JP2019041068A - Method of manufacturing dust core not requiring annealing treatment - Google Patents
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本発明は、焼鈍処理を不要とする圧粉磁心の製造方法である。つまり、圧粉磁心の原料である金属ないしは合金からなる磁性粉に、熱分解で絶縁性の金属酸化物を析出する有機金属化合物を吸着させる。次に、磁性粉の集まりを金型に充填し、金型を昇温して有機金属化合物を熱分解させ、磁性粉の表面に金属酸化物の微粒子の集まりを析出させる。さらに、磁性粉の集まりに、金属酸化物の微粒子の破壊が終了するまで、徐々に増大する圧縮応力を加える。これらの処理を連続して実施することで、金型内に圧粉磁心を製造する。 The present invention is a method of manufacturing a dust core that does not require annealing. That is, an organometallic compound that deposits an insulating metal oxide by thermal decomposition is adsorbed to a magnetic powder made of a metal or alloy that is a raw material of the dust core. Next, a collection of magnetic powder is filled in the mold, the mold is heated to thermally decompose the organometallic compound, and a collection of metal oxide fine particles is deposited on the surface of the magnetic powder. Further, a gradually increasing compressive stress is applied to the collection of magnetic powders until the destruction of the metal oxide fine particles is completed. By carrying out these processes continuously, a dust core is produced in the mold.
圧粉磁心は、表面を絶縁化させた磁性粉を圧縮成形し、圧縮成形による磁性粉の加工歪を、還元雰囲気で磁気焼鈍して製造される。この圧粉磁心は、モータにおけるステーターやローターを構成する磁心、電源回路におけるリアクトルやノイズフィルターやチョークコイルなどを構成する磁心として用いられている。このような磁心に、絶縁層を介して電磁鋼板を積層した積層電磁鋼板磁心、断面が四角形からなる角型や断面が円からなるリングからなるフェライト磁心、表面を絶縁化させた磁性粉を圧縮成形した圧粉磁心の３種類の磁心がある。圧粉磁心は積層電磁鋼板磁心に比べて、１．磁性粉の高抵抗化が可能であるため、高周波領域まで磁気特性が安定し、磁心の発熱や渦電流損失が少ない、２．磁気ギャップが不要になるため、磁歪による騒音や漏洩磁束による誤動作がない、３．形状の自由度が高く、電磁鋼板の積層ではできない３次元形状の加工が容易である、４．打抜きの残材がないため材料の歩留まりが高く、廃棄物が少ない、５．粉砕が可能であるため、銅線との分離が容易でリサイクル性に優れる、などの特徴を有する。また、圧粉磁心は飽和磁束密度が低いフェライト磁心に比べ、１．磁束密度が高いため大電流を流しても磁気飽和せず、磁気素子としての機能が発揮できる、２．磁気キュリー点がフェライトより高く、高温においても磁気特性が安定する、３．磁性粉の加圧成形で製造するため、焼結で製造するフェライトより寸法変化が少なく、金型の設計が容易になり、また、成形後の機械加工が不要になる、などの特徴を有する。 The dust core is manufactured by compression-molding magnetic powder whose surface is insulated, and magnetically annealing the processing strain of the magnetic powder by compression molding in a reducing atmosphere. The dust core is used as a magnetic core that constitutes a stator and a rotor in a motor, and a magnetic core that constitutes a reactor, a noise filter, a choke coil, and the like in a power supply circuit. Compressed laminated magnetic steel sheet cores, in which magnetic steel sheets are laminated via an insulating layer, such as a magnetic core, a ferrite core consisting of a square with a square cross section and a ring with a circular cross section, and magnetic powder with an insulated surface. There are three types of magnetic cores, a molded powder magnetic core. Compared with laminated magnetic steel sheet cores, the dust core is 1. 1. Since the magnetic powder can have a high resistance, the magnetic characteristics are stable up to the high frequency range, and the heat generation of the magnetic core and eddy current loss are small. 2. Since no magnetic gap is required, there is no noise due to magnetostriction or malfunction due to leakage magnetic flux. 3. The degree of freedom of shape is high, and it is easy to process a three-dimensional shape that cannot be done by laminating electromagnetic steel sheets. 4. Since there is no punching remaining material, the material yield is high and there is little waste. Since it can be pulverized, it has features such as easy separation from copper wire and excellent recyclability. In addition, the powder magnetic core is 1. 1. Since the magnetic flux density is high, the magnetic saturation does not occur even when a large current is passed, and the function as a magnetic element can be exhibited. 2. Magnetic Curie point is higher than that of ferrite, and magnetic properties are stable even at high temperatures. Since it is manufactured by pressure molding of magnetic powder, it has features such as less dimensional change than ferrite manufactured by sintering, facilitating the design of the mold, and eliminating the need for machining after molding.
圧粉磁心は前記した優れた特徴を持つが、圧粉磁心の用途をさらに拡大するには、製造コストを大幅に下げる、新たな製造方法を実現することが課題になる。つまり、最も多くの製造コストを占める焼鈍処理が不要な製造方法を実現することが、第一の課題である。次に多くの製造コストを占める磁性粉の絶縁化の製造コストを下げることが、第二の課題である。つまり、安価な材料を用い、極めて簡単な処理によって、磁性粉を絶縁化させる新たな製造方法を実現することである。こうした新たな製造方法で製造した圧粉磁心が、従来の製造方法で製造した圧粉磁心と比べ、１．圧縮成形体の高密度化で磁束密度がさらに増大し、２．磁性粉の絶縁性の増大で渦電流損失がさらに低減し、３．磁性粉の加工歪みが存在せず、ヒステリシス損失がさらに低減する、などの作用効果が付加的にもたらされれば、圧粉磁心が汎用的な部品として、新たな用途に使用される。
いっぽう、圧粉磁心の多くの課題は、磁性粉を絶縁化させる手段に関わる。しかしながら、絶縁化の課題を同時に解決するには困難を伴う。例えば、成形時に印加する圧力を増大させると、成形体の磁束密度と機械的強度とが増大するが、磁性粉に加工歪が残り、成形体のヒステリシス損失が増大する。このため、焼鈍によって磁性粉の加工歪を除去することが必須になる。しかし、多くの絶縁物は、焼鈍が６００℃以上の温度を超えると、絶縁物が熱分解あるいは変質して、磁性粉の絶縁性が確保できないという問題をもたらす。
従って、磁性粉の集まりを加圧成形する際に、絶縁層が剥がれず、６００℃以上の高温でも熱分解あるいは変質しない絶縁物を、磁性粉の表面全体に強固に固着させることが必要になる。このような取り組みとして、例えば、特許文献１に、アトマイズ鉄粉ないしはアトマイズ合金粉の表面に酸化物の層を積極的に形成し、その上にアルミナゾル、シリカゾル、チタニアゾルや金属アルコキシド溶液を吸着させ、７５０℃以上の不活性ガスや還元性ガスの雰囲気で熱処理して、アトマイズ粉の表面に形成した酸化物の層と後処理で形成した絶縁物の層とを反応させる技術が開示されている。特許文献２には、鉄粉の表面にフッ化マグネシウムＭｇＦ２になる原料を塗布し、５×１０−５Ｔｏｒｒの減圧下で６００℃の熱処理を行い、鉄粉の表面にＭｇＦ２の絶縁層を形成した事例が記載されている。
しかしながら、特許文献１−２に記載された方法では、特殊な薬品を用い、特殊な環境下で絶縁層を形成するため、絶縁層の形成が圧粉磁心の製造コストを増大させる。
Although the dust core has the above-described excellent characteristics, in order to further expand the uses of the dust core, it is a problem to realize a new manufacturing method that greatly reduces the manufacturing cost. That is, the first problem is to realize a manufacturing method that does not require an annealing process that occupies the most manufacturing cost. Next, the second problem is to reduce the manufacturing cost of insulating the magnetic powder, which occupies a large amount of manufacturing cost. In other words, it is to realize a new manufacturing method for insulating the magnetic powder by using an inexpensive material and performing extremely simple processing. Compared with the powder magnetic core manufactured by the conventional manufacturing method, the powder magnetic core manufactured by such a new manufacturing method is 1. 1. Increasing the density of the compression molded body further increases the magnetic flux density. 2. Increased insulation of magnetic powder further reduces eddy current loss; If there are additional effects such as the absence of processing distortion of magnetic powder and further reduction in hysteresis loss, the dust core is used as a general-purpose component for new applications.
