Anisotropic bonded magnet and preparation method thereof

Abstract

The invention relates to the technical field of magnets, and particularly discloses an anisotropic bonded magnet and a preparation method thereof. The anisotropic bonded magnet comprises spherical Fe-Ni alloy powder, modified epoxy resin and a coupling agent, the mass ratio of the spherical Fe-Ni alloy powder to the modified epoxy resin is (7-9): (1-3), the adding amount of the coupling agent is 0.5-2 wt% of the total mass of the bonding agent, and the modified epoxy resin is obtained by modifying epoxy resin through a hyperbranched polymer; the preparation method of the anisotropic bonded magnet comprises the following steps: mixing spherical Fe-Ni alloy powder with modified epoxy resin, adding a coupling agent to form uniform slurry, placing the slurry in a directional magnetic field with the strength of 1800-2000 Oersted, keeping for 10-15 minutes, and heating and curing the oriented slurry to obtain the anisotropic bonded magnet. The anisotropic bonded magnet has the advantages that the magnetic performance is high, and the directional arrangement uniformity of the magnetic powder is improved at low cost.

Description

Technical Field

[0001] This application relates to the technical field of magnets, and more specifically, it relates to an anisotropic bonded magnet and a preparation method thereof. Background Art

[0002] In recent years, anisotropic bonded magnets have become a research hotspot in the field of magnetic materials due to their high magnetic energy product, precision forming ability, and complex shape processing capabilities. Currently, the mainstream preparation techniques include injection molding and compression molding. The core lies in the directional arrangement of magnetic powder through an external field (such as a magnetic field or pressure), and the structural curing of the magnet is achieved with the help of a binder. However, there are significant bottlenecks in the uniformity of magnetic powder directional arrangement and the interfacial compatibility between the binder and magnetic powder in the existing processes. Research shows that magnetic powder is easily affected by uneven rheological stress distribution and magnetic field gradient attenuation during the forming process, resulting in an orientation degree fluctuation exceeding 15%, directly affecting the stability of the remanence (Br) and coercivity (Hcj) of the magnet. At the same time, the lack of polar matching between the binder system and magnetic powder often forms micron-sized voids or chemical weak bonds at the interface, causing a magnetic property loss rate as high as 10% - 20%, which has become a key factor restricting the industrial application of high-performance magnets.

[0003] In response to the above problems, the existing technology mainly adopts two improvement paths: optimizing the morphology of magnetic powder and compounding binders. The former improves the orientation response by controlling the size distribution and surface energy of magnetic powder, while the latter enhances the interfacial binding force through polar group regulation. However, these methods expose obvious defects in practical applications: although the spheroidization treatment of magnetic powder can improve fluidity, it will weaken the orientation potential of anisotropic magnetic crystals; the introduction of a multi-component binder system improves compatibility, but there is a conflict between the cross-linking reaction temperature window and the thermal stability of magnetic powder, resulting in thermal stress cracks during the forming process. Moreover, the existing processes rely on high-precision molds and complex post-treatment, increasing the production cost by more than 35%, making it difficult to meet the requirements of the consumer electronics field for low-cost and large-scale production. Summary of the Invention

[0004] To solve the above problems, this application provides an anisotropic bonded magnet and a preparation method thereof.

[0005] The anisotropic bonded magnet provided by this application adopts the following technical solution: An anisotropic bonded magnet includes spherical Fe-Ni alloy powder, modified epoxy resin, and a coupling agent. The mass ratio of the spherical Fe-Ni alloy powder to the modified epoxy resin is (7 - 9):(1 - 3). The particle size distribution of the spherical Fe-Ni alloy powder is 2 - 5 μm. The addition amount of the coupling agent is 0.5 - 2 wt% of the total mass of the binder. The modified epoxy resin is obtained by modifying epoxy resin with a hyperbranched polymer.

[0006] By adopting the above technical solutions, the spherical Fe-Ni alloy powder with a particle size of 2-5 μm balances the fluidity and anisotropic orientation potential of the magnetic powder, making the magnetic powder easier to be oriented in the magnetic field, reducing the fluctuation of the orientation degree, and improving the stability of the remanence and coercivity. The hyperbranched polymer-modified epoxy resin optimizes the molecular structure, enhances the polar matching with the magnetic powder, and the coupling agent further promotes the interfacial chemical bonding, reduces the micron-sized voids and weak bonds at the interface, and the magnetic property loss rate decreases. The high magnetic powder content ensures a high magnetic energy product, and the low binder ratio reduces the interference of the non-magnetic phase, improving the overall performance of the magnet.

