Si3n4-sic ceramic powder, converter slag stopping slide plate brick and preparation method thereof

Abstract

The application discloses Si3N4-SiC ceramic powder, a converter slag stopping slide plate brick and a preparation method thereof, and belongs to the technical field of refractory materials. The slide plate brick is composed of, in percentage by mass, tabular corundum particles 39-48%, zircon mullite particles 6-8%, zircon corundum particles 8%, silicon carbide particles 3-5%, 35-40% of co-milling powder, and 3-4% of phenolic resin. The co-milling powder comprises 15-20% of Si3N4-SiC ceramic powder and 3-5% of metallic silicon powder. When sintering under a nitrogen atmosphere, the Si3N4-SiC ceramic powder, the metallic silicon powder and the carbon decomposed from the resin in the matrix react to form a ceramic combined structure of SiC-Si3N4-SiC, and three ceramic interfaces are formed, so that the material has good thermal shock resistance and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and more specifically, relates to a Si3N4-SiC ceramic powder, a converter slag baffle brick, and their preparation methods. Background Technology

[0002] With the rapid development of the steel industry, many large steel companies both domestically and internationally have shifted their focus to the production of low-carbon steel and ultra-low-carbon steel. The smelting requirements for low-carbon and ultra-low-carbon steel necessitate that refractory materials have as low a carbon content as possible to reduce carbon inclusions. As a core component of converter slag-blocking technology, the slide gate brick must withstand not only the chemical erosion and physical scouring of high-temperature molten steel but also severe thermal shock and mechanical wear. Therefore, the slide gate brick needs to possess high high-temperature hot-state performance and corrosion resistance. Ordinary slide gate bricks exhibit good performance due to the carbon network structure formed in their matrix. However, reducing the carbon content will inevitably affect the performance of the slide gate, thus impacting its durability. This invention uses silicon carbide-metallic silicon powder as a precursor and organosilicon resin as the main binder. The Si3N4-SiC ceramic powder is produced by high-temperature sintering under a nitrogen atmosphere and then high-pressure ball milling. Introducing 10-15% of Si3N4-SiC ceramic powder into the skateboard brick material enables the formation of ceramic bonds in the skateboard matrix, thereby improving the high-temperature performance and corrosion resistance of the skateboard brick.

[0003] According to the search, patent CN101591190A uses silicon nitride particles and fine powder, silicon carbide particles and fine powder, and electrically calcined anthracite particles and fine powder as the main raw materials, with pitch, tar, and resin as binders and other additives, mixed in a certain proportion, and then processed through mixing, aging, molding, drying, and firing to prepare Si3N4-SiC-C refractory bricks. Patent CN101724860A uses Si3N4-SiC-C prepared by carbothermic reduction nitriding of natural quartz as raw material, and adds a small amount of industrial-grade silicon carbide particles, a certain amount of electrically calcined anthracite particles and fine powder, and resin, pitch, and tar as binders, mixed in a certain proportion, and then processed through mixing, aging, molding, drying, and heat treatment to directly prepare non-fired Si3N4-SiC-C refractory bricks for aluminum electrolytic cell sidewalls without high-temperature nitriding sintering. However, this refractory brick is not suitable for use in the slag-blocking environment of converters. The Si3N4 and SiC in the refractory brick can easily react with the free [O] and [CaO] in molten steel and slag to form low-melting-point C2S, which damages the performance of the refractory brick and causes a significant decrease in durability.

[0004] Patent CN101939273A discloses a silicon carbide (SiC) based sintering material, which is reactively sintered between 1100℃ and 1700℃ to form a silicon nitride binder (Si3N4). The β-type silicon nitride Si3N4 accounts for at least 80% by weight of all β-type and α-type silicon nitride Si3N4. This refractory brick is used for the sidewalls of aluminum electrolytic cells. However, the presence of α-type Si3N4, which is unstable during heat treatment, easily causes cracks during the slide plate firing process, making it unsuitable for direct application in the slide plate bricks of this application.

