KR20150062140A

KR20150062140A - Dust core using soft magnetic powder and method of manufacturing the dust core

Info

Publication number: KR20150062140A
Application number: KR1020140167256A
Authority: KR
Inventors: 게이코 츠치야; 히사토 고시바
Original assignee: 알프스 그린 디바이스 가부시키가이샤
Priority date: 2013-11-28
Filing date: 2014-11-27
Publication date: 2015-06-05
Also published as: TWI537994B; JP2015106593A; CN104681227A; TW201521049A; JP6262504B2; KR101633190B1; CN104681227B

Abstract

Provided are a dust core with excellent magnetic property and mechanical strength and a method for producing the dust core. The dust core (1) is obtained by heat-treating a formed object obtained by compressing and forming coarse dusts with an insulative binding material and soft magnetic powders (2). The dust core has a powder filling rate of 75 vol% or more and a radial crushing strength of 3.9-11 N/mm^2, measured according to JIS Z2507: 2000.

Description

TECHNICAL FIELD [0001] The present invention relates to a compacted core using soft magnetic powder and a method for manufacturing the compacted powder core. [0002]

The present invention relates to a compacted core using a soft magnetic powder and a method for producing the compacted core.

A compacting core used for a booster circuit of a hybrid car or the like, a reactor used for power generation, a power transmission facility, a transformer or a choke coil can be obtained by heat-treating a compact obtained by compacting a large number of soft magnetic powders. The following Patent Document discloses an example of a compact cored core.

Japanese Laid-Open Patent Publication No. 2012-212853

The compacting core may be subjected to a step of fitting to fit other parts, a step of winding a coil material such as copper wire, a barrel plating step, etc. until a product using the compacted core is obtained. In such a case, it is preferable that the press compaction core is excellent in mechanical strength because it is gripped by the mounting jig or collides with other parts or other press compaction cores.

Particularly, when the soft magnetic powder as the raw material for producing the press compaction core is a relatively hard material such as the Fe-based amorphous alloy powder, soft magnetic powder such as crystalline soft magnetic alloy powder has soft magnetic properties It is not easy to increase the filling density of the powder. Since the filling density is hardly increased in this way, it is difficult to improve magnetic properties and mechanical properties of a compacted core using a material having relatively hard soft magnetic powder. Further, since the Fe-based amorphous alloy generally has a large magnetostriction, it is preferable that the compacted core made of the Fe-based amorphous alloy powder relaxes the strain by heat treatment. In this case, in order to achieve both high magnetic properties and high mechanical properties, strict control of the heat treatment conditions may be required.

It is an object of the present invention to provide a compacted core having excellent magnetic properties as well as excellent mechanical strength and a method for producing such compacted core.

In order to solve the above problems, the inventors of the present invention have found that an insulating binder used for binding a soft magnetic powder in a powder compact core not only affects the mechanical properties of the powder compact core but also affects magnetic properties. I got knowledge. Specifically, in the case of obtaining a compacted core by subjecting a compact obtained by compression molding granulated powder containing a soft magnetic powder and an insulating binder to heat treatment, the hardening of the insulating binder caused by the heat treatment It has become clear that the degree of thermal decomposition affects the powder filling rate and pressure ring strength in the compaction core, and the magnetic properties are affected by these influences.

The present invention, provided based on the above-described new knowledge, is as follows.

(1) A compacted particulate core obtained by compression molding a granulated powder having a soft magnetic powder and an insulating binder to obtain a compact, and subjecting the obtained compacted body to a heat treatment, wherein the compacted powder core has a powder filling rate of 75% by volume or more and JIS Z2507: 2000 , And the pressing strength measured according to the following formula is 3.9 N / mm2 or more and 11 N / mm2 or less.

(2) The compact powder core according to (1), wherein the soft magnetic powder contains an Fe-based amorphous alloy powder.

(3) The Fe-based amorphous alloy powder has a composition represented by Fe _100-abcxyzt Ni _a Sn _b Cr _c P _x C _y B _z Si _t where 0 at% ≤ a ≤ 10 at%, 0 at% ≤ b 0 at% ≤ c ≤ 6 at%, 3.0 at% ≤ x ≤ 10.8 at%, 2.0 at% ≤ y ≤ 9.8 at%, 0 at% ≤ z ≤ 8.0 at%, 0 at% ≤ t &Lt; / = 5.0 at%.

(4) The compaction core according to any one of (1) to (3) above, wherein the powder filling rate of the compaction core is 80 volume% or more.

(5) The compaction core according to any one of (1) to (4), wherein the Young's modulus is 50 MPa or more.

(6) The potting core according to any one of (1) to (5) above, wherein the rate of change R of the powder filling rate defined by the following formula (i) is more than 0%.

R = (F ₁ / F ₀ -1) × 100 (i)

Here, F ₀ is the powder filling rate (unit: volume%) of the compact before the heat treatment, and F ₁ is the powder filling rate (unit: volume%) of the compact powder core obtained by the heat treatment.

(7) The compacting core according to any one of (1) to (6), wherein the cured product of the insulating binder has a glass transition temperature of -30 占 폚 to 100 占 폚.

(8) The compact powder core according to any one of (1) to (7), wherein the granulated powder is prepared as a granulated powder obtained by binding a plurality of the soft magnetic powders with the insulating binder.

(9) The heating temperature for the heat treatment is a temperature at which the core loss is lowest when measured at a frequency of 100 kHz and a maximum magnetic flux density of 100 mT to the compacted core obtained by the heat treatment. The compacting core according to any one of the preceding claims.

(10) The compact powder core according to any one of (1) to (9), wherein the compacted core contains a pyrolysis residue of a binder which is a component derived from the insulating binder, and the content of the pyrolysis residue of the binder is 0.05 mass% The compacted particulate core described.

