NdFeB melt-spinning cooling device based on double-sided forced cooling device and refining method

Abstract

The invention provides a neodymium iron boron melt-spinning cooling device based on a double-sided forced cooling device and a refining method. The neodymium iron boron melt-spinning cooling device comprises a copper wheel cooling unit, a liquid argon forced cooling unit, a drum-type cooler and a crusher. Carrying out melt-spinning forming on the neodymium-iron-boron melt through a high-speed rotating copper wheel, and realizing primary cooling through a sticking roller surface; a liquid argon nozzle array is arranged above the free surface of the melt-spinning sheet, liquid argon is sprayed at an angle of 30-60 degrees, and secondary forced cooling is formed; and then entering a drum-type cooler for heat conduction cooling, and finally treating by a crusher. According to the device, a double-face cooling system of the roller pasting face and the free face is constructed, the cooling efficiency is effectively improved, the grain size is refined, the heavy rare earth adding amount is reduced, and the device is suitable for preparing the high-performance neodymium-iron-boron magnet.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet material preparation, in particular to a neodymium iron boron strip cooling device based on a double-sided strong cooling device and a thinning method. Background Art

[0002] Due to its excellent magnetic properties, NdFeB permanent magnets are widely used in high-end fields such as new energy vehicles, wind power generation, high-performance motors, intelligent manufacturing, and electronic communications. Among them, high coercivity, high remanence, and excellent magnetic energy product are the keys to improving the application performance of NdFeB magnets. However, in the traditional NdFeB material preparation process, in order to improve the coercivity, it is usually necessary to add a certain proportion of heavy rare earth elements (such as dysprosium and terbium) to the alloy to construct a coated hard magnetic phase structure and enhance the magnetic anisotropy between grains. Although this method is effective, it significantly increases material costs and is limited by the tight supply of heavy rare earth resources, which has become a bottleneck restricting the development of the industry.

[0003] In the production process, the NdFeB melt is rapidly solidified into thin sheets through the belt spinning process, which is a key step in determining the final microstructure and performance of the magnet. Existing belt spinning equipment usually uses a single-sided copper wheel roller cooling method for cooling. The free surface of the belt spinning sheet lacks a strong cooling mechanism, resulting in a slow temperature drop. Figure 4 As shown in Figure 1, prolonged exposure to high temperatures (700-900°C) can lead to grain coarsening and uneven microstructure, which in turn affects magnetic properties. To address this, some technical solutions have attempted to increase the copper wheel speed or optimize the alloy composition, but with limited success, achieving efficient and cost-effective grain refinement has been difficult.

[0004] In addition, the current common cooling methods mostly use air, water cooling or single-stage gas cooling, which have low heat conduction efficiency and cannot meet the process requirements of quickly cooling from a red-hot state to a stable range. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a NdFeB strip cooling device and refinement method based on a double-sided strong cooling device, which can effectively control the strong cooling of the free surface of the strip, and cooperate with the roller surface cooling to improve the cooling efficiency, refine the grains, and reduce the dependence on heavy rare earths, thereby meeting the urgent needs of the high-performance NdFeB magnet industry for material organization controllability and performance consistency.

[0006] The present invention is achieved through the following technical solutions: a neodymium iron boron belt cooling device based on a double-sided strong cooling device, comprising:

[0007] A copper wheel cooling unit for receiving NdFeB melt, which spins the NdFeB melt into a strip with a thickness of 0.2-0.4mm and a width of about 400mm while rotating, and achieves primary cooling through the roller surface;

[0008] A liquid argon forced cooling unit is provided above the free surface of the stripping piece in the discharge direction of the copper wheel. The liquid argon forced cooling unit comprises a plurality of liquid argon nozzle arrays distributed along the width direction of the stripping piece. The nozzle spray angle is 30° to 60° and is set at an acute angle to the conveying direction of the stripping piece. The spray distance is 20-50 mm and the spray pressure is 0.1-0.4 MPa.

[0009] The drum cooler is installed after the liquid argon forced cooling unit and is used to further cool the stripping blades through heat conduction;

[0010] The crusher is installed after the drum cooler and is used to crush the cooled sling pieces into granular materials;

[0011] The copper wheel roller surface cooling and the free surface liquid argon jet strong cooling work together to form a double-sided cooling system for the roller surface and the free surface.

