Aging low-thermal-conductivity refractory material as well as preparation method and use method thereof

Abstract

The invention belongs to the technical field of refractory materials and relates to an aging low-thermal-conductivity refractory material as well as a preparation method and a use method thereof. The preparation method of the aged low-thermal-conductivity refractory material comprises the following steps: respectively crushing the special-grade alumina clinker and the low-thermal-conductivity mullite-silicon aggregate into four particle sizes of 5-8 mm, 3-5 mm, 1-3 mm and 0-1 mm for later use; the preparation method comprises the following steps: mixing special-grade alumina clinker fine powder with the particle size of 0-1mm, low-thermal-conductivity mullite-silicon aggregate fine powder with the particle size of 0-1mm, sintered alumina fine powder, calcium aluminate cement fine powder, alpha-Al2O3 fine powder and kyanite fine powder according to a ratio to obtain matrix fine powder; the preparation method comprises the following steps: mixing special-grade alumina clinker particles with the particle size of 5-8 mm, special-grade alumina clinker particles with the particle size of 3-5 mm, special-grade alumina clinker particles with the particle size of 1-3 mm, low-thermal-conductivity mullite-silicon aggregate particles with the particle size of 5-8 mm, low-thermal-conductivity mullite-silicon aggregate particles with the particle size of 3-5 mm and low-thermal-conductivity mullite-silicon aggregate particles with the particle size of 1-3 mm according to the proportion, and adding silica powder while stirring; and after mixing, adding the matrix fine powder, uniformly mixing, finally adding the explosion-proof fiber, and stirring to obtain the aging low-thermal-conductivity refractory material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractory materials, and particularly relates to a low-thermal-conductivity aging refractory material and a preparation method and use method thereof. BACKGROUND

[0002] The thermal conductivity of the refractory material for the working lining of a cold-rolled heating furnace made of stainless steel, carbon steel or silicon steel changes differently with the extension of the service time. Specifically, the newly built refractory material (such as high-alumina brick and mullite castable) has small pores in the interior, and after being heated, part of the pores are closed, the density is increased, and the thermal conductivity is temporarily and slightly decreased. After a short-term sintering, the material reaches the initial design performance, and the thermal conductivity tends to be stable. After several months to several years, the metal vapors such as Fe and Zn in the furnace gas penetrate into the pores of the refractory material, forming high-thermal-conductivity metal oxides (such as Fe2O3), which causes the thermal conductivity to rise; under long-term high temperature, the internal grains of the material grow, the glass phase increases, the density deepens, and the heat conduction path is more continuous, so the thermal conductivity rises; the thermal conductivity of the high-alumina castable of the silicon steel ring furnace of TISCO increases by 21.51% after being operated at 1250℃ for one year.

[0003] The repeated change of the thermal conductivity of the refractory material for the working lining of the heating furnace leads to the change of the heat treatment temperature, and further leads to the grain growth, burning loss and inclusion of the cold-rolled product. In order to keep the temperature stable, the work rules need to be constantly modified, and the burden of the enterprise is increased. Therefore, it is particularly important to keep the stability of the refractory material for the working lining of the heating furnace. SUMMARY

[0004] In view of the defects of the prior art, the application provides a low-thermal-conductivity aging refractory material and a preparation method and use method thereof.

[0005] Specifically, the preparation method of the low-thermal-conductivity aging refractory material provided by the application comprises the following steps: (1) special-grade bauxite clinker is crushed into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for standby use; low-thermal-conductivity mullite aggregate is crushed into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for standby use; (2) 5-10 parts of special-grade bauxite clinker fine powder with a particle size of 0-1mm, 10-15 parts of low-thermal-conductivity mullite aggregate fine powder with a particle size of 0-1mm, 15-20 parts of sintered alumina fine powder, 4-6 parts of calcium aluminate cement fine powder, 2-3 parts of alpha-Al2O3 fine powder and 2-5 parts of kyanite fine powder are uniformly mixed to obtain a matrix fine powder; (3) Mix 2-6 parts of 5-8mm high-grade bauxite clinker particles, 8-17 parts of 3-5mm high-grade bauxite clinker particles, 2-6 parts of 1-3mm high-grade bauxite clinker particles, 3-7 parts of 5-8mm low-thermal-conductivity molybdenum silicate aggregate particles, 10-20 parts of 3-5mm low-thermal-conductivity molybdenum silicate aggregate particles, and 3-7 parts of 1-3mm low-thermal-conductivity molybdenum silicate aggregate particles evenly, and then add 3-5 parts of silica powder while stirring. After mixing evenly, add the matrix fine powder and mix evenly. Finally, add 0.1-0.3 parts of explosion-proof fiber and stir evenly to obtain the aging low-thermal-conductivity refractory material.

[0006] The above-mentioned method for preparing low-thermal-conductivity refractory materials with aging processes involves a high-grade bauxite clinker with an Al2O3 content of 85-92%, an Fe2O3 content of 0-1.5%, and a K2O+Na2O content of 0-0.2%; its bulk density is 3.11-3.50 g / cm³. 3 The apparent porosity is 1.0-6.0%, the linear change after reheating at 1500℃ is -0.1-0.1%, and the particle size is 10-60mm.

[0007] The preparation method of the aforementioned low-thermal-conductivity refractory material, wherein the low-thermal-conductivity mullite aggregate contains 35-45% mullite, 35-45% glass phase, 0-5% corundum phase, 50-60% Al2O3, 30-45% SiO2, 0-0.5% Fe2O3, and 0.7-0.9% K2O+Na2O; and has a bulk density of 1.95-2.21 g / cm³. 3 The apparent porosity is 20.3-26.5%, and the coefficient of thermal expansion at 20-1000℃ is 0.5-1.2×10⁻⁶. -6 / ℃, compressive strength of 120-200MPa, refractoriness of 1795-1805℃, compressive strength retention rate of 50-80% after 20 water coolings at 1100℃, thermal conductivity of 0.432-0.685W / (m·K) at 1000℃, pore size of less than 1μm of 50-90 vol%, median pore size of less than 1μm, and particle size of 10-60mm.

