JP2015088529A - Powder-compact magnetic core, powder for magnetic core, and manufacturing method thereof - Google Patents
Powder-compact magnetic core, powder for magnetic core, and manufacturing method thereof Download PDFInfo
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本発明は、体積比抵抗値（以下単に「比抵抗」という。）および強度に優れる圧粉磁心、その製造に用いられる磁心用粉末およびそれらの製造方法に関する。 The present invention relates to a dust core excellent in volume resistivity (hereinafter simply referred to as “resistivity”) and strength, a magnetic core powder used in the production thereof, and a production method thereof.
変圧器（トランス）、電動機（モータ）、発電機、スピーカ、誘導加熱器、各種アクチュエータ等、我々の周囲には電磁気を利用した製品が多々ある。これらの製品は交番磁界を利用したものが多く、局所的に大きな交番磁界を効率的に得るために、通常、磁心（軟磁石）をその交番磁界中に設けている。 There are many products that use electromagnetism around us, such as transformers, motors, generators, speakers, induction heaters, and various actuators. Many of these products use an alternating magnetic field. In order to efficiently obtain a large alternating magnetic field locally, a magnetic core (soft magnet) is usually provided in the alternating magnetic field.
磁心は、交番磁界中において高磁気特性を発揮するのみならず、交番磁界中で使用する際に高周波損失（以下、磁心の材質に拘らず単に「鉄損」という。）が少ないことが求められる。鉄損には、渦電流損失、ヒステリシス損失および残留損失があるが、特に交番磁界の周波数と共に高くなる渦電流損失の低減が強く求められている。 The magnetic core is required not only to exhibit high magnetic properties in an alternating magnetic field, but also to have a low high-frequency loss (hereinafter simply referred to as “iron loss” regardless of the material of the magnetic core) when used in an alternating magnetic field. . The iron loss includes eddy current loss, hysteresis loss, and residual loss. In particular, reduction of eddy current loss that increases with the frequency of the alternating magnetic field is strongly demanded.
そこで絶縁被覆された軟磁性粒子（絶縁被覆粒子）を加圧成形した圧粉磁心の開発、研究が盛んに行われてきた。このような圧粉磁心は、形状自由度が高く、種々の電磁機器に適用し易いと共に、絶縁層の存在により高比抵抗で低鉄損を図り得る。このような圧粉磁心に関する記載は、例えば下記の特許文献にある。 Therefore, development and research of a powder magnetic core obtained by press-molding soft magnetic particles (insulating coated particles) with insulation coating have been actively conducted. Such a powder magnetic core has a high degree of freedom in shape, is easy to apply to various electromagnetic devices, and can achieve low iron loss with a high specific resistance due to the presence of an insulating layer. The description regarding such a powder magnetic core exists in the following patent document, for example.
特許文献１では、粒子表面に酸化アルミニウム皮膜を形成したセンダスト合金（Ｆｅ−１０ｗｔ％Ｓｉ−６ｗｔ％Ａｌ）からなる球状粉末と金属酸化物（Ｂ２Ｏ３等）の粉末とを混合した粉末をホットプレス（加圧しつつ焼結）することにより、その金属酸化物が無添加な試料よりも高比抵抗な高密度複合体（複合軟磁性材）を得ている（特許文献１の実施例１欄）。
In
この特許文献１では、球状粉末の粒子表面に形成された酸化アルミニウム皮膜に関して詳細な記載は全くなされていない。ただ、基粒子中のＡｌ量が相対的に多く、上述した金属酸化物の添加量が、その粒子表面に形成されるＡｌ２Ｏ３皮膜に対する比率として規定されていることから考えて（同文献の表１の注釈）、その酸化アルミニウム皮膜は一般的なアルミナ（Ａｌ２Ｏ３）からなると考えられる。
In
特許文献１のように、絶縁被覆された粒子からなる粉末をホットプレスすると、粒子表面の絶縁被膜が破損し易く、必ずしも比抵抗や強度に優れた圧粉磁心が得られるとは限らない。
As in
本発明はこのような事情に鑑みてなされたものであり、比抵抗および強度に優れる圧粉磁心またはそれを得ることができる新たな製造方法を提供することを目的とする。また、その圧粉磁心の製造に適した磁心用粉末およびその製造方法を提供することも目的とする This invention is made | formed in view of such a situation, and it aims at providing the new manufacturing method which can obtain the powder magnetic core which is excellent in a specific resistance, and intensity | strength. Another object of the present invention is to provide a powder for a magnetic core suitable for the production of the dust core and a method for producing the same.
本発明者はこの課題を解決すべく鋭意研究し、試行錯誤を重ねた結果、ＡｌおよびＳｉを含む鉄合金からなり、表面に酸化鉄を有する軟磁性粒子（酸化粒子）を非酸化雰囲気で加熱処理すると、その粒子表面に酸化アルミニウムからなる絶縁層が形成されることを新たに見出した。そして、この絶縁層の形成により、圧粉磁心の比抵抗および強度が向上することを確認した。この成果を発展させることにより、以降に述べる本発明を完成するに至った。 As a result of extensive research and trial and error, the present inventor has heated soft magnetic particles (oxidized particles) made of an iron alloy containing Al and Si and having iron oxide on the surface in a non-oxidizing atmosphere. It has been newly found that an insulating layer made of aluminum oxide is formed on the surface of the particles when treated. And it confirmed that the specific resistance and intensity | strength of a powder magnetic core improved by formation of this insulating layer. By developing this result, the present invention described below has been completed.
《磁心用粉末の製造方法》
（１）本発明の磁心用粉末の製造方法は、圧粉磁心の製造に用いられる磁心用粉末の製造方法であって、ＡｌおよびＳｉを含む鉄合金の軟磁性粒子からなり該軟磁性粒子の表面近傍に酸化鉄を有する酸化粒子を、非酸化雰囲気で加熱することにより酸化アルミニウムからなる絶縁層により少なくとも一部表面が被覆された絶縁被覆粒子を得る非酸化処理工程を備え、前記磁心用粉末は該絶縁被覆粒子からなることを特徴とする。
<Method for producing magnetic core powder>
(1) A method for producing a magnetic core powder according to the present invention is a method for producing a magnetic core powder used in the production of a dust core, comprising soft magnetic particles of an iron alloy containing Al and Si. A powder for magnetic core comprising a non-oxidation treatment step for obtaining insulating coated particles at least partially coated with an insulating layer made of aluminum oxide by heating oxidized particles having iron oxide near the surface in a non-oxidizing atmosphere, Is characterized by comprising the insulating coating particles.
（２）本発明の製造方法によれば、Ａｌ含有量が少ない軟磁性粒子であっても、その粒子表面に酸化アルミニウムからなる絶縁層が安定的に形成された絶縁被覆粒子を得ることができる。この絶縁被覆粒子からなる磁心用粉末を用いると、酸化アルミニウムからなる絶縁層が隣接する軟磁性粒子間（適宜、「隣接粒子間」または単に「粒界」という。）に介在した圧粉磁心を容易に得ることができる。こうして得られた圧粉磁心は、優れた高比抵抗または高強度を発揮し得る。さらに、本発明に係る絶縁層は、非酸化雰囲気で高温加熱して安定しており、シリコン樹脂等とは異なる優れた耐熱性も発揮する。このため本発明に係る圧粉磁心は、高温焼鈍等されることにより、保磁力またはヒステリシス損失の低減も容易になされる。 (2) According to the production method of the present invention, insulating coated particles in which an insulating layer made of aluminum oxide is stably formed on the surface of the particles can be obtained even with soft magnetic particles having a small Al content. . When the magnetic core powder made of the insulating coating particles is used, a dust magnetic core having an insulating layer made of aluminum oxide interposed between adjacent soft magnetic particles (appropriately called “between adjacent particles” or simply “grain boundaries”) is used. Can be easily obtained. The powder magnetic core thus obtained can exhibit excellent high specific resistance or high strength. Furthermore, the insulating layer according to the present invention is stable when heated at a high temperature in a non-oxidizing atmosphere, and exhibits excellent heat resistance different from that of silicon resin or the like. For this reason, the dust core according to the present invention can be easily reduced in coercive force or hysteresis loss by being annealed at a high temperature.
（３）ちなみに、詳細は必ずしも定かではないが、本発明に係る非酸化処理工程により、酸化粒子の表面に存在していた酸化鉄が酸化アルミニウムに変化することがわかっている。さらに、このような変化は、基粒子である軟磁性粒子がＳｉを含有する鉄合金（適宜、Ｆｅ−Ａｌ−Ｓｉ系合金という。）からなる場合に生じ、その軟磁性粒子がＳｉを含有していない鉄合金（適宜、Ｆｅ−Ａｌ系合金という。）からなる場合には生じないこともわかっている。 (3) Incidentally, although details are not necessarily clear, it has been found that the iron oxide existing on the surface of the oxidized particles is changed into aluminum oxide by the non-oxidation treatment step according to the present invention. Further, such a change occurs when the soft magnetic particles as the base particles are made of an iron alloy containing Si (referred to as an Fe-Al-Si alloy as appropriate), and the soft magnetic particles contain Si. It has also been found that it does not occur when it is made of an iron alloy that is not made (referred to as an Fe-Al alloy as appropriate).