[0005] Patent CN110372388A discloses a SiC-bonded Si3N4 castable that can completely replace blast furnace cooling wall lining bricks and its preparation method. The technical solution involves using 63-68 wt% silicon carbide particles as aggregate, and 13-17 wt% silicon carbide micro powder and 18-22 wt% silicon nitride micro powder as matrix materials. The aggregate and matrix materials are mechanically mixed according to the above mass ratio. Then, 8-10 wt% of silica sol (the sum of the aggregate and matrix materials' mass) is added as a binder, and the mixture is stirred evenly to obtain a SiC-bonded Si3N4 castable that can completely replace blast furnace cooling wall lining bricks. The prepared castable is poured or sprayed onto the belly and waist of the blast furnace, with a thickness of approximately 100-120 mm, and then dried. However, the SiC-bonded Si3N4 formed by adding silicon nitride micro powder and silicon carbide in this patent, where SiC and Si3N4 are directly added, has poor bonding performance, resulting in poor performance under high-temperature conditions. Summary of the Invention

[0006] 1. The problem to be solved

[0007] To address the problem of poor high-temperature performance of existing sliding bricks, this invention provides a Si3N4-SiC ceramic powder and its preparation method, the obtained Si3N4-SiC ceramic powder exhibiting excellent high-temperature stability;

[0008] The present invention also discloses a sliding plate brick containing the above-mentioned Si3N4-SiC ceramic powder and its preparation method. The obtained sliding plate brick has good thermal shock resistance and good erosion resistance.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A converter slag stopping sliding plate brick, which is composed of 39-48% tabular corundum particles, 6-8% zircon mullite particles, 8% zircon corundum particles, 3-5% silicon carbide particles, 35-40% co-milling powder and 3-4% phenolic resin, with the total percentage being 100%.

[0012] The Si3N4-SiC ceramic powder of the present application is prepared by nitriding and sintering of silicon carbide and organic silicon resin, and comprises the following steps:

[0013] Step one: mixing: add into a mixing mill and mix for 5 minutes, add organic silicon resin, mix for 3-5 minutes, then add 30% 200-mesh metal silicon powder and 1-um alpha-Al2O3 micro powder, mix for 12-18 minutes, and then discharge the mud;

[0014] The mass ratio of the silicon carbide, metal silicon powder, alpha-Al2O3 micro powder and organic silicon resin is (60-90):(30-45):0.2:(2.5-4.5).

[0015] The silicon carbide particles are selected from silicon carbide particles 5-3mm, silicon carbide particles 3-1mm and silicon carbide particles 1-0mm, and preferably, the mass ratio is 1:1.25:1.25. Three different particle size grades of silicon carbide particles are selected as the base, and different particle sizes of silicon carbide play different roles. The 5-3mm, 3-1mm and 1-0mm particles serve as the skeleton, and the metal silicon serves as the matrix, which on the one hand realizes the best packing and wrapping of the particles, and on the other hand is conducive to the pressing into balls and the forming.

[0016] The present application selects 1-um ultra-fine alpha-Al2O3 micro powder to disperse in the whole matrix to promote the sintering, which on the one hand can promote the generation of stable beta-Si3N4 from silicon nitride in the high-temperature reaction process, and on the other hand can promote the crystal growth.

[0017] Step two: pressing: the mud is pressed into balls on a 1000-ton electric friction press; and

[0018] Step three: drying: place the above-mentioned spherical brick into a drying kiln, set the initial temperature of the kiln to 50℃, and keep the temperature at this value for 12 hours; increase the temperature to 80℃, and keep the temperature at this value for 6 hours; increase the temperature to 120℃, and keep the temperature at this value for 12 hours; increase the temperature to 150℃, and keep the temperature at this value for 6 hours; increase the temperature to between 200-220℃, and keep the temperature at this value for 12 hours; the total drying time is 48 hours or more;

[0019] Step four: nitriding sintering: nitriding sintering is performed in a 15m shuttle kiln, the temperature in the kiln is increased at a rate of 20-25℃ / h, the temperature is kept at 1500-1580℃ for 24h, the sintering time is 86-98h, the cooling time is 48-60h, and the kiln door is opened when the temperature is cooled to below 80℃; nitrogen is introduced into the shuttle kiln during the sintering process;

[0020] Step five: place the above-mentioned brick into a high-pressure spherical grinding machine to grind, and obtain Si3N4-SiC ceramic powder with a particle size of 6-8um.

[0021] The present application first uses metal silicon powder as a silicon source, an organic silicon resin as a binding agent, and Al2O3 as a sintering aid to form a Si3N4 coating layer on the surface of SiC particles, and under the condition of low oxygen partial pressure, β-Si3N4 phase is generated in situ around the silicon carbide particles. The material has excellent high-temperature stability. In the Si3N4-SiC ceramic powder prepared, Si3N4 is coated on the surface of SiC particles, the mass ratio of SiC to Si3N4 is (1-3):(0.5-1.5), and a small amount of Al2O3 and residual carbon remains after nitriding sintering, wherein the residual carbon reacts to generate a non-oxide reinforcing phase, and the mass fraction of Al2O3 is ≤0.2%.