[0008] In the above-mentioned method for preparing low-thermal-conductivity refractory materials with aging, the sintered alumina fine powder has an Al2O3 content of 99.5-100%, a SiO2 content of 0-0.03%, a Na2O content of 0-0.05%, and a true density of 3.95-4.02 g / cm³. 3 The particle size is 0-0.044 mm; the Al2O3 content of the calcium aluminate cement fine powder is... 3The content is 69-75%, CaO content is 25-30%, SiO2 content is 0-0.3%, Fe2O3 content is 0-0.4%, and specific surface area (BET) is 0.60-18.00m². 2 ·g -1 The true density is 3.00-3.30 g / cm³. 3 .

[0009] In the above-mentioned method for preparing low-thermal-conductivity refractory materials with aging, the α-Al₂O₃ fine powder has an Al₂O₃ content of 99.5-100%, a SiO₂ content of 0-0.02%, a Na₂O content of 0-0.05%, a Fe₂O₃ content of 0-0.01%, and a true density of 3.97-4.05 g / cm³. 3 The particle size is 0-0.010 mm.

[0010] The above-mentioned method for preparing low-thermal-conductivity refractory materials with aging involves kyanite fine powder that, after calcination at 1500℃, exhibits a mullite conversion rate of 70-78%, an Al2O3 content of 61-64%, a SiO2 content of 35-39%, a K2O+Na2O content of 0-0.3%, a Fe2O3 content of 0-1.2%, a TiO2 content of 0-0.5%, and a true density of 3.53-3.65 g / cm³. 3 The particle size is 0.044-0.074 mm, and the volume expansion is 16-18%.

[0011] In the above-mentioned method for preparing low thermal conductivity refractory materials with aging, the silicon micropowder has a SiO2 content of 95-98%, a CaO content of 0-0.5%, a Fe2O3 content of 0-1.5%, an Al2O3 content of 0-0.8%, and a particle size of 0-1 μm.

[0012] The present invention also provides an aging low thermal conductivity refractory material, which is prepared by the above-described preparation method.

[0013] The present invention also provides a method of using an aging low thermal conductivity refractory material, comprising: (1) Dissolve 0.3-0.6 parts of high-efficiency water-reducing agent in 0.1-0.5 parts of water to obtain high-efficiency water-reducing agent solution; (2) Mix the high-efficiency water-reducing agent liquid with 100 parts of aged low thermal conductivity refractory material, then add 3-6 parts of water while stirring, and mix evenly before applying it to the heating furnace; (3) After construction is completed, cure at room temperature for 18-24 hours, then raise the temperature at a rate of 0-10℃ to 110-150℃ and keep it at that temperature for 24-48 hours, then raise the temperature at a rate of 10-15℃ / h to 300-350℃ and keep it at that temperature for 6-12 hours, then raise the temperature at a rate of 15-25℃ / h to 1200-1350℃ and keep it at that temperature for 4-8 hours, and finally let the heating furnace cool naturally to room temperature.

[0014] The water reduction rate of the high-efficiency water-reducing agent described above is 40-65%.

[0015] The technical solution of the present invention has the following beneficial effects: The low-efficiency thermal conductivity refractory material of the present invention has low bulk density, high strength, excellent high-temperature stability, excellent thermal shock stability, small linear change, and low thermal conductivity. After long-term use, the thermal conductivity remains stable with little fluctuation. Detailed Implementation

[0016] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided to illustrate the invention in detail. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms used below have the meanings commonly understood by those skilled in the art. Unless otherwise specified, "%" in this invention refers to weight percentage.

[0017] The present invention relates to an aging low thermal conductivity refractory material, comprising: crushing and pulverizing high-grade bauxite clinker and low thermal conductivity silica aggregate into particles and fine powders of different sizes; uniformly mixing high-grade bauxite clinker fine powder, low thermal conductivity silica aggregate fine powder, sintered alumina fine powder, calcium carbonate cement fine powder, α-Al2O3 fine powder, and kyanite fine powder to obtain matrix fine powder; uniformly mixing high-grade bauxite clinker particles and low thermal conductivity silica aggregate particles of different sizes, adding silica powder and stirring, then adding matrix fine powder and continuing stirring, then adding explosion-proof fiber and stirring evenly, and finally automatically bagging and packaging to obtain the aging low thermal conductivity refractory material.

[0018] In this invention, the low thermal conductivity mullite aggregate is prepared from fly ash and bauxite. The reaction between the two not only generates a large amount of glassy phase, significantly promoting sintering and forming a mullite phase, but also retains a large number of micropores smaller than 1 μm in the mullite phase. The activity of the mullite phase is also reduced to an extremely low level, with very low reactivity. Therefore, the low thermal conductivity mullite aggregate has excellent volume stability. An interwoven needle-like secondary mullite phase forms between the glassy phase and the mullite phase in the low thermal conductivity mullite aggregate, resulting in a high strength retention rate after thermal shock. During use, the microporous mullite phase remains stable and is not affected by alkaline gases. The presence of the glassy phase can integrate and adsorb metal vapors such as Fe and Zn in the furnace gas. Kyanite and silica powder effectively stabilize the glassy phase, making it difficult for the glassy phase to deform.

[0019] Low thermal conductivity mullite-silica aggregate mainly consists of mullite and glass phases. Its pore size exhibits a bimodal distribution, with micropores smaller than 1 μm accounting for 50-90% of the total volume. The median pore size is less than 1 μm, resulting in high porosity and consequently, significant surface roughness. Using it as a raw material increases the contact area with surrounding materials, creating interlocking and reducing or even eliminating gaps between the aggregate and matrix. This also enhances the thermal shock resistance and strength of the refractory material, improving its high-temperature volume stability. Furthermore, due to its small pore size and high porosity, its use as aggregate significantly reduces thermal conductivity, increasing the insulation effect of the refractory material. Because of the stable presence of the mullite phase in the mullite-silica aggregate, the micropores persist, and combined with the stability of the glass phase, the thermal conductivity remains essentially constant from the initial stage of use to the end of the furnace service life. The existing dense castable working lining and insulation layer have too large a difference in properties. However, by using the low thermal conductivity silica aggregate particles and fine powder, the difference will be reduced, which will enable the insulation layer and working lining to have better compatibility and make it less likely for the two layers to peel off.

