High slag resistance castable and preparation method thereof

Abstract

The application discloses a high-slag-resistance castable and a preparation method thereof, and belongs to the technical field of metallurgical materials. The high-slag-resistance castable comprises the following components in percentage by mass: aggregate 58-70%; powder 20-30%; binding agent 5-10%; additive 1-3%; the aggregate comprises the following components in percentage by mass: activated pre-treated bauxite clinker 30-45%; silicon carbide particles coated with a silicon nitride-silicon sol composite combined phase on the surface 10-20%; electrically fused zirconia-corundum particles coated with a mullite-zirconia composite layer on the surface 5-10%; and electrically fused magnesia particles coated with a magnesium-aluminum spinel microcrystalline layer on the surface 3-8%. The castable has excellent slag resistance, thermal shock resistance, high-temperature structural stability and service life, and can meet the use requirements of large-scale and long service life of blast furnaces.

Description

Technical Field

[0001] This invention relates to the field of metallurgical materials technology, and more specifically, to a high slag-resistant castable and its preparation method. Background Technology

[0002] Blast furnace slag channels are critical passageways used in ironmaking processes to transport high-temperature molten slag. Their operating conditions are extremely harsh; the slag temperature typically reaches 1400–1550°C and contains various oxide components such as CaO, SiO2, Al2O3, FeO, and MnO, exhibiting strong corrosiveness and permeability. Simultaneously, the slag channel lining material must withstand multiple destructive effects, including periodic temperature fluctuations, high-speed molten slag erosion, and chemical corrosion. Therefore, the castable refractory for slag channels must possess excellent resistance to slag erosion, permeability, thermal shock resistance, and high-temperature structural stability.

[0003] Currently, although traditional cement-bonded high-alumina castables have advantages such as convenient construction and low cost, they also have defects such as low mid-temperature strength, poor slag erosion resistance, and short service life. With the development of large-scale and long-life blast furnace technology, the performance requirements for slag trench lining materials are increasing. Developing high-slag-resistant castables that combine construction performance and long service life has become an urgent need in the industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a high slag-resistant castable and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A first aspect of the present invention provides a high slag-resistant castable comprising the following components by weight percentage:

[0007] Aggregate 58-70%; powder 20-30%; binder 5-10%; admixtures 1-3%;

[0008] The aggregate comprises the following components by mass percentage of the castable:

[0009] 30-45% of the high-alumina bauxite clinker underwent activation pretreatment;

[0010] 10-20% of silicon carbide particles are coated with a silicon nitride-silica sol composite phase.

[0011] 5-10% fused zirconium corundum particles with a mullite-zirconia composite coating on the surface;

[0012] 3-8% of the electrofused magnesia particles are coated with a magnesium-aluminum spinel microcrystalline layer.

[0013] In some embodiments, the aggregate includes one or more of the following characteristics:

[0014] (A) The mass content of Al2O3 in the high-alumina bauxite clinker is ≥85%;

[0015] (B) The particle size distribution of the high-alumina bauxite clinker is as follows: 20-30% by mass of particles with a size of 5-3mm, 25-35% by mass of particles with a size of 3-1mm, 20-30% by mass of particles with a size of 1-0mm, and 15-25% by mass of particles with a size ≤0.074mm;

[0016] (C) The silicon carbide particles contain ≥90% SiC by mass and have a particle size of 1-3 mm;

[0017] (D) The ZrO2 content in the fused zirconium corundum particles is ≥30%, and the particle size is 1-3 mm;

[0018] (E) The fused magnesia particles contain ≥95% MgO by mass and have a particle size of 0.5-2 mm;

[0019] (F) The mullite-zirconia composite layer has a double-shell structure, with the inner layer being a mullite transition layer and the outer layer being a zirconia dense layer.

[0020] In some embodiments, the aggregate further includes one or more of the following features:

[0021] (G) The activation pretreatment method for the high-alumina bauxite clinker is as follows: the high-alumina bauxite clinker is activated by holding it at 1300-1400℃ for 2-4 hours, then cooled to 700-800℃ at a rate of 5-10℃ / min, and then air-cooled to room temperature at a rate of 2-3℃ / min to obtain the activated pretreated high-alumina bauxite clinker;

[0022] (H) The method of coating the surface of silicon carbide particles with silicon nitride-silica sol composite phase is as follows: silicon nitride micro powder and silicon carbide particles are dry-mixed and coated, silica sol is added after dry mixing, and the mixture is dried at 100-110℃ for 2-3 hours to solidify, thereby obtaining silicon carbide particles coated with silicon nitride-silica sol composite phase.

[0023] (I) The method for coating the surface of the fused zirconia corundum particles with a mullite-zirconia composite layer is as follows: First, immerse the fused zirconia corundum particles in aluminum sol for 12-24 hours, and sinter at 1200-1300℃ for 2-4 hours; then immerse them in zirconium sol for 6-12 hours, and sinter at 1300-1350℃ for 1-2 hours to obtain fused zirconia corundum particles with a mullite-zirconia composite layer on the surface.

[0024] (J) The method for coating the surface of the fused magnesia particles with a magnesium aluminum spinel microcrystalline layer is as follows: The fused magnesia particles are immersed in a saturated calcium aluminate solution, sodium fluoride is added and the immersion time is 6-10 hours, and then heat-treated at 900-1000℃ for 3-5 hours to obtain fused magnesia particles with a magnesium aluminum spinel microcrystalline layer on the surface.

[0025] In some embodiments, the aggregate further includes one or more of the following features:

[0026] (F1) The thickness of the mullite-zirconia composite layer is 50-200 μm;

[0027] (F2) The thickness of the mullite transition layer is 20-80 μm;

[0028] (F3) The thickness of the dense zirconium oxide layer is 30-120 μm;

[0029] (F4) The thickness ratio of the mullite transition layer to the zirconia dense layer is 1:(1.2-1.8);

[0030] (H1) The mass ratio of silicon nitride micro powder to silicon carbide particles is (3-5):100;

[0031] (H2) The silica sol accounts for 0.5-1% of the total mass of silicon carbide particles and silicon nitride micro powder;

[0032] (I1) The mass content of Al2O3 in the aluminum sol is 15-20%;

[0033] (I2) The ZrO2 content in the zirconium sol is 10-15% by mass;

[0034] (J1) The saturated calcium aluminate solution contains 8-12% Al2O3 and 5-8% CaO by mass.

[0035] (J2) The sodium fluoride constitutes 0.3-0.5% of the saturated calcium aluminate solution by mass.

[0036] (J3) The thickness of the magnesium aluminum spinel microcrystalline layer is 10-50 μm and the grain size is 2-5 μm.

[0037] In some embodiments, the aggregate further includes 5-12% by mass of aluminum titanate-mullite composite ceramic particles, based on the mass percentage of the castable.

[0038] In some embodiments, the preparation steps of the aluminum titanate-mullite composite ceramic particles are as follows:

[0039] Tetrabutyl titanate and tetraethyl orthosilicate were prepared into a sol with a TiO2:SiO2 molar ratio of (1-2):(1-2). Alumina micro powder accounting for 15-20% of the sol mass was added. After gelation and drying, the mixture was sintered at 1400-1450℃ for 3-4 hours to obtain aluminum titanate-mullite composite ceramic particles.

