A method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss

Abstract

The present invention provides a method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss. The method comprises the following steps: selecting carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity as raw materials; using phosphoric acid (H3PO4) to react with the surface of the carbonyl iron magnetic powder particles to generate a dense and uniform phosphate insulating material, which is used as a coating for the carbonyl iron raw powder to prepare the carbonyl iron magnetic powder core; using a silane coupling agent KH550 to regulate the surface physical properties of the FeSiCrB raw powder; and using tetraethyl orthosilicate (TEOS) to hydrolyze to obtain high-resistance nano-silicon dioxide (SiO2), which is used as a coating for the FeSiCrB raw powder to prepare the FeSiCrB magnetic powder core; and mixing the carbonyl iron magnetic powder core and the FeSiCrB magnetic powder core to obtain a composite magnetic powder core. The present invention uses an iron-based amorphous FeSiCrB magnetic powder core with low coercivity and high resistivity to modify a carbonyl ferromagnetic powder core. At the same time, the large particle size of the iron-based amorphous FeSiCrB magnetic powder core is utilized to reduce the dense packing degree of powder particles in the composite system, increase the number of distributed air gaps, and improve the DC superposition characteristics of the carbonyl ferromagnetic powder core. The result is a composite magnetic powder core with high DC superposition characteristics and low loss, which is of great significance for high-frequency and high-power applications of the carbonyl ferromagnetic powder core.

Description

Technical Field

[0001] The invention belongs to the technical field of soft magnetic composite material preparation, and particularly relates to a method for preparing a composite magnetic powder core with high direct current superposition characteristics and low loss. Background Art

[0002] Driven by the rapid development of 5G communications and new energy sources such as solar-powered storage and charging, electronic devices are being required to operate under increasingly stringent conditions. The performance of their power supplies is directly related to their stable operation. Switching converters, which serve as DC-DC power modules, are moving towards higher frequencies and higher powers. This is driving the development of magnetic powder core materials in switching converters towards low core losses and high DC superposition characteristics.

[0003] In high-frequency, high-power applications, the large current and voltage fluctuations in the inductor of the magnetic components in switching converters can cause severe electromagnetic interference to surrounding signal devices. This issue is often addressed by using fully shielded, one-piece molded inductors. Carbonyl ferromagnetic powder cores are suitable for use as the core material for one-piece molded inductors due to their low cost, ease of molding, and excellent magnetic properties. However, when the application frequency reaches the MHz level, the resistivity of carbonyl ferromagnetic powder cores is relatively low, resulting in significant eddy current losses. Furthermore, the relatively small particle size of carbonyl ferromagnetic powder cores facilitates close packing between the powder particles, resulting in a sparse number of distributed air gaps within the powder cores and poor DC superposition characteristics at high powers. With the development of high-frequency, high-power switching converter magnetic components, there is an urgent need to modify carbonyl ferromagnetic powder cores to improve their practical applicability in these high-frequency, high-power applications.

[0004] From the perspective of the preparation process of carbonyl iron powder cores, it is usually difficult to simultaneously improve DC superposition performance and reduce core loss. When the powder composition and particle size distribution are determined, the improvement of DC superposition performance often restricts the improvement of the density of the magnetic powder core, resulting in poor magnetic properties. For example, increasing the molding pressure, increasing the magnetic powder filling factor, and increasing the core density are beneficial to reducing core loss, but reducing the distributed air gap, resulting in a decrease in the demagnetization field strength formed by the distributed air gap in the magnetic powder core. When a DC magnetic field is applied to the magnetic powder core, the magnetic powder core's resistance to the DC magnetic field is weakened, and the effective magnetic permeability of the magnetic powder core decreases at a faster rate as the DC magnetic field increases, thereby deteriorating the DC bias performance. When the amount of insulating coating agent is increased, the gaps between the powder particles increase, the non-magnetic air gap of the magnetic powder core increases, and the DC superposition performance improves, but this will lead to a decrease in the density of the magnetic powder core and an increase in core loss. Air sintering can promote the formation of oxides on the powder surface. The formation of surface oxides will reduce the thermal conductivity of the magnetic powder core and inhibit the recrystallization process of the deformed particles inside the magnetic powder core, thereby improving the DC superposition performance. However, the introduction of oxygen elements will consume the ferromagnetic elements on the powder surface, which is not conducive to obtaining high saturation magnetic induction intensity. In addition, the presence of oxygen elements will increase hysteresis losses. Summary of the Invention

