Pressed powder compact

Abstract

To provide a powder compact capable of preventing the occurrence of chips and cracks.SOLUTION: A powder compact includes soft magnetic powder and an insulation coating layer coating around the soft magnetic powder. The insulation coating layer includes a silicone resin and a silane coupling agent, the silicone resin being a methyl phenyl-based resin. The silane coupling agent has a glycidoxy group. Such silane coupling agent having a glycidoxy group can prevent the occurrence of chips and cracks in the powder compact.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a compacted molded body.

Background Art

[0002] Coil components such as reactors are used in various applications including OA equipment, solar power generation systems, automobiles, and uninterruptible power supplies. For example, a reactor is an electromagnetic component that converts electrical energy into magnetic energy for storage and release. A reactor mainly includes a core and a coil. The coil is wound around the core. When power is supplied to the coil, a magnetic flux is generated. The core has an annular shape. The core serves as a magnetic path through which the magnetic flux generated by the coil flows.

[0003] A compacted magnetic core may be used as the core of a reactor. The compacted magnetic core is produced by heat-treating a compacted molded body. The compacted molded body is formed, for example, by pressure-molding soft magnetic powder having an insulating film formed on its surface. In this pressure-molding, a generally high pressure of 10 to 20 ton / cm 2 is applied.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In pressure-molding performed at a high pressure, if the bonding force between the soft magnetic powders is weak, chipping or cracking may occur in the compacted molded body. In some cases, there is a risk that the legs of the compacted molded body may break off, and it may not be possible to form a compacted molded body having a desired shape.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a compacted molded body capable of preventing chipping and cracking.

Means for Solving the Problems

[0007] It includes a soft magnetic powder and an insulating coating layer that coats the periphery of the soft magnetic powder. The insulating coating layer contains a silicone resin and a silane coupling agent. The silicone resin is a methylphenyl-based resin, and the silane coupling agent has a glycidoxy group and the addition amount of the silane coupling agent is 0.5 wt% or more based on the soft magnetic powder characterized by that.

Effects of the Invention

[0008] According to the present invention, a compacted molded body capable of preventing chipping and cracking can be obtained.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] The configuration of the compacted molded body of this embodiment will be described. Note that the present invention is not limited to the embodiments described below.

[0011] Coil components such as reactors include a core containing a magnetic material. As the core, a compacted magnetic core is used. The compacted magnetic core is produced by producing a compacted molded body by pressing a soft magnetic powder and subjecting the compacted molded body to a heat treatment called annealing.

[0012] The compacted molded body of this embodiment includes a soft magnetic powder and an insulating coating layer. The insulating coating layer coats the surface of the soft magnetic powder. The insulating coating layer is composed of a silane coupling agent and a silicone resin.

[0013] The soft magnetic powder is mainly composed of iron. As the soft magnetic powder, pure iron powder, permalloy (Fe-Ni alloy) mainly composed of iron, Si-containing iron alloy (Fe-Si alloy), sendust alloy (Fe-Si-Al alloy), or a mixed powder of two or more of these powders can be used. Further, an amorphous alloy or a nanocrystalline alloy powder may be used as the soft magnetic powder. The particle diameter (median diameter D50) of the soft magnetic powder is desirably 1 μm or more and 200 μm or less.

[0014] The Fe-Si-Al alloy powder contains, for example, about 7 wt% to 11 wt% of Si and about 4 wt% to 8 wt% of Al with respect to Fe. The Fe-Si-Al alloy powder may contain, for example, about 1 wt% to 3 wt% of Ni with respect to Fe. Further, the Fe-Si-Al alloy powder may contain Co, Cr or Mn.

[0015] The Si-containing iron alloy may contain Co, Al, Cr or Mn. When using permalloy (Fe-Ni alloy), the ratio of Ni to Fe is preferably 50:50 or 25:75, but other ratios may also be used. For example, Fe-80Ni, Fe-36Ni, Fe-78Ni, Fe-47Ni may be used. In addition to Fe and Ni, it may contain Si, Cr, Mo, Cu, Nb, Ta, etc. Examples of the Fe-Si alloy powder include Fe-3.5% Si alloy powder and Fe-6.5% Si alloy powder, but the ratio of Si to Fe may be other than 3.5% and 6.5%. The pure iron powder contains 99% or more of Fe.

