A method and tooling for preparing high-performance circular NdFeB magnets
By employing magnetization and rotary drying techniques, combined with solution state improvers in heavy rare earth solutions, the problem of uneven performance in NdFeB ring products was solved, achieving stable performance improvement and uniformity enhancement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SINOSTEEL ANHUI TIANYUAN TECH
- Filing Date
- 2022-11-07
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies offer limited and uneven performance improvements for NdFeB ring products, particularly in the heavy rare earth coating process, where uneven coating amounts and significant fluctuations in product performance persist.
Magnetization and rotary drying technologies are employed, along with a solution state improver in the heavy rare earth solution. The coating amount of heavy rare earth is ensured to be uniform by rotary drying or rotary blowing, and diffusion heat treatment is carried out in a tube furnace.
The performance stability and uniformity of NdFeB ring products have been improved, the squareness of the products has been enhanced, and the irreversible loss at high temperatures has been reduced, resulting in higher magnetic properties and smaller performance fluctuations.
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Figure CN115547670B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sintered NdFeB magnetic materials technology, specifically to a method and tooling for preparing high-performance circular NdFeB magnets. Background Technology
[0002] Many household appliances use a large number of neodymium iron boron (NdFeB) permanent magnets. Air conditioner compressors use a large number of square NdFeB magnets, and electric fan motors use a large number of tile-shaped NdFeB magnets. Vacuum cleaners, electric toy cars, and other products require a large number of toroidal components due to their characteristics. To improve their performance, they often need high-performance NdFeB toroidal components with both high remanence and coercivity. Producing high-performance toroidal components through grain boundary diffusion is a breakthrough, but how to consistently achieve almost the same performance improvement as square NdFeB components remains a major challenge.
[0003] Currently, most manufacturers still use the traditional soaking and drying method in the production of NdFeB ring grain boundary diffusion. For example, the invention patent application with publication number CN104681225A, entitled "A Processing Method for Improving the Performance of Sintered NdFeB Materials", discloses that the NdFeB blank is soaked in a solvent, drained, dried with hot air or placed in a drying oven, and then subjected to heat treatment. This method has been widely recognized for its performance in the production of rectangular products, but when used for ring products, the diffusion Tb increase is only 8 KOe at most, and the increase fluctuates greatly within the same batch of products, often by ±1 KOe. The squareness of a single ring product is poor, only about 80%, and its high-temperature irreversible loss is poor. The open-circuit aging test of 48UH ring products at 180℃ exceeds 10%. Summary of the Invention
[0004] The purpose of this invention is to provide a method and tooling for preparing high-performance circular NdFeB magnets to solve the problems of poor performance and uniformity of NdFeB circular magnet products.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a high-performance circular ring neodymium iron boron magnet, comprising the following steps:
[0006] S1 processes the NdFeB blank into a ring-shaped blank, and then pickles and dries it;
[0007] S2 magnetizes the dried billet until it has a certain degree of magnetism;
[0008] S3 involves immersing the magnetic billet in a heavy rare earth solution.
[0009] After being soaked in S4, the billets are removed, dried, and finally placed in a tube furnace for diffusion heat treatment.
[0010] Preferably, the heavy rare earth solution contains 10-30% by mass of a solution condition improver.
[0011] Preferably, the heavy rare earth solution state improver is one or more of phenolic resin, rosin-modified alkyd resin, and urea-formaldehyde resin.
[0012] Preferably, in step S2, the blank is magnetized to 5-20% of the saturation flux.
[0013] Preferably, in step S4, the drying is rotary drying or rotary blowing, and during the drying process, the spatial position of any point on the outer periphery of the billet relative to the center of the billet changes continuously.
[0014] Preferably, in the heavy rare earth solution, Tb accounts for 85% of the solute weight.
[0015] Preferably, in step S4, the heat treatment includes first performing diffusion at 900℃ for 8 hours, and then tempering at 510℃ for 3.5 hours.
[0016] Another technical solution provided by the present invention: a high-performance circular NdFeB magnet preparation fixture for clamping blanks for rotary drying or rotary blowing, including a rotating shaft, a first fixed plate and a second fixed plate. The middle part of one side of the first fixed plate is fixedly connected to one end of the rotating shaft, and the rotating shaft passes through the middle of the second fixed plate and is fixedly connected to it. Multiple sets of clamps are provided between the first fixed plate and the second fixed plate. Each set of clamps includes a fixed clamp and a movable clamp, which are used to clamp the blank. One end of the fixed clamp is fixedly connected to one of the first fixed plate and the second fixed plate, and one end of the movable clamp is fixedly connected to the other fixed plate or can be fixedly connected in a fixed position. The other end of the movable clamp moves towards or away from the fixed clamp. The rotating shaft is driven to a motor to provide rotational power.
