JP4278147B2 - Powder for magnetic core, dust core and method for producing the same - Google Patents
Powder for magnetic core, dust core and method for producing the same Download PDFInfo
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Description
本発明は、モータ、リアクトル等の各種磁心として利用できる圧粉磁心と、その圧粉磁心の製造に適した磁心用粉末と、そららの製造方法に関するものである。 The present invention relates to a powder magnetic core that can be used as various magnetic cores such as motors and reactors, a magnetic core powder suitable for manufacturing the powder magnetic core, and a method of manufacturing the same.
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、その交番磁界は、通常、磁心（軟磁石）を中央に配設したコイルによって発生される。このため、電磁機器の性能は、そのコイルの性能に左右され、コイルの性能は、上記磁心の性能に左右される。よって、電磁機器の性能向上や小型化等を図る上で、磁心の性能向上を図ることが非常に重要である。 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, and the alternating magnetic field is usually generated by a coil having a magnetic core (soft magnet) disposed in the center. For this reason, the performance of the electromagnetic device depends on the performance of the coil, and the performance of the coil depends on the performance of the magnetic core. Therefore, it is very important to improve the performance of the magnetic core in order to improve the performance and size of the electromagnetic equipment.
このような磁心には、先ず、交番磁界中で大きな磁束密度が得られることが求められる。次に、交番磁界中で使用したときに、その周波数に応じて生じる高周波損失（鉄損）が少ないことが求められる。この高周波損失には、渦電流損、ヒステリシス損および残留損失があるが、主に問題となるのは、渦電流損とヒステリシス損である。 Such a magnetic core is first required to obtain a large magnetic flux density in an alternating magnetic field. Next, when used in an alternating magnetic field, it is required that the high frequency loss (iron loss) generated according to the frequency is small. The high-frequency loss includes eddy current loss, hysteresis loss, and residual loss. The main problems are eddy current loss and hysteresis loss.
また、電磁機器の部品に応じた磁心の成形性や小型化等を図るために、従来の電磁鋼板に替えて圧粉磁心が磁心として多用されつつある。圧粉磁心は、粒子表面に絶縁被膜を設けた磁性粉末を加圧成形したものである。絶縁被膜を設けることで比抵抗値を高めて渦電流損の低減を図れるし、その高密度化によって磁束密度等の磁気特性を高めることもできる。ちなみに、圧粉磁心に使用される絶縁被膜については、例えば、下記の特許文献１や特許文献２に開示がある。また、圧粉磁心の成形性等に関して、例えば、下記の特許文献３に開示がある。
Further, in order to achieve the formability and miniaturization of the magnetic core according to the parts of the electromagnetic equipment, a dust core is being frequently used as the magnetic core instead of the conventional electromagnetic steel sheet. The dust core is obtained by pressure-molding magnetic powder having an insulating coating on the particle surface. By providing an insulating film, the specific resistance value can be increased to reduce eddy current loss, and magnetic properties such as magnetic flux density can be enhanced by increasing the density. Incidentally, the insulating film used for the dust core is disclosed in, for example,
圧粉磁心の高性能化を図る上で、その高密度化による磁束密度の増加および比抵抗値の確保による渦電流損の低減を図ることは確かに重要である。しかし、最近では、モータのエネルギー効率等を一層向上させるために、その圧粉磁心による損失低減がより強く求められている。前述したように、圧粉磁心による主たる損失として渦電流損の他にヒステリシス損があるところ、このヒステリシス損の低減も非常に重要となっている。特に、数十〜数百ｋＨｚもの高周波数域でのみ圧粉磁心を使用する場合ならいざしらず、それ以下の周波数域で圧粉磁心を使用することを考えれば、ヒステリシス損の低減は圧粉磁心の全体的な損失低減を図る上で非常に重要である。 In order to improve the performance of the powder magnetic core, it is certainly important to increase the magnetic flux density by increasing the density and to reduce the eddy current loss by securing the specific resistance value. However, recently, in order to further improve the energy efficiency and the like of the motor, there is a strong demand for reducing the loss due to the dust core. As described above, as a main loss due to the dust core, there is a hysteresis loss in addition to the eddy current loss. Reduction of this hysteresis loss is also very important. In particular, if a dust core is used only in the high frequency range of several tens to several hundreds of kHz, considering the use of the dust core in a frequency range lower than that, the hysteresis loss can be reduced. This is very important in reducing the overall loss of the magnetic core.
ヒステリシス損の低減を図るには、圧粉磁心の保磁力の低減が有効である。この保磁力は、磁性粉末粒子内に残留する歪み（残留歪）の影響を受け、その歪が多いと保磁力も大きくなる。圧粉磁心は磁性粉末を加圧成形して得られるため、その構成粒子内には多かれ少なかれ残留歪が生じる。従って、ヒステリシス損の低減には、磁性粉末粒子内に一旦生じたその残留歪を除去することが有効である。この歪除去のために、下記特許文献３にもあるように、焼鈍等の熱処理がなされることが多い。磁性粉末の組成にも依るが、Ｆｅを主成分とする圧粉磁心で十分に歪みを除去するには、４５０℃以上、５００℃以上さらには７００℃以上にも加熱することが必要となる。 In order to reduce the hysteresis loss, it is effective to reduce the coercive force of the dust core. This coercive force is affected by the strain (residual strain) remaining in the magnetic powder particles, and the coercive force increases when the strain is large. Since the dust core is obtained by pressure-molding magnetic powder, a residual strain is produced in the constituent particles more or less. Therefore, to reduce the hysteresis loss, it is effective to remove the residual strain once generated in the magnetic powder particles. In order to remove the strain, as described in Patent Document 3 below, heat treatment such as annealing is often performed. Although it depends on the composition of the magnetic powder, it is necessary to heat to 450 ° C. or higher, 500 ° C. or higher, and 700 ° C. or higher in order to sufficiently remove distortion with a powder magnetic core mainly composed of Fe.
ところが、圧粉磁心をそこまで高温加熱すると、例えば、上記特許文献１にあるリン酸塩からなる絶縁被膜や特許文献２にある熱可塑性材料からなる絶縁被膜は、結晶化して焼結・凝集を生じたり、分解、破壊等してしまう。その結果、ヒステリシス損の低減を図れたとしても、比抵抗値が急減して渦電流損が急増してしまい、結局、鉄損を低減することは難しい。
However, when the dust core is heated to such a high temperature, for example, the insulating coating made of phosphate described in
上記特許文献３には、水ガラスの絶縁被膜を表面に形成した磁性粉末からなる圧粉磁心に、７００℃ｘ１時間の焼鈍熱処理を施した実施例が開示されている。そこに記載された比抵抗値を観ると、焼鈍後においても相応の比抵抗値が確保されている。しかし、この場合、１６６６ＭＰａもの高圧で成形しているにも拘わらず、水ガラス量が多いために、言い換えるなら絶縁被膜が厚いために、相対密度が相当に低く、その結果、磁束密度も低いものとなっている。これでは、圧粉磁心の磁気特性向上と損失低減との両立を図れない。 Patent Document 3 discloses an example in which an annealing heat treatment at 700 ° C. × 1 hour is performed on a powder magnetic core made of a magnetic powder having a water glass insulating film formed on the surface thereof. When the specific resistance value described there is observed, a corresponding specific resistance value is ensured even after annealing. However, in this case, although the molding is performed at a high pressure of 1666 MPa, since the amount of water glass is large, in other words, because the insulating film is thick, the relative density is considerably low, and as a result, the magnetic flux density is also low. It has become. With this, it is impossible to achieve both improvement in magnetic characteristics and loss reduction of the dust core.
なお、上記特許文献３には、Ｆｅ−Ｓｉ系磁性粉末の製造過程（アトマイズの過程）において、その表面にＳｉＯ2被膜が形成され、その電気抵抗率を高める上で好ましい旨が記載されている。しかし、このときに生じるＳｉＯ2被膜は、１００〜５００ｎｍ以上の被膜として生成している。この磁性粉末を用いて圧粉磁心を製造すると、その相対密度の増加が望めず、その磁束密度も向上しない。また、比較的厚いＳｉＯ2被膜が圧粉成形前から形成されている場合、高圧成形した際に、そのＳｉＯ2被膜が破壊されるため、圧粉磁心の電気抵抗率が却って低下することもある。圧粉磁心の比抵抗値の回復や維持を図るために、さらに、シリコーン系樹脂などを添加し熱処理を行うこともあるが、その場合、圧粉磁心の相対密度および磁束密度がさらに低下することとなる。そこで、磁性粉末の表面に、比較的薄く、耐熱性等に優れた絶縁被膜を形成することが求められていた。 In Patent Document 3, it is described that a SiO 2 film is formed on the surface of the Fe—Si based magnetic powder in the manufacturing process (atomizing process), which is preferable for increasing the electrical resistivity. . However, SiO 2 film produced at this time is generated as more coatings 100 to 500 nm. When a powder magnetic core is produced using this magnetic powder, an increase in the relative density cannot be expected, and the magnetic flux density is not improved. In addition, when a relatively thick SiO 2 film is formed before dust molding, the SiO 2 film is destroyed when high-pressure molding is performed, and the electrical resistivity of the dust core may decrease instead. . In order to recover and maintain the specific resistance of the dust core, heat treatment may be performed by adding silicone resin, etc., but in that case, the relative density and magnetic flux density of the dust core may be further reduced. It becomes. Therefore, it has been required to form an insulating film that is relatively thin and excellent in heat resistance and the like on the surface of the magnetic powder.
本発明は、このような事情に鑑みて為されたものであり、磁性粉末の表面に形成する絶縁被膜を比較的薄く、かつ、耐熱性等に優れたものとすることによって、圧粉磁心の高磁気特性および低損失を両立し得る圧粉磁心用粉末、圧粉磁心およびそれらの製造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and by making the insulating coating formed on the surface of the magnetic powder relatively thin and having excellent heat resistance, etc., An object of the present invention is to provide a powder for a powder magnetic core, a powder magnetic core, and a method for producing them, which can achieve both high magnetic properties and low loss.
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、Ｆｅ−Ｓｉ系磁性粉末の表面に、薄く耐熱性に優れた酸化被膜を形成することに成功し、本発明を完成するに至った。 As a result of extensive research and trial and error, the present inventors have succeeded in forming a thin oxide film with excellent heat resistance on the surface of the Fe-Si magnetic powder, and the present invention has been achieved. It came to be completed.
（磁心用粉末）
すなわち、本発明の磁心用粉末は、鉄（Ｆｅ）およびケイ素（Ｓｉ）を主成分とする磁性粉末と、該磁性粉末の粒子表面に形成された絶縁被膜とからなる磁心用粉末において、 前記絶縁被膜は、前記磁性粉末を水蒸気分圧（Ｐ Ｈ２Ｏ ）の水素分圧（Ｐ Ｈ２ ）に対する分圧比（Ｐ Ｈ２Ｏ ／Ｐ Ｈ２ ）が６．５ｘ１０ −６ 〜３．０ｘ１０ −４ となる水素気流中からなる酸化雰囲気中に保持すると共に該酸化雰囲気中で６００℃〜９００℃に加熱処理する外部酸化処理して得られ、厚さが１〜１００ｎｍの二酸化ケイ素（ＳｉＯ２）被膜からなると共に該磁性粉末の単位表面積（ｍ２）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ２）が０．００５〜０．０５ｇ／ｍ２であることを特徴とする。
(Powder for magnetic core)
That is, the magnetic core powder of the present invention is a magnetic core powder comprising a magnetic powder mainly composed of iron (Fe) and silicon (Si), and an insulating coating formed on the particle surface of the magnetic powder. The film is formed from a hydrogen gas stream in which the magnetic powder has a partial pressure ratio (PH 2 O / PH 2 ) of water vapor partial pressure (PH 2 O ) to hydrogen partial pressure (PH 2 ) of 6.5 × 10 −6 to 3.0 × 10 −4. And a magnetic powder comprising a silicon dioxide (SiO 2 ) coating having a thickness of 1 to 100 nm , obtained by external oxidation treatment in an oxidizing atmosphere and heat-treated at 600 ° C. to 900 ° C. wherein the amount of oxygen (g) the ratio of oxygen amount indicating the per unit surface area of (m 2) (g / m 2) is 0.005~0.05g / m 2.
本発明の圧粉磁心用粉末は、Ｆｅ−Ｓｉ系磁性粉末の表面に、これまでになく、薄くて均一な耐熱性に優れた酸化被膜（絶縁被膜）が形成されたものである。先ず、この絶縁被膜は薄いために、圧粉磁心の高密度化が可能となり、ひいては圧粉磁心の磁気特性を向上させることができる。しかも、この絶縁被膜は均一で耐熱性に優れるため、焼鈍等の熱処理を行った場合でも、あまり破壊等せず、圧粉磁心の比抵抗値も急減しない。従って、本発明の磁心用粉末を用いて加圧成形した粉末成形体に焼鈍等を施してなる圧粉磁心は、高密度化による高磁気特性化に加えて、比抵抗値の急減抑止による低渦電流損の確保および保磁力の低下に伴って生じるヒステリシス損の低減を同時に可能とする。つまり、本発明の圧粉磁心によれば、磁気特性の向上および鉄損の低減を非常に高レベルで達成できる。 The powder for a powder magnetic core of the present invention has an unprecedented thin and uniform oxide film (insulating film) formed on the surface of the Fe-Si magnetic powder. First, since this insulating film is thin, it is possible to increase the density of the powder magnetic core, and consequently improve the magnetic properties of the powder magnetic core. In addition, since this insulating film is uniform and excellent in heat resistance, even when heat treatment such as annealing is performed, it does not break down so much and the specific resistance value of the dust core does not decrease rapidly. Accordingly, a powder magnetic core obtained by subjecting a powder compact that has been pressure-molded using the magnetic core powder of the present invention to annealing or the like has a low magnetic resistance by suppressing the rapid decrease in specific resistance in addition to increasing the magnetic properties by increasing the density. It is possible to simultaneously secure eddy current loss and reduce hysteresis loss caused by a decrease in coercive force. That is, according to the dust core of the present invention, improvement of magnetic characteristics and reduction of iron loss can be achieved at a very high level.
