CN106531388A - Composite magnetic powder and preparation method therefor - Google Patents

Abstract

The invention belongs to the preparation field of a magnetic material, and particularly relates to composite magnetic powder and a preparation method therefor. The preparation method comprises the following steps of a), preparing an iron-silicon-aluminum alloy (which also can be called as sendust in the specification) thin belt by a melt rapid quenching method; in the preparation process, applying a directional magnetic field in belt-spinning; and performing crushing on the prepared iron-silicon-aluminum alloy thin belt to obtain an iron-silicon-aluminum alloy fragment; b), enabling the iron-silicon-aluminum alloy fragment and ferrite powder to be mixed and ball grinded to obtain composite magnetic powder; and c), enabling a binder, a lubricating agent and the composite magnetic powder to be mixed and pressed in sequence to obtain a composite magnetic powder core. Experiment results prove that the effective magnetic conductivity of the magnetic powder core prepared by the method can be higher than 40 at the test frequency of 100kHz; and the loss is lower than 83W/kg in the test conditions of 100kHz when Bm is equal to 300mT.

Description

A kind of preparation method of composite magnetic powder and composite magnetic powder core

technical field

The invention belongs to the field of magnetic material preparation, and in particular relates to a preparation method of composite magnetic powder and composite magnetic powder core.

Background technique

Sendust soft magnetic alloy, also known as Sendust alloy, has a chemical composition of 5.4wt.% Al, 9.6

wt.% Si, the rest is Fe (85wt.%). Sensil is very brittle and is easily broken into powder. It is generally prepared as a magnetic powder core for use.

Compared with iron-silicon cores and iron powder cores, sendust magnetic powder cores have lower high-frequency loss, and have higher saturation magnetic induction and magnetic permeability, and are inexpensive, which is conducive to miniaturization. In addition, the magnetostriction coefficient λ _s of sendust is close to zero, which is beneficial to eliminate the auditory frequency noise generated when the filter inductor is working. Due to the characteristics of low loss, low cost, etc., and the incomparable comprehensive performance of other magnetic powder cores, sendust magnetic powder cores have developed rapidly, and have been widely used in devices such as output inductors, line filters, and power factor correctors. application.

The early sendust magnetic powder cores had a relatively low operating frequency and only required high magnetic permeability but not high requirements for loss. With the use of sendust magnetic powder cores, the operating frequency is getting higher and higher, and the high-frequency loss is large. How to reduce the high-frequency loss of the magnetic core while ensuring the high magnetic permeability of the magnetic powder core has become a prominent problem. Therefore, it is particularly important to study the influencing factors of magnetic powder core permeability and core loss. The research on metal magnetic powder cores at home and abroad is mainly to improve the magnetic properties of magnetic powder cores by improving the performance of magnetic powder, selecting appropriate insulating agents and particle size of magnetic powder, and adjusting pressing parameters. With the deepening of the research, considering the improvement of the process, such as the impact of molding pressure, insulation coating process and heat treatment on the magnetic permeability and loss of the magnetic powder core, more and more attention has been paid. One of the most critical processes in the production process of sendust magnetic powder cores is the powder insulation coating process. The electrical contact between the magnetic powders can be blocked by insulating coating, so that the resistivity of the magnetic powders can be increased and the high-frequency loss can be reduced.

At present, the commonly used sendust magnetic powder core preparation method at home and abroad adopts the insulation coating process, and the non-magnetic insulating layer used dilutes the magnetism, resulting in low magnetic permeability; the insulating layer is unstable (pyrolysis) and low in strength (magnetic powder core pressing The cladding layer is easily crushed during the molding process) resulting in high high-frequency loss. In addition, the currently commonly used sendust magnetic powder is not flat enough, which is not conducive to further improving the magnetic permeability and reducing high-frequency loss.

Contents of the invention

In view of this, the object of the present invention is to provide a method for preparing composite magnetic powder and composite magnetic powder core. The magnetic powder core prepared by the method provided by the present invention has higher magnetic permeability and lower high-frequency loss.

