Iron-based soft magnetic composite powder for dust core and method for producing same

Abstract

Provided are: an iron-based soft magnetic composite powder for a dust core, which has an insulating layer and has high fluidity; and a method for easily producing the composite powder. The iron-based soft magnetic composite powder for a powder magnetic core contains coated particles in which an insulating layer is formed on the particle surface of iron-based soft magnetic particles, and the insulating layer has: a first coating layer that is arranged on the particle surface and is formed of aluminum triphosphate, and a second coating layer that is arranged on the particle surface and is formed of aluminum triphosphate; the second coating layer is disposed on the first coating layer and is formed of a silicone resin, and the coating rate of the insulating layer on the particle surface is 85% or more.

Description

Technical Field

[0001] The present disclosure relates to an iron-based soft magnetic composite powder for a compacted powder core and a method for manufacturing the same. Background Art

[0002] Cores used in power conversion devices such as motors and transformers have been made of laminated electromagnetic steel sheets. However, in recent years, the use of compacted powder cores has been increasing. A compacted powder core is produced by filling an iron-based soft magnetic powder into a metal mold and compression molding it. Therefore, the degree of freedom in the shape of the component is high, and a motor with a complex shape can be realized. In addition, since a compacted powder core can be formed by compression molding, a molded body close to the final component shape can be obtained, and the yield is improved.

[0003] In a compacted powder core, since each iron-based soft magnetic particle is insulated, eddy currents can be suppressed compared to laminated electromagnetic steel sheets, and high efficiency of a power conversion device can be achieved. To manufacture a compacted powder core, a powder of coated particles having an insulating film formed on the surface (iron-based soft magnetic composite powder) is required.

[0004] Now, in order to obtain the desired performance as a core, it is necessary to densify the compacted powder core. To densify the compacted powder core, it is desirable that the coated particles having an insulating film in the iron-based soft magnetic composite powder use a small amount of coating raw material for insulation and have an insulating film with a high coating rate.

[0005] In addition, in order to obtain appropriate moldability, it is desirable that the frictional resistance between the molded body and the metal mold when the compacted powder core is removed from the metal mold after compression molding is small. Therefore, in order to reduce the frictional resistance between the molded body and the metal mold, a lubricant is sometimes added to the iron-based soft magnetic composite powder. However, sometimes the fluidity of the iron-based soft magnetic composite powder added with the lubricant deteriorates. When the fluidity of the iron-based soft magnetic composite powder is poor, clogging sometimes occurs in the storage container of the iron-based soft magnetic composite powder, or uniform filling is hindered when the iron-based soft magnetic composite powder is filled into the molding metal mold. Therefore, it is desirable to ensure the fluidity of the iron-based soft magnetic composite powder added with the lubricant.

[0006] JP-A-2008-63651 (Patent Document 1) discloses an iron-based soft magnetic powder for a compacted magnetic core, a method for producing the same, and a compacted magnetic core. In the iron-based soft magnetic powder for a compacted magnetic core, a phosphoric acid-based chemical conversion film and a silicone resin film are successively formed on the surface. In the method for producing the iron-based soft magnetic powder for a compacted magnetic core, after mixing a phosphoric acid solution and the iron-based soft magnetic powder, the solvent is evaporated to form a phosphoric acid-based chemical conversion film on the surface of the iron-based soft magnetic powder. Further, in the method for producing the iron-based soft magnetic powder for a compacted magnetic core, a silicone resin is dissolved in an organic solvent, and after mixing the silicone resin solution and the iron-based soft magnetic powder, the solvent is evaporated to form a silicone resin film on the above-mentioned phosphoric acid-based chemical conversion film.

[0007] WO 2021 / 199525 (Patent Document 2) discloses an iron-based soft magnetic powder for a compacted magnetic core, a compacted magnetic core, and a method for producing the same. In the iron-based soft magnetic powder for a compacted magnetic core, a condensed aluminum phosphate layer is present on the surface of the iron-based soft magnetic powder, and a silicone resin layer is present on the surface of the condensed aluminum phosphate layer. The condensed aluminum phosphate layer is considered to be a continuous film. It should be noted that in the iron-based soft magnetic powder for a compacted magnetic core, the continuous film may be a complete coating or a partial coating, and the coated portions are continuous due to the powders fusing with each other, which is different from the state where the powders are discretely attached as they are. In the iron-based soft magnetic powder for a compacted magnetic core, it is preferable that most of the surface of the iron-based soft magnetic powder is covered with the continuous film, and it is more preferable that substantially the whole surface is covered. In the method for producing the iron-based soft magnetic powder for a compacted magnetic core, the iron-based soft magnetic powder and the condensed aluminum phosphate powder are heated and mixed, and after obtaining an iron-based soft magnetic powder having a condensed aluminum phosphate layer on the surface, a silicone resin is made to adhere to the surface of the condensed aluminum phosphate layer to form a silicone resin layer.

[0008] JP-T-2007-535134 (Patent Document 3) discloses a powder composition. The powder composition is composed of electrically insulated particles of a soft magnetic material of iron or an iron-based powder, and a lubricant selected from fatty acid amides having 14 to 22 carbon atoms in an amount of 0.1 to 2% by weight.

