JP2006183121A - Iron based powder for powder magnetic core and powder magnetic core using the same - Google Patents
Iron based powder for powder magnetic core and powder magnetic core using the same Download PDFInfo
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本発明は、モーターやトランスの磁芯用として好適な軟磁気特性に優れた鉄を主成分とする粉末（鉄基粉末）に係り、とくにSi含有鉄基粉末（Fe-Si系合金粉末）の圧縮性の向上に関する。 The present invention relates to iron-based powders (iron-based powders) excellent in soft magnetic properties suitable for use in motor and transformer magnetic cores, and in particular, Si-containing iron-based powders (Fe-Si alloy powders). It relates to the improvement of compressibility.
モーターやトランスの磁芯には、大きなエネルギーの伝達を可能ならしめるため、高い磁束密度を持ち、かつ損失が小さいことが求められる。
従来、モーターやトランスの磁芯には、表面を電気絶縁処理した電磁鋼板を何層にも積層したものが用いられてきた。しかし、積層した電磁鋼板を磁芯として用いた場合には、つぎのような問題がある。
The magnetic core of a motor or transformer is required to have a high magnetic flux density and low loss in order to enable large energy transmission.
Conventionally, the magnetic cores of motors and transformers have been made by laminating multiple layers of electrical steel sheets whose surfaces are electrically insulated. However, when laminated magnetic steel sheets are used as magnetic cores, there are the following problems.
まず、第一には、平板である電磁鋼板から打ち抜き、積層して磁芯を成形するため、材料歩留が低く、コスト増に繋がり経済的に不利となるという問題がある。また第二には、磁気回路を磁束が積層面に沿う二元的な回路として設計しなければならないため、必ずしも機器の効率やサイズを最適に設計できないという問題がある。
このような問題に対して、圧粉磁芯を利用することが提案されている。圧粉磁芯は、純鉄粉等の磁性粉末に樹脂などの絶縁剤兼バインダを適宜添加し、攪拌・混合し加圧成形することにより所定形状に製造する磁芯である。圧粉磁芯は、電磁鋼板利用の磁芯のような二次元的な磁路回路設計を行う必要はなく、三次元的な磁気回路を設計することができる。これにより、機器の小型化や高効率化をより推進することも可能となる。さらに、圧粉磁芯は、複雑な形状の磁芯でもプレス成形で製造できるため、電磁鋼板利用の磁芯に比べて成形工数の削減や材料歩留の向上などが期待できる。なお、鉄損成分の一つである渦電流損失を抑制するために、磁性粉末として、絶縁処理を施された磁性粉末を使用する磁芯も提案されている。
First, since a magnetic core is formed by punching out from a magnetic steel plate that is a flat plate, there is a problem that the material yield is low, leading to an increase in cost and being economically disadvantageous. Secondly, since the magnetic circuit must be designed as a dual circuit in which the magnetic flux follows the laminated surface, there is a problem that the efficiency and size of the device cannot always be optimally designed.
It has been proposed to use a dust core for such a problem. The dust core is a magnetic core manufactured in a predetermined shape by appropriately adding an insulating agent / binder such as a resin to magnetic powder such as pure iron powder, stirring, mixing, and pressure forming. The dust core does not need to be designed in a two-dimensional magnetic circuit like a magnetic core using a magnetic steel sheet, and a three-dimensional magnetic circuit can be designed. Thereby, it is possible to further promote downsizing and high efficiency of the device. Furthermore, since the dust core can be manufactured by press molding even with a complicated shape, it can be expected to reduce the number of forming steps and improve the material yield as compared with the magnetic core using the magnetic steel sheet. In addition, in order to suppress eddy current loss which is one of iron loss components, a magnetic core using magnetic powder subjected to insulation treatment as magnetic powder has been proposed.
圧粉磁芯では、磁性粉末として、良好な軟磁気特性、すなわち低保磁力、高飽和磁束密度を有する磁性粉末が利用されている。このような磁性粉末としては、Fe系粉末、Fe-Ni系合金粉末、Fe-Si-Al系合金粉末、Fe-Si系合金粉末等が例示される。なかでも、Fe-Si系合金粉末は、軟磁気特性に優れる材料として知られている。
例えば、特許文献１には、Fe-Si系合金粉末を用いた圧粉磁芯が提案されている。特許文献１に記載された技術では、水アトマイズ法で製造した平均粒径が10〜100μｍで、組成がSiを２〜12％、酸素を0.05〜0.95％含有し、あるいはさらにAl、Cr、Tiを単独ないし複合して３％以下含有し、残部が実質的にFeよりなるFe-Si系合金粉末を用いて、圧粉磁芯としている。
For example, Patent Document 1 proposes a dust core using an Fe—Si alloy powder. In the technique described in Patent Document 1, the average particle diameter produced by the water atomization method is 10 to 100 μm, the composition contains 2 to 12% Si, 0.05 to 0.95% oxygen, or Al, Cr, Ti These are contained alone or in combination, and 3% or less is contained, and a Fe—Si based alloy powder substantially consisting of Fe is used to form a dust core.