[0017] Preferably, the fixed chuck and the moving chuck are coaxially arranged, and the diameter of both is larger than the inner diameter of the blank.
[0018] Preferably, the movable chuck is a gas spring rod; or the movable chuck is a threaded rod, and one of the fixed plates 1 and 2 connected to the movable chuck has a threaded hole that matches the threaded rod; or the movable chuck is a sliding rod, and one of the fixed plates 1 and 2 connected to the movable chuck has a through hole, and the side wall of the through hole has a set screw hole and a set screw is threaded on it.
[0019] Compared with the prior art, the beneficial effects of the present invention are:
[0020] 1. The method for preparing high-performance circular NdFeB magnets improves the fluctuation of heavy rare earth coating amount, enhances uniformity, and makes the performance more stable through magnetization treatment.
[0021] 2. The method for preparing high-performance circular NdFeB magnets significantly improves the amount of heavy rare earth coating by changing the solution state, and also enhances the relative performance.
[0022] 3. The method and tooling for preparing high-performance circular NdFeB magnets improve the squareness of the product, reduce irreversible thermal loss of magnetic flux, and improve the uniformity of product performance through rotary drying or rotary blowing. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of one embodiment of the clamping fixture of the present invention.
[0024] In the diagram: 1. Rotating shaft; 2. Fixed plate one; 3. Fixed chuck; 4. Fixed plate two; 5. Moving chuck; 6. Blank. Detailed Implementation
[0025] This invention investigates the performance improvement mechanism of NdFeB grain boundary diffusion, revealing that the primary factor affecting product performance during NdFeB diffusion is the heavy rare earth coating applied before diffusion. Due to the inherent shape characteristics of ring-shaped products, it is difficult to achieve the same level of heavy rare earth coating as with cube-shaped products, resulting in less than ideal performance improvement. Furthermore, maintaining uniform coating amounts between products leads to significant performance fluctuations and poor consistency. On individual rings, the rapid flow of the slurry during heavy rare earth coating causes uneven coating amounts, ultimately resulting in low squareness and poor high-temperature irreversible loss. Therefore, this invention proposes a method for preparing high-performance ring-shaped NdFeB magnets, including processing NdFeB blanks into ring-shaped blanks, followed by acid washing and drying; magnetizing the dried blanks to a certain degree of magnetism; immersing the magnetic blanks in a heavy rare earth solution; removing and drying the immersed blanks; and finally, subjecting them to diffusion heat treatment in a tube furnace.
[0026] Furthermore, the heavy rare earth solution should contain 10-30% by mass of a solution state improver; the heavy rare earth solution state improver can be one or more of phenolic resin, rosin-modified alkyd resin, and urea-formaldehyde resin, used to improve the viscosity of the heavy rare earth solution and / or the adhesion to the NdFeB billet surface, so that the product can obtain more heavy rare earth adhesion.
[0027] Before the above-mentioned blanks are immersed and coated, they are magnetized to ensure that each ring product has the same adsorption force for heavy rare earth elements, so as to achieve a uniform coating amount between different products. Specifically, the magnetization can be selected to 5-20% of the saturation magnetic flux, for example, 10%.
[0028] In a preferred embodiment, unlike the drying oven or hot air drying in the prior art, the above-mentioned drying adopts rotary drying or rotary blowing. During the drying process, the spatial position of any part of the outer periphery of the billet relative to the center of the billet changes continuously. This ensures that the heavy rare earth elements are not unevenly distributed on the surface of the ring due to the influence of gravity.
[0029] These solutions can improve the magnetic properties of toroidal products.
[0030] Comparative example:
[0031] 50M grade NdFeB blanks were selected and processed into products with a diameter of 12mm*6mm*20mm. After acid washing with 3% volume fraction dilute nitric acid and drying, they were labeled A0 to A6, and weighed and recorded. A1 to A6 were immersed in ordinary alcohol solution A containing heavy rare earth Tb (Tb accounts for 95% of the solute weight). After immersion, they were removed and placed directly on a tray to dry. After drying, they were weighed again and the Tb weight gain was calculated. A0 to A6 were then placed in a material box and subjected to diffusion at 900℃ for 8 hours in a tube furnace, followed by tempering at 510℃ for 3.5 hours. The magnetic properties and irreversible flux loss of the diffused samples were tested, and the results are shown in Table 1.
