A soft magnetic composite powder and a method for producing the same

Abstract

This invention provides a soft magnetic composite powder and its preparation method, belonging to the field of soft magnetic materials technology. The raw materials for preparing the soft magnetic composite powder of this invention include a matrix powder and a release agent; the matrix powder is composed of a first soft magnetic powder with a particle size D50 of 30-50 μm and a second soft magnetic powder with a particle size D50 not greater than 10 μm; the mass of the first soft magnetic powder accounts for 20%-50% of the mass of the matrix powder, and the mass of the release agent is 0.05%-0.2% of the mass of the matrix powder. By controlling the proportion of large soft magnetic powder particles with a particle size D50 of 30-50 μm in the soft magnetic powder, and using these large soft magnetic powder particles in combination with a specific amount of release agent, the soft magnetic composite powder obtained can prevent adhesion to the mold during the pressing and molding process and has high magnetic permeability.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, and in particular to a soft magnetic composite powder and its preparation method. Background Technology

[0002] In existing technologies, during the pressing and molding process of soft magnetic powder, factors such as air humidity, powder adhesive selection, and improper curing can easily lead to film adhesion during product demolding. When the bonding force between powder particles and the mold surface is greater than the bonding force between powder particles, during demolding, powder particles on the mold contact surface adhere to the mold surface and detach from other powder particles, ultimately resulting in poor appearance and performance of the pressed product / semi-finished product. Furthermore, improper handling of film adhesion can easily lead to high mold wear, low production capacity, and a significant impact on product qualification rate.

[0003] At present, the industry usually wipes the mold surface with alcohol after setting a certain number of molds. In case of severe film adhesion, even sharp objects are used to carve off the powder adhering to the mold surface. This seriously affects production efficiency and has high labor and equipment costs. For example: (1) High film cleaning frequency, 300-500pcs / time, mold needs to be cleaned about 5 minutes after starting the machine; (2) High labor cost: 2 machines / person; (3) Low single machine capacity: 80-110kpcs / unit.

[0004] To reduce powder adhesion, patent application CN119282924A uses a rubber-diamond mixture as the abrasive to polish the surface of the mold steps in a toothed powder metallurgy mold, improving surface smoothness and preventing powder adhesion while significantly increasing production output. Patent application CN217556076U, similar to CN119282924A, addresses the issue of powder detachment by applying an anti-adhesion layer to the mold body surface. This involves a composite film system of metal and DLC carbon films of appropriate thickness. However, these existing technologies increase mold costs, and due to the high hardness of the magnetic powder, the coating surface is easily damaged again with continued use, leading to recurring adhesion. This necessitates periodic mold replacement or repair of the coating surface.

[0005] Patent application CN211307291U describes a method to prevent film sticking by creating an injection groove at the top of the lower mold and embedding a top mold box at the bottom (with a sliding rod fixed to the inner bottom wall of the mold box, and a rack rod and rack plate slidably connected to the outer surface of the sliding rod). A rotating rod (with a gear fixedly connected to its outer surface, and the rack rod meshing with the gear) is connected to the inner wall of the top mold box. However, this mold is mainly suitable for injection molding products or semi-finished products made from high-temperature cast materials. Applying it to small-sized (e.g., mm-level) semi-finished products pressed from magnetic powder at room temperature is costly and difficult, or even unsuitable. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a soft magnetic composite powder that can prevent adhesion to the mold during the pressing process and has high magnetic permeability and high strength, as well as a method for preparing the powder.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a soft magnetic composite powder, wherein the raw materials for preparing the soft magnetic composite powder include a matrix powder and a release agent; the matrix powder is composed of a first soft magnetic powder with a particle size D50 of 30-50 μm and a second soft magnetic powder with a particle size D50 of no more than 10 μm; The first soft magnetic powder accounts for 20%-50% of the mass of the matrix powder, the second soft magnetic powder accounts for 50%-80% of the mass of the matrix powder, and the release agent accounts for 0.05%-0.2% of the mass of the matrix powder.

