Method and device for improving coercive force of neodymium iron boron based on grain boundary diffusion technology

Abstract

The invention relates to the field of neodymium-iron-boron permanent magnet materials, and discloses a method for improving neodymium-iron-boron coercive force based on a grain boundary diffusion technology, which comprises the following steps: a pretreatment process: etching the surface of a magnet workpiece by adopting plasma to form a nanoscale groove on the surface of the magnet workpiece; a diffusion source film layer is sprayed, specifically, a diffusion source is sprayed to the magnet workpiece, the diffusion source can be attached to the interior of the nanoscale groove, and a film layer with the thickness smaller than or equal to 5 micrometers is formed; step heating diffusion: heating the coated magnet workpiece to 400 DEG C, keeping the temperature for 30 minutes, heating the magnet workpiece to 900 DEG C, and keeping the temperature for 2 hours to obtain a diffused magnet; and a post-treatment process: cooling the diffusion magnet in nitrogen. Efficient and uniform grain boundary diffusion of the magnet is achieved, the coercive force is improved, the use amount of heavy rare earth is reduced, the diffusion time is shortened, the production efficiency is improved, the automation degree of the device is high, and the operation mode is simple.

Description

Technical Field

[0001] The present invention relates to the field of neodymium iron boron permanent magnet materials, and specifically relates to a method and device for improving the coercivity of neodymium iron boron based on grain boundary diffusion technology. Background Art

[0002] Neodymium iron boron (NdFeB) permanent magnet materials are widely used in the field of new energy vehicle motors due to their high magnetic energy product and cost performance. However, the insufficient coercivity (Hcj) leads to easy demagnetization at high temperatures, which becomes a bottleneck restricting its application in high-temperature scenarios. How to improve the coercivity of neodymium iron boron (NdFeB) permanent magnet materials has become a hot issue.

[0003] Traditional methods for improving coercivity include alloying method and grain boundary diffusion technology. The alloying method adds heavy rare earth elements (such as Dy, Tb), and its defect is high cost and significant decrease in the magnetic energy product of the material. The grain boundary diffusion technology optimizes the grain boundary phase by surface diffusion of heavy rare earth elements. To ensure the spraying uniformity, different equipment (such as PVD, screen printing, etc.) is required for magnets of different sizes / shapes, and matching fixtures are needed to clamp the magnetic materials. The single processing volume is small, the process efficiency is low, the diffusion uniformity is poor, and it is only suitable for specific-shaped magnets, with insufficient tooling compatibility.

[0004] At the same time, the traditional grain boundary diffusion technology (GBD) relies on the penetration of heavy rare earth elements (such as Tb, Dy). The cost of heavy rare earth elements is high, the diffusion efficiency is low, and it is difficult to achieve large-scale continuous production. At the same time, the optimization of process parameters (temperature, time, atmosphere) is insufficient, which will lead to uneven improvement of coercivity and high defective product rate. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for improving the coercivity of neodymium iron boron based on grain boundary diffusion technology, so as to solve the technical problems of large usage amount of heavy rare earth elements, low diffusion efficiency, and insufficient improvement of coercivity in the traditional grain boundary diffusion technology in the prior art.

[0006] To solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] A method for improving the coercivity of neodymium iron boron based on grain boundary diffusion technology, comprising the following steps:

[0008] S100, Pretreatment process: Etching the surface of the magnet workpiece by plasma to form nanoscale grooves on the surface of the magnet workpiece;

[0009] S200, Spraying the diffusion source film layer: Spraying the diffusion source onto the magnet workpiece, and the diffusion source can adhere to the nanoscale grooves to form a film layer with a thickness ≤ 5μm;

[0010] S300, Step - by - step temperature - rising diffusion: Heat the magnet workpiece after film - covering to 400 °C, keep it warm for 30 min, then raise the temperature of the magnet workpiece to 900 °C and keep it warm for 2 h to obtain a diffusion magnet;

[0011] S400, Post - treatment process: Cool the diffusion magnet in nitrogen.

[0012] As a preferred embodiment of the present invention, in the step S100, the gas used for etching is an Ar / H2 mixed gas, and the molar ratio of Ar to H2 in the mixed gas is 4:1;

[0013] The nano - scale grooves are nano - scale pores, and the pore diameter of the nano - scale pores is 50 - 200 nm.

