Magnet diffusion source film, and preparation method therefor and use thereof

Abstract

The present invention belongs to the technical field of rare-earth permanent magnet materials, and relates to a magnet diffusion source film, and a preparation method therefor and the use thereof. The preparation method for the diffusion source film comprises the following steps: preparing a diffusion source sol; adhering the diffusion source sol to an under-layer base film; covering same with an upper-layer base film to form an initial diffusion source film having a "sandwich" structure; and heating, drying and cooling the initial diffusion source film to obtain the diffusion source film. When the diffusion source film of the present invention is used for diffusion, a good diffusion coercive force amplification effect is achieved, and damage to the remanence of the magnet is small; moreover, the finally prepared diffusion magnet has good performance uniformity and consistency, and improvement to the effect is more stable.

Description

Magnet diffusion source film and preparation method and application thereof TECHNICAL FIELD

[0001] The application belongs to the technical field of rare earth permanent magnet materials, and relates to a magnet diffusion source film and a preparation method and application thereof. BACKGROUND

[0002] As a key magnetic functional material, Nd-Fe-B permanent magnet supports the rapid development of the new energy vehicle industry. At present, the consumption of high-performance high-coercivity Nd-Fe-B magnets in new energy vehicles is 3-5 kg. According to the prediction, by 2025, the consumption of Nd-Fe-B magnets for new energy vehicles will increase from less than 0.3 million tons in 2020 to 3.51 million tons, and the demand will show explosive growth. Nd-Fe-B magnets for new energy vehicles need to have high coercivity (H cj ) to meet the requirements of anti-demagnetization and stability under extreme service conditions, and need to have uniform and consistent remanence (B r ) to meet the requirements of precise magnetic circuit design and motor operation noise reduction.

[0003] The development and application of grain boundary diffusion technology have promoted the rapid development of Nd-Fe-B magnets for new energy vehicles. The principle is to attach a small amount of diffusion source containing modified elements to the surface of the magnet in a certain way, and then through a special heat treatment process, the diffusion source enters the magnet along the grain boundary of the magnet, optimizes the composition and microstructure of the magnet, and finally achieves the purpose of improving the coercivity of the magnet without damaging the remanence of the magnet.

[0004] At present, the composition system of the diffusion source has developed from single rare earth element to multi-element coexisting multi-component alloy or compound (mixture), and the corresponding diffusion source attachment method has also gradually diversified, including evaporation, magnetron sputtering, immersion, screen printing and spraying. Among them, evaporation and magnetron sputtering are to make the diffusion source volatilize preferentially by high temperature or high voltage, and then deposit on the surface of the magnet in the form of free ions, so the attachment efficiency is low, and because the volatilization and deposition rates of different elements fluctuate, it is difficult to generate a specific (specified) and uniform multi-element target component diffusion source on the surface of the magnet, which makes it unsuitable for precise attachment of the latest multi-component diffusion source developed by the industry. Immersion, screen printing and spraying are to prepare the diffusion source into powder first, then mix it with organic solvent to prepare diffusion source slurry, and finally attach the diffusion source slurry to the surface of the magnet by liquid immersion, dipping paste attachment or atomization spraying. Because it is suitable for all diffusion source composition systems and has high attachment efficiency, the grain boundary diffusion technology based on immersion, screen printing and spraying has attracted widespread attention and research in the industry.

[0005] However, a large number of studies have found that the viscosity or adhesion effect of the flowable liquid slurry is greatly affected by environmental conditions, and the quality of the diffusion source adhered after the magnet is immersed or adhered with the liquid slurry fluctuates due to the difference in roughness of the surface of the pre-processed magnet, so that the consistency of the diffusion source weight increase cannot be guaranteed in the large batch (batch) adhesion process, resulting in differences in the performance of the diffusion magnet product in industrial production, which cannot meet the strict requirements of high-end new energy vehicle magnets on high uniformity and consistency (the difference in magnet remanence will affect the magnetic moment uniformity of the magnet block in the motor, and slight magnetic moment fluctuation will cause the permanent magnet rotor to vibrate during rotation).

[0006] At the same time, the cost and maintenance cost of silk screen printing and spraying equipment are high, and the process is complex. This means that the intrinsic flowable liquid property of the diffusion source slurry brings certain instability and limitations, which greatly limits the application of neodymium iron boron grain boundary diffusion technology and its products in high-end fields. Therefore, it is of great significance to develop a stable and suitable solid diffusion source system and diffusion method for batch adhesion of multi-component diffusion source and subsequent diffusion for the application of diffusion technology and the development of high-performance neodymium iron boron permanent magnet materials. TECHNICAL PROBLEM

[0007] The technical problem to be solved by the present application is to provide a magnet diffusion source film with good stability, which can be used for batch preparation of high-performance and high-consistency neodymium iron boron magnets. TECHNICAL SOLUTION

[0008] In order to solve the above-mentioned problems existing in the prior art, the purpose of the present application is to provide a magnet diffusion source film, a preparation method and application thereof, to overcome the shortcomings of the prior art.

[0009] One object of the present application is achieved by the following technical scheme:

[0010] A magnet diffusion source film, comprising an upper substrate film, a diffusion source and a lower substrate film in sequence;

[0011] The diffusion source comprises an alloy with a general formula of RE a W b , and a binder, wherein RE is at least one of Dy, Tb, Pr, Nd, La, Ce, Y, Gd, Ho; W is at least one of Cu, Al, Ga, In, Sn, Fe, Co, Ni, Ti, Zr, Mg; a and b are mass percentages, 50≤a≤100, and a+b=100.

