JP2006233295A - Soft magnetic metallic powder for powder magnetic core and powder magnetic core - Google Patents
Soft magnetic metallic powder for powder magnetic core and powder magnetic core Download PDFInfo
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Abstract
Description
本発明は、圧粉磁心用の軟磁性金属粉末およびこの軟磁性金属粉末を用いて作製した磁束密度が高くかつ鉄損が低い圧粉磁心に関するものである。 The present invention relates to a soft magnetic metal powder for a dust core and a dust core having a high magnetic flux density and a low iron loss produced using the soft magnetic metal powder.
1997年の京都会議における CO2排出量削減の目標設定を受けて、近年、そのための化石燃料消費量抑制のための技術開発やそれを受けた商品開発が広く行われている。例えば、日本国内では CO2排出量の相当割合を発電による化石燃料消費が占めているため、これを削減すべく、太陽電池や燃料電池などの分散型電力源の開発が、ベースロードの原子力発電化推進と並行して精力的に進められている。
また、同様に CO2排出量の相当割合を占めている自動車についても、ハイブリッド化などを通じた化石燃料の削減技術の開発が進められている。
In response to the goal of reducing CO 2 emissions at the Kyoto Conference in 1997, in recent years, technology development for reducing fossil fuel consumption and product development in response to it have been widely conducted. For example, in Japan, fossil fuel consumption by power generation accounts for a significant proportion of CO 2 emissions. To reduce this, the development of distributed power sources such as solar cells and fuel cells has been It is being pursued energetically in parallel with the promotion of computerization.
Similarly, for automobiles that account for a significant proportion of CO 2 emissions, fossil fuel reduction technologies are being developed through hybridization.
ところで、これらの技術においては、動力や太陽光によって得られたエネルギーを一旦電力に変換し、再度目的の形態のエネルギーに変換するという手法が広く採用されている。この理由は、電力が比較的制御し易いエネルギーというだけでなく、別形態のエネルギーへの変換が容易なためである。
従って、電力変換効率を改善することは、新技術でのエネルギー効率の改善に極めて重要な意味をもっている。
By the way, in these techniques, the technique of once converting the energy obtained by motive power or sunlight into electric power and converting it again into the target form of energy is widely adopted. This is because the power is not only easily controlled energy but also easily converted into another form of energy.
Therefore, improving power conversion efficiency is extremely important for improving energy efficiency with new technologies.
電力変換回路には種々の素子があり、それぞれの特性および制御方法が効率に強く影響する。その中でも取り分け効率に強く影響するものの一つとして、トランスやリアクトルなどに代表されるコイルと鉄心から構成される磁気素子が挙げられる。これらの素子は、変換回路において常に動作する素子であるため、僅かな効率改善であっても変換回路全体の効率改善に多大な影響を与えることが多い。そのため、常に効率改善が求められる素子である。 There are various elements in the power conversion circuit, and their characteristics and control methods strongly influence the efficiency. Among them, one of the elements that have a strong influence on the efficiency is a magnetic element composed of a coil and an iron core typified by a transformer and a reactor. Since these elements are elements that always operate in the conversion circuit, even a slight improvement in efficiency often greatly affects the improvement in the efficiency of the entire conversion circuit. Therefore, this element is always required to improve efficiency.
また、かような磁気素子は、鉄心に巻き線をするという構造を持つため、半導体素子などに比べて大型でかつ大重量であることが多い。巻き線部分が多いことは、重量や形状だけでなく製造コストの増大にも直結するため、小型化に対する要求も効率改善と並んで大きい。 In addition, since such a magnetic element has a structure in which an iron core is wound, it is often larger and heavier than a semiconductor element or the like. The large number of winding portions directly leads to an increase in manufacturing cost as well as weight and shape. Therefore, the demand for downsizing is great along with efficiency improvement.
上記した二つの問題の改善を図るため、種々の開発が広く行われている。
開発内容を具体的に記述すると、巻き線数の削減や鉄心の小型化が可能になる透磁率や磁束密度の向上、効率改善に直結する鉄損低減が挙げられる。これらは磁気素子中でも鉄心に強く依存する性質である。そのため、鉄心素材の改良は磁気素子の特性改善のためには避けては通れない非常に重要な課題である。特に電力変換回路では、一旦電流を周波数１kHz〜50kHz 程度の交流に変換し、さらにそれを目的とする出力に変換することが多いため、かような周波数域における特性改善が極めて重要である。
In order to improve the above two problems, various developments have been widely performed.
To describe the details of the development, the permeability and magnetic flux density, which can reduce the number of windings and the size of the iron core, and the iron loss directly linked to the efficiency improvement can be mentioned. These are properties that strongly depend on the iron core even in the magnetic element. Therefore, improvement of the iron core material is a very important issue that cannot be avoided to improve the characteristics of the magnetic element. In particular, in a power conversion circuit, the current is once converted into an alternating current having a frequency of about 1 kHz to 50 kHz and further converted into an intended output. Therefore, improvement of characteristics in such a frequency range is extremely important.
一般に磁気素子の鉄心としては、ソフトフェライトコアや電磁鋼板、電磁鉄板などを積層して作製される積層鉄心が広く利用されている。
しかしながら、積層鋼板は、使用する周波数域が高くなるに伴って渦電流損失が大きくなるため、実用的でないという問題があった。また、ソフトフェライトは、透磁率は優れるものの、飽和磁束密度が低いため、動作時の磁気飽和を考慮する必要があり、例えば動作中の磁気飽和を防止するため回路設計が制限されたり、部品形状の大型化が不可避であるなどの問題があった。
In general, laminated iron cores produced by laminating soft ferrite cores, electromagnetic steel plates, electromagnetic iron plates and the like are widely used as iron cores of magnetic elements.
However, the laminated steel sheet has a problem that it is not practical because the eddy current loss increases as the frequency range to be used increases. Soft ferrite has excellent permeability but low saturation magnetic flux density, so it is necessary to consider magnetic saturation during operation.For example, circuit design is restricted to prevent magnetic saturation during operation, and component shape There were problems such as inevitable enlargement.
上記のような背景から、変換回路の一層の効率改善のために、積層鉄心やソフトフェライトコアに代わる、新しい鉄心材料の開発が強く求められていた。 In view of the above background, there has been a strong demand for the development of a new core material to replace the laminated core and the soft ferrite core in order to further improve the efficiency of the conversion circuit.
このような背景を受けて、軟磁性金属粉末に適宜樹脂などのバインダーを添加した混合粉末を、加圧成形することで作製される圧粉磁心が注目を浴び始めている。この理由は、圧粉磁心が次の２つのメリットを持つからである。
すなわち、一つは、粉末を原料とし、さらに樹脂など絶縁性の優れる材料をバインダーとして使用するため、渦電流の発生を抑制することができ、その結果積層鉄心に比べて鉄損を低減することが可能であるということである。さらにもう一つは、原料に軟磁性金属を利用するので、ソフトフェライトに比べて飽和磁束密度が高く、磁気飽和を起こし難い鉄心が得られるということである。
In view of such a background, a powder magnetic core produced by pressing a mixed powder obtained by appropriately adding a binder such as a resin to a soft magnetic metal powder has begun to attract attention. This is because the dust core has the following two merits.
That is, one is that powder is used as a raw material, and furthermore, a material having excellent insulation properties such as resin is used as a binder, so that generation of eddy current can be suppressed, and as a result, iron loss can be reduced as compared with a laminated core. Is possible. Furthermore, since a soft magnetic metal is used as a raw material, an iron core having a higher saturation magnetic flux density than that of soft ferrite and hardly causing magnetic saturation can be obtained.
これらの特長を受けて、圧粉磁心が、電磁鋼板やソフトフェライトにかわる鉄心材料として強い注目を集めている。
しかしながら、変換回路で用いられる周波数域では圧粉磁心の鉄損は依然として大きく、また透磁率や磁束密度も十分ではないという問題がある。圧粉磁心を電磁鋼板やソフトフェライトに変わる新たな鉄心材料とするためには、圧粉磁心の磁束密度の向上および鉄損の低減が不可欠である。
In view of these features, dust cores are attracting a great deal of attention as iron core materials that replace magnetic steel sheets and soft ferrite.
However, there is a problem that the iron loss of the dust core is still large in the frequency range used in the conversion circuit, and the permeability and magnetic flux density are not sufficient. In order to use a dust core as a new iron core material that can be replaced with a magnetic steel sheet or soft ferrite, it is essential to improve the magnetic flux density of the dust core and reduce the iron loss.
上述した圧粉磁心の課題、すなわち鉄損の低減と磁束密度の向上という目標を達成するために、従来からいくつかの技術が提案されている。
例えば、圧粉磁心の磁束密度は、成形体密度の上昇に伴い向上することが広く知られているが、この知見に基づき圧粉磁心の成形体密度を向上するための技術開発が広く行われている。
In order to achieve the above-mentioned problem of the dust core, that is, the goal of reducing iron loss and improving magnetic flux density, several techniques have been proposed.
For example, it is widely known that the magnetic flux density of a dust core increases with an increase in the density of the compact, but based on this finding, technological development for improving the density of the compact core is widely conducted. ing.
一方、圧粉磁心の鉄損は、大きくヒステリシス損失と渦電流損失に分けられるが、このうち渦電流損失を低減するためにいくつかの技術が提案されている。
例えば、軟磁性金属粉末の粒径を制御方法（例えば特許文献１）や、軟磁性金属粉末と樹脂などの絶縁性物質を混合する方法（例えば特許文献２）などが挙げられる。
一方、ヒステリシス損失の低減を図るためにも種々の検討が行なわれている。そもそも圧粉磁心においてヒステリシス損失が顕著となるのは、軟磁性金属粉末を加圧成形して圧粉磁心とする際、軟磁性金属粉末に巨大な加工歪みが加えられることに起因する。従って、ヒステリシス損失の低減には、加圧成形後、成形体を焼鈍することにより、軟磁性金属粉末中に加えられた歪みを解放することが有効であると指摘されている（例えば非特許文献１）。特に、600℃ 以上での焼鈍が有効であるといわれている。しかしながら、渦電流損失の低減を図るために使用される樹脂は一般に耐熱性に劣るため、ヒステリシス損失を低減するための焼鈍を行うと、絶縁物質が分解してしまい、絶縁性が著しく劣化してしまう。その結果、渦電流損失の低減とヒステリシス損失の低減を両立させることは非常に困難であるという問題があった。
On the other hand, the iron loss of the dust core is largely divided into hysteresis loss and eddy current loss. Among these, several techniques have been proposed to reduce eddy current loss.
For example, a method for controlling the particle size of the soft magnetic metal powder (for example, Patent Document 1), a method for mixing the soft magnetic metal powder and an insulating substance such as resin (for example, Patent Document 2), and the like can be mentioned.
On the other hand, various studies have been made to reduce hysteresis loss. In the first place, the hysteresis loss becomes prominent in the dust core due to the fact that enormous processing strain is applied to the soft magnetic metal powder when the soft magnetic metal powder is pressed and formed into a dust core. Therefore, it has been pointed out that it is effective to reduce the strain applied to the soft magnetic metal powder by annealing the molded body after pressure molding to reduce the hysteresis loss (for example, non-patent document). 1). In particular, annealing at 600 ° C. or higher is said to be effective. However, since the resin used to reduce eddy current loss is generally inferior in heat resistance, when annealing is performed to reduce hysteresis loss, the insulating material is decomposed, resulting in a significant deterioration in insulation. End up. As a result, there is a problem that it is very difficult to achieve both reduction in eddy current loss and reduction in hysteresis loss.
そこで、かかる問題を解決するため、軟磁性金属粉末表面を耐熱性に優れた絶縁材料で被覆する技術が従来からいくつか報告されている。
例えば、特許文献３，４には、シリコンを予合金として加えた軟磁性金属粉末に用いる技術が提案されている。これは、シリコンが金属表面に濃化し易いという特徴を利用した技術である。すなわち、アトマイズ処理およびその後の熱処理においてシリコンを表面に濃化させ、さらに酸化させることにより、軟磁性金属粉末表面に耐熱性に優れた絶縁被膜を形成し、さらにその上にシリコーン樹脂などによる絶縁被覆処理を行うことにより、耐熱性に優れた絶縁被覆を持つ軟磁性金属粉末を得ようとするものである。
金属粉末表面に濃化したシリコンは酸化物として存在すると推定され、このシリコン酸化物が下地として存在することにより、絶縁被覆処理後の絶縁性が向上していることとが、これらの公報に指摘されている。
In order to solve this problem, several techniques for coating the surface of the soft magnetic metal powder with an insulating material having excellent heat resistance have been reported.
