Thermal-state repairing material for aluminum industrial furnace and preparation method of thermal-state repairing material

Abstract

The invention relates to the technical field of industrial furnace repairing, and particularly discloses a hot-state repairing material for an aluminum industrial furnace and a preparation method thereof.Sodium metasilicate pentahydrate and borax are introduced as composite additives, and the repairing material can be rapidly spread in a repairing area by combining the self-lubricating effect of lamellar graphite; polypropylene short fibers are introduced to form a net-shaped structure, cracks are effectively plugged, and meanwhile dry powder is prevented from leaking into a hearth to pollute molten aluminum; pretreated secondary aluminum ash fine powder and silica powder are introduced, pores are filled, meanwhile, a stable mullite phase is generated at a high temperature, and the strength of the sintered repairing material is improved; the silicon oxynitride is also introduced, so that the thermal conductivity is good, the thermal expansion coefficient is small, and the thermal stability and the oxidation resistance of the repair material after sintering are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial furnace repair, and specifically to a hot repair material for aluminum industrial furnaces and a preparation method thereof. Background Art

[0002] The reverberatory furnace is a key thermal equipment in the aluminum melting and casting process. As the furnace lining refractory material of the aluminum reverberatory furnace usually has a long service life, the furnace roof lining of the reverberatory furnace is generally a flat-top structure and is spliced by a form of sectional pouring. During the long-term operation in a high-temperature environment, due to mechanical collisions during the feeding and slag skimming processes and thermal shocks of alternating heat and cold, the furnace roof lining often peels and chips at the splicing seams, resulting in flames passing through the furnace lining and the steel structure of the furnace shell. The traditional maintenance method is to break the old furnace lining after stopping the furnace, re-pour and repair it, and then put it into production after baking. The maintenance cycle is long and the cost is high.

[0003] Checking the existing patented technology "CN115286403" (a heat-receiving self-flowing rapid repair dry powder material and a preparation method thereof), the patented heat-receiving self-flowing repair dry powder material prepared from bauxite clinker, alumina micro-powder, potassium silicate powder, potassium alum, silica powder, zircon corundum powder and a composite phosphate binder can achieve hot repair without stopping the furnace. However, on the one hand, the use temperature of the repair material is required to be above 400°C. When repairing the furnace roof, the insulation layer material needs to be removed first, and the operation risk at a high working temperature is high. On the other hand, additives such as nitro-naphthalene and potassium alum used in the formula will decompose when heated to produce harmful gases, which does not conform to green production. Summary of the Invention

[0004] The purpose of the present invention is to provide a hot repair material for aluminum industrial furnaces and a preparation method thereof, so as to solve the problem of difficult maintenance caused by local damage of the furnace lining of the aluminum melting and casting reverberatory furnace under high-temperature working conditions.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A hot repair material for aluminum industrial furnaces, calculated by mass fraction, contains 30-60wt% of mullite aggregate, 10-20wt% of pretreated secondary aluminum ash, 5-15wt% of a composite additive, 3-8wt% of aluminum dihydrogen phosphate powder, 2-6wt% of silica powder, 0.2-2wt% of flake graphite and 0.5-2wt% of polypropylene short fibers.

[0007] The particle size of the mullite aggregate is 0.075 - 5 mm, the alumina content is > 60%, and the proportion of the mullite phase is > 95%; the purity of the aluminum dihydrogen phosphate powder is > 98%, and the particle size is 200 mesh; the particle size D50 of the silica fume is 0.5 - 1 μm, and the silica content is > 95%; the lamellar thickness of the flake graphite is < 20 μm, the particle size distribution D50 is 5 - 20 μm, and the carbon content is > 99.8%; the fiber length of the polypropylene short fiber is 3 - 5 μm, and the softening point is < 120 °C.

[0008] As a limitation of the present invention, the chemical composition of the pretreated secondary aluminum ash is: 60 - 80 wt% of alumina, 5 - 15 wt% of silica, 0.5 - 3 wt% of iron oxide, 0.5 - 3 wt% of calcium oxide, 1 - 5 wt% of potassium oxide, and 0.5 - 3 wt% of sodium oxide.