[0007] Optionally, the specific method for modifying the epoxy resin is as follows: Mix bisphenol A epoxy resin and hyperbranched polymer in a mass ratio of (8-9):1 to obtain a mixture, and add a coupling agent; Under nitrogen protection, heat the mixture to 120-130 °C and stir at 500-800 rpm for 2-3 hours to obtain the modified epoxy resin.

[0008] By adopting the above technical solutions, the hyperbranched polymer introduces a large number of branched structures, increases the crosslinking density and flexibility of the binder, broadens the crosslinking reaction temperature window, alleviates the conflict with the thermal stability of the magnetic powder, and reduces the thermal stress during the curing process. Nitrogen protection and medium-speed stirring avoid the oxidation of the epoxy resin, ensure the uniform dispersion of the hyperbranched polymer, and improve the overall compatibility and interfacial bonding force of the binder.

[0009] Optionally, the surface of the spherical Fe-Ni alloy powder is coated with a layer of nano-silica, and the nano-silica is pretreated with a silane coupling agent. The surface hydroxyl density of the nano-silica pretreated with the silane coupling agent is ≥ 3.5 groups / nm 2 。

[0010] By adopting the above technical solutions, the nano-silica coating forms a uniform interfacial layer to isolate the direct polar conflict between the magnetic powder and the binder. The hydroxyl groups of the silane coupling agent react chemically with the epoxy groups of the epoxy resin to form covalent bonds, improving the interfacial bonding force and reducing the porosity. The high hydroxyl density enhances the surface activity, promotes the chemical adsorption of the coupling agent and the binder, further reduces the weak bonds at the interface, and improves the structural stability and magnetic property retention rate of the magnet.

[0011] Optionally, it further includes a liquid crystal epoxy monomer. The addition amount of the liquid crystal epoxy monomer is 5-15% of the mass of the modified epoxy resin. The mesogenic group of the liquid crystal epoxy monomer is a biphenyl structure, and its molecular weight is 400-800 g / mol.

[0012] By adopting the above technical solution, the liquid crystal epoxy monomer with a biphenyl structure can cooperate with magnetic powder to be directionally arranged in a magnetic field, forming a "double orientation" effect, reducing the influence of uneven distribution of rheological stress, decreasing the fluctuation of orientation degree, and improving the remanence uniformity. The molecular weight of 400 - 800 g / mol ensures good dispersion of the liquid crystal monomer in the binder, having both fluidity and orientation ability, and avoiding the hindrance of macromolecular chain segments to the movement of magnetic powder.

[0013] In a second aspect, the present application provides a method for preparing an anisotropic bonded magnet, adopting the following technical solution: A method for preparing an anisotropic bonded magnet, comprising the following steps: Mix spherical Fe-Ni alloy powder with modified epoxy resin, and add a coupling agent to form a uniform slurry. Place the slurry in a directional magnetic field with a strength of 1800 - 2000 oersteds for 10 - 15 minutes, and cure the directional slurry at 115 - 125 °C for 5 - 6 hours to obtain an anisotropic bonded magnet.

[0014] Optionally, perform pulsed magnetic field treatment on the cured anisotropic bonded magnet. The magnetic field strength of the pulsed magnetic field treatment is 2500 - 3000 oersteds, the pulse frequency is 1 - 5 Hz, and the treatment time is 30 - 60 seconds.

[0015] By adopting the above technical solution, the high-frequency disturbance of the pulsed magnetic field can adjust the slight deflection of magnetic powder caused by stress relaxation during the curing process, further improving the orientation degree and enhancing the stability of coercivity. The pulsed treatment promotes further alignment of magnetic domains, increases the remanence (Br), and synchronously optimizes the magnetic energy product (BHmax).

[0016] Optionally, place the slurry in a directional magnetic field with a strength of 1000 - 1400 oersteds for 5 - 10 minutes, and then increase the directional magnetic field to 1800 - 2000 oersteds and keep it for 5 - 10 minutes.