For example, Patent Documents 3 and 4 propose a technique for using soft magnetic metal powder in which silicon is added as a prealloy. This is a technique utilizing the feature that silicon is easily concentrated on the metal surface. In other words, silicon is concentrated on the surface in the atomization treatment and subsequent heat treatment, and further oxidized to form an insulating film with excellent heat resistance on the surface of the soft magnetic metal powder. By carrying out the treatment, an attempt is made to obtain a soft magnetic metal powder having an insulating coating excellent in heat resistance.
It is estimated that silicon concentrated on the surface of the metal powder exists as an oxide, and it is pointed out in these publications that the insulation after the insulation coating treatment is improved by the presence of this silicon oxide as a base. Has been.
そこで発明者らは、これらの手法に従って試験を行った結果、この技術によって得られた軟磁性金属粉末では、ある程度絶縁性が改善されることを確認した。しかしながら、絶縁性は依然として不十分である上に、シリコン添加による軟磁性金属粉末の硬度上昇が原因となって圧粉体密度の低下が生じ、結果として十分な磁束密度が得られないという問題があることが判明した。 Therefore, the inventors conducted tests according to these methods, and as a result, confirmed that the soft magnetic metal powder obtained by this technique improved the insulation to some extent. However, the insulation is still insufficient, and the density of the green compact is reduced due to the increase in hardness of the soft magnetic metal powder due to the addition of silicon. As a result, a sufficient magnetic flux density cannot be obtained. It turned out to be.
シリコンによる密度低下を避けるために、鉄粉に酸化物粉末を用いることで上述の技術と同等の効果を得ることを狙った技術も公開されている（例えば特許文献５）。これは、酸化物粉末と鉄粉を混合、あるいはゾル状の酸化物で鉄粉を被覆し、場合によってはその後メカノフュージョンなどの強力なせん断力を粉末に作用させる手法を用いることで、軟磁性金属粉末表面へ酸化物粒子を付着させ、上述したシリコン入り軟磁性金属粉末原料と同様の状態になることを狙ったものである。
しかしながら、発明者らが試験したところ、単に混合したり被覆しただけでは、酸化物の付着力が弱すぎるために均一な絶縁被覆が形成されず、加圧成形時に被覆が剥がれてしまうために、所望の絶縁性を得ることはできなかった。
In order to avoid a decrease in density due to silicon, a technique aiming to obtain an effect equivalent to the above-described technique by using an oxide powder as iron powder has also been disclosed (for example, Patent Document 5). This is done by mixing the oxide powder and iron powder, or coating the iron powder with a sol-like oxide, and in some cases, using a method of applying a strong shearing force such as mechanofusion to the powder. The aim is to deposit oxide particles on the surface of the metal powder and to achieve the same state as the above-mentioned soft magnetic metal powder raw material containing silicon.
However, when the inventors tested, simply mixing or coating, because the oxide adhesion is too weak, a uniform insulating coating is not formed, and the coating peels off during pressure molding, A desired insulating property could not be obtained.
また、発明者らは、せん断力を付与して加工した場合についても試験した結果、表面に絶縁物を主体とする被覆層が形成されることが確認された。
しかしながら、この粉末から作製した成形体を熱処理したところ、十分な絶縁性が得られないことが判明した。
そこで、得られた粉末の内部を観察した結果、一部の粒子間では焼結が進んでいることが判明した。
In addition, as a result of testing the inventors for processing with shearing force applied, it was confirmed that a coating layer mainly composed of an insulator was formed on the surface.
However, it was found that when a molded body made from this powder was heat-treated, sufficient insulation could not be obtained.
Therefore, as a result of observing the inside of the obtained powder, it was found that sintering progressed between some of the particles.
この理由は、熱処理時、被覆層内部に存在する金属を介して被覆層を超えた金属粒子の拡散が起き、その結果焼結が進んだためと推定される。
しかしながら、せん断力を用いた加工では、被覆層の内部に金属相が混入することを防止することは、工法上極めて難しい。
The reason for this is presumed that during the heat treatment, diffusion of metal particles beyond the coating layer occurred through the metal present in the coating layer, and as a result, sintering proceeded.
However, in processing using a shearing force, it is extremely difficult in terms of construction method to prevent the metal phase from being mixed inside the coating layer.
また、特許文献６には、鉄粉などの軟磁性金属粉末の表面を高抵抗物質で被覆し、さらにその高抵抗物質の表面をリン酸系化成処理液で処理して二層の絶縁層をもった粉末を用いることで、比抵抗が高く高密度な軟磁性成形体を得る方法が提案されている。
しかしながら、この技術は、リン酸系化成膜が高温で変質してしまうため600℃以上の温度では熱処理できないという問題があった。
また，発明者らが試験したところ、400℃以上で焼鈍すると比抵抗が大幅に 低下してしまい所期の狙いを実現することは困難であることが判明した。
In Patent Document 6, the surface of a soft magnetic metal powder such as iron powder is coated with a high-resistance material, and the surface of the high-resistance material is further treated with a phosphoric acid chemical conversion treatment solution to form two insulating layers. There has been proposed a method of obtaining a soft magnetic compact having a high specific resistance and a high density by using the powder.
However, this technique has a problem that heat treatment cannot be performed at a temperature of 600 ° C. or higher because the phosphoric acid-based film is deteriorated at a high temperature.
In addition, when the inventors tested, it was found that if the annealing was performed at 400 ° C or higher, the specific resistance decreased significantly, and it was difficult to achieve the intended aim.
本発明は、上述した課題を有利に解決するもので、低鉄損でかつ高磁束密度を有する圧粉磁心用の軟磁性金属粉末を提供することであり、具体的には圧縮性の高い純鉄粉を原料として、その上に耐熱性の高い絶縁被膜を被覆した軟磁性金属粉末を提供することを第１の目的とする。
また、本発明は、上記の軟磁性金属粉末を素材として製造した磁束密度が高くかつ鉄損が低い圧粉磁心を提供することを第２の目的とする。
The present invention advantageously solves the above-mentioned problems, and provides a soft magnetic metal powder for a dust core having a low iron loss and a high magnetic flux density. A first object is to provide a soft magnetic metal powder using iron powder as a raw material and coated with a heat-resistant insulating coating thereon.
A second object of the present invention is to provide a dust core produced from the soft magnetic metal powder as described above, having a high magnetic flux density and low iron loss.
さて、発明者らは、上記の問題を解決すべく鋭意研究を重ねた結果、素材である軟磁性金属粉末として、軟質なため圧縮性優れ、また高い磁束密度が得られる純鉄粉を用いるものとし、この純鉄粉の表面に直接シリコーン樹脂を被覆するのではなく、まず純鉄粉の表面に鉄酸化物を存在させ、次にその上に耐熱性に優れた絶縁物質を存在させたのち、結合強化処理を施して、これら２つの部分を互いに強固に固着させ、その後さらにシリコーン樹脂を被覆した粉末を、加圧成形して圧粉磁心を作製した場合に、その絶縁性が飛躍的に向上するとの知見を得た。
また、結合強化処理方法について鋭意検討した結果、熱処理条件を適正に制御して、鉄粉表面上の酸化物とその上に存在する絶縁物質間の拡散結合を行った場合に、被覆層内部への金属相分散が防止されて、絶縁性が飛躍的に向上することが確認された。
本発明は、上記の知見に立脚するものである¢
As a result of intensive studies to solve the above problems, the inventors use pure iron powder that is soft and excellent in compressibility and obtains a high magnetic flux density as a soft magnetic metal powder. Rather than directly coating the surface of the pure iron powder with silicone resin, first, iron oxide is present on the surface of the pure iron powder, and then an insulating material having excellent heat resistance is present on the surface. When the two parts are firmly fixed to each other by applying a bond strengthening treatment, and then the powder coated with the silicone resin is pressure-molded to produce a powder magnetic core, the insulation is dramatically improved. The knowledge that it improves is obtained.
In addition, as a result of diligent study on the bond strengthening treatment method, when diffusion treatment is performed between the oxide on the iron powder surface and the insulating material present on the iron powder surface by appropriately controlling the heat treatment conditions, the inside of the coating layer It was confirmed that the metal phase was prevented from being dispersed and the insulation property was dramatically improved.
The present invention is based on the above findings.
すなわち、本発明の要旨構成は次のとおりである。
（１）表面の全面又は一部に鉄酸化物を備える純鉄粉の該表面に、酸化物、炭酸塩及び硫酸塩のうちから選んだ少なくとも一種の絶縁層を被覆し、さらにその上にシリコーン樹脂層を被覆した構造になる純鉄粉であって、上記純鉄粉の表面と上記絶縁層とを熱処理による結合強化処理により固着したことを特徴とする圧粉磁心用の軟磁性金属粉末。
That is, the gist configuration of the present invention is as follows.
(1) The surface of pure iron powder having iron oxide on the entire surface or a part of the surface is coated with at least one insulating layer selected from oxide, carbonate and sulfate, and silicone is further formed thereon. A soft magnetic metal powder for a dust core, which is a pure iron powder having a structure coated with a resin layer, wherein the surface of the pure iron powder and the insulating layer are fixed by a bond strengthening process by heat treatment.
（２）上記（１）において、結合強化処理が、非酸化性雰囲気中、500〜1200℃、20〜240分の加熱処理であることを特徴とする圧粉磁心用の軟磁性金属粉末。 (2) The soft magnetic metal powder for a dust core according to (1), wherein the bond strengthening treatment is a heat treatment at 500 to 1200 ° C. for 20 to 240 minutes in a non-oxidizing atmosphere.
（３）上記（１）または（２）において、絶縁層が、Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni, Al, Si等の金属元素の酸化物、炭酸塩および硫酸塩のうちから選んだ一種または二種以上であることを特徴とする圧粉磁心用の軟磁性金属粉末。 (3) In the above (1) or (2), the insulating layer is made of oxides, carbonates and sulfates of metal elements such as Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni, Al, and Si. A soft magnetic metal powder for a dust core, which is one or more selected from among them.
（４）上記（１）〜（３）のいずれかに記載の軟磁性金属粉末を、金型に充填し、加圧成形後、焼鈍処理を施して得たことを特徴とする磁束密度が高くかつ鉄損が低い圧粉磁心。 (4) A magnetic flux density characterized by being obtained by filling the mold with the soft magnetic metal powder according to any one of (1) to (3) above and performing an annealing treatment after pressure molding. A dust core with low iron loss.
（５）上記（４）において、焼鈍処理が、非酸化性雰囲気中、600℃以上、30分以上 の処理であることを特徴とする磁束密度が高くかつ鉄損が低い圧粉磁心。 (5) A dust core having a high magnetic flux density and low iron loss, characterized in that, in (4) above, the annealing treatment is a treatment at 600 ° C. or higher and 30 minutes or longer in a non-oxidizing atmosphere.
本発明によれば、磁束密度、圧縮性に優れ、かつ高い絶縁性を有する軟磁性金属粉末を得ることができる。
従って、上記の軟磁性金属粉末を素材とすることにより、磁束密度が高くかつ鉄損が低い圧粉磁心を得ることができる。
According to the present invention, it is possible to obtain a soft magnetic metal powder having excellent magnetic flux density, compressibility, and high insulation.
Therefore, by using the soft magnetic metal powder as a raw material, a dust core having a high magnetic flux density and a low iron loss can be obtained.
以下、本発明を具体的に説明する。
図１に、本発明に従う軟磁性金属粉末の代表的な被覆構造を示す。なお、この図では、分かり易いように、粉末形状が球形の場合について示している。
図中番号１は素材である純鉄粉であり、かかる純鉄粉の製造法としてはアトマイズ法がとりわけ有利に適合する。番号２はその表面に形成させた鉄酸化物であり、かかる鉄酸化物は、アトマイズ法で作製する時の製造条件により、図１(a)に 示したように、純鉄粉１の表面全面に形成される場合もあれば、同図(b)に示したように、純鉄粉１の表面の一部に島状に形成される場合もある。なお、この鉄酸化物の組成は、通常FeＯ−Fe2O3で示されるが、FeＯ−Fe2O3−Fe3O4の場合もある。また、アモルファスの鉄酸化物として存在する場合もある。番号３は、上記したように表面の全面または一部に鉄酸化物２をそなえる純鉄粉１の表面に形成された絶縁層、そして４がその上にさらに被覆されたシリコーン樹脂層である。
The present invention will be specifically described below.