しかし、特許文献１に記載された技術で製造された圧粉磁芯においても、磁芯の使用周波数が商用周波数よりも高い場合には、用いるFe-Si系合金粉末のSi含有量が3.5mass％以下ではFe-Si系合金粉末そのものの電気抵抗が低く、渦電流により鉄損が大きくなるという不利がある。そのため、商用周波数よりも高い周波数域で使用する圧粉磁芯の場合には、高周波数域での鉄損特性を改善するために、Fe-Si系合金粉末中のSi量を増加することが考えられる。Fe-Si系粉末中のSi量の増加は、粉末自体の電気抵抗を増大することになり、高い周波域での鉄損を低減するうえでは有利となる。しかし、Si量が3.5mass％を超えると、粉末が極めて硬く脆くなり、圧縮性が低下し、圧粉密度が低下して圧粉磁芯の軟磁気特性が低下する場合や、さらにSi量が高くなるとプレスによる成形が困難となり、所望の部品形状にうまく成形できない場合や金型寿命が短くなるなど、生産性が顕著に低下する場合があるという問題がある。特にSi量が5.0mass％を超える場合には、室温でのプレス成形はもちろんのこと、温間でのプレス成形によっても圧粉体を製造することが困難になる。 However, even in the dust core manufactured by the technique described in Patent Document 1, when the use frequency of the magnetic core is higher than the commercial frequency, the Si content of the Fe—Si based alloy powder to be used is 3.5 mass. % Or less, there is a disadvantage that the Fe-Si alloy powder itself has a low electric resistance and an eddy current increases the iron loss. Therefore, in the case of a dust core used in a frequency range higher than the commercial frequency, the amount of Si in the Fe-Si alloy powder may be increased to improve the iron loss characteristics in the high frequency range. Conceivable. An increase in the amount of Si in the Fe-Si powder increases the electrical resistance of the powder itself, which is advantageous for reducing iron loss in a high frequency range. However, if the Si amount exceeds 3.5 mass%, the powder becomes extremely hard and brittle, the compressibility is reduced, the dust density is reduced and the soft magnetic properties of the dust core are reduced, and the Si amount is further reduced. If it is high, molding by a press becomes difficult, and there is a problem that productivity may be remarkably lowered, for example, when it cannot be molded well into a desired part shape or a mold life is shortened. In particular, when the Si content exceeds 5.0 mass%, it is difficult to produce a green compact not only by press molding at room temperature but also by warm press molding.
本発明は、かかる従来技術の問題を有利に解決し、圧粉磁芯用として好適な、温間圧縮性に優れプレス成形が可能で、かつ圧粉磁芯としたときの軟磁気特性に優れた鉄基粉末を提供することを目的とする。 The present invention advantageously solves such problems of the prior art, is suitable for dust cores, has excellent warm compressibility, can be press-molded, and has excellent soft magnetic properties when used as a dust core. An object of the present invention is to provide an iron-based powder.
本発明者らは、上記課題を達成すべく、軟磁気特性に優れたFe-Si系合金粉末に着目し、Fe-Si系合金粉末の圧縮性に及ぼす各種要因の影響、さらには圧粉磁芯としたときの比抵抗、軟磁気特性に及ぼす各種要因の影響について鋭意研究を行った。その結果、Fe-Si系合金粉末にSiとともにCrを適正量含有させることにより、意外にもFe-Si系合金粉末の温間成形圧縮性（以下、温間圧縮性ともいう）が顕著に向上することを新規に見出した。従来、Crの添加は、鉄基粉末の圧縮性を低下させると考えられてきたが、とくにSiが３mass％以上含有したFe-Si系合金粉末に、適正量のCrを含有させることにより、Crを含有しないFe-Si系合金粉末にくらべてむしろ、圧縮性が向上し、とくに温間成形した場合に大幅に向上することを見いだした。 In order to achieve the above-mentioned problems, the present inventors have focused on Fe-Si alloy powders having excellent soft magnetic properties, the influence of various factors on the compressibility of Fe-Si alloy powders, We conducted intensive research on the effects of various factors on the resistivity and soft magnetic properties of the core. As a result, the Fe-Si alloy powder contains a proper amount of Cr together with Si, which surprisingly improves the hot forming compressibility (hereinafter also referred to as warm compressibility) of the Fe-Si alloy powder. Newly found to do. Conventionally, the addition of Cr has been thought to reduce the compressibility of iron-based powders. In particular, by adding an appropriate amount of Cr to an Fe-Si alloy powder containing 3 mass% or more of Si, Cr is added. Rather, it has been found that the compressibility is improved compared to Fe-Si alloy powders containing no iron, especially when it is warm-formed.