[0009] Japanese Patent Laid-Open No. 9-104901 (Patent Document 4) discloses an iron-based powder mixture for powder metallurgy and a method for manufacturing the same. The iron-based powder mixture for powder metallurgy includes an iron-based powder, a lubricant, and a powder for alloying. One or more selected from the iron-based powder, the lubricant, and the powder for alloying are preferably powders coated with a surface treatment agent, and the surface treatment agent is one or more selected from organic alkoxysilanes, organic silicon nitrides, silicone oils, titanate coupling agents, fluorine-based coupling agents, and mineral oils. Patent Document 4 discloses the following: Since the frictional resistance and adhesion between metal powders and organic compounds are large, the fluidity of metal powders mixed with organic compounds such as lubricants is extremely poor compared to metal powders not mixed with organic compounds such as lubricants.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent Laid-Open No. 2008-63651

[0013] Patent Document 2: International Publication No. 2021 / 199525

[0014] Patent Document 3: Japanese Patent Publication No. 2007-535134

[0015] Patent Document 4: Japanese Patent Laid-Open No. 9-104901 Summary of the Invention

[0016] In the method for manufacturing an iron-based soft magnetic powder for a compacted magnetic core disclosed in Patent Document 1, it is necessary to dry the solvent of the phosphoric acid solution after mixing the phosphoric acid solution with the iron-based soft magnetic powder. Therefore, iron-based powders with a large specific surface area may be easily oxidized. In addition, when evaporating the organic solvent after mixing the organosilicon resin solution with the iron-based soft magnetic powder, safety considerations for explosions and the like are required. In addition, powder aggregation is likely to occur in the film formation method using a solution, and sometimes the fluidity of the powder decreases.

[0017] In the method for manufacturing an iron-based soft magnetic powder for a compacted magnetic core disclosed in Patent Document 2, powders with a sufficiently high coating rate may sometimes not be obtained when the iron-based soft magnetic powder and the condensed aluminum phosphate powder are heated and mixed.

[0018] In the powder composition disclosed in Patent Document 3, a decrease in fluidity sometimes occurs due to the addition of a lubricant when the powder composition is stored in a stationary state.

[0019] Based on the above background, there is an expectation to provide an iron-based soft magnetic composite powder for a compacted magnetic core having an insulating layer and high fluidity, and a manufacturing method for easily manufacturing the same.

[0020] The present disclosure has been made in view of the above actual situation, and an object thereof is to provide an iron-based soft magnetic composite powder for a powder compact magnetic core having an insulating layer and high fluidity, and a manufacturing method for easily manufacturing the same.

[0021] The iron-based soft magnetic composite powder for a powder compact magnetic core according to the present disclosure for achieving the above object is as follows.

[0022] [1] An iron-based soft magnetic composite powder for a powder compact magnetic core,

[0023] including coated particles in which an insulating layer is formed on the particle surface of iron-based soft magnetic particles,

[0024] The above insulating layer has:

[0025] a first coating layer, which is disposed on the above particle surface and formed of aluminum tripolyphosphate; and

[0026] a second coating layer, which is disposed on the above first coating layer and formed of silicone resin;

[0027] The coating rate of the above insulating layer on the above particle surface is 85% or more.

[0028] The iron-based soft magnetic composite powder for a powder compact magnetic core according to the present disclosure may further be as follows.

[0029] [2] The iron-based soft magnetic composite powder for a powder compact magnetic core according to the above [1], wherein the above coating rate is a value calculated as follows,

[0030] when the energy spectrum area attributed to Fe measured for the above iron-based soft magnetic particles by low energy ion scattering spectroscopy is set as α and the energy spectrum area attributed to Fe measured for the above coated particles by low energy ion scattering spectroscopy is set as β, the value calculated by the following formula.

[0031] (1 - β / α) × 100 ··· (Formula 1)

[0032] [3] The iron-based soft magnetic composite powder for a powder compact magnetic core according to the above [1] or [2], wherein it contains 0.20% by mass to 0.60% by mass of an organic lubricant.

[0033] The iron-based soft magnetic composite powder for a powder compact magnetic core according to any one of the above [1] to [3] can be manufactured by the following manufacturing method.

[0034] [4] A manufacturing method for an iron-based soft magnetic composite powder for a powder compact magnetic core, in which silicone resin powder is added to and mixed with a powder composed of coated particles having only the above first coating layer formed thereon to form the above second coating layer.

[0035] [5]The manufacturing method of the iron-based soft magnetic composite powder for the compacted powder magnetic core according to [4] above, wherein the powder of the organic lubricant is mixed with the powder containing the coated particles described above.

[0036] According to the present disclosure, an iron-based soft magnetic composite powder for a compacted powder magnetic core having an insulating layer and high fluidity and a manufacturing method for easily manufacturing the composite powder can be provided. Detailed Description

[0037] Hereinafter, the iron-based soft magnetic composite powder for a compacted powder magnetic core and a manufacturing method thereof according to the present disclosure will be described.

[0038] First, an outline of the iron-based soft magnetic composite powder for a compacted powder magnetic core (hereinafter, simply referred to as the iron-based soft magnetic composite powder) according to the present embodiment will be described.

[0039] The iron-based soft magnetic composite powder according to the present embodiment includes coated particles having an insulating layer formed on the particle surface of the iron-based soft magnetic particles. The insulating layer has a first coating layer and a second coating layer. The first coating layer is disposed on the particle surface and formed of aluminum tripolyphosphate; the second coating layer is disposed on the first coating layer and formed of an organosilicon resin. Here, the coating rate of the insulating layer on the particle surface is 85% or more.

[0040] As an example, the iron-based soft magnetic composite powder according to the present embodiment is manufactured by a manufacturing method in which an organosilicon resin powder is added to and mixed with a powder composed of coated particles having only the first coating layer formed thereon to form the second coating layer.

[0041] The iron-based soft magnetic composite powder according to the present embodiment is a powder having an insulating layer and high fluidity. In addition, the iron-based soft magnetic composite powder according to the present embodiment can be easily manufactured, for example, by the above manufacturing method. For example, the iron-based soft magnetic composite powder according to the present embodiment does not use an organic solvent during its manufacturing process, and can be manufactured by an easy manufacturing method that does not include a process of drying an organic solvent.