[0005] The purpose of the present invention is to address the problems existing in the background technology and propose a method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss. The present invention composites an iron-based amorphous FeSiCrB magnetic powder core with a carbonyl ferromagnetic powder core to prepare a composite magnetic powder core. The iron-based amorphous FeSiCrB magnetic powder core has a long-range disordered and short-range ordered atomic arrangement structure, which makes the rotation of magnetic domains and the arrangement of magnetic moments easier, effectively improving the saturation magnetic induction intensity of the material; at the same time, due to the absence of grain boundaries and dislocations, the resistance when the magnetic domain moves is reduced, so that the material has low hysteresis loss; in addition, the FeSiCrB magnetic powder core has a high resistivity and can maintain a stable magnetic permeability at high frequencies, and has low eddy current loss. The composite magnetic powder core prepared by the present invention reduces the core loss while improving the DC superposition characteristics of the magnetic powder core, thereby realizing the application of the carbonyl ferromagnetic powder core in high-frequency and high-power switching converters.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss, comprising the following steps:

[0008] Step 1: Raw material particle size gradation:

[0009] Carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity are selected as raw materials. Among them, the ratio of the D50 of the carbonyl iron magnetic powder particles to the D50 of the FeSiCrB magnetic powder particles is 0.35-0.55. The smaller carbonyl iron magnetic powder particles can well fill the larger packing gaps of the FeSiCrB magnetic powder particles.

[0010] Step 2: Preparation of carbonyl ferromagnetic powder core:

[0011] Weigh the carbonyl iron magnetic powder particles from step 1, dissolve the weighed carbonyl iron magnetic powder particles and H3PO4 solution in acetone solution, stir at room temperature for 20 to 50 minutes, and after the acetone in the solution is basically volatilized, bake the resulting powder at 40 to 80°C for 1 hour to obtain a carbonyl iron magnetic powder core; wherein the H3PO4 solution accounts for 0.45wt.% of the mass of the carbonyl iron magnetic powder particles;

[0012] Step 3: Preparation of FeSiCrB magnetic powder core:

[0013] Weigh the FeSiCrB magnetic powder particles obtained in step 1, and dissolve the weighed FeSiCrB magnetic powder particles and analytically pure TEOS solution in a mixed solvent. After stirring at room temperature for 5 minutes, analytically pure ammonia water is added dropwise to the resulting mixture, and then heated and stirred in a water bath at 50-90° C. until all the liquid evaporates. Bake the resulting powder at 40-120° C. for 1 hour to obtain a FeSiCrB magnetic powder core. The TEOS solution accounts for 4.5% by weight of the FeSiCrB magnetic powder particles, the ammonia water accounts for 5% by weight of the FeSiCrB magnetic powder particles, and the mixed solvent includes anhydrous ethanol, deionized water, and a silane coupling agent KH550. The anhydrous ethanol accounts for 12% by weight of the FeSiCrB magnetic powder particles, the deionized water accounts for 5% by weight of the FeSiCrB magnetic powder particles, and the silane coupling agent KH550 accounts for 0.05% by weight of the FeSiCrB magnetic powder particles.

[0014] Step 4: Preparation of carbonyl iron / FeSiCrB composite particles:

[0015] The carbonyl ferromagnetic powder core prepared in step 2 and the FeSiCrB magnetic powder core prepared in step 3 are mixed in a ratio of "45 wt.% carbonyl ferromagnetic powder core + 55 wt.% FeSiCrB magnetic powder core" to obtain a mixed powder; based on the total mass of the mixed powder, 5 wt.% of a diluted epoxy resin A solution, 1 wt.% of a diluted epoxy resin B solution, and 0.08 wt.% of KH550 are weighed, and the weighed diluted epoxy resin A solution, the diluted epoxy resin B solution, and the KH550 are dissolved in an acetone solution, stirred for reaction for 2 minutes, and then the mixed powder is added, and the mixture is heated and stirred in a water bath at 40-80° C. until the acetone is completely volatilized; the obtained powder is baked at 40-80° C. for 1 hour and passed through a 40-100 mesh sieve to obtain carbonyl iron / FeSiCrB composite particles;

[0016] Step 5: Molding:

[0017] The carbonyl iron / FeSiCrB composite particles obtained in step 4 are mixed with zinc stearate equivalent to 0.3 wt.% of the mass of the carbonyl iron / FeSiCrB composite particles, and pressed into a 10 mm × 6 mm × 4 mm magnetic ring at 560-1460 MPa. The magnetic ring is baked at 100-200° C. in a precisely temperature-controlled oven for 1 hour and then taken out to obtain a carbonyl iron / FeSiCrB composite magnetic powder core material.

