Carbon-carbon material containing device applied to preparation process of sintered magnetic material

Abstract

The invention discloses a carbon-carbon material containing device applied to the preparation process of sintered magnetic materials, and relates to the technical field of sintered magnetic material preparation. Comprising a containing device box body, a layering plate and a containing device box cover, the layering plate is placed in the containing device box body through a layering support, the containing device box body is provided with an airflow circulation speed increasing mechanism, and gas generated in the sintering process passes through the airflow circulation speed increasing mechanism until the interior of the box body reaches the optimal vacuum speed; a drainage groove is formed in the middle of the containing device box cover, and gas generated in the sintering process in the box is rapidly concentrated on the top of the containing device box cover through the drainage groove and guided out. The novel to-be-sintered blank containing device for high-temperature vacuum sintering is prepared from the carbon-carbon composite material of the carbon fiber reinforced carbon matrix, so that the containing device achieves shorter temperature rise time, lighter mass and better high-temperature resistance.

Description

Technical Field

[0001] The invention relates to the technical field of sintered magnetic material preparation, in particular to a carbon-carbon material containing device used in the process of sintered magnetic material preparation. Background Art

[0002] my country is a major producer of magnetic materials, with NdFeB production accounting for 90% of the world's total. The development trend of the NdFeB industry has also been extremely strong in recent years, with an annual growth rate of 6-7%. And with the widespread application and development of magnetic materials, their application in emerging industries such as new energy vehicles, wind power generation, and electronic communications has become increasingly widespread, which has greatly promoted the growth of demand for magnetic materials. In terms of magnetic materials in 2021, the output of sintered NdFeB blanks was 207,100 tons, a year-on-year increase of 16%. In the first half of 2022, the output of sintered NdFeB blanks was 116,000 tons, a year-on-year increase of 15%. In 2023, the output of sintered NdFeB blanks reached 247,000 tons, an increase of 11.2% over 2022. It is expected that the output of sintered magnetic material blanks in my country will exceed 500,000 tons in 2027.

[0003] Sintering is the key technology for manufacturing sintered NdFeB magnets. The traditional sintering process is to put the blanks to be sintered into graphite boxes, and then put them into a high-temperature vacuum sintering furnace for sintering after stacking them layer by layer. The main purpose of using graphite boxes to hold sintered blanks is to protect the blanks to be sintered during the sintering process. At the same time, because graphite materials have the characteristics of high temperature resistance and extremely small deformation at high temperatures, graphite boxes can be used repeatedly. However, with the increasingly fierce market competition, how to improve product performance, save energy and reduce emissions, reduce costs, and increase production capacity has become an urgent problem to be solved in the development of the magnetic material industry. During the sintering process, how to improve the vacuum environment of the blank and effectively prevent the blank from oxidizing with oxygen; how to improve the removal of adsorbed gas (water vapor) on the surface of powder particles, and effectively discharge the evaporation and volatilization of organic matter; how to make the blank quickly reach a high temperature environment in the sintering furnace to achieve energy saving and efficiency improvement; how to effectively increase the blank production capacity; how to reduce the damage rate of auxiliary materials during sintering, reduce losses and reduce costs have become urgent problems to be solved.

[0004] Chinese patent CN102568806A discloses a method for preparing rare earth permanent magnets by infiltration method and a graphite box is used in the method, and the performance of the graphite box is used to hold the blank to be sintered.

[0005] Chinese patent CN112254534A discloses a graphite box for a high temperature vacuum sintering furnace. The equipment disclosed has nothing to do with the sintered NdFeB preparation process, and the materials used have nothing to do with the materials of the present invention.

[0006] There are no published patents with content similar to this application. Summary of the invention

[0007] The object of the present invention is to provide a carbon-carbon material holding device used in the process of preparing sintered magnetic materials, so as to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a carbon-carbon material holding device used in the preparation process of sintered magnetic materials, comprising: A containing device box body, a layered plate and a containing device box cover, wherein the layered plate is placed in the containing device box body through a layered bracket; The containing device box body is provided with an airflow circulation accelerating mechanism, and the gas generated during the sintering process passes through the airflow circulation accelerating mechanism until the optimal vacuum speed is reached in the box body; a drainage groove is opened in the middle of the containing device box cover, and the gas generated in the box during the sintering process is quickly concentrated on the top of the containing device box cover and discharged through the drainage groove.