《圧粉磁心の製造方法》
本発明は、磁心用粉末の製造方法としてのみならず、その磁心用粉末を用いた圧粉磁心の製造方法としても把握できる。また本発明は、上述した酸化アルミニウムからなる絶縁層の形成過程に基づき、次のような圧粉磁心の製造方法としても把握できる。
<Production method of dust core>
The present invention can be grasped not only as a method for producing a magnetic core powder, but also as a method for producing a powder magnetic core using the magnetic core powder. The present invention can also be grasped as the following method for manufacturing a dust core based on the process of forming the insulating layer made of aluminum oxide.
（１）すなわち本発明は、ＡｌおよびＳｉを含む鉄合金の軟磁性粒子からなり該軟磁性粒子の表面近傍に酸化鉄を有する酸化粒子の粉末である酸化粉末を加圧成形した成形体を得る成形工程と、該成形体を非酸化雰囲気で加熱することにより、該軟磁性粒子の隣接間の少なくとも一部に酸化アルミニウムからなる絶縁層が形成された圧粉磁心を得る成形体加熱工程と、を備えることを特徴とする圧粉磁心の製造方法でもよい。 (1) That is, the present invention obtains a molded body formed by press-molding oxide powder, which is composed of iron alloy soft magnetic particles containing Al and Si, and which is a powder of oxidized particles having iron oxide near the surface of the soft magnetic particles. A molding step, and a heating step for heating the molded body in a non-oxidizing atmosphere to obtain a dust core in which an insulating layer made of aluminum oxide is formed on at least a portion between adjacent soft magnetic particles; and A method of manufacturing a dust core characterized by comprising:
（２）本発明の製造方法により得られる圧粉磁心は、高比抵抗のみならず高強度であり、両者が高次元で両立した優れた特性を発揮する。このように優れた圧粉磁心が得られる理由は必ずしも定かではないが、現状では次のように考えられる。本発明の製造方法の場合、成形体加熱工程により、成形体を構成する酸化粒子の粒界等に存在していた酸化鉄が酸化アルミニウムに変化し、その酸化アルミニウムにより隣接粒子間に絶縁層が形成される。この絶縁層は、上述した磁心用粉末のように、孤立した（分離独立した）軟磁性粒子の各表面に形成されているのではなく、隣接する成形体の構成粒子間に介在した状態となっている。このため本発明に係る絶縁層は、圧粉磁心の構成粒子間の絶縁性を確保するのみならず、酸化アルミニウムの生成を介して構成粒子同士を強く結合し得る。換言するなら、成形体加熱工程により、隣接する軟磁性粒子同士は、酸化アルミニウムからなる絶縁層の生成によって、単なる物理的な密接状態から化学的な結合状態へ変化し、強固に結合され得る。このようにして、上述した高比抵抗で高強度な圧粉磁心が得られるようになったと考えられる。 (2) The dust core obtained by the production method of the present invention has not only high specific resistance but also high strength, and both exhibit excellent characteristics that are compatible in a high dimension. The reason why such an excellent dust core can be obtained is not necessarily clear, but at present, it is considered as follows. In the case of the production method of the present invention, the iron oxide existing at the grain boundaries of the oxidized particles constituting the molded body is changed to aluminum oxide by the molded body heating step, and the insulating layer is formed between adjacent particles by the aluminum oxide. It is formed. This insulating layer is not formed on each surface of isolated (separate and independent) soft magnetic particles as in the above-described magnetic core powder, but is interposed between the constituent particles of the adjacent molded body. ing. For this reason, the insulating layer according to the present invention not only ensures the insulation between the constituent particles of the dust core, but also can strongly bond the constituent particles through the formation of aluminum oxide. In other words, adjacent soft magnetic particles are changed from a simple physical close state to a chemically bonded state by the formation of an insulating layer made of aluminum oxide, and can be firmly bonded by the molded body heating step. In this way, it is considered that the above-described high specific resistance and high strength powder magnetic core can be obtained.
（３）本発明の圧粉磁心の製造方法は、上述した成形工程や成形体加熱工程以外に、適宜、成形工程前に粉末を金型に充填する充填工程、成形工程後または成形体加熱工程後の成形体を加熱して軟磁性粒子内に導入された残留歪み等を除去する焼鈍工程等を適宜備えてもよい。但し、本発明に係る成形体加熱工程は、その焼鈍工程を兼ね得る。従って本発明の製造方法によれば、磁気特性（保磁力またはヒステリシス損失）にも優れる圧粉磁心も効率的に得ることが可能となる。 (3) In addition to the above-described molding step and molded body heating step, the method for producing a powder magnetic core according to the present invention suitably includes a filling step of filling a mold with powder before the molding step, after the molding step, or a molded body heating step. An annealing step or the like for removing the residual strain introduced into the soft magnetic particles by heating the subsequent molded body may be appropriately provided. However, the molded body heating process according to the present invention can also serve as the annealing process. Therefore, according to the manufacturing method of the present invention, it is possible to efficiently obtain a dust core having excellent magnetic characteristics (coercive force or hysteresis loss).
《磁心用粉末および圧粉磁心》
本発明は、上述したような製造方法に留まらず、それらの製造方法により得られる磁心用粉末または圧粉磁心としても把握される。
<Magnetic core powder and dust core>
The present invention is not limited to the manufacturing methods as described above, but is understood as a magnetic core powder or a dust core obtained by these manufacturing methods.
（１）例えば、本発明は、ＡｌおよびＳｉを含む鉄合金からなる軟磁性粒子と該軟磁性粒子の少なくとも一部表面を被覆する絶縁層とを有する絶縁被覆粒子からなり、圧粉磁心の製造に用いられる磁心用粉末であって、前記絶縁層が上述した酸化アルミニウムからなることを特徴とする磁心用粉末としても把握できる。 (1) For example, the present invention is a production of a dust core comprising insulating coated particles having soft magnetic particles made of an iron alloy containing Al and Si and an insulating layer covering at least a part of the surface of the soft magnetic particles. It can also be grasped as a magnetic core powder, characterized in that the insulating layer is made of the above-described aluminum oxide.
（２）また、本発明は、ＡｌおよびＳｉを含む鉄合金からなる軟磁性粒子と、該軟磁性粒子の隣接間に介在する絶縁層と、からなる圧粉磁心であって、前記絶縁層は、上述した酸化アルミニウムからなることを特徴とする圧粉磁心としても把握できる。この圧粉磁心は、上述した磁心用粉末を加圧成形したものでもよいし、酸化粉末を加圧成形した成形体に上述した成形体加熱工程を施したものでもよい。 (2) Further, the present invention is a powder magnetic core comprising soft magnetic particles made of an iron alloy containing Al and Si, and an insulating layer interposed between adjacent soft magnetic particles, the insulating layer comprising: It can also be grasped as a dust core characterized by comprising the above-described aluminum oxide. This powder magnetic core may be one obtained by pressure-molding the above-described powder for magnetic core, or one obtained by subjecting a molded body obtained by pressure-molding an oxidized powder to the above-described molded body heating step.
《その他》
（１）本発明でいう酸化鉄および酸化アルミニウムは、その具体的な組成を問わず、また、単種からなる酸化物でも複数種の酸化物が混在したものでもよい。例えば、本発明に係る酸化鉄には、ＦｅＯで表される酸化鉄（II）、Ｆｅ３Ｏ４で表される酸化鉄（II、III）、Ｆｅ２Ｏ３（α型、β型等を含む）で表される酸化鉄（III）などの他、ＦｅＯＯＨ（α型、β型等を含む）などのオキシ水酸化物、Ｆｅ（ＯＨ）２、Ｆｅ（ＯＨ）３などの水酸化鉄も含まれる。本発明に係る酸化鉄は、それらの一種以上であればよいが、通常はＦｅＯ、Ｆｅ３Ｏ４またはＦｅ２Ｏ３のいずれか一種以上である。
<Others>
(1) The iron oxide and aluminum oxide referred to in the present invention are not limited to specific compositions, and may be a single oxide or a mixture of a plurality of oxides. For example, the iron oxide according to the present invention includes iron oxide (II) represented by FeO, iron oxide (II, III) represented by Fe 3 O 4 , Fe 2 O 3 (α-type, β-type, etc. In addition to iron oxide (III) represented by oxyhydroxide such as FeOOH (including α-type and β-type), and iron hydroxide such as Fe (OH) 2 and Fe (OH) 3 included. The iron oxide according to the present invention may be one or more of them, but is usually one or more of FeO, Fe 3 O 4, or Fe 2 O 3 .