[0014] As a preferred embodiment of the present invention, in the step S200, the diffusion source contains mixed particles and an environmental protection additive;

[0015] Among them, the particle size of the mixed particles is 1 - 3 μm;

[0016] By mass percentage, the mixed particles are composed of 70% DyF3, 15% Al, 10% Cu, and 5% nano - carbon powder.

[0017] As a preferred embodiment of the present invention, the environmental protection additive is H3BO3, and the added mass of H3BO3 is 1% of the total mass of the diffusion source.

[0018] As a preferred embodiment of the present invention, in the step S300, the following steps are further included: Before heating, evacuate the air pressure in the reaction chamber to a vacuum value of 5×10 -3 Pa, and then introduce argon to raise the air pressure in the reaction chamber to 0.1 MPa.

[0019] An apparatus for improving the coercivity of neodymium - iron - boron based on grain - boundary diffusion technology, comprising:

[0020] A vacuum double - chamber device, the vacuum double - chamber device includes a reaction chamber one and a reaction chamber two, an insertion valve is arranged between the reaction chamber one and the reaction chamber two, a transmission device is laid under the reaction chamber one and the reaction chamber two, a grid for placing magnet workpieces is arranged on the transmission device, and when the insertion valve is opened, the transmission device can drive the grid to slide reciprocally between the reaction chamber one and the reaction chamber two;

[0021] An ion source etching device and a gas-solid two-phase diffusion source injection device are arranged in the first reaction chamber. The ion source etching device is used to sputter plasma onto a magnet workpiece located in the first reaction chamber, and the gas-solid two-phase diffusion source injection device is used to sputter the diffusion source onto the magnet workpiece located in the first reaction chamber;

[0022] A vacuum-inert gas circulation system and a partition temperature control module system are arranged in the second reaction chamber. The vacuum-inert gas circulation system includes a vacuum pump, an intake pump, and a nitrogen circulation device. The vacuum pump is used to evacuate the second reaction chamber, the intake pump is used to introduce an inert gas into the second reaction chamber, and the nitrogen circulation device is used to introduce cooled nitrogen into the second reaction chamber; the partition temperature control module system is used to heat the second reaction chamber.

[0023] As a preferred embodiment of the present invention, the grid frame includes a frame body arranged on the transmission device. A plurality of layers of high-temperature resistant ceramic mesh plates are arranged on the frame body. The mesh plates are arranged parallel to each other and are used to place magnet workpieces;

[0024] The frame body is located at the corners of the mesh plate and is used to support the mesh plate. The bottom of the frame body is connected to a base. The base is arranged at the bottom of the first reaction chamber and is installed on the transmission device.

[0025] As a preferred embodiment of the present invention, the transmission device includes a trough buried horizontally under the first reaction chamber and the second reaction chamber. A transmission seat is arranged on the trough. The transmission seat reciprocates in the trough through a motion group module, and the base is fixedly installed on the transmission seat;

[0026] As the motion group module moves, the transmission seat can drive the mesh plate to slide in the first reaction chamber and the second reaction chamber;

[0027] The bottom of the plug valve is recessed downward into the trough.

[0028] As a preferred embodiment of the present invention, a plurality of trays are arranged in the second reaction chamber. The mesh plate can be horizontally fitted on the trays, and the trays divide the second reaction chamber into several heating layers;

[0029] The partition temperature control module system includes an infrared radiation element and an induction heating element arranged in the heating layer. The infrared radiation element can perform partition heating on the layers of the heating layer, and the induction heating element is used to control the temperature of the heating layer.

[0030] As a preferred embodiment of the present invention, an air flow channel is provided in the first reaction chamber. The air flow channel is connected to an air pump, and the air pump drives the plasma to circulate in the first reaction chamber through high-speed air flow.

[0031] The present invention has the following beneficial effects compared with the prior art:

[0032] (1) For the method for improving the coercivity of NdFeB provided by the present invention, before spraying the diffusion source, the surface of the magnet workpiece is etched with plasma prepared from an Ar / H2 mixed reaction gas, so that nano-scale grooves with a width of 50-200 nm are formed on the surface of the magnet workpiece. The surface grooves enhance the particle diffusion depth, which helps to establish a diffusion channel for low-melting-point metals, thereby reducing the amount of rare earth used and shortening the diffusion time.

