Aluminum titanate fiber and BN nanosheet coupling reinforced and toughened MgO skateboard and its preparation process

Abstract

The present invention relates to a MgO slide plate reinforced and toughened by coupling aluminum titanate fibers and BN nanosheets, and a preparation process thereof. The process utilizes magnesia, BN nanosheets, aluminum titanate fiber composite powder, metallic silicon powder, and a binder as raw materials. After mixing and rolling, the material is formed and then sintered at 1400-1500°C for 6-9 hours. The MgO slide plate prepared by the present invention exhibits excellent mechanical strength, thermal shock resistance, and corrosion resistance. When used for continuous casting of calcium-treated steel, the slide plate has a longer service life and can be used for more than four continuous casting cycles.

Description

Technical Field

[0001] The invention relates to an aluminum titanate fiber and BN nanosheet coupled reinforced and toughened MgO slide plate and a preparation process thereof, and belongs to the field of inorganic non-metallic materials, high-temperature ceramics and refractory materials. Background Art

[0002] The Al2O3-C and Al2O3-ZrO2-C slides commonly used in domestic continuous casting processes can meet the continuous casting needs of general steel grades. However, when used in the continuous casting of calcium-treated steel, they tend to react to form liquid phases such as 12CaO·7Al2O3, 3CaO·Al2O3, and CaO·SiO2, leading to abnormal corrosion of the slides. This not only shortens the service life of the material but can also cause steel breakout accidents, impacting continuous casting safety. MgO-based materials do not form liquid phases within the continuous casting temperature range and offer excellent resistance to corrosion from calcium-treated slag. However, MgO-based materials have low thermal conductivity and high thermal expansion coefficient, resulting in poor thermal shock resistance. While adding a large amount of carbon source can improve the thermal shock resistance of MgO-C and MgAl2O4-C slides, it can also lead to a decrease in strength and carbon contamination of the molten steel.

[0003] Patent CN108585797B discloses a self-lubricating magnesia slag-blocking slide brick with added boron nitride and its preparation method. Although the invention makes the slide have good corrosion resistance, thermal shock resistance and self-lubrication by adding boron nitride with good oxidation resistance, corrosion resistance and lubricity, it does not consider the dispersibility of boron nitride. h-BN) is a soft phase with good lubricity. Once agglomerated, it will negatively impact the thermal shock resistance and mechanical strength of the skateboard. Patent CN102898153B discloses a carbon-free skateboard and its preparation method. This invention uses aluminum titanate synthesized by electrofusion as the primary raw material. Leveraging aluminum titanate's high melting point, low thermal expansion coefficient, good thermal shock resistance, and excellent erosion resistance, it improves the skateboard's thermal shock resistance, erosion resistance, and erosion resistance. While this invention can prevent carbon accumulation during continuous casting, it fails to consider the inherent mechanical strength of aluminum titanate. Using aluminum titanate as the primary raw material to prepare the skateboard will result in numerous microcracks within the skateboard at room temperature. These numerous microcracks will also affect the porosity, negatively impacting the skateboard's mechanical strength. Patent CN106001532B discloses a corundum-zirconium corundum-aluminum titanate unfired and unimpregnated skateboard brick and its preparation method. The invention introduces aluminum titanate raw material to reduce the thermal expansion coefficient of the skateboard brick material. Although it improves the thermal shock stability, spalling resistance and erosion resistance of the skateboard brick, it does not take into account the easy decomposition and low strength of the directly introduced 0.212mm~1mm aluminum titanate particles in the medium temperature stage (750~1300℃), which has a negative impact on the performance of the skateboard. Patent CN110451938B discloses an aluminum titanate whisker reinforced aluminum-titanium refractory material. This invention improves the high-temperature strength and thermal shock stability of the aluminum-titanium refractory material by in-situ generating aluminum titanate whiskers in the aluminum-titanium refractory material. However, the in-situ generation of aluminum titanate whiskers is a complex reaction process. If this process is used for the preparation of skateboards, it is very difficult to simultaneously take into account the skateboard sintering performance and the quality of the generated whiskers: if the number of generated aluminum titanate whiskers is small, the crystal morphology is poor, the crystal particle size is uneven, and the aspect ratio is low, the reinforcement and toughening effect will not be achieved; and if the number of generated whiskers is too large, it will affect the interfacial bonding performance of the material, resulting in poor mechanical strength of the material.