[0020] When silica powder is fused with aggregate, it further increases the bonding ability between aggregate and matrix, giving refractory materials a higher degree of integration. In addition, the interlocking between low thermal conductivity silica aggregate and matrix and the formation of secondary needle-like mullite can effectively increase the wear resistance of refractory materials.

[0021] To further improve the initial toughness of refractory materials and reduce spalling, explosion-proof fibers are added to the refractory materials. The strong tensile strength of the explosion-proof fibers will effectively prevent the propagation of initial cracks in the refractory materials, and reduce or even eliminate cracking caused by temperature changes during curing and baking.

[0022] In some preferred embodiments, the method for preparing the aging low thermal conductivity refractory material includes: (1) Crush the high-grade bauxite clinker into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for later use; crush the low thermal conductivity molybdenum silica aggregate into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for later use; (2) Mix 5-10 parts of high-grade bauxite clinker fine powder with a particle size of 0-1mm, 10-15 parts of low thermal conductivity molybdenum silica aggregate fine powder with a particle size of 0-1mm, 15-20 parts of sintered alumina fine powder, 4-6 parts of calcium aluminate cement fine powder, 2-3 parts of α-Al2O3 fine powder and 2-5 parts of kyanite fine powder evenly to obtain matrix fine powder; (3) Mix 2-6 parts of 5-8mm high-grade bauxite clinker particles, 8-17 parts of 3-5mm high-grade bauxite clinker particles, 2-6 parts of 1-3mm high-grade bauxite clinker particles, 3-7 parts of 5-8mm low-thermal-conductivity molybdenum silicate aggregate particles, 10-20 parts of 3-5mm low-thermal-conductivity molybdenum silicate aggregate particles, and 3-7 parts of 1-3mm low-thermal-conductivity molybdenum silicate aggregate particles evenly, and then add 3-5 parts of silica powder while stirring. After mixing evenly, add the matrix fine powder and mix evenly. Finally, add 0.1-0.3 parts of explosion-proof fiber and stir evenly to obtain the aging low-thermal-conductivity refractory material.

[0023] The crushing method for the premium bauxite clinker and low thermal conductivity molybdenum silica aggregate in step (1) is as follows: the raw materials are first crushed into three particle sizes of 5-8mm, 3-5mm, and 1-3mm by a crusher, and then ground into 0-1mm by a Raymond mill. In order to maintain the block balance, a double roll crusher is set in the middle to maintain the percentage of the 3-5mm and 1-3mm particle sizes.

[0024] Optionally, the crusher is model PEX-300×1300, with a feed particle size of 0-100mm, a finished particle size of 0-8mm, and an output of 50-180 t / h; the Raymond mill is model 4R3216, with 4 grinding rollers, a feed particle size of 0-20mm, a finished particle size of 0.044-0.080mm, and an output of 1-5 t / h; the double roll crusher is model 2PGY200-100, with a feed particle size of 0-10mm, a gap adjustment range of 0.5-20mm, a finished particle size of 0-3mm, and an output of 20-80 t / h.

[0025] High-grade bauxite clinker and low-thermal-conductivity molybdenum silicate aggregate are crushed into four particle sizes. This process ensures a denser packing, effectively increasing the density and strength of the aged low-thermal-conductivity refractories. Furthermore, it prevents particle size segregation during transportation. The graded particle size distribution also helps balance the material and reduce waste.

[0026] The low thermal conductivity molybdenum silicate aggregate preparation method adopted in this invention involves mixing 40-50% fly ash and 50-60% bauxite evenly, pressing the mixture into briquettes under a pressure of 20-25 MPa, drying it in a rotary kiln preheating zone of 110-250℃ for 6-8 hours, and then sintering it in a rotary kiln at a firing temperature of 1450-1550℃ for 12-24 hours.

[0027] The fly ash contains 36-40% Al2O3, 45-50% SiO2, 0-0.5% Fe2O3, 0.5-1.3% K2O+Na2O, and has a particle size of 0-0.088 mm. The bauxite contains 50-53% Al2O3, 29-31% SiO2, 0-0.5% Fe2O3, 0.3-0.5% K2O+Na2O, has a loss on ignition of 10-15%, and has a particle size of 0-0.088 mm.

[0028] In some preferred embodiments, the premium bauxite clinker contains 85-92% Al2O3, 0-1.5% Fe2O3, and 0-0.2% K2O+Na2O.

[0029] The bulk density of the premium bauxite clinker is 3.11-3.50 g / cm³. 3 The apparent porosity is 1.0-6.0%, the linear change after reheating at 1500℃ is -0.1-0.1%, and the particle size is 10-60mm.

[0030] In some preferred embodiments, the low thermal conductivity mullite aggregate contains 35-45% mullite, 35-45% glass phase, 0-5% corundum phase, 50-60% Al2O3, 30-45% SiO2, 0-0.5% Fe2O3, and 0.7-0.9% K2O+Na2O.

[0031] The low thermal conductivity silica aggregate has a bulk density of 1.95-2.21 g / cm³. 3 The apparent porosity is 20.3-26.5%, and the coefficient of thermal expansion at 20-1000℃ is 0.5-1.2×10⁻⁶. -6 / ℃, compressive strength of 120-200MPa, refractoriness of 1795-1805℃, compressive strength retention rate of 50-80% after 20 water coolings at 1100℃, thermal conductivity of 0.432-0.685W / (m·K) at 1000℃, pore size of less than 1μm of 50-90 vol%, median pore size of less than 1μm, and particle size of 10-60mm.

[0032] In some preferred embodiments, the sintered alumina fine powder has an Al2O3 content of 99.5-100%, a SiO2 content of 0-0.03%, a Na2O content of 0-0.05%, and a true density of 3.95-4.02 g / cm³. 3 The particle size is 0-0.044 mm.