On the other hand, many problems of the powder magnetic core relate to means for insulating the magnetic powder. However, it is difficult to solve the problem of insulation at the same time. For example, when the pressure applied during molding increases, the magnetic flux density and mechanical strength of the molded body increase, but processing strain remains in the magnetic powder, and the hysteresis loss of the molded body increases. For this reason, it is essential to remove the processing distortion of the magnetic powder by annealing. However, many insulators cause the problem that when the annealing exceeds a temperature of 600 ° C. or more, the insulator is thermally decomposed or deteriorated, and insulation of the magnetic powder cannot be secured.
Therefore, it is necessary to firmly fix an insulating material that does not peel off and is not thermally decomposed or deteriorated even at a high temperature of 600 ° C. or more to the entire surface of the magnetic powder when the magnetic powder cluster is pressure-molded. . As such an approach, for example, in
However, in the method described in Patent Document 1-2, a special chemical is used and the insulating layer is formed under a special environment. Therefore, the formation of the insulating layer increases the manufacturing cost of the dust core.
いっぽう、絶縁化された磁性粉の集まりを圧縮成形する際に、絶縁物が次の２つの性質を持てば、３段落に記載した第一の課題が解決され、合わせて、３つの作用効果が付加的にもたらされる。第一に、加圧成形時に絶縁物が優先して破壊する。これによって、破壊された絶縁物が圧縮成形体の空孔を埋め、成形体の密度が高まる。また、磁性粉に加工歪が発生しない。この結果、磁気焼鈍処理が不要になり、圧縮成形体の絶縁性が高まり、磁性粉のヒステリシス損失が発生しない。第二に、絶縁物が微粒子で、微粒子が成形体に占める体積割合を１％以下とし、また、微粒子の硬度が磁性粉の硬度より低い。これによって、圧縮成形時に微粒子の破壊が連続して進み、空孔が微細になった微粒子で埋められ、微粒子が成形体に占める割合が１％以下になり、磁性粉の表面が絶縁物の微粒子の集まりで覆われる。この結果、圧縮成形体の密度が磁性粉の密度に近づき、磁性粉の絶縁性が増大する。これによって、３段落に記載した圧粉磁心の多くの課題が解決される。
いっぽう、圧粉磁心は、モータや電源装置などの汎用機器の部品として用いるため、磁性粉の多くは大量生産による安価な磁性粉である。このため、磁性粉を安価な処理費用で絶縁化することが必須になる。これに対し、特許文献１−２に記載された技術のように、特殊の環境下で高価な材料を用い、分断された複数の処理によって磁性粉を絶縁化する方法では、安価な磁性粉を高価な絶縁化された磁性粉にする。従って、安価な材料を用い、簡単な処理を連続して実施することで、磁性粉が絶縁化される新たな製造方法を見出すこととして、３段落に記載した第二の課題が残る。また、圧粉磁心の製造方法について、圧粉磁心の機械的強度をどのようにして実現させるかが課題として残る。
ここで、本発明が解決しようとする課題を説明する。第一に、磁気焼鈍が不要な圧粉磁心を製造する製造方法を実現する。第二に、磁性粉を安価な手段で絶縁化する。第三に、磁性粉の絶縁化から圧粉磁心の製造に至るまでの製造方法が、簡単な処理を連続して実施する製造方法である。第四に、製造する圧粉磁心の形状と大きさに制約がない。第五に、従来の圧粉磁心に比べ、磁束密度と機械的強度と絶縁性とが増大する。本発明は、このような５つの要件を満たす圧粉磁心を製造する新たな製造方法を実現することにある。なお従来の圧粉磁心の成形時の加圧力は８００−１５００ＭＰａであり、磁気焼鈍は還元性雰囲気の６００−８００℃で熱処理する。
On the other hand, if the insulating material has the following two properties when compression-molding a collection of insulated magnetic powders, the first problem described in the third paragraph is solved, and the three effects are combined. Additionally. First, the insulator breaks preferentially during pressure molding. Thereby, the destroyed insulator fills the pores of the compression molded body, and the density of the molded body increases. Further, no processing distortion occurs in the magnetic powder. As a result, magnetic annealing treatment is not required, the insulation of the compression molded body is enhanced, and hysteresis loss of magnetic powder does not occur. Second, the insulating material is fine particles, and the volume ratio of the fine particles to the molded body is 1% or less, and the hardness of the fine particles is lower than the hardness of the magnetic powder. As a result, the destruction of the fine particles progresses continuously during compression molding, the pores are filled with fine particles, the proportion of the fine particles in the compact becomes 1% or less, and the surface of the magnetic powder is an insulating fine particle Covered with a gathering of. As a result, the density of the compression molded body approaches the density of the magnetic powder, and the insulating property of the magnetic powder increases. This solves many problems of the dust core described in the third paragraph.
On the other hand, since the dust core is used as a part of a general-purpose device such as a motor or a power supply device, most of the magnetic powder is inexpensive magnetic powder by mass production. For this reason, it is essential to insulate the magnetic powder at a low processing cost. On the other hand, as in the technique described in Patent Document 1-2, an inexpensive material is used in a method in which an expensive material is used in a special environment and the magnetic powder is insulated by a plurality of divided processes. Make expensive insulated magnetic powder. Therefore, the second problem described in the third paragraph remains as finding a new manufacturing method in which the magnetic powder is insulated by continuously carrying out simple processing using an inexpensive material. In addition, regarding the method of manufacturing a dust core, how to realize the mechanical strength of the dust core remains as an issue.
Here, problems to be solved by the present invention will be described. First, a manufacturing method for manufacturing a dust core that does not require magnetic annealing is realized. Second, the magnetic powder is insulated by inexpensive means. Thirdly, the manufacturing method from the insulation of magnetic powder to the manufacture of the dust core is a manufacturing method in which simple processing is continuously performed. Fourth, there is no restriction on the shape and size of the dust core to be produced. Fifth, the magnetic flux density, mechanical strength, and insulation are increased as compared with the conventional dust core. It is an object of the present invention to realize a new manufacturing method for manufacturing a dust core that satisfies these five requirements. In addition, the pressurization force at the time of shaping | molding of the conventional dust core is 800-1500 Mpa, and magnetic annealing is heat-processed at 600-800 degreeC of reducing atmosphere.
圧粉磁心を製造する製造方法は、熱分解で絶縁性の金属酸化物からなる微粒子を析出する有機金属化合物を、アルコールに分散してアルコール分散液を作成する、この後、前記金属酸化物の微粒子より硬度が高い第一の性質と、前記金属酸化物の微粒子の大きさより平均粒径が３桁大きい第二の性質とを兼備する金属ないしは合金からなる磁性粉の集まりを、前記アルコール分散液に混合して懸濁液を作成する、さらに、前記懸濁液を金型に充填し、該金型を前記有機金属化合物が熱分解する温度に昇温し、この後、室温に戻す、さらに、前記金型内の磁性粉の集まりに、前記磁性粉の表面に析出した金属酸化物の微粒子の破壊が終了するまで、徐々に増大する圧縮応力を連続して加える、これによって、前記金型内に圧粉磁心が製造される、圧粉磁心の製造方法である。 A manufacturing method for manufacturing a powder magnetic core is a method in which an organometallic compound that precipitates fine particles of an insulating metal oxide by pyrolysis is dispersed in alcohol to form an alcohol dispersion. A collection of magnetic powders made of a metal or alloy having both a first property having a hardness higher than that of the fine particles and a second property having an average particle size three orders of magnitude larger than the size of the fine particles of the metal oxide. In addition, the suspension is mixed to prepare a suspension, the mold is filled with the suspension, the mold is heated to a temperature at which the organometallic compound is thermally decomposed, and then returned to room temperature. A gradually increasing compressive stress is continuously applied to the collection of magnetic powder in the mold until the destruction of the fine particles of the metal oxide deposited on the surface of the magnetic powder is completed. The dust core is manufactured inside It is a method for producing a dust core.