また、本発明者らは、Fe-Si系合金粉末にSiと適正量のCrを複合して含有させることによりFe-Si系合金粉末の圧縮性が向上し、これにより圧粉体が高密度化して、圧粉磁芯の飽和磁束密度が向上し、軟磁気特性が向上することも見いだした。また、本発明者らは、Fe-Si系合金粉末にSiとともに適正量のCrを複合して含有させることにより、電気抵抗の相乗的な増加が図れ、Siのみを添加したFe-Si系合金粉末に比べて、特に高周波数域での鉄損を格段に低減することができることも見出した。さらに、Siとともに適正量のCrを複合して含有するFe-Si系合金粉末の耐食性は、従来のSiのみを添加したFe-Si系合金粉末に比べて確実に向上することも知見している。 In addition, the present inventors have improved the compressibility of the Fe-Si alloy powder by combining the Fe-Si alloy powder with Si and an appropriate amount of Cr, thereby increasing the density of the green compact. It has also been found that the saturation magnetic flux density of the dust core is improved and the soft magnetic properties are improved. In addition, the present inventors can increase the electrical resistance synergistically by adding a proper amount of Cr together with Si to the Fe-Si alloy powder, and Fe-Si alloy containing only Si is added. It has also been found that iron loss can be significantly reduced particularly in the high frequency range as compared with powder. Furthermore, we have also found that the corrosion resistance of Fe-Si alloy powders containing a proper amount of Cr combined with Si is certainly improved compared to conventional Fe-Si alloy powders containing only Si. .
本発明は、上記した知見に立脚し、さらに検討を加えて完成されたものであり、その要旨は次のとおりである。
（１）鉄を主成分とする粉末であって、mass％で、Cr：1.5〜６％、Si：２〜７％を含有し、残部Fe及び不可避的不純物からなることを特徴とする圧粉磁芯用鉄基粉末。
（２）（１）において、前記不可避的不純物として、Ｃ、Ｎ、Ｏの合計量がmass％で0.15％以下であることを特徴とする圧粉磁芯用鉄基粉末。
（３）（１）又は（２）に記載の圧粉磁芯用鉄基粉末を用いて、所定の形状に成形し、あるいはさらに熱処理を施してなる圧粉磁芯。
（４）mass％で、Cr：1.5〜６％、Si：２〜７％を含有し、残部Fe及び不可避的不純物からなる組成の鉄基粉末を原料粉として、該原料粉に、絶縁剤を、前記原料粉100重量部に対し、0.01〜５重量部配合し、攪拌・混合して混合粉としたのち、所定の形状に成形し、あるいはさらに熱処理を施すことを特徴とする圧粉磁芯の製造方法。
（５）（４）において、前記鉄基粉末が、不可避的不純物であるＣ、Ｎ、Ｏの合計量がmass％で0.15％以下に調整してなる粉末であることを特徴とする圧粉磁芯の製造方法。
（６）（４）又は（５）において、前記絶縁剤の一部又は全部を、噴霧配合することを特徴とする圧粉磁芯の製造方法。
（７）（４）ないし（６）のいずれかにおいて、前記成形が、60〜300℃で行う温間成形であることを特徴とする圧粉磁芯の製造方法。
（８）（４）ないし（７）のいずれかにおいて、前記成形が、金型潤滑を施して行う金型潤滑成形であることを特徴とする圧粉磁芯の製造方法。
（９）（４）ないし（８）のいずれかにおいて、前記熱処理が、400℃以上の温度域に加熱し保持する処理であることを特徴とする圧粉磁芯の製造方法。
The present invention has been completed based on the above-described findings and further studies, and the gist thereof is as follows.
(1) Powdered powder containing iron as a main component and containing mass: Cr: 1.5-6%, Si: 2-7%, and the balance Fe and inevitable impurities Iron-based powder for magnetic cores.
(2) The iron-based powder for a dust core according to (1), wherein the total amount of C, N, and O is 0.15% or less in mass% as the inevitable impurities.
(3) A dust core formed by using the iron-based powder for dust core according to (1) or (2), or by further heat treatment.