[0012] Preferably, the upper substrate film is a flexible film, and the material thereof is one or more of polyvinyl alcohol, polyurethane, polycarbonate and polyethylene terephthalate.

[0013] Preferably, the lower base film is a flexible film made of one or more of polyvinyl alcohol, polyurethane, polycarbonate, polyethylene terephthalate.

[0014] The material of the upper base film and the lower base film can be the same or different, and is selected as needed.

[0015] Preferably, the thickness of the upper base film and the lower base film is 0.001-2 mm, and further preferably 0.01-1 mm. The thickness of the upper base film and the lower base film can be the same or different, and is selected as needed.

[0016] The length of the lower base film is greater than or equal to the length of the diffusion source, and the width of the lower base film is greater than or equal to the width of the diffusion source. The length and width of the upper base film are not particularly limited, and preferably, the length and width of the upper base film are greater than or equal to the length and width of the diffusion source, respectively.

[0017] Preferably, the RE a W b , wherein 50≤a≤99, and a+b=100 is satisfied.

[0018] Preferably, the adhesive in the diffusion source is one or more of polyurethane adhesive, polyacrylate adhesive, polyvinyl alcohol adhesive, polyvinyl formal adhesive, epoxy resin, and phenolic resin.

[0019] Preferably, the alloy of the general formula RE a W b , and the mass ratio of the adhesive is 2-10:1-2; further preferably, the mass ratio is 3-4:1-2.

[0020] The second object of the present application is achieved by the following technical solution:

[0021] A preparation method of a magnet diffusion source film, comprising the following steps:

[0022] 1) preparing a diffusion source sol;

[0023] 2) attaching the diffusion source sol to a lower base film;

[0024] 3) covering an upper base film to form an initial diffusion source film with a "sandwich" structure;

[0025] 4) performing heating and drying and cooling treatment on the initial diffusion source film to obtain a diffusion source film.

[0026] Preferably, the preparation method of the diffusion source sol comprises the following steps:

[0027] a general formula RE aW b The alloy is made into alloy powder; the alloy powder is mixed with dispersant and binder to obtain initial colloid; the initial colloid is stirred to discharge gas, i.e. to obtain diffusion source sol, wherein RE is at least one of Dy, Tb, Pr, Nd, La, Ce, Y, Gd, Ho; W is at least one of Cu, Al, Ga, In, Sn, Fe, Co, Ni, Ti, Zr, Mg; a and b are mass percentages, 50≤a≤100, and a+b=100.

[0028] The general formula is RE a W b The alloy is made into alloy powder by one or more of the following processes, such as rough crushing (using a crusher, the particle size of the rough powder after crushing is between 1-50 mm), hydrogen crushing, and air flow grinding process. Preferably, the average particle size of the alloy powder is 2-50 microns.

[0029] In the preparation method of the diffusion source sol, preferably, the dispersant is a liquid solvent, including one or more of alcohol solvents (such as ethanol, propanol, butanol, etc.), ketone solvents (such as acetone, butanone, cyclohexanone, etc.), ether solvents (such as diethyl ether, isopropyl ether, butyl ether, tetrahydrofuran, etc.), ester solvents (such as ethyl acetate, propyl acetate, etc.).

[0030] In the preparation method of the diffusion source sol, preferably, the mass ratio of the alloy powder, the dispersant, and the binder is 2-10:1-10:1-2; further preferably, the mass ratio is 3-4:2-4:1-2.

[0031] In the preparation method of the diffusion source sol, preferably, the mixing of the alloy powder, the dispersant, and the binder is carried out in an oxygen-controlled environment, and the oxygen content in the oxygen-controlled environment is ≤100 ppm.

[0032] In the preparation method of the diffusion source sol, preferably, the stirring time of the initial colloid is ≥30 min, and further preferably 30-300 min. The stirring speed can be listed as 100-2000 rpm.

[0033] Preferably, the viscosity of the diffusion source sol is 100-3000 mPa·s.

[0034] In step 2) of the preparation method of the diffusion source film, there are many ways to attach the diffusion source sol to the lower layer of the substrate film, such as spray coating, screen printing, brushing, and pouring. Preferably, the diffusion source sol is attached to the lower layer of the substrate film by spray coating. In the spray coating process, the diffusion source sol is deposited on the surface of the lower layer of the substrate film by a spray gun, the height of the spray gun is 10-50 cm, and the liquid flow rate of the spray gun is 50-500 ml / min.

[0035] In step 2 of the method for preparing the diffusion source film, preferably, the thickness of the diffusion source sol attached to the lower substrate film is 0.001-2 mm, and more preferably 0.01-1 mm.

[0036] In step 3 of the method for preparing the diffusion source film, preferably, the upper substrate film is pressed together with the lower substrate film having the diffusion source sol attached thereto by two rollers to form an initial diffusion source film. Preferably, the radial pressure of the two rollers is 0.5-5 N. The two rollers rotate in opposite directions under the action of the tail end traction force, and no self-spin driving force is generated by the rollers.

[0037] In step 4 of the method for preparing the diffusion source film, preferably, the heating and drying can be at least one of, for example, heat source drying, hot air drying, infrared drying, and microwave drying, and the heating and drying time is ≥10 min. More preferably, the heating and drying time is 20-100 min.

[0038] The heating and drying can be carried out in a tunnel heating and drying device. The initial diffusion source film passes through the tunnel heating and drying device under the action of the tail end traction force of the roller. The heating and drying mode of the tunnel heating and drying device is at least one of, for example, heat source drying, hot air drying, infrared drying, and microwave drying.

