JP5382424B2 - Method for producing magnetic core powder - Google Patents
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- JP5382424B2 JP5382424B2 JP2009070839A JP2009070839A JP5382424B2 JP 5382424 B2 JP5382424 B2 JP 5382424B2 JP 2009070839 A JP2009070839 A JP 2009070839A JP 2009070839 A JP2009070839 A JP 2009070839A JP 5382424 B2 JP5382424 B2 JP 5382424B2
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- 239000000843 powder Substances 0.000 title claims description 39
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000006247 magnetic powder Substances 0.000 claims description 40
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 37
- 229910052710 silicon Inorganic materials 0.000 claims description 37
- 239000010703 silicon Substances 0.000 claims description 37
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 28
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 16
- 239000001569 carbon dioxide Substances 0.000 claims description 14
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 14
- 239000001257 hydrogen Substances 0.000 claims description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims description 14
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 230000001590 oxidative effect Effects 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 229910017082 Fe-Si Inorganic materials 0.000 claims description 5
- 229910017133 Fe—Si Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000000835 fiber Substances 0.000 claims 1
- 150000002431 hydrogen Chemical class 0.000 claims 1
- 239000002245 particle Substances 0.000 description 45
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 38
- 239000000377 silicon dioxide Substances 0.000 description 19
- 235000012239 silicon dioxide Nutrition 0.000 description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 17
- 239000001301 oxygen Substances 0.000 description 17
- 229910052760 oxygen Inorganic materials 0.000 description 17
- 238000000465 moulding Methods 0.000 description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 11
- 239000000428 dust Substances 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 229910052742 iron Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910004298 SiO 2 Inorganic materials 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 239000011863 silicon-based powder Substances 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000314 lubricant Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 235000000396 iron Nutrition 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- FTQWRYSLUYAIRQ-UHFFFAOYSA-N n-[(octadecanoylamino)methyl]octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(=O)NCNC(=O)CCCCCCCCCCCCCCCCC FTQWRYSLUYAIRQ-UHFFFAOYSA-N 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Description
本発明は、圧粉磁心に適した磁心用粉末と、その製造方法に関するものである。 The present invention relates to a magnetic core powder suitable for a dust core and a method for producing the same.
磁心用粉末は、例えば、鉄（Ｆｅ）等を主成分とする磁性粉末の粒子表面に絶縁被膜が形成されたものである。
圧粉磁心は、このような磁心用粉末を金型で加圧成形したものであり、モータ等の電磁機器の磁心として広く利用されている。
圧粉磁心に関する性能（磁束密度、鉄損等）の良否は、材料となる磁心用粉末に大きく依存する。即ち、磁束密度が高く、鉄損も少ない圧粉磁心を製造するためには、より薄くて均一な絶縁被膜を有する磁心用粉末を用いることが重要である。
従来の磁心用粉末の製造方法としては、鉄（Ｆｅ）及び珪素（Ｓｉ）を主成分とする磁性粉末を、所定の酸素分圧の酸化雰囲気中で加熱処理することによって、当該磁性粉末の粒子表面に絶縁被膜として二酸化珪素（ＳｉＯ2）被膜を形成させる方法が知られている（特許文献１参照）。
The magnetic core powder is obtained by, for example, forming an insulating coating on the particle surface of a magnetic powder mainly composed of iron (Fe) or the like.
The powder magnetic core is obtained by pressure-molding such a magnetic core powder with a mold, and is widely used as a magnetic core of electromagnetic equipment such as a motor.
The quality of the dust core (flux density, iron loss, etc.) depends greatly on the magnetic core powder used as the material. That is, in order to manufacture a dust core having a high magnetic flux density and low iron loss, it is important to use a magnetic core powder having a thinner and uniform insulating coating.
As a conventional method for producing a powder for a magnetic core, a magnetic powder mainly composed of iron (Fe) and silicon (Si) is heat-treated in an oxidizing atmosphere having a predetermined oxygen partial pressure to thereby obtain particles of the magnetic powder. A method of forming a silicon dioxide (SiO 2 ) film as an insulating film on the surface is known (see Patent Document 1).