[0016] The soft magnetic powder may be produced by a pulverization method or an atomization method. The atomization method may be any of a water atomization method, a gas atomization method, and a water-gas atomization method.

[0017] However, since the crushed powder produced by the crushing method is non-circular, soft magnetic powders are likely to adhere to each other, and chips and cracks are less likely to occur in the compacted body. On the other hand, since the gas atomized powder produced by the atomization method, particularly the gas atomization method, is circular, the binding property is weak and the compacted body is likely to become brittle. Therefore, the gas atomized powder, in which the effect of the present invention that chips and cracks can be prevented from occurring in the compacted body is remarkably manifested, is preferable for the soft magnetic powder.

[0018] The circularity of the soft magnetic powder is preferably 0.8 or more in the powder having an average particle diameter (median diameter D50). When the circularity is 0.8 or more, the binding property between the soft magnetic powders is weak, and the compacted body is likely to become brittle. Therefore, when the circularity of the soft magnetic powder is 0.8 or more, the effect of the present invention is remarkably manifested. Further, the Vickers hardness of the soft magnetic powder is preferably 400 HV or more. A hard soft magnetic powder having a Vickers hardness of 400 HV or more has a weak binding force between the soft magnetic powders, and the compacted body is likely to become brittle, so the effect of the present invention is remarkably manifested.

[0019] An insulating coating layer is formed on the surface of the soft magnetic powder. The insulating coating layer contains a silane coupling agent and a silicone resin. As the mode of coating of the insulating coating layer, the case of coating the surface of each particle of the soft magnetic powder and the case of coating the surface of the combined particles in which some particles are combined are included. Further, the case of coating the entire surface or a part of the surface of the particles is included. That is, the insulating coating layer does not necessarily completely cover the surface of the soft magnetic powder, and the case where it adheres to a part of the surface of the soft magnetic powder is also included.

[0020] The silane coupling agent has a glycidoxy group. As the silane coupling agent, for example, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, etc. can be used. Since the silane coupling agent has a glycidoxy group, it is possible to prevent chips and cracks from occurring in the compacted body.

[0021] In particular, as the silane coupling agent, 3-glycidoxypropylmethyldiethoxysilane is preferred. By using 3-glycidoxypropylmethyldiethoxysilane, in addition to preventing chips and cracks from occurring in the compacted powder compact, the magnetic properties also become good.

[0022] The addition amount of the silane coupling agent is preferably 0.3 wt% or more based on the soft magnetic powder. When the addition amount of the silane coupling agent is 0.3 wt% or more, the effect of preventing chips and cracks from occurring in the compacted powder compact becomes remarkable.

[0023] Note that the upper limit of the addition amount of the silane coupling agent is preferably 1.5 wt% based on the soft magnetic powder. This is because when the addition amount of the silane coupling agent exceeds 1.5 wt%, the iron loss deteriorates.

[0024] The silicone resin is composed of a methylphenyl-based resin. Although not limited thereto, it is presumed that by combining a methylphenyl-based silicone resin and a silane coupling agent having a glycidoxy group, organic substances are likely to remain in the insulating coating layer even after heat drying, and the LATR value becomes good. As the methylphenyl-based silicone resin, a methylphenyl-based silicone resin, a silicone oligomer, or the like can be used. When a methylphenyl-based silicone resin is used, an insulating coating layer with little heat loss and excellent heat resistance can be formed. Also, when a methylphenyl-based silicone oligomer is used, a thick and hard insulating coating layer can be formed.

[0025] The addition amount of the silicone resin is preferably 0.3 wt% or more and 2.0 wt% or less based on the soft magnetic powder. If the addition amount is less than 0.3 wt%, it does not function as an insulating coating layer, and the magnetic properties deteriorate due to an increase in eddy current loss. If the addition amount is more than 2.0 wt%, it causes a decrease in the density of the compacted powder compact.

[0026] After adding and mixing a silane coupling agent and a silicone resin to soft magnetic powder and then heating and drying, an insulating coating layer is formed on the surface of the soft magnetic powder. The heating and drying conditions are not limited to this, but are about 2 hours at a temperature of 25°C or higher and 350°C or lower.

