JP2009176974A - Injection molding soft-magnetic material, and soft-magnetic kneading material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding soft-magnetic material and a soft-magnetic kneading material which reduce magnetic core-losses. <P>SOLUTION: The injection molding soft-magnetic material contains a soft-magnetic powder and an organic high-molecule material. The powder of an Fe-radical soft-magnetic alloy containing Si: 7-9 mass% is used as the soft-magnetic powder. Also, the soft-magnetic kneading material contains a soft-magnetic material and the organic high-molecule material. The powder of the Fe-radical soft-magnetic alloy containing Si: 7-9 mass% is used as the soft-magnetic powder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection-molded soft magnetic material and a soft magnetic kneaded material. More specifically, the present invention relates to an injection-molded soft magnetic material suitable as a soft magnetic core, a soft magnetic material that can be suitably used for manufacturing an injection-molded soft magnetic material, and the like. It relates to a kneaded product.

  The soft magnetic material is a material having a purpose of obtaining a high magnetic flux density by obtaining a large magnetization from a small external magnetic field. Such soft magnetic materials are widely used, for example, in magnetic cores such as motors, generators, and transformers.

  As the soft magnetic core, for example, a soft magnetic alloy powder and an insulating binder (water glass, silicone resin, etc.) are mixed and press molded. A dust core obtained by removing accumulated distortion is known (Patent Document 1).

  In addition, it is also known that a soft magnetic core is manufactured by applying an injection molding method (Patent Document 2). Specifically, in Patent Document 2, a soft magnetic alloy powder and a molding resin are kneaded to bring the resin into a molten state, the molten kneaded product is injected into a mold, cooled, and a soft magnetic core is attached. The point to manufacture is described.

JP 2005-183442 A JP 2004-363384 A

  However, the soft magnetic material produced by injection molding has the following problems.

  That is, the soft magnetic material produced by the injection molding method has a drawback that the core loss is large. In order to overcome this drawback, it is conceivable to perform a heat treatment after injection molding as in the case of the dust core.

  However, the soft magnetic material by the injection molding method is formed using an organic polymer such as a resin. For this reason, if the heat treatment is performed at a high temperature, problems such as melting of the resin or the like and collapse of the shape occur. Therefore, it is difficult to perform heat treatment after injection molding.

  Therefore, attempts have been made to reduce the core loss by heat-treating the soft magnetic powder in advance before mixing with resin or the like to reduce distortion or coarsen the crystal grains.

  However, even if such a method is used, there is a limit in reducing the core loss of the soft magnetic material by the injection molding method.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection-molded soft magnetic material with reduced core loss. Another object of the present invention is to provide a soft magnetic kneaded material with reduced core loss.

  In order to solve the above problems, the present inventors have intensively studied, and as a result, strain is accumulated in the soft magnetic powder due to the stress acting at the time of kneading or injection of the material containing the soft magnetic powder, which causes an increase in core loss. It came to think that it might have become. Therefore, as a result of various experiments, it has been found that even when the injection molding method is applied, the core loss can be reduced by using a soft magnetic alloy powder having a specific component.

  The present invention has been made based on the above knowledge, and an injection-molded soft magnetic body according to the present invention is an injection-molded soft magnetic body containing a soft magnetic powder and an organic polymer, and the soft magnetic powder is The main point is that the Fe-based soft magnetic alloy powder contains Si: 7% to 9% by mass.

  Here, the Fe-based soft magnetic alloy preferably further contains Cr: 5% or less by mass.

  The soft magnetic kneaded material according to the present invention is a soft magnetic kneaded material containing a soft magnetic powder and an organic polymer, and the soft magnetic powder contains Fe: Si: 7% to 9% by mass. The gist is that it is a powder of a base soft magnetic alloy.

  Here, the Fe-based soft magnetic alloy preferably further contains Cr: 5% or less by mass.

  The conventional injection-molded soft magnetic material has strain accumulated in the soft magnetic powder due to the stress acting during kneading and injection even when using a soft magnetic powder that has been heat-treated in advance and has a relatively small strain. This leads to an increase in coercive force, resulting in an increase in hysteresis loss. As a result, it is presumed that a core loss, which is the sum of hysteresis loss and eddy current loss, has increased.

  On the other hand, the injection-molded soft magnetic body according to the present invention uses a Fe-based soft magnetic alloy powder of a specific component as the soft magnetic powder constituting the same. Therefore, even if injection molding is performed, an increase in the coercive force (Hc) of the powder is suppressed, and core loss can be reduced.

