Silicon carbide-magnesia-alumina spinel refractory article and method of making

Abstract

The present application belongs to the technical field of new refractory material, and particularly relates to a silicon carbide-magnesia-alumina spinel refractory product and a preparation method thereof. The raw material composition of the silicon carbide-magnesia-alumina spinel refractory product comprises, in terms of mass percentage, 50-70% of silicon carbide with a particle size of 0.1-3 mm, 10-30% of magnesia-alumina spinel powder with a particle size of 0.045-1 mm, 1-10% of a binding agent, 1-10% of alumina micropowder, 1-10% of passivated aluminum powder and 0.1-10% of an additive, and 0.1-1% of a water reducing agent is additionally added to the total mass of the above raw materials; the binding agent is light-burned magnesia powder; and the binding agent is light-burned magnesia powder. The silicon carbide-magnesia-alumina spinel refractory product prepared by the present application has high strength, good resistance to slag erosion and penetration, and also has the advantages of convenient construction, long construction time during pouring, low production energy consumption and the like.

Description

Technical Field

[0001] This invention belongs to the field of new refractory materials technology, specifically relating to a silicon carbide-magnesium aluminum spinel refractory product and its preparation method. Background Technology

[0002] Looking at the structure of my country's fossil energy reserves, coal accounts for over 90% of the total proven fossil energy resources, while oil and natural gas combined account for less than 10%. Currently, direct combustion and thermal power generation remain the main methods of coal utilization in my country, which leads to problems such as low energy efficiency and serious environmental pollution. Therefore, achieving clean and efficient utilization of coal is of great significance.

[0003] Coal gasification is the most effective means of clean and efficient utilization of coal, and water-coal slurry gasification technology, as a typical representative process, is the most widely used in China. Refractory materials used in water-coal slurry gasifiers face harsh working environments such as high temperatures (1300–1600℃), high pressures (2–6.5MPa), slag erosion, thermal erosion from gas flow, and rapid temperature fluctuations. Therefore, the refractory materials used need to possess good high-temperature mechanical properties, thermal shock resistance, and resistance to molten slag erosion and permeability. Currently, the most commonly used refractory material for gasifiers in China is chromium-aluminum-zirconium (Cr2O3-Al2O3-ZrO2) brick, whose raw material and main component is Cr2O3. However, chromium-containing refractory materials have some drawbacks: on the one hand, my country's chromium resources are scarce, resulting in high raw material costs; on the other hand, there is the problem of chromium pollution, with potential chromium contamination during preparation, use, and post-use. 6+ It poses a threat to human health and the environment. Therefore, the development of chromium-free refractory materials for coal-water slurry gasification furnaces is urgently needed.

[0004] Currently, the chromium-free treatment of refractory materials for coal-water slurry gasification furnaces is mostly in the laboratory stage, with material selection largely focusing on designing the chemical composition of the material for coal slag erosion resistance tests. Research has shown that oxide-non-oxide composite materials possess superior resistance to coal slag erosion and impermeability, representing the future direction for chromium-free refractory materials used in coal gasification. Based on this, patent (CN 202010646418.5) discloses a silicon carbide-magnesium aluminum spinel-aluminum composite refractory material. This material uses silicon carbide particles as aggregate, magnesium aluminum spinel fine powder or micro powder as matrix, and coated aluminum powder is added to the matrix. A resin-based binder is used, and the material is pressed into a green body and then fired into refractory bricks at 1500–1600℃ in a carbonized atmosphere. The silicon carbide-magnesium aluminum spinel-aluminum composite refractory material described herein has good resistance to slag erosion and penetration. However, compression molding has significant limitations on the size and shape of the product, only allowing the production of small-sized, simple-shaped items. Furthermore, the strength of the compressed green body is low when it is not dried, and the skin and edges are prone to peeling off, failing to guarantee the integrity of the green body. In addition, compression molding is labor-intensive, energy-intensive, and has low construction efficiency, which is not conducive to automated production. Summary of the Invention

