Magnetic powder material, magnetic powder core and preparation method of magnetic powder core

Abstract

The invention discloses a magnetic powder material, a magnetic powder core and a preparation method of the magnetic powder core, and relates to a magnetic material technology. The magnetic powder material comprises magnetic powder and a coating layer coating the surface of the magnetic powder, the material of the coating layer comprises PVB and silicon resin, and based on the mass of the magnetic powder, the content of PVB is 0.1-1.0 wt%, and the content of silicon resin is 0.1-1.0 wt%; and the magnetic powder is FeSiAl powder. According to the FeSiAl magnetic powder core and the preparation method thereof, the adding amount of non-magnetic substances is reduced, the high magnetic conductivity can be kept, the magnetic hysteresis loss cannot be greatly increased, meanwhile, the eddy-current loss is reduced, and the obtained FeSiAl magnetic powder core has the low total loss.

Description

Technical Field

[0001] The present invention relates to magnetic material technology. Background Art

[0002] With the rapid development of modern electronic information technology, the performance and application characteristics of soft magnetic composite materials are constantly improving. Magnetic powder core is a soft magnetic composite material made by mixing and pressing ferromagnetic powder and insulating medium. The electromagnetic properties of magnetic powder core mainly depend on the magnetic permeability of ferromagnetic powder, their filling factor, the size and shape of powder particles, the content of insulating medium, molding pressure and heat treatment process. According to the chemical composition of magnetic powder, magnetic powder core can be divided into iron powder, iron silicon powder, iron silicon aluminum powder, iron nickel powder and iron-based amorphous / nanocrystalline. FeSiAl magnetic powder core has the advantages of high magnetic permeability and high saturation magnetic induction intensity. It does not contain precious metals and is cheap. It is widely used in electronic components such as inductors, transformers and filters.

[0003] The selection of insulating binder is the primary issue in the preparation of FeSiAl magnetic powder cores, and the selection of binder directly affects the electromagnetic properties of FeSiAl magnetic powder cores. The insulating binder should have good adhesion and high temperature resistance to make the FeSiAl magnetic powder core have a good molding effect, and can withstand high temperature annealing to remove stress, so that the FeSiAl magnetic powder core has a high magnetic permeability. The loss of magnetic materials is mainly composed of eddy current loss, hysteresis loss and residual loss. The hysteresis loss is mainly negatively correlated with the magnetic permeability, and the eddy current loss is mainly negatively correlated with the resistivity. A suitable binder can make the FeSiAl magnetic powder core have a high magnetic permeability, and at the same time act as an insulating agent to coat the surface of the FeSiAl magnetic powder, increase its resistivity, and thus reduce its loss.

[0004] The Chinese patent announcement number is CN108987022A, which discloses "A FeSiAl magnetic powder core and its preparation method", which prepares the FeSiAl magnetic powder core by powder screening, powder pretreatment, particle grading, insulation coating, and pressing annealing. The magnetic powder core prepared by this method increases the density of the magnetic powder core material, so that the magnetic powder core has excellent properties such as low loss under low frequency conditions. However, the magnetic permeability of the FeSiAl magnetic powder core prepared by this patent is low, and its effective magnetic permeability is less than 50 at 50kHz.

[0005] The Chinese patent announcement number is CN113658768A, which discloses "Stable magnetic permeability and low loss FeSiAl / MnZn ferrite soft magnetic composite powder core and its preparation method". The raw materials of the powder core include a binder, a lubricant and FeSiAl / MnZn ferrite composite magnetic powder. The high-frequency performance of the FeSiAl powder core can be improved by phosphating the FeSiAl powder and then coating the phosphated FeSiAl powder with MnZn ferrite through high-energy ball milling. It has a relatively stable magnetic permeability and low loss at high frequencies. However, the experimental process of this method is complicated, and the phosphating process will cause environmental pollution, which is not conducive to large-scale production and industrial application.

[0006] The Chinese patent announcement number is CN104992806B, which discloses "A composite FeSiAl material with a magnetic permeability of 75 and its manufacturing method". The composite FeSiAl material includes FeSiAl powder and ZnCu powder, and the binder includes propyl acetate, polyvinyl butyral, butyl phthalate, trioleyl glycerol and water glass. The FeSiAl magnetic powder core prepared by this method has a magnetic permeability of 75, and the surface insulation resistance is as high as 500MΩ and the bonding strength is 10kgf / mm 2 However, the patent does not take into account the loss of the FeSiAl magnetic powder core, which is one of the most important properties of the FeSiAl magnetic powder core.