[0033] (2) The present invention optimizes the diffusion source formula. A binder H3BO3 is added to the diffusion source particles. The binder and the nano-grooves act synergistically. The binder adsorbs the diffusion source particles into the grooves, enhancing the adhesion ability of the diffusion source. Compared with the magnet without pretreatment, the diffusion source particles can quickly complete the construction on the surface of the pretreated magnet to form a film structure, reducing the amount of heavy rare earth by 30% and the diffusion time by 50%. At the same time, the binder H3BO3 can reduce the high-temperature volatilization pollution of the diffusion source and improve the environmental protection degree of the reaction.

[0034] (3) By optimizing the process parameters (temperature, time, atmosphere, etc.), the present invention can increase the typical value of the coercivity of the magnet from 21.5 kOe to 29 kOe, and the coercivity of the magnet is increased by more than 66% compared with the same type of diffusion process.

[0035] (4) The vacuum double-chamber device of the present invention can realize the continuous production process of the magnet workpiece without manual operation, with high automation and convenient use. In actual application, spraying + diffusion can be carried out in the same furnace, which can reduce the oxidation of the magnet surface, improve the diffusion efficiency, and increase the coercivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, other implementation drawings can be obtained according to the provided drawings without creative efforts.

[0037] Figure 1 It is a flow chart of the method for improving the coercivity of NdFeB based on the grain boundary diffusion technology provided by the present invention;

[0038] Figure 2 It is the figure shown in Embodiment 1 provided by the present invention;

[0039] Figure 3 Provide the figure shown in Embodiment 1 of the present invention;

[0040] Figure 4 Schematic structural diagram of the device for improving the coercivity of NdFeB based on grain boundary diffusion technology provided by the present invention;

[0041] Figure 5 Provided by the present invention Figure 4 Schematic structural diagram of the grid in the embodiment shown;

[0042] Figure 6 Provided by the present invention Figure 4 Schematic structural diagram of the engagement of the grid and the tray in the embodiment shown;

[0043] Figure 7 Provided by the present invention Figure 4 Schematic structural diagram of the mesh plate in the embodiment shown.

[0044] The reference numerals in the figure respectively represent as follows:

[0045] 1 - Reaction chamber 1; 2 - Reaction chamber 2; 3 - Slide valve; 4 - Transmission device; 5 - Grid; 6 - Ion source etching device; 7 - Gas - solid two - phase diffusion source injection device; 8 - Vacuum pump; 9 - Intake pump; 10 - Nitrogen circulation device; 11 - Tray; 12 - Heating layer; 13 - Air flow channel; 14 - Air pump;

[0046] 401 - Tank body; 402 - Transmission seat; 403 - Movement group die;

[0047] 501 - Frame body; 502 - Mesh plate; 503 - Base. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] As Figure 1 shown, the present invention discloses a method for improving the coercivity of NdFeB based on grain boundary diffusion technology, including the following steps:

[0050] (1) Pretreatment process: Use plasma to etch the surface of the magnet workpiece, so that nano - scale grooves are formed on the surface of the magnet workpiece to enhance the adhesion of the diffusion source;

[0051] (2) Spraying the diffusion source film layer: Spraying the diffusion source onto the magnet workpiece. The diffusion source can adhere to the nano-scale grooves, forming a film layer with a thickness ≤ 5 μm. The nano-scale grooves can improve the adhesion speed of the diffusion source, reduce particle reflection, improve the uniformity of adhesion, and reduce the usage of heavy rare earths;

[0052] (3) Stepwise temperature-raising diffusion: Heating the magnet workpiece with the coated film to 400 °C and holding for 30 min, then raising the temperature of the magnet workpiece to 900 °C and holding for 2 h to avoid excessive melting of the grain boundary phase, obtaining a diffusion magnet;

[0053] (4) Post-treatment process: Rapidly cooling the diffusion magnet in nitrogen with a cooling rate of 50 °C / min to inhibit abnormal grain growth.