  At this time, when the Fe-based soft magnetic alloy further contains Cr: 5% or less by mass%, the core loss can be further reduced.

  The soft magnetic kneaded material according to the present invention uses Fe-based soft magnetic alloy powder as a specific component as the soft magnetic powder constituting the same. Therefore, an increase in coercive force (Hc) of the powder due to kneading is suppressed, and core loss can be reduced.

  Therefore, by applying this to, for example, injection molding, extrusion molding, press molding, etc., a soft magnetic material with reduced core loss can be obtained.

  At this time, when the Fe-based soft magnetic alloy further contains Cr: 5% or less by mass%, the core loss can be further reduced.

  Hereinafter, an injection-molded soft magnetic body (hereinafter sometimes referred to as “the present magnetic body”), a soft magnetic kneaded material (hereinafter sometimes referred to as “the present kneaded material”), and injection according to an embodiment of the present invention. A method for producing a molded soft magnetic material (hereinafter sometimes referred to as “the present production method”) will be described in detail.

1. This magnetic body This magnetic body is formed by injection molding. Examples of the use of the magnetic material include a magnetic core and a yoke.

  The shape of the magnetic body can be determined according to the application. For example, when this magnetic body is applied to uses such as a magnetic core, shapes such as a toroidal shape, an EI type, and a pot type can be exemplified.

  This magnetic body mainly contains soft magnetic powder and organic polymer. Here, in the present magnetic body, as the soft magnetic powder, Fe-based soft magnetic alloy powder containing Si: 7% to 9% by mass% is used.

  When the Si content is less than 7%, the increase in coercive force due to kneading or injection becomes large, and it becomes difficult to reduce the core loss.

  On the other hand, if the Si content exceeds 9%, the increase in coercive force due to kneading and injection is increased, and it is difficult to reduce the core loss.

  Further, the Fe-based soft magnetic alloy preferably contains Cr: 5% or less by mass%. In this case, the core loss can be further reduced. The Cr content is preferably 4.5% or less, more preferably 4% or less, and even more preferably 3.5% or less from the viewpoint of facilitating the reduction of core loss.

  The lower limit of the Cr content is not particularly limited, but is preferably 0.5% or more, more preferably 1.0% or more, from the viewpoint of sufficiently obtaining the effect. good.

  As described above, the Fe-based soft magnetic alloy contains Fe as a base, Si as an essential element, and Cr as an optional element. Examples of other elements that can be included include Mn and Ni. From the viewpoint of easily maintaining a low coercive force, these elements are preferably 1% or less by mass as a whole. .

  More preferably, the Fe-based soft magnetic alloy contains a predetermined amount of Si and the balance is Fe and an inevitable impurity, or contains the predetermined amounts of Si and Cr, and the balance is Fe and an inevitable impurity. It should be an alloy.

  In addition, this magnetic body may contain only the soft magnetic powder with the same chemical composition, and may contain two or more soft magnetic powders with different chemical compositions.

  The soft magnetic powder can be obtained by atomizing by water spray, gas spray, centrifugal spray, combinations thereof (for example, gas / water spray), cooling immediately after gas spray, jet mill, stamp mill, ball mill, etc. Powders obtained by mechanical pulverization or chemical reduction can be preferably used.

  The soft magnetic powder is preferably an atomized powder from the viewpoint of relatively small distortion, easily spherical and excellent in dispersibility, and no mechanical energy is required for pulverization. More preferably, it is a powder by a gas atomizing method from the viewpoint of small distortion and little oxidation.

  The particle size of the soft magnetic powder is, for example, in the range of 1 to 500 μm from the viewpoint of powder yield during atomization, kneading torque and seizure during kneading, fluidity during injection molding, frequency used in the magnetic core, and the like. Of these, preferably in the range of 5 to 250 μm, more preferably in the range of 10 to 150 μm.

  That is, as the powder has a smaller particle size, the effect of reducing the eddy current loss is greater, but the hysteresis loss tends to increase. Therefore, the upper and lower limits of the particle size of the powder, the distribution of the particle size, and the like may be determined from the balance between the yield (ie, cost) of the powder and the effect (ie, core loss), the frequency used, and the like.

