A high-strength refractory material for local rapid repair and its preparation method and application method

Abstract

The present invention relates to a high-strength refractory material for local rapid repair, and a preparation method and an application method thereof. The high-strength refractory material comprises the following materials in weight percentage: 60-70% high-alumina bauxite, 5-15% corundum, 1-10% α-Al2O3 fine powder, 1-4% hardener, 1-5% sintering agent, 1-5% explosion-proof agent, and 5-10% aluminum dihydrogen phosphate powder; wherein the sintering agent is boron phosphate and / or boron sulfate. The repair material of the present invention can be used to conveniently repair vulnerable parts of aluminum processing reverberatory furnaces by applying or other methods, has excellent bonding performance with the main body, and simultaneously has excellent strength and non-wetting performance by aluminum liquid. The excellent comprehensive performance solves the technical problem of difficult repair of vulnerable parts of reverberatory furnace refractory materials currently on the market.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory casting materials, and in particular to a high-strength refractory material for local rapid repair and a preparation method and an application method thereof. Background Art

[0002] The reverberatory furnace is a commonly used smelting equipment for aluminum and aluminum alloy production. During the reverberatory furnace production process, due to frequent slagging operations, the refractory materials at the furnace threshold and slagging ramp are subjected to alternating hot and cold temperatures, mechanical impact, and erosion and penetration by molten aluminum and various additives, making them vulnerable areas. Traditionally, different refractory materials are used for these two areas: the ramp uses the same non-stick aluminum castable as the furnace floor, while the threshold uses a high-temperature, high-strength, low-cement castable. This compromise is not ideal. When the refractory lining is damaged, the traditional repair method involves shutting down the furnace, allowing the temperature to cool to room temperature, removing the damaged lining, and recasting the lining. The repair material, typically a cement-bonded castable, requires further baking to remove moisture after repair. The entire repair process takes approximately one month, significantly impacting production schedules and wasting energy.

[0003] In addition, since the melting point of aluminum is only 720-760℃, the aluminum processing reverberatory furnace operates in an environment of 1200℃ and below for a long time. Under this temperature condition, the compressive strength of conventional refractory materials is less than half of that of cement-bonded refractory materials, which cannot meet the high strength requirements of the reverberatory furnace threshold and slag slope for refractory materials. Summary of the Invention

[0004] To address the technical issues of difficult repair of vulnerable parts of existing reverberatory furnace refractory materials and the low strength of conventional refractory materials, a high-strength refractory material for rapid local repair, as well as its preparation and application methods, is provided. The repair material of the present invention, applied through methods such as smearing, facilitates the repair of vulnerable parts of reverberatory furnaces. It exhibits excellent bonding properties, combined with excellent strength and resistance to wettability by molten aluminum. These superior overall performance addresses the current technical issues of difficult repair of vulnerable parts of reverberatory furnace refractory materials on the market.

[0005] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A high-strength refractory material for local rapid repair, comprising the following materials in percentage by weight: 60-72% high-alumina bauxite, 5-15% corundum, 1-10% α-Al2O3 fine powder, 1-4% hardener, 1-5% sintering agent, 0.1-0.2% explosion-proof agent, and 5-10% aluminum dihydrogen phosphate powder;

[0007] The sintering agent is boron phosphate powder and / or boron sulfate powder.

[0008] Furthermore, the alumina content in the high-alumina bauxite is ≥85wt%, and the particle size range of the high-alumina bauxite is selected from 1-3mm, or 3-5mm, or 5-8mm, or a combination of these three particle sizes.

[0009] Furthermore, the corundum is white corundum or plate-shaped corundum, and the particle size range of the corundum is selected from a combination of 1.0-0 mm and 0.075-0.1 mm, wherein the corundum with a particle size range of 1.0-0 mm accounts for 20-30% of the total weight of the corundum used.

