【０００１】
【発明の属する技術分野】
この発明は、トランスコア、チョークコイルあるいは磁気ヘッド等に用いられる圧粉磁心の改良に関し、従来のＮｉ−Ｍｏ−Ｆｅ系磁性合金と同等以上の飽和磁束密度、直流重畳特性を有するＦｅ−Ａｌ−Ｓｉ系圧粉磁心に関する。
【０００２】
【従来の技術】
電源回路などに多用されるトランスコアや各種チョークコイルには、所謂けい素鋼板を用いた積層型磁心が使用されていたが、磁性合金粉末を絶縁性バインダーとともに混練成形して所要形状にして焼き固めることから、複雑形状を容易に実現でき、種々組成の磁性合金粉末を用いることで、目的の磁気特性を得易いことから、今日では圧粉磁心が多用されている。
【０００３】
圧粉磁心は、所定の粒度範囲にある軟磁性合金粉末を用い、絶縁性バインダー樹脂などと混練することで、粉末粒子表面を樹脂で被覆し、この粉末を金型に充填して圧縮成形することで所定形状の成形体にし、この成形体に加熱処理を行い圧縮成形時の成形歪みを解放するとともに前記バインダ成分を硬化して製造する。
【０００４】
また、圧粉磁心は従来のフェライト磁心に比較してコアロスが大きいが、飽和磁束密度、直流重畳特性は高い特徴がある。さらに、圧粉磁芯の透磁率や直流重畳特性は、その嵩密度との間に相関関係があり、通常、圧粉磁芯を高密度化すると、前記特性は向上することが知られている。
【０００５】
【発明が解決しようとする課題】
従来のＮｉ−Ｍｏ−Ｆｅ軟磁性合金は、該合金自体の飽和磁束密度は低いが、粉末の圧粉時の相対密度が高いことで、結果として飽和磁束密度並びに直流重畳特性がよい圧粉磁心を製造することができる。しかし、該Ｎｉ−Ｍｏ−Ｆｅ系合金は、Ｎｉを多量に含有して原料コストを要することが問題である。
【０００６】
一方、材料組成的に安価でかつ前記の飽和磁束密度並びに直流重畳特性にすぐれた材料として、Ｆｅ−Ｓｉ合金が知られているが、コア損失が極めて大きく、例えばトランスコアとした際の発熱等の問題があり、トランスコア、チョークコイル等の用途に用いる圧粉磁心用の磁性合金としては実用的とは言い難い。
【０００７】
この発明は、材料組成的に安価に得られる磁性合金粉末を用い、トランスコア、チョークコイルあるいは磁気ヘッド等の用途で、Ｎｉ−Ｍｏ−Ｆｅ系磁性合金と同等以上の飽和磁束密度、直流重畳特性が得られる圧粉磁芯とその合金粉末並びに製造方法の提供を目的としている。
【０００８】
【課題を解決するための手段】
発明者らは、組成的に安価に得られる従来のＦｅ−Ａｌ−Ｓｉ系磁性合金について、特に直流重畳特性との関係を種々検討した結果、Ｆｅ−６Ｓｉ‐４Ａｌなる組成の合金粉末に予め熱処理を施して結晶性を向上させて、圧粉磁芯を作製すると、得られる飽和磁束密度、直流重畳特性が従来の５０Ｎｉ−Ｆｅ系や８１Ｎｉ−２Ｍｏ−Ｆｅ系合金などのＮｉ基合金を上回ることを知見し、この発明を完成した。
【０００９】
すなわち、この発明は、Ａｌ ３．０ｗｔ％〜５．０ｗｔ％、Ｓｉ ４．０ｗｔ％〜７．０ｗｔ％、残部Ｆｅを主成分とする合金粉末と絶縁材との混練物より圧縮成形された成形体を熱処理して得たことを特徴とする圧粉磁芯である。
【００１０】
【発明の実施の形態】
この発明による圧粉磁芯用の軟磁性合金粉末は、Ａｌ ３．０ｗｔ％〜５．０ｗｔ％、Ｓｉ ４．０ｗｔ％〜７．０ｗｔ％、残部Ｆｅを主成分とする。Ａｌ ３．０ｗｔ％未満、Ｓｉ ４．０ｗｔ％未満ではコアロスが大きくなりまた目的の飽和磁束密度並びに直流重畳特性が得難くなり、Ａｌ ５．０ｗｔ％を超え、Ｓｉ ７．０ｗｔ％を超えると合金粉末の圧縮時の密度が低下により透磁率が低下し好ましくない。残部のＦｅ以外はできるだけ不純物の含有がないことが望ましいが、製造上不可避的な微量の成分の含有は認められる。
【００１１】
この発明のＡｌ ３．０ｗｔ％〜５．０ｗｔ％、Ｓｉ ４．０ｗｔ％〜７．０ｗｔ％、残部Ｆｅを主成分とする合金は、通常の溶融、鋳込み、合金の機械的粉砕にて得る方法、またガスアトマイズ法、水アトマイズ法などで製造することができる。また、通常得られた際の結晶構造は磁性合金として理想的な構造ではないが、そのまま合金粉末として圧粉磁芯を製造しても、成形体の焼鈍工程を経ることで改善される可能性がある。しかし、圧粉磁芯の特性の向上を目的に、予め合金粉末に熱処理を施して結晶化を促進して軟磁性合金粉末となすことが望ましい。
【００１２】
この発明の合金粉末に施す熱処理としては、雰囲気は非酸化性で、処理温度７００℃〜１２００℃の範囲に、３０分以上保持することが望ましい。しかし、保持時間が３時間を超えても得られる効果が飽和し、生産性が悪化するため好ましくなく、好ましい保持時間は１時間〜３時間である。
【００１３】