FIG. 1 shows a typical coating structure of soft magnetic metal powder according to the present invention. In addition, in this figure, it has shown about the case where a powder shape is a spherical form so that it may be easy to understand.
In the figure, reference numeral 1 denotes a pure iron powder as a raw material, and the atomizing method is particularly advantageously adapted as a method for producing such pure iron powder. No. 2 is an iron oxide formed on the surface, and this iron oxide is formed on the entire surface of the pure iron powder 1 as shown in FIG. Or may be formed in an island shape on a part of the surface of the pure iron powder 1 as shown in FIG. The composition of the iron oxide is represented by the normal FeO-Fe 2 O 3, in some cases the FeO-Fe 2 O 3 -Fe 3 O 4. Moreover, it may exist as an amorphous iron oxide. The number 3 is an insulating layer formed on the surface of the pure iron powder 1 having the iron oxide 2 on the entire surface or a part of the surface as described above, and a silicone resin layer 4 is further coated thereon.
そして、本発明では、表面の全面または一部に鉄酸化物２をそなえる純鉄粉１の表面に、絶縁層３を被覆したのち、これらの接合強度を高めるための接合強化処理が施されているところに特徴を有している。 And in this invention, after coat | covering the insulating layer 3 on the surface of the pure iron powder 1 which has the iron oxide 2 in the whole surface or a part, the joint reinforcement | strengthening process for raising these joint strength is performed. It has a feature in some places.
従来は、鉄酸化物２を介在させずに、純鉄粉１の表面に直接、絶縁層３を被覆していたので、純鉄粉１と絶縁層３の結合力は極めて小さかった。そのため、加圧成形時に絶縁被膜が剥がれ、結果として歪取り焼鈍後の絶縁性低下を余儀なくされていた。
これに対し、本発明の軟磁性金属粉末では、純鉄粉の表面が酸化して形成された鉄酸化物２に絶縁層３が結合強化処理により強く固着されている。鉄酸化物２は、素材である純鉄粉の表面が酸化されて形成されたものであり、純鉄粉１と鉄酸化物２の界面は連続的となるため、鉄酸化物２と純鉄粉１の結合力は極めて高い。さらに、この鉄酸化物２と絶縁層３とは、接合強化処理を経て結合されているので、最終的に絶縁層３は鉄酸化物２を介して純鉄粉１と強く結合する。
Conventionally, since the insulating layer 3 was directly coated on the surface of the pure iron powder 1 without interposing the iron oxide 2, the bonding force between the pure iron powder 1 and the insulating layer 3 was extremely small. For this reason, the insulating coating is peeled off during the pressure molding, and as a result, the insulating property is inevitably lowered after the strain relief annealing.
On the other hand, in the soft magnetic metal powder of the present invention, the insulating layer 3 is firmly fixed to the iron oxide 2 formed by oxidizing the surface of the pure iron powder by the bond strengthening treatment. The iron oxide 2 is formed by oxidizing the surface of pure iron powder as a raw material, and the interface between the pure iron powder 1 and the iron oxide 2 becomes continuous. The binding power of the powder 1 is extremely high. Further, since the iron oxide 2 and the insulating layer 3 are bonded through the joint strengthening process, the insulating layer 3 is finally strongly bonded to the pure iron powder 1 through the iron oxide 2.
かような構造を採ることにより、加圧成形時に粉末表面に作用する応力によっても絶縁被膜が剥がれることなくなり、作製された圧粉磁心は 600℃以上の温度にて歪み取り焼鈍を行った後も、依然として高い絶縁性を示す。そのため、従来困難であったヒステリシス損失と渦電流損失の双方を低減させることが可能になるので、非常に鉄損が低い圧粉磁心が得られる。 By adopting such a structure, the insulation coating will not be peeled off even by stress acting on the powder surface during pressure molding, and the produced powder magnetic core will be subjected to strain relief annealing at a temperature of 600 ° C or higher. It still shows high insulation. Therefore, it is possible to reduce both hysteresis loss and eddy current loss, which has been difficult in the past, and thus a dust core with very low iron loss can be obtained.
また、従来のシリコーン樹脂だけを被覆した技術の場合には、600℃以上の温度でシリコーン樹脂の分解による絶縁性の低下が生じていた。しかしながら、本発明では、シリコーン樹脂の下に純鉄粉と強く結合し、さらに高い耐熱性と絶縁性を示す２層の絶縁被膜が形成されているので、600℃以上の温度での加熱によりシリコーン樹脂の分解が若干進行しても、下層の絶縁被膜によって鉄粉間の絶縁性が維持されるため、十分満足のいく絶縁性が確保される。 Moreover, in the case of the technique which coat | covered only the conventional silicone resin, the insulation fall by decomposition | disassembly of the silicone resin had arisen at the temperature of 600 degreeC or more. However, in the present invention, a two-layer insulating coating that is strongly bonded to pure iron powder and exhibits higher heat resistance and insulation is formed under the silicone resin, so that the silicone is heated by heating at a temperature of 600 ° C. or higher. Even if the decomposition of the resin proceeds slightly, the insulation between the iron powders is maintained by the lower insulating coating, so that a sufficiently satisfactory insulation is ensured.
図２は、アトマイズ法で作製する時の製造条件を調整して、得られる粉末の形状を凹凸の多い形にした純鉄粉の断面を示すものである。
断面積をＳ、粒子周囲の長さをＬとし、このＳとＬを用いて、パラメータｘを
ｘ＝Ｌ／｛２（πＳ）1/2｝
と定義したとき、本発明では、ｘが大きい、すなわち形状の凹凸が大きい粉末を利用することがより好適である。このように凹凸が大きい粉末を用いれば、圧縮成形した時の粉末同士の接触面積が、凹凸の小さい粉末を用いた場合に比べて小さくなる。これが、上述の絶縁被膜と複合することによって、極めて高い絶縁性が確保されるのである。
FIG. 2 shows a cross section of a pure iron powder in which the manufacturing conditions for the production by the atomizing method are adjusted and the resulting powder has a shape with many irregularities.
S is the cross-sectional area, L is the length of the circumference of the particle, and using this S and L, the parameter x is x = L / {2 (πS) 1/2 }
In the present invention, it is more preferable to use a powder having a large x, that is, a large shape. If a powder with large irregularities is used in this way, the contact area between the powders when compression-molded becomes smaller than when a powder with small irregularities is used. When this is combined with the above-described insulating film, extremely high insulation is ensured.
以下、本発明の各構成要件について詳細に説明する。
（純鉄粉）
本発明で用いる原料粉末は、強磁性で、圧縮性に優れる純鉄粉である。好適には、アトマイズ法により製造した純鉄粉が挙げられる。
本発明において、素材として純鉄粉を用いることにした理由は、純鉄粉は合金粉末に比べて、軟質なだけでなく、磁束密度が高いので、圧粉磁心として場合に、合金粉末を用いた場合に比べて、より高い磁気特性が得られるからである。
また、純鉄粉の粒度については特に制限はなく、圧粉磁心の用途や要求特性に応じて、適宜決定すればよい。
Hereinafter, each component of the present invention will be described in detail.
(Pure iron powder)
The raw material powder used in the present invention is pure iron powder that is ferromagnetic and excellent in compressibility. Preferable examples include pure iron powder produced by the atomizing method.
In the present invention, the reason for using pure iron powder as the material is that pure iron powder is not only softer than alloy powder, but also has a higher magnetic flux density. This is because higher magnetic characteristics can be obtained than in the case of the conventional case.
Moreover, there is no restriction | limiting in particular about the particle size of pure iron powder, What is necessary is just to determine suitably according to the use and required characteristic of a powder magnetic core.
なお、本発明における純鉄粉とは、Feの濃度が99.8mass％以上のものを指す。残りの不純物は、主にＣとＯとＮである。その他、SiやMn，Al，Ni等が不可避に混入する場合があるが、これらはそれぞれSi：0.005mass％未満、Mn：0.02mass％以下、Al：0.005mass％以下、Ni：0.01mass％以下であれば許容できる。 In addition, the pure iron powder in this invention points out the thing whose density | concentration of Fe is 99.8 mass% or more. The remaining impurities are mainly C, O and N. In addition, Si, Mn, Al, Ni, etc. may be inevitably mixed, but these are Si: less than 0.005 mass%, Mn: 0.02 mass% or less, Al: 0.005 mass% or less, Ni: 0.01 mass% or less, respectively. Is acceptable.
（純鉄粉の形状）
本発明では、純鉄粉の形状については特に限定することはないが、表面凹凸が多い方が圧粉体強度および絶縁性の面で有利である。
すなわち、図２(a)に示すように、純鉄粉の断面を光学顕微鏡により観察し、その断面積をＳ（図２(b)参照）、粒子周囲の長さをＬ（図２(c)参照）とし、このＳとＬを用いて、パラメータｘを
ｘ＝Ｌ／｛２（πＳ）1/2｝
と定義したとき、本発明では、ｘが大きい純鉄粉を用いることが好ましい。
好適には、ｘ：1.1 以上であり、より好ましくはｘ：1.2 以上である。なお、ｘの上限は特に定義されないが、ｘが４以上の粉末を工業的に生産することは困難である。
(Pure iron powder shape)
In the present invention, the shape of the pure iron powder is not particularly limited. However, it is advantageous in terms of the green compact strength and the insulating property that the surface roughness is large.
That is, as shown in FIG. 2 (a), the cross section of the pure iron powder is observed with an optical microscope, the cross sectional area is S (see FIG. 2 (b)), and the length around the particle is L (FIG. 2 (c). )), And using this S and L, the parameter x is x = L / {2 (πS) 1/2 }
In the present invention, it is preferable to use pure iron powder having a large x.
Preferably, x: 1.1 or more, more preferably x: 1.2 or more. The upper limit of x is not particularly defined, but it is difficult to industrially produce a powder having x of 4 or more.
鉄粉形状の制御方法としては、アトマイズ法で粉末化する媒体や圧力などの条件を調整することによって行う方法、鉄粉をボールミルやジェットミルなどで粉砕することによって調整する方法、ロールなどで粉砕と圧延を同時に行う装置を用いて調整する方法、リン酸や硝酸などの薬品で表面を化学的に処理することによって制御する方法などが挙げられる。勿論、ここに挙げた以外の方法を用いても構わない。その中でもアトマイズ時の調整は、制御性が優れる上、加工工程が少なく、歩留りや加工時間が短くなるので、工業的な製造に向いているという特徴があり、好ましい。中でも水アトマイズ法は、形状調整が極めて容易であるので、特に好ましい。 The iron powder shape is controlled by adjusting the conditions such as the medium to be powdered by the atomizing method and pressure, adjusting the iron powder by crushing it with a ball mill or jet mill, etc., crushing with a roll, etc. And a method of adjusting using a device that simultaneously performs rolling, and a method of controlling by chemically treating the surface with a chemical such as phosphoric acid or nitric acid. Of course, methods other than those listed here may be used. Among them, the adjustment at the time of atomization is preferable because it has excellent controllability, has few processing steps, shortens yield and processing time, and is suitable for industrial production. Among these, the water atomization method is particularly preferable because the shape adjustment is extremely easy.
（純鉄粉の表面の鉄酸化物）
この鉄酸化物は、素材である純鉄粉を、好適にはアトマイズ法で製造する過程で積極的に形成させる。従来、アトマイズ粉の製造に際しては、かような酸化物の形成は極力回避するのが常であったが、本発明ではこれとは逆に積極的に表面を酸化させて、純鉄粉の表面全面または一部に鉄酸化物を形成するのである。
形成される鉄酸化物の組成は、通常FeＯ−Fe2O3であるが、FeＯ−Fe2O3−Fe3O4の場合またはアモルファスとなっている場合もある。本発明の鉄酸化物としては、これらのいずれでも構わない。
また、かかる鉄酸化物の量は、アトマイズ法における製造条件（例えばアトマイズ時粉末化に用いられる媒質［例えば水を用いる方法など］、アトマイズを行う雰囲気中の酸素濃度の調整、アトマイズ後の加熱あるいは媒質の乾燥条件［温度、時間、雰囲気］等）を制御することによって、適宜調整することができる。
ここに、鉄酸化物の好適量は、例えば鉄粉の全面を酸化膜で覆う場合には、膜厚で概ね0.5〜1000nm程度が好適である。
(Iron oxide on the surface of pure iron powder)
This iron oxide is positively formed in the process of producing pure iron powder as a material, preferably by an atomizing method. Conventionally, in the production of atomized powder, it was usual to avoid the formation of such oxides as much as possible. However, in the present invention, the surface of pure iron powder is actively oxidized contrary to this. Iron oxide is formed on the entire surface or a part thereof.