[0012] As a preferred technical solution, the liquid argon nozzle array has a spray coverage width of not less than 400 mm, and the nozzles can be replaced with atomizing nozzles or air-cooling nozzles to adapt to spray cooling or air-cooling cooling modes.

[0013] As a preferred technical solution, a closed channel structure is provided between the liquid argon strong cooling unit and the crusher. The channel length is 1.5 meters, which is used to form a closed cooling zone, enhance the liquid argon cooling effect and realize gas-solid co-flow heat exchange.

[0014] As a preferred technical solution, the drum cooler is a double-drum structure, the two drums are maintained at a low temperature through an external cooling circulation system, and are in direct contact with the surface of the belt-swinging plate to achieve heat conduction cooling.

[0015] As a preferred technical solution, the crusher has a belt-swinging blade guide structure and an argon gas outlet. The argon gas and the belt-swinging blade enter the crushing cavity together and are then led out from the outlet to remove heat and reduce dust pollution.

[0016] The present invention provides a method for refining grains of NdFeB strip-spinning sheets based on a cooling device, comprising the following steps:

[0017] a) The molten NdFeB alloy is injected into the high-speed rotating copper wheel, and the roller surface is cooled to form a preliminary formed strip;

[0018] By combining roller surface cooling with free surface liquid argon jet cooling, a double-sided cooling system is constructed to quickly reduce the temperature of the stripping sheet.

[0019] b) When the strip leaves the copper wheel and is in a red-hot state, liquid argon is sprayed from the free surface by an array of liquid argon nozzles at an angle of 30° to 60° to achieve a strong cooling treatment of the red-hot surface, reducing the strip temperature from over 800°C to 500°C or below within 2 seconds;

[0020] c) The strip is further introduced into a drum cooler and further cooled to no higher than 350°C by heat conduction and maintained for 30 minutes to stabilize the microstructure;

[0021] d) The cooled strips are introduced into a crusher for pulverization, and the alloy particles with refined grains are collected.

[0022] As a preferred technical solution, the liquid argon nozzle injection pressure is 0.1-0.4 MPa, and the liquid argon flow rate is 0.2-1.5m 3 / h, the purity of argon is not less than 99.999%.

[0023] As a preferred technical solution, the distance between the liquid argon nozzle and the strip-swinging plate is 20-50 mm, and the nozzle spray coverage width is 400 mm, so as to achieve uniform cooling of the free surface of the strip-swinging plate as a whole.

[0024] As a preferred technical solution, the crusher is provided with a guide channel and an argon gas discharge device. The stripper and the argon gas move together in the guide channel. The argon gas takes away heat and inhibits metal oxidation during the crushing process.

[0025] As a preferred technical solution, by adjusting the liquid argon cooling parameters and the roller cooling time, the grain size of the strip-spinning sheet can be adjusted to 2-5 μm, and the coercive force can be increased by no less than 15%.

[0026] The beneficial effects of the present invention are as follows: the present invention provides a NdFeB strip cooling device based on a double-sided strong cooling device, which, on the basis of traditional roller surface cooling, introduces a liquid argon jet strong cooling unit on the free surface of the strip, thereby constructing a double-sided cooling system in which the roller surface and the free surface work together. This structure significantly improves the overall cooling rate of the strip in the red-hot range, and can quickly reduce the temperature of the strip from 800 degrees Celsius to 500 degrees Celsius or lower within two seconds after the strip is separated from the copper wheel, thereby effectively inhibiting grain growth and refining the grain size to two to five microns, which is significantly better than the seven to fifteen microns in the traditional process, and is helpful to improve the coercive force of the magnet. The coercive force of the cooling system magnet can be increased by more than 15%. At the same time, due to the excellent grain refinement effect, the dependence on heavy rare earth elements such as dysprosium and terbium can be reduced, and the addition amount can be reduced by 20 to 30%, thereby effectively reducing material costs and alleviating resource shortages. In addition, the liquid argon nozzle array supports the replacement of nozzles and can flexibly realize liquid argon direct spray cooling or argon air cooling and other cooling modes to adapt to different equipment conditions and user needs, thereby improving the system's versatility and engineering adaptability. During the cooling process, the strips co-flow with the argon gas through the closed cooling channel and enter the crusher, which can significantly remove the waste heat and inhibit metal oxidation and dust diffusion, thereby improving the safety and environmental protection level of the overall system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 is a block diagram of the device system of the present invention;