[0040] In some embodiments, the powder comprises the following components by mass percentage of the castable:

[0041] Activated alumina micro powder 8-15%; silicon micro powder 3-6%; zircon powder 2-5%; silicon nitride powder 2-4%; rare earth oxide composite powder 1-3%.

[0042] In some embodiments, the powder further includes one or more of the following features:

[0043] (1) The active alumina micro powder contains ≥99% Al2O3 by mass and has a Dv50 particle size ≤3μm;

[0044] (2) The mass content of SiO2 in the silicon micro powder is ≥92%, and the Dv50 particle size is ≤1μm;

[0045] (3) The zircon powder contains ZrO2 at a mass content of ≥60% and has a Dv50 particle size of ≤45μm;

[0046] (4) The mass content of Si3N4 in the silicon nitride powder is ≥90%, and the Dv50 particle size is ≤10μm;

[0047] (5) The maximum particle size of the rare earth oxide composite powder is ≤5μm;

[0048] (6) The rare earth oxide composite powder includes yttrium oxide, lanthanum oxide and cerium oxide, and the mass ratio of yttrium oxide, lanthanum oxide and cerium oxide is (1-2):(0.5-1):(0.3-0.8).

[0049] In some embodiments, the binder comprises the following components by mass percentage of the castable: 3-7% pure calcium aluminate cement; 2-3% silica sol;

[0050] And / or, the admixture comprises the following components in weight percentage: water-reducing agent 0.3-0.8%; explosion-proof fiber 0.2-0.5%; expansion agent 0.3-0.8%; retarder 0.2-0.4%.

[0051] A second aspect of the present invention provides a method for preparing a high-slag-resistant castable, comprising the following steps:

[0052] Aggregates, powders, binders, and additives are mixed evenly to obtain a castable with high slag resistance.

[0053] The beneficial effects of this invention are as follows:

[0054] This invention employs multiple surface modification treatments on aggregates: high-alumina bauxite clinker undergoes high-temperature activation to form a microporous structure that adsorbs low-melting-point oxides; silicon carbide particles are coated with a silicon nitride-silica sol composite phase, which reacts with the active alumina micropowder in the castable matrix to generate a SiAlON ceramic phase; fused zirconia corundum particles are coated with a mullite-zirconia composite layer; and fused magnesia particles have an in-situ grown magnesium aluminum spinel microcrystalline layer. These components collectively construct a ternary anti-slag system of MgO-MgAl2O4-Al2O3, forming a gradient protective layer in the aggregate gaps. This significantly enhances the interfacial bonding strength, prevents slag penetration and erosion along the interface, and improves the slag resistance, thermal shock resistance, and high-temperature structural stability of the castable, extending its service life and meeting the requirements for larger and longer-life blast furnaces. Attached Figure Description

[0055] The embodiments of this invention are not limited to the drawings described below, which are only some embodiments of this invention. Those skilled in the art can obtain drawings of other embodiments based on the content of this invention.

[0056] Figure 1 This is a schematic diagram of the preparation process of the high slag resistance castable of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0059] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0060] This invention provides a high slag-resistant castable, comprising the following components by mass percentage:

[0061] Aggregate 58-70%; powder 20-30%; binder 5-10%; admixtures 1-3%;

[0062] The aggregate comprises the following components by mass percentage of the castable:

[0063] 30-45% of the high-alumina bauxite clinker underwent activation pretreatment;

[0064] 10-20% of silicon carbide particles are coated with a silicon nitride-silica sol composite phase.

[0065] 5-10% fused zirconium corundum particles with a mullite-zirconia composite coating on the surface;

[0066] 3-8% of the electrofused magnesia particles are coated with a microcrystalline layer of magnesium aluminum spinel (MgAl2O4).

[0067] This invention employs multiple surface modification treatments on aggregates: high-alumina bauxite clinker undergoes high-temperature activation to form a microporous structure that adsorbs low-melting-point oxides; silicon carbide particles are coated with a silicon nitride-silica sol composite phase, which reacts with the active alumina micropowder in the castable matrix to generate a SiAlON ceramic phase; fused zirconia corundum particles are coated with a mullite-zirconia composite layer; and fused magnesia particles have an in-situ grown magnesium aluminum spinel microcrystalline layer. These components collectively construct a ternary anti-slag system of MgO-MgAl2O4-Al2O3, forming a gradient protective layer in the aggregate gaps. This significantly enhances the interfacial bonding strength, prevents slag penetration and erosion along the interface, and improves the slag resistance, thermal shock resistance, and high-temperature structural stability of the castable, extending its service life and meeting the requirements for larger and longer-life blast furnaces.

[0068] In some embodiments, the mass content of Al2O3 in the high-alumina bauxite clinker is ≥85%.

[0069] In some embodiments, the particle size distribution of the high-alumina bauxite clinker is as follows: 20-30% by mass of particles with a size of 5-3mm, 25-35% by mass of particles with a size of 3-1mm, 20-30% by mass of particles with a size of 1-0mm, and 15-25% by mass of particles with a size ≤0.074mm.

[0070] In this invention, the standard gradation of high-alumina bauxite clinker is a four-level continuous close-packed skeleton system, which can take into account the workability, density, and high-temperature slag resistance and thermal shock resistance. If the proportion of any interval exceeds the standard or is insufficient, it will lead to the simultaneous deterioration of workability, room temperature mechanical properties, and high-temperature properties.

[0071] In some embodiments, the high-alumina bauxite clinker is pretreated by high-temperature activation as follows: the high-alumina bauxite clinker is kept at 1300-1400℃ for 2-4 hours for high-temperature activation treatment, then cooled to 700-800℃ at a rate of 5-10℃ / min, and then air-cooled to room temperature at a rate of 2-3℃ / min to obtain high-alumina bauxite clinker pretreated by high-temperature activation.

[0072] After pretreatment, the surface of high-alumina bauxite clinker forms a microporous structure with a porosity of 15-25% and an average pore size of 0.5-2μm, which can directionally adsorb low-melting-point oxides of FeO and MnO in the slag, thus preventing the diffusion of low-melting-point phases inside the matrix.

[0073] In this invention, the porosity is determined by the liquid vacuum saturation immersion method in GB / T 2997-2015 "Test Methods for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products", and the test result is the apparent porosity.

[0074] In this invention, the average pore size is tested by mercury intrusion porosimetry according to YB / T 118-2020 "Test Method for Pore Size Distribution of Refractory Materials". The average pore size is the pore volume weighted average pore size specified in the standard, which is used to adsorb low melting point oxides of FeO and MnO in molten slag.

[0075] In some embodiments, the silicon carbide particles contain ≥90% SiC by mass and have a particle size of 1-3 mm.