また本発明に係る酸化アルミニウムには、Ａｌ２Ｏ３で表される酸化アルミニウム（III）の他、Ａｌ２Ｏで表される酸化アルミニウム（I）、ＡｌＯで表される酸化アルミニウム（II）も含まれる。また酸化アルミニウム（III）は、結晶構造の異なるスピネル型酸化アルミニウム（γ−Ａｌ２Ｏ３）またはコランダム型酸化アルミニウム（α−Ａｌ２Ｏ３）のいずれでもよい。本発明に係る酸化アルミニウムは、それらの一種以上であればよい。なお、本発明に係る絶縁層は、酸化アルミニウムを含めば足り、軟磁性粒子を構成する鉄合金組成に応じて、それ以外の酸化物（酸化ケイ素、残存する酸化鉄等）が混在していてもよい。また、本発明に係る酸化アルミニウムは、完全な結晶構造からなる場合の他、結晶構造の一部に酸素欠損が生じた不完全な結晶構造からなる場合でも、さらには、それらが混在している場合でもよい。本発明に係る酸化アルミニウムは、絶縁性が確保される限り、その具体的な結晶構造を問わない。 The aluminum oxide according to the present invention includes aluminum oxide (III) represented by Al 2 O 3 , aluminum oxide (I) represented by Al 2 O, and aluminum oxide (II) represented by AlO. included. Aluminum oxide (III) may be either spinel type aluminum oxide (γ-Al 2 O 3 ) or corundum type aluminum oxide (α-Al 2 O 3 ) having a different crystal structure. The aluminum oxide according to the present invention may be one or more of them. The insulating layer according to the present invention only needs to contain aluminum oxide, and other oxides (silicon oxide, remaining iron oxide, etc.) are mixed depending on the iron alloy composition constituting the soft magnetic particles. Also good. In addition to the case where the aluminum oxide according to the present invention has a complete crystal structure, even when the aluminum oxide has an incomplete crystal structure in which part of the crystal structure has oxygen deficiency, they are further mixed. It may be the case. The aluminum oxide according to the present invention may have any specific crystal structure as long as insulation is ensured.
（２）本発明でいう「絶縁層」は、軟磁性粒子自体よりも抵抗値が大きければよく、その具体的な抵抗値は問わない。絶縁層は、軟磁性粒子の全外表面を均一的または均質的に被覆している必要はない。絶縁層は、軟磁性粒子の表面の少なくとも一部、または圧粉磁心の隣接粒子間の少なくとも一部に存在すればよい。 (2) The “insulating layer” in the present invention only needs to have a resistance value larger than that of the soft magnetic particle itself, and the specific resistance value is not limited. The insulating layer need not uniformly or uniformly cover the entire outer surface of the soft magnetic particles. The insulating layer may be present on at least a part of the surface of the soft magnetic particle or at least a part between adjacent particles of the dust core.
（３）特に断らない限り本明細書でいう「ｘ〜ｙ」は下限値ｘおよび上限値ｙを含む。また本明細書に記載した種々の数値や数値範囲内に含まれる数値を任意に組み合わせて「ａ〜ｂ」のような新たな数値範囲を構成し得る。 (3) Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. Moreover, a new numerical value range such as “ab” can be configured by arbitrarily combining various numerical values and numerical values included in the numerical value range described in this specification.
発明の実施形態を挙げて本発明をより詳しく説明する。上述した本発明の構成に本明細書中から任意に選択した一つまたは二つ以上の構成を付加し得る。本明細書で説明する内容は、本発明に係る磁心用粉末、圧粉磁心およびそれらの製造方法にも適用され得る。製造方法に関する構成は、プロダクトバイプロセスとして理解すれば物に関する構成ともなり得る。いずれの実施形態が最良であるか否かは、対象、要求性能等によって異なる。 The present invention will be described in more detail with reference to embodiments of the invention. One or two or more configurations arbitrarily selected from the present specification may be added to the configuration of the present invention described above. The contents described in the present specification can also be applied to the magnetic core powder, the dust core and the manufacturing method thereof according to the present invention. A configuration related to a manufacturing method can be a configuration related to an object if understood as a product-by-process. Which embodiment is the best depends on the target, required performance, and the like.
《軟磁性粒子（軟磁性粉末）》
本発明に係る軟磁性粒子は、ＡｌおよびＳｉを含む鉄合金からなる。その主成分であるＦｅの一部は、強磁性元素であるＣｏ、Ｎｉ等と置換し得る。Ａｌは、軟磁性粒子の表面近傍に酸化アルミニウムを形成するために必要である。同様にＳｉも、その酸化アルミニウムの形成に必要である。さらにＳｉは、軟磁性粒子の電気抵抗率の向上、圧粉磁心の比抵抗の向上（渦電流損失の低減）または強度向上等にも寄与し得る。
《Soft magnetic particles (soft magnetic powder)》
The soft magnetic particles according to the present invention are made of an iron alloy containing Al and Si. A part of Fe, which is the main component, can be substituted with ferromagnetic elements such as Co and Ni. Al is necessary for forming aluminum oxide near the surface of the soft magnetic particles. Similarly, Si is necessary for the formation of the aluminum oxide. Further, Si can contribute to improvement of the electrical resistivity of the soft magnetic particles, improvement of the specific resistance of the dust core (reduction of eddy current loss) or improvement of strength.
本発明に係る鉄合金は、その組成を問わない。もっとも、圧粉磁心の磁気特性、磁心用粉末の成形性、酸化アルミニウムを含む絶縁層の形成性等を考慮して、本発明に係る鉄合金は全体を１００質量％（単に「％」で表す。）としたときに、Ａｌが０．５〜５％、１〜４．５％さらには１．５〜４％であり、Ｓｉが０．５〜９％、１〜７％さらには１．５〜６．５％であり、主たる残部がＦｅからなると好ましい。 The composition of the iron alloy according to the present invention is not limited. However, in consideration of the magnetic properties of the powder magnetic core, the moldability of the magnetic core powder, the formability of the insulating layer containing aluminum oxide, etc., the iron alloy according to the present invention is 100% by mass (simply expressed as “%”) .), Al is 0.5 to 5%, 1 to 4.5%, further 1.5 to 4%, Si is 0.5 to 9%, 1 to 7%, and 1. It is preferably 5 to 6.5%, and the main remainder is preferably made of Fe.
ＡｌおよびＳｉは、過少なら酸化アルミニウムからなる絶縁層の形成が困難となり、過多なら圧粉磁心の磁気特性や成形性の低下、コストの増大等となり好ましくない。特にＡｌが過多になると、酸化アルミニウムが当初から軟磁性粒子の表面に生成され易くなる。その結果、非酸化処理工程または成形体加熱工程における酸化鉄から酸化アルミニウムへ変化が難くなり、酸化アルミニウムからなる均一な絶縁層の形成が阻害される。 If Al and Si are too small, it is difficult to form an insulating layer made of aluminum oxide, and if too large, the magnetic properties and moldability of the powder magnetic core are lowered, and the cost is increased. In particular, when Al is excessive, aluminum oxide tends to be generated on the surface of the soft magnetic particles from the beginning. As a result, it is difficult to change from iron oxide to aluminum oxide in the non-oxidation treatment step or the molded body heating step, and the formation of a uniform insulating layer made of aluminum oxide is hindered.
なお、この鉄合金には、Ｆｅ以外の残部として、不可避不純物が当然含まれ得る、また鉄合金は、圧粉磁心の磁気特性や比抵抗、磁心用粉末の成形性、酸化アルミニウムの生成性等を改善し得る改質元素を一種以上含有し得る。このような改質元素として、例えばＭｎ、Ｃｒ、Ｍｏ、Ｔｉ、Ｎｉ等が考えられる。通常、改質元素量は微量であり、その合計量は３％以下さらには１％以下であると好ましい。 This iron alloy may naturally contain inevitable impurities as the balance other than Fe. Also, the iron alloy has magnetic properties and specific resistance of the powder magnetic core, moldability of the powder for the magnetic core, productivity of aluminum oxide, etc. One or more modifying elements that can improve the above can be contained. As such a modifying element, for example, Mn, Cr, Mo, Ti, Ni and the like are conceivable. Usually, the amount of the modifying element is very small, and the total amount is preferably 3% or less, more preferably 1% or less.
軟磁性粉末は、その製法を問わず、アトマイズ粉でも粉砕粉でもよい。アトマイズ粉は、水アトマイズ粉、ガスアトマイズ粉、ガス水アトマイズ粉のいずれでもよい。擬球状をした粒子からなるアトマイズ粉を用いると、粒子相互間の攻撃性が低くなり、絶縁層の破壊等による比抵抗値の低下等を抑制し得る。 The soft magnetic powder may be atomized powder or pulverized powder regardless of its production method. The atomized powder may be any of water atomized powder, gas atomized powder, and gas water atomized powder. When atomized powder made of pseudospherical particles is used, the aggression between the particles is reduced, and a decrease in specific resistance due to destruction of the insulating layer or the like can be suppressed.
軟磁性粒子の粒径は問わないが、通常、１０〜３００μｍさらには５０〜２５０μｍであると好ましい。粒径が過大になると圧粉磁心の渦電流損失が増加し、粒径が過小になると圧粉磁心のヒステリシス損失が増加等して好ましくない。なお、本明細書でいう粉末の粒径は、所定のメッシュサイズの篩いを用いて分級する篩い分法で定まる粒度により規定することとする。 The particle size of the soft magnetic particles is not limited, but it is usually preferably 10 to 300 μm, more preferably 50 to 250 μm. If the particle size is too large, the eddy current loss of the dust core increases, and if the particle size is too small, the hysteresis loss of the dust core increases. In addition, the particle size of the powder referred to in the present specification is defined by the particle size determined by a sieving method in which classification is performed using a sieve having a predetermined mesh size.