つまり、本製造方法によれば、極めて簡単な５つの処理を連続して実施することで、圧粉磁心が製造される。第一の処理では、有機金属化合物をアルコールに分散し、アルコール分散液を作成する。第二の処理では、アルコール分散液に磁性粉の集まりを混合し、懸濁液を作成する。第三の処理では、懸濁液を圧粉磁心の形状を有する金型に充填する。第四の処理では、金型を有機金属化合物が熱分解する温度に昇温し、熱分解温度に数分程度保持したのちに室温に戻す。第五の処理では、金型内の磁性粉の集まりに、金属酸化物の微粒子の破壊が終了するまで、徐々に増大する圧縮応力を加える。これら５つの処理はいずれも簡単な処理であり、５つの処理を連続して実施すると、金型内に圧粉磁心が製造される。また、金型の昇温温度は最高でも３３０℃程度で、従来の磁気焼鈍に比べると著しく低い。さらに、全ての処理は大気雰囲気で行われる。このため、安価な製造費用で圧粉磁心が製造される。
本製造方法で金型を昇温すると、温度に応じて次の現象が連続して起こる。アルコールの沸点に達すると、懸濁液からアルコールが気化し、磁性粉の表面に有機金属化合物の微細結晶が析出し、磁性粉は微細結晶の集まりで覆われる。なお、微細結晶の大きさは、熱分解で析出する金属酸化物の微粒子の大きさに近い。次に、有機金属化合物を構成する有機物の沸点に達すると、有機金属化合物が有機物と金属酸化物とに分解する。有機物の密度が金属酸化物の密度より小さいため、有機物が上層に金属酸化物が下層になるように析出し、上層の有機物が気化した後に、金属酸化物が１０−１００ｎｍの間に入る粒状の微粒子を析出し、有機金属化合物の熱分解反応を終える。この結果、金属酸化物の微粒子より平均粒径が３桁大きい磁性粉の表面は、金属酸化物の微粒子の集まりで覆われる。有機金属化合物の熱分解が、磁性粉の表面を覆った状態で進むため、磁性粉の表面は外界に触れず、磁性粉は酸化されない。なお、金属酸化物の微粒子が占める体積が１％以下の体積で、磁性粉が９９％以上の体積を占めるように、有機金属化合物を磁性粉に吸着させる。このため、アルコールへの有機金属化合物の分散濃度は極めて低く、全ての磁性粉の表面が、有機金属化合物のアルコール分散液と接触する。従って、アルコール分散液からアルコールを気化させると、すべての磁性粉の表面は有機金属化物の微細結晶で覆われる。このため、全ての磁性粉の表面に金属酸化物の微粒子の集まりが析出する。
いっぽう、多くの磁性粉は、溶湯を急冷させた磁性粉を、ないしは、ミルスケールを加熱還元した磁性粉を、機械的に粉砕して製造する。従って、磁性粉は表面が海綿状で多くの凹凸を有し、様々な異形形状で、分級しても大きさには偏差がある。さらに、磁性粉の中には、磁性粉の異形形状によって、磁性粉自体に空孔を持つ磁性粉がある。このような磁性粉を有機金属化合物の微細結晶で覆い、磁性粉の集まりを金型に充填すると、ランダムに混じり合った磁性粉の集まりには、多くの空孔が形成される。さらに、金型を昇温して有機金属化合物を熱分解すると、前記したように、大きさが磁性粉の平均粒径より３桁小さい金属酸化物の微粒子の集まりが一斉に析出し、磁性粉の表面の凹凸を埋めるとともに、表面全体を覆う。また、磁性粉の空孔内にも微粒子が析出する。この後、加える応力を少しずつ増大して磁性粉の集まりを圧縮する。
磁性粉の集まりに応力を加えると、金属酸化物の微粒子と磁性粉に応力が伝達される。いっぽう、磁性粉の集まりには多くの空孔が存在するため、空孔を埋めるように、磁性粉が微粒子を伴って移動し、磁性粉が再配列する。つまり、磁性粉が微粒子の集まりで覆われているため、磁性粉同士が接触せず、磁性粉に摩擦力が発生せず、磁性粉の移動が容易になり、磁性粉が再配列する。さらに応力が増大すると、磁性粉が移動できる大きさの空孔がなくなり、磁性粉より３桁も小さい金属酸化物の微粒子が移動して空孔を埋める。また、磁性粉自体の空孔も埋める。さらに応力が増大すると、微粒子が移動できる大きさの空孔がなくなり、応力は微粒子同士が接触する局所的な部位と、磁性粉の表面に微粒子が接触する局所的な部位とに直接加わり、金属酸化物の微粒子の硬度が磁性粉の硬度より低いため、微粒子が優先して破壊され、より微細な微粒子となって全ての空孔を埋める。さらに応力が増大すると、空孔が微粒子の破壊で埋められない数ナノ程度の大きさに縮減され、微粒子の破壊が終了する。さらに応力が増大すると、微粒子同士が接触する局所的な部位に過大な摩擦熱が発生し、接触部位が軟化し、圧縮応力によって接触部位で微粒子同士が接合する。同様に、微粒子が磁性粉の表面と接触する局所的な部位にも、過大な摩擦熱が発生し、接触部位が軟化し、磁性粉の全ての表面に微粒子が接合する。この結果、様々な大きさからなる全ての金属酸化物の微粒子同士が接触部位で互いに接合し、磁性粉の表面と接触する全ての微粒子が磁性粉に接合する。これによって、金型内の磁性粉の集まりは一定の機械的強度を持つ。さらに応力が増大すると、磁性粉の塑性変形が始まる。この段階で応力の印加を停止し、金型内に圧粉磁心を製造する。この圧粉磁心は、数ナノから数十ナノの様々な大きさからなる金属酸化物の微粒子の数十個近くが全ての磁性粉を取り囲み、また、磁性粉自体の空孔を埋め、空孔が僅かに数ナノ程度の大きさからなる稠密構造で形成される。また、圧粉磁心は、金属酸化物の微粒子が１％より少ない体積で、磁性粉が９９％より多い体積を占めるため、磁性粉の密度に近い密度を持つ。なお、磁性粉の集まりの金型内における挙動は、応力を加えた際の金型が受ける反発力の大きさから判断でき、磁性粉の塑性変形が開始された際に反発力が最大となり、この時点で応力の印加を停止する。従って、磁性粉には加工歪は発生せず、磁気焼鈍の処理が不要になる。
以上に説明した方法で製造した圧粉磁心は、次の作用効果をもたらす。
第一に、焼鈍処理が不要な圧粉磁心の製造方法である。つまり、磁性粉の塑性変形が始まる段階で、磁性粉に加える圧縮応力を停止させるため、磁性粉の塑性変形に伴う加工歪が発生しない。これによって、磁気焼鈍の処理が不要になる。従来は、絶縁体で覆われた磁性粉の集まりが形成する空孔に対し、過大な圧縮応力を磁性粉に加えて磁性粉を塑性変形させ、磁性粉の塑性変形で空孔を埋めた。これに対し、本発明では、金属酸化物の微粒子の集まりで覆われた磁性粉の集まりに圧縮応力を加え、硬度が相対的に低い金属酸化物の微粒子を優先して破壊させ、破壊された金属酸化物の微粒子の集まりによって空孔が埋められるため、磁性粉に加工歪が発生しない。
第二に、安価な手段で磁性粉が絶縁化される。つまり、磁性粉を絶縁化させる原料が有機金属化合物で、汎用的な有機酸からなる有機金属化合物であるため、有機金属化合物の合成が容易で安価な工業用材料である。また、絶縁化させる材料は金属酸化物の微粒子であり、安価な有機金属化合物を、大気雰囲気の３３０℃程度の温度で熱分解させて微粒子が生成されるため、安価な原料を用い、安価な処理費用で磁性粉が絶縁化される。
第三に、圧粉磁心を製造する製造方法が、簡単な５つの処理を連続して実施する製造方法である。このため、安価な製造コストで圧粉磁心が製造できる。
第四に、安価な圧粉磁心が連続して製造できる。つまり、複数の金型の各々金型が順番に、磁性粉の充填工程、磁性粉の昇温工程、磁性粉の圧縮工程を連続して実施する工法を採用すれば、圧粉磁心が連続して製造され、安価な圧粉磁心が連続して製造できる。
第五に、製造する圧粉磁心の形状と大きさに制約がない。つまり、磁性粉の集まりを充填する金型の形状に制約がないため、製造する圧粉磁心の形状と大きさに制約がない。
第六に、金属酸化物の微粒子と磁性粉との稠密構造で圧粉磁心が構成され、金属酸化物の微粒子が１％より少ない体積で、磁性粉が９９％より多い体積を占めるため、圧粉磁心は従来の圧粉磁心に比べ、磁束密度と絶縁性とが優れる。
第七に、磁性粉の全ての表面に金属酸化物の微粒子が摩擦接合し、全ての金属酸化物の微粒子が互いに摩擦接合するミクロな接合で、圧粉磁心を形成するため、従来の磁性粉の塑性変形によるマクロな接合より、圧粉磁心の機械的強度が高まる。
以上に説明したように、本製造方法は、５段落に記載した５つの課題の全てを解決する圧粉磁心の製造方法である。これによって、本発明が解決すべき課題が解決された。
That is, according to this manufacturing method, a powder magnetic core is manufactured by carrying out 5 extremely simple processes in succession. In the first treatment, an organometallic compound is dispersed in alcohol to produce an alcohol dispersion. In the second treatment, a collection of magnetic powder is mixed with the alcohol dispersion to create a suspension. In the third treatment, the suspension is filled in a mold having the shape of a dust core. In the fourth treatment, the mold is heated to a temperature at which the organometallic compound is thermally decomposed, held at the thermal decomposition temperature for about several minutes, and then returned to room temperature. In the fifth treatment, a gradually increasing compressive stress is applied to the collection of magnetic powder in the mold until the destruction of the metal oxide fine particles is completed. These five processes are all simple processes, and when the five processes are carried out continuously, a dust core is produced in the mold. Further, the temperature rise temperature of the mold is about 330 ° C. at the highest, which is significantly lower than the conventional magnetic annealing. Furthermore, all processing is performed in an air atmosphere. For this reason, the dust core is manufactured at a low manufacturing cost.
When the temperature of the mold is increased by this manufacturing method, the following phenomenon occurs continuously according to the temperature. When the boiling point of the alcohol is reached, the alcohol is evaporated from the suspension, and fine crystals of the organometallic compound are deposited on the surface of the magnetic powder, and the magnetic powder is covered with a collection of fine crystals. The size of the fine crystal is close to the size of the metal oxide fine particles deposited by thermal decomposition. Next, when the boiling point of the organic substance constituting the organometallic compound is reached, the organometallic compound is decomposed into an organic substance and a metal oxide. Since the density of the organic substance is smaller than the density of the metal oxide, the organic substance is deposited in the upper layer so that the metal oxide is in the lower layer, and after the organic substance in the upper layer is vaporized, the particulate metal oxide enters between 10-100 nm. Fine particles are deposited to complete the thermal decomposition