[0018] Furthermore, in step 1, the D50 of the carbonyl iron magnetic powder particles is in the range of 3 to 6 μm, and the D50 of the FeSiCrB magnetic powder particles is in the range of 12 to 18 μm.

[0019] Furthermore, in the acetone solution of step 2, the mass percentage of acetone is 12 wt.%.

[0020] Furthermore, in the acetone solution of step 4, the mass percentage of acetone is 10 wt.%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss. The method comprises the following steps: selecting carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity as raw materials; using phosphoric acid (H3PO4) to react with the surface of the carbonyl iron magnetic powder particles to generate a dense and uniform phosphate insulating material, which is used as a coating for the carbonyl iron raw powder to prepare the carbonyl iron magnetic powder core; using a silane coupling agent KH550 to regulate the surface physical properties of the FeSiCrB raw powder; and using tetraethyl orthosilicate (TEOS) to hydrolyze to obtain high-resistance nano-silicon dioxide (SiO2), which is used as a coating for the FeSiCrB raw powder to prepare the FeSiCrB magnetic powder core; and mixing the carbonyl iron magnetic powder core and the FeSiCrB magnetic powder core to obtain a composite magnetic powder core. The present invention uses an iron-based amorphous FeSiCrB magnetic powder core with low coercivity and high resistivity to modify a carbonyl ferromagnetic powder core. At the same time, the large particle size of the iron-based amorphous FeSiCrB magnetic powder core is utilized to reduce the dense packing degree of powder particles in the composite system, increase the number of distributed air gaps, and improve the DC superposition characteristics of the carbonyl ferromagnetic powder core. The result is a composite magnetic powder core with high DC superposition characteristics and low loss, which is of great significance for high-frequency and high-power applications of the carbonyl ferromagnetic powder core. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The micromorphology of the carbonyl iron magnetic powder particles (a) and the FeSiCrB magnetic powder particles (b) selected in Example 1;

[0024] Figure 2 The microstructure of the carbonyl iron / FeSiCrB composite magnetic powder core prepared in Example 1;

[0025] Figure 3 Element distribution of the carbonyl ferromagnetic powder core (a) and the FeSiCrB magnetic powder core (b) of Example 1;

[0026] Figure 4 The DC superposition characteristics of the magnetic powder cores prepared in Example 1, Comparative Example 1, and Comparative Example 2 are measured under the conditions of 0 to 100 Oe.

[0027] Figure 5 The core loss characteristics of the magnetic powder cores prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown in FIG. 1 , under the test conditions of 20 mT and 50-2000 kHz. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] The present invention provides a method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss, and the samples of Example 1 and Comparative Examples 1 and 2 are prepared by the following steps:

[0030] Example 1

[0031] Step 1: Raw material particle size gradation:

[0032] Carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity are selected as raw materials. Among them, the D50 of carbonyl iron magnetic powder particles is 5.6μm, and the D50 of FeSiCrB magnetic powder particles is 13.6μm. The carbonyl iron magnetic powder particles with smaller particle size can well fill the larger stacking gaps of FeSiCrB magnetic powder particles. The micromorphology of the selected carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles is as follows: Figure 1 (a) and 1(b);

[0033] Step 2: Preparation of carbonyl ferromagnetic powder core:

[0034] Weigh 200 g of the carbonyl iron magnetic powder particles from step 1, and dissolve the weighed carbonyl iron magnetic powder particles and the H3PO4 solution in a 12 wt.% acetone solution. Stir at room temperature for 30 minutes. After the acetone in the solution is substantially evaporated, bake the resulting powder at 60°C for 1 hour to obtain a carbonyl iron magnetic powder core; wherein the H3PO4 solution accounts for 0.45 wt.% of the mass of the carbonyl iron magnetic powder particles;

[0035] Step 3: Preparation of FeSiCrB magnetic powder core:

[0036] Weigh 200 g of the FeSiCrB magnetic powder particles obtained in step 1, and dissolve the weighed FeSiCrB magnetic powder particles and analytically pure TEOS solution in a mixed solvent. After stirring at room temperature for 5 minutes, analytically pure ammonia water is added dropwise to the resulting mixture, and then heated and stirred in a 70° C. water bath to react until all the liquid evaporates. The resulting powder is baked at 80° C. for 1 hour to obtain a FeSiCrB magnetic powder core. The TEOS solution accounts for 4.5 wt.% of the mass of the FeSiCrB magnetic powder particles, the ammonia water accounts for 5 wt.% of the mass of the FeSiCrB magnetic powder particles, and the mixed solvent includes anhydrous ethanol, deionized water, and a silane coupling agent KH550, wherein the anhydrous ethanol accounts for 12 wt.% of the mass of the FeSiCrB magnetic powder particles, the deionized water accounts for 5 wt.% of the mass of the FeSiCrB magnetic powder particles, and the silane coupling agent KH550 accounts for 0.05 wt.% of the mass of the FeSiCrB magnetic powder particles.

