Core-shell structure lightweight corundum-spinel-carbon refractory material and preparation method thereof

Abstract

The invention relates to a core-shell structure lightweight corundum-spinel-carbon refractory material and a preparation method thereof. According to the technical scheme, the preparation method comprises the following steps: mixing aluminum hydroxide fine powder and magnesium-aluminum hydrotalcite micro powder, adding water, stirring, forming and drying; heating to 1650-1800 DEG C according to a two-stage heating system, cooling along with a furnace, crushing and screening to obtain a refractory aggregate I, a refractory aggregate I and a refractory aggregate I I which are called total aggregates; tabular corundum fine powder, monatomic silicon powder and crystalline flake graphite powder are used as a total matrix; and mixing the liquid thermosetting phenolic resin, the magnesium aluminate spinel micro powder and the magnesium aluminum hydrotalcite micro powder to obtain the modified liquid thermosetting phenolic resin. Then putting the total aggregate into a stirrer, additionally adding the modified liquid thermosetting phenolic resin, stirring, adding the total matrix, and mixing; and carrying out mechanical pressing, heat preservation, carbon burying high-temperature treatment and natural cooling to prepare the core-shell structure light-weight corundum-spinel-carbon refractory material. The material has the advantages of low heat conductivity coefficient, good mechanical properties, good thermal shock stability and strong erosion permeability resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of corundum-spinel-carbon refractories. In particular, it relates to a core-shell structure light-weight corundum-spinel-carbon refractory and a preparation method thereof. BACKGROUND

[0002] Corundum-spinel-carbon refractories are widely used in key functional refractory devices such as slide plates and water gaps due to their excellent thermal shock stability and corrosion resistance. Therefore, the preparation of corundum-spinel-carbon refractories has attracted the attention of those skilled in the art: Document (Li You-sheng et al., Effect of Si powder on the properties of low-carbon alumina-magnesia-carbon materials. Refractories, 2007, 41(4): 245-248) uses fused white corundum, fused magnesia-alumina spinel, alumina powder, fused magnesia, silicon powder and thermosetting phenolic resin as raw materials to prepare a low-carbon alumina-magnesia-carbon refractory. This technology uses dense fused white corundum as aggregate, which has a high thermal conductivity coefficient, resulting in a high thermal conductivity coefficient of the refractory and a large heat loss.

[0003] For example, the patent technology "Alumina-magnesia-carbon refractory for steel refining and preparation method thereof" (CN201610385196.X) uses waste alumina-magnesia-carbon brick particles, diamond, fused magnesia, sub-white corundum, mullite, graphite and epoxy resin as raw materials to prepare an alumina-magnesia-carbon refractory. This technology uses waste alumina-magnesia-carbon brick particles and dense materials such as fused magnesia as aggregate, which also has the problems of high thermal conductivity coefficient and low aggregate / matrix interface bonding strength, limiting the mechanical properties and thermal shock stability of the product; and the high impurity content of waste alumina-magnesia-carbon brick particles results in poor corrosion resistance of the product.

[0004] For another example, the patent technology "Low-carbon alumina-magnesia refractory and preparation method thereof" (CN201810946462.0) uses fused magnesia particles, fused magnesia powder, bauxite particles, corundum powder, light-burned magnesia powder, flake graphite and micro-nano graphene as raw materials to prepare a low-carbon alumina-magnesia-carbon refractory. This technology uses dense fused magnesia particles and bauxite particles as aggregate, and uses micro-nano graphene instead of ordinary flake graphite, resulting in a larger density and higher thermal conductivity coefficient of the refractory, and poor interface bonding between the aggregate and the matrix and lower mechanical properties.

[0005] For another example, the patent technology "Low-carbon alumina-magnesia-carbon brick and preparation method thereof" (CN201910173858.0) uses special-grade bauxite clinker, fused magnesia, magnesia-alumina spinel, nano-carbon and thermosetting phenolic resin as raw materials to prepare a low-carbon alumina-magnesia-carbon brick. This technology uses dense fused magnesia as aggregate, which has poor aggregate / matrix interface bonding, limiting the mechanical properties of the product.

[0006] For example, the patent technology of "a kind of lightweight spinel-corundum-carbon refractory material and its preparation method" (CN202110025199.3), which uses modified porous spinel-corundum ceramic particles, porous spinel-corundum ceramic fine powder, elemental silicon powder and flake graphite as raw materials to prepare a lightweight spinel-corundum-carbon refractory material, but this technology uses aluminum hydroxide fine powder and light-burned magnesite micro powder as raw materials to prepare porous spinel-corundum ceramic particles, with large pore size and random distribution of spinel, resulting in poor mechanical properties and poor corrosion and penetration resistance of the refractory material. SUMMARY

[0007] The present application aims to overcome the shortcomings of existing technologies, and the purpose is to provide a core-shell structure lightweight corundum-spinel-carbon refractory material with low thermal conductivity, excellent mechanical properties, good thermal shock stability and strong corrosion and penetration resistance, and a preparation method thereof.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: Step 1, mix 74.6-91.8wt% of aluminum hydroxide fine powder and 8.2-25.4wt% of magnesium-aluminum hydrotalcite micro powder to obtain a mixed powder, and add 4.5-5.5wt% of water to the mixed powder, stir to obtain a mixed material.

[0009] The mixed material is machine-pressed under the condition of 120-240MPa, dried at 110-220°C for 24-48h; then placed in a high-temperature furnace, heated to 320-450°C at a rate of 1-3°C / min, and kept for 1-3h; then heated to 1650-1800°C at a rate of 3-5°C / min, and kept for 3-5h, cooled with the furnace, crushed and sieved to obtain three particle size grades of microporous corundum-spinel refractory aggregates: refractory aggregate I, refractory aggregate II and refractory aggregate III.