[0009] As a limitation of the present invention, the preparation method of the pretreated secondary aluminum ash is:

[0010] Add the secondary aluminum ash to hydrochloric acid, soak and react at 50 - 60 °C for 2 - 3 h. After soaking, wash with deionized water until neutral, then dry at 100 - 110 °C, and then screen to remove impurities to obtain the pretreated secondary aluminum ash.

[0011] As a limitation of the present invention, the preparation method of the composite additive is:

[0012] Mix sodium metasilicate pentahydrate and borax in a mass ratio of (2 - 5):1, and mechanically stir for 5 - 15 min to make them evenly mixed to obtain the composite additive.

[0013] A preparation method of a hot repair material for an aluminum industrial furnace is specifically as follows:

[0014] Mix the flake graphite, polypropylene short fiber, one-third mass portion of silica fume, and polycarboxylic acid dispersant, and mechanically stir for 20 - 30 min at a stirring speed of 400 - 500 rpm. After stirring, obtain the mixed dry material A;

[0015] Mix the mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, two-thirds mass portion of silica fume, and the composite additive, and mechanically stir for 3 - 5 min at a stirring speed of 80 - 100 rpm. After stirring, add the mixed dry material A and continue to stir for 8 - 10 min at a stirring speed of 40 - 50 rpm to obtain the hot repair material for the aluminum industrial furnace.

[0016] The electrostatic repulsion and steric hindrance effects of the polycarboxylic acid dispersant can evenly disperse the silica fume in the dry material on the surfaces of the flake graphite and polypropylene fiber.

[0017] As a limitation of the present invention, the hot repair material for the aluminum industrial furnace contains silicon oxynitride, and the preparation method is:

[0018] Mix elemental silicon and silicon dioxide, and ball mill for 3 - 5 h to obtain a mixed powder with a particle size D50 of 5 - 10 μm. Under nitrogen protection, put the mixed powder into a graphite crucible lined with graphite paper, and sinter at 1400 - 1450 °C for 12 - 15 h. After sintering, cool naturally to room temperature, and then crush and screen the sintered product to obtain silicon oxynitride.

[0019] As a limitation of the present invention, the mass fraction of the silicon oxynitride in the hot - state repair material for aluminum industrial furnaces is 1 - 3%.

[0020] As a limitation of the present invention, the mass ratio of the elemental silicon to the silicon dioxide is (6 - 10):(5 - 8).

[0021] As a limitation of the present invention, pretreat the secondary aluminum ash impregnated modification slurry to obtain modified secondary aluminum ash. The preparation method of the modification slurry is as follows:

[0022] Add zirconium oxychloride octahydrate to ethanol, and continuously stir to dissolve it to obtain a zirconium chloride alcohol solution. Add a bentonite suspending agent to the zirconium chloride alcohol solution, stir at 800 - 1000 rpm for 5 - 10 min to disperse it in the zirconium chloride alcohol solution, and then add fused magnesia powder and corundum powder, and continue to stir at 800 - 1000 rpm for 15 - 20 min to obtain the modification slurry.

[0023] As a limitation of the present invention, the mass ratio of zirconium oxychloride octahydrate, fused magnesia powder, and corundum powder is (15 - 18):(12 - 15):(5 - 7).

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention introduces sodium metasilicate pentahydrate and borax as composite additives. Utilize the waste heat of the furnace lining to enable sodium metasilicate pentahydrate to undergo a dehydration reaction at 100 - 150 °C, and use the "self - boiling" effect of the dehydration reaction to promote the dry powder material to flow and spread on the surface of the furnace lining. By utilizing the self - lubricating effect of the lamellar structure of graphite, further reduce the friction of particles and help the dry material quickly spread over the repair area. As the temperature of the furnace lining rises, sodium metasilicate pentahydrate is completely dehydrated to form sodium silicate. By introducing an appropriate amount of borax and utilizing the function of borax as a sintering aid, an oxidation boron - sodium silicate composite system is formed, enabling sodium silicate to form a eutectic at a relatively low temperature of 700 - 800 °C, realizing low - viscosity flow to fill pores and improving the densification of the sintered material. At the same time, the introduction of the borax sintering aid improves the problem of low mid - temperature sintering strength of the aluminum dihydrogen phosphate binding system at about 1000 °C.

