusting the raw material ratio: Keeping other raw materials unchanged and increasing the proportion of aluminum fluoride (in the range of 2 - 10 wt.%), the number of wafers increases, and the size and morphology do not change significantly.
[0033] Example 4 The Al2O3 - SiC - C refractory castable and its preparation method provided in this embodiment are specific selections within the scope recorded in the basic embodiment. It is basically the same as Example 2, and the differences are as follows: The weighed wafer composite micropowder raw materials are: 10 wt% silicon carbide powder, 4 wt% aluminum powder, 4 wt% silicon powder, 4 wt% carbon black, and 10 wt% aluminum fluoride, and they are mixed for 6 hours.
[0034] In this embodiment, the wafer size, morphology, and distribution can be precisely controlled by further adjusting the raw material ratio: Keeping aluminum fluoride unchanged and simultaneously increasing the proportions of aluminum powder, silicon powder, and carbonaceous raw materials (all in the range of 2 - 5 wt.%), the number of wafers increases, and the size and morphology do not change significantly.
[0035] Example 5 The Al2O3-SiC-C refractory castable and its preparation method provided in this embodiment are specific selections within the scope recorded in the basic embodiment. It is basically the same as Embodiment 2, and the differences are as follows: For the raw materials for preparing the refractory castable, weigh 55 wt% of brown fused alumina particles, 12 wt% of silicon carbide particles, 7 wt% of dense fused alumina, 2 wt% of calcium aluminate cement, 3 wt% of α-Al2O3 micropowder, 2.5 wt% of spherical pitch, 0.25 wt% of boron carbide, and 0.15 wt% of sodium tripolyphosphate, and mix them for 3 hours to obtain the raw materials for the refractory castable. In this embodiment, the wafer size, morphology, and distribution can be precisely controlled by further adjusting the raw material ratio: when other raw materials remain unchanged and the silicon carbide ratio is increased (in the range of 5 - 15 wt.%), the distribution can be promoted to be uniform, and there is no obvious change in the size and morphology.
[0036] Example 6 The Al2O3-SiC-C refractory castable and its preparation method provided in this embodiment are specific selections within the scope recorded in the basic embodiment. It is basically the same as Embodiment 2, and the differences are as follows: For the raw materials for preparing the refractory castable, weigh 50 wt% of brown fused alumina particles, 14 wt% of silicon carbide particles, 8 wt% of dense fused alumina, 2.5 wt% of calcium aluminate cement, 4 wt% of α-Al2O3 micropowder, 3 wt% of spherical pitch, 0.3 wt% of boron carbide, and 0.2 wt% of sodium tripolyphosphate, and mix them for 3 hours to obtain the raw materials for the refractory castable.
[0037] Comparative Example 1 This comparative example provides a preparation method for a conventional refractory castable. It is basically the same as Embodiment 2, and the difference is that aluminum fluoride for synthesizing wafers is not added to the raw materials.
[0038] First, weigh 7.6 wt% of silicon carbide powder, 2.4 wt% of aluminum powder, 2.4 wt% of silicon powder, and 2.4 wt% of carbon black as the raw materials for the wafer composite micropowder and mix them for 6 hours.
[0039] Second, weigh 58 wt% of brown fused alumina particles, 16 wt% of silicon carbide particles, 9 wt% of dense fused alumina, 2 wt% of calcium aluminate cement, 2 wt% of α-Al2O3 micropowder, 2 wt% of spherical pitch, 0.2 wt% of boron carbide, and 0.1 wt% of sodium tripolyphosphate and mix them for 3 hours., Third, mix it with the raw materials for the wafer composite micropowder for 2 hours to obtain the final mixture.
[0040] Finally, add 6 wt% of water to the final mixture, then mechanically stir for 3 minutes and pour it into a mold and vibrate it into a cast test block.