[0033] In some preferred embodiments, the calcium aluminate cement powder is grade CA71, Al2O3 The content is 69-75%, CaO content is 25-30%, SiO2 content is 0-0.3%, Fe2O3 content is 0-0.4%, and specific surface area (BET) is 0.60-18.00m². 2 ·g -1 The true density is 3.00-3.30 g / cm³. 3 .

[0034] In some preferred embodiments, the α-Al₂O₃ fine powder has an Al₂O₃ content of 99.5-100%, a SiO₂ content of 0-0.02%, a Na₂O content of 0-0.05%, a Fe₂O₃ content of 0-0.01%, and a true density of 3.97-4.05 g / cm³. 3 The particle size is 0-0.010 mm.

[0035] In some preferred embodiments, the kyanite powder, after calcination at 1500℃, has a mullite conversion rate of 70-78%, an Al2O3 content of 61-64%, a SiO2 content of 35-39%, a K2O+Na2O content of 0-0.3%, a Fe2O3 content of 0-1.2%, a TiO2 content of 0-0.5%, and a true density of 3.53-3.65 g / cm³. 3 The particle size is 0.044-0.074 mm, and the volume expansion is 16-18%.

[0036] In some preferred embodiments, the silicon micropowder has a SiO2 content of 95-98%, a CaO content of 0-0.5%, a Fe2O3 content of 0-1.5%, an Al2O3 content of 0-0.8%, and a particle size of 0-1 μm.

[0037] In this invention, the role of explosion-proof fiber is to effectively prevent the spread of initial cracks in refractory materials by means of its strong tensile strength. During the curing and baking process, it forms micro-nano diameter channels to allow volatile water vapor and other gases to be discharged, thereby reducing or even eliminating cracking caused by temperature changes.

[0038] This invention does not have special requirements for the composition and type of explosion-proof fibers. Any explosion-proof fiber that does not burst at 25-1050℃ and has a metal oxide coating on its surface can be used in this invention. The metal oxide adheres to the surface of the micro-nano diameter channels after the explosion-proof fibers are ablated, preventing the channels from being corroded by volatile gases (such as zinc vapor) in the steel during use, thereby extending the service life of the low-thermal-conductivity refractory material.

[0039] In some preferred embodiments, the explosion-proof fiber generates controllable air pore channels at 300-350°C, is compatible with the high-efficiency water-reducing agent, and exhibits no flocculation when used together.

[0040] Optionally, the explosion-proof fiber is a polypropylene fiber with a metal oxide coating, with a fiber length of 6-12 mm, a diameter of 10-50 μm, a tensile strength of 350-600 MPa, and no agglomeration observed under a microscope.

[0041] Optionally, the polypropylene fiber has a molecular weight distribution of 3.5-7 and a number average molecular weight of 143,410-364,900, and the polymer is polymethyl methacrylate (PMMA) and polybutyl acrylate (PBA); the metal oxide is two or more of Al2O3, TiO2, ZnO and SiO2.

[0042] On the other hand, the present invention also provides a method of using the aforementioned low thermal conductivity refractory material, comprising: (1) Dissolve 0.3-0.6 parts of high-efficiency water-reducing agent in 0.1-0.5 parts of water to obtain high-efficiency water-reducing agent solution; (2) Mix the high-efficiency water-reducing agent liquid with 100 parts of aged low thermal conductivity refractory material, then add 3-6 parts of water while stirring, and mix evenly before applying it to the heating furnace; (3) After construction is completed, cure at room temperature for 18-24 hours, then raise the temperature at a rate of 0-10℃ to 110-150℃ and keep it at that temperature for 24-48 hours, then raise the temperature at a rate of 10-15℃ / h to 300-350℃ and keep it at that temperature for 6-12 hours, then raise the temperature at a rate of 15-25℃ / h to 1200-1350℃ and keep it at that temperature for 4-8 hours, and finally let the heating furnace cool naturally to room temperature.

[0043] This invention utilizes a high-efficiency composite water-reducing agent to reduce inter-particle friction through dispersion, significantly lowering the water requirement during refractory mixing to approximately 5 wt%. This reduction in moisture not only decreases porosity, preventing cracking during curing and baking, and reducing the number of cracks while increasing strength, but also enhances the high-temperature volume stability of the refractory, reduces high-temperature thermal stress, minimizes crack propagation sources, and improves thermal shock resistance. It releases trapped free water, enhancing slurry fluidity and facilitating construction. Electrostatic repulsion or steric hindrance maintains particle suspension stability, preventing aggregate separation from the matrix during construction. Furthermore, it promotes sintering.

[0044] The low thermal conductivity refractory material of this invention contains a large amount of fine powder. When water is added, the water is encapsulated by the fine powder, forming a flocculent structure that cannot be drained, thus affecting the construction effect. To avoid this problem, this invention uses a high-efficiency water-reducing agent to disrupt the above structure, thereby greatly reducing the amount of water added.

[0045] In some preferred embodiments, the high-efficiency water-reducing agent used in this invention is suitable for aluminosilicate refractory materials, with a water reduction rate of 40-65%. This invention does not have specific requirements for the specific composition of the high-efficiency water-reducing agent, as long as its performance meets the above requirements.

[0046] In some preferred embodiments, the high-efficiency water-reducing agent can be purchased from Shandong Kona Fine Chemical Co., Ltd., model SF-1216. This high-efficiency water-reducing agent is a composite water-reducing agent of PCE + retarder / dispersant, which has good compatibility with aluminate cement, no abnormal setting, a water reduction rate of 40-65%, a solid content of 20-40%, and a chloride ion content of 0-0.1%.

[0047] After the heating furnace is constructed, the present invention allows the low thermal conductivity refractory material to develop strength and lose most of its free water by curing at room temperature for 18-24 hours; by baking at 110-150℃ for 24-48 hours, the low thermal conductivity refractory material loses its free water; by baking at 300-350℃ for 6-12 hours, most of the hydration product structural water can be removed, and the explosion-proof fibers form channels; by baking at 1200-1350℃, the low thermal conductivity refractory material undergoes high-temperature sintering, develops strength, and exhibits good high-temperature volume stability.