圧粉磁芯の製造方法の一例を説明すると、磁性合金粉末と絶縁材バインダーを混練し、乾燥、整粒後、必要に応じて潤滑剤を添加し、得られた粉末を金型に充填して所望形状に成形、得られた成形体は歪み取りのための熱処理を施され、さらに強度向上のために樹脂含浸を行う工程がある。なお、前記の各工程において、生産性の向上や熱処理の効率化のために省略、併合、順序変更などが適宜行われる。
【００１４】
この発明による磁性合金は、溶融法で得られた鋳片を機械粉砕される場合、あるいはアトマイズ法等で得られた所要の粒度の合金粉末は、それぞれ平均粒度１０μｍ〜１００μｍの合金粉末となすことが望ましい。
【００１５】
この発明において絶縁材としては、合金粉末の結合材と兼ねることが望ましく、公知の絶縁性結着剤のいずれも採用でき、例えばエポキシ樹脂、フェノール樹脂、塩化ビニール樹脂、ブチラール樹脂、有機シリコーン樹脂、などがある。樹脂としては、後工程の熱処理時に磁性合金粉末へ拡散し難い性状のものが望ましい。
【００１６】
この発明において、磁性合金粉末と絶縁材と混練して圧縮成形するが、かかる成形歪みを解放して磁気特性を向上させるための熱処理としては、７００℃〜１２００℃の範囲に比較的短時間、保持することが好ましい。この熱処理時の雰囲気は、金属の酸化防止のために非酸化性雰囲気が望ましい。非酸化性雰囲気は、真空中や不活性ガス中のいずれでもよい。また、成形体の硬化、焼鈍処理条件は、絶縁材の種類やその量等に応じて適宜選定される。
【００１７】
熱処理後、絶縁性含浸剤で含浸することが好ましい。熱処理によって脆化した圧粉磁心の機械強度を向上させるためである。含浸剤としては、公知のエボキシ系樹脂、アクリル系樹脂などがある。
【００１８】
【実施例】
実施例１
ガスアトマイズ法により６Ｓｉ−４Ａｌ−ｂａｌＦｅ組成となるよう合金粉末（平均粒径３０μｍ）を作製した。この合金粉末に、非酸化性雰囲気で温度８００℃、１時間保持する熱処理を施した。比較のため、８．８Ｓｉ‐５．８Ａｌ−Ｆｅ組成のセンダスト合金粉末（平均粒径３０μｍ）をガスアトマイズ法により作製した。また、８１Ｎｉ−２Ｍｏ−Ｆｅ組成の磁性合金粉末をガスアトマイズ法にて作製した。
【００１９】
これら合金粉末におけるＶＳＭによるＢ−Ｈ曲線を図１に示す。この発明の合金粉末は、従来のセンダスト合金粉末、Ｎｉ−Ｍｏ−Ｆｅ系合金粉末に比べ飽和磁束密度が高いことが確認された。
【００２０】
これらの合金粉末と有機シリコーン樹脂を添加後混練し、乾燥整粒後に潤滑剤を添加し、外径１７ｍｍ、内径９ｍｍのリング成形体となるように金型に充填し、成型圧８〜１８Ｔ／ｃｍ２にて圧縮成形した。次いで、窒索中で７００℃×ｌ時間の熱処理を行つた後、圧粉磁心のＢ−Ｈ評価を行った。各合金粉末より得られたコアのＢ−Ｈ曲線を図２に示す。
【００２１】
また、成型圧１３Ｔ／ｃｍ２で得られた１００ｋＨｚでのμ’＝６０となる材料について、直流重畳特性の評価を行った。図３に直流重畳特性を示す。この発明では比較センダスト合金、Ｎｉ−Ｍｏ−Ｆｅ系合金に比べ特性の向上が認められ、飽和磁束密度との相関が確認できた。
【００２２】
実施例２
６．５Ｓｉ−３．５Ａｌ−ｂａｌＦｅ組成となるよう溶融合金を作製して鋳込み、得られた鋳片を機械的粉砕して平均粒度３０μｍの合金粉末を得た。この合金粉末に、非酸化性雰囲気で温度８００℃、１時間保持する熱処理を施した。
【００２３】
得られたこの発明の磁性合金粉末について、実施例１と同様にＶＳＭによるＢ−Ｈ曲線を評価し、さらに、実施例１と同様方法で圧粉磁心を作製してコアのＢ−Ｈ評価を行ったところ、実施例１のこの発明合金と同様の特性が得られることを確認した。
【００２４】
また、成型圧１３Ｔ／ｃｍ２で得られた１００ｋＨｚでのμ’＝６０となる圧粉磁心について、直流重畳特性の評価を行ったところ、Ｎｉ−Ｍｏ−Ｆｅ系合金と同等の性能を有することを確認した。
【００２５】
【発明の効果】
この発明は、Ａｌ ３．０ｗｔ％〜５．０ｗｔ％、Ｓｉ ４．０ｗｔ％〜７．０ｗｔ％、残部Ｆｅを主成分とする合金粉末と絶縁材との混練物より圧縮成形された成形体を熱処理して得ることで、Ｎｉ−Ｍｏ−Ｆｅ系磁性合金から得る圧粉磁心と同等以上の飽和磁束密度、直流重畳特性を有し、特にトランスコア、チョークコイルあるいは磁気ヘッド等の用途で、これら従来のＮｉ基合金の代替として有用である。
【図面の簡単な説明】
【図１】合金粉末におけるＶＳＭによるＢ−Ｈ曲線を示すグラフである。
【図２】圧粉磁心におけるＢ−Ｈ曲線を示すグラフである。