[0009] Further regarding this solution, the containing device box body is in a rectangular shape, and the airflow circulation speed increasing mechanism includes airflow acceleration fillets opened at the four corners of the inner wall of the containing device box body, and air guide holes penetrating to the inner wall of the containing device box body are also opened on both sides of the containing device box body. The two air guide holes are located at opposite corners of the containing device box body and are both adjacent to one of the airflow acceleration fillets.

[0010] Further to this solution, the layered bracket is in the form of a column that matches the shape of the airflow acceleration fillet, and the length of the airflow acceleration fillet is not greater than half the height of the box body of the containing device.

[0011] Further to this solution, the layering plate is matched with the inner wall of the containing device box, and airflow guiding grooves are provided around the layering plate near the airflow acceleration corners.

[0012] Further to this solution, the top and bottom of the airflow guide groove are designed with a slope, and the slope ranges from 15° to 48.3°.

[0013] Further regarding this solution, the containing device box body, layered plate, layered bracket and containing device box cover are all prepared by liquid impregnation process, chemical vapor infiltration process and isothermal method based on a fiber preform including a filament fiber and a staple fiber matrix. Carbon-carbon material.

[0014] Further regarding this solution, the density of the containing device box body, layered plate, layered bracket and containing device box cover is 1.5-17.g / cm, the thermal expansion coefficient ranges from -0.4-1.8×10-6 / K, the thermal conductivity is (1650<℃) 0.38.-0.45cal / cm*s*℃, the specific heat (<1930℃): 0.3Kcal / Kg*℃, and the bending strength is 25-30MPa.

[0015] Further to this solution, the four outer corners of the containing device box body and the containing device box cover are also configured to be curved to reduce bumps during transportation.

[0016] Further to this solution, the drainage groove is opened at the center line of the side of the containing device box cover facing the containing device box body, and at the center line between the two ends of the containing device box cover. The drainage groove extends from the middle of the containing device box cover to the two ends until it passes through the containing device box cover, and the drainage groove connects the inside of the containing device box body with the external air.

[0017] The four corners of the containing device box body are provided with through holes adapted to the pillars, one side of the pillar is provided with a hole, a block slides in the hole, a spring is provided between the block and the inner wall of one end of the hole, a notch is provided on the surface of the pillar, a limiting rod is fixed on the side of the block facing the hole, a paddle is provided at the end of the limiting rod and is located at the notch, the spring is sleeved on the surface of the limiting rod, and a raised edge is fixed on the bottom of the containing device box body.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The carbon-carbon material holding device used in the preparation process of sintered magnetic materials uses a carbon-carbon composite material with a carbon fiber reinforced carbon matrix to prepare a new type of sintered blank holding device for high-temperature vacuum sintering, so that the holding device can achieve a shorter heating time, lighter weight, better high-temperature resistance, and longer service life. The air circulation speed increase design of the four-corner arc and the four-side specific openings accelerates the exhaust of air in the device during the vacuum process, and the device cover gas guide groove is designed using the unique gas density characteristics generated by sintering NdFeB during the sintering process to accelerate the discharge of gas impurities generated during the sintering process from the device. The arrangement of the airflow guide groove 8 on the layered plate 3 and the drainage slope of the airflow guide groove 8 accelerate the guidance of the gas flow to the corresponding air guide hole.

[0019] At the same time, the carbon-carbon composite material with carbon fiber reinforced carbon matrix has a mass reduction of more than 15% compared with the traditional graphite container material of the same volume; the thermal expansion coefficient of the new material is much lower than that of the graphite material, and it is less likely to crack at high temperatures; the thermal conductivity of the new material is much higher than that of the graphite material, which significantly shortens the heating time; the specific heat of the new material is better than that of the graphite material, which can make the sintered blank have a better isothermal environment and improve the consistency of the blank; the bending strength of the new material is much better than that of the graphite material, and it is less likely to deform during use, and the wall thickness of the container can be significantly reduced compared with the traditional graphite material; the ash content of the new material is half that of the graphite material, and the service life is longer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the gas flow structure of the box body of the containing device of the present invention; Figure 3 It is a schematic diagram of the gas flow structure after the containing device box body and the containing device box cover of the present invention are closed; Figure 4 It is a schematic diagram of the structure after the container box and the layered plate of the present invention are installed; Figure 5 A schematic diagram of the airflow guide groove structure of the present invention; Figure 6 It is a schematic diagram of the structure of the box body of the containing device of the present invention; Figure 7 It is a schematic diagram of the airflow guide groove structure of the present invention.