The invention provides a kind of preparation method of composite magnetic powder, comprises the following steps:

a) Using a melt quenching method to prepare sendust aluminum alloy strips; during the preparation process, applying a directional magnetic field when the strips are thrown; breaking the prepared sendust aluminum alloy thin strips to obtain sendust aluminum alloy fragments;

b) Mixing and ball milling the sendust powder and ferrite powder to obtain composite magnetic powder.

Preferably, the magnetic field strength of the orientation magnetic field is 500-2000 Oe.

Preferably, a directional magnetic field is applied all the time during the belt throwing process.

Preferably, the thickness of the sendust aluminum strip is 5-50 μm.

Preferably, the particle diameter of the ferrite powder is 10 nm˜2 μm.

Preferably, the mass ratio of the sendust pieces to the ferrite powder is 100:(2-20).

Preferably, the ball-to-material mass ratio in the ball milling process is (10-15):1.

Preferably, the diameter of the balls used in the ball mill is 3-15 mm.

The invention provides a preparation method of a composite magnetic powder core, comprising the following steps:

The binder, the lubricant, and the composite magnetic powder prepared according to the method described in the above technical solution are mixed and pressed in sequence to obtain a composite magnetic powder core.

Preferably, the pressing pressure is 1500-2000 MPa; the pressing time is 3-8 minutes.

Compared with the prior art, the present invention provides a preparation method of composite magnetic powder and composite magnetic powder core, the preparation method of the composite magnetic powder core provided by the present invention comprises the following steps: a) preparing sendust by melt rapid quenching Alloy thin strip; during the preparation process, a directional magnetic field is applied when the strip is thrown; the prepared sendust aluminum strip is broken to obtain sendust aluminum fragments; b) combining the sendust aluminum alloy fragments with ferrite The powders are mixed and ball milled to obtain a composite magnetic powder; c) sequentially mixing and pressing a binder, a lubricant and the composite magnetic powder to obtain a composite magnetic powder core. In the present invention, a directional magnetic field is firstly applied during the belt throwing process when preparing the sendust aluminum strip, and in this way the saturation magnetization and magnetic permeability of the sendust aluminum strip are improved. Afterwards, the crushed sendust aluminum alloy fragments are ball milled with ferrite powder, and the ferrite powder is evenly embedded on the surface of the sendust aluminum alloy fragments by means of the rolling action during ball milling to form a ferrite insulating coating layer. The present invention mixes ferrite powder and sendust fragments by ball milling, which not only enables ferrite to coat the surface of sendust fragments evenly and firmly, but also makes the ferrite powder less ferrite powder The ferrite powder can completely cover the surface of the sendust, which reduces the influence of the introduction of ferrite on the magnetic permeability of the magnetic powder, and maintains the magnetic permeability of the magnetic powder at a high level. At the same time, ball milling can also Further realize the flattening of the magnetic powder, thereby further improving the magnetic permeability of the magnetic powder and reducing the high-frequency loss of the magnetic powder core made of it. The magnetic powder core made of the composite magnetic powder provided by the invention has high magnetic permeability and low high-frequency loss, and has broad application prospects. It can be used not only in telecommunications and radar, but also in the fields of wave absorption and electromagnetic shielding. Experimental results show that the effective magnetic permeability of the magnetic powder core made by the method provided by the invention is higher than 40 at the test frequency of 100kHz, and the loss is lower than 83W/kg under the test condition of 100kHz and Bm=300mT.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the effective magnetic permeability of the composite magnetic powder core of different proportioning provided by embodiment 6 of the present invention;

Fig. 2 is the loss of the composite magnetic powder core of different proportioning provided by embodiment 6 of the present invention;

Fig. 3 is the effective magnetic permeability of the composite magnetic powder core with different annealing temperatures provided by Embodiment 12 of the present invention;

Fig. 4 shows the losses of the composite magnetic powder cores provided by Example 12 of the present invention with different annealing temperatures.

detailed description

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a kind of preparation method of composite magnetic powder, comprises the following steps:

a) Using a melt quenching method to prepare sendust aluminum alloy strips; during the preparation process, applying a directional magnetic field when the strips are thrown; breaking the prepared sendust aluminum alloy thin strips to obtain sendust aluminum alloy fragments;

b) Mixing and ball milling the sendust powder and ferrite powder to obtain composite magnetic powder.