[0029] Figure 2 This is a structural diagram of the liquid argon forced cooling unit of the present invention;

[0030] Figure 3 It is a temperature curve diagram of the present invention;

[0031] Figure 4 It is a temperature curve diagram of the prior art; DETAILED DESCRIPTION

[0032] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0033] Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0034] like Figure 1-Figure 3 As shown, in a specific embodiment of the NdFeB belt-swing cooling device based on a double-sided strong cooling device of the present invention, the molten NdFeB alloy melt is first introduced into a copper wheel cooling unit provided at the front end of the device. When the copper wheel rotates at high speed, its outer roller surface is in contact with the NdFeB melt, and the surface temperature of the copper wheel is continuously maintained at a low level by utilizing the water-cooling channel or other cooling medium circulation system inside the copper wheel, thereby achieving the first-time cooling of the spun NdFeB melt to form a preliminarily formed belt-swinging sheet.

[0035] Under the centrifugal force of the copper wheel, the molten metal is ejected in a very short time and adheres to the surface of the copper wheel, stretching into a strip. The thickness of the strip is controlled between 0.2 mm and 0.4 mm, and the width can reach about 400 mm. Because the roller surface of the copper wheel provides the primary cooling surface, the back of the strip is quickly cooled to about 800 degrees Celsius, creating conditions for subsequent deeper free surface cooling.

[0036] When the strip-swinging plate rotates with the copper wheel in the discharge direction, its free surface is completely exposed to the outside space. If it is not cooled in time, it is very likely to cause problems such as grain growth, uneven structure, and even surface oxidation. In this embodiment, a liquid argon forced cooling unit is installed above the free surface of the strip-swinging plate in the discharge direction of the copper wheel. This unit consists of multiple liquid argon nozzles arranged in an array along the width of the strip-swinging plate. The nozzle spray angle is set between 30 and 60 degrees and is arranged at an acute angle with the forward direction of the strip.

[0037] The distance between the nozzle and the stripping blade is controlled between 20 and 50 mm to ensure that the high-pressure liquid argon can precisely impact the stripping blade surface with strong impact force. The injection pressure can be adjusted between 0.1 MPa and 0.4 MPa, and the liquid argon flow rate is controlled between 0.2 and 1.5 cubic meters per hour. The argon used must be at least 99.999% pure to ensure it does not participate in chemical reactions and enhance cooling uniformity. The nozzle array sprays over a width of at least 400 mm, ensuring that the free surface of the stripping blade is cooled completely.

[0038] A double-sided collaborative cooling system is formed by liquid argon injection and copper wheel back cooling. When the strip just leaves the copper wheel and is still in a red-hot state, the temperature of the strip can be quickly reduced from over 800 degrees Celsius to below 500 degrees Celsius within 2 seconds through free surface injection.

[0039] This cooling rate has significant advantages over the existing technology that relies solely on single-sided copper wheel roller cooling.

[0040] In traditional single-sided cooling devices, the natural convection heat exchange efficiency between the free surface of the strip and the air is low, and the temperature drops slowly, resulting in a much higher grain growth rate on the free surface than on the roller surface, which easily leads to problems such as asymmetric structure and coarse grains.

[0041] The present invention controls the cooling time to be completed within 2 seconds through the liquid argon strong cooling technology, so that the temperature quickly passes through the critical region of grain growth, and significantly improves the grain refinement effect.

[0042] In order to prolong the cooling effect of liquid argon on the strips and avoid oxidation reactions caused by direct contact of the cooled high-temperature strips with air, a closed channel structure is set between the liquid argon injection unit and the subsequent crushing mechanism. The channel is 1.5 meters long and maintains a closed argon environment inside. The strips are transported at a lower speed and continuously carry out gas-solid co-flow heat exchange.

[0043] This structure can enhance the heat conduction efficiency between the argon gas and the stripping plate, prevent the entry of external oxygen in a closed environment, and improve the stability and protection effect of the cooling process.