[0010] Furthermore, the α-Al2O3 fine powder is an active α-Al2O3 fine powder with a bimodal distribution of particle sizes of 1.5-2.5 μm and 11-15 μm.

[0011] Furthermore, the hardener is a composite of pure calcium aluminate cement (CA-70) and fused magnesia (325 mesh), and the mass ratio of the pure calcium aluminate cement to the fused magnesia is 2-5:1.

[0012] Furthermore, the explosion-proof agent is selected from a combination of basic aluminum lactate and short-cut polyacrylonitrile fibers, wherein the short-cut polyacrylonitrile fibers have a diameter of 5-10 μm and a length of 1-5 mm; and the mass ratio of the basic aluminum lactate to the short-cut polyacrylonitrile fibers is 6-8:1.

[0013] The method for preparing the high-strength refractory material for local rapid repair comprises the following steps:

[0014] Place high-alumina bauxite, corundum, α-Al2O3 powder and aluminum dihydrogen phosphate powder in a mixer and premix for 3-5 minutes to obtain premix A;

[0015] Premix the hardener, sintering agent and explosion-proof agent for 5-10 minutes, and check the dispersion of the explosion-proof agent. If agglomeration is found, continue to extend the mixing time until no agglomeration occurs, thereby obtaining premix B.

[0016] The premix A and the premix B are placed in a forced mixer and mixed for 5-10 minutes. After being mixed evenly, the premix A and the premix B are discharged and sealed in a kraft paper bag with a waterproof film.

[0017] The application method of the high-strength refractory material for local rapid repair is to clean the part to be repaired of the aluminum processing reverberatory furnace, mainly to clean the residual aluminum, residual refractory materials, etc., and to support the formwork with wooden formwork as needed. The evenly mixed high-strength refractory material is mixed with water to form a mud material, which is applied to the part to be repaired by smearing, pouring, spraying, etc., and naturally cured. If wooden formwork is used, pouring construction is selected, and the wooden formwork is removed 6-8 hours after pouring to complete the construction.

[0018] Beneficial technical effects:

[0019] Under the condition of adding water, the high-strength refractory material for repair of the present invention is given a certain initial demoulding strength by the reaction of phosphate (aluminum dihydrogen phosphate and boron phosphate in the sintering agent) with the hardener, among which the reaction of fused magnesia with phosphate is more intense, and its addition amount needs to be precisely controlled. Within the scope of the present invention, it can be ensured that the refractory material for repair has a reasonable hardening time and strong workability; in addition, at room temperature, the reaction of phosphate with the hardener is an exothermic reaction, thereby providing the heat required for the decomposition of the explosion-proof agent basic aluminum lactate, forming a channel for baking and draining the refractory material, and improving the permeability and anti-burst performance of the material; in addition, the combination of the present invention can reduce the formation of low-melting Mg3(PO4)2, which will cause the high-temperature resistance of the material to decrease; during the baking process, when the temperature is raised to 1000°C or above, in addition to reacting with the hardener to form phosphates of Ca and Mg, the phosphate will also react with Al2O3 to form AlPO4 crystal phase, while gradually discharging water, playing a bonding role, so that the refractory material has a certain medium and low temperature strength;

[0020] The present invention introduces boron phosphate and boron sulfate sintering agents to lower the sintering temperature of the various phosphates generated above, allowing the crystalline phase, which originally transforms at 1200°C or above, to transform into a liquid phase at as low as 800-1000°C, thereby accelerating the low-temperature sintering of the material. This allows the refractory material to achieve a higher strength similar to that of cement-bonded refractory materials, thus meeting the requirements of the aluminum processing industry. Compared with cement-bonded systems, the refractory material system of the present invention discharges water more evenly during the heating process.