《磁心用粉末の製造方法》
（１）非酸化処理工程
非酸化処理工程は、表面近傍に酸化鉄を有する軟磁性粒子である酸化粒子またはその酸化粒子の集合体である酸化粉末を、非酸化雰囲気中で加熱することにより、粒子表面に酸化アルミニウムを含む絶縁層（膜）を生成する工程である。非酸化雰囲気は、酸素が実質的に存在しない雰囲気であれば、不活性ガス雰囲気でも真空雰囲気でもよい。不活性ガスはＮ２、Ｈｅ、Ａｒ等のいずれでもよい。
<Method for producing magnetic core powder>
(1) Non-oxidation treatment step In the non-oxidation treatment step, oxidized particles that are soft magnetic particles having iron oxide near the surface or oxidized powder that is an aggregate of the oxidized particles are heated in a non-oxidizing atmosphere. This is a step of forming an insulating layer (film) containing aluminum oxide on the particle surface. The non-oxidizing atmosphere may be an inert gas atmosphere or a vacuum atmosphere as long as oxygen is substantially absent. The inert gas may be any of N 2 , He, Ar, and the like.
非酸化雰囲気を不活性ガス雰囲気とする場合、不活性ガスの気流中に酸化粒子（酸化粉末）をおくことにより、粒子表面近傍を安定的に非酸化雰囲気とすることができる。この際、非酸化雰囲気の露点は−４０℃以下さらには−５０℃以下であると好ましい。軟磁性粉末の加熱温度は、６５０〜１０００℃さらには７００〜９５０℃とするとよい。加熱時間は０．３〜２時間さらには０．５〜１．５時間とすると効率的である。 When the non-oxidizing atmosphere is an inert gas atmosphere, by placing oxidized particles (oxidized powder) in an inert gas stream, the vicinity of the particle surface can be stably made a non-oxidizing atmosphere. At this time, the dew point of the non-oxidizing atmosphere is preferably −40 ° C. or lower, more preferably −50 ° C. or lower. The heating temperature of the soft magnetic powder is preferably 650 to 1000 ° C, more preferably 700 to 950 ° C. It is efficient that the heating time is 0.3 to 2 hours, and further 0.5 to 1.5 hours.
ところで、本発明に係る非酸化処理工程（特に断らない限り、成形体加熱工程についても同様）により酸化アルミニウムを含む絶縁層が形成される理由は必ずしも定かではないが、次のように考えられる。先ず、相応に酸素（Ｏ２）が存在する酸化雰囲気中におかれた軟磁性粒子の表面には、Ｏ２が付着または吸着し（図４Ａ参照）、自然にまたは加熱されることにより、その粒子表面には軟磁性粒子の主成分であるＦｅと反応した酸化鉄（Ｆｅ２Ｏ３、Ｆｅ３Ｏ４、ＦｅＯ等）が多く生成され得る（図４Ｂ参照）。この際、酸化鉄以外にＡｌやＳｉの酸化物も軟磁性粒子の表面近傍に一部生成されてもよい。 By the way, although the reason why the insulating layer containing aluminum oxide is formed by the non-oxidation treatment process according to the present invention (the same applies to the molded body heating process unless otherwise specified) is not necessarily clear, it can be considered as follows. First, O 2 adheres to or adsorbs on the surface of soft magnetic particles in an oxidizing atmosphere correspondingly with oxygen (O 2 ) (see FIG. 4A), and is heated naturally or by heating. A large amount of iron oxide (Fe 2 O 3 , Fe 3 O 4 , FeO, etc.) reacted with Fe, which is the main component of the soft magnetic particles, can be generated on the particle surface (see FIG. 4B). At this time, in addition to iron oxide, an oxide of Al or Si may be partially generated in the vicinity of the surface of the soft magnetic particles.
次に、このような酸化鉄を表面に有する軟磁性粒子が、実質的にＯ２が存在しない非酸化雰囲気中におかれて、Ｏ欠乏状態で加熱されると、Ｆｅよりも酸化物生成エネルギーが低いＡｌが、軟磁性粒子の表面近傍に存在していた酸化鉄からＯを奪い、酸化鉄よりも安定な酸化アルミニウムを生成し得る（図４Ｃ）。但し、軟磁性粒子中にＳｉが含まれない場合、酸化鉄から酸化アルミニウムが生成されないことから、軟磁性粒子中のＳｉが触媒のように作用して上記の反応が進行すると考えられる。 Next, when such soft magnetic particles having iron oxide on the surface are placed in a non-oxidizing atmosphere substantially free of O 2 and heated in an O-deficient state, the oxide formation energy is higher than that of Fe. Low Al can take O from the iron oxide existing in the vicinity of the surface of the soft magnetic particles, and can produce aluminum oxide that is more stable than iron oxide (FIG. 4C). However, when Si is not contained in the soft magnetic particles, since aluminum oxide is not generated from iron oxide, it is considered that Si in the soft magnetic particles acts like a catalyst and the above reaction proceeds.
いずれにしても、本発明に係る非酸化処理工程により、ＡｌおよびＳｉを含む鉄合金からなる軟磁性粒子の表面に存在する酸化鉄が、酸化アルミニウムに変化して、高比抵抗および高耐熱性の絶縁層が形成されることは確かである。 In any case, the non-oxidation treatment process according to the present invention changes the iron oxide present on the surface of the soft magnetic particles made of an iron alloy containing Al and Si into aluminum oxide, resulting in high specific resistance and high heat resistance. It is certain that the insulating layer is formed.
（２）酸化処理工程
非酸化処理工程の前提として、軟磁性粒子の表面に酸化鉄を有する酸化粒子の存在が必要となる。このような酸化粒子（酸化粉末）は、その生成過程または生成方法をとわないが、例えば、軟磁性粒子を酸化雰囲気中で加熱する酸化処理工程により得られると好ましい。これにより軟磁性粒子の表面に酸化アルミニウムに変化する十分な酸化鉄が安定的に生成される。
(2) Oxidation process As the premise of the non-oxidation process, the presence of oxidized particles having iron oxide on the surface of the soft magnetic particles is required. Such oxidized particles (oxidized powder) do not depend on the generation process or generation method thereof, but are preferably obtained, for example, by an oxidation treatment step in which soft magnetic particles are heated in an oxidizing atmosphere. Thereby, sufficient iron oxide which changes to aluminum oxide is stably generated on the surface of the soft magnetic particles.
酸化雰囲気は、適度な酸素（特にＯ２）を含む環境であれば、混合ガス雰囲気でも真空雰囲気でもよい。例えば、Ｏ２と不活性ガス（Ｎ２、Ａｒ等）の混合ガス（気流）を用いる場合なら、Ｏ２量は０．１〜３０体積％さらには０．５〜２５体積％とするとよい。 The oxidizing atmosphere may be a mixed gas atmosphere or a vacuum atmosphere as long as the environment contains appropriate oxygen (particularly O 2 ). For example, in the case of using a mixed gas (air flow) of O 2 and an inert gas (N 2 , Ar, etc.), the amount of O 2 is preferably 0.1 to 30% by volume, more preferably 0.5 to 25% by volume.
さらに酸化処理工程は大気中で行うことも可能であるが、そのときの酸化雰囲気の露点は−４０℃以下さらには−５０℃以下とすると好ましい。軟磁性粉末の加熱温度は、酸化雰囲気中のガス組成（特に酸素濃度）にも依るが、８００〜１１００℃さらには８５０〜１０５０℃とするとよい。加熱時間は、酸化雰囲気中の酸素濃度や加熱温度にも依るが、０．５〜１０時間さらには１〜３時間とすると効率的である。 Furthermore, although the oxidation treatment step can be performed in the air, the dew point of the oxidizing atmosphere at that time is preferably −40 ° C. or lower, more preferably −50 ° C. or lower. The heating temperature of the soft magnetic powder depends on the gas composition (particularly the oxygen concentration) in the oxidizing atmosphere, but is preferably 800 to 1100 ° C., more preferably 850 to 1050 ° C. Although the heating time depends on the oxygen concentration in the oxidizing atmosphere and the heating temperature, it is efficient to set the heating time to 0.5 to 10 hours and further to 1 to 3 hours.
《圧粉磁心の製造》
本発明の圧粉磁心は、所望形状のキャビティを有する金型へ粉末（軟磁性粉末、酸化粉末または磁心用粉末）を充填する充填工程と、その粉末を加圧成形して成形体とする成形工程と、その成形体を焼鈍する焼鈍工程または本発明に係る成形体加熱工程を適宜行うことにより得られる。ここでは成形工程と、焼鈍工程または成形体加熱工程について説明する。
<Manufacture of dust core>
The dust core of the present invention includes a filling step of filling a mold having a cavity of a desired shape with a powder (soft magnetic powder, oxide powder or magnetic core powder), and molding the powder into a molded body by pressure molding It is obtained by appropriately performing the step and the annealing step for annealing the molded body or the molded body heating step according to the present invention. Here, a forming process and an annealing process or a molded body heating process will be described.