上記従来の磁心用粉末の製造方法は、鉄（Ｆｅ）及び０．５重量％〜１０重量％の珪素（Ｓｉ）を含む磁性粉末を、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）が、およそ−５〜−３．５となる酸化雰囲気中に保持して、６００℃〜９００℃で加熱処理するものである。 The above-described conventional method for manufacturing a magnetic core powder is obtained by using a magnetic powder containing iron (Fe) and 0.5 wt% to 10 wt% silicon (Si) as a hydrogen partial pressure (PH 2 O) of water vapor partial pressure (PH 2 O). 2 ) is maintained in an oxidizing atmosphere where the partial pressure ratio Log (PH 2 O / PH 2 ) is approximately −5 to −3.5, and heat treatment is performed at 600 ° C. to 900 ° C.
上記従来の製造方法では、二酸化珪素被膜の生成速度が遅く、磁性粉末の粒子表面全体を二酸化珪素被膜で均一に覆うためには処理時間が非常に長くなるという問題がある。処理時間が不足すると、磁性粉末の粒子表面を覆う二酸化珪素被膜は不均一なものとなり、鉄が部分的に露出して十分な比抵抗が得られなくなるため、渦電流損失が増加する原因となる。 The conventional manufacturing method has a problem that the generation rate of the silicon dioxide film is slow and the processing time becomes very long in order to uniformly cover the entire particle surface of the magnetic powder with the silicon dioxide film. If the treatment time is insufficient, the silicon dioxide film covering the particle surface of the magnetic powder becomes non-uniform, and iron is partially exposed and sufficient specific resistance cannot be obtained, which causes an increase in eddy current loss. .
また、従来の製造方法で使用する磁性粉末は、０．５重量％〜１０重量％、好ましくは１．０重量％〜３．０重量％という比較的多量の珪素を含むものでなければならない（特許文献１の段落番号〔００４２〕参照）。
しかし、磁心用粉末の材料硬度は珪素含有量に比例した分だけ高くなる。そのため、当該磁心用粉末を加圧成形して圧粉磁心を製造する際、特殊な高圧成形装置を使用しなければ所望する高い成形密度が得られ難く、設備コストが嵩むという問題も生じている。
Further, the magnetic powder used in the conventional production method should contain a relatively large amount of silicon of 0.5 wt% to 10 wt%, preferably 1.0 wt% to 3.0 wt% ( (See paragraph number [0042] of Patent Document 1).
However, the material hardness of the magnetic core powder is increased by an amount proportional to the silicon content. For this reason, when a powder magnetic core is produced by pressure molding the magnetic core powder, it is difficult to obtain a desired high molding density unless a special high-pressure molding apparatus is used, and there is a problem that equipment costs increase. .
本発明は、上記実情に鑑みてなされたものであって、その目的は、珪素含有量の少ない磁性粉末において、その粒子の表面全体を覆う薄くて均一な二酸化珪素被膜を短時間で形成させる方法を提供することにある。 The present invention has been made in view of the above circumstances, and its object is to form a thin and uniform silicon dioxide film covering the entire surface of the particles in a short time in a magnetic powder having a low silicon content. Is to provide.
本発明に係る特徴構成は、鉄（Ｆｅ）を主成分として０．３重量％〜１．０重量％の珪素（Ｓｉ）を含むＦｅ−Ｓｉ系磁性粉末を、水素と二酸化炭素と窒素とを導入して所定比率に調整した回転炉内において、大気圧下における水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）が−４〜−１となる酸化雰囲気中で１０００℃〜１２００℃に昇温して加熱処理する点にある。 FEATURES configuration according to the present invention, iron Fe-Si-based magnetic powder containing 0.3 wt% to 1.0 wt% of silicon with a (Fe) as a main component (Si), hydrogen and carbon dioxide and nitrogen the introduced in a rotary furnace is adjusted to a predetermined ratio, the partial pressure ratio Log (PH 2 O / PH 2 ) with respect to hydrogen partial pressure of water vapor partial pressure in the atmospheric pressure (PH 2 O) (PH 2 ) - 4~ It is in the point which heat-processes by heating up to 1000 to 1200 degreeC in the oxidation atmosphere used as -1.