[0026] The present invention introduces polypropylene short fibers. By physically winding and bonding the dry materials with the fibers to form a network structure, and through a reasonable particle size grading design, when the dry materials fall on the furnace lining by means of spraying or the like, the overall effect is utilized to effectively plug the cracks, prevent the dry materials from leaking into the furnace hearth and polluting the molten aluminum, and it can meet the hot repair of cracks within 10 mm in width. The polypropylene short fibers start to soften after being heated and completely decompose without residue as the temperature rises. Adding an appropriate amount of polypropylene short fibers does not affect the heat-induced fluidity of the dry material.

[0027] The present invention introduces ultrafine pre-treated secondary aluminum ash fine powder and silica fume to fill the pores. Utilizing the high activity of the ultrafine powder, a sintering reaction occurs to generate plate-like mullite phases with excellent high-temperature resistance and thermal shock stability. The mullite phases interpenetrate in the matrix, significantly improving the high-temperature performance. At the same time, the reactive alumina in the secondary aluminum ash reacts with the binder aluminum dihydrogen phosphate when heated to generate aluminum phosphate, improving the strength of the material and realizing the renewable use of the industrial hazardous waste secondary aluminum ash.

[0028] Through the synergistic effect of the composite additive, high-temperature binder and flake graphite, the dry material can start to flow at about 200 °C using the waste heat of the furnace lining and has excellent fluidity at about 300 °C. At about 400 °C, it has initial strength by means of the sintering of aluminum dihydrogen phosphate and the solidification of sodium metasilicate pentahydrate. In the working environment of an aluminum reverberatory furnace above 800 °C, using the anti-oxidation of graphite and the strengthening effect of mullitization, it meets the requirements of the high-temperature working conditions of the furnace lining, and has the advantages of environmental protection, low cost and high performance, and is suitable for the hot and rapid repair of the aluminum reverberatory furnace.

[0029] Introducing silicon oxynitride into the hot repair material, aluminum nitride and aluminum carbide-aluminum nitride-silicon carbide-based compounds are generated during the repair process. It has good thermal conductivity and a small thermal expansion coefficient, which helps to improve the thermal stability and oxidation resistance of the repair material after sintering. In addition, silicon oxynitride has good slag resistance and good resistance to slag liquid erosion. The silicon oxide generated by thermal decomposition at high temperature can block the pores that cannot be repaired, slowing down the penetration and erosion of the slag liquid into the interior of the repair material, thereby improving the mechanical properties of the repair material after sintering.

[0030] The secondary aluminum ash is impregnated and modified with a slurry containing fused magnesia powder, corundum powder and zirconium oxychloride before use. Zirconium oxychloride decomposes to generate zirconia at 600 °C. When eroded by the slag liquid, it reacts with the slag liquid and expands in volume, blocking the pores to avoid slag liquid erosion and at the same time generating microcracks, which can refine the cracks generated by the phase transformation of the aggregate and other materials during the sintering process, and improve the thermal shock resistance of the dry material after sintering; the fused magnesia powder and corundum powder generate magnesium aluminate spinel phases during the sintering process, further improving the strength and thermal stability of the dry material after sintering. Description of the Drawings

[0031] Figure 1It is a graph showing the test results of the bonding performance between the dry material and the original lining material, where the dry material is the hot repair material for aluminum industrial furnaces prepared in Example 1;

[0032] Figure 2 It is a graph showing the test results of the bonding performance between the dry material and the original lining material, where the dry material is the hot repair material for aluminum industrial furnaces prepared in Example 2. Specific embodiments