[0007] The Chinese patent announcement number is CN113658769A, which discloses "A high-frequency, high-Q value FeSiAl@MnZn ferrite soft magnetic composite magnetic powder core and its preparation method". Through powder particle size screening, chemical coprecipitation coating of MnZn ferrite shell, composite magnetic powder pre-sintering, adding sodium silicate and zinc stearate for pressing and molding, annealing and other process steps, a high-frequency, high-Q value FeSiAl magnetic powder core is prepared. This method effectively isolates the electrical contact between metal magnetic powder particles by coating with MnZn ferrite, improves the quality factor of the composite magnetic powder core, and broadens the application frequency range of the FeSiAl magnetic powder core. However, after coating MnZn ferrite by this method, the effective magnetic permeability decreases significantly, from 95 of the uncoated to 35-70 at 100kHz.

[0008] The following points can be summarized from the above-mentioned published patent applications or authorized patent documents: first, the FeSiAl magnetic powder core mainly improves its resistivity and reduces its eddy current loss through insulation coating, thereby reducing its loss under high frequency, but its magnetic permeability decreases significantly after insulation coating; second, FeSiAl needs to add non-magnetic binder to enable it to be smoothly formed, and the addition of non-magnetic binder will inevitably lead to a further decrease in the magnetic permeability of the FeSiAl magnetic powder core. Therefore, the present invention provides a method for preparing a FeSiAl magnetic powder core based on the composite addition of binder, using PVB and silicone resin as both a binder and an insulating coating agent, reducing the addition of non-magnetic substances, while also playing the role of insulating coating, improving its resistivity, thereby maintaining its high magnetic permeability, and effectively reducing its loss.

[0009] In addition, "powder core" is now commonly expressed as "powder heart", so please explain. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a magnetic powder material, a magnetic powder core and a method for preparing a magnetic powder core based on composite addition of a binder by selecting a suitable insulating binder, in view of the problems of difficulty in molding a magnetic powder core and excessive high-frequency loss in the prior art.

[0011] The technical solution adopted by the present invention to solve the technical problem is:

[0012] The magnetic powder material comprises magnetic powder and a coating layer coated on the surface of the magnetic powder, wherein the material of the coating layer comprises PVB and silicone resin.

[0013] Based on the mass of the magnetic powder, the content of PVB is 0.1-1.0 wt %, and the content of the silicone resin is 0.1-1.0 wt %.

[0014] Furthermore, the magnetic powder is FeSiAl powder.

[0015] The present invention also provides a magnetic powder core, which is obtained by pressing and annealing a magnetic powder material. The magnetic powder material comprises magnetic powder and a coating layer coated on the surface of the magnetic powder. The material of the coating layer comprises PVB and silicone resin.

[0016] The magnetic powder is FeSiAl powder. Based on the mass of the magnetic powder, the content of PVB is 0.1-1.0 wt %, and the content of silicone resin is 0.1-1.0 wt %.

[0017] The present invention also provides a method for preparing a magnetic powder core, comprising the following steps:

[0018] (1) preheating the FeSiAl powder at 500-700° C. for 60-100 min under a protective atmosphere to reduce partial oxidation products on the FeSiAl surface;

[0019] (2) Based on the mass of FeSiAl powder, 0.1-1.0 wt% of PVB and 0.1-1.0 wt% of silicone resin are weighed and added to a 20-30 wt% acetone solution, stirred evenly, and then the FeSiAl powder obtained in step (1) is added, mixed evenly, dried, sieved, and pressed at 1800 MPa-2400 MPa to obtain a green body;

[0020] (3) The green body obtained in step (2) is subjected to annealing heat treatment at 600-800° C. in nitrogen or argon to obtain a FeSiAl magnetic powder core.

[0021] In the step (2), the density of the green body obtained by pressing is 5.95 to 6.05 g / cm 3 .

[0022] In the present invention, the numerical range represented by "~" includes the end values, for example, 0.1-1.0wt% includes the two values ​​of 0.1wt% and 1.0wt%.