[0076] In some embodiments, the method for coating the surface of the silicon carbide particles with a silicon nitride-silica sol composite phase is as follows: silicon nitride micro powder and silicon carbide particles are dry-mixed and coated, and silica sol is added as a binder after dry mixing. The mixture is then dried at 100-110℃ for 2-3 hours to cure, thereby obtaining silicon carbide particles coated with a silicon nitride-silica sol composite phase.

[0077] The silicon nitride-silica sol composite phase reacts synergistically with the active alumina micropowder and silicon micropowder in the castable matrix at high temperature to generate a SiAlON ceramic phase. This SiAlON ceramic phase fills the gaps between the aggregates to form a gradient protective layer, which not only helps to improve the high-temperature strength of the castable, but also achieves a dual improvement in slag resistance and thermal shock resistance.

[0078] In some embodiments, the mass ratio of silicon nitride micro powder to silicon carbide particles is (3-5):100, for example, it can be a range of 3:100, 3.5:100, 4:100, 4.5:100, 5:100 or any combination thereof.

[0079] In some embodiments, the silica sol accounts for 0.5-1% of the total mass of silicon carbide particles and silicon nitride micro powder, for example, it can be a range of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination thereof.

[0080] In some embodiments, the ZrO2 content in the fused zirconia corundum particles is ≥30%, and the particle size is 1-3 mm.

[0081] In some embodiments, the mullite-zirconia composite layer has a double-shell structure, with an inner mullite transition layer and an outer zirconia dense layer.

[0082] In some embodiments, the thickness of the mullite-zirconia composite layer is 50-200 μm, for example, it can be a range of 50 μm, 70 μm, 90 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm or any combination thereof.

[0083] In some embodiments, the thickness of the mullite transition layer is 20-80 μm, for example, it can be a range of 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or any combination thereof.

[0084] In some embodiments, the thickness of the zirconia dense layer is 30-120 μm, for example, it can be a range of 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm or any combination thereof.

[0085] In some embodiments, the thickness ratio of the mullite transition layer to the zirconia dense layer is 1:(1.2-1.8), for example, it can be a range of 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8 or any combination thereof.

[0086] In some embodiments, the method for coating the surface of the fused zirconia alumina particles with a mullite-zirconia composite layer is as follows: First, the fused zirconia alumina particles are immersed in aluminum sol for 12-24 hours and sintered at 1200-1300℃ for 2-4 hours to form a mullite transition layer on the surface of the fused zirconia alumina particles; then, they are immersed in zirconium sol for 6-12 hours and sintered at 1300-1350℃ for 1-2 hours to form a dense zirconium oxide layer on the surface of the mullite transition layer, thus obtaining fused zirconia alumina particles with a mullite-zirconia composite layer on the surface.

[0087] In some embodiments, the mass content of Al2O3 in the aluminum sol is 15-20%, for example, it can be a range of 15%, 16%, 17%, 18%, 19%, 20%, or any combination thereof.

[0088] In some embodiments, the ZrO2 content in the zirconium sol is 10-15% by mass, for example, it can be a range of 10%, 11%, 12%, 13%, 14%, 15%, or any combination thereof.

[0089] In this invention, the fused zirconia alumina particles after surface coating treatment have a three-layer core-shell structure: a core of fused zirconia alumina, an inner mullite transition layer, and an outer zirconia dense layer. The three-layer structure of the fused zirconia alumina particles was verified by a combination of SEM cross-sectional morphology observation, EDS line / surface scanning, and XRD phase analysis: After radial cutting, polishing, and carbon spraying of the particles, field emission SEM was used to observe the complete cross-sectional layered structure and measure the actual thickness of each layer; EDS elemental line scanning was performed along the radial direction of the cross-section, revealing three stepped abrupt changes in the intensity of Al, Si, and Zr elements, corresponding to the fused zirconia alumina core, mullite transition layer, and zirconia dense layer, respectively; the EDS surface distribution visually presented the elemental zoning characteristics of the three layers; and with accompanying XRD phase testing, the finished particles simultaneously showed characteristic diffraction peaks of zirconia alumina, mullite, and high-purity zirconia. Comparison with uncoated and single-coated control groups confirmed that the two-step impregnation process successfully prepared fused zirconia alumina particles with a surface-coated mullite-zirconia composite layer.

[0090] In some embodiments, the fused magnesia particles contain ≥95% MgO by mass and have a particle size of 0.5-2 mm.

[0091] In some embodiments, the method for coating the surface of the fused magnesia particles with a magnesium aluminum spinel microcrystalline layer is as follows: the fused magnesia particles are immersed in a saturated calcium aluminate solution, sodium fluoride is added as a mineralizing agent, the immersion time is 6-10 hours, and then heat-treated at 900-1000℃ for 3-5 hours to obtain fused magnesia particles with a magnesium aluminum spinel microcrystalline layer on the surface.

[0092] In some embodiments, the mass content of Al2O3 in the saturated calcium aluminate solution is 8-12%, for example, it can be a range of 8%, 9%, 10%, 11%, 12% or any two of these.

[0093] In some embodiments, the mass content of CaO in the saturated calcium aluminate solution is 5-8%, for example, it can be a range of 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any combination thereof.

[0094] In some embodiments, the sodium fluoride accounts for 0.3-0.5% of the mass of the saturated calcium aluminate solution, for example, it can be a range of 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any combination thereof.

[0095] In some embodiments, the thickness of the magnesium aluminum spinel microcrystalline layer is 10-50 μm, and the grain size is 2-5 μm.

[0096] The magnesium-aluminum spinel microcrystalline layer forms a continuous bonded phase with the active alumina micropowder and silicon nitride powder in the castable matrix at high temperature, constructing a MgO-MgAl2O4-Al2O3-SiAlON multi-component anti-slag system inside the castable. Furthermore, the MgAl2O4 has a thermal expansion coefficient of approximately 8.0 × 10⁻⁶. -6 / ℃ (room temperature - 1000℃), the coefficient of thermal expansion of the matrix is ​​approximately 5.5 × 10⁻⁶. -6 The difference in thermal expansion coefficients between the two elements (room temperature - 1000℃) creates a microcrack buffer zone at the interface, absorbing thermal stress and avoiding the problem of interface cracking that easily occurs in existing single magnesia modification. This microcrystalline layer forms a continuous bonded phase with the active alumina powder in the matrix at high temperatures, constructing a ternary anti-slag system of MgO-MgAl2O4-Al2O3 inside the castable.

[0097] In some embodiments, the aggregate further includes 5-12% by mass of aluminum titanate-mullite composite ceramic particles, which may be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or any combination thereof, based on the mass percentage of the castable.

[0098] If the content of aluminum titanate-mullite composite ceramic particles in the aggregate of the present invention is too low, the supply of low thermal expansion buffer phase and high temperature titanium release anti-slag phase will be insufficient, resulting in a simultaneous decrease in thermal shock resistance, slag erosion resistance and volume stability. If its content is too high, the high-strength hard aggregate skeleton will be excessively diluted by the low-strength aluminum titanate phase, and the mullite stabilizing phase will be insufficient to inhibit the intermediate temperature decomposition of aluminum titanate, thereby causing a sharp increase in the porosity of the green body, a sharp drop in high temperature strength, easy cracking during baking and deterioration of load softening performance, while also significantly increasing the raw material cost.

