Method for improving surface performance of bonded neodymium-iron-boron magnet

Abstract

The invention discloses a method for improving the surface performance of a bonded neodymium-iron-boron magnet, which comprises the following steps: injecting glue into a vacuum infiltration tank, putting a workpiece into the vacuum infiltration tank, carrying out vacuum pressure maintaining on the vacuum infiltration tank, releasing the pressure after the pressure maintaining is completed, taking out the workpiece, carrying out multi-stage cleaning on the workpiece, carrying out first-time hanging on the workpiece by utilizing a hanging tool, and carrying out second-time hanging on the workpiece by utilizing a hanging tool. The method comprises the following steps: carrying out pretreatment on a workpiece and a hanger, putting the hanger loaded with the workpiece into a first electrophoresis tank, carrying out first electrophoresis treatment to form a first surface coating, adjusting the contact position of the workpiece and the hanger, keeping away from the original contact point position, and carrying out second mounting and hanging on the workpiece; and the workpiece is put into a second electrophoresis tank to be subjected to second electrophoresis treatment so as to form a second surface coating. The invention provides a method for improving the coating quality of a bonded neodymium-iron-boron magnet so as to improve the surface performance of the bonded neodymium-iron-boron magnet.

Description

Technical Field

[0001] This invention relates to the field of NdFeB production, specifically a method for improving the surface properties of bonded NdFeB magnets. Background Technology

[0002] Bonded NdFeB magnets possess exceptional malleability, superior magnetic properties, and high cost-effectiveness, making them widely used in electronics, rail transportation, automotive, electrical engineering, aerospace, and communications technologies. However, bonded NdFeB magnets are highly reactive and have very high porosity with relatively large pore sizes, making them easily permeable to liquids such as water and solvents. This leads to problems such as corrosion, expansion, rusting, and pulverization, resulting in reduced or even lost magnetism, significantly limiting their lifespan and application areas.

[0003] Electrophoretic coatings offer better corrosion protection than spray paint coatings. However, because electrophoretic coatings are insulating after curing, they cannot be electrophoretically coated again to improve their corrosion protection or meet more complex corrosion protection requirements. Generally, paints with different corrosion protection properties are selected, and a composite coating method of electrophoresis + multiple spray paints is used to achieve higher (or more complex) corrosion protection requirements.

[0004] During the drying and curing process of the protective layer formed by electrophoresis and painting, air and moisture in the phosphate layer mesh on the surface of the bonded magnet, water and solvents in the coating adhering to the surface of the bonded magnet, and the opening and re-crosslinking of polymer chains (functional groups) during the curing reaction of the paint layer will generate gas that evaporates from the coating and forms gas channels. Since the coating does not have time to level and cure, some gas channels will form capillaries. These capillaries are exposed to the air and the usage environment. Corrosive substances such as water, acid and alkali liquids, and solvents in the air and the usage environment will gradually seep into the protective layer through the capillaries, resulting in poor moisture resistance and solvent resistance of the protective layer. When water, acid and alkali and other corrosive substances in the capillaries penetrate the protective layer, they will come into contact with the bonded magnet in the protective layer, thus also resulting in poor corrosion resistance. Experimental results show that bonded NdFeB magnets treated with existing surface treatment methods have extremely poor resistance to high humidity PCT (Potentially 24-48 hours) under normal conditions, 48 ​​hours under neutral salt spray test, and 48 hours under high temperature and humidity (85℃×85%RH). This makes them unsuitable for applications in industries with high requirements for moisture resistance and corrosion resistance, such as automotive safety components. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the coating quality of bonded NdFeB magnets, thereby enhancing the surface properties of bonded NdFeB magnets.

[0006] The technical solution adopted by this invention to solve the above problems is as follows: a method for improving the surface properties of bonded NdFeB magnets, comprising the following steps: S1: Inject glue into the vacuum impregnation tank; S2: Place the workpiece made of bonded NdFeB into a vacuum impregnation tank, with the glue level higher than the workpiece height; S3: Vacuum impregnation tank is subjected to vacuum pressure maintenance; S4: After completing the vacuum pressure holding, release the pressure and open the cover; S5: Remove the workpiece and spin-dry it; S6: Perform multi-stage cleaning on the workpiece; S7: Vibratory grinding and chamfering of the workpiece; S8: Use the hanger to hang the workpiece for the first time; S9: Perform the first pre-processing on the workpiece and fixture; S10: The fixture containing the workpiece is placed into the first electrophoresis tank for the first electrophoresis treatment to form the first surface coating; S11: Adjust the contact position between the workpiece and the hanger strip, avoiding the original contact point, and perform a second hang on the workpiece; S12: Place the workpiece into the second electrophoresis tank for a second electrophoresis treatment to form a second surface coating.

[0007] Compared with the prior art, the advantages of this invention are as follows: Through steps S1-S4, adhesive is impregnated into the pores of the bonded NdFeB magnet. This impregnation not only enhances the adhesion of the powder within the bonded NdFeB magnet but also fills the pores, thus preventing the infiltration of fluids such as water and solvents. This prevents problems such as corrosion, expansion, rusting, pulverization, or reduction or even loss of magnetism in the bonded NdFeB magnet. Then, through the design of steps S5 and S6, excess adhesive on the surface of the bonded NdFeB magnet is removed, ensuring the quality of subsequent processing and allowing time for the adhesive impregnated into the bonded NdFeB magnet to initially cure, ensuring the stability of the impregnated adhesive. The design of S7 increases the surface smoothness of the workpiece, thereby greatly improving the uniformity of the coating thickness on the surface of the bonded NdFeB magnet and enhancing the overall performance of the magnet in neutral salt spray tests, thus improving its corrosion resistance. Through the design of steps S8-S12, the workpiece undergoes two electrophoretic surface coating treatments. In step S11, the mounting and connection positions are adjusted. During the second electrophoretic treatment, the hanging points and marks from the first mounting are eliminated, thereby preventing corrosive substances such as water, acid and alkali liquids, and solvents in the air and the use environment from gradually seeping into the coating through the hanging points and marks, thus ensuring the quality of the coating and improving the surface quality of the bonded NdFeB magnet.

[0008] As an improvement of the present invention, step S10 includes a first curing: leveling at 80-100℃ for 10-30 minutes, followed by baking at 160±10℃ for 10-40 minutes; step S12 includes a second curing: leveling at 80-100℃ for 10-30 minutes, followed by baking at 180±10℃ for 30-40 minutes. Through this improvement, the temperature in the first curing is 5-20℃ lower than that in conventional curing and baking, so that a small portion of the polymer chains in the coating are not fully opened for cross-linking and curing, which helps to combine with the second surface coating in the second curing process. In the second curing process, the curing and leveling temperature and the curing and baking temperature are the same as those in the conventional curing process, but the baking time needs to be kept within a longer range to ensure that the polymer chains in both the first and second surface coatings are fully opened. Then, the first and second surface coatings are fully interleaved and recombined to form a new integral organic coating.

