Amorphous nanocrystalline magnetic powder core preparation method based on hot pressing process

Abstract

The invention provides an amorphous nanocrystalline magnetic powder core preparation method based on a hot pressing process, which comprises the following steps: passivating metal powder and phosphoric acid, adding the passivated metal powder and phosphoric acid into an organic coating solvent, and uniformly stirring to obtain surface-coated metal soft magnetic powder, the organic coating solvent is organic silicon resin with phenyl groups; carrying out hot press molding on the surface-coated metal soft magnetic powder to obtain a metal soft magnetic composite material magnetic core; the metal soft magnetic composite material magnetic core is subjected to annealing treatment to obtain the metal soft magnetic core with better compactness and magnetic conductivity, specifically, organic silicon resin with phenyl groups is adopted as a coating solvent, and the problem of coating failure can be effectively avoided when an amorphous nanocrystalline magnetic powder core is subjected to hot pressing; the low-pressure forming process is adopted, the situation that the service life of the mold is affected due to too large pressure is avoided, meanwhile, due to the adoption of the low-pressure forming process, an insulating layer on the surface of the magnetic powder cannot be damaged, and magnetic loss of the magnetic powder core is prevented from rising.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic material processing, and particularly relates to a method for preparing amorphous nanocrystalline magnetic powder cores based on a hot pressing process. Background Art

[0002] As a new type of soft magnetic composite material with magnetoelectric conversion function, magnetic powder cores are mainly made by mixing magnetic powders and insulating coating agents. Nanocrystalline / amorphous materials have higher magnetostriction coefficients and lower coercive forces, and they have characteristics such as high resistivity and high saturation magnetic induction intensity, and have broad application prospects in the field of electronics and electric power. However, due to their physical properties, the molded density of the magnetic powder cores prepared by traditional methods is low, and the magnetic permeability is low; the strong corrosion resistance makes it difficult to coat the insulation, and the loss is high. Therefore, how to improve the magnetic permeability of the magnetic powder cores and reduce their magnetic losses is the main challenge currently faced.

[0003] The preparation of amorphous or nanocrystalline soft magnetic magnetic powder cores is basically the same as that of traditional metal soft magnetic magnetic powder cores, and both use powder metallurgy processes. However, due to the different compositions of amorphous or nanocrystalline soft magnetic materials and the differences in preparation processes, the hardness of amorphous or nanocrystalline soft magnetic powders is high and the compressibility is poor. The green compact density prepared by conventional methods is very low, resulting in poor performance. The current pressing preparation schemes all use ultra-high pressure forming, and the highest forming pressure can reach 2500 MPa. Such a high forming pressure has self-evident high requirements for the mold and adverse effects on the mold life. Moreover, the ultra-high pressure will also damage the insulation layer on the surface of the magnetic powder, resulting in an increase in the magnetic loss of the magnetic powder core.

[0004] In order to improve the magnetic permeability of amorphous / nanocrystalline magnetic powder cores, most of them currently use the method of powder compounding (i.e., adding other high-conductivity powders). In addition, there are also those using the hot pressing process. This method can greatly improve the density of the magnetic powder core, thereby improving the magnetic permeability of the magnetic powder core. However, the hot pressing has high requirements for the binder used for coating the magnetic powder core. It should be noted that the main purpose of coating metal soft magnetic particles is to achieve insulation between particles, thereby reducing the eddy current loss between metal magnetic powder core particles. Therefore, the quality of the insulation coating layer determines the quality of its high-frequency magnetic properties and losses. Most of the organic coating agents currently used on the market will have the situation of high-temperature failure, and too low hot pressing temperature cannot play the role of improving the density of the magnetic powder core, which is also a drawback of hot pressing. Summary of the Invention

[0005] Based on this, the embodiments of the present invention provide a method for preparing amorphous nanocrystalline magnetic powder cores based on a hot pressing process, aiming to improve the performance and density of nanocrystalline / amorphous powder material magnetic powder cores, and at the same time avoid reducing the service life of the mold due to high pressure.