[0008] Existing technologies, to prevent powder from sticking to the mold during the pressing process, involve polishing the mold or adding a metal film, which increases costs. Furthermore, when pressing high-hardness materials, the coating is easily damaged, requiring mold repair or replacement. This invention addresses this by technically processing the pressing material to control the proportion of large-particle soft magnetic powder (30-50 μm particle size). This reduces the contact area between the soft magnetic powder and the mold surface during pressing, while increasing the contact area between small and large soft magnetic powder particles. Consequently, the bonding force between the mold and the soft magnetic powder particles is less than the bonding force between the soft magnetic powder particles themselves. Simultaneously, by adding a release agent to the soft magnetic powder, an anti-release layer is formed on the surface of the soft magnetic powder and the mold, further preventing the soft magnetic composite powder from sticking to the mold.

[0009] The study also found that the particle size of the first soft magnetic powder, its proportion in the matrix powder, and the amount of release agent in this invention simultaneously affect the anti-sticking effect and magnetic properties of the soft magnetic composite powder used in the pressing process. When the proportion of the first soft magnetic powder and the amount of release agent are within the range of this invention, the soft magnetic composite powder not only achieves a 100% anti-sticking effect in the pressing process, but also produces products or semi-finished products with high magnetic properties and strength after pressing, especially with an effective magnetic permeability of 30-40. If only the first soft magnetic powder is replaced with nanocrystalline or amorphous raw powder with a particle size D50 of no more than 25 μm, it is found that the magnetic properties of products or semi-finished products pressed from the obtained soft magnetic composite powder will be significantly reduced, with a reduction of up to 25%.

[0010] Furthermore, this invention prevents the pressing material from sticking to the mold by improving the pressing material itself, which can reduce labor and material costs and significantly increase production capacity.

[0011] In this invention, the particle size D50 of the first soft magnetic powder can be any value among 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or 30-50 μm. In some preferred embodiments, the particle size D50 of the first soft magnetic powder is 40-50 μm; particularly preferably, the particle size D50 of the first soft magnetic powder is 40 μm or 50 μm.

[0012] In some embodiments, the particle size D50 of the first soft magnetic powder is 40-50 μm, the mass of the first soft magnetic powder accounts for 30%-40% of the mass of the matrix powder, and the mass of the release agent is 0.05%-0.1% of the mass of the matrix powder. Under these conditions, the soft magnetic composite powder of the present invention can maintain its anti-sticking effect, and more importantly, its effective magnetic permeability is further increased to 34-40.

[0013] In some embodiments, the particle size D50 of the second soft magnetic powder is 3-10 μm, preferably 4-8 μm.

[0014] Adding a second soft magnetic powder helps increase the filling density of the core, thereby improving the strength and permeability of the core (magnetic ring). If the core (magnetic ring) is fabricated using 100% first soft magnetic powder, there will be many air gaps. Adding second soft magnetic powder (particle size ≤ 10 μM) for filling improves the density, permeability, and strength of the pressed core, while also reducing losses (by reducing insulation oxidation losses during the curing process). After addressing the air gap issue, the particle size of the powder itself also affects permeability. If the particle size is too small, the permeability will be lower than that of larger particles; if the particle size is too large, the air gaps will increase, further reducing permeability and worsening losses. Therefore, the particle size of the second soft magnetic powder is further preferably 4-8 μm.

[0015] In some preferred embodiments, the second soft magnetic powder is composed of two types of powder with a particle size D50 of 4 μm and 8 μm. By selecting these two specific particle sizes, the influence of air gap and powder particle size can be combined to achieve optimal magnetic permeability.

[0016] In some embodiments, the first soft magnetic powder and the second soft magnetic powder are each independently selected from at least one of amorphous soft magnetic powder, nanocrystalline soft magnetic powder, iron-silicon alloy, and carbonyl iron powder. The first soft magnetic powder and the second soft magnetic powder may be coated or uncoated.

[0017] In some embodiments, the first soft magnetic powder is at least one of amorphous soft magnetic powder and nanocrystalline soft magnetic powder, and the second soft magnetic powder is carbonyl iron powder.

[0018] In some embodiments, the release agent is fluorinated graphene and / or fluorinated graphite.