[0009] As an improvement of the present invention, in step S10, the first electrophoresis treatment uses a graphene two-component black conductive cationic cathodic electrophoretic coating with an electrophoretic film thickness of 10-35 μm. Through this improvement, the core problem to be solved in the double electrophoretic coating process is the conductivity of the second electrophoresis process. If the first surface coating does not have conductivity after being formed in the first electrophoresis process, the coating of the second surface coating cannot adhere to the first surface coating in the second electrophoresis process. This is why the second surface coating is usually applied by spraying. However, by using a graphene two-component black conductive cationic cathodic electrophoretic coating for the first electrophoresis treatment, the conductivity of the first surface coating can be guaranteed, thereby ensuring that the second surface coating can be successfully adhered to the first surface coating through the electrophoresis treatment.

[0010] As an improvement of the present invention, in step S12, the second electrophoresis treatment uses a nano-bicomponent cationic cathodic electrophoretic coating with an electrophoretic film thickness of 10-35 μm. Through the above improvement, the second surface coating is formed.

[0011] As an improvement of the present invention, in step S1, the gel time of the glue is adjusted to 20-30 minutes. When adjusting the gel time, a glass test tube with a diameter of 10mm × 75mm containing 2 ml of glue is placed in a water bath at 55±1℃, and the time is recorded. The time is checked every minute until gelation occurs, and the gel time is recorded. After step S6, the glue is initially cured. Through this improvement, by controlling the gel time of the glue, the integrity of the glue in the impregnation process is ensured, avoiding premature gelation that would cause premature interruption of the glue impregnation process. Furthermore, the initial curing of the glue is completed in the subsequent step S6, avoiding glue delamination in the steps after step S6, thus ensuring the impregnation quality of the glue and achieving higher processing efficiency.

[0012] As an improvement of the present invention, in step S3, the vacuum impregnation tank is evacuated to -0.098MPa or better, and the pressure is maintained for 10 minutes, with a total time not exceeding 14 minutes. This improvement ensures that the air in the bonded NdFeB magnet is fully removed, at which point foam will form in the adhesive. The foam will continue until it completely disappears and the liquid surface becomes calm like water. Then, during the depressurization process, because the internal pressure of the micropores in the workpiece is less than the external adhesive pressure, the adhesive is forced into the micropores of the workpiece, thus ensuring the integrity of the impregnation. The limited total time is to ensure that the workpiece can be removed from the vacuum impregnation tank after the adhesive has completed the negative pressure impregnation stage, avoiding the situation where the workpiece is difficult to remove from the vacuum impregnation tank after the adhesive has solidified. It also facilitates subsequent multiple cleanings to remove the adhesive from the surface of the workpiece.

[0013] As an improvement of the present invention, step S6 includes the following steps: S6.1: Level 1 cleaning: Move the workpiece to the first cleaning tank for cleaning. The water should be kept overflowing and agitated with compressed air. The workpiece should be turned over continuously during the process for more than 2 minutes; or clean manually for more than 2 minutes. S6.2: Secondary cleaning: Transfer the workpiece to the second cleaning tank and agitate it with compressed air, continuously turning the workpiece over during the process, for more than 2 minutes; or clean it manually for more than 2 minutes. S6.3: Three-stage cleaning: The workpiece is transferred to a third cleaning tank and agitated with compressed air. During this process, the workpiece is continuously turned over, and the water temperature is controlled at 50-60℃ for at least 2 minutes. Alternatively, it can be manually cleaned with warm water at 50-60℃ for at least 2 minutes. Through the aforementioned improvements, the multiple cleaning steps S6.1, S6.2, and S6.3 ensure that the adhesive on the workpiece surface is thoroughly removed, thereby guaranteeing the quality of subsequent processes. In step S6.3, controlling the water temperature to 50-60℃ during cleaning ensures that the adhesive has completed its initial curing at this point, preventing adhesive delamination in subsequent steps and ensuring the quality of adhesive penetration to achieve higher processing efficiency.

[0014] As an improvement of the present invention, in step S9, the pretreatment includes the following steps: S9.1: Degreasing and oil removal: Transfer the rack containing the workpiece to the degreasing solution, the pH value of the degreasing solution is 9-11; S9.2: First ultrasonic water wash; S9.3: Rust removal. The fixture containing the workpiece is placed in a rust removal solution for rust removal treatment. The pH value of the rust removal solution is 2 to 7. S9.4: Second ultrasonic water wash; S9.5: Surface conditioning, the fixture containing the workpiece is moved into the surface conditioning solution for surface conditioning treatment, the pH value of the surface conditioning solution is 9 to 11; S9.6: Medium-high temperature phosphating. The fixture containing the workpiece is moved into the phosphating solution for medium-high temperature phosphating treatment. The pH value of the phosphating solution is 2-4, the concentration of the phosphating solution is 8-20%, the temperature is 60-80℃, and the phosphating time is 10-30 minutes. S9.7: Medium-high temperature pure water washing. The fixtures containing workpieces are cleaned with medium-high temperature pure water. The temperature of the medium-high temperature pure water is 70-90℃, the washing time is 30-120 seconds, and the conductivity of the medium-high temperature pure water is ≤50μs / cm. S9.8: Rinse with pure water at room temperature for 1 minute. Through the above improvements, the bonded NdFeB magnets are thoroughly cleaned and treated, ensuring the adhesion of the paint film formed by subsequent electrophoresis and helping to ensure the quality of the paint film. In steps S8.6-S8.8, a phosphating layer of about 3μm will be formed on the surface of the bonded NdFeB magnets and the phosphating layer will be kept in a neutral state. By sealing the pores with glue, the electroplating solution, phosphating solution or electrophoresis solution will not remain in the magnet during subsequent electroplating, phosphating, electrophoresis and other processes, thus ensuring that the magnet performance will not be affected during long-term use.

[0015] As an improvement of the present invention, the hanging device is made of spring steel with a blade hanging strip. With this improvement, the hanging device can be mainly selected from two types: rigid blade hanging devices and spring hanging devices. The spring hanger in this invention has a significant drawback: 1. This invention involves multiple high-temperature processes, and after high temperature, the elasticity of the spring hanger will decrease, the hanging point position will change, and it will become coarse and unstable, which is not conducive to the high-quality forming of the electrophoretic coating. 2. Spring hangers also undergo electrophoretic coating, but their coating removal ability is weak, which makes the spring hangers non-recyclable and wastes resources; 3. During the suspension of a ring-shaped workpiece by the spring hanger, the size of the spring pull ensures that the contact point between the spring and the workpiece is at the end of the opening of the workpiece's inner hole, that is, at the connection between the inner hole of the workpiece and the end face of the workpiece, thus ensuring the minimum contact area between the spring and the workpiece. However, changes in the spring size reduce the controllability of the spring pull, making it more difficult to use. The rigid structure of the hanger also has obvious drawbacks. During the electrophoresis process, the workpiece oscillates in the electrophoresis solution, but the rigid structure hanger does not oscillate synchronously with the workpiece. This will change the position of the conductive point, resulting in defects such as the hanger point being too large or hanger marks, especially for workpieces that are conductive and are hung through the inner hole. The blade hanger strip structure made of spring steel combines the advantages of spring hangers and rigid structure hanger strips while avoiding their disadvantages. It does not lose elasticity due to high temperature, ensuring the stability of the contact between the blade hanger strip and the workpiece. It can also swing synchronously with the workpiece during electrophoresis, thereby ensuring the consistency of the conductive point position and avoiding the formation of excessively large hanging points or hanging marks.