（磁心用粉末の製造方法）
本発明は、上記磁心用粉末に限らず、例えば、その製造に適した次のような製造方法としても把握できる。
(Method for producing magnetic core powder)
The present invention is not limited to the magnetic core powder, and can be grasped as, for example, the following manufacturing method suitable for the manufacturing thereof.
すなわち、本発明は、ＦｅおよびＳｉを主成分とする磁性粉末を、水蒸気分圧（ＰH2O）の水素分圧（ＰH2）に対する分圧比（ＰH2O／ＰH2）が６．５ｘ１０-6〜３．０ｘ１０-4 となる水素気流中からなる酸化雰囲気中に保持する雰囲気保持工程と、該磁性粉末を該酸化雰囲気中で６００℃〜９００℃に加熱処理する加熱処理工程とからなり、前記磁性粉末の単位表面積（ｍ 2 ）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ 2 ）が０．００５〜０．０５ｇ／ｍ 2 である絶縁被膜が該磁性粉末の表面に形成された本発明に係る磁心用粉末が得られることを特徴とする磁心用粉末の製造方法としても良い。 That is, according to the present invention, a magnetic powder mainly composed of Fe and Si has a partial pressure ratio (P H2O / P H2 ) of water vapor partial pressure (P H2O ) to hydrogen partial pressure (P H2 ) of 6.5 × 10 −6 to 3.0x10 -4 and the atmosphere holding step of holding in an oxidizing atmosphere consisting of hydrogen gas stream comprising, becomes a magnetic powder and a heat treatment step of heat treatment 600 ° C. to 900 ° C. in an oxidizing atmosphere, the magnetic unit surface area of the powder (m 2) oxygen per (g) a ratio of oxygen quantity indicating a (g / m 2) shape formed in the 0.005~0.05g / m 2 surface insulation coating of the magnetic powder is It is good also as a manufacturing method of the powder for magnetic cores characterized by the above-mentioned obtained.
（圧粉磁心）
本発明は、上記磁心用粉末に限らず、例えば、それを使用して製造した圧粉磁心としても把握できる。
(Dust core)
The present invention can be grasped not only as the above-mentioned powder for magnetic cores but also as, for example, a dust core produced by using it.
すなわち、本発明は、ＦｅおよびＳｉを主成分とする磁性粉末と、該磁性粉末の粒子表面に形成された絶縁被膜とからなる磁心用粉末を加圧成形して得られる圧粉磁心であって、 前記絶縁被膜は、前記磁性粉末を水蒸気分圧（Ｐ Ｈ２Ｏ ）の水素分圧（Ｐ Ｈ２ ）に対する分圧比（Ｐ Ｈ２Ｏ ／Ｐ Ｈ２ ）が６．５ｘ１０ −６ 〜３．０ｘ１０ −４ となる水素気流中からなる酸化雰囲気中に保持すると共に該酸化雰囲気中で６００℃〜９００℃に加熱処理する外部酸化処理して得られ、厚さが１〜１００ｎｍの二酸化ケイ素（ＳｉＯ２）被膜からなると共に該磁性粉末の単位表面積（ｍ２）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ２）が０．００５〜０．０５ｇ／ｍ２であることを特徴とする圧粉磁心としても良い。 That is, the present invention is a dust core obtained by pressure molding a magnetic core powder comprising a magnetic powder mainly composed of Fe and Si and an insulating coating formed on the particle surface of the magnetic powder. the insulating film, the hydrogen magnetic powder partial pressure ratio of hydrogen partial pressure (P H2) of the steam partial pressure (P H2O) (P H2O / P H2) is 6.5x10 -6 ~3.0x10 -4 obtained by external oxidation heat treatment to 600 ° C. to 900 ° C. in an oxidizing atmosphere while maintained in an oxidizing atmosphere consisting of air stream, together with the thickness made of silicon dioxide (SiO 2) coating 1~100nm as the dust core, wherein the unit surface area of the magnetic powder (m 2) oxygen per (g) a ratio of oxygen quantity indicating a (g / m 2) is 0.005~0.05g / m 2 Also good.
（圧粉磁心の製造方法）
本発明は、上記圧粉磁心に限らず、例えば、その製造に適した次のような製造方法としても把握できる。
(Production method of dust core)
The present invention is not limited to the above-described dust core, and can be grasped as, for example, the following manufacturing method suitable for manufacturing the same.
すなわち、本発明は、本発明に係る磁心用粉末を成形用金型内へ充填する充填工程と、該成形用金型内の磁心用粉末を加圧成形する成形工程とからなることを特徴とする圧粉磁心の製造方法としても良い。 That is, the present invention comprises a filling step of filling the magnetic core powder according to the present invention into a molding die, and a molding step of pressure-molding the magnetic core powder in the molding die. It is good also as a manufacturing method of the powder magnetic core to do.
ところで、上述の優れた絶縁被膜の形態や発生メカニズム等の詳細は定かではないが、現状、次のように考えられる。
先ず、本発明の前記絶縁被膜は、磁性粉末の表面に外部酸化によって形成され、主に二酸化ケイ素（ＳｉＯ2）被膜からなると考えられる。その被膜は、非晶質であるため、酸素や金属イオンの透過性が非常に低くて成長速度は小さいが、薄くて均一な皮膜となり得る。この絶縁被膜は、高圧成形時にも破壊されることなくその絶縁性が保持されると考えられる。
By the way, although the details of the above-described excellent insulating coating form and generation mechanism are not clear, it is considered as follows.
First, it is considered that the insulating coating of the present invention is formed by external oxidation on the surface of a magnetic powder and mainly comprises a silicon dioxide (SiO 2 ) coating. Since the film is amorphous, the permeability of oxygen and metal ions is very low and the growth rate is low, but it can be a thin and uniform film. This insulating film is considered to retain its insulating properties without being broken even during high pressure molding.
このように、外部酸化によって生じた非常に薄くて（例えば、数十ｎｍレベル）均一な皮膜は、磁性粉末の酸化処理後に、少ない酸素が表面のみに理想的に存在した状態となっていなければならない。内部酸化が生じた被膜であれば、数十μｍレベルの厚さまで酸化が進行して、磁性粉末表面の酸素量が多くなり、ＳｉＯ2が不均一に点在した状態となるからである。そこで、本発明でいう絶縁被膜を明確に特定し、外部酸化によって得られた絶縁被膜と内部酸化によって得られた絶縁被膜とを区別するために、酸化処理された磁性粉末の比表面積に対する酸素量として定義される比酸素量を導入することとした。 In this way, a very thin (eg, several tens of nm level) uniform film generated by external oxidation must be in a state where little oxygen is ideally present only on the surface after the oxidation of the magnetic powder. Don't be. This is because in the case of a film in which internal oxidation occurs, the oxidation proceeds to a thickness of several tens of μm, the amount of oxygen on the surface of the magnetic powder increases, and SiO 2 is scattered unevenly. Therefore, in order to clearly identify the insulating coating referred to in the present invention and to distinguish between the insulating coating obtained by external oxidation and the insulating coating obtained by internal oxidation, the amount of oxygen relative to the specific surface area of the oxidized magnetic powder It was decided to introduce a specific oxygen amount defined as
すなわち、比酸素量は、絶縁被膜が形成された磁性粉末の単位表面積あたりの酸素量を示すものであり、本発明では、この比酸素量を０．００５〜０．０５ｇ／ｍ2とした。比酸素量が０．００５ｇ／ｍ2未満では、ＳｉＯ2被膜が均一に生成されず、比抵抗値の低下を招くために好ましくない。０．０５ｇ／ｍ2を超えると高圧成形時に高密度化および高磁束密度化が困難となり好ましくない。比酸素量の下限が０．００７ｇ／ｍ2、０．００８ｇ／ｍ2さらには０．０１０ｇ／ｍ2であると好ましく、比酸素量の上限が０．０５ｇ／ｍ2、０．０４ｇ／ｍ2さらには０．０３ｇ／ｍ2であると好ましい。なお、これらの下限および上限は、任意に組み合わせることができる。 That is, the specific oxygen amount indicates the oxygen amount per unit surface area of the magnetic powder on which the insulating film is formed. In the present invention, the specific oxygen amount is set to 0.005 to 0.05 g / m 2 . When the specific oxygen amount is less than 0.005 g / m 2 , the SiO 2 film is not uniformly formed and the specific resistance value is lowered, which is not preferable. If it exceeds 0.05 g / m 2 , high density and high magnetic flux density are difficult during high pressure molding, which is not preferable. The ratio of oxygen lower limit of the amount of 0.007g / m 2, 0.008g / m 2 and even more preferable to be 0.010 g / m 2, the ratio of oxygen of the upper limit is 0.05g / m 2, 0.04g / m 2 Further, 0.03 g / m 2 is preferable. These lower limits and upper limits can be arbitrarily combined.
次に、本発明の絶縁被膜は、非常に薄い酸化被膜と考えられ、大気雰囲気中での単なる加熱等により容易に得られるものではない。大気雰囲気中で単に加熱しただけであれば、ＦｅおよびＳｉとＯとの複合的な化合物から形成され、良好な絶縁被膜は得られないからである。本発明者は、大気雰囲気よりも相当に酸素濃度（酸素分圧）の低い酸化雰囲気中に磁性粉末をおき（雰囲気保持工程）、そこで加熱処理することで、耐熱性に優れた絶縁被膜が得られることを新たに見いだした（加熱処理工程）。 Next, the insulating coating of the present invention is considered to be a very thin oxide coating and is not easily obtained by simple heating or the like in the air atmosphere. This is because if it is simply heated in the air atmosphere, it is formed from a composite compound of Fe and Si and O, and a good insulating film cannot be obtained. The inventor puts magnetic powder in an oxidizing atmosphere having an oxygen concentration (oxygen partial pressure) considerably lower than that in the air atmosphere (atmosphere holding step), and heat-treats there to obtain an insulating film having excellent heat resistance. Newly found (heat treatment process).
このような酸化雰囲気は、単なる真空引き等だけで安定的に得られる訳ではない。そこで本発明者は、例えば、水素気流中の蒸気圧を管理することで、そのような酸化雰囲気を形成することを考えついた。この場合、２Ｈ2Ｏ⇔２Ｈ2＋Ｏ2からなる平衡反応によって、酸化雰囲気中の酸素濃度（酸素分圧）を所望範囲内に調整できる。勿論、本発明の絶縁被膜は、この製造方法のみに限られない。例えば、ＣＯ2の気流中で、２ＣＯ2⇔２ＣＯ＋Ｏ2 等を生じさせて酸化雰囲気を形成しても良い。具体的な酸化雰囲気の制御については後述する。 Such an oxidizing atmosphere cannot be obtained stably by mere evacuation or the like. Therefore, the present inventor has come up with the idea of forming such an oxidizing atmosphere by, for example, managing the vapor pressure in a hydrogen stream. In this case, the oxygen concentration (oxygen partial pressure) in the oxidizing atmosphere can be adjusted within a desired range by an equilibrium reaction composed of 2H 2 O⇔2H 2 + O 2 . Of course, the insulating coating of the present invention is not limited to this manufacturing method. For example, an oxidizing atmosphere may be formed by generating 2CO 2 ⇔2CO + O 2 or the like in a CO 2 air stream. Specific control of the oxidizing atmosphere will be described later.
なお、便宜上、本発明では、絶縁被膜を形成する工程を雰囲気保持工程と加熱処理工程とを分けて記載したが、両工程は同時に進行するものであっても、交互に繰り返し行われるものであって良い。つまり、加熱処理工程を行う酸化雰囲気が所望の雰囲気に維持されるものであれば良い。 For convenience, in the present invention, the process for forming the insulating film is described separately for the atmosphere holding process and the heat treatment process. However, even if both processes proceed simultaneously, they are alternately repeated. Good. That is, it is sufficient if the oxidizing atmosphere for performing the heat treatment step is maintained in a desired atmosphere.
また、本発明の磁心用粉末の製造方法でいう、「外部酸化処理」とは、ＳｉＯ2被膜が薄く均一に生成されるような磁性粉末を製造するための熱処理であり、内部酸化処理に対するものである。ちなみに、内部酸化処理とは、磁性粉末の表面に厚さ数μｍの範囲で、不均一に点在したＳｉＯ2が形成される熱処理である。また、内部酸化および外部酸化の２種類ある表面酸化の形態に関して、例えばＣ．Ｗａｇｎｅｒ（Ｚ．Ｅｌｅｋｔｒｏｃｈｅｍ、６３（１９５９）、７７２）に、それらの現象および転移について詳しく論じられている。 In addition, the “external oxidation treatment” referred to in the method for producing a magnetic core powder of the present invention is a heat treatment for producing a magnetic powder in which a SiO 2 coating is thinly and uniformly formed, and is for internal oxidation treatment. It is. Incidentally, the internal oxidation treatment is a heat treatment in which SiO 2 scattered in a non-uniform manner within a thickness range of several μm is formed on the surface of the magnetic powder. Further, regarding two types of surface oxidation, internal oxidation and external oxidation, C.I. Wagner (Z. Elektrochem, 63 (1959), 772) discusses these phenomena and transitions in detail.