[0021] The present invention adds the explosion-proof agent basic aluminum lactate. During the hardening process of the phosphate-bonded refractory material, the magnesia sand reacts violently with the binder, releasing a large amount of heat. The temperature of the refractory material body reaches above 50°C, and the high temperature promotes the in-situ gelation of the basic aluminum lactate, forming a network of fine cracks in the matrix, thereby improving the low-temperature air permeability and anti-burst properties of the material. The chopped polyacrylonitrile fiber is an organic fiber and gradually decomposes into carbon fibers at high temperature. The decomposition process provides a channel for drainage of the refractory material, thereby making the refractory material have higher strength and improving the anti-burst property of the refractory material at high temperature. The refractory material is heated and baked at a rate of 50°C / min without bursting, thereby greatly shortening the oven time and reducing energy consumption. In addition, the formation of the carbon fibers is conducive to improving the high-temperature toughness and resistance to aluminum liquid corrosion of the material.

[0022] The present invention provides a quick-repair high-strength refractory material. On the one hand, through the reaction of a phosphate binder with a refractory lining, it has good bonding strength with the lining and will not peel off from the substrate during the baking process. On the other hand, phosphate is an excellent aluminum non-wetting agent. Compared with commonly used non-wetting agents such as barium salts and fluorides, it is easy to decompose at high temperatures and has a higher usable temperature. In addition, through the introduction of a composite explosion-proof agent, the material's anti-explosion performance in the low and medium temperature stages is improved, and rapid re-furnace heating and baking are achieved. At the same time, the introduction of a sintering agent makes the material's compressive strength and flexural strength at medium and low temperatures of 800-1000°C close to the level of low-cement castables. Taking into account the above properties, the refractory material can meet the requirements of the operating conditions. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. Technology and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and methods should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments can have different values.

[0025] In the following examples, experimental methods without specific conditions are generally measured according to national standards. If there are no corresponding national standards, they are measured according to the general international standards or the standards proposed by relevant companies. Unless otherwise stated, all parts are by weight and all percentages are by weight.

[0026] Example 1

[0027] A high-strength refractory material for local rapid repair, comprising the following materials in percentage by weight: 67.85% high-alumina bauxite, 12% corundum, 7% α-Al2O3 fine powder, 3% hardener, 3% sintering agent, 0.15% explosion-proof agent, and 7% aluminum dihydrogen phosphate powder;

[0028] The sintering agent is boron phosphate powder and boron sulfate powder in a mass ratio of 2:1;

[0029] The alumina content in the high-alumina bauxite is ≥85wt%, the particle size range is selected from a combination of 1-3mm and 5-8mm, and the mass ratio of the high-alumina bauxite with a particle size of 1-3mm to the high-alumina bauxite with a particle size of 5-8mm is 3:2;

[0030] The corundum is white corundum, which is a combination of white corundum with a particle size of 1.0-0 mm and white corundum with a particle size of 0.075-0.1 mm, wherein the white corundum with a particle size range of 1.0-0 mm accounts for 30% of the total weight of the corundum used;

[0031] The α-Al2O3 powder is an active α-Al2O3 powder with a bimodal distribution of particle sizes of 2.5 μm and 12 μm;

[0032] The hardener is a composite of pure calcium aluminate cement (CA-70) and fused magnesia (325 mesh), with the mass ratio of pure calcium aluminate cement to fused magnesia being 2:1.

[0033] The explosion-proof agent is a combination of basic aluminum lactate and short-cut polyacrylonitrile fiber. The mass ratio of basic aluminum lactate to short-cut polyacrylonitrile fiber is 8:1. The diameter of the short-cut polyacrylonitrile fiber is 5-10 μm and the length is 1-5 mm.

[0034] The method for preparing the high-strength refractory material for local rapid repair comprises the following steps:

[0035] Place high-alumina bauxite, corundum, α-Al2O3 powder and aluminum dihydrogen phosphate powder in a mixer and premix for 4 minutes to obtain premix A;

[0036] Premix the hardener, sintering agent and explosion-proof agent for 8 minutes, and check the dispersion of the explosion-proof agent. If agglomeration is found, continue to extend the mixing time until no agglomeration occurs, thereby obtaining premix B.