〔作用及び効果〕
本発明では、磁性粉末を１０００℃〜１２００℃の高温で加熱処理することによって、磁性粉末の粒子中の珪素の拡散速度を高めている。
粒子の表面に存在する珪素は、粒子周囲の酸素により酸化されて二酸化珪素となる。その結果、粒子表面近くの珪素濃度は、粒子内部の珪素濃度と比べて低くなり、珪素の濃度勾配が生じて、粒子内の珪素が、粒子表面に向かって移動する。ただし、珪素は高温になるほど酸素と結合し難くなる。
[Action and effect]
In the present invention, the diffusion rate of silicon in the particles of the magnetic powder is increased by heat-treating the magnetic powder at a high temperature of 1000 ° C. to 1200 ° C.
Silicon present on the surface of the particles is oxidized by oxygen around the particles to form silicon dioxide. As a result, the silicon concentration near the particle surface is lower than the silicon concentration inside the particle, a silicon concentration gradient is generated, and the silicon in the particle moves toward the particle surface. However, silicon becomes harder to combine with oxygen at higher temperatures.
本発明においては、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）を−４〜−１に設定する。これにより、酸素分圧は従来の製造方法と比べて高く設定される。粒子周囲にはより多くの酸素が存在するため、粒子の表面に到達した珪素は、酸素と速やかに結合する。尚、分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）をこれより高く設定して酸素分圧を上げ過ぎると、粒子内部で珪素が酸化されるため好ましくない。
また、基本的に、２Ｈ 2 Ｏ⇔２Ｈ 2 ＋Ｏ 2 からなる平衡反応（ａ）において、水蒸気分圧（ＰＨ 2 Ｏ）の水素分圧（ＰＨ 2 ）に対する分圧比Ｌｏｇ（ＰＨ 2 Ｏ/ＰＨ 2 ）を管理することで、酸化雰囲気中の酸素分圧を所望の範囲内に調整するものである。
本構成のように、二酸化炭素を使用し、二酸化炭素の流量比を調整することによって上記平衡反応（ａ）を調整することができる。二酸化炭素は、常温で気体であるため取り扱いが容易である。このため、分圧比Ｌｏｇ（ＰＨ 2 Ｏ/ＰＨ 2 ）の制御が容易になる。
さらに、炭素含有量の多い磁性粉末を原料として磁心用粉末を製造し、当該磁心用粉末を材料として製造した圧粉磁心は、その保磁力が大きく、ヒステリシス損失が大きくなるので、磁性粉末中の炭素含有量は少ないほど良い。二酸化炭素は、ＣＯ 2 ＋Ｃ→２ＣＯのように炭素と反応して一酸化炭素を生じさせるため、磁性粉末中の炭素を脱炭することができる。従って、炭素含有量の多い安価な磁性粉末を原料として使用することができる。
In the present invention, the partial pressure ratio Log (PH 2 O / PH 2 ) of the water vapor partial pressure (PH 2 O) to the hydrogen partial pressure (PH 2 ) is set to −4 to −1. Thereby, oxygen partial pressure is set high compared with the conventional manufacturing method. Since more oxygen is present around the particle, silicon that has reached the surface of the particle is quickly bonded to oxygen. If the partial pressure ratio Log (PH 2 O / PH 2 ) is set higher than this and the oxygen partial pressure is increased too much, silicon is oxidized inside the particles, which is not preferable.
Basically, in the equilibrium reaction (a) composed of 2H 2 O⇔2H 2 + O 2 , the partial pressure ratio Log (PH 2 O / PH 2 ) of the water vapor partial pressure (PH 2 O) to the hydrogen partial pressure (PH 2 ) ) Is controlled to adjust the oxygen partial pressure in the oxidizing atmosphere within a desired range.
As in this configuration, the equilibrium reaction (a) can be adjusted by using carbon dioxide and adjusting the flow rate ratio of carbon dioxide. Since carbon dioxide is a gas at room temperature, it is easy to handle. This facilitates control of the partial pressure ratio Log (PH 2 O / PH 2 ).
Furthermore, a magnetic core powder is manufactured using a magnetic powder having a high carbon content as a raw material, and a dust core manufactured using the magnetic core powder as a material has a large coercive force and a large hysteresis loss. The lower the carbon content, the better. Since carbon dioxide reacts with carbon to generate carbon monoxide as in CO 2 + C → 2CO, carbon in the magnetic powder can be decarburized. Therefore, an inexpensive magnetic powder with a high carbon content can be used as a raw material.