  The soft magnetic powder may be heat-treated in order to remove strain and increase the size of crystal grains. Examples of the heat treatment conditions include a temperature of 700 ° C. to 1000 ° C., a time of 30 minutes to 10 hours, and the like in an atmosphere of one or both of hydrogen and argon.

  The soft magnetic powder may have its surface treated for the purpose of improving wettability with an organic polymer. Specific examples of the surface treatment include coupling treatment with various coupling agents such as silane coupling agents, titanate coupling agents, fatty acids, and fatty acid metal salts.

  In the coupling treatment, for example, soft magnetic powder, a coupling agent of about 0.3 to 0.8% by mass with respect to the soft magnetic powder, water, and alcohol are mixed, and this mixture is mixed with an appropriate amount. What is necessary is just to dry at temperature (for example, 100-140 degreeC) and suitable time (for example, 30 minutes-5 hours).

  The organic polymer contained in the magnetic body holds the soft magnetic powder and forms the shape of the molded body.

  Examples of the organic polymer include resins such as various thermoplastic resins and thermosetting resins, rubbers, elastomers, and the like. These may be contained alone or in combination of two or more. Preferably, a resin is suitably used from the viewpoints of heat resistance, mechanical strength, and the like.

  Specific examples of the resin include polyphenylene sulfide resin, polyamide resin (nylon resin, etc.), polyester resin, polyethylene resin, polypropylene resin, epoxy resin, and the like. Of these, polyphenylene sulfide resins, polyamide resins (such as nylon resins), and the like are preferable from the viewpoints of heat resistance, flame retardancy, insulating properties, moldability, mechanical strength, and the like.

  The ratio of the soft magnetic powder in the present magnetic body is preferably 30% by volume or more, more preferably 50% by volume or more, from the viewpoint of increasing the magnetic flux density or increasing the magnetic permeability.

  In addition to the soft magnetic powder and the organic polymer, the magnetic material may be added with various additives such as an antioxidant, an antioxidant, an ultraviolet absorber, a filler, a stabilizer, a reinforcing agent, and a colorant as necessary. One or more agents may be contained.

2. This kneaded material This kneaded material mainly contains soft magnetic powder and an organic polymer, and these are kneaded. The contents of the soft magnetic powder and the organic polymer, the ratio of the soft magnetic powder, the additives, and the like are the same as those described above in “1.

  Examples of the use of the kneaded product include various raw materials for molding such as injection molding, extrusion molding, and press molding. The use of the kneaded material is preferably a molding raw material from the viewpoints of low core loss and pre-kneading, so that the soft magnetic powder has good dispersibility and is advantageous for molding.

  The shape of this kneaded material can be determined according to a use etc. For example, when applied to the use of a forming raw material, shapes such as pellets, spheres, and ellipsoids can be exemplified.

  This kneaded product is prepared, for example, by blending soft magnetic powder, a powdery organic polymer, and various additives added as necessary at an appropriate ratio, and mixing this with a biaxial kneader. It can manufacture by passing through processes, such as kneading | mixing various compounds by making an organic polymer into a molten state using kneading machines.

3. This Manufacturing Method This manufacturing method includes at least a step of injecting a soft magnetic kneaded material containing soft magnetic powder and an organic polymer. This production method is a method capable of producing the above-described injection-molded soft magnetic material. Therefore, the soft magnetic powder, the content of the organic polymer, the ratio of the soft magnetic powder and the additives contained in the soft magnetic kneaded material to be injected conform to the contents described above in “1. Omitted.

  Here, in this production method, a kneaded material in which soft magnetic powder and an organic polymer are kneaded in advance, for example, the kneaded material described above, is supplied as a soft magnetic kneaded material to an injection molding apparatus, and this is plasticized. (Molded) and injected into the mold. In addition, the soft magnetic powder and the powdery organic polymer are supplied individually or in a mixed state to the injection molding device, and the organic polymer is melted in the device so that the soft magnetic powder and the organic polymer are in a molten state. It is also possible to produce a soft magnetic kneaded material by kneading the polymer and inject it into a mold.

  If the soft magnetic kneaded material is injected into the mold and then cooled for an appropriate time, an injection-molded soft magnetic body having a predetermined shape corresponding to the cavity shape of the mold can be obtained. The obtained injection-molded soft magnetic material may be subjected to processing such as machining as required.

  Hereinafter, the present invention will be described more specifically with reference to examples.

1. Preparation of a mixture of soft magnetic powder and resin First, a mixture of soft magnetic powder and resin was prepared by the following procedure.