実施形態を挙げ、本発明をより詳しく説明する。以下に説明する内容は、本発明の磁心用粉末、圧粉磁心およびそれらの製造方法のいずれにも、適宜該当するものである。また、いずれの形態が最良であるかは、圧粉磁心の仕様等により異なるため、一概に特定することはできない。 The present invention will be described in more detail with reference to embodiments. The contents described below appropriately correspond to any of the magnetic core powder, the dust core and the manufacturing method thereof of the present invention. Also, which form is best depends on the specifications of the powder magnetic core and so on, and therefore cannot be specified in general.
（１）絶縁被膜
Ｆｅ−Ｓｉ系磁性粉末の表面に形成される本発明の絶縁被膜は、前述したように、ＳｉＯ2からなると考えられるが、現状、その組成や構造が詳細に解明されている訳ではない。この絶縁被膜は、非常に薄く、厚さが１〜５０ｎｍ程度である。さらに厚さが１０〜３０ｎｍであれば、圧粉磁心の磁気特性を向上させる上で非常に好ましい。
(1) Insulating coating Although the insulating coating of the present invention formed on the surface of the Fe-Si based magnetic powder is considered to be composed of SiO 2 as described above, its composition and structure have been elucidated in detail at present. Not a translation. This insulating film is very thin and has a thickness of about 1 to 50 nm. Furthermore, if thickness is 10-30 nm, it is very preferable when improving the magnetic characteristic of a dust core.
また、この絶縁被膜は耐熱性に優れる。Ｆｅ−Ｓｉ系磁性粉末からなる圧粉磁心を焼鈍する際に、その温度を４５０℃以上、５００℃以上、６００℃以上さらには７００℃以上としても、完全に破壊されることはない。 Moreover, this insulating film is excellent in heat resistance. When a powder magnetic core made of Fe—Si based magnetic powder is annealed, even if the temperature is set to 450 ° C. or higher, 500 ° C. or higher, 600 ° C. or higher, or 700 ° C. or higher, it is not completely destroyed.
但し、このことは、本発明の絶縁被膜を伴う磁心用粉末や圧粉磁心が、必ずしも焼鈍等の熱処理が施されなければならないことを意味しない。圧粉磁心を高周波数域で使用する場合のように、圧粉磁心の用途や要求仕様によっては、高密度化による高磁気特性と渦電流損の低減で十分な場合もある。本発明の絶縁被膜は非常に薄いため、それらの両立が容易である。さらに、磁気特性の向上よりも損失、特に渦電流損の損失を低減したい場合もある。このような場合、本発明の絶縁被膜に加えて、さらにその表面を被覆する外部絶縁被膜（第２絶縁被膜）を設けても良い。外部絶縁被膜は、本発明の絶縁被膜（適宜、この絶縁被膜を内部絶縁被膜または第１絶縁被膜という。）と同種の耐熱性を有する酸化被膜（例えば、ＳｉＯ2被膜）等であっても良いし、あまり高い耐熱性が要求されないなら、従来の樹脂被膜等であっても良い。このような外部絶縁被膜は、ケイ酸系ガラス、シリコーン樹脂、フェノール樹脂、エポキシ樹脂等の絶縁剤を本発明の磁心用粉末に添加、混合することで容易に形成される。また、外部絶縁被膜は、例えば、従来のバインダ（結合剤）と兼用されるものでも良い。 However, this does not mean that the magnetic core powder or dust core with the insulating coating of the present invention must be subjected to a heat treatment such as annealing. As in the case where the dust core is used in a high frequency range, depending on the application and required specifications of the dust core, high magnetic properties and reduction of eddy current loss due to high density may be sufficient. Since the insulating coating of the present invention is very thin, it is easy to achieve both. Furthermore, there is a case where it is desired to reduce the loss, particularly the loss of eddy current loss, rather than improving the magnetic characteristics. In such a case, in addition to the insulating coating of the present invention, an external insulating coating (second insulating coating) that covers the surface may be further provided. The external insulating film may be an oxide film (for example, SiO 2 film) having the same heat resistance as the insulating film of the present invention (as appropriate, this insulating film is referred to as an internal insulating film or a first insulating film). If a high heat resistance is not required, a conventional resin film may be used. Such an external insulating film can be easily formed by adding and mixing an insulating agent such as silicate glass, silicone resin, phenol resin, epoxy resin or the like to the magnetic core powder of the present invention. The external insulating film may be used also as, for example, a conventional binder (binder).
いずれにしても絶縁被膜は、多層化、併合等されて全体的に厚くなる程、圧粉磁心の比抵抗値が増加し、渦電流損が低減されると考えられる。外部絶縁被膜の種類にも依るが、絶縁被膜が全体的に厚くなる程、焼鈍等の熱処理を施した後でも、その比抵抗値は高い値で維持され易い。従って、絶縁被膜の多層化等により、磁気特性が少し犠牲になるとしても、渦電流損の低減のみならずヒステリシス損の低減も図られ、全体的な鉄損も低減され易い。 In any case, it is considered that the specific resistance value of the powder magnetic core increases and the eddy current loss is reduced as the insulating coating becomes thicker as a result of being multi-layered or merged. Although depending on the type of the external insulating film, the thicker the insulating film is, the more easily the specific resistance value is maintained even after heat treatment such as annealing. Therefore, even if the magnetic properties are sacrificed to some extent due to the multilayering of the insulating coating, not only the eddy current loss but also the hysteresis loss can be reduced, and the overall iron loss is easily reduced.
さらに、従来の絶縁被膜が単体で存在する場合に比べて、本発明の絶縁被膜（内部絶縁被膜）がその下地として存在する場合の方が、その絶縁被膜の安定性、耐熱性等が増し、大きな比抵抗値が確保され得る。この理由は現状定かではないが、本発明の絶縁被膜（内部絶縁被膜）が従来の絶縁被膜（外部絶縁被膜）を磁性粉末表面へ強固に結合させるためではないかと考えられる。特に、内部絶縁被膜（第１絶縁被膜）で被覆された磁性粉末とこの縁被膜をさらに被覆する外部絶縁被膜（第２絶縁被膜）を加熱により形成する絶縁剤とを混合した混合粉末を加圧成形してなる圧粉磁心に焼鈍等の加熱処理を施した場合、この傾向は顕著となる。特に、内部絶縁被膜および外部絶縁被膜が主にＳｉＯ2被膜からなる場合にその傾向は顕著である。そこで上記絶縁剤として、加熱によりＳｉＯ2被膜を形成（または焼成）し易い、シラン系カップリング剤、水ガラス、シリコーン樹脂等を用いると好ましい。ちなみに、こうして得られた外部絶縁被膜の厚さは、通常５０〜５００ｎｍ程度である。また、ＳｉＯ2被膜が焼成される焼鈍については後述する。 Furthermore, compared to the case where the conventional insulating coating exists alone, the stability, heat resistance, etc. of the insulating coating increase when the insulating coating of the present invention (internal insulating coating) is present as the base, A large specific resistance value can be secured. The reason for this is not clear at present, but it is thought that the insulating coating (internal insulating coating) of the present invention strongly bonds the conventional insulating coating (external insulating coating) to the surface of the magnetic powder. In particular, a mixed powder obtained by mixing magnetic powder coated with an inner insulating film (first insulating film) and an insulating agent that forms an outer insulating film (second insulating film) that further covers this edge film by heating is pressed. This tendency becomes prominent when heat treatment such as annealing is applied to the molded powder magnetic core. In particular, the tendency is remarkable when the inner insulating film and the outer insulating film are mainly composed of SiO 2 films. Therefore, it is preferable to use, as the insulating agent, a silane coupling agent, water glass, a silicone resin, or the like that can easily form (or fire) a SiO 2 film by heating. Incidentally, the thickness of the external insulating film thus obtained is usually about 50 to 500 nm. The annealing for firing the SiO 2 film will be described later.
なお、シラン系カップリング剤は、Ｓｉを含む界面活性剤であり、１つの分子中に反応性の異なる２種類の官能基を持っている。その一つは、有機質材料と化学結合する反応基であり、もう一つは、無機質材料と化学結合する反応基である。シラン系カップリング剤を添加することで、上記効果に加えて、磁心用粉末の各粒子間のなじみ性が増し、圧粉磁心の成形性が向上する。また、シラン系カップリング剤の少量添加により、圧粉磁心の磁気特性は僅かに低下するとしても、十分な比抵抗値が確保されるようになる。しかも、焼鈍等を行った後にも高い比抵抗値が維持されるため、渦電流損のみならずヒステリシス損も併せた鉄損が十分に低減される。この理由は定かではないが、シラン系カップリング剤を熱処理することでＳｉＯ2が焼成し、本発明のＳｉＯ2皮膜との界面での整合性が向上するためと考えられる。このようなシラン系カップリング剤の添加は、本発明の絶縁被膜処理後の磁心用粉末１００質量％に対して０．０００１〜０．５０質量％さらには０．００５〜０．１０質量％であると好適である。シラン系カップリング剤が過多となると磁気特性の低下が顕著となり、それが過少では効果が少ない。 The silane coupling agent is a surfactant containing Si, and has two types of functional groups having different reactivity in one molecule. One is a reactive group that chemically bonds to an organic material, and the other is a reactive group that chemically bonds to an inorganic material. By adding the silane coupling agent, in addition to the above effects, the conformability between the particles of the magnetic core powder is increased, and the moldability of the dust core is improved. Moreover, even if the magnetic properties of the dust core are slightly lowered by adding a small amount of the silane coupling agent, a sufficient specific resistance value can be secured. Moreover, since a high specific resistance value is maintained even after annealing or the like, iron loss including not only eddy current loss but also hysteresis loss is sufficiently reduced. Although this reason is not certain, it is considered that SiO 2 is baked by heat-treating the silane coupling agent, and the consistency at the interface with the SiO 2 film of the present invention is improved. The addition of such a silane coupling agent is 0.0001 to 0.50 mass%, further 0.005 to 0.10 mass%, with respect to 100 mass% of the magnetic core powder after the insulation coating treatment of the present invention. It is preferable. When the amount of the silane coupling agent is excessive, the magnetic property is remarkably deteriorated. When the amount is too small, the effect is small.
（２）絶縁被膜の形成
本発明の絶縁被膜は、例えば、特定の酸素濃度（酸素分圧）に保持された酸化雰囲気中で、Ｆｅ−Ｓｉ系磁性粉末を６００℃〜９００℃に加熱処理することで得られる。その酸化雰囲気中の酸素が過少でも過多でも良好な絶縁被膜は形成され難い。
(2) Formation of Insulating Film The insulating film of the present invention heats Fe—Si based magnetic powder to 600 ° C. to 900 ° C. in an oxidizing atmosphere maintained at a specific oxygen concentration (oxygen partial pressure), for example. Can be obtained. Even if the oxygen in the oxidizing atmosphere is too little or too much, a good insulating film is hardly formed.
もっとも、上記酸素濃度や酸素分圧を直接的に特定することは現実には困難である。また、そのような酸化雰囲気（還元雰囲気）は、通常、水素ガスの気流中または一酸化炭素ガスの気流中で形成されることが多い。そこで、次のような分圧比を用いて本発明の酸化雰囲気を特定するのが現実的であり、好ましい。 However, it is actually difficult to specify the oxygen concentration and oxygen partial pressure directly. Such an oxidizing atmosphere (reducing atmosphere) is usually formed in a hydrogen gas stream or a carbon monoxide gas stream in many cases. Therefore, it is practical and preferable to specify the oxidizing atmosphere of the present invention using the following partial pressure ratio.
すなわち、酸化雰囲気を水素気流中で形成する場合、例えば、水蒸気分圧（ＰH2O）の水素分圧（ＰH2）に対する分圧比（ＰH2O／ＰH2）が１０〜３００ｘ１０-6 となるようにすると良い。この分圧比（ＰH2O／ＰH2）は、さらに３０〜２００ｘ１０-6であると一層好ましい。 That is, when forming an oxide atmosphere in a hydrogen stream, for example, so that the partial pressure ratio of hydrogen partial pressure (P H2) of the steam partial pressure (P H2O) (P H2O / P H2) is 10～300X10 -6 Good. This partial pressure ratio (P H2O / P H2 ) is more preferably 30 to 200 × 10 −6 .
また、酸化雰囲気を一酸化炭素気流中で形成する場合、例えば、二酸化炭素分圧（ＰCO2）の一酸化炭素（ＰCO）に対する分圧比（ＰCO2／ＰCO）が１〜３０ｘ１０-6 となるようにすると良い。この分圧比（ＰCO2／ＰCO）は、さらに３〜２０ｘ１０-6であると一層好ましい。 In the case of forming an oxidation atmosphere with carbon monoxide gas stream, for example, partial pressure of carbon dioxide partial pressure ratio of carbon monoxide (P CO) in (P CO2) (P CO2 / P CO) is a 1～30X10 -6 It is good to be. This partial pressure ratio (P CO2 / P CO ) is more preferably 3 to 20 × 10 −6 .