[0004] In order to solve the problems of low strength and poor thermal shock resistance of existing MgO skateboards, the present invention utilizes BN nanosheets which not only have good thermal conductivity, thermal stability and chemical stability, but also have good mechanical strength; aluminum titanate fiber not only has excellent thermal shock resistance, but also will not decompose during the hot and cold cycle process of 750~1300℃; by uniformly introducing aluminum titanate fiber and BN nanosheets to replace the carbon source in the skateboard, the difficult problem of in-situ generation technology having to take into account the sintering performance and reinforcement phase quality of the skateboard is avoided, the temperature volume effect of the skateboard is effectively slowed down, the thermal conductivity is improved, the thermal stress difference caused by the temperature difference inside the skateboard is reduced, the thermal shock resistance of MgO is improved, and carbon increase pollution of molten steel is avoided, the use conditions and service life requirements of calcium-treated steel continuous casting production are met, and a MgO skateboard reinforced and toughened by coupling aluminum titanate fiber and BN nanosheets is developed. Summary of the Invention

[0005] The present invention provides a MgO skateboard reinforced and toughened by coupling aluminum titanate fibers and BN nanosheets. The raw materials in the formula are as follows by weight percentage:

[0006] (1) 29~43% of magnesia with a particle size of 3~1mm,

[0007] (2) 10~15% magnesia with a particle size of 1~0mm,

[0008] (3) 15~22% of magnesia with particle size ≤0.045mm,

[0009] (4) 18-25% magnesia with a particle size of 2-5 μm,

[0010] (5) 5~8% of aluminum titanate fibers with a diameter of 8~10μm,

[0011] (6) h -BN powder 2~4%,

[0012] (7) 2~4% of metallic silicon powder with particle size ≤0.045mm,

[0013] (8) Addition of binder 3~6%,

[0014] (9) Add grinding aid dispersant,

[0015] (10) Add water,

[0016] The binder is prepared by mixing phenolic resin and organosilicon modified resin in a ratio of 3:7;

[0017] The grinding aid dispersant is carboxymethyl cellulose salt;

[0018] The raw material (8) binder, raw material (9) grinding aid dispersant, and raw material (10) water are added separately and are not included in the total mass percentage of the raw materials;

[0019] The specific process steps are as follows:

[0020] (1) Preparation of BN nanosheets: weigh according to the proportion h -BN powder, and h Prepare a slurry of BN powder, 3mm diameter zirconium oxide grinding balls, and water in a mass ratio of 1:10:4. Add 1% carboxymethyl cellulose salt (based on the total mass of the slurry (excluding the zirconium oxide grinding balls)) to the ball mill and mill at a speed of 800-1000 rpm for 5-10 hours. Use a funnel with a filter to separate the milled slurry from the zirconium oxide grinding balls.

[0021] (2) Dispersion of BN nanosheets and aluminum titanate fibers: aluminum titanate fibers were weighed in proportion and added to the milled slurry. The slurry was ultrasonicated in an ultrasonic machine for 30 min to uniformly disperse the BN nanosheets and aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain a composite powder of BN nanosheets and aluminum titanate fibers.

[0022] (3) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm are weighed in proportion, and the above fine powders are placed together with BN nanosheets and aluminum titanate fiber composite powder into an air flow mixer. The premixing of the fine powders is completed within 3-10 minutes by the impact of the spiral rising compressed gas in the equipment;

[0023] (4) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed of 100-200 r / min for 3 minutes, add half of the binder, mix at a high speed of 400-500 r / min for 5 minutes, then add all the pre-mixed fine powder while mixing at a low speed within 2 minutes, and finally mix at a high speed for 10-15 minutes;

[0024] (5) Discharging and trapping: Screen out large agglomerates of false particles from the mixture and trap the mixture at 25°C and 50% relative humidity for 24 to 36 hours;