[0017] By adopting the above technical solution, the low magnetic field initially arranges the magnetic powder preliminarily, avoiding stress concentration caused by a sudden increase in slurry viscosity under a high magnetic field, and then the high magnetic field strengthens the orientation, solving the problem of uneven distribution of rheological stress in the traditional process, improving the uniformity of orientation degree, and narrowing the fluctuation range of magnetic properties. The staged treatment reduces the energy consumption of long-term action of the high magnetic field, and at the same time ensures the directional effect, which is suitable for industrial mass production.

[0018] Optionally, preheat the directional slurry at 80 - 85 °C for 1 - 1.5 hours, and then increase the temperature to 115 - 125 °C at a rate of 2 °C / min and keep it warm for 5 - 6 hours. The curing pressure is 0.5 - 1 MPa.

[0019] By adopting the above technical solutions, during the preheating stage, the volatilization of the solvent in the slurry and the preliminary wetting of the magnetic powder by the binder are promoted, and the temperature is raised slowly to avoid the concentration of thermal stress. The low-pressure curing at 0.5-1 MPa ensures the close arrangement of the magnetic powder, reduces the internal voids, and at the same time avoids the damage to the magnetic powder orientation caused by high pressure, thus improving the magnet density.

[0020] In summary, the present application has the following beneficial effects: 1. Due to the modification of epoxy resin by hyperbranched polymer, the pretreatment of nano-silica-coated magnetic powder with silane coupling agent, and the introduction of liquid crystal epoxy monomer in the present application, a binder-magnetic powder interface with strong polar matching is constructed, eliminating micron-level voids and chemical weak bonds, reducing the magnetic property loss rate, enhancing the interfacial bonding force, and significantly enhancing the structural stability.

[0021] 2. In the present application, the staged gradient magnetic field treatment and the secondary correction of the pulsed magnetic field are preferably adopted, combined with the synergistic orientation effect of the liquid crystal epoxy monomer, to overcome the problems of uneven rheological stress and magnetic field gradient attenuation, reduce the fluctuation of the orientation degree, improve the stability of the remanence (Br) and coercivity (Hcj), and synchronously optimize the magnetic energy product (BHmax).

[0022] 3. The method of the present application solves the problem of thermal stress cracks in the traditional process through the design of low-temperature curing, stepwise temperature rise and low-pressure curing, reduces the dependence on high-precision molds and complex post-treatment, has a low production cost, and meets the requirements of low-cost and large-volume production in consumer electronics. Specific Embodiments

[0023] The following further elaborates on the present application in conjunction with embodiments. It should be specifically noted that: for those conditions not specified in the following embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. Except for special instructions, the raw materials used in the following embodiments can all be obtained from ordinary commercial sources.

[0024] Preparation Example of Modified Epoxy Resin Preparation Example 1 A preparation method of a modified epoxy resin: Prepare the following raw materials: Bisphenol A epoxy resin (E-51, epoxy value 0.48-0.54 eq / 100 g), hyperbranched polyester (HBP, hydroxyl-terminated, molecular weight 5000 g / mol), γ-glycidoxypropyltrimethoxysilane (KH-560, purity ≥98%).

[0025] The epoxy resin is dehydrated in a vacuum drying oven at 80 °C for 2 hours, and the vacuum degree is -0.08 MPa. The hyperbranched polymer is dried with molecular sieve for 48 hours before use.

[0026] Weigh 850 g of epoxy resin and 100 g of hyperbranched polymer into a container, add 20 g of KH-560 coupling agent, and pre-disperse with a high-speed shear emulsifier at 3000 rpm for 5 min until the system is homogeneous.

[0027] Under a nitrogen atmosphere, heat the container to 125 ± 2 °C, stir at 650 rpm, and react at a constant temperature for 2.5 hours.

[0028] After stopping heating, continue stirring until the temperature drops below 80 °C. Transfer the product to a vacuum degassing tank, with a vacuum degree of -0.1 MPa, degas for 30 min, and filter through a 200-mesh stainless steel filter screen to obtain the modified epoxy resin.

[0029] Preparation Example 2 A method for preparing a modified epoxy resin: The difference from Preparation Example 1 is that 750 g of epoxy resin and 100 g of hyperbranched polymer are weighed into a container.