[0022] The organic silicon resin is selected from methylphenyl silicone resin with high residual carbon, high dispersibility, and Si-O functional groups. Compared with the silica sol in CN110372388A, the higher residual carbon makes the material have better room temperature bonding performance. Compared with the perhydrogen polysilazane precursor solution, the higher residual carbon is beneficial to the generation of silicon carbide during high-temperature sintering, and the high-activity carbon and silicon remaining after the resin cracking promote the generation of silicon carbide and the growth of crystals.

[0023] Si3N4-SiC ceramic powder is introduced into the aluminum zirconium carbon material, and when sintering under nitrogen atmosphere, complex in-situ reaction occurs among Si3N4-SiC ceramic powder, metal silicon powder and carbon decomposed from the binder in the matrix, further forming a SiC coating layer on the surface of Si3N4-SiC ceramic powder, forming a SiC-Si3N4-SiC layer layer-wrapped three-phase ceramic interface, and the ratio of the inner layer SiC-Si3N4-outer layer SiC is (1-3):(0.5-1.5):(0.5-1.5), preferably, the ratio of the inner layer SiC:Si3N4:outer layer SiC is 1:1:1. In the composite structure, Si3N4 is coated on the surface of SiC, and SiC formed by metal silicon powder and carbon decomposed from the resin is coated on the surface of Si3N4. In order to form a SiC-Si3N4-SiC three-phase ceramic structure in the skateboard substrate, the Si3N4 crystal size is controlled to be 1-3 um, the inner layer SiC crystal size is 3-5 um, and the outer layer SiC crystal size is 1-3 um; at the same time, a methyl phenyl silicone resin with high residual carbon (800℃*7min≥55%), high dispersity (25℃ 3500-4500cP) and Si-O functional groups is selected, and the prepared SiC-Si3N4-SiC three-phase ceramic structure is dispersed in the skateboard brick structure, and the particle size is 6-8 um. Compared with the two-phase Si3N4-SiC ceramic, the three-phase ceramic has the advantages of high bonding strength and ceramic bonding strength after the outermost structure is damaged during use.

[0024] A small amount of Al2O3 is still present on the surface of the finally obtained skateboard brick SiC-Si3N4-SiC three-phase ceramic structure, and surprisingly, it is found that the part of Al2O3 and the remaining components in the skateboard brick, such as metal silicon powder and free oxygen, further generate mullite in-situ under high-temperature use conditions, thereby enhancing the high-temperature strength of the skateboard brick, and the high-temperature strength is continuously improved with the use of the skateboard brick. The skateboard brick and the SiC-Si3N4-SiC three-phase ceramic structure formed in-situ around the particle framework with tabular corundum, zircon corundum and zircon mullite as the framework, on the one hand, improve the bonding strength of the skateboard, and on the other hand, form a network structure with the particle framework, so that the material is more uniform, which is beneficial to improve the high-temperature strength.

[0025] Preferably, the particle size of the tabular corundum is (2-1, 1-0.5, 0.5-0, 325 mesh) mm, and the weight percentage of each particle size is: 10%-15% of tabular corundum with a particle size of 2-1 mm, 14%-18% of tabular corundum with a particle size of 1-0.5 mm, 15% of tabular corundum with a particle size of 0.5-0 mm, and 5.2%-14.4% of tabular corundum with a particle size of 325 mesh; the content of Al2O3 in the tabular corundum is 99.5%, the content of Fe2O3 is ≤0.1%, and the content of R2O is ≤0.2%.

[0026] Preferably, the particle size of the zircon mullite is (2-1, 1-0.5) mm, and the weight percentage of each particle size is: 5% of zircon mullite with a particle size of 2-1 mm, and 1-3% of zircon mullite with a particle size of 1-0.5 mm; the content of Al2O3 in the zircon mullite is 44-48%, the content of ZrO2 is 32-40%, the content of SiO2 is 16-18%, the content of Fe2O3 is ≤0.1%, and the content of R2O is ≤0.3%.