また、酸化雰囲気を水素気流中で形成する場合、その酸化雰囲気は、例えば、前記水素気流中の露点（温度）を管理することでも達成できる。露点は、市販の露点温度計等により容易に観察できる。本発明の場合、水素気流中の水蒸気の露点を−６５〜−３０℃とすると良い。ちなみに、露点（温度）とは、気体中の水蒸気が飽和に達して結露する温度であり、例えば、相対湿度１００％のときの周囲温度である。 酸化雰囲気中の水分量が少ないとこの露点温度が低くなり、逆に、酸化雰囲気中の水分量が多いいとこの露点温度が高くなる。要するに、酸化雰囲気中に水分がどの程度含有されているかを示す指標であって、露点温度と酸化雰囲気自体の温度とは無関係である。但し、露点温度の測定は、熱処理を実施する炉体への雰囲気ガスの出入口において、ガス圧が１気圧の条件下で行われ、本明細書でいう露点は１気圧下（０．１ＭＰａ）における値を意味する。 Further, when the oxidizing atmosphere is formed in a hydrogen stream, the oxidizing atmosphere can also be achieved, for example, by managing the dew point (temperature) in the hydrogen stream. The dew point can be easily observed with a commercially available dew point thermometer or the like. In the case of the present invention, the dew point of water vapor in the hydrogen stream is preferably −65 to −30 ° C. Incidentally, the dew point (temperature) is a temperature at which water vapor in the gas reaches saturation and dew condensation, for example, an ambient temperature at a relative humidity of 100%. If the amount of water in the oxidizing atmosphere is small, the dew point temperature is lowered. Conversely, if the amount of water in the oxidizing atmosphere is large, the dew point temperature is increased. In short, it is an index indicating how much moisture is contained in the oxidizing atmosphere, and is independent of the dew point temperature and the temperature of the oxidizing atmosphere itself. However, the measurement of the dew point temperature is carried out under the condition that the gas pressure is 1 atm at the inlet / outlet of the atmospheric gas to the furnace body where the heat treatment is performed, and the dew point in this specification is at 1 atm (0.1 MPa). Mean value.
本発明者が上記処理をした種々の磁心用粉末からなる圧粉磁心を製作して、その圧粉磁心の比抵抗値および成形体密度を測定した。その結果、磁性粉末を処理した露点がある温度以下に低下すると、その処理後の磁性粉末から得られた圧粉磁心の比抵抗値がその露点の低下と共に増加することが解った。また、成形体密度は、その露点の低下と共に上昇し、ある露点以下から真密度に近づくことが確認された。これらのことは、後述の図２および図３からも明らかである。なお、その際、露点が−３０℃〜−４０℃のときに臨界的な挙動を示すこともわかった（磁性粉末の組成：Ｆｅ−１質量％Ｓｉ）。 The inventor manufactured dust cores made of various magnetic core powders treated as described above, and measured the specific resistance value and compact density of the dust cores. As a result, when the dew point which processed the magnetic powder fell below a certain temperature, it turned out that the specific resistance value of the powder magnetic core obtained from the magnetic powder after the process increases with the fall of the dew point. Further, it was confirmed that the compact density increased with a decrease in the dew point, and approached the true density from a certain dew point or less. These are also apparent from FIGS. 2 and 3 described later. At that time, it was also found that a critical behavior was exhibited when the dew point was −30 ° C. to −40 ° C. (composition of magnetic powder: Fe-1 mass% Si).
ちなみに、加熱処理工程は、高温環境下の酸化雰囲気中でなされているので、絶縁被膜処理の促進と磁性粉末の焼結防止のために、その加熱処理工程を回転加熱炉中で行うのが好ましい。 Incidentally, since the heat treatment step is performed in an oxidizing atmosphere under a high temperature environment, it is preferable to perform the heat treatment step in a rotary heating furnace in order to promote the insulating coating treatment and prevent the magnetic powder from sintering. .
（３）磁性粉末
本発明で対象とする磁性粉末は、前述のように、ＦｅおよびＳｉを主成分とするＦｅ−Ｓｉ系磁性粉末である。Ｆｅ−Ｓｉ系磁性粉末は、電気抵抗率が比較的高く、比較的安価であることから、軟質磁性粉末として多用されている。そのＳｉ量は、圧粉磁心に求められる比抵抗値、磁束密度、強度、高周波特性、重畳特性等とのかね合いで決定される。例えば、Ｓｉ量は、１〜１０質量％、１〜７質量％さらには２〜５質量％であると好適である。Ｓｉ量が過少では電気抵抗率が小さく渦電流損の低減を図れず、Ｓｉ量が過多となると磁気特性が低下したり成形性が低下して好ましくない。本発明の場合、高圧成形した際の磁性粉末の成形性の点から、Ｓｉ量は０．５〜４．０％さらには１．０〜３．０％であると好ましい。
(3) Magnetic powder The magnetic powder made into object by this invention is the Fe-Si type magnetic powder which has Fe and Si as a main component as mentioned above. Fe-Si-based magnetic powders are frequently used as soft magnetic powders because of their relatively high electrical resistivity and relatively low cost. The amount of Si is determined by the balance with the specific resistance value, magnetic flux density, strength, high frequency characteristics, superposition characteristics, etc. required for the dust core. For example, the amount of Si is preferably 1 to 10% by mass, 1 to 7% by mass, and further 2 to 5% by mass. If the amount of Si is too small, the electrical resistivity is small and eddy current loss cannot be reduced. If the amount of Si is too large, the magnetic properties are deteriorated or the formability is lowered, which is not preferable. In the case of the present invention, the Si content is preferably 0.5 to 4.0%, more preferably 1.0 to 3.0%, from the viewpoint of moldability of the magnetic powder during high pressure molding.
磁性粉末はＦｅ−Ｓｉは、所定量のＳｉと残部Ｆｅと不可避不純物とからなる合金粉末でも良いし、その二元系に限らず、アルミニウム（Ａｌ）、スズ（Ｓｎ）、ニッケル（Ｎｉ）、コバルト（Ｃｏ）等を適宜含んでも良い。 The magnetic powder may be Fe-Si, which may be an alloy powder composed of a predetermined amount of Si, the remaining Fe, and inevitable impurities, and is not limited to its binary system, but also aluminum (Al), tin (Sn), nickel (Ni), Cobalt (Co) or the like may be included as appropriate.
磁性粉末は、ガスアトマイズや水アトマイズ等のアトマイズ粉末でも良いし、合金インゴットをボールミル等で粉砕した粉砕粉でも良い。もっとも、球状の粒子からなるアトマイズ粉末よりも、各粒子の形状が異なる粉砕粉の方が形状効果によって高強度で高強度の圧粉磁心が得られる。 The magnetic powder may be atomized powder such as gas atomized or water atomized, or pulverized powder obtained by pulverizing an alloy ingot with a ball mill or the like. However, a pulverized powder having a different shape of each particle than the atomized powder made of spherical particles can provide a high-strength and high-strength powder magnetic core due to the shape effect.
磁性粉末の粒径は、圧粉磁心の高密度化の観点から、２０〜３００μｍ、さらには５０〜２００μｍであると好ましい。本発明者が試験したところ、渦電流損の低減を図る観点からは、その粒径が細かい程好ましく、例えば、５０μｍ以下とすると良い。一方、ヒステリシス損の低減を図る観点からは、粒径を粗くする方が好ましく、例えば、１００μｍ以上とすると良い。なお、磁性粉末の分級は、篩い分法等により容易に行えるが、上記粒径は質量累積５０％の平均粒径で考えても良い。 The particle size of the magnetic powder is preferably 20 to 300 μm, more preferably 50 to 200 μm, from the viewpoint of increasing the density of the dust core. From the viewpoint of reducing the eddy current loss, the present inventor has tested. The smaller the particle size, the better, for example, 50 μm or less. On the other hand, from the viewpoint of reducing the hysteresis loss, it is preferable to make the particle diameter coarse, for example, 100 μm or more. The magnetic powder can be easily classified by a sieving method or the like, but the particle size may be considered as an average particle size with a mass accumulation of 50%.
（４）圧粉磁心の特性
本発明の圧粉磁心は、薄くて耐熱性のある絶縁被膜で被覆された磁性粉末からなるため、高密度化による高磁気特性と、渦電流損およびヒステリシス損の両面で優れたものとなり得る。
(4) Characteristics of the dust core Since the dust core of the present invention is made of a magnetic powder coated with a thin and heat-resistant insulating film, it has high magnetic characteristics due to high density, eddy current loss and hysteresis loss. It can be excellent on both sides.
例えば、圧粉磁心の比抵抗値が５μΩｍ以上であり、磁性粉末の真密度（ρ0）に対する該圧粉磁心の嵩密度（ρ）の比である相対密度（ρ／ρ0）が９６％以上であり、０．４ｋＨｚおよび１．０Ｔの条件下での鉄損が５５０ｋＷ／ｍ3以下にもなる。また、圧粉磁心の比抵抗値が５μΩｍ以上であり、１０ｋＡ／ｍの磁場中における磁束密度Ｂ10kが１．５Ｔ以上であり、保磁力（ｂＨｃ）が２００Ａ／ｍ以下ともできる。 For example, the specific resistance value of the dust core is 5 μΩm or more, and the relative density (ρ / ρ 0 ), which is the ratio of the bulk density (ρ) of the dust core to the true density (ρ 0 ) of the magnetic powder, is 96%. Thus, the iron loss under the conditions of 0.4 kHz and 1.0 T is 550 kW / m 3 or less. Further, the specific resistance value of the dust core is 5 μΩm or more, the magnetic flux density B 10k in a magnetic field of 10 kA / m is 1.5 T or more, and the coercive force (bHc) is 200 A / m or less.
圧粉磁心の相対密度は、９７％以上さらには９８％以上となる。圧粉磁心の磁束密度Ｂ10kは１．６Ｔ以上さらには１．７Ｔ以上となる。
圧粉磁心の比抵抗値は、焼鈍をしていない場合であれば５μΩｍ以上さらには１５μΩｍ以上となる。焼鈍をした場合でも５μΩｍ以上さらには１０μΩｍ以上となる。
The relative density of the dust core is 97% or more, further 98% or more. The magnetic flux density B 10k of the dust core is 1.6T or more, and further 1.7T or more.
The specific resistance value of the dust core is 5 μΩm or more, and further 15 μΩm or more if not annealed. Even in the case of annealing, it becomes 5 μΩm or more, further 10 μΩm or more.
圧粉磁心の保磁力（ｂＨｃ）は、焼鈍をした場合２００Ａ／ｍ以下さらには１６０Ａ／ｍ以下となる。０．４ｋＨｚおよび１．０Ｔの条件下での鉄損は５５０ｋＷ／ｍ3以下さらには５００ｋＷ／ｍ3以下とでき、焼鈍をした場合はより低く４００ｋＷ／ｍ3以下さらには３００ｋＷ／ｍ3以下とできる。 The coercive force (bHc) of the dust core is 200 A / m or less, further 160 A / m or less when annealed. The iron loss under the conditions of 0.4 kHz and 1.0 T can be 550 kW / m 3 or less, further 500 kW / m 3 or less, and lower when annealing is 400 kW / m 3 or less, further 300 kW / m 3 or less. it can.
ここで、上述した圧粉磁心の各特性について説明しておく。先ず、比抵抗値は、圧粉磁心の電気的特性を指標する代表的なものである。この比抵抗値は、形状に依存しない圧粉磁心ごとの固有値であり、同形状の圧粉磁心であれば比抵抗が大きいほど、渦電流損は小さくなる。本明細書では、圧粉磁心の磁気的特性を指標する代表的なものとして所定の磁束密度（例えば、Ｂ10k）および保磁力を用いた。透磁率を用いることも可能ではあるが、一般的なＢ−Ｈ曲線からも解るようにその値は一定ではない。そこで、その代替として、特定強さの磁界中においたときにできる磁束密度により、圧粉磁心の磁気的特性を指標した。勿論、リアクトルのように、比較的安定した透磁率μや飽和磁化Ｍｓが重要なものもある。従って、本明細書で磁束密度Ｂ10k等は、磁気特性の例示にすぎないことを断っておく。また、圧粉磁心の損失は、渦電流損やヒステリシス損が個別に問題となることもあるが、通常は圧粉磁心全体としての損失、つまり鉄損が問題となる。そこで本明細書では、それらを含めた鉄損により圧粉磁心の損失を評価することとした。ちなみに、高密度成形した圧粉磁心は機械的特性にも優れ、その強度は４点曲げ強度σ等によって指標される。 Here, each characteristic of the powder magnetic core mentioned above is demonstrated. First, the specific resistance value is a representative value indicating the electrical characteristics of the dust core. This specific resistance value is an eigenvalue for each dust core that does not depend on the shape. For a dust core having the same shape, the larger the specific resistance, the smaller the eddy current loss. In the present specification, a predetermined magnetic flux density (for example, B 10k ) and a coercive force are used as representatives for indicating the magnetic characteristics of the dust core. Although it is possible to use the magnetic permeability, the value is not constant as can be seen from a general BH curve. Therefore, as an alternative, the magnetic properties of the powder magnetic core were indicated by the magnetic flux density when placed in a magnetic field of a specific strength. Of course, there are some reactors in which relatively stable permeability μ and saturation magnetization Ms are important, such as a reactor. Therefore, it should be noted that the magnetic flux density B 10k and the like are merely examples of magnetic characteristics in this specification. In addition, the loss of the powder magnetic core may cause eddy current loss and hysteresis loss individually, but usually the loss of the powder magnetic core as a whole, that is, iron loss becomes a problem. Therefore, in this specification, the loss of the dust core is evaluated by the iron loss including them. Incidentally, a high density molded powder magnetic core is also excellent in mechanical properties, and its strength is indicated by a four-point bending strength σ and the like.
