JP2008143720A - Magnetite-iron composite powder, its manufacturing method and dust core - Google Patents
Magnetite-iron composite powder, its manufacturing method and dust core Download PDFInfo
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本発明は、高周波で用いられるインダクタ素子用の磁芯材料として用いられる高性能な鉄粉系の磁性材料であるマグネタイト−鉄複合粉末と、その製造方法およびこれを用いた圧粉磁芯に関するものである。 The present invention relates to a magnetite-iron composite powder that is a high-performance iron powder-based magnetic material used as a magnetic core material for inductor elements used at high frequencies, a method for producing the same, and a dust core using the same. It is.
近年、パソコンのＣＰＵ処理速度の高速化が目覚しく、これに伴い、供給電源の大電流化が急速に進んでいる。 In recent years, the CPU processing speed of a personal computer has been remarkably increased, and accordingly, the supply current of the power supply has been increased rapidly.
従来、ＣＰＵ駆動用のパワーインダクタにはフェライトコアが用いられていたが、フェライトの飽和磁束密度Ｂｓは０．３〜０．５Ｔと低いため、大電流印加時に磁気飽和状態に陥り易く、大電流化に対応することが困難である。これに対し、鉄粉を用いたダストコアはＢｓが０．８Ｔ程度あり、大電流印加時でも磁気飽和を起こさず、大電流化に対応可能である。 Conventionally, a ferrite core has been used as a power inductor for driving a CPU. However, since the saturation magnetic flux density Bs of ferrite is as low as 0.3 to 0.5 T, it easily falls into a magnetic saturation state when a large current is applied. It is difficult to cope with On the other hand, the dust core using iron powder has Bs of about 0.8 T, and does not cause magnetic saturation even when a large current is applied, and can cope with a large current.
しかし、鉄粉を用いたダストコアは、圧粉体とした時の電気抵抗が低いため、部品としての安全性に問題がある。また、フェライトコアに比べてコアロスが高いため、磁芯が発熱し易い。さらに、酸化物であるフェライトコアが変質し難いのに対して、純鉄系のダストコアは錆び易いという欠点がある。
上記のような問題に対して、本発明者らは、近年のＣＰＵ駆動電源の大電流化に対応するためには、Ｂｓの高い鉄粉系の磁性粉を用いて、高周波での磁気損失を低減するために鉄粉の粒子径をより微細にすることが有利との知見を得ている。このような知見のもとに、本発明者らは、特願２００５−３４５３７０、特願２００６−８９００５、特願２００６−２１２２２９および上記特許文献１において、平均一次粒径が０．７〜５μｍのマグネタイト−鉄複合粉末を圧粉磁芯用として使用する技術について出願を行った。 In order to cope with the recent increase in current of CPU drive power supply, the present inventors have used magnetic powder of high Bs iron powder to reduce magnetic loss at high frequency. It has been found that it is advantageous to make the particle size of the iron powder finer in order to reduce it. Based on such knowledge, the present inventors in Japanese Patent Application No. 2005-345370, Japanese Patent Application No. 2006-89005, Japanese Patent Application No. 2006-212229, and Patent Document 1 described above have an average primary particle size of 0.7 to 5 μm. An application was filed for a technique of using magnetite-iron composite powder for a dust core.
上記の発明によれば、飽和磁束密度の高い鉄系の圧粉磁芯で電気抵抗を高めることができるため、高い周波数で用いても渦電流損失を抑制することができ、高い安全性と低いコアロスを併せ持つ圧粉磁芯を得ることができる。 According to the above invention, since the electric resistance can be increased with the iron-based dust core having a high saturation magnetic flux density, eddy current loss can be suppressed even when used at a high frequency, and the safety is low. A dust core having both core losses can be obtained.
しかし、ノートパソコンのさらなる小型化、省電力化を図るために、パワーインダクタのさらなる高性能化の要求は依然として強く、より高い絶縁性と耐食性、かつ、より低いコアロスを兼ね備えた圧粉磁芯が求められている。 However, in order to further reduce the size and power consumption of notebook PCs, there is still a strong demand for higher performance of power inductors, and a dust core with higher insulation and corrosion resistance and lower core loss is required. It has been demanded.
一方、特許文献２には、Ｎｉを含有するマグネタイト−鉄複合粉末が開示さている。このマグネタイト−鉄複合粉末のＮｉ含有量は、５０質量％以下、好ましくは５〜１０質量％と記載されている。このように、Ｎｉの含有量が多いと、飽和磁束密度が低下する。 On the other hand, Patent Document 2 discloses a magnetite-iron composite powder containing Ni. The Ni content of this magnetite-iron composite powder is 50% by mass or less, preferably 5-10% by mass. Thus, when there is much content of Ni, a saturation magnetic flux density will fall.