[0005] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a silicon carbide-magnesium aluminum spinel refractory product and its preparation method.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0007] The first aspect of this invention provides a silicon carbide-magnesium aluminum spinel refractory product, wherein the raw material composition of the silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, is: 50%-70% silicon carbide with a particle size of 0.1-3 mm, 10%-30% magnesium aluminum spinel powder with a particle size of 0.045-1 mm, 1%-10% binder, 1%-10% alumina micro powder, 1%-10% passivated metallic aluminum powder, and 0.1%-10% additives, plus a water-reducing agent accounting for 0.1%-1% of the total mass of the above raw materials; the binder is lightly calcined magnesium oxide powder.

[0008] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory product, preferably, by mass percentage, the raw material composition of the silicon carbide-magnesium aluminum spinel refractory product is: 63% silicon carbide with a particle size of 0.1-3mm, 18.2% magnesium aluminum spinel powder with a particle size of 0.045-1mm, 4% binder, 5% alumina micro powder, 9% passivated aluminum powder, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials.

[0009] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory product, preferably, the method for preparing the passivated aluminum powder is as follows: calcining aluminum powder at 500-620°C for 1-20 hours, and then cooling to obtain the passivated aluminum powder.

[0010] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory product, preferably, the additive is lactate.

[0011] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory product, preferably, the lactate is at least one of aluminum lactate and magnesium lactate; more preferably, the lactate is aluminum lactate.

[0012] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory products, preferably, the alumina micro powder is calcined alumina micro powder or active alumina micro powder; more preferably, the alumina micro powder is active alumina micro powder; most preferably, the active alumina micro powder is bimodal active alumina micro powder.

[0013] According to the aforementioned silicon carbide-magnesium aluminum spinel refractory products, preferably, the silicon carbide is fused silicon carbide. Fused silicon carbide particles have a complete crystal structure, high density, and good resistance to coal slag erosion and oxidation. More preferably, the purity of the fused silicon carbide is ≥98.0%. Because impurities such as SiO2, Fe2O3, Na2O, and K2O in silicon carbide raw materials can form low-melting-point substances at high temperatures, reducing the high-temperature mechanical properties and slag erosion resistance of the refractory products, this invention controls the purity of the fused silicon carbide to ≥98.0%. At this purity, the content of impurities such as SiO2, Fe2O3, Na2O, and K2O in the fused silicon carbide is very low, effectively reducing the formation of low-melting-point substances during the high-temperature calcination of the castable and reducing the impact of impurities on the high-temperature mechanical properties and slag erosion resistance of the refractory products.

[0014] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory products, preferably, the purity of the magnesium aluminum spinel powder w(Al2O3+MgO) ≥ 99.0%, which ensures that the prepared refractory products have good resistance to coal slag erosion; the mass fraction of Al2O3 in the magnesium aluminum spinel powder ≥ 72.0%, which ensures that the MgO in the raw materials exists in a stable spinel phase and that no low-melting phase (Al2O3+MgO+SiO2) is generated during the firing process.

[0015] According to the above-mentioned silicon carbide-magnesium aluminum spinel refractory product, preferably, the particle size of the passivated aluminum powder is 0.048-0.11 mm, the particle size of the alumina micro powder is 2-4 μm, and the water-reducing agent is a polycarboxylate water-reducing agent or a naphthalene-based water-reducing agent.

[0016] A second aspect of the present invention provides a method for preparing the silicon carbide-magnesium aluminum spinel refractory product described in the first aspect above, comprising the following steps:

[0017] (1) Mix silicon carbide, magnesium aluminum spinel powder, binder, alumina micro powder, passivated aluminum powder, additives and water-reducing agent evenly to obtain a mixture; add water to the mixture and mix evenly to obtain a mud.