【図３】直流重畳特性を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of a dust core used for a transformer core, a choke coil, a magnetic head, or the like, and relates to an Fe—Al— alloy having a saturation magnetic flux density equal to or higher than that of a conventional Ni—Mo—Fe magnetic alloy and a DC superimposition characteristic. It relates to a Si-based dust core.
[0002]
[Prior art]
Laminated magnetic cores using so-called silicon steel plates have been used for transformer cores and various choke coils often used in power supply circuits, etc. Since hardening makes it easy to realize a complicated shape, and using magnetic alloy powders of various compositions makes it easy to obtain desired magnetic properties, powder magnetic cores are frequently used today.
[0003]
The dust core uses a soft magnetic alloy powder having a predetermined particle size range, and is kneaded with an insulating binder resin or the like, so that the surface of the powder particles is coated with the resin, and the powder is filled in a mold and compression molded. Thus, a molded article having a predetermined shape is formed, and the molded article is subjected to a heat treatment to release molding distortion at the time of compression molding and to cure and manufacture the binder component.
[0004]
The dust core has a larger core loss than the conventional ferrite core, but is characterized by high saturation magnetic flux density and high DC superimposition characteristics. Further, the magnetic permeability and DC superimposition characteristics of the dust core have a correlation with the bulk density, and it is generally known that the above characteristics are improved when the dust core is increased in density. .
[0005]
[Problems to be solved by the invention]
The conventional Ni-Mo-Fe soft magnetic alloy has a low saturation magnetic flux density of the alloy itself, but has a high relative magnetic flux density when the powder is compacted. Can be manufactured. However, there is a problem in that the Ni-Mo-Fe alloy contains a large amount of Ni and requires a raw material cost.