[0021] In the figure: 1. container box; 101. raised edge; 102. perforation; 2. container box cover; 3. layered plate; 4. layered bracket; 401. support; 402. connection frame; 403. block; 404. spring; 405. limit rod; 406. notch; 5. air guide hole; 6. drainage groove; 7. airflow acceleration fillet; 8. airflow guide groove. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, the present invention provides a technical solution: a carbon-carbon material holding device used in the preparation process of sintered magnetic materials, comprising: A containing device box body 1, a layered plate 3 and a containing device box cover 2, wherein the layered plate 3 is placed in the containing device box body 1 through a layered bracket 4; The containing device box body 1 is provided with an airflow circulation accelerating mechanism, and the gas generated during the sintering process passes through the airflow circulation accelerating mechanism until the optimal vacuum speed is reached in the box body; a drainage groove 6 is opened in the middle of the containing device box cover 2, and the drainage groove 6 allows the gas generated in the box during the sintering process to be quickly concentrated on the top of the containing device box cover 2 and discharged.

[0024] The holding device is made of a carbon-carbon composite material of a carbon fiber reinforced carbon matrix. The blank to be sintered is placed in the holding device box body 1 according to the blank sintering requirements, the holding device box cover 2 is closed, and the holding device containing the blank to be sintered is placed in a high-temperature sintering vacuum furnace at one time, and the sintering furnace is started to enter the vacuum sintering stage.

[0025] like Figure 1 and Figure 2As shown, in order to ensure the smooth implementation of this embodiment, it is necessary to understand that the containing device box body 1 is a rectangular box body, and the airflow circulation speed increasing mechanism includes airflow acceleration fillets 7 opened at the four corners of the inner wall of the containing device box body 1. Air guide holes 5 that penetrate the inner wall of the containing device box body 1 are also opened on both sides of the containing device box body 1. The two air guide holes 5 are located at the diagonal positions of the containing device box body 1 and are close to one of the airflow acceleration fillets 7. During the vacuum pumping process of sintering, the air in the box will flow along the arrow to accelerate the airflow in the box. At the same time, when the airflow approaches the four corners of the box body and flows along the arc, it will accelerate to flow to the air guide holes and discharge from the box body. The relationship between the arc of the four corners of the internal airflow acceleration fillet 7 and the position and aperture of the air guide hole 5 conforms to the design relationship of the airflow circulation speed increasing, and the design principle conforms to the Bernoulli equation, p is the pressure at a point in the fluid, v is the flow velocity of the fluid at that point, p is the gas density, g is the gravitational acceleration, h is the height of the point, and the following formula: .

[0026] That is, the opening position corresponds to the gas characteristics generated during the sintering process, and the box volume makes the vacuum process achieve the best vacuum speed. At the same time, the curvature of the four internal corners produces gas flow acceleration corresponding to the opening position relationship.

[0027] like Figure 1 and Figure 3 As shown, the support 401 of the layered support 4 is a columnar body that is compatible with the shape of the airflow acceleration fillet 7, and the length of the support 401 is not greater than half of the height of the containing device box body 1. If the height of the blank is lower than half of the internal height of the box body, the blank to be sintered can be placed in the containing device box body 1 according to the blank sintering requirements. After the sintered blank fills the bottom of the box, the layered support 4 is placed at the four corners of the box body, the opening of the layered plate 3 is aligned with the air guide hole 5 of the containing device box body 1, and the second layer of the blank to be sintered is placed on the layered plate 3. After it is full, the containing device box cover 2 is closed. , put the holding device containing the blanks to be sintered into the high-temperature sintering vacuum furnace at one time, start the sintering furnace and enter the vacuum sintering stage. It should be noted that the four corners of the holding device box body 1 are provided with through holes 102 that are compatible with the pillars 401. The blanks are placed in the inner chamber of the holding device box body 1, and the pillars of the layered bracket 4 pass through the through holes 102 and fall to the bottom, which does not affect the placement space in the box body. A raised edge 101 is fixed to the bottom of the holding device box body 1. After the pillars 401 of the layered bracket 4 pass through the through holes 102, they do not touch the bottom and are supported by the raised edge 101.

[0028] like Figure 3 and Figure 4As shown, a hole is provided on one side of the pillar 401, and a block 403 slides in the hole, a spring 404 is provided between the block 403 and the inner wall of one end of the hole, a notch 406 is provided on the surface of the pillar 401, and a limiting rod 405 is fixed on the side of the block 403 facing the hole, a paddle is provided at the end of the limiting rod 405 and is located at the notch 406, the block 403 can be retracted in the hole under the effect of the spring 404, and the top of the block 403 is in an inclined shape, so that the layered bracket 4 can be pulled into the box, and the block 403 will support the layered bracket 4, so as to realize the placement of the second layer of the blank.