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Mullite aggregate (aluminum oxide content > 60%, particle size: 0.075 - 5 mm) is provided by Zhengzhou Daorui Refractories, aluminum dihydrogen phosphate powder (particle size: 200 mesh) is provided by Henan Bangnai, silica fume (particle size D50: 0.5 - 1 μm) is provided by Lianyungang Huawei, flake graphite (particle size D50: 5 - 20 μm) is provided by Henan Huiju, polypropylene short fiber (length: 3 - 5 μm) is provided by Henan Tiansheng, secondary aluminum ash (particle size: < 270 μm) is provided by Henan Mingtai, polycarboxylic acid dispersant (brand: PAA, free monomer AA ≤ 0.5) is provided by Zaozhuang Jialu, fused magnesia powder (particle size: 200 mesh) is provided by Qingdao Western Beauty Industry, corundum powder (particle size: 200 mesh) and bentonite suspending agent (particle size: 325 mesh, swelling degree: > 12.5) are from Lingshou County Aokai Mineral Products Processing Factory.

[0035] Example 1: A preparation method of a hot repair material for aluminum industrial furnaces, specifically as follows:

[0036] Step 1: Mix flake graphite, polypropylene short fiber, a part of silica fume (1 / 3 of the total mass of silica fume) and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring, obtain mixed dry material A;

[0037] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 4:1, and mechanically stir for 10 min to make them evenly mixed to obtain a composite additive;

[0038] Step 3: Add secondary aluminum ash to hydrochloric acid with a mass fraction of 5%, soak and react at 60 °C for 2 h. After soaking, wash with deionized water until neutral, then dry at 110 °C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0039] Step 4: Mix mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, the remaining silica fume (2 / 3 of the total mass of silica fume), and the composite additive, and mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring is completed, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain the hot repair material for aluminum industrial furnaces.

[0040] In the hot repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 55%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of the composite additive is 10%, the mass fraction of aluminum dihydrogen phosphate powder is 8%, the mass fraction of silica fume is 4.5%, the mass fraction of flake graphite is 1%, the mass fraction of polypropylene short fibers is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0041] Example 2: A preparation method of a hot repair material for aluminum industrial furnaces, specifically:

[0042] Step 1: Mix flake graphite, polypropylene short fibers, a part of silica fume (1 / 3 of the total mass of silica fume), and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring is completed, obtain mixed dry material A;

[0043] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 3:1, and mechanically stir for 10 min to make them evenly mixed to obtain the composite additive;

[0044] Step 3: Add secondary aluminum ash to hydrochloric acid with a mass fraction of 5%, soak and react at 60 °C for 2 h. After soaking is completed, wash with deionized water until neutral, then dry at 110 °C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0045] Step 4: Mix mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, the remaining silica fume (2 / 3 of the total mass of silica fume), and the composite additive, and mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring is completed, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain the hot repair material for aluminum industrial furnaces.

[0046] In the hot repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 60%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of the composite additive is 5%, the mass fraction of aluminum dihydrogen phosphate powder is 7%, the mass fraction of silica fume is 5%, the mass fraction of flake graphite is 1.5%, the mass fraction of polypropylene short fibers is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0047] Example 3: A preparation method of a hot repair material for aluminum industrial furnaces, specifically:

[0048] Step 1: Mix flake graphite, polypropylene short fibers, a part of silica fume (1 / 3 of the total mass of silica fume), and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring is completed, obtain mixed dry material A;

[0049] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 4:1, and mechanically stir for 10 min to make them evenly mixed to obtain a composite additive;

[0050] Step 3: Add secondary aluminum ash to hydrochloric acid with a mass fraction of 5%, soak and react at 60 °C for 2 h. After soaking is completed, wash with deionized water until neutral, then dry at 110 °C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0051] Step 4: Mix mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, the remaining silica fume (2 / 3 of the total mass of silica fume), and the composite additive, and mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring is completed, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain a hot repair material for aluminum industrial furnaces.