[0006]
On the other hand, an Fe-Si alloy is known as a material which is inexpensive in terms of material composition and excellent in the above-mentioned saturation magnetic flux density and DC superimposition characteristics, but has a very large core loss, such as heat generation when used as a transformer core. Therefore, it is hard to say that it is practical as a magnetic alloy for a dust core used for a transformer core, a choke coil and the like.
[0007]
The present invention uses a magnetic alloy powder obtained inexpensively in terms of material composition, and is used for a transformer core, a choke coil, a magnetic head, or the like, and has a saturation magnetic flux density equal to or higher than that of a Ni-Mo-Fe magnetic alloy and a DC superposition characteristic. It is an object of the present invention to provide a dust core, an alloy powder thereof, and a production method, which can be obtained.
[0008]
[Means for Solving the Problems]
The present inventors have conducted various studies on a conventional Fe-Al-Si-based magnetic alloy which can be obtained inexpensively in terms of composition, particularly as a result of examining various relationships with the DC bias characteristics. When the dust core is manufactured by improving the crystallinity, the obtained saturation magnetic flux density and DC superimposition characteristics exceed those of conventional Ni-based alloys such as 50Ni-Fe-based and 81Ni-2Mo-Fe-based alloys. And completed the present invention.
[0009]
That is, the present invention provides a compression molding method using a kneaded product of an alloy powder mainly containing 3.0 wt% to 5.0 wt% of Al, 4.0 wt% to 7.0 wt% of Si, and a balance of Fe, and an insulating material. A dust core obtained by heat-treating a body.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The soft magnetic alloy powder for a dust core according to the present invention mainly contains 3.0 wt% to 5.0 wt% of Al, 4.0 wt% to 7.0 wt% of Si, and the balance Fe. If the Al content is less than 3.0 wt% and the Si content is less than 4.0 wt%, the core loss increases, and it becomes difficult to obtain the desired saturation magnetic flux density and DC bias characteristics. If the Al content exceeds 5.0 wt% and the Si content exceeds 7.0 wt%, the alloy becomes It is not preferable because the magnetic permeability decreases due to the decrease in the density of the powder at the time of compression. It is desirable that impurities other than Fe be contained as little as possible, but the presence of trace components inevitable in production is recognized.
[0011]
The alloy of the present invention mainly containing 3.0 wt% to 5.0 wt% of Al, 4.0 wt% to 7.0 wt% of Si, and the balance of Fe is obtained by ordinary melting, casting, and mechanical pulverization of the alloy. It can be produced by a gas atomizing method, a water atomizing method, or the like. In addition, the crystal structure obtained as usual is not an ideal structure as a magnetic alloy, but even if a dust core is manufactured as it is as an alloy powder, it may be improved through the annealing process of the compact. There is. However, for the purpose of improving the properties of the dust core, it is desirable to heat-treat the alloy powder in advance to promote crystallization to form a soft magnetic alloy powder.
[0012]
As the heat treatment applied to the alloy powder of the present invention, the atmosphere is preferably non-oxidizing, and the treatment temperature is preferably maintained at 700 ° C. to 1200 ° C. for 30 minutes or more. However, even if the holding time exceeds 3 hours, the obtained effect is saturated and productivity is deteriorated, which is not preferable. The preferable holding time is 1 hour to 3 hours.
[0013]
An example of a method for manufacturing a dust core is as follows. A magnetic alloy powder and an insulating binder are kneaded, dried and sized, a lubricant is added as necessary, and the resulting powder is filled in a mold. The resulting molded body is subjected to a heat treatment for removing strain, and a step of impregnating with a resin for improving the strength is provided. In each of the above-described steps, omission, merging, order change, and the like are appropriately performed in order to improve productivity and increase the efficiency of heat treatment.
[0014]
In the magnetic alloy according to the present invention, when a cast slab obtained by a melting method is mechanically pulverized, or an alloy powder having a required particle size obtained by an atomizing method or the like is to be an alloy powder having an average particle size of 10 μm to 100 μm. Is desirable.