[0010] Step 2, mix liquid thermosetting phenolic resin, magnesium-aluminum spinel micro powder and magnesium-aluminum hydrotalcite micro powder according to the mass ratio of liquid thermosetting phenolic resin:magnesium-aluminum spinel micro powder:magnesium-aluminum hydrotalcite micro powder=100:20-60:10-20 to obtain modified liquid thermosetting phenolic resin.

[0011] Step 3, use 15-23wt% of refractory aggregate I, 20-30wt% of refractory aggregate II and 15-23wt% of refractory aggregate III as total aggregate, and use 26-39wt% of tabular corundum fine powder, 2-5wt% of elemental silicon powder and 1-3.5wt% of flake graphite powder as total matrix.

[0012] The total aggregate is placed in a mixer, 3-6wt% of the modified liquid thermosetting phenolic resin of the total aggregate and the total matrix is added, stirred, then the total matrix is added, mixed; under the condition of 150-200MPa, the machine is pressed into a shape, under the condition of 200-300°C, heat preservation for 12-36h, then under the condition of 1100-1300°C and carbon embedding, heat preservation for 3-8h, natural cooling, the core-shell structure lightweight corundum-spinel-carbon refractory material is prepared.

[0013] The particle size of the aluminum hydroxide fine powder is <50μm; the Al2O3 content of the aluminum hydroxide fine powder is 64-66wt%.

[0014] The particle size of the magnesium-aluminum hydrotalcite micro powder is <5μm, the Mg6Al2CO3(OH) 16 The Mg6Al2CO3(OH)

[0015] The carbon residue rate of the liquid thermosetting phenolic resin is ≥40wt%.

[0016] The particle size of the magnesium-aluminum spinel micro powder is <10μm; the Al2O3 content of the magnesium-aluminum spinel micro powder is 70-75wt%.

[0017] The particle size of the tabular corundum fine powder is <88μm; the Al2O3 content of the tabular corundum fine powder is >99wt%.

[0018] The particle size of the elemental silicon powder is <10μm; the Si content of the elemental silicon powder is >98.5wt%.

[0019] The particle size of the flaky graphite powder is <18μm; the C content of the flaky graphite powder is >98.5wt%.

[0020] The refractory aggregate I, the refractory aggregate II and the refractory aggregate III are respectively: the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 5mm and greater than or equal to 3mm is the refractory aggregate I, the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 3mm and greater than or equal to 1mm is the refractory aggregate II, and the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 1mm and greater than or equal to 0.088mm is the refractory aggregate III.

[0021] The multi-microporous corundum-spinel refractory aggregate has a micron-scale core-shell structure with multi-microporous alumina micro-particles containing nano-pores as the core and continuous dense spinel as the shell, the particle size of the multi-microporous alumina micro-particles is 26-41μm, and the thickness of the continuous dense spinel shell layer is 2-4μm; the multi-microporous corundum-spinel refractory aggregate has an apparent porosity of 22.5-33.6%, a bulk density of 2.53-2.85g / cm 3The average pore size is 482-861 nm, and the compressive strength is 80-150 MPa.

[0022] The light-weight corundum-spinel-carbon refractory material has a micro-millimeter scale core-shell structure with the micrometer scale core-shell structure of the microporous corundum-spinel refractory aggregate as the core and the continuous spinel layer between the aggregate and the matrix as the shell.

[0023] Compared with the prior art, the present application has the following advantages: The present application designs the whole process from the refractory aggregate to the product. In the aspect of the aggregate, the magnesium-aluminum hydrotalcite with a particle size of less than 5 μm is introduced between the aluminum hydroxide microparticles with a particle size of less than 50 μm, the microporous alumina microparticles with micro-nano pores are formed by in-situ decomposition of the aluminum hydroxide, the MgO and Al2O3 are formed by in-situ decomposition of the magnesium-aluminum hydrotalcite, the continuous magnesium-aluminum spinel layer is formed by in-situ reaction between the microporous alumina microparticles with micro-nano pores, the micrometer scale core-shell structure of the microporous corundum-spinel refractory aggregate is obtained, the micrometer scale core-shell structure has the microporous alumina microparticles with a particle size of 26-41 μm as the core and the continuous dense spinel shell layer with a thickness of 2-4 μm as the shell. Compared with the prior art, the microporous corundum-spinel refractory aggregate prepared by the present application has the advantages of smaller pore size, lower thermal conductivity and more accurate control of the distribution of the magnesium-aluminum spinel. In the aspect of the structure design of the aggregate / matrix interface of the product, the magnesium-aluminum spinel micropowder and the magnesium-aluminum hydrotalcite micropowder are wrapped on the surface of the aggregate to form a continuous wrapping layer, the continuous spinel layer with a thickness of 0.15-0.32 mm is formed by in-situ reaction, the millimeter scale core-shell structure with the micrometer scale core-shell structure of the microporous corundum-spinel aggregate as the core and the continuous spinel layer with a thickness of 0.15-0.32 mm as the shell is formed. The millimeter scale core-shell structure has the sawtooth occlusion structure at the core-shell interface by virtue of the rough surface of the microporous aggregate and the flake graphite-plate-shaped corundum-spinel mosaic structure at the shell-matrix interface. Through the whole process design from the refractory aggregate to the aggregate / matrix interface of the product, the light-weight corundum-spinel-carbon refractory material with the micro-millimeter scale core-shell structure is prepared, the micro-millimeter scale core-shell structure has the micrometer scale core-shell structure of the microporous corundum-spinel refractory aggregate with the microporous alumina microparticles with micro-nano pores as the core and the continuous dense spinel as the shell as the core and the continuous spinel layer between the aggregate and the matrix as the shell.