[0099] Therefore, by controlling the content of aluminum titanate-mullite composite ceramic particles in the aggregate, this invention ensures the high-temperature strength and structural stability of the aggregate skeleton while imparting a lower coefficient of thermal expansion and good thermal shock buffering capacity to the castable, significantly reducing the risk of structural spalling caused by periodic temperature fluctuations. Furthermore, during high-temperature service, aluminum titanate can slowly precipitate TiO2, which can react with CaO in the slag to form a high-melting-point perovskite phase, filling the pores at the slag interface and preventing further inward penetration and erosion by the molten slag, thereby further improving the slag resistance of the castable.

[0100] In some embodiments, the aluminum titanate-mullite composite ceramic particles are prepared by a sol-gel method coupled with conventional sintering, as follows:

[0101] Tetrabutyl titanate and tetraethyl orthosilicate were prepared into a sol at a TiO2:SiO2 molar ratio of (1-2):(1-2). Alumina micro powder accounting for 15-20% of the sol mass was added. After gelation and drying at 120℃, the mixture was sintered at 1400-1450℃ for 3-4 hours to obtain aluminum titanate-mullite composite ceramic particles.

[0102] The coefficient of thermal expansion of the aluminum titanate-mullite composite ceramic particles is 2.5 × 10⁻⁶. -6 / ℃~4.0×10 -6 / ℃, forming a gradient thermal expansion match with the matrix material; and the TiO2 generated by the decomposition of the aluminum titanate phase at high temperature reacts with CaO and FeO in the slag to form a high-melting-point perovskite solid solution, forming a dense reaction layer with a thickness of 0.3-1.0 mm and a porosity of ≤8% on the surface of the castable.

[0103] In some embodiments, the aggregate is prepared as follows:

[0104] (1) Weigh out the high-alumina bauxite clinker, and then subject the high-alumina bauxite clinker to high-temperature activation pretreatment;

[0105] Weigh out silicon carbide particles, and then pretreat the silicon carbide particles by coating them with a silicon nitride-silica sol composite phase.

[0106] Weigh out fused zirconia corundum particles, and then pre-treat the fused zirconia corundum particles by coating them with a mullite-zirconia composite layer.

[0107] Weigh out fused magnesia particles, and then pretreat the fused magnesia particles by coating them with a dense microcrystalline layer of magnesium aluminum spinel.

[0108] (2) The high-alumina bauxite clinker that has been pretreated by high temperature activation, silicon carbide particles coated with silicon nitride-silica sol composite phase, fused zirconium corundum particles coated with mullite-zirconia composite layer, and fused magnesia particles coated with magnesium aluminum spinel microcrystalline layer are mixed evenly to obtain aggregate.

[0109] In some embodiments, the mass percentage of aggregate in the high slag-resistant castable is 58-70%, for example, it can be a range of 58%, 60%, 62%, 64%, 66%, 68%, 70%, or any combination thereof.

[0110] In some embodiments, the mass percentage of powder in the high slag-resistant castable is 20-30%, for example, it can be a range of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any combination thereof.

[0111] In some embodiments, the powder comprises the following components by mass percentage of the castable: 8-15% activated alumina micro powder; 3-6% silicon micro powder; 2-5% zircon powder; 2-4% silicon nitride powder; and 1-3% rare earth oxide composite powder.

[0112] In some embodiments, the mass percentage of activated alumina micropowder in the powder is 8-15%, for example, it can be a range of 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of these.

[0113] In some embodiments, the mass percentage of silicon micropowder in the powder is 3-6%, for example, it can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or any combination thereof.

[0114] In some embodiments, the zircon powder in the powder is 2-5% by mass, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any combination thereof.

[0115] In some embodiments, the mass percentage of silicon nitride powder in the powder is 2-4%, for example, it can be a range of 2%, 2.5%, 3%, 3.5%, 4%, or any two of these.

[0116] In some embodiments, the mass percentage of rare earth oxide composite powder in the powder is 1-3%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3% or any combination thereof.

[0117] In some embodiments, the activated alumina micro powder has an Al2O3 mass content ≥99% and a Dv50 particle size ≤3μm.

[0118] In some embodiments, the silicon micropowder has a SiO2 mass content ≥92% and a Dv50 particle size ≤1μm.

[0119] In some embodiments, the zircon powder contains ≥60% ZrO2 by mass and has a Dv50 particle size ≤45μm.

[0120] In some embodiments, the silicon nitride powder contains ≥90% Si3N4 by mass and has a Dv50 particle size ≤10μm.

[0121] In some embodiments, the maximum particle size of the rare earth oxide composite powder is ≤5μm.

[0122] In some embodiments, the rare earth oxide composite powder includes yttrium oxide, lanthanum oxide, and cerium oxide, and the mass ratio of yttrium oxide, lanthanum oxide, and cerium oxide is (1-2):(0.5-1):(0.3-0.8), for example, it can be 1:0.5:0.3, 1:0.5:0.8, 1:1:0.3, 1:1:0.8, 2:0.5:0.3, 2:0.5:0.8, 2:1:0.3, 2:1:0.8, or any combination thereof.

[0123] This invention utilizes a specific ratio of yttrium oxide, lanthanum oxide, and cerium oxide to improve the sintering density of castables. During high-temperature sintering, it promotes the formation of a low-viscosity liquid phase, accelerates the sintering reaction, refines grains, and strengthens grain boundary bonding, significantly enhancing the high-temperature structural stability of the castable. This is beneficial for improving the high-temperature mechanical, slag-resistant, and oxidation-resistant properties of high-slag-resistant castables.

[0124] If other rare earth oxides are used to replace any of the components in yttrium oxide, lanthanum oxide, and cerium oxide, the synergistic effect of the compounded powder will be lost, failing to refine the grains and strengthen the grain boundaries. The sintering density of the castable will be limited, making it difficult to achieve the expected high-temperature structural stability. Furthermore, the resistance to slag erosion and permeation will not meet the service requirements of the blast furnace slag ditch. Moreover, it is necessary to increase the total rare earth content and adjust the silica sol / powder ratio, thus increasing production costs.

[0125] In some embodiments, the mass percentage of binder in the high slag-resistant castable is 5-10%, for example, it can be a range of 5%, 6%, 7%, 8%, 9%, 10%, or any two of these.

[0126] In some embodiments, the binder comprises the following components by mass percentage of the castable: 3-7% pure calcium aluminate cement; 2-3% silica sol.

[0127] In some embodiments, the pure calcium aluminate cement has a mass percentage of 3-7%, for example, it can be a range of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, or any combination thereof.

[0128] In some embodiments, the silica sol is 2-3% by mass, for example, it can be a range of 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any combination thereof.

[0129] In some embodiments, the mass content of SiO2 in the silica sol is 25-30%, for example, it can be a range of 25%, 26%, 27%, 28%, 29%, 30%, or any combination thereof.

[0130] In some embodiments, the mass percentage of the admixture in the high slag-resistant castable is 1-3%, for example, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, or any combination thereof.