  That is, various soft magnetic powders having the alloy compositions shown in Tables 1 to 3 were prepared by an atomizing method. At this time, the powders shown in Table 1 were sprayed with high-pressure argon gas, and fine powder droplets in a molten state were quickly cooled with water immediately after spraying to prepare powder. About what was shown in Table 2, the powder was produced by spraying with high-pressure argon gas. About what was shown in Table 3, the powder was produced by spraying with high pressure water. In addition, each obtained soft-magnetic powder was classified and used for 150 micrometers or less.

  Next, each of the classified soft magnetic powders in Table 1 is 3 hours at 950 ° C. in a hydrogen atmosphere for those in Table 1, and 3 hours at 750 ° C. in argon atmosphere for those in Table 2. The sample was heat-treated at 950 ° C. for 3 hours in a hydrogen atmosphere.

  Next, 0.5 mass% of the silane coupling agent with respect to the soft magnetic powder, pure water, and alcohol are added to the soft magnetic powder after the heat treatment, and the soft magnetic powder is dried at 120 ° C. for 3 hours. The surface was coupled.

  Next, the above-mentioned soft magnetic powder subjected to the coupling treatment and polyphenylene sulfide resin powder (average particle size: 20 μm) were mixed using a universal mixer (manufactured by Kodaira Seisakusho, “ACM-5LVT”). Thereby, a mixture of soft magnetic powder and polyphenylene sulfide resin powder was produced. The mixing ratio of the soft magnetic powder in the mixture was 55% by volume.

2. Next, a soft magnetic kneaded material was prepared according to the following procedure.

  That is, using a continuous twin-screw kneader (manufactured by Toshiba Machine Co., Ltd., “TEM37BS”), the resin in the mixture obtained above was heated to about 300 ° C. while being melted and soft magnetic powder. And a resin were kneaded, and then extruded from the nozzle of a kneader and cut into a size of about several millimeters by a cutting means to prepare a pellet-like soft magnetic kneaded product.

  In this example, from the viewpoint of uniform dispersibility and the like, a mixture of soft magnetic powder and resin was prepared in advance and kneaded to prepare a soft magnetic kneaded product. The method is not limited to this. For example, soft magnetic powder and resin can be directly kneaded to produce a soft magnetic kneaded product. As for the apparatus, for example, it may be kneaded batchwise with a heating kneader, and a pelletized soft magnetic kneaded material may be produced with a pelletizer.

3. Production of Injection Molded Soft Magnetic Material Next, an injection molded soft magnetic material was produced by the following procedure.

  That is, using a vertical in-line screw type injection molding machine, the pellet-like soft magnetic kneaded material obtained above is heated at about 300 ° C. to be in a molten state, which is injected into a mold and then cooled. As a result, a disk-shaped injection-molded soft magnetic material was produced.

4). Evaluation 4.1 Measurement of coercivity Hc meter (Tohoku Special Steel Co., Ltd., “K-HC1000”) for soft magnetic powder, soft magnetic powder after coupling treatment, soft magnetic kneaded material, and injection-molded soft magnetic material Was used to measure the coercive force.

  The coercive force was measured using a sample obtained by placing 100 mg of each powder in a plastic container and solidifying with paraffin for the soft magnetic powder. Moreover, about the soft magnetic kneaded material, 300 mg of the kneaded material was measured as it was. Moreover, about the injection-molded soft magnetic body, what was injection-molded into the shape of outer diameter φ17 mm × thickness 7 mm was measured as it was.

4.2 Measurement of Core Loss As shown in FIG. 1, a disk-shaped injection-molded soft magnetic body having an outer diameter of φ30 mm × thickness of 22 mm is machined into a ring shape having an outer diameter of φ28 mm × inner diameter of φ20 mm × thickness of 5 mm. A core loss measurement sample E was prepared by winding an enameled wire (150 turns) of φ0.65 mm as the primary winding M1 and an enameled wire (20 turns) of φ0.26 mm as the secondary winding M2. In FIG. 1, L is the magnetic path length (L = 75.4 mm), and S is the cross-sectional area (S = 20 mm ² ).

  And the core loss was measured about the core loss measurement sample S using AC BH analyzer (Iwasaki Tsushinki Co., Ltd. make, "SY-8232"). At this time, there were two measurement conditions: an excitation magnetic flux density of 0.1 Tesla and a frequency of 10 kHz, and an excitation magnetic flux density of 0.1 Tesla and a frequency of 100 kHz. The method of separating the hysteresis loss Ph and the eddy current loss Pe in the core loss Pc was as follows.