[0006] The first aspect of the embodiment of the present invention provides a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process, comprising the following steps:

[0007] After passivating the metal powder with phosphoric acid, it is added to an organic coating solvent with high temperature resistance performance and stirred evenly to obtain surface-coated metal soft magnetic powder. Among them, the metal powder is nanocrystalline powder or amorphous powder, and the organic coating solvent achieves high temperature resistance by introducing phenyl groups, silicon-oxygen bond structures and controlling the crosslinking density in the molecular structure of the silicone resin;

[0008] The surface-coated metal soft magnetic powder is hot pressed into a metal soft magnetic composite core, where the hot pressing pressure is 100 MPa to 500 MPa;

[0009] The metal soft magnetic composite core is annealed to obtain a metal soft magnetic core.

[0010] Preferably, the metal powder can also be carbonyl iron powder or alloy powder containing iron element.

[0011] Preferably, the metal powder is the powder passing through a 50-mesh to 70-mesh sieve.

[0012] Preferably, in the step of passivating the metal powder with phosphoric acid, adding it to the organic coating solvent and stirring evenly to obtain the surface-coated metal soft magnetic powder, the passivation and coating are carried out at 25°C to 40°C, the stirring is carried out in a closed container, and the stirring duration is 10 min to 14 min.

[0013] Preferably, in the step of hot pressing the surface-coated metal soft magnetic powder into a metal soft magnetic composite core, the hot pressing temperature is 250°C to 550°C, and the hot pressing time is 18 s to 22 s.

[0014] Preferably, in the step of annealing the metal soft magnetic composite core to obtain a metal soft magnetic core, the annealing temperature is 450°C to 550°C, and the annealing time is 1 h to 2 h.

[0015] Preferably, the annealing treatment is carried out in a vacuum or inert gas environment.

[0016] The second aspect of the embodiment of the present invention provides an amorphous nanocrystalline magnetic powder core, which is prepared by using the above-mentioned preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process.

[0017] Compared with the prior art, implementing the present invention has the following beneficial effects:

[0018] After passivating the metal powder with phosphoric acid and adding it to an organic coating solvent, stirring evenly to obtain a surface-coated metal soft magnetic powder, where the metal powder is a nanocrystalline powder or an amorphous powder, and the organic coating solvent is an organosilicon resin with a phenyl group; hot-pressing the surface-coated metal soft magnetic powder to form a metal soft magnetic composite core; annealing the metal soft magnetic composite core to obtain a metal soft magnetic core with better density and magnetic permeability. Specifically, using an organosilicon resin with a phenyl group as the coating solvent, the amorphous nanocrystalline magnetic powder core can effectively avoid the problem of coating failure during hot pressing; adopting a low-pressure forming process to avoid affecting the service life of the mold due to excessive pressure; because of the low-pressure forming process, it will not damage the insulating layer on the surface of the magnetic powder and avoid the increase in magnetic loss of the magnetic powder core. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. is a flowchart of the implementation of a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process proposed in an embodiment of the present invention.

[0020] The following specific embodiments will be further described in conjunction with the above drawings. SPECIFIC EMBODIMENTS

[0021] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0022] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a middle element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] Please refer to Figure 1 , which is a flowchart of the implementation of a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process proposed in an embodiment of the present invention. The preparation method includes the following steps:

[0025] In step S01, after passivating the metal powder with phosphoric acid, it is added to an organically coated solvent with high temperature resistance and stirred evenly to obtain a surface-coated metal soft magnetic powder.