[0024] The microporous corundum-spinel refractory aggregate adopted by the application is constructed with microporous alumina microparticles with a particle size of 26-41 microns as a core and a continuous dense spinel shell layer with a thickness of 2-4 microns as a shell to form a micron-scale core-shell structure, which increases the crack propagation path and improves the strength and thermal shock stability of the aggregate. The light-weight corundum-spinel-carbon refractory material prepared by the application is constructed with the microporous corundum-spinel aggregate with a micron-scale core-shell structure, higher strength and better thermal shock stability as a core and a continuous spinel layer with a thickness of 0.15-0.32 mm as a shell to form a millimeter-scale core-shell structure, which bridges the interface between the aggregate (core) and the matrix, and improves the thermal shock stability and mechanical properties of the product.

[0025] The microporous corundum-spinel aggregate adopted by the application has micropores with a smaller pore size than the existing porous corundum-spinel aggregate, and the microporous alumina microparticles in the aggregate are bridged by a continuous dense spinel layer, which forms a tight bond between the microporous alumina microparticles and the spinel, and the stronger corrosion resistance of the spinel improves the corrosion and penetration resistance of the product. The light-weight corundum-spinel-carbon refractory material prepared by the application is constructed with a continuous spinel shell layer with a thickness of 0.15-0.32 mm on the surface of the aggregate, which forms a sawtooth occlusion structure at the interface between the aggregate (core) and the shell, making the interface bond tighter and hindering the penetration of the slag along the interface. On the other hand, the inlaid structure formed at the interface between the shell and the matrix hinders the corrosion of the slag by the spinel and flaky graphite, which improves the corrosion and penetration resistance of the product.

[0026] The application forms a full-process lightweight corundum-spinel-carbon refractory material structure design and preparation technology by designing the composition of raw materials, the microstructure of aggregates, the aggregate-shell interface structure and the shell-matrix interface structure. First, by adjusting the particle size and composition of aluminum hydroxide fine powder and magnesium-aluminum hydrotalcite, a green body with a structure of aluminum hydroxide microparticles as a skeleton and magnesium-aluminum hydrotalcite with a large particle size difference filled between the aluminum hydroxide microparticles is obtained. Then, by adjusting the heating rate from room temperature to 320-450°C, the holding temperature and time, and the heating rate, holding temperature and time from 320-450°C to 1650-1800°C, the in-situ decomposition under the condition of 320-450°C and the in-situ reaction, mass transfer and pore evolution under high temperature are controlled, to obtain a multi-porous corundum-spinel refractory aggregate with a multi-porous alumina microparticle with a particle size of 26-41 μm as a core and a continuous dense spinel shell layer with a thickness of 2-4 μm as a shell. Finally, the proportions of magnesium-aluminum spinel micropowder, magnesium-aluminum hydrotalcite micropowder and liquid thermosetting phenolic resin are designed, and in the reaction sintering process, the MgO generated by the decomposition of magnesium-aluminum hydrotalcite micropowder reacts with the aggregate and the matrix respectively to form a continuous dense magnesium-aluminum spinel shell. Through the volume expansion formed in the magnesium-aluminum spinel reaction process, a tightly bonded interface of aggregate-shell and shell-matrix is formed, and together with the micron-scale core-shell structure inside the aggregate, a multi-scale core-shell structure is formed, which significantly improves the mechanical properties, thermal shock stability and anti-erosion and penetration performance of the product on the basis of reducing the thermal conductivity of the lightweight corundum-spinel-carbon refractory material with a core-shell structure.

[0027] The lightweight corundum-spinel-carbon refractory material with a core-shell structure prepared by the application has the following properties: the apparent porosity is 25-28%; the bulk density is 2.45-2.64 g / cm 3 ; and the compressive strength is 60-72 MPa.

[0028] Therefore, the lightweight corundum-spinel-carbon refractory material with a core-shell structure prepared by the application has the characteristics of low thermal conductivity, excellent mechanical properties, good thermal shock stability and strong anti-erosion and penetration performance. DETAILED DESCRIPTION

[0029] The application will be further described below in conjunction with the specific embodiments, which are not intended to limit the scope of protection.

[0030] A lightweight corundum-spinel-carbon refractory material with a core-shell structure and a preparation method thereof. The steps of the preparation method described in the specific embodiment are as follows: Step 1, mix 74.6-91.8 wt% of aluminum hydroxide fine powder and 8.2-25.4 wt% of magnesium-aluminum hydrotalcite micropowder to obtain a mixed powder, and add 4.5-5.5 wt% of water to the mixed powder, and stir to obtain a mixed material.

[0031] The mixture is pressed into shape at 120-240 MPa and dried at 110-220°C for 24-48 hours. The mixture is then placed in a high-temperature furnace, heated to 320-450°C at a rate of 1-3°C / min, and kept warm for 1-3 hours. The mixture is then heated to 1650-1800°C at a rate of 3-5°C / min, and kept warm for 3-5 hours. The mixture is then cooled in the furnace, crushed, and sieved to obtain three particle size grades of multi-microporous corundum-spinel refractory aggregates: refractory aggregate I, refractory aggregate ⅠⅠ, and refractory aggregate ⅢⅠⅠ.