[0027] Note that the insulating coating layer may be a mixed layer of a silane coupling agent and a silicone resin, or a layer of a silane coupling agent and a layer of a silicone resin may be laminated. For example, when the insulating coating layer is laminated in the order of a layer of a silane coupling agent and a layer of a silicone resin, first, a silane coupling agent is added and mixed to the soft magnetic powder, and heating and drying are performed. Then, a silicone resin is added and mixed to the soft magnetic powder on which the layer of the silane coupling agent is formed, and heating and drying are performed to form a layer of the silicone resin on the surface of the layer of the silane coupling agent.

[0028] A lubricant may be added to the soft magnetic powder on which the insulating coating layer is formed. Examples of the lubricant include, but are not limited to, stearic acid, calcium stearate, lithium stearate, aluminum stearate, zinc stearate, ethylene bisstearamide, ethylene bisstearoamide, ethylene bisstearate amide, and the like. By mixing the lubricant, the slipperiness between the soft magnetic powders can be improved, so that the density of the compacted molded body can be increased. Further, it is possible to reduce the extraction pressure of the upper punch during pressure molding and prevent the generation of vertical streaks on the core wall surface due to the contact between the mold and the soft magnetic powder.

[0029] The addition amount of the lubricant is preferably about 0.2 wt% to 0.8 wt% with respect to the soft magnetic powder. By setting it within this range, the slipperiness between the soft magnetic powders can be further improved. Note that the lubricant may be added in two portions before and after the insulating coating layer is formed. That is, a lubricant may be added to the soft magnetic powder at a stage before adding the silane coupling agent and the silicone resin, and then a lubricant may be added to the soft magnetic powder on which the insulating coating layer is formed.

[0030] After adding the lubricant, the soft magnetic powder is injected into a mold and pressure molding is performed. By performing this pressure molding, a compacted molded body is produced. In the pressure molding, a pressure of about 10 to 20 tons / cm 2 is applied to the soft magnetic powder to produce a compacted molded body. The average pressure is more preferably about 12 to 15 tons / cm 2 .

[0031] Thereafter, the compacted molded body produced by pressure molding is heat-treated in nitrogen gas, in a non-oxidizing atmosphere such as a mixed gas of nitrogen and hydrogen, or in the atmosphere, at a temperature lower than 600°C and lower than the temperature at which the insulating coating layer covering the soft magnetic powder is broken (for example, 900°C). By undergoing this heat treatment, a compacted magnetic core is produced

[0032] (Example) The present invention will be described in more detail based on the examples. Note that the present invention is not limited to the following examples. Compacted molded bodies of Examples 1 to 13 and Comparative Examples 1 to 2 were produced. The compacted molded bodies of Examples 1 to 13 and Comparative Examples 1 to 2 differ only in the type of silane coupling agent added and its addition amount.

[0033] First, a compacted molded body of Example 1 was produced. As the soft magnetic powder, Fe-Si-Al alloy powder produced by the gas atomization method was used. The particle size and circularity of the Fe-Si-Al alloy powder are as shown in Table 1 below

[0034]

Table 1

[0035] First, a lubricant was added to the Fe-Si-Al alloy powder. As the lubricant, stearic acid (D50 = 100 μm, melting point 57°C) was used. Stearic acid was added to the Fe-Si-Al alloy powder at 0.3 wt% and mixed.

[0036] After adding and mixing stearic acid, a silane coupling agent was added and mixed. Thereafter, a silicone resin was added and mixed. As the silane coupling agent, "B 3-glycidoxypropylmethyldiethoxysilane" (product name: KBE-402) shown in Table 2 below was used. 3-glycidoxypropylmethyldiethoxysilane was added at 0.3 wt% with respect to the Fe-Si-Al alloy powder.

[0037]

Table 2

[0038] As the silicone resin, a methylphenyl-based silicone resin was used. The silicone resin was added at 1.2 wt% with respect to the Fe-Si-Al alloy powder. After adding and mixing the silicone resin, heat drying was performed. The drying temperature was 130°C and the drying time was 2 hours. Thereby, an insulating coating layer was formed around the Fe-Si-Al alloy powder.

[0039] After heat drying, the Fe-Si-Al alloy powder was passed through a sieve with an opening of 850 μm for the purpose of crushing aggregation. Thereafter, a lubricant was added again and mixed. As the lubricant at this time, aluminum stearate (D50 = 21 μm, melting point 110°C) was used. Aluminum stearate was added at 0.2 wt% with respect to the Fe-Si-Al alloy powder.