[0016] As an improvement of the present invention, step S10 includes the following steps: back-dissolution detection, taking one or more electrophoretically coated workpieces or hangers and placing them back into the first electrophoresis tank, and judging the usage status of the liquid in the first electrophoresis tank based on the melting time of the first surface coating of the magnets on the workpiece or hanger. Through this improvement, during the electrophoresis process, it is necessary to ensure that the coating adheres smoothly to the workpiece. If the back-dissolution time is too short, it indicates that the electrophoretic coating material has too good fluidity, and the electrophoretic coating formed during the electrophoresis process is easily dissolved again, causing problems such as insufficient electrophoretic coating thickness, watermarks, and dull coating. If the back-dissolution time is too long, it indicates that the electrophoretic coating material has poor solubility, poor conductivity, and decreased stability, resulting in insufficient electrophoretic coating thickness and a rough surface with defects such as pinholes, orange peel, streaks, accumulation, particles, and dirt. The back-dissolution time is generally controlled within 4-20 minutes. If the back-dissolution time is outside this range, it is adjusted by adding acid or alkali and ultrafiltration. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall workpiece mounting structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the connection structure between the workpiece and the hanger in Embodiment 1 of the present invention.

[0019] Figure 3 This is a schematic diagram of the connection structure between the workpiece and the hanger in Embodiment 2 of the present invention.

[0020] Figure 4 This is a schematic diagram of the workpiece and fixture connection structure in Embodiment 3 of the present invention.

[0021] The diagram shows: 1. Workpiece, 2. Hanger. Detailed Implementation

[0022] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0023] like Figure 1-2 As shown in Example 1: A ring-shaped bonded NdFeB magnet with dimensions of outer diameter D26.5mm × D21.93mm × 17.55mm was selected. The weight of the bonded NdFeB magnet was 18.25 grams. The following method was used to perform surface anti-corrosion treatment on the bonded NdFeB magnet to improve its solvent resistance, anti-corrosion performance, and high temperature and high humidity resistance.

[0024] A method for improving the surface properties of bonded NdFeB magnets, comprising the following steps: S1: Inject glue into the vacuum impregnation tank and adjust the glue gel time to 20-30 minutes. While adjusting the gel time, place a D10mm×75mm glass test tube containing 2 ml of glue into a water bath at 55±1℃ and start recording the time. Check the time every minute until gelation occurs and record the gel time. S2: When the workpiece temperature cools down to below 37°C, use compressed air to blow away the adhering substances on the surface of workpiece 1. First, put workpiece 1 made of bonded NdFeB magnets into a clean mesh bag, and then put the mesh bag into a vacuum impregnation tank. The height of the glue should be at least 20mm higher than all workpieces 1, and the temperature of the glue should be kept below 20°C. Close the lid of the vacuum impregnation tank to ensure the glue's submerging effect on the bonded NdFeB magnets. During the glue impregnation process, the bonded NdFeB magnets will not be completely submerged due to the decrease in glue height caused by impregnation. The glue temperature is kept at 20°C to prevent the glue from curing prematurely and to ensure the stability of the glue, so as to prevent the glue reaction from occurring prematurely and to ensure the continuity of glue impregnation. S3: Vacuum impregnation tank is vacuum pressure maintained. The vacuum impregnation tank is evacuated to -0.098MPa or better, and the pressure is maintained for 10 minutes, with a total time not exceeding 14 minutes, to remove all air from the micropores of workpiece 1 and allow the adhesive to impregnate. During the vacuuming process, the height of the foam should be observed at any time. If the foam exceeds the vacuum port, the vacuum pump should be turned off in time. After the foam descends, the vacuuming should be turned on again. At the same time, pay attention to the adhesive level. If any workpiece 1 is found to be exposed above the adhesive surface, the entire bag of workpiece 1 containing that workpiece 1 must be re-impregnated. S4: After vacuum impregnation is completed, depressurize and open the lid. During the depressurization process, because the internal pressure of the micropores in workpiece 1 is less than the external colloid pressure, the colloid is forced into the micropores of workpiece 1. After opening the lid to complete impregnation, close the lid and introduce oxygen into the vacuum impregnation tank. At the same time, open the valve at the bottom of the vacuum impregnation tank to recover the glue. Uncured glue in the vacuum impregnation tank can be recovered. In the process of recovering glue, the recovery equipment does not need to come into contact with workpiece 1 and can recover glue to a large extent, ensuring the surface quality of workpiece 1. S5: Take out workpiece 1 and spin it dry. Transfer the mesh bag to the centrifuge tank and spin the glue at a speed of 80-150 RPM for 2-3 minutes each time, for a total of 4-5 times. Alternatively, use an air gun to blow off the excess glue on the surface of workpiece 1. The glue should be recycled and reused in a timely manner. S6: Perform multi-stage cleaning on workpiece 1; S6.1: Level 1 cleaning: Transfer the mesh bag to the first cleaning tank for cleaning. The water should be kept overflowing and agitated with compressed air. The mesh bag should be turned over continuously during the process for more than 2 minutes; or it can be cleaned by hand for more than 2 minutes. S6.2: Secondary cleaning: Transfer the mesh bag to the second cleaning tank and agitate it with compressed air, turning the mesh bag over continuously for at least 2 minutes; or clean it by hand for at least 2 minutes. S6.3: Three-stage cleaning: Transfer the mesh bag to the third cleaning tank and agitate it with compressed air. During this process, the mesh bag should be continuously turned over. Control the water temperature to 50-60℃ and clean for more than 2 minutes; or use warm water at 50-60℃ for manual cleaning for more than 2 minutes. At this point, the adhesive has completed its initial curing, which avoids the phenomenon of adhesive delamination in subsequent steps and ensures the quality of adhesive penetration, so as to achieve high processing efficiency. S7: Perform vibratory grinding and chamfering on workpiece 1; S7.1: Prepare a vibratory grinding and chamfering fluid, which is made by soaking round abrasive and pentahedral abrasive in a liquid rust inhibitor, wherein the pH value of the liquid rust inhibitor is 9; S7.2: Transfer workpiece 1 to a vibratory beveling machine containing vibratory beveling fluid for processing; S7.3: After vibratory grinding and chamfering for 10 minutes, take workpiece 1 for inspection. If the chamfer is 0.25mm, stop chamfering. S7.4: Move workpiece 1 to a spin dryer for spin drying, with the rotation speed controlled at 40 rpm, or dry it with an air gun; S7.5: Place workpiece 1 on gauze, with workpiece 1 spaced apart and not overlapping, dry workpiece 1 at 115℃ for 60 minutes, and perform vibratory grinding and chamfering on workpiece 1 to improve the uniformity of the surface coating thickness, thereby improving the corrosion resistance of bonded NdFeB magnets in neutral salt spray tests, etc. S8: Use fixture 2 to hang workpiece 1 for the first time; S9: Perform pretreatment on workpiece 1 and fixture 2; S9.1: Degreasing and oil removal. Transfer workpiece 1 to a degreasing solution (15% sodium carbonate, 10% sodium tripolyphosphate, 10% sodium dodecyl sulfonate). The pH of the degreasing solution is 9, and the time is 5 minutes. S9.2: First ultrasonic water wash, 1 minute; S9.3: Rust removal. Transfer workpiece 1 to the rust removal solution for rust removal treatment. The rust removal solution is TIWO830 with a concentration of 1.5% and a pH value of 2. The treatment time is 2 minutes. S9.4: Second ultrasonic water wash, 1 minute; S9.5: Surface conditioning. Move workpiece 1 into the surface conditioning solution for surface conditioning treatment. The surface conditioning solution is XH-12, the pH value of the surface conditioning solution is 11, and the time is 2 minutes. S9.6: Medium and high temperature phosphating. Workpiece 1 is transferred to the phosphating solution for medium and high temperature phosphating treatment. The phosphating solution is XH-34B, the pH value of the phosphating solution is 3, the concentration of the phosphating solution is 15%, the temperature is 60℃, and the phosphating time is 20 minutes. S9.7: Medium-high temperature pure water washing. Workpiece 1 is cleaned with medium-high temperature pure water at a temperature of 90℃ for 120 seconds. The conductivity of the medium-high temperature pure water is 5μs / cm. S9.8: Wash with room temperature grade 3 pure water for 1 minute; S10: Place the hanger 2 containing workpiece 1 into the first electrophoresis tank for the first electrophoresis treatment to form the first surface coating; use a graphene-added two-component black conductive cationic cathodic electrophoresis coating, measure the reverse dissolution time as 6.5 minutes, voltage as 180 volts, energize for 50 seconds twice, and the electrophoresis film thickness as 20 μm. S10.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S10.2: Ultrafiltration spray cleaning to further recover the paint on the surface of hanger 2 and magnet; S10.3: Wash with pure water; S10.4: Rinse again with pure water; S10.5: Dehydration; S10.6: Drying; S10.7: Curing: First, level at 80℃ for 20 minutes, then bake at 160℃ for 30 minutes; S10.8: Cool to room temperature; S11: Slightly rotate the position of workpiece 1 on hanger 2 to avoid placing it at the original hanging point position, and place the new hanging point on the first surface coating so that the original hanging point position will be electrophoresed with the new coating during the next electrophoresis, thereby forming a full electrophoretic coating coverage of the entire workpiece 1 without dead angles. S12: Place workpiece 1 into the second electrophoresis tank for a second electrophoresis treatment to form a second surface coating. Use nano-two-component cationic cathodic electrophoretic coating, electrophoresis voltage 170 volts, energize for 50 seconds twice, and electrophoretic film thickness 20 μm. S12.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S12.2: Ultrafiltrate spray cleaning to further recover the loose paint on the surface of hanger 2 and magnet; S12.3: Wash with pure water; S12.4: Rinse again with pure water; S12.5: Dehydration; S12.6: Drying; S12.7: Curing: First, level at 80℃ for 20 minutes, then bake at 180℃ for 40 minutes; S12.8: Cool to room temperature.