[0032] The microporous corundum-spinel refractory aggregate has an apparent porosity of 22.5-33.6% and a bulk density of 2.53-2.85 g / cm 3 The average pore size is 482~861nm and the compressive strength is 80~150MPa.

[0033] Step 2: mixing the liquid thermosetting phenolic resin, magnesium aluminum spinel powder and magnesium aluminum hydrotalcite powder at a mass ratio of liquid thermosetting phenolic resin: magnesium aluminum spinel powder: magnesium aluminum hydrotalcite powder of 100:20-60:10-20 to obtain a modified liquid thermosetting phenolic resin.

[0034] Step 3: 15-23wt% of refractory aggregate I, 20-30wt% of refractory aggregate II and 15-23wt% of refractory aggregate III are used as the total aggregate, and 26-39wt% of plate-shaped corundum fine powder, 2-5wt% of elemental silicon powder and 1-3.5wt% of flake graphite powder are used as the total matrix.

[0035] The total aggregate is placed in a mixer, and a modified liquid thermosetting phenolic resin of 3 to 6 wt% of the total aggregate and the total matrix is ​​added and stirred, and then the total matrix is ​​added and mixed; the mixture is machine-pressed under 150 to 200 MPa conditions, kept warm at 200 to 300°C for 12 to 36 hours, and then kept warm at 1100 to 1300°C and carbon buried conditions for 3 to 8 hours, and naturally cooled to obtain a core-shell structured lightweight corundum-spinel-carbon refractory material.

[0036] The Al2O3 content of the aluminum hydroxide fine powder is 64-66wt%.

[0037] The magnesium aluminum hydrotalcite powder Mg6Al2CO3 (OH) 16 4H2O content>99wt%; the magnesium aluminum hydrotalcite powder in step 1 is the same as the magnesium aluminum hydrotalcite powder in step 2.

[0038] The residual carbon rate of the liquid thermosetting phenolic resin is ≥40wt%.

[0039] The Al2O3 content of the magnesium-aluminum spinel powder is 70-75wt%.

[0040] The Al2O3 content of the tabular corundum fine powder is > 99wt%.

[0041] The Si content of the elemental silicon powder is > 98.5wt%.

[0042] The C content of the flake graphite powder is > 98.5wt%.

[0043] In the specific embodiment: The particle size of the aluminum hydroxide fine powder is < 50μm; The particle size of the magnesium-aluminum hydrotalcite micro powder is < 5μm; The particle size of the magnesium-aluminum spinel micro powder is < 10μm; The particle size of the tabular corundum fine powder is < 88μm; The particle size of the elemental silicon powder is < 10μm; The particle size of the flake graphite powder is < 18μm; The refractory aggregate I, the refractory aggregate II and the refractory aggregate III are respectively: the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 5mm and greater than or equal to 3mm is the refractory aggregate I, the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 3mm and greater than or equal to 1mm is the refractory aggregate II, and the multi-microporous corundum-spinel refractory aggregate with a particle size of less than 1mm and greater than or equal to 0.088mm is the refractory aggregate III; The multi-microporous corundum-spinel refractory aggregate has a micron-scale core-shell structure with multi-microporous alumina micro-particles containing nano-pores as a core and a continuous dense spinel as a shell, the particle size of the multi-microporous alumina micro-particles is 26-41μm, and the thickness of the continuous dense spinel shell layer is 2-4μm; The core-shell structure light-weighted corundum-spinel-carbon refractory material is a multi-microporous corundum-spinel refractory aggregate with a micron-scale core-shell structure with multi-microporous alumina micro-particles containing micro-nano-pores as a core and a continuous dense spinel as a shell as a core and a multi-scale core-shell structure with a continuous spinel layer distributed between the aggregate and the matrix as a shell; wherein: the thickness of the continuous spinel layer distributed between the aggregate and the matrix is 0.15-0.32mm.

[0044] The embodiments are not described again.

[0045] Embodiment 1 A core-shell structure light-weighted corundum-spinel-carbon refractory material and a preparation method thereof. The steps of the preparation method in the embodiment are: Step 1, mix 81.5wt% of aluminum hydroxide fine powder and 18.5wt% of magnesium-aluminum hydrotalcite micro powder to obtain a mixed powder, and add 4.5wt% of water to the mixed powder, stir to obtain a mixed material.

[0046] The mixture is molded under the condition of 180 MPa, dried at 220 °C for 38 h, then placed in a high-temperature furnace, heated to 380 °C at a rate of 2 °C / min, kept for 3 h, then heated to 1700 °C at a rate of 3 °C / min, kept for 3 h, cooled in the furnace, crushed, and sieved to obtain three particle size grades of microporous corundum-spinel refractory aggregate: refractory aggregate I, refractory aggregate II, and refractory aggregate III.

[0047] The microporous corundum-spinel refractory aggregate has an apparent porosity of 25.8%, a bulk density of 2.78 g / cm 3 , an average pore size of 758 nm, and a compressive strength of 134 MPa.

[0048] Step 2: The liquid thermosetting phenolic resin, magnesium-aluminum spinel powder, and magnesium-aluminum hydrotalcite powder are mixed in a mass ratio of 100:45:15 to obtain modified liquid thermosetting phenolic resin.

[0049] Step 3: 15 wt% of the refractory aggregate I, 30 wt% of the refractory aggregate II, and 18 wt% of the refractory aggregate III are used as total aggregate, and 33 wt% of the tabular corundum powder, 2 wt% of the elemental silicon powder, and 2 wt% of the flaky graphite powder are used as total matrix.