以上より、本発明によれば、高温で酸化処理することによって粒子中の珪素の拡散速度を高めると共に、粒子周囲の酸素分圧を高めることによって、粒子表面における二酸化珪素被膜の形成速度を、従来の製造方法よりも向上させることができる。その結果、珪素含有量の少ない磁性粉末においても、その粒子の表面全体を覆う薄くて均一な二酸化珪素被膜を短時間で形成させることができる。 As described above, according to the present invention, the silicon dioxide coating rate on the particle surface can be increased by increasing the diffusion rate of silicon in the particle by oxidizing at a high temperature and increasing the oxygen partial pressure around the particle. It is possible to improve the manufacturing method. As a result, a thin and uniform silicon dioxide film covering the entire surface of the particles can be formed in a short time even in a magnetic powder having a low silicon content.
その上、磁性粉末中の珪素含有量が０．３重量％〜１．０重量％と少ないので、磁心用粉末の材料硬度が高くなることもない。その結果、当該磁心用粉末を加圧成形して圧粉磁心を製造する際、特殊な高圧成形装置ではなく、通常のプレス成形装置を用いて高密度の圧粉磁心を製造することがきる。即ち、本発明によれば、成形性の良い磁心用粉末を得ることができる。 In addition, since the silicon content in the magnetic powder is as low as 0.3 to 1.0% by weight, the material hardness of the magnetic core powder does not increase. As a result, when a powder magnetic core is manufactured by press molding the magnetic core powder, a high-density powder magnetic core can be manufactured using a normal press molding apparatus instead of a special high pressure molding apparatus. That is, according to the present invention, it is possible to obtain a magnetic core powder with good moldability.
本発明に係る特徴構成は、
前記分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）を、−２．５〜−１．５に設定する点にある。
FEATURES configuration according to the present invention,
The partial pressure ratio Log (PH 2 O / PH 2 ) is set to -2.5 to -1.5.
〔作用及び効果〕
本発明によれば、磁性粉末の粒子内部における珪素酸化を確実に抑えると共に、粒子表面における二酸化珪素被膜の形成をより一層促進させることができる。
[Action and effect]
According to the present invention, it is possible to reliably suppress silicon oxidation inside the particles of the magnetic powder and further promote the formation of a silicon dioxide film on the particle surface.
（１）磁性粉末
本発明に適用可能な磁性粉末は、鉄（Ｆｅ）を主成分として０．３重量％〜１．０重量％の珪素（Ｓｉ）を含むＦｅ―Ｓｉ系磁性粉末である。当該磁性粉末の平均粒径は約１００μｍ、粒度分布は５０μｍ〜３００μｍであることが好ましい。また、本発明に適用可能なＦｅ−Ｓｉ系磁性粉末には、０．０２重量％以上の炭素を含む比較的安価なＦｅ−Ｓｉ系磁性粉末も含まれる。
(1) Magnetic powder A magnetic powder applicable to the present invention is an Fe—Si based magnetic powder containing iron (Fe) as a main component and containing 0.3 wt% to 1.0 wt% of silicon (Si). The magnetic powder preferably has an average particle size of about 100 μm and a particle size distribution of 50 μm to 300 μm. Further, the Fe—Si based magnetic powder applicable to the present invention includes a relatively inexpensive Fe—Si based magnetic powder containing 0.02% by weight or more of carbon.
（２）磁心用粉末の製造方法
本発明は、上記磁性粉末を、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）が−４〜−１、特に好ましくは、−２．５〜−１．５となる酸化雰囲気中に保持する雰囲気保持工程と、当該磁性粉末を酸化雰囲気中で９００℃〜１２００℃で加熱処理する加熱処理工程とを包含するものである。本発明は、例えば、公知の回転加熱炉（ロータリーキルン）を用いて実施することができる。
(2) Method for Producing Magnetic Core Powder In the present invention, the magnetic powder has a partial pressure ratio Log (PH 2 O / PH 2 ) of hydrogen partial pressure (PH 2 O) to hydrogen partial pressure (PH 2 ) of −4 to -1, particularly preferably, an atmosphere holding step for holding in an oxidizing atmosphere of −2.5 to −1.5, and a heat treatment step for heat-treating the magnetic powder at 900 ° C. to 1200 ° C. in an oxidizing atmosphere Is included. This invention can be implemented using a well-known rotary heating furnace (rotary kiln), for example.