[0025] Experiments were conducted on samples of bonded NdFeB magnets treated using the above method: Workpiece 1 (D26.5×D21.93×17.55) was immersed in room temperature acetone for 1000 hours; the product strength remained essentially unchanged. After neutral salt spray corrosion for 1000 hours, the surface of the bonded NdFeB magnet sample showed virtually no abnormalities. The sample was then subjected to high temperature and humidity (85℃×85%RH) for 2000 hours; the surface of the bonded NdFeB magnet sample showed virtually no abnormalities after a 2000-hour PCT test. The experiments demonstrate that the method of this invention is feasible and effective, significantly enhancing the solvent resistance, corrosion resistance, high temperature and humidity resistance, and moisture resistance of bonded NdFeB magnets. like Figure 3 As shown in Example 2: A ring-shaped bonded NdFeB magnet with outer dimensions of D27.6mm × D25.2mm × 7.6mm was selected. The weight of the bonded NdFeB magnet was 4.61 grams. The following method was used to perform surface anti-corrosion treatment on the bonded NdFeB magnet to improve its solvent resistance, anti-corrosion performance, and high temperature and high humidity resistance.

[0026] A method for improving the surface properties of bonded NdFeB magnets, comprising the following steps: S1: Inject glue into the vacuum impregnation tank and adjust the glue gel time to 20-30 minutes. While adjusting the gel time, place a D10mm×75mm glass test tube containing 2 ml of glue into a water bath at 55±1℃ and start recording the time. Check the time every minute until gelation occurs and record the gel time. S2: When the workpiece temperature cools down to below 37°C, use compressed air to blow away the adhering substances on the surface of workpiece 1. First, put workpiece 1 made of bonded NdFeB magnets into a clean mesh bag, and then put the mesh bag into a vacuum impregnation tank. The height of the glue should be at least 15mm higher than all workpieces 1, and the temperature of the glue should be kept below 20°C. Close the lid of the vacuum impregnation tank to ensure the glue's submerging effect on the bonded NdFeB magnets. During the glue impregnation process, the bonded NdFeB magnets will not be completely submerged due to the decrease in glue height caused by impregnation. The glue temperature is kept at 20°C to prevent the glue from curing prematurely and to ensure the stability of the glue, so as to prevent the glue reaction from occurring prematurely and to ensure the continuity of glue impregnation. S3: Vacuum impregnation tank is vacuum pressure maintained. The vacuum impregnation tank is evacuated to -0.098MPa or better, and the pressure is maintained for 10 minutes, with a total time not exceeding 14 minutes, to remove all air from the micropores of workpiece 1 and allow the adhesive to impregnate. During the vacuuming process, the height of the foam should be observed at any time. If the foam exceeds the vacuum port, the vacuum pump should be turned off in time. After the foam descends, the vacuuming should be turned on again. At the same time, pay attention to the adhesive level. If any workpiece 1 is found to be exposed above the adhesive surface, the entire bag of workpiece 1 containing that workpiece 1 must be re-impregnated. S4: After vacuum impregnation is completed, depressurize and open the lid. During the depressurization process, because the internal pressure of the micropores in workpiece 1 is less than the external colloid pressure, the colloid is forced into the micropores of workpiece 1. After opening the lid to complete impregnation, close the lid and introduce oxygen into the vacuum impregnation tank. At the same time, open the valve at the bottom of the vacuum impregnation tank to recover the glue. Uncured glue in the vacuum impregnation tank can be recovered. In the process of recovering glue, the recovery equipment does not need to come into contact with workpiece 1 and can recover glue to a large extent, ensuring the surface quality of workpiece 1. S5: Take out workpiece 1 and spin it dry. Transfer the mesh bag to the centrifuge tank and spin the glue at a speed of 80-150 RPM for 2-3 minutes each time, for a total of 4-5 times. Alternatively, use an air gun to blow off the excess glue on the surface of workpiece 1. The glue should be recycled and reused in a timely manner. S6: Perform multi-stage cleaning on workpiece 1; S6.1: Level 1 cleaning: Transfer the mesh bag to the first cleaning tank for cleaning. The water should be kept overflowing and agitated with compressed air. The mesh bag should be turned over continuously during the process for more than 2 minutes; or it can be cleaned by hand for more than 2 minutes. S6.2: Secondary cleaning: Transfer the mesh bag to the second cleaning tank and agitate it with compressed air, turning the mesh bag over continuously for at least 2 minutes; or clean it by hand for at least 2 minutes. S6.3: Three-stage cleaning: Transfer the mesh bag to the third cleaning tank and agitate it with compressed air. During this process, the mesh bag should be turned over continuously. Control the water temperature to 50-60℃ and clean for more than 2 minutes; or use warm water at 50-60℃ for manual cleaning for more than 2 minutes. At this time, the adhesive has completed its initial curing. S7: Perform vibratory grinding and chamfering on