[0023] The present invention adopts a composite addition of PVB with high adhesion and high temperature resistant silicone resin as an insulating adhesive, which can not only play a bonding role, but also serve as an insulating coating layer to improve its resistivity, reduce the amount of non-magnetic material added, so that it can maintain a high magnetic permeability, and the hysteresis loss will not increase significantly. At the same time, its eddy current loss is reduced, and the obtained FeSiAl magnetic powder core has a lower total loss.

[0024] The magnetic powder core using the technology of the present invention has an initial magnetic permeability of about 80 (10kHz) at 25°C and a power loss density of about 63mW / cm 3 (50kHz, 50mT). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a thermogravimetric curve of the insulating adhesive used in Examples 1 to 4.

[0026] Figure 2 Graph showing the permeability frequency characteristics of the FeSiAl magnetic powder cores of Examples 1 to 4 at 25°C.

[0027] Figure 3 The power loss density curves of the FeSiAl magnetic powder cores in Examples 1 to 4 at 25°C, (a) is 50 mT; (b) is 100 mT.

[0028] Figure 4 This is a scanning electron microscope image of the FeSiAl magnetic powder core prepared in Example 2. DETAILED DESCRIPTION

[0029] The losses of magnetic powder core are mainly hysteresis loss and eddy current loss. FeSiAl is a metal powder with a small resistivity of about 8×10 -7 Ω·m, and its eddy current loss is large at high frequencies, which limits its high-frequency application. At the same time, compared with other metal powders such as FeSiCr and FeSi, FeSiAl magnetic powder cores are more difficult to form. The coating of FeSiAl magnetic powder cores is generally through insulating coating, and then adding a binder to form. Although it can increase its resistivity and reduce eddy current loss, it cannot solve the problem of a sharp drop in its magnetic permeability after coating. Therefore, the core idea of ​​the present invention is to add PVB and silicone resin as an insulating adhesive, both as a binder and as a coating agent, reduce the addition of non-magnetic materials, increase magnetic permeability, and reduce its loss. The present invention uses PVB with high adhesion and high temperature resistant silicone resin as an insulating adhesive, which can not only play a bonding role, but also serve as an insulating coating layer to increase its resistivity. The amount of non-magnetic material added is reduced, so that it can maintain a high magnetic permeability, the hysteresis loss will not increase significantly, and at the same time, its eddy current loss is reduced, and the obtained FeSiAl magnetic powder core has a lower total loss.

[0030] The raw materials of the preparation method provided by the present invention include FeSiAl powder and an insulating binder, wherein the FeSiAl powder includes 9.2-9.8wt% Si and 5.2-5.8wt% Al, and the rest is Fe; the insulating binder includes 0.1-1.0wt% PVB and 0.1-1.0wt% silicone resin (based on the mass of the FeSiAl powder).

[0031] The FeSiAl magnetic powder core preparation method of the present invention comprises the following steps:

[0032] (1) preheating the FeSiAl powder at 500-700° C. for 60-100 min under a protective atmosphere to reduce partial oxidation products on the FeSiAl surface;

[0033] (2) Based on the mass of FeSiAl powder, 0.1-1.0 wt% of PVB and 0.1-1.0 wt% of silicone resin are weighed and added to a 20-30 wt% acetone solution, stirred evenly, and then the FeSiAl powder obtained in step (1) is added, mixed evenly, dried, sieved, and pressed at 1800 MPa-2400 MPa to obtain a green body;

[0034] (3) The green body obtained in step (2) is subjected to annealing heat treatment at 600-800° C. in nitrogen or argon to obtain a FeSiAl magnetic powder core.

[0035] PVB has a good bonding effect on FeSiAl powder, so that FeSiAl can be pressed into a green body with good strength. Silicone resin has slightly poor bonding properties, but has good high temperature resistance, so that the FeSiAl magnetic powder core can still maintain a high strength after high temperature annealing. The present invention adds PVB and silicone resin together, combining the advantages of the two. With the addition of a small amount of non-magnetic insulating binder, the FeSiAl powder can be smoothly formed and insulated, so that the FeSiAl magnetic powder core has high magnetic permeability and low loss. The green density of the FeSiAl magnetic powder core is 5.95~6.05g / cm 3 After annealing, the density is 5.98~6.10g / cm 3 The initial permeability of FeSiAl magnetic powder core at 25°C is about 80 (10kHz), and the power loss density is about 63mW / cm 3 (50kHz, 50mT).

