A near-net shaped profiled oriented magnet and a method of manufacturing

Abstract

The present application relates to the technical field of magnetic material manufacturing, and particularly relates to a near-net-shape special-shaped oriented magnet and a preparation method thereof. The method comprises the following steps: performing single hot deformation treatment on a hot-pressed blank in a mold to shape the hot-pressed blank into a preset special-shaped magnet; during the hot deformation, the easy magnetization axis direction of the special-shaped magnet rotates with the change of the outer curved surface of the special-shaped magnet, and finally aligns along the normal direction of the curved surface of the special-shaped magnet; the single hot deformation treatment satisfies one of the following conditions: the surface of the hot-pressed blank is coated with a composite lubricant, the composite lubricant comprises at least two of molybdenum disulfide, graphite and boron nitride; the temperature uniformity of the mold is controlled within ±5°C; the punch pressing speed is 0.2-0.6 mm / s when contacting the hot-pressed blank, and increases after the pressing amount reaches at least 1 mm. The above scheme overcomes the problems of uneven material flow, cracking, sticking to the mold and the like, realizes the near-net-shape forming of the complex-shaped magnet, ensures the ideal grain orientation along the normal direction of the curved surface, and greatly improves the magnetic performance.

Description

Technical Field

[0001] This invention relates to the field of magnetic material manufacturing technology, and in particular to a near-net-shape irregularly oriented magnet and its preparation method. Background Technology

[0002] High-performance permanent magnets, such as sintered NdFeB magnets, are core functional components in modern precision instruments, micro sensors, and high-efficiency motors. As these devices become more miniaturized, efficient, and precise, higher demands are placed on the magnets used in them: they not only need to possess high magnetic properties, but they also often need to be designed with specific complex geometries (such as tile-shaped, S-shaped, horseshoe-shaped, etc.) to achieve optimal magnetic field distribution within a limited space.

[0003] Currently, high-performance magnets with complex shapes are mainly produced using sintered NdFeB magnets manufactured through powder metallurgy. A typical manufacturing process involves pressing alloy powder into shape in a magnetic field (achieving initial orientation), followed by high-temperature sintering to obtain high density, and finally, through numerous machining processes such as wire cutting and grinding, shaping the sintered billet into the desired final shape.

[0004] However, this traditional process has several significant technical drawbacks:

[0005] Low material utilization and high cost: Complex machining processes generate a large amount of expensive magnetic waste, resulting in low material utilization and a significant increase in production costs.

[0006] Unidirectional orientation: Traditional magnetic field orientation technology can only achieve unidirectional orientation in the pressing direction, and cannot make the easy magnetization axis of the magnet change continuously along the normal direction of a complex curved surface. This greatly limits the performance of the magnet in high-end applications that require complex magnetic field distribution.

[0007] In existing technologies, hot deformation (hot pressing) technology has also been attempted to manufacture magnets. For example, Chinese invention patent CN108615596A discloses a method for preparing a hot-deformable magnet. This method typically involves first hot pressing deformation, followed by a separate hot shaping process to precisely control the shape. This multi-step hot processing flow has the following drawbacks: First, it requires the design and manufacture of two sets of molds, increasing tooling costs; second, the blank undergoes two high-temperature processes, resulting in a long total heat exposure time, which can easily lead to excessive grain growth, thereby deteriorating its coercivity and other key magnetic properties; finally, in the second shaping process, because the thermoplasticity of the material decreases after the initial hot deformation, it is very prone to cracking when in contact with the mold punch, leading to a decrease in product yield.

[0008] Therefore, there is an urgent need in the field for a new method that can overcome the above-mentioned defects and achieve efficient and low-cost manufacturing of high-performance, complex-shaped oriented magnets. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies, such as repeated heating, grain growth, and performance degradation, and to provide a near-net-shape irregularly oriented magnet and its preparation method.

[0010] In a first aspect, the present invention provides a method for manufacturing a near-net-shape irregularly oriented magnet, comprising the following steps: Preparation of hot-pressed blanks; The hot-pressed blank is subjected to a single hot deformation process in a mold to form a pre-designed irregular magnet; During the heat deformation process, the easy magnetization axis of the irregular magnet rotates with the change of the outer surface and eventually aligns along the normal of the irregular magnet surface. The single heat deformation treatment satisfies at least one of the following conditions: a. The surface of the hot-pressed blank is coated with a composite lubricant, which includes at least molybdenum disulfide, graphite and boron nitride; b. The temperature uniformity of the mold is controlled within ±5°C; c. During a single hot deformation process, the pressing speed of the die punch is 0.2-0.6 mm / s when it contacts the hot-pressed blank, and increases to 0.8-2.5 mm / s after the pressing amount reaches at least 1 mm.