[0131] In some embodiments, the admixture comprises the following components by mass percentage of the castable:

[0132] Water-reducing agent 0.3-0.8%; explosion-proof fiber 0.2-0.5%; expansion agent 0.3-0.8%; retarder 0.2-0.4%.

[0133] In some embodiments, the water-reducing agent in the admixture is 0.3-0.8% by mass, for example, it can be a range of 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any combination thereof.

[0134] In some embodiments, the mass percentage of explosion-proof fiber in the admixture is 0.2-0.5%, for example, it can be a range of 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any combination thereof.

[0135] In some embodiments, the mass percentage of the expanding agent in the admixture is 0.3-0.8%, for example, it can be a range of 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any combination thereof.

[0136] In some embodiments, the retarder in the admixture is 0.2-0.4% by mass, for example, it can be a range of 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, or any combination thereof.

[0137] In some embodiments, the water-reducing agent is PC-2000 type polycarboxylate water-reducing agent.

[0138] In some embodiments, the explosion-proof fiber is polypropylene explosion-proof fiber with a single filament diameter of 12-20 μm and a length of 3-6 mm.

[0139] In some embodiments, the expanding agent is a calcium-magnesium composite expanding agent, preferably a calcium oxide-magnesium oxide expanding agent.

[0140] In some embodiments, the retarder is a mixture of citric acid, sodium citrate, and sodium gluconate in a mass ratio of (1.5-2.5):(2-3.5):(4-6).

[0141] This invention does not have any particular limitation on the source of water-reducing agent, explosion-proof fiber, expansion agent, and retarder, as long as the purpose of this invention can be achieved.

[0142] This invention provides a method for preparing a high-slag-resistant castable, comprising the following steps:

[0143] Aggregates, powders, binders, and additives are mixed evenly to obtain a castable with high slag resistance.

[0144] In some embodiments, the powder is prepared as follows: activated alumina micro powder, silicon micro powder, zircon powder, silicon nitride powder, and rare earth oxide powder are added to a mixer in proportion and dry-mixed for 5-8 minutes at a speed of 30-50 rpm to obtain the powder.

[0145] In some embodiments, the binder is prepared as follows: first, pure calcium aluminate cement is dry-mixed with aggregates and powders for 3-5 minutes; then, 60-70% of the total mass of the castable (aggregates + powders + binder + admixtures) of mixing water is added and wet-mixed for 2-3 minutes; finally, silica sol is added and 0.1-0.2% of silane coupling agent of the total mass of the castable is added, and mixing continues for 3-5 minutes.

[0146] This invention employs a silane coupling agent suitable for this system (silica sol-SiO2-Al2O3-Si3N4 inorganic system), preferably an aminosilane coupling agent; further preferably KH-550 (γ-aminopropyltriethoxysilane), and KH-560 epoxysilane coupling agent can also be used. The function of the silane coupling agent is to improve the interfacial compatibility of silica sol and inorganic powder, and to promote the formation of the Si-O-Si three-dimensional network structure.

[0147] In some embodiments, the pH of the silica sol is adjusted to 9-10.5 before it is added.

[0148] The binder described in this invention is a composite binder of pure calcium aluminate cement and silica sol, added in steps: the silica sol undergoes a polymerization reaction with silica powder under alkaline conditions to form a Si-O-Si three-dimensional network structure. This three-dimensional network structure, after drying at 110°C, forms a nanoscale silica gel binding phase, which reacts with the CAH produced during the hydration of pure calcium aluminate cement. 10 The synergistic effect of C2AH8 hydration products improves the medium-temperature strength and anti-cracking properties of castables, which helps to solve the problem of poor synergistic effect caused by simple mixing of existing composite binders.

[0149] In some embodiments, the high slag-resistant castable is obtained by mixing, molding, curing and heat treatment.

[0150] In some embodiments, during the mixing and molding process, an organic-inorganic composite dispersant is added at 0.1-0.3% of the total weight of the castable. This organic-inorganic composite dispersant is a mixture of polycarboxylate superplasticizer and sodium hexametaphosphate at a mass ratio of 1-2:1. The organic-inorganic composite dispersant is first dissolved in the mixing water and then added before the addition of pure calcium aluminate cement. The organic-inorganic composite dispersant, through electrostatic repulsion and steric hindrance, uniformly disperses the powder particles, reducing the water content of the castable slurry to 4-6% and simultaneously increasing the slurry's flowability to 180-220 mm.

[0151] In some embodiments, the curing process employs a combination of moist heat curing and microwave-assisted drying: after 24 hours of curing, the billet is heated and dehydrated using microwaves with a frequency of 2450MHz and a power of 2-4kW for 30-45 minutes; the microwave-assisted drying, combined with hot air drying, ensures a uniform increase in the internal temperature of the billet, reducing the total drying time to less than 36 hours.

[0152] In some embodiments, the heat treatment process employs a three-stage gradient temperature control process:

[0153] The first step involves heating from 500℃ to 800℃ at a rate of 20℃ / h and holding for 2 hours to decompose the pure calcium aluminate cement hydrate and initially form a ceramic bond.

[0154] The second stage involves heating from 800℃ to 1000℃ at a rate of 25℃ / h and holding for 2 hours to promote the mullitization reaction and the formation of the SiAlON phase.

[0155] The third stage involves heating from 1000℃ to 1200℃ at a rate of 30℃ / h and holding at that temperature for 2-4 hours to complete the sintering and densification process.

[0156] In the following embodiments, unless otherwise specified, all the raw materials of the present invention are commercially available or prepared according to conventional methods in the art.

[0157] Raw material source:

[0158] High-alumina bauxite clinker: Xiaoyi Jiexin Refractory Materials Co., Ltd., Al2O3≥85%, can be crushed and classified into four particle sizes: 5-3mm, 3-1mm, 1-0mm, and ≤0.074mm;

[0159] Silicon carbide particles: Ningxia Xingkai Silicon Industry, SiC≥97%, can be screened to a particle size of 1-3mm;

[0160] Fused zirconia alumina particles: Shiyan Xindan Refractory AZ-30 type fused zirconia alumina, ZrO2≥30%, particle size controlled 1-3mm;

[0161] Fused magnesia particles: Yingkou Qinghua Refractory 97% fused magnesia, MgO≥95%, particle size 0.5-2mm.

[0162] Example 1

[0163] This embodiment discloses a high slag-resistant castable, comprising the following raw material components by mass percentage:

[0164] Aggregate 65%; powder 25%; binder 8%; admixture 2%.

[0165] The aggregate comprises the following components by mass percentage of the castable:

[0166] 40% of the high-alumina bauxite clinker underwent activation pretreatment;

[0167] 15% silicon carbide particles with a silicon nitride-silica sol composite phase on the surface;

[0168] 5% of fused zirconia corundum particles with a mullite-zirconia composite coating on the surface;

[0169] 5% of the electrofused magnesia particles are coated with a magnesium-aluminum spinel microcrystalline layer.