[0037] Step 4: Preparation of carbonyl iron / FeSiCrB composite particles:

[0038] The carbonyl ferromagnetic powder core prepared in step 2 and the FeSiCrB magnetic powder core prepared in step 3 are mixed in a ratio of "45 wt.% carbonyl ferromagnetic powder core + 55 wt.% FeSiCrB magnetic powder core" to obtain a mixed powder with a total mass of 200 g; based on the total mass of the mixed powder, 5 wt.% of a diluted epoxy resin A solution, 1 wt.% of a diluted epoxy resin B solution, and 0.08 wt.% of KH550 are weighed, and the weighed diluted epoxy resin A solution, the diluted epoxy resin B solution, and the KH550 are dissolved in a 10 wt.% acetone solution. After stirring for 2 minutes, the mixed powder is added, and the mixture is heated and stirred in an 80°C water bath to react until the acetone is completely volatilized; the obtained powder is baked at 60°C for 1 hour and passed through a 40-100 mesh sieve to obtain carbonyl iron / FeSiCrB composite particles;

[0039] Step 5: Molding:

[0040] The carbonyl iron / FeSiCrB composite particles obtained in step 4 were mixed with zinc stearate equivalent to 0.3 wt.% of the mass of the carbonyl iron / FeSiCrB composite particles, and pressed into a 10 mm × 6 mm × 4 mm magnetic ring under 1000 MPa. The magnetic ring was baked at 120°C in a precisely temperature-controlled oven for 1 hour and then taken out to obtain a carbonyl iron / FeSiCrB composite magnetic powder core material.

[0041] Comparative Example 1

[0042] Step 1: Raw material particle size gradation:

[0043] Carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity were selected as raw materials. Among them, the D50 of carbonyl iron magnetic powder particles was 5.6μm, and the D50 of FeSiCrB magnetic powder particles was 13.6μm. The smaller carbonyl iron magnetic powder particles can well fill the larger packing gaps of FeSiCrB magnetic powder particles.

[0044] Step 2: Preparation of carbonyl ferromagnetic powder core:

[0045] Weigh 200 g of the carbonyl iron magnetic powder particles from step 1 and dissolve them in a 12 wt.% acetone solution. Stir at room temperature for 30 minutes. After the acetone in the solution is substantially evaporated, bake the resulting powder at 60° C. for 1 hour to obtain a carbonyl iron magnetic powder core.

[0046] Step 3: Coating of carbonyl ferromagnetic powder core:

[0047] Weigh 200 g of the carbonyl ferromagnetic powder core from step 2, a 5 wt.% epoxy resin A diluted solution, a 1 wt.% epoxy resin B diluted solution, and 0.08 wt.% KH550 solution, which is equivalent to the carbonyl ferromagnetic powder core; dissolve the weighed epoxy resin A diluted solution, epoxy resin B diluted solution, and KH550 in a 10 wt.% acetone solution, stir and react for 2 minutes, then add 200 g of the carbonyl ferromagnetic powder core, heat and stir in an 80°C water bath to react until the acetone is completely volatilized; bake the obtained powder at 60°C for 1 hour and pass through a 40-100 mesh sieve to obtain a coated carbonyl ferromagnetic powder core;

[0048] Step 4: Molding:

[0049] The coated carbonyl ferromagnetic powder core obtained in step 3 is mixed with zinc stearate equivalent to 0.3 wt.% of the mass of the coated carbonyl ferromagnetic powder core, and pressed into a 10 mm × 6 mm × 4 mm magnetic ring under 1000 MPa. The magnetic ring is baked at 120°C in a precisely temperature-controlled oven for 1 hour and then taken out to obtain a carbonyl ferromagnetic powder core material.

