A kind of in situ formation magnesium-zinc-aluminum composite spinel phase reinforced air brick and preparation method

Abstract

The application discloses an in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced gas permeable brick and a preparation method thereof, and solves the problems of low strength, poor thermal shock resistance and poor corrosion resistance of the existing slit type gas permeable brick, and completely solves the problems of low strength of the material micro area on both sides of the slit channel due to the boundary effect without aggregate in the preparation process, easy penetration of high-temperature molten steel and slag into the slit and corrosion to cause damage to the gas permeation function of the gas permeable brick and low service life. The technical scheme of the application is as follows: the weight parts of the original material are as follows: the aggregate is tabular corundum 50-55 parts, white corundum 10-20 parts, the fine powder is tabular corundum or white corundum 5-15 parts, alumina micropowder 5-10 parts, spinel particle size 1-0 mm, 0-10 parts, spinel fine powder 5-15 parts, pure calcium aluminate cement 2-5 parts, and ZnO micropowder 0.5-3 parts; the dispersant is added in an amount of 0.05-0.2% of the total weight of the original material.

Description

Technical Field

[0001] This invention relates to permeable bricks for steel ladles, specifically a permeable brick reinforced with an in-situ magnesium-zinc-aluminum composite spinel phase and its preparation method. Background Technology

[0002] Aerated concrete blocks are essential functional components for bottom-blowing argon in steel refining. The materials used for aerated concrete blocks in ladles are generally divided into corundum spinel and chromium corundum. The former has better thermal shock resistance, while the latter has better resistance to slag erosion. However, chromium-containing materials pose a problem of hexavalent chromium contamination, so research mainly focuses on corundum spinel. The existing process for slotted aerated concrete blocks involves: mold preparation—casting and curing—demolding—baking at 300℃—firing at temperatures above 1500℃. However, existing corundum spinel aerated concrete blocks suffer from problems such as porosity, low strength, poor slag resistance, and poor erosion resistance. Especially in the micro-regions on both sides of the slotted channel, the material lacks aggregate due to boundary effects, resulting in lower strength compared to the block itself. Furthermore, due to the presence of gaps, high-temperature molten slag and molten steel easily seep in along the gaps and erode the surface of the gaps first. Under high-temperature service conditions, the area with the most prominent stress concentration in permeable bricks is around the gas channel outlet, and one of the main damage modes is slit blockage, which prevents the permeability from meeting smelting requirements, affecting the lifespan of the permeable bricks and the normal turnover of the ladle. Therefore, to address the shortcomings of existing corundum spinel slit-type permeable bricks, it is necessary to strengthen the micro-area material of the slit gas channel through refined design and control to improve its erosion resistance, slag resistance, resistance to high-temperature molten intrusion, and thermal shock resistance. Summary of the Invention

[0003] The purpose of this invention is to provide an in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick and its preparation method, which solves the problems of low strength, poor thermal shock resistance, and poor erosion resistance of existing slotted permeable bricks. It also completely solves the problems of low strength caused by the lack of aggregate in the micro-regions of the material on both sides of the slot channel due to boundary effect during the preparation process, and the easy penetration and erosion of high-temperature molten steel and slag into the slot, resulting in damage to the air permeability function and short service life of the permeable brick.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: an in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick, wherein the weight parts of the raw materials added are as follows: aggregate is 50-55 parts of tabular corundum, white corundum is 10-20 parts, fine powder is 5-15 parts of tabular corundum or white corundum, alumina micro powder is 5-10 parts, spinel particle size is 1-0 mm, 0-10 parts, spinel fine powder is 5-15 parts, pure calcium aluminate cement is 2-5 parts, and ZnO micro powder is 0.5-3 parts; the amount of dispersant added is 0.05-0.2% of the total weight of the raw materials.

[0005] The dispersant is a polycarboxylic acid polymer compound; specifically, it is any one or a mixture of several of polyacrylic acid, polyacrylate, and polymethacrylic acid.

[0006] The particle size of ZnO is ≤5 micrometers.

[0007] A method for preparing an in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick is as follows:

[0008] Prepare the mold, using the above raw materials and dispersant as raw materials, and after casting and curing, demold the green body. After demolding, bake the green body in a drying kiln at 120-300℃ for 24 hours, then raise the temperature to 500-600℃ and hold for 12 hours. At this temperature, the slit precursor is completely burned off, producing slit air channels, and obtaining the corundum spinel slit permeable brick green body.

[0009] Method 1: The temperature of the obtained corundum spinel slotted permeable brick blank is further increased to 900℃~1450℃ and held for 16h to obtain a lightly fired, in-situ formed magnesium zinc aluminum composite spinel phase-reinforced permeable brick.