[0027] Preferably, the particle size of the zircon mullite is (2-1, 1-0.5) mm, and the weight percentage of each particle size is: 5% of zircon mullite with a particle size of 2-1 mm, and 1-3% of zircon mullite with a particle size of 1-0.5 mm; the content of Al2O3 in the zircon mullite is 44-48%, the content of ZrO2 is 32-40%, the content of SiO2 is 16-18%, the content of Fe2O3 is ≤0.1%, and the content of R2O is ≤0.3%.

[0028] Preferably, the particle size of the silicon carbide is 5-3 mm, 3-1 mm, and 1-0 mm; the content of SiC in the silicon carbide is ≥97%, the content of Fe2O3 is ≤0.4%, the content of free carbon is ≤0.5%, the content of water is ≤0.2%, and the content of SiO2 is ≤0.6%.

[0029] Preferably, the particle size of the α-Al2O3 micro powder is 1 um; the content of Al2O3 in the α-Al2O3 micro powder is ≥99%, the content of Fe2O3 is ≤0.08%, the content of SiO2 is ≤0.2%, and the content of R2O is ≤0.25%.

[0030] Preferably, the particle size of the metal silicon powder is 200 mm; the content of Si in the metal silicon powder is ≥98%, the content of Fe is ≤1%, the content of Al is ≤0.6%, and the content of Ca is ≤1%.

[0031] Preferably, the particle size of the boron carbide is 325 mm; the content of B4C in the boron carbide is ≥95%, the content of B 总 is ≥76.5%, the content of C 总 is ≥20%, the content of B2O3 is ≤0.15%, the content of C 游离 is ≤3%, the content of Fe2O3 is ≤0.24%, the content of Al2O3 is ≤0.25%, and the content of SiO2 is ≤0.1%.

[0032] Preferably, the particle size of the 95 micro silicon powder is 3-5 um; the content of SiO2 in the 95 micro silicon powder is ≥95%, the content of Fe2O3 is ≤1%, the content of Fe2O3 is ≤1%, the content of R2O is ≤1%, and the loss on ignition is ≤1.5%.

[0033] Preferably, the organic silicon resin has a viscosity (25℃) of 3500-4500 cP, a solid content (200℃*2h) of ≥78%, and a carbon residue (800℃*7min) of ≥55%, and a R:Si value of 1.5.

[0034] Preferably, the phenolic resin has a viscosity (25℃) of 11000-16000 cP, a solid content (200℃*2h) of ≥80%, and a carbon residue (800℃*7min) of ≥50%.

[0035] Another object of the present application is to provide a preparation method of the converter slag stopping slide plate brick, which is specifically performed in the following steps:

[0036] Step one, particle batching: uniformly mixing tabular corundum particles, zircon mullite particles, zircon corundum particles, and silicon carbide particles according to weight percentage to obtain particle batching;

[0037] Step two, co-milling powder preparation: uniformly mixing tabular corundum fine powder, Si3N4-SiC ceramic powder, α-Al2O3 micro powder, metallic silicon powder, boron carbide, and 95 micro silicon powder according to weight percentage to obtain co-milling powder;

[0038] Step three, mixing: dry mixing the particle aggregate with a wet mill for 3-5 minutes, then slowly adding 3%-4% of the binder to wet mix for 5-8 minutes, and then adding the co-milling powder to mix for 25-30 minutes to obtain the mud;

[0039] Step four, molding: molding the mud on a 1000t electric screw brick press to obtain a green brick, and naturally cooling for 8 hours;

[0040] Step five, drying: placing the green brick in a drying kiln, setting the initial temperature to 50℃, and maintaining the temperature for 8 hours; increasing the temperature to 80℃, and maintaining the temperature for 8 hours; increasing the temperature to 120℃, and maintaining the temperature for 16 hours; increasing the temperature to 150℃, and maintaining the temperature for 2 hours; increasing the temperature to 200-220℃, and maintaining the temperature for 16 hours; the total drying time is 50 hours or more; and selecting qualified semi-finished products after the kiln is taken out;

[0041] Step six, nitriding firing: performing nitriding firing in a 15m shuttle kiln, increasing the temperature in the kiln at 15-20℃ / h, maintaining the temperature at 1400-1480℃ for 24h, firing for 96-120h, and cooling for 48-60h, and opening the kiln door when the temperature is lowered to 80℃ or below; and introducing nitrogen into the shuttle kiln during the firing process;

[0042] Step seven, hoop punching: the iron hoop is located in the middle, the iron hoop weld seam is not more than 1mm, and the gap between the iron hoop and the slide plate is not more than 1mm;

[0043] Step eight, grinding: grinding on a numerical control vertical axis round table surface grinder, the flatness of the slide plate working surface is less than 0.05mm, the thickness tolerance of the slide plate is ±0.5mm, and the moisture generated in the grinding process of the slide plate is dried by using an infrared dryer;

[0044] Step nine, veneering, coating, inspection and packaging to obtain the finished product.