また、特許文献３には、粒径が１５０μｍ以下、好ましくは１０〜１００μｍ程度の強磁性金属粉末と無機絶縁物、有機絶縁物との混合物に対して強力な圧縮・剪断作用を機械的に反復負荷する処理を施す技術が開示されている。この強磁性金属粉末は粒径が大きいため、高周波数での磁気特性が低下する。 In Patent Document 3, a powerful compression / shearing action is mechanically repeated for a mixture of a ferromagnetic metal powder having a particle size of 150 μm or less, preferably about 10 to 100 μm, and an inorganic insulator or organic insulator. A technique for performing processing to load is disclosed. Since this ferromagnetic metal powder has a large particle size, the magnetic properties at high frequencies are reduced.
本発明はこのような事情のもとになされたものであり、飽和磁束密度の高い鉄系の粉末を用いて、高い絶縁性および低いコアロスと高い耐食性を兼ね備えた高性能な圧粉磁芯を提供すること、および、これを実現するために好適な金属粉末であるマグネタイト−鉄複合粉末およびその製造方法を提供することを目的とする。 The present invention has been made under such circumstances, and by using an iron-based powder having a high saturation magnetic flux density, a high-performance dust core having high insulation, low core loss and high corrosion resistance is obtained. An object of the present invention is to provide a magnetite-iron composite powder, which is a metal powder suitable for realizing this, and a method for producing the same.
圧粉磁芯の絶縁性および耐食性を高める手段として、本発明者らはマグネタイト−鉄複合粉末の粒子表面を絶縁性の高いタルクを含有する粒子で被覆することを試み、タルクを用いることで圧粉磁芯の絶縁性および耐食性が改善し、同時にコアロスが低減することを見出した。 As means for improving the insulation and corrosion resistance of the dust core, the present inventors tried to coat the particle surface of the magnetite-iron composite powder with particles containing highly insulating talc, and by using talc, It has been found that the insulation and corrosion resistance of the magnetic powder core are improved and at the same time the core loss is reduced.
本発明は、上記の知見に基づきなされたもので以下のような特徴を有する。
［１］平均一次粒径が０．７〜５．０μｍであり、粒子表面に、０．０１〜５mass％のタルクが付着し、Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上を合計で０．０１mass％以上、５mass％未満ならびにマグネタイトを含有することを特徴とするマグネタイト−鉄複合粉末。
［２］上記［１］において、マグネタイト−鉄複合粉末が、圧粉磁芯用であることを特徴とするマグネタイト−鉄複合粉末。
［３］Ｃｏ、Ｎｉ、Ｃｒ、Ｂ及びＶの中から選ばれる１種または２種以上を含有する酸化鉄を還元性雰囲気下で還元した後、さらに、酸化性雰囲気下で酸化処理を行い、マグネタイトを生成させた粉末と、タルクとを衝突させて、前記粉末の粒子表面にタルクを付着させることを特徴とするマグネタイト−鉄複合粉末の製造方法。
［４］上記［３］において、マグネタイト−鉄複合粉末が、上記［１］に記載のマグネタイト−鉄複合粉末であることを特徴とする請求項３に記載のマグネタイト−鉄複合粉末の製造方法。
［５］上記［３］または［４］において、粉末とタルクとの衝突を、それぞれの粒子同士の相対速度が５０ｍ／ｓｅｃ以上となる速度で行うことを特徴とするマグネタイト−鉄複合粉末の製造方法。
［６］上記［１］に記載のマグネタイト−鉄複合粉末と、樹脂および／または無機絶縁材料とを含有することを特徴とする圧粉磁芯。
The present invention has been made based on the above findings and has the following characteristics.
[1] One type selected from Co, Ni, Cr, B, and V having an average primary particle size of 0.7 to 5.0 μm, 0.01 to 5 mass% of talc adhered to the particle surface Alternatively, a magnetite-iron composite powder characterized by containing two or more in total of 0.01 mass% or more and less than 5 mass% and magnetite.
[2] The magnetite-iron composite powder according to [1], wherein the magnetite-iron composite powder is for a dust core.