[0052] In the hot repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 50%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of the composite additive is 12%, the mass fraction of aluminum dihydrogen phosphate powder is 10%, the mass fraction of silica fume is 5.5%, the mass fraction of flake graphite is 1.5%, the mass fraction of polypropylene short fibers is 1.5%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0053] Example 4: A preparation method of a hot repair material for aluminum industrial furnaces, specifically:

[0054] Step 1: Mix flake graphite, polypropylene short fibers, a part of silica fume (1 / 3 of the total mass of silica fume), and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring is completed, obtain mixed dry material A;

[0055] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 4:1, and mechanically stir for 10 min to make them evenly mixed to obtain a composite additive;

[0056] Step 3: Add secondary aluminum ash to hydrochloric acid with a mass fraction of 5%, soak and react at 60 °C for 2 h. After soaking is completed, wash with deionized water until neutral, then dry at 110 °C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0057] Step 4: Add 16 g of zirconium oxychloride octahydrate to 100 mL of ethanol, and continuously stir to dissolve it to obtain a zirconium chloride alcohol solution. Add 0.52 g of bentonite suspending agent to the zirconium chloride alcohol solution, stir at 1000 rpm for 10 min to disperse it in the zirconium chloride alcohol solution, then add 14 g of fused magnesia powder and 6 g of corundum powder, and continue to stir at 1000 rpm for 15 min to form a modified slurry. Subsequently, immerse the pretreated secondary aluminum ash in the modified slurry for 30 min. After 30 min, filter and dry at 110 °C for 1 h to obtain modified secondary aluminum ash;

[0058] Step 5: Mix silicon and silicon dioxide in a mass ratio of 7:5.8 evenly, transfer them to a vibratory ball mill and ball mill for 5 h to obtain a mixed powder with a particle size D50 of 5 μm. Under nitrogen protection, put the mixed powder into a graphite crucible lined with graphite paper, and sinter at 1430 °C for 14 h. After sintering, cool naturally to room temperature, and then crush the sintered product and pass through a 325-mesh sieve to obtain silicon oxynitride;

[0059] Step 6: Mix mullite aggregate, modified secondary aluminum ash, aluminum dihydrogen phosphate powder, silicon oxynitride, the remaining silicon micro-powder (2 / 3 of the total mass of silicon micro-powder) and a composite additive, and mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain a hot-state repair material for aluminum industrial furnaces.

[0060] In the hot-state repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 53%, the mass fraction of modified secondary aluminum ash is 20%, the mass fraction of silicon oxynitride is 2%, the mass fraction of composite additive is 10%, the mass fraction of aluminum dihydrogen phosphate powder is 8%, the mass fraction of silicon micro-powder is 4.5%, the mass fraction of flake graphite is 1%, the mass fraction of polypropylene short fiber is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0061] Next, based on Example 1, control experiments are carried out, specifically Comparative Example 1, Comparative Example 2 and Comparative Example 3, as described below:

[0062] Comparative Example 1: This comparative example relates to a preparation method of a hot-state repair material for aluminum industrial furnaces, and the difference from Example 1 is that no composite additive is added. Specifically:

[0063] Step 1: Mix flake graphite, polypropylene short fiber, a part of silicon micro-powder (1 / 3 of the total mass of silicon micro-powder) and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring, obtain mixed dry material A;

[0064] Step 2: Add secondary aluminum ash into hydrochloric acid with a mass fraction of 5%, soak and react at 60°C for 2 h. After soaking, wash with deionized water until neutral, then dry at 110°C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0065] Step 3: Mix mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, the remaining silica fume (2 / 3 of the total mass of silica fume) and the composite additive, mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain a hot-state repair material for aluminum industrial furnaces.