[0048] Testing revealed that the aging low thermal conductivity refractory material prepared according to the method of this invention has an apparent porosity of 21.4-35.1% and a bulk density of 1.96-2.31 L / cm³. 3 Compressive strength: 82.6-168 MPa; flexural strength: 13-29 MPa; compressive strength retention rate after one thermal shock at 1100℃: 76.5-97.4%; flexural strength retention rate: 29.5-42.6%; linear change at 1550℃: -0.12-0.09%; abrasion resistance: 3-7 cm. 3 The thermal conductivity is 0.835-0.913 W / (m·K), and after one full-cycle furnace service, the thermal conductivity is 0.837-0.924 W / (m·K).

[0049] Therefore, the low-heat-conductivity refractory material prepared by this invention has low bulk density, high strength, excellent high-temperature stability, excellent thermal shock stability, small linear change, and low thermal conductivity. After long-term use, the thermal conductivity remains stable with minimal fluctuations.

[0050] Example The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0051] To avoid repetition, the materials involved in the specific implementation methods are described uniformly as follows, and will not be repeated in the examples: The premium grade bauxite clinker has an Al₂O₃ content of 85-92%, an Fe₂O₃ content of 0-1.5%, a K₂O + Na₂O content of 0-0.2%, and a bulk density of 3.11-3.50 g / cm³. 3 The apparent porosity is 1.0-6.0%, the linear change after reheating at 1500℃ is -0.1-0.1%, and the particle size is 10-60mm.

[0052] The low thermal conductivity mullite-silica aggregate contains 35-45% mullite, 35-45% glass phase, and 0-5% corundum phase; Al2O3 content is 50-60%, SiO2 content is 30-45%, Fe2O3 content is 0-0.5%, K2O+Na2O content is 0.7-0.9%, and bulk density is 1.95-2.21 g / cm³. 3 The apparent porosity is 20.3-26.5%, and the coefficient of thermal expansion is 0.5-1.2×10⁻⁶ at 20-1000℃. -6 / ℃, compressive strength of 120-200MPa, refractoriness of 1795-1805℃, compressive strength retention rate of 50-80% after 20 water coolings at 1100℃, thermal conductivity of 0.432-0.685W / (m·K) at 1000℃, pore size of less than 1μm of 50-90 vol%, median pore size of less than 1μm, and particle size of 10-60mm.

[0053] The method for preparing low thermal conductivity molybdenum silicate aggregate involves uniformly mixing 45% fly ash and 55% bauxite, pressing the mixture into briquettes under a pressure of 25 MPa, drying it at 150°C for 6 hours in a rotary kiln preheating zone, and then sintering it in a rotary kiln at a firing temperature of 1500°C for 24 hours. The fly ash contains 36-40% Al2O3, 45-50% SiO2, 0-0.5% Fe2O3, 0.5-1.3% K2O+Na2O, and has a particle size of 0-0.088 mm. The bauxite contains 50-53% Al2O3, 29-31% SiO2, 0-0.5% Fe2O3, 0.3-0.5% K2O+Na2O, has a loss on ignition of 10-15%, and a particle size of 0-0.088 mm.

[0054] The sintered alumina fine powder has an Al2O3 content of 99.5-100%, a SiO2 content of 0-0.03%, a Na2O content of 0-0.05%, and a true density of 3.95-4.02 g / cm³. 3 The particle size is 0-0.044 mm.

[0055] The grade of calcium aluminate cement fine powder is CA71, with an Al2O3 content of 69-75%, a CaO content of 25-30%, a SiO2 content of 0-0.3%, a Fe2O3 content of 0-0.4%, and a specific surface area (BET) of 0.60-18.00 m². 2 ·g -1 The true density is 3.00-3.30 g / cm³. 3 .

[0056] The α-Al₂O₃ fine powder contains 99.5-100% Al₂O₃, 0-0.02% SiO₂, 0-0.05% Na₂O, and 0-0.01% Fe₂O₃, with a true density of 3.97-4.05 g / cm³. 3 The particle size is 0-0.010 mm.

[0057] The fine kyanite powder, at 1500℃, contains 70-78% mullite, 61-64% Al₂O₃, 35-39% SiO₂, 0-0.3% K₂O + Na₂O, 0-1.2% Fe₂O₃, and 0-0.5% TiO₂, with a true density of 3.53-3.65 g / cm³. 3 The particle size is 0.044-0.074 mm, and the volume expansion is 16-18%.

[0058] The silicon micropowder has a SiO2 content of 95-98%, a CaO content of 0-0.5%, a Fe2O3 content of 0-1.5%, an Al2O3 content of 0-0.8%, and a particle size of 0-1μm.

[0059] The explosion-proof fiber was purchased from Shandong Oude Chemical Fiber Products Co., Ltd., and its model number is JX-3.

[0060] The high-efficiency water-reducing agent was purchased from Shandong Kona Fine Chemical Co., Ltd., model number SF-1216.

[0061] Example 1 A low-thermal-conductivity refractory material with aging properties and its preparation method. The steps of the preparation method described in this embodiment are as follows: Step 1: Crush the premium bauxite clinker into three particle sizes: 5-8mm, 3-5mm, and 1-3mm using a crusher, and then grind them into 0-1mm using a Raymond mill. To maintain particle size balance, a double-roll crusher is installed in the middle to maintain the percentage of the 3-5mm and 1-3mm particle sizes. Following the same steps, crush and grind the low thermal conductivity molybdenum silicate aggregate into 5-8mm, 3-5mm, 1-3mm, and 0-1mm sizes.

[0062] Step 2: Pour 10 parts of 0-1mm high-grade bauxite clinker fine powder, 15 parts of 0-1mm low thermal conductivity molybdenum silicate aggregate fine powder, 15 parts of sintered alumina fine powder, 6 parts of calcium aluminate cement fine powder, 2 parts of α-Al2O3 fine powder and 2 parts of kyanite fine powder into a high-speed mixer and stir for 5 minutes to obtain matrix fine powder.