[0011] This invention combines hot deformation and surface normal orientation into one process, achieving near-net-shape forming of magnets with complex shapes. More importantly, by introducing at least one specific process condition among lubrication, temperature control, and variable-speed pressing, it successfully overcomes the technical challenges that easily arise in actual production from this combined process, such as uneven material flow, mold adhesion, and blank cracking. The synergistic or individual effects of these conditions enable the hot-pressed blank to flow and fill the mold cavity uniformly and stably under high temperature and pressure, while ensuring the ideal orientation of internal grains along the surface normal. This allows for the direct production of high-performance irregularly shaped magnets with minimal or no subsequent machining.

[0012] Preferably, the high-temperature friction coefficient of the composite lubricant is in the range of 0.10-0.15. The high temperature is at least not lower than 700°C, preferably 700°C-850°C.

[0013] Preferably, the friction coefficient of molybdenum disulfide is in the range of 0.01-0.20, the friction coefficient of graphite is in the range of 0.03-0.30, and the friction coefficient of BN is in the range of 0.16-0.30.

[0014] Controlling the high-temperature friction coefficient of the composite lubricant within the specific range of 0.10-0.15 is the optimal range obtained through extensive experimental screening in this invention. If the friction coefficient is too high (such as with a single molybdenum disulfide lubricant), it will lead to high material flow resistance, easily causing cracks or insufficient deformation; if the friction coefficient is too low, it may cause the front end of the blank to flow too quickly, and subsequent material cannot be replenished in time, thus causing cracking. The friction coefficient within this range ensures a moderate lubrication effect between the blank and the mold at high temperatures (such as 800°C), which promotes the smooth flow of material to fill complex cavities.

[0015] Preferably, the coating thickness of the composite lubricant is 0.01-0.3 mm.

[0016] Limiting the coating thickness of the composite lubricant to 0.01-0.3 mm is crucial for balancing lubrication performance and dimensional accuracy. A coating that is too thin (<0.01 mm) makes it difficult to form a continuous and stable lubricating film, which is prone to cracking and failure under high temperature and pressure, leading to direct contact between the blank and the mold and causing sticking. A coating that is too thick (>0.3 mm) will affect the original dimensional accuracy of the mold cavity, and excess lubricant may migrate to the product surface at high temperatures, affecting the magnet's appearance and subsequent processing. This thickness range allows for near-net-shape dimensional control while ensuring excellent lubrication performance.

[0017] Preferably, the cavity size (B) of the mold and the target product size (A) of the irregular magnet satisfy the formula: A = B × (1 + α), where α is the heat shrinkage compensation coefficient, and the value range is 0.005~0.007.

[0018] This invention is the first to propose a thermal shrinkage compensation formula for near-net-shape irregular magnets. After high-temperature heat deformation, the magnet undergoes thermal shrinkage during cooling. If the mold size is directly equal to the product size, the product size will be too large after cooling. By introducing a compensation coefficient of α=0.005-0.007, the mold cavity is pre-enlarged, ensuring that the magnet size after cooling to room temperature after heat deformation accurately falls within the target tolerance range. This truly achieves near-net-shape forming, completely eliminating subsequent machining processes such as grinding and wire cutting, and achieving a material utilization rate close to 100%.

[0019] Preferably, the heat shrinkage compensation coefficient α is determined based on the heat distortion temperature: When the mold temperature is 600-700°C, α is taken as 0.005; When the mold temperature is 700-800°C, α is taken as 0.006; When the mold temperature is 800-900°C, α is taken as 0.007.

[0020] This invention further reveals that the shrinkage rate of materials at different heat distortion temperatures is not constant, but increases with increasing temperature. Therefore, optimizing the correlation between the compensation coefficient α and the mold temperature range enables more precise dimensional control. For example, using a compensation coefficient of 0.007 in the high-temperature range of 800-900°C effectively compensates for greater heat shrinkage, preventing products from being too large; while using a compensation coefficient of 0.005 in the low-temperature range of 600-700°C prevents products from being too small. This refined compensation strategy for different temperature zones allows this method to adapt to the production needs of different material systems and different process windows, offering strong versatility and high yield.