(11) A compacted powder core comprising a compression-molding step of compression-molding a granulated powder having a soft magnetic powder and an insulating binder to obtain a compact, and a heat treatment step of obtaining a compacted core obtained by heat-treating the compact obtained by the compression- As a method, the pressing force of the compression molding performed in the compression molding step is set so that the powder filling rate of the compacting core obtained by the heat treatment step is 75 volume% or more, and the heating temperature of the heat treatment performed in the heat treatment step is , The core loss measured under the conditions of a frequency of 100 kHz and a maximum magnetic flux density of 100 mT for the compacted core obtained by the heat treatment step is set to be lowest, and the compacted core obtained by the heat treatment step is measured according to JIS Z2507: 2000 And a pressure reduction strength of not less than 3.9 N / mm < 2 > and not more than 11 N / The method of manufacture.

(12) The compacting core according to (11), wherein the pressing force of the compression molding is 0.3 GPa or more.

The compact cored core according to the present invention has excellent magnetic properties and excellent mechanical strength. According to the present invention, there is also provided a method for manufacturing a compact cored core having excellent magnetic properties and excellent mechanical strength.

1 is a perspective view conceptually showing the shape of a compacting core according to an embodiment of the present invention.
2 is a view showing a result of observation of a part of a section of a compacted core according to an embodiment of the present invention.
3 is a plan view conceptually showing the shape of a compact dust core in which a coil is enclosed according to an embodiment of the present invention.
Fig. 4 is a view conceptually showing a spray dryer apparatus and its operation used in an example of a method for manufacturing granular powder.
5 is a graph showing the relationship between the initial permeability based on the results of this embodiment and the powder filling rate of the powder compact core.
6 is a graph showing the relationship between the initial magnetic permeability and the pressing strength based on the results of this embodiment.
7 is a graph showing the relationship between the core loss and the pressing strength based on the results of this embodiment.
8 is a graph showing the relationship between the initial permeability and the rate of change of the powder filling rate based on the results of this embodiment.
9 is a graph showing the relationship between core loss and Young's modulus based on the results of this embodiment.
10 is a graph showing the relationship between the initial permeability and the Young's modulus based on the results of this embodiment.
11 is a graph showing the relationship between the powder filling rate and the Young's modulus of the compaction core based on the results of this embodiment.
12 is a graph showing the relationship between the powder filling rate of the molded article and the glass transition temperature of the insulating binder based on the results of this embodiment.
13 is a graph showing the relationship between the core loss and the mass change rate upon heating of the insulating binder, based on the results of this embodiment.

Hereinafter, embodiments of the present invention will be described in detail.

1. Popcorn core

(1) Structure and shape

The compact powder core 1 according to one embodiment of the present invention shown in Fig. 1 is obtained by compression-molding a granulated powder having a soft magnetic powder and an insulating binder, obtaining a compact, and heat-treating the compact. Since the insulating binder is hardened or thermally decomposed by this heat treatment, the compacted powder 1 according to one embodiment of the present invention contains a component derived from the insulating binder. In the present specification, the component derived from the insulating binder is also referred to as " pyrolysis residue of the binder ".

2 is a view showing a result of observation of a part of a section of the compacting core 1 according to one embodiment of the present invention. 2, the compaction core 1 according to an embodiment of the present invention is composed of a plurality of soft magnetic powders 2, a pyrolysis residue 3 of a binder, and a cavity 4. The pyrolytic residue 3 of the binder surrounds the soft magnetic powder 2 to insulate the plurality of soft magnetic powders 2 from each other and sandwich the soft magnetic powder 2 between adjacent soft magnetic powders 2, . At least a part of the gap portion 4 is a portion where the insulating binder is present in the molding step before the heat treatment, and is formed by hardening or pyrolysis of the insulating binder.

The state of dispersion of soft magnetic powder 2 in compact powder core 1 according to one embodiment of the present invention is not particularly limited. The soft magnetic powders 2 may be bonded to each other so that the soft magnetic powders 2 are dispersed substantially uniformly in the compaction core 1 and the soft magnetic powders 2 may form a partial structure. As an example of such a partial structure, there is a case in which a plurality of soft magnetic powders 2 are relatively densely bound to form a granular structure, and a plurality of granular structures are further bonded to form an entire structure.

The shape of the dust compact core (1) is not particularly limited. It may have a ring-shaped shape as shown in Fig. 1, or it may have the shape of a coil-enclosed dust compactor 10 as shown in Fig. 3, the coil-containing dust core 10 includes a dust compact core 11 and a coil 12 having a portion covered with the dust compact core 11. The coil 12 may be an edge-wise coil.

(2) Charging characteristics

The compact powder core 1 according to one embodiment of the present invention is a compact powder core 1 in which the filling ratio of the soft magnetic powder 2 (in this specification, the powder filling rate of the soft magnetic powder 2 is referred to as the " powder filling ratio & Or more.

In the present specification, the powder filling rate F ₀ (unit: volume%) and the powder filling rate F ₁ (unit: volume%) of the compacted core 1 before the heat treatment means the values measured by the following method. First, the content C (unit: mass%) of the soft magnetic powder in the granulated powder is obtained from the composition of the granulated powder having the soft magnetic powder and the insulating binder, which are provided for compression molding. Next, the mass W ₀ (unit: g) of the molded article before the heat treatment is measured. From these values, the mass W _M (unit: g) of the soft magnetic powder contained in the molded article before the heat treatment can be obtained.

W _M = W ₀ x C / 100

The volume V ₀ (unit: cm 3) of the outer appearance of the molded article before the heat treatment is obtained. Here, the case where the formed article has a ring-like shape as shown in Fig. 1 is a specific example.

V ₀ = {(outer diameter / 2) ² - (inner diameter / 2) ² } × π × height

Here, the outer diameter, the inner diameter, and the height are measured values (unit: cm) of the molded article before the heat treatment.

Based on the above values (W _M and V ₀ ) and the density? (Unit: g / cm 3) of the soft magnetic powder, the powder filling rate F ₀ of the compact before the heat treatment is obtained by the following formula.

F ₀ = W _M / V ₀ / ρ × 100

Subsequently, the dimensions of the compacted core 1 obtained by the heat treatment are measured in the same manner as in the case of the compacted body, and the volume V ₁ (unit: cm 3) of the appearance of the compacted core 1 is obtained.