The composition of the iron oxide formed is usually FeO—Fe 2 O 3 , but may be FeO—Fe 2 O 3 —Fe 3 O 4 or amorphous. Any of these may be used as the iron oxide of the present invention.
In addition, the amount of the iron oxide depends on the production conditions in the atomizing method (for example, a medium used for atomization during powderization [for example, a method using water], adjustment of oxygen concentration in the atmosphere in which atomization is performed, heating after atomization, or By adjusting the drying conditions [temperature, time, atmosphere, etc.] of the medium, it can be adjusted as appropriate.
Here, the preferable amount of iron oxide is, for example, about 0.5 to 1000 nm in thickness when the entire surface of the iron powder is covered with an oxide film.
このようにして形成された鉄酸化物は、原料粉末である鉄粉と鉄酸化物の界面部における成分濃度変化が連続的なものとなるため、例えば接着した場合のように成分濃度が非連続的に変化する場合に比べると、原料粉末との密着性は極めて優れている。 The iron oxide formed in this way has a continuous change in the component concentration at the interface between the iron powder and the iron oxide, which is the raw material powder. As compared with the case where the temperature changes, the adhesion with the raw material powder is extremely excellent.
（絶縁層）
本発明において、絶縁層の材質は、好ましくは上記した鉄酸化物よりも絶縁性が高く、かつ鉄酸化物との間で結合強化処理が可能であるならば、どのようなものでも構わない。その中でも、絶縁性に優れ、なおかつ耐熱性に優れた材質は、本発明の重要な目的である耐熱性に優れた絶縁被膜を形成するという目的を達成するためにとりわけ好適である。
(Insulating layer)
In the present invention, the material of the insulating layer is not particularly limited as long as it has higher insulating properties than the above-described iron oxide and can be subjected to bond strengthening treatment with the iron oxide. Among them, a material having excellent insulating properties and excellent heat resistance is particularly suitable for achieving the purpose of forming an insulating film having excellent heat resistance, which is an important object of the present invention.
このような絶縁物質としては、例えば絶縁性の高い Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni,Al, Siなどの金属元素の酸化物、炭酸塩や硫酸塩などに代表される塩などが挙げられる。本発明においては、これらを単体で用いても構わないし、併用しても構わない。
また、これらの材料の原料や前駆体となるものを用いても構わない。このようなものとしては、例えば、アルミナゾル、シリカゾル、チタニアゾルのように酸化物を水和した溶液、あるいは上記した金属の錯体溶液やアルコキシド溶液などの前駆体を分散・溶解した溶液などが挙げられる。また、溶液に粉末を分散した形態のものなど、複数の形態が混在した状態のものを用いても構わない。勿論、ここに挙げたもの以外の形態であっても、最終的に絶縁層が形成されるのであれば、それを用いても構わない。
Examples of such insulating materials include oxides, carbonates and sulfates of metal elements such as Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni, Al, and Si, which have high insulating properties. Examples include salt. In the present invention, these may be used alone or in combination.
Moreover, you may use what becomes the raw material and precursor of these materials. Examples of such a solution include a solution in which an oxide is hydrated, such as alumina sol, silica sol, and titania sol, or a solution in which a precursor such as the above metal complex solution or alkoxide solution is dispersed and dissolved. Moreover, you may use the thing of the state in which several forms were mixed, such as the form which disperse | distributed the powder to the solution. Of course, other forms than those listed here may be used as long as an insulating layer is finally formed.
かような絶縁層を形成する方法としては、例えば、上記した鉄酸化物をそなえる純鉄粉に、絶縁物質を添加した上で混合して材料を被覆する方法、ＣＶＤ、ＰＶＤなどの気相蒸着法で被覆する方法、あるいはこれらの方法を複数組み合わせた方法などが挙げられる。勿論、ここに記載した方法以外の方法を用いても構わない。 As a method of forming such an insulating layer, for example, a method of coating the material by adding an insulating substance to pure iron powder having the above-described iron oxide, and vapor deposition such as CVD and PVD A method of coating by a method, a method of combining these methods, or the like. Of course, methods other than those described here may be used.
上記の方法の中でも、原料粉末に絶縁物質を混合して被覆する方法は、被覆成分、被覆成分の付着量、被覆層厚み等の調整が容易であるため、確実に所望の絶縁被膜が得られるので好ましい。
かような混合手段としては、アトライター、ヘンシェルミキサー、ボールミルなどの混合装置を用いた混合処理が挙げられる。
Among the above methods, the method of coating the raw material powder with an insulating material is easy to adjust the coating component, the coating amount of the coating component, the thickness of the coating layer, etc., so that a desired insulating film can be obtained reliably. Therefore, it is preferable.
Examples of such mixing means include a mixing process using a mixing device such as an attritor, a Henschel mixer, or a ball mill.
また、絶縁層の材料として、前記したアルミナゾル、シリカゾル、チタニアゾルのように酸化物を水和した溶液、あるいは前記した金属の錯体溶液やアルコキシド溶液などの前駆体を分散・溶解した溶液などを用いると、粉末を原料とする場合に比べ、緻密かつ均一な状態で絶縁層を形成することが可能である。このような絶縁層を形成することにより、得られた粉末は最終的に高い絶縁性を示すようになり、本発明においては特に好適である。さらに、酸化物を水和した溶液の場合、加熱によって分子中の水分を飛散させれば、加熱しても重量減少や体積減少が起き難い耐熱性に優れた絶縁被膜を形成するので、本発明においてはさらに好ましい。 Further, as the material of the insulating layer, a solution in which an oxide is hydrated, such as the above-mentioned alumina sol, silica sol, or titania sol, or a solution in which a precursor such as a metal complex solution or alkoxide solution is dispersed or dissolved is used. Compared with the case where powder is used as a raw material, the insulating layer can be formed in a dense and uniform state. By forming such an insulating layer, the obtained powder finally shows a high insulating property, which is particularly suitable in the present invention. Furthermore, in the case of a solution in which the oxide is hydrated, if the moisture in the molecule is scattered by heating, an insulating film excellent in heat resistance that does not easily reduce weight or volume even when heated is formed. Is more preferable.
本発明では、原料粉末である純鉄粉に対する絶縁層形成物質の添加量は0.01〜5.0 mass％程度とすることが好ましい。というのは、添加量が0.01mass％を下回ると、添加量が少なすぎるために被覆が不均一となって、十分な絶縁性が得難く、さらに強度も低下する。一方 5.0mass％を超えると、圧粉磁心中の原料粉末の割合が低下するので、その分磁束密度の低下を招き好ましくない。 In this invention, it is preferable that the addition amount of the insulating layer forming substance with respect to the pure iron powder which is a raw material powder shall be about 0.01-5.0 mass%. This is because when the amount added is less than 0.01 mass%, the amount added is too small, so that the coating becomes non-uniform, it is difficult to obtain sufficient insulation, and the strength is further reduced. On the other hand, if it exceeds 5.0 mass%, the ratio of the raw material powder in the powder magnetic core is decreased, and accordingly, the magnetic flux density is decreased accordingly.
（結合強化処理）
さて、本発明においては、上記した鉄酸化物と絶縁層の密着性を向上させるために、結合強化処理を施す。この処理を施すことにより、耐熱性に優れた鉄酸化物と絶縁層を強固に固着させると同時に、最終的に得られる軟磁性金属粉末において３つの部分で構成される絶縁被覆が確実に得られるようになる。従って、本発明においては、この処理は極めて重要である。
なお、この処理に、熱処理を用いる方法は、既知の知見を利用することによる柔軟な物質設計が可能であることに加え、機械的手法や化学反応を利用する方法に比べて局所的な反応が起き難いため、処理粉末全体で均一な状態を得ることが容易であり、工業的な生産も容易であり、さらには装置全体が簡便であるという特徴をもち、本発明の軟磁性金属粉末を作製するための結合強化処理方法として、極めて有効である。
(Bond strengthening process)
In the present invention, in order to improve the adhesion between the iron oxide and the insulating layer, a bond strengthening treatment is performed. By applying this treatment, an iron oxide excellent in heat resistance and an insulating layer are firmly fixed, and at the same time, an insulating coating composed of three parts is surely obtained in the finally obtained soft magnetic metal powder. It becomes like this. Therefore, this process is extremely important in the present invention.
In addition to the fact that the method using heat treatment for this treatment allows flexible material design by utilizing known knowledge, the local reaction is less than the method using mechanical method or chemical reaction. Since it is difficult to occur, it is easy to obtain a uniform state in the entire treated powder, industrial production is easy, and the entire device is simple, and the soft magnetic metal powder of the present invention is produced. It is extremely effective as a bond strengthening treatment method for achieving this.
この点、メカノフュージョン等の強力なせん断力を付与する手法を結合強化処理として利用した場合、処理度合いにムラが生じ易いため、前述したような鉄酸化物をそなえる純鉄粉の表面に均一に絶縁層を形成することが極めて難しいことに加え、装置の原理上被覆の厚み方向の状態を細かく制御することが困難であるため、不可避的に被覆層内部に金属が混入してしまうことから、十分に満足行くほどの絶縁性は得られない。また、加工ひずみに起因する圧縮性の低下、加工による粉末の球形化による成形体強度の低下などがあるため実用上の取り扱いが難しいという問題もある。 In this regard, when a method of applying a strong shearing force such as mechanofusion is used as a bond strengthening treatment, unevenness is likely to occur in the degree of treatment, so that the surface of pure iron powder having iron oxide as described above is evenly distributed. In addition to being extremely difficult to form an insulating layer, it is difficult to finely control the thickness direction of the coating due to the principle of the device, so unavoidably metal is mixed inside the coating layer, It is not possible to obtain sufficient insulation. In addition, there is a problem that practical handling is difficult because there is a reduction in compressibility due to processing strain and a reduction in strength of the compact due to spheroidization of the powder by processing.
かような熱処理の際における、処理温度、時間、雰囲気などの条件は、用いる材料の組み合わせによって変化するが、原料粉末や絶縁物質の融点、それぞれの物質相互間および材料内での物質の拡散係数、酸素などに代表される各成分量、それぞれ材料の粒径、絶縁物質の添加量などを考慮して決定すればよい。例えば、絶縁層材料がAl2O3やSiO2などの高融点材料の場合には、500℃以上、1200℃以下程度とするのが好ましい。というのは、処理温度が500℃未満では物質拡散が不十分になるので密着性向上の効果が小さく、一方 1200℃超では、原料粉末相互での拡散が著しくなり粉末同士が焼結してしまうからである。一旦焼結した材料を再度粉末化するには、巨大な力を加えて粉砕する必要がある。このような巨大な力が作用すると、一旦原料粉末と接合した絶縁物質が脱落してしまい、絶縁性改善の効果が不十分になる。その上、巨大な力によって原料粉末に加工歪みが入るため加工硬化が起きる。このような粉末を成形して得られる試料の圧粉体密度は極めて低いものになるため、磁束密度の低下が避けられない。
また、時間についても、用途に応じて適宜決定すればよい。好適には20〜240分である。
The conditions such as processing temperature, time, and atmosphere during such heat treatment vary depending on the combination of materials used, but the melting point of the raw material powder and the insulating material, the diffusion coefficient of the materials between and within each material The amount of each component typified by oxygen, the particle size of the material, the amount of insulating material added, etc. may be taken into consideration. For example, when the insulating layer material is a high melting point material such as Al 2 O 3 or SiO 2 , the temperature is preferably about 500 ° C. or higher and 1200 ° C. or lower. This is because if the processing temperature is less than 500 ° C, the material diffusion becomes insufficient and the effect of improving the adhesion is small. On the other hand, if it exceeds 1200 ° C, the diffusion between the raw material powders becomes remarkable and the powders sinter. Because. In order to pulverize the material once sintered, it is necessary to apply a huge force to pulverize the material. When such a huge force acts, the insulating material once bonded to the raw material powder falls off, and the effect of improving the insulation becomes insufficient. In addition, work hardening occurs because the raw material powder is strained by enormous force. Since the green compact density of a sample obtained by molding such powder is extremely low, a decrease in magnetic flux density is inevitable.