reaction of the organometallic compound. As a result, the surface of the magnetic powder having an average particle size three orders of magnitude larger than the metal oxide fine particles is covered with a collection of metal oxide fine particles. Since the thermal decomposition of the organometallic compound proceeds while covering the surface of the magnetic powder, the surface of the magnetic powder does not touch the outside and the magnetic powder is not oxidized. The organometallic compound is adsorbed on the magnetic powder so that the volume occupied by the metal oxide fine particles is 1% or less and the magnetic powder occupies 99% or more. For this reason, the dispersion | distribution density | concentration of the organometallic compound to alcohol is very low, and the surface of all the magnetic powders contacts the alcohol dispersion liquid of an organometallic compound. Therefore, when the alcohol is vaporized from the alcohol dispersion, the surfaces of all the magnetic powders are covered with fine crystals of the organometallic compound. For this reason, a collection of metal oxide fine particles is deposited on the surface of all the magnetic powders.
On the other hand, many magnetic powders are produced by mechanically pulverizing magnetic powder obtained by quenching a molten metal or magnetic powder obtained by heating and reducing a mill scale. Accordingly, the magnetic powder has a spongy surface and many irregularities, and has various irregular shapes. Even when classified, there is a deviation in size. Further, among magnetic powders, there are magnetic powders having holes in the magnetic powder itself due to the irregular shape of the magnetic powder. When such magnetic powder is covered with fine crystals of an organometallic compound and a collection of magnetic powder is filled in a mold, many holes are formed in the randomly mixed magnetic powder collection. Furthermore, when the mold is heated to thermally decompose the organometallic compound, as described above, a collection of metal oxide fine particles whose size is three orders of magnitude smaller than the average particle size of the magnetic powder is deposited all at once. As well as filling the surface irregularities, cover the entire surface. Fine particles are also deposited in the pores of the magnetic powder. Thereafter, the applied stress is gradually increased to compress the collection of magnetic powders.
When stress is applied to the collection of magnetic powder, the stress is transmitted to the metal oxide fine particles and the magnetic powder. On the other hand, since many vacancies exist in the gathering of magnetic powder, the magnetic powder moves with fine particles so as to fill the vacancies, and the magnetic powder rearranges. That is, since the magnetic powder is covered with a collection of fine particles, the magnetic powders do not contact each other, no friction force is generated in the magnetic powder, the magnetic powder is easily moved, and the magnetic powder is rearranged. When the stress further increases, there are no vacancies large enough to move the magnetic powder, and metal oxide fine particles that are three orders of magnitude smaller than the magnetic powder move to fill the vacancies. It also fills the holes in the magnetic powder itself. As the stress further increases, there are no vacancies large enough to move the microparticles, and the stress is directly applied to the local sites where the microparticles are in contact with each other and the local sites where the microparticles are in contact with the surface of the magnetic powder. Since the hardness of the oxide fine particles is lower than the hardness of the magnetic powder, the fine particles are preferentially broken to form finer fine particles and fill all vacancies. When the stress further increases, the pores are reduced to a size of several nanometers that cannot be filled by the destruction of the fine particles, and the destruction of the fine particles ends. When the stress further increases, excessive frictional heat is generated at a local site where the microparticles come into contact with each other, the contact site is softened, and the microparticles are joined at the contact site due to the compressive stress. Similarly, excessive frictional heat is also generated at a local portion where the fine particles come into contact with the surface of the magnetic powder, the contact portion is softened, and the fine particles are bonded to all surfaces of the magnetic powder. As a result, all the metal oxide fine particles having various sizes are bonded to each other at the contact site, and all the fine particles in contact with the surface of the magnetic powder are bonded to the magnetic powder. As a result, the collection of magnetic powder in the mold has a certain mechanical strength. When the stress further increases, plastic deformation of the magnetic powder starts. At this stage, the application of stress is stopped, and a dust core is manufactured in the mold. In this powder magnetic core, dozens of fine particles of metal oxides of various sizes from several nanometers to several tens of nanometers surround all the magnetic powder, and also fill the pores of the magnetic powder itself, Is formed in a dense structure having a size of only a few nanometers. The dust core has a density close to that of the magnetic powder because the metal oxide fine particles have a volume of less than 1% and the magnetic powder has a volume of more than 99%. The behavior of the gathering of magnetic powder in the mold can be judged from the magnitude of the repulsive force received by the mold when stress is applied, and the repulsive force is maximized when plastic deformation of the magnetic powder is started. At this point, the application of stress is stopped. Therefore, processing distortion does not occur in the magnetic powder, and magnetic annealing treatment is not necessary.