[3] After reducing iron oxide containing one or more selected from Co, Ni, Cr, B, and V under a reducing atmosphere, an oxidation treatment is further performed under an oxidizing atmosphere, A method for producing a magnetite-iron composite powder, characterized in that magnetite-produced powder and talc are collided to attach talc to the particle surface of the powder.
[4] The method for producing a magnetite-iron composite powder according to [3], wherein the magnetite-iron composite powder is the magnetite-iron composite powder according to [1].
[5] Production of magnetite-iron composite powder characterized in that in [3] or [4], the collision between the powder and talc is carried out at a speed at which the relative speed between the respective particles is 50 m / sec or more. Method.
[6] A dust core comprising the magnetite-iron composite powder according to [1] above and a resin and / or an inorganic insulating material.
本発明によれば、飽和磁束密度の高い鉄系の圧粉磁芯で、１ＭΩｃｍ以上の高い比抵抗と、５０ｋＨｚ，１００ｍＴの条件下で１０００ｋＷ／ｍ３以下の低いコアロス、従来のダストコアに比べて優れた耐食性を併せ持つ圧粉磁芯、および、このような圧粉磁芯を得るのに好適なマグネタイト−鉄複合粉末およびその製造方法が提供される。 According to the present invention, an iron-based dust core with a high saturation magnetic flux density, a high specific resistance of 1 MΩcm or more, a low core loss of 1000 kW / m 3 or less under the conditions of 50 kHz and 100 mT, compared to a conventional dust core Provided are a dust core having excellent corrosion resistance, a magnetite-iron composite powder suitable for obtaining such a dust core, and a method for producing the same.
以下、本発明を実施するための最良の形態の一例を説明する。 Hereinafter, an example of the best mode for carrying out the present invention will be described.
まず、本発明のマグネタイト−鉄複合粉末は、平均一次粒径が０．７〜５．０μｍ、より好ましくは０．８〜３．０μｍの範囲内で良好な高周波磁気特性を示す。平均一次粒径が０．７μｍ未満では単磁区構造をとる粒子の頻度が高くなるため、粒子の保持力が著しく増大して圧粉磁芯のコアロスが劣化する。平均一次粒径が５．０μｍを超える範囲では、渦電流や磁壁共鳴などの影響を受けるため、高周波域での磁気特性が低下する。なお、前記平均一次粒径は、ＳＥＭ写真を解析して得た値である。視野の対角線上に１０〜２０個程度の粒子が入るような倍率でＳＥＭ写真を撮影し、対角線上の粒子の個数と倍率から、平均一次粒径を算出した。すなわち、平均一次粒径は、対角線の写真上の長さ（対角線の実際の長さを写真の倍率で除したもの）を、該対角線を横切る粒子数で除した値である。 First, the magnetite-iron composite powder of the present invention exhibits good high-frequency magnetic properties when the average primary particle size is in the range of 0.7 to 5.0 μm, more preferably 0.8 to 3.0 μm. When the average primary particle size is less than 0.7 μm, the frequency of particles having a single magnetic domain structure increases, so that the retention force of the particles is remarkably increased and the core loss of the dust core is deteriorated. In the range where the average primary particle size exceeds 5.0 μm, it is affected by eddy currents, domain wall resonance, and the like, so that the magnetic characteristics in the high frequency range are degraded. The average primary particle size is a value obtained by analyzing an SEM photograph. SEM photographs were taken at a magnification such that about 10 to 20 particles were placed on the diagonal of the visual field, and the average primary particle size was calculated from the number and magnification of the particles on the diagonal. That is, the average primary particle diameter is a value obtained by dividing the length of the diagonal line on the photograph (the actual length of the diagonal line divided by the magnification of the photograph) by the number of particles crossing the diagonal line.
また、本発明のマグネタイト−鉄複合粉末は、Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上の合計の含有量が０．０１mass％以上、５mass％未満、好ましくは０．１〜３mass％であることが重要である。Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上の合計の含有量が０．０１mass％未満では、絶縁性及びコアロスを改善する効果が小さいため好ましくない。また、Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上の合計の含有量が５mass％以上の場合、却って絶縁性が低下し、また、コアロスが劣化するため、好ましくない。Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶそれぞれの好ましい含有量は、Ｃｏ：０．０１mass％以上、５mass％未満、Ｎｉ：０．０１mass％以上、５mass％未満、Ｃｒ：０．０１mass％以上、５mass％未満、Ｂ：０．０１mass％以上、５mass％未満、Ｖ：０．０１mass％以上、５mass％未満である。 The magnetite-iron composite powder of the present invention has a total content of one or more selected from Co, Ni, Cr, B and V of 0.01 mass% or more and less than 5 mass%, preferably It is important that it is 0.1-3 mass%. If the total content of one or more selected from Co, Ni, Cr, B and V is less than 0.01 mass%, the effect of improving insulation and core loss is small, which is not preferable. In addition, when the total content of one or more selected from Co, Ni, Cr, B and V is 5 mass% or more, the insulation is lowered and the core loss is deteriorated. Absent. The preferable contents of each of Co, Ni, Cr, B and V are Co: 0.01 mass% or more and less than 5 mass%, Ni: 0.01 mass% or more and less than 5 mass%, Cr: 0.01 mass% or more, 5 mass% Less than, B: 0.01 mass% or more and less than 5 mass%, V: 0.01 mass% or more and less than 5 mass%.