[0042] Hereinafter, the iron-based soft magnetic composite powder and a manufacturing method thereof according to the present embodiment will be described in detail.

[0043] The iron-based soft magnetic composite powder according to this embodiment includes coated particles. Moreover, the above-mentioned coated particles refer to coated particles having an insulating layer formed on the particle surface of iron-based soft magnetic particles. The above-mentioned iron-based soft magnetic particles are the particles constituting the iron-based soft magnetic powder. In other words, the iron-based soft magnetic composite powder according to this embodiment includes coated particles having an insulating layer formed on the surface of the particles constituting the iron-based soft magnetic powder. Here, the iron-based powder refers to a metal powder containing 50% by mass or more of Fe. That is, the above-mentioned iron-based soft magnetic composite powder and the above-mentioned iron-based soft magnetic powder contain 50% by mass or more of Fe. Moreover, the composite powder refers to a powder containing composite particles. The composite particles refer to particles containing at least two kinds of materials. For example, since the above-mentioned coated particles have an insulating layer formed on the particle surface of the iron-based soft magnetic particles as core particles (nuclear particles), they are composite particles.

[0044] The iron-based soft magnetic composite powder according to this embodiment may contain any additives (for example, lubricants) other than the above-mentioned coated particles, may be composed of the above-mentioned coated particles and an organic lubricant, or may be composed only of the above-mentioned coated particles.

[0045] In the following description, the above-mentioned iron-based soft magnetic powder may sometimes be simply referred to as iron-based powder.

[0046] The above-mentioned iron-based soft magnetic powder is preferably iron powder. Iron powder refers to a powder composed of Fe and inevitable impurities, and is generally called pure iron powder in the technical field of the present invention.

[0047] The above-mentioned iron-based soft magnetic powder can be manufactured by any method. For example, the above-mentioned iron-based soft magnetic powder can be a reduced iron-based powder, an atomized iron-based powder, or a mixture thereof. The reduced iron-based powder is an iron-based powder manufactured by reducing iron oxide. The atomized iron-based powder is an iron-based powder manufactured by the atomization method. Examples of the atomized iron-based powder include water-atomized iron-based powder and gas-atomized iron-based powder. Here, the above-mentioned iron-based soft magnetic powder is preferably water-atomized iron-based powder. Since the water-atomized iron-based powder has multiple irregularities on the particle surface, particle entanglement is likely to occur. In the case of forming a powder compact magnetic core, the strength of the powder compact magnetic core can sometimes be improved. In addition, the above-mentioned iron-based soft magnetic powder preferably has good compressibility. If the compressibility is good, the formability during compression molding of the powder compact magnetic core is improved.

[0048] The apparent density of the above-mentioned iron-based soft magnetic powder is preferably 2.8 Mg / m 3 or more. If the apparent density is less than 2.8 Mg / m 3 , the density of the powder compact magnetic core may sometimes decrease.

[0049] In terms of the median particle size based on volume (50% particle size, so-called D 50)When evaluating, the particle size of the above-mentioned iron-based soft magnetic powder is preferably 40 μm or more. In the following description, when only the particle size is mentioned, it means the median particle size. If the particle size is less than 40 μm, the fluidity of the iron-based soft magnetic powder may sometimes decrease. In addition, the fillability of the iron-based soft magnetic composite powder into the mold may sometimes decrease, and the formability may also deteriorate when the powder compact core is compression molded. Therefore, from the viewpoint of further improving fluidity, the particle size is preferably 40 μm or more. On the other hand, if the particle size exceeds 400 μm, the fluidity of the iron-based soft magnetic powder may sometimes decrease. In addition, the fillability of the iron-based soft magnetic composite powder into the mold may sometimes decrease, and the formability may also deteriorate when the powder compact core is compression molded. Therefore, from the viewpoint of further improving fluidity, the particle size is preferably 400 μm or less. It should be noted that the particle size can be measured by the median value measured by a particle size distribution measuring device using the laser diffraction method. For example, as the particle size distribution measuring device, Partica LA-960V2 manufactured by Horiba, Ltd. can be used.

[0050] The coated particles according to this embodiment have an insulating layer formed on the particle surface of the above-mentioned iron-based soft magnetic particles. The above-mentioned insulating layer has a first coating layer and a second coating layer.

[0051] The above-mentioned first coating layer is disposed on the particle surface and is formed of aluminum tripolyphosphate. Here, the first coating layer is a layer having insulating properties.

[0052] The above-mentioned aluminum tripolyphosphate is a raw material for forming a first coating layer having insulating properties on the surface of the iron-based soft magnetic particles. Aluminum tripolyphosphate has good reactivity with iron, and a first coating layer with high adhesion and adherence to the surface of the iron-based soft magnetic particles and having insulating properties is formed through aluminum tripolyphosphate powder. As the above-mentioned aluminum tripolyphosphate, for example, aluminum dihydrogen tripolyphosphate can be cited. In addition, as the above-mentioned aluminum tripolyphosphate, any hydrated state of aluminum tripolyphosphate such as dihydrate can be used.

[0053] As the above-mentioned aluminum tripolyphosphate, for example, aluminum tripolyphosphate in powder form is preferably used. An example of a preferred aluminum tripolyphosphate powder is K-FRESH#100P manufactured by TAYCA Corporation. The particle size (median particle size) of the aluminum tripolyphosphate powder is preferably 10 μm or less, more preferably 5 μm or less. The smaller the particle size of the aluminum tripolyphosphate powder becomes, the larger the specific surface area of the powder becomes, and thus the coating rate is increased. The lower limit of the above-mentioned particle size is not limited, and for example, it can be 0.1 μm.