[0015]
In the present invention, as the insulating material, it is desirable to also serve as a binder for the alloy powder, and any of known insulating binders can be employed. For example, epoxy resin, phenol resin, vinyl chloride resin, butyral resin, organic silicone resin, and so on. Desirably, the resin has a property of hardly diffusing into the magnetic alloy powder during the heat treatment in the subsequent step.
[0016]
In the present invention, the magnetic alloy powder and the insulating material are kneaded and compression-molded. The heat treatment for releasing the molding strain and improving the magnetic properties is performed at a temperature in the range of 700 ° C to 1200 ° C for a relatively short time. It is preferable to hold. The atmosphere during this heat treatment is desirably a non-oxidizing atmosphere to prevent oxidation of the metal. The non-oxidizing atmosphere may be in a vacuum or in an inert gas. The curing and annealing conditions of the molded body are appropriately selected according to the type and amount of the insulating material.
[0017]
After the heat treatment, it is preferable to impregnate with an insulating impregnating agent. This is for improving the mechanical strength of the dust core which has been embrittled by the heat treatment. Examples of the impregnating agent include known ethoxy resins and acrylic resins.
[0018]
【Example】
Example 1
An alloy powder (average particle size: 30 μm) was prepared by a gas atomization method to have a 6Si-4Al-balFe composition. This alloy powder was subjected to a heat treatment at 800 ° C. for 1 hour in a non-oxidizing atmosphere. For comparison, a sendust alloy powder (average particle size: 30 μm) having a composition of 8.8Si-5.8Al—Fe was produced by a gas atomization method. Further, a magnetic alloy powder having a composition of 81Ni-2Mo-Fe was produced by a gas atomizing method.
[0019]
FIG. 1 shows BH curves of these alloy powders by VSM. It has been confirmed that the alloy powder of the present invention has a higher saturation magnetic flux density than conventional sendust alloy powder and Ni-Mo-Fe alloy powder.
[0020]
These alloy powders and the organic silicone resin are added and kneaded, and after drying and sizing, a lubricant is added, and the mixture is filled into a mold so as to form a ring molded body having an outer diameter of 17 mm and an inner diameter of 9 mm. It was compression molded in cm 2 . Next, after performing a heat treatment at 700 ° C. for 1 hour in the nitriding, the BH of the dust core was evaluated. FIG. 2 shows a BH curve of a core obtained from each alloy powder.
[0021]
In addition, the DC superposition characteristics of the material with μ ′ = 60 at 100 kHz obtained at a molding pressure of 13 T / cm 2 were evaluated. FIG. 3 shows the DC superimposition characteristics. In the present invention, the characteristics were improved as compared with the comparative sendust alloy and the Ni-Mo-Fe alloy, and the correlation with the saturation magnetic flux density was confirmed.
[0022]
Example 2
A molten alloy was prepared and cast to have a composition of 6.5Si-3.5Al-balFe, and the obtained slab was mechanically pulverized to obtain an alloy powder having an average particle size of 30 µm. This alloy powder was subjected to a heat treatment at 800 ° C. for 1 hour in a non-oxidizing atmosphere.
[0023]
With respect to the obtained magnetic alloy powder of the present invention, a BH curve by VSM was evaluated in the same manner as in Example 1, and a dust core was prepared in the same manner as in Example 1 to evaluate the BH of the core. As a result, it was confirmed that characteristics similar to those of the alloy of the present invention of Example 1 were obtained.
[0024]
The evaluation of the DC superposition characteristics of the powder magnetic core with μ ′ = 60 at 100 kHz obtained at a molding pressure of 13 T / cm 2 showed that the powder magnetic core had the same performance as that of the Ni—Mo—Fe alloy. It was confirmed.
[0025]
【The invention's effect】
The present invention provides a compact formed from a kneaded product of an alloy powder mainly composed of 3.0 wt% to 5.0 wt% of Al, 4.0 wt% to 7.0 wt% of Si, and the balance Fe, and an insulating material. By obtaining by heat treatment, it has the same or higher saturation magnetic flux density and DC superimposition characteristics as the dust core obtained from the Ni-Mo-Fe based magnetic alloy, and especially in applications such as transformer cores, choke coils or magnetic heads. It is useful as a substitute for a conventional Ni-based alloy.
[Brief description of the drawings]
FIG. 1 is a graph showing a BH curve by VSM in an alloy powder.
FIG. 2 is a graph showing a BH curve in a dust core.
FIG. 3 is a graph showing DC superimposition characteristics.