加熱処理工程では、磁性粉末を９００℃〜１２００℃の高温で加熱処理することによって、磁性粉末の粒子中の珪素の拡散速度を高めている。
粒子中の珪素が移動して粒子の表面に到達すると、当該珪素は、粒子周囲の酸素により酸化されて二酸化珪素となる。その結果、粒子表面近くの珪素濃度は、粒子内部の珪素濃度と比べて低くなり珪素の濃度勾配が生じる。これにより、粒子内の珪素の、粒子表面に向かう移動が促進される。
In the heat treatment step, the diffusion rate of silicon in the particles of the magnetic powder is increased by heat-treating the magnetic powder at a high temperature of 900 ° C. to 1200 ° C.
When silicon in the particles moves and reaches the surface of the particles, the silicon is oxidized by oxygen around the particles to become silicon dioxide. As a result, the silicon concentration near the particle surface is lower than the silicon concentration inside the particle, resulting in a silicon concentration gradient. Thereby, the movement of the silicon in the particles toward the particle surface is promoted.
一方、高温になるほど、珪素は酸素と結合し難くなる。しかし、雰囲気保持工程において、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）を−４〜−１に設定することによって、酸素分圧は従来の製造方法と比べて高く設定される。そのため、粒子周囲により多くの酸素が存在することとなり、粒子の表面に到達した珪素は、酸素と速やかに結合する。尚、分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）をこれより高く設定して酸素分圧を上げ過ぎると、粒子内部で珪素が酸化されるため好ましくない。 On the other hand, the higher the temperature, the less likely silicon will bond with oxygen. However, in the atmosphere holding step, the oxygen partial pressure is set by setting the partial pressure ratio Log (PH 2 O / PH 2 ) to the hydrogen partial pressure (PH 2 ) of the water vapor partial pressure (PH 2 O) to −4 to −1. Is set higher than the conventional manufacturing method. Therefore, more oxygen is present around the particle, and silicon that has reached the surface of the particle is quickly bonded to oxygen. If the partial pressure ratio Log (PH 2 O / PH 2 ) is set higher than this and the oxygen partial pressure is increased too much, silicon is oxidized inside the particles, which is not preferable.
雰囲気保持工程においては、水素及び二酸化炭素の混合ガスを使用することが望ましい。雰囲気保持工程は、例えば、２Ｈ2Ｏ⇔２Ｈ2＋Ｏ2からなる平衡反応（ａ）を利用する。即ち、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）を管理することで、酸化雰囲気中の酸素分圧を所望の範囲内に調整する。
この雰囲気保持工程においては、さらに二酸化炭素を使用することができる。その場合、二酸化炭素の流量比を調整することによって上記平衡反応（ａ）を調整することができる。二酸化炭素は、常温で気体であるため取り扱いが容易である。このため、分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）の制御が容易になる。
In the atmosphere maintaining step, it is desirable to use a mixed gas of hydrogen and carbon dioxide. In the atmosphere holding step, for example, an equilibrium reaction (a) composed of 2H 2 O⇔2H 2 + O 2 is used. That is, by controlling the partial pressure ratio Log (PH 2 O / PH 2 ) of water vapor partial pressure (PH 2 O) to hydrogen partial pressure (PH 2 ), the oxygen partial pressure in the oxidizing atmosphere is adjusted within a desired range. To do.
In this atmosphere holding step, carbon dioxide can be further used. In that case, the equilibrium reaction (a) can be adjusted by adjusting the flow rate ratio of carbon dioxide. Since carbon dioxide is a gas at room temperature, it is easy to handle. This facilitates control of the partial pressure ratio Log (PH 2 O / PH 2 ).