[0037] The premix A and the premix B were placed in a forced mixer and mixed for 8 minutes. After being mixed evenly, the premix A and the premix B were discharged and sealed in a kraft paper bag with a waterproof film.

[0038] The application method of the above-mentioned high-strength refractory materials for local rapid repair is as follows: clean the part to be repaired of the aluminum processing reverberatory furnace, mainly clean the residual aluminum, residual refractory materials, etc., and use wooden formwork as needed. Mix the above-mentioned evenly mixed high-strength refractory materials with water to form mud, and apply it to the part to be repaired by smearing, pouring, spraying, etc., and naturally maintain it; if wooden formwork is used, choose pouring construction, remove the wooden formwork 6-8 hours after pouring, and complete the construction.

[0039] Example 2

[0040] A high-strength refractory material for local rapid repair, comprising the following materials in percentage by weight: 64.85% high-alumina bauxite, 15% corundum, 10% α-Al2O3 fine powder, 4% hardener, 1% sintering agent, 0.15% explosion-proof agent, and 5% aluminum dihydrogen phosphate powder;

[0041] The sintering agent is boron phosphate powder and boron sulfate powder in a mass ratio of 2:1;

[0042] The alumina content in the high-alumina bauxite is ≥85wt%, the particle size range is selected from a combination of 1-3mm and 5-8mm, and the mass ratio of the high-alumina bauxite with a particle size of 1-3mm to the high-alumina bauxite with a particle size of 5-8mm is 3:2;

[0043] The corundum is white corundum, which is a combination of white corundum with a particle size of 1.0-0 mm and white corundum with a particle size of 0.075-0.1 mm, wherein the white corundum with a particle size range of 1.0-0 mm accounts for 25% of the total weight of the corundum used;

[0044] The α-Al2O3 powder is an active α-Al2O3 powder with a bimodal distribution of particle sizes of 2.5 μm and 12 μm;

[0045] The hardener is a composite of pure calcium aluminate cement (CA-70) and fused magnesia (325 mesh), with the mass ratio of pure calcium aluminate cement to fused magnesia being 3:1.

[0046] The explosion-proof agent is a combination of basic aluminum lactate and short-cut polyacrylonitrile fiber. The mass ratio of basic aluminum lactate to short-cut polyacrylonitrile fiber is 6:1. The diameter of the short-cut polyacrylonitrile fiber is 5-10 μm and the length is 1-5 mm.

[0047] The method for preparing the high-strength refractory material for local rapid repair comprises the following steps:

[0048] Place high-alumina bauxite, corundum, α-Al2O3 powder and aluminum dihydrogen phosphate powder in a mixer and premix for 3 minutes to obtain premix A;

[0049] Premix the hardener, sintering agent and explosion-proof agent for 10 minutes, and check the dispersion of the explosion-proof agent. If agglomeration is found, continue to extend the mixing time until no agglomeration occurs, thereby obtaining premix B.

[0050] The premix A and the premix B were placed in a forced mixer and mixed for 10 minutes. After being mixed evenly, the premix A and the premix B were discharged and sealed in a kraft paper bag with a waterproof film.

[0051] The application method of the above-mentioned high-strength refractory materials for local rapid repair is as follows: clean the part to be repaired of the aluminum processing reverberatory furnace, mainly clean the residual aluminum, residual refractory materials, etc., and use wooden formwork as needed. Mix the above-mentioned evenly mixed high-strength refractory materials with water to form mud, and apply it to the part to be repaired by smearing, pouring, spraying, etc., and naturally maintain it; if wooden formwork is used, choose pouring construction, remove the wooden formwork 6-8 hours after pouring, and complete the construction.