[0054] The addition amount of the above-mentioned aluminum tripolyphosphate is preferably 0.10% by mass or more, more preferably 0.15% by mass or more, relative to the above-mentioned iron-based soft magnetic powder. In addition, the addition amount is preferably 0.50% by mass or less, more preferably 0.30% by mass or less.

[0055] Next, a method for forming a first coating layer on the surface of the above-described iron-based soft magnetic particles will be described. For example, by adding aluminum tripolyphosphate to the iron-based soft magnetic powder and mixing, a first coating layer is formed on the particle surface of the iron-based soft magnetic particles, and a powder composed of coated particles having only the first coating layer formed thereon can be obtained. The addition amount of aluminum tripolyphosphate can be as described above. The formation of the first coating layer can be carried out by a dry method without using water or an organic solvent. Therefore, the formation of the first coating layer can be easily carried out without the need for a solvent drying operation.

[0056] The mixing for forming the first coating layer can use a mixing device commonly used for stirring and mixing powders. An example of a preferred mixing device is a stirring blade type mixer provided with stirring blades rotating along a horizontal plane at the bottom of a mixing container. An example of a preferred stirring blade type mixer is the FM mixer series manufactured by Nippon Coke Industry Co., Ltd. and the high-speed mixer series manufactured by Earth Technica Co., Ltd.

[0057] In order to improve the adhesion between aluminum tripolyphosphate and the iron-based soft magnetic particles, the above mixing is preferably heat mixing. The maximum temperature reached by the powder in the stirring and mixing for forming the first coating layer is preferably 130 °C or higher, more preferably 150 °C or higher. By setting the maximum temperature reached by the mixing temperature to 130 °C or higher, the adhesion between the first coating layer and the iron-based soft magnetic particles is improved. Moreover, the higher the temperature of the powder, the easier it is for aluminum tripolyphosphate to form the first coating layer. On the other hand, if the mixing temperature exceeds 200 °C, the oxidation of the iron-based soft magnetic composite powder proceeds, resulting in a decrease in the density of the compacted magnetic core. Therefore, the above maximum temperature reached is preferably 200 °C or lower. It should be noted that the temperature of the powder in the stirring and mixing is, for example, the temperature measured by a thermocouple inserted into the trough of the mixing container of the mixing device. When the temperature of the powder in the stirring and mixing is measured in this way using a thermocouple, the thermocouple is set at a position buried in the powder layer (layer of powder) that is stationary in the trough of the mixing container in a state where the mixing device is stationary.

[0058] After forming the first coating layer, the powder composed of coated particles having only the first coating layer formed thereon can be cooled. The above cooling preferably sets the temperature to 80 °C or lower. Thereby, the subsequent iron-based soft magnetic composite powder becomes easier to handle. Hereinafter, the process of cooling the powder composed of coated particles after forming the first coating layer will be referred to as a cooling process. The cooling process is preferably carried out in a state where the coated particles are stirred and mixed.

[0059] The trough of the mixing container can be filled with an inert gas such as nitrogen. Thereby, oxidation of the iron-based soft magnetic powder during stirring and mixing can be prevented.

[0060] Next, a description will be given of the second coating layer according to an embodiment of the present invention. The second coating layer is a layer that forms an insulating layer together with the first coating layer. The second coating layer is formed on the first coating layer and is made of a silicone resin.

[0061] The above silicone resin has poor wettability with the particle surface of the iron-based soft magnetic powder and poor adhesion and attachment to the iron-based soft magnetic powder compared with aluminum tripolyphosphate, but has excellent heat resistance. Further, as will be described later, it has the characteristic of being able to coat the iron-based soft magnetic powder by softening caused by heating, and thus is suitable as a material for the insulating layer used together with aluminum tripolyphosphate.

[0062] The above silicone resin is not particularly limited, but a silicone resin having a methyl-based side chain is preferred. As the above silicone resin, a powdery silicone resin can be used, that is, a silicone resin powder can be used. An example of a preferred silicone resin powder is SILRES MK POWDER manufactured by Wacker Asahikasei Silicone Corporation or KR-220LP manufactured by Shin-Etsu Chemical Co., Ltd.

[0063] The addition amount of the above silicone resin is preferably 0.10% by mass or more with respect to the above iron-based soft magnetic powder. If it is less than 0.10% by mass, it may be difficult to exhibit the effect of improving the flexibility of the insulating layer due to the addition of the silicone resin. Further, the addition amount is preferably 1.50% by mass or less with respect to the iron-based soft magnetic powder. Moreover, by adjusting the addition amount of the silicone resin, the physical properties (for example, resistivity) of the insulating property of the iron-based soft magnetic composite powder can be controlled. As a specific example, the addition amount can be relatively reduced, for example, it can be 0.50% by mass or less, particularly 0.30% by mass or less. In this case, the resistivity of the iron-based soft magnetic composite powder is sometimes adjusted to an appropriate value (as an example, the resistivity is 100 μΩm to 2000 μΩm), and an iron-based soft magnetic composite powder particularly suitable as a magnetic core for a motor can be provided. Further, the addition amount of the silicone resin can be made relatively large, for example, it can exceed 0.50% by mass. In this case, when the resistivity of the iron-based soft magnetic composite powder is adjusted to a value larger than the value suitable for use as a magnetic core for a motor (as an example, the resistivity exceeds 2000 μΩm), an iron-based soft magnetic composite powder particularly suitable as a magnetic core for a reactor or an inverter can be provided.