また、本発明のマグネタイト−鉄複合粉末は、マグネタイトの含有量が多すぎると飽和磁束密度が低下する。また、マグネタイトの含有量が少なすぎると、酸化鉄を還元した後、還元炉から取り出す際に燃え易く、危険である。そのため、マグネタイトの好ましい含有量は、０．３mass％程度以下である。 In addition, when the magnetite-iron composite powder of the present invention has an excessive magnetite content, the saturation magnetic flux density decreases. On the other hand, if the content of magnetite is too small, after iron oxide is reduced, it tends to burn when taken out from the reduction furnace, which is dangerous. Therefore, the preferable content of magnetite is about 0.3 mass% or less.
ここで、前記本発明のマグネタイト−鉄複合粉末は、製造後のマグネタイト−鉄複合粉末中の合計の含有量が０．０１mass％以上、５mass％未満となる量のＣｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上を含有する酸化鉄を出発原料として用い、これを水素或いは窒素などの還元性雰囲気中で還元処理し、さらに、酸素濃度１〜１０vol.％の酸化性雰囲気中で表面を酸化処理（マグネタイト生成）して安定化した後に、炉より取り出すことで製造することができる。 Here, the magnetite-iron composite powder of the present invention has a total content in the magnetite-iron composite powder after production of 0.01 mass% or more and less than 5 mass% of Co, Ni, Cr, B and Using iron oxide containing one or more selected from V as a starting material, this is reduced in a reducing atmosphere such as hydrogen or nitrogen, and further oxidized with an oxygen concentration of 1 to 10 vol.%. It can be manufactured by removing from the furnace after stabilizing the surface by oxidizing (generating magnetite) in an acidic atmosphere.
前記原料である酸化鉄中にＣｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上を含有することで圧粉磁芯の電磁気特性が改善する機構については明らかではないが、還元処理過程で酸化鉄（ヘマタイト）が鉄（α-Ｆｅ）に還元する際にこれらの成分が存在すると粒子形状が丸みを帯び、かつ、粒度分布が均一化する傾向があることから、粒子表面の平滑化効果が得られること、また、これらの成分が還元処理過程で粒子の表面に濃化し表面絶縁層を形成して粒子の絶縁性を改善することなどによる可能性が考えられる。従って、本発明では、酸化鉄の還元処理過程で原料中にＣｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上の成分が存在することが重要であり、還元後の鉄粉に後からこれらの成分を添加する方法では本発明で得られるような電気抵抗増大効果およびコアロス改善効果を得ることはできない。 Although it is not clear about the mechanism of improving the electromagnetic characteristics of the dust core by containing one or more selected from Co, Ni, Cr, B and V in the iron oxide as the raw material. When these components are present when iron oxide (hematite) is reduced to iron (α-Fe) during the reduction process, the particle shape tends to be rounded and the particle size distribution tends to be uniform. There is a possibility that a surface smoothing effect can be obtained, and that these components are concentrated on the surface of the particles during the reduction treatment to form a surface insulating layer to improve the insulating properties of the particles. Therefore, in the present invention, it is important that one or more components selected from Co, Ni, Cr, B, and V are present in the raw material during the iron oxide reduction treatment process. The method of adding these components to iron powder later cannot obtain the effect of increasing electrical resistance and the effect of improving core loss as obtained in the present invention.