[0054] The above steps (2) and (3) can be carried out in the same furnace, spraying + diffusion in the same furnace under vacuum, which limits the reduction of magnet surface oxidation, improves the diffusion efficiency, and greatly improves the coercivity

[0055] The plasma etching technology adopted in the present invention is a dry etching technology. Gas is introduced into the reaction chamber. Under the action of radio frequency, the gas is ionized into plasma. The plasma has energy and leaves traces when it sputters on the surface of the magnet workpiece. Specifically, in step S100, the gas used for etching is an Ar / H2 mixed gas, and the molar ratio of Ar to H2 in the mixed gas is 4:1. Under the conditions of a sputtering power of 200 W and a time of 5 min, the morphology of the nano-scale grooves is generally nano-scale pores, and the pore diameter of the nano-scale pores is 50 - 200 nm.

[0056] The surface of the magnet without pretreatment is smooth. If particles are directly used for sputtering, the diffusion source particles are easily ejected by the magnet into the reaction chamber, resulting in waste of the diffusion source. The diffusion source contains rare earth particles, and the wasted cost is high. At the same time, it will also lead to a long particle adhesion time and uneven film coating.

[0057] After surface treatment, grooves with a size of 50 - 200 nm are formed on the surface of the magnet workpiece. The subsequent sputtered diffusion source can be bonded in the grooves. The surface grooves enhance the particle diffusion depth, contribute to the establishment of a diffusion channel for low-melting-point metals, thereby reducing the usage of rare earths and reducing the diffusion time.

[0058] In step S200, the particle size of the diffusion source is 1 - 3 μm, and the diffusion source particles can be adsorbed in the nano-scale grooves. Compared with the magnet without pretreatment, the diffusion source particles can quickly complete the construction on the surface of the pretreated magnet and form a film structure.

[0059] Furthermore, in order to reduce the agglomeration of the diffusion source, the diffusion source contains mixed particles and an environmentally friendly additive. By mass percentage, the mixed particles are composed of 70% DyF3, 15% Al, 10% Cu, and 5% carbon nanoflour. Among them, the carbon nanoflour acts as a fluidity aid, which can reduce the agglomeration of the diffusion source and improve the uniformity of the film body. In actual applications, cost reduction and efficiency improvement can be achieved through different proportion formulations.

[0060] In the present invention, treating the workpiece at a high temperature of 900 °C may cause volatilization pollution. To solve this problem, the diffusion source contains an environmentally friendly additive, and the environmentally friendly additive is H3BO3. The added mass of H3BO3 is 1% of the total mass of the diffusion source. 1% boric acid (H3BO3) acts as an adhesive, which can adsorb the diffusion source particles to the tank body, enhance the adhesion ability of the diffusion source, and enable the diffusion source particles to quickly complete the construction on the surface of the pre-treated magnet to form a film body structure. At the same time, during the subsequent high-temperature diffusion process, the adhesive can reduce the high-temperature volatilization pollution of the diffusion source and improve the environmental protection level of the reaction.

[0061] To reduce oxidation impurities and accelerate the penetration of the diffusion source, in step S300, the following steps are further included: before heating, evacuate the air pressure in the reaction chamber to a vacuum value of 5×10 -3 Pa, and then introduce argon to raise the air pressure in the reaction chamber to 0.1 MPa.

[0062] The following is illustrated through method embodiments:

[0063] (1) Product selection: Taking the magnet of a new energy vehicle motor as an example, take several sintered neodymium iron boron magnets with dimensions of 20 mm × 20 mm × 3 mm, place the magnets on a high-temperature resistant ceramic mesh plate, place 20 pieces in each layer, a total of 5 layers, and load them into the diffusion reaction chamber;

[0064] (2) Pretreatment: Introduce an Ar / H2 mixed gas (ratio 4:1), etch for 5 minutes to form nano-scale pores (pore diameter 50 - 200 nm);

[0065] (3) Spraying the diffusion source film layer: Use Dy 70 Al 15 Cu 10 alloy powder (metal mixture powder) and H3BO3 powder (particle size 1 - 3 μm) and H3BO3 are sprayed through aerosol to form a film layer with a thickness of ≤ 5 μm. (The mass fraction ratio of Dy 70 Al 15 Cu 10 alloy powder to H3BO3 is 99:1);

[0066] (4) Diffusion treatment: Evacuate the reaction chamber to 5×10 -3Introduce argon gas to 0.1 MPa, heat it up to 400 °C at a rate of 10 °C / min and hold for 30 min, then heat it up to 900 °C at a rate of 5 °C / min and hold for 2 h;

[0067] (5) Turn off the heating, introduce high-purity nitrogen gas to quickly cool it to room temperature to obtain Example 1.