[0064] It should be noted that the total amount of the coating materials used to form the insulating layer, that is, the above-mentioned aluminum tripolyphosphate and the above-mentioned silicone resin, is preferably 2.00% by mass or less, more preferably 0.60% by mass or less, and further preferably 0.50% by mass or less, relative to the iron-based soft magnetic powder. The lower limit of the total amount of the above-mentioned addition amount is not particularly limited, but it is preferably 0.20% by mass or more relative to the iron-based soft magnetic powder.

[0065] It should be noted that, as described above, the wettability between the silicone resin and the surface of the iron-based soft magnetic particles is poor. Therefore, when attempting to form a coating layer only from the softened silicone resin, the coating rate tends to be low. In contrast, as described above, aluminum tripolyphosphate has good adhesion to the surface of the iron-based soft magnetic particles, and an insulating layer can be easily formed on the particle surface by mixing with the iron-based soft magnetic powder. However, in order to achieve a high coating rate, a large amount of aluminum tripolyphosphate needs to be added. Therefore, when using these coating materials for insulation alone, it is difficult to achieve a high coating rate, or even if a high coating rate is achieved, a large amount will be added and appropriate properties as a powder compact magnetic core cannot be obtained. However, by forming an insulating layer by making a composite film containing a silicone resin and aluminum tripolyphosphate, an insulating layer with a high coating rate (85% or more) can be formed even when a small amount of the coating material is added. Such a high coating rate is achieved by significantly improving the wettability between the softened silicone resin and the particle surface by forming an aluminum tripolyphosphate layer on the particle surface.

[0066] Hereinafter, a method for forming a second coating layer on the particle surface of the powder composed of the coated particles having only the above-mentioned first coating layer formed thereon will be described. For example, by adding a silicone resin powder to the powder composed of the coated particles having only the first coating layer formed thereon and mixing, a second coating layer formed of the silicone resin can be formed on the first coating layer. The addition amount of the silicone resin can be as described above. By including the second coating layer formed of the silicone resin in the insulating layer, the softness of the insulating layer can be improved and the damage of the insulating layer during compression molding can be suppressed.

[0067] The formation of the second coating layer can be carried out by a dry method without using water or an organic solvent. Therefore, the drying operation of the solvent can be omitted when forming the second coating layer, and it can be easily carried out.

[0068] The mixing for forming the second coating layer can use a mixing device generally used for stirring and mixing powders. An example of a preferred mixing device is the same as the preferred device when forming the first coating layer.

[0069] The temperature of the powder in the stirring and mixing for forming the second coating layer is preferably 100°C or higher. If the temperature of the powder in the stirring and mixing is lower than 100°C, the silicone resin cannot be sufficiently softened, and sometimes the adhesion of the second coating layer or the coating rate may decrease. The upper limit of the above temperature is not particularly limited, but it is preferably 200°C or lower.

[0070] The mixing for forming the second coating layer is preferably carried out in the cooling process after the heating and mixing for forming the first coating layer. That is, it is preferable to stir and mix the powder composed of the coated particles having only the first coating layer formed thereon in the above cooling process and add the silicone resin powder to the powder. Thus, by utilizing the heat storage of the powder layer of the coated particles immediately after the first coating layer is formed, the manufacturing cost can be suppressed and the second coating layer with good adhesion can be efficiently formed. Specifically, compared with the case where the powder is fully cooled after the first coating layer is formed and then reheated to form the second coating layer, the effort and time for reheating can be omitted, and at the same time, the temperature of the powder required for forming the second coating layer can be ensured.

[0071] In summary, a preferred manufacturing method of the iron-based soft magnetic composite powder according to an embodiment of the present disclosure is a method of adding aluminum tripolyphosphate to the iron-based soft magnetic powder and mixing, and further adding the silicone resin powder and mixing. By adding aluminum tripolyphosphate to the iron-based soft magnetic powder and mixing, a powder composed of only the coated particles having the first coating layer formed thereon can be manufactured. Furthermore, by adding the silicone resin powder to the powder and mixing, an iron-based soft magnetic composite powder containing the coated particles having an insulating layer formed with the first coating layer and the second coating layer can be manufactured. Here, the above iron-based soft magnetic composite powder may be an iron-based soft magnetic composite powder composed of the coated particles having an insulating layer formed with the first coating layer and the second coating layer.

[0072] That is to say, the above manufacturing method is as follows: adding aluminum tripolyphosphate to the iron-based soft magnetic powder and mixing to make a powder composed of only the coated particles having the first coating layer formed thereon, and further adding the silicone resin powder to the powder and mixing to make an iron-based soft magnetic composite powder containing the coated particles having an insulating layer formed with the first coating layer and the second coating layer.

[0073] Moreover, the above manufacturing method may also be as follows: adding aluminum tripolyphosphate to the iron-based soft magnetic powder and mixing to make a powder composed of only the coated particles having the first coating layer formed thereon, and further adding the silicone resin powder to the powder and mixing to make an iron-based soft magnetic composite powder composed of the coated particles having an insulating layer formed with the first coating layer and the second coating layer.

[0074] Similarly, a preferred manufacturing method of the above-mentioned iron-based soft magnetic composite powder is as follows: adding silicone resin powder to a powder composed of coated particles forming only the first coating layer and mixing them to produce an iron-based soft magnetic composite powder containing coated particles having an insulating layer formed with the first coating layer and the second coating layer.

[0075] Moreover, the above manufacturing method can be as follows: adding silicone resin powder to a powder composed of coated particles forming only the first coating layer and mixing them to produce an iron-based soft magnetic composite powder composed of coated particles having an insulating layer, and the insulating layer has the first coating layer and the second coating layer.

[0076] In this way, it is possible to manufacture an iron-based soft magnetic composite powder containing coated particles having an insulating layer formed on the particle surface of iron-based soft magnetic particles.