Moreover, what is necessary is just to determine suitably also according to a use also about time. It is preferably 20 to 240 minutes.
さらに、かかる熱処理における雰囲気は、用途に応じて大気や酸素雰囲気のような酸化性雰囲気、窒素ガスやアルゴンガスなどの不活性雰囲気、水素ガス、アンモニアガス、RXガスなどの還元性雰囲気あるいは真空下などから適宜選べばよい。また、熱処理中に雰囲気を切り替えても構わない。なお、雰囲気が酸化性の場合には、結合強化処理時に金属が酸化して磁気特性や圧縮性の低下を招く場合がある。従って、本発明においては、不活性あるいは還元性雰囲気あるいは真空下などの非酸化性雰囲気中で行うことがより好ましい。必要に応じて水蒸気露点を調整しても良い。 Furthermore, the atmosphere in such heat treatment may be an oxidizing atmosphere such as air or oxygen atmosphere, an inert atmosphere such as nitrogen gas or argon gas, a reducing atmosphere such as hydrogen gas, ammonia gas or RX gas, or a vacuum depending on the application. You may choose from the appropriate. Further, the atmosphere may be switched during the heat treatment. In the case where the atmosphere is oxidizing, the metal may be oxidized during the bond strengthening treatment, resulting in a decrease in magnetic properties and compressibility. Therefore, in the present invention, it is more preferable to carry out in an inert or reducing atmosphere or a non-oxidizing atmosphere such as under vacuum. The water vapor dew point may be adjusted as necessary.
なお、ここでの熱処理温度は、後述する成形体の焼鈍温度よりも高いことが好ましい。温度が低いと強化処理が十分でなくなるだけでなく、結合強化処理時に未反応だった部分が成形体焼鈍時に反応し、その際ガスが発生して成形体破壊を引き起こしたりするので好ましくない。従って、結合強化のための熱処理温度は、成形体の焼鈍温度に対して＋10〜＋150℃程度とすることが好まし い。特に好ましくは＋50〜＋150℃の範囲である。 In addition, it is preferable that the heat processing temperature here is higher than the annealing temperature of the molded object mentioned later. If the temperature is low, not only does the strengthening treatment become insufficient, but the unreacted part during the bond strengthening treatment reacts when the molded body is annealed, and at this time, gas is generated and the molded body is destroyed, which is not preferable. Accordingly, the heat treatment temperature for strengthening the bond is preferably about +10 to + 150 ° C. with respect to the annealing temperature of the compact. Especially preferably, it is the range of + 50- + 150 degreeC.
上記したような加熱結合強化処理を行う場合、図１に示した絶縁層３が酸化物や金属塩の場合には、金属と酸化物を結合する場合に比べると、強い結合が得られる。これは、熱エネルギーによって酸化物中に含まれる酸素の拡散が金属原子の拡散よりも容易に進行するため、まず酸素の交換が最初に生じ、ついでその酸素の拡散によって金属成分の拡散が、単なる金属−酸化物の場合よりも加速された状態になり、結果として成分全体の拡散が加速されるためである。特に酸化物同士の場合にはこの現象が顕著に生じるのでとりわけ有利である。 When the heat bond strengthening treatment as described above is performed, when the insulating layer 3 shown in FIG. 1 is an oxide or a metal salt, a stronger bond can be obtained as compared with a case where a metal and an oxide are bonded. This is because the diffusion of oxygen contained in the oxide by thermal energy proceeds more easily than the diffusion of metal atoms, so that the exchange of oxygen occurs first, and then the diffusion of the metal component is simply caused by the diffusion of oxygen. This is because the state is accelerated as compared with the case of the metal-oxide, and as a result, the diffusion of the entire component is accelerated. Particularly in the case of oxides, this phenomenon is remarkable, which is particularly advantageous.
なお、本発明に従う３つの部分から構成される絶縁被膜のうち、鉄酸化物と絶縁層は特に耐熱性を持つことが好ましい。この部分の耐熱性が低いと、シリコーン樹脂層の耐熱性が十分に高くても所望の耐熱性が得られなくなる場合がある。なお、ここでいう耐熱性を持つとは、軟磁性金属粉末を圧粉磁心にして、さらにその圧粉磁心を焼鈍した後にも絶縁性が維持されていることを意味する。従って、この条件を満たす物質なら、どのような物質を用いてもかまわないし、評価に利用する指標にも特に制限はない。
その中でも重量減少率Δmは、簡便に測定できる上、圧粉磁心に成形し、焼鈍した後の絶縁性を評価した場合との対応がよく取れるので、特に酸化物と絶縁層の耐熱性を評価する指標として好適である。
Of the insulating coating composed of three parts according to the present invention, the iron oxide and the insulating layer preferably have heat resistance. If the heat resistance of this portion is low, the desired heat resistance may not be obtained even if the heat resistance of the silicone resin layer is sufficiently high. Here, having heat resistance means that insulation is maintained even after soft magnetic metal powder is used as a powder magnetic core and the powder magnetic core is annealed. Therefore, any substance that satisfies this condition may be used, and the index used for evaluation is not particularly limited.
Among them, the weight loss rate Δm can be easily measured, and it can be well matched with the case of evaluating the insulation after molding into a powder magnetic core and annealing, so the heat resistance of oxide and insulating layer is especially evaluated It is suitable as an index to perform.
酸化物と絶縁層の重量減少率Δmを評価する方法としては、被覆部分の物質単体を取り出して測定する方法、酸化物と絶縁層をそなえる軟磁性金属粉末全体で測定する方法が挙げられる。勿論、これら以外の方法で測定してもかまわない。
単体で取り出す場合は、軟磁性金属粉末の金属部分を酸、アルカリあるいはその他の溶解性物質で溶解させ、その残渣を取り出す方法、軟磁性金属粉末に機械的エネルギーを与えた濃化部分だけを分離する方法、濃化部分の破壊が起きない程度の低圧力で加圧成形したものを電極として、電気的に金属部分だけを溶解する方法などが挙げられる。
重量減少率Δm は、加熱前質量をMb、不活性ガス雰囲気中で加熱したときの質量をMaとするとき、Δm＝Ma／Mbなる関係から算出される。
本発明においては、N2ガス中で800℃まで加熱した後の重量をMa 、加熱前の重量をMbとしたとき、好ましいΔmは 0.3以上、1.0以下である。特に好ましくは 0.5以上、1.0以下であり、さらに好ましくは 0.7以上、1.0以下である。
As a method for evaluating the weight reduction rate Δm of the oxide and the insulating layer, there are a method of taking out and measuring the substance alone of the covering portion, and a method of measuring the whole soft magnetic metal powder having the oxide and the insulating layer. Of course, you may measure by methods other than these.
When taking it out as a single unit, the metal part of the soft magnetic metal powder is dissolved with acid, alkali or other soluble substance, and the residue is taken out. Only the concentrated part where mechanical energy is given to the soft magnetic metal powder is separated. And a method in which only a metal part is electrically dissolved using an electrode formed by pressure molding at a low pressure that does not cause destruction of the concentrated part.
The weight reduction rate Δm is calculated from the relationship Δm = Ma / Mb, where Mb is the mass before heating and Ma is the mass when heated in an inert gas atmosphere.
In the present invention, when the weight after heating to 800 ° C. in N 2 gas is Ma and the weight before heating is Mb, a preferable Δm is 0.3 or more and 1.0 or less. Especially preferably, it is 0.5 or more and 1.0 or less, More preferably, it is 0.7 or more and 1.0 or less.
本発明では、上記の手順によって得た軟磁性金属粉末において、表面の鉄酸化物と絶縁層の元素濃度合計をCs(at％)、最外表面から深さ10μmでの主要元素 濃度合計をCb(at％)としたとき、Cs／Cbが 1.5以上であることが好ましい。Cs／Cbが 1.5未満の場合には、表面での濃化が不十分なため圧粉磁心にしたとき十分な絶縁性が得られない。
CsおよびCbの測定は、オージェ電子分光法を用いた表面分析装置(AES)によ って行えばよい。測定対象部分の面積は、使用する原料粉末の粒径により適宜決定すればよいが、例えば粒径が30〜100μm 程度の粉末を対象とする場合は 、一辺が５μmから30μm 程度の正方形の部分で評価すればよい。また測定値 の精度を向上させるために、Cs／Cbは複数の粒子について測定することが好ましい。好ましい測定数は、５以上、15以下である。
In the present invention, in the soft magnetic metal powder obtained by the above procedure, the total element concentration of the surface iron oxide and insulating layer is Cs (at%), and the total concentration of main elements at a depth of 10 μm from the outermost surface is Cb. When (at%), Cs / Cb is preferably 1.5 or more. When Cs / Cb is less than 1.5, sufficient insulation cannot be obtained when a dust core is formed because of insufficient concentration on the surface.
Cs and Cb may be measured by a surface analyzer (AES) using Auger electron spectroscopy. The area of the measurement target portion may be appropriately determined depending on the particle size of the raw material powder to be used. For example, when a powder having a particle size of about 30 to 100 μm is targeted, a square portion with a side of about 5 to 30 μm is used. You should evaluate. In order to improve the accuracy of the measurement value, Cs / Cb is preferably measured for a plurality of particles. A preferable measurement number is 5 or more and 15 or less.
また、本発明において、鉄酸化物と絶縁層は、鉄粉の表面全体に均一に存在していることが好ましく、その形態は図１(a)に示したような状態であることが好ましい。鉄酸化物２と絶縁層３の分布が不均一になると、本発明である軟磁性金属粉末を加圧成形して得られる圧粉磁心の絶縁性が焼鈍前から低下し、焼鈍後はさらに低下してしまう場合があるので、好ましくない。
かような鉄酸化物と絶縁層は、AESにて絶縁被膜成分をマッピングしたとき、 総測定面積をSa、絶縁被膜成分の元素が存在する面積をStとした場合、St／Sa が 0.1以上、1.0以下とすることが好ましい。この値が 0.1を下回る場合、絶縁被膜が存在する部分が少なすぎて、本発明である軟磁性金属粉末から作製される圧粉磁心は十分な絶縁性が得られない。好適なSt／Saの範囲は 0.3以上、1.0以下であり、さらに 好ましくは0.5以上、1.0以下である。
測定対象部分の面積は、使用する原料粉末の粒径により適宜決定すればよいが、例えば粒径が30〜100μm 程度の純鉄粉を対象とする場合には、一辺が５μmから30μm 程度の正方形の部分で評価すればよい。なお、本測定値も精度向上のため、St／Saは複数の粒子について測定されることが好ましい。好ましい測定数は、Cs／Cb の場合と同様、５以上、 15以下である。St／Saについては、Csを評価する際に、併せて評価すると効率的な評価ができるので好ましい。
Moreover, in this invention, it is preferable that an iron oxide and an insulating layer exist uniformly on the whole surface of iron powder, and it is preferable that the form is a state as shown to Fig.1 (a). When the distribution of the iron oxide 2 and the insulating layer 3 becomes non-uniform, the insulation of the powder magnetic core obtained by press-molding the soft magnetic metal powder according to the present invention is lowered before annealing, and further lowered after annealing. This is not preferable because it may occur.
Such an iron oxide and insulating layer, when mapping the insulating film component by AES, when the total measurement area is Sa and the area where the element of the insulating film component is St is St / Sa is 0.1 or more, It is preferable to set it to 1.0 or less. When this value is less than 0.1, there are too few portions where the insulating coating exists, and the dust core produced from the soft magnetic metal powder of the present invention cannot obtain sufficient insulation. A preferable range of St / Sa is 0.3 or more and 1.0 or less, and more preferably 0.5 or more and 1.0 or less.