[0050] The total aggregate is placed in a blender, and 3 wt% of the modified liquid thermosetting phenolic resin, which is the sum of the total aggregate and the total matrix, is added, stirred, and then the total matrix is added and mixed. The mixture is molded under the condition of 180 MPa, dried at 280 °C for 36 h, then kept at 1300 °C and carbon-embedded for 7 h, and naturally cooled to obtain a core-shell structure lightweight corundum-spinel-carbon refractory material.

[0051] The Al2O3 content of the aluminum hydroxide powder is 64 wt%.

[0052] The Mg6Al2CO3(OH) 16 ·4H2O content of the magnesium-aluminum hydrotalcite powder is 99.2 wt%. The magnesium-aluminum hydrotalcite powder in step 1 is the same as the magnesium-aluminum hydrotalcite powder in step 2.

[0053] The carbon residue rate of the liquid thermosetting phenolic resin is 40 wt%.

[0054] The Al2O3 content of the magnesium-aluminum spinel powder is 73 wt%.

[0055] The Al2O3 content of the tabular corundum powder is 99.1 wt%.

[0056] The Si content of the elemental silicon powder is 98.8 wt%.

[0057] The C content of the flaky graphite powder is 98.6wt%.

[0058] The core-shell structure lightweight corundum-spinel-carbon refractory material prepared by the method has the following properties: the apparent porosity is 27%; the bulk density is 2.52 g / cm 3 ; and the compressive strength is 64 MPa.

[0059] Example 2 A core-shell structure lightweight corundum-spinel-carbon refractory material and a preparation method thereof. The preparation method of the present embodiment comprises the following steps: Step 1, mixing 74.6wt% of aluminum hydroxide fine powder and 25.4wt% of magnesium-aluminum hydrotalcite micropowder to obtain a mixed powder, and adding 5.5wt% of water to the mixed powder and stirring to obtain a mixed material.

[0060] The mixed material is formed by machine pressing under the condition of 120 MPa, dried at 110°C for 30h, then heated to 320°C at a rate of 1°C / min in a high-temperature furnace, kept for 2h, then heated to 1750°C at a rate of 5°C / min, kept for 4h, cooled in the furnace, crushed and sieved to obtain three kinds of microporous corundum-spinel refractory aggregates: refractory aggregate I, refractory aggregate II and refractory aggregate III.

[0061] The microporous corundum-spinel refractory aggregate has the following properties: the apparent porosity is 33.6%, the bulk density is 2.53 g / cm 3 , the average pore size is 482 nm, and the compressive strength is 80 MPa.

[0062] Step 2, mixing liquid thermosetting phenolic resin, magnesium-aluminum spinel micropowder and magnesium-aluminum hydrotalcite micropowder according to the mass ratio of liquid thermosetting phenolic resin:magnesium-aluminum spinel micropowder:magnesium-aluminum hydrotalcite micropowder=100:20:10 to obtain modified liquid thermosetting phenolic resin.

[0063] Step 3, taking 21wt% of refractory aggregate I, 28wt% of refractory aggregate II and 15wt% of refractory aggregate III as total aggregate, and taking 30wt% of tabular corundum fine powder, 5wt% of elemental silicon powder and 1wt% of flaky graphite powder as total matrix.

[0064] The total aggregate is placed in a stirrer, and 5wt% of modified liquid thermosetting phenolic resin is added to the total aggregate and the total matrix, and then the total matrix is added and mixed; the mixture is formed by machine pressing under the condition of 150 MPa, kept for 28h at 300°C, and then kept for 3h at 1250°C and under carbon embedding conditions, and naturally cooled to obtain the core-shell structure lightweight corundum-spinel-carbon refractory material.

[0065] The Al2O3 content of the aluminum hydroxide fine powder is 65.8 wt%.

[0066] The Mg6Al2CO3(OH) 16 The Mg6Al2CO3(OH) content of the magnesium-aluminum hydrotalcite micro powder in step 1 is the same as that of the magnesium-aluminum hydrotalcite micro powder in step 2.

[0067] The carbon residue rate of the liquid thermosetting phenolic resin is 41 wt%.

[0068] The Al2O3 content of the magnesium-aluminum spinel micro powder is 70 wt%.

[0069] The Al2O3 content of the tabular corundum fine powder is 99.2 wt%.

[0070] The Si content of the elemental silicon powder is 98.6 wt%.

[0071] The C content of the flake graphite powder is 98.9 wt%.

[0072] The core-shell structure lightweight corundum-spinel-carbon refractory material prepared in the present application is detected to have a porosity of 28%, a bulk density of 2.45 g / cm 3 , and a compressive strength of 60 MPa.

[0073] Example 3 A core-shell structure lightweight corundum-spinel-carbon refractory material and a preparation method thereof. The preparation method in the present example comprises the following steps: Step 1, mixing 91.8 wt% of aluminum hydroxide fine powder and 8.2 wt% of magnesium-aluminum hydrotalcite micro powder to obtain a mixed powder, and adding 4.9 wt% of water to the mixed powder and stirring to obtain a mixed material.

[0074] The mixed material is formed by machine pressing under a pressure of 200 MPa, dried at 160°C for 48 h, then heated to 450°C at a rate of 2°C / min in a high-temperature furnace, kept at 450°C for 1 h, then heated to 1650°C at a rate of 3°C / min, kept at 1650°C for 4 h, cooled in the furnace, crushed, and sieved to obtain three particle size grades of microporous corundum-spinel refractory aggregates, namely refractory aggregate I, refractory aggregate II, and refractory aggregate III.