Based on the obtained volume V ₁ , the powder filling rate F ₁ (unit: volume%) of the compaction core ₁ is obtained by the following equation.

F ₁ = W _M / V ₁ / ρ × 100

When the powder filling rate F ₁ of the dust compact core ₁ is 75 volume% or more, the Young's modulus of the dust compact core 1 is easily increased and the magnetic powder characteristic of the dust compact core 1 is easily improved. Among these magnetic properties, the initial permeability is likely to be positively correlated to the powder filling rate F ₁ of the compaction core 1. From the viewpoint of more stably improving both mechanical properties and magnetic properties including the Young's modulus as well as the pressing strength, the powder filling rate F ₁ of the dust compact core 1 is preferably 80% by volume or more.

The powder filling rate F ₁ of the compacted powder core 1 according to the embodiment of the present invention can be increased by increasing the pressing force in the compression molding of the granular material to be formed to form the green body. From the viewpoint of increasing the powder filling rate F ₁ of the dust presser core 1, it is preferable to suitably select the kind of the insulating binder contained in the granulated powder. In the case where the insulating binder is made of an excessively soft material, it is apt to increase the powder filling rate F ₀ of the molded product due to the influence of spring back during compression molding. Therefore, the powder filling rate F ₁ of the powder compact core ₁ is lowered, and mechanical and magnetic properties of the powder compact core ₁ are liable to be deteriorated. On the other hand, in the case where the insulating binder is made of an excessively hard material, it tends to be difficult to increase the powder filling rate F ₁ of the dust compactor ₁ , or tends to cause a high residual stress in the soft magnetic powder 2 There is a case. When this tendency is observed, the recovery of the magnetic properties by the heat treatment becomes insufficient, and the magnetic properties of the dust compact core 1 are likely to be deteriorated.

The compact powder core 1 according to one embodiment of the present invention preferably has a rate of change R (unit:%) of the powder filling rate defined by the following formula (i)

R = (F ₁ / F ₀ -1) × 100 (i)

As described above, F ₀ is the powder filling rate (unit: volume%) of the compact before the heat treatment is performed, and F ₁ is the powder filling rate (unit: volume%) of the powder compact core 1 obtained by the heat treatment.

When the rate of change R of the powder filling rate is a positive value, that is, exceeding 0%, it means that the compact is compressed by the heat treatment, that is, reduced due to firing. This volume change may be caused by shrinkage of the volume when the pyrolysis residue 3 is generated from the binder. In this case, the filling ratio of the dust compact core 1 increases, which contributes to an improvement in magnetic properties (permeability). On the other hand, when the rate of change R of the powder filling rate is a negative value, that is, when the compact is expanded by the heat treatment, the pyrolysis residue 3 of the binder is mixed with the adjacent soft magnetic powder ( 2) is spaced apart from each other. In this case, there is a high possibility that the initial magnetic permeability is lowered and the core loss is increased or the magnetic characteristic of the compacted core 1 is lowered. When the change rate R of the powder filling rate is 0.5% or more, the possibility that the pyrolysis residue 3 of the binder is present at the position to separate the adjacent soft magnetic powder 2 in the compaction core 1 is reduced, Both of the mechanical properties and the magnetic properties (particularly, the initial permeability) of the magnetic recording medium 1 can be improved more stably. From the viewpoint of particularly improving both the mechanical properties and the magnetic properties of the compaction core 1, the rate of change R of the powder filling rate is preferably 1.0% or more. When the rate of change R of the powder filling rate is less than 0.5%, the insulating binder 3 or the pyrolysis residue 3 of the binder is hardly pyrolyzed, (2). Therefore, deterioration of the magnetic characteristic of the compacted core 1 in which the initial permeability is lowered and core loss is increased is likely to become present.

(3) Mechanical characteristics

(3-1) Pressing strength

The compacting core (1) according to one embodiment of the present invention has a pressing strength of 3.9 N / mm2 or more and 11 N / mm2 or less. The pressing strength can be measured by a test according to JIS Z2507: 2000 (corresponding to "Sintered Bearing - Pressure Test Method", ISO 2739: 1973).

When the compacting core 1 according to the embodiment of the present invention has a pressing strength of 3.9 N / mm 2 or more, there arises a problem that the compacting core 1 is cracked or broken at the time of manufacturing a component using the compacting core 1 The possibility can be reduced. When the compacting strength of the compacting core 1 is excessively low, there is a high possibility that the compacting core 1 is cracked or defected in the fitting step of the compacting core 1, the coil winding process, the barrel plating process, and the like. From the viewpoint of more stably reducing the possibility of these problems, the compression strength of the compacted core 1 is preferably 5 N / mm 2 or more, more preferably 6 N / mm 2 or more.

On the other hand, when the compacted core 1 according to the embodiment of the present invention has a pressing strength of 11 N / mm 2 or less, the initial permeability is lowered, and the magnetic properties of the core loss increases. When the compacting strength of the compacting core 1 is excessively high, the content of the pyrolysis residue 3 of the binder in the compacting core 1 tends to be high. Therefore, the powder filling rate of the powder compact core 1 is easily lowered, the initial magnetic permeability of the powder compact core 1 is lowered, and the soft magnetic powder 2 contained in the powder compact core 1 obtained by the heat treatment is deformed So that the core loss of the compaction core 1 is increased or the deterioration of the magnetic properties of the compaction core 1 is apt to become remarkable.

(3-2) Young's modulus

The compacted powder cores 1 according to one embodiment of the present invention preferably have a Young's modulus of 50 MPa or more. In the present specification, the Young's modulus means a value obtained from the slope of the initial straight portion in the stress-strain curve obtained at the time of the test for measuring the above-mentioned pressing strength.