[0045] 3. Beneficial effects

[0046] Compared with the prior art, the beneficial effects of the present application are:

[0047] (1) The present application uses silicon carbide particles and silicon metal powder as main raw materials, and organosilicon resin as a binder, and Si3N4-SiC ceramic powder is prepared by nitriding under a nitrogen atmosphere. Under the condition of low oxygen partial pressure, β-Si3N4 phase is generated in situ around the silicon carbide particles. The material has excellent high-temperature stability.

[0048] (2) The Si3N4-SiC ceramic powder prepared by the present application forms a three-dimensional solid solution combination in the form of a solid solution phase. During use, the outermost ceramic phase is destroyed, but the overall matrix still exists in the form of a two-phase ceramic combination, so that the material has high high-temperature strength during high-temperature use.

[0049] (3) The SiC-Si3N4 ceramic powder is added to the slide plate brick. During the preparation process, the Si3N4-SiC ceramic powder, silicon metal powder and carbon decomposed from the binder in the matrix undergo complex in-situ reactions under a nitrogen atmosphere during sintering, further forming a SiC coating layer on the surface of the Si3N4-SiC ceramic powder, forming a SiC-Si3N4-SiC layer-by-layer wrapped three-phase ceramic interface, improving the thermal shock resistance and corrosion resistance of the slide plate brick.

[0050] (4) The SiC-Si3N4-SiC three-phase ceramic structure prepared by the present application also has a small amount of Al2O3 on the surface. When added to the slide plate brick, the Al2O3 and the remaining components in the slide plate brick, such as silicon metal powder and free oxygen, further generate mullite in-situ under high-temperature use conditions, enhancing the high-temperature strength of the slide plate brick, and the high-temperature strength and corrosion resistance are continuously improved with the use of the slide plate brick.

[0051] (5) The slide plate brick prepared by the present application does not add additional carbon source, and the residual carbon decomposed from the binder reacts to form a non-oxide reinforcing phase at high temperature. There is no free elemental carbon source in the matrix, and the pollution to the molten steel during use is small. BRIEF DESCRIPTION OF DRAWINGS

[0052] The technical solutions of the present application will be described in further detail below in combination with the drawings and examples, but it should be understood that these drawings are designed only for the purpose of explanation, and thus do not limit the scope of the present application. In addition, unless specifically indicated, these drawings are only intended to conceptually illustrate the structural configurations described herein, and are not necessarily drawn to scale.

[0053] Figure 1 SiC-Si3N4 ceramic powder in the slide plate for the electron microscope image;

[0054] Figure 2 The contrast chart before and after the use of the slide plate brick. DETAILED DESCRIPTION

[0055] The following detailed description of exemplary embodiments of the present application refers to the accompanying drawings, that show by way of example exemplary embodiments in which the present application can be practiced. These exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the present application, and it is to be understood that other embodiments can be utilized and that logical, mechanical and electrical changes can be made without departing from the spirit and scope of the present application. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present application is defined only by the appended claims.

[0056] A converter slag stopping slide plate brick, which is composed of 39% tabular corundum particles, 8% zircon mullite particles, 8% zircon corundum particles, 5% silicon carbide particles, 40% co-milling powder, and 3.5% phenolic resin, with the total percentage being 100%.

[0057] The Si3N4-SiC ceramic powder is prepared by the following method:

[0058] Step one: 20% silicon carbide particles 5-3mm, 25% silicon carbide particles 3-1mm, and 25% silicon carbide particles 1-0mm are added to a mixing mill and mixed for 5 minutes, 3.5% silicone resin is added, mixed for 3 minutes, then 30% metal silicon powder 200 mesh and 0.2% α-Al2O3 micro powder with a particle size of 1um are added, mixed for 15 minutes, and then the mud is discharged;

[0059] Step two: the mud is pressed into a ball on a 1000-ton electric friction press; and cooled for 6 hours;