workpiece 1; S7.1: Prepare a vibratory grinding and chamfering fluid, which is made by soaking round abrasive and pentahedral abrasive in a liquid rust inhibitor, wherein the pH value of the liquid rust inhibitor is 8; S7.2: Transfer workpiece 1 to a vibratory beveling machine containing vibratory beveling fluid for processing; S7.3: After 8 minutes of vibratory grinding and chamfering, take workpiece 1 for inspection. The chamfer is 0.22mm. Stop chamfering. S7.4: Move workpiece 1 to a spin dryer for spin drying, with the rotation speed controlled at 35 rpm, or dry it with an air gun; S7.5: Place workpiece 1 on gauze, with workpiece 1 spaced apart and not overlapping, and dry workpiece 1 at a temperature of 110℃ for 60 minutes. S8: Use fixture 2 to hang workpiece 1 for the first time; S8: Perform pretreatment on workpiece 1 and fixture 2; S9.1: Degreasing and oil removal. Transfer workpiece 1 to a degreasing solution (15% sodium carbonate, 12% sodium tripolyphosphate, 11% sodium dodecyl sulfonate). The pH of the degreasing solution is 9.5, and the time is 5 minutes. S9.2: First ultrasonic water wash, 1 minute; S9.3: Rust removal. Transfer workpiece 1 to the rust removal solution for rust removal treatment. The rust removal solution is TIWO830 with a concentration of 2% and a pH value of 2. The treatment time is 2 minutes. S9.4: Second ultrasonic water wash, 2 minutes; S9.5: Surface conditioning. Move workpiece 1 into the surface conditioning solution for surface conditioning treatment. The surface conditioning solution is XH-12, the pH value of the surface conditioning solution is 11, and the time is 2 minutes. S9.6: Medium and high temperature phosphating. Workpiece 1 is transferred to the phosphating solution for medium and high temperature phosphating treatment. The phosphating solution is XH-34B, the pH value of the phosphating solution is 3.2, the concentration of the phosphating solution is 10%, the temperature is 60℃, and the phosphating time is 20 minutes. S9.7: Medium-high temperature pure water washing. Workpiece 1 is cleaned with medium-high temperature pure water at a temperature of 90℃ for 120 seconds. The conductivity of the medium-high temperature pure water is 5μs / cm. S9.8: Wash with room temperature grade 3 pure water for 1 minute; S10: Place the hanger 2 containing the workpiece 1 into the first electrophoresis tank for the first electrophoresis treatment to form the first surface coating; use a graphene-added two-component black conductive cationic cathodic electrophoretic coating, with a re-dissolution time of 7 minutes, a voltage of 190 volts, an energizing time of 50 seconds twice, and an electrophoretic film thickness of 20 μm. S10.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S10.2: Ultrafiltration spray cleaning to further recover the paint on the surface of hanger 2 and magnet; S10.3: Wash with pure water; S10.4: Rinse again with pure water; S10.5: Dehydration; S10.6: Drying; S10.7: Curing: First, level at 80℃ for 20 minutes, then bake at 160℃ for 30 minutes; S10.8: Cool to room temperature; S11: Slightly rotate the position of workpiece 1 on hanger 2 to avoid placing it at the original hanging point position, and place the new hanging point on the first surface coating so that the original hanging point position will be electrophoresed with the new coating during the next electrophoresis, thereby forming a full electrophoretic coating coverage of the entire workpiece 1 without dead angles. S12: Place workpiece 1 into the second electrophoresis tank for a second electrophoresis treatment to form a second surface coating. Use nano-two-component cationic cathodic electrophoretic coating, electrophoresis voltage 180 volts, 50 seconds twice, electrophoresis film thickness 20 μm. S12.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S12.2: Ultrafiltrate spray cleaning to further recover the loose paint on the surface of hanger 2 and magnet; S12.3: Wash with water; S12.4: Wash with pure water; S12.5: Dehydration; S12.6: Drying; S12.7: Curing: First, level at 80℃ for 20 minutes, then bake at 180℃ for 40 minutes; S12.8: Cool to room temperature.

[0027] Experiments were conducted on samples of bonded NdFeB magnets treated using the above method: A product with dimensions of D27.6mm × D25.2mm × 7.6mm was immersed in acetone at room temperature for 1000 hours; the product strength remained essentially unchanged. After neutral salt spray corrosion for 1000 hours, the surface of the bonded NdFeB magnet sample showed virtually no abnormalities. The sample was then subjected to high temperature and humidity (85℃ × 85%RH) for 2000 hours; the surface of the bonded NdFeB magnet sample showed virtually no abnormalities after a 2000-hour PCT test. These experiments demonstrate that the method of this invention is feasible and effective, significantly enhancing the solvent resistance, corrosion resistance, high temperature and humidity resistance, and moisture resistance of bonded NdFeB magnets. like Figure 4 As shown in Example 3: A tile-shaped bonded NdFeB magnet with outer dimensions of R16.26mm × R12.7mm × 29.97mm × 29.46mm was selected. The weight of the bonded NdFeB magnet was 19.30 grams. The following method was used to perform surface anti-corrosion treatment on the bonded NdFeB magnet to improve its solvent resistance, anti-corrosion performance, and high temperature and high humidity resistance.