[0018] (2) The clay is poured into a mold, cured at room temperature, demolded and dried to obtain a blank;

[0019] (3) The billet is calcined at 1000℃~1600℃ in a nitrogen atmosphere to obtain silicon carbide-magnesium aluminum spinel refractory products.

[0020] According to the above preparation method, preferably, the drying temperature in step (2) is 110°C and the drying time is 24h.

[0021] Compared with the prior art, the positive and beneficial effects achieved by the present invention are as follows:

[0022] (1) The silicon carbide-magnesium aluminum spinel refractory product of the present invention adds passivated aluminum powder to the matrix. During the casting process, on the one hand, the passivation layer on the surface of the passivated aluminum powder can effectively prevent the aluminum powder from reacting with the free water in the casting to generate gas. On the other hand, the aluminum powder and the hydration products of lightly calcined magnesium oxide have a synergistic effect to generate dense magnesium aluminum hydrotalcite, which further prevents the hydration of aluminum powder and avoids the expansion of the billet. Moreover, during the high-temperature calcination process, the aluminum reacts with N2 in the atmosphere in liquid or gaseous form to generate AlN with morphologies such as whiskers, rods, and plates. It forms a firm bond with the matrix at the microscale, thereby improving the bonding strength of the material and improving its resistance to corrosion and thermal shock.

[0023] (2) The present invention calcines aluminum powder at 500-620°C for 1-20 hours, and its surface is oxidized to form a dense aluminum oxide layer. After cooling, passivated aluminum powder is obtained. The passivated aluminum powder has a simple preparation process, a relatively uniform coating layer, and can be mass-produced. At the same time, it can avoid the easy agglomeration of aluminum sol coating, which causes the passivation layer to peel off when broken, thus affecting the passivation effect.

[0024] (3) The present invention uses lightly calcined magnesium oxide powder as a binder to prepare refractory products. At room temperature, lightly calcined magnesium oxide powder generates hydrate [Mg(OH)2] through hydration reaction, which solidifies and hardens to obtain strength. Low-temperature drying can form high bonding strength, thereby providing high demolding and drying strength, avoiding partial peeling and powdering during the storage and transportation of green blanks at room temperature. At high temperature, lightly calcined magnesium oxide powder can react with active alumina micro powder in the matrix to generate magnesium aluminum spinel in situ. The divalent and trivalent ions in the solid solution slag not only improve the bonding strength of the refractory products, but also greatly enhance the refractory products' resistance to slag erosion and penetration. Furthermore, compared to phenolic resin binders, this invention uses lightly calcined magnesia powder as a binder, which avoids the harmful gases and residual carbon produced by the decomposition of phenolic resin during high-temperature calcination. This solves the technical problem that when refractory products using phenolic resin as a binder are calcined at high temperatures, metallic aluminum reacts with the carbon produced by the decomposition of phenolic resin to form Al4C3 (Al4C3 is highly hydrated), leading to cracking and pulverization of the refractory products during storage and use, resulting in scrapping or a significantly reduced service life. Additionally, compared to calcium aluminate cement, a commonly used binder in castables, this invention uses lightly calcined magnesia powder as a binder, which avoids the introduction of CaO into the castable. This solves the technical problem that introducing CaO into the castable when using calcium aluminate cement as a binder reduces the refractory products' resistance to slag erosion and penetration.

[0025] (4) The refractory products of the present invention are prepared by casting. After curing and demolding, the refractory green products have a room temperature flexural strength of 2.9 to 5.9 MPa and a compressive strength of 11.1 to 23.6 MPa, and a high demolding strength. Compared with the silicon carbide-magnesium aluminum spinel shaped products prepared by machine pressing, the present invention can effectively reduce green cracking and improve the yield. Moreover, the casting process is simpler, has higher labor productivity, and is more adaptable to the shape and size of the product than the pressing process, which is conducive to mechanized construction.