The compact powder core 1 according to the embodiment of the present invention is likely to have a higher Young's modulus as the powder filling rate F ₁ is higher. The compact powder core 1 according to one embodiment of the present invention has a positive correlation with the powder filling rate F ₁ , Young's modulus and initial permeability as a basic tendency. Therefore, when the Young's modulus is high, the compacted cored core 1 having a high initial permeability tends to be obtained. In contrast, when the powder filling rate F ₁ of the compaction core ₁ is lowered, the Young's modulus of the compaction core 1 is easily lowered to less than 50 MPa. As a result, the initial magnetic permeability of the compaction core 1 is likely to decrease. The Young's modulus of the compacted core 1 is preferably 70 MPa or more from the viewpoints of more stably increasing the initial permeability of the compaction core 1 and further stably reducing the core loss of the compacted core 1, MPa or more. The upper limit of the Young's modulus of the dust compact core 1 is not particularly limited. The higher the Young's modulus of the compacting core 1 is, the less the problem caused by the deformation of the compacting core 1 when the compacting core 1 is used or when the compacting core 1 is used.

(4) Magnetic properties

The compact powder core 1 according to one embodiment of the present invention has excellent magnetic properties because the powder filling rate F ₁ is 75 volume% or more and the pressing strength is 3.9 N / mm 2 or more and 11 N / mm 2 or less as described above . Specifically, the initial permeability of the compaction core 1 tends to be high, and the core loss of the compaction core 1 tends to be low. The lower limit of the initial magnetic permeability of the compaction core 1 is not particularly limited and should be appropriately set in accordance with the use of the compaction core 1. For example, the initial permeability of the compaction core 1 is preferably 40 or more, more preferably 60 or more, as a value obtained by measurement under the condition of 100 kHz. The upper limit of the core loss of the compaction core 1 is not particularly limited and should be set appropriately according to the application of the compaction core 1. For example, the core loss of the compaction core 1 is preferably 600 W / cm 3 or less, more preferably 400 W / cm 3 or less, as a value obtained by measurement under the condition of a frequency of 100 kHz and a maximum magnetic flux density of 100 mT, Particularly preferably 300 W / cm < 3 > or less.

(5) Composition

(5-1) Soft magnetic powder

The composition of the soft magnetic powder (2) contained in the compacted powder (1) according to one embodiment of the present invention is not particularly limited as long as the soft magnetic powder (2) has a property as a soft magnetic material. Specific examples of the soft magnetic powder 2 include soft magnetic alloy powders such as Fe-based amorphous alloy powder, Fe-Ni-based alloy powder, Fe-Si-based alloy powder and pure iron powder (high purity iron powder), oxide soft magnetic powders such as ferrite And the like. The Fe-PCB-Si amorphous alloy, which is one kind of Fe-based amorphous alloy, is also called Fe-based metal glass alloy. A specific example of such an amorphous alloy is represented by Fe _100-abcxyzt Ni _a Sn _b Cr _c P _x C _y B _z Si _t where 0 at% ≤ a ≤ 10 at%, 0 at% ≤ b ≤ 3 at At% ≤ c ≤ 6 at%, 3.0 at% ≤ x ≤ 10.8 at%, 2.0 at% ≤ y ≤ 9.8 at%, 0 at% ≤ z ≤ 8.0 at%, 0 at% ≤ t ≤ 5.0 at %.

The average particle diameter of the soft magnetic powder 2 (particle diameter when the volume cumulative value of the soft magnetic powder particle size measured by the laser diffraction scattering method is 50%, D50) is not particularly limited. From the viewpoint of improving the handling property, it is preferable that the average particle diameter is in the range of about 3 탆 to about 100 탆.

(5-2) Insulating binder

The insulating binder which imparts the pyrolysis residue 3 of the binder can retain the soft magnetic powder 2 in the state of being contained in the molded body and the pyrolysis residue 3 of the binder derived from the insulating binder is contained in the compacted powder core 2, So long as it can retain the soft magnetic powder 2 in a state insulated from each other in the soft magnetic powder 1 without any particular limitation. Examples of the insulating binder include organic resins. Specific examples of organic resins include acrylic resins, silicone resins, epoxy resins, phenol resins, urea resins, and melamine resins. As another example of the insulating binder, inorganic materials such as water glass can be mentioned. The insulating binder may be composed of one kind of material or a plurality of materials. The insulating binder may be a mixture of an organic material and an inorganic material.

In the case where the insulating binder is composed of an organic resin, the glass transition temperature (Tg) of the resin or the glass transition temperature (Tg) of the cured product when the resin is a curable material (collectively referred to as " Glass transition temperature (Tg) of the ash ") is preferably from -30 占 폚 to 100 占 폚. When the glass transition temperature (Tg) of the insulating binder is excessively high, the insulating binder often tends not to shrink at the time of compression molding. When this tendency is observed, the mechanical properties and magnetic properties of the compacted powder core 1 obtained by heat-treating the compacted body are liable to be deteriorated. On the other hand, when the glass transition temperature (Tg) of the insulating binder is excessively low, the binder function of the binder resulting from the insulating binder tends to fail to exhibit the binding function of the thermal decomposition residue 3. When such a tendency is observed, the mechanical properties of the obtained molded article are likely to remarkably deteriorate. From the viewpoint of more stably improving the mechanical properties of the dust compact core 1, it is preferable that the insulating binder has a glass transition temperature (Tg) of -25 캜 to 60 캜.

In the case where the insulating binder is made of an organic resin, the core loss of the powder compact core 1 tends to exhibit a lower value as the insulating binder is thermally decomposed by thermal treatment applied to the molded body, . Specifically, when the insulating binder material causes a mass change of 30 mass% or more, it is preferable that the core loss tends to be 300 kW / m 3 or less. Further, with respect to the initial permeability, there is a tendency that the heat-resistant property of the insulating binder is lower, but the influence is not remarkably noticeable as much as the core loss.

The content of the pyrolysis residue 3 of the binder contained in the compacted powder 1 according to the embodiment of the present invention is not particularly limited as long as the component can appropriately fulfill desired functions (insulating function, holding function) . The content of the pyrolysis residue 3 of the binder is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.30% by mass or more from the viewpoint of achieving the above function more stably. The content of the pyrolysis residue 3 of the binder is preferably 2.0 mass% or less, more preferably 1.6 mass% or less, and more preferably 1.3 mass% or more, from the viewpoint of more stably obtaining the compaction core 1 having good magnetic properties Particularly preferred.