[0060] Step three: put the above-mentioned spherical brick into a drying kiln, set the initial temperature of the kiln to 50℃, keep the temperature for 12 hours; increase the temperature to 80℃, keep the temperature for 6 hours; increase the temperature to 120℃, keep the temperature for 12 hours; increase the temperature to 150℃, keep the temperature for 6 hours; increase the temperature to 200-220℃, keep the temperature for 12 hours; the total drying time is 48 hours or more;

[0061] Step four: nitriding sintering: in a 15m shuttle kiln, the temperature in the kiln is increased at a rate of 20-25℃ / h, the temperature is kept at 1550℃ for 24h, the sintering time is 86-98h, the cooling time is 48-60h, the kiln door is opened when the temperature is cooled to 80℃ or less; nitrogen is introduced into the shuttle kiln during the sintering process;

[0062] Step five: put the above-mentioned brick into a high-pressure spherical grinding machine to obtain Si3N4-SiC ceramic powder with a particle size of 6-8um;

[0063] The Si3N4-SiC ceramic powder prepared in Example 1 has an electron microscope image as shown in Figure 1 Since the silicon nitride is dispersed around the silicon carbide during the in-situ reaction, the particles are smaller than the silicon carbide, so only the overall appearance of the silicon carbide is found under the scanning electron microscope.

[0064] The particle size of the tabular corundum is (2-1, 1-0.5, 0.5-0, 325 mesh) mm, and the weight percentage of each particle size is: 10% of tabular corundum with a particle size of 2-1mm, 14% of tabular corundum with a particle size of 1-0.5mm, 15% of tabular corundum with a particle size of 0.5-0mm, and 14.4% of tabular corundum with a particle size of 325 mesh; the content of Al2O3 in the tabular corundum is 99.5%, the content of Fe2O3 is ≤0.1%, and the content of R2O is ≤0.2%.

[0065] The particle size of the zircon mullite is (2-1, 1-0.5) mm, and the weight percentage of each particle size is: 5% of zircon mullite with a particle size of 2-1mm, and 1%-3% of zircon mullite with a particle size of 1-0.5mm; the content of Al2O3 in the zircon mullite is 44-48%, the content of ZrO2 is 32-40%, the content of SiO2 is 16-18%, the content of Fe2O3 is ≤0.1%, and the content of R2O is ≤0.3%;

[0066] Preferably, the zirconia corundum has a particle size of (2-1, 1-0.5) mm, and the weight percentage of each particle size is: 5% of zirconia corundum with a particle size of 2-1 mm, and 3% of zirconia corundum with a particle size of 1-0.5 mm; the zirconia corundum contains 52-62% of Al2O3, 40-45% of ZrO2, ≤0.2% of Fe2O3, and ≤0.2% of R2O.

[0067] Preferably, the silicon carbide has a particle size of 5-3 mm, 3-1 mm, or 1-0 mm; the silicon carbide contains ≥97% of SiC, ≤0.4% of Fe2O3, ≤0.5% of free carbon, ≤0.2% of water, and ≤0.6% of SiO2.

[0068] Preferably, the α-Al2O3 micropowder has a particle size of 1 um; the α-Al2O3 micropowder contains ≥99% of Al2O3, ≤0.08% of Fe2O3, ≤0.2% of SiO2, and ≤0.25% of R2O.

[0069] Preferably, the metallic silicon powder has a particle size of 200 mm; the metallic silicon powder contains ≥98% of Si, ≤1% of Fe, ≤0.6% of Al, and ≤1% of Ca.

[0070] Preferably, the boron carbide has a particle size of 325 mm; the boron carbide contains ≥95% of B4C, ≥76.5% of total B, ≥20% of total C, ≤0.15% of B2O3, ≤3% of free C, ≤0.24% of Fe2O3, ≤0.25% of Al2O3, and ≤0.1% of SiO2.

[0071] Preferably, the 95-micron silicon powder has a particle size of 3-5 um; the 95-micron silicon powder contains ≥95% of SiO2, ≤1% of Fe2O3, ≤1% of Fe2O3, ≤1% of R2O, and ≤1.5% of ignition loss.

[0072] Preferably, the silicone resin has a viscosity (25°C) of 3500-4500 cP, a solid content (200°C*2h) of ≥78%, a carbon residue (800°C*7min) of ≥55%, and an R:Si value of 1.5.

[0073] Preferably, the phenolic resin has a viscosity (25°C) of 11000-16000 cP, a solid content (200°C*2h) of ≥80%, and a carbon residue (800°C*7min) of ≥50%.