[0030] Preparation Example 3 A method for preparing a modified epoxy resin: The difference from Preparation Example 1 is that 950 g of epoxy resin and 100 g of hyperbranched polymer are weighed into a container. Examples

[0031] Example 1 A method for preparing an anisotropic bonded magnet: Prepare the following raw materials: Spherical Fe-Ni alloy powder (particle size 2 - 5 μm, surface coated with a nano-SiO2 layer, SiO2 hydroxyl density ≥ 3.5 groups / nm 2 , and the nano-silica is pretreated with a silane coupling agent), modified epoxy resin (prepared from Preparation Example 1), silane coupling agent (KH-550, purity ≥ 98%), liquid crystal epoxy monomer (biphenyl mesogenic group, molecular weight 400 - 800 g / mol), anhydrous ethanol (analytical grade).

[0032] Weigh 800 g of Fe-Ni alloy powder and 200 g of modified epoxy resin according to a mass ratio of 8:2, add 30 g of liquid crystal epoxy monomer, and then add 4 g of silane coupling agent. Place the above raw materials in a planetary mixer, first mix at 1000 rpm for 10 min under normal pressure, then evacuate to -0.08 MPa and disperse at 1500 rpm for 15 min. Measure the slurry viscosity to be 3000 ± 500 mPa·s (measured at 25 °C with Brookfield DV2T).

[0033] Inject the slurry into a mold and apply a magnetic field for orientation according to the following procedure: First stage: 1400 Oe, hold for 5 min; Second stage: 2000 Oe, hold for 10 min; The magnetic field direction is parallel to the forming pressure direction; Then, preheat the green body in an oven at 85°C for 1 h, transfer it to a hot pressing furnace, heat it up to 125°C at a rate of 2°C / min, apply a pressure of 0.8 MPa, and cure it at a constant temperature for 5.5 h. Pulse magnetic field strengthening is performed on the cured green body, with 2800 Oersteds, 3 Hz, and a duration of 45 seconds.

[0034] Cool down the temperature to 60°C in a programmed manner and then demold to obtain an anisotropic bonded magnet.

[0035] Example 2 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that 900 g of Fe-Ni alloy powder and 100 g of modified epoxy resin are weighed according to a mass ratio of 9:1.

[0036] Example 3 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that 700 g of Fe-Ni alloy powder and 300 g of modified epoxy resin are weighed according to a mass ratio of 7:3.

[0037] Example 4 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that the modified epoxy resin is prepared from Preparation Example 2.

[0038] Example 5 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that the modified epoxy resin is prepared from Preparation Example 3.

[0039] Example 6 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that the surface of the spherical Fe-Ni alloy powder is not coated with nano-silica.

[0040] Example 7 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that the surface hydroxyl density of the nano-silica pretreated with the silane coupling agent is < 3.5 groups / nm 2 .

[0041] Example 8 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that no liquid crystal epoxy monomer is added.

[0042] Example 9 A method for preparing an anisotropic bonded magnet: The difference from Example 1 is that the cured anisotropic bonded magnet is not subjected to pulse magnetic field treatment.

[0043] Example 10 A method for preparing an anisotropic bonded magnet: Different from Example 1, the slurry is placed in a directional magnetic field with a strength of 2000 Oersteds for 15 minutes without performing the first-stage treatment.

[0044] Example 11 A method for preparing an anisotropic bonded magnet: Different from Example 1, the slurry after orientation is not preheated.

[0045] Comparative example Comparative example 1 A method for preparing an anisotropic bonded magnet: Different from Example 1, 600 g of Fe-Ni alloy powder and 400 g of modified epoxy resin are weighed according to a mass ratio of 6:4.

[0046] Comparative example 2 A method for preparing an anisotropic bonded magnet: Different from Example 1, 950 g of Fe-Ni alloy powder and 50 g of modified epoxy resin are weighed according to a mass ratio of 9.5:0.5.

[0047] Comparative example 3 A method for preparing an anisotropic bonded magnet: Different from Example 1, the particle size distribution of the spherical Fe-Ni alloy powder is 5 - 10 μm.

[0048] Comparative example 4 A method for preparing an anisotropic bonded magnet: Different from Example 1, the epoxy resin is not modified.

[0049] Performance detection test Detection method Residual magnetism (Br): Measured at room temperature using a vibrating sample magnetometer (VSM, LakeShore 7404) according to GB / T 3217 - 2013; Coercivity (Hcj): The same as above, calculated through the hysteresis loop Maximum magnetic energy product ((BH)max): Calculated by integrating the B-H curve.

[0050] Flexural strength: According to GB / T 6569 - 2006, the three-point bending method (Instron 3365, span 20 mm, loading rate 1 mm / min) is adopted.