2. Manufacturing method of potato core

The production method of the compacted powder cores 1 according to the embodiment of the present invention is not particularly limited, but it is possible to manufacture the compacted cores 1 more efficiently by employing the production method described below.

A method for manufacturing a compacted powder (1) according to one embodiment of the present invention is a method for producing compacted powder (1), which comprises a compression molding process for obtaining a compact by compression molding of a granulated powder having soft magnetic powder (2) And a heat treatment step of obtaining a green compact 1 by heat treatment.

(1) Compression molding process

In the compression molding step, the granulated powder having the soft magnetic powder 2 and the insulating binder is filled in a mold, and the granulated powder in the mold is compression molded to obtain a molded body having the same shape as the powder compact core 1. Since the granules have excellent handling properties, the workability of the compression molding process can be improved.

(1-1) Assembly Part

The granulated powder contains the aforementioned soft magnetic powder (2) and the above-mentioned insulating binder. The content of the insulating binder in the assembly is not particularly limited. When such a content is excessively low, it is difficult for the insulating binder to retain the soft magnetic powder 2. In this case, it is difficult for the pyrolytic residue 3 of the binder material to insulate the plurality of soft magnetic powders 2 from each other in the compaction core 1 obtained through the heat treatment process. On the other hand, when the content of the insulating binder is excessively high, the content of the pyrolysis residue 3 of the binder contained in the compacted powder core 1 obtained through the heat treatment process tends to be high. When the content of the pyrolysis residue 3 of the binder in the green compact 1 is increased, the magnetic properties of the green compact 1 are likely to deteriorate. Therefore, it is preferable that the content of the insulating binder in the granulated powder is 0.5% by mass or more and 5.0% by mass or less with respect to the granulated powder. It is preferable that the content of the insulating binder in the granulated powder is 1.0 mass% or more and 2.5 mass% or less with respect to the granulated powder from the viewpoint of more stably reducing the possibility that the magnetic powder characteristic of the compacting core 1 is lowered , And more preferably not less than 1.2 mass% and not more than 2.0 mass%.

The granulated powder may contain a material other than the soft magnetic powder (2) and the insulating binder. Examples of such a material include a lubricant, a silane coupling agent, and an insulating filler. When a lubricant is contained, the kind thereof is not particularly limited. It may be an organic lubricant or an inorganic lubricant. Specific examples of the organic lubricant include metallic soaps such as zinc stearate and aluminum stearate. It is considered that such an organic lubricant is vaporized in the heat treatment step and hardly remains in the pressurized core 1.

The production method of the granules is not particularly limited. The slurry obtained by directly kneading the component imparting the granules and pulverizing the resulting granulation product by a known method may be used to obtain granules, and a dispersion medium (water, for example) may be added to the granules. , And the slurry is dried and pulverized to obtain granulated powder. After the pulverization, sieving or classification may be carried out to control the particle size distribution of the granules.

As an example of a method of obtaining granules from the slurry, a spray dryer is used. 4, the rotor 21 is formed in the spray dryer apparatus 20, and the slurry 19 is injected toward the rotor 21 from the upper part of the apparatus. The rotor 21 rotates in accordance with a predetermined number of rotations and atomizes the slurry 19 in the chamber inside the apparatus 20 as a droplet of water by centrifugal force. Further, hot air is introduced into the chamber inside the apparatus 20, whereby the dispersion medium (water) contained in the slurry 19 on the small water droplet is volatilized while maintaining a small droplet shape. As a result, the granules (22) are formed from the slurry (19). This assembly 22 is withdrawn from the lower part of the device 20. The rotational speed of the rotor 21, the temperature of hot air to be introduced into the spray drier 20, and the temperature of the lower portion of the chamber may be appropriately set. As a specific example of the setting range of these parameters, the number of rotations of the rotor 21 is 4000 to 6000 rpm, the temperature of hot air introduced into the spray drier 20 is 130 to 170 DEG C, and the temperature of the lower portion of the chamber is 80 to 90 DEG C . The atmosphere in the chamber and its pressure may be set appropriately. As an example, the inside of the chamber is made to be an air (air) atmosphere and the pressure is set to 2 mmH ₂ O (about 0.02 kPa). The particle size distribution of the obtained granules 22 may be further controlled by sieving or the like.

(1-2) Pressurizing conditions

The pressing conditions in the compression and pressurizing step are not particularly limited. The composition of the granules, the shape of the molded product, and the like. If the pressing force at the time of compression molding of the granular component is excessively low, the mechanical strength of the molded product is lowered. Thus, the handling property of the molded article is lowered, the pressing strength of the compacted powder core 1 obtained from the molded article is lowered, and the magnetic characteristic of the compacted powder core 1 is liable to be deteriorated. On the other hand, when the pressing force at the time of compression molding of the granulated powder is excessively high, it becomes difficult to manufacture a molding die capable of withstanding the pressure. From the viewpoint of more stably reducing the possibility that the compression pressurizing process adversely affects the mechanical characteristics and magnetic properties of the press compaction core 1 and facilitating mass production on an industrial scale, the pressing force at the time of compression- More preferably 0.3 GPa or more and 2 GPa or less, still more preferably 0.5 GPa or more and 2 GPa or less, and particularly preferably 1 GPa or more and 2 GPa or less.

In the compression and pressurization step, pressurization may be performed while heating, or pressurization may be performed at room temperature.

(2) Heat treatment process

In the heat treatment step, the molded body obtained by the above-mentioned compression-pressing step is heated to soften the deformation imparted to the soft magnetic powder (2) in the compression-pressurizing step to adjust the magnetic properties to obtain the compacted cores (1).

Since the heat treatment process is for the purpose of adjusting the magnetic properties of the powder compact core 1 as described above, the heat treatment conditions such as the heat treatment temperature are set so as to make the magnetic powder characteristic of the powder compact core 1 the best. As an example of the method of setting the heat treatment conditions, it is possible to change the heating temperature of the formed body and to keep the other conditions such as the heating rate and the holding time at the heating temperature constant.