[0010] Method 2: Vapor deposition method; The permeable brick blank treated with slotted precursor material is placed in a closed high-temperature furnace, and zinc granules are placed around the permeable brick blank. First, a vacuum pump is used to evacuate the furnace to a negative pressure of 0.1 atmospheres, and then the temperature is increased to 950℃-1000℃, so that the zinc is vaporized in the closed furnace. The temperature is kept constant and held for 3-4 hours. Then, the air valve is opened to allow air to enter the furnace until the pressure inside the furnace reaches the normal ambient atmospheric pressure. The temperature is held for another 3-4 hours, and then the furnace is stopped and allowed to cool naturally to room temperature. Then, the temperature of the permeable brick blank after zinc vaporization treatment is further increased to 900℃~1450℃ and held for 16 hours, thus obtaining a lightly sintered, in-situ formed magnesium-zinc-aluminum composite spinel phase-reinforced permeable brick.

[0011] The equipment used for high-temperature firing includes high-temperature gas-fired kilns, high-temperature electric kilns, and high-temperature tunnel kilns; firing temperature: 900℃~1450℃.

[0012] The addition of ZnO micro powder allows for the in-situ reaction between ZnO and Al2O3 to form zinc-aluminum spinel, which begins at 700℃ and is completed at around 900-1000℃. This solid solution reaction has an activating effect, promoting the reaction and bonding of other crystalline phases. Therefore, the firing temperature of the permeable brick can be reduced by 50-700℃ compared to the original corundum-spinel permeable brick, which requires high-temperature firing of 1500-1680℃ in existing technologies. It is difficult to reduce the firing temperature in existing technologies. This invention achieves low-temperature firing by adding ZnO micro powder, which is more energy-efficient and reduces production costs.

[0013] In Method 2, the weight of the zinc granules added is 0.5%-1% of the total weight of the permeable brick blank;

[0014] When using method two, the amount of ZnO micro powder added is 0.5 to 2 parts;

[0015] This invention adds ZnO micro powder to a corundum-spinel permeable brick system. The added ZnO reacts in situ with Al2O3 in the matrix at relatively low temperatures (~700℃) to form a zinc-aluminum spinel (chemical formula ZnAl2O4, abbreviated as ZA) phase, which has a reinforcing effect. At higher heat treatment temperatures, ZnO and ZnAl2O4 can further dissolve with magnesium-aluminum spinel (chemical formula MgAl2O4, abbreviated as MA) in the system to transform into magnesium-zinc-aluminum composite spinel (chemical formula Mg... 1-x Zn x Al2O4 (x=0~1) achieves higher bonding strength. The final in-situ generated magnesium-zinc-aluminum composite spinel phase can improve the hot strength, thermal shock resistance and slag resistance of the permeable brick material, and improve the performance of the permeable brick while reducing the firing temperature.

[0016] This invention utilizes the fact that when zinc reaches temperatures above 907°C, it begins to vaporize. In a zinc vapor atmosphere, gaseous zinc migrates to the surface of the slit-like gas channel. After the valve is opened and air is introduced into the furnace, the zinc vapor in the slit-like gas channel region is rapidly oxidized to ZnO and deposited on the channel surface. The ZnO deposited on the channel surface can react in situ with Al2O3 in the permeable brick matrix to form zinc-aluminum spinel (chemical formula: ZnAl2O4), and can also react in situ with magnesium-aluminum spinel (chemical formula: MgAl2O4) in the permeable brick matrix to form magnesium-zinc-aluminum multiphase spinel (chemical formula: (Mg... 1-x Zn x Al2O4). The resulting effects are as follows: improving the slag resistance of the micro-area material on the gas passage surface; promoting the sintering of the micro-area material on the gas passage surface in the subsequent high-temperature firing process, improving the strength and erosion resistance of the micro-area material on the gas passage surface; utilizing the volume expansion effect accompanying the formation of zinc-aluminum spinel and magnesium-zinc-aluminum multiphase spinel, not only can the width of the slit gas passage be negatively adjusted slightly, but the micro-roughness of the surface micro-area can also be increased, further increasing the difficulty of wetting the gas passage surface by molten steel and slag, and reducing the probability of steel clogging the gas passage.

[0017] This invention introduces a solid form (0.5-2% ZnO micro powder) into the bulk material to make a permeable brick body, and then uses zinc vapor oxidation deposition to micro-enhance the surface of the air channels of the permeable brick to obtain better performance.