[0075] The microporous corundum-spinel refractory aggregate has a porosity of 30.4%, a bulk density of 2.65 g / cm 3 , an average pore size of 595 nm, and a compressive strength of 102 MPa.

[0076] Step 2, the liquid thermosetting phenolic resin: magnesium-aluminum spinel micro powder: magnesium-aluminum hydrotalcite micro powder is mixed in a mass ratio of 100:60:18, and a modified liquid thermosetting phenolic resin is obtained.

[0077] Step 3, 23wt% of the refractory aggregate I, 20wt% of the refractory aggregate II and 23wt% of the refractory aggregate III are used as the total aggregate, and 26wt% of the tabular corundum powder, 4.5wt% of the elemental silicon powder and 3.5wt% of the flake graphite powder are used as the total matrix.

[0078] The total aggregate is placed in a mixer, 4wt% of the modified liquid thermosetting phenolic resin is added to the total aggregate and the total matrix, and then stirred, and then the total matrix is added and mixed; the core-shell structure light-weight corundum-spinel-carbon refractory material is prepared by molding under the condition of 200MPa, heat preservation at 200°C for 12h, and then heat preservation at 1100°C and carbon embedding for 8h, and natural cooling.

[0079] The Al2O3 content of the aluminum hydroxide powder is 66wt%.

[0080] The Mg6Al2CO3(OH) 16 The Mg6Al2CO3(OH) content of the magnesium-aluminum hydrotalcite micro powder in step 1 is the same as that of the magnesium-aluminum hydrotalcite micro powder in step 2.

[0081] The carbon residue rate of the liquid thermosetting phenolic resin is 45wt%.

[0082] The Al2O3 content of the magnesium-aluminum spinel micro powder is 72wt%.

[0083] The Al2O3 content of the tabular corundum powder is 99.5wt%.

[0084] The Si content of the elemental silicon powder is 98.7wt%.

[0085] The C content of the flake graphite powder is 98.8wt%.

[0086] The core-shell structure light-weight corundum-spinel-carbon refractory material prepared in the application is detected: the apparent porosity is 25%; the bulk density is 2.64g / cm 3 ; the compressive strength is 69MPa.

[0087] Example 4 A core-shell structure light-weight corundum-spinel-carbon refractory material and a preparation method thereof. The preparation method in the embodiment comprises the following steps: Step 1, mixing 87wt% of aluminum hydroxide fine powder and 13wt% of magnesium-aluminum hydrotalcite micro-powder to obtain a mixed powder, adding 5.1wt% of water to the mixed powder, stirring to obtain a mixture.

[0088] The mixture is molded under the condition of 240MPa, dried at 210°C for 24h, then placed in a high-temperature furnace, heated to 420°C at a rate of 3°C / min, kept for 2h, then heated to 1800°C at a rate of 4°C / min, kept for 5h, cooled with the furnace, crushed and sieved to obtain three kinds of multi-microporous corundum-spinel refractory aggregates: refractory aggregate I, refractory aggregate II and refractory aggregate III.

[0089] The multi-microporous corundum-spinel refractory aggregate has a apparent porosity of 22.5%, a bulk density of 2.85g / cm 3 , an average pore size of 861nm and a compressive strength of 150MPa.

[0090] Step 2, mixing liquid thermosetting phenolic resin, magnesium-aluminum spinel micro-powder and magnesium-aluminum hydrotalcite micro-powder according to the mass ratio of liquid thermosetting phenolic resin:magnesium-aluminum spinel micro-powder:magnesium-aluminum hydrotalcite micro-powder = 100:55:20 to obtain modified liquid thermosetting phenolic resin.

[0091] Step 3, taking 16wt% of refractory aggregate I, 23wt% of refractory aggregate II and 16wt% of refractory aggregate III as total aggregate, taking 39wt% of tabular corundum fine powder, 3wt% of elemental silicon powder and 3wt% of flake graphite powder as total matrix.

[0092] Placing the total aggregate in a stirrer, adding 6wt% of modified liquid thermosetting phenolic resin to the total aggregate and total matrix, stirring, then adding the total matrix and mixing; molding under the condition of 160MPa, keeping at 240°C for 31h, then keeping at 1150°C and carbon-embedding condition for 5h and naturally cooling to obtain a core-shell structure lightweight corundum-spinel-carbon refractory material.

[0093] The Al2O3 content of the aluminum hydroxide fine powder is 64.5wt%.

[0094] The Mg6Al2CO3(OH) 16 ·4H2O content of the magnesium-aluminum hydrotalcite micro-powder is 99.6wt%; the magnesium-aluminum hydrotalcite micro-powder in step 1 is the same as the magnesium-aluminum hydrotalcite micro-powder in step 2.

[0095] The carbon residue rate of the liquid thermosetting phenolic resin is 42wt%.

[0096] The Al2O3 content of the magnesium-aluminum spinel micro-powder is 75wt%.

[0097] The Al2O3 content of the tabular corundum fine powder is 99.4wt%.

[0098] The Si content of the elemental silicon powder is 98.6wt%.

[0099] The C content of the flake graphite powder is 98.6wt%.

[0100] The core-shell structure lightweight corundum-spinel-carbon refractory material prepared in the present application is detected to have a porosity of 26%, a bulk density of 2.59g / cm 3 , and a compressive strength of 72MPa.