[0063] Step 3: Pour 4 parts of 5-8mm high-grade bauxite clinker particles, 12 parts of 3-5mm high-grade bauxite clinker particles, 4 parts of 1-3mm high-grade bauxite clinker particles, 5 parts of 5-8mm low thermal conductivity molybdenum silicate aggregate particles, 15 parts of 3-5mm low thermal conductivity molybdenum silicate aggregate particles, and 5 parts of 1-3mm low thermal conductivity molybdenum silicate aggregate particles into a mixer and stir for 5 minutes. Then, while stirring, add 5 parts of silica powder and continue stirring for 1 minute. After that, add the matrix fine powder and stir for 6 minutes. Then, add 0.15 parts of explosion-proof fiber and stir for 1 minute. Finally, automatically bag and package the material to obtain the aged low thermal conductivity refractory material.

[0064] Step 4: When using, first add 0.5 parts of the high-efficiency water-reducing agent to 0.2 parts of water and mix well. Pour the aged low thermal conductivity refractory material into the engineering mixer, stir for 2 minutes, then add the water containing the high-efficiency water-reducing agent. Then, while stirring, add 6 parts of water and mix well before applying it to the heating furnace.

[0065] Step 5: After the heating furnace is completed, cure it at room temperature for 18 hours. Then, raise the temperature to 110℃ at a rate of 10℃ and hold for 24 hours. Next, raise the temperature to 300℃ at a rate of 15℃ / h and hold for 6 hours. Then, raise the temperature to 1200℃ at a rate of 20℃ / h and hold for 6 hours. Finally, allow the heating furnace to cool naturally to room temperature.

[0066] The low thermal conductivity refractory material prepared by this invention and its preparation method were tested and found to have an apparent porosity of 22.4% and a bulk density of 2.26 g / cm³. 3 Compressive strength: 85.4 MPa; flexural strength: 15.6 MPa; compressive strength retention rate: 82.5% after one thermal shock at 1100℃; flexural strength retention rate: 31.3%; linear change at 1550℃: -0.11%; abrasion resistance: 7cm. 3 The thermal conductivity is 0.913 W / (m·K), and after one full furnace cycle, the thermal conductivity is 0.924 W / (m·K). During the furnace cycle, the temperature process parameters of 304 stainless steel and 430 stainless steel are adjusted zero times.

[0067] Example 2 A low-thermal-conductivity refractory material with aging properties and its preparation method. The steps of the preparation method described in this embodiment are as follows: Step 1: Crush the premium bauxite clinker into three particle sizes: 5-8mm, 3-5mm, and 1-3mm using a crusher, and then grind them into 0-1mm using a Raymond mill. To maintain particle size balance, a double-roll crusher is installed in the middle to maintain the percentage of the 3-5mm and 1-3mm particle sizes. Following the same steps, crush and grind the low thermal conductivity molybdenum silicate aggregate into 5-8mm, 3-5mm, 1-3mm, and 0-1mm sizes.

[0068] Step 2: Pour 10 parts of 0-1mm high-grade bauxite clinker fine powder, 10 parts of 0-1mm low thermal conductivity molybdenum silicate aggregate fine powder, 18 parts of sintered alumina fine powder, 5 parts of calcium aluminate cement fine powder, 2 parts of α-Al2O3 fine powder and 4 parts of kyanite fine powder into a high-speed mixer and stir for 6 minutes to obtain matrix fine powder.

[0069] Step 3: Pour 5 parts of 5-8mm high-grade bauxite clinker particles, 17 parts of 3-5mm high-grade bauxite clinker particles, 5 parts of 1-3mm high-grade bauxite clinker particles, 3 parts of 5-8mm low thermal conductivity molybdenum silica aggregate particles, 12 parts of 3-5mm low thermal conductivity molybdenum silica aggregate particles, and 5 parts of 1-3mm low thermal conductivity molybdenum silica aggregate particles into a mixer and stir for 5 minutes. Then, while stirring, add 4 parts of silica powder and continue stirring for 1 minute. After that, add the matrix fine powder and stir for 6 minutes. Then, add 0.2 parts of explosion-proof fiber and stir for 2 minutes. Finally, automatically bag and package the material to obtain the aged low thermal conductivity refractory material.

[0070] Step 4: When using, first add 0.5 parts of the high-efficiency water-reducing agent to 0.2 parts of water and mix well. Pour the aged low thermal conductivity refractory material into the engineering mixer, stir for 3 minutes, then add the water containing the high-efficiency water-reducing agent. Then, while stirring, add 5 parts of water and mix well before applying it to the heating furnace.

[0071] Step 5: After the heating furnace is completed, cure it at room temperature for 20 hours. Then, raise the temperature to 140℃ at a rate of 10℃ and hold for 24 hours. Next, raise the temperature to 350℃ at a rate of 15℃ / h and hold for 6 hours. Then, raise the temperature to 1250℃ at a rate of 15℃ / h and hold for 6 hours. Finally, allow the heating furnace to cool naturally to room temperature.

[0072] The low thermal conductivity refractory material prepared by this invention and its preparation method were tested and found to have an apparent porosity of 25.8% and a bulk density of 2.19 g / cm³. 3 Compressive strength: 124 MPa; flexural strength: 19.5 MPa; compressive strength retention rate: 85.4% after one thermal shock at 1100℃; flexural strength retention rate: 35.6%; linear change at 1550℃: -0.06%; abrasion resistance: 7 cm. 3The thermal conductivity is 0.895 W / (m·K), and after one full-cycle furnace service, the thermal conductivity is 0.904 W / (m·K). The number of temperature process parameter adjustments for 304 stainless steel and 430 stainless steel is zero.