[0018] These composite protective layers modify the micro-region materials on both sides of the slit channels of the permeable brick. This not only improves the strength and slag resistance of the micro-region materials on the channel surface, but also increases the wetting angle with high-temperature molten steel by increasing the micro-roughness of the channel surface, preventing high-temperature melt from penetrating and clogging the slits. This solves the problems in the existing slit-type permeable brick preparation process, such as low strength of the micro-region materials on both sides of the slit channel due to the lack of aggregate in the boundary effect, and the easy penetration and erosion of the slits by high-temperature molten steel and slag, which easily damages the permeability of the permeable brick. By improving the overall performance and use of the permeable brick, it can effectively improve the ladle refining effect, ensure the quality of molten steel, and extend the service life of the ladle. Implementation

[0019] The following examples illustrate the implementation and features of the present invention, but the present invention is not limited to the following embodiments.

[0020] Example 1:

[0021] The raw materials are added in the following weight proportions: 50 parts of tabular corundum, 20 parts of white corundum, 5 parts of fine powder (tabular corundum or white corundum), 5 parts of alumina micro powder, 7 parts of spinel with a particle size of 1~0mm, 5 parts of spinel fine powder, 5 parts of pure calcium aluminate cement, and 3 parts of ZnO micro powder; the amount of dispersant added is 0.15% of the total weight of the raw materials, and the dispersant is polyacrylic acid.

[0022] Prepare the mold, using the above raw materials and dispersant as raw materials, and after casting and curing, demold the green body. After demolding, bake the green body in a drying kiln at 120-300℃ for 24 hours, then raise the temperature to 500-600℃ and hold for 12 hours. At this temperature, the slit precursor is completely burned off, producing slit air channels, and obtaining the corundum spinel slit permeable brick green body.

[0023] The temperature of the obtained corundum spinel slotted permeable brick blank is further increased to 900℃ and held for 16 hours to obtain a lightly fired, in-situ formed magnesium-zinc-aluminum composite spinel phase-reinforced permeable brick.

[0024] Example 2:

[0025] A permeable brick reinforced with an in-situ formed magnesium-zinc-aluminum composite spinel phase, wherein the raw materials are added in the following weight proportions: 55 parts of tabular corundum, 10 parts of white corundum, 15 parts of fine powder (tabular corundum or white corundum), 10 parts of alumina micro powder, 2.5 parts of spinel with a particle size of 1~0 mm, 5 parts of spinel fine powder, 2 parts of pure calcium aluminate cement, and 0.5 parts of ZnO micro powder; the amount of dispersant added is 0.07% of the total weight of the raw materials, and the dispersant is polymethyl methacrylate.

[0026] The preparation method is as follows:

[0027] Prepare molds using the aforementioned raw materials and dispersant. After casting, molding, and curing, demold the green body. The demolded green body is then baked in a drying kiln at 120-300℃ for 24 hours, followed by heating to 500-600℃ and holding for 12 hours. At this temperature, the slit precursor is completely burned off, creating slit air channels, resulting in a corundum spinel slit-type permeable brick green body. The permeable brick green body treated with the slit precursor material is placed in a sealed high-temperature furnace, first using a vacuum... The pump draws the negative pressure inside the furnace to 0.1 atmospheres, then raises the temperature to 1000℃ and holds it there, allowing the zinc metal to vaporize in the sealed furnace while maintaining a constant temperature. After holding for 3 hours, the air valve is opened to allow air into the furnace until the pressure inside the furnace reaches normal atmospheric pressure. After holding for another 4 hours, the furnace is shut down and allowed to cool naturally to room temperature. Then, it is fired at 1400℃ and held for 16 hours to obtain this corundum spinel slotted permeable brick with modified air passage surface.

[0028] Example 3:

[0029] The raw materials are added in the following weight proportions: 53 parts of tabular corundum, 15 parts of white corundum, 10 parts of fine powder (tabular corundum or white corundum), 10 parts of alumina micro powder, 3 parts of spinel with a particle size of 1~0 mm, 5 parts of spinel fine powder, 2 parts of pure calcium aluminate cement, and 2 parts of ZnO micro powder; the amount of dispersant added is 0.1% of the total weight of the raw materials, and the dispersant is polyacrylic acid and polyacrylate.