[0025] (6) Pressing and molding;

[0026] (7) Drying: After natural drying for 24 to 36 hours, dry at 220 to 260°C for 36 to 48 hours;

[0027] (8) Firing: Place the dried semi-finished product into an atmosphere furnace, introduce nitrogen gas at a pressure of 0.2 MPa, and heat treat at 1400-1500°C for 6-9 hours;

[0028] (9) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0029] The present invention adopts BN nanosheets instead of carbon source to prepare MgO slide plates, which not only solves the problem of poor thermal shock resistance of MgO materials, but also avoids the problem of carbon increase pollution in molten steel. h -BN has excellent properties such as low thermal expansion coefficient, high thermal conductivity, good thermal stability and chemical stability, but due to the weak bonding between the layers in its structure, it has the problem of low strength. hThe BN nanosheets obtained from the BN-BN composite not only possess these excellent properties but also overcome the drawback of low strength, possessing excellent mechanical strength. The introduction of BN nanosheets can reduce the thermal expansion coefficient of the skateboard, lowering the material's temperature-volume effect and the internal thermal stress, thereby improving the skateboard's thermal shock resistance. Furthermore, by increasing the skateboard's thermal conductivity, the temperature differential within the material is reduced, thereby reducing the resulting stress differential and improving the skateboard's thermal shock resistance. By increasing the skateboard's mechanical strength, the skateboard's ability to withstand thermal stress without damage is enhanced, thereby improving the skateboard's thermal shock resistance.

[0030] The present invention not only adds BN nanosheets as a reinforcing material, but also introduces aluminum titanate fibers to further toughen the skateboard. Aluminum titanate has the advantages of a high melting point, a low thermal expansion coefficient, good thermal shock resistance, excellent corrosion resistance, and is not easily wetted by metals, but it has the problem of being easily decomposed at 750-1300°C. Aluminum titanate fibers not only have excellent high-temperature stability, a smooth surface, a compact structure, and a low thermal expansion coefficient, but also do not decompose during temperature cycles of 750-1300°C. By adding aluminum titanate fibers, the thermal expansion coefficient of the skateboard can be reduced, the thermal shock resistance of the skateboard can be improved, and the toughening of the skateboard can be achieved by relying on the bridging effect of the fibers.

[0031] The present invention constructs a continuous three-dimensional network of aluminum titanate fibers and BN nanosheets in the skateboard matrix, achieving effective overlap of one-dimensional and two-dimensional materials, bearing part of the stress load, and utilizing the coupling effect of the two to achieve the toughening of the skateboard. Although both aluminum titanate fibers and BN nanosheets have excellent performance, the specific surface area of ​​both materials is relatively large, so the materials have poor dispersibility, and agglomeration easily affects the performance of the skateboard. Therefore, the present invention solves the dispersion problem of the two in the skateboard by adding a carboxymethyl cellulose salt dispersant and ultrasonic treatment, ensuring the performance of the skateboard.

[0032] Compared with the existing technology, the technical features of the aluminum titanate fiber and BN nanosheet coupled reinforced and toughened MgO skateboard of the present invention are:

[0033] (1) Using aluminum titanate fibers and BN nanosheets to replace carbon sources avoids carbon contamination in molten steel, improves the thermal shock resistance of MgO materials, and meets the use conditions and service life requirements of calcium-treated steel continuous casting production;

[0034] (2) By adding carboxymethyl cellulose salt, BN nanosheets and aluminum titanate fibers are evenly dispersed in the skateboard matrix, and the skateboard is strengthened and toughened through the coupling effect of the two. Implementation Method

[0035] Example 1

[0036] The following formula (weight and particle size content) is as follows:

[0037] (1) 29% magnesia with a particle size of 3~1mm,

[0038] (2) 15% magnesia with a particle size of 1~0mm,

[0039] (3) 22% magnesia with particle size ≤ 0.045 mm,

[0040] (4) 18% magnesia with a particle size of 2~5μm,

[0041] (5) 8% aluminum titanate fiber with a diameter of 8~10μm,

[0042] (6) h -BN powder 4%,

[0043] (7) 4% metallic silicon powder with particle size ≤ 0.045 mm,

[0044] (8) Addition, binder 6%, phenolic resin and silicone modified resin ratio of 3:7, not included in the total mass percentage of raw materials,

[0045] (9) Add 0.2% grinding aid dispersant, not included in the total mass percentage of raw materials.