[0073] Example 3 A low-thermal-conductivity refractory material with aging properties and its preparation method. The steps of the preparation method described in this embodiment are as follows: Step 1: Crush the premium bauxite clinker into three particle sizes: 5-8mm, 3-5mm, and 1-3mm using a crusher, and then grind them into 0-1mm using a Raymond mill. To maintain particle size balance, a double-roll crusher is installed in the middle to maintain the percentage of the 3-5mm and 1-3mm particle sizes. Following the same steps, crush and grind the low thermal conductivity molybdenum silicate aggregate into 5-8mm, 3-5mm, 1-3mm, and 0-1mm sizes.

[0074] Step 2: Pour 8 parts of 0-1mm high-grade bauxite clinker fine powder, 10 parts of 0-1mm low thermal conductivity molybdenum silicate aggregate fine powder, 15 parts of sintered alumina fine powder, 4 parts of calcium aluminate cement fine powder, 2 parts of α-Al2O3 fine powder and 2 parts of kyanite fine powder into a high-speed mixer and stir for 7 minutes to obtain matrix fine powder.

[0075] Step 3: Pour 6 parts of 5-8mm high-grade bauxite clinker particles, 14 parts of 3-5mm high-grade bauxite clinker particles, 6 parts of 1-3mm high-grade bauxite clinker particles, 7 parts of 5-8mm low thermal conductivity molybdenum silicate aggregate particles, 16 parts of 3-5mm low thermal conductivity molybdenum silicate aggregate particles, and 7 parts of 1-3mm low thermal conductivity molybdenum silicate aggregate particles into a mixer and stir for 5 minutes. Then, while stirring, add 3 parts of silica powder and continue stirring for 1 minute. After that, add the matrix fine powder and stir for 7 minutes. Then, add 0.2 parts of explosion-proof fiber and stir for 3 minutes. Finally, automatically bag and package the material to obtain the aged low thermal conductivity refractory material.

[0076] Step 4: When using, first add 0.5 parts of the high-efficiency water-reducing agent to 0.2 parts of water and mix well. Pour the aged low thermal conductivity refractory material into an engineering mixer, stir for 4 minutes, then add the water containing the high-efficiency water-reducing agent. Then, while stirring, add 5 parts of water and mix well before applying it to the heating furnace.

[0077] Step 5: After the heating furnace is completed, cure it at room temperature for 24 hours. Then, raise the temperature to 140℃ at a rate of 10℃ and hold it for 36 hours. Next, raise the temperature to 350℃ at a rate of 15℃ / h and hold it for 12 hours. Then, raise the temperature to 1300℃ at a rate of 25℃ / h and hold it for 6 hours. Finally, allow the heating furnace to cool naturally to room temperature.

[0078] The low thermal conductivity refractory material prepared by this invention and its preparation method were tested and found to have an apparent porosity of 30.5% and a bulk density of 2.24 g / cm³. 3 Compressive strength: 142 MPa; flexural strength: 25.1 MPa; compressive strength retention rate: 90.3% after one thermal shock at 1100℃; flexural strength retention rate: 37.5%; linear change at 1550℃: 0.04%; abrasion resistance: 4 cm. 3 The thermal conductivity is 0.862 W / (m·K), and after one full-cycle furnace service, the thermal conductivity is 0.875 W / (m·K). The number of temperature process parameter adjustments for 304 stainless steel and 430 stainless steel is zero.

[0079] Example 4 A low-thermal-conductivity refractory material with aging properties and its preparation method. The steps of the preparation method described in this embodiment are as follows: Step 1: Crush the premium bauxite clinker into three particle sizes: 5-8mm, 3-5mm, and 1-3mm using a crusher, and then grind them into 0-1mm using a Raymond mill. To maintain particle size balance, a double-roll crusher is installed in the middle to maintain the percentage of the 3-5mm and 1-3mm particle sizes. Following the same steps, crush and grind the low thermal conductivity molybdenum silicate aggregate into 5-8mm, 3-5mm, 1-3mm, and 0-1mm sizes.

[0080] Step 2: Pour 5 parts of 0-1mm high-grade bauxite clinker fine powder, 10 parts of 0-1mm low thermal conductivity molybdenum silicate aggregate fine powder, 17 parts of sintered alumina fine powder, 4 parts of calcium aluminate cement fine powder, 3 parts of α-Al2O3 fine powder and 5 parts of kyanite fine powder into a high-speed mixer and stir for 8 minutes to obtain matrix fine powder.

[0081] Step 3: Pour 3 parts of 5-8mm high-grade bauxite clinker particles, 10 parts of 3-5mm high-grade bauxite clinker particles, 5 parts of 1-3mm high-grade bauxite clinker particles, 7 parts of 5-8mm low thermal conductivity silica aggregate particles, 20 parts of 3-5mm low thermal conductivity silica aggregate particles, and 7 parts of 1-3mm low thermal conductivity silica aggregate particles into a mixer and stir for 7 minutes. Then, while stirring, add 4 parts of silica powder, continue stirring for 1 minute, add the matrix fine powder, stir for 8 minutes, add 0.15 parts of explosion-proof fiber, stir for 3 minutes, and then automatically bag and package to obtain the aged low thermal conductivity refractory material.

[0082] Step 4: When using, first add 0.5 parts of the high-efficiency water-reducing agent to 0.2 parts of water and mix well. Pour the aged low thermal conductivity refractory material into the engineering mixer, stir for 5 minutes, then add the water containing the high-efficiency water-reducing agent. Then, while stirring, add 4 parts of water and mix well before applying it to the heating furnace.

[0083] Step 5: After the heating furnace is completed, cure it at room temperature for 24 hours. Then, raise the temperature to 150℃ at a rate of 10℃ and hold it for 48 hours. Next, raise the temperature to 350℃ at a rate of 15℃ / h and hold it for 12 hours. Then, raise the temperature to 1350℃ at a rate of 20℃ / h and hold it for 8 hours. Finally, allow the heating furnace to cool naturally to room temperature.