As shown in Equation (1) and Equation (2), the core loss Pc obtained at each frequency was divided by the frequency f [unit: kHz] to obtain the frequency dependency of Pc / f. A value obtained by extrapolating this Pc / f to 0 Hz (direct current) was defined as a hysteresis loss coefficient per cycle (Kh = Ph / f), and hysteresis loss Ph at each frequency was calculated therefrom. The eddy current loss Pe was calculated as the remainder obtained by subtracting Ph from Pc. In the equation, Ke (Pe = Ke · f ⁿ ) represents an eddy current loss coefficient.
Pc = Ph + Pe = Kh · f + Ke · f ⁿ : Formula (1)
Pc / f = Kh + Ke · f ⁿ⁻¹ : Formula (2)

  Various measurement results are shown in Tables 1 to 3 together with the alloy composition.

5. Results The following can be seen by comparing the Examples and Comparative Examples relative to each other. That is, first of all, it can be said in common to all of the examples and comparative examples that the soft magnetic powder after spray classification has its coercive force lowered by heat treatment, and the value of the coercive force does not change so much until the coupling treatment. However, the value of the coercive force is increased again through kneading and injection. This phenomenon in which the coercive force increases again is particularly remarkable in the comparative example.

  This is considered to be caused by the accumulation of strain in the soft magnetic powder due to the stress acting during kneading and injection.

  That is, from this, even if heat-treated soft magnetic powder with a small distortion is used, the coercive force rises due to the external force due to subsequent kneading and injection, and as a result, the core loss tends to increase. I understand that there is. This is supported by the core loss values measured for each injection-molded soft magnetic material.

  Conventionally, when a relatively high pressure (molding pressure of 1200 to 1800 MPa) is applied as in the case of a dust core, large distortion is accumulated. Therefore, when heat treatment (magnetic annealing) is not performed after molding, the core loss is large. Although it has been publicly known, it has been clarified by the present invention that the core loss is increased by an external force such as kneading or injection.

  Since the soft magnetic kneaded material and the injection-molded soft magnetic material use a resin, it is difficult to perform heat treatment after that to remove distortion and reduce core loss. In this regard, in this embodiment, this problem is solved by adjusting the alloy composition of the soft magnetic powder.

  That is, in the examples, since soft magnetic alloy powder having an alloy composition within a specific range specified in the present application is used, a comparative example using soft magnetic alloy powder having an alloy composition outside the above specific range. As compared with the above, it can be seen that the increase in coercive force due to kneading and injection is suppressed, and the core loss can be reduced.

  Further, as can be seen from Examples 2 and 3, when the soft magnetic alloy contains Cr, the effect of reducing the core loss is greater.

  Moreover, it turns out that Examples 1-4 of Table 1 using the powder water-cooled rapidly after gas spraying have the most favorable magnetic characteristics, and a core loss reduction effect is large.

  In addition, Examples 9 to 12 in Table 3 using water spray powder are Examples 1 to 4 in Table 1 using powder that is water-cooled immediately after gas spraying, and Examples 2 in Table 2 using gas spray powder. Compared with 5-6, the core loss is slightly larger, but this does not mean that the product is inferior. That is, the water spray powder has an advantage such as low cost, and can have a sufficient value as a product depending on required performance and price.

  As described above, the injection-molded soft magnetic material and the soft magnetic kneaded material according to the present invention have been described. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the gist of the present invention. Various modifications are possible.

It is the figure which showed typically the core loss measurement sample produced in the Example.

Claims (4)

An injection-molded soft magnetic material containing a soft magnetic powder and an organic polymer,
The soft magnetic powder is
An injection-molded soft magnetic material, characterized by being a powder of an Fe-based soft magnetic alloy containing Si: 7% to 9% by mass.   2. The injection-molded soft magnetic body according to claim 1, wherein the Fe-based soft magnetic alloy further contains Cr: 5% or less by mass%. A soft magnetic kneaded material containing a soft magnetic powder and an organic polymer,
The soft magnetic powder is
A soft magnetic kneaded product, which is a powder of an Fe-based soft magnetic alloy containing Si: 7% to 9% by mass%.   The soft magnetic kneaded product according to claim 3, wherein the Fe-based soft magnetic alloy further contains Cr: 5% or less by mass.

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