[0021] Preferably, the irregularly shaped magnet is a non-straight magnet, including magnets with two-dimensional curved shapes or three-dimensional curved surface shapes. Examples include tile-shaped, S-shaped, and horseshoe-shaped magnets. This invention is particularly suitable for manufacturing magnets that are curved in a two-dimensional plane (such as S-shaped) or have complex three-dimensional curved surfaces, offering significant technical advantages in achieving grain orientation along the surface normal in these shapes.

[0022] Preferably, the single heat deformation treatment refers to completing the process in a single mold through heating and pressurization, combining the two processes of heat deformation treatment and shaping treatment into one process.

[0023] In this solution, by combining hot deformation and shaping into a single process, not only is the manufacturing cost of a single mold reduced, but more importantly, the total dwell time of the blank at high temperatures is shortened. This significantly improves performance and reduces costs. Excessive grain growth is avoided. The shorter hot processing cycle allows the material to maintain a finer grain structure and superior hot deformability, directly leading to improvements in key performance indicators such as magnet coercivity (Hcj) and maximum energy product (BHmax). Furthermore, one-step forming avoids the risk of point contact cracking caused by decreased material hot deformability during secondary high-temperature shaping, thus significantly improving production yield.

[0024] Preferably, the mold includes at least an upper punch and a lower punch, and the hot-pressed blank is extruded and formed by the engagement of the upper punch and the lower punch.

[0025] Preferably, the hot-pressed blank is pre-designed as a multi-cavity connected structure, and after heat deformation treatment, multiple independent irregularly shaped magnets are obtained by cutting off the connected portions; alternatively, the hot-pressed blank is designed as a single-cavity structure, and the irregularly shaped magnets obtained after heat deformation treatment are the net-formed products. No further machining is required.

[0026] The multi-cavity connection design enables multiple parts from a single mold, significantly improving production efficiency per batch; while the single-cavity net-shape design completely eliminates subsequent processing steps, achieving 100% material utilization, making it particularly suitable for high-value, high-volume product production. It balances production efficiency and material utilization.

[0027] Secondly, the present invention provides a near-net-shape irregularly oriented magnet, which is prepared by the above-described manufacturing method of a near-net-shape irregularly oriented magnet, wherein the easy magnetization axis of the magnet is distributed along the normal of the outer surface of the magnet.

[0028] The magnet of this invention is neither a body of revolution nor a body with a constant cross-section. That is, the magnet of this invention has at least one non-planar magnetized curved surface. This overcomes the technical obstacle of traditional processes being unable to achieve effective orientation on such structures, providing greater freedom for the design of high-end magnetic devices.

[0029] Preferably, the irregularly shaped magnet has a tile-shaped, S-shaped, or horseshoe-shaped shape.

[0030] The technical solution of this invention can stably manufacture magnets with specific complex shapes such as tile-shaped (for high-performance motors), S-shaped, and horseshoe-shaped, and ensure their orientation accuracy, directly entering high-end market fields such as servo motors, precision magnetic levitation, and special sensors.

[0031] Preferably, the magnet size of the present invention can be as low as less than 10 mm or as large as more than 60 mm. It is not limited by size.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a single-stage hot deformation process, integrating the forming of complex shapes with the orientation of curved surfaces, achieving near-net-shape forming of irregularly shaped magnets. Compared to the traditional two-step method of "hot deformation + separate shaping," this invention simplifies the process flow, reduces mold costs, and shortens the high-temperature exposure time of the material, thereby effectively inhibiting grain growth and improving or maintaining key magnetic properties such as coercivity of the magnet. More importantly, by introducing at least one specific process condition among composite lubrication, uniform mold temperature control, and variable-speed pressing, this invention successfully overcomes technical challenges such as uneven material flow, mold adhesion, and blank cracking that easily occur in single-stage hot deformation processes. This ensures that the hot-pressed blank can flow and fill the mold cavity uniformly and stably under high temperature and pressure, while guaranteeing the ideal orientation of internal grains along the curved surface normal. Therefore, this invention can directly obtain high-performance irregularly oriented magnets without or with minimal subsequent machining, significantly improving material utilization and production yield. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the irregularly oriented magnet in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram showing the orientation of the irregularly shaped oriented magnet #1 of the present invention, with the easy magnetization axis direction arranged along the normal of the curved surface; Figure 3 This is a schematic diagram of the blank shape after heat deformation treatment according to the present invention; Figure 4 This is a schematic diagram of the internal grain orientation in different regions of the blank after the heat deformation treatment of the present invention; Figure 5 This is a schematic diagram of the longitudinal cross-sectional structure of the mold of the present invention and its cooperation with the magnet (a schematic diagram of the thermal deformation process). Figure 6 This is a schematic diagram showing the orientation of the irregularly shaped oriented magnet #2 of the present invention, with the easy magnetization axis direction arranged along the normal of the curved surface; Figure 7 This is a speed curve showing the change in punch pressing speed with pressing amount during a single heat deformation process of the present invention.