[0101] Compared with the prior art, the present embodiment has the following positive effects: The present embodiment designs the whole process from refractory aggregate to product. In the aspect of aggregate, magnesium-aluminum hydrotalcite with a particle size of less than 5μm is introduced between aluminum hydroxide microparticles with a particle size of less than 50μm, and the characteristics of in-situ decomposition of aluminum hydroxide to form microporous aluminum oxide microparticles with micro-nano pores and in-situ decomposition of magnesium-aluminum hydrotalcite to form MgO and Al2O3 are utilized to form a continuous magnesium-aluminum spinel layer between the microporous aluminum oxide microparticles with micro-nano pores, so as to obtain microporous corundum-spinel refractory aggregate with a micron-scale core-shell structure, wherein the micron-scale core-shell structure is microporous aluminum oxide microparticles with a particle size of 26-41μm as core and a continuous dense spinel shell layer with a thickness of 2-4μm as shell. Compared with the prior art, the microporous corundum-spinel refractory aggregate prepared in the present embodiment has the advantages of smaller pore size, lower thermal conductivity, and more accurate control of magnesium-aluminum spinel distribution. In the aspect of the aggregate / matrix interface structure design of the product, magnesium-aluminum spinel micropowder and magnesium-aluminum hydrotalcite micropowder are wrapped on the surface of the aggregate to form a continuous wrapping layer, and a continuous spinel layer with a thickness of 0.15-0.32mm is formed by in-situ reaction, so as to form a millimeter-scale core-shell structure with the microporous corundum-spinel aggregate with a micron-scale core-shell structure as core and the continuous spinel layer with a thickness of 0.15-0.32mm as shell. The millimeter-scale core-shell structure forms a zigzag occlusion structure at the core-shell interface by utilizing the rough surface characteristics of the microporous aggregate, and forms a flake graphite-tabular corundum-spinel inlaid structure at the shell-matrix interface. Through the whole process design from refractory aggregate to the aggregate / matrix interface of the product, the microporous corundum-spinel refractory aggregate with a micron-scale core-shell structure with microporous aluminum oxide microparticles with micro-nano pores as core and a continuous dense spinel shell as shell is obtained as core, and the multi-scale core-shell structure lightweight corundum-spinel-carbon refractory material with the continuous spinel layer distributed between the aggregate and the matrix as shell.

[0102] The multi-microporous corundum-spinel refractory aggregate adopted in the embodiment has a micron-scale core-shell structure with multi-microporous alumina microparticles with a particle size of 26-41 μm as the core and a continuous dense spinel shell layer with a thickness of 2-4 μm as the shell, which increases the crack propagation path and improves the strength and thermal shock stability of the aggregate. The light-weighted corundum-spinel-carbon refractory material prepared in the embodiment has a millimeter-scale core-shell structure with the multi-microporous corundum-spinel aggregate with higher strength and better thermal shock stability and a continuous spinel shell layer with a thickness of 0.15-0.32 mm as the shell, which bridges the interface between the aggregate (core) and the matrix, and improves the thermal shock stability and mechanical properties of the product.

[0103] The multi-microporous corundum-spinel aggregate adopted in the embodiment has smaller micropores and nanometer pores than the existing porous corundum-spinel aggregate, and the multi-microporous alumina microparticles in the aggregate are bridged by a continuous dense spinel shell layer, which forms a tight bond between the multi-microporous alumina microparticles and the spinel, and the stronger corrosion resistance of the spinel improves the corrosion and penetration resistance of the product. The light-weighted corundum-spinel-carbon refractory material prepared in the embodiment has a continuous spinel shell layer with a thickness of 0.15-0.32 mm on the surface of the aggregate, which forms a sawtooth occlusion structure at the interface between the aggregate (core) and the shell, making the interface bond tighter and hindering the penetration of the molten slag along the interface; on the other hand, the inlaid structure formed at the interface between the shell and the matrix hinders the corrosion of the molten slag by the spinel and flaky graphite, which improves the corrosion and penetration resistance of the product.

[0104] The embodiment forms a full-process lightweight corundum-spinel-carbon refractory material structure design and preparation technology by designing the composition of raw materials, the microstructure of aggregates, the aggregate-shell interface structure, and the shell-matrix interface structure. First, by adjusting the particle size and composition of aluminum hydroxide fine powder and magnesium-aluminum hydrotalcite, a green body with a structure of aluminum hydroxide microparticles as a skeleton and magnesium-aluminum hydrotalcite with a large particle size difference filled between the aluminum hydroxide microparticles is obtained. Then, by adjusting the heating rate from room temperature to 320-450°C, the holding temperature and time, and the heating rate from 320-450°C to 1650-1800°C, the holding temperature and time, the in-situ decomposition under 320-450°C and the in-situ reaction, mass transfer and pore evolution under high temperature are controlled, to obtain a multi-microporous corundum-spinel refractory aggregate with a multi-microporous alumina microparticle with a particle size of 26-41 μm as a core and a continuous dense spinel shell layer with a thickness of 2-4 μm as a shell. Finally, the proportions of magnesium-aluminum spinel micropowder, magnesium-aluminum hydrotalcite micropowder and liquid thermosetting phenolic resin are designed, so that in the reaction sintering process, the MgO generated by the decomposition of magnesium-aluminum hydrotalcite micropowder reacts with the aggregate and the matrix respectively to form a continuous dense magnesium-aluminum spinel shell, and through the volume expansion formed in the magnesium-aluminum spinel reaction process, a tightly bonded interface of aggregate-shell and shell-matrix is formed, which together with the micron-scale core-shell structure inside the aggregate forms a multi-scale core-shell structure, thereby significantly improving the mechanical properties, thermal shock stability and anti-erosion and penetration performance of the product on the basis of reducing the thermal conductivity of the lightweight corundum-spinel-carbon refractory material with a core-shell structure.