[0046] (10) Add 16% water, not included in the total weight percentage of raw materials.

[0047] The specific process steps include the following parts:

[0048] (11) Preparation of BN nanosheets: h-BN powder was weighed in proportion and a slurry was prepared by mixing h-BN powder, 3 mm diameter zirconia grinding balls, and water in a mass ratio of 1:10:4. 1% of the total mass of the slurry (excluding the zirconia grinding balls) was added to a ball mill and milled at a speed of 1000 r / min for 10 h. The milled slurry was separated from the zirconia grinding balls using a funnel with a filter.

[0049] (12) Dispersion of BN nanosheets and aluminum titanate fibers: aluminum titanate fibers were weighed in proportion and added to the milled slurry. The slurry was ultrasonicated in an ultrasonic machine for 30 min to uniformly disperse the BN nanosheets and aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain a composite powder of BN nanosheets and aluminum titanate fibers.

[0050] (13) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm were weighed in proportion, and the above fine powders were placed together with BN nanosheets and aluminum titanate fiber composite powder into an air flow mixer. The premixing of fine powders was completed within 3 minutes by the impact of the spiral rising compressed gas in the equipment.

[0051] (14) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (100 r / min) for 3 minutes, add half of the binder, mix at a high speed (400 r / min) for 5 minutes, then add all the pre-mixed fine powder while mixing at a low speed within 2 minutes, and finally mix at a high speed for 15 minutes;

[0052] (15) Discharging and trapping: Screen out the large aggregates of false particles in the mixture and trap the mixture at 25°C and 50% relative humidity for 36 hours;

[0053] (16) Pressing and molding;

[0054] (17) Drying: After natural drying for 36 hours, dry at 220℃ for 48 hours;

[0055] (18) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1400 ° C for 9 h;

[0056] (19) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0057] Table 1 lists the raw material specifications, formula and properties of Example 1. After testing, the volume density of the product is 3.05 g / cm 3 The apparent porosity is 9.2%, the compressive strength at room temperature reaches 112MPa, the high temperature flexural strength (1400℃×0.5h) is 15MPa, and the number of water-cooling rapid cooling cycles at 1100℃ is greater than 6 times. It was tried in a 120-ton ladle casting calcium-treated steel in a steel plant with an average lifespan of 4 times. After use, the slide plate had micro-cracks, no through cracks, and no peeling, which met the use requirements of calcium-treated steel continuous casting production.

[0058] Example 2

[0059] The following formula (weight and particle size content) is as follows:

[0060] (1) 43% magnesia with a particle size of 3~1mm,

[0061] (2) 10% magnesia with a particle size of 1~0mm,

[0062] (3) 15% magnesia with particle size ≤ 0.045 mm,

[0063] (4) 23% magnesia with a particle size of 2~5μm,

[0064] (5) 5% aluminum titanate fiber with a diameter of 8~10μm,

[0065] (6) h-BN powder 2%,

[0066] (7) 2% of metallic silicon powder with particle size ≤ 0.045 mm,

[0067] (8) Addition, binder 3%, phenolic resin and silicone modified resin ratio of 3:7, not included in the total mass percentage of raw materials,

[0068] (9) Add 0.1% grinding aid dispersant, not included in the total mass percentage of raw materials

[0069] (10) Add 8% water, not included in the total weight percentage of raw materials

[0070] The specific process steps include the following parts:

[0071] (11) Preparation of BN nanosheets: h-BN powder was weighed in proportion and a slurry was prepared by mixing h-BN powder, 3 mm diameter zirconia grinding balls, and water in a mass ratio of 1:10:4. 1% of the total mass of the slurry (excluding the zirconia grinding balls) was added to a ball mill and milled at a speed of 800 r / min for 5 h. The milled slurry was separated from the zirconia grinding balls using a funnel with a filter.