[0034] Marked in the image: 1-Upper punch; 2-Hot-pressed blank; 3-Lower punch; 4-Irregularly shaped oriented magnet. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0036] Example 1 This embodiment provides a method for manufacturing a near-net-shape irregularly oriented magnet. Near-net-shape refers to a part whose shape and size, after forming, are very close to the requirements of the final product, requiring only minimal or no subsequent machining (such as grinding, wire cutting, polishing, etc.) before it can be used directly as a product. Combined with... Figures 1-6 The specific steps shown are as follows: Preparation of hot-pressed blanks: The hot-pressed blank is subjected to a single hot deformation process in a mold to form a pre-designed irregular magnet; Specifically, the hot-pressed blank is prepared in the following manner: Neodymium iron boron (NdFeB) magnetic powder with a PrNd content of 25-35 wt.% was cold-pressed into a powder blank at room temperature. The powder blank was then placed into a hot-pressing mold and hot-pressed under vacuum or inert gas protection. The hot-pressing temperature was 730°C, the hot-pressing pressure was 300 MPa, and the holding time was 5 minutes, resulting in an isotropic, dense hot-pressed blank. The initial shape of the blank was a cube. In this embodiment, the temperature for a single hot deformation was 800°C, the pressure was 120 MPa, and the holding time for hot deformation was 1 minute. No further shaping processing was performed in this method.

[0037] Mold preparation and lubrication: The mold used in this embodiment includes an upper punch 1 and a lower punch 3, which cooperate to form a cavity with an irregular curved surface. A composite lubricant is uniformly coated on the surface of the hot-pressed blank. The composite lubricant comprises molybdenum disulfide, graphite, and boron nitride, wherein the coefficient of friction of molybdenum disulfide is 0.04, the coefficient of friction of graphite ranges from 0.05 to 0.15, and the coefficient of friction of boron nitride is 0.16.

[0038] The composite lubricant coating thickness is 0.01-0.3 mm. The three main components of the composite lubricant are solid lubricants, and a stable high-temperature friction coefficient of 0.10-0.15 is achieved through formulation optimization. Calculation of the high-temperature friction coefficient of composite lubricants: μ=μA wA ×μB wB ×μC wC ×(1+k×wA×wC) Where μ is the coefficient of friction of the composite lubricant; μA and wA are the friction coefficient and content of component 1, respectively; μB and wB are the friction coefficient and content of component 2, respectively; μC and wC are the friction coefficient and content of component 3, respectively.

[0039] This composite lubricant is composed of molybdenum disulfide (MoS2), graphite, and boron nitride (BN), with a coating thickness of 0.05 mm. Measured using a high-temperature friction coefficient tester, the coefficient of friction of this composite lubricant is 0.12 at 800°C, falling within the optimal range of 0.10-0.15.

[0040] Single heat deformation treatment: The hot-pressed blank is placed in the mold and heated to 800°C, with the temperature uniformity of each part of the mold controlled within ±5°C (the measured temperature difference between the center and edge of the mold is ≤3°C). After the temperature stabilizes, the press is started for hot deformation treatment. The upper punch descends at an initial speed of 0.4 mm / s, maintaining this speed when the punch just contacts the hot-pressed blank; when the reduction reaches 1 mm, the reduction speed is gradually increased to 1.1 mm / s and maintained until the deformation is complete. The hot deformation pressure is 120 MPa, and the holding time is 1 minute. During this process, the hot-pressed blank undergoes plastic flow within the mold cavity, gradually filling the irregular curved surface cavity. Simultaneously, the easy magnetization axes of the internal grains rotate with the material flow direction, eventually aligning along the normal direction of the irregular magnet surface.