[0068] Through statistics, it can be known that for the workpieces obtained by the above method, compared with the general method, the consumption of heavy rare earths is reduced by 30%, and the diffusion time is reduced by 50%.

[0069] The conventional diffusion process only increases from 21.5 kOe to 26 kOe. The coercivity characterization of Example 1 is shown in Figure 2 And Figure 3 , the typical value of Example 1 increases from 21.5 kOe to 29 kOe, and the coercivity of the magnet is increased by more than 66% compared with the same type of diffusion process magnet.

[0070] The existing device tooling has poor compatibility. Different sizes / shape magnets require different equipment (such as PVD, screen printing, etc.), increasing production costs. In order to improve the compatibility of magnet workpieces, as Figures 4 to 7 shown, the present invention further discloses a device for improving the coercivity of NdFeB based on grain boundary diffusion technology, including a vacuum double-chamber device. The vacuum double-chamber device includes a reaction chamber 1 and a reaction chamber 2. A grid 5 capable of placing multiple magnet workpieces is arranged in the reaction chamber 1. The reaction chamber 1 is used for plasma pretreatment and diffusion source spraying of the magnet workpieces. The reaction chamber 2 is used for heating and cooling the magnet workpieces on the grid 5.

[0071] The reaction chamber 1 and the reaction chamber 2 are connected. The connection between the reaction chamber 1 and the reaction chamber 2 is sealed by a gate valve 3. A power system is arranged on the gate valve 3, and this power system can automatically control the opening or closing of the gate valve 3. When the gate valve 3 is opened, the reaction chamber 1 and the reaction chamber 2 are connected. When the gate valve 3 is closed, the reaction chamber 1 and the reaction chamber 2 are in a closed state.

[0072] Other valves can also be arranged on the sides of the reaction chamber 1 and the reaction chamber 2 to open the reaction chamber from other directions, and the specific chamber doors can be set arbitrarily.

[0073] A transmission device 4 is laid under the first reaction chamber 1 and the second reaction chamber 2. A grid 5 for placing magnet workpieces is arranged on the transmission device 4. When the flap valve 3 is closed, the magnet workpieces are etched and sprayed in the first reaction chamber 1. After the spraying is completed, the flap valve 3 is opened, and the transmission device 4 drives the grid 5 to move from the first reaction chamber 1 to the second reaction chamber 2 for subsequent diffusion operations. The vacuum dual-chamber device disclosed in the present invention can realize the continuous progress of the magnet workpiece production process without manual operation, has a high degree of automation, is convenient to use. In practical applications, spraying + diffusion can be carried out in the same furnace, which can reduce the surface oxidation of the magnet, improve the diffusion efficiency, and greatly improve the coercivity.

[0074] Specifically, an ion source etching device 6 and a gas-solid two-phase diffusion source spraying device 7 are arranged in the first reaction chamber 1. The ion source etching device 6 is an existing finished product device, including a motor arranged on the first reaction chamber 1. This motor can generate a radio frequency electric field. A negative electrode is arranged below the first reaction chamber 1, and the grid 5 is installed on this negative electrode. A nozzle for quantitatively introducing reaction gas is arranged on the side of the first reaction chamber 1. When the nozzle introduces the reaction gas, the reaction gas is ionized into plasma under the action of radio frequency. The plasma is composed of negatively charged electrons and positively charged ions. The positively charged ions are attracted to the side of the magnet, and the surface of the magnet can be etched away.

[0075] In the present invention, the ion source etching device 6 is used to sputter the plasma onto the magnet workpieces located in the first reaction chamber 1. The reaction gas introduced into the ion source etching device 6 is a mixed gas with a ratio of Ar to H2 of 4:1. The plasma energies of H2 and the inert gas are inconsistent, so height differences will occur during etching, generating nanoscale grooves.

[0076] A gas-solid two-phase diffusion source spraying device 7 is also arranged on the first reaction chamber 1. The gas-solid two-phase diffusion source spraying device 7 is an existing device. After the etching is completed, the gas-solid two-phase diffusion source spraying device 7 is used to sputter the diffusion source onto the magnet workpieces located in the first reaction chamber 1 under the drive of the aerosol until a film layer with a thickness ≤ 5μm is formed on the surface of the workpiece.