[0030] The preparation method is as follows:

[0031] Prepare molds using the aforementioned raw materials and dispersant. After casting, molding, and curing, demold the green body. The demolded green body is then baked in a drying kiln at 120-300℃ for 24 hours, followed by heating to 500-600℃ and holding for 12 hours. At this temperature, the slit precursor is completely burned off, creating slit air channels, resulting in a corundum spinel slit-type permeable brick green body. The permeable brick green body treated with the slit precursor material is placed in a sealed high-temperature furnace, first using a vacuum... The pump draws the negative pressure inside the furnace to 0.1 atmospheres, then raises the temperature to 1000℃ and holds it there, allowing the zinc metal to vaporize in the sealed furnace while maintaining a constant temperature. After holding for 3 hours, the air valve is opened to allow air into the furnace until the pressure inside the furnace reaches normal atmospheric pressure. After holding for another 4 hours, the furnace is shut down and allowed to cool naturally to room temperature. Then, it is fired at 1450℃ and held for 16 hours to obtain this corundum spinel slotted permeable brick with modified air passage surface.

[0032] The key performance indicators of the materials before and after the process modification, as well as the performance of the permeable bricks, are shown in the table below:

[0033]

[0034] The raw materials in the table above are permeable bricks processed using existing technologies.

[0035] For the performance indicators of the materials before and after process modification in Examples 1-3, such as chemical composition, room temperature compressive strength, high temperature flexural strength, and surface hardness, the test samples were standard-sized specimens (25mm*25mm*150mm, 40mm*40mm*160mm) prepared in the laboratory with the same formula. The specimen treatment conditions were the same as those for the corresponding permeable bricks, and the firing process was the same. Each cast crucible sample was treated with 80g of steel slag at the firing temperature and then naturally cooled. The erosion area of ​​the crucible's longitudinal section was measured, and the ratio of this area to the original inner hole section of the crucible was the slag erosion index.

Claims

1. A breathable brick reinforced with an in-situ formed magnesium-zinc-aluminum composite spinel phase, characterized in that: The raw materials are added in the following weight proportions: 50-55 parts of tabular corundum, 10-20 parts of white corundum, 5-15 parts of fine powder (tabular or white corundum), 5-10 parts of alumina micro powder, 0-10 parts of spinel (1-0 mm particle size), 5-15 parts of spinel fine powder, 2-5 parts of pure calcium aluminate cement, and 0.5-3 parts of ZnO micro powder; the dispersant is added at 0.05-0.2% of the total weight of the raw materials; the preparation method is as follows: prepare a mold, use the above raw materials and dispersant as raw materials, cast and mold, cure, and then demold. After demolding, the green body is baked in a drying kiln at 120-300℃ for 24 hours, then heated to 500-600℃ and held for 12 hours. At this temperature, the slit precursor is completely burned off. A narrow slit air passage is generated to obtain a corundum spinel slit-type permeable brick blank; vapor deposition method; the permeable brick blank treated with slit precursor material is placed in a closed high-temperature furnace, and metallic zinc particles are placed around the permeable brick blank. First, the vacuum pump is used to evacuate the furnace to a negative pressure of 0.1 atmospheres, and then the temperature is increased to 950℃-1000℃, so that the metallic zinc is vaporized in the closed furnace. The temperature is kept constant and held for 3-4 hours. Then, the air valve is opened to allow air to enter the furnace until the pressure in the furnace reaches the normal ambient atmospheric pressure. The temperature is held for another 3-4 hours, and then the furnace is stopped and allowed to cool naturally to room temperature. Then, the permeable brick blank after zinc vapor treatment is fired at high temperature and held for 16 hours to obtain a permeable brick with in-situ formation of magnesium zinc aluminum composite spinel phase reinforcement.

2. The in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 1, characterized in that: The particle size of ZnO is ≤5 micrometers.

3. The in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 1, characterized in that: The dispersant is a polycarboxylic acid polymer.

4. The in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 3, characterized in that: The dispersant is any one or a mixture of several of polyacrylic acid, polyacrylate, and polymethacrylic acid.

5. The method for preparing in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 1, characterized in that: Prepare a mold, using the above-mentioned raw materials and dispersant as raw materials, and after casting and curing, demold the green body. After demolding, bake the green body in a drying kiln at 120-300℃ for 24 hours, then raise the temperature to 500-600℃ and hold for 12 hours. At this temperature, the slit precursor is completely burned off, creating slit air channels, and obtaining a corundum spinel slit permeable brick green body. The obtained corundum spinel slit permeable brick green body is then fired at high temperature and held for 16 hours to obtain a lightly fired in-situ formed magnesium zinc aluminum composite spinel phase reinforced permeable brick.

6. The method for preparing in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 5, characterized in that: The high-temperature firing temperature is 900℃~1450℃.

7. The method for preparing in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 5, characterized in that: The amount of ZnO micro powder added is 0.5 to 2 parts.

8. The method for preparing in-situ formed magnesium-zinc-aluminum composite spinel phase reinforced permeable brick according to claim 5, characterized in that: The weight of zinc granules added is 0.5%-1% of the total weight of the permeable brick blank.

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