[0039] After the diffusion source sol is heated and dried, the dispersant volatilizes, and a diffusion source including an alloy with the general formula RE a W b and a binder is formed.

[0040] In step 4 of the method for preparing the diffusion source film, preferably, the cooling treatment can be at least one of, for example, cold source cooling, cold air cooling, and cold liquid cooling, and the cooling treatment time is ≥10 min. More preferably, the cooling treatment time is 20-100 min.

[0041] The cooling treatment can be carried out in a tunnel cooling device. The initial diffusion source film passes through the tunnel cooling device under the action of the tail end traction force of the roller. The cooling mode of the tunnel cooling device is at least one of, for example, cold source cooling, cold air cooling, and cold liquid cooling.

[0042] Preferably, after the heating and drying and the cooling treatment, the diffusion source film is obtained, and the diffusion source film is collected and stored by a winding drum. The diffusion source film is collected by the winding drum with a traction roller at the tail end.

[0043] The third object of the present application is achieved by the following technical scheme:

[0044] The application of the magnet diffusion source film includes the following steps: covering the diffusion source film to the upper and lower surfaces of the magnet to be diffused, and performing diffusion heat treatment to obtain a diffusion magnet product.

[0045] The diffusion source film is cut before use so that the diffusion source film completely covers the diffusion surface of the magnet to be diffused.

[0046] Preferably, the magnet to be diffused is a sintered neodymium-iron-boron magnet with a thickness of 1-10 mm. The thickness is defined as the straight-line distance between the upper and lower surfaces of the magnet to be diffused covered by the diffusion source film.

[0047] Preferably, the diffusion heat treatment is carried out in a vacuum heat treatment furnace with a vacuum degree of ≤1×10 -2 Pa.

[0048] Preferably, the diffusion heat treatment comprises: heating from room temperature to 450-600 ℃ for 1-3 hours, then heating to 800-950 ℃ for 1-8 hours and cooling to room temperature, and finally heating to 400-550 ℃ for 1-8 hours and cooling to room temperature. The cooling is preferably air cooling. Advantages

[0049] Compared with the prior art, the present application has the following advantages:

[0050] 1. The diffusion source film prepared by the present application is a solid diffusion source, has good uniformity and stability, and has a certain flexibility, can be collected by a winding drum collecting device to form a roll, and is convenient for long-term mass storage and long-distance transportation.

[0051] 2. The diffusion source film prepared by the present application is suitable for diffusion source attachment of magnets of various sizes, and the diffusion source attachment process is simple to operate, suitable for neodymium-iron-boron enterprises of various scales, and only needs to spread the diffusion source film on the upper and lower surfaces of the magnet during the operation process, which is convenient for controlling the weight gain of the diffusion source.

[0052] 3. The diffusion source film prepared by the present application has good matching with the magnet to be diffused, has no diffusion source blank area, and after grain boundary diffusion, the prepared diffusion magnet has good uniformity and consistency of performance, the effect is more stable, and can be applied to fields with higher requirements for magnet performance precision.

[0053] 4. The diffusion source film prepared by the present application has good diffusion coercivity amplification effect, has less damage to the residual magnetism of the magnet, and can fully play the advantages of grain boundary diffusion.

[0054] 5、The upper and lower layer film material of the present application is carefully designed, and the film made of polyvinyl alcohol, polyurethane, polycarbonate and polyethylene terephthalate is preferentially adopted, and the heat treatment is carried out at 450-600 DEG C first, and the polyvinyl alcohol, polyurethane, polycarbonate and polyethylene terephthalate film is chemically reacted and cracked into small molecules at this temperature, and small molecule gases including CO, H2O or CO2 are released, and are pumped out by the diffusion pump, and a small amount of residual small molecules such as cyclic compounds have little harmful effect on the grain boundary diffusion effect.

[0055] 6、The present application adopts double-layer film to cover and protect the intermediate diffusion source, and compared with the diffusion source film attached to the single-layer film, has more excellent coercivity improvement effect and more stable improvement effect.

[0056] 7、The diffusion source film prepared by the technical scheme of the present application is suitable for various diffusion source component systems, has simple preparation process, high production efficiency, and can be used for batch preparation of high-consistency neodymium-iron-boron magnets for new energy vehicles. BRIEF DESCRIPTION OF DRAWINGS

[0057] Fig. 1 is a structure schematic view of a magnet diffusion source film of the present application;

[0058] Fig. 2 is a simplified flow chart of the process steps used in the preparation method of a magnet diffusion source film of the present application;

[0059] Fig. 3 is a scanning electron microscope graph of the cross section of the magnet diffusion source film prepared in Example 1 of the present application.

[0060] In Fig. 1, 1 is a diffusion source, 2 is a lower layer substrate film, and 3 is an upper layer substrate film.