[0077] Next, the coating rate (hereinafter, simply referred to as the coating rate) of the insulating layer on the particle surface of the iron-based soft magnetic particles will be described.

[0078] The above coating rate is set to 85% or more, preferably 90% or more. If the coating rate is less than 85%, the regions where the insulating layer is missing on the surface of the coated particles come into contact with each other, and the insulation of the compacted powder core is significantly reduced. In addition, the regions where the insulating layer is missing on the surface of the coated particles are likely to become the starting points of the destruction of the compacted powder core. From the viewpoint of maintaining mechanical strength, it is also set to 85% or more. The upper limit of the coating rate is not particularly limited and can be 100%.

[0079] In one embodiment of the present invention, the above coating rate is preferably the value calculated using the above formula 1 [(1 - β / α) × 100]. Here, the energy spectrum area attributed to Fe measured for the iron-based soft magnetic particles using the low-energy ion scattering spectrometry is set to α, and the energy spectrum area attributed to Fe measured for the coated particles using the low-energy ion scattering spectrometry is set to β. When measuring α, iron-based soft magnetic powder can be used as the iron-based soft magnetic particles. Moreover, the iron-based soft magnetic powder can be either the iron-based soft magnetic powder as the raw material of the iron-based soft magnetic composite powder or the powder obtained by removing the insulating layer from the iron-based soft magnetic composite powder. In addition, when measuring β, the iron-based soft magnetic composite powder can be used as the coated particles. That is, the above coating rate can be calculated by measuring the energy spectrum area attributed to Fe for the powder before and after forming the insulating layer and using the area ratio β / α.

[0080] Since the low-energy ion scattering spectrometry has extremely high surface sensitivity and is affected by the outermost layer of atoms, it is possible to correctly analyze the presence or absence of coating. That is to say, if the above formula 1 is used, the coating rate can be correctly obtained.

[0081] The coating rate calculated using the above formula (1) is preferably 85% or more, more preferably 90% or more. The upper limit of the above coating rate is not particularly limited and may be 100%.

[0082] Next, the lubricant will be described. The above iron-based soft magnetic composite powder may not contain a lubricant or may contain it at 0 mass%. However, it is preferable that the iron-based soft magnetic composite powder according to an embodiment of the present invention contains a lubricant. Thereby, the friction between the iron-based soft magnetic composite particles can be reduced, and the damage to the insulating layer during compression molding can be suppressed. Especially in the case of compression molding under high pressure, if a lubricant is added to the iron-based soft magnetic composite powder in advance, the suppression effect of the damage to the insulating layer during compression molding is sometimes improved. From such a viewpoint, it is preferable to contain 0.20 mass% or more of the lubricant. However, if the lubricant is excessively mixed, the fluidity sometimes decreases. Therefore, the above iron-based soft magnetic composite powder preferably contains 0.60 mass% or less of the lubricant. Here, the content of the above lubricant is expressed as the ratio of the mass of the lubricant to the total mass of the iron-based soft magnetic composite powder excluding the lubricant.

[0083] The upper limit of the ratio of the above coated particles to the above iron-based soft magnetic composite powder is not particularly limited and may be 100 mass%, but from the viewpoint of reducing friction by containing a lubricant, it is preferably 99.80 mass% or less. In addition, the lower limit of the above ratio is not particularly limited, but it is preferably 90.00 mass% or more, and more preferably 99.40 mass% or more from the viewpoint of improving fluidity.

[0084] As the above lubricant, for example, an organic lubricant can be used. As the above organic lubricant, waxes and metal soaps can be cited. As the above waxes, stearic acid amide, erucic acid amide, N,N'-ethylene bisstearic acid amide, etc. can be cited. As the above metal soaps, lithium stearate, zinc stearate, etc. can be cited. In addition, a lubricant obtained by mixing multiple organic lubricants can also be used as the above organic lubricant, and a lubricant obtained by mixing multiple organic lubricants in a molten state can also be used as the above organic lubricant. The form of the above lubricant is not particularly limited, and a powder can be used.

[0085] In the manufacturing method of the iron-based soft magnetic composite powder according to an embodiment of the present invention, it is preferable to mix a powder containing an organic lubricant with a powder containing coated particles. In other words, a preferable manufacturing method of the iron-based soft magnetic composite powder according to an embodiment of the present invention is a method of mixing a powder containing coated particles formed with a first coating layer and a second coating layer with a powder containing an organic lubricant.

[0086] Next, the compression molding of the above-mentioned iron-based soft magnetic composite powder will be described. After the above-mentioned iron-based soft magnetic composite powder is filled into a metal mold, it is compression molded (pressure molded) into a desired size and shape to form a molded body (compact) of a specified shape. As a compression molding method for manufacturing a molded body by compression molding the iron-based soft magnetic composite powder, for example, ordinary molding methods such as a normal temperature molding method and a metal mold lubrication molding method can be used.

[0087] In the compression molding of the above-mentioned iron-based soft magnetic composite powder, the lower limit of the molding pressure is not particularly limited, and it can be set to any molding pressure as long as it can impart the required strength to the molded body. However, the above-mentioned molding pressure can be set to 980 MPa or more. Since an increase in the molding pressure increases the powder compacting density, thereby, the strength of the molded body is sometimes improved.

[0088] In the compression molding of the above-mentioned iron-based soft magnetic composite powder, a lubricant can be applied to the wall surface of the metal mold as needed, or a lubricant can be added to the iron-based soft magnetic composite powder in advance as described above. By applying or adding a lubricant, the moldability during compression molding can be improved. That is, during compression molding, the friction between the metal mold and the iron-based soft magnetic composite powder can be reduced. In addition, a decrease in the density of the molded body during compression molding can be suppressed. In addition, after compression molding, the friction when removing the molded body from the metal mold can be reduced. In addition, thereby, cracking of the molded body during molding or when removing the molded body from the metal mold can be suppressed.