(4) Mass%, Cr: 1.5 to 6%, Si: 2 to 7%, iron-based powder of the composition consisting of the remainder Fe and unavoidable impurities as raw material powder, insulating material to the raw material powder In addition, 0.01 to 5 parts by weight with respect to 100 parts by weight of the raw material powder, and after stirring and mixing to form a mixed powder, the powder core is formed into a predetermined shape or further subjected to heat treatment Manufacturing method.
(5) In (4), the iron-based powder is a powder formed by adjusting the total amount of C, N, and O, which are inevitable impurities, to 0.15% or less in mass%. A manufacturing method of the lead.
(6) The method for producing a dust core according to (4) or (5), wherein a part or all of the insulating agent is spray blended.
(7) The method for producing a dust core according to any one of (4) to (6), wherein the molding is warm molding performed at 60 to 300 ° C.
(8) The method for producing a dust core according to any one of (4) to (7), wherein the molding is mold lubrication molding performed by performing mold lubrication.
(9) The method for producing a dust core according to any one of (4) to (8), wherein the heat treatment is a treatment of heating and holding in a temperature range of 400 ° C. or higher.
本発明によれば、圧粉磁芯用の磁性粉末として好適な、圧縮性に優れプレス成形が可能で、かつ圧粉磁芯としたときの軟磁気特性に優れた鉄基粉末を容易に得ることができ、産業上格段の効果を奏する。また、本発明によれば、軟磁気特性に優れ、かつ高い比抵抗を有し高周波数域での鉄損が格段に低減した圧粉磁芯を生産性高く安価に製造することが可能となるという格段の効果を奏する。なお、本発明によれば、耐食性が従来より格段に向上した圧粉磁芯が得られるという効果もある。 According to the present invention, an iron-based powder that is suitable as a magnetic powder for a dust core, excellent in compressibility, can be press-molded, and has excellent soft magnetic properties when used as a dust core is easily obtained. It is possible to achieve a remarkable industrial effect. In addition, according to the present invention, it is possible to manufacture a dust core having excellent soft magnetic properties, high specific resistance, and extremely low iron loss in a high frequency range with high productivity and low cost. There is a remarkable effect. In addition, according to this invention, there also exists an effect that the powder magnetic core which corrosion resistance improved significantly conventionally is obtained.
本発明の鉄基粉末は、鉄を主成分とする粉末で、Cr：1.5〜６％およびSi：２〜７％を含有し、残部Feおよび不可避的不純物からなる圧粉磁芯用鉄基粉末である。まず、本発明の鉄基粉末の組成限定理由について説明する。以下、組成におけるmass％は、単に％で記す。
Cr：1.5〜６％
Crは、Fe-Si系合金粉末の圧縮性を向上させるのに極めて有効に作用する元素である。とくに、温間成形した場合にその効果が大きい。さらに、Crは、Siとの相乗効果によってFe-Si系合金粉末の比抵抗を大幅に向上させ、圧粉磁芯の高周波数域での鉄損を低減するとともに、耐食性を向上させる作用を有する元素である。このような効果を得るために、本発明では、Cr：1.5％以上の含有を必要とする。一方、６％を超える含有は、圧縮性向上効果が逆に低下する。このため、Crは1.5〜６％の範囲に限定した。なお、好ましくは２％以上、より好ましくは３％超えである。Siを3.5％以上含有するFe-Si系合金粉末の圧縮性を向上させるためには、上記した範囲内でかつ２％以上、より好ましくは３％以上のCrを含有させることが望ましい。Si量が3.5％未満の場合には、上記した３％より少ない1.5〜３％のCr含有量としても何ら問題はない。
The iron-based powder of the present invention is a powder containing iron as a main component, containing Cr: 1.5 to 6% and Si: 2 to 7%, and the iron-based powder for a dust core consisting of the balance Fe and inevitable impurities. It is. First, the reasons for limiting the composition of the iron-based powder of the present invention will be described. Hereinafter, mass% in the composition is simply expressed as%.
Cr: 1.5-6%
Cr is an element that works extremely effectively to improve the compressibility of the Fe—Si alloy powder. In particular, the effect is great when warm forming is performed. In addition, Cr has the effect of significantly improving the specific resistance of Fe-Si alloy powders by synergistic effects with Si, reducing iron loss in the high frequency range of the dust core, and improving corrosion resistance. It is an element. In order to obtain such effects, the present invention requires Cr: 1.5% or more. On the other hand, when the content exceeds 6%, the effect of improving compressibility is adversely reduced. For this reason, Cr was limited to a range of 1.5 to 6%. In addition, Preferably it is 2% or more, More preferably, it exceeds 3%. In order to improve the compressibility of the Fe—Si based alloy powder containing 3.5% or more of Si, it is desirable to contain 2% or more, more preferably 3% or more of Cr within the above range. When the Si content is less than 3.5%, there is no problem even if the Cr content is 1.5 to 3%, which is less than 3%.