[0077] It can be seen that the first reaction chamber 1 of the present invention can successively perform pretreatment and spraying on the magnetic workpieces. After the spraying treatment, when the flap valve 3 is opened, the magnetic workpieces can automatically enter the second reaction chamber 2 under the drive of the transmission device 4, ensuring the continuity of the magnetic workpiece treatment and at the same time reducing the requirements for the reaction device itself.

[0078] Further, a vacuum-inert gas circulation system and a partition temperature control module system are provided in the second reaction chamber 2. The vacuum-inert gas circulation system includes a vacuum pump 8, an intake pump 9, and a nitrogen circulation device 10. The vacuum pump 8 is used to evacuate the second reaction chamber 2, the intake pump 9 is used to introduce an inert gas into the second reaction chamber 2, and the nitrogen circulation device 10 is used to introduce cooled nitrogen into the second reaction chamber 2 to rapidly cool the magnetic workpiece.

[0079] The partition temperature control module system is used to heat the second reaction chamber 2.

[0080] The use of the above device for improving the coercivity of NdFeB based on the grain boundary diffusion technology is described below. The usage method of the device for improving the coercivity of NdFeB based on the grain boundary diffusion technology is as follows:

[0081] ① Open the first reaction chamber 1, place the magnetic workpiece on the grid 5 of the first reaction chamber 1, close the first reaction chamber 1, and keep the first reaction chamber 1 in a sealed state;

[0082] ② Open the ion source etching device 6, introduce a reaction gas. The reaction gas is an Ar / H2 mixed gas, and the etching time is 5 min. After the etching is completed, close the ion source etching device 6, open the gas-solid two-phase diffusion source spraying device 7, and spray a mixture of the diffusion source powder and the auxiliary agent onto the surface of the magnetic workpiece through an aerosol to form a film layer with a thickness of ≤5 μm, and then close the gas-solid two-phase diffusion source spraying device 7;

[0083] ③ Open the gate valve 3, and the transmission device 4 drives the grid 5 to move into the second reaction chamber 2. Use the vacuum pump 8 to evacuate the vacuum degree of the reaction chamber to 5×10 -3 Pa, then introduce argon through the intake pump 9 to raise the air pressure of the reaction chamber to 0.1 MPa. Turn on the partition temperature control module system and heat it to 400 °C at a rate of 10 °C / min and hold for 30 min, then raise it to 900 °C at a rate of 5 °C / min and hold for 2 h;

[0084] ④ After the heat preservation is completed, turn off the partition temperature control module system, and introduce cooled nitrogen into the reaction chamber through the nitrogen circulation device 10 to rapidly cool the magnetic workpiece.

[0085] First of all, the device provided by the present invention can realize the continuous progress of pretreatment, spraying, diffusion, and cooling. The workpiece can use a connected chamber in the spraying and diffusion steps, reducing the oxidation of the magnet surface, improving the diffusion efficiency, and improving the coercivity; at the same time, the device has a small volume, a high degree of automation, and is convenient for actual production use.

[0086] The above-mentioned motor, ion source etching device 6, gas-solid two-phase diffusion source injection device 7, gate valve 3, transmission device 4, vacuum pump 8, intake pump 9, partition temperature control module system, and nitrogen circulation device 10 can all be connected to a control system. This control system includes an integrated PLC and AI algorithm, enabling real-time monitoring of temperature, air pressure, and diffusion source concentration and dynamic adjustment. The control system is used to simplify the difficulty of manual operation.

[0087] In order to further improve production efficiency, the grid 5 includes a frame body 501 disposed on the transmission device 4. A multi-layer high-temperature resistant ceramic mesh plate 502 is provided on the frame body. The mesh plates 502 are arranged parallel to each other and are used to place magnet workpieces. During specific use, each layer of the mesh plate 502 can hold multiple magnets.

[0088] Although a multi-layer mesh plate structure is provided, it will not cause a significant decrease in the etching and sputtering speeds. This is because: ① The mesh plate 502 is provided with a porous structure. The pore structure facilitates the dropping of plasma. When placing the magnets, they can be placed in a staggered layer, facilitating the passage of plasma or sprayed particles through the mesh holes to contact the magnets; ② This mesh plate is made of high-temperature resistant ceramic. The high-temperature resistant ceramic has high hardness and smoothness, and can eject the particles sputtered onto the mesh plate 502 to other positions, thus facilitating the rapid distribution of the particles and sputtering the particles onto the magnets.