さらに、本発明のマグネタイト−鉄複合粉末は、上記の酸化処理工程の後に、タルクを添加して、酸化処理で得られた粉末とタルクとを、好ましくは、それぞれの粒子同士の相対速度が５０ｍ／ｓｅｃ以上の高速で衝突させて粒子表面を平滑にすると同時に、粒子表面にタルクを付着させ、固定化して被覆層を形成する。これにより、圧粉磁芯の電気抵抗がより増大し、コアロスがより低減し、耐食性が向上するからである。 Furthermore, in the magnetite-iron composite powder of the present invention, talc is added after the above-mentioned oxidation treatment step, and the powder and talc obtained by the oxidation treatment preferably have a relative velocity of each particle of 50 m. The particle surface is smoothed by colliding at a high speed of / sec or more, and at the same time, talc is adhered to the particle surface and fixed to form a coating layer. This is because the electric resistance of the dust core is further increased, the core loss is further reduced, and the corrosion resistance is improved.
この平滑化処理により圧粉磁芯の電気抵抗が増大する理由は、衝突により粒子表面の突起が消滅することで圧粉体における粒子同士の接触頻度が低減し、粒子間の絶縁性が向上するためと考えられる。また、コアロスが低減する理由は、衝突により粒子表面の突起が消失したことと、粒子表面に潤滑性の良いタルクの層が形成されたことで成形歪が軽減し、ヒステリシス損失が低減するためと考えられる。また、耐食性が向上する理由は、無機質のタルクの層によって金属粒子が被覆されたことに伴う防錆効果によるものと考えられる。 The reason why the electrical resistance of the powder magnetic core is increased by this smoothing treatment is that the protrusions on the particle surface disappear due to the collision, thereby reducing the contact frequency between particles in the powder compact and improving the insulation between the particles. This is probably because of this. The core loss is reduced because the protrusion on the particle surface disappears due to the collision, and the formation of a talc layer with good lubricity on the particle surface reduces the molding strain and reduces the hysteresis loss. Conceivable. The reason why the corrosion resistance is improved is considered to be due to the rust-preventing effect accompanying the coating of the metal particles with the inorganic talc layer.
それぞれの粒子同士の衝突の際における相対速度が小さすぎると、衝突による衝撃力が小さいために平滑化効果が不十分であり、十分な電気抵抗増大効果を得ることができない。また、衝撃力が小さすぎると、タルクを粒子表面に薄く均一に付着させ、固定化することができないため、耐食性の改善効果が得られない。そのため、好ましい相対速度は、５０ｍ／ｓｅｃ以上である。 If the relative velocity at the time of collision between the respective particles is too small, the impact force due to the collision is small, so that the smoothing effect is insufficient and a sufficient electric resistance increasing effect cannot be obtained. On the other hand, if the impact force is too small, talc cannot be thinly and evenly adhered to the particle surface and cannot be fixed, so that the effect of improving corrosion resistance cannot be obtained. Therefore, a preferable relative speed is 50 m / sec or more.
高速で粒子同士を衝突させる手段としては、例えば、（株）奈良機械製作所製のハイブリダイザーシステムなどのような機械的表面改質装置を用いることができる。ただし、同様の効果が得られる手段であれば、これに限定されるものではない。なお、本発明の方法では、耐食性を改善するためにタルクを粒子表面に薄く均一に付着させ、固定化することが特に重要であり、平滑化処理を施した後のマグネタイト−鉄複合粉末（タルク被覆なし）に、後からタルクを添加、混合して、圧粉磁芯を作製しても、耐食性を改善する効果は得られない。 As means for causing particles to collide with each other at high speed, for example, a mechanical surface reformer such as a hybridizer system manufactured by Nara Machinery Co., Ltd. can be used. However, it is not limited to this as long as the same effect can be obtained. In the method of the present invention, in order to improve corrosion resistance, it is particularly important that talc is thinly and uniformly attached to the particle surface and fixed, and the magnetite-iron composite powder (talc) after smoothing treatment is applied. Even if talc is added and mixed later without coating), an effect of improving the corrosion resistance cannot be obtained.
製造後のマグネタイト−鉄複合粉末中におけるタルク添加量が０．０１mass％未満では、タルクによる金属粒子の被覆効果が不十分であり、絶縁性、コアロス、耐食性を改善する効果がほとんど得られない。また、タルク添加量が、５mass％を超えると、非磁性成分が多くなるため飽和磁束密度が低下し、また、コアロスが劣化するため好ましくない。より好ましいタルクの添加量は０．１〜２mass％である。 When the amount of talc added in the magnetite-iron composite powder after production is less than 0.01 mass%, the effect of covering the metal particles with talc is insufficient, and the effect of improving insulation, core loss, and corrosion resistance is hardly obtained. On the other hand, if the amount of talc added exceeds 5 mass%, the nonmagnetic component increases, so that the saturation magnetic flux density decreases and the core loss deteriorates, which is not preferable. A more preferable amount of talc added is 0.1 to 2 mass%.