[0040] After adding and mixing the lubricant, the Fe-Si-Al alloy powder with the lubricant attached was filled into a mold and press-molded to produce a cylindrical compacted powder compact having an outer diameter of 11.3 mm and a height of 10.0 mm (height dimensional tolerance ±0.1 mm). The pressure for press molding was 12.0 ton / cm 2 and it was carried out. Five compacted powder compacts of this Example 1 were produced.

[0041] Examples 2 to 5 are the same as Example 1 in terms of the materials, manufacturing methods, and conditions, except that the addition amount of the silane coupling agent is different from that of Example 1. The addition amounts of the silane coupling agent are 0.5 wt% for Example 2, 0.7 wt% for Example 3, 1.0 wt% for Example 4, and 1.5 wt% for Example 5.

[0042] Example 6 is the same as Example 1 in terms of the materials, manufacturing methods, and conditions, except that only the type of the silane coupling agent is different from that of Example 1. The silane coupling agent used in Example 6 is "C 3-glycidoxypropylmethyldimethoxysilane" (product name: KBM-402) shown in Table 2 above.

[0043] Examples 7 to 9 are the same as Example 6 in terms of the materials, manufacturing methods, and conditions, except that the addition amount of the silane coupling agent is different from that of Example 6. The addition amounts of the silane coupling agent are 0.5 wt% for Example 7, 1.0 wt% for Example 8, and 1.5 wt% for Example 9.

[0044] Example 10 is the same as Example 1 in terms of the materials, manufacturing methods, and conditions, except that only the type of the silane coupling agent is different from that of Example 1. The silane coupling agent used in Example 10 is "D 3-glycidoxypropyltrimethoxysilane" (product name: KBM-403) shown in Table 2 above.

[0045] Examples 11 to 13 are the same as Example 10 in terms of the materials, manufacturing methods, and conditions, except that the addition amount of the silane coupling agent is different from that of Example 10. The addition amounts of the silane coupling agent are 0.5 wt% for Example 11, 1.0 wt% for Example 12, and 1.5 wt% for Example 13.

[0046] Next, the production of the compacted compacts of Comparative Examples 1 and 2 will be described. Comparative Example 1 differs from Example 1 only in that no silane coupling agent is added. That is, the insulating coating layer of Comparative Example 1 contains only silicone resin and does not contain a silane coupling agent. In Comparative Example 1, for the rest, the same materials, the same manufacturing method, and the same conditions as in Example 1 are used.

[0047] Comparative Example 2 differs from Example 1 only in the type and addition amount of the silane coupling agent. For the rest, the same materials, the same manufacturing method, and the same conditions as in Example 1 are used. The silane coupling agent used in Comparative Example 2 was "A tetraethoxysilane" (product name: TES28) shown in Table 2 above. The addition amount of the silane coupling agent is 0.5 wt%.

[0048] The Lattr values of the compacted compacts of Examples 1 to 13 and Comparative Examples 1 and 2 produced as described above were measured. A Lattr tester (manufactured by Intesco Co., Ltd.) was used for the measurement of the Lattr value. The Lattr value was measured based on the method for measuring the Lattr value of metal powder compacts (JPMA P11 1992) of the Japan Powder Metallurgy Industry Association (JPMA) standard.

[0049] First, the total weight of five compacted compacts of Examples 1 to 13 and Comparative Examples 1 and 2 was measured before being put into the Lattr tester. Then, five compacted compacts were put into a cylindrical cage with a 14-mesh stainless steel wire mesh stretched over it and rotated 100 times at a rotational speed of 87 rpm. Finally, the total weight of the five compacted compacts taken out from the Lattr tester was measured. And the Lattr value was calculated by subtracting the total weight measured after rotation from the total weight measured before rotation to obtain the weight reduction rate. That is, the Lattr value was calculated from the following calculation formula (1). S = ((A - B) / A) × 100 ··· (1) S: Lattr value (%) A: Total weight of five compacted compacts before the test (g) B: Total weight of five compacted compacts after the test (g)

[0050] The calculation results are shown in Table 3 below. Also, Fig. 1 shows a graph of the LATR values of Examples 2, 7, 11 and Comparative Example 2 to which 0.5 wt% of a silane coupling agent was added.

[0051]

Table 3

[0052] As shown in Table 3, in Examples 1 to 13 to which a silane coupling agent having a glycidoxy group was added, even the highest LATR value was lower than 29.2% and 30%, and lower than those of Comparative Examples 1 and 2. Therefore, it was confirmed that by using a silane coupling agent having a glycidoxy group, the LATR value can be reduced and the occurrence of chips and cracks in the compact can be prevented.