[0032] Table 1: Comparative Example Process and Test Results
[0033]
[0034]
[0035] Example 1:
[0036] 50M grade NdFeB blanks were selected and processed into products with a diameter of 12mm*6mm*20mm. After being acid-washed and dried with 3% (v / v) dilute nitric acid, they were labeled B0 to B6, weighed, and the weight was recorded. B1 to B6 were immersed in an alcohol solution B containing heavy rare earth element Tb (the solution contained 10% by mass of mixed resin, with Tb accounting for 85% of the solute weight). After immersion, they were removed and placed directly on a tray to air dry. After drying, they were weighed again, and the Tb weight gain was calculated. B0 to B6 were then placed in a material box and subjected to diffusion at 900℃ for 8 hours in a tube furnace, followed by tempering at 510℃ for 3.5 hours. The magnetic properties and irreversible flux loss of the diffused samples were tested, and the results are shown in Table 2.
[0037] Table 2: Process and Test Results of Example 1
[0038]
[0039] Example 2:
[0040] 50M grade NdFeB blanks were selected and processed into products with a diameter of 12mm*6mm*20mm. After being acid-washed and dried with 3% volume fraction dilute nitric acid, they were labeled C0 to C6, weighed, and recorded. C1 to C6 were placed in a magnetizing coil to induce a weak magnetization (magnetism of 10% of their saturation flux), and then immersed in an alcohol solution B containing heavy rare earth element Tb (the solution contains 10% by mass of mixed resin, with Tb accounting for 85% of the solute weight). After immersion, they were removed and placed directly on a tray to air dry. After drying, they were weighed again, and the Tb weight gain was calculated. C0 to C6 were then placed in a material box and subjected to diffusion at 900℃ for 8 hours in a tube furnace, followed by tempering at 510℃ for 3.5 hours. The magnetic properties and irreversible flux loss of the diffused samples were tested, and the results are shown in Table 3.
[0041] Table 3: Process and Test Results of Example 2
[0042]
[0043] Example 3:
[0044] 50M grade NdFeB blanks were selected and processed into products with dimensions D12mm*D6mm*20mm. After acid washing with 3% volume fraction dilute nitric acid and drying, they were labeled D0 to C6, and weighed and recorded. D1 to D6 were placed in a magnetizing coil to be weakly magnetized (magnetism of 10% of its saturation flux), and then immersed in an alcohol solution B containing heavy rare earth Tb (the solution contains 10% by mass of mixed resin, and Tb accounts for 85% of the solute weight). After immersion, the products were removed, rotated and dried, and weighed again to calculate the Tb weight gain.
[0045] In this embodiment, the rotary drying is achieved using the following fixture, see reference. Figure 1 It includes a rotating shaft 1, a first fixing plate 2, and a second fixing plate 4. The middle of one side of the first fixing plate 2 is fixedly connected to one end of the rotating shaft 1. The rotating shaft 1 passes through the middle of the second fixing plate 4 and is fixedly connected to it. Multiple sets of clamps are provided between the first fixing plate 2 and the second fixing plate 4. Each set of clamps includes a fixed chuck 3 and a movable chuck 5, which are used to clamp the blank 6, such as... Figure 1 The two annular surfaces of the circular blank 6 are respectively pressed against the fixed chuck 3 and the movable chuck 5; one end of the fixed chuck 3 is fixedly connected to one of the fixed plate 2 and the fixed plate 4, and one end of the movable chuck 5 is fixedly connected to the other or can be fixed in a fixed position; the other end of the movable chuck 5 moves toward or away from the fixed chuck 3; the rotating shaft 1 is driven to the motor to provide rotational power.
[0046] In the preferred embodiment, the fixed chuck 3 and the movable chuck 5 are coaxially arranged, and the diameters of both are larger than the inner diameter of the blank 6.
[0047] The aforementioned movable chuck 5 can be a gas spring rod, telescopic rod, or spring, etc.; it can also be a threaded rod, with one of the fixed plates 2 and 4 connected to the movable chuck 5 having a threaded hole that matches the threaded rod, and clamping by rotational feeding; it can also be a sliding rod, with one of the fixed plates 2 and 4 connected to the movable chuck 5 having a through hole, and a set screw hole having a set screw threaded on the side wall of the through hole, and positioning by the set screw. Of course, other common clamping methods can also be used, but it is best not to obstruct the side of the billet.