なお、タルクに替えてステアリン酸亜鉛やステアリン酸リチウムを用いることができるが、これらを用いた場合、圧粉磁芯の製造直後の磁気特性はタルクを用いた場合と同等であるが、数週間、大気中に放置すると、粒子が固く凝集して磁気特性が低下してしまう場合がある。また、タルクに替えて、アルミナ、シリカを用いることもできる。 In addition, zinc stearate or lithium stearate can be used instead of talc, but when these are used, the magnetic properties immediately after production of the dust core are the same as when talc is used, but for several weeks If left in the atmosphere, the particles may aggregate tightly and the magnetic properties may deteriorate. Further, alumina or silica can be used instead of talc.
以上のような方法で、本発明の圧粉磁芯用マグネタイト−鉄複合粉末を得ることができる。 By the method as described above, the magnetite-iron composite powder for dust core of the present invention can be obtained.
次に、上述の本発明に係るマグネタイト−鉄複合粉末と、樹脂および／または無機絶縁材料とを混合した後、圧縮成形し、必要に応じて樹脂の熱硬化処理を施すことで、１ＭΩｃｍ以上の高い絶縁性と、５０ｋＨｚ，１００ｍＴで１０００ｋＷ/ｍ３以下の低いコアロスと、従来のダストコアより優れた耐食性を示す圧粉磁芯を得ることができる。 Next, after mixing the magnetite-iron composite powder according to the present invention and a resin and / or an inorganic insulating material, compression molding is performed, and if necessary, a thermosetting treatment of the resin is performed, so that it is 1 MΩcm or more. It is possible to obtain a dust core having high insulation properties, a low core loss of 1000 kW / m 3 or less at 50 kHz and 100 mT, and a corrosion resistance superior to that of a conventional dust core.
ここで、前記樹脂は、結合用として用いられるが、その種類としては、例えば、フェノール樹脂、アクリル樹脂、シリコーン樹脂、エポキシ樹脂等を用いることができる。 Here, although the said resin is used for a coupling | bonding, as the kind, a phenol resin, an acrylic resin, a silicone resin, an epoxy resin etc. can be used, for example.
また、前記無機絶縁材料としては、絶縁性粉末、例えば、ＳｉＯ２、Ａｌ２Ｏ３等の微粉末を用いることができる。 Further, as the inorganic insulating material, insulating powder, for example, fine powder such as SiO 2 and Al 2 O 3 can be used.
また、前記圧縮成形は、その方法は特に限定されず、通常用いられる圧縮成形の他、温間圧縮成形、射出成形等の成形方法を用いることができる。 The compression molding method is not particularly limited, and a molding method such as warm compression molding, injection molding, or the like can be used in addition to compression molding that is usually used.
以下に本発明の具体的実施例を記載する。 Specific examples of the present invention will be described below.
［実施例１］
フェライト用酸化鉄（ＪＦＥケミカル社製ＪＣ−ＤＣ、空気透過法により測定した平均粒径０．８μｍ）に対し、酸化コバルト（ＣｏＯ）を添加し、純水とスチールボールを用いてボールミルで湿式混合した後、乾燥、整粒してＣｏ含有酸化鉄を作製した。これを水素雰囲気中５００〜８００℃の温度で還元処理して、平均一次粒径の異なる種々の鉄粉を得た。その後、炉を開放する前に５vol.％Ｏ２−Ｎ２雰囲気で保持することにより、鉄粉の表層にマグネタイトを生成させてから炉外に取り出した。得られた鉄粉に、表１に示す種々の量のタルクを添加し（Ｎｏ.７以外）、機械的表面改質装置（（株）奈良機械製作所製のハイブリダイザーシステム）を用いて、粒子同士を、相対速度８０ｍ／ｓｅｃで衝突させて粒子表面の平滑化および粒子表面へのタルクの固定化処理を施した。Ｎｏ．７のみ、タルクを添加せずに平滑化処理を施した後、タルクを添加した。
[Example 1]
Cobalt oxide (CoO) is added to iron oxide for ferrite (JC-DC manufactured by JFE Chemical Co., Ltd., average particle diameter of 0.8 μm measured by air permeation method), and wet-mixed in a ball mill using pure water and steel balls Then, it was dried and sized to prepare a Co-containing iron oxide. This was reduced at a temperature of 500 to 800 ° C. in a hydrogen atmosphere to obtain various iron powders having different average primary particle sizes. Then, before opening the furnace, it was held in a 5 vol.% O 2 —N 2 atmosphere to generate magnetite on the surface layer of the iron powder and then taken out of the furnace. To the obtained iron powder, various amounts of talc shown in Table 1 were added (other than No. 7), and particles were obtained using a mechanical surface reformer (hybridizer system manufactured by Nara Machinery Co., Ltd.). The particles were collided with each other at a relative speed of 80 m / sec to smooth the particle surface and fix talc on the particle surface. No. Only talc was added after carrying out the smoothing process without adding talc only to 7.