[0019] In some embodiments, the first soft magnetic powder is at least one of amorphous soft magnetic powder and nanocrystalline soft magnetic powder, the particle size D50 of the first soft magnetic powder is 30-50 μm, and the mass of the first soft magnetic powder accounts for 20%-50% of the mass of the matrix powder; the second soft magnetic powder is composed of two carbonyl iron powders with particle sizes D50 of 4 μm and 8 μm, the release agent is fluorinated graphene and / or fluorinated graphite, and the mass of the release agent is 0.05%-0.2% of the mass of the matrix powder.

[0020] In some embodiments, the raw materials for preparing the soft magnetic composite powder also include a binder; preferably, the main component of the binder is at least one of epoxy resin and polyurethane; more preferably, the mass of the main component of the binder is 1%-3% of the mass of the matrix powder, preferably 2.4%.

[0021] In some embodiments, the binder further includes additives and solvents, wherein the additives include at least one of curing agents, catalysts, and coupling agents; the additives account for 20%-40% of the mass percentage of the main component of the binder, and the solvent accounts for 8%-15% of the mass percentage.

[0022] In some embodiments, the solvent is acetone.

[0023] Secondly, the present invention provides a method for preparing the above-mentioned soft magnetic composite powder, which includes the following steps: S1. Mix the first soft magnetic powder, the second soft magnetic powder and the binder, and coat the surface of the first soft magnetic powder and the second soft magnetic powder with the binder until the solvent in the binder completely evaporates to obtain a mixture; S2. After granulating, pre-curing, sieving and pre-curing again, the mixture obtained in step S1 is mixed with a release agent.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention controls the proportion of large-particle soft magnetic powder with a particle size D50 of 30-50μm in the soft magnetic powder, and uses the large-particle soft magnetic powder in combination with a specific amount of release agent. The resulting soft magnetic composite powder can prevent sticking to the mold during the pressing process and has high magnetic permeability and strength. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the preparation process of the soft magnetic composite powder of the present invention.

[0027] Figure 2 This is a graph showing the curing and baking curve of the magnetic ring after 9.5 hours in the example of the effect of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] In the following examples, all soft magnetic powders used were coated. The amorphous soft magnetic powder and nanocrystalline soft magnetic powder were purchased from Atmix Inc. (full name: Epson Atmix Co., Ltd.), Japan, and the carbonyl iron powder was purchased from Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd.

[0030] Examples 1-10 and Comparative Examples 1-10 The raw materials for preparing the soft magnetic composite powders in Examples 1-10 and Comparative Examples 4-10 were matrix powder, release agent, and binder. The raw materials for preparing the soft magnetic composite powders in Comparative Examples 1-3 were matrix powder and binder. The matrix powder consisted of a first soft magnetic powder and a second soft magnetic powder. The second soft magnetic powder consisted of two types of carbonyl iron powder with particle sizes D50 of 4 μm and 8 μm. The binder included epoxy resin, a catalyst, and a solvent, with acetone as the solvent. The mass of the catalyst was 25% of the mass of the epoxy resin, and the mass of the acetone was 10% of the mass of the epoxy resin.

[0031] The types of materials and particle size D50 of the first soft magnetic powder, the types of materials of the release agent, and the amounts of the first soft magnetic powder, the second soft magnetic powder, the release agent, and the epoxy resin are all shown in Table 1.