尚、炭素含有量の多い磁性粉末を原料として製造された圧粉磁心は、ヒステリシス損失が大きくなる。よって、磁性粉末中の炭素含有量は少ないほど良い。
二酸化炭素は、ＣＯ2＋Ｃ→２ＣＯのように炭素と反応して一酸化炭素を生じさせるため、磁性粉末中の炭素を脱炭することができる。
従って、雰囲気保持工程においてさらに二酸化炭素を使用した場合、二酸化炭素の脱炭作用によって、炭素含有量の多い安価な磁性粉末を原料として使用することができる。
A dust core produced from magnetic powder having a high carbon content as a raw material has a large hysteresis loss. Therefore, the smaller the carbon content in the magnetic powder, the better.
Since carbon dioxide reacts with carbon to generate carbon monoxide as in CO 2 + C → 2CO, carbon in the magnetic powder can be decarburized.
Therefore, when carbon dioxide is further used in the atmosphere holding step, an inexpensive magnetic powder having a high carbon content can be used as a raw material due to the decarburization action of carbon dioxide.
以上より、本発明によれば、高温で酸化処理することによって粒子中の珪素の拡散速度を高めると共に、粒子周囲の酸素分圧を高めることによって、粒子表面における二酸化珪素被膜の形成速度を、従来の製造方法よりも向上させることができる。その結果、珪素含有量の少ない磁性粉末においても、その粒子の表面全体に、膜厚約１００ｎｍ以下の薄くて均一な二酸化珪素被膜を１時間程度の短時間で形成させることができる。 As described above, according to the present invention, the silicon dioxide coating rate on the particle surface can be increased by increasing the diffusion rate of silicon in the particle by oxidizing at a high temperature and increasing the oxygen partial pressure around the particle. It is possible to improve the manufacturing method. As a result, even in a magnetic powder having a low silicon content, a thin and uniform silicon dioxide film having a thickness of about 100 nm or less can be formed on the entire surface of the particles in a short time of about 1 hour.
（３）圧粉磁心の製造方法
圧粉磁心は、上述のようにして製造された磁心用粉末を、成形用金型に充填する充填工程と、当該磁心用粉末を加圧成形する成形工程と、加圧成形後、非酸化雰囲気炉内において５００℃〜１０００℃で焼鈍して歪を除去する歪除去熱処理工程とを経て得られる。尚、充填工程においては、磁心用粉末に、必要に応じて適当な結合剤や潤滑剤等を添加混合したものを充填するようにしても良い。
(3) Manufacturing method of powder magnetic core The powder magnetic core includes a filling step of filling the magnetic core powder manufactured as described above into a molding die, and a molding step of pressure-molding the magnetic core powder. After the pressure molding, it is obtained through a strain removing heat treatment step of removing strain by annealing at 500 ° C. to 1000 ° C. in a non-oxidizing atmosphere furnace. In the filling step, the magnetic core powder may be filled with a suitable binder or lubricant added and mixed as necessary.
本発明によって製造された磁心用粉末は、磁性粉末中の珪素含有量が０．３重量％〜１．０重量％と少ないので、材料硬度が高くなることはない。そのため、成形工程の際、特殊な高圧成形装置を使用しなくとも、通常のプレス成形装置を用いて高い成形密度を確保することができ、成形性が良く設備コストが嵩む虞もない。 The magnetic core powder produced according to the present invention has a low silicon content of 0.3 wt% to 1.0 wt% in the magnetic powder, so that the material hardness does not increase. Therefore, a high molding density can be ensured by using a normal press molding apparatus without using a special high pressure molding apparatus in the molding process, and there is no risk that the moldability is good and the equipment cost is increased.
さらに、本発明によって製造された磁心用粉末には、その粒子表面全体を覆う薄くて均一な二酸化珪素被膜が形成されており、鉄が露出した部分がない。このため、露出した鉄同士の接触による粒子間の焼結を防ぐことができる。その結果、歪除去熱処理工程では５００℃〜１０００℃という高温で処理することが可能となり、圧粉磁心の歪が十分に除去されるため、保磁力が低下し、ヒステリシス損失が低減される。 Furthermore, the magnetic core powder produced according to the present invention is formed with a thin and uniform silicon dioxide film covering the entire particle surface, and there is no portion where iron is exposed. For this reason, sintering between particles due to contact between exposed irons can be prevented. As a result, in the strain removal heat treatment step, the treatment can be performed at a high temperature of 500 ° C. to 1000 ° C., and the distortion of the dust core is sufficiently removed, so that the coercive force is lowered and the hysteresis loss is reduced.