（１）成形工程
成形工程の成形圧力は問わないが、高圧成形するほど高密度で高磁束密度の圧粉磁心が得られる。このような高圧成形方法として、金型潤滑温間高圧成形法がある。金型潤滑温間高圧成形法は、高級脂肪酸系潤滑剤を内面に塗布した金型へ粉末を充填する充填工程と、粉末と金型の内面との間に、高級脂肪酸系潤滑剤とは別の金属石鹸被膜が生成される成形温度と成形圧力で加圧成形する温間高圧成形工程とからなる。
(1) Molding process The molding pressure in the molding process is not limited, but the higher the density, the higher the density and the higher magnetic flux density of the dust core. As such a high pressure molding method, there is a mold lubrication warm high pressure molding method. The mold lubrication warm high-pressure molding method is separate from the higher fatty acid lubricant between the filling process of filling the mold with the higher fatty acid lubricant applied to the inner surface and the powder and the inner surface of the mold. The metal soap film is formed at a forming temperature and a warm high pressure forming step in which the metal soap film is pressure-formed at a forming pressure.
ここで「温間」とは、表面被膜（または絶縁層）への影響や高級脂肪酸系潤滑剤の変質などを考慮して、例えば、成形温度を７０℃〜２００℃さらには１００〜１８０℃とすることをいう。この金型潤滑温間高圧成形法の詳細については、日本特許公報特許３３０９９７０号公報、日本特許４０２４７０５号公報など多くの公報に詳細が記載されている。この金型潤滑温間高圧成形法によれば、金型寿命を延しつつも超高圧成形が可能となり、高密度な圧粉磁心を容易に得ることが可能となる。 Here, “warm” means, for example, a molding temperature of 70 ° C. to 200 ° C. or even 100 to 180 ° C. in consideration of the influence on the surface coating (or insulating layer) and the alteration of the higher fatty acid lubricant. To do. Details of the mold lubrication warm high pressure molding method are described in many publications such as Japanese Patent Publication No. 3309970 and Japanese Patent No. 4024705. According to this mold lubrication warm high-pressure molding method, ultra-high pressure molding is possible while prolonging the mold life, and a high-density powder magnetic core can be easily obtained.
（２）焼鈍工程
酸化アルミニウムからなる絶縁層が既に形成されている絶縁被覆粒子からなる本発明の磁心用粉末を用いた圧粉磁心の場合、その成形体中の残留歪みや残留応力の除去を目的として、焼鈍工程を行うと好ましい。これにより圧粉磁心の保磁力やヒステリシス損失の低減が図られる。焼鈍温度は、軟磁性粉末の組成等に応じて適宜選択し得るが、例えば、５００〜９００℃さらには６００〜８００℃とすると好ましい。加熱時間は、例えば０．１〜５時間さらには０．５〜２時間として、加熱雰囲気は不活性雰囲気とすると好ましい。なお、本発明に係る絶縁層は耐熱性に優れるため、高温焼鈍が可能であり、圧粉磁心の比抵抗や強度を劣化させることなく、その磁気特性の向上やヒステリシス損失の低減等が図られる。
(2) Annealing process In the case of a powder magnetic core using the magnetic core powder of the present invention consisting of insulating coating particles in which an insulating layer made of aluminum oxide has already been formed, the residual strain and residual stress in the molded body are removed. For the purpose, an annealing step is preferably performed. Thereby, the coercive force and hysteresis loss of the dust core can be reduced. The annealing temperature can be appropriately selected according to the composition of the soft magnetic powder, but is preferably 500 to 900 ° C., more preferably 600 to 800 ° C., for example. The heating time is preferably 0.1 to 5 hours, more preferably 0.5 to 2 hours, and the heating atmosphere is preferably an inert atmosphere. In addition, since the insulating layer according to the present invention is excellent in heat resistance, it can be annealed at a high temperature, and its magnetic characteristics can be improved and hysteresis loss can be reduced without deteriorating the specific resistance and strength of the dust core. .
（３）上述した非酸化処理工程前の酸化粉末を用いた圧粉磁心の場合、成形体に対して成形体加熱工程を行うことにより、隣接粒子間に酸化アルミニウムを含む絶縁層が形成された圧粉磁心が得られる。この成形体加熱工程は、基本的に上述した非酸化処理工程と同様な条件で行うことができる。なお、圧粉磁心の密度（気孔率）にも依るが、圧粉磁心の内部は通常、微細な気孔が存在するとしても密閉された状態となっている。このため表面に酸化物が形成された軟磁性粒子は、ほぼ非酸化処理工程と同様な条件下におかれることになり、軟磁性粒子の表面には酸化アルミニウムを含む絶縁層が形成されると考えられる。 (3) In the case of the powder magnetic core using the oxidized powder before the non-oxidation treatment process described above, an insulating layer containing aluminum oxide is formed between adjacent particles by performing a molded body heating process on the molded body. A dust core is obtained. This molded body heating step can be performed basically under the same conditions as the non-oxidation treatment step described above. Although depending on the density (porosity) of the dust core, the inside of the dust core is normally sealed even if fine pores exist. For this reason, soft magnetic particles having oxides formed on the surface are subjected to substantially the same conditions as in the non-oxidation treatment step, and when an insulating layer containing aluminum oxide is formed on the surface of the soft magnetic particles. Conceivable.
ところで、適切な加熱温度の成形体加熱工程は焼鈍工程を兼ねるため、上述した焼鈍工程を省略できる。従って本発明に係る成形体加熱工程は、成形体を７００〜９５０℃に加熱する焼鈍工程であると好適である。また、前述したように、この成形体加熱工程も窒素を含む不活性ガス中で行うとより好ましい。 By the way, since the molded object heating process of suitable heating temperature serves as an annealing process, the annealing process mentioned above can be abbreviate | omitted. Therefore, the molded body heating step according to the present invention is preferably an annealing step in which the molded body is heated to 700 to 950 ° C. Moreover, as described above, it is more preferable that this heating step of the molded body is also performed in an inert gas containing nitrogen.
《圧粉磁心》
（１）本発明の圧粉磁心は、その詳細な特性を問わないが、例えば、軟磁性粒子の真密度（ρ０）に対する圧粉磁心の嵩密度（ρ）の比である密度比（ρ／ρ０）が９０％以上、９５％以上さらには９７％以上であると、高磁気特性が得られて好ましい。
<Dust core>
(1) The powder magnetic core of the present invention does not ask about the detailed characteristics. For example, the density ratio (ρ, which is the ratio of the bulk density (ρ) of the powder magnetic core to the true density (ρ 0 ) of the soft magnetic particles. / Ρ 0 ) is preferably 90% or more, 95% or more, and more preferably 97% or more, because high magnetic properties can be obtained.
圧粉磁心の比抵抗は、形状に依存しない圧粉磁心ごとの固有値であり、例えば、１０μΩ・ｍ以上、５０μΩ・ｍ以上さらには１０２μΩ・ｍ以上であると好ましい。また圧粉磁心の強度は、高いほどその用途が拡大して好ましい。例えば、圧粉磁心の曲げ強度は４０ＭＰａ以上、５０ＭＰａ以上さらには６０ＭＰａ以上であると好ましい。 The specific resistance of the dust core is an eigenvalue for each dust core independent of the shape, and is preferably 10 μΩ · m or more, 50 μΩ · m or more, further 10 2 μΩ · m or more, for example. Further, the higher the strength of the dust core, the more preferable the use is expanded. For example, the bending strength of the dust core is preferably 40 MPa or more, 50 MPa or more, and more preferably 60 MPa or more.
本発明の圧粉磁心は、軟磁性粒子の表面に酸化アルミニウムを含む絶縁層が形成されているため、軟磁性粒子を絶縁被覆するためのシリコン樹脂や低融点ガラス等の絶縁材を用いるまでもなく、高比抵抗、高強度を発揮し得る。また本発明の圧粉磁心は、そのような絶縁材を使用する必要がないため高密度化による磁気特性の向上を図り易い。但し本発明は、そのような絶縁材やバインダー等を用いた圧粉磁心を排除するものではない。 In the dust core of the present invention, an insulating layer containing aluminum oxide is formed on the surface of the soft magnetic particles, so that it is possible to use an insulating material such as silicon resin or low melting point glass for insulating coating the soft magnetic particles. And can exhibit high specific resistance and high strength. Moreover, since the dust core of the present invention does not require the use of such an insulating material, it is easy to improve the magnetic characteristics by increasing the density. However, the present invention does not exclude a dust core using such an insulating material or a binder.
（２）用途
本発明の圧粉磁心は、その形態を問わず、各種の電磁機器、例えば、モータ、アクチュエータ、トランス、誘導加熱器（ＩＨ）、スピーカ、リアクトル等に利用され得る。具体的には、電動機または発電機の界磁または電機子を構成する鉄心に用いられると好ましい。中でも、低損失で高出力（高磁束密度）が要求される駆動用モータ用の鉄心に本発明の圧粉磁心は好適である。ちなみに駆動用モータは自動車等に用いられる。
(2) Applications The dust core of the present invention can be used for various electromagnetic devices such as motors, actuators, transformers, induction heaters (IH), speakers, reactors, etc., regardless of the form. Specifically, it is preferably used for an iron core constituting a field or armature of an electric motor or generator. Among these, the dust core of the present invention is suitable for an iron core for a drive motor that requires low loss and high output (high magnetic flux density). Incidentally, the drive motor is used in automobiles and the like.