[0032] Table 1

[0033] The preparation methods of the soft magnetic composite powders in Examples 1-10 and Comparative Examples 4-10 are as follows: Figure 1 As shown, specifically: (1) Adhesive preparation: Mix epoxy resin, curing agent, catalyst, coupling agent and solvent according to the formula until epoxy resin, curing agent, catalyst and coupling agent are completely dissolved in solvent; (2) Preparation of matrix powder: Weigh the first soft magnetic powder and the second soft magnetic powder according to the formula ratio, mix them evenly to obtain matrix powder; (3) Kneading: Mix the binder and matrix powder processed in steps (1) and (2) above, coat the surface of the matrix powder particles with epoxy resin until the solvent evaporates and the matrix powder and binder form a soft dough (the whole process should be controlled within 15-25 minutes). (4) Granulation: The material obtained in step (3) is granulated by passing it through a steel mesh to prepare powder (granulation can be done by a granulator, manual granulation, etc.); the mesh size of the steel mesh is selected according to the design scheme of the semi-finished / finished product to be pressed. Usually, the mesh size of the rotatable steel mesh is between 40 and 250 mesh. (5) Pre-curing: The granulated powder obtained in step (4) above is pre-cured once by ventilation / room temperature / low temperature heating (usually ≤60℃ / ≤30min), mainly to volatilize the residual solvent and the resin is in a solid state; (6) Sieving: The granulated powder that has been pre-cured in step (5) above is sieved through a sieve to obtain the granulated powder with the required particle size distribution. The sieve mesh size is usually selected according to the design scheme of the semi-finished / finished products (usually between 40 and 300 mesh). (7) Secondary pre-curing: The granulated powder after sieving in step (6) above is subjected to secondary pre-curing under nitrogen protection or vacuum environment and low temperature heating (≤60℃ / ≤30min, depending on the selected auxiliary catalyst). The main purpose is to allow the resin in the granulated powder to be cured to a small extent to prevent the granulated powder particles from sticking together. (8) Adding release agent: Add release agent to the granulated powder obtained by secondary pre-curing in step (7) above in proportion and mix well; (9) Packaging and storage: Vacuum packaging shall be carried out according to packaging requirements and stored at low temperature (≤0℃); (10) Ball milling and sieving: The sphericity of the granulated powder is processed to obtain soft magnetic composite powder; (11) Use soft magnetic composite powder for the preparation of semi-finished / finished products in the later stage.

[0034] The difference between the preparation methods of the soft magnetic composite powder in Comparative Examples 1-3 and those in Examples 1-10 and 4-10 is that the preparation methods of the soft magnetic composite powder in Comparative Examples 1-3 do not include the above step (8).

[0035] Example 11 The raw materials for preparing the soft magnetic composite powder in this embodiment are matrix powder, release agent, and binder. The matrix powder consists of a first soft magnetic powder and a second soft magnetic powder. The first soft magnetic powder is an amorphous soft magnetic powder with a particle size D50 of 40 μm, and its mass accounts for 40% of the matrix powder's mass. The second soft magnetic powder is carbonyl iron powder with a particle size D50 of 3 μm, and its mass accounts for 60% of the matrix powder's mass. The release agent is fluorinated graphene, and its mass accounts for 0.1% of the matrix powder's mass. The binder includes epoxy resin, a catalyst, and a solvent, with acetone as the solvent. The epoxy resin accounts for 3% of the matrix powder's mass, the catalyst accounts for 40% of the epoxy resin's mass, and the acetone accounts for 15% of the epoxy resin's mass.

[0036] The preparation method of the soft magnetic composite powder in this embodiment is the same as that of the soft magnetic composite powder in Examples 1-10.

[0037] Example 12 The raw materials for preparing the soft magnetic composite powder in this embodiment are matrix powder, release agent, and binder. The matrix powder consists of a first soft magnetic powder and a second soft magnetic powder. The first soft magnetic powder is a nanocrystalline soft magnetic powder with a particle size D50 of 40 μm, and its mass accounts for 40% of the matrix powder's mass. The second soft magnetic powder is carbonyl iron powder with a particle size D50 of 10 μm, and its mass accounts for 60% of the matrix powder's mass. The release agent is fluorinated graphite, and its mass accounts for 0.1% of the matrix powder's mass. The binder includes epoxy resin, a catalyst, and a solvent, with acetone as the solvent. The epoxy resin accounts for 1% of the matrix powder's mass, the catalyst accounts for 20% of the epoxy resin's mass, and the acetone accounts for 8% of the epoxy resin's mass.

[0038] The preparation method of the soft magnetic composite powder in this embodiment is the same as that of the soft magnetic composite powder in Examples 1-10.

[0039] Example of effect The soft magnetic composite powders of Examples 1-12 and Comparative Examples 1-10 were directly pressed to confirm whether the mold had powder sticking or the appearance of the semi-finished product. Using 16 cavities per mold and 500-600 MPa as a baseline, 1000 molds were pressed, totaling 16000 pieces, to observe whether the pressed product had any film sticking.