（５）圧粉磁心の成形
本発明の圧粉磁心は、前述したように、例えば、磁心用粉末を成形用金型へ充填する充填工程と、この磁心用粉末を加圧成形する成形工程とを経て得られる。成形用金型へ充填する磁心用粉末は、本発明の絶縁被膜を伴う磁性粉末に、前述したシラン系カップリング剤や他の絶縁剤等を添加した混合粉末であっても良い。成形用金型へ充填した磁心用粉末（上記混合粉末を含む）の加圧成形は、冷間、温間、熱間を問わず、粉末中に内部潤滑剤等を混合した一般的な成形法により行っても良い。しかし、圧粉磁心の高密度化による磁気特性の向上を図る観点から、次に述べる金型潤滑温間加圧成形法を採用するのがより好ましい。これにより、成形圧力を大きくしても、成形用金型の内面と磁性粉末との間でかじりを生じたり抜圧が過大となったせず、金型寿命の低下も抑制できる。そして、高密度な圧粉磁心を試験レベルではなく、工業レベルで量産可能となる。
(5) Molding of the dust core As described above, the dust core of the present invention includes, for example, a filling step of filling the core powder into a molding die, and a molding step of pressing the core powder. It is obtained through The magnetic core powder to be filled in the molding die may be a mixed powder obtained by adding the above-described silane coupling agent or other insulating agent to the magnetic powder with the insulating coating of the present invention. Press molding of magnetic core powder (including the above mixed powder) filled into a molding die is a general molding method in which an internal lubricant is mixed in the powder regardless of whether it is cold, warm or hot. May be performed. However, from the viewpoint of improving the magnetic characteristics by increasing the density of the powder magnetic core, it is more preferable to employ the mold lubrication warm pressing method described below. As a result, even if the molding pressure is increased, galling is not caused between the inner surface of the molding die and the magnetic powder, or the release pressure is not excessive, and a reduction in the mold life can be suppressed. And it becomes possible to mass-produce high-density powder magnetic cores not at the test level but at the industrial level.
本出願人が開発した金型潤滑温間加圧成形法は、前記充填工程を高級脂肪酸系潤滑剤が内面に塗布された成形用金型内へ磁心用粉末を充填する工程とし、前記成形工程をその成形用金型内に充填された磁心用粉末を温間で加圧成形して磁心用粉末と成形用金型の内面との間に金属石鹸皮膜を生成させる工程とするものである。 In the mold lubrication warm pressure molding method developed by the present applicant, the filling step is a step of filling a powder for magnetic core into a molding die in which a higher fatty acid-based lubricant is applied on the inner surface, and the molding step Is a step of forming a metal soap film between the magnetic core powder and the inner surface of the molding die by warm pressing the magnetic core powder filled in the molding die.
次に、この金型潤滑温間加圧成形法についてさらに詳述する。
（ａ）上記充填工程に際して、成形用金型の内面に高級脂肪酸系潤滑剤を塗布する必要がある（塗布工程）。塗布する高級脂肪酸系潤滑剤としては、高級脂肪酸自体の他、高級脂肪酸の金属塩であると好適である。高級脂肪酸の金属塩には、リチウム塩、カルシウム塩又は亜鉛塩等がある。特に、ステアリン酸リチウム、ステアリン酸カルシウム、ステアリン酸亜鉛等が好ましい。この他、ステアリン酸バリウム、パルミチン酸リチウム、オレイン酸リチウム、パルミチン酸カルシウム、オレイン酸カルシウム等を用いることもできる。
Next, this die lubrication warm pressure molding method will be described in further detail.
(A) In the filling step, it is necessary to apply a higher fatty acid-based lubricant to the inner surface of the molding die (application step). The higher fatty acid lubricant to be applied is preferably a metal salt of a higher fatty acid in addition to the higher fatty acid itself. Examples of the higher fatty acid metal salts include lithium salts, calcium salts, and zinc salts. In particular, lithium stearate, calcium stearate, zinc stearate and the like are preferable. In addition, barium stearate, lithium palmitate, lithium oleate, calcium palmitate, calcium oleate, and the like can also be used.
この塗布工程は、加熱された成形用金型内に溶媒（水、アルコール、水溶液等）に分散させた高級脂肪酸系潤滑剤を噴霧する工程であると好ましい。高級脂肪酸系潤滑剤が水等に分散していると、成形用金型の内面へ高級脂肪酸系潤滑剤を均一に噴霧し易い。さらに、加熱された成形用金型内にそれを噴霧すると、水分等が素早く蒸発して、成形用金型の内面へ高級脂肪酸系潤滑剤が均一に付着する。そのときの成形用金型の加熱温度は、後述の成形工程の温度を考慮する必要があるが、例えば、１００℃以上に加熱しておけば足る。もっとも、高級脂肪酸系潤滑剤の均一な膜を形成するために、その加熱温度を高級脂肪酸系潤滑剤の融点未満にすることが好ましい。例えば、高級脂肪酸系潤滑剤としてステアリン酸リチウムを用いた場合、その加熱温度を２２０℃未満とすると良い。 This coating step is preferably a step of spraying a higher fatty acid-based lubricant dispersed in a solvent (water, alcohol, aqueous solution, etc.) in a heated molding die. When the higher fatty acid-based lubricant is dispersed in water or the like, the higher fatty acid-based lubricant is easily sprayed uniformly on the inner surface of the molding die. Further, when it is sprayed into the heated molding die, moisture and the like are quickly evaporated, and the higher fatty acid-based lubricant uniformly adheres to the inner surface of the molding die. The heating temperature of the molding die at that time needs to consider the temperature of the molding process described later, but it is sufficient to heat it to 100 ° C. or higher, for example. However, in order to form a uniform film of a higher fatty acid-based lubricant, it is preferable that the heating temperature be lower than the melting point of the higher fatty acid-based lubricant. For example, when lithium stearate is used as the higher fatty acid-based lubricant, the heating temperature is preferably less than 220 ° C.
なお、高級脂肪酸系潤滑剤を水等に分散させる際、その水溶液全体の質量を１００質量％としたときに、高級脂肪酸系潤滑剤を０．１〜５質量％さらには０．５〜２質量％の割合で含ませるようにすると、均一な潤滑膜が成形用金型の内面に形成されて好ましい。 When the higher fatty acid-based lubricant is dispersed in water or the like, when the total mass of the aqueous solution is 100% by mass, the higher fatty acid-based lubricant is 0.1 to 5% by mass, and further 0.5 to 2% by mass. %, It is preferable that a uniform lubricating film is formed on the inner surface of the molding die.
また、高級脂肪酸系潤滑剤を水等へ分散させる際、界面活性剤をその水に添加しておくと、高級脂肪酸系潤滑剤の均一な分散が図れる。そのような界面活性剤として、例えば、アルキルフェノール系の界面活性剤、ポリオキシエチレンノニルフェニルエーテル（ＥＯ）６、ポリオキシエチレンノニルフェニルエーテル（ＥＯ）１０、アニオン性非イオン型界面活性剤、ホウ酸エステル系エマルボンＴ−８０等を用いることができる。これらを２種以上組合わせて使用しても良い。例えば、高級脂肪酸系潤滑剤としてステアリン酸リチウムを用いた場合、ポリオキシエチレンノニルフェニルエーテル（ＥＯ）６、ポリオキシエチレンノニルフェニルエーテル（ＥＯ）１０及びホウ酸エステルエマルボンＴ−８０の３種類の界面活性剤を同時に用いると好ましい。それらの１種のみを添加する場合に較べて複合添加した場合、ステアリン酸リチウムの水等への分散性が一層活性化されるからである。 Further, when the higher fatty acid-based lubricant is dispersed in water or the like, if the surfactant is added to the water, the higher fatty acid-based lubricant can be uniformly dispersed. Examples of such surfactants include alkylphenol surfactants, polyoxyethylene nonylphenyl ether (EO) 6, polyoxyethylene nonyl phenyl ether (EO) 10, anionic nonionic surfactants, and boric acid. Ester-based Emulbon T-80 or the like can be used. Two or more of these may be used in combination. For example, when lithium stearate is used as a higher fatty acid-based lubricant, three types of polyoxyethylene nonylphenyl ether (EO) 6, polyoxyethylene nonylphenyl ether (EO) 10 and borate ester Emulbon T-80 are available. It is preferable to use a surfactant at the same time. This is because the dispersibility of lithium stearate in water or the like is further activated when added in combination as compared with the case of adding only one of them.
また、噴霧に適した粘度の高級脂肪酸系潤滑剤の水溶液を得るために、その水溶液全体を１００体積％とした場合、界面活性剤の割合を１．５〜１５体積％とすると好ましい。 In order to obtain an aqueous solution of a higher fatty acid-based lubricant having a viscosity suitable for spraying, when the total amount of the aqueous solution is 100% by volume, the ratio of the surfactant is preferably 1.5 to 15% by volume.
この他、少量の消泡剤（例えば、シリコン系の消泡剤等）を添加しても良い。水溶液の泡立ちが激しいと、それを噴霧したときに成形用金型の内面に均一な高級脂肪酸系潤滑剤の被膜が形成され難いからである。消泡剤の添加割合は、その水溶液の全体積を１００体積％としたときに、例えば０．１〜１体積％程度であればよい。 In addition, a small amount of an antifoaming agent (for example, a silicon-based antifoaming agent) may be added. This is because when the foaming of the aqueous solution is intense, it is difficult to form a uniform higher fatty acid lubricant film on the inner surface of the molding die when sprayed. The addition ratio of the antifoaming agent may be, for example, about 0.1 to 1% by volume when the total volume of the aqueous solution is 100% by volume.
水等に分散した高級脂肪酸系潤滑剤の粒子は、最大粒径が３０μｍ未満であると、好適である。最大粒径が３０μｍ以上となると、高級脂肪酸系潤滑剤の粒子が水溶液中に沈殿し易く、成形用金型の内面に高級脂肪酸系潤滑剤を均一に塗布することが困難となるからである。 The higher fatty acid-based lubricant particles dispersed in water or the like preferably have a maximum particle size of less than 30 μm. When the maximum particle size is 30 μm or more, the higher fatty acid-based lubricant particles are likely to be precipitated in the aqueous solution, and it becomes difficult to uniformly apply the higher fatty acid-based lubricant to the inner surface of the molding die.
高級脂肪酸系潤滑剤の分散した水溶液の塗布には、例えば、塗装用のスプレーガンや静電ガン等を用いて行うことができる。なお、本発明者が高級脂肪酸系潤滑剤の塗布量と粉末成形体の抜出力との関係を実験により調べた結果、膜厚が０．５〜１．５μｍ程度となるように高級脂肪酸系潤滑剤を成形用金型の内面に付着させると好ましいことが解った。 Application of the aqueous solution in which the higher fatty acid-based lubricant is dispersed can be performed using, for example, a spray gun for painting, an electrostatic gun, or the like. In addition, as a result of investigating the relationship between the coating amount of the higher fatty acid-based lubricant and the output of the powder molded body by the present inventor, the higher fatty acid-based lubrication is performed so that the film thickness is about 0.5 to 1.5 μm. It has been found that it is preferable to attach the agent to the inner surface of the molding die.
（ｂ）上記成形工程で、前述の金属石鹸皮膜がメカノケミカル反応によって生成されると考えられる。すなわち、磁心用粉末と高級脂肪酸系潤滑剤とが化学的に結合し、この高級脂肪酸系潤滑剤とは異なる金属石鹸の被膜（例えば、高級脂肪酸の鉄塩被膜）が粉末成形体の表面に形成される。この金属石鹸の被膜は、その粉末成形体の表面に強固に結合し、成形用金型の内表面に付着していた高級脂肪酸系潤滑剤よりも遙かに優れた潤滑性能を発揮する。そして、成形用金型の内面と粉末成形体の外面との接触面間での摩擦力は著しく低減される。こうして、高圧成形したにも拘らず、かじり等を生ぜず、非常に低い抜圧で粉末成形体を成形用金型から取出させ、金型寿命を伸ばすこともできた。この金属石鹸皮膜の代表例は、高級脂肪酸系潤滑剤であるステアリン酸リチウムとＦｅとが反応して生成されたステアリン酸鉄皮膜である。 (B) It is considered that the metal soap film described above is generated by a mechanochemical reaction in the molding step. That is, the magnetic core powder and the higher fatty acid lubricant are chemically bonded, and a metal soap film (for example, an iron salt film of higher fatty acid) different from the higher fatty acid lubricant is formed on the surface of the powder molded body. Is done. This metal soap film is firmly bonded to the surface of the powder molded body and exhibits a lubricating performance far superior to the higher fatty acid-based lubricant adhered to the inner surface of the molding die. And the frictional force between the contact surfaces of the inner surface of the molding die and the outer surface of the powder compact is significantly reduced. In this way, despite the high pressure molding, it was possible to extend the die life by removing the powder compact from the molding die with a very low pressure without causing galling or the like. A typical example of this metal soap film is an iron stearate film formed by the reaction of lithium stearate, which is a higher fatty acid lubricant, and Fe.
なお、金属石鹸皮膜を形成する際に必要となるＦｅ等は、磁性粉末の各粒子が絶縁被膜で被覆されていることから、基本的にはその絶縁被膜に存在すると考えられる。絶縁被膜がもともとＦｅ等の金属を含む場合もあり得るが、そうでなくても、磁性粉末と絶縁被膜との間の反応や拡散により、Ｆｅ等が絶縁被膜中に出現していることもある。 In addition, it is considered that Fe and the like necessary for forming the metal soap film basically exist in the insulating film because each particle of the magnetic powder is covered with the insulating film. The insulating coating may originally contain a metal such as Fe, but otherwise Fe or the like may appear in the insulating coating due to reaction or diffusion between the magnetic powder and the insulating coating. .
成形工程における「温間」は、例えば、磁心用粉末と高級脂肪酸系潤滑剤との反応を促進するために、概して成形温度を１００℃以上とするのが好ましい。また、高級脂肪酸系潤滑剤の変質を防止するために、概して成形温度を２００℃以下とするのが好ましい。成形温度を１２０〜１８０℃とするとより好適である。 In the “warm” in the molding step, for example, the molding temperature is preferably set to 100 ° C. or higher in order to promote the reaction between the magnetic core powder and the higher fatty acid lubricant. In order to prevent deterioration of the higher fatty acid-based lubricant, it is generally preferable that the molding temperature is 200 ° C. or lower. It is more preferable that the molding temperature is 120 to 180 ° C.