In the preparation method provided by the present invention, sendust aluminum strips are firstly prepared. The invention adopts the melt rapid quenching method to prepare the iron-silicon-aluminum alloy thin strip, and always applies a directional magnetic field during the strip throwing process. In the present invention, the magnetic field strength of the orientation magnetic field is preferably 500-2000 Oe, more preferably 1000-1200 Oe. In the present invention, during the stripping process, the thickness of the thin strip can be controlled by adjusting the copper roll speed, the faster the copper roll speed, the thinner the thickness, and the copper roll speed is preferably 30-80m/s. The present invention has no particular limitation on the equipment for preparing the sendust thin strip, and is preferably an induction melt quenching equipment well known to those skilled in the art. After the preparation is completed, the sendust aluminum strip is obtained. In the present invention, the sendust aluminum strip is composed of Si, Al and Fe, wherein the content of Si in the alloy strip is preferably 9.3-9.7wt%, more preferably 9.6wt%; The content in the ribbon is preferably 5.2-5.6 wt%, more preferably 5.4 wt%; the balance is Fe. In the present invention, the thickness of the sendust aluminum strip is preferably 5-50 μm, more preferably 5-30 μm, and most preferably 5-15 μm. After the sendust aluminum strip is obtained, the prepared sendust aluminum strip is crushed to obtain sendust aluminum alloy fragments.

After the sendust shards are obtained, the sendust shards are mixed with ferrite powder for ball milling. Among them, the ferrite powder is preferably manganese zinc ferrite powder, whose general chemical formula is Mn _x Zn _1-x Fe ₂ O ₄ , 0<x<1. In an embodiment provided by the present invention, the general chemical formula of the manganese zinc ferrite powder is Mn _0.4 Zn _0.6 Fe ₂ O ₄ . In the present invention, the particle size of the ferrite powder is preferably 10 nm to 2 μm. In the present invention, the source of the ferrite powder is not particularly limited, and it can be prepared by chemical co-precipitation. Taking manganese-zinc ferrite powder as an example, it can be prepared according to the following method:

(1), iron salt, zinc salt, manganese salt and water are mixed, obtain mixed salt solution;

(2), adjust the pH value of described mixed salt solution with soluble alkali, carry out reaction, obtain manganese zinc ferrite precursor;

(3) The manganese zinc ferrite precursor is calcined to obtain manganese zinc ferrite powder.

In the above-mentioned method for preparing manganese-zinc ferrite powder provided by the present invention, first mix iron salt, zinc salt, manganese salt and water, wherein, the iron salt is a soluble salt of iron or a hydrate thereof, including but Not limited to one or more of FeCl ₃ , Fe(NO ₃ ) ₃ and Fe ₂ (SO ₄ ) ₃ ; the zinc salt is a soluble salt of zinc or a hydrate thereof, including but not limited to ZnCl ₂ , Zn One or more of (NO ₃ ) ₂ and ZnSO ₄ ; the manganese salt is a soluble salt of manganese or a hydrate thereof, including but not limited to MnCl ₂ , MnCl ₂ ·4H ₂ O, Mn(NO ₃ ) ₂ and one or more of MnSO ₄ . After the iron salt, zinc salt and manganese salt are completely dissolved in water, a mixed salt solution is obtained.

After the mixed salt solution is obtained, the pH value of the mixed salt solution is adjusted to alkaline with a soluble base. Wherein, the soluble base is preferably NaOH or its aqueous solution, and the concentration of the NaOH aqueous solution is preferably 1-2 mol/L. In the present invention, the pH value of the mixed salt solution is preferably adjusted to 9-13, more preferably 10-11. In the present invention, it is preferred to adjust the pH value of the mixed liquid solution after heating it to 50-90°C, more preferably 70-80°C. After the pH is adjusted, the ions in the mixed salt solution react to obtain a solid precipitate, which is the precursor of manganese zinc ferrite. In the present invention, the reaction time is preferably 10-60 min, more preferably 30-40 min.