[0061] In Fig. 3, A is an upper layer substrate film, B is a lower layer substrate film, and C is a diffusion source. Embodiment of the present application

[0062] The technical scheme of the present application is further described and explained below by specific examples and drawings, and it should be understood that the specific examples described herein are only used to help understand the present application, and are not used to limit the present application. The drawings used herein are only used to better illustrate the disclosed content of the present application, and do not limit the scope of protection. If not specially stated, the raw materials used in the examples of the present application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0063] Figure 1 is a schematic diagram of a structure of a magnet diffusion source film provided by the present application. As shown, the magnet diffusion source film comprises, from top to bottom, an upper substrate film 2, a diffusion source 1, and a lower substrate film 3. Figure 2 shows a simplified process flow diagram for preparing the magnet diffusion source film in an embodiment. The preparation process is simple and comprises, in brief: spraying the diffusion source sol onto the lower substrate film; pressing the upper substrate film and the lower substrate film with the diffusion source sol attached thereto together through two rollers to form an initial diffusion source film; passing the initial diffusion source film through a tunnel heating and drying device under the traction of a tail end roller; then passing the initial diffusion source film through a tunnel cooling device under the traction of the tail end roller to obtain the diffusion source film; and collecting the diffusion source film through a winding drum collecting device to form a winding drum storage. Example 1

[0064] The alloy of general formula Pr 20 Tb 50 Cu 30 The alloy with mass percentage of 80% was prepared into alloy powder with an average particle size of 15 μm through coarse crushing, hydrogen crushing, and air flow milling processes; the alloy powder was stirred (500 rpm) with a dispersant (a mixture of ethanol and diethyl ether with a volume ratio of 4:1) and a binder (polyacrylate adhesive) in a mass ratio of 3:2:2 in an environment with an oxygen content of 80 ppm for a stirring time of 50 min to obtain a diffusion source sol with a viscosity of 500 mPa•s; the diffusion source sol was attached to the lower substrate film (polycarbonate film with an average thickness of 70 μm) through spraying (spraying thickness of 350 μm), the spraying gun height was 15 cm, and the liquid flow rate of the spraying gun was 350 ml / min; the upper substrate film (polycarbonate film with an average thickness of 70 μm) and the lower substrate film with the diffusion source sol attached thereto were pressed together through two rollers to form an initial diffusion source film, the radial pressure of the two rollers was selected to be 4 N, and the rollers were turned with traction; the initial diffusion source film was passed through a tunnel heating and drying device under the traction of a tail end roller, and the initial diffusion source film was dried for 40 min through hot air drying; after drying, the diffusion source film was further passed through a conveyor belt and then passed through a tunnel cooling device, and the diffusion source film was cooled for 20 min by passing cooling nitrogen gas to obtain the diffusion source film; finally, the diffusion source film was collected through a winding drum with a traction roller at the tail end.

[0065] Figure 3 is a scanning electron microscope image of a cross section of the magnet diffusion source film prepared in Example 1 of the present application. As shown, the diffusion source is located between the upper and lower substrate films, and the thickness is uniform.

[0066] First, 5 commercial N55 magnets with same composition were selected as the base, and wire electrical discharge machining was performed on the base to obtain 5 cylindrical magnets with a diameter of 4*φ10 and a thickness of 4 mm, which were polished and labeled as 1-1, 1-2, 1-3, 1-4 and 1-5, respectively; then 8 diffusion source discs were cut from the diffusion source film roll, which can completely cover the diffusion surface of the magnet to be diffused;

[0067] The diffusion source discs were attached to the upper and lower surfaces of the magnets 1-1, 1-2, 1-3 and 1-4, respectively, and then placed in the mold on the sintering furnace tray together with the magnet 1-5 without diffusion source;

[0068] The heat treatment tray with the diffusion source film and the magnet to be diffused was placed in the vacuum heat treatment furnace, and after the furnace door was closed and vacuumized, the program for sintering neodymium-iron-boron magnet grain boundary diffusion treatment was set. The specific program is as follows: first, the temperature in the furnace is raised to 480 ℃, and the temperature is kept for 2 hours. Then the temperature is continuously raised to 900 ℃, and the temperature is kept for 6 hours, and then air-cooled to room temperature. Finally, the temperature is raised to 500 ℃, and the temperature is kept for 4 hours, and then air-cooled to room temperature. During the process, the vacuum degree is less than 7.5*10 -3 Pa.

[0069] The diffused magnets were tested for magnetic properties, and the test results are shown in Table 1.

[0070] Table 1

[0071]

[0072] In this example, the magnet surface did not oxidize and rust, and there was no diffusion source blank area, indicating that the diffusion source and the diffusion base of the present application have good matching. In addition, from the data comparison, it can be seen that the remanence and magnetic energy product of the magnets 1-1, 1-2, 1-3 and 1-4 are reduced, and the coercive force is greatly increased compared with the magnet 1-5. Therefore, the diffusion source film prepared by the technical scheme of the present application can effectively improve the coercive force of the neodymium-iron-boron magnet. Example 2

[0073] Comparison of the effects of different diffusion heat treatment methods

[0074] The general formula of the diffusion source is Nd 15 Dy 70 Al 15The alloy with a mass percentage of 99.9% is prepared into alloy powder with an average particle size of 25 μm through coarse crushing, hydrogen crushing and air flow milling processes; the alloy powder is stirred (500 rpm) with a dispersant (ethanol) and a binder (a mixed agent formed by polyurethane adhesive and polyacrylate adhesive in a volume ratio of 3:2) in a mass ratio of 3:2:2 in an environment with an oxygen content of 80 ppm, and a stirring time of 50 min, to obtain a diffusion source sol with a viscosity of 500 mPa•s; the diffusion source sol is attached on a lower substrate film (a polyurethane film with an average thickness of 100 μm) by spraying (a spraying thickness of 500 μm), a spray gun height of 15 cm and a liquid flow rate of the spray gun of 400 ml / min; an upper substrate film (a polyurethane film with an average thickness of 100 μm) and the lower substrate film with the diffusion source sol attached thereon are pressed together by two upper and lower rollers to form an initial diffusion source film, a radial pressure of the two rollers is 4 N, and the rollers are free to turn; the initial diffusion source film is dried by a tunnel heating and drying device under the traction of a tail-end roller, and the diffusion source film is dried by hot air for 40 min; after drying, the diffusion source film is further conveyed into a tunnel cooling device and cooled by cold air for 20 min, to obtain a diffusion source film; finally, the diffusion source film is collected by a winding drum with a tail-end traction roller.