[0050] Comparative Example 2

[0051] Step 1: Raw material particle size gradation:

[0052] Carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles with good sphericity were selected as raw materials. Among them, the D50 of carbonyl iron magnetic powder particles was 5.6μm, and the D50 of FeSiCrB magnetic powder particles was 13.6μm. The smaller carbonyl iron magnetic powder particles can well fill the larger packing gaps of FeSiCrB magnetic powder particles.

[0053] Step 2: Preparation of carbonyl ferromagnetic powder core:

[0054] Weigh 200 g of the carbonyl iron magnetic powder particles from step 1, and dissolve the weighed carbonyl iron magnetic powder particles and the H3PO4 solution in a 12 wt.% acetone solution. Stir at room temperature for 30 minutes. After the acetone in the solution is substantially evaporated, bake the resulting powder at 60°C for 1 hour to obtain a carbonyl iron magnetic powder core; wherein the H3PO4 solution accounts for 0.45 wt.% of the mass of the carbonyl iron magnetic powder particles;

[0055] Step 3: Coating of carbonyl ferromagnetic powder core:

[0056] Weigh 200 g of the carbonyl ferromagnetic powder core from step 2, a 5 wt.% epoxy resin A diluted solution, a 1 wt.% epoxy resin B diluted solution, and 0.08 wt.% KH550 solution, which is equivalent to the carbonyl ferromagnetic powder core; dissolve the weighed epoxy resin A diluted solution, epoxy resin B diluted solution, and KH550 in a 10 wt.% acetone solution, stir and react for 2 minutes, then add 200 g of the carbonyl ferromagnetic powder core, heat and stir in an 80°C water bath to react until the acetone is completely volatilized; bake the obtained powder at 60°C for 1 hour and pass through a 40-100 mesh sieve to obtain a coated carbonyl ferromagnetic powder core;

[0057] Step 4: Molding:

[0058] The coated carbonyl ferromagnetic powder core obtained in step 3 is mixed with zinc stearate equivalent to 0.3 wt.% of the mass of the coated carbonyl ferromagnetic powder core, and pressed into a 10 mm × 6 mm × 4 mm magnetic ring under 1000 MPa. The magnetic ring is baked at 120°C in a precisely temperature-controlled oven for 1 hour and then taken out to obtain a carbonyl ferromagnetic powder core material.

[0059] The initial magnetic permeability μ of the magnetic ring samples of Example 1, Comparative Example 1 and Comparative Example 2 was measured using a Tonghui TH2826 LCR digital bridge. i Test: Superimpose a DC power supply on the digital bridge to test the magnetic ring sample μ i The attenuation rate with the increase of DC magnetic field, that is, DC superposition characteristics; the core loss P of the magnetic ring sample was measured using Iwasaki SY-8218B-H analyzer. cv Test: Use vibrating sample magnetometer Lake Shore 8604 to test the saturation magnetic induction intensity B of the sample s The test results are shown in Table 1:

[0060] Table 1 Test results of Example 1, Comparative Example 1 and Comparative Example 2

[0061] Material Type <![CDATA[B s (T)]]> <![CDATA[μ i (μ0)]]> <![CDATA[μ i (100Oe) / m i (0Oe)(%)]]> <h2 style=";text-align:left;direction:ltr"><![CDATA[P <h2 style=";text-align:left;direction:ltr"> cv <h2 style=";text-align:left;direction:ltr"> (kW / m3,1MHz 20mT)]]><h2 style=";text-align:left;direction:ltr"> Example 1 1.38 38.5 85.7 749.4 Comparative Example 1 1.75 49.5 78.3 1209.3 Comparative Example 2 1.71 42.2 82.4 1390.5

[0062] The test shows that by compounding the low coercive force and high resistivity iron-based amorphous FeSiCrB magnetic powder core with the carbonyl ferromagnetic powder core, the DC superposition characteristics of the carbonyl ferromagnetic powder core are improved and its core loss is reduced. Its DC superposition characteristics are improved by 9.5% while P cv Comparative Example 1 is a carbonyl ferromagnetic powder core with only organic epoxy resin curing agent added. The method of modifying the surface micromorphology of carbonyl ferromagnetic powder particles by H3PO4 inorganic insulation coating only improves its DC superposition characteristics, but the increase in the number of distributed air gaps leads to an increase in its pores. cv An increase of 15%, see the test data of Comparative Example 2.