[0029] like Figure 5 and Figure 6 As shown, the layering plate 3 is matched with the inner wall of the box body 1 of the containing device, and the layering plate 3 is provided with air flow guiding grooves 8 near the air flow acceleration fillet 7 around the layering plate 3. During the high-temperature remelting process of sintering, the gas adsorbed on the surface of the powder particles, the evaporation and volatile gas of organic matter, and the gas generated during the liquid phase sintering of the grains at about 1080°C rise to the drainage groove 6 on the top of the box due to thermodynamics and are discharged. During the high-temperature remelting process of sintering, the gas generated by the upper and lower layers of the blank during the sintering process will be discharged along the layering plate 3. The airflow guiding groove 8 on the plate 3 guides to the air guide hole 5 and is discharged from the air guide hole 5. When sintering is completed, the containing device for containing the sintered blank is taken out, the box cover is opened, the blank is taken out, and the empty containing box body and box cover are stored for use in the next sintering of the blank. When sintering is completed, the containing device for containing the sintered blank is taken out, the box cover is opened, the blank is taken out in turn, and the empty containing box body 1, box cover 2, layered plate 3 and layered bracket 4 are stored for use in the next sintering of the blank.

[0030] like Figure 6 and Figure 7 As shown, the top and bottom of the airflow guiding groove 8 are designed with a slope, and the slope range is 15°-48.3°. The drainage slope of the airflow guiding groove 8 is designed according to the aerodynamic local resistance formula: In the formula: Z—local resistance, Pa; ξ—local resistance coefficient; υ—air flow rate, m / s; ρ—air density, kg / m3.

[0031] ; When the slope of the diversion hole is 15°-48.3°, the corresponding resistance coefficient is the smallest, which accelerates the flow of gas in the box body. The arrangement of the airflow guiding grooves 8 on the layered plate 3 and the specific drainage slope of the airflow guiding grooves 8 accelerate the flow of gas to the corresponding air guide holes 5. When the fired blanks are lower than half of the internal height of the containing box, the layered plate 3 can be used to stack two layers of blanks, the layered brackets 4 can be placed at the four corners of the containing box, and the layered plate 3 can be placed on the layered bracket 4.

[0032] like Figure 1As shown, the containing device box body 1, the layered plate 3, the layered bracket 4 and the containing device box cover 2 are all prepared by a carbon-carbon material prepared by a liquid impregnation process, a chemical vapor infiltration process and an isothermal method based on a fiber preform including a filament fiber and a staple fiber matrix.

[0033] To ensure the smooth implementation of this embodiment, it is necessary to understand that the density of the containing device box body 1, the layered plate 3, the layered bracket 4 and the containing device box cover 2 is 1.5-1.7g / cm3, the thermal expansion coefficient ranges from -0.4-1.8×10-6 / K, the thermal conductivity is <1650℃0.38-0.45cal / cm*s*℃, the specific heat is <1930℃: 0.3Kcal / Kg*℃, and the bending strength is 25-30MPa.

[0034] In order to ensure the smooth implementation of this embodiment, it should be understood that the four outer corners of the containing device box body 1 and the containing device box cover 2 are also configured to be curved to reduce bumps during transportation.

[0035] like Figure 1 and Figure 5 As shown, the drainage groove 6 is opened at the center line of the side of the containing device box cover 2 facing the containing device box body 1, and at the center line between the two ends of the containing device box cover 2. The drainage groove 6 extends from the middle of the containing device box cover 2 to the two ends until it passes through the containing device box cover 2. The drainage groove 6 connects the inside of the containing device box body 1 with the external air.

[0036] After the sintering process is completed, the relevant data are counted:

[0037] Taking the sintered magnetic material products currently used in new energy vehicle motors, the experimental samples respectively used the same batch of sintered NdFeB blanks with the commercial brand N52 to be sintered, and the traditional graphite box and the holding device of the present invention were used as blank holding utensils for sintering process. It can be seen from the above table that the magnetic performance of the carbon-carbon material holding device is higher than the sintering performance of the traditional graphite box (BR represents the residual magnetism, which can reflect the magnetic field strength of the permanent magnetic material in the absence of an external magnetic field, Hcb represents the magnetic coercive force, which can measure the ability of the permanent magnetic material to resist demagnetization by the external magnetic field, Hcj represents the intrinsic coercive force, which can reflect the ability of the permanent magnetic material to maintain magnetism in harsh environments such as high temperature, and (BH)m represents the maximum magnetic energy product, which represents the maximum magnetic energy stored per unit volume of the permanent magnetic material).