[0041] The cast specimens were heated to 1450 °C and held for 3 hours. After cooling, their cold flexural and compressive strengths were measured. The measured results of the properties are shown in Table 1. The thermal shock resistance was tested by the water-cooling method. The burned specimens were heated to 1200 °C and then dropped into water and circulated 3 times. The ratio of the flexural strength after thermal shock to the flexural strength before thermal shock was obtained as the residual strength ratio, as shown in Table 1. The cross-section of the burned specimens after oxidation in air atmosphere at 1000 °C for 3 hours (see Figure 4 ), from left to right, are the cast samples with a diameter of 5 cm of Comparative Example 1, Example 3, Example 4, Example 5, and Example 6. The antioxidant area ratio (the ratio of the uncompletely oxidized black area to the cross-sectional area of the specimen) is shown in Table 1.
[0042]
[0043] The Al2O3-SiC-C refractory castables and their preparation methods provided by the above embodiments of the present invention are centered around in-situ synthesizing Al4Si2C5 wafers under high-temperature conditions of about 1500 °C in a reducing atmosphere. The present invention realizes the directional growth of Al4Si2C5 wafers by controlling the raw material ratio and reaction conditions. The obtained wafers have the characteristics of high purity, controllable size, and good thermal stability. When the refractory castables prepared from this raw material system are applied to high-temperature reducing environments such as blast furnace tapping troughs, Al4Si2C5 wafers are continuously in-situ generated during service, significantly improving the high-temperature strength, oxidation resistance, and thermal shock resistance of the materials, and effectively solving the structural failure problems caused by high-temperature softening or volume expansion of traditional refractory materials.
[0044] The present invention uses industrial-grade raw materials to achieve low-cost in-situ synthesis. The process flow is simple and controllable. The synergistic effect between the wafers and the matrix effectively improves the comprehensive performance of the composite material, providing a high-performance refractory solution for the metallurgical high-temperature field. The process parameters during the synthesis process are easy to control, and the cost advantage is significant. It has broad application prospects in high-temperature projects such as iron and steel smelting and non-ferrous metal smelting.
[0045] It should be noted that in other embodiments of the present invention, within the scope of the steps, components, ratios, and process parameters recorded in the present invention, other different schemes obtained by specific selection can all achieve the technical effects recorded in the present invention. Therefore, the present invention will not list them one by one.
[0046] The above embodiments are only one or several implementation manners among numerous embodiments of the present invention, rather than limitations on the present invention. Any technical solutions such as equivalent changes, modifications, and equivalent substitutions to the above-described embodiments, as long as they conform to the scope of the essential spirit of the present invention, will fall within the scope protected by the claims of the present invention.
Claims
1. A preparation method of Al2O3-SiC-C refractory castable, characterized in that, It includes the following steps: S1: Prepare the raw material of wafer micropowder proportionally Weigh the raw materials of wafer micropowder according to the mass fraction ratio, including 5-10 wt.% of silicon carbide, 2-4 wt.% of aluminum powder, 2-4 wt.% of silicon powder, 2-4 wt.% of carbonaceous raw material, and 2-10 wt.% of aluminum fluoride, and mix them evenly to obtain the raw material of wafer micropowder; S2: Prepare the raw material of refractory castable proportionally Prepare brown fused alumina particles, silicon carbide particles, dense corundum, calcium aluminate cement, ɑ-Al2O3 micropowder, pitch coke, boron carbide, and sodium tripolyphosphate according to the proportion, and mix them evenly to obtain the raw material of refractory castable; Among them, brown fused alumina particles are 50-55 wt.%, silicon carbide particles are 12-16 wt.%, dense corundum is 6-9 wt.%, calcium aluminate cement is 2-3 wt.%, ɑ-Al2O3 micropowder is 2-4 wt.%, pitch coke is 2-3 wt.%, boron carbide is 0.2-0.3 wt.%, and sodium tripolyphosphate is 0.1-0.2 wt.%; S3: Mix the raw materials again Mix the raw material of wafer micropowder and the raw material of refractory castable evenly to obtain the final mixed raw material; S4: Molding of refractory castable block Add water accounting for 3.5-8 wt% of the total weight of the final mixed raw material to the final mixed raw material, stir mechanically and then pour it into a mold, and vibrate to form the matrix of refractory castable block; S5: High-temperature internal strengthening Heat the dried matrix of refractory castable block to 1400℃-1600℃ under the protection of reducing gas. After the components in the matrix react for 0.5-1 h, uniformly dispersed hexagonal flake Al4Si2C5 wafers grow in-situ between the pores of the raw material particles inside the refractory castable block, filling the microscopic pore defects existing in the matrix of the castable block to form a rigid phase; at the same time, the dispersion distribution of silicon carbide particles is promoted during the formation of Al4Si2C5 wafers to reduce the local stress concentration of the refractory castable block.