[0026] (5) In the preparation process of the silicon carbide-magnesium aluminum spinel refractory products of the present invention, the refractory green blanks are calcined in a nitrogen atmosphere. Compared with a carbon-buried atmosphere, a nitrogen atmosphere can avoid further oxidation of metallic Al, which would result in a thicker passivation layer, making it difficult for molten Al to escape and thus hindering its participation in whisker formation and mechanical property improvement. In addition, the partial pressure of nitrogen atmosphere decreases with increasing heating time under a carbon-buried atmosphere, while the partial pressure of atmosphere in the furnace remains consistent at all stages of heating under a flowing nitrogen atmosphere, which is more conducive to the nitriding reaction of metallic Al.

[0027] (6) The apparent porosity of the silicon carbide-magnesium aluminum spinel refractory product of the present invention after calcination is 18%–22%, and the bulk density is 2.6 g / cm³. 3 ~2.7g / cm 3The room temperature flexural strength reaches 5.4-18.3 MPa, and the room temperature compressive strength reaches 62.0-99.0 MPa. Therefore, the silicon carbide-magnesium aluminum spinel refractory products of the present invention have high strength, good resistance to slag erosion and penetration, and also have the advantages of convenient construction, long construction time during casting, and low production energy consumption.

[0028] (7) The refractory products of the present invention contain additives, preferably lactate. Lactate can make Mg(OH)2 grow uniformly on the surface of MgO particles, thereby preventing the MgO-bonded castable from expanding in volume during curing and drying, and forming cracks in the castable. Attached Figure Description

[0029] Figure 1 The graph shows the volume change test results of green samples prepared using the matrix components of the refractory product formulations in Examples 1-1 and Comparative Examples 1-1.

[0030] Figure 2 The image shown is a secondary electron image obtained by scanning electron microscopy of the refractory product prepared in Example 1 of this invention. Detailed Implementation

[0031] The following embodiments are only for further elaboration of the present invention. It should be noted that all techniques and scientific terms used in this invention, unless otherwise stated, have the same meaning as those in the technical field to which this invention pertains. Experimental methods in the following embodiments that do not specify specific conditions all employ conventional techniques in this technical field or follow the conditions recommended by the manufacturer; reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0033] Example 1: Discussion on the types of metallic aluminum powder

[0034] To investigate the effect of passivation of metallic aluminum powder on the performance of the prepared silicon carbide-magnesium aluminum spinel refractories, Example 1-1 and Comparative Example 1-1 were conducted in this invention. The specific details of Example 1-1 and Comparative Example 1-1 are as follows:

[0035] Example 1-1:

[0036] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 20.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 7% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0037] The specific steps for preparing the above-mentioned silicon carbide-magnesium aluminum spinel refractory products are as follows:

[0038] (1) Mix silicon carbide, magnesium aluminum spinel powder, binder, alumina micro powder, passivated aluminum powder, additives and water-reducing agent evenly to obtain a mixture; add water to the mixture and mix evenly to obtain a mud.

[0039] (2) The clay is poured into a mold, cured at room temperature for 24 hours, then demolded, and then dried at 110°C for 24 hours to obtain a blank.

[0040] (3) The billet is calcined at 1500°C for 5 hours under a flowing nitrogen atmosphere to obtain silicon carbide-magnesium aluminum spinel refractory products.

[0041] Comparative Example 1-1:

[0042] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1-3 mm, 20.2% magnesium aluminum spinel powder with a particle size of 0.045-1 mm, 4% binder, 5% alumina micro powder with a particle size of 2-4 μm, 7% metallic aluminum powder with a particle size of 0.048-0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is polycarboxylate water-reducing agent.

[0043] The specific steps for preparing the above-mentioned silicon carbide-magnesium aluminum spinel refractory products are as follows:

[0044] (1) Mix silicon carbide, magnesium aluminum spinel powder, binder, alumina micro powder, metallic aluminum powder, additives and water reducing agent evenly to obtain a mixture; add water to the mixture and mix evenly to obtain mud;

[0045] (2) The clay is poured into a mold, cured at room temperature for 24 hours, then demolded, and then dried at 110°C for 24 hours to obtain a blank.