（磁心用粉末の製造）
原料となる磁性粉末として、Ｆｅ―１重量％Ｓｉ粉末（大同特殊鋼社製水アトマイズ粉）、Ｆｅ―０．６重量％Ｓｉ粉末（エプソンアトミックス社製水アトマイズ粉）、及びＦｅ―０．３重量％Ｓｉ粉末（エプソンアトミックス社製水アトマイズ粉）を用意した。粒径は１５０μｍ以下とした。
(Manufacture of magnetic core powder)
As magnetic powders used as raw materials, Fe-1 wt% Si powder (water atomized powder manufactured by Daido Steel Co., Ltd.), Fe-0.6 wt% Si powder (water atomized powder manufactured by Epson Atomix Corporation), and Fe-0. A 3 wt% Si powder (water atomized powder manufactured by Epson Atmix Co., Ltd.) was prepared. The particle size was 150 μm or less.
室温にて、回転加熱炉内の真空排気と窒素置換とを計３回交互に行い、回転加熱炉内の空気を除いた後、水素と二酸化炭素とを所定のガス比率になるように調整し、水蒸気分圧（ＰＨ2Ｏ）の水素分圧（ＰＨ2）に対する分圧比Ｌｏｇ（ＰＨ2Ｏ/ＰＨ2）が−０．６２〜−４．３の範囲で磁心用粉末の製造を行った。ガスの比率は絶縁被膜（二酸化珪素被膜）形成に大きく影響するため、ガスの充填（置換）は、３０分間以上行うことが必要である。 At room temperature, evacuation and nitrogen replacement in the rotary heating furnace are alternately performed three times in total, and after removing the air in the rotary heating furnace, hydrogen and carbon dioxide are adjusted to a predetermined gas ratio. , water vapor partial pressure (PH 2 O) hydrogen partial pressure (PH 2) partial pressure ratio Log (PH 2 O / PH 2 ) is subjected to production of magnetic core powder in a range of -0.62～-4.3 . Since the ratio of the gas greatly affects the formation of the insulating coating (silicon dioxide coating), it is necessary to fill (replace) the gas for 30 minutes or more.
回転加熱炉内の温度を５℃/分で８５０℃〜１２００℃まで昇温し、所定温度になった回転加熱炉内に上記磁性粉末を投入した。磁性粉末同士が焼結せず、均一にガスと接触するよう回転加熱炉を８ｒｐｍ〜１２ｒｐｍで回転させて１５分間〜６０分間加熱処理を行った。 The temperature in the rotary heating furnace was raised to 850 ° C. to 1200 ° C. at 5 ° C./min, and the magnetic powder was put into the rotary heating furnace at a predetermined temperature. The rotary heating furnace was rotated at 8 rpm to 12 rpm and the heat treatment was performed for 15 minutes to 60 minutes so that the magnetic powders were not sintered and contacted uniformly with the gas.
上述のようにして、組成及び処理条件の異なる複数種の磁心用粉末を製造し、各磁心用粉末について、イオンミリングで断面を切り出し、組織観察と組成分析を行い、結晶粒径、内部酸化の有無、膜厚とその均一性、及び成分を調べた。その結果、外部酸化による膜厚１００ｎｍ程度の二酸化珪素（ＳｉＯ2）被膜の形成が確認された。 As described above, a plurality of types of magnetic core powders having different compositions and processing conditions are manufactured. For each magnetic core powder, a cross-section is cut out by ion milling, a structure observation and a composition analysis are performed. Existence, film thickness and uniformity thereof, and components were examined. As a result, formation of a silicon dioxide (SiO 2 ) film having a thickness of about 100 nm by external oxidation was confirmed.