[0053] Also, in Examples 1, 6 and 10 to which 0.3 wt% of a silane coupling agent having a glycidoxy group was added, the LATR value was lower than that of Comparative Example 1 to which no silane coupling agent was added. Therefore, it was confirmed that by adding 0.3 wt% or more of a silane coupling agent having a glycidoxy group, the effect of reducing the LATR value appears.

[0054] In particular, when comparing Examples 2, 7, 11 to which 0.5 wt% of a silane coupling agent having a glycidoxy group was added with Comparative Example 2 to which a silane coupling agent having no glycidoxy group was added, the LATR values of Examples 2, 7 and 11 are less than 1 / 2 of that of Comparative Example 2, as shown in Table 3 and Fig. 1. From this, it was confirmed that by configuring a silane coupling agent having a glycidoxy group as an insulating coating layer, the LATR value can be reduced.

[0055] Furthermore, in Examples 4, 5, 8, and 9 where 3-glycidoxypropylmethyldiethoxysilane or 3-glycidoxypropylmethyldimethoxysilane was added at 1.0 wt% or more as a silane coupling agent, the ratola value was lower than 15%, showing extremely good numerical values. Therefore, it was confirmed that by adding 3-glycidoxypropylmethyldiethoxysilane or 3-glycidoxypropylmethyldimethoxysilane at 1.0 wt% or more as a silane coupling agent, it is possible to more effectively prevent chips and cracks from occurring in the compacted powder compact.

[0056] Note that the ratola value is an index related to the chippability of the compact and has no correlation with strength. That is, it cannot be immediately said that if the strength increases, the ratola value will also decrease.

[0057] Next, compacted powder compacts of Example 14 and Comparative Example 3 were further produced. Example 14 differs from Example 2 only in that the pulverized powder of the Fe-Si-Al alloy powder was produced by a pulverization method. Except for the type and addition amount of the silane coupling agent, the other materials, production methods, and conditions are the same as those of Example 2.

[0058] Comparative Example 3 differs from Comparative Example 2 only in that the pulverized powder of the Fe-Si-Al alloy powder was produced by a pulverization method. Except for the type and addition amount of the silane coupling agent, the other materials, production methods, and conditions are the same as those of Comparative Example 2.

[0059] Five compacted powder compacts each of Example 14 and Comparative Example 3 were produced, and the ratola value was calculated. The calculation of the ratola value was performed under the same apparatus and measurement conditions as above. The calculation results are shown in Table 4 below.

[0060]

Table 4

[0061] As shown in Table 4, even when the Fe-Si-Al alloy powder is a pulverized powder, it was confirmed that Example 14 to which a silane coupling agent having a glycidoxy group was added had a lower LATR value than Comparative Example 3. That is, it was confirmed that the type of soft magnetic powder is not limited to gas atomized powder, and the effect of reducing the LATR value also occurs even with pulverized powder.

[0062] However, looking at Comparative Example 3, the LATR value is 3.9%, which is originally a low value, and it is difficult to say that the LATR value of Example 14 has decreased dramatically. On the other hand, the LATR value of Comparative Example 2, which is a gas atomized powder, is as high as 58.0%. And the LATR value of Example 2 is 29.0%, which has decreased dramatically to half that of Comparative Example 2. Therefore, it was confirmed that when a silane coupling agent having a glycidoxy group is added to a soft magnetic powder that is a gas atomized powder, the effect of reducing the LATR value appears more significantly.

[0063] (Other Embodiments) In this specification, embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. Embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Claims

1. A soft magnetic powder, an insulating coating layer covering the periphery of the soft magnetic powder, and comprising, the insulating coating layer contains a silicone resin and a silane coupling agent, the silicone resin is a methylphenyl-based resin, the silane coupling agent has a glycidoxy group, the addition amount of the silane coupling agent is 0.5 wt% or more based on the soft magnetic powder, A compacted powder compact characterized by the above.

2. The soft magnetic powder is a gas atomized powder, A compacted powder compact according to claim 1, characterized by the above.

3. The upper limit of the addition amount of the silane coupling agent is 1.5 wt% or less based on the soft magnetic powder, A compacted powder compact according to claim 1 or 2, characterized by the above.

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