[0026] Among them, the metal powder is a nanocrystalline powder or an amorphous powder. Both the nanocrystalline powder and the amorphous powder are powders passing through a 50-mesh to 70-mesh sieve. Exemplarily, both the nanocrystalline powder and the amorphous powder are powders passing through a 50-mesh, 55-mesh, 60-mesh, 65-mesh or 70-mesh sieve, but not limited thereto. In some other embodiments of the present invention, the metal powder can also be carbonyl iron powder or an alloy powder containing iron element. Exemplarily, the alloy powder containing iron element includes Fe-Ni-Mo alloy powder, Fe-Ni alloy powder, Fe-Co alloy powder, Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Si-Cr alloy powder, etc., but not limited thereto.

[0027] It should be noted that the organically coated solvent achieves high temperature resistance by introducing phenyl groups, silicon-oxygen bond structures and controlling the crosslinking density in the molecular structure of the organosilicon resin. Specifically, introducing phenyl (Phenyl) groups can effectively improve its high temperature resistance. Because the conjugated structure of the phenyl group can provide additional stability and prevent the resin from crosslinking or degrading at high temperatures. It is composed of silicon-oxygen (Si-O-Si) bonds. The bond energy of this kind of bond is relatively high, about 444 kJ / mol, much higher than the bond energy of carbon-carbon (C-C) bonds (about 348 kJ / mol). This makes the organosilicon resin have higher thermal stability at high temperatures and is not easily decomposed or degraded. The increase in crosslinking density can improve the heat resistance and mechanical strength of the material. By controlling the type and dosage of the crosslinking agent, the crosslinking density of the resin can be optimized, thereby enhancing its high temperature resistance. Exemplarily, when using two crosslinking agents, phenyl silane and methyl silane, and mixing them in a molar ratio of 1:1, and forming methylphenylsiloxane resin through hydrolysis and polycondensation reaction, the high temperature resistance of the material is significantly improved and can withstand 700 °C.

[0028] In this embodiment, passivation and coating are carried out at 25 °C to 40 °C, and stirring is carried out in a closed container (non-vacuum). The stirring time is 10 min to 14 min. Exemplarily, the stirring time is 10 min, 11 min, 12 min, 13 min or 14 min, etc., but not limited thereto.

[0029] In step S02, the surface-coated metal soft magnetic powder is hot-pressed into a shape to obtain a metal soft magnetic composite core.

[0030] Specifically, the hot pressing temperature is 250°C to 550°C. Exemplarily, the hot pressing temperature is 250°C, 300°C, 350°C, 400°C, 500°C or 550°C, etc., but not limited thereto. The hot pressing pressure is 100 MPa to 500 MPa. Exemplarily, the hot pressing pressure is 100 MPa, 200 MPa, 300 MPa, 400 MPa or 500 MPa, etc., but not limited thereto. The hot pressing time is 18 s to 22 s. Exemplarily, the hot pressing time is 18 s, 19 s, 20 s, 21 s or 22 s, etc., but not limited thereto. It can be found that due to the short hot pressing time, the production efficiency of the product can be greatly increased.

[0031] Step S03: Anneal the metal soft magnetic composite core to obtain a metal soft magnetic core.

[0032] Specifically, the annealing treatment is carried out in a vacuum or an inert gas environment. The inert gas can be nitrogen or argon, etc. In this embodiment, the annealing temperature is 450°C to 550°C. Exemplarily, the annealing temperature is 450°C, 480°C, 500°C, 520°C or 550°C, etc., but not limited thereto. The annealing time is 1 h to 2 h. Exemplarily, the annealing time is 1 h, 1.5 h or 2 h, etc., but not limited thereto.

[0033] On the other hand, the present invention also provides an amorphous nanocrystalline magnetic powder core prepared by using the above-mentioned method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process.