[0052] Example 3

[0053] A high-strength refractory material for local rapid repair, comprising the following materials in percentage by weight: 70.8% high-alumina bauxite, 8% corundum, 4% α-Al2O3 fine powder, 2% hardener, 5% sintering agent, 0.2% explosion-proof agent, and 10% aluminum dihydrogen phosphate powder;

[0054] The sintering agent is boron phosphate powder and boron sulfate powder in a mass ratio of 2:1;

[0055] The alumina content in the high-alumina bauxite is ≥85wt%, the particle size range is selected from a combination of 1-3mm and 5-8mm, and the mass ratio of the high-alumina bauxite with a particle size of 1-3mm to the high-alumina bauxite with a particle size of 5-8mm is 3:2;

[0056] The corundum is white corundum, which is a combination of white corundum with a particle size of 1.0-0 mm and white corundum with a particle size of 0.075-0.1 mm, wherein the white corundum with a particle size range of 1.0-0 mm accounts for 20% of the total weight of the corundum used;

[0057] The α-Al2O3 powder is an active α-Al2O3 powder with a bimodal distribution of particle sizes of 2.5 μm and 12 μm;

[0058] The hardener is a composite of pure calcium aluminate cement (CA-70) and fused magnesia (325 mesh), with the mass ratio of pure calcium aluminate cement to fused magnesia being 4:1.

[0059] The explosion-proof agent is a combination of basic aluminum lactate and short-cut polyacrylonitrile fiber. The mass ratio of basic aluminum lactate to short-cut polyacrylonitrile fiber is 7:1. The diameter of the short-cut polyacrylonitrile fiber is 5-10 μm and the length is 1-5 mm.

[0060] The method for preparing the high-strength refractory material for local rapid repair comprises the following steps:

[0061] Place high-alumina bauxite, corundum, α-Al2O3 powder and aluminum dihydrogen phosphate powder in a mixer and premix for 3 minutes to obtain premix A;

[0062] Premix the hardener, sintering agent and explosion-proof agent for 10 minutes, and check the dispersion of the explosion-proof agent. If agglomeration is found, continue to extend the mixing time until no agglomeration occurs, thereby obtaining premix B.

[0063] The premix A and the premix B were placed in a forced mixer and mixed for 10 minutes. After being mixed evenly, the premix A and the premix B were discharged and sealed in a kraft paper bag with a waterproof film.

[0064] The application method of the above-mentioned high-strength refractory materials for local rapid repair is as follows: clean the part to be repaired of the aluminum processing reverberatory furnace, mainly clean the residual aluminum, residual refractory materials, etc., and use wooden formwork as needed. Mix the above-mentioned evenly mixed high-strength refractory materials with water to form mud, and apply it to the part to be repaired by smearing, pouring, spraying, etc., and naturally maintain it; if wooden formwork is used, choose pouring construction, remove the wooden formwork 6-8 hours after pouring, and complete the construction.

[0065] Comparative Example 1

[0066] The formula of the high-strength refractory material of this comparative example is the same as that of Example 1, except that no sintering agent is present.

[0067] Comparative Example 2

[0068] The formula, preparation method and application method of the high-strength refractory material of this comparative example are the same as those of Example 1, except that a single sintering agent, boron phosphate powder, is used.

[0069] Comparative Example 3

[0070] The formula, preparation method and application method of the high-strength refractory material of this comparative example are the same as those of Example 1, except that no explosion-proof agent is present.

[0071] Comparative Example 4

[0072] The formula, preparation method and application method of the high-strength refractory material of this comparative example are the same as those of Example 1, except that a single hardener, fused magnesia, is used.

[0073] Comparative Example 5

[0074] The formula, preparation method and application method of the high-strength refractory material of this comparative example are the same as those of Example 1, except that the α-Al2O3 micropowder uses activated alumina with a single-peak distribution of particle size of 2.5 μm.