[0046] (3) The billet is calcined at 1500°C for 5 hours under a flowing nitrogen atmosphere to obtain silicon carbide-magnesium aluminum spinel refractory products.

[0047] The demolding strength of the billets prepared in Example 1-1 and Comparative Example 1-1 was tested, and the mechanical properties of the silicon carbide-magnesium aluminum spinel refractory products prepared after calcination were also tested. The demolding strength test method was as follows: the strength of the demolded billets was tested according to GB / T3001-2007. The mechanical properties of the calcined billets were tested according to GB / T 3001-2007 and GB / T5702-2008, respectively, for flexural strength and compressive strength of the refractory materials after firing at 1500℃; and according to GB / T2997-2000, for bulk density and apparent porosity of the refractory materials after firing at 1500℃. The demolding strength and mechanical properties of the calcined billets in Example 1-1 and Comparative Example 1-1 are shown in Table 1.

[0048] Table 1 shows the test results of the demolding strength and mechanical properties of the green blanks after calcination in Examples 1-1 and Comparative Example 1-1.

[0049]

[0050] As shown in Table 1, compared with Comparative Example 1-1, the samples prepared in Example 1-1 have higher green body strength, higher post-firing strength, and lower apparent porosity. This is because the green body samples prepared in Comparative Example 1-1 undergo significant volume expansion during curing, which damages the internal structure of the green body and causes obvious cracks on the surface, resulting in poor performance of the products prepared in Comparative Example 1-1. This demonstrates that the use of passivated aluminum powder in this invention can improve the physical properties of silicon carbide-magnesium aluminum spinel refractory products.

[0051] Because aluminum powder reacts with water to generate gas, it causes the castable to expand in volume. To investigate the effect of passivation treatment on the volume expansion of the castable billet, this invention further uses the matrix raw materials from Examples 1-1 and Comparative Examples 1-1 (comprising, by mass percentage, 27% silicon carbide with a particle size of 0.1–0.5 mm, 27.6% magnesium aluminum spinel powder with a particle size of 0.045 mm, 10.8% binder, and alumina with a particle size of 2–4 μm). Green samples were prepared using a mixture of 13.5% micronized aluminum powder, 18.9% passivated aluminum powder with a particle size of 0.048–0.11 mm, and 2.2% additives, plus 0.4% polycarboxylate superplasticizer by mass of the total raw materials. The preparation method for the green samples was as follows: each raw material was weighed according to the above matrix composition and placed in a plastic cup. Water was added and the mixture was stirred evenly. After curing at room temperature for 24 hours, the green samples were obtained. The volume change of the green samples was photographed and recorded. The results of the volume change detection of the green samples are as follows: Figure 1 As shown.

[0052] Depend on Figure 1 It can be seen that, compared with Example 1-1, the green sample prepared in Comparative Example 1-1 experienced severe expansion. This is because the aluminum powder in Comparative Example 1-1 was not passivated, and a large amount of it reacted with water during the casting process, generating a large amount of H2, which led to the expansion of the green body. The matrix sample prepared in Example 1 showed almost no expansion. This indicates that the use of passivated aluminum powder in this invention can reduce the reaction between aluminum powder and water during the casting process, avoid large volume expansion, and thus improve the volume stability of silicon carbide-magnesium aluminum spinel refractory products.

[0053] Example 2: Discussion on the Dosage of Passivating Aluminum Powder

[0054] To investigate the effect of the amount of passivating aluminum powder in refractory products on the properties of the prepared silicon carbide-magnesium aluminum spinel refractory products, Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2 were conducted in this invention. The specific details of Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2 are as follows:

[0055] Example 2-1:

[0056] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 24.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 3% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0057] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0058] Example 2-2:

[0059] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 22.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 5% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0060] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0061] Examples 2-3:

[0062] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 18.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0063] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0064] Comparative Example 2-1:

[0065] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 14.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 13% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is lightly calcined magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0066] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0067] Comparative Example 2-2:

[0068] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 27.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 0% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is aluminum lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0069] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0070] The demolding strength of the refractory product blanks (green blanks) prepared in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2 was tested, and the mechanical properties of the green blanks after calcination were also tested. The test results are shown in Table 2.