After the manganese zinc ferrite precursor is obtained, the manganese zinc ferrite precursor is calcined. Wherein, the temperature of the calcination is preferably 800-900° C., more preferably 850-870° C.; the calcination time is preferably 1-5 hours, more preferably 2-3 hours. After calcination, manganese zinc ferrite powder is obtained. In the present invention, the manganese zinc ferrite precursor is preferably washed and dried before being fired. The drying temperature is preferably 90-100° C.; the drying time is preferably 1-2 hours.

In the present invention, during the ball milling process of ferrite powder and sendust shards, the mass ratio of the sendust shards to ferrite powder is preferably 10:(2-20), more preferably 100 :2, 100:4, 100:6, 100:10, or 100:20. In the present invention, the ball-to-material mass ratio in the ball milling process is preferably (10-15):1, more preferably (12-13):1. In the present invention, the grinding balls used in the ball mill are preferably steel balls; the diameter of the steel balls is preferably 3-15 mm, more preferably 5-10 mm; in an embodiment provided by the present invention, the grinding balls include Steel balls with a diameter of 5 mm and steel balls with a diameter of 10 mm, the number ratio of the steel balls with a diameter of 5 mm to the steel balls with a diameter of 10 mm is preferably (3-10):1, more preferably 5:1. In the present invention, the rotational speed of the ball mill is preferably 30-80 rpm, more preferably 50-60 rpm; the time of the ball mill is preferably 20-60 h, more preferably 30-40 h. After ball milling, composite magnetic powder is obtained.

In the present invention, a directional magnetic field is firstly applied during the spin-off process when preparing the sendust aluminum strip, and in this way the saturation magnetization and magnetic permeability of the sendust aluminum strip can be improved. Afterwards, the broken sendust aluminum strip is ball-milled with ferrite powder, and the ferrite powder is evenly embedded on the surface of the sendust aluminum fragment by means of rolling during ball milling to form a ferrite insulating coating layer. The present invention mixes ferrite powder and sendust shards by means of ball milling, not only can ferrite be evenly and firmly coated on the surface of sendust shards, but also when the amount of ferrite powder is low It can realize the complete coating of the surface of sendust aluminum alloy by ferrite powder, reduce the influence of the introduction of ferrite on the magnetic permeability of magnetic powder, and maintain the magnetic permeability of magnetic powder at a high level. At the same time, ball milling can also achieve The flattening of the magnetic powder further improves the magnetic permeability of the magnetic powder and reduces the high-frequency loss of the magnetic powder core made of it. The magnetic powder core made of the composite magnetic powder prepared by the method provided by the present invention has high magnetic permeability and low high-frequency loss, and has broad application prospects. It can be used not only in telecommunications and radar, but also in the fields of wave absorption and electromagnetic shielding . Experimental result shows, with the composite magnetic powder that the method provided by the present invention makes is that the effective magnetic permeability of the composite magnetic powder core that raw material is made is higher than 40 at the test frequency of 100kHz, at 100kHz, the loss under Bm=300mT test condition is low At 83W/kg.

The present invention also provides a composite magnetic powder prepared according to the above-mentioned method. The composite magnetic powder includes sendust magnetic powder and ferrite powder coated on the surface of the sendust magnetic powder. The composite magnetic powder is flat and has Higher permeability, higher saturation magnetization and lower high-frequency loss, broad application prospects.

The present invention also provides a preparation method of a composite magnetic powder core, comprising the following steps:

The binder, the lubricant, and the composite magnetic powder prepared according to the method described in the above technical solution are mixed and pressed in sequence to obtain a composite magnetic powder core.