[0075] The above materials were tested for performance, and the test results are shown in Table 1. Resistance to aluminum molten infiltration: According to Alcoa standard test methods, under test conditions of 1000°C × 72h, the material's resistance to infiltration by 7075 aluminum alloy molten liquid was tested. Cross-section analysis showed excellent performance, reaching the GOOD level.

[0076] Table 1 Performance test results

[0077]

[0078] As shown in Table 1, by comparing Example 1, Comparative Example 1 and Comparative Example 2, the composite sintering agent used in Example 1 can significantly improve the flexural strength and compressive strength of the material, and the effect of the composite sintering agent is better than that of a single sintering agent, especially the improvement effect of the high-temperature compressive strength is better. It can be seen from Example 1 and Comparative Example 4 that the addition amount of the hardener magnesia should be properly controlled. On the one hand, the material has sufficient construction time, and on the other hand, it is ensured that the material has excellent high-temperature resistance. Since the low-temperature strength of the phosphate-bound material is low, the sintering agent does not play a role in the low-temperature stage. In order to avoid the risk of bursting of the material during baking, it is necessary to add an explosion-proof agent. In addition, thanks to the excellent particle size distribution of bimodal alumina, which fills the gaps and improves the sintering performance, it has better high-temperature flexural and compressive strength than unimodal distribution alumina.

[0079] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A high-strength refractory material for local rapid repair, characterized in that: The invention comprises the following materials in percentage by weight: 60-70.8% of high-alumina bauxite, 5-15% of corundum, 4-10% of α-Al2O3 micro powder, 2-4% of hardener, 1-5% of sintering agent, 0.1-0.2% of explosion-proof agent, and 5-10% of aluminum dihydrogen phosphate powder; wherein the sintering agent is boron phosphate powder; The high-alumina bauxite has an alumina content of ≥85 wt %, a particle size range selected from a combination of 1-3 mm and 5-8 mm, and a mass ratio of 1-3 mm high-alumina bauxite to 5-8 mm high-alumina bauxite is 3:2; The α-Al2O3 fine powder is active α-Al2O3 with a bimodal distribution of particle sizes of 2.5 μm and 12 μm; The hardener is a composite of pure calcium aluminate cement and fused magnesia, and the mass ratio of the pure calcium aluminate cement to the fused magnesia is 2-5:1; The explosion-proof agent is basic aluminum lactate and short-cut polyacrylonitrile fibers, wherein the short-cut polyacrylonitrile fibers have a diameter of 5-10 μm and a length of 1-5 mm; the mass ratio of the basic aluminum lactate to the short-cut polyacrylonitrile fibers is 6-8:

1.

2. The high-strength refractory material for local rapid repair according to claim 1, characterized in that: The corundum is white corundum or plate-shaped corundum, and the particle size range of the corundum is selected from a combination of 1.0-0 mm and 0.075-0.1 mm, wherein the corundum with a particle size range of 1.0-0 mm accounts for 20-30% of the total weight of the corundum used.

3. A method for preparing a high-strength refractory material for local rapid repair according to any one of claims 1-2, characterized in that: The steps include: Place high-alumina bauxite, corundum, α-Al2O3 powder and aluminum dihydrogen phosphate powder in a mixer and premix for 3-5 minutes to obtain premix A; Premix the hardener, sintering agent and explosion-proof agent for 5-10 minutes, and check the dispersion of the explosion-proof agent. If agglomeration is found, continue to extend the mixing time until no agglomeration occurs, thereby obtaining premix B. The premix A and the premix B are placed in a forced mixer and mixed for 5-10 minutes. After being mixed evenly, the premix A and the premix B are discharged and sealed in a kraft paper bag with a waterproof film.

4. A method for applying the high-strength refractory material for local rapid repair according to any one of claims 1-2, characterized in that: Clean the part of the aluminum processing reverberatory furnace to be repaired, support it with wooden formwork as needed, mix the evenly mixed high-strength refractory material with water to form mud, and apply it to the part to be repaired for natural curing.

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