[0051] Magnetic powder orientation degree: Calculated by the X-ray diffraction (XRD, Rigaku SmartLab) of the orientation factor of the (004) crystal plane.

[0052] Table 1 Detection data Combining Example 1 and Comparative Examples 1-2 and referring to Table 1, it can be seen that in Comparative Example 1 and Comparative Example 2, due to the excessive or too low proportion of the binder, the magnetic properties of the magnet decreased significantly. Compared with Example 1, too much binder in Comparative Example 1 would increase the interference of the non-magnetic phase, and the magnetic energy product decreased from 85 kJ / m 3 to 42 kJ / m 3 , and the flexural strength decreased from 162 MPa to 98 MPa; in Comparative Example 2, the too high proportion of magnetic powder led to insufficient binder for effective curing, the orientation degree decreased from 92% to 72%, and the remanence (Br) decreased from 0.78 T to 0.61 T. It shows that when the mass ratio of spherical Fe-Ni alloy powder to modified epoxy resin is in the range of (7-9):(1-3), the high filling amount of magnetic powder and the curing effect of the binder can be balanced, avoiding the decrease of magnetic properties and mechanical properties caused by the imbalance of the ratio.

[0053] Combining Example 1 and Comparative Example 3 and referring to Table 1, it can be seen that in Comparative Example 3, magnetic powder with a particle size of 5-10 μm was used, and its orientation degree, remanence and coercivity were all significantly lower than those in Example 1. A particle size of 2-5 μm can balance the fluidity of magnetic powder and the potential of anisotropic orientation. Too large a particle size will lead to uneven directional arrangement and a decrease in the orientation degree due to the increase in the movement resistance of magnetic powder and the reduction in the magnetic field response efficiency.

[0054] Combining Example 1 and Comparative Example 4 and referring to Table 1, it can be seen that hyperbranched polymer modification can optimize the polarity matching and crosslinking density of the binder through the branched structure. Due to poor interfacial compatibility and thermal stress crack problems of unmodified epoxy resin, the magnetic property loss rate exceeded 35%, verifying the key role of the modification treatment in enhancing the interfacial bonding force and structural stability.

[0055] Combining Examples 1-3 and referring to Table 1, it can be seen that a mass ratio of 8:2 is the optimal ratio. At this time, the high filling amount of magnetic powder ensures a high magnetic energy product, and at the same time, 20% binder can be fully cured and reduce the interference of the non-magnetic phase; too high or too low proportion of magnetic powder will lead to a decrease in the orientation degree and mechanical properties due to insufficient or excessive binder.

[0056] Combining Example 1 and Examples 4-5 and referring to Table 1, it can be seen that when the mass ratio of bisphenol A epoxy resin to hyperbranched polymer is 8-9:1, the best crosslinking density and flexibility can be formed. Excessive epoxy resin will reduce the modification effect of hyperbranched polymer, while insufficient epoxy resin will lead to insufficient branched structure, ultimately affecting the interfacial compatibility and magnet orientation degree, verifying the key role of ratio optimization in the performance of the binder.

[0057] Combining Example 1 and Example 6 and referring to Table 1, it can be seen that the nano-silica coating layer can isolate the polarity conflict between magnetic powder and binder, and the hydroxyl groups formed by the pretreatment of silane coupling agent can promote interfacial covalent bond binding. When not coated, the interfacial porosity increases, resulting in a magnetic property loss of about 20% and a 30% decrease in mechanical properties.

[0058] Combining Example 1 and Example 7 and referring to Table 1, it can be seen that sufficient hydroxyl density is a prerequisite for the effective adsorption and interfacial chemical bonding of silane coupling agents. Insufficient hydroxyl density will lead to a decrease in the grafting efficiency of the coupling agent, an increase in weak bonds at the interface, and a magnetic property loss of about 10%, verifying the key influence of surface activity on interfacial compatibility.

[0059] Combining Example 1 and Example 8 and referring to Table 1, it can be seen that the liquid crystal epoxy monomer with a biphenyl structure synergistically arranges magnetic powder through the "bi - orientation" effect, reducing the influence of uneven rheological stress. When not added, the degree of orientation decreases by 7%, and the maximum energy product ((BH)max) decreases from 85 kJ / m 3 to 72 kJ / m 3 , proving the important role of liquid crystal monomers in improving the orientation uniformity and magnetic properties.