[0071] Table 2 shows the test results of the demolding strength and mechanical properties of the green blanks after calcination in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2.

[0072]

[0073] Table 2 shows that with the increase of the amount of passivating aluminum powder added, the physical properties of the prepared silicon carbide-magnesium aluminum spinel refractories, both in the green and after firing, first increase and then decrease. When the amount of passivating aluminum powder added is 9%, the silicon carbide-magnesium aluminum spinel refractories exhibit superior physical properties in both the green and after firing. This indicates that adding 9% passivating aluminum powder is more beneficial for preparing high-performance silicon carbide-magnesium aluminum spinel refractories.

[0074] Example 3: Discussion of Additive Types

[0075] To investigate the effect of different types of additives on the properties of the prepared silicon carbide-magnesium aluminum spinel refractory products, Example 3-1 and Comparative Example 3-1 were conducted in this invention. The specific details of Example 3-1 and Comparative Example 3-1 are as follows:

[0076] Example 3-1:

[0077] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 18.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; wherein the binder is light-burned magnesium oxide powder, the additive is magnesium lactate, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0078] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0079] Comparative Example 3-1:

[0080] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 19% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is light-burned magnesium oxide powder, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0081] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0082] The demolding strength of the refractory product blanks (green blanks) prepared in Example 3-1 and Comparative Example 3-1 was tested, and the mechanical properties of the green blanks after calcination were also tested. The test results are shown in Table 3.

[0083] Table 3 shows the test results of the demolding strength and mechanical properties of the green bodies after calcination in Example 3-1 and Comparative Example 3-1.

[0084]

[0085] As shown in Table 3, the physical properties of the silicon carbide-magnesium aluminum spinel refractory products prepared in Examples 3-1 and 2-3 are similar in both green and fired forms, and are superior to those in Comparative Example 3-1. This is because during the hydration of lightly calcined magnesium oxide, Mg(OH)2 particles of varying sizes are generated on the surface of MgO particles, leading to microcracks in the castable blank, thus resulting in the poorer physical properties of Comparative Example 3-1. This indicates that the addition of lactate is more beneficial for preparing high-performance silicon carbide-magnesium aluminum spinel refractory products.

[0086] Example 4: Experiment exploring the types of binders

[0087] In order to study the effect of binder type on the properties of prepared silicon carbide-magnesium aluminum spinel refractory products, comparative example 4-1 was conducted in this invention. The specific contents of comparative example 4-1 are as follows.

[0088] Comparative Example 4-1:

[0089] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 23.0% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 5% alumina micro powder with a particle size of 2–4 μm, and 9% metallic aluminum powder with a particle size of 0.048–0.11 mm, plus a binder comprising 4% of the total mass of the above raw materials; the binder is phenolic resin.

[0090] The demolding strength of the refractory product blanks (green blanks) prepared in Examples 2-3 and Comparative Example 4-1 was tested, and the mechanical properties of the green blanks after calcination were also tested. The test results are shown in Table 4.

[0091] Table 4 shows the test results of the demolding strength and mechanical properties of the green blanks after calcination in Examples 2-3 and Comparative Example 4-1.

[0092]

[0093] As shown in Table 4, the green strength of Examples 2-3 is significantly higher than that of Comparative Example 4-1, while the physical properties of Example 4-1 after firing at 1500℃ are slightly lower than those of Comparative Example 4-1. This indicates that the silicon carbide-magnesium aluminum spinel refractory products prepared by casting molding using lightly calcined magnesia powder as a binder in this invention have superior green strength, ensuring the integrity of the sample before drying and avoiding partial peeling and pulverization during room temperature storage and transportation. Moreover, when using lightly calcined magnesia powder as a binder, silicon carbide-magnesium aluminum spinel refractory products with good mechanical properties can be prepared by casting molding. Compared with pressing molding, the manufacturing process is simpler, has higher labor productivity, is more adaptable to product shape and size, and is more energy-efficient and environmentally friendly.