The dust core produced by the method described above has the following effects.
The first is a method of manufacturing a dust core that does not require annealing. That is, since the compressive stress applied to the magnetic powder is stopped at the stage where the plastic deformation of the magnetic powder starts, the processing strain accompanying the plastic deformation of the magnetic powder does not occur. This eliminates the need for magnetic annealing. Conventionally, an excessive compressive stress is applied to the magnetic powder with respect to the holes formed by the gathering of the magnetic powder covered with the insulator to plastically deform the magnetic powder, and the holes are filled with the plastic deformation of the magnetic powder. On the other hand, in the present invention, a compressive stress is applied to a collection of magnetic powders covered with a collection of metal oxide fine particles, and the metal oxide fine particles having a relatively low hardness are preferentially broken and destroyed. Since the pores are filled with the collection of metal oxide fine particles, no processing distortion occurs in the magnetic powder.
Second, the magnetic powder is insulated by inexpensive means. That is, since the raw material for insulating the magnetic powder is an organometallic compound, which is an organometallic compound composed of a general-purpose organic acid, it is an industrial material that is easy to synthesize and is inexpensive. Further, the insulating material is metal oxide fine particles, and an inexpensive organometallic compound is thermally decomposed at a temperature of about 330 ° C. in the air atmosphere, so that fine particles are generated. Magnetic powder is insulated at processing costs.
Thirdly, the manufacturing method for manufacturing a dust core is a manufacturing method for carrying out five simple processes in succession. For this reason, a dust core can be manufactured at an inexpensive manufacturing cost.
Fourth, inexpensive powder magnetic cores can be manufactured continuously. In other words, if each die of a plurality of dies is used in sequence, the magnetic powder filling process, the magnetic powder temperature raising process, and the magnetic powder compression process, the powder magnetic core is continuous. Thus, an inexpensive dust core can be manufactured continuously.
Fifth, there is no restriction on the shape and size of the dust core to be produced. That is, since there is no restriction on the shape of the mold that fills the collection of magnetic powders, there is no restriction on the shape and size of the dust core to be manufactured.
Sixth, the dust core is composed of a dense structure of metal oxide fine particles and magnetic powder, and the metal oxide fine particles occupy less than 1% volume and the magnetic powder occupies more than 99% volume. The powder magnetic core is superior in magnetic flux density and insulation compared to conventional powder magnetic cores.
Seventh, since the metal oxide fine particles are friction bonded to all the surfaces of the magnetic powder and all the metal oxide fine particles are friction bonded to each other to form a dust core, the conventional magnetic powder The mechanical strength of the powder magnetic core is higher than that of the macro joining by plastic deformation.
As described above, this manufacturing method is a method for manufacturing a dust core that solves all of the five problems described in the fifth paragraph. Thus, the problem to be solved by the present invention has been solved.
前記した圧粉磁心の製造方法は、前記磁性粉が、アトマイズ純鉄粉、還元鉄粉ないしはアトマイズ合金粉である、前記した圧粉磁心の製造方法である。 The above-described method for producing a dust core is the above-described method for producing a dust core, wherein the magnetic powder is atomized pure iron powder, reduced iron powder or atomized alloy powder.
つまり、アトマイズ純鉄粉、還元鉄粉ないしはアトマイズ合金粉は、いずれも強磁性の性質を持ち、金属酸化物の微粒子より硬度が高く、有機金属化合物の熱分解で析出した金属酸化物の微粒子より平均粒径が３桁大きい性質を持つ磁性粉が存在するため、圧粉磁心の原料として用いられる。また、これらの磁性粉は、アトマイズ法ないしは還元法で製造した磁性粉を、粉砕、分級、磁選を行った後に、仕上げ還元を行い、さらに、粉砕、分級によって大量の磁性粉を連続して製造するため、安価な磁性粉である。このため、モータや電源装置などの汎用機器の部品として用いられる圧粉磁心の原料として適切である。 In other words, atomized pure iron powder, reduced iron powder or atomized alloy powder are all ferromagnetic and have higher hardness than metal oxide fine particles, and more than metal oxide fine particles deposited by pyrolysis of organometallic compounds. Since magnetic powder having the property that the average particle diameter is three orders of magnitude exists, it is used as a raw material for the dust core. In addition, these magnetic powders are produced by pulverizing, classifying, and magnetically selecting magnetic powders manufactured by the atomizing method or reduction method, and then performing final reduction. Further, a large amount of magnetic powder is continuously manufactured by pulverizing and classifying. Therefore, it is an inexpensive magnetic powder. For this reason, it is suitable as a raw material of a powder magnetic core used as a component of general-purpose equipment such as a motor and a power supply device.
前記した圧粉磁心の製造方法は、前記有機金属化合物が、カルボン酸におけるカルボキシル基を構成する酸素イオンが、金属イオンに配位結合したカルボン酸金属化合物である
、前記した圧粉磁心の製造方法である。
The above-described method for producing a dust core is the above-described method for producing a dust core, wherein the organometallic compound is a carboxylic acid metal compound in which an oxygen ion constituting a carboxyl group in a carboxylic acid is coordinated to a metal ion. It is.