実施例を挙げて本発明をより具体的に説明する。
《磁心用粉末》
［製造］
（１）軟磁性粉末
Ｓｉ含有鉄合金（Ｆｅ−６％Ａｌ−２％Ｓｉ／合金組成は特に断らない限り質量％とする。）からなるガス水アトマイズ粉と、Ｓｉ非含有鉄合金（Ｆｅ−６％Ａｌ）からなるガス水アトマイズ粉とをそれぞれ用意した。これらの粉末を所定のメッシュサイズの篩いにより分級し、粒度が１０６〜２１２μｍとなる２種の軟磁性粉末（原料粉末）を得た。なお、本明細書でいう粉末粒度「ｘ−ｙ」は、篩目開きがｘ（μｍ）の篩いを通過せず、篩目開きがｙ（μｍ）の篩いを通過する大きさの軟磁性粒子により原料粉末が構成されていることを意味する。同様に、粉末粒度「−ｙ」は、篩目開きがｙ（μｍ）の篩いを通過する大きさの軟磁性粒子により原料粉末が構成されていることを意味する。
The present invention will be described more specifically with reference to examples.
<Magnetic core powder>
[Manufacturing]
(1) Soft magnetic powder Gas water atomized powder made of Si-containing iron alloy (Fe-6% Al-2% Si / mass composition unless otherwise specified) and Si-free iron alloy (Fe- Gas water atomized powder made of 6% Al) was prepared. These powders were classified with a sieve having a predetermined mesh size to obtain two types of soft magnetic powders (raw material powders) having a particle size of 106 to 212 μm. The powder particle size “xy” in the present specification is a soft magnetic particle having a size that does not pass through a sieve having a sieve opening of x (μm) and passes through a sieve having a sieve opening of y (μm). Means that the raw material powder is constituted. Similarly, the powder particle size “−y” means that the raw material powder is composed of soft magnetic particles having a size that passes through a sieve having a sieve opening of y (μm).
（２）酸化処理工程（第１粉末加熱工程）
各原料粉末を回転炉に入れて９００℃×２時間加熱した。この加熱処理は、大気（露点：−６０℃）を０．５Ｌ／ｍｉｎの割合で回転炉へ流入させる酸化雰囲気中で行った。こうして原料粉末を酸化処理した２種の酸化粉末を得た。
(2) Oxidation process (first powder heating process)
Each raw material powder was put into a rotary furnace and heated at 900 ° C. for 2 hours. This heat treatment was performed in an oxidizing atmosphere in which air (dew point: −60 ° C.) was introduced into the rotary furnace at a rate of 0.5 L / min. Thus, two kinds of oxidized powders obtained by oxidizing the raw material powder were obtained.
（３）非酸化処理工程（第２粉末加熱工程）
同じ回転炉を用いて、各酸化粉末をさらに９００℃×１時間加熱した。この加熱処理は、窒素ガス（露点：−６０℃）を０．５Ｌ／ｍｉｎの割合で回転炉へ流入させる非酸化雰囲気中で行った。こうして酸化粉末に非酸化処理を施した２種類の磁心用粉末を得た。
(3) Non-oxidation treatment process (second powder heating process)
Using the same rotary furnace, each oxidized powder was further heated at 900 ° C. for 1 hour. This heat treatment was performed in a non-oxidizing atmosphere in which nitrogen gas (dew point: −60 ° C.) was introduced into the rotary furnace at a rate of 0.5 L / min. In this way, two kinds of magnetic core powders obtained by subjecting the oxidized powder to non-oxidation treatment were obtained.
また、Ｓｉ含有鉄合金からなる酸化粉末については、その窒素ガス雰囲気をアルゴンガス雰囲気と真空雰囲気にそれぞれ替えて、同様な非酸化処理を行った。なお、適宜、原料粉末がＳｉ含有鉄合金からなる一連の粉末をＳｉ含有粉末、原料粉末がＳｉ非含有鉄合金からなる一連の粉末をＳｉ非含有粉末という。 Moreover, about the oxidation powder which consists of Si containing iron alloys, the nitrogen gas atmosphere was changed into the argon gas atmosphere and the vacuum atmosphere, respectively, and the same non-oxidation process was performed. As appropriate, a series of powders whose raw material powder is made of an Si-containing iron alloy is called Si-containing powder, and a series of powders whose raw material powder is made of an Si-free iron alloy is called Si-free powder.
［分析］
上述したそれぞれの原料粉末（処理前）、酸化粉末（酸化処理後）および磁心用粉末（非酸化処理後）のそれぞれから任意に抽出した粉末粒子について、オージェ電子分光分析（ＡＥＳ）を行い、各粒子の表面近傍（最表面から２０００ｎｍの深さまでの範囲）の成分組成を調べた。それらの結果を図１Ａ〜図１Ｅ（Ｓｉ含有粉末）と図２Ａ〜図２Ｃ（Ｓｉ非含有粉末）に示した。
[analysis]
For the powder particles arbitrarily extracted from each of the above raw material powder (before treatment), oxidation powder (after oxidation treatment) and magnetic core powder (after non-oxidation treatment), Auger electron spectroscopy analysis (AES) is performed, The component composition in the vicinity of the particle surface (range from the outermost surface to a depth of 2000 nm) was examined. The results are shown in FIGS. 1A to 1E (Si-containing powder) and FIGS. 2A to 2C (Si-free powder).
また、Ｓｉ含有粉末については、ＡＥＳから得られた結果に基づいて、各粉末粒子の表面近傍（最表面から１０００ｎｍの深さまでの範囲）に存在する元素の濃度（原子％）を積分平均により算出した。その結果を表１に示した。 For Si-containing powders, based on the results obtained from AES, the concentration (atomic%) of the elements present in the vicinity of the surface of each powder particle (range from the outermost surface to a depth of 1000 nm) is calculated by integral averaging. did. The results are shown in Table 1.
［評価］
（１）酸化処理の影響
Ｓｉ含有粉末の場合、図１Ａ、図１Ｂおよび表１に示す結果からわかるように、原料粉末に酸化処理を行うことにより、その粒子表面の近傍で、Ａｌ量が増加する一方、Ｆｅ量およびＳｉ量は減少している。これは、粉末粒子の表面でＡｌの一部が酸化されて濃化した結果、ＦｅおよびＳｉがその分希釈されたためと考えられる。但し、この段階では、いずれの元素量もさほど大きく変動はしていないことから、酸化粉末の粒子表面近傍は、Ｆｅ２Ｏ３、Ａｌ２Ｏ３等の複数種の酸化物が混在した状態になっていると考えられる。
[Evaluation]
(1) Effect of oxidation treatment In the case of Si-containing powder, as can be seen from the results shown in FIG. 1A, FIG. 1B and Table 1, the amount of Al increases in the vicinity of the particle surface by oxidizing the raw material powder. On the other hand, the amount of Fe and the amount of Si are decreasing. This is presumably because Fe and Si were diluted by that amount as a result of a part of Al being oxidized and concentrated on the surface of the powder particles. However, at this stage, since the amount of any element does not change so much, the vicinity of the particle surface of the oxidized powder is in a state where a plurality of types of oxides such as Fe 2 O 3 and Al 2 O 3 are mixed. It is thought that it has become.
Ｓｉ非含有粉末の場合、図２Ａと図２Ｂの比較からわかるように、酸化処理により、粒子表面の近傍でＯ量が増加し、Ｆｅ量はそのＯ量に対して略一定割合となると共に、Ａｌ量は減少している。このことから、Ｓｉ非含有粉末は酸化処理によって粒子表面が酸化鉄からなる酸化物層で被覆された状態になったと考えられる。 In the case of the Si-free powder, as can be seen from the comparison between FIG. 2A and FIG. 2B, the amount of O increases in the vicinity of the particle surface by the oxidation treatment, and the amount of Fe becomes a substantially constant ratio to the amount of O. The amount of Al is decreasing. From this, it is considered that the Si-free powder was in a state where the particle surface was coated with an oxide layer made of iron oxide by oxidation treatment.
（２）非酸化処理の影響
Ｓｉ含有粉末の場合、図１Ｃ〜図１Ｅおよび表１からわかるように、酸化粉末に非酸化処理を行うことにより、粒子表面近傍において、Ｏ量はあまり変動していないが、Ｆｅ量が急減し、逆にＡｌ量が急増している。しかも、Ｏ量とＡｌ量は表面から奥深くまでほぼ同組成となっている。これらのことから、非酸化処理によって、粒子表面近傍に存在していた酸化物（Ｆｅ２Ｏ３、Ａｌ２Ｏ３等）の大部分が、酸化アルミニウムに収束されたと考えられる。つまり、非酸化処理により、粒子表面に存在していた酸化鉄中のＯが、Ｆｅから離れてＡｌと新たに結合し、酸化アルミニウムを生成するに至ったと考えられる。従って、非酸化処理されたＳｉ含有粉末は、非酸化処理により、酸化アルミニウムから主になる絶縁層で表面が被覆された軟磁性粒子（絶縁被覆粒子）になることがわかった。
(2) Influence of non-oxidation treatment In the case of Si-containing powder, as can be seen from FIGS. 1C to 1E and Table 1, the amount of O fluctuates in the vicinity of the particle surface by performing non-oxidation treatment on the oxidized powder. Although there is no Fe amount, the amount of Fe is decreasing rapidly and conversely, the amount of Al is increasing rapidly. Moreover, the amount of O and the amount of Al have almost the same composition from the surface to the depth. From these facts, it is considered that most of the oxides (Fe 2 O 3 , Al 2 O 3, etc.) existing in the vicinity of the particle surface were converged on the aluminum oxide by the non-oxidation treatment. That is, it is considered that O in the iron oxide existing on the particle surface is separated from Fe and newly combined with Al by the non-oxidation treatment, thereby generating aluminum oxide. Therefore, it was found that the non-oxidized Si-containing powder became soft magnetic particles (insulating coated particles) whose surfaces were coated with an insulating layer mainly made of aluminum oxide by non-oxidizing treatment.