[0048] After drying, samples D0 to D6 were placed in a material box and subjected to diffusion at 900℃ for 8 hours in a tube furnace, followed by tempering at 510℃ for 3.5 hours. The magnetic properties and irreversible flux loss of the diffused samples were then tested, and the results are shown in Table 4.
[0049] Table 4: Process and Test Results of Example 3
[0050]
[0051] Based on the comparative and example data, it can be seen that by changing the solution state, the heavy rare earth coating amount increased from about 0.3% to about 0.6%, significantly improving the adhesion and relative performance. Through magnetization treatment, the fluctuation of the heavy rare earth coating amount improved from 0.55%–0.64% to 0.64%–0.66%, showing significantly better uniformity and more stable performance. Through rotary drying or rotary blowing, the squareness of the product increased from about 80% to about 91%, and the irreversible temperature loss of magnetic flux decreased from about 8% to about 4%, resulting in significantly better product performance uniformity.
[0052] In the above three embodiments, the soaking solution has the same composition. If the mass fraction of the mixed resin in the solution is 30%, or a single resin is used, the difference from the three embodiments is also very small. However, when the amount of resin is less than 10%, the effect is poor and the Tb weight gain cannot be guaranteed. When it is higher than 30%, it is easy to make it too viscous and difficult to soak completely. Instead, it will increase the soaking time required for coating and will not improve the product performance on the basis of the above embodiments.
[0053] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
[0054] Any aspects of this invention not described in detail are well-known to those skilled in the art.
Claims
1. A method for preparing a high-performance circular ring neodymium iron boron magnet, characterized in that, Includes the following steps: S1 processes the NdFeB blank into a ring-shaped blank, and then pickles and dries it; S2 magnetizes the dried billet to 5-20% of its saturation flux; S3 involves immersing the magnetic billet in a heavy rare earth solution; the heavy rare earth solution contains 10-30% by mass of a solution condition improver, which is one or more of phenolic resin, rosin-modified alkyd resin, and urea-formaldehyde resin. After being soaked in S4, the billet is removed and dried, and finally placed in a tube furnace for diffusion heat treatment. The drying process is either rotary drying or rotary blowing. During the drying process, the spatial position of any point on the outer periphery of the billet relative to the center of the billet changes continuously.
2. The method for preparing a high-performance circular ring neodymium iron boron magnet according to claim 1, characterized in that: In the heavy rare earth solution, Tb accounts for 85% of the solute weight.
3. The method for preparing a high-performance circular ring neodymium iron boron magnet according to claim 1, characterized in that: In step S4, the heat treatment includes first performing diffusion at 900℃ for 8 hours, and then tempering at 510℃ for 3.5 hours.
4. A high-performance circular NdFeB magnet manufacturing fixture, used to implement the manufacturing method described in claim 1, for clamping the blank for rotary drying or rotary blowing, characterized in that: It includes a rotating shaft (1), a first fixed plate (2) and a second fixed plate (4). The middle part of one side of the first fixed plate (2) is fixedly connected to one end of the rotating shaft (1). The rotating shaft (1) passes through the middle of the second fixed plate (4) and is fixedly connected to it. Multiple sets of clamps are provided between the first fixed plate (2) and the second fixed plate (4). Each set of clamps includes a fixed chuck (3) and a movable chuck (5). The two are used to clamp the blank (6). One end of the fixed chuck (3) is fixedly connected to one of the first fixed plate (2) and the second fixed plate (4). One end of the movable chuck (5) is fixedly connected to the other or can be fixed in a fixed position. The other end of the movable chuck (5) moves towards or away from the fixed chuck (3). The rotating shaft (1) is driven to a motor to provide rotational power.
5. The tooling according to claim 4, characterized in that: The fixed chuck (3) and the movable chuck (5) are coaxially arranged, and the diameter of both is greater than the inner diameter of the blank (6).
6. The tooling according to claim 4, characterized in that: The movable chuck (5) is a gas spring rod; or the movable chuck (5) is a threaded rod, and one of the fixed plates (2) and (4) connected to the movable chuck (5) has a threaded through hole that matches the threaded rod; or the movable chuck (5) is a sliding rod, and one of the fixed plates (2) and (4) connected to the movable chuck (5) has a through hole, and the side wall of the through hole has a set screw hole and a set screw is threadedly installed.