[0066] In the hot-state repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 65%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of aluminum dihydrogen phosphate powder is 8%, the mass fraction of silica fume is 4.5%, the mass fraction of flake graphite is 1%, the mass fraction of polypropylene short fiber is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0067] Comparative Example 2: This comparative example relates to a preparation method of a hot-state repair material for aluminum industrial furnaces. The difference from Example 1 is that polypropylene short fiber is not added. Specifically:

[0068] Step 1: Mix flake graphite, a part of silica fume (1 / 3 of the total mass of silica fume) and polycarboxylic acid dispersant, mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring, obtain mixed dry material A;

[0069] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 4:1, mechanically stir for 10 min to make them evenly mixed to obtain a composite additive;

[0070] Step 3: Add secondary aluminum ash into hydrochloric acid with a mass fraction of 5%, soak and react at 60°C for 2 h. After soaking, wash with deionized water until neutral, then dry at 110°C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0071] Step 4: Mix mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, the remaining silica fume (2 / 3 of the total mass of silica fume) and the composite additive, mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain a hot-state repair material for aluminum industrial furnaces.

[0072] In the hot-state repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 56%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of composite additive is 10%, the mass fraction of aluminum dihydrogen phosphate powder is 8%, the mass fraction of silica fume is 4.5%, the mass fraction of flake graphite is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0073] Comparative Example 3: This comparative example relates to a preparation method of a hot-state repair material for aluminum industrial furnaces. The difference from Example 1 is that aluminum dihydrogen phosphate powder is not added. Specifically:

[0074] Step 1: Mix flake graphite, polypropylene short fibers, a part of silica fume (1 / 3 of the total mass of silica fume), and polycarboxylic acid dispersant, and mechanically stir for 30 min at a stirring speed of 500 rpm. After stirring is completed, obtain mixed dry material A;

[0075] Step 2: Mix sodium metasilicate pentahydrate and borax in a mass ratio of 4:1, and mechanically stir for 10 min to make them evenly mixed to obtain a composite additive;

[0076] Step 3: Add secondary aluminum ash to hydrochloric acid with a mass fraction of 5%, soak and react at 60 °C for 2 h. After soaking is completed, wash with deionized water until neutral, then dry at 110 °C, and then pass through a 325-mesh sieve to remove impurities to obtain pretreated secondary aluminum ash;

[0077] Step 4: Mix mullite aggregate, pretreated secondary aluminum ash, the remaining silica fume (2 / 3 of the total mass of silica fume), and the composite additive, and mechanically stir for 5 min at a stirring speed of 100 rpm. After stirring is completed, add mixed dry material A and continue to stir for 10 min at a stirring speed of 50 rpm to obtain a hot-state repair material for aluminum industrial furnaces.

[0078] In the hot-state repair material for aluminum industrial furnaces, the mass fraction of mullite aggregate is 63%, the mass fraction of pretreated secondary aluminum ash is 20%, the mass fraction of composite additive is 10%, the mass fraction of silica fume is 4.5%, the mass fraction of flake graphite is 1%, the mass fraction of polypropylene short fibers is 1%, and the mass fraction of polycarboxylic acid dispersant is 0.5%.

[0079] Detection experiment: Prepare test samples of hot-state repair materials for aluminum industrial furnaces according to the preparation methods in each example and comparative example respectively, and conduct dry material fluidity test, 400 °C flexural strength test, 800 °C water-cooled thermal shock strength retention test, 1000 °C calcination for 3 h cold-state linear change test, and dry material and original lining material bonding performance test.

[0080] Dry material flowability test: Place a mold with inner dimensions of φ50mm and φ100mm for the upper and lower parts respectively and a height of 50mm on a high-temperature resistant ceramic plate. After mixing the repair material sample well, pile it into the mold and level it. Then transfer the mold together with the sample into the test furnace, heat it at a constant temperature of 300°C for 10 minutes, take it out after heating, cool it to room temperature, remove the mold, measure the diagonal diameter of the dry material, and take the average value as the method for evaluating the heat flowability of the repair material.

[0081] Flexural strength test at 400°C: Fill the repair material sample into a metal mold. Then transfer the metal mold filled with the repair material into the test furnace, sinter it into shape at 400°C, cool it to room temperature, take out the formed standard sample block from the mold with dimensions of 160mm×40mm×40mm, fix the standard sample block on the fixture of the high-temperature flexural testing equipment, and use the high-temperature flexural testing equipment to test the hot flexural strength of each formed standard sample block at 400°C.