得られた前記粉末の構成相をＸ線回折で調べた結果、全試料とも、マグネタイト相は、０．３mass％以下であった。ＳＥＭ写真より算出した平均一次粒径を表１に示す。 As a result of examining the constituent phases of the obtained powder by X-ray diffraction, the magnetite phase of all the samples was 0.3 mass% or less. Table 1 shows the average primary particle size calculated from the SEM photograph.
引き続き、マグネタイト−鉄複合粉末に対して５mass％のフェノール樹脂を混合し、成形圧力７ｔ／ｃｍ２（６８６ＭＰａ）で圧縮成形して、外径１２ｍｍφのリング型試料を作製し、１５０℃×３０分の熱処理を施してフェノール樹脂を硬化させた。得られたリング型試料の両端をワニ口クリップで挟み、印加電圧１０Ｖで電気抵抗を測定し、試料寸法を用いて比抵抗を算出した。コアロスは交流ＢＨアナライザーを用いて、周波数５０ｋＨｚ，励磁条件１００ｍＴの条件下で測定した。耐食性については、５mass％食塩水に試料の半分の高さまでを浸漬した時の溶解状況を観察した。浸漬してから１時間以内に溶解が観察された場合は「×」、２４時間以内に溶解が観察された場合は「△」、２４時間時点で溶解しない場合は「○」とした。 Subsequently, 5 mass% phenol resin was mixed with the magnetite-iron composite powder, compression molding was performed at a molding pressure of 7 t / cm 2 (686 MPa), and a ring-shaped sample having an outer diameter of 12 mmφ was prepared, and 150 ° C. × 30 minutes. The phenol resin was cured by the heat treatment. Both ends of the obtained ring-shaped sample were sandwiched between alligator clips, the electrical resistance was measured at an applied voltage of 10 V, and the specific resistance was calculated using the sample dimensions. The core loss was measured using an AC BH analyzer under the conditions of a frequency of 50 kHz and an excitation condition of 100 mT. About corrosion resistance, the dissolution condition when the half height of a sample was immersed in 5 mass% salt solution was observed. When dissolution was observed within 1 hour after immersion, it was indicated as “x”, when dissolution was observed within 24 hours, “Δ”, and when dissolution was not observed at 24 hours, “◯”.
本発明例および比較例の比抵抗、コアロス、耐食性の評価結果を表１に併せて示す。表１に示すように、本発明に係る範囲のマグネタイト−鉄複合粉末を用いることにより、１ＭΩｃｍ以上の高い比抵抗、１０００ｋＷ／ｍ３以下の低いコアロス、良好な耐食性を同時に満足することができる。 The evaluation results of specific resistance, core loss, and corrosion resistance of the inventive examples and comparative examples are also shown in Table 1. As shown in Table 1, by using the magnetite-iron composite powder in the range according to the present invention, a high specific resistance of 1 MΩcm or more, a low core loss of 1000 kW / m 3 or less, and good corrosion resistance can be satisfied at the same time.