成形工程における「加圧」の程度は、圧粉磁心の仕様や製造設備等により適宜選択されるが、上記金型潤滑温間加圧成形法を用いた場合、従来の成形圧力を超越した高圧力下で成形可能である。このため、硬質なＦｅ−Ｓｉ系磁性粉末であっても、高密度な圧粉磁心を容易に得ることができる。その成形圧力は、例えば、７００ＭＰａ以上、７８５ＭＰａ以上、１０００ＭＰａ以上、１５００ＭＰａ以上、２０００ＭＰａさらには２５００ＭＰａともできる。成形圧力が高圧である程、高密度の圧粉磁心が得られる。もっとも、通常は、２０００ＭＰａ以下で十分である。そこまで高圧成形すると圧粉磁心の密度は真密度に近づき、それ以上の高密度化が実質的に望めず、また、金型寿命や生産性を考慮すればその必要性もないからである。そこで例えば、成形圧力を９８０〜２０００ＭＰａとすると好適である。 The degree of “pressurization” in the molding process is appropriately selected depending on the specifications of the powder magnetic core, manufacturing equipment, etc., but when using the above-mentioned mold lubrication warm pressure molding method, Moldable under pressure. For this reason, even if it is hard Fe-Si system magnetic powder, a high-density powder magnetic core can be obtained easily. The molding pressure can be, for example, 700 MPa or more, 785 MPa or more, 1000 MPa or more, 1500 MPa or more, 2000 MPa, or even 2500 MPa. The higher the molding pressure, the higher the density magnetic core. However, 2000 MPa or less is usually sufficient. This is because if the high-pressure molding is performed, the density of the powder magnetic core approaches the true density, and further increase in density cannot be substantially desired, and there is no need for it in consideration of the mold life and productivity. Therefore, for example, the molding pressure is preferably 980 to 2000 MPa.
なお、この成形法を用いた場合、成形圧力がある値以上になると抜出力がむしろ急に減少することを本発明者は確認している。例えば、純Ｆｅ粉をこの金型潤滑温間加圧成形法で加圧成形した場合、成形圧力が約６００ＭＰａで抜出力が最大となり、それ以上の成形圧力ではむしろ抜出力が低下することを確認している。そして、成形圧力が９００〜２０００ＭＰａの範囲でさえ、抜出力は５ＭＰａ程度の非常に低い値となる。このような抜出力の減少は、粉末成形体と成形用金型の内面との間の潤滑が、成形用金型の内面に塗布した高級脂肪酸系潤滑剤の被膜による潤滑から、それとは別の金属石鹸被膜による潤滑に移行したためと思われる。このような現象は、高級脂肪酸系潤滑剤としてステアリン酸リチウムを用いた場合に限らず、ステアリン酸カルシウムやステアリン酸亜鉛を用いた場合でも同様に生じる。 In addition, when this shaping | molding method is used, this inventor has confirmed that a drawing output will reduce rather suddenly when a shaping | molding pressure becomes more than a certain value. For example, when pure Fe powder is pressure-molded by this mold lubrication warm pressure molding method, it is confirmed that the punching power is maximized at a molding pressure of about 600 MPa, and that the punching power is rather lowered at higher molding pressures. is doing. And even if a shaping | molding pressure is the range of 900-2000 MPa, an extraction output becomes a very low value of about 5 MPa. Such reduction in the output force is different from that in which the lubrication between the powder compact and the inner surface of the molding die is caused by the lubrication with the higher fatty acid lubricant film applied to the inner surface of the molding die. This seems to be due to the shift to lubrication with a metal soap film. Such a phenomenon occurs not only when lithium stearate is used as the higher fatty acid-based lubricant, but also when calcium stearate or zinc stearate is used.
なお、金型潤滑温間加圧成形法を用いた場合、従来必要とした内部潤滑剤を磁心用粉末に添加する必要はない。これにより、圧粉磁心の高密度化、高磁束密度化を図れる。但し、本発明の場合、この内部潤滑剤の添加を排除するものではない。金型潤滑温間加圧成形法を採用した場合であっても、内部潤滑剤を添加することで、粉末粒子の塑性歪が抑制され得る。その結果、圧粉磁心の保磁力が低下してヒステリシス損の低減を図れる。内部潤滑剤は、例えば、絶縁被膜で被覆された磁心用粉末１００質量％に対して０．１〜０．６質量％さらには０．２〜０．５質量％であると好ましい。過少ではその効果がなく、過多では圧粉磁心の高密度化が図れずに磁気的特性の低下を招く。なお、内部潤滑剤として前述の高級脂肪酸系潤滑剤を使用すると、取扱いが容易となり好ましい。例えば、ステアリン酸リチウムやステアリン酸亜鉛等である。 When the mold lubrication warm pressing method is used, it is not necessary to add the conventionally required internal lubricant to the magnetic core powder. Thereby, it is possible to increase the density and the magnetic flux density of the dust core. However, in the present invention, the addition of this internal lubricant is not excluded. Even when the mold lubrication warm pressing method is adopted, the plastic strain of the powder particles can be suppressed by adding the internal lubricant. As a result, the coercive force of the dust core can be reduced and the hysteresis loss can be reduced. For example, the internal lubricant is preferably 0.1 to 0.6% by mass, more preferably 0.2 to 0.5% by mass with respect to 100% by mass of the magnetic core powder coated with an insulating coating. If the amount is too small, the effect is not obtained. If the amount is too large, the density of the dust core cannot be increased and the magnetic characteristics are deteriorated. In addition, it is preferable to use the above-described higher fatty acid-based lubricant as an internal lubricant because it is easy to handle. For example, lithium stearate or zinc stearate.
ちなみに、内部潤滑剤を添加して成形した粉末成形体を焼鈍工程等で高温加熱（例えば、７００℃以上）すると、その内部潤滑剤は分解する。 Incidentally, when the powder compact formed by adding an internal lubricant is heated at a high temperature (for example, 700 ° C. or higher) in an annealing process or the like, the internal lubricant is decomposed.
ところで、上記金型潤滑温間加圧成形法に限らず、磁心用粉末を加圧成形すると、その内部には残留応力や残留歪を生じる。これを除去するために、成形工程後の粉末成形体を加熱、徐冷する焼鈍工程を施すと好適である。これにより、圧粉磁心の保磁力が低減され、ヒステリシス損が低減される。また、交番磁界に対する追従性等の良好な圧粉磁心が得られる。なお、焼鈍工程で除去される残留歪等は、成形工程前から磁性粉末の粒子内に蓄積された歪等であっても良い。 By the way, not only the above-mentioned mold lubrication warm pressure molding method, but when the magnetic core powder is pressure-molded, residual stress and residual strain are generated inside. In order to remove this, it is preferable to perform an annealing process in which the powder compact after the molding process is heated and gradually cooled. Thereby, the coercive force of the dust core is reduced, and the hysteresis loss is reduced. In addition, a good dust core such as followability to an alternating magnetic field can be obtained. The residual strain removed in the annealing step may be strain accumulated in the magnetic powder particles before the molding step.
残留歪等は、焼鈍温度が高い程、有効に除去される。もっとも、あまり焼鈍温度が高すぎると、本発明の耐熱性を有する絶縁被膜であっても少なくとも部分的な破壊を生じる。そこで、絶縁被膜の耐熱性をも考慮して焼鈍温度を決定することが好ましい。例えば、焼鈍温度を４５０〜８００℃とすると良い。焼鈍温度を５００〜７００℃とすると、残留歪の除去と絶縁被膜の保護の両立を図れて好ましい。加熱時間は、効果と経済性とから考えて、１〜３００分、好ましくは５〜６０分である。 Residual strain and the like are effectively removed as the annealing temperature is higher. However, if the annealing temperature is too high, at least partial destruction occurs even in the insulating coating having heat resistance of the present invention. Therefore, it is preferable to determine the annealing temperature in consideration of the heat resistance of the insulating coating. For example, the annealing temperature is preferably 450 to 800 ° C. An annealing temperature of 500 to 700 ° C. is preferable because it can achieve both removal of residual strain and protection of the insulating film. The heating time is 1 to 300 minutes, preferably 5 to 60 minutes, in view of the effect and economy.
焼鈍を行うときの雰囲気は、非酸化雰囲気中が好ましい。例えば、真空雰囲気や不活性ガス雰囲気である。なお、焼鈍工程を非酸化雰囲気中で行うのは、圧粉磁心やそれを構成する磁性粉末が過度に酸化されて、磁気特性や電気特性が低下するのを抑止するためである。例えば、絶縁被膜を形成している薄いＳｉＯ2被膜が過度に酸化されてＦｅ、ＳｉおよびＯ等からなる化合物に変化したりするからである。具体的には、ＦｅＯのスケールの生成やＦｅ2ＳｉＯ4層が生成する場合がある。また、前述した第２絶縁被膜の形成に加熱が必要な場合、つまり、第２絶縁被膜を焼成する場合、第２絶縁被膜の加熱処理として上記焼鈍工程を兼用すると効率的で好ましい。 The atmosphere during annealing is preferably in a non-oxidizing atmosphere. For example, a vacuum atmosphere or an inert gas atmosphere. The reason why the annealing process is performed in a non-oxidizing atmosphere is to prevent the powder magnetic core and the magnetic powder constituting the powder from being excessively oxidized and deteriorating magnetic characteristics and electrical characteristics. This is because, for example, the thin SiO 2 film forming the insulating film is excessively oxidized to change into a compound made of Fe, Si, O, or the like. Specifically, the generation of FeO scale or the Fe 2 SiO 4 layer may occur. Further, when heating is necessary for the formation of the second insulating film, that is, when the second insulating film is fired, it is efficient and preferable that the annealing step is also used as the heat treatment for the second insulating film.
（６）圧粉磁心の用途
本発明の圧粉磁心は、例えば、モータ（特に、コアやヨーク）、アクチュエータ、トランス、誘導加熱器（ＩＨ）、スピーカ等の各種の電磁機器に利用できる。特に、本発明の絶縁被膜は薄くて耐熱性を有するため、それにより被覆された磁性粉末からなる圧粉磁心は、高磁束密度と共に焼鈍等によるヒステリシス損の低減も図れ、比較的低周波数域で使用される機器等に有効である。
(6) Use of dust core The dust core of the present invention can be used in various electromagnetic devices such as motors (particularly, cores and yokes), actuators, transformers, induction heaters (IH), and speakers. In particular, since the insulating coating of the present invention is thin and heat resistant, the dust core made of magnetic powder coated thereby can reduce hysteresis loss due to annealing or the like with a high magnetic flux density, and in a relatively low frequency range. It is effective for the equipment used.
実施例を挙げて本発明をより具体的に説明する。 The present invention will be described more specifically with reference to examples.
（磁心用粉末の製造）
原料粉末（磁性粉末）として、市販のＦｅ−１％Ｓｉ粉末、Ｆｅ−２％Ｓｉ粉末およびＦｅ−３％Ｓｉ粉末（大同特殊鋼社製水アトマイズ粉）を用意した。なお、単位は質量％である（以下、同様）。ここでは、原料粉末はその分級等を特に行わずに、入手した状態のままで使用した。その粒径は約２０〜１５０μｍであった。
(Manufacture of magnetic core powder)
As the raw material powder (magnetic powder), commercially available Fe-1% Si powder, Fe-2% Si powder and Fe-3% Si powder (water atomized powder manufactured by Daido Steel) were prepared. The unit is mass% (hereinafter the same). Here, the raw material powder was used as it was obtained without any particular classification. The particle size was about 20 to 150 μm.
これらの各粉末に、図１に示す被覆処理装置を用いて、絶縁被膜のコーティング処理を行った。先ず、上記の各磁性粉末を回転式粉末加熱用管状炉（回転加熱炉）中に入れる。この回転加熱炉内を真空排気した後、そこへ水素（Ｈ2）ガスを導入した。このガス配管の途中には、水素ガスの露点を調整できる露点調整装置を接続した。この露点調整装置の下流側にある、回転加熱炉の入口側の露点と出口側の露点とを、静電容量式の露点計（日本冶金化学工業株式会社製）で測定した。そして、回転加熱炉内の露点が一定値に安定するようにした（雰囲気保持工程）。なお、本実施例の場合、回転加熱炉内の露点は、熱処理直後（回転加熱炉直後）の上記出口側の露点（出口露点）にほぼ等しいと考えて取扱っている（以下、同様）。また、露点は、露点調整後の水素ガスを１気圧下での状態で特定したものである。 Each of these powders was coated with an insulating film using the coating processing apparatus shown in FIG. First, each magnetic powder is placed in a rotary powder heating tubular furnace (rotary heating furnace). After evacuating the inside of the rotary heating furnace, hydrogen (H 2 ) gas was introduced thereto. A dew point adjusting device capable of adjusting the dew point of hydrogen gas was connected in the middle of the gas pipe. The dew point on the inlet side and the dew point on the outlet side of the rotary heating furnace on the downstream side of the dew point adjusting device were measured with a capacitance type dew point meter (manufactured by Nippon Yakin Kagaku Kogyo Co., Ltd.). And it was made for the dew point in a rotary heating furnace to stabilize to a fixed value (atmosphere maintenance process). In the case of the present embodiment, the dew point in the rotary heating furnace is handled assuming that it is almost equal to the dew point on the outlet side (exit dew point) immediately after the heat treatment (immediately after the rotary heating furnace) (the same applies hereinafter). Further, the dew point is obtained by specifying the hydrogen gas after adjusting the dew point in a state under 1 atm.