The area of the measurement target portion may be determined as appropriate depending on the particle size of the raw material powder to be used. For example, when pure iron powder having a particle size of about 30 to 100 μm is targeted, a square having a side of about 5 to 30 μm. You should evaluate in the part of. In addition, it is preferable that St / Sa is measured for a plurality of particles in order to improve the accuracy of this measurement value. The preferred number of measurements is 5 or more and 15 or less as in the case of Cs / Cb. As for St / Sa, when evaluating Cs, it is preferable to evaluate it together because efficient evaluation can be performed.
さらに、鉄酸化物と絶縁層の合計厚みは0.5nm〜4000nm程度とすることが好ましい。特に好ましくは１〜1000nmの範囲である。なお、鉄酸化物と絶縁層の合計厚みは、軟磁性金属粉末の断面を切り出し、基地鉄部の最外表面と、絶縁層の最外表面の距離によって定義される。距離は、基地鉄部の最外表面での垂線と基地鉄表面の交点１と、交点１を通るように引いた垂線と、絶縁層表面での交点２の間の長さによって定義される。この測定点は１粒子の外周を均等に分割するように複数配置することが好ましい。分割数は100以上とすることが好ましい。これを複数の粒子に対して繰り返し行い、それぞれの点で測定した結果の平均値を鉄酸化物と絶縁層の合計厚みＳ、その分散値を鉄酸化物と絶縁層の合計厚みの変動Ｖとする。 Furthermore, the total thickness of the iron oxide and the insulating layer is preferably about 0.5 nm to 4000 nm. Especially preferably, it is the range of 1-1000 nm. The total thickness of the iron oxide and the insulating layer is defined by the distance between the outermost surface of the base iron part and the outermost surface of the insulating layer by cutting a cross section of the soft magnetic metal powder. The distance is defined by the length between the perpendicular line on the outermost surface of the base iron portion and the intersection point 1 of the surface of the base iron, the perpendicular line drawn through the intersection point 1, and the intersection point 2 on the surface of the insulating layer. It is preferable to arrange a plurality of measurement points so that the outer periphery of one particle is evenly divided. The number of divisions is preferably 100 or more. This is repeated for a plurality of particles, the average value of the results measured at each point is the total thickness S of the iron oxide and the insulating layer, and the dispersion value is the variation V of the total thickness of the iron oxide and the insulating layer. To do.
鉄酸化物と絶縁層の合計厚みＳと鉄酸化物と絶縁層の合計厚みの変動Ｖの比Ｖ／Ｓは、0.0以上、0.90以下であることが好ましい。特に好ましくは0.0 以上、 0.50以下であり、さらに好ましくは0.0 以上、0.40以下である。Ｖ／Ｓが0.90を上回る場合、加圧成形後、被膜がごく薄くなり、成形体内部での軟磁性金属粉末粒子間の距離が十分に離れないところが発生するので、圧粉磁心は十分な絶縁性が得られないので好ましくない。また、鉄酸化物と絶縁層の内部は稠密であることが好ましい。鉄酸化物と絶縁層を断面から観察したとき、鉄酸化物と絶縁層全体の面積をCa、鉄酸化物と絶縁層の被膜部分内部に存在する空孔部分の面積をCpとそれぞれ定義するとき、Cp／Caは0.0以上、0.3未満であることが好ましい。特に好ましくは0.0以上、0.1未満である。Cp／Caが大きいと、鉄酸化物と絶縁層の被膜部分の強度が弱くなるため加圧成形時、被膜部分が破壊されてしまう。その結果、絶縁被膜の厚み変動が増大し、軟磁性金属粉末を加圧成形して作製される圧粉磁心の絶縁性が低下してしまう。なお、軟磁性金属粉末の断面側から見た粉末表面近傍での鉄酸化物と絶縁層の大きさおよび内部の充填状態は、軟磁性金属粉末を樹脂に埋め込み研磨して断面を観察できるようにした試料の走査型電子顕微鏡(SEM)による観察結果を用いて評価すればよい。 The ratio V / S between the total thickness S of the iron oxide and the insulating layer and the variation V of the total thickness of the iron oxide and the insulating layer is preferably 0.0 or more and 0.90 or less. Particularly preferably, it is 0.0 or more and 0.50 or less, and more preferably 0.0 or more and 0.40 or less. When V / S exceeds 0.90, the film becomes very thin after pressure molding, and there are places where the distance between the soft magnetic metal powder particles is not sufficiently separated inside the compact, so that the dust core is sufficiently insulated. It is not preferable because the property cannot be obtained. Moreover, it is preferable that the inside of an iron oxide and an insulating layer is dense. When the iron oxide and the insulating layer are observed from the cross section, the area of the iron oxide and the entire insulating layer is defined as Ca, and the area of the void portion existing inside the coating portion of the iron oxide and the insulating layer is defined as Cp. Cp / Ca is preferably 0.0 or more and less than 0.3. Particularly preferred is 0.0 or more and less than 0.1. When Cp / Ca is large, the strength of the coating portion of the iron oxide and the insulating layer is weakened, so that the coating portion is destroyed during pressure molding. As a result, the thickness variation of the insulating coating increases, and the insulating property of the powder magnetic core produced by press-molding the soft magnetic metal powder is lowered. The size of the iron oxide and the insulating layer in the vicinity of the powder surface as viewed from the cross-sectional side of the soft magnetic metal powder and the filling state inside the powder can be observed by embedding and polishing the soft magnetic metal powder in a resin. What is necessary is just to evaluate using the observation result by the scanning electron microscope (SEM) of the obtained sample.
（シリコーン樹脂層）
このようにして得た軟磁性金属粉末に、さらに耐熱性に優れたシリコーン樹脂を被覆して最外層を形成する。これにより、圧粉磁心の絶縁性がさらに向上し、その上成形体強度まで向上する。このシリコーン樹脂は、他の被覆可能な樹脂と比べて密着性に優れ、その上耐熱性、絶縁性にも優れている。
(Silicone resin layer)
The soft magnetic metal powder thus obtained is further coated with a silicone resin having excellent heat resistance to form the outermost layer. Thereby, the insulation of a powder magnetic core improves further and also improves to a molded object strength. This silicone resin is excellent in adhesiveness as compared with other resins that can be coated, and is also excellent in heat resistance and insulation.
本発明におけるシリコーン樹脂とは、分子内に３官能性（Ｔ単位）、あるいは４官能性（Ｑ単位）シロキサン単位を含有するポリオルガノシロキサンを指す。かかるシリコーン樹脂は、シリコーンオイルやシリコーンゴムなどに比べ架橋密度が高く、硬化物は硬いという特徴があり、本発明に好適である。ところで、シリコーン樹脂は、成分がシリコーンのみから構成されるストレートシリコン樹脂と、シリコーン成分と有機樹脂の共重合体であるシリコーン変成有機樹脂に大別されるが、本発明においては、そのいずれを使用しても構わない。ストレートシリコーン樹脂は、MQレジンとDTレジンに大別されるが、本発明においては、そのいずれを用いても構わない。シリコーン変成有機樹脂としては、アルキド変成型、エポキシ変成型、ポリエステル変成型、アクリル変成型、フェノール変成型などが挙げられるが、本発明においては、そのいずれを用いても構わない。また、シリコーン樹脂には、加熱すると硬化するタイプのものと、室温においても硬化が進行するタイプのものがあるが、本発明においてはその何れを用いても構わない。シリコーン樹脂の硬化反応には、いくつかのタイプがあり、例えば加熱硬化型シリコーン樹脂の硬化の機構は大きく分けて、脱水縮合反応、付加反応、過酸化物反応によるものに、室温硬化型シリコーン樹脂の硬化の機構は、脱オキシム反応、脱アルコール反応によるものに区別することができる。本発明において用いられるシリコーン樹脂は、上記にある何れかの硬化反応によって硬化するものであれば良い。 The silicone resin in the present invention refers to a polyorganosiloxane containing a trifunctional (T unit) or tetrafunctional (Q unit) siloxane unit in the molecule. Such a silicone resin is characterized in that it has a higher crosslink density and a cured product is harder than silicone oil or silicone rubber, and is suitable for the present invention. By the way, silicone resins are roughly classified into straight silicone resins whose components are composed only of silicone, and silicone-modified organic resins that are copolymers of silicone components and organic resins. In the present invention, any of them is used. It doesn't matter. Straight silicone resins are roughly classified into MQ resins and DT resins, and any of them may be used in the present invention. Examples of the silicone-modified organic resin include alkyd modification, epoxy modification, polyester modification, acrylic modification, and phenol modification, and any of them may be used in the present invention. Silicone resins include a type that cures when heated and a type that cures even at room temperature. Any of these types may be used in the present invention. There are several types of curing reactions for silicone resins. For example, the mechanism of curing thermosetting silicone resins can be broadly divided into those based on dehydration condensation reactions, addition reactions, and peroxide reactions. The curing mechanism can be distinguished by deoxime reaction and dealcoholization reaction. The silicone resin used in the present invention only needs to be cured by any of the above curing reactions.
本発明で使用されるシリコーン樹脂としては、たとえば東レダウコーニングシリコーン社の製造する、SH805 , SH805, SH806A ,SH840, SH997, SR620, SR2306, SR2309, SR2310, SR2316, DC12577, SR2400, SR2402, SR2404, SR2405, SR2406, SR2410, SR2411, SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC6-2230, DC3037, DC3074, QP8-5314や、信越化学の製造する KR251, KR255, KR114A, KR112, KR2610B, KR2621-1, KR230B, KR220, KR220L, KR285, K295, KR300,KR2019, KR2706, KR165, KR166, KR169, KR2038, KR221, KR155, KR240, KR101-10, KR120, KR105, KR271, KR282, KR311, KR211, KR212, KR216, KR213, KR217, KR9218, SA-4, KR206, KR5206, ES1001N, ES1002T, ES1004, KR9706, KR5203, KR5221,X-52-1435などが挙げられる。勿論、ここに挙げ た以外のシリコーン樹脂を使用しても構わない。また、これらの物質、あるいはこれらの原料物質を変成したシリコーン樹脂を使用しても構わない。さらに、種類、分子量、官能基が異なる２種以上のシリコーン樹脂を、適当な割合で混合したシリコーン樹脂 を使用しても構わない。 Examples of the silicone resin used in the present invention include SH805, SH805, SH806A, SH840, SH997, SR620, SR2306, SR2309, SR2310, SR2316, DC12577, SR2400, SR2402, SR2404, SR2405 manufactured by Toray Dow Corning Silicone. , SR2406, SR2410, SR2411, SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC6-2230, DC3037, DC3074, QP8-5314, manufactured by Shin-Etsu Chemical KR251, KR255, KR114A, KR112, KR2610B, KR2621-1 , KR230B, KR220, KR220L, KR285, K295, KR300, KR2019, KR2706, KR165, KR166, KR169, KR2038, KR221, KR155, KR240, KR101-10, KR120, KR105, KR271, KR282, KR311, KR211, KR212, KR211, KR212 , KR213, KR217, KR9218, SA-4, KR206, KR5206, ES1001N, ES1002T, ES1004, KR9706, KR5203, KR5221, X-52-1435, and the like. Of course, silicone resins other than those listed here may be used. Moreover, you may use the silicone resin which modified these substances or these raw material substances. Furthermore, you may use the silicone resin which mixed the 2 or more types of silicone resin from which a kind, molecular weight, and a functional group differ in a suitable ratio.