[0089] Examples

[0090] Hereinafter, the manufacturing method and the iron-based soft magnetic composite powder according to the present disclosure will be described based on examples. It should be noted that the present embodiment is not limited to the examples.

[0091] (Example 1)

[0092] First, Example 1 will be described.

[0093] Water atomized iron powder (JIP 304AS manufactured by JFE Steel Corporation) with an apparent density of 3.0 Mg / m 3 and a median particle size of 100 μm was used as the iron-based soft magnetic powder. In addition, aluminum tripolyphosphate powder (K-FRESH #100P manufactured by TAYCA Corporation, aluminum dihydrogen tripolyphosphate dihydrate powder) with a median particle size of about 5 μm was used as the aluminum tripolyphosphate. In addition, silicone resin powder (KR-220LP manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicone resin. An EarthTechnica Corporation-made high-speed mixer LFS-GS2J type was used as the mixing device.

[0094] First, an iron-based soft magnetic powder as a raw material powder and an aluminum tripolyphosphate powder are stirred and mixed to obtain a powder of coated particles having a first coating layer. The details are as follows. As shown in Table 1, the addition amount of the aluminum tripolyphosphate powder is 0.2% by mass. The stirring and mixing of the raw material powder is carried out using the above mixing device with the rotation speed of the stirring blade set to 500 rpm (revolutions / min). Then, the raw material powder is stirred and mixed for 20 minutes to obtain a powder of coated particles having a first coating layer. It should be noted that the input amount of the raw material powder into the mixing device is set to 1.5 kg. It should be noted that the addition amount of the aluminum tripolyphosphate shown in Table 1 is the ratio with respect to the mass of the iron-based soft magnetic powder. The stirring and mixing is carried out while heating the mixing container. The maximum temperature reached by the powder during the stirring and mixing is controlled to 170°C. Nitrogen is supplied into the tank of the mixing container during the mixing, and the tank of the mixing container is in a state filled with nitrogen.

[0095]

[0096] Furthermore, a silicone resin powder is added to the powder in the tank of the mixing container at the addition amount (0.2% by mass) shown in Table 1 and stirred and mixed to obtain a powder of coated particles having a second coating layer. Here, the addition amount of the silicone resin powder shown in Table 1 is the ratio with respect to the mass of the iron-based soft magnetic powder. It should be noted that the addition and stirring and mixing of the silicone resin powder are carried out in the cooling process after the above 20-minute stirring and mixing (the rotation speed of the stirring blade is 500 rpm). The addition of the silicone resin powder to the powder in the tank is carried out when the temperature of the powder in the mixing device drops to 150°C. After adding the silicone resin powder, the mixing is continued until the temperature of the powder in the mixing device is cooled to 60°C to obtain a powder (iron-based soft magnetic composite powder for powder cores) containing coated particles having a first coating layer and a second coating layer.

[0097] After the temperature of the powder in the mixing device is cooled to 60°C, an organic lubricant with the components and addition amounts shown in Table 1 is added to the powder in the tank of the mixing container, and further stirred and mixed at a rotation speed of 500 rpm of the stirring blade for 5 minutes, and then taken out from the tank of the mixing container to obtain the iron-based soft magnetic composite powder related to Example 1. It should be noted that EBS in Table 1 refers to N,N'-ethylenebisstearamide. In addition, the mixed lubricant is an organic lubricant prepared by melting and mixing 50% by mass of stearamide and 50% by mass of N,N'-ethylenebisstearamide.

[0098] The surface analysis was carried out on the iron-based soft magnetic composite powder according to Example 1 thus manufactured and the iron-based soft magnetic powder (the iron-based soft magnetic composite powder with the insulating layer removed) as the raw material of the iron-based soft magnetic composite powder by using the low-energy ion scattering method, and the peak area ratio (β / α) and the coating rate [(1 - β / α) × 100] were calculated. The measurement was carried out using a low-energy ion scattering spectrometer (Qtac 100 ) manufactured by ION-TOF, with 20Ne + at 5 keV as the incident ion, and the coating rate was calculated using the energy spectrum attributed to Fe. These measurement results are shown together in Table 1.

[0099] In addition, regarding the fluidity of the iron-based soft magnetic composite powder according to Example 1, the flowability (sec / 50 g) was measured according to JIS Z2502:2020. These measurement results are shown together in Table 1.

[0100] (Examples 2 to 14)

[0101] The iron-based soft magnetic composite powders according to Examples 2 to 14 were manufactured under the same conditions as in Example 1 except that the type or addition amount of the organic lubricant was different from that in Example 1. The types and addition amounts of the organic lubricants of the iron-based soft magnetic composite powders according to Examples 2 to 14 are shown in Table 1. The flowability, peak area ratio, and coating rate of the iron-based soft magnetic composite powders according to Examples 2 to 14 are also shown in Table 1.

[0102] In Examples 2 to 6, only the type of the organic lubricant was different from that in Example 1.

[0103] Example 7 was under the same conditions as in Example 1 except that the addition amount of the silicone resin was different from that in Example 1.

[0104] Example 8 was under the same conditions as in Example 1 except that no organic lubricant was added.

[0105] In Examples 9 to 11, the addition amount of the organic lubricant was different from that in Example 1 while other conditions were the same as in Example 1.

[0106] In Examples 12 to 14, the type of the organic lubricant was the same as that in Example 2, and the addition amount of the organic lubricant was different from that in Example 1 while other conditions were the same as in Example 1.