[0075] First, six commercial N55 magnets with the same composition were selected as the matrix, and the six 4*φ10 cylindrical magnets were obtained by wire electrical discharge machining, and were polished and labeled as 2-1, 2-2, 2-3, 2-4, 2-5 and 2-6; then, 12 diffusion source discs capable of completely covering the diffusion surfaces of the to-be-diffused magnets were cut from the diffusion source film roll;

[0076] The diffusion source discs were attached to the upper and lower surfaces of the magnets 2-1, 2-2, 2-3, 2-4, 2-5 and 2-6 respectively, and then were placed in the molds on the sintering furnace tray;

[0077] The heat treatment tray with the diffusion source film and the to-be-diffused magnets was placed in different vacuum heat treatment furnaces, the furnace door was closed and vacuumized, and different programs were set for diffusion treatment.

[0078] The specific procedure is as follows: 1, 2 magnet first furnace temperature to 300 ℃, 2 hours. Then continue to heat to 900 ℃, 6 hours, air cooling fast cooling to room temperature after re-heating to 500 ℃, 4 h after air cooling fast cooling to room temperature; 3, 4 magnet first furnace temperature to 450 ℃, 2 hours. Then continue to heat to 900 ℃, 6 hours, air cooling fast cooling to room temperature after re-heating to 500 ℃, 4 h after air cooling fast cooling to room temperature; 5, 6 magnet directly to the furnace to 900 ℃, 6 hours, air cooling fast cooling to room temperature after re-heating to 500 ℃, 4 h after air cooling fast cooling to room temperature, during the vacuum degree is less than 7.5*10 -3 Pa.

[0079] The diffused magnet is subjected to magnetic property test, and the test results are shown in Table 2.

[0080] Table 2

[0081]

[0082] In the present example, the magnet surface is not oxidized and rusted, and the diffusion source blank area does not appear, which indicates that the diffusion source and the diffusion matrix of the present application have good matching. In addition, from the data comparison, it can be seen that the remanence and magnetic energy product of all the magnets are reduced, but the reduction amplitude of the 2-3, 2-4 magnets is lower than that of the 2-1, 2-2, 2-5, 2-6 magnets; the coercive force of the 2-1, 2-2, 2-5, 2-6 magnets is higher than that of the 2-3, 2-4. Among them, the 2-3, 2-4 magnets are subjected to grain boundary diffusion treatment by using the diffusion heat treatment process in the technical scheme of the present application, and have the best comprehensive performance. Therefore, the diffusion source of the neodymium-iron-boron magnet prepared by the present application needs to be first heat treated in a specific temperature range to make the upper and lower substrate films completely crack and decompose, and then discharged, and then subjected to high-temperature diffusion, the effect will be better. Example 3

[0083] Comparison of the effects of different hot air drying times

[0084] The general formula is Tb 75 Fe 10 Al 10Ga5 (mass percentage) alloy is prepared into alloy powder with an average particle size of 25 μm through coarse crushing, hydrogen crushing and air flow milling processes; the alloy powder is stirred (600 rpm) with a dispersant (a mixed solution of ethanol and acetone with a volume ratio of 4:1) and a binder (a mixed agent formed by polyvinyl formal adhesive and phenolic resin with a volume ratio of 6:1) in a mass ratio of 3:2:2 in an environment with an oxygen content of 80 ppm, and a diffusion source sol with a viscosity of 500 mPa•s is obtained after stirring for 50 min; the diffusion source sol is attached to a lower substrate film (polyethylene terephthalate film with an average thickness of 100 μm) by spraying (a spraying thickness of 500 μm), a spray gun height of 15 cm and a liquid flow rate of the spray gun of 400 ml / min; an upper substrate film (polyethylene terephthalate film with an average thickness of 100 μm) is pressed together with the lower substrate film with the diffusion source sol attached thereto by two upper and lower rollers to form an initial diffusion source film, a radial pressure of the two rollers is selected as 4 N, and the rollers are free to rotate; the initial diffusion source film is dried by a tunnel heating and drying device under the traction of a tail end roller, and the diffusion source film with a length of one meter is dried for 10, 20, 30 and 40 minutes respectively corresponding to labels A, B, C and D by hot air drying.

[0085] After drying, the diffusion source film is further conveyed into a tunnel cooling device by a conveying belt and cooled for 20 minutes by cold air cooling to obtain the diffusion source film; finally, the diffusion source film is collected by a winding drum with a traction roller at the tail end.