つまり、カルボン酸のカルボキシル基を構成する酸素イオンが、配位子になって金属イオンに近づいて配位結合するカルボン酸金属化合物は、熱分解によって金属酸化物を析出する。このため、７段落に記載した圧粉磁心の製造方法で、有機金属化合物をカルボン酸金属化合物で構成し、磁性粉をカルボン酸金属化合物の微細結晶で覆い、カルボン酸金属化合物を大気雰囲気で熱処理すると、最高でも３３０℃程度の温度で、カルボン酸金属化合物が熱分解し、大きさが４０−６０ｎｍの範囲に入る粒状の金属酸化物の微粒子の集まりが、磁性粉の表面および磁性粉の空孔に析出する。この結果、磁性粉の材質や大きさや形状に拘わらず、微粒子が磁性粉の表面の凹凸に入り込み、表面全体が金属酸化物の微粒子で覆われる。さらに、微粒子の破壊が終了するまで、磁性粉の集まりに圧縮応力を加えると、金型内に圧粉磁心が製造される。なお、カルボン酸金属化合物の大気雰囲気での熱分解は、窒素雰囲気での熱分解より３０−５０℃低いため、大気雰囲気での熱分解が、熱処理費用が安価で済む。
すなわち、カルボキシル基を構成する酸素イオンが配位子になって、金属イオンに近づいて配位結合するカルボン酸金属化合物は、最も大きいイオンである金属イオンに酸素イオンが近づいて配位結合するため、両者の距離は短くなる。これによって、金属イオンに配位結合する酸素イオンが、金属イオンの反対側で共有結合するイオンとの距離が最も長くなる。こうした分子構造上の特徴を持つカルボン酸金属化合物は、カルボン酸金属化合物を構成するカルボン酸の沸点を超えると、カルボキシル基を構成する酸素イオンが金属イオンの反対側で共有結合するイオンとの結合部が最初に分断され、金属イオンと酸素イオンとの化合物である金属酸化物とカルボン酸とに分解する。さらに昇温すると、カルボン酸が気化熱を奪って気化し、カルボン酸の気化が完了した後に金属酸化物が析出する。こうしたカルボン酸金属化合物として、酢酸金属化合物、カプリル酸金属化合物、安息香酸金属化合物、ナフテン酸金属化合物などがある。
また、カルボン酸金属化合物は、いずれも容易に合成できる安価な工業用薬品である。すなわち、汎用的なカルボン酸を強アルカリと反応させるとカルボン酸アルカリ金属化合物が生成される。この後、カルボン酸アルカリ金属化合物を無機金属化合物と反応させることで、カルボン酸金属化合物が合成される。また、原料となるカルボン酸は、有機酸の沸点の中で相対的に低い沸点を有する有機酸であるため、大気雰囲気においては３３０℃程度の低い熱処理で金属酸化物の微粒子が析出する。
以上に説明したように、７段落の圧粉磁心の製造方法において、磁性粉の表面が金属酸化物の微粒子の集まりで覆われるため、７段落の圧粉磁心の製造方法において、カルボン酸金属化合物は有機金属化合物を構成する。
なお、鉄の酸化物であるマグネタイトＦｅ３Ｏ４を除く金属酸化物は、不純物を含まなければ絶縁性であり、酸化錫ＳｎＯ２と酸化チタンＴｉＯ４とは、不純物として金属をドーピングすることで半導体性を持つ。従って、前記したカルボン酸金属化合物の熱分解で析出した多くの金属酸化物は絶縁性である。
In other words, the metal carboxylate compound in which the oxygen ion constituting the carboxyl group of the carboxylic acid becomes a ligand and approaches the metal ion to coordinate bond precipitates a metal oxide by thermal decomposition. For this reason, in the method for manufacturing a dust core described in paragraph 7, the organometallic compound is composed of a carboxylic acid metal compound, the magnetic powder is covered with fine crystals of the carboxylic acid metal compound, and the carboxylic acid metal compound is heat-treated in the atmosphere. Then, the carboxylic acid metal compound is thermally decomposed at a temperature of about 330 ° C. at the maximum, and a collection of particulate metal oxide fine particles having a size in the range of 40 to 60 nm is formed on the surface of the magnetic powder and the magnetic powder. Precipitate in the pores. As a result, regardless of the material, size, and shape of the magnetic powder, the fine particles enter the irregularities on the surface of the magnetic powder, and the entire surface is covered with the metal oxide fine particles. Further, when compressive stress is applied to the collection of magnetic powders until the destruction of the fine particles is completed, a dust core is produced in the mold. Note that the thermal decomposition of the carboxylic acid metal compound in the air atmosphere is 30-50 ° C. lower than the thermal decomposition in the nitrogen atmosphere, so that the thermal decomposition in the air atmosphere can reduce the heat treatment cost.
In other words, the carboxylate metal compound that forms a coordinate bond near the metal ion becomes a ligand because the oxygen ion constituting the carboxyl group becomes a ligand, and the oxygen ion approaches the metal ion, which is the largest ion. The distance between the two becomes shorter. This maximizes the distance between the oxygen ion coordinated to the metal ion and the ion covalently bonded to the opposite side of the metal ion. Carboxylic acid metal compounds with these molecular structural characteristics bind to ions that covalently bond oxygen ions constituting the carboxyl group on the opposite side of the metal ions when the boiling point of the carboxylic acid constituting the carboxylic acid metal compound is exceeded. The portion is first divided and decomposed into a metal oxide and a carboxylic acid which are compounds of metal ions and oxygen ions. When the temperature is further increased, the carboxylic acid takes the heat of vaporization and vaporizes, and the metal oxide is deposited after the vaporization of the carboxylic acid is completed. Examples of such a carboxylic acid metal compound include an acetic acid metal compound, a caprylic acid metal compound, a benzoic acid metal compound, and a naphthenic acid metal compound.
In addition, carboxylic acid metal compounds are inexpensive industrial chemicals that can be easily synthesized. That is, when a general-purpose carboxylic acid is reacted with a strong alkali, a carboxylic acid alkali metal compound is produced. Thereafter, the carboxylic acid metal compound is synthesized by reacting the carboxylic acid alkali metal compound with the inorganic metal compound. Further, since the carboxylic acid used as a raw material is an organic acid having a relatively low boiling point among the boiling points of the organic acid, metal oxide fine particles are precipitated by a heat treatment as low as about 330 ° C. in an air atmosphere.
As described above, since the surface of the magnetic powder is covered with a collection of metal oxide fine particles in the method for manufacturing a powder magnetic core in the seventh paragraph, the metal carboxylate compound in the method for manufacturing the powder magnetic core in the seventh paragraph. Constitutes an organometallic compound.
Metal oxides other than magnetite Fe 3 O 4 , which is an iron oxide, are insulative unless they contain impurities, and tin oxide SnO 2 and titanium oxide TiO 4 are doped with metal as impurities. Has semiconductor properties. Therefore, many metal oxides deposited by the thermal decomposition of the carboxylic acid metal compound are insulative.
前記した圧粉磁心の製造方法は、前記金属酸化物が、酸化銅ＣｕＯないしは酸化亜鉛ＺｎＯからなるいずれかの金属酸化物である、前記した圧粉磁心の製造方法である。 The above-described method for producing a dust core is the above-described method for producing a dust core, wherein the metal oxide is any metal oxide made of copper oxide CuO or zinc oxide ZnO.
つまり、本製造方法による圧粉磁心の製造に当たっては、磁性粉の表面を覆う金属酸化物は、以下の５つの性質を兼備することが望ましい。
第一に、絶縁性の金属酸化物である。
第二に、前記した酢酸金属化合物、カプリル酸金属化合物、安息香酸金属化合物ないしはナフテン酸金属化合物からなるカルボン酸金属化合物は、熱分解で金属酸化物が析出する。いっぽう、酢酸金属化合物の多くは、アルコールに溶解するため望ましくない。つまり、アルコールに溶解するカルボン酸金属化合物は、アルコールが気化した後にカルボン酸金属化合物の微細結晶が析出しない。また、安息香酸金属化合物は、酸素イオンが金属イオンに近づいて配位結合して複核錯塩を形成するが、熱分解の途上においては不安定な物質を生成する安息香酸金属化合物が存在する。このため、熱分解で金属酸化物を析出するカルボン酸金属化合物は、カプリル酸金属化合物ないしはナフテン酸金属化合物が望ましい。従って、カプリル酸金属化合物ないしはナフテン酸金属化合物の合成が容易で、熱分解で金属酸化物を析出することが望ましい。
第三に、加水分解性を有する、あるいは、水との反応を伴う、アルカリ金属とアルカリ土類金属の金属酸化物は望ましくない。また、アルカリ金属とアルカリ土類金属からなるカプリル酸金属化合物ないしはナフテン酸金属化物の多くは、アルコールに溶解する。
第四に、磁性粉より硬度が低いことが望ましい。つまり、金属酸化物微粒子の硬度が、磁性粉より低ければ、圧縮成形時に金属酸化物微粒子が、より微細な微粒子に破壊され、圧縮成形体における空孔を、破壊された金属酸化物の微粒子が埋め尽くし、稠密構造からなる圧粉磁心が容易に製造できる。また、成形時に過度な圧縮応力が不要になるため、磁性粉のヒステリシス損失を増大させる加工歪が発生しない。なお、磁性粉を圧縮成形する際の圧縮応力が小さければ、磁性粉の加工歪が少なくなるため、磁性粉のビッカース硬度は８５ＨＶより低い。
いっぽう金属酸化物の粒子は、酸化アルミ二ウムＡｌ２Ｏ３、酸化ケイ素ＳｉＯ２、酸化錫ＳｎＯ２、酸化クロムＣｒ２Ｏ３、酸化マグネシウムＭｇＯ、酸化チタンＴｉＯ２、酸化マンガンＭｎＯ２、酸化ニッケルＮｉＯの順で硬度が高く、磁性粉より硬度が高い。
第五に、カプリル酸金属化合物ないしはナフテン酸金属化合物が安価に合成できる。このため、銅を除く貴金属元素、白金族元素及び重金属元素からなるカプリル酸金属化合物ないしはナフテン酸金属化合物は、高価な有機金属化合物であるため望ましくない。なお酸化鉄ＦｅＯは、非磁性でかつ絶縁性で脆い性質を持つが、熱力学的に不安定な物質で、高温で導電性のマグネタイトＦｅ３Ｏ４に徐々に変化する性質を持つため望ましくない。
以上に説明した５つの性質を兼備する金属酸化物として、酸化銅ＣｕＯないしは酸化亜鉛ＺｎＯがある。また、こうした金属酸化物を熱分解で析出するカプリル酸金属化合物とナフテン酸金属化合物とは、合成が容易であるため、金属酸化物の安価な原料になる。
That is, in manufacturing the dust core by this manufacturing method, the metal oxide covering the surface of the magnetic powder preferably has the following five properties.