Si：２〜７％
Siは、鉄基粉末の軟磁気特性を向上させるとともに、Crを複合含有させた場合には、Crとの相乗効果によって鉄基粉末の電気抵抗を大幅に上昇させ、圧粉磁芯における高周波数域での鉄損を低減するのに有効に作用する元素である。このような効果は２％以上の含有で認められる。一方、７％を超える含有は、Fe-Si系合金粉末を硬化させて、粉末の圧縮性が低下し、Crを含有させても温間成形が可能なまでに圧縮性を向上させることが困難となる。このため、Siは２〜７％の範囲に限定した。
Si: 2-7%
Si improves the soft magnetic properties of iron-based powders, and when Cr is compounded, the electric resistance of iron-based powders is greatly increased by the synergistic effect with Cr, and the high frequency in the dust core. It is an element that works effectively to reduce iron loss in the region. Such an effect is recognized when the content is 2% or more. On the other hand, if the content exceeds 7%, the Fe-Si alloy powder is hardened, and the compressibility of the powder decreases. Even if Cr is contained, it is difficult to improve the compressibility until warm forming is possible. It becomes. For this reason, Si was limited to the range of 2 to 7%.
上記した成分以外の残部は、Fe及び不可避的不純物からなる。不可避的不純物は、圧縮性向上の観点からできる限り低減することが望ましい。とくに圧縮性を高く確保するためには、Ｏ、Ｃ、Ｎの合計量を0.15％以下に調整することが好ましい。さらに好ましくは0.10％以下、より好ましくはＯ、Ｃ、Ｎの合計量で0.0600％以下である。なお、Ｃ単独では、0.0100％以下、Ｎ単独では0.0080％以下に調整することが好ましく、より好ましくはＣ：0.0030％以下、Ｎ：0.0020％以下である。また、Ｏ単独では0.1000％以下に調整することが好ましく、より好ましくは、Ｏ：0.0800％以下、さらに好ましくは0.0600％以下である。 The balance other than the components described above consists of Fe and inevitable impurities. It is desirable to reduce inevitable impurities as much as possible from the viewpoint of improving compressibility. In particular, in order to ensure high compressibility, it is preferable to adjust the total amount of O, C, and N to 0.15% or less. More preferably, it is 0.10% or less, More preferably, it is 0.0600% or less in the total amount of O, C, and N. In addition, it is preferable to adjust to 0.0100% or less for C alone, and 0.0080% or less for N alone, more preferably C: 0.0030% or less and N: 0.0020% or less. O alone is preferably adjusted to 0.1000% or less, more preferably O: 0.0800% or less, and further preferably 0.0600% or less.
なお、本発明の効果を損なわない範囲で、上記した成分以外の成分を含有する場合も本発明の範囲内であることはいうまでもない。
本発明鉄基粉末は、その製造方法をとくに限定する必要はなく、通常公知の方法がいずれも適用できるが、水アトマイズ法、ガスアトマイズ法などを用いて粉末とすることが生産性、経済性等の観点から好ましい。また、鋳造粉砕法を用いてもよいことはいうまでもない。なお、Ｃ、Ｎ、Ｏ等の不可避的不純物を低減するため、水素中、又は真空中で還元処理を施してもよい。
Needless to say, the present invention also includes components other than the above-described components within a range not impairing the effects of the present invention.
The iron-based powder of the present invention is not particularly limited in its production method, and any of the conventionally known methods can be applied. However, it is possible to use a water atomizing method, a gas atomizing method, etc. to obtain a powder, productivity, economy, etc. From the viewpoint of Needless to say, a casting pulverization method may be used. In order to reduce inevitable impurities such as C, N, and O, reduction treatment may be performed in hydrogen or in vacuum.
本発明の圧粉磁芯は、上記した鉄基粉末を用いて、所定の形状に成形し、あるいはさらに熱処理を施してなる圧粉磁芯である。
本発明の圧粉磁芯の好ましい製造方法について説明する。
本発明の圧粉磁芯は、上記した組成を有する鉄基粉末を原料粉として用いる。なお、原料粉として使用する鉄基粉末の粒径については、圧粉磁芯の用途や要求特性によって適宜決めることが望ましく、特に限定する必要はない。
The dust core of the present invention is a dust core formed by using the above-described iron-based powder and molding the powder into a predetermined shape or further performing a heat treatment.
A preferred method for producing the dust core of the present invention will be described.