なお、このようなＳｉ含有粉末の特徴は、非酸化処理がＮ２雰囲気に限らず、Ａｒ雰囲気または真空雰囲気でなされても同様であることが、図１Ｃ〜図１Ｅおよび表１からわかる。 1C to FIG. 1E and Table 1 show that the characteristics of such a Si-containing powder are the same even if the non-oxidation treatment is performed not only in the N 2 atmosphere but also in an Ar atmosphere or a vacuum atmosphere.
Ｓｉ非含有粉末の場合、図２Ａ〜図２Ｃを対比するとわかるように、酸化粉末に非酸化処理を行うことにより、粒子表面近傍においてＯ量が急減し、Ｆｅ量が急増する一方、Ａｌ量はあまり変化しないことがわかった。つまり、Ｓｉ非含有粉末の場合、原料粉末（図２Ａ）に対して酸化処理がなされることにより粒子表面のＯ量およびＦｅ量（ひいては酸化鉄）が増加するが（図２Ｂ）、その酸化粉末に非酸化処理がなされると、粒子表面のＯ量およびＦｅ量（ひいては酸化鉄）が減少して、原料粉末に近い状態に戻る（つまり還元される）ことがわかった（図２Ｃ）。 In the case of non-Si-containing powder, as can be seen by comparing FIGS. 2A to 2C, by performing non-oxidation treatment on the oxidized powder, the amount of O rapidly decreases and the amount of Al rapidly increases near the particle surface, while the amount of Al increases. It turns out that there is not much change. That is, in the case of a powder containing no Si, the amount of O and Fe (and hence iron oxide) on the surface of the particles are increased by oxidizing the raw material powder (FIG. 2A) (FIG. 2B). It was found that when non-oxidizing treatment was performed, the amount of O and Fe (and thus iron oxide) on the particle surface decreased and returned to a state close to the raw material powder (that is, reduced) (FIG. 2C).
このように非酸化処理後のＳｉ含有粉末とＳｉ非含有粉末の比較から、Ｓｉが存在する場合に粒子表面に酸化アルミニウムからなる絶縁層が安定的に形成されることが明らかとなった。 Thus, it became clear from the comparison between the Si-containing powder after the non-oxidation treatment and the Si-free powder that an insulating layer made of aluminum oxide is stably formed on the particle surface when Si is present.
《圧粉磁心》
［製造］
（１）軟磁性粉末および酸化粉末
表２に示す各種の軟磁性粉末（試料Ｃ１、Ｃ３およびＣ４を除く）に、表２に示す酸化処理工程を施した各種の酸化粉末を用意した。表２に示した各軟磁性粉末は、その組成を除き、前述した軟磁性粉末と同様に製造したものである。また、酸化処理工程も、表２に示した条件を除き、前述した酸化処理工程と同様に行った。なお、試料８〜９に係る酸化処理工程は、酸化雰囲気を大気フローから表２に示す酸素ガス（体積％）と残部が窒素ガスからなる混合ガスフローに替えて行った。さらに試料Ｃ１、Ｃ３およびＣ４では、そのような酸化処理を施さない軟磁性粉末（原料粉末）を用いた。
<Dust core>
[Manufacturing]
(1) Soft magnetic powder and oxidized powder Various oxidized powders obtained by subjecting various soft magnetic powders shown in Table 2 (except samples C1, C3, and C4) to the oxidation treatment step shown in Table 2 were prepared. Each soft magnetic powder shown in Table 2 was produced in the same manner as the soft magnetic powder described above except for its composition. Moreover, the oxidation treatment process was also performed in the same manner as the oxidation treatment process described above except for the conditions shown in Table 2. In addition, the oxidation treatment process according to Samples 8 to 9 was performed by changing the oxidizing atmosphere from an atmospheric flow to a mixed gas flow including oxygen gas (volume%) shown in Table 2 and the balance of nitrogen gas. Further, in samples C1, C3 and C4, soft magnetic powder (raw material powder) not subjected to such oxidation treatment was used.
（２）成形工程
各粉末を用いて、金型潤滑温間高圧成形法により、円板状（外径：φ２３ｍｍ×厚さ２〜３ｍｍ）の成形体を得た。この際、内部潤滑剤や樹脂バインダー等は一切使用しなかった。具体的には次のようにして各粉末を成形した。
(2) Molding step Using each powder, a disk-shaped (outside diameter: φ23 mm ×
所望形状に応じたキャビティを有する超硬製の金型を用意した。この金型をバンドヒータで予め１３０℃に加熱しておいた。また、この金型の内周面には、予めＴｉＮコート処理を施し、その表面粗さを０．４Ｚとした。 A cemented carbide mold having a cavity corresponding to a desired shape was prepared. This mold was previously heated to 130 ° C. with a band heater. Further, the inner peripheral surface of this mold was previously subjected to TiN coating treatment, and the surface roughness was set to 0.4Z.
加熱した金型の内周面に、ステアリン酸リチウム（１％）の水分散液をスプレーガンにて１０ｃｍ３／分程度の割合で均一に塗布した。なお、この水分散液は、水に界面活性剤と消泡剤とを添加したものである。その他の詳細は、日本特許公報特許３３０９９７０号公報、日本特許４０２４７０５号公報等に記載に沿って行った。 An aqueous dispersion of lithium stearate (1%) was uniformly applied to the inner peripheral surface of the heated mold with a spray gun at a rate of about 10 cm 3 / min. This aqueous dispersion is obtained by adding a surfactant and an antifoaming agent to water. Other details were made in accordance with the descriptions in Japanese Patent Publication No. 3309970, Japanese Patent No. 4024705, and the like.
各粉末をステアリン酸リチウムが内面に塗布された金型へ充填し（充填工程）、金型を１３０℃に保持したまま１５６８ＭＰａで温間成形した（成形工程）。なお、この温間成形時、いずれの成形体も金型とかじり等を生じることはなく、低い抜圧で金型からの取り出しが可能であった。 Each powder was filled into a mold in which lithium stearate was applied on the inner surface (filling process), and warm-molded at 1568 MPa while the mold was held at 130 ° C. (molding process). In this warm molding, none of the molded bodies generated galling or the like with the mold, and the mold could be taken out from the mold with a low pressure.
（３）成形体加熱工程（焼鈍工程）
試料Ｃ２を除き、得られた各成形体を加熱炉に入れ、表２に示す温度で１時間の加熱処理を行った。この加熱処理は、窒素ガスを０．５Ｌ／ｍｉｎの割合で加熱炉へ流入させる非酸化雰囲気中で行った。なお、この非酸化処理は、成形体の焼鈍を兼ねている。こうして表２に示す各種の圧粉磁心（試料）を得た。
(3) Molded body heating process (annealing process)
Except for the sample C2, each molded body obtained was placed in a heating furnace and subjected to heat treatment at the temperature shown in Table 2 for 1 hour. This heat treatment was performed in a non-oxidizing atmosphere in which nitrogen gas was introduced into the heating furnace at a rate of 0.5 L / min. This non-oxidation treatment also serves as annealing of the molded body. Thus, various dust cores (samples) shown in Table 2 were obtained.
［測定］
各試料に係る圧粉磁心の比抵抗および曲げ強度を求めた。比抵抗は、デジタルマルチメータ（メーカ：（株）エーディーシー、型番：Ｒ６５８１）を用いて４端子法により測定した電気抵抗と、各試料を実際に採寸して求めた体積とから算出した。曲げ強度は、円板状の試料に対して３点曲げ強度試験より算出した。これらの結果を表２に併せて示した。また、各試料の比抵抗と曲げ強度の関係を図３に示した。
[Measurement]
The specific resistance and bending strength of the powder magnetic core according to each sample were determined. The specific resistance was calculated from the electrical resistance measured by a four-terminal method using a digital multimeter (manufacturer: ADC Corporation, model number: R6581) and the volume obtained by actually measuring each sample. The bending strength was calculated from a three-point bending strength test for a disk-shaped sample. These results are also shown in Table 2. The relationship between the specific resistance and bending strength of each sample is shown in FIG.
［観察］
試料４に係る圧粉磁心の構成粒子の表面近傍（隣接する軟磁性粒子の粒界部分）を、前述したＡＥＳで観察した。その結果、前述した磁心用粉末の絶縁層と同様に、その粒界部分にも酸化アルミニウムからなる絶縁層が生成されることが確認された。
[Observation]
The vicinity of the surface of the constituent particles of the dust core according to Sample 4 (grain boundary portion of the adjacent soft magnetic particles) was observed with the AES described above. As a result, it was confirmed that an insulating layer made of aluminum oxide was also formed at the grain boundary portion in the same manner as the above-described insulating layer of the magnetic core powder.