The first is an insulating metal oxide.
Secondly, in the carboxylic acid metal compound composed of the aforementioned metal acetate metal compound, caprylic acid metal compound, benzoic acid metal compound or naphthenic acid metal compound, a metal oxide is deposited by thermal decomposition. On the other hand, many metal acetate compounds are undesirable because they dissolve in alcohol. That is, the carboxylic acid metal compound dissolved in the alcohol does not precipitate fine crystals of the carboxylic acid metal compound after the alcohol is vaporized. In addition, in the metal benzoate compound, oxygen ions approach the metal ion to form a coordinated bond to form a binuclear complex salt. However, there are metal benzoate compounds that generate unstable substances in the course of thermal decomposition. For this reason, the carboxylic acid metal compound which deposits a metal oxide by thermal decomposition is desirably a caprylic acid metal compound or a naphthenic acid metal compound. Accordingly, it is desirable to easily synthesize a caprylic acid metal compound or a naphthenic acid metal compound, and to deposit a metal oxide by thermal decomposition.
Third, alkali metal and alkaline earth metal oxides that are hydrolysable or that react with water are undesirable. In addition, most of the caprylic acid metal compounds or metallized naphthenic acids composed of alkali metals and alkaline earth metals are soluble in alcohol.
Fourth, it is desirable that the hardness is lower than that of the magnetic powder. That is, if the hardness of the metal oxide fine particles is lower than that of the magnetic powder, the metal oxide fine particles are broken into finer fine particles at the time of compression molding, and the voids in the compression molded body are replaced with the broken metal oxide fine particles. It is possible to easily produce a dust core that is filled up and has a dense structure. Further, since excessive compressive stress is not required at the time of molding, processing strain that increases the hysteresis loss of the magnetic powder does not occur. In addition, since the processing distortion of magnetic powder will decrease if the compressive stress at the time of compression-molding magnetic powder is small, the Vickers hardness of magnetic powder is lower than 85HV.
On the other hand, the metal oxide particles are aluminum oxide Al 2 O 3 , silicon oxide SiO 2 , tin oxide SnO 2 , chromium oxide Cr 2 O 3 , magnesium oxide MgO, titanium oxide TiO 2 , manganese oxide MnO 2 , nickel oxide. The hardness is higher in the order of NiO and higher than the magnetic powder.
Fifth, caprylic acid metal compounds or naphthenic acid metal compounds can be synthesized at low cost. For this reason, caprylic acid metal compounds or naphthenic acid metal compounds composed of noble metal elements excluding copper, platinum group elements and heavy metal elements are undesirable because they are expensive organometallic compounds. Iron oxide FeO is non-magnetic, insulating and brittle, but is a thermodynamically unstable substance and is undesirable because it gradually changes to high-temperature conductive magnetite Fe 3 O 4. .
Examples of the metal oxide having the five properties described above include copper oxide CuO or zinc oxide ZnO. In addition, a caprylic acid metal compound and a naphthenic acid metal compound in which such a metal oxide is deposited by thermal decomposition are easy to synthesize, and thus become an inexpensive raw material for the metal oxide.
本実施形態は、熱分解で金属酸化物を析出する金属化合物に関する実施形態である。
熱分解で金属酸化物を析出する金属化合物は、第一にアルコールに分散する性質と、第二に合金微粒子の表面で、金属酸化物微粒子の集まりを析出する性質とを兼備する。以下の説明では、酸化亜鉛ＺｎＯを析出する原料を例として説明する。
無機亜鉛合物は、熱分解で酸化亜鉛を析出しないため、アルコールに分散する有機亜鉛化合物が望ましい。また、有機亜鉛化合物から酸化亜鉛が生成される化学反応の中で、最も簡単な化学反応に熱分解反応がある。つまり、有機亜鉛化合物を昇温するだけで、熱分解によって酸化亜鉛が析出する。さらに、有機亜鉛化合物の合成が容易でれば、有機亜鉛化合物が安価に製造できる。これら２つの性質を兼備する有機亜鉛化合物に、カルボン酸亜鉛化合物がある。
つまり、カルボン酸亜鉛化合物を構成する物質の中で、最も大きい共有結合半径を持つ物質は亜鉛イオンＺｎ２＋である。いっぽう、亜鉛イオンＺｎ２＋とカルボキシル基を構成する酸素イオンＯ−とが共有結合するカルボン酸亜鉛化合物は、亜鉛イオンと酸素イオンとの距離が最大になる。この理由は、亜鉛の共有結合半径は１１２ｐｍであり、酸素の単結合の共有結合半径は６３ｐｍであり、炭素の二重結合の共有結合半径は６７ｐｍであることによる。このため、亜鉛イオンとカルボキシル基を構成する酸素イオンとが共有結合するカルボン酸亜鉛化合物は、カルボン酸の沸点において、結合距離が最も長い亜鉛イオンとカルボキシル基を構成する酸素イオンとの結合部が最初に分断され、亜鉛とカルボン酸とに分離する。さらに昇温すると、カルボン酸が気化熱を奪って気化し、カルボン酸の気化が完了した後に亜鉛が析出する。従って、熱分解で酸化亜鉛ＺｎＯを析出するカルボン酸亜鉛化合物は、亜鉛イオンＺｎ２＋と結合する酸素イオンＯ−との距離が短く、酸素イオンＯ−が亜鉛イオンＺｎ２＋の反対側で結合するイオンと結合する距離が長い分子構造上の特徴を持つ必要がある。これによって、酸素イオンＯ−が亜鉛イオンＮｉ２＋の反対側で結合するイオンと結合する部位が最初に切れ、酸化亜鉛ＺｎＯとカルボン酸とに分解する。このような分子構造上の特徴を持つカルボン酸亜鉛化合物として、カルボキシル基を構成する酸素イオンＯ−が配位子になって亜鉛イオンＺｎ２＋に近づいて配位結合するカルボン酸亜鉛化合物がある。
また、カルボン酸亜鉛化合物は合成が容易で、安価な有機亜鉛化合物である。つまり、カルボン酸を水酸化ナトリウムなどの強アルカリ溶液と反応させると、カルボン酸アルカリ金属化合物が生成される。カルボン酸アルカリ金属化合物を、硫酸亜鉛などの無機亜鉛化合物と反応させると、カルボン酸亜鉛化合物が生成される。さらに、カルボン酸の沸点が低いため熱分解温度が相対的に低い。このため、カルボキシル基を構成する酸素イオンが、配位子となって金属イオンに近づいて配位結合するカルボン酸亜鉛化合物は、安価な化学薬品であり、熱処理費用も安価で済む。こうしたカルボン酸亜鉛化合物として、酢酸亜鉛、カプリル酸亜鉛、安息香酸亜鉛、ナフテン酸亜鉛などが挙げられる。なお、酢酸亜鉛は、アルコールに溶解するため望ましくない。また、安息香酸亜鉛は、熱分解の途上においては不安定な物質を生成する。従って、酸化亜鉛の原料として、カプリル酸亜鉛ないしはナフテン酸亜鉛が望ましい。
The present embodiment is an embodiment relating to a metal compound that deposits a metal oxide by thermal decomposition.