[0084] The low thermal conductivity refractory material prepared by this invention and its preparation method were tested and found to have an apparent porosity of 34.9% and a bulk density of 2.28 g / cm³. 3 The compressive strength is 159 MPa; the flexural strength is 28.4 MPa; after one thermal shock at 1100℃, the compressive strength retention rate is 97.2% and the flexural strength retention rate is 42.6%; the linear change at 1550℃ is 0.01%; and the abrasion resistance is 3 cm. 3 The thermal conductivity is 0.836 W / (m·K), and after one full-cycle furnace service, the thermal conductivity is 0.839 W / (m·K). The number of temperature process parameter adjustments for 304 stainless steel and 430 stainless steel is zero.

[0085] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0086] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0087] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a low-thermal-conductivity refractory material with aging properties, characterized in that, include: (1) Crush the high-grade bauxite clinker into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for later use; crush the low thermal conductivity molybdenum silica aggregate into four particle sizes of 5-8mm, 3-5mm, 1-3mm and 0-1mm for later use; (2) Mix 5-10 parts of high-grade bauxite clinker fine powder with a particle size of 0-1mm, 10-15 parts of low thermal conductivity molybdenum silica aggregate fine powder with a particle size of 0-1mm, 15-20 parts of sintered alumina fine powder, 4-6 parts of calcium aluminate cement fine powder, 2-3 parts of α-Al2O3 fine powder and 2-5 parts of kyanite fine powder evenly to obtain matrix fine powder; (3) Mix 2-6 parts of 5-8mm high-grade bauxite clinker particles, 8-17 parts of 3-5mm high-grade bauxite clinker particles, 2-6 parts of 1-3mm high-grade bauxite clinker particles, 3-7 parts of 5-8mm low-thermal-conductivity molybdenum silicate aggregate particles, 10-20 parts of 3-5mm low-thermal-conductivity molybdenum silicate aggregate particles, and 3-7 parts of 1-3mm low-thermal-conductivity molybdenum silicate aggregate particles evenly, and then add 3-5 parts of silica powder while stirring. After mixing evenly, add the matrix fine powder and mix evenly. Finally, add 0.1-0.3 parts of explosion-proof fiber and stir evenly to obtain the aging low-thermal-conductivity refractory material.

2. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The premium-grade bauxite clinker contains 85-92% Al2O3, 0-1.5% Fe2O3, and 0-0.2% K2O + Na2O; its bulk density is 3.11-3.50 g / cm³. 3 The apparent porosity is 1.0-6.0%, the linear change after reheating at 1500℃ is -0.1-0.1%, and the particle size is 10-60mm.

3. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The low thermal conductivity mullite-silica aggregate contains 35-45% mullite, 35-45% glass phase, 0-5% corundum phase, 50-60% Al2O3, 30-45% SiO2, 0-0.5% Fe2O3, and 0.7-0.9% K2O + Na2O; its bulk density is 1.95-2.21 g / cm³. 3 The apparent porosity is 20.3-26.5%, and the coefficient of thermal expansion at 20-1000℃ is 0.5-1.2×10⁻⁶. -6 / ℃, compressive strength of 120-200MPa, refractoriness of 1795-1805℃, compressive strength retention rate of 50-80% after 20 water coolings at 1100℃, thermal conductivity of 0.432-0.685W / (m·K) at 1000℃, pore size of less than 1μm of 50-90 vol%, median pore size of less than 1μm, and particle size of 10-60mm.

4. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The sintered alumina fine powder has an Al2O3 content of 99.5-100%, a SiO2 content of 0-0.03%, a Na2O content of 0-0.05%, and a true density of 3.95-4.02 g / cm³. 3 The particle size is 0-0.044 mm; the Al2O3 content of the calcium aluminate cement fine powder is... 3 The content is 69-75%, CaO content is 25-30%, SiO2 content is 0-0.3%, Fe2O3 content is 0-0.4%, and specific surface area (BET) is 0.60-18.00m². 2 ·g -1 The true density is 3.00-3.30 g / cm³. 3 .

5. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The α-Al₂O₃ fine powder has an Al₂O₃ content of 99.5-100%, a SiO₂ content of 0-0.02%, a Na₂O content of 0-0.05%, a Fe₂O₃ content of 0-0.01%, and a true density of 3.97-4.05 g / cm³. 3 The particle size is 0-0.010 mm.

6. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The kyanite powder, after calcination at 1500℃, exhibits a mullite conversion rate of 70-78%, an Al₂O₃ content of 61-64%, a SiO₂ content of 35-39%, a K₂O + Na₂O content of 0-0.3%, a Fe₂O₃ content of 0-1.2%, a TiO₂ content of 0-0.5%, and a true density of 3.53-3.65 g / cm³. 3 The particle size is 0.044-0.074 mm, and the volume expansion is 16-18%.

7. The method for preparing the low thermal conductivity refractory material according to claim 1, characterized in that, The silicon micropowder has a SiO2 content of 95-98%, a CaO content of 0-0.5%, a Fe2O3 content of 0-1.5%, an Al2O3 content of 0-0.8%, and a particle size of 0-1 μm.

8. A low-thermal-conductivity refractory material with aging properties, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The method of using the low thermal conductivity refractory material according to claim 8, characterized in that, include: (1) Dissolve 0.3-0.6 parts of high-efficiency water-reducing agent in 0.1-0.5 parts of water to obtain high-efficiency water-reducing agent solution; (2) Mix the high-efficiency water-reducing agent liquid with 100 parts of aged low thermal conductivity refractory material, then add 3-6 parts of water while stirring, and mix evenly before applying it to the heating furnace; (3) After construction is completed, cure at room temperature for 18-24 hours, then raise the temperature at a rate of 0-10℃ to 110-150℃ and keep it at that temperature for 24-48 hours, then raise the temperature at a rate of 10-15℃ / h to 300-350℃ and keep it at that temperature for 6-12 hours, then raise the temperature at a rate of 15-25℃ / h to 1200-1350℃ and keep it at that temperature for 4-8 hours, and finally let the heating furnace cool naturally to room temperature.

10. The method of use according to claim 9, characterized in that, The water reduction rate of the high-efficiency water-reducing agent is 40-65%.