[0105] The lightweight corundum-spinel-carbon refractory material with a core-shell structure prepared in the embodiment has a porosity of 25-28%, a bulk density of 2.45-2.64 g / cm 3 , and a compressive strength of 60-72 MPa.

[0106] Therefore, the lightweight corundum-spinel-carbon refractory material with a core-shell structure prepared in the embodiment has the characteristics of low thermal conductivity, excellent mechanical properties, good thermal shock stability and strong anti-erosion and penetration performance.

Claims

1. A method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material, characterized in that The steps of the preparation method are: Step 1, mixing 74.6-91.8 wt% of aluminum hydroxide fine powder and 8.2-25.4 wt% of magnesium aluminum hydrotalcite fine powder to obtain a mixed powder, adding 4.5-5.5 wt% of water to the mixed powder, stirring to obtain a mixture; The mixture is pressed into shape at 120-240 MPa and dried at 110-220°C for 24-48 hours. The mixture is then placed in a high-temperature furnace and heated to 320-450°C at a rate of 1-3°C / min and kept at that temperature for 1-3 hours. The mixture is then heated to 1650-1800°C at a rate of 3-5°C / min and kept at that temperature for 3-5 hours. The mixture is then cooled in the furnace, crushed, and sieved to obtain three particle size grades of multi-microporous corundum-spinel refractory aggregates: refractory aggregate I, refractory aggregate ⅠⅠ, and refractory aggregate ⅢⅠⅠ. Step 2, mixing the liquid thermosetting phenolic resin, the magnesium aluminum spinel powder and the magnesium aluminum hydrotalcite powder at a mass ratio of 100:20 to 60:10 to 20 to obtain a modified liquid thermosetting phenolic resin; Step 3, using 15-23wt% of refractory aggregate I, 20-30wt% of refractory aggregate II and 15-23wt% of refractory aggregate III as the total aggregate, and using 26-39wt% of plate-shaped corundum fine powder, 2-5wt% of elemental silicon powder and 1-3.5wt% of flake graphite powder as the total matrix; The total aggregate is placed in a mixer, and 3 to 6 wt% of the total aggregate and the total matrix of the modified liquid thermosetting phenolic resin is added and stirred, and then the total matrix is ​​added and mixed; The core-shell structure lightweight corundum-spinel-carbon refractory material is obtained by machine pressing under 150-200MPa conditions, keeping warm at 200-300°C for 12-36h, then keeping warm at 1100-1300°C under carbon burial conditions for 3-8h, and naturally cooling.

2. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the aluminum hydroxide fine powder is less than 50 μm; the Al 2 O 3 content of the aluminum hydroxide fine powder is 64-66 wt %.

3. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the magnesium aluminum hydrotalcite powder is less than 5 μm, and the Mg6Al2CO3(OH) 16 4H2O content>99wt%; the magnesium aluminum hydrotalcite powder in step 1 is the same as the magnesium aluminum hydrotalcite powder in step 2.

4. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The residual carbon rate of the liquid thermosetting phenolic resin is ≥40wt%.

5. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the magnesium-aluminum spinel powder is less than 10 μm; the Al 2 O 3 content of the magnesium-aluminum spinel powder is 70-75 wt %.

6. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the plate-like corundum fine powder is less than 88 μm; and the Al 2 O 3 content of the plate-like corundum fine powder is greater than 99 wt %.

7. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the elemental silicon powder is less than 10 μm; and the Si content of the elemental silicon powder is greater than 98.5 wt %.

8. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The particle size of the flake graphite powder is less than 18 μm; and the C content of the flake graphite powder is greater than 98.5 wt %.

9. The method for preparing a core-shell structure lightweight corundum-spinel-carbon refractory material according to claim 1, characterized in that The refractory aggregate I, refractory aggregate Ⅰ and refractory aggregate ⅢⅠ are respectively: microporous corundum-spinel refractory aggregate with a particle size of less than 5 mm and greater than or equal to 3 mm is refractory aggregate I, microporous corundum-spinel refractory aggregate with a particle size of less than 3 mm and greater than or equal to 1 mm is refractory aggregate II, and microporous corundum-spinel refractory aggregate with a particle size of less than 1 mm and greater than or equal to 0.088 mm is refractory aggregate III; The microporous corundum-spinel refractory aggregate has a micron-scale core-shell structure with microporous alumina microparticles containing nanopores as the core and continuous dense spinel as the shell. The particle size of the microporous alumina microparticles is 26-41 μm, and the thickness of the continuous dense spinel shell is 2-4 μm. The microporous corundum-spinel refractory aggregate has an apparent porosity of 22.5-33.6% and a bulk density of 2.53-2.85 g / cm 3 The average pore size is 482~861nm and the compressive strength is 80~150MPa.

10. A core-shell structure lightweight corundum-spinel-carbon refractory material, characterized in that The core-shell structure lightweight corundum-spinel-carbon refractory material is a core-shell structure lightweight corundum-spinel-carbon refractory material prepared by the preparation method of the core-shell structure lightweight corundum-spinel-carbon refractory material according to any one of claims 1 to 9; The core-shell structure lightweight corundum-spinel-carbon refractory material is a multi-scale core-shell structure with microporous alumina microparticles containing micro-nanopores as the core, a micron-scale core-shell structured microporous corundum-spinel refractory aggregate as the core with continuous dense spinel as the shell, and a continuous spinel layer distributed between the aggregate and the matrix as the shell; wherein: the thickness of the continuous spinel layer distributed between the aggregate and the matrix is ​​0.15~0.32mm.