[0074] A converter slag stopping sliding plate brick is specifically prepared according to the following steps:

[0075] S1, particle batching: uniformly mix tabular corundum particles, zircon mullite particles, zircon corundum particles and silicon carbide particles by weight percentage to obtain particle batching;

[0076] S2, co-milling powder preparation: uniformly mix tabular corundum fine powder, Si3N4-SiC ceramic powder, α-Al2O3 micro powder, metallic silicon powder, boron carbide and 95 micro silicon powder by weight percentage to obtain co-milling powder;

[0077] S3, mixing: dry mix the particle aggregate with a wet mill for 3-5 minutes, then slowly add 3%-4% of the binder to wet mix for 5-8 minutes, and then add the co-milling powder, mix for 25-30 minutes to obtain the mud;

[0078] S4, molding: mold the mud on a 1000t electric screw brick press to obtain a green brick, and naturally cool for 8 hours;

[0079] S5, drying: place the green brick in a drying kiln, set the initial temperature to 50℃, and keep the temperature at this value for 8 hours; increase the temperature to 80℃, and keep the temperature at this value for 8 hours; increase the temperature to 120℃, and keep the temperature at this value for 16 hours; increase the temperature to 150℃, and keep the temperature at this value for 2 hours; increase the temperature to between 220℃, and keep the temperature at this value for 16 hours; the total drying time is more than 50 hours; select qualified semi-finished products after taking out of the kiln;

[0080] S6, nitriding firing: perform nitriding firing in a 15m shuttle kiln, the temperature in the kiln is increased at a rate of 15℃ / h, the temperature is kept at 1450℃ for 24h, the firing time is 120h, the cooling time is 60h, the kiln door is opened when the temperature is cooled to below 80℃; nitrogen is introduced into the shuttle kiln during the firing process;

[0081] S7, hoop: the iron hoop is located in the middle, the iron hoop weld seam is not more than 1mm, and the gap between the iron hoop and the slide plate is not more than 1mm;

[0082] S8, grinding: grind on a numerical control vertical shaft round table surface grinding machine, the flatness of the slide plate working surface is less than 0.05mm, the thickness tolerance of the slide plate is ±0.5mm, and the moisture generated during the grinding of the slide plate is dried using an infrared dryer;

[0083] S9, veneer, coating, inspection and packaging to obtain the finished product.

[0084] Example 2

[0085] In this embodiment, the Si3N4-SiC ceramic powder is the Si3N4-SiC ceramic powder prepared in Example 1, which is added to the converter slag stopping slide plate brick. The composition and weight percentage of the converter slag stopping slide plate brick are shown in Table 2, and the preparation method is the same as that of Example 1.

[0086] Example 3

[0087] In this embodiment, the Si3N4-SiC ceramic powder used is the Si3N4-SiC ceramic powder obtained in Example 1. This Si3N4-SiC ceramic powder is added to the converter slag-blocking slide block. The composition and weight percentage of the converter slag-blocking slide block are as shown in Table 2. The preparation method is the same as in Example 1.

[0088] Comparative Example 1

[0089] Table 1. Preparation process parameters of Si3N4-SiC ceramic powder in various embodiments of the present invention.

[0090]

[0091]

[0092] This application uses the Si3N4-SiC ceramic powder obtained in Example 1 as raw material to prepare sliding plate bricks.

[0093] Table 2. Particle type and percentage of ingredients used in each embodiment of the present invention.

[0094]

[0095]

[0096] Table 3 shows a comparison of the physicochemical properties and average service life parameters of the Si3N4-SiC ceramic powder and converter slag baffle brick of the present invention with those of ordinary alumina-zirconium-carbon baffle brick.

[0097] Table 3 Comparison of the physicochemical properties and average service life of the Si3N4-SiC ceramic powder, converter slag baffle bricks, and ordinary alumina-zirconium-carbon baffle bricks of the present invention.

[0098]

[0099] like Figure 1 The image shown is an electron microscope image of SiC-Si3N4 ceramic powder in a slide plate. The absence of obvious particles on the surface indicates that the in-situ generated Si3N4 coating layer and the outer SiC layer are dispersed on the surface of the substrate SiC particles. The generated SiC-Si3N4-SiC three-phase ceramic structure has high bonding strength. During the use of the material, even after the outermost ceramic phase is destroyed, the overall matrix can still exist in the form of two-phase ceramic bonding, which makes the material have high high-temperature strength during high-temperature use.