The criteria for evaluating the magnetic properties of the dust compact core 1 when setting the heat treatment conditions are not particularly limited. As a specific example of the evaluation item, core loss of the press compaction core (1) can be mentioned. In this case, the heating temperature of the compact may be set so that the core loss of the compacting core 1 is the lowest. The measurement conditions of the core loss are appropriately set, for example, a condition that the frequency is 100 kHz and the maximum magnetic flux density is 100 mT.

In the present specification, the heating temperature at which the core loss of the compaction core 1 set by the above method is the lowest is referred to as " optimal heat treatment temperature ".

The atmosphere at the time of heat treatment is not particularly limited. In the case of an oxidizing atmosphere, thermal cracking of the insulating binder is likely to proceed excessively, and oxidation of the soft magnetic powder 2 is likely to proceed. Therefore, heat treatment is performed in an inert atmosphere such as nitrogen or argon or a reducing atmosphere such as hydrogen .

The embodiments described above are described for the purpose of facilitating understanding of the present invention and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents falling within the technical scope of the present invention.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

(Example 1)

(1) Preparation of Fe-based amorphous alloy powder

The amorphous soft magnetic powder was obtained by weighing the composition so that Fe _{74.43 at%} Cr _{1.96 at%} P _{9.04 at%} C _{2.16 at%} B _{7.54 at%} Si _{4.87 at%} using the water _atomization method as the soft magnetic powder . The particle size distribution of the obtained soft magnetic powder was measured by volume distribution using "Microtrack particle size distribution measuring apparatus MT3300EX" manufactured by Nikkiso Co., Ltd. As a result, the average particle diameter (D50) of 50% in the volume distribution was 10.6 mu m.

(2) Manufacture of granules

, 98.3 parts by mass of the soft magnetic powder, 1.4 parts by mass of an insulating binder composed of a silicone resin (glass transition temperature (Tg) of a cured product is -120 DEG C) and 0.3 parts by mass of a lubricant composed of zinc stearate as xylene To obtain a slurry.

The obtained slurry was pulverized after drying, and finely divided powders of 300 mu m or less and coarse powders of 850 mu m or more were removed using a sieve having a size of 300 mu m and a sieve of 850 mu m to obtain granulated powder.

(3) Compression molding

The obtained granulated powder was filled in a metal mold and pressure-molded at a surface pressure of 2 GPa to obtain a molded body having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 6.8 mm.

(4) Heat treatment

The obtained molded body was placed in a furnace in a nitrogen atmosphere and the furnace temperature was heated from room temperature (23 DEG C) to 480 DEG C as the optimum core heat treatment temperature at a heating rate of 40 DEG C / min. And then subjected to a heat treatment in which the furnace was cooled to room temperature to obtain a compacted core.

The optimum core heat treatment temperature in the heat treatment was determined as follows. Seven moldings prepared by the above-mentioned method were prepared, and heat treatment (holding time at a heating rate and a heating temperature was constant) in which the heating temperature was varied from 440 DEG C to 500 DEG C at intervals of 10 DEG C was applied to each formed article The core loss was measured under the conditions described below with respect to the compacted powder core subjected to the heat treatment at different heating temperatures obtained and the heating temperature of the heat treatment applied to the compacted core having the lowest measured value of the core loss was set at the optimum core heat treatment temperature Respectively.

(Examples 2 to 14)

The same operation as in Example 1 was carried out except that the following insulating binder was used in place of the insulating binder made of the silicone resin used in Example 1 to obtain a compact core. The optimum core heat treatment temperature of the heat treatment in each example is shown in Table 1.

Example 2: Acrylic resin, glass transition temperature (Tg): 95 占 폚

Example 3: Acrylic resin, glass transition temperature (Tg): -23 DEG C

Example 4: Acrylic resin, glass transition temperature (Tg): -6 ° C

Example 5: The glass transition temperature (Tg) of the acrylic resin and the cured product was -9 DEG C

Example 6: The glass transition temperature (Tg) of the epoxy resin and the cured product was 60 DEG C

Example 7: The glass transition temperature (Tg) of the epoxy resin and the cured product was 165 DEG C

Example 8: The glass transition temperature (Tg) of the modified silicone resin and the cured product was 55 DEG C

Example 9: The glass transition temperature (Tg) of the modified silicone resin and the cured product was 18 DEG C

Example 10: The glass transition temperature (Tg) of the acrylic resin and the cured product was -13 DEG C

Example 11: The glass transition temperature (Tg) of the acrylic resin and the cured product was 10 DEG C

Example 12: phenol resin, glass transition temperature (Tg): 99 DEG C

Example 13: The glass transition temperature (Tg) of the silicone resin and the cured product was 55 占 폚

Example 14: Silicone resin, glass transition temperature (Tg): 65 占 폚

(Examples 15 to 20)

The same operation as in Example 8 was carried out except that either the amount of the insulating binder to the soft magnetic powder and the pressing force in the compression molding were changed as shown in Table 2 in Example 8, .

(Test Example 1) Mass change of insulating binder

(TG-DTA, manufactured by Rigaku Corporation) was used, and the insulating binder used in each example was subjected to heat treatment under the same conditions as the thermal history in the heat treatment conducted in each of the Examples And the change in mass of the insulating binder (unit: mass%) was measured. The measurement results are shown in Table 1.

(Test Example 2) Measurement of powder filling rate, calculation of rate of change of powder filling rate

The rate of change R of the filling rate of the ring phase powder prepared in the examples was obtained by the following method.

First, the content C (unit: mass%) of the soft magnetic powder in the granulated powder was determined from the composition of the granular powder having the soft magnetic powder and the insulating binder, which were provided for compression molding. Next, the mass W ₀ (unit: g) of the molded article before the heat treatment was measured. From these values, the mass W _M (unit: g) of the soft magnetic powder contained in the molded article before the heat treatment was obtained.

W _M = W ₀ x C / 100

The volume V ₀ (unit: cm 3) of the outer appearance of the molded article before ring-shaped heat treatment was obtained.

V ₀ = {(outer diameter / 2) ² - (inner diameter / 2) ² } × π × height

Here, the outer diameter, the inner diameter, and the height are measured values (unit: cm) of the molded article before ring-shaped.