（圧粉磁心の製造）
上述の各磁心用粉末に０．３重量％の潤滑剤（エチレンビスアマイド、大日化学工業社製ＢＡ−５００）を添加して混合した。
金型形状は、リング状（外径φ３５ｍｍ、内径φ２７ｍｍ、厚み約５ｍｍ）とし、金型を８０℃に加熱した後、前記混合粉末を金型内に充填し、７８４ＭＰａ〜１１７６ＭＰａ（８ｔ/ｃｍ2〜１２ｔ/ｃｍ2）で加圧成形を行い、成形体を得た。
得られた成形体を真空中にて５００℃〜１０００℃で焼鈍して、上記磁心用粉末に対応する複数の試験片を得た。各試験片について、密度、圧環強度、磁束密度、交流磁束鉄損を測定した。測定値を以下の表１に示す。尚、表１中の被膜の状態の欄における○印は、均一で良好な二酸化珪素（ＳｉＯ2）被膜が形成されたことを示し、×印は、形成された二酸化珪素（ＳｉＯ2）被膜が不均一（不良）であることを示す。また、試験片Ｎｏ．１８及びＮｏ.１９は、従来の製造方法で製造されたものである。
(Manufacture of dust core)
0.3% by weight of a lubricant (ethylene bisamide, BA-500 manufactured by Dainichi Chemical Industry Co., Ltd.) was added to and mixed with each of the above magnetic core powders.
Mold shape, a ring-shaped (outer diameter 35mm, inner diameter Fai27mm, thickness of about 5 mm), after heating the mold to 80 ° C., by filling the mixed powder into the mold, 784MPa~1176MPa (8t / cm 2 ˜12 t / cm 2 ) was subjected to pressure molding to obtain a molded body.
The obtained molded body was annealed at 500 ° C. to 1000 ° C. in a vacuum to obtain a plurality of test pieces corresponding to the magnetic core powder. About each test piece, the density, the crushing strength, the magnetic flux density, and the AC magnetic flux iron loss were measured. The measured values are shown in Table 1 below. In the column of the state of the coating in Table 1, the ◯ mark indicates that a uniform and good silicon dioxide (SiO 2 ) film was formed, and the X mark indicates that the formed silicon dioxide (SiO 2 ) film was Indicates non-uniformity (defective). In addition, test piece No. No. 18 and No. 19 are manufactured by a conventional manufacturing method.
図１には、上記表１の、試験片Ｎｏ.１〜１９に係る処理温度（℃）と分圧比（Ｌｏｇ（ＰＨ2Ｏ／ＰＨ2））をプロットしたものが示されている。図１中の各符号１〜１９のそれぞれは、上記表１中の各試験片の番号を示す。
図１中の破線で囲まれた範囲Ａが、磁性粉末の粒子表面全体を覆う薄くて均一な二酸化珪素（ＳｉＯ2）被膜が形成される処理温度（℃）と分圧比（Ｌｏｇ（ＰＨ2Ｏ／ＰＨ2））との範囲である。また、図１中の別の破線で囲まれた範囲Ｂは、磁性粉末の粒子内部における珪素酸化をより確実に抑えると共に、粒子表面における二酸化珪素被膜の形成をより一層促進させることができる処理温度（℃）と分圧比（Ｌｏｇ（ＰＨ2Ｏ／ＰＨ2））との範囲である。
FIG. 1 shows a plot of the processing temperature (° C.) and the partial pressure ratio (Log (PH 2 O / PH 2 )) according to test pieces No. 1 to 19 in Table 1 above. Each code | symbol 1-19 in FIG. 1 shows the number of each test piece in the said Table 1. FIG.
A range A surrounded by a broken line in FIG. 1 is a processing temperature (° C.) and a partial pressure ratio (Log (PH 2 O) at which a thin and uniform silicon dioxide (SiO 2 ) film covering the entire particle surface of the magnetic powder is formed. / PH 2 )). Further, a range B surrounded by another broken line in FIG. 1 is a treatment temperature capable of more reliably suppressing silicon oxidation inside the magnetic powder particles and further promoting the formation of a silicon dioxide film on the particle surface. (° C.) and the partial pressure ratio (Log (PH 2 O / PH 2 )).
以上説明したように、本発明は、圧粉磁心の材料となる磁心用粉末を製造する際に有用であり、珪素含有量の少ない磁性粉末において、その粒子の表面全体を覆う薄くて均一な二酸化珪素被膜を短時間で形成させる場合に適している。 As described above, the present invention is useful in producing a magnetic core powder as a material for a dust core, and in a magnetic powder with a low silicon content, a thin and uniform dioxide dioxide covering the entire surface of the particles. It is suitable for forming a silicon film in a short time.
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