[0060] Combining Example 1 and Example 9 and referring to Table 1, it can be seen that pulsed magnetic field treatment can correct the slight deflection of magnetic powder during the curing process, increasing the degree of orientation by 3% and the remanence by 4%, and enhancing the stability of the coercive force, verifying the optimization effect of secondary magnetic field treatment on the refined arrangement of magnetic domains.

[0061] Combining Example 1 and Example 10 and referring to Table 1, it can be seen that low - field pre - alignment (1400 Oe for 5 minutes) can avoid stress concentration caused by a sudden increase in the slurry viscosity under high magnetic fields. Then, high - field strengthening (2000 Oe for 10 minutes) can significantly improve the orientation uniformity. When not processed in stages, due to uneven rheological stress, the degree of orientation decreases by 9%, and the magnetic property loss is about 20%, proving the necessity of the staged strategy for industrial orientation processes.

[0062] Combining Example 1 and Example 11 and referring to Table 1, it can be seen that the pre - heating stage can promote the volatilization of the solvent and the preliminary wetting of magnetic powder by the binder. The step - by - step temperature increase reduces the concentration of thermal stress. When not pre - heated, due to the sudden increase in temperature during the curing process, internal stress accumulates, the mechanical properties decrease by 10%, and the degree of orientation decreases by 5%, verifying the role of pre - heating treatment in improving the structural stability of magnets.

[0063] This specific embodiment is only an explanation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. An anisotropic bonded magnet, characterized in that, It includes spherical Fe-Ni alloy powder, modified epoxy resin and a coupling agent. The mass ratio of the spherical Fe-Ni alloy powder to the modified epoxy resin is (7 - 9):(1 - 3). The particle size distribution of the spherical Fe-Ni alloy powder is 2 - 5 μm. The addition amount of the coupling agent is 0.5 - 2 wt% of the total mass of the binder. The modified epoxy resin is obtained by modifying epoxy resin with a hyperbranched polymer.

2. The anisotropic bonded magnet according to claim 1, wherein: The specific method for the modified epoxy resin is as follows: Mix bisphenol A epoxy resin and a hyperbranched polymer in a mass ratio of (8 - 9):1 to obtain a mixture, and add a coupling agent; Under nitrogen protection, heat the mixture to 120 - 130 °C and stir at 500 - 800 rpm for 2 - 3 hours to obtain the modified epoxy resin.

3. The anisotropic bonded magnet according to claim 1, wherein: The surface of the spherical Fe-Ni alloy powder is coated with a layer of nano-silica. The nano-silica is pretreated with a silane coupling agent, and the surface hydroxyl density of the nano-silica pretreated with the silane coupling agent is ≥3.5 groups / nm².

4. The anisotropic bonded magnet according to claim 1, wherein: It also includes a liquid crystal epoxy monomer. The addition amount of the liquid crystal epoxy monomer is 5 - 15% of the mass of the modified epoxy resin. The mesogenic group of the liquid crystal epoxy monomer is a biphenyl structure, and its molecular weight is 400 - 800 g / mol.

5. A method for preparing an anisotropic bonded magnet according to any one of claims 1-4, characterized in that: It includes the following steps: Mix the spherical Fe-Ni alloy powder with the modified epoxy resin, add a coupling agent to form a uniform slurry. Place the slurry in a directional magnetic field with a strength of 1800 - 2000 Oe and keep it for 10 - 15 minutes. Cure the oriented slurry at 115 - 125 °C for 5 - 6 hours to obtain an anisotropic bonded magnet.

6. The method for preparing the anisotropic bonded magnet according to claim 5, wherein: Perform pulse magnetic field treatment on the cured anisotropic bonded magnet. The magnetic field strength of the pulse magnetic field treatment is 2500 - 3000 Oe, the pulse frequency is 1 - 5 Hz, and the treatment time is 30 - 60 seconds.

7. The method for preparing an anisotropic bonded magnet according to claim 5, wherein: Place the slurry in a directional magnetic field with a strength of 1000 - 1400 Oe and keep it for 5 - 10 minutes, and then raise the directional magnetic field to 1800 - 2000 Oe and keep it for 5 - 10 minutes.

8. The method for preparing the anisotropic bonded magnet according to claim 5, characterized in that: Preheat the oriented slurry at 80 - 85 °C for 1 - 1.5 hours, then raise the temperature at a rate of 2 °C / min to 115 - 125 °C and keep it warm for 5 - 6 hours. The curing pressure is 0.5 - 1 MPa.

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