[0170] The mullite-zirconia composite layer has a double-shell structure, with an inner mullite transition layer and an outer zirconia dense layer; the thickness of the mullite-zirconia composite layer is 50-200 μm; the thickness of the mullite transition layer is 20-80 μm; and the thickness of the zirconia dense layer is 30-120 μm.

[0171] The surface of the fused magnesia particles is coated with a magnesium aluminum spinel microcrystalline layer; the thickness of the magnesium aluminum spinel microcrystalline layer is 10-50 μm, and the grain size is 2-5 μm.

[0172] The high-alumina bauxite clinker contains ≥85% Al2O3 by mass; the particle size distribution of the high-alumina bauxite clinker is as follows: 20% by mass of particles with a size of 5-3mm, 35% by mass of particles with a size of 3-1mm, 30% by mass of particles with a size of 1-0mm, and 15% by mass of particles with a size of ≤0.074mm.

[0173] The silicon carbide particles contain ≥90% SiC by mass and have a particle size of 1-3 mm.

[0174] The fused zirconium corundum particles contain ≥30% ZrO2 by mass and have a particle size of 1-3 mm.

[0175] The fused magnesia particles contain ≥95% MgO by mass and have a particle size of 0.5-2 mm.

[0176] The powder comprises the following components by mass percentage: 12% activated alumina micro powder; 4% silicon micro powder; 4% zircon powder; 3% silicon nitride powder; and 2% rare earth oxide composite powder.

[0177] The activated alumina micro powder is: Henan Hecheng α-Al2O3 micro powder, with Al2O3 mass content ≥99% and Dv50 particle size ≤3μm;

[0178] The silicon micro powder: Tiankai silicon powder material, with SiO2 mass content ≥92%, Dv50 particle size ≤1μm, spherical particles;

[0179] The zircon powder: Guangdong Dongfang Zircon Industry Technology Z-60 zircon powder, ZrO2 mass content ≥60%, Dv50 particle size ≤45μm;

[0180] The silicon nitride powder: Anyang Hongxing Nitride Material Co., Ltd., with a Si3N4 mass content ≥90% and a Dv50 particle size ≤10μm;

[0181] The rare earth oxide composite powder is made from high-purity yttrium oxide (Y2O3) (99.99%), lanthanum oxide (La2O3) (99.99%), and cerium oxide (CeO2) (99.99%), mixed in a certain mass ratio and then air-jet pulverized to a maximum particle size of ≤5μm.

[0182] The rare earth oxide composite powder includes yttrium oxide, lanthanum oxide, and cerium oxide, and the mass ratio of yttrium oxide, lanthanum oxide, and cerium oxide is 1:1:0.5.

[0183] The binder comprises the following components by mass percentage of the castable: 5% pure calcium aluminate cement; 3% silica sol; and the silica sol contains 30% SiO2 by mass.

[0184] The admixture comprises the following components by mass percentage of the castable: 0.6% PC-2000 polycarboxylate superplasticizer; 0.5% polypropylene explosion-proof fiber; 0.5% calcium oxide-magnesium oxide expanding agent; and 0.4% retarder. The retarder is a mixture of citric acid, sodium citrate, and sodium gluconate in a mass ratio of 2:3:5.

[0185] This embodiment also discloses a method for preparing a high-slag-resistant castable, such as... Figure 1 As shown, it includes the following steps:

[0186] Step 1: Aggregate pretreatment and gradation:

[0187] (1) Weigh the high-alumina bauxite clinker according to the particle size distribution, and then perform high-temperature activation pretreatment on the high-alumina bauxite clinker: first, keep the high-alumina bauxite clinker at 1400℃ for 2 hours for high-temperature activation treatment, then cool it to 800℃ at a rate of 5℃ / min, and then air cool it to room temperature at a rate of 3℃ / min to obtain high-alumina bauxite clinker with high-temperature activation pretreatment;

[0188] (2) Weigh silicon carbide particles and then pretreat the silicon carbide particles by coating with silicon nitride-silica sol composite phase: dry mix silicon nitride micro powder and silicon carbide particles at a mass ratio of 4:100, add silica sol accounting for 1% of the total mass (silicon nitride micro powder and silicon carbide particles) after dry mixing, and dry at 110℃ for 3 hours to obtain silicon carbide particles with silicon nitride-silica sol composite phase coating on the surface.

[0189] (3) Weigh the fused zirconia corundum particles, and then pretreat the fused zirconia corundum particles by coating them with a mullite-zirconia composite layer: first, immerse the fused zirconia corundum particles in aluminum sol (Al2O3 mass content is 20%) for 12 hours, and sinter at 1200℃ for 4 hours; then immerse them in zircon sol (ZrO2 mass content is 10%) for 12 hours, and sinter at 1300℃ for 2 hours to obtain fused zirconia corundum particles with a mullite-zirconia composite layer on the surface.

[0190] (4) Weigh the fused magnesia particles and then pretreat the fused magnesia particles by coating them with a dense microcrystalline layer of magnesium aluminum spinel: Immerse the fused magnesia particles in a saturated calcium aluminate solution (Al2O3 mass content is 12%, CaO mass content is 8%), add 0.5% sodium fluoride, immerse for 10 hours, and then heat treat at 1000℃ for 3 hours to obtain fused magnesia particles with a surface coating of magnesium aluminum spinel microcrystalline layer;

[0191] (5) The pre-treated high-alumina bauxite clinker, silicon carbide particles, fused zirconium corundum particles and fused magnesia particles are mixed evenly according to the particle size distribution requirements to obtain aggregate.

[0192] Step 2: Premixing of powders:

[0193] Add activated alumina micro powder, silicon micro powder, zircon powder, silicon nitride powder, and rare earth oxide powder to a planetary mixer in a certain proportion, dry mix for 8 minutes at a speed of 50 rpm, and stop the mixer for 10 seconds every minute during the process to ensure that the powder is fully dispersed and uniform.

[0194] Step 3: Preparation of binder: Weigh out pure calcium aluminate cement and silica sol separately according to the ratio and set aside; adjust the pH of silica sol to 9 before use.

[0195] Step 4: Mixing and Molding

[0196] The aggregate prepared above was added to a forced mixer, along with the powder prepared above, and dry-mixed for 5 minutes; then 60% of the total amount of mixing water was added, and wet-mixed for 3 minutes; then 0.3% of the total weight of the castable was added, the organic-inorganic composite dispersant being a compound of polycarboxylate superplasticizer and sodium hexametaphosphate in a mass ratio of 2:1; then pure calcium aluminate cement was added, and mixing continued for 5 minutes; finally, silica sol and 0.2% of silane coupling agent and the remaining mixing water were added, and high-speed mixing was carried out for 8 minutes at a stirring speed of 80 rpm to obtain the castable slurry;

[0197] The slurry is poured into a mold and formed by segmented vibration. First, it is vibrated at 50Hz with an amplitude of 0.5-1mm for 1 minute, then left to stand for 30 seconds, and then vibrated at 45Hz with an amplitude of 0.3-0.5mm for 1-2 minutes. This avoids the problems of air holes and uneven density that are easily generated by existing single vibration, thus obtaining the slurry blank.