[0094] Example 5: Discussion on the Dosage of Binder

[0095] To investigate the effect of binder dosage on the properties of the prepared silicon carbide-magnesium aluminum spinel refractory products, Examples 5-1 to 5-4 were conducted in this invention. The specific details of Examples 5-1 to 5-4 are as follows:

[0096] Example 5-1:

[0097] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 21.8% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 1% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm / μm, and 0.2% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is light-burned magnesium oxide powder, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0098] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0099] Example 5-2:

[0100] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 19.4% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 3% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.6% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is light-burned magnesium oxide powder, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0101] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0102] Example 5-3:

[0103] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 17% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 5% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 1% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is lightly calcined magnesium oxide powder, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0104] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0105] Example 5-4:

[0106] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 14.6% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 7% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 1.4% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is light-burned magnesium oxide powder, and the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0107] The preparation method of the above silicon carbide-magnesium aluminum spinel refractory products is the same as that in Examples 1-1.

[0108] The demolding strength of the refractory product blanks (green blanks) prepared in Examples 5-1 to 5-4 was tested, and the mechanical properties of the green blanks after calcination were also tested. The test results are shown in Table 5.

[0109] Table 5 shows the test results of the demolding strength and mechanical properties of the green blanks after calcination in Examples 5-1 to 5-4.

[0110]

[0111] Table 5 shows that with the increase of the amount of lightly calcined magnesia powder added as a binder, the physical properties of the prepared silicon carbide-magnesia-alumina spinel refractories first increase and then decrease. When the amount of lightly calcined magnesia powder added is 4%, the silicon carbide-magnesia-alumina spinel refractories exhibit superior physical properties in both the green and fired forms. This indicates that adding 4% lightly calcined magnesia powder is more beneficial for preparing high-performance silicon carbide-magnesia-alumina spinel refractories.

[0112] Example 6: Exploration of Calcination Gas Atmosphere

[0113] To investigate the effect of the calcination gas atmosphere on the properties of the prepared silicon carbide-magnesium aluminum spinel refractories, Comparative Example 6-1 was conducted. The specific details of Comparative Example 6-1 are as follows:

[0114] Comparative Example 6-1:

[0115] A silicon carbide-magnesium aluminum spinel refractory product, by mass percentage, comprises: 63% silicon carbide with a particle size of 0.1–3 mm, 18.2% magnesium aluminum spinel powder with a particle size of 0.045–1 mm, 4% binder, 5% alumina micro powder with a particle size of 2–4 μm, 9% passivated aluminum metal powder with a particle size of 0.048–0.11 mm, and 0.8% additives, plus a water-reducing agent accounting for 0.15% of the total mass of the above raw materials; the binder is light-burned magnesium oxide powder; the water-reducing agent is a polycarboxylate water-reducing agent; the passivated aluminum metal powder is prepared by calcining aluminum metal powder at 500–620℃ for 1–20 h, and then cooling to obtain passivated aluminum metal powder.

[0116] The preparation method of the silicon carbide-magnesium aluminum spinel refractory product in this embodiment includes the following specific steps:

[0117] (1) Mix silicon carbide, magnesium aluminum spinel powder, binder, alumina micro powder, passivated aluminum powder, additives and water-reducing agent evenly to obtain a mixture; add water to the mixture and mix evenly to obtain a mud.

[0118] (2) The clay is poured into a mold, cured at room temperature for 24 hours, then demolded, and then dried at 110°C for 24 hours to obtain a blank.

[0119] (3) The billet is calcined at 1500°C for 5 hours in a flowing carbon atmosphere to obtain silicon carbide-magnesium aluminum spinel refractory products.