[0082] Water-cooled thermal shock strength retention test at 800°C: Fill the repair material sample into a metal mold. Then transfer the metal mold filled with the repair material into the test furnace, sinter it into shape at 400°C, cool it to room temperature, take out the formed standard sample block from the mold with dimensions of 230mm×115mm×64mm. After testing the initial compressive strength of each standard sample block at room temperature, fix the standard sample block on the water-cooled thermal shock testing machine, conduct 10 water-cooled thermal shock cycles at 800°C, then take down the standard sample block, measure the compressive strength of the sample block after the 800°C water-cooled thermal shock test, and compare it with the initial compressive strength of the sample block, which is the strength retention rate after 800°C water-cooled thermal shock.

[0083] Cold linear change test after calcination at 1000°C for 3h: Fill the repair material sample into a metal mold. Then transfer the metal mold filled with the repair material into the test furnace, sinter it into shape at 400°C, cool it to room temperature, take out the formed standard sample block from the mold with dimensions of 160mm×40mm×40mm, measure the initial length of the sample block, then send the sample block into the test furnace, conduct heat treatment at 1000°C for 3h, cool it to room temperature after the heat treatment is completed, test the length of the sample block after the heat treatment, and the change rate between the length after the heat treatment and the initial length is the cold linear change after calcination at 1000°C for 3h.

[0084] Testing the bonding performance of the dry material and the original lining material: The original lining material was cast into standard specimen blocks of 160 mm × 40 mm × 40 mm using a standard triple mold. After firing at 1000 °C for 3 h, according to the "Test Method for Cold Modulus of Rupture of Refractory Materials" (GB / T 3001-2007), the fired standard specimen blocks were broken in the middle. Subsequently, the two half-standard specimen blocks after breaking were respectively placed in the standard triple mold, with the end faces of the specimen blocks aligned with the mold, exposing the fracture surfaces. Then, the standard triple mold was transferred to a high-temperature furnace, and the standard triple mold containing half of the standard specimen block was filled with the dry material. The temperature was raised to 1000 °C and held for 3 h. After holding for 3 h, it was naturally cooled to room temperature to obtain the bonded specimen for testing. According to the "Test Method for Flexural Strength of Fine Ceramics" (GB / T 6569-2006), the four-point flexural strength of the bonded specimen was tested.

[0085]

[0086] Conclusion: Figure 1 、 Figure 2 Figure is the test result diagram of the bonding performance between the dry material and the original lining material in the bonding performance test. Among them, Figure 1 the specimen block in uses the hot-state repair material for aluminum industrial furnaces prepared in Example 1, Figure 2 the specimen block in uses the hot-state repair material for aluminum industrial furnaces prepared in Example 2, Figure 1 in, the fracture is not at the bonding position, indicating that the strength of the hot-state repair material after sintering is higher than its own strength, and the bonding performance between the hot-state repair material and the original lining material is good. Figure 2 in, the fracture is at the bonding position, indicating that compared with Example 1, the bonding ability between the hot-state repair material prepared in Example 2 and the original lining material is poor.

[0087] It can be seen from the test data that the hot-state repair material for aluminum industrial furnaces prepared by the present invention has good fluidity at 300 °C, which is convenient for the repair material to spread on the surface of the original lining material and quickly repair the damaged area of the original lining. After sintering, the repair material not only has high flexural strength, but also can still maintain a high strength range after water-cooled thermal shock, and has good bonding performance with the original lining material, which can meet the high-temperature working conditions requirements of the furnace lining and is suitable for the rapid repair of aluminum reaction furnaces.

[0088] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A hot repair material for an aluminum industrial furnace, characterized in that: Calculated by mass fraction, the invention comprises 30-60wt% of mullite aggregate, 10-20wt% of pretreated secondary aluminum ash, 5-15wt% of composite additives, 3-8wt% of aluminum dihydrogen phosphate powder, 2-6wt% of silicon micropowder, 0.2-2wt% of lamellar graphite and 0.5-2wt% of polypropylene short fibers.