[0198] Step 5: Curing and Heat Treatment

[0199] The formed green body is cured in an environment of 25℃ and relative humidity ≥90% for 24 hours. After curing for 24 hours, the temperature is increased to 110℃ at a rate of 5℃ / h and kept at that temperature for 24 hours for hot air drying. Then, a process combining moist heat curing and microwave-assisted drying is adopted: microwaves with a frequency of 2450MHz and a power of 4kW are used to assist in heating and dehydrating the green body, and the microwave treatment time is 30 minutes. The combination of microwave-assisted drying and hot air drying makes the internal temperature of the green body rise evenly, and the total drying time is shortened to less than 36 hours.

[0200] The temperature is then increased to 500℃ at a rate of 20℃ / h and held for 3 hours to remove the crystal water. Then, the temperature is increased from 500℃ to 800℃ at a rate of 20℃ / h and held for 2 hours to decompose the pure calcium aluminate cement hydrate and initially form ceramic bonds. Next, the temperature is increased from 800℃ to 1000℃ at a rate of 25℃ / h and held for 2 hours to promote the mullite reaction and the formation of the SiAlON phase. Finally, the temperature is increased from 1000℃ to 1200℃ at a rate of 30℃ / h and held for 4 hours to complete the sintering and densification. After natural cooling, the high slag-resistant castable is obtained.

[0201] Example 2

[0202] The difference from Example 1 is that the aggregate comprises the following components by weight percentage:

[0203] 32% high-alumina bauxite clinker after activation pretreatment; 20% silicon carbide particles with silicon nitride-silica sol composite phase on the surface; 5% fused zirconium corundum particles with mullite-zirconia composite layer on the surface; and 8% fused magnesia particles with magnesium aluminum spinel microcrystalline layer on the surface.

[0204] Example 3

[0205] The difference from Example 1 is that the aggregate comprises the following components by weight percentage:

[0206] 45% high-alumina bauxite clinker after activation pretreatment; 10% silicon carbide particles with silicon nitride-silica sol composite phase on the surface; 6% fused zirconium corundum particles with mullite-zirconia composite layer on the surface; and 4% fused magnesia particles with magnesium aluminum spinel microcrystalline layer on the surface.

[0207] Example 4

[0208] The difference from Example 1 is that, based on the mass percentage of the castable, the aggregate comprises the following components by mass percentage:

[0209] 30% of the high-alumina bauxite clinker underwent activation pretreatment;

[0210] 15% silicon carbide particles with a silicon nitride-silica sol composite phase on the surface;

[0211] 5% of fused zirconia corundum particles with a mullite-zirconia composite coating on the surface;

[0212] 5% of the electrofused magnesia particles are coated with a magnesium-aluminum spinel microcrystalline layer.

[0213] 10% aluminum titanate-mullite composite ceramic particles.

[0214] The preparation steps of the aluminum titanate-mullite composite ceramic particles are as follows:

[0215] Tetrabutyl titanate and tetraethyl orthosilicate were mixed at a TiO2:SiO2 molar ratio of 1:1 to form a sol. Alumina micro powder accounting for 15% of the sol mass was added. After gelation and drying at 120℃, the mixture was sintered at 1450℃ for 3 hours to obtain aluminum titanate-mullite composite ceramic particles.

[0216] Example 5

[0217] The difference from Example 1 is that yttrium oxide is used instead of lanthanum oxide in the rare earth oxide composite powder of the example.

[0218] Example 6

[0219] The difference from Example 1 is that in the rare earth oxide composite powder, the mass ratio of yttrium oxide, lanthanum oxide, and cerium oxide is 1:2:1.

[0220] Comparative Example 1

[0221] The difference from Example 1 is that the aggregate in this example does not undergo high-temperature activation pretreatment of the high-alumina bauxite clinker.

[0222] Comparative Example 2

[0223] The difference from Example 1 is that the aggregate does not have a surface coating of silicon carbide particles.

[0224] Comparative Example 3

[0225] The difference from Example 1 is that the aggregate does not have surface coating on the fused zirconia corundum particles.

[0226] Comparative Example 4

[0227] The difference from Example 1 is that the fused magnesia particles in the aggregate are not surface-coated.

[0228] Comparative Example 5

[0229] The difference from Example 1 is that the aggregate comprises the following components by weight percentage:

[0230] 50% high-alumina bauxite clinker that has undergone activation pretreatment; 5% silicon carbide particles with a silicon nitride-silica sol composite phase on the surface; 5% fused zirconium corundum particles with a mullite-zirconia composite layer on the surface; and 5% fused magnesia particles with a magnesium aluminum spinel microcrystalline layer on the surface.

[0231] Comparative Example 6

[0232] The difference from Example 1 is that the aggregate comprises the following components by weight percentage:

[0233] 28% high-alumina bauxite clinker that has undergone activation pretreatment; 25% silicon carbide particles with a silicon nitride-silica sol composite phase on the surface; 2% fused zirconium corundum particles with a mullite-zirconia composite layer on the surface; and 10% fused magnesia particles with a magnesium aluminum spinel microcrystalline layer on the surface.

[0234] Comparative Example 7

[0235] The difference from Example 1 is that the particle size distribution of the high-alumina bauxite clinker is as follows: 10% by mass of particles with a size of 5-3 mm, 45% by mass of particles with a size of 3-1 mm, 10% by mass of particles with a size of 1-0 mm, and 35% by mass of particles with a size ≤0.074 mm.

[0236] Performance testing

[0237] 1. Apparent porosity and bulk density: Tested in accordance with GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products".

[0238] 2. Flexural strength at room temperature: Tested in accordance with GB / T 3001-2017 "Test method for flexural strength of refractory materials at room temperature".

[0239] 3. Compressive strength at room temperature: Tested in accordance with GB / T 5072-2023 "Test method for compressive strength of refractory materials at room temperature".

[0240] 4. High-temperature flexural strength at 1400℃*0.5h: Tested according to GB / T 3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials".

[0241] 5. Static slag erosion resistance depth at 1500℃: The test was conducted using the static crucible method in accordance with GB / T 8931-2007 "Test Method for Slag Resistance of Refractory Materials".

[0242] 6. Flexural strength retention rate after 20 water cooling cycles at 1000℃: according to GB / T 30873-2014 "Test method for thermal shock resistance of refractory materials (water quenching method)".

[0243] 7. Number of thermal shock cycles: Tested according to GB / T 30873-2014 "Test Method for Thermal Shock Resistance of Refractory Materials" (Water Cooling Method).

[0244] The test results are shown in Table 1.

[0245] Table 1

[0246]

[0247] As can be seen from Examples 1-6 in Table 1, the castable of the present invention has excellent slag resistance, thermal shock resistance, high-temperature structural stability and service life, which can meet the requirements of large-scale and long-life blast furnaces.

[0248] Comparing Comparative Examples 1-4 with Example 1, it can be seen that without modification treatment of high-alumina bauxite clinker, silicon carbide particles, fused zirconium corundum particles, or fused magnesia particles, a ternary anti-slag system of MgO-MgAl2O4-Al2O3 cannot be constructed. Consequently, a gradient protective layer cannot be formed between the aggregates, resulting in reduced interfacial bonding strength and slag penetration and erosion along the interface, thus affecting the performance of the castable. Therefore, this invention, through multiple surface modification treatments of the aggregates, is beneficial to improving the slag resistance, thermal shock resistance, high-temperature structural stability, and service life of the castable.