[0041] like Figure 7 The ideal speed curve is shown: when the punch is about to contact the hot-pressed blank, it descends at a relatively slow pressing speed (0.2~0.6mm / s). After the pressing amount reaches 1mm, the pressing speed of the punch gradually increases to 0.8~2.5mm / s, and then gradually reaches a stable level.

[0042] Demolding and post-processing: After heat deformation, the magnet is directly demolded and air-cooled. The resulting irregularly shaped magnet has a tile-like structure, such as... Figure 1 As shown, its geometric dimensions are: 30 mm in the arc length direction, 20 mm in the width direction, and 5 mm in the thickness direction. The magnet has a smooth surface, no cracks, no sticking defects, and its dimensional accuracy meets the design requirements. It is a net-formed product without any subsequent machining.

[0043] Samples were taken from the thermally deformed irregularly shaped magnet, and backscattered electron (BSE) imaging was used to observe the microstructure of different regions. The results are as follows: Figure 3-4 As shown. Figure 3 This demonstrates the shape change process of a hot-pressed blank, which is formed from an initial cube into a pre-designed tile-shaped magnet after a single hot deformation process. Figure 4 for Figure 3 BSE images of different regions (such as the bottom curved surface and sidewalls) show that, based on the principle of electron channel contrast, grains with different orientations exhibit different grayscale contrasts. Observations show that the preferred orientation direction of the grains in each region is aligned along the normal direction of the curved surface at their location, proving that a single thermal deformation process achieves the ideal normal orientation of the curved surface.

[0044] Magnetic property test: The magnetic properties of the magnet obtained in Example 1 were tested using the NIM-62000 permanent magnet material measurement system. The results are shown in Table 1: remanence Br = 13.378 kGs, coercivity Hcb = 12.371 kOe, intrinsic coercivity Hcj = 17.229 kOe, and maximum energy product (BH)max = 41.64 MGOe.

[0045] In this embodiment, the mold includes an upper punch and a lower punch. The hot-pressed blank is extruded and formed by the engagement of the upper punch and the lower punch. The mold also includes a cavity component for forming a special cavity to accommodate the forming of irregularly shaped magnets with complex three-dimensional curved surfaces.

[0046] Example 2 The only difference between this embodiment and Embodiment 1 is the thermal deformation parameters. Specifically: The hot-pressed blank was prepared in the same manner as in Example 1 (30mm × 20mm). The heat deformation temperature was 750℃, the heat deformation pressure was 120 MPa, and the holding time was 2 minutes. The lubricant, coating thickness, pressure speed control, and mold temperature uniformity control were all the same as in Example 1.

[0047] The shape and size of the magnet after heat deformation are consistent with those of Example 1. The magnetic performance test results are shown in Table 1: Br = 13.364 kGs, Hcb = 12.488 kOe, Hcj = 17.171 kOe, (BH)max = 41.55 MGOe. Compared with Example 1, the grain orientation is slightly different due to the slightly lower heat deformation temperature, but the overall performance remains at a high level.

[0048] Example 3 The difference between this embodiment and Embodiment 1 is that the product size is smaller, and the hot-pressed blank size and hot-pressing and hot-deformation time are adjusted accordingly.

[0049] Hot pressing blank preparation The target product dimensions are 15mm × 10mm × 3mm (length × width × thickness). The size of the hot-pressed blank is reduced accordingly. The hot-pressing temperature is 730℃, the hot-pressing pressure is 300 MPa, and the holding time is 3 minutes (the holding time is shortened due to the reduced blank volume).

[0050] Single heat deformation treatment The heat distortion temperature was 750℃, the pressure was 120 MPa, and the holding time was 1 minute. The lubricant, coating thickness (0.13 mm), and pressure speed control (initial speed of 0.4 mm / s) were the same as in Example 1.

[0051] The obtained irregularly shaped magnet is tile-shaped with acceptable dimensional accuracy. The magnetic properties are shown in Table 1: Br=13.173 kGs, Hcb=12.305kOe, Hcj=16.171 kOe, (BH)max=41.148 MGOe.

[0052] Example 4 The difference between this embodiment and Embodiment 1 is that the product size is larger and the hot pressing parameters have been adjusted accordingly.

[0053] Hot pressing blank preparation The target product dimensions are 40mm × 50mm × 8mm (length × width × thickness). The hot pressing temperature is 750℃ (due to the increased volume of the blank, the hot pressing temperature is appropriately increased to ensure internal density), the hot pressing pressure is 300 MPa, and the holding time is 5 minutes.