[0086] First, five commercial N55 magnets with the same composition are selected as the matrix, and the five N55 magnets are processed by wire electrical discharge machining to obtain five cylindrical magnets with a diameter of 4*φ10 and a thickness of 4 mm, which are polished and labeled as 3-1, 3-2, 3-3, 3-4 and 3-5 respectively;

[0087] Then, two diffusion source discs capable of completely covering the diffusion surfaces of the magnets to be diffused are cut from the A, B, C and D diffusion source film rolls respectively, and the A, B, C and D diffusion source discs are attached to the upper and lower surfaces of the 3-1, 3-2, 3-3 and 3-4 magnets respectively, and then the magnets with the diffusion source discs are placed in the mold on the sintering furnace tray together with the 5th magnet without the diffusion source disc;

[0088] The heat treatment tray with the diffusion source film and the magnet to be diffused is placed in a vacuum heat treatment furnace, the furnace door is closed and vacuumized, and then a diffusion treatment program is set. The specific program is as follows: first, the furnace is heated to 500 ℃, and then the temperature is kept for 2 hours, and then the temperature is increased to 900 ℃, and then the temperature is kept for 6 hours, and then the furnace is air-cooled to room temperature, and finally the temperature is increased to 520 ℃, and then the temperature is kept for 8 hours, and then the furnace is air-cooled to room temperature, and the vacuum degree is less than 7.5×10 -3Pa;

[0089] The magnetic properties of the diffused magnet were tested, and the results are shown in Table 3.

[0090] Table 3

[0091]

[0092] In this embodiment, no oxidation or rust occurred on the magnet surface, nor were there any blank areas in the diffusion source, indicating that the diffusion source and the diffusion substrate of this invention have good matching. Furthermore, data comparison shows that the remanence of magnets 3-1, 3-2, 3-3, and 3-4 decreased. Regarding coercivity, the increase in coercivity for magnets 3-1 and 3-2 was lower than that for magnets 3-3 and 3-4, but both were higher than that for magnet 3-5. This indicates that sufficient drying time is required during the diffusion source film preparation process to ensure the stability of its diffusion performance and improve coercivity. Example 4

[0093] Let the general formula be Tb 70 Cu 30 The alloy (by mass percentage) was prepared into alloy powder with an average particle size of 15 μm through coarse crushing, hydrogen crushing, and air jet milling. The alloy powder was then stirred with a dispersant (ethanol) and a binder (polyvinyl alcohol adhesive) at a mass ratio of 3:2:2 (500 rpm) for 50 min in an environment with an oxygen content of 80 ppm, yielding a diffusion source sol with a viscosity of 500 mPa•s. This diffusion source sol was then applied to a lower substrate film (polycarbonate film, average thickness 70 μm) by spraying (350 μm thickness) at a spray gun height of 15 cm and a liquid flow rate of 350 mPa•s. ml / min; the upper substrate film (polycarbonate film, average film thickness 70μm) and the lower substrate film with diffusion source sol attached are pressed together by two rollers to form the initial diffusion source film. The radial pressure of the two rollers is 4N, and the rollers can rotate freely; the initial diffusion source film is passed through the tunnel heating and drying device under the traction force of the tail roller and dried with hot air for 40 minutes; after drying, it is further fed into the tunnel cooling device by conveyor belt and cooled with cold air for 20 minutes to obtain the diffusion source film; finally, the diffusion source film is collected by a drum with a traction roller at the tail end.

[0094] Thirty commercial N55 magnets of the same composition from the same batch were selected as the base material and subjected to wire electrical discharge machining to obtain 30 cylindrical magnets with a thickness of 4 mm and a diameter of 4 mm. The surface of the magnets was polished and labeled as 4-1, 4-2, 4-3, 4-4, ... 4-28, 4-29, 4-30.

[0095] 20 diffusion source wafer pieces which can completely cover the diffusion surface of the magnet to be diffused were cut from the diffusion source film roll of Example 4; the diffusion source wafer pieces were respectively attached to the upper and lower surfaces of the magnets No. 4-1 to 4-10, and then placed in the mold on the sintering furnace tray;

[0096] The heat treatment tray bearing the diffusion source film and the magnet to be diffused was placed in the vacuum heat treatment furnace, the furnace door was closed and vacuumized, and then the diffusion process was set. The specific process was as follows: first, the furnace was heated to 480 ℃, and kept for 2 hours. Then, the temperature was continuously increased to 900 ℃, and kept for 6 hours, and then air-cooled and rapidly cooled to room temperature. Finally, the temperature was increased to 500 ℃, and kept for 4 hours, and then air-cooled and rapidly cooled to room temperature, and the vacuum degree was less than 7.5 × 10 -3 Pa.

[0097] The magnetic properties of the diffused magnets No. 4-1 to 4-10 were tested, and the test results are shown in Table 4.

[0098] Table 4

[0099] Comparative Example 1

[0100] The diffusion source sol prepared in Example 4 (spraying thickness 350 μm) was sprayed onto the upper and lower surfaces of the magnets No. 4-11 to 4-20 by the direct spraying method in the conventional process. Then, the heat treatment tray bearing the magnet to be diffused was placed in the vacuum heat treatment furnace, the furnace door was closed and vacuumized, and then the diffusion process was set. The specific process was as follows: first, the furnace was heated to 480 ℃, and kept for 2 hours. Then, the temperature was continuously increased to 900 ℃, and kept for 6 hours, and then air-cooled and rapidly cooled to room temperature. Finally, the temperature was increased to 500 ℃, and kept for 4 hours, and then air-cooled and rapidly cooled to room temperature, and the vacuum degree was less than 7.5 × 10 -3 Pa.

[0101] The magnetic properties of the diffused magnets No. 4-11 to 4-20 were tested, and the test results are shown in Table 5.