出口露点が安定したのを確認後、回転加熱炉中の温度を１０℃／ｍｉｎで昇温させて、８５０℃で１時間保持した後に冷却した（加熱処理工程）。なお、この加熱処理工程中、回転加熱炉は約３ｒｐｍで回転させた。これにより、磁性粉末の粒子同士が焼結するのを妨げると共に磁性粉末への被覆処理能力を高めた。こうして、絶縁被膜処理を施した磁心用粉末を得た。 After confirming that the outlet dew point was stabilized, the temperature in the rotary heating furnace was increased at 10 ° C./min, held at 850 ° C. for 1 hour, and then cooled (heat treatment step). During this heat treatment step, the rotary heating furnace was rotated at about 3 rpm. As a result, the particles of the magnetic powder were prevented from sintering, and the ability to coat the magnetic powder was enhanced. In this way, the powder for magnetic cores which performed the insulating film process was obtained.
なお、本実施例では、磁性粉末の被覆処理に用いる水素気流中の露点に着目したが、水素気流中の水蒸気の水素に対する分圧比に着目しても同様である。そこで、各試験片の磁心用粉末の被覆処理を行ったときの分圧比を表１に併せて示した。ちなみに、１気圧下での分圧比と露点とは容易に換算できる。 In this embodiment, attention is paid to the dew point in the hydrogen stream used for the coating treatment of the magnetic powder, but the same applies to the partial pressure ratio of water vapor to hydrogen in the hydrogen stream. Therefore, Table 1 also shows the partial pressure ratio when the test piece was coated with the magnetic core powder. Incidentally, the partial pressure ratio and dew point under 1 atm can be easily converted.
（圧粉磁心の製造）
上記磁心用粉末に金型潤滑温間加圧成形を行って、リング状（外径：φ３９ｍｍ×内径φ３０ｍｍ×厚さ５ｍｍ）と板状（５ｍｍ×１０ｍｍ×５５ｍｍ）との２種の試験片を各試料ごとに製作した。リング状試験片は磁気特性評価用であり、板状試験片は電気抵抗評価用である。
(Manufacture of dust core)
The above powder for magnetic core is subjected to mold-lubricating warm pressure molding, and two types of test pieces of a ring shape (outer diameter: φ39 mm × inner diameter φ30 mm ×
具体的には次のようにして金型潤滑温間加圧成形を行った。
（ａ）上記の各試験片形状に応じたキャビティを有する超硬製の成形用金型を用意した。この成形用金型をバンドヒータで予め１５０℃に加熱しておいた。また、この成形用金型の内周面には、予めＴｉＮコート処理を施し、その表面粗さを０．４Ｚとしておいた。加熱した成形用金型の内周面に、水溶液に分散させたステアリン酸リチウム（高級脂肪酸系潤滑剤）をスプレーガンにて、１ｃｍ3／秒程度の割合で均一に塗布した（塗布工程）。ここで用いた水溶液は、水に界面活性剤と消泡剤とを添加したものである。界面活性剤には、ポリオキシエチレンノニルフェニルエーテル（ＥＯ）６、（ＥＯ）１０及びホウ酸エステルエマルボンＴ−８０を用い、それぞれを水溶液全体（１００体積％）に対して１体積％づつ添加した。また、消泡剤には、ＦＳアンチフォーム８０を用い、水溶液全体（１００体積％）に対して０．２体積％添加した。ここで用いたステアリン酸リチウムは、融点が約２２５℃で平均粒径が２０μｍである。その分散量は、上記水溶液１００ｃｍ3に対して２５ｇとした。これをさらにボールミル式粉砕装置で微細化処理（テフロン（登録商標）コート鋼球：１００時間）し、得られた原液を２０倍に希釈して最終濃度１％の水溶液として上記塗布工程に供した。
Specifically, the mold lubrication warm pressure molding was performed as follows.
(A) A cemented carbide molding die having a cavity corresponding to each test piece shape described above was prepared. This molding die was preheated to 150 ° C. with a band heater. Further, the inner peripheral surface of this molding die was previously subjected to TiN coating treatment, and the surface roughness was set to 0.4Z. Lithium stearate (higher fatty acid-based lubricant) dispersed in an aqueous solution was uniformly applied at a rate of about 1 cm 3 / sec on the inner peripheral surface of the heated molding die (application step). The aqueous solution used here is obtained by adding a surfactant and an antifoaming agent to water. As the surfactant, polyoxyethylene nonylphenyl ether (EO) 6, (EO) 10 and boric acid ester Emulbon T-80 were used, and each was added by 1% by volume with respect to the entire aqueous solution (100% by volume). did. As the antifoaming agent, FS Antifoam 80 was used and 0.2% by volume was added to the entire aqueous solution (100% by volume). The lithium stearate used here has a melting point of about 225 ° C. and an average particle size of 20 μm. The dispersion amount was 25 g with respect to 100 cm 3 of the aqueous solution. This was further refined with a ball mill type pulverizer (Teflon (registered trademark) coated steel balls: 100 hours), and the resulting stock solution was diluted 20 times to give an aqueous solution having a final concentration of 1% for the coating step. .
（ｂ）ステアリン酸リチウムが内面に塗布されたその成形用金型へ、それと同温の１５０℃に加熱しておいた上記の各磁心用粉末を自然充填した（充填工程）。なお、一部の圧粉磁心は、上記絶縁被膜（第１絶縁被膜）を被覆した磁性粉末に、シラン系カップリング剤（信越化学工業株式会社製、ＫＢＭ−４０３）またはシリコーン樹脂（東レ・ダウコーニング・シリコーン株式会社製、ＳＲ−２４００）を適量添加した混合粉末を加圧成形して得た。また、一部の圧粉磁心は、上記絶縁被膜処理をせずに、磁性粉末に上記シリコーン樹脂を適量添加した混合粉末を加圧成形して得た。なお、これらの混合粉末はＶ型ミキサーや回転ボールミルにより混合した。 (B) Each of the above magnetic core powders, which had been heated to 150 ° C. at the same temperature, was naturally filled into the molding die coated with lithium stearate on the inner surface (filling step). Some of the powder magnetic cores are made of a magnetic powder coated with the insulating coating (first insulating coating) with a silane coupling agent (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) or a silicone resin (Toray Dow). A mixed powder to which an appropriate amount of SR-2400) manufactured by Corning Silicone Co., Ltd. was added was obtained by pressure molding. Moreover, some powder magnetic cores were obtained by pressure-molding a mixed powder obtained by adding an appropriate amount of the silicone resin to the magnetic powder without performing the insulating coating treatment. These mixed powders were mixed by a V-type mixer or a rotating ball mill.
（ｃ）成形用金型を１５０℃に保持したまま、１９６０ＭＰａの成形圧力で充填された各磁心用粉末を温間加圧成形して粉末成形体を得た（成形工程）。なお、この温間加圧成形で、成形用金型の内壁面とかじり等を生じるものはなく、粉末成形体の抜出力も５ＭＰａ程度と低いものであった。 (C) While maintaining the molding die at 150 ° C., each magnetic core powder filled at a molding pressure of 1960 MPa was warm-pressed to obtain a powder compact (molding step). In this warm press molding, there was no galling or the like with the inner wall surface of the molding die, and the output power of the powder compact was as low as about 5 MPa.
（ｄ）得られた粉末成形体の一部には、非酸素雰囲気（Ｎ2ガス雰囲気）中で、焼鈍温度５００〜７５０℃、焼鈍時間３０分の焼鈍を施した。 (D) Part of the obtained powder compact was annealed in an oxygen-free atmosphere (N 2 gas atmosphere) at an annealing temperature of 500 to 750 ° C. and an annealing time of 30 minutes.
こうして得られた圧粉磁心からなる各試験片の製造条件を表１に示した。 Table 1 shows the manufacturing conditions of the test pieces made of the powder magnetic core thus obtained.
（圧粉磁心の測定）
前述したリング状試験片と板状試験片とをそれぞれ用いて、それらの磁気的特性と電気的特性とを評価した。測定結果を表１に併せて示す。なお、比抵抗の測定は、マイクロオームメータ（メーカ：ヒューレットパカード（ＨＰ）社、型番：３４４２０Ａ）を用いて４端子法により測定した。
(Measurement of dust core)
Using the above-described ring-shaped test piece and plate-shaped test piece, their magnetic characteristics and electrical characteristics were evaluated. The measurement results are also shown in Table 1. The specific resistance was measured by a four-terminal method using a micro-ohm meter (manufacturer: Hewlett-Packard (HP), model number: 34420A).
磁気的特性の内、静磁場特性は直流自記磁束計（メーカ：東英工業、型番：ＭＯＤＥＬ−ＴＲＦ）により測定した。交流磁場特性は交流Ｂ−Ｈカーブトレーサ（メーカ：理研電子、型番：ＡＣＢＨ−１００Ｋ）により測定した。表中の交流磁場特性は、圧粉磁心を０．４ｋＨｚ、１．０Ｔの磁場中に置いたときの高周波損失（鉄損）を測定したものである。 Among the magnetic characteristics, the static magnetic field characteristics were measured with a direct current magnetic flux meter (manufacturer: Toei Kogyo, model number: MODEL-TRF). The AC magnetic field characteristics were measured with an AC BH curve tracer (manufacturer: RIKEN ELECTRONICS, model number: ACBH-100K). The AC magnetic field characteristics in the table are obtained by measuring high-frequency loss (iron loss) when the dust core is placed in a magnetic field of 0.4 kHz and 1.0 T.
静磁場中の磁束密度は、２ｋＡ／ｍ、５ｋＡ／ｍおよび１０ｋＡ／ｍ中にできる磁束密度を示したものであり、各表中ではそれぞれＢ2k、Ｂ5kおよびＢ10kとして示した。圧粉磁心の密度（ρ）は、アルキメデス法により測定した。なお、Ｆｅ−１％Ｓｉ、Ｆｅ−２％ＳｉおよびＦｅ−３％Ｓｉの真密度（ρ0）はそれぞれ、７．８１ｘ１０3ｋｇ／ｍ3、７．７４ｘ１０3ｋｇ／ｍ3、７．６７ｘ１０3ｋｇ／ｍ3である。これらに基づいて、相対密度（ρ／ρ0）を算出し、表１に併せて示した。 The magnetic flux density in the static magnetic field indicates the magnetic flux density generated at 2 kA / m, 5 kA / m, and 10 kA / m, and is shown as B 2k , B 5k, and B 10k in each table. The density (ρ) of the dust core was measured by the Archimedes method. The true densities (ρ 0 ) of Fe-1% Si, Fe-2% Si, and Fe-3% Si are 7.81 × 10 3 kg / m 3 , 7.74 × 10 3 kg / m 3 , and 7.67 × 10 respectively. 3 kg / m 3 . Based on these, the relative density (ρ / ρ 0 ) was calculated and shown together in Table 1.
（評価）
（ａ）表１に示した各試験片中、Ｆｅ−１％Ｓｉの組成をもつ磁性粉末に８５０℃の熱処理を施して被膜処理した試験片Ｎｏ．１〜５について、水素気流中の露点と圧粉磁心の比抵抗値との関係を図２のグラフに示した。また、水素気流中の露点と圧粉磁心の成形体密度との関係を図３のグラフに示した。これらの圧粉磁心はいずれも加圧成形後に焼鈍を行っていないものである。
(Evaluation)
(A) In each test piece shown in Table 1, a test piece No. 1 was formed by applying a heat treatment at 850 ° C. to a magnetic powder having a composition of Fe-1% Si. For 1 to 5, the relationship between the dew point in the hydrogen stream and the specific resistance value of the dust core is shown in the graph of FIG. The relationship between the dew point in the hydrogen stream and the compact density of the dust core is shown in the graph of FIG. None of these powder magnetic cores are annealed after pressure molding.
図２のグラフから明らかなように、上記被覆処理の露点が−３０℃あたりを境としてそれよりも低下すると、圧粉磁心の比抵抗値が増加している。また、図３のグラフから明らかなように、上記の被覆処理時の露点が−３０℃あたりを境として、それよりも低下したときの圧粉磁心の密度は、真密度に近づき、高密度で安定していた。 As is clear from the graph of FIG. 2, when the dew point of the coating process decreases below about −30 ° C., the specific resistance value of the dust core increases. Further, as is apparent from the graph of FIG. 3, the density of the dust core when the dew point at the time of the above coating process falls below about -30 ° C. approaches the true density, It was stable.
従って、少なくともＦｅ−１％Ｓｉの磁性粉末を使用した場合であれば、上記被覆処理の露点を−３０℃以下に低下させることで圧粉磁心の比抵抗値を増加させつつその高密度化（つまりは磁束密度の増加）を図れる。 Accordingly, if magnetic powder of at least Fe-1% Si is used, the dew point of the coating treatment is lowered to -30 ° C. or lower to increase the specific resistance value of the dust core while increasing the specific resistance value ( In other words, an increase in magnetic flux density can be achieved.