最外層を構成するシリコーン樹脂を軟磁性金属粉末に添加あるいは被覆する際は、粉末状のものを混合してもよいし、あるいはシリコーン樹脂を溶剤に溶かし、その溶液と軟磁性金属粉末を接触させることで混合あるいは被覆してもかまわない。溶液にする場合、溶剤にはシリコーン樹脂が溶解するものであれば、いずれを用いてもよい。このような材料としては、例えばエタノールやメタノールに代表されるアルコール系溶剤、アセトンやメチルエチルケトンに代表されるケトン系溶剤、ベンゼン、トルエン、キシレン、フェノール、安息香酸などに代表される芳香族系溶剤、リグロイン、ケロシンなどの石油系溶剤が挙げられる。シリコーン樹脂を溶解し易い芳香族系溶媒が、特に好ましい。また、シリコーン樹脂が可溶なら、水を用いても構わない。その溶液の濃度は、施工のし易さや乾燥時間などを勘案して決めれば良い。さらに、シリコーン樹脂溶液の粘度・チキソトロピー性・レベリング性、また塗布後の乾燥時間、樹脂が硬化するまでの時間、樹脂の硬化温度や硬化時の架橋密度などを制御するために、上記塗料に若干の添加物を加えてもよい。このような添加物としては、シリコーン樹脂の硬化を制御するステアリン酸金属塩などの金属石鹸、パーフルオロアルキルなどの界面活性剤などがあげられる。なお、溶剤にして添加するとシリコーン樹脂の偏析が防止できるため、添加量が同一であっても粉末を用いた場合に比べ圧粉磁心の絶縁性が改善されるので、本発明においては溶液状にして添加することが好ましい。 When the silicone resin constituting the outermost layer is added to or coated on the soft magnetic metal powder, the powdered material may be mixed, or the silicone resin is dissolved in a solvent and the solution is brought into contact with the soft magnetic metal powder. It may be mixed or coated. In the case of preparing a solution, any solvent may be used as long as it can dissolve the silicone resin. Examples of such materials include alcohol solvents such as ethanol and methanol, ketone solvents such as acetone and methyl ethyl ketone, aromatic solvents such as benzene, toluene, xylene, phenol, and benzoic acid, Examples include petroleum solvents such as ligroin and kerosene. An aromatic solvent that easily dissolves the silicone resin is particularly preferred. If the silicone resin is soluble, water may be used. The concentration of the solution may be determined in consideration of ease of construction and drying time. Furthermore, in order to control the viscosity, thixotropy and leveling properties of the silicone resin solution, the drying time after application, the time until the resin is cured, the curing temperature of the resin and the crosslink density during curing, etc. Additives may be added. Examples of such additives include metal soaps such as metal stearates that control the curing of the silicone resin, and surfactants such as perfluoroalkyl. When added as a solvent, segregation of the silicone resin can be prevented. Therefore, even if the amount added is the same, the insulation of the powder magnetic core is improved compared to the case where powder is used. Is preferably added.
なお、最外層を構成するシリコーン樹脂の添加は、最初に全量添加しても良いし、撹拌の途中で分割して添加しても良い。また、撹拌時にスプレーノズルを通して噴霧してもよい。本発明で用いられるシリコーン樹脂溶液をスプレーノズルを通して噴霧・添加すると、本発明で用いられるシリコーン樹脂溶液が軟磁性金属粉末に対して均一に添加され、皮膜も均一になるので好適である。撹拌混合には、アトライタ、ヘンシェルミキサー、ボールミル、流動造粒機、転動造粒機などを利用するのが一般的である。流動造粒機や転動造粒機のように、流動槽による撹拌を行なうと、粉体同士の凝集が抑制されるので好適である。また、流動槽に対してスプレーを通して本発明で用いられるシリコーン樹脂溶液を噴霧すると、スプレー噴霧による効果と、流動槽を利用した効果が複合し、一層均一な被覆が得られるので、特に好ましい。溶媒の乾燥を促進やシリコーン樹脂の硬化などを目的として、混合中あるいは混合後に加熱処理を行なっても良い。 In addition, the addition of the silicone resin constituting the outermost layer may be added first in total, or may be added in the middle of stirring. Moreover, you may spray through a spray nozzle at the time of stirring. When the silicone resin solution used in the present invention is sprayed and added through a spray nozzle, the silicone resin solution used in the present invention is added uniformly to the soft magnetic metal powder, and the film is also uniform. For stirring and mixing, an attritor, a Henschel mixer, a ball mill, a fluidized granulator, a rolling granulator or the like is generally used. Agitation using a fluidized tank as in a fluidized granulator or a rolling granulator is preferable because aggregation of powders is suppressed. Further, it is particularly preferable to spray the silicone resin solution used in the present invention on the fluidized tank through spraying, since the effect of the spray spraying and the effect using the fluidized tank are combined and a more uniform coating can be obtained. Heat treatment may be performed during or after mixing for the purpose of accelerating the drying of the solvent or curing the silicone resin.
本発明において、最外層を構成するシリコーン樹脂の添加量は、軟磁性金属粉末全体に対してシリコーン樹脂の固形分量(固形分量＝添加した溶液量−溶液中 の溶剤量)で0.01〜５mass％程度とすることが好まし い。添加量が0.01mass％を下回ると、シリコーン樹脂が少なすぎるために原料粉末の被覆が不均一となり絶縁性改善の効果が不十分となり、一方５mass％を超えた場合には、圧粉磁心中の原料粉末の割合が著しく低下するので、磁束密度の低下を招き好ましくない。 In the present invention, the addition amount of the silicone resin constituting the outermost layer is about 0.01 to 5 mass% in terms of the solid content of the silicone resin (solid content = added solution amount−solvent amount in the solution) with respect to the entire soft magnetic metal powder. Is preferred. If the added amount is less than 0.01 mass%, the amount of the silicone resin is too small, so that the coating of the raw material powder becomes non-uniform, and the effect of improving the insulation becomes insufficient. On the other hand, if it exceeds 5 mass%, Since the ratio of the raw material powder is remarkably reduced, the magnetic flux density is lowered, which is not preferable.
以上の方法によって作製された、絶縁被覆付き軟磁性金属粉末は、必要に応じて潤滑剤などが添加された後、金型などを用いて加圧成形される。潤滑剤としては、ステアリン酸リチウム、ステアリン酸亜鉛、ステアリン酸カルシウムなどの金属石鹸、あるいは脂肪酸アミドなどのワックスが挙げられる。軟磁性金属粉末に対して潤滑剤を添加せず、金型表面に潤滑剤を塗布する金型潤滑を用いてもよい。
成形圧は、用途に応じて適宜決定すれば良いが490〜1960MPa程度とするのが好ましい。成形圧が490MPaを下回ると、成形体密度が低くなるため磁束密度が低くなるという問題が生じ、一方1960MPaを超えると成形時の金型磨耗が顕著となり実用的でない。
The soft magnetic metal powder with an insulation coating produced by the above method is pressure-molded using a mold or the like after a lubricant or the like is added as necessary. Examples of the lubricant include metal soaps such as lithium stearate, zinc stearate, and calcium stearate, and waxes such as fatty acid amides. Mold lubrication in which a lubricant is applied to the mold surface without adding a lubricant to the soft magnetic metal powder may be used.
The molding pressure may be appropriately determined according to the application, but is preferably about 490 to 1960 MPa. When the molding pressure is less than 490 MPa, the density of the molded body is lowered, resulting in a problem that the magnetic flux density is lowered. On the other hand, when the molding pressure is more than 1960 MPa, the mold wear during molding becomes remarkable, which is not practical.
上記の成形後、加圧時に鉄基粉末に加えられた歪を解放してヒステリシス損失を低減させるために、成形体を 600℃以上の温度で保持しながら、焼鈍することが特に好ましい。特に好ましい焼鈍温度は800℃以上である。また前述した理由より、かかる焼鈍温度は、結合強化処理時の温度より−10℃〜−150℃ 程度とすることが好ましい。特に好ましくは−50℃〜−150℃である。また、 焼鈍時間は30分以上とすることが好ましい。焼鈍雰囲気は、ArやN2などの不活性雰囲気、水素などの還元性雰囲気、あるいは真空などの非酸化性雰囲気とすることが好ましい。水蒸気の露点は用途等に応じて適宜決定すれば良い。焼鈍の際の昇温速度、降温速度は、熱膨張率の違いにより絶縁被覆の破壊、急冷による軟磁性金属粉末の金属組織内での熱歪みの発生などを防止するため、20℃／分以下程度とすることが好ましい。また、昇温時あるいは降温時に、一定の温度で保持する段階を設けてもよい。 In order to release the strain applied to the iron-based powder during pressurization and reduce the hysteresis loss after the above molding, it is particularly preferable to anneal the molded body while maintaining it at a temperature of 600 ° C. or higher. A particularly preferable annealing temperature is 800 ° C. or higher. For the reasons described above, the annealing temperature is preferably about −10 ° C. to −150 ° C. from the temperature during the bond strengthening treatment. Particularly preferred is -50 ° C to -150 ° C. The annealing time is preferably 30 minutes or longer. Annealing atmosphere is an inert atmosphere such as Ar or N 2, be a non-oxidizing atmosphere such as a reducing atmosphere or vacuum, such as hydrogen preferable. What is necessary is just to determine suitably the dew point of water vapor | steam according to a use etc. The temperature rise rate and temperature drop rate during annealing are 20 ° C / min or less in order to prevent the insulation coating from being destroyed due to the difference in thermal expansion coefficient and the occurrence of thermal distortion in the metal structure of the soft magnetic metal powder due to rapid cooling. It is preferable to set the degree. Further, a step of holding at a constant temperature may be provided when the temperature is raised or lowered.
実施例１
原料粉末としては、アトマイズ法により製造した表１に示す成分の純鉄粉を用いた。各鉄粉の成分、粒度分布および粉体特性（見かけ密度）を表１に示す。
また、これらの粉末を樹脂に埋め込み研磨して作製した試料を用いて、粉末断面を光学顕微鏡により倍率400倍で観察した。そして、５mm×５mmの領域に存在する全ての粒子に対して、面積Ｓと周囲の長さＬを計測し、粉末の凹凸の指標であるｘ（＝Ｌ／｛２（πＳ）1/2｝）を算出した。測定個数とｘの平均値も表１に併せて示す。
Example 1
As the raw material powder, pure iron powder having the components shown in Table 1 manufactured by the atomizing method was used. Table 1 shows the components, particle size distribution, and powder characteristics (apparent density) of each iron powder.
Further, using a sample prepared by embedding and polishing these powders in a resin, the powder cross section was observed with an optical microscope at a magnification of 400 times. Then, the area S and the peripheral length L are measured for all particles existing in a 5 mm × 5 mm region, and x (= L / {2 (πS) 1/2 }, which is an index of powder irregularities. ) Was calculated. Table 1 also shows the number of measurements and the average value of x.
次に、絶縁層の形成を行った。ここでは表２に示す材料を使用した。溶液状のものは濃度：10mass％の溶液を準備した後、転動流動層によって被覆処理を施した。粉末状のものは原料粉末に耐熱性に優れた絶縁材料を添加した後、ヘンシェルミキサーで10分間混合した。
さらに、表２に併せて示した熱処理による結合強化処理を行った。結合強化処理後、目開き180μmのふるいで分級して本発明の軟磁性金属粉末を得た。ただし、粉末３は16メッシュふるい（めびらき１mm）で分級したものを用いた。これらの粉末を別途熱天秤にて不活性雰囲気中での重量変化を調査し、その結果からΔmを算出した。
その結果も表２に併記する。
Next, an insulating layer was formed. Here, the materials shown in Table 2 were used. After preparing a solution having a concentration of 10 mass%, the solution was coated with a rolling fluidized bed. In the powder form, an insulating material having excellent heat resistance was added to the raw material powder, and then mixed for 10 minutes with a Henschel mixer.
Furthermore, the bond reinforcement | strengthening process by the heat processing shown collectively in Table 2 was performed. After the bond strengthening treatment, classification was performed with a sieve having an opening of 180 μm to obtain the soft magnetic metal powder of the present invention. However, powder 3 was classified using a 16-mesh sieve (Merakira 1 mm). These powders were separately examined for changes in weight in an inert atmosphere using a thermobalance, and Δm was calculated from the results.
The results are also shown in Table 2.
上記のようにして得た粉末について、AESを用いてCs／Cb、St／Sa を求めた。なお AESの測定条件は、PHYSICAL ELECTONICS社製 PHI MODEL 660 にて加速電圧：10kV、試料電流量：0.2μA、測定領域：20μm平方の正方形、試料傾斜 角：30°とした。Cbは、表面測定後、イオン銃で上記の測定面積分を10μm深 さ方向でスパッタリングしてから、同一条件で測定した。表２に、Cs／CbおよびSt／Saの評価に際して用いた元素、測定点数、測定したそれぞれの平均値と分散を示す。なお、Stを確認した際、併せて酸素原子の分布についても調査した。いずれの結果においても、酸素の濃度分布はSt／Saの評価に用いた元素の分布と一致していた。これより、表面で観察される原子は、SiO2やAl2O3、TiO2、ZrO2など耐熱性に優れた絶縁酸化物の形で存在していることが判明した。 For the powder obtained as described above, Cs / Cb and St / Sa were determined using AES. The AES measurement conditions were PHI MODEL 660 manufactured by PHYSICAL ELECTONICS, with acceleration voltage of 10 kV, sample current amount: 0.2 μA, measurement area: square of 20 μm square, and sample tilt angle: 30 °. Cb was measured under the same conditions after the surface measurement, after sputtering the above measurement area in the depth direction of 10 μm with an ion gun. Table 2 shows the elements used in the evaluation of Cs / Cb and St / Sa, the number of measurement points, and the measured average values and variances. When St was confirmed, the distribution of oxygen atoms was also investigated. In any result, the oxygen concentration distribution was consistent with the element distribution used for the St / Sa evaluation. Thus, it was found that the atoms observed on the surface exist in the form of insulating oxides having excellent heat resistance such as SiO 2 , Al 2 O 3 , TiO 2 , and ZrO 2 .