[0034] To facilitate the understanding of the present invention, several embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0035] Embodiment 1

[0036] In this embodiment, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is provided. The size of the mold used is OD×ID×HT = 26.92 mm×14.73 mm×11.18 mm, where "OD" represents "Outer Diameter", i.e., the outer diameter; "ID" represents "Inner Diameter", i.e., the inner diameter; "HT" represents "Height" or "Thickness", i.e., the height or thickness. The preparation method specifically includes the following steps:

[0037] (1) Select the amorphous powder passing through a 60-mesh sieve. Place the amorphous powder in an automatic stirring tank, then put the solution with a ratio of 1% phosphoric acid + 3% alcohol into the powder, stir until it is completely dry, and finally add the solution with a ratio of 1% organic coating solvent with high-temperature resistance + 3% alcohol and stir again until dry. Among them, the organic coating solvent is a methylphenylsiloxane resin formed by mixing two cross-linking agents, phenyl silane and methyl silane, in a molar ratio of 1:1 and through hydrolysis and polycondensation reaction.

[0038] (2) Uniformly fill the processed powder into the mold. The mold is pre-heated to 450 °C in advance, that is, the hot pressing temperature used is 450 °C, and hot press for 20 s under a low pressure of 100 MPa.

[0039] (3) Anneal the hot-pressed magnetic powder core at 450 °C for 1 h in a vacuum environment.

[0040] Comparative Example 1

[0041] In this Comparative Example 1, a preparation method of an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing temperature is different. Among them, the hot pressing temperature is 250 °C.

[0042] Comparative Example 2

[0043] In this Comparative Example 2, a preparation method of an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing temperature is different. Among them, the hot pressing temperature is 350 °C.

[0044] Comparative Example 3

[0045] In this Comparative Example 3, a preparation method of an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing pressure is different. Among them, the hot pressing pressure is 300 MPa.

[0046] Comparative Example 4

[0047] In this Comparative Example 4, a preparation method of an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing pressure is different. Among them, the hot pressing pressure is 500 MPa.

[0048] Comparative Example 5

[0049] In this Comparative Example 5, a preparation method of an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the powder is graded in a way of (coarse:fine = 1:3 ratio) this time, the D50 of the coarse powder is above 50 μm, the D50 of the fine powder is below 10 μm, and at the same time, the hot pressing pressure is different. Among them, the hot pressing pressure is 500 MPa.

[0050] Comparative Example 6

[0051] In this Comparative Example 6, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 1 is that in step (2), a molding pressure of 2200 MPa is used and the traditional cold pressing method is adopted. Among them, the traditional cold pressing process realizes molding by applying high pressure to the powder material at room temperature, and a green body is formed by physical compaction and slight plastic deformation between powder particles.

[0052] Example 2

[0053] In this Example 2, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 1 is that the amorphous powder is replaced by nanocrystalline powder; in step (2), the mold is preheated to 550 °C; in step (3), annealing is carried out at 550 °C in a vacuum environment.

[0054] Comparative Example 7

[0055] In this Comparative Example 7, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 2 is that the hot pressing temperature is different, and among them, the hot pressing temperature is 250 °C.

[0056] Comparative Example 8

[0057] In this Comparative Example 8, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 2 is that the hot pressing temperature is different, and among them, the hot pressing temperature is 450 °C.

[0058] Comparative Example 9

[0059] In this Comparative Example 9, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 2 is that the hot pressing pressure is different, and among them, the hot pressing pressure is 300 MPa.

[0060] Comparative Example 10

[0061] In this Comparative Example 10, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 2 is that the hot pressing pressure is different, and among them, the hot pressing pressure is 500 MPa.

[0062] Comparative Example 11

[0063] In this Comparative Example 11, a preparation method of amorphous nanocrystalline magnetic powder cores based on a hot pressing process is also provided. The difference from Example 2 is that this time the powder is graded according to the ratio of (coarse:fine = 1:3), the D50 of the coarse powder is above 40 μm, the D50 of the fine powder is below 10 μm, and at the same time, the hot pressing pressure is different, and among them, the hot pressing pressure is 500 MPa.

[0064] Comparative Example 12

[0065] In this Comparative Example 12, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 2 is that in step (2), a forming pressure of 2200 MPa is used, and at the same time, a traditional cold pressing method is adopted.