[0028] A method for improving the surface properties of bonded NdFeB magnets, comprising the following steps: S1: Inject glue into the vacuum impregnation tank and adjust the glue gel time to 20-30 minutes. While adjusting the gel time, place a D10mm×75mm glass test tube containing 2 ml of glue into a water bath at 55±1℃ and start recording the time. Check the time every minute until gelation occurs and record the gel time. S2: When the workpiece temperature cools down to below 37°C, use compressed air to blow away the adhering substances on the surface of workpiece 1. First, put workpiece 1 made of bonded NdFeB magnets into a clean mesh bag, and then put the mesh bag into a vacuum impregnation tank. The height of the glue should be at least 15mm higher than all workpieces 1, and the temperature of the glue should be kept below 20°C. Close the lid of the vacuum impregnation tank to ensure the glue's submerging effect on the bonded NdFeB magnets. During the glue impregnation process, the bonded NdFeB magnets will not be completely submerged due to the decrease in glue height caused by impregnation. The glue temperature is kept at 20°C to prevent the glue from curing prematurely and to ensure the stability of the glue, so as to prevent the glue reaction from occurring prematurely and to ensure the continuity of glue impregnation. S3: Vacuum impregnation tank is vacuum pressure maintained. The vacuum impregnation tank is evacuated to -0.098MPa or better, and the pressure is maintained for 10 minutes, with a total time not exceeding 14 minutes, to remove all air from the micropores of workpiece 1 and allow the adhesive to impregnate. During the vacuuming process, the height of the foam should be observed at any time. If the foam exceeds the vacuum port, the vacuum pump should be turned off in time. After the foam descends, the vacuuming should be turned on again. At the same time, pay attention to the adhesive level. If any workpiece 1 is found to be exposed above the adhesive surface, the entire bag of workpiece 1 containing that workpiece 1 must be re-impregnated. S4: After vacuum impregnation is completed, depressurize and open the lid. During the depressurization process, because the internal pressure of the micropores in workpiece 1 is less than the external colloid pressure, the colloid is forced into the micropores of workpiece 1. After opening the lid to complete impregnation, close the lid and introduce oxygen into the vacuum impregnation tank. At the same time, open the valve at the bottom of the vacuum impregnation tank to recover the glue. Uncured glue in the vacuum impregnation tank can be recovered. In the process of recovering glue, the recovery equipment does not need to come into contact with workpiece 1 and can recover glue to a large extent, ensuring the surface quality of workpiece 1. S5: Take out workpiece 1 and spin it dry. Transfer the mesh bag to the centrifuge tank and spin the glue at a speed of 80-150 RPM for 2-3 minutes each time, for a total of 4-5 times. Alternatively, use an air gun to blow off the excess glue on the surface of workpiece 1. The glue should be recycled and reused in a timely manner. S6: Perform multi-stage cleaning on workpiece 1; S6.1: Level 1 cleaning: Transfer the mesh bag to the first cleaning tank for cleaning. The water should be kept overflowing and agitated with compressed air. The mesh bag should be turned over continuously during the process for more than 2 minutes; or it can be cleaned by hand for more than 2 minutes. S6.2: Secondary cleaning: Transfer the mesh bag to the second cleaning tank and agitate it with compressed air, turning the mesh bag over continuously for at least 2 minutes; or clean it by hand for at least 2 minutes. S6.3: Three-stage cleaning: Transfer the mesh bag to the third cleaning tank and agitate it with compressed air. During this process, the mesh bag should be continuously turned over. Control the water temperature to 50-60℃ and clean for more than 2 minutes; or use warm water at 50-60℃ for manual cleaning for more than 2 minutes. At this point, the adhesive has completed its initial curing, which avoids the phenomenon of adhesive delamination in subsequent steps and ensures the quality of adhesive penetration, so as to achieve high processing efficiency. S7: Perform vibratory grinding and chamfering on workpiece 1; S7.1: Prepare a vibratory grinding and chamfering fluid, which is made by soaking circular abrasive and pentahedral abrasive in a liquid rust inhibitor, wherein the pH value of the liquid rust inhibitor is 8.5; S7.2: Transfer workpiece 1 to a vibratory beveling machine containing vibratory beveling fluid for processing; S7.3: After 10 minutes of vibratory grinding and chamfering, take workpiece 1 for inspection. The chamfer is 0.28mm. Stop chamfering. S7.4: Move workpiece 1 to a spin dryer for spin drying, with the rotation speed controlled at 45 rpm, or dry it with an air gun; S7.5: Place workpiece 1 on gauze, with workpiece 1 spaced apart and not overlapping, and dry workpiece 1 at 120℃ for 60 minutes; perform vibratory grinding and chamfering on workpiece 1 to improve the uniformity of the surface coating thickness, thereby improving the corrosion resistance of bonded NdFeB magnets in neutral salt spray tests, etc. S8: Use fixture 2 to hang workpiece 1 for the first time; S9: Perform pretreatment on workpiece 1 and fixture 2; S9.1: Degreasing and oil removal. Transfer workpiece 1 to a degreasing solution (15% sodium carbonate, 10% sodium tripolyphosphate, 10% sodium dodecyl sulfonate). The pH of the degreasing solution is 9, and the time is 5 minutes. S9.2: First ultrasonic water wash, 1 minute; S9.3: Rust removal. Transfer workpiece 1 to the rust removal solution for rust removal treatment. The rust removal solution is TIWO830 with a concentration of 1.5% and a pH value of 2. The treatment time is 2 minutes. S9.4: Second ultrasonic water wash, 1 minute; S9.5: Surface conditioning. Move workpiece 1 into the surface conditioning solution for surface conditioning treatment. The surface conditioning solution is XH-12, the pH value of the surface conditioning solution is 11, and the time is 2 minutes. S9.6: Medium and high temperature phosphating. Workpiece 1 is transferred to the phosphating solution for medium and high temperature phosphating treatment. The phosphating solution is XH-34B, the pH value of the phosphating solution is 3, the concentration of the phosphating solution is 15%, the temperature is 60℃, and the phosphating time is 20 minutes. S9.7: Medium-high temperature pure water washing. Workpiece 1 is cleaned with medium-high temperature pure water at a temperature of 90℃ for 120 seconds. The conductivity of the medium-high temperature pure water is 5μs / cm. S9.8: Wash with room temperature grade 3 pure water for 1 minute; S10: Place the hanger 2 containing the workpiece 1 into the first electrophoresis tank for the first electrophoresis treatment to form the first surface coating; use a graphene-added two-component black conductive cationic cathodic electrophoresis coating, with a re-dissolution time of 8 minutes, an electrophoresis voltage of 150 volts, 50 seconds twice, and an electrophoresis film thickness of 20 μm. S10.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S10.2: Ultrafiltration spray cleaning to further recover the paint on the surface of hanger 2 and magnet; S10.3: Wash with pure water; S10.4: Rinse again with pure water; S10.5: Dehydration; S10.6: Drying; S10.7: Curing: First, level at 80℃ for 20 minutes, then bake at 160℃ for 30 minutes; S10.8: Cool to room temperature; S11: Slightly rotate the position of workpiece 1 on hanger 2 to avoid placing it at the original hanging point position, and place the new hanging point on the first surface coating so that the original hanging point position will be electrophoresed with the new coating during the next electrophoresis, thereby forming a full electrophoretic coating coverage of the entire workpiece 1 without dead angles. S12: Place workpiece 1 into the second electrophoresis tank for a second electrophoresis treatment to form a second surface coating; use nano-two-component cationic cathodic electrophoretic coating, electrophoresis voltage 150 volts, energize for 50 seconds twice, and the electrophoretic film thickness is 20 μm. S12.1: Immerse in the recovery solution for cleaning to fully recover the paint residue on the surface of the hanger 2 and the magnet; S12.2: Ultrafiltrate spray cleaning to further recover the loose paint on the surface of hanger 2 and magnet; S12.3: Wash with pure water; S12.4: Rinse again with pure water; S12.5: Dehydration; S12.6: Drying; S12.7: Curing: First, level at 80℃ for 20 minutes, then bake at 180℃ for 40 minutes; S12.8: Cool to room temperature.