[0072] (12) Dispersion of BN nanosheets and aluminum titanate fibers: aluminum titanate fibers were weighed in proportion and added to the milled slurry. The slurry was ultrasonicated in an ultrasonic machine for 30 min to uniformly disperse the BN nanosheets and aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain a composite powder of BN nanosheets and aluminum titanate fibers.

[0073] (13) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm were weighed in proportion, and the above fine powders were placed together with BN nanosheets and aluminum titanate fiber composite powder into an air flow mixer. The premixing of fine powders was completed within 10 minutes by the impact of the spiral rising compressed gas in the equipment.

[0074] (14) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (200 r / min) for 3 minutes, add half of the binder, mix at a high speed (500 r / min) for 5 minutes, then add all the pre-mixed fine powder while mixing at a low speed within 2 minutes, and finally mix at a high speed for 10 minutes;

[0075] (15) Discharging and trapping: Screen out the large aggregates of false particles in the mixture and trap the mixture at 25°C and 50% relative humidity for 24 hours;

[0076] (16) Pressing and molding;

[0077] (17) Drying: After natural drying for 24 hours, dry at 260°C for 36 hours;

[0078] (18) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1500 ° C for 6 h;

[0079] (19) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0080] Table 1 lists the raw material specifications, formula and properties of Example 2. After testing, the volume density of the product is 3.03 g / cm 3 The apparent porosity is 9.9%, the compressive strength at room temperature reaches 103MPa, the high temperature flexural strength (1400℃×0.5h) is 13MPa, and the number of water-cooling rapid cooling cycles at 1100℃ is greater than 6 times. It was tried in a 120-ton ladle casting calcium-treated steel in a steel plant with an average lifespan of 4 times. After use, the slide plate had micro-cracks, no through cracks, and no peeling, which met the use requirements of calcium-treated steel continuous casting production.

[0081] Example 3

[0082] The following formula (weight and particle size content) is as follows:

[0083] (1) 34% magnesia with a particle size of 3~1mm,

[0084] (2) 12% magnesia with a particle size of 1~0mm,

[0085] (3) 17% magnesia with particle size ≤ 0.045 mm,

[0086] (4) 25% magnesia with a particle size of 2~5μm,

[0087] (5) 6% aluminum titanate fiber with a diameter of 8~10μm,

[0088] (6) h-BN powder 3%,

[0089] (7) 3% of metallic silicon powder with particle size ≤ 0.045 mm,

[0090] (8) Addition, binder 4.5%, phenolic resin and silicone modified resin ratio of 3:7, not included in the total mass percentage of raw materials,

[0091] (9) Add 0.15% grinding aid dispersant, not included in the total mass percentage of raw materials,

[0092] (10) Add 12% water, not included in the total weight percentage of raw materials.

[0093] The specific process steps include the following parts:

[0094] (11) Preparation of BN nanosheets: h-BN powder was weighed in proportion and a slurry was prepared by mixing h-BN powder, 3 mm diameter zirconia grinding balls, and water in a mass ratio of 1:10:4. 1% of the total mass of the slurry (excluding the zirconia grinding balls) was added to a ball mill and milled at a speed of 900 r / min for 7.5 h. The milled slurry was separated from the zirconia grinding balls using a funnel with a filter.

[0095] (12) Dispersion of BN nanosheets and aluminum titanate fibers: aluminum titanate fibers were weighed in proportion and added to the milled slurry. The slurry was ultrasonicated in an ultrasonic machine for 30 min to uniformly disperse the BN nanosheets and aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain a composite powder of BN nanosheets and aluminum titanate fibers.

[0096] (13) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm were weighed in proportion, and the above fine powders were placed together with BN nanosheets and aluminum titanate fiber composite powder into an air flow mixer. The premixing of fine powders was completed within 7 minutes by the impact of the spiral rising compressed gas in the equipment.

[0097] (14) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (150 r / min) for 3 min, add half of the binder, mix at a high speed (450 r / min) for 5 min, then add all the pre-mixed fine powder while mixing at a low speed for 2 min, and finally mix at a high speed for 13 min.