[0054] Single heat deformation treatment The heat distortion temperature was 800℃, the pressure was 120 MPa, and the holding time was 2 minutes. The thickness of the lubricant coating was 0.1 mm, and the pressure speed was controlled in the same way as in Example 1 (initial speed of 0.4 mm / s, speed increased after the pressure reduction was ≥1 mm).

[0055] The obtained magnet has acceptable dimensional accuracy and no surface defects. The magnetic properties are shown in Table 1: Br=13.250 kGs, Hcb=12.437kOe, Hcj=16.018 kOe, (BH)max=41.706 MGOe.

[0056] Example 5 The difference between this embodiment and Embodiment 1 is that the product size is larger (50mm×60mm×10mm), and the hot pressing and heat deformation time are adjusted accordingly.

[0057] Hot pressing blank preparation The hot pressing temperature is 750℃, the pressure is 300 MPa, and the holding time is 7 minutes.

[0058] Single heat deformation treatment The heat distortion temperature is 800℃, the pressure is 120 MPa, and the holding time is 3 minutes. The lubricant coating thickness is 0.12mm.

[0059] The dimensional accuracy of the obtained magnet is qualified. The magnetic properties are shown in Table 1: Br=13.226 kGs, Hcb=12.284 kOe, Hcj=15.727 kOe, (BH)max=41.059 MGOe.

[0060] Comparative Example 1 (The process of heat deformation and shaping is carried out in stages) In this comparative example, the difference in Example 1 is that the single heat deformation process is changed to a two-step process of "heat deformation + separate shaping". An irregularly shaped oriented magnet is obtained, and the specific parameters are shown in Table 1.

[0061] Comparative Example 2 (The process of heat deformation and shaping is carried out in stages) In this comparative example, the difference in Example 1 is that the single heat deformation process is changed to a two-step process of "heat deformation + separate shaping". An irregularly shaped oriented magnet is obtained, and the specific parameters are shown in Table 1.

[0062] Comparative Example 3 (The process of heat deformation and shaping is carried out in stages) In this comparative example, the difference in Example 1 is that the single heat deformation process is changed to a two-step process of "heat deformation + separate shaping". An irregularly shaped oriented magnet is obtained, and the specific parameters are shown in Table 1.

[0063] Taking Comparative Example 1 as an example: First, the magnet was heat-deformed at 800℃ and 120 MPa for 1 minute to obtain a preliminary magnet; then, the magnet was transferred to another shaping mold and shaped at 850℃ and 200 MPa for 1 minute. The remaining parameters were the same as in Example 1.

[0064] The magnetic performance test results showed that the remanence Br (12.769-12.865 kGs) and maximum energy product (38.474~39.012 MGOe) of Comparative Examples 1-3 were significantly lower than those of Example 1 (41.64 MGOe). The above results indicate that the step-by-step thermal processing leads to grain growth and deterioration of magnetic properties. Furthermore, the products in Comparative Examples 1–3 exhibited defects such as slight oxidation, edge burrs, or deformation on their surfaces, resulting in low yields.

[0065] Comparative Example 4 (Uneven mold temperature) The only difference between Comparative Example 4 and Example 1 is that the mold temperature uniformity was not controlled during the heat deformation process, resulting in a local temperature difference exceeding ±10℃ (measured fluctuation of 780-810℃). The results are shown in Table 1; cracks appeared at the product edges, making it impossible to obtain a complete magnet. This indicates that controlling the mold temperature uniformity within ±5℃ is one of the key conditions for the success of this method.

[0066] Comparative Example 5 (Single Lubricant) The difference between Comparative Example 5 and Example 1 is that the hot-pressed blank surface was coated with only a single molybdenum disulfide lubricant (excluding graphite and boron nitride), with a friction coefficient of 0.04 and a coating thickness of 0.13 mm. The results, as shown in Table 1, revealed severe sticking to the mold, making demolding impossible. This indicates that the three components of the composite lubricant of this invention work synergistically to provide a stable and suitable high-temperature friction coefficient (0.10-0.15), which a single lubricant cannot meet.