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is limited by the attached embodiments and their equivalents.

Claims

1. A carbon-carbon material holding device used in the preparation process of sintered magnetic materials, characterized in that: include: A containing device box body (1), a layered plate (3) and a containing device box cover (2), wherein the layered plate (3) is placed in the containing device box body (1) via a layered bracket (4); The containing device box body (1) is provided with an airflow circulation speed-increasing mechanism, and the gas generated during the sintering process passes through the airflow circulation speed-increasing mechanism until the optimal vacuum speed is reached in the box body; a drainage groove (6) is provided in the middle of the containing device box cover (2), and the gas generated in the box during the sintering process is quickly concentrated on the top of the containing device box cover 2 and discharged through the drainage groove (6).

2. The carbon-carbon material holding device used in the preparation process of sintered magnetic materials according to claim 1, characterized in that: The containing device box body (1) is in the form of a rectangular box body. The airflow circulation speed increasing mechanism comprises airflow acceleration fillets (7) formed at the four corners of the inner wall of the containing device box body (1). Air guide holes (5) penetrating the inner wall of the containing device box body (1) are also formed on both sides of the containing device box body (1). The two air guide holes (5) are located at the diagonal positions of the containing device box body (1) and are both adjacent to one of the airflow acceleration fillets (7).

3. The carbon-carbon material holding device used in the preparation process of sintered magnetic materials according to claim 1, characterized in that: The layered support (4) comprises a support (401), the support (401) being a columnar body adapted to the shape of the airflow acceleration fillet (7), and the length of the airflow acceleration fillet (7) is no greater than half the height of the containing device box body (1), the support (401) being connected to each other via a connecting frame (402), and the connecting frame (402) being adapted to the inner wall of the containing device box body (1).

4. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 1, characterized in that: The layered plate (3) is adapted to the inner wall of the containing device box body (1), and airflow guiding grooves (8) are provided around the layered plate (3) near the airflow acceleration fillet (7).

5. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 4, characterized in that: The top and bottom of the airflow guide groove (8) are designed with a slope, and the slope ranges from 15° to 48.3°.

6. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 1, characterized in that: The containing device box body (1), the layered plate (3), the layered bracket (4) and the containing device box cover (2) are all prepared by using a carbon-carbon material prepared by a liquid phase impregnation process, a chemical vapor infiltration process and an isothermal method based on a fiber preform including a filament fiber and a staple fiber matrix.

7. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 1, characterized in that: The density of the containing device box body (1), the layered plate (3), the layered bracket (4) and the containing device box cover (2) is 1.5-1.7 g / cm3, the thermal expansion coefficient ranges from -0.4 to 1.8×10-6 / K, the thermal conductivity is (<1650°C) 0.38-0.45 cal / cm*s*°C, the specific heat (<1930°C) is 0.3 Kcal / Kg*°C, and the bending strength is 25-30 MPa.

8. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 1, characterized in that: The four outer corners of the containing device box body (1) and the containing device box cover (2) are also arranged to be curved to reduce bumps during transportation.

9. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 1, characterized in that: The drainage groove (6) is formed at the midline of the side of the containing device box cover (2) facing the containing device box body (1), and at the midline between the midline and the two ends of the containing device box cover (2). The drainage groove (6) extends from the middle of the containing device box cover (2) to the two ends until it penetrates the containing device box cover (2). The drainage groove (6) connects the inside of the containing device box body (1) with the outside air.

10. The carbon-carbon material holding device used in the process of preparing sintered magnetic materials according to claim 3, characterized in that: The four corners of the containing device box body (1) are provided with through holes (102) adapted to the pillar (401); a hole is provided on one side of the pillar (401); a block (403) slides in the hole; a spring (404) is provided between the block (403) and the inner wall of one end of the hole; a notch (406) is provided on the surface of the pillar (401); a limiting rod (405) is fixed on the side of the block (403) facing the inside of the hole; a paddle is provided at the end of the limiting rod (405) and is located at the notch (406); the spring (404) is sleeved on the surface of the limiting rod (405); and a raised peripheral edge (101) is fixed on the bottom of the containing device box body (1).

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