In the preparation method of the composite magnetic powder core provided by the present invention, firstly, the binder, the lubricant and the composite magnetic powder are mixed. Wherein, the binder is preferably epoxy resin; the mass ratio of the binder to the composite magnetic powder is preferably (1-2):100, more preferably 1.5:100. The lubricant is preferably magnesium stearate; the mass ratio of the lubricant to the composite magnetic powder is preferably (0.5-2):100, more preferably (1-1.5):100. After mixing, press. Wherein, the pressing pressure is preferably 1500-2000 MPa, more preferably 1700-1800 MPa; the pressing time is preferably 3-8 minutes. After pressing, a composite magnetic powder core is obtained. In the present invention, it is preferable to anneal the obtained composite magnetic powder core to eliminate its internal stress and increase the magnetic permeability. Wherein, the temperature of the annealing treatment is preferably 600-700° C., more preferably 650-690° C.; the holding time of the annealing treatment is preferably 1-2 hours.

The composite magnetic powder core prepared by the method provided by the invention has high magnetic permeability and low high-frequency loss, and has broad application prospects. It can be used not only in telecommunications and radar, but also in the fields of wave absorption and electromagnetic shielding. Experimental results show that the effective magnetic permeability of the composite magnetic powder core provided by the present invention is higher than 40 at a test frequency of 100 kHz, and the loss is lower than 83 W/kg under test conditions of 100 kHz and Bm=300mT.

Comprehensive evaluation technical scheme that the present invention provides, it has the following advantages:

1) The induction-type melt quenching equipment is used to prepare the sendust aluminum alloy thin strip, and a directional magnetic field is applied during the stripping process to make the easy axis oriented along the external magnetic field, which improves the saturation magnetization of the prepared sendust aluminum alloy thin strip and magnetic permeability;

2) Mix ferrite powder and sendust debris by ball milling, and use the rolling action of ball milling to embed ferrite powder evenly on the surface of sendust debris to form uniform and firm ferrite Insulation coating layer; avoids the instability of the insulation layer (pyrolysis), low strength (the coating layer is easily crushed during the pressing molding process), discontinuity and difficulty in the thickness of the sendust magnetic powder during the insulation coating process. issues of control;

3) Mixing ferrite powder and sendust fragments by ball milling can completely cover the surface of sendust with ferrite powder when the amount of ferrite powder is low. Reduce the influence of the introduction of ferrite on the magnetic permeability of magnetic powder, maintain the magnetic permeability of magnetic powder at a high level, and provide technical support for obtaining magnetic powder cores with high magnetic permeability;

4) Flattened magnetic powder can be obtained by ball milling the sendust aluminum alloy fragments, thereby further improving the magnetic permeability of the magnetic powder and reducing the high-frequency loss of the magnetic powder core made of it;

5), it is preferable to adopt chemical co-precipitation method to prepare ferrite powder, which has fast reaction speed and high yield;

6) Preferably, the composite magnetic powder core obtained by pressing is annealed to eliminate the internal stress of the magnetic powder core and further increase the magnetic permeability of the magnetic powder core.

For more clarity, detailed description is given below through the following examples.

Example 1

(1) In the induction type melt quenching equipment, prepare a standard composition iron-silicon-aluminum alloy strip (5.4wt% Al, 9.6wt% Si, the rest Fe) with a thickness of 5-15 μm. During the preparation of the alloy strip, the strip The rotational speed of the copper roller is 60m/s, and a directional magnetic field of 1000Oe is always applied during the belt throwing process. After the sendust strip is obtained, it is crushed in a stainless steel tank to obtain sendust fragments.

(2) Using FeCl ₃ , ZnCl ₂ and MnCl ₂ 4H ₂ O as raw materials, according to the molar ratio n[Fe ³⁺ ] of Fe ³⁺ , Zn ²⁺ , and Mn ²⁺ in Mn _0.4 Zn _0.6 Fe ₂ O ₄ : n[Zn ²⁺ ]:n[Mn ²⁺ ]=10:3:2 Weigh the required raw materials respectively, add an appropriate amount of deionized water, and stir continuously to completely dissolve the raw material particles to obtain Fe-Zn-Mn mixed salt solution, Heat to 80°C, drop NaOH solution with a concentration of 2mol/L at the same time, keep stirring, adjust the pH value of the solution to 10, and react for 30 minutes to synthesize the precursor of manganese zinc ferrite; after the reaction, wash the ferrite with deionized water The body precursor was dried several times in a drying oven at 100 °C for 1 h. The dried ferrotrophic precursor is placed in a muffle furnace and calcined at 850° C. for 2 hours to obtain MnZn ferrite powder with a particle size of 10 nm˜2 μm.