[0098] (15) Discharging and trapping: Screen out the large aggregates of false particles in the mixture and trap the mixture at 25°C and 50% relative humidity for 30 hours;

[0099] (16) Pressing and molding;

[0100] (17) Drying: After natural drying for 30 hours, dry at 240°C for 42 hours;

[0101] (18) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1450 ° C for 7 h;

[0102] (19) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0103] Table 1 lists the raw material specifications, formula and properties of Example 3. After testing, the volume density of the product is 3.03 g / cm 3The apparent porosity is 9.3%, the compressive strength at room temperature reaches 107MPa, the high temperature flexural strength (1400℃×0.5h) is 14Mpa, and the number of water-cooling rapid cooling cycles at 1100℃ is greater than 6 times. It was tried in a 120-ton ladle casting calcium-treated steel in a steel plant with an average lifespan of 4 times. After use, the slide plate had micro-cracks, no through cracks, and no peeling, which met the use requirements of calcium-treated steel continuous casting production.

[0104] Comparative Example 1

[0105] The following formula (weight and particle size content) is as follows:

[0106] (1) 43% magnesia with a particle size of 3~1mm,

[0107] (2) 12% magnesia with a particle size of 1~0mm,

[0108] (3) Magnesia with a particle size of ≤0.045 mm 18%,

[0109] (4) 23% magnesia with a particle size of 2~5μm,

[0110] (5) h-BN powder 2%,

[0111] (6) 2% of metallic silicon powder with particle size ≤ 0.045 mm,

[0112] (7) Addition, binder 3%, phenolic resin and silicone modified resin ratio of 3:7, not included in the total mass percentage of raw materials,

[0113] (8) Add 0.1% grinding aid dispersant, not included in the total mass percentage of raw materials,

[0114] (9) Add 8% water, not included in the total weight percentage of raw materials.

[0115] The specific process steps include the following parts:

[0116] (10) Preparation of BN nanosheets: h-BN powder was weighed in proportion and slurry was prepared by mixing h-BN powder, zirconia grinding balls with a diameter of 3 mm, and water in a mass ratio of 1:10:4. 1% of the total mass of the slurry (excluding the zirconia grinding balls) was added to the ball mill and milled at a speed of 800 r / min for 5 h. The milled slurry was separated from the zirconia grinding balls using a funnel with a filter.

[0117] (11) Dispersion of BN nanosheets: The milled slurry was placed in an ultrasonic machine and ultrasonicated for 30 min to uniformly disperse the BN nanosheets. The slurry was then dried at a constant temperature of 110 °C to obtain BN nanosheet powder.

[0118] (12) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm were weighed in proportion, and the above fine powders were placed together with BN nanosheet powder in an air flow mixer. The premixing of fine powders was completed within 10 minutes by the impact of the spiral rising compressed gas in the equipment.

[0119] (13) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (200 r / min) for 3 minutes, add half of the binder, mix at a high speed (500 r / min) for 5 minutes, then add all the pre-mixed fine powder while mixing at a low speed within 2 minutes, and finally mix at a high speed for 10 minutes;

[0120] (14) Discharging and trapping: Screen out large agglomerates of false particles from the mixture and trap the mixture at 25°C and 50% relative humidity for 24 hours;

[0121] (15) Pressing and molding;

[0122] (16) Drying: After natural drying for 24 hours, dry at 260°C for 36 hours;

[0123] (17) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1500 ° C for 6 h;

[0124] (18) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0125] Table 1 lists the raw material specifications, formula and properties of Comparative Example 1. After testing, the volume density of the product is 2.98g / cm 3 The apparent porosity is 10.6%, the room-temperature compressive strength reaches 73 MPa, the high-temperature flexural strength (1400°C x 0.5h) is 9 MPa, and the number of water quenching cycles at 1100°C is 5. Compared with Example 2, the formula without the addition of 5% aluminum titanate fiber significantly reduces the mechanical strength of the material, and the thermal shock resistance and density after sintering also slightly decrease. If used in the continuous casting production of calcium-treated steel, the number of continuous sliding cycles will inevitably be reduced. Therefore, the addition of 5-8% aluminum titanate fiber is very necessary.