2. The hot repair material for aluminum industrial furnace according to claim 1, characterized in that: The chemical composition of the pre-treated secondary aluminum ash is: 60-80wt% aluminum oxide, 5-15wt% silicon dioxide, 0.5-3wt% ferric oxide, 0.5-3wt% calcium oxide, 1-5wt% potassium oxide, and 0.5-3wt% sodium oxide.

3. The hot repair material for aluminum industrial furnace according to claim 2, characterized in that: The preparation method of pretreated secondary aluminum ash is as follows: adding secondary aluminum ash to hydrochloric acid, soaking and reacting at 50-60°C for 2-3 hours, washing with deionized water to neutrality after soaking, and then drying at 100-110°C, followed by sieving to remove impurities to obtain pretreated secondary aluminum ash.

4. The hot repair material for aluminum industrial furnace according to claim 1, characterized in that: The preparation method of the composite additive is: Sodium metasilicate pentahydrate and borax are mixed in a mass ratio of (2-5):1, and mechanically stirred for 5-15 minutes to make the mixture uniform, thereby obtaining a composite additive.

5. A method for preparing hot repair material for aluminum industrial furnace, characterized in that: Specifically: The flake graphite, polypropylene short fibers, one third of the mass fraction of silicon powder and polycarboxylic acid dispersant are mixed, and mechanically stirred for 20 to 30 minutes at a stirring speed of 400 to 500 rpm. After the stirring is completed, a mixed dry material A is obtained; Mullite aggregate, pretreated secondary aluminum ash, aluminum dihydrogen phosphate powder, two-thirds of silicon powder by mass and composite additives are mixed, mechanically stirred for 3 to 5 minutes at a stirring speed of 80 to 100 rpm. After the stirring is completed, mixed dry material A is added, and stirring is continued for 8 to 10 minutes at a stirring speed of 40 to 50 rpm to obtain a hot repair material for an aluminum industrial furnace.

6. The method for preparing a hot repair material for an aluminum industrial furnace according to claim 5, characterized in that: The hot repair material for aluminum industrial furnace contains silicon oxynitride, and the preparation method is as follows: Mix elemental silicon and silicon dioxide, ball-mill for 3 to 5 hours to obtain a mixed powder with a particle size D50 of 5 to 10 μm. Under nitrogen protection, put the mixed powder into a graphite crucible lined with graphite paper, and sinter at 1400 to 1450°C for 12 to 15 hours. After sintering, naturally cool to room temperature, and then crush and sieve the sintered product to obtain silicon oxynitride.

7. The method for preparing a hot repair material for an aluminum industrial furnace according to claim 6, characterized in that: The mass fraction of silicon oxynitride in the hot repair material for aluminum industrial furnaces is 1 to 3%.

8. The method for preparing a hot repair material for an aluminum industrial furnace according to claim 6, characterized in that: The mass ratio of elemental silicon to silicon dioxide is (6-10):(5-8).

9. The method for preparing a hot repair material for an aluminum industrial furnace according to claim 5, characterized in that: The modified slurry is impregnated with pretreated secondary aluminum ash to obtain modified secondary aluminum ash. The preparation method of the modified slurry is as follows: Add basic zirconium chloride octahydrate to ethanol, stir continuously to dissolve it, and obtain zirconium chloride alcohol solution; add bentonite suspending agent to the zirconium chloride alcohol solution, stir at 800-1000 rpm for 5-10 minutes to disperse it in the zirconium chloride alcohol solution; then add fused magnesia powder and corundum powder, continue stirring at 800-1000 rpm for 15-20 minutes, and obtain modified slurry.

10. The method for preparing a hot repair material for an aluminum industrial furnace according to claim 9, characterized in that: The mass ratio of basic zirconium chloride octahydrate, fused magnesia powder and corundum powder is (15-18):(12-15):(5-7).

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