[0036] Example

[0037] As an embodiment, the method for preparing a FeSiAl magnetic powder core includes the following preparation steps:

[0038] (1) heat treating the FeSiAl powder at 650° C. for 1.5 hours under argon protection to obtain preheat-treated FeSiAl powder;

[0039] (2) Based on the mass of FeSiAl powder obtained in step (1), the following examples were carried out:

[0040] And silicone resin as insulating adhesive, the added content is shown in the following table:

[0041]

[0042] Dissolve the insulating binder in a 20-30 wt% acetone solution, add the FeSiAl powder obtained in step (1), stir evenly, dry the acetone at 60° C., and sieve through 40 mesh to obtain FeSiAl coated powder;

[0043] (3) The FeSiAl coated powder obtained in step (2) is pressed into The magnetic ring has a molding pressure of 2200MPa and is maintained at a pressure of 20s;

[0044] (4) Place the formed green body in a tubular furnace under argon protection for heat treatment at a temperature of 750°C for 1.5 hours;

[0045] (5) The inductance L of the sample was tested by Tonghui TH2826 precision LCR tester and converted into the starting magnetic permeability. The saturation magnetization intensity of the sample was tested by Lake Shore 8604 of the United States. The loss and magnetic permeability frequency characteristics were tested by Iwasaki SY-8218B-H analyzer. The microscopic morphology of the sample was tested by Hitachi JSM-6490LV.

[0046] Experiments and data

[0047] The basic properties of the samples of Examples 1 to 4 are shown in the table below:

[0048]

[0049] Figure 1 It can be seen that the mass loss of PVB at 750℃ is 95.6%, while that of silicone resin is only 19.4%, indicating that silicone resin has better high temperature resistance.

[0050] Figure 2 The permeability frequency characteristics of the FeSiAl magnetic powder core of the present invention at 25°C are reflected; Example 2 has the highest permeability, and all samples have good permeability stability within 10 to 1000 kHz.

[0051] Figure 4 It shows that the FeSiAl magnetic powder core obtained by using this binder addition scheme has a smooth surface, the FeSiAl particles are densely bonded, and there are few pores.

Claims

1. Magnetic powder material, including magnetic powder and a coating layer coated on the surface of the magnetic powder, It is characterized in that The material of the coating layer includes PVB and silicone resin. Based on the mass of the magnetic powder, the content of PVB is 0.1-1.0wt%, and the content of silicone resin is 0.1-1.0wt%; The magnetic powder is FeSiAl powder.

2. A magnetic powder core, which is obtained by pressing and annealing a magnetic powder material, wherein the magnetic powder material includes magnetic powder and a coating layer coated on the surface of the magnetic powder, and the material of the coating layer includes PVB and silicone resin; the magnetic powder is FeSiAl powder, and based on the mass of the magnetic powder, the content of PVB is 0.1-1.0wt%, and the content of silicone resin is 0.1-1.0wt%.

3. Preparation method of magnetic powder core, It is characterized in that The steps include: (1) preheating the FeSiAl powder at 500-700° C. for 60-100 min under a protective atmosphere to reduce partial oxidation products on the FeSiAl surface; (2) Based on the mass of FeSiAl powder, 0.1-1.0 wt% of PVB and 0.1-1.0 wt% of silicone resin are weighed and added to a 20-30 wt% acetone solution, stirred evenly, and then the FeSiAl powder obtained in step (1) is added, mixed evenly, dried, sieved, and pressed at 1800 MPa-2400 MPa to obtain a green body; (3) The green body obtained in step (2) is subjected to annealing heat treatment at 600-800° C. in nitrogen or argon to obtain a FeSiAl magnetic powder core.

4. The method for preparing a magnetic powder core according to claim 3, It is characterized in that In the step (2), the density of the green body obtained by pressing is 5.95 to 6.05 g / cm 3 .

5. The method for preparing the magnetic powder core according to claim 3, It is characterized in that The content of PVB is 0.5wt%, and the content of silicone resin is 0.5wt%.

6. The method for preparing a magnetic powder core according to claim 3, It is characterized in that The protective atmosphere in step (1) is argon.

Images