[0029] Experiments were conducted on samples of bonded NdFeB magnets treated using the above method: Products with an outer diameter of 16.26mm × 12.7mm × 29.97mm × 29.46mm were immersed in room temperature acetone for 1000 hours, after which the product strength remained essentially unchanged. After neutral salt spray corrosion for 1000 hours, the surface of the bonded NdFeB magnet samples showed virtually no abnormalities. After high temperature and humidity (85℃ × 85%RH) for 2000 hours, the surface of the bonded NdFeB magnet samples showed virtually no abnormalities. After a 2000-hour PCT test, the surface of the bonded NdFeB magnet samples showed virtually no abnormalities. The experiments demonstrate that the method of this invention is feasible and effective, significantly enhancing the solvent resistance, corrosion resistance, high temperature and humidity resistance, and moisture resistance of bonded NdFeB magnets.

[0030] The aforementioned hanger 2 is a blade hanger strip made of spring steel, and the blade hanger strip has a conventional structure.

[0031] The second electrophoretic treatment uses a non-conductive nano-bicomponent cationic cathodic electrophoretic coating to ensure the safety of bonding NdFeB magnets. This nano-bicomponent cationic cathodic electrophoretic coating is a conventional electrophoretic coating. The first electrophoretic treatment uses a graphene-based bicomponent black conductive cationic cathodic electrophoretic coating. To ensure the conductivity of the coating for the second electrophoretic treatment, graphene was added. Therefore, the graphene-based bicomponent black conductive cationic cathodic electrophoretic coating is made by adding graphene to the nano-bicomponent cationic cathodic electrophoretic coating, with a graphene content of 0%-10%.

[0032] Solvent maintenance methods in the first and second electrophoresis tanks: Maintaining a constant solvent content in both tanks during electrophoresis is crucial for ensuring its normal operation. The following three factors cause variations in solvent content: 1. The daily solvent evaporation rate of the electrophoresis tank system is calculated as the total amount of electrophoretic solution in the electrophoresis tank multiplied by the evaporation percentage (approximately 0.2%-0.4% in spring and winter, approximately 0.3%-0.6% in summer, and approximately 0.25%-0.45% in autumn). 2. The amount of solvent carried out during electrophoresis is the electrophoretic area × the percentage carried out by the paint film (0.5%-0.8%). 3. When adjusting the electrophoresis tank, the amount of solvent carried out by the discharged ultrafiltrate is the discharge volume of ultrafiltrate × the percentage of solvent carried out by the ultrafiltration discharge (1%-5%). Then, based on the electrophoresis operation and adjustment status of the day, calculate the corresponding amount of solvent to be added that day, mix it with pure water (or purified water) at a 1:1 ratio, and add it directly to the corresponding electrophoresis tank.

[0033] The back-dissolution time in step S10 is used to detect the back-dissolution of the electrophoretic solution. The steps are as follows: Take one or more electrophoresed workpieces 1 or hangers 2 and put them back into the first electrophoresis tank. The state of the liquid in the first electrophoresis tank is judged based on the dissolution time of the first surface coating on the workpiece 1 or hanger 2. During the electrophoresis process, it is necessary to ensure that the coating adheres smoothly to the workpiece 1. If the back-dissolution time is too short, it means that the electrophoretic coating material has too good fluidity. The electrophoretic coating formed during the electrophoresis process is easily dissolved again, resulting in problems such as insufficient coating thickness, watermarks, and dull coating. If the back-dissolution time is too long, it means that the electrophoretic coating material has poor fluidity and poor conductivity. The electrophoretic coating thickness is insufficient, and the surface is rough with defects such as particles and dirt. The back-dissolution time is generally controlled within 4-20 minutes. If the back-dissolution time is outside this range, it is adjusted by adding acid or alkali and ultrafiltration.

[0034] In the above embodiments, the impregnation effect of the adhesive-bonded NdFeB magnet can be detected by fluorescence method. This involves irradiating the cured workpiece 1 with a banknote detector, then slicing the magnet and checking for complete fluorescent columns in the micropores to determine if 100% impregnation has occurred. The weight gain method, however, can only determine whether the workpiece 1 has been impregnated with adhesive, but cannot determine the effectiveness of the adhesive impregnation. Through the design of phosphating layers, graphene electrophoretic coatings, and nano-electrophoretic coatings, the impregnation process ensures that the capillaries of each coating layer are interwoven and sealed, forming a dense anti-corrosion layer with functions such as impermeability, moisture resistance, oxidation resistance, high temperature and humidity resistance, wear resistance, and good heat dissipation for bonded NdFeB magnets. Bonded NdFeB magnets treated using this method can withstand organic solvent immersion and neutral salt spray tests for over 1000 hours, high temperature and humidity (85℃×85%RH) for over 2000 hours, and PCT tests for 2000 hours. Compared to the traditional combination of electrophoresis and painting processes in existing technologies, this significantly improves resistance to organic solvent immersion, moisture resistance, corrosion resistance, and high temperature and humidity resistance. The first electrophoresis of the graphene material... After treatment, the first surface coating penetrates into the micropores of the magnet and the phosphating layer, forming a protective layer on top of the anti-corrosion layer. The second surface coating then forms another protective layer on top of the first surface coating, effectively isolating the capillaries during the drying process of the graphene material electrophoretic coating. This enhances the bonding strength between the anti-corrosion layer and the bonded NdFeB magnet, and further improves the anti-corrosion performance, high temperature and humidity resistance, and moisture resistance of the bonded NdFeB magnet. The bonded NdFeB magnet after electrophoretic treatment can achieve more than 2000 hours in the neutral salt spray test. Compared with the traditional combination of impregnation, pretreatment, and painting processes in existing technologies, this method greatly improves the solvent resistance, anti-corrosion performance, high temperature and humidity resistance, and moisture resistance.