[0100] In the formula, the Si3N4-SiC ceramic powder is coated with metal silicon powder, and the metal silicon powder on the surface of the ceramic powder and the carbon decomposed from the resin in-situ react to form SiC ceramic during the sintering process in a nitrogen atmosphere. Both silicon carbide and silicon nitride are covalent compounds, and have strong affinity between the crystals at high temperature. After nitriding, the Si3N4-SiC interface is further reacted to form a three-dimensional ceramic interface. The Si3N4-SiC-SiC three-phase ceramic combination is mainly in the form of solid solution, and the three-dimensional solid solution combination is in a three-dimensional solid solution form. During the use of the material, after the outermost ceramic phase is damaged, the overall matrix can exist in the form of two-phase ceramic combination, so that the material has high high-temperature strength during the use at high temperature.

[0101] The converter slag stopping slide plate bricks obtained in the above examples are used in a converter, and after the test, the invented slide plate bricks and common aluminum-zirconium-carbon products are compared and analyzed in terms of corrosion and cracks. The service life of the invented slide plate reaches more than 18 furnaces, the average diameter expansion is 28 mm, and the average corrosion rate is 1.47 mm / time. Through the comparison and measurement data analysis of the common aluminum-zirconium-carbon slide plate bricks, the average corrosion rate of the invented slide plate is 1.47 mm / time, which is better than the average corrosion rate of 2.6 mm / furnace of the existing aluminum-zirconium-carbon slide plate bricks. The slide plate crack condition is that the common aluminum-zirconium-carbon slide plate bricks have more surface cracks and poor thermal shock resistance. Therefore, the invented slide plate has good high-temperature strength, thermal shock resistance and corrosion resistance, and the before and after use of the slide plate is shown in the accompanying drawings. Figure 2 ​

Claims

1. A converter slag-blocking slide block, characterized in that, Includes granular material, said granular material comprising: (A) 60%–75% aggregate: including 39%–48% tabular corundum particles, 6%–8% zircon-mullite particles, 8% zircon-corundum particles and 3%–5% silicon carbide particles; (B) 35%–40% co-milled powder: prepared by uniformly mixing 5.2%–14.4% tabular corundum powder, 15%–20% Si3N4-SiC ceramic powder, 3%–5% metallic silicon powder, 5% α-Al2O3 micro powder, 0.4%–1.2% boron carbide and 0.2%–0.6% 95 micro silica powder; The mass of the aggregate and the co-ground powder is 100%. In the Si3N4-SiC ceramic powder, Si3N4 is coated on the surface of SiC, and the Si3N4 is β-Si3N4; the preparation method of the Si3N4-SiC ceramic powder includes the following steps: Step 1: Mixing: Add silicone resin to silicon carbide particles and mix evenly. The particle size of the added silicon metal powder and α-Al2O3 micro powder is 1μm. After mixing evenly, discharge to obtain mud. The mass ratio of silicon carbide, silicon metal powder, α-Al2O3 micro powder and silicone resin is (60-90):(30-45):0.2:(2.5-4.5). Step Two: Suppression; Step 3: Drying; Step 4: Nitriding and firing: Hold at 1500-1580℃ for 24 hours, firing time 86-98 hours, cooling time 48-60 hours, nitrogen gas is introduced during the firing process; Step 5: Grind the powder in a high-pressure ball mill to obtain Si3N4-SiC ceramic powder with a particle size of 6-8 μm.

2. The converter slag-blocking slide block according to claim 1, characterized in that, The mass ratio of SiC to Si3N4 is (1-3):(0.5-1.5).

3. The converter slag-blocking slide block according to claim 2, characterized in that, The organosilicon resin has Si-O functional groups and meets the following requirements: 800*7min, residual carbon ≥55%, viscosity: 3500-4500 cP at 25℃.

4. The converter slag-blocking slide block according to claim 1, characterized in that, It also includes a binder, the mass of which is 3% to 4% of the granules.

5. A method for preparing the converter slag-blocking slide block according to any one of claims 1-4, characterized in that, Including the following steps: Mixing; molding; drying; nitriding and firing; hooping; grinding; veneer, coating; inspection and packaging are then carried out to obtain the finished product.

6. The method for preparing converter slag-blocking slide block according to claim 5, characterized in that, The nitriding firing temperature is 1400-1480℃, and the firing time is 96-120h.

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