[0044] After passing through the closed channel, the strip enters the drum cooler for secondary cooling. The drum cooler adopts a double drum structure, which is respectively located on the upper and lower sides of the strip. The two drums are in direct contact with the free surface of the strip and the surface of the roller respectively.

[0045] A coolant circulation system is provided inside the drum. The drum is made of high thermal conductivity metal and the outer surface is kept at a constant low temperature, which further conducts heat conduction cooling on the belt-spinning blades.

[0046] By clamping the strips up and down, a more stable and uniform cooling process is applied to the strips, further reducing the overall temperature to no more than 350 degrees Celsius. This temperature is maintained for 30 minutes to stabilize the strips' microstructure, promote metastable structural transformation, and eliminate internal thermal stress. This process plays an important role in improving material performance and stabilizing subsequent magnetic properties.

[0047] When the strips have completed double-drum cooling, their physical state is close to room temperature and can safely enter the crushing process. In the present invention, the crusher is arranged at the end of the cooling system and is internally provided with a strip guide structure to ensure that the strip material is smoothly fed into the crushing cavity and to avoid the occurrence of unstable conditions such as material entanglement and accumulation. The crusher structure is internally equipped with a high-efficiency rotary cutting or crushing mechanism, which can crush the cooled strips into granular alloy materials with uniform particle size.

[0048] Inside the crusher, an argon outlet is installed. Argon gas, guided by a closed channel before the slinger enters the crusher, enters the crushing chamber along with the argon gas and is discharged through the outlet. During this process, the argon gas effectively removes heat generated during the crushing process and forms an inert gas shield in the crushing area, inhibiting oxidation of metal particles and significantly improving particle purity and the crushing environment.

[0049] This embodiment realizes a rapid cooling process of the strip in full range, high intensity and short time through a double-sided collaborative cooling design, which significantly improves the cooling efficiency and grain refinement capability.

[0050] Compared with the single-sided cooling or natural air cooling solutions in the existing technology, it is impossible to achieve the rapid cooling goal of reducing the temperature from 800 degrees Celsius to below 500 degrees Celsius within 2 seconds, nor can it effectively prevent grain growth and surface oxidation problems.

[0051] The present invention adopts a coordinated method of roller cooling and free surface liquid argon injection, combined with roller heat conduction cooling and argon protection channel, to systematically construct a high-strength cooling system. It not only controls the grain size of the strip-spinning sheet within the range of 2 to 5 microns, but also can measure the coercive force increase by no less than 15% under experimental conditions, greatly improving the overall performance of the NdFeB magnetic alloy material, and providing high-efficiency, high-quality, controllable and stable technical support for the batch preparation of high-performance magnet materials.

[0052] The present invention provides a NdFeB strip cooling device based on a double-sided strong cooling device. On the basis of traditional roller surface cooling, a liquid argon jet strong cooling unit is introduced on the free surface of the strip, thereby constructing a double-sided cooling system in which the roller surface and the free surface work together. This structure significantly improves the overall cooling rate of the strip in the red-hot range, and can quickly reduce the temperature of the strip from 800 degrees Celsius to 500 degrees Celsius or lower within two seconds after the strip is separated from the copper wheel, thereby effectively inhibiting grain growth and refining the grain size to 2 to 5 microns, which is significantly better than the 7 to 15 microns in the traditional process, and helps to improve the coercive force of the magnet. The coercive force of the magnet can be increased by more than 15% through this cooling system. At the same time, due to the excellent grain refinement effect, the dependence on heavy rare earth elements such as dysprosium and terbium can be reduced, and the addition amount thereof can be reduced by 20 to 30%, thereby effectively reducing material costs and alleviating resource shortages.