The dust core of the present invention uses an iron-based powder having the above composition as a raw material powder. In addition, about the particle size of the iron-based powder used as raw material powder, it is desirable to determine suitably according to the use and required characteristic of a powder magnetic core, and it does not need to specifically limit.
例えば、分級により粒径の大きな粒子を取り出して原料粉として使用した場合には、圧縮性が改善され、さらに粒子間で発生する磁気的ギャップも大幅に低減される。そのため、高透磁率かつ高磁束密度で、かつ磁気的ギャップの低減によるヒステリシス損失が著しく低減した圧粉磁芯を得ることができる。このような圧粉磁芯は、たとえば使用周波数が１kHz以下であり、かつ高い磁束密度が要求されるような用途に好適である。このような用途向けの場合には、原料粉として用いる鉄基粉末の粒径は75μm以上とすることが好ましく、さらに好ましいは106μm以上である。 For example, when particles having a large particle diameter are taken out by classification and used as a raw material powder, the compressibility is improved and the magnetic gap generated between the particles is greatly reduced. Therefore, it is possible to obtain a dust core having a high magnetic permeability, a high magnetic flux density, and significantly reduced hysteresis loss due to a reduction in magnetic gap. Such a dust core is suitable for applications where, for example, the operating frequency is 1 kHz or less and a high magnetic flux density is required. For such applications, the particle size of the iron-based powder used as the raw material powder is preferably 75 μm or more, and more preferably 106 μm or more.
また、分級で粒径の小さな粒子を取り出して原料粉として使用した場合には、粒子が小さくなることで粒子内に発生する渦電流に起因する損失が大幅に低減される。そのため、高周波数領域での鉄損が著しく低減した圧粉磁芯を得ることができる。このような圧粉磁芯は、たとえば使用周波数が10kHz〜500kHz程度の範囲で低損失であることが要求される用途に好適である。このような用途向けの場合には、原料粉として用いる鉄基粉末の粒径は75μm未満とすることが好ましい。 Further, when particles having a small particle diameter are taken out and used as a raw material powder by classification, the loss due to the eddy current generated in the particles is greatly reduced due to the small particles. Therefore, it is possible to obtain a dust core in which iron loss in a high frequency region is remarkably reduced. Such a dust core is suitable, for example, for applications that require a low loss within a frequency range of about 10 kHz to 500 kHz. For such applications, the iron-based powder used as the raw material powder preferably has a particle size of less than 75 μm.
上記したような鉄基粉末を原料粉として、ついで、該原料粉に、絶縁剤を、前記原料粉100重量部に対し、0.01〜５重量部程度配合し、攪拌・混合し混合粉としたのち、好ましくはプレス成形で、所定の形状に成形し、あるいはさらに熱処理を施して、圧粉磁芯とすることが好ましい。
原料粉に配合する絶縁剤は、電気絶縁性を有するとともに粘着能をも有し、バインダとしても兼用できる材料を用いることが好ましい。このような材料としては、水ガラス、リン酸、シリコーン樹脂、フェノール樹脂、イミド樹脂等が例示できるが、本発明ではこれらに限定されることはなく、公知の絶縁剤がいずれも適用可能である。絶縁剤の配合量は、原料粉100重量部に対し、0.01〜５重量部程度とすることが好ましい。絶縁剤の配合量が0.01重量部未満では、所期した効果が期待できない。一方、５重量部を超えて配合しても、所期した効果が飽和するうえ、圧粉密度が低下し、飽和磁束密度が低下する。
After using the iron-based powder as described above as a raw material powder, then blending the raw material powder with an insulating agent in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the raw material powder, stirring and mixing to obtain a mixed powder Preferably, it is preferably formed by press molding into a predetermined shape or further subjected to heat treatment to form a dust core.
It is preferable to use a material that can be used as a binder as the insulating agent to be blended with the raw material powder as well as having electrical insulating properties and adhesiveness. Examples of such a material include water glass, phosphoric acid, silicone resin, phenol resin, and imide resin, but the present invention is not limited to these, and any known insulating agent can be applied. . The blending amount of the insulating agent is preferably about 0.01 to 5 parts by weight with respect to 100 parts by weight of the raw material powder. If the blending amount of the insulating agent is less than 0.01 parts by weight, the expected effect cannot be expected. On the other hand, even if it exceeds 5 parts by weight, the intended effect is saturated, the dust density is reduced, and the saturation magnetic flux density is reduced.