[0120] The demolding strength of the refractory product blanks (green blanks) prepared in Examples 2-3 and Comparative Example 6-1 was tested, and the mechanical properties of the green blanks after calcination were also tested. The test results are shown in Table 6.

[0121] Table 6 shows the test results of the demolding strength and mechanical properties of the green blanks after calcination in Examples 2-3 and Comparative Example 6-1.

[0122]

[0123] As shown in Table 6, the physical properties of Examples 2-3 after firing at 1500℃ are significantly higher than those of Comparative Example 6-1. This indicates that a flowing nitrogen atmosphere is more conducive to the preparation of high-performance silicon carbide-magnesium aluminum spinel refractory products. The reason is that the partial pressure of the atmosphere in the furnace remains consistent throughout the heating process under a flowing nitrogen atmosphere, which is more conducive to the nitriding reaction of metallic Al powder, generating AlN with whisker-like, rod-like, and plate-like morphologies. The silicon carbide-magnesium aluminum spinel refractory products prepared in Examples 2-3 of this invention were analyzed using scanning electron microscopy, and their fracture microstructure is shown below. Figure 2 As shown. By Figure 2 It can be seen that a large number of sheet-like AlN are interspersed in the matrix around the aluminum shell, forming a strong bond with the matrix at the microscale, thereby improving the bonding strength of the material and thus improving the physical properties of the refractory products.

[0124] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may use the above technical content as inspiration to make changes or modifications. These are equivalent embodiments with variations. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical concept of the present invention still fall within the protection scope of the claims of the present invention.

Claims

1. A silicon carbide-magnesio-alumina spinel refractory article, characterized in that, The raw material composition of the silicon carbide-magnesio-alumina spinel refractory product by mass percentage comprises: 50-70% of silicon carbide with a particle size of 0.1-3 mm, 10-30% of magnesio-alumina spinel powder with a particle size of 0.045-1 mm, 1-10% of a binder, 1-10% of alumina micropowder, 1-10% of passivated aluminum powder and 0.1-10% of an additive, plus 0.1-1% of a water reducing agent based on the total mass of the above raw materials; the binder is light-burned magnesium oxide powder; the passivated aluminum powder is prepared by calcining aluminum powder at 500-620 ℃ for 1-20 h and then cooling; the additive is a lactate; and the silicon carbide-magnesio-alumina spinel refractory product is prepared by calcining at 1000-1600 ℃ under a nitrogen atmosphere.

2. The silicon carbide-magnesio-alumina spinel refractory article of claim 1, wherein, The lactate is at least one of aluminum lactate and magnesium lactate.

3. The silicon carbide-magnesio-alumina spinel refractory article of claim 2, wherein, The alumina micropowder is calcined alumina micropowder or active alumina micropowder.

4. The silicon carbide-magnesio-alumina spinel refractory article of claim 3, wherein, The silicon carbide is fused silicon carbide with a purity of ≥98.0%; the magnesio-alumina spinel powder has a purity of ≥99.0% and a mass fraction of Al2O3 of ≥72.0%.

5. The silicon carbide-magnesio-alumina spinel refractory article of claim 4, wherein, The passivated aluminum powder has a particle size of 0.048-0.11 mm, the alumina micropowder has a particle size of 2-4 μm, and the water reducing agent is polycarboxylic acid water reducing agent or naphthalene water reducing agent.

6. A method of making a silicon carbide-magnesio-alumina spinel refractory article according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) uniformly mixing silicon carbide, magnesio-alumina spinel powder, a binder, alumina micropowder, passivated aluminum powder, an additive and a water reducing agent to obtain a mixture; adding water to the mixture and uniformly mixing to obtain a mud; (2) pouring the mud into a mold, demolding and drying after curing at room temperature to obtain a blank; (3) calcining the blank at 1000-1600 ℃ under a nitrogen atmosphere to obtain a silicon carbide-magnesio-alumina spinel refractory product.

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