[0107] (Comparative Example 1)

[0108] The mixed powder of the iron-based soft magnetic powder according to Comparative Example 1 was manufactured under the same conditions as in Example 1 except that no coating material was arbitrarily added. The flowability, peak area ratio, and coating rate of the mixed powder of the iron-based soft magnetic powder according to Comparative Example 1 are also shown in Table 1.

[0109] (Comparative Examples 2 and 3)

[0110] Comparative Examples 2 and 3 are different from Example 1 in that neither aluminum tripolyphosphate nor silicone resin is added to the iron-based soft magnetic composite powder, and the others are the same as in Example 1 for manufacturing. It should be noted that in Comparative Examples 2 and 3, the total amount of the coating material added is the same as that in Example 1. The types and amounts of the coating material and the organic lubricant of the iron-based soft magnetic composite powder involved in Comparative Examples 2 and 3 are shown in Table 1. The fluidity, peak area ratio, and coating rate of the iron-based soft magnetic composite powder involved in Comparative Examples 2 and 3 are also shown in Table 1.

[0111] (Comparative Example 4)

[0112] Comparative Example 4 is different from Example 1 in that the amount of the coating material added to the iron-based soft magnetic composite powder is less, and the others are the same as in Example 1 for manufacturing. The amount of the coating material added to the iron-based soft magnetic composite powder involved in Comparative Example 4 is shown in Table 1. The fluidity, peak area ratio, and coating rate of the iron-based soft magnetic composite powder involved in Comparative Example 4 are also shown in Table 1.

[0113] It should be noted that in Table 1, for the values of the coating rate less than 85%, the values of the coating rate (numerical values) are underlined.

[0114] As shown in Table 1, regarding the mixed powder of the iron-based soft magnetic powder (refer to Comparative Example 1) or the iron-based soft magnetic composite powder (refer to Comparative Examples 2 to 4) involved in the comparative examples, its fluidity is so poor that it cannot be evaluated for fluidity (non-flowing). In contrast, the fluidity of the iron-based soft magnetic composite powder involved in the examples is improved to the extent that the fluidity can be evaluated. In particular, the iron-based soft magnetic composite powders involved in the examples other than Examples 11 and 14 have an insulating layer and achieve a fluidity of 27 sec / 50 g or less, which is extremely good.

[0115] In addition, among the iron-based soft magnetic composite powders involved in the examples, the fluidity of the example without mixing the organic lubricant (refer to Example 8) does not decrease extremely compared with the examples with the organic lubricant mixed (refer to Examples 1 to 7 and Examples 9 to 14). Therefore, the iron-based soft magnetic composite powders involved in the examples do not get blocked in the storage containers of the iron-based soft magnetic composite powders, and in addition, the fluidity is ensured to such an extent that it does not hinder the uniform filling when filling the iron-based soft magnetic composite powder into the molding die.

[0116] However, in the case where 0.70% by mass of an organic lubricant is added (see Examples 11 and 14), even when the coating rate of the coating material is 85% or more, for example, more than 90%, a decrease in its fluidity occurs compared to other examples. However, even in this case, high fluidity is achieved compared to the powder of the comparative example. From the comparison of Examples 1, 8 to 12 and the comparison of Examples 2, 8, 12 to 14, it can be seen that as the addition amount of the organic lubricant decreases, the fluidity further improves.

[0117] As described above, it is possible to provide an iron-based soft magnetic composite powder for a compacted powder core having an insulating layer and high fluidity, and a manufacturing method for easily manufacturing the composite powder.

[0118] It should be noted that the above-described embodiments are illustrative, and the embodiments of the present disclosure are not limited thereto, and appropriate changes can be made without departing from the purpose of the present disclosure.

[0119] Industrial availability

[0120] The present disclosure can be applied to an iron-based soft magnetic composite powder for a compacted powder core and a manufacturing method thereof.

Claims

1. An iron-based soft magnetic composite powder for a compacted powder magnetic core, comprising coated particles having an insulating layer formed on the particle surface of iron-based soft magnetic particles, The insulating layer has: A first coating layer disposed on the particle surface and formed of aluminum tripolyphosphate; and A second coating layer disposed on the first coating layer and formed of silicone resin; The coating rate of the insulating layer on the particle surface is 85% or more.

2. The iron-based soft magnetic composite powder for a compacted powder magnetic core according to claim 1, wherein, The coating rate is a value calculated as follows, When the energy spectrum area attributed to Fe measured for the iron-based soft magnetic particles using low energy ion scattering spectroscopy is set as α, and the energy spectrum area attributed to Fe measured for the coated particles using low energy ion scattering spectroscopy is set as β, the value calculated using the following formula, (1−β / α)×100 ··· (Formula 1).

3. The iron-based soft magnetic composite powder for a compacted powder magnetic core according to claim 1, wherein, It contains 0.20% by mass to 0.60% by mass of an organic lubricant.

4. The iron-based soft magnetic composite powder for a compacted powder magnetic core according to claim 2, wherein, It contains 0.20% by mass to 0.60% by mass of an organic lubricant.

5. A method for manufacturing an iron-based soft magnetic composite powder for a compacted powder magnetic core, which is a method for manufacturing the iron-based soft magnetic composite powder for a compacted powder magnetic core according to any one of claims 1 to 4, An organic silicone resin powder is added to and mixed with a powder composed of coated particles having only the first coating layer formed thereon to form the second coating layer.

6. The method for manufacturing an iron-based soft magnetic composite powder for a compacted powder magnetic core according to claim 5, wherein, A powder of an organic lubricant is mixed with a powder containing the coated particles.

Images