なお、原料粉に絶縁剤を配合し、攪拌・混合し混合粉とする際には、両者を一度に混合しても、また原料粉に絶縁剤の一部を混合し、攪拌・混合中に残りの絶縁剤を添加してもよい。攪拌・混合には、アトライタ、ヘンシェルミキサー、ポールミル、流動造粒機、転動造粒機などを利用することができる。なかでも、流動造粒機や転動造粒機は、流動槽による攪拌を行なうため、粒体同士の擬集が抑制され、均一な粒径の混合粉とすることができる。 In addition, when an insulating agent is blended into the raw material powder and stirred and mixed to make a mixed powder, even if both are mixed at once, a part of the insulating agent is mixed into the raw material powder, The remaining insulating agent may be added. For stirring and mixing, an attritor, a Henschel mixer, a pole mill, a fluidized granulator, a rolling granulator, or the like can be used. Especially, since a fluid granulator and a rolling granulator perform stirring by a fluid tank, the false collection of particles is suppressed and it can be set as the mixed powder of a uniform particle size.
また、絶縁剤は、スプレーノズルにより噴霧することにより原料粉に配合してもよい。絶縁剤を噴霧配合することにより、絶縁剤が均一に添加され、絶縁剤により原料粉末表面に形成される被膜も均一になる。なお、流動状態の原料粉に、絶縁剤をスプレーなどで噴霧すると、噴霧による効果と、流動槽を利用した効果が相乗され、一層均一な被膜が原料粉表面に形成される。絶縁剤の噴霧に際しては、溶媒の乾燥具合を適切にし、さらに粒子の擬集を防ぐ観点から、噴霧量を調整することが好ましい。 Moreover, you may mix | blend an insulating agent with raw material powder by spraying with a spray nozzle. By spray-blending the insulating agent, the insulating agent is uniformly added, and the film formed on the surface of the raw material powder by the insulating agent becomes uniform. In addition, when an insulating agent is sprayed on the raw material powder in a fluidized state by spraying or the like, the effect of spraying and the effect of using the fluid tank are synergized, and a more uniform film is formed on the surface of the raw material powder. In spraying the insulating agent, it is preferable to adjust the spray amount from the viewpoint of making the solvent dry appropriately and preventing particles from being collected.
なお、溶媒の乾燥促進や、絶縁剤の硬化などを目的として、攪拌・混合中あるいは攪拌・混合後に加熱処理を施してもよい。
また、本発明の鉄基粉末は、SiおよびCrを含有しており、粉末の表面の一部または全部が、Cr、Siを主成分とする酸化皮膜で被覆されて、粉末表面は電気絶縁性になっている。このため、本発明の鉄基粉末を用いた圧粉磁芯では、鉄基粉末表面にさらに形成された電気絶縁性に富む被膜が、圧粉磁芯の成形時や熱処理の過程で破損して磁性粉末が相互に接触するようなことがあっても、各粉末の表面が電気絶縁性になっているため、圧粉磁芯は高い電気抵抗を維持することができる。
Note that heat treatment may be performed during stirring or after mixing or after stirring / mixing for the purpose of accelerating the drying of the solvent or curing the insulating agent.
Further, the iron-based powder of the present invention contains Si and Cr, and a part or all of the surface of the powder is coated with an oxide film mainly containing Cr and Si, and the powder surface is electrically insulating. It has become. For this reason, in the dust core using the iron-based powder of the present invention, the coating having high electrical insulation further formed on the surface of the iron-based powder is damaged during the molding of the dust core or in the heat treatment process. Even if the magnetic powders come into contact with each other, the surface of each powder is electrically insulating, so that the dust core can maintain high electrical resistance.
また、本発明では、混合粉の成形は、常温での成形、60〜300℃程度の温度で行う温間成形などの公知の成形方法を用いることができる。また、混合粉の成形に際しては、公知の潤滑剤を添加してもよく、また公知の金型潤滑を行ってもよい。また、混合粉の成形に際しては、成形圧力は、用途に応じて適宜決定すれば良い。
成形後、成形体（圧粉磁芯）に、加圧時に鉄基粉末に加えられた歪を解放しヒステリシス損失を低減させる目的で、熱処理を施してもよい。熱処理は、400℃以上の温度で保持する処理とすることが好ましい。熱処理の雰囲気は、アルゴンや窒素などの不活性雰囲気、水素などの還元性雰囲気、あるいは、真空のいずれでもよい。また、雰囲気中の露点は、用途等に応じ適宜決定すれば良い。熱処理時の昇温速度、降温速度は、用途、設備に応じて適宜決めれば良い。昇温時に、一定の温度で保持する段階を設けてもよいことは言うまでもない。
Moreover, in this invention, well-known shaping | molding methods, such as shaping | molding at normal temperature and warm shaping | molding performed at the temperature of about 60-300 degreeC, can be used for shaping | molding of mixed powder. In forming the mixed powder, a known lubricant may be added, or a known mold lubrication may be performed. Moreover, what is necessary is just to determine a shaping | molding pressure suitably according to a use in the case of shaping | molding of mixed powder.