(3) Put the sendust aluminum alloy fragments in the stainless steel ball milling tank of the ball mill, and the mass ratio of the manganese zinc ferrite powder to the sendust aluminum alloy fragments is 2%, put the manganese zinc ferrite powder of corresponding quality into The stainless steel ball milling tank is used for ball milling with FeSiAl alloy fragments; the balls used for ball milling are steel balls with diameters of 10mm and 5mm, and the number ratio of large balls to small balls is 1:5; the mass ratio of balls to materials during ball milling is 12 : 1, the rotating speed of the ball mill is 50rpm, after ball milling for 30 hours, sendust/ferrite composite magnetic powder is obtained.

(4) Add 1.5wt% epoxy resin and 1wt.% magnesium stearate to the obtained composite magnetic powder, and then cold press at 1800Mpa for 5min to obtain a composite magnetic powder core blank.

(5) Anneal the composite magnetic powder core blank at 600° C. for 2 hours in nitrogen to obtain a composite magnetic powder core product.

Embodiment 2-5

Referring to the preparation method of Example 1, the mass ratios of manganese-zinc-ferrite powder and sendust-aluminum fragments were sequentially adjusted to 4%, 6%, 10%, and 20%, to prepare composite magnetic powder core products.

Comparative example 1

Referring to the preparation method of Example 1, adjust the mass ratio of manganese zinc ferrite powder and sendust aluminum alloy fragments to 0 to prepare a composite magnetic powder core product.

Example 6

Under the test frequency of 100kHz, test the effective magnetic permeability of the composite magnetic powder core products that embodiment 1～5 and comparative example 1 make respectively, the result is as shown in Figure 1, and Figure 1 is the different proportioning provided by Example 6 of the present invention The effective magnetic permeability of the composite magnetic powder core can be seen from Figure 1 that the effective magnetic permeability of the magnetic powder core prepared by the method provided in Examples 1-5 is higher than 40.

At 100kHz, the loss (Core loss) of the composite magnetic powder core product that embodiment 1～5 and comparative example 1 make are tested respectively under the test condition of Bm=300mT, and result is as shown in Figure 2, and Figure 2 is embodiment 6 of the present invention The losses of the composite magnetic powder cores provided with different proportions can be seen from FIG. 2 , the losses of the magnetic powder cores prepared by the method provided in Examples 1-5 are lower than 83W/kg.

Example 7

(1) In the induction type melt quenching equipment, prepare a standard composition iron-silicon-aluminum alloy strip (5.4wt% Al, 9.6wt% Si, the rest Fe) with a thickness of 5-15 μm. During the preparation of the alloy strip, the strip The rotational speed of the copper roller is 60m/s, and a directional magnetic field of 1000Oe is always applied during the belt throwing process. After the sendust strip is obtained, it is crushed in a stainless steel tank to obtain sendust fragments.

(2) Using FeCl ₃ , ZnCl ₂ and MnCl ₂ 4H ₂ O as raw materials, according to the molar ratio n[Fe ³⁺ ] of Fe ³⁺ , Zn ²⁺ , and Mn ²⁺ in Mn _0.4 Zn _0.6 Fe ₂ O ₄ : n[Zn ²⁺ ]:n[Mn ²⁺ ]=10:3:2 Weigh the required raw materials respectively, add an appropriate amount of deionized water, and stir continuously to completely dissolve the raw material particles to obtain Fe-Zn-Mn mixed salt solution, Heat to 80°C, drop NaOH solution with a concentration of 2mol/L at the same time, keep stirring, adjust the pH value of the solution to 10, and react for 30 minutes to synthesize the precursor of manganese zinc ferrite; after the reaction, wash the ferrite with deionized water The body precursor was dried several times in a drying oven at 100 °C for 1 h. The dried ferrotrophic precursor is placed in a muffle furnace and calcined at 850° C. for 2 hours to obtain MnZn ferrite powder with a particle size of 10 nm˜2 μm.