[0102] Table 5

[0103] Comparative Example 2

[0104] The diffusion source sol prepared in Example 4 (spraying thickness 350 μm) was sprayed onto the upper and lower surfaces of the magnets No. 4-11 to 4-20 by the direct spraying method in the conventional process. Then, the heat treatment tray bearing the magnet to be diffused was placed in the vacuum heat treatment furnace, the furnace door was closed and vacuumized, and then the diffusion process was set. The specific process was as follows: first, the furnace was heated to 480 ℃, and kept for 2 hours. Then, the temperature was continuously increased to 900 ℃, and kept for 6 hours, and then air-cooled and rapidly cooled to room temperature. Finally, the temperature was increased to 500 ℃, and kept for 4 hours, and then air-cooled and rapidly cooled to room temperature, and the vacuum degree was less than 7.5 × 10 70 Cu 30The alloy with a mass percentage of 100% is prepared into alloy powder with an average particle size of 15 μm through coarse crushing, hydrogen crushing and air flow milling processes. The diffusion source alloy powder is uniformly dispersed in anhydrous ethanol, and the diffusion source powder is attached to the surface of the 4-21 to 4-30 magnet through a conventional impregnation process. Then, the heat treatment tray with the magnet to be diffused is placed in a vacuum heat treatment furnace, the furnace door is closed and vacuumized, and then a program is set for diffusion treatment. The specific program is as follows: first, the furnace is heated to 480 ℃, and then kept for 2 hours. Then, the temperature is continuously increased to 900 ℃, and then kept for 6 hours, and then rapidly cooled to room temperature. Finally, the temperature is increased to 500 ℃, and then kept for 4 hours, and then rapidly cooled to room temperature. During the process, the vacuum degree is less than 7.5×10 -3 Pa.

[0105] The magnetic properties of the diffused 4-21 to 4-30 magnets are tested, and the test results are shown in Table 6.

[0106] Table 6

[0107]

[0108] In the examples and comparative examples, no oxidation and rusting occurs on the surface of the magnet, and no diffusion source blank area occurs, which indicates that the diffusion source and the diffusion substrate have good matching. In addition, through the analysis of the performance of the 4-1 to 4-30 magnets, it is found that the remanence of the first batch of 4-1 to 4-10 magnets is reduced, but the coercivity is well improved. Further analysis and calculation show that the data variance of the coercivity of the 4-1 to 4-10 magnets is 0.0321, indicating that the improvement effect is very stable. The remanence of the second batch of 4-11 to 4-20 magnets is also reduced, and the coercivity can also be improved to a certain extent. However, further analysis and calculation show that the data variance of the coercivity of the 4-11 to 4-20 magnets is 0.2912, indicating that the improvement effect fluctuates relatively large, and the performance consistency deteriorates. Finally, the remanence of the third batch of 4-21 to 4-30 magnets is also reduced, and the coercivity can also be improved to a certain extent. However, further analysis and calculation show that the data variance of the coercivity of the 4-21 to 4-30 magnets is 2.6898, indicating that the improvement effect fluctuates greatly and is unstable. In summary, the same grain boundary diffusion process is adopted, the thin film of the magnet diffusion source of the present application is used for grain boundary diffusion of the sintered neodymium-iron-boron magnet, the improvement effect is more stable, and it can be applied to the field with higher requirements for magnet performance precision. Comparative Example 3

[0109] The general formula of the alloy is Pr 20 Tb 50 Cu 30The alloy with a mass percentage of 99.5% is prepared into alloy powder with an average particle size of 15 μm through coarse crushing, hydrogen crushing and air flow milling processes; the alloy powder is stirred (500 rpm) with a dispersant (a mixed solution of ethanol and diethyl ether with a volume ratio of 4:1) and a binder (a polyacrylate adhesive) in a mass ratio of 3:2:2 in an environment with an oxygen content of 80 ppm for 50 min to obtain a diffusion source sol with a viscosity of 500 mPa·s; the diffusion source sol is attached to a substrate film (a polycarbonate film with an average thickness of 70 μm) by spraying (a spraying thickness of 350 μm) at a spray gun height of 15 cm and a liquid flow rate of the spray gun of 350 ml / min; then the film with the attached diffusion source slurry is dried by hot air in a tunnel heating and drying device under the action of roller traction for 40 min; after drying, the diffusion source film is further conveyed into a tunnel cooling device by a conveying belt, cooled by nitrogen for 20 min, and a diffusion source film with a single-layer film structure is obtained.

[0110] Five commercial N55 magnets with the same composition are selected as the substrates, and are processed by wire electrical discharge machining to obtain five cylindrical magnets with a diameter of 4*φ10 and a thickness of 4 mm. The magnets are polished and labeled as 5-1, 5-2, 5-3, 5-4 and 5-5, respectively. Then, eight diffusion source discs capable of completely covering the diffusion surfaces of the magnets to be diffused are cut from the diffusion source film with a single-layer film structure. The diffusion source discs are attached to the upper and lower surfaces of the magnets 5-1, 5-2, 5-3 and 5-4, respectively, and then are placed in a mold on a sintering furnace tray together with the magnet 5-5 without the diffusion source disc.

[0111] The heat treatment tray with the diffusion source film and the magnets to be diffused is placed in a vacuum heat treatment furnace. After the furnace door is closed and vacuumized, a program for sintering Nd-Fe-B magnets is set for grain boundary diffusion treatment. The specific program is as follows: first, the furnace is heated to 480 ℃ and kept for 2 hours. Then, the temperature is continuously increased to 900 ℃, kept for 6 hours and then air-cooled to room temperature. Finally, the temperature is increased to 500 ℃, kept for 4 hours and then air-cooled to room temperature. During the process, the vacuum degree is less than 7.5×10 -3 Pa. The magnetic properties of the diffused magnets are tested, and the test results are shown in Table 7.