[0089] To reduce occlusion, the frame body 501 is located at the corners of the mesh plate 502 and is used to support the mesh plate 502. The bottom of the frame body 501 is connected to a base 503. The base 503 is disposed at the bottom of the reaction chamber 1 and is installed on the transmission device 4.

[0090] Preferably, the transmission device 4 includes a trough body 401 horizontally buried under the reaction chamber 1 and the reaction chamber 2. A transmission seat 402 is provided on the trough body 401. The transmission seat 402 reciprocally slides in the trough body 401 through a motion group module 403. The base 503 is fixedly installed on the transmission seat 402. A motor is provided in the motion group module 403, which can drive the entire grid 5 to move.

[0091] As the motion group module 403 moves, the transmission seat 402 can drive the mesh plate 502 to slide from the reaction chamber 1 to the reaction chamber 2, or move from the reaction chamber 2 to the reaction chamber 1.

[0092] The bottom of the gate valve 3 is recessed downward into the trough body 401 to maintain the sealing function of the gate valve 3.

[0093] Preferably, different magnets may require different temperatures during diffusion. In order to diffuse magnets of different volumes that may be on different stencils 502, a number of trays 11 are provided in the second reaction chamber 2. The stencil 502 can be horizontally fitted on the tray 11, and the tray 11 divides the second reaction chamber 2 into a number of heating layers 12.

[0094] The zone temperature control module system includes an infrared radiation element and an induction heating element provided in the heating layer 12. The infrared radiation element can perform zone heating on the layers of the heating layer 12, and the induction heating element is used to control the temperature of the heating layer 12, achieving precise control of the temperature gradient in the reaction chamber, preferably ±2 °C, adapting to different magnet sizes, reducing thermal stress, and independently controlling the temperature of each layer of the second reaction chamber 2, supporting synchronous processing of multiple magnets.

[0095] As a preferred solution, an air flow channel 13 is provided in the first reaction chamber 1, and the air flow channel 13 is connected to an air pump 14. The air pump 14 drives the plasma to circulate in the first reaction chamber 1 through high-speed air flow.

[0096] Through the method and device for improving the coercivity of NdFeB by grain boundary diffusion technology in this embodiment, efficient and uniform grain boundary diffusion can be achieved, the coercivity can be improved, and the production efficiency can be increased. It can be increased from 21.5 kOe to 29 kOe, the coercivity of the magnet is increased by more than 66% compared with the same type of diffusion process, the usage of heavy rare earth is reduced by 30%, the diffusion time is reduced by 50%, and it has a high degree of automation and a simple operation method.

[0097] The present invention relates to the technical field of NdFeB permanent magnet material manufacturing, and specifically relates to a method and a supporting device for improving the coercivity of NdFeB by grain boundary diffusion technology, which are applicable to high coercivity demand scenarios such as new energy vehicle drive motors and 3C consumer electronics.

[0098] The above embodiments are only exemplary embodiments of the present application and are not used to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements within the essence and protection scope of the present application, and such modifications or equivalent replacements should also be regarded as falling within the protection scope of the present application.

Claims

1. A method for improving the coercivity of NdFeB based on grain boundary diffusion technology, characterized in that: The steps include: S100, pretreatment process: using plasma to etch the surface of the magnetic workpiece so that nano-scale grooves are formed on the surface of the magnetic workpiece; S200, spraying a diffusion source film layer: spraying a diffusion source onto the magnetic workpiece, wherein the diffusion source can be attached to the nanoscale groove to form a film layer with a thickness of ≤5 μm; S300, step-by-step temperature diffusion: heating the coated magnet workpiece to 400° C., keeping the temperature for 30 min, and then heating the magnet workpiece to 900° C., keeping the temperature for 2 h, to obtain a diffused magnet; S400, post-processing process: cooling the diffusion magnet in nitrogen.

2. The method for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 1, characterized in that: In the step S100, the gas used for etching is an Ar / H2 mixed gas, and the amount of Ar and H2 in the mixed gas is 4:1; The nanoscale grooves are nanoscale pores, and the pore diameter of the nanoscale pores is 50-200 nm.