(3) Put the sendust aluminum alloy fragments in the stainless steel ball milling tank of the ball mill, and the mass ratio of the manganese zinc ferrite powder to the sendust aluminum alloy fragments is 6%, put the manganese zinc ferrite powder of the corresponding quality into The stainless steel ball milling tank is used for ball milling with FeSiAl alloy fragments; the balls used for ball milling are steel balls with diameters of 10mm and 5mm, and the number ratio of large balls to small balls is 1:5; the mass ratio of balls to materials during ball milling is 12 : 1, the rotating speed of the ball mill is 50rpm, the ball mill is 30h, and after the ball mill is finished, sendust/ferrite composite magnetic powder is obtained.

(4) Add 1.5wt% epoxy resin and 1wt.% magnesium stearate to the obtained composite magnetic powder, and then cold press at 1800Mpa for 5min to obtain a composite magnetic powder core blank.

(5) Anneal the composite magnetic powder core blank at 600° C. for 1 h in nitrogen to obtain a composite magnetic powder core product.

Embodiment 8～11

Referring to the preparation method in Example 7, the annealing temperature of the composite magnetic powder core blank was sequentially adjusted to 630° C., 660° C., 690° C., and 720° C. to prepare a composite magnetic powder core product.

Example 12

Under the test frequency of 100kHz, test the effective magnetic permeability of the composite magnetic powder core products that embodiment 7～11 makes respectively, the result is as shown in Figure 3, and Figure 3 is the composite magnetic powder core of the different annealing temperature that embodiment 12 of the present invention provides It can be seen from FIG. 3 that the effective magnetic permeability of the magnetic powder core prepared by the method provided in Examples 7-11 is higher than 60.

At 100kHz, the loss (Core loss) of the composite magnetic powder core product that embodiment 7～11 makes is tested respectively under the test condition of Bm=300mT, and the result is as shown in Figure 4, and Figure 4 is the different annealing that embodiment 12 of the present invention provides The loss of the composite magnetic powder core according to the temperature can be seen from Figure 4, the loss of the magnetic powder core prepared by the method provided in Examples 7-11 is lower than 68W/kg.

Comparative example 2

Refer to the preparation method of Example 1, except that no directional magnetic field is applied during the stripping process, the mass ratio of manganese-zinc-ferrite powder to sendust aluminum alloy fragments is 6%, and a composite magnetic powder core product is prepared. After medium annealing for 1 hour, detect the effective permeability and loss. The effective permeability is only 51.2 at the test frequency of 100kHz. Under the test conditions of 100kHz and Bm=300mT, the loss is 71W/kg.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a kind of preparation method of composite magnetic powder, comprises the following steps：

A) sendust strip is prepared using melt-quenching method,；In preparation process, when getting rid of band, magnetic field is applied directional；To be obtained Sendust strip crushed, obtain sendust fragment；

B), by the sendust fragment and ferrite powder mixing and ball milling, obtain composite magnetic powder.

2. preparation method according to claim 1, it is characterised in that the magnetic field intensity of the directional magnetic field is 500～ 2000Oe。

3. preparation method according to claim 2, it is characterised in that apply directional magnetic field always during getting rid of band.

4. preparation method according to claim 1, it is characterised in that the thickness of the sendust strip is 5～50 μ m。

5. preparation method according to claim 1, it is characterised in that the particle diameter of the ferrite powder is 10nm～2 μm.

6. preparation method according to claim 1, it is characterised in that the sendust fragment and ferrite powder Mass ratio is 100：(2～20).

7. preparation method according to claim 1, it is characterised in that the ball material mass ratio in the mechanical milling process is (10 ～15):1.

8. preparation method according to claim 1, it is characterised in that the ball radius that the ball milling is adopted are for 3～15mm.

9. a kind of preparation method of composite magnetic powder core, comprises the following steps：

Binding agent, lubricant and the composite magnetic powder prepared according to claim 1～8 any one methods described are mixed successively Close and suppress, obtain composite magnetic powder core.

10. preparation method according to claim 9, it is characterised in that the pressure of the compacting is 1500～2000MPa； The time of the compacting is 3～8min.