2. The preparation method of the Al2O3-SiC-C refractory castable according to claim 1, characterized in that, In step S1, the purity of silicon carbide is greater than 97 wt%, and the particle size is less than 75 μm; the purity of aluminum powder is greater than 95 wt%, and the particle size is less than 75 μm; the purity of silicon powder is greater than 95 wt%, and the particle size is less than 75 μm; the carbonaceous raw material is one or a mixture of carbon black, pitch coke, graphite, activated carbon, and coke, and the particle size is less than 3 mm.
3. The preparation method of the Al2O3-SiC-C refractory castable according to claim 1, characterized in that, In step S2, Al2O3 in the brown fused alumina particles is >96%, and the particle sizes include 8-5 mm, 5-3 mm, 3-1 mm, and 1-0 mm; SiC3 in the silicon carbide particles is >98%, and the particle sizes include 3-1 mm and 1-0 mm; Al2O3 in the dense corundum is >99%, and the particle size is 325 mesh; Al2O3 in the calcium aluminate cement is >70%, and the particle size is <40 μm; Al2O3 in the ɑ-Al2O3 micropowder is >99%, and the particle size is 2-5 μm; the fixed carbon content in the pitch coke is >50%, and the particle size is 0.2-0.7 mm; B4C in the boron carbide is >99%, and the particle size is 200 mesh; the purity of sodium tripolyphosphate is greater than 95%, and the particle size is 100 mesh.
4. The preparation method of the Al2O3-SiC-C refractory castable according to claim 1, wherein In step S3, a horizontal mixer is used for mechanical mixing for 2 hours at a rotation speed of 50 revolutions per minute.
5. The preparation method of the Al2O3-SiC-C refractory castable according to claim 1, characterized in that, The said step S5 includes the following steps: S5-1 By adjusting the temperature range in the reaction conditions, including the temperature rise rate and heating duration, to precisely control the wafer size, morphology, and distribution: When slowly heating at 5 °C / min, with a relatively low heating temperature of 1450 °C and a short heating duration of 1 h, the resulting wafer has a relatively small thickness size of 100 nm to 300 nm and a uniform distribution; when quickly heating at 10 °C / min, with a relatively high heating temperature of 1600 °C and a long heating duration of 3 h, the resulting wafer has a relatively large thickness size of 300 nm to 500 nm and local agglomeration.
6. The preparation method of the Al2O3-SiC-C refractory castable according to claim 1, characterized in that, The said step S5 includes the following steps: S5-2 By adjusting the raw material ratio in step S1 to precisely control the wafer size, morphology, and distribution: Under the condition of keeping the ratios of other raw materials unchanged, increasing the ratio of aluminum fluoride by 2 to 10 wt.% increases the number of wafers, with no obvious change in size and morphology; keeping the aluminum fluoride unchanged and simultaneously increasing the ratios of aluminum powder, silicon powder, and carbonaceous raw materials by 2 to 5 wt.% increases the number of wafers, with no obvious change in size and morphology; keeping other raw materials unchanged and increasing the silicon carbide by 5 to 15 wt.% promotes the uniform distribution of wafers, with no obvious change in size and morphology.
7. An Al2O3-SiC-C refractory castable, characterized in that, It is prepared by the method according to any one of claims 1 to 6.