[0126] Comparative Example 2

[0127] The following formula (weight and particle size content) is as follows:

[0128] (1) 36% magnesia with a particle size of 3~1mm

[0129] (2) Magnesium sand with a particle size of 1~0mm 12%

[0130] (3) Magnesia sand with a particle size of ≤0.045 mm 18%

[0131] (4) 25% magnesia with a particle size of 2~5μm

[0132] (5) Aluminum titanate fiber with a diameter of 8~10μm 6%

[0133] (6) 3% metallic silicon powder with particle size ≤ 0.045 mm

[0134] (7) Addition: 4.5% binder, 3:7 ratio of phenolic resin and silicone modified resin, not included in the total mass percentage of raw materials

[0135] (8) Add 0.1% grinding aid dispersant, not included in the total mass percentage of raw materials,

[0136] (9) Add 12% water, not included in the total weight percentage of raw materials

[0137] The specific process steps include the following parts:

[0138] (1) Dispersion of aluminum titanate fibers: aluminum titanate fibers were weighed in proportion, added to water with carboxymethyl cellulose salt, and placed in an ultrasonic machine for 30 min to uniformly disperse the aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain aluminum titanate fibers.

[0139] (2) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, and metallic silicon powder with a particle size of ≤0.045 mm are weighed in proportion, and the above fine powders are placed together with aluminum titanate fiber in an air flow mixer. The premixing of fine powders is completed within 7 minutes by the impact of the spiral rising compressed gas in the equipment;

[0140] (3) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (150 r / min) for 3 min, add half of the binder, mix at a high speed (450 r / min) for 5 min, then add all the pre-mixed fine powder while mixing at a low speed for 2 min, and finally mix at a high speed for 13 min.

[0141] (4) Discharging and trapping: Screen out large agglomerates of false particles from the mixture and trap the mixture at 25°C and 50% relative humidity for 30 hours;

[0142] (5) Pressing and molding;

[0143] (6) Drying: After natural drying for 30 hours, dry at 240°C for 42 hours;

[0144] (7) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1450 ° C for 7 h;

[0145] (8) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0146] Table 1 lists the raw material specifications, formula and properties of Comparative Example 2. After testing, the volume density of the product is 3.00 g / cm 3 , the apparent porosity is 12.3%, the compressive strength at room temperature reaches 79MPa, the high temperature flexural strength (1400℃×0.5h) is 10MPa, and the number of water quenching cycles at 1100℃ is only 1. Compared with Example 3, the formula does not add 3% h -BN powder, BN nanosheets are not introduced into the skateboard, the thermal shock resistance of the material is significantly reduced, and the mechanical strength and density after sintering are also slightly reduced. If used in calcium treated steel continuous casting production, cracks will inevitably appear after one use. Therefore, 2~4% of the raw materials in the formula h -BN powder is indispensable.

[0147] Comparative Example 3

[0148] The following formula (weight and particle size content) is as follows:

[0149] (1) 34% magnesia with a particle size of 3~1mm

[0150] (2) Magnesium sand with a particle size of 1~0mm 12%

[0151] (3) Magnesia with a particle size of ≤0.045 mm 16%

[0152] (4) 25% magnesia with a particle size of 2~5μm

[0153] (5) Aluminum titanate fiber with a diameter of 8~10μm 6%

[0154] (6) N220 carbon black 4%

[0155] (7) 3% metallic silicon powder with particle size ≤ 0.045 mm

[0156] (8) Addition: 4.5% binder, 3:7 ratio of phenolic resin and silicone modified resin, not included in the total mass percentage of raw materials

[0157] (9) Add 0.15% grinding aid dispersant, not included in the total mass percentage of raw materials

[0158] (10) Add 12% water, not included in the total weight percentage of raw materials

[0159] The specific process steps include the following parts:

[0160] (11) Dispersion of aluminum titanate fibers: aluminum titanate fibers were weighed in proportion, and carboxymethyl cellulose salt was added to water. The mixture was ultrasonicated in an ultrasonic machine for 30 min to uniformly disperse the aluminum titanate fibers. The slurry was dried at a constant temperature of 110 °C to obtain aluminum titanate fibers.