[0249] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high slag-resistant castable, characterized in that, Includes the following components by mass percentage: Aggregate 58-70%; powder 20-30%; binder 5-10%; admixtures 1-3%; The aggregate comprises the following components by mass percentage of the castable: 30-45% of the high-alumina bauxite clinker underwent activation pretreatment; 10-20% of silicon carbide particles are coated with a silicon nitride-silica sol composite phase. 5-10% fused zirconium corundum particles with a mullite-zirconia composite coating on the surface; 3-8% of the electrofused magnesia particles are coated with a magnesium-aluminum spinel microcrystalline layer.

2. The high slag-resistant castable according to claim 1, characterized in that, The aggregate includes one or more of the following characteristics: (A) The mass content of Al2O3 in the high-alumina bauxite clinker is ≥85%; (B) The particle size distribution of the high-alumina bauxite clinker is as follows: 20-30% by mass of particles with a size of 5-3mm, 25-35% by mass of particles with a size of 3-1mm, 20-30% by mass of particles with a size of 1-0mm, and 15-25% by mass of particles with a size ≤0.074mm; (C) The silicon carbide particles contain ≥90% SiC by mass and have a particle size of 1-3 mm; (D) The ZrO2 content in the fused zirconium corundum particles is ≥30%, and the particle size is 1-3 mm; (E) The fused magnesia particles contain ≥95% MgO by mass and have a particle size of 0.5-2 mm; (F) The mullite-zirconia composite layer has a double-shell structure, with the inner layer being a mullite transition layer and the outer layer being a zirconia dense layer.

3. The high slag-resistant castable according to claim 1, characterized in that, The aggregate also includes one or more of the following characteristics: (G) The activation pretreatment method for the high-alumina bauxite clinker is as follows: the high-alumina bauxite clinker is activated by holding it at 1300-1400℃ for 2-4 hours, then cooled to 700-800℃ at a rate of 5-10℃ / min, and then air-cooled to room temperature at a rate of 2-3℃ / min to obtain the activated pretreated high-alumina bauxite clinker; (H) The method of coating the surface of silicon carbide particles with silicon nitride-silica sol composite phase is as follows: silicon nitride micro powder and silicon carbide particles are dry-mixed and coated, silica sol is added after dry mixing, and the mixture is dried at 100-110℃ for 2-3 hours to solidify, thereby obtaining silicon carbide particles coated with silicon nitride-silica sol composite phase. (I) The method for coating the surface of the fused zirconia corundum particles with a mullite-zirconia composite layer is as follows: First, immerse the fused zirconia corundum particles in aluminum sol for 12-24 hours, and sinter at 1200-1300℃ for 2-4 hours; then immerse them in zirconium sol for 6-12 hours, and sinter at 1300-1350℃ for 1-2 hours to obtain fused zirconia corundum particles with a mullite-zirconia composite layer on the surface. (J) The method for coating the surface of the fused magnesia particles with a magnesium aluminum spinel microcrystalline layer is as follows: The fused magnesia particles are immersed in a saturated calcium aluminate solution, sodium fluoride is added and the immersion time is 6-10 hours, and then heat-treated at 900-1000℃ for 3-5 hours to obtain fused magnesia particles with a magnesium aluminum spinel microcrystalline layer on the surface.

4. The high slag-resistant castable according to claim 2 or 3, characterized in that, The aggregate also includes one or more of the following characteristics: (F1) The thickness of the mullite-zirconia composite layer is 50-200 μm; (F2) The thickness of the mullite transition layer is 20-80 μm; (F3) The thickness of the dense zirconium oxide layer is 30-120 μm; (F4) The thickness ratio of the mullite transition layer to the zirconia dense layer is 1:(1.2-1.8); (H1) The mass ratio of silicon nitride micro powder to silicon carbide particles is (3-5):100; (H2) The silica sol accounts for 0.5-1% of the total mass of silicon carbide particles and silicon nitride micro powder; (I1) The mass content of Al2O3 in the aluminum sol is 15-20%; (I2) The ZrO2 content in the zirconium sol is 10-15% by mass; (J1) The saturated calcium aluminate solution contains 8-12% Al2O3 and 5-8% CaO by mass. (J2) The sodium fluoride constitutes 0.3-0.5% of the saturated calcium aluminate solution by mass. (J3) The thickness of the magnesium aluminum spinel microcrystalline layer is 10-50 μm and the grain size is 2-5 μm.

5. The high slag-resistant castable according to claim 1, characterized in that, The aggregate also includes 5-12% aluminum titanate-mullite composite ceramic particles by mass percentage of the castable.

6. The high slag resistance castable according to claim 5, characterized in that, The preparation method of the aluminum titanate-mullite composite ceramic particles is as follows: Tetrabutyl titanate and tetraethyl orthosilicate were prepared into a sol with a TiO2:SiO2 molar ratio of (1-2):(1-2). Alumina micro powder accounting for 15-20% of the sol mass was added. After gelation and drying, the mixture was sintered at 1400-1450℃ for 3-4 hours to obtain aluminum titanate-mullite composite ceramic particles.

7. The high slag-resistant castable according to claim 1, characterized in that, The powder comprises the following components by mass percentage of the castable: Activated alumina micro powder 8-15%; silicon micro powder 3-6%; zircon powder 2-5%; silicon nitride powder 2-4%; rare earth oxide composite powder 1-3%.

8. The high slag-resistant castable according to claim 7, characterized in that, The powder also includes one or more of the following characteristics: (1) The active alumina micro powder contains ≥99% Al2O3 by mass and has a Dv50 particle size ≤3μm; (2) The mass content of SiO2 in the silicon micro powder is ≥92%, and the Dv50 particle size is ≤1μm; (3) The zircon powder contains ZrO2 at a mass content of ≥60% and has a Dv50 particle size of ≤45μm; (4) The mass content of Si3N4 in the silicon nitride powder is ≥90%, and the Dv50 particle size is ≤10μm; (5) The maximum particle size of the rare earth oxide composite powder is ≤5μm; (6) The rare earth oxide composite powder includes yttrium oxide, lanthanum oxide and cerium oxide, and the mass ratio of yttrium oxide, lanthanum oxide and cerium oxide is (1-2):(0.5-1):(0.3-0.8).

9. The high slag-resistant castable according to claim 1, characterized in that, The binder comprises the following components by mass percentage of the castable: 3-7% pure calcium aluminate cement; Silica sol 2-3%; And / or, the admixture comprises the following components in weight percentage: water-reducing agent 0.3-0.8%; explosion-proof fiber 0.2-0.5%; expansion agent 0.3-0.8%; retarder 0.2-0.4%.

10. A method for preparing a high-slag-resistant castable as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Aggregates, powders, binders, and additives are mixed evenly to obtain a castable with high slag resistance.

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