After molding, the molded body (powder magnetic core) may be subjected to heat treatment for the purpose of releasing the strain applied to the iron-based powder during pressurization and reducing hysteresis loss. The heat treatment is preferably performed at a temperature of 400 ° C. or higher. The atmosphere for the heat treatment may be an inert atmosphere such as argon or nitrogen, a reducing atmosphere such as hydrogen, or a vacuum. In addition, the dew point in the atmosphere may be appropriately determined according to the application. What is necessary is just to determine suitably the temperature increase rate and temperature decrease rate at the time of heat processing according to a use and an installation. Needless to say, a step of holding at a constant temperature may be provided at the time of raising the temperature.
以下、さらに実施例に基づいて、本発明をさらに詳細に説明する。 Hereinafter, the present invention will be described in more detail based on examples.
水アトマイズ法又はガスアトマイズ法により所定のCr、Si含有量に調整した鉄基粉末に、真空中で還元処理を施してＣ、Ｎ、Ｏを低減し、ついで分級して平均粒径80μｍの粉末とし、圧粉磁芯用の原料粉とした。原料粉の化学組成を表１に示す。
これら原料粉に、絶縁剤を配合し、攪拌・混合して混合粉を得た。使用した絶縁剤は、シリコーン樹脂（東レダウコーニング社製のSR-2410）を使用した。なお、絶縁剤の配合量は、原料粉100重量部に対し、0.5重量部とした。また、絶縁剤と原料粉の攪拌・混合には、ヘンシェルミキサを利用し、混合時間は400ｓとした。攪拌・混合したのち、室温で10ｈ風乾した。
Iron-base powder adjusted to the specified Cr and Si contents by water atomization method or gas atomization method is reduced in vacuum to reduce C, N and O, then classified to obtain powder with an average particle size of 80μm A raw material powder for a dust core was obtained. Table 1 shows the chemical composition of the raw material powder.
These raw material powders were mixed with an insulating agent, stirred and mixed to obtain mixed powders. The insulating agent used was a silicone resin (SR-2410 manufactured by Toray Dow Corning). The blending amount of the insulating agent was 0.5 parts by weight with respect to 100 parts by weight of the raw material powder. In addition, a Henschel mixer was used for stirring and mixing the insulating agent and the raw material powder, and the mixing time was 400 s. After stirring and mixing, the mixture was air-dried at room temperature for 10 hours.
得られた混合粉に、さらに潤滑剤としてステアリン酸リチウムを混合粉100重量部に対し、0.6重量部添加したのち、金型に充填し、プレス成形して、圧粉成形体（高さ6.2mm×幅10mm×長さ35mm）とした。なお、成形圧力は686MPa、成形温度は130℃とした。ついで、これら圧粉成形体に、歪取りを目的とした熱処理（歪取り焼鈍）を施し、試験体とした。なお、熱処理は、窒素雰囲気中で、500℃に加熱しその温度で１ｈ保持する処理とした。 After adding 0.6 parts by weight of lithium stearate as a lubricant to 100 parts by weight of the mixed powder, the resulting mixed powder was filled into a mold, press-molded, and compacted (height 6.2 mm) X width 10 mm x length 35 mm). The molding pressure was 686 MPa and the molding temperature was 130 ° C. Next, these compacted bodies were subjected to heat treatment (strain relief annealing) for the purpose of strain relief to obtain test specimens. The heat treatment was performed by heating to 500 ° C. and holding at that temperature for 1 h in a nitrogen atmosphere.
得られた試験体を用いて、圧粉密度、比抵抗を測定した。圧粉密度は、試験体の質量と体積を測定して、それらの値から算出した。比抵抗は、４端子法を用いた。
得られた結果を表２に示す。
The green compact density and specific resistance were measured using the obtained specimen. The green density was calculated from these values by measuring the mass and volume of the specimen. For the specific resistance, a four-terminal method was used.
The obtained results are shown in Table 2.
本発明例はいずれも、圧縮性が高く、加圧成形が可能で、圧粉成形後に高い圧粉密度を有し、しかも比抵抗も高い。一方、本発明範囲を外れる比較例は、圧縮性が低く、加圧成形が不可となるか、あるいは圧粉密度が低いか、あるいは比抵抗が低い。 Each of the inventive examples has high compressibility, can be pressure-molded, has a high powder density after compacting, and has a high specific resistance. On the other hand, the comparative examples that are outside the scope of the present invention have low compressibility and are unable to be pressure-molded, have a low powder density, or have a low specific resistance.
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