[実施例２]
フェライト用酸化鉄（ＪＦＥケミカル社製ＪＣ−ＤＣ）に対し、Ｃｏ、Ｎｉ、Ｃｒ、Ｂ、Ｖの酸化物を添加し、純水とスチールボールを用いてボールミルで湿式混合した後、乾燥、整粒してＣｏ、Ｎｉ、Ｃｒ、Ｂ、Ｖを含有する酸化鉄を作製した。これを水素雰囲気中５７５℃の温度で還元処理して、Ｃｏ、Ｎｉ、Ｃｒ、Ｂ、Ｖ含有量の異なる種々の鉄粉を得た。その後、炉を開放する前に３vol.％Ｏ２−Ｎ２雰囲気で保持することにより、鉄粉の表層にマグネタイトを生成させてから炉外に取り出し、表２に示す種々のマグネタイト−鉄複合粉末を得た。さらに、このマグネタイト−鉄複合粉末に対して、タルクを０.５mass％添加した後、機械的表面改質装置（（株）奈良機械製作所製のハイブリダイザーシステム）を用いて、粒子同士を、相対速度８０ｍ／ｓｅｃで衝突させて粒子表面の平滑化処理を施した。
[Example 2]
Co, Ni, Cr, B, and V oxides are added to iron oxide for ferrite (JC-DC manufactured by JFE Chemical Co., Ltd.), wet-mixed in a ball mill using pure water and steel balls, and then dried and conditioned. The iron oxide containing Co, Ni, Cr, B, and V was produced by granulating. This was reduced at a temperature of 575 ° C. in a hydrogen atmosphere to obtain various iron powders having different contents of Co, Ni, Cr, B, and V. Thereafter, by holding in a 3 vol.% O 2 —N 2 atmosphere before opening the furnace, magnetite is generated on the surface layer of the iron powder and then taken out of the furnace, and various magnetite-iron composite powders shown in Table 2 are obtained. Got. Furthermore, after adding 0.5 mass% of talc to the magnetite-iron composite powder, the particles were compared with each other using a mechanical surface reformer (hybridizer system manufactured by Nara Machinery Co., Ltd.). The particle surface was smoothed by colliding at a speed of 80 m / sec.
得られた前記粉末の平均粒径（ＳＥＭ写真より算出した平均一次粒径）は１〜３μｍの範囲であった。また、マグネタイトの含有量は、Ｘ線回折で調べた結果、０．３mass％以下であった。 The average particle size (average primary particle size calculated from the SEM photograph) of the obtained powder was in the range of 1 to 3 μm. Moreover, as a result of investigating by X-ray diffraction, content of magnetite was 0.3 mass% or less.
引き続き、マグネタイト−鉄複合粉末に対して３mass％のフェノール樹脂を混合し、成形圧力７ｔ／ｃｍ２（６８６ＭＰａ）で圧縮成形して、外径１２ｍｍφのリング型試料を作製し、１５０℃×３０分の熱処理を施してフェノール樹脂を硬化させた。得られたリング型試料に対して、実施例１と同様に方法で、比抵抗、コアロス、耐食性を測定した。 Subsequently, 3 mass% phenol resin was mixed with the magnetite-iron composite powder and compression molded at a molding pressure of 7 t / cm 2 (686 MPa) to produce a ring-shaped sample having an outer diameter of 12 mmφ, 150 ° C. × 30 minutes. The phenol resin was cured by the heat treatment. The specific resistance, core loss, and corrosion resistance of the obtained ring-type sample were measured in the same manner as in Example 1.
本発明例および比較例の比抵抗、コアロス、耐食性の評価結果を表２に併せて示す。表２に示すように、本発明に係る範囲のマグネタイト−鉄複合粉末を用いることにより、１ＭΩｃｍ以上の高い比抵抗、低いコアロス、優れた耐食性を同時に満足することができる。 Table 2 shows the evaluation results of specific resistance, core loss, and corrosion resistance of the inventive examples and comparative examples. As shown in Table 2, by using the magnetite-iron composite powder in the range according to the present invention, a high specific resistance of 1 MΩcm or more, a low core loss, and excellent corrosion resistance can be satisfied at the same time.
以上の実施例１，２で示した通り、本発明に係るマグネタイト−鉄複合粉末を用いることで、飽和磁束密度の高い金属系の圧粉磁芯で、高い絶縁性と低いコアロス、優れた耐食性を同時に満足することができ、本発明の効果が確認できた。 As shown in Examples 1 and 2 above, by using the magnetite-iron composite powder according to the present invention, it is a metal-based dust core having a high saturation magnetic flux density, high insulation, low core loss, and excellent corrosion resistance. At the same time, the effect of the present invention was confirmed.
Claims (6)
粒子表面に、０．０１〜５mass％のタルクが付着し、
Ｃｏ、Ｎｉ、Ｃｒ、ＢおよびＶの中から選ばれる１種または２種以上を合計で０．０１mass％以上、５mass％未満ならびにマグネタイトを含有することを特徴とするマグネタイト−鉄複合粉末。 The average primary particle size is 0.7 to 5.0 μm,
0.01-5 mass% talc adheres to the particle surface,
A magnetite-iron composite powder characterized by containing one or more selected from Co, Ni, Cr, B and V in a total of 0.01 mass% to less than 5 mass% and magnetite.
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