[0112] Table 7

[0113]

[0114] Compared with Example 1, the diffusion source film with a single-layer film structure has a poor diffusion effect and a lower coercivity improvement effect than Example 1. In addition, the consistency of the single-layer film structure diffusion magnet is not as good as the diffusion source film with a double-layer structure in the technical solution of the present application.

[0115] Aspects, embodiments, features of the present application should be considered in all aspects as illustrative and not restrictive, the scope of the present application being defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art, and the foregoing description is not to be construed as limiting the application. The scope of the application is defined by the claims.

[0116] In the preparation method of the present application, the order of each step is not limited to the order listed, and for those of ordinary skill in the art, changes in the order of each step without creative effort are within the protection scope of the present application. In addition, two or more steps or actions can be carried out simultaneously.

[0117] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the scope of the application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, and it is not necessary or possible to fully describe all embodiments here. Any obvious changes or variations derived from the spirit of the present application are still within the protection scope of the present application, and any additional limitations are contrary to the spirit of the present application.

Claims

1. A magnetically diffusive source film, characterized in that, The diffusion source is sequentially arranged between the upper base film and the lower base film. The diffusion source includes an alloy and a binder, and has a general formula of REaWb a W b wherein RE is at least one of Dy, Tb, Pr, Nd, La, Ce, Y, Gd, and Ho; W is at least one of Cu, Al, Ga, In, Sn, Fe, Co, Ni, Ti, Zr, and Mg; a and b are mass percentages, 50 ≤ a ≤ 100, and a + b = 100.

2. A magnetically diffusive source thin film according to claim 1, wherein The upper base film and the lower base film are flexible films, and the materials of the upper base film and the lower base film are one or more of polyvinyl alcohol, polyurethane, polycarbonate and polyethylene terephthalate.

3. A method of producing a magnetically diffusive source film, characterized by, The method comprises the following steps: 1) preparing a diffusion source sol; 2) attaching the diffusion source sol to the lower base film; 3) covering the upper base film to form an initial diffusion source film in a sandwich structure; 4) performing heating drying and cooling treatment on the initial diffusion source film to obtain the diffusion source film.

4. The preparation method according to claim 3, characterized in that, The preparation method of the diffusion source sol comprises the following steps: An alloy of general formula RE a W b is made into an alloy powder; the alloy powder is mixed with a dispersant and a binder to obtain an initial colloid; the initial colloid is stirred to discharge gas, i.e. a diffusion source sol is obtained; wherein RE is at least one of Dy, Tb, Pr, Nd, La, Ce, Y, Gd and Ho; W is at least one of Cu, Al, Ga, In, Sn, Fe, Co, Ni, Ti, Zr and Mg; a and b are mass percentages, 50≤a≤100, and a+b=100.

5. The preparation method according to claim 4, characterized in that, The average particle size of the alloy powder is 2-50 microns.

6. The preparation method according to claim 4, characterized in that, The dispersant is a liquid solvent, which comprises one or more of an alcohol solvent, a ketone solvent, an ether solvent and an ester solvent. The adhesive is one or more of a polyurethane adhesive, a polyacrylate adhesive, a polyvinyl alcohol adhesive, a polyvinyl formal adhesive, an epoxy resin and a phenolic resin.

7. The preparation method according to claim 4, characterized in that, The mass ratio of the alloy powder, the dispersant and the adhesive is 2-10:1-10:1-2.

8. The preparation method according to claim 4, characterized in that, The mixing of the alloy powder, the dispersant and the adhesive is performed in an oxygen-controlled environment, and the oxygen content in the oxygen-controlled environment is ≤100 ppm.

9. The preparation method according to claim 4, characterized in that, The viscosity of the diffusion source sol is 100-3000 mPa·s.

10. The method of claim 3, wherein, The diffusion source sol is attached to the lower base film by a spraying method, the height of the spray gun is 10-50 cm, and the liquid flow rate of the spray gun is 50-500 ml / min.

11. The preparation method according to claim 3, characterized in that, The upper base film and the lower base film with the diffusion source sol attached thereto are pressed together by two rollers to form an initial diffusion source film, and the radial pressure of the two rollers is 0.5-5 N.

12. The method of claim 3, wherein, The heating drying is performed in a tunnel heating drying device, and the heating drying mode of the tunnel heating drying device is at least one of heat source drying, hot air drying, infrared drying and microwave drying. The cooling treatment is performed in a tunnel cooling device, and the cooling mode of the tunnel cooling device is at least one of cold source cooling, cold air cooling and cold liquid cooling.

13. Use of a magnet diffusion source film prepared by the production method according to claim 3, characterized by, The method comprises the following steps: The diffusion source film is covered on the upper and lower surfaces of the magnet to be diffused, and diffusion heat treatment is performed to obtain a diffusion magnet product.

14. Use according to claim 13, characterized in that, The diffusion source film is cut before use to completely cover the diffusion surface of the magnet to be diffused. The magnet to be diffused is a sintered neodymium-iron-boron magnet, and the thickness thereof is 1-10 mm. The diffusion heat treatment is performed in a vacuum heat treatment furnace at a vacuum degree of < 1 x 10 -2 Pa.

15. The use according to claim 13, characterized in that, The diffusion heat treatment comprises the following steps: heating from room temperature to 450-600 ℃, maintaining for 1-3 hours, then heating to 800-950 ℃, maintaining for 1-8 hours, cooling to room temperature, finally heating to 400-550 ℃, maintaining for 1-8 hours, and cooling to room temperature.

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