[0040] The soft magnetic composite powders of Examples 1-12 and Comparative Examples 1-10 were respectively press-molded into magnetic rings with an outer diameter of 8mm, an inner diameter of 5mm, and a height of 2mm, 1 piece / mold, with a molding pressure between 2T; then according to Figure 2The curing and baking curve was used for vacuum curing (nitrogen was introduced into the oven throughout the curing process). The cured magnetic ring was subjected to a compression test using a strength tester to evaluate its strength.

[0041] Additionally, the cured magnetic ring was wound in parallel using two strands of black and red enameled wire with a diameter of 0.3 mm, with 14.5 turns in the coil. The inductance was then tested at 1 MHz and 1 V using an impedance analyzer or an LCR meter, and the effective permeability was calculated using the following formula.

[0042] The results of observing the appearance of the pressed product for any sticky film, strength assessment, and effective magnetic permeability calculation are shown in Table 2.

[0043] Table 2

[0044] As can be seen from Table 2, the soft magnetic composite powder of the present invention not only achieves 100% anti-sticking effect when used in the pressing and molding process, but also produces products or semi-finished products with high magnetic properties and strength after pressing, especially its effective magnetic permeability can reach 30-40.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A soft magnetic composite powder, characterized in that, The raw materials for preparing the soft magnetic composite powder include matrix powder and release agent; the matrix powder is composed of a first soft magnetic powder with a particle size D50 of 30-50 μm and a second soft magnetic powder with a particle size D50 of no more than 10 μm. The mass of the first soft magnetic powder accounts for 20%-50% of the mass of the matrix powder, and the mass of the release agent is 0.05%-0.2% of the mass of the matrix powder.

2. The soft magnetic composite powder according to claim 1, characterized in that, The particle size D50 of the first soft magnetic powder is 40-50 μm, and can be selected as 40 μm or 50 μm.

3. The soft magnetic composite powder according to claim 2, characterized in that, The first soft magnetic powder has a particle size D50 of 40-50 μm, the mass of the first soft magnetic powder accounts for 30%-40% of the mass of the matrix powder, and the mass of the release agent is 0.05%-0.1% of the mass of the matrix powder.

4. The soft magnetic composite powder according to any one of claims 1-3, characterized in that, The particle size D50 of the second soft magnetic powder is 3-10 μm, preferably 4-8 μm; more preferably, the second soft magnetic powder is composed of two powders with a particle size D50 of 4 μm and a particle size D50 of 8 μm.

5. The soft magnetic composite powder according to any one of claims 1-4, characterized in that, The first soft magnetic powder and the second soft magnetic powder are each independently selected from at least one of amorphous soft magnetic powder, nanocrystalline soft magnetic powder, iron-silicon alloy, and carbonyl iron powder.

6. The soft magnetic composite powder according to claim 5, characterized in that, The first soft magnetic powder is at least one of amorphous soft magnetic powder and nanocrystalline soft magnetic powder, and the second soft magnetic powder is carbonyl iron powder.

7. The soft magnetic composite powder according to any one of claims 1-6, characterized in that, The release agent is fluorinated graphene and / or fluorinated graphite.

8. The soft magnetic composite powder according to any one of claims 1-7, characterized in that, The raw materials for preparing the soft magnetic composite powder also include a binder; preferably, the main component of the binder is at least one of epoxy resin and polyurethane; more preferably, the mass of the main component of the binder is 1%-3% of the mass of the matrix powder.

9. The soft magnetic composite powder according to claim 8, characterized in that, The binder further includes additives and solvents, wherein the additives include at least one of curing agents, catalysts, and coupling agents; based on the mass percentage of the main component of the binder, the additives account for 20%-40% by mass, and the solvent accounts for 8%-15% by mass.

10. A method for preparing the soft magnetic composite powder according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the first soft magnetic powder, the second soft magnetic powder and the binder, and coat the surface of the first soft magnetic powder and the second soft magnetic powder with the binder until the solvent in the binder completely evaporates to obtain a mixture; S2. After granulating, pre-curing, sieving and pre-curing again, the mixture obtained in step S1 is mixed with a release agent.

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