[0053] In addition, the liquid argon nozzle array supports the replacement of nozzles, which can flexibly realize various cooling modes such as liquid argon direct spray cooling or argon air cooling to adapt to different equipment conditions and user needs, improve the system versatility and engineering adaptability. During the cooling process, the belt-swinging blades co-flow with the argon gas through the closed cooling channel and enter the crusher, which can significantly remove the waste heat and inhibit metal oxidation and dust diffusion, improving the safety and environmental protection level of the overall system.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

Claims

1. A NdFeB belt cooling device based on a double-sided strong cooling device, characterized in that: include: A copper wheel cooling unit for receiving NdFeB melt, which spins the NdFeB melt into a strip with a thickness of 0.2-0.4mm and a width of about 400mm while rotating, and achieves primary cooling through the roller surface; A liquid argon forced cooling unit is provided above the free surface of the stripping piece in the discharge direction of the copper wheel. The liquid argon forced cooling unit comprises a plurality of liquid argon nozzle arrays distributed along the width direction of the stripping piece. The nozzle spray angle is 30° to 60° and is set at an acute angle to the conveying direction of the stripping piece. The spray distance is 20-50 mm and the spray pressure is 0.1-0.4 MPa. The drum cooler is installed after the liquid argon forced cooling unit and is used to further cool the stripping blades through heat conduction; The crusher is installed after the drum cooler and is used to crush the cooled sling pieces into granular materials; The copper wheel roller surface cooling and the free surface liquid argon jet strong cooling work together to form a double-sided cooling system for the roller surface and the free surface.

2. The NdFeB strip cooling device based on a double-sided strong cooling device according to claim 1 is characterized in that: The liquid argon nozzle array has a spray coverage width of not less than 400 mm, and the nozzles can be replaced with atomizing nozzles or air-cooling nozzles to adapt to spray cooling or air-cooling cooling modes.

3. The NdFeB strip cooling device based on a double-sided forced cooling device according to claim 1, characterized in that: A closed channel structure is provided between the liquid argon strong cooling unit and the crusher. The channel length is 1.5 meters, which is used to form a closed cooling area, enhance the liquid argon cooling effect and realize gas-solid co-flow heat exchange.

4. The NdFeB strip cooling device based on a double-sided strong cooling device according to claim 1, characterized in that: The drum cooler is a double-drum structure. The two drums are maintained at a low temperature through an external cooling circulation system and are in direct contact with the surface of the belt-swinging plate to achieve heat conduction cooling.

5. The NdFeB strip cooling device based on a double-sided strong cooling device according to claim 1, characterized in that: The crusher has a belt-swinging blade guiding structure and an argon gas outlet. The argon gas and the belt-swinging blade enter the crushing cavity together and are then led out from the outlet to remove heat and reduce dust pollution.

6. A method for grain refinement of NdFeB strip sheets based on the cooling device of claim 1, characterized in that: The steps include: a) The molten NdFeB alloy is injected into the high-speed rotating copper wheel, and the roller surface is cooled to form a preliminary formed strip; By combining roller surface cooling with free surface liquid argon jet cooling, a double-sided cooling system is constructed to quickly reduce the temperature of the stripping sheet. b) When the strip leaves the copper wheel and is in a red-hot state, liquid argon is sprayed from the free surface by an array of liquid argon nozzles at an angle of 30° to 60° to achieve a strong cooling treatment of the red-hot surface, reducing the strip temperature from over 800°C to 500°C or below within 2 seconds; c) The strip is further introduced into a drum cooler and further cooled to no higher than 350°C by heat conduction and maintained for 30 minutes to stabilize the microstructure; d) The cooled strips are introduced into a crusher for pulverization, and the alloy particles with refined grains are collected.

7. The method for grain refinement of NdFeB strip-spinning sheet according to claim 6, characterized in that: The liquid argon nozzle injection pressure is 0.1-0.4 MPa, and the liquid argon flow rate is 0.2-1.5m 3 / h, the purity of argon is not less than 99.999%.

8. The method for grain refinement of NdFeB strip-spinning sheet according to claim 6, characterized in that: The distance between the liquid argon nozzle and the strip-swinging plate is 20-50 mm, and the nozzle spray coverage width is 400 mm, so as to achieve uniform cooling of the free surface of the strip-swinging plate as a whole.

9. The method for grain refinement of NdFeB strip-spinning sheet according to claim 6, characterized in that: The crusher is provided with a guide channel and an argon gas discharge device. The stripping piece and the argon gas move together in the guide channel. The argon gas takes away heat and inhibits metal oxidation during the crushing process.

10. The method for grain refinement of NdFeB strip-spinning sheet according to claim 6, characterized in that: By adjusting the liquid argon cooling parameters and the roller cooling time, the grain size of the strip-spun sheets can be adjusted to 2-5μm, and the coercive force can be increased by no less than 15%.

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