The powder filling rate F ₀ (unit: volume%) of the compact before the heat treatment was determined by the following equation using the density? Of the soft magnetic powder (specifically, 7.064 g / cm 3).

F ₀ = W _M / V ₀ / ρ × 100

Subsequently, the volume V ₁ (unit: cm 3) of the outer appearance of the compacted powder core obtained by the heat treatment was determined on the basis of the dimensional measurement in the same manner as in the case of V ₀ .

Using the obtained volume V ₁ , the powder filling rate F ₁ (unit: volume%) of the compaction core was obtained from the following equation.

F ₁ = W _M / V ₁ / ρ × 100

The rate of change R (unit:%) of the powder filling rate defined by the following formula was obtained from the powder filling rate F ₀ of the molded article before the heat treatment and the powder filling rate F ₁ of the powdered core.

R = (F ₁ / F ₀ -1) x 100

As described above, to represent a rate of change R of the powder filling factor F ₁ and a powder filling rate of the powder filling rate F ₀ and the compressed metal powder core of the molded article obtained are shown in Table 1 and Table 2.

(Test Example 3) Measurement of the pressing strength

The compact cores prepared in the examples were measured by the test method in accordance with JIS Z2507: 2000 to determine the pressing strength. Table 1 and Table 2 show the obtained pressing strengths.

In the examples, a molded article to be positioned as an intermediate product in the production of a press compaction core was separately prepared, and the pressing strength of the molded article was determined by the above-mentioned procedure. Table 1 and Table 2 show the obtained pressing strengths.

(Test Example 4) Measurement of Young's modulus

A stress strain curve for each of the press compaction core and the compact was measured. The Young's modulus of the compacted core and the Young's modulus of the compact were determined from the slope of the initial straight portion in these curves. The results are shown in Tables 1 and 2.

(Test Example 5) Rate of change of the cored core thickness

The thickness H ₀ (unit: cm) of the formed body manufactured in the example was measured before the heat treatment was performed, and the height H ₁ (unit: cm) of the compacted core obtained by the heat treatment was measured. And the change rate R _H (unit:%) of the core thickness was obtained.

R _H = (H ₁ / H ₀ -1) × 100

Table 1 and Table 2 show the rate of change R _H of the obtained compacted core thickness.

(Test Example 6) Content of pyrolysis residue of binder

The mass W ₁ (unit: g) of the compacted core obtained by the heat treatment was measured.

From the following equation, the content C _tr (unit: mass%) of the pyrolysis residue of the binder material for the soft magnetic powder contained in the compacted powder core after the heat treatment was obtained.

C _tr = (W ₁ / W _M -1) × 100

Further, W _M is the mass (unit: g) of the soft magnetic powder obtained in Test Example 2.

Table 1 and Table 2 show the content C _tr of the pyrolytic residue of the obtained binder.

(Test Example 7) Measurement of density

The apparent density (unit: g / cm 3) of the compact cored core was measured according to JIS Z2501: 2000 (ISO 2738: 1996). The obtained densities are shown in Tables 1 and 2.

(Test Example 8) Measurement of magnetic properties

The copper powder was wound on a compacted core having a ring-shaped shape prepared according to the example, and the initial permeability at a frequency of 100 kHz was measured using an impedance analyzer (" 4192A " Core loss was measured under the conditions of a frequency of 100 kHz and a maximum magnetic flux density of 100 mT using a " SY-8217 " manufactured by Iwasaki Communication Co., Ltd.). The results of these measurements are shown in Tables 1 and 2.

As shown in Tables 1 and 2, when the powder filling rate F ₁ of the compaction core is not less than 75% by volume and the pressing strength is not less than 3.9 N / mm 2 and not more than 11 N / mm 2, An excellent compaction core is easily obtained. A graph showing the relationship between the initial permeability and the powder filling rate F ₁ of the powder compact core is shown in Fig. A graph showing the relationship between the initial permeability and the pressing strength is shown in Fig. A graph showing the relationship between the core loss and the pressing strength is shown in Fig. It is also understood from Table 1 and Table 2 that the powder filling rate F ₁ of the compaction core is preferably 80% by volume or more from the viewpoint of more stably achieving excellent mechanical properties and magnetic properties.

Particularly, when the pressing strength is 6.2 N / mm 2 or more and 8.3 N / mm 2 or less (Examples 4, 8, 10, 11), a good compacting core having a core loss of 300 kW / m 3 or less and an initial permeability of 60 or more can be obtained. The powder filling rate F ₁ of the compaction core at this time is 80.8% or more and 81.4% or less. Referring to FIG. 5, when the powder filling rate F ₁ of the compaction core exceeds 80%, the powder filling rate F ₁ is high It can be seen that a high initial permeability is obtained in the compaction core. On the other hand, in Examples 1 and 2 where the pressing strength is lower than 3.9 N / mm 2, the core loss is low, but the initial permeability is as low as 25.2 to 51.8. When the pressing strength is low, the stress applied to the Fe-based amorphous alloy powder is small and the core loss is low. On the other hand, the powder filling rate F ₁ of the powder compact core can not be made sufficiently high.

From Table 1 and Figs. 6 and 7, it can be seen that in Examples 13 and 14 where the pressing strength is higher than 11 N / mm < 2 >, core loss is greatly deteriorated and initial permeability is lowered to less than 40. [ It is considered that the stress applied to the Fe-based amorphous alloy powder affects the compacted cores having a high pressing strength.

It can be seen from Table 2 that when the content of the insulating binder is increased, the pressing strength tends to increase but the initial permeability tends to decrease (Example 20). Further, when the pressure is low, the pressing force at the time of compression molding does not become high (Example 16), and the powder filling rate F ₁ of the powder compact core does not increase. As a result, the core loss becomes high and the initial permeability becomes low. On the other hand, in the case of Example 15 in which the insulating binder is 1 mass% or more and 2 mass% or less, the pressing force in compression molding is 2 GPa, and the core loss in the case of Example 19 is as low as 265 kW / m3 to 350 kW / And an initial permeability as high as 57.8 to 65.7 is obtained. This is because by making the content of the insulating binder as low as possible and increasing the pressing strength, the powder filling rate F ₁ of the compaction core is increased while the stress on the Fe-based amorphous alloy powder is appropriately suppressed, and the amount of pyrolysis residues of the binder The core loss can be reduced and the initial permeability can be improved at the same time.