3. The method and device for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 1, characterized in that: In the step S200, the diffusion source contains mixed particles and environmentally friendly additives; Wherein, the particle size of the mixed particles is 1-3 μm; In terms of mass percentage, the mixed particles consist of 70% DyF3, 15% Al, 10% Cu, and 5% nano-carbon powder.

4. The method for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 1 is characterized in that: The environmentally friendly additive is H3BO3, and the added mass of the H3BO3 is 1% of the total mass of the diffusion source.

5. The method for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 1 is characterized in that: In the step S300, the following steps are also included: before heating, the pressure in the reaction chamber is evacuated to a value of 5×10 -3 Pa, and then argon gas was introduced to raise the pressure of the reaction chamber to 0.1 MPa.

6. A device for improving the coercivity of NdFeB based on grain boundary diffusion technology, based on the method for improving the coercivity of NdFeB based on grain boundary diffusion technology according to any one of claims 1 to 5, characterized in that: include: A vacuum double-chamber device, the vacuum double-chamber device comprising a first reaction chamber (1) and a second reaction chamber (2), a gate valve (3) being arranged between the first reaction chamber (1) and the second reaction chamber (2), a transmission device (4) being arranged below the first reaction chamber (1) and the second reaction chamber (2), a grid frame (5) being arranged on the transmission device (4) for placing a magnetic workpiece, and when the gate valve (3) is opened, the transmission device (4) can drive the grid frame (5) to slide back and forth between the first reaction chamber (1) and the second reaction chamber (2); An ion source etching device (6) and a gas-solid two-phase diffusion source injection device (7) are arranged in the first reaction chamber (1); the ion source etching device (6) is used to sputter plasma onto a magnetic workpiece located in the first reaction chamber (1); and the gas-solid two-phase diffusion source injection device (7) is used to sputter the diffusion source onto the magnetic workpiece located in the first reaction chamber (1); The second reaction chamber (2) is provided with a vacuum-inert gas circulation system and a zoned temperature control module system. The vacuum-inert gas circulation system comprises a vacuum pump (8), an air intake pump (9) and a nitrogen circulation device (10). The vacuum pump (8) is used for evacuating the second reaction chamber (2), the air intake pump (9) is used for introducing an inert gas into the second reaction chamber (2), and the nitrogen circulation device (10) is used for introducing cooled nitrogen into the second reaction chamber (2); and the zoned temperature control module system is used for heating the second reaction chamber (2).

7. The device for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 6, characterized in that: The grid frame (5) comprises a frame body (501) arranged on the transmission device (4), and a plurality of layers of high-temperature resistant ceramic mesh plates (502) are arranged on the frame body. The mesh plates (502) are arranged parallel to each other, and the mesh plates (502) are used to place magnetic workpieces; The frame (501) is located at the corner of the mesh plate (502) and is used to support the mesh plate (502). The bottom of the frame (501) is connected to a base (503). The base (503) is arranged at the bottom of the reaction chamber (1). The base (503) is installed on the transmission device (4).

8. The device for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 7, characterized in that: The transmission device (4) comprises a trough body (401) transversely buried under the first reaction chamber (1) and the second reaction chamber (2); a transmission seat (402) is arranged on the trough body (401); the transmission seat (402) reciprocates and slides in the trough body (401) through a motion assembly die (403); and the base (503) is fixedly mounted on the transmission seat (402); As the motion assembly die (403) moves, the transmission seat (402) can drive the mesh plate (502) to slide in the first reaction chamber (1) and the second reaction chamber (2); The bottom of the gate valve (3) is recessed downward into the groove body (401).

9. The device for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 8, characterized in that: A plurality of trays (11) are arranged in the second reaction chamber (2); the mesh plate (502) can be horizontally embedded in the tray (11); and the tray (11) divides the second reaction chamber (2) into a plurality of heating layers (12); The zoned temperature control module system comprises an infrared radiation element and an induction heating element arranged in the heating layer (12); the infrared radiation element is capable of performing zoned heating between layers of the heating layer (12); and the induction heating element is used to control the temperature of the heating layer (12).

10. The device for improving the coercivity of NdFeB based on grain boundary diffusion technology according to claim 9, characterized in that: An airflow channel (13) is provided in the reaction chamber (1), and the airflow channel (13) is connected to an air pump (14). The air pump (14) drives the plasma to circulate in the reaction chamber (1) through a high-speed airflow.

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