また、軟磁性金属粉末：５ｇを樹脂に埋め込んだ後、樹脂ごと研磨して粉末断面を観察できるようにした研磨試料を走査型電子顕微鏡(SEM)で観察し、１mm平方の観察視野内で確認されるすべての粉末を対象として、表面濃化部分の耐熱性及び絶縁性に優れた物質部分の濃化部分の分布状態および大きさの平均値と分散、および濃化内部の充填率Cp／Caを求めた。なお、これらの値は、粒子の外周部分を、倍率：100,000倍で連続的に観察した結果を用いて算出して いる。視野内での粉末個数およびそれらの測定結果も併せて表２に示す。 Moreover, after embedding 5 g of soft magnetic metal powder in the resin, the polished sample which was polished with the resin so that the cross section of the powder could be observed was observed with a scanning electron microscope (SEM) and confirmed within an observation field of 1 mm square. For all the powders, the distribution and average value of the distribution and size of the concentrated portion of the material portion with excellent heat resistance and insulation at the surface concentrated portion and the filling rate Cp / Ca inside the concentrated portion Asked. These values are calculated using the results of continuously observing the outer peripheral portion of the particles at a magnification of 100,000. Table 2 also shows the number of powders in the field of view and their measurement results.
上記のようにして絶縁層を形成した軟磁性金属粉末に、シリコーン樹脂による最外層を形成した。シリコーン樹脂としては、東レダウコーニング社のSR2400を用いた。被覆に当たっては、樹脂をキシレンにて濃度：５mass％とした溶液を用いた。軟磁性金属粉末に対するシリコーン樹脂の被覆は、転動流動槽型被覆装置により実施した。シリコーン樹脂溶液の添加は、原料粉末を装置容器内で流動化させた上で、スプレーを用いてその流動状態にある粉末に対し、被覆材を固形分量が表２に示す量になるように噴霧することにより行った。噴霧終了後、乾燥のために20分間流動状態を保持して、原料粉末の上に被覆材を被覆した軟磁性金属粉末を得、さらに大気雰囲気中にて、250℃で60分間加熱することでシリコーン樹脂を加熱硬化して、軟磁性金属粉末試料を得た。 An outermost layer made of silicone resin was formed on the soft magnetic metal powder having the insulating layer formed as described above. SR2400 from Toray Dow Corning was used as the silicone resin. For coating, a solution in which the resin was made of xylene with a concentration of 5 mass% was used. The coating of the silicone resin on the soft magnetic metal powder was performed by a rolling fluidized tank type coating apparatus. Addition of the silicone resin solution is performed by spraying the coating material so that the solid content is the amount shown in Table 2 with respect to the powder in the fluid state using a spray after the raw material powder is fluidized in the apparatus container. It was done by doing. After completion of spraying, keep the fluid state for 20 minutes for drying to obtain a soft magnetic metal powder coated with a coating material on the raw material powder, and further heating in air at 250 ° C for 60 minutes The silicone resin was cured by heating to obtain a soft magnetic metal powder sample.
かくして得られた軟磁性金属粉末を、金型に充填し、加圧成形して測定用のリング試料(外径：38mm，内径：25mm，高さ：6.2mm)を得た。成形圧は 980MPaとした。加圧の際の潤滑は、水にステアリン酸亜鉛を分散させた潤滑剤溶液を金型面に塗布する金型潤滑とした。その試料を、窒素雰囲気中にて、800℃で60分の焼鈍を行った。
表３に、成形時における成形圧および成形体試料の焼鈍温度を示す。
The soft magnetic metal powder thus obtained was filled into a mold and pressure-molded to obtain a ring sample for measurement (outer diameter: 38 mm, inner diameter: 25 mm, height: 6.2 mm). The molding pressure was 980 MPa. The lubrication at the time of pressurization was mold lubrication in which a lubricant solution in which zinc stearate was dispersed in water was applied to the mold surface. The sample was annealed at 800 ° C. for 60 minutes in a nitrogen atmosphere.
Table 3 shows the molding pressure at the time of molding and the annealing temperature of the molded body sample.
上記のようにして得られた試料を用いて、圧粉体密度、比抵抗、磁束密度、鉄損を測定した。圧粉体密度は、試料の寸法と重量を測定し、その値を用いて算出した。比抵抗は四端子法にて測定した。通電電流は１Ａとした。圧環強度はJIS Z 2507において「焼結含油軸受けの圧環強さ試験方法」として規定されている方法に準拠して測定した。磁束密度は、リング試料にφ0.6mm のホルマル被覆導線を １次側：100巻、２次側：20巻したコイルを用い、磁界Ｈ＝10 kA/mでの磁束密度Ｂ10kで評価した。鉄損は、リング試料にφ0.6mm のホルマル被覆導線を１次側：40巻、２次側：40巻したコイルを用いて、周波数：200Hz 〜10kHz、磁束密度Ｂm＝0.2Ｔの条件で評価した。鉄損については、周波数：５kHz, 磁束密度：0.2Ｔ(Ｗ2/5k)の値を、その他の値については各測定値を表３に示す。 Using the sample obtained as described above, the green density, specific resistance, magnetic flux density, and iron loss were measured. The green density was calculated by measuring the dimensions and weight of the sample and using the values. The specific resistance was measured by the four probe method. The energizing current was 1A. The crushing strength was measured in accordance with the method defined in “JIS Z 2507 as“ crushing strength test method for sintered oil-impregnated bearing ””. The magnetic flux density was evaluated by a magnetic flux density B 10k at a magnetic field H = 10 kA / m using a coil in which a formal coated conductor of φ0.6 mm was used as a ring sample on the primary side: 100 turns and the secondary side: 20 turns. Iron loss was evaluated on the condition of frequency: 200Hz to 10kHz and magnetic flux density Bm = 0.2T using a coil with a φ0.6mm formal coated conductor on the primary side: 40 turns, secondary side: 40 turns. did. For iron loss, the frequency: 5 kHz, magnetic flux density: 0.2 T (W 2 / 5k ), and other values are shown in Table 3.
発明例と比較例との比較から明らかなように、本発明に従い３層構造を採用することによって絶縁性が大幅に向上することが分かる。また、発明例１〜４と５，６の比較から、ｘが1.1以上の粉末を用いた場合には、絶縁性を示す比抵抗が大きくなり、その結果鉄損が大幅に低減することが分かる。 As is clear from the comparison between the inventive examples and the comparative examples, it can be seen that the insulation is greatly improved by adopting the three-layer structure according to the present invention. In addition, it can be seen from comparison between Invention Examples 1 to 4 and 5 and 6 that when a powder having x of 1.1 or more is used, the specific resistance indicating insulation is increased, and as a result, iron loss is significantly reduced. .
比較例３は、粉末１にシリカ粉末（平均粒径：20nm）を混合した後、ホソカワミクロン製メカノフュージョンシステムを用いてメカノケミカル処理を実施して結合強化処理を行った。一回あたりの処理量は1.0kg/ch、処理時間は10分、 回転数は2.600rpmとした。このときの回転動力は1.2kW±0.05kWであった。
原料粉末に、このメカノフュージョン処理を行った粉末、シリコーン樹脂を被覆する前の発明例１の粉末について、Ｘ線電子分光法を用いて鉄の電子軌道２ｐ近傍のピークを調べてみた。その結果、原料粉末でのFeの２ｐ軌道のピーク強度を100とすると、発明例１の粉末では５となった。一方、メカノフュージョ ン処理した比較例３の粉末では76となった。これにより、比較例であるメカノフュージョン 処理した粉末は表面に金属Feが分散しているのに対して、発明例で得られた粉末は金属Feが表面に現れない状態になっていることが分かる。
次に、比較例３についても、他の発明例と同様にシリコーン樹脂からなる最外層の形成および成形体試料の作製と熱処理を行い、その特性を評価した。
メカノフュージョン処理時、鉄粉に加えられた加工歪みのため、圧縮性が低下した。その結果、同様の組成で熱処理による結合強化処理を施した発明例１に比べると、圧粉体密度や磁束密度が低下した。さらに、比抵抗が大幅に低下して、鉄損が大幅に上昇してしまった。これより、熱処理による結合強化処理が有効なことが分かる。
In Comparative Example 3, silica powder (average particle size: 20 nm) was mixed with powder 1, and then mechanochemical treatment was performed using a mechanofusion system manufactured by Hosokawa Micron to perform bond strengthening treatment. The processing amount per time was 1.0 kg / ch, the processing time was 10 minutes, and the rotation speed was 2.600 rpm. The rotational power at this time was 1.2 kW ± 0.05 kW.
With respect to the powder obtained by subjecting the raw material powder to this mechanofusion treatment and the powder of Invention Example 1 before the silicone resin was coated, the peak in the vicinity of the iron orbit 2p of iron was examined using X-ray electron spectroscopy. As a result, assuming that the peak intensity of the 2p orbit of Fe in the raw material powder was 100, it was 5 in the powder of Invention Example 1. On the other hand, the powder of Comparative Example 3 treated with mechanofusion was 76. As a result, it can be seen that the mechanofusion-treated powder as a comparative example has metal Fe dispersed on the surface, whereas the powder obtained in the invention example is in a state where the metal Fe does not appear on the surface. .
Next, in Comparative Example 3, as in the case of the other invention examples, the formation of the outermost layer made of silicone resin, the production of a molded body sample, and heat treatment were performed, and the characteristics were evaluated.
During the mechanofusion treatment, compressibility decreased due to processing distortion added to the iron powder. As a result, the green compact density and magnetic flux density were reduced as compared with Invention Example 1 in which the bond strengthening treatment was performed by heat treatment with the same composition. Furthermore, the specific resistance has been greatly reduced, and the iron loss has been greatly increased. This shows that the bond strengthening process by heat treatment is effective.
また、比較例２は、酸素およびその他成分を他粉末より多く含んだ粉末７を用いた場合の結果である。比抵抗は、発明例と比較して遜色のない値を示したが、その他成分により圧縮性が悪く、圧粉体密度が著しく低下した。その結果、磁束密度は、いずれの発明例よりも低かった。従って、本発明の目的である低鉄損かつ高磁束密度となる圧粉磁心が得られなかった。 Further, Comparative Example 2 is a result of using a powder 7 containing more oxygen and other components than other powders. The specific resistance was inferior to that of the inventive examples, but the compressibility was poor due to other components, and the green density was significantly reduced. As a result, the magnetic flux density was lower than any of the inventive examples. Therefore, a dust core having a low iron loss and a high magnetic flux density, which is the object of the present invention, could not be obtained.
本発明により、圧縮性に優れかつ高い絶縁性を有する軟磁性金属粉末およびかかる軟磁性金属粉末を使用して磁束密度が高くかつ鉄損が低い圧粉磁心を得ることができ、その結果、積層鉄心やソフトフェライトコアの代替となる圧粉磁心を得ることができる。 According to the present invention, it is possible to obtain a soft magnetic metal powder having excellent compressibility and high insulation and a dust core having high magnetic flux density and low iron loss using such soft magnetic metal powder. A dust core can be obtained as an alternative to the iron core and soft ferrite core.
１ 純鉄粉
２ 鉄酸化物
３ 絶縁層
４ シリコーン樹脂層
1 Pure iron powder 2 Iron oxide 3 Insulating layer 4 Silicone resin layer
Claims (5)
5. The dust core according to claim 4, wherein the annealing treatment is a treatment at 600 ° C. or higher and 30 minutes or longer in a non-oxidizing atmosphere, and the magnetic flux density is high and the iron loss is low.
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