8 is a graph showing the relationship between the initial permeability and the change rate R of the powder filling rate based on the results of this embodiment. In order to obtain a cored core having a high initial permeability, it is preferable that the rate of change R of the powder filling rate is 0.5 or more, more preferably 1 or more.

9 to 11 are graphs showing the relationship between core loss (FIG. 9), initial permeability (FIG. 10) and powder filling rate F ₁ (FIG. 11) based on the results of this embodiment and Young's modulus. From these figures, it is understood that the Young's modulus of the compacted core is preferably 70 MPa or more and more preferably 90 MPa or more in order to obtain a compacted powder core having a high initial permeability and a low core loss.

12 is a graph showing the relationship between the powder filling rate F ₀ of the molded article based on the results of this embodiment and the glass transition temperature (Tg) of the insulating binder. 12, the following matters are understood. That is, as the insulating binder has a low glass transition temperature (Tg), its flexibility is excellent, so that a molded article having a high density at the time of compression molding tends to be obtained. However, if the glass transition temperature (Tg) of the insulating binder is lower than -30 占 폚, the flexibility of the insulating binder tends to become excessively high. When the flexibility of the insulating binder is excessively high, the following phenomenon tends to occur.

- Expansion of the molded body based on springback after compression molding is made present and the density of the dust core is lowered.

The handling strength is deteriorated due to the low pressing strength and Young's modulus at the molding step.

Since it is preferable that these phenomena do not occur, it is preferable that the glass transition temperature (Tg) of the insulating binder is -30 캜 or higher.

13 is a graph showing the relationship between the core loss and the mass change rate upon heating of the insulating binder, based on the results of this embodiment. It can be understood from FIG. 13 that the core loss of the powder compacted core 1 tends to exhibit a lower value as the insulative binder is thermally decomposed by heat treatment applied to the molded body, thereby easily causing mass reduction, that is, the lower the heat resistance is. Specifically, when the insulating binder material causes a mass change of 30 mass% or more, it is preferable that the core loss tends to be 300 kW / m 3 or less. With respect to the initial permeability, it is advantageous that the heat-resistant property of the insulating binder is low, but the influence of heat resistance of the insulating binder is not as effective as in the case of core loss.

The compacting core of the present invention is preferably used as a booster circuit for a hybrid vehicle or the like, a reactor used for power generation, a substation facility, a transformer or a choke coil, or the like.

1: potato core
2: soft magnetic powder
3: Pyrolysis residue of binder
4:
10: Coil-enclosed plaster core
11:
12: Coil
19: Slurry
20: Spray dryer device
21: Rotor
22: Assembly section

Claims

A compacted particulate core obtained by compression molding a granulated powder having a soft magnetic powder and an insulating binder to obtain a molded body and heat-treating the obtained molded body,
Wherein the compacted core has a powder filling rate of 75% by volume or more,
And the pressing strength measured according to JIS Z2507: 2000 is 3.9 N / mm2 or more and 11 N / mm2 or less.

The method according to claim 1,
Wherein the soft magnetic powder contains an Fe-based amorphous alloy powder.

3. The method of claim 2,
The Fe-based amorphous alloy powder has a composition of Fe _100-abcxyzt Ni _a Sn _b Cr _c P _x C _y B _z Si _t where 0 at% ≤ a ≤ 10 at%, 0 at% ≤ b ≤ 3 at At% ≤ c ≤ 6 at%, 3.0 at% ≤ x ≤ 10.8 at%, 2.0 at% ≤ y ≤ 9.8 at%, 0 at% ≤ z ≤ 8.0 at%, 0 at% ≤ t ≤ 5.0 at %, Potato core.

4. The method according to any one of claims 1 to 3,
And the powder filling rate of the press compaction core is 80 vol% or more.

The method according to claim 1,
Young's modulus of 50 MPa or more.

The method according to claim 1,
Wherein the rate of change R of the powder filling rate defined by the following formula (i) is more than 0%.
R = (F ₁ / F ₀ -1) × 100 (i)
Here, F ₀ is the powder filling rate (unit: volume%) of the compact before the heat treatment, and F ₁ is the powder filling rate (unit: volume%) of the compact powder core obtained by the heat treatment.

The method according to claim 1,
Wherein the cured product of the insulating binder has a glass transition temperature of from -30 占 폚 to 100 占 폚.

The method according to claim 1,
Wherein the granulated powder is prepared as granulated powder obtained by binding a plurality of the soft magnetic powders by the insulating binder.

The method according to claim 1,
Wherein the heating temperature of the heat treatment is a temperature at which the core loss is lowest when measured at a frequency of 100 kHz and a maximum magnetic flux density of 100 mT for a compacted core obtained by the heat treatment.

The method according to claim 1,
Wherein the compaction core contains a pyrolysis residue of a binder which is a component derived from the insulating binder, and the content of the pyrolysis residue of the binder is 0.05 mass% or more.

A compression molding step of compression molding a granulated powder having soft magnetic powder and insulating binder to obtain a molded body, and
And a heat treatment step of heat treating the formed body obtained by the compression molding step to obtain a compaction core,
The pressing force of the compression molding performed in the compression molding step is set so that the powder filling rate of the compacting core obtained by the heat treatment step is 75 volume%
The heating temperature of the heat treatment performed in the heat treatment step is set so that the core loss measured at a frequency of 100 kHz and a maximum magnetic flux density of 100 mT is lowest for the compacted core obtained by the heat treatment step,
Wherein the compacted core obtained by the heat treatment step has a pressing strength measured according to JIS Z2507: 2000 of 3.9 N / mm < 2 > to 11 N / mm < 2 >.

12. The method of claim 11,
Wherein the pressing force of the compression molding is 0.3 GPa or more.