[0067] Comparative Example 6 (Two Lubricants) The difference between Comparative Example 6 and Example 1 is that the surface of the hot-pressed blank is only coated with graphite and boron nitride, and the friction coefficient after the ratio is 0.156. The process conditions are exactly the same as those of Comparative Example 5. Under these parameters, there are defects such as large deformation resistance, insufficient deformation, and sticking to the mold.

[0068] Comparative Example 7 (Pressure speed too fast) The difference between Comparative Example 7 and Example 1 is that the pressing speed when the punch contacts the blank is 1.5 mm / s (instead of 0.2~0.6 mm / s). The results are shown in Table 1, and cracks appeared at the edge of the product. This indicates that an excessively fast initial pressing speed will cause the blank surface to bear excessive impact stress, leading to cracking; the variable speed control strategy of the present invention (slow first, then fast) is an important means to ensure the integrity of the molding.

[0069] Comparative Example 8 (without size compensation) The difference between Comparative Example 8 and Example 1 is that the mold cavity dimensions were designed directly according to the nominal product dimensions (30mm × 20mm), without considering heat shrinkage compensation (α = 0). As shown in Table 2, after heat deformation and cooling to room temperature, the actual product dimensions were 30.19~30.25mm (length) and 20.13~20.17mm (width), significantly exceeding the target tolerance range (±0.05mm). This indicates that the heat shrinkage compensation formula A = B × (1 + α) and the values ​​of α = 0.005~0.007 in this invention are crucial for achieving near-net-shape forming.

[0070] Table 1 Comparison of main process parameters and magnetic properties of each embodiment and comparative example

[0071] Table 2 shows the process parameters and performance characteristics of Example 1 and Comparative Examples 4-7.

[0072] Table 3 shows the main process parameters and dimensional comparisons of Example 1 and Comparative Example 8.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an irregularly shaped oriented magnet, characterized in that, Includes the following steps: Preparation of hot-pressed blanks; The hot-pressed blank is subjected to a single hot deformation process in a mold to form a pre-designed irregular magnet; During the heat deformation process, the easy magnetization axis of the irregular magnet rotates with the change of the outer surface and eventually aligns along the normal of the irregular magnet surface. The single heat deformation treatment satisfies at least one of the following conditions: a. The surface of the hot-pressed blank is coated with a composite lubricant, which includes molybdenum disulfide, graphite, and boron nitride; b. The temperature uniformity of the mold is controlled within ±5°C; c. During a single hot deformation process, the pressing speed of the die punch is 0.2-0.6 mm / s when it contacts the hot-pressed blank, and increases to 0.8-2.5 mm / s after the pressing amount reaches at least 1 mm.

2. The method for manufacturing an irregularly shaped oriented magnet according to claim 1, characterized in that, The high-temperature friction coefficient of the composite lubricant is in the range of 0.10-0.

15.

3. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The coating thickness of the composite lubricant is 0.01mm-0.3mm.

4. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The cavity dimensions of the mold and the target product dimensions of the irregularly shaped magnet satisfy the following formula: A = B×(1+α), Where α is the heat shrinkage compensation coefficient, with a value range of 0.005-0.007, A represents the target product size, and B represents the cavity size.

5. The method for manufacturing an irregularly oriented magnet according to claim 4, characterized in that, The heat shrinkage compensation coefficient is determined based on the heat distortion temperature: When the mold temperature is 600-700°C, α is taken as 0.005; When the mold temperature is 700-800°C, α is taken as 0.006; When the mold temperature is 800-900°C, α is taken as 0.

007.

6. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The irregularly shaped magnet is a non-straight magnet: including magnets with two-dimensional curved shapes or three-dimensional curved surface shapes.

7. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The single-stage heat deformation process refers to completing the process in a single mold through heating and pressurization, combining the two processes of heat deformation and shaping into one process.

8. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The mold includes at least an upper punch and a lower punch, and the hot-pressed blank is extruded and formed by the engagement of the upper punch and the lower punch.

9. The method for manufacturing an irregularly oriented magnet according to claim 1, characterized in that, The hot-pressed blank is pre-designed as a multi-cavity connection structure. After the hot deformation process is completed, multiple independent irregular magnets are obtained by cutting off the connection parts; or, the hot-pressed blank is designed as a single-cavity structure, and the irregular magnets obtained after the hot deformation process are the net-formed products.

10. An irregularly shaped oriented magnet, characterized in that, The magnet is prepared by the manufacturing method according to any one of claims 1-9, and the easy magnetization axis of the magnet is distributed along the normal of the outer surface of the magnet.

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