[0066] Comparative Example 13

[0067] In this Comparative Example 13, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that in step (1), epoxy resin is used as the organic coating solvent.

[0068] Comparative Example 14

[0069] In this Comparative Example 14, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing temperature is different. Among them, the hot pressing temperature is 600 °C.

[0070] Comparative Example 15

[0071] In this Comparative Example 15, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing temperature is different. Among them, the hot pressing temperature is 1000 °C.

[0072] Comparative Example 16

[0073] In this Comparative Example 16, a method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process is also provided. The difference from Example 1 is that the hot pressing pressure is different. Among them, the hot pressing pressure is 600 MPa.

[0074] It should be noted that the performance of the prepared amorphous nanocrystalline magnetic powder cores was tested. Among them, the density was tested by the Archimedes' law method, and the loss was tested by an Iwaki device, as shown in Table 1:

[0075] Table 1

[0076]

[0077]

[0078] The data shows that under high pressure, the coating layer of the magnetic powder core is prone to breakage, resulting in coating failure and an increase in loss. However, by using the organic coating solvent in the invention example, a magnetic powder core with excellent performance and density can be prepared under high temperature and low pressure environments. That is, the magnetic powder core prepared by the method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process of the present invention can avoid this situation.

[0079] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0080] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process, characterized in that: The following steps are involved: After the metal powder is passivated with phosphoric acid, it is added into an organic coating solvent with high temperature resistance and stirred evenly to obtain a surface-coated metal soft magnetic powder, wherein the metal powder is a nanocrystalline powder or an amorphous powder, and the organic coating solvent achieves high temperature resistance by introducing a phenyl group, a silicon-oxygen bond structure and controlling the crosslinking density into the molecular structure of the organic silicone resin; Hot pressing the metal soft magnetic powder coated on the surface to obtain a metal soft magnetic composite material magnetic core, wherein the hot pressing pressure is 100MPa to 500MPa; The metal soft magnetic composite material magnetic core is subjected to annealing treatment to obtain a metal soft magnetic magnetic core.

2. The method for preparing an amorphous nanocrystalline magnetic powder core based on a hot pressing process according to claim 1, characterized in that: The metal powder may also be carbonyl iron powder or alloy powder containing iron element.

3. The method for preparing an amorphous nanocrystalline magnetic powder core based on hot pressing process according to claim 1 or 2, characterized in that: The metal powder is a powder under a sieve of 50-70 meshes.

4. The method for preparing an amorphous nanocrystalline magnetic powder core based on hot pressing process according to claim 1 or 2, characterized in that: In the step of passivating the metal powder with phosphoric acid, adding it to an organic coating solvent, and stirring it evenly to obtain a surface-coated metal soft magnetic powder, the passivation and coating are carried out at 25° C. to 40° C., and the stirring is carried out in a closed container for 10 min to 14 min.

5. The method for preparing an amorphous nanocrystalline magnetic powder core based on hot pressing process according to claim 1 or 2, characterized in that: In the step of hot pressing the surface-coated soft magnetic metal powder to obtain a soft magnetic metal composite material magnetic core, the hot pressing temperature is 250° C. to 550° C. and the hot pressing time is 18s to 22s.

6. The method for preparing an amorphous nanocrystalline magnetic powder core based on hot pressing process according to claim 1 or 2, characterized in that: In the step of annealing the metal soft magnetic composite material core to obtain the metal soft magnetic core, the annealing temperature is 450° C. to 550° C. and the annealing time is 1 hour to 2 hours.

7. The method for preparing an amorphous nanocrystalline magnetic powder core based on hot pressing process according to claim 6, characterized in that: The annealing process is performed in a vacuum or inert gas environment.

8. An amorphous nanocrystalline magnetic powder core, characterized in that: The amorphous nanocrystalline magnetic powder core is prepared by the hot pressing process-based preparation method described in any one of claims 1 to 7.

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