［評価］
（１）表２および図３から明らかなように、試料１〜１０（特に試料１〜７）は十分な比抵抗および曲げ強度を発揮していることがわかる。そして、軟磁性粉末中のＳｉ量またはＡｌ量が多くなると、圧粉磁心の比抵抗または強度が向上する傾向にあることもわかる。また酸化処理工程が高温、長時間、高酸素濃度であるほど、比抵抗または強度が向上する傾向にあることもわかる。さらには、粉末粒度が小さくなり粉末全体としての表面積が増加する圧粉磁心（試料７、９および１０）ほど、比抵抗または強度が向上する傾向にあることもわかる。そして粒径が小さい低粒度のＳｉ含有粉末の場合、酸化処理中の酸素濃度が低くても、十分な比抵抗または強度が得られることもわかった。
[Evaluation]
(1) As is clear from Table 2 and FIG. 3, it can be seen that
（２）酸化処理を施さない原料粉末をそのまま成形した成形体を、非酸化雰囲気で加熱して得られた圧粉磁心（試料Ｃ１）は、比抵抗および強度が共に低くなった。このことから、酸化アルミニウムを含む高絶縁性の絶縁層を形成するには、成形体加熱工程（非酸化処理工程）前に、粒子表面に酸化物（主に酸化鉄）が十分に生成された酸化粉末を用いることが好ましいといえる。 (2) A powder magnetic core (sample C1) obtained by heating a molded body obtained by directly molding a raw material powder not subjected to oxidation treatment in a non-oxidizing atmosphere has a low specific resistance and strength. From this, in order to form a highly insulating insulating layer containing aluminum oxide, oxide (mainly iron oxide) was sufficiently generated on the particle surface before the heating step of the compact (non-oxidation treatment step). It can be said that it is preferable to use oxidized powder.
また、十分な酸化処理がなされた酸化粉末を用いた場合でも、成形体加熱工程（非酸化処理工程）がなされなかった圧粉磁心（試料Ｃ２）では、やはり比抵抗および強度が共に低くなった。これは隣接粒子間にある酸化鉄等の酸化物層が、酸化アルミニウムからなる絶縁層に変化しなかったためと考えられる。このことから、酸化アルミニウムを含む高絶縁性の絶縁層を形成するには、酸化粉末を用いると共に、成形体加熱工程（非酸化処理工程）を行うことが必要であるといえる。 Further, even when the oxidized powder that has been sufficiently oxidized is used, both the specific resistance and the strength are lowered in the powder magnetic core (sample C2) in which the molded body heating process (non-oxidation process) has not been performed. . This is presumably because the oxide layer such as iron oxide between adjacent particles did not change to an insulating layer made of aluminum oxide. From this, it can be said that, in order to form a highly insulating insulating layer containing aluminum oxide, it is necessary to use an oxide powder and to carry out a molded body heating step (non-oxidation treatment step).
さらに、試料Ｃ３、Ｃ４の圧粉磁心のように、軟磁性粉末中にＡｌが含まれず、酸化処理工程もなされない粉末からなる圧粉磁心では、比抵抗および強度がかなり低くなった。このことから、軟磁性粉末として一般的なＦｅ−Ｓｉ系粉末からなる圧粉磁心を単に非酸化雰囲気中で加熱（つまり焼鈍）しても、本発明のようなに高比抵抗で高強度な圧粉磁心は得られないことがわかる。 Furthermore, the specific resistance and strength of the dust core made of powder that does not include Al in the soft magnetic powder and is not subjected to the oxidation treatment step, such as the dust cores of Samples C3 and C4, are considerably low. Therefore, even if a powder magnetic core made of a general Fe-Si powder as a soft magnetic powder is simply heated (that is, annealed) in a non-oxidizing atmosphere, it has a high specific resistance and high strength as in the present invention. It turns out that a dust core cannot be obtained.
また、試料１等と同様な酸化処理工程および成形体加熱工程を行っても、Ｓｉ非含有粉末からなる圧粉磁心（試料Ｃ５）では、比抵抗および強度が共に低くなることもわかった。これは、磁心用粉末の場合と同様に、酸化アルミニウムからなる絶縁層が隣接粒子間に形成されないためと考えられる。
It was also found that both the resistivity and strength of the powder magnetic core (sample C5) made of Si-free powder were lowered even when the oxidation treatment step and the molded body heating step similar to those of
以上から、ＡｌおよびＳｉを含む鉄合金からなる軟磁性粒子の表面に十分な酸化物（主に酸化鉄）を形成した後に、その粉末またはその粉末からなる成形体を非酸化雰囲気で加熱することにより、酸化アルミニウムからなる絶縁層が生成されて、比抵抗と強度を高次元で両立させ得る圧粉磁心が得られることが明らかとなった。 From the above, after forming a sufficient oxide (mainly iron oxide) on the surface of soft magnetic particles made of an iron alloy containing Al and Si, the powder or a compact made of the powder is heated in a non-oxidizing atmosphere. As a result, it has been clarified that an insulating layer made of aluminum oxide is generated, and a dust core capable of achieving both high specific resistance and high strength can be obtained.
実施例を挙げて本発明をより具体的に説明する。
《磁心用粉末》
［製造］
（１）軟磁性粉末
Ｓｉ含有鉄合金（Ｆｅ−６％Ｓｉ−２％Ａｌ／合金組成は特に断らない限り質量％とする。）からなるガス水アトマイズ粉と、Ｓｉ非含有鉄合金（Ｆｅ−６％Ａｌ）からなるガス水アトマイズ粉とをそれぞれ用意した。これらの粉末を所定のメッシュサイズの篩いにより分級し、粒度が１０６〜２１２μｍとなる２種の軟磁性粉末（原料粉末）を得た。なお、本明細書でいう粉末粒度「ｘ−ｙ」は、篩目開きがｘ（μｍ）の篩いを通過せず、篩目開きがｙ（μｍ）の篩いを通過する大きさの軟磁性粒子により原料粉末が構成されていることを意味する。同様に、粉末粒度「−ｙ」は、篩目開きがｙ（μｍ）の篩いを通過する大きさの軟磁性粒子により原料粉末が構成されていることを意味する。
The present invention will be described more specifically with reference to examples.
<Magnetic core powder>
[Manufacturing]
(1) Soft magnetic powder A gas-water atomized powder composed of a Si-containing iron alloy (Fe-6% Si- 2% Al / alloy composition unless otherwise specified) and a Si-free iron alloy (Fe- Gas water atomized powder made of 6% Al) was prepared. These powders were classified with a sieve having a predetermined mesh size to obtain two types of soft magnetic powders (raw material powders) having a particle size of 106 to 212 μm. The powder particle size “xy” in the present specification is a soft magnetic particle having a size that does not pass through a sieve having a sieve opening of x (μm) and passes through a sieve having a sieve opening of y (μm). Means that the raw material powder is constituted. Similarly, the powder particle size “−y” means that the raw material powder is composed of soft magnetic particles having a size that passes through a sieve having a sieve opening of y (μm).
Claims (8)
ＡｌおよびＳｉを含む鉄合金の軟磁性粒子からなり該軟磁性粒子の表面近傍に酸化鉄を有する酸化粒子を、非酸化雰囲気で加熱することにより酸化アルミニウムからなる絶縁層により少なくとも一部表面が被覆された絶縁被覆粒子を得る非酸化処理工程を備え、
前記磁心用粉末は該絶縁被覆粒子からなることを特徴とする磁心用粉末の製造方法。 A method for producing a powder for a magnetic core used for producing a dust core,
At least part of the surface is covered with an insulating layer made of aluminum oxide by heating, in a non-oxidizing atmosphere, oxidized particles having iron oxide near the surface of the iron alloy soft magnetic particles containing Al and Si. A non-oxidation treatment step for obtaining insulated insulating particles,
The method for producing a magnetic core powder, wherein the magnetic core powder comprises the insulating coating particles.
Ａｌ：０．５〜５％、
Ｓｉ：０．５〜９％、
残部：Ｆｅと不可避不純物または改質元素、
からなる請求項１または２に記載の磁心用粉末の製造方法。 When the total amount of the iron alloy is 100% by mass (simply expressed as “%”),
Al: 0.5-5%
Si: 0.5-9%
The rest: Fe and inevitable impurities or modifying elements,
The manufacturing method of the powder for magnetic cores of Claim 1 or 2 consisting of these.
該成形体を非酸化雰囲気で加熱することにより、該軟磁性粒子の隣接間の少なくとも一部に酸化アルミニウムからなる絶縁層が形成された圧粉磁心を得る成形体加熱工程と、
を備えることを特徴とする圧粉磁心の製造方法。 A molding step of obtaining a molded body formed by press-molding oxide powder, which is composed of soft magnetic particles of an iron alloy containing Al and Si, and which is a powder of oxide particles having iron oxide near the surface of the soft magnetic particles;
A molded body heating step of obtaining a dust core in which an insulating layer made of aluminum oxide is formed on at least a part between adjacent soft magnetic particles by heating the molded body in a non-oxidizing atmosphere;
A method for producing a powder magnetic core comprising the steps of:
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