[0035] The above-mentioned organic solvent immersion uses industrial acetone solvent. The test is conducted according to the company's requirements and is carried out in an immersion test chamber.

[0036] The above neutral salt spray test was conducted according to GB / T10125-2012, using a 5% saline solution concentration, with an ambient temperature of 35℃ and a salt spray deposition rate of 1.5 ml / (cm²). 2 The test environment pressure was 1 atmosphere, and the test was conducted in a salt spray corrosion test chamber.

[0037] The above high temperature and high humidity resistance test was conducted in accordance with GB / T2423.3-2006, using a high temperature and humidity test chamber at an environment of 85℃×85%RH.

[0038] The aforementioned PCT test refers to the pressure cooking test, a test method that simulates extreme environmental conditions. It evaluates the performance of samples under harsh conditions by placing them in environments with high temperature (100℃~132℃), high humidity (100%RH saturated steam), and high pressure (1~2 atm). The core of this test is to simulate the high-humidity environment that products may encounter in actual use, thereby identifying potential problems in advance, optimizing product design and manufacturing processes, and ensuring the reliability and competitiveness of products in the market. It is a conventional testing method. The PCT test of this invention is conducted according to GB / T2423.40-2013, using a high-speed aging test chamber at 120℃×100%RH×2 atm.

[0039] The aforementioned immersion test chamber, salt spray corrosion test chamber, high temperature and humidity test chamber, and high speed aging test chamber are all standard testing equipment. The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A method of improving the surface properties of bonded neodymium-iron-boron magnets, characterized in that The steps are as follows: S1: inject glue into the vacuum impregnation tank; S2: put the workpiece (1) made of bonded neodymium iron boron into the vacuum impregnation tank, and the height of the glue is higher than the height of the workpiece (1); S3: vacuum and pressure preservation is performed on the vacuum impregnation tank; S4: after completing the vacuum and pressure preservation, pressure relief is performed, and the cover is opened; S5: take out the workpiece (1), and spin dry the workpiece (1); S6: perform multi-stage cleaning on the workpiece (1); S7: perform shock grinding and chamfering on the workpiece (1); S8: perform first-time hanging of the workpiece (1) by using the hanger (2); S9: perform pretreatment on the workpiece (1) and the hanger (2); S10: put the hanger (2) with the workpiece (1) into the first electrophoresis tank to perform first-time electrophoresis treatment to form a first-time surface coating; S11: adjust the contact position of the workpiece (1) and the hanger to avoid the original contact point position, and perform second-time hanging of the workpiece (1); S12: put the workpiece (1) into the second electrophoresis tank to perform second-time electrophoresis treatment to form a second-time surface coating.

2. The method for improving the surface performance of bonded neodymium iron boron magnets according to claim 1, characterized in that: in step S10, first-time solidification is included: first 80-100℃ leveling for 10-30 minutes, and then 160±10℃ baking for 10-40 minutes; in step S12, second-time solidification is included: first 80-100℃ leveling for 10-30 minutes, and then 180±10℃ baking for 30-40 minutes.

3. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 1, characterized in that in step S10, graphene two-component black conductive cationic cathode electrophoretic paint is used for first-time electrophoresis treatment, and the electrophoretic film thickness is 10-35μm.

4. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 3, characterized in that: in step S12, nano two-component cationic cathode electrophoretic paint is used for second-time electrophoresis treatment, and the electrophoretic film thickness is 10-35μm.

5. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 1, characterized in that in step S1, the glue gel time is adjusted to 20-30 minutes, and when adjusting the gel time, a D10mm×75mm glass test tube containing 2ml of glue is placed in a 55±1℃ water bath tank, and the time is started to be recorded, and the glue is checked every minute until the glue is gelled, and the gel time is recorded, and the glue is preliminarily solidified after step S6 is completed.

6. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 5, characterized in that in step S3, the vacuum impregnation tank is vacuumized to -0.098MPa or a more optimal vacuum degree, and pressure preservation is performed for 10 minutes, and the total time is not more than 14min.

7. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 6, characterized in that in step S6, the following steps are included: S6.1: first-stage cleaning: move the workpiece (1) to the first cleaning tank for cleaning, the water should be kept in an overflow state and stirred with compressed air, and the workpiece (1) is constantly turned over during the process, and the time is more than 2 minutes; or manually clean, and the time is more than 2 minutes; S6.2: second-stage cleaning: move the workpiece (1) to the second cleaning tank for cleaning, and stir with compressed air, and the workpiece (1) is constantly turned over during the process, and the time is more than 2 minutes; or manually clean, and the cleaning time is more than 2 minutes; S6.3: third-stage cleaning: move the workpiece (1) to the third cleaning tank for cleaning, and stir with compressed air, and the workpiece (1) is constantly turned over during the process, and the water temperature is controlled to be 50-60℃, and the cleaning time is more than 2 minutes; or manually clean with warm water at 50-60℃, and the cleaning time is more than 2 minutes.

8. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 1, characterized in that In step S9, the pre-treatment includes the following steps: S9.1: degreasing, moving the hanger (2) with the workpiece (1) to a degreasing solution with a pH value of 9-11; S9.2: first ultrasonic water washing; S9.3: rust removal, moving the hanger (2) with the workpiece (1) to a rust removal solution for rust removal treatment, the rust removal solution has a pH value of 2-7; S9.4: second ultrasonic water washing; S9.5: surface conditioning, moving the hanger (2) with the workpiece (1) to a surface conditioning solution for surface conditioning treatment, the surface conditioning solution has a pH value of 9-11; S9.6: medium-high temperature phosphating, moving the hanger (2) with the workpiece (1) to a phosphating solution for medium-high temperature phosphating treatment, the phosphating solution has a pH value of 2-4, a concentration of 8-20%, a temperature of 60-80°C, and a phosphating time of 10-30 minutes; S9.7: medium-high temperature pure water washing, using medium-high temperature pure water to clean the hanger (2) with the workpiece (1), the medium-high temperature pure water has a temperature of 70-90°C, a washing time of 30-120 seconds, and an electric conductivity of the medium-high temperature pure water ≤50 μs / cm; S9.8: normal temperature three-stage pure water washing, cleaning for 1 minute.

9. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 1, characterized in that The hanger (2) is a knife-edge hanger strip made of spring steel.

10. The method for improving the surface properties of bonded Nd-Fe-B magnets according to claim 1, characterized in that In step S10, the following step is included: reverse solution detection, taking one or several electrophoresed workpieces (1) or hangers (2) and putting them back into the first electrophoresis tank, and judging the use state of the liquid in the first electrophoresis tank according to the melting time of the first surface coating of the magnetic steel on the workpiece (1) or the hanger (2).

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