（ｂ）表１に示した試験片Ｎｏ．１および試験片Ｎｏ．５で用いた上記被覆処理後の磁性粉末（磁心用粉末）の各粒子を光学顕微鏡で観察した。そらの写真をそれぞれ図４（ａ）、（ｂ）にそれぞれ示した。これらの写真から、被覆処理した際の水素気流中の露点が−３０℃以下で磁性粉末の表面が適切に外部酸化処理された場合、薄く均一な絶縁皮膜が形成されていることがわかる。一方、その露点が−３０℃より高い場合、磁性粉末の表面から内部深くまで酸化されて（つまり、内部酸化されて）、酸化物が点在した状態となり、薄い均一な絶縁被膜は形成されていない。このため後者の場合、圧粉磁心の比抵抗値、密度および磁気特性の低下を招いたと考えられる。ここでは、磁性粉末の組成がＦｅ−１％Ｓｉの場合について説明したが、Ｆｅ−２％ＳｉおよびＦｅ−３％Ｓｉの場合でも同様の傾向を示すことを本発明者は確認している。 (B) Specimen No. shown in Table 1 1 and test piece No. 1 Each particle of the magnetic powder (magnetic core powder) after the coating treatment used in 5 was observed with an optical microscope. The photographs are shown in FIGS. 4 (a) and 4 (b), respectively. From these photographs, it can be seen that a thin and uniform insulating film is formed when the dew point in the hydrogen stream during the coating treatment is −30 ° C. or less and the surface of the magnetic powder is appropriately externally oxidized. On the other hand, when the dew point is higher than −30 ° C., it is oxidized deeply from the surface of the magnetic powder (that is, it is internally oxidized), and the oxide is scattered, and a thin uniform insulating film is formed. Absent. For this reason, in the latter case, it is considered that the specific resistance value, density, and magnetic properties of the dust core were reduced. Here, although the case where the composition of the magnetic powder is Fe-1% Si has been described, the present inventors have confirmed that the same tendency is exhibited even in the case of Fe-2% Si and Fe-3% Si.
（ｃ）表１に示した試験片Ｎｏ．１〜３と、それらに５００℃ｘ３０分の焼鈍を施した試験片Ｎｏ．８〜１０を対比するとわかるように、焼鈍を施しても圧粉磁心の比抵抗値はさほど低下せず、保磁力ｂＨｃは大きく低下している。その結果、焼鈍を施した圧粉磁心の鉄損は、試験片Ｎｏ．１０を除き大きく低下した。しかも、磁性粉末中のＳｉ量の多い試験片Ｎｏ．１１およびＮｏ．１２の圧粉磁心の場合、その傾向はより顕著となった。 (C) Test piece No. shown in Table 1 1 to 3 and test pieces No. 1 and No. 3 which were annealed at 500 ° C. for 30 minutes As can be seen by comparing 8 to 10, even if annealing is performed, the specific resistance value of the dust core does not decrease so much, and the coercive force bHc greatly decreases. As a result, the iron loss of the powder magnetic core subjected to the annealing was determined as follows. It was greatly reduced except for 10. Moreover, the test piece No. with a large amount of Si in the magnetic powder was used. 11 and no. In the case of 12 dust cores, the tendency was more pronounced.
（ｄ）表１に示した試験片Ｎｏ．１２と試験片Ｎｏ．１３〜１５とを対比するとわかるように、シラン系カップリング剤やシリコーン樹脂の絶縁剤を添加した圧粉磁心（試験片Ｎｏ．１３〜１５）の場合、相対密度や磁気特性をさほど犠牲にすることなく、比抵抗値が大幅に増加して鉄損が低減した。 (D) Specimen No. shown in Table 1 12 and test piece no. As can be seen from comparison with 13 to 15, in the case of a dust core (test pieces No. 13 to 15) to which a silane coupling agent or a silicone resin insulating agent is added, the relative density and magnetic properties are sacrificed to a great extent. The specific resistance value was greatly increased and the iron loss was reduced.
一方、表１に示した試験片Ｎｏ．１５と試験片Ｎｏ．１６とを対比するとわかるように、下地処理として本発明の絶縁被膜処理を施した圧粉磁心（試験片Ｎｏ．１５）の場合、焼鈍後の比抵抗値が明らかに大きく、かつ、保磁力ｂＨｃが小さくて、鉄損が大幅に低下した。しかも、試験片Ｎｏ．１５の圧粉磁心の方が試験片Ｎｏ．１６よりも磁気特性に優れた。 On the other hand, the test piece No. shown in Table 1 was used. 15 and test piece no. As shown in FIG. 16, in the case of the dust core (test piece No. 15) subjected to the insulating coating treatment of the present invention as the base treatment, the specific resistance value after annealing is obviously large and the coercive force bHc. The iron loss was greatly reduced. Moreover, the test piece No. No. 15 powder magnetic core is the specimen No. Excellent magnetic properties than 16.
このように、本発明の絶縁被膜（第１絶縁被膜）を備えた磁性粉末からなる圧粉磁心は、その絶縁被膜が薄いため高密度化が容易で磁気特性の向上を図り易い。さらにその圧粉磁心に焼鈍を施した場合、高比抵抗値と低保磁力との両立が可能となり、鉄損が大幅に低減する。これは、本発明の絶縁被膜が優れた耐熱性を備え、高温焼鈍を施した場合でもほとんど破壊されないためと考えられる。また、その絶縁被膜を施した磁性粉末に、シラン系カップリング剤等の絶縁剤をさらに添加して、加圧成形および焼鈍してなる圧粉磁心は、その磁性粉末に絶縁被膜処理を施さなかった圧粉磁心に比べて、高比抵抗値で低鉄損であった。これは、前者の圧粉磁心の場合、シラン系カップリング剤等によって焼成される第２絶縁被膜の下地として第１絶縁被膜が有効に機能して、第２絶縁被膜の耐熱性がより向上したと考えられる。 As described above, the dust core made of the magnetic powder having the insulating coating (first insulating coating) of the present invention is easy to increase the density and easily improve the magnetic characteristics because the insulating coating is thin. Furthermore, when the powder magnetic core is annealed, it is possible to achieve both a high specific resistance value and a low coercive force, and the iron loss is greatly reduced. This is presumably because the insulating coating of the present invention has excellent heat resistance and is hardly destroyed even when subjected to high temperature annealing. In addition, a powder magnetic core obtained by further adding an insulating agent such as a silane coupling agent to the magnetic powder coated with the insulating film, and press-molding and annealing the magnetic powder is not subjected to the insulating film treatment. Compared with the dust core, the specific resistance was high and the iron loss was low. This is because, in the case of the former powder magnetic core, the first insulating film effectively functions as a base of the second insulating film fired by a silane coupling agent or the like, and the heat resistance of the second insulating film is further improved. it is conceivable that.
Claims (15)
前記絶縁被膜は、前記磁性粉末を水蒸気分圧（Ｐ Ｈ２Ｏ ）の水素分圧（Ｐ Ｈ２ ）に対する分圧比（Ｐ Ｈ２Ｏ ／Ｐ Ｈ２ ）が６．５ｘ１０ −６ 〜３．０ｘ１０ −４ となる水素気流中からなる酸化雰囲気中に保持すると共に該酸化雰囲気中で６００℃〜９００℃に加熱処理する外部酸化処理して得られ、厚さが１〜１００ｎｍの二酸化ケイ素（ＳｉＯ２）被膜からなると共に該磁性粉末の単位表面積（ｍ２）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ２）が０．００５〜０．０５ｇ／ｍ２であることを特徴とする磁心用粉末。 In a magnetic core powder comprising a magnetic powder mainly composed of iron (Fe) and silicon (Si) and an insulating coating formed on the particle surface of the magnetic powder,
The insulating coating, the magnetic powder partial pressure of water vapor partial pressure ratio of hydrogen partial pressure (P H2) of (P H2O) (P H2O / P H2) is 6.5x10 -6 ~3.0x10 -4 become hydrogen stream the together obtained by external oxidation heat treatment to 600 ° C. to 900 ° C. in an oxidizing atmosphere, thick silicon dioxide (SiO 2) coating 1~100nm holds in an oxidizing atmosphere consisting of a powder for a magnetic core unit surface area of the magnetic powder (m 2) oxygen per (g) a ratio of oxygen quantity indicating a (g / m 2) is characterized in that it is a 0.005~0.05g / m 2.
該磁性粉末を該酸化雰囲気中で６００℃〜９００℃に加熱処理する加熱処理工程とからなり、
前記磁性粉末の単位表面積（ｍ ２ ）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ ２ ）が０．００５〜０．０５ｇ／ｍ ２ である絶縁被膜が該磁性粉末の表面に形成された請求項１に記載の磁心用粉末が得られることを特徴とする磁心用粉末の製造方法。 A magnetic powder mainly composed of Fe and Si has a partial pressure ratio (PH 2 O / PH 2 ) of water vapor partial pressure (P H2O ) to hydrogen partial pressure (P H2 ) of 6.5 × 10 −6 to 3.0 × 10 −4 . An atmosphere holding step for holding in an oxidizing atmosphere consisting of a hydrogen stream,
A heat treatment step of heat-treating the magnetic powder at 600 ° C. to 900 ° C. in the oxidizing atmosphere,
The magnetic unit surface area of the powder (m 2) oxygen per (g) a ratio of oxygen quantity indicating a (g / m 2) is 0.005~0.05g / m 2 at which the insulating film surface of the magnetic powder method for producing a powder for a magnetic core, characterized in that the magnetic core powder according to claim 1 which is made form is obtained.
前記絶縁被膜は、前記磁性粉末を水蒸気分圧（Ｐ Ｈ２Ｏ ）の水素分圧（Ｐ Ｈ２ ）に対する分圧比（Ｐ Ｈ２Ｏ ／Ｐ Ｈ２ ）が６．５ｘ１０ −６ 〜３．０ｘ１０ −４ となる水素気流中からなる酸化雰囲気中に保持すると共に該酸化雰囲気中で６００℃〜９００℃に加熱処理する外部酸化処理して得られ、厚さが１〜１００ｎｍの二酸化ケイ素（ＳｉＯ２）被膜からなると共に該磁性粉末の単位表面積（ｍ２）あたりの酸素量（ｇ）を示す比酸素量（ｇ／ｍ２）が０．００５〜０．０５ｇ／ｍ２であることを特徴とする圧粉磁心。 A powder magnetic core obtained by pressure molding a magnetic core powder comprising a magnetic powder mainly composed of Fe and Si and an insulating coating formed on the particle surface of the magnetic powder,
The insulating coating, the magnetic powder partial pressure of water vapor partial pressure ratio of hydrogen partial pressure (P H2) of (P H2O) (P H2O / P H2) is 6.5x10 -6 ~3.0x10 -4 become hydrogen stream the together obtained by external oxidation heat treatment to 600 ° C. to 900 ° C. in an oxidizing atmosphere, thick silicon dioxide (SiO 2) coating 1~100nm holds in an oxidizing atmosphere consisting of dust core unit surface area of the magnetic powder (m 2) oxygen per (g) a ratio of oxygen quantity indicating a (g / m 2) is characterized in that it is a 0.005~0.05g / m 2.
前記磁性粉末の真密度（ρ０）に対する該圧粉磁心の嵩密度（ρ）の比である相対密度（ρ／ρ０）が９６％以上であり、
０．４ｋＨｚおよび１．０Ｔの条件下での鉄損が５５０ｋＷ／ｍ３以下である請求項５に記載の圧粉磁心。 The specific resistance value of the dust core is 5 μΩm or more,
The relative density (ρ / ρ 0 ), which is the ratio of the bulk density (ρ) of the dust core to the true density (ρ 0 ) of the magnetic powder, is 96% or more,
The powder magnetic core according to claim 5, wherein the iron loss under conditions of 0.4 kHz and 1.0 T is 550 kW / m 3 or less.
１０ｋＡ／ｍの磁場中における磁束密度Ｂ１０ｋが１．５Ｔ以上であり、
保磁力（ｂＨｃ）が２００Ａ／ｍ以下である請求項５に記載の圧粉磁心。 The specific resistance value of the dust core is 5 μΩm or more,
The magnetic flux density B 10k in a magnetic field of 10 kA / m is 1.5 T or more,
The dust core according to claim 5, wherein the coercive force (bHc) is 200 A / m or less.
該成形用金型内の磁心用粉末を加圧成形する成形工程と、
からなることを特徴とする圧粉磁心の製造方法。 A filling step of filling the magnetic core powder according to claim 1 into a molding die;
A molding step of pressure-molding the magnetic core powder in the molding die;
A method for producing a powder magnetic core comprising:
前記成形工程は、該磁心用粉末と該成形用金型の内面との間に金属石鹸皮膜を生成させる工程である請求項９に記載の圧粉磁心の製造方法。 The filling step is a step of filling the magnetic core powder into the molding die coated with a higher fatty acid-based lubricant on the inner surface,
The method of manufacturing a dust core according to claim 9, wherein the molding step is a step of forming a metal soap film between the magnetic core powder and the inner surface of the molding die.
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| WO2020012667A1 (en) * | 2018-07-13 | 2020-01-16 | 日本製鉄株式会社 | Base sheet for grain-oriented electrical steel sheets, grain-oriented silicon steel sheet that serves as material for base sheet for grain-oriented electrical steel sheets, method for producing base sheet for grain-oriented electrical steel sheets, and method for producing grain-oriented electrical steel sheets |
| JP7288341B2 (en) * | 2019-05-09 | 2023-06-07 | 山陽特殊製鋼株式会社 | soft magnetic powder |
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| DE4030054C2 (en) * | 1990-09-20 | 1995-11-02 | Mannesmann Ag | Process and plant for the reduction annealing of iron powder |
| JP2698003B2 (en) * | 1992-08-25 | 1998-01-19 | 新日本製鐵株式会社 | Method for forming insulating film on unidirectional silicon steel sheet |
| JP2001085211A (en) * | 1999-09-16 | 2001-03-30 | Aisin Seiki Co Ltd | Soft magnetic particle, soft magnetic molded body, and their manufacture |
| JP3815563B2 (en) * | 2001-01-19 | 2006-08-30 | 株式会社豊田中央研究所 | Powder magnetic core and manufacturing method thereof |
| JP4849500B2 (en) * | 2002-04-02 | 2012-01-11 | 株式会社豊田中央研究所 | Powder magnetic core and manufacturing method thereof |
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