[0063] Figure 2The surface micromorphology of the magnetic core material of Example 1 shows that the carbonyl iron magnetic powder core with fine particle size fills the particle gap of the FeSiCrB magnetic powder core well, and due to the presence of inorganic insulating materials on the surface of the two magnetic powder core particles ( Figure 3 (a) and (b) illustrate that the inorganic insulating materials on the surfaces of the carbonyl iron powder and FeSiCrB powder core (phosphate and nano-silica, respectively) promote friction and resistance between the powders, thereby facilitating magnetic domain rotation. The resulting more uniform and continuous magnetic domain structure significantly reduces core loss. Because the FeSiCrB powder core carries more distributed air gaps, the DC superposition characteristics of the entire composite system are also improved, achieving a balanced performance balance between DC superposition characteristics and core loss.

Claims

1. A method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss, characterized in that: The following steps are involved: Step 1: Raw material particle size gradation: Carbonyl iron magnetic powder particles and FeSiCrB magnetic powder particles are selected as raw materials, wherein the ratio of carbonyl iron magnetic powder particles D50 to FeSiCrB magnetic powder particles D50 is 0.35-0.55; Step 2: Preparation of carbonyl ferromagnetic powder core: Weigh the carbonyl iron magnetic powder particles from step 1, dissolve the weighed carbonyl iron magnetic powder particles and H3PO4 solution in acetone solution, stir at room temperature for 20 to 50 minutes, and bake the resulting powder at 40 to 80°C for 1 hour to obtain a carbonyl iron magnetic powder core; wherein the H3PO4 solution accounts for 0.45 wt.% of the mass of the carbonyl iron magnetic powder particles; Step 3: Preparation of FeSiCrB magnetic powder core: Weigh the FeSiCrB magnetic powder particles obtained in step 1, and dissolve the weighed FeSiCrB magnetic powder particles and the TEOS solution in a mixed solvent. After stirring at room temperature for 5 minutes, add ammonia water dropwise to the obtained mixture, and then heat and stir the mixture in a water bath at 50-90° C. until all the liquid evaporates. Bake the obtained powder at 40-120° C. for 1 hour to obtain a FeSiCrB magnetic powder core. The TEOS solution accounts for 4.5 wt.% of the mass of the FeSiCrB magnetic powder particles, the ammonia water accounts for 5 wt.% of the mass of the FeSiCrB magnetic powder particles, and the mixed solvent includes anhydrous ethanol, deionized water, and a silane coupling agent KH550. The anhydrous ethanol accounts for 12 wt.% of the mass of the FeSiCrB magnetic powder particles, the deionized water accounts for 5 wt.% of the mass of the FeSiCrB magnetic powder particles, and the silane coupling agent KH550 accounts for 0.05 wt.% of the mass of the FeSiCrB magnetic powder particles. Step 4: Preparation of carbonyl iron / FeSiCrB composite particles: The carbonyl ferromagnetic powder core prepared in step 2 and the FeSiCrB magnetic powder core prepared in step 3 are mixed in a ratio of "45 wt.% carbonyl ferromagnetic powder core + 55 wt.% FeSiCrB magnetic powder core" to obtain a mixed powder; based on the total mass of the mixed powder, 5 wt.% of a diluted epoxy resin A solution, 1 wt.% of a diluted epoxy resin B solution, and 0.08 wt.% of KH550 are weighed, and the weighed diluted epoxy resin A solution, the diluted epoxy resin B solution, and the KH550 are dissolved in an acetone solution, stirred for reaction for 2 minutes, and then the mixed powder is added, and the mixture is heated and stirred in a water bath at 40-80°C until the acetone is completely volatilized; the obtained powder is baked at 40-80°C for 1 hour and passed through a 40-100 mesh sieve to obtain carbonyl iron / FeSiCrB composite particles; Step 5: Molding: The carbonyl iron / FeSiCrB composite particles obtained in step 4 are mixed with zinc stearate equivalent to 0.3 wt.% of the mass of the carbonyl iron / FeSiCrB composite particles, pressed into a magnetic ring at 560-1460 MPa, and the magnetic ring is baked at 100-200° C. for 1 hour and then taken out to obtain a carbonyl iron / FeSiCrB composite magnetic powder core material.

2. The method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss according to claim 1, characterized in that: In step 1, the D50 of the carbonyl iron magnetic powder particles is in the range of 3 to 6 μm, and the D50 of the FeSiCrB magnetic powder particles is in the range of 12 to 18 μm.

3. The method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss according to claim 1, characterized in that: In the acetone solution of step 2, the mass percentage of acetone is 12 wt.%.

4. The method for preparing a composite magnetic powder core with high DC superposition characteristics and low loss according to claim 1, characterized in that: In the acetone solution of step 4, the mass percentage of acetone is 10 wt.%.

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