[0161] (12) Premixing of fine powders: Magnesium sand with a particle size of ≤0.045 mm, magnesium sand with a particle size of 2-5 μm, N220 carbon black, and metallic silicon powder with a particle size of ≤0.045 mm were weighed in proportion, and the above fine powders were placed together with aluminum titanate fiber in an air flow mixer. The premixing of fine powders was completed within 7 minutes by the impact of the spiral rising compressed gas in the equipment.

[0162] (13) Mixing: Mix magnesia with a particle size of 3-1 mm and 1-0 mm at a low speed (150 r / min) for 3 min, add half of the binder, mix at a high speed (450 r / min) for 5 min, then add all the pre-mixed fine powder while mixing at a low speed for 2 min, and finally mix at a high speed for 13 min.

[0163] (14) Discharging and trapping: Screen out large agglomerates of false particles from the mixture and trap the mixture at 25°C and 50% relative humidity for 30 hours;

[0164] (15) Pressing and molding;

[0165] (16) Drying: After natural drying for 30 hours, dry at 240°C for 42 hours;

[0166] (17) Firing: The dried semi-finished product is placed in an atmosphere furnace, nitrogen gas at a pressure of 0.2 MPa is introduced, and heat treated at 1450 ° C for 7 h;

[0167] (18) Finishing treatment: The semi-finished products after firing and cooling are ground, hooped, non-working surface veneered, inspected and packaged.

[0168] Table 1 lists the raw material specifications, formula and properties of Comparative Example 3. After testing, the volume density of the product is 3.00 g / cm 3 , the apparent porosity is 10.0%, the compressive strength at room temperature reaches 92MPa, the high temperature flexural strength (1400℃×0.5h) is 12MPa, and the number of water quenching cycles at 1100℃ is greater than 6 times. Compared with Example 3, the formula does not add 3% h -BN powder, which uses carbon black, has good thermal shock resistance, but slightly poor mechanical strength and density. This proves that BN nanosheets can effectively replace carbon sources to improve the thermal shock resistance of MgO-based materials and effectively increase the mechanical strength of skateboards.

[0169] The raw material specifications, formulations and test performances of the skateboards prepared in the above examples and comparative examples are shown in Table 1 below:

[0170] Table 1 Skateboard raw material specifications, formula and test performance

[0171]

[0172] The bulk density of Example 1 is 3.03 g / cm 3 The apparent porosity is 7.8%, the compressive strength at room temperature reaches 90MPa, the high temperature flexural strength (1400℃×0.5h) is 12MPa, the number of water-cooling rapid cooling cycles at 1100℃ is more than 6 times, the oxidation area ratio in air (1500℃×24h) is 15.3%, and the average life of the 120-ton ladle special steel continuous casting in a special steel plant is 4 times. After use, the slide plate has micro-cracks, no through cracks, and no peeling.

Claims

1. A MgO skateboard reinforced and toughened by coupling aluminum titanate fibers and BN nanosheets, characterized in that: The formula is as follows by weight percentage: (1) 29~43% of magnesia with a particle size of 3~1mm, (2) 10% to 15% of magnesia with a particle size of 1 to 0 mm, (3) 15~22% of magnesia with particle size ≤0.045mm, (4) 18-25% magnesia with a particle size of 2-5 μm, (5) 5~8% of aluminum titanate fibers with a diameter of 8~10μm, (6) h-BN powder 2~4%, (7) 2~4% of metallic silicon powder with particle size ≤0.045mm, (8) Addition of binder 3~6%, (9) Add carboxymethyl cellulose salt as a grinding aid and dispersant, (10) Add water.

2. The aluminum titanate fiber and BN nanosheet coupled reinforced and toughened MgO slide plate according to claim 1, characterized in that: The binder is prepared by mixing phenolic resin and organosilicon modified resin in a ratio of 3:7; the binder, grinding aid dispersant and water are added separately and are not included in the total weight percentage of the raw materials.

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