The metal compound that deposits the metal oxide by pyrolysis has the first property of dispersing in alcohol and the second property of precipitating a collection of metal oxide fine particles on the surface of the alloy fine particles. In the following description, a raw material for depositing zinc oxide ZnO will be described as an example.
Since the inorganic zinc compound does not precipitate zinc oxide by thermal decomposition, an organic zinc compound dispersed in alcohol is desirable. Among the chemical reactions in which zinc oxide is generated from an organic zinc compound, the simplest chemical reaction is a thermal decomposition reaction. That is, zinc oxide is precipitated by thermal decomposition only by raising the temperature of the organic zinc compound. Furthermore, if the synthesis of the organic zinc compound is easy, the organic zinc compound can be produced at a low cost. Among the organic zinc compounds having these two properties, there is a zinc carboxylate compound.
That is, among the substances constituting the zinc carboxylate compound, the substance having the largest covalent bond radius is zinc ion Zn 2+ . On the other hand, in the zinc carboxylate compound in which the zinc ion Zn 2+ and the oxygen ion O − constituting the carboxyl group are covalently bonded, the distance between the zinc ion and the oxygen ion is maximized. This is because the covalent bond radius of zinc is 112 pm, the covalent bond radius of oxygen single bond is 63 pm, and the covalent bond radius of carbon double bond is 67 pm. For this reason, the zinc carboxylate compound in which the zinc ion and the oxygen ion constituting the carboxyl group are covalently bonded has a bond portion between the zinc ion having the longest bond distance and the oxygen ion constituting the carboxyl group at the boiling point of the carboxylic acid. It is divided first and separated into zinc and carboxylic acid. When the temperature is further increased, the carboxylic acid takes the heat of vaporization and vaporizes, and zinc is deposited after the vaporization of the carboxylic acid is completed. Therefore, the zinc carboxylate compound that deposits zinc oxide ZnO by thermal decomposition has a short distance from the oxygen ion O − that binds to the zinc ion Zn 2+, and the ion that binds the oxygen ion O − on the opposite side of the zinc ion Zn 2+. It is necessary to have the characteristics of the molecular structure with a long distance to bond with. As a result, the site where the oxygen ion O − is bonded to the ion bonded to the opposite side of the zinc ion Ni 2+ is first cut and decomposed into zinc oxide ZnO and carboxylic acid. As a carboxylate zinc compound having such a molecular structural feature, there is a zinc carboxylate compound in which an oxygen ion O − constituting a carboxyl group becomes a ligand and coordinates with a zinc ion Zn 2+ .
The zinc carboxylate compound is an organic zinc compound that is easy to synthesize and inexpensive. That is, when a carboxylic acid is reacted with a strong alkali solution such as sodium hydroxide, a carboxylic acid alkali metal compound is produced. When an alkali metal carboxylate compound is reacted with an inorganic zinc compound such as zinc sulfate, a zinc carboxylate compound is produced. Furthermore, since the boiling point of carboxylic acid is low, the thermal decomposition temperature is relatively low. For this reason, the zinc carboxylate compound in which the oxygen ions constituting the carboxyl group act as ligands and coordinate bond with the metal ions is an inexpensive chemical and the heat treatment cost is low. Examples of such zinc carboxylate compounds include zinc acetate, zinc caprylate, zinc benzoate, and zinc naphthenate. Zinc acetate is not desirable because it dissolves in alcohol. In addition, zinc benzoate generates an unstable substance in the course of thermal decomposition. Accordingly, zinc caprylate or zinc naphthenate is desirable as a raw material for zinc oxide.
実施例
本実施例は、酸化亜鉛ＺｎＯの微粒子で覆われた鉄粉の集まりを圧縮成形して、圧粉磁心を製造する実施例である。鉄粉は、株式会社神戸製鋼所の製品のアトマイズ純鉄粉であるアトメル３００ＮＨを用いた。アトメル３００ＮＨは、マンガン、リン、イオウの含有量が極めて微量のアトマイズ純鉄粉であり、純度が高いため磁気特性に優れ、粉の形状から圧縮性に優れる。また、有機亜鉛化合物として、カプリル酸亜鉛Ｚｎ（Ｃ７Ｈ１５ＣＯＯ）２（例えば、三津和化学薬品株式会社の製品）を用いた。なお、アトマイズ鉄粉は、還元鉄粉のように、鉄粉自体に空孔を持たない形状からなる。
最初に、カプリル酸亜鉛の２．４ｇを、１００ｃｃのｎ−ブタノールが充填された容器に混合し分散液を作成した。この分散液に、アトマイズ純鉄粉の２００ｇを混合し、懸濁液を作成した。この懸濁液を金型に充填した。金型は外径が４０ｍｍ、内径が２５ｍｍ、高さが６ｍｍのリング形状の成形体が成形される形状を持つ。次に、金型を２９０℃まで昇温し、２９０℃に１分間放置し、カプリル酸亜鉛を熱分解した。金型を室温に戻した後に、金型内の鉄粉の集りに、１０ＭＰａ／分の昇圧速度で圧力を加え、圧粉磁心を成形した。プレス機が受ける反発力が最大になった時点で昇圧を停止し、圧粉磁心を製作した。なお、２００ｇの鉄粉の集まりに２．４ｇのカプリル酸亜鉛が熱分解して酸化亜鉛の微粒子が覆うと、酸化亜鉛の微粒子が圧粉磁心に占める体積割合は０．３％と極めて少ない。
次に、製作した圧粉磁心の観察と分析とを行なった。圧粉磁心を厚み方向に２つに切断し、切断面を電子顕微鏡で観察した。電子顕微鏡は、ＪＦＥテクノリサーチ株式会社の極低加速電圧ＳＥＭを用いた。この装置は、１００Vからの極低加速電圧による観察が可能で、試料に導電性の被膜を形成せずに直接試料が観察できる特徴を有する。
最初に、反射電子線の９００−１０００Ｖの間にある２次電子線を取り出して画像処理を行い、切断面を観察した。５−６０ｎｍに及ぶ様々な大きさからなる粒状の微粒子が、磁性粉の間隙を満遍なく埋め尽くし、４ｎｍ以下の大きさからなる空隙が、ランダムに多くの場所で形成されていることが確認できた。また、隣り合う鉄粉が最も近づく箇所で、様々な大きさの３０−４０個の粒状微粒子が存在し、鉄粉で囲まれた箇所では、様々な大きさの５０−１００個の粒状微粒子が存在した。次に、特性X線のエネルギーとその強度を画像処理し、粒状微粒子を構成する元素の種類とその分布状態を分析した。亜鉛原子と酸素原子の双方が均一に分散して存在し、特段に偏在する箇所が見られず、酸化亜鉛の粒状微粒子が、鉄粉の間隙を満遍なく埋め尽くしていることが確認できた。図１に、切断面の一部を拡大した様子を模式的に示す。１は鉄粉で、２は酸化亜鉛の微粒子である。
次に、圧粉磁心について圧粉体密度、比抵抗、磁束密度、鉄損を測定した。圧粉体密度は、試料の寸法と重量を測定し、これらの値から算出した。比抵抗は四端子法にて測定した。磁束密度は、圧粉磁心に直径が０．６ｍｍのホルマル被覆導線を１次側に１００巻、２次側に２０巻したコイルを用い、磁界の大きさが１０ｋＡ／ｍでの磁束密度Ｂで評価した。鉄損は、圧粉磁心に直径０．６ｍｍのホルマル被覆導線を１次側に４０巻、２次側に４０巻したコイルを用いて、周波数が２００−１０ｋＨｚ、磁束密度Ｂが０．２Ｔの条件で、住友金属テクノロジー株式会社の磁気特性測定装置を用いて測定した。なお、鉄損の数値は、励磁周波数が５ｋＨｚ、励磁磁束密度が０．２Ｔの値で代表した。
圧粉磁心の密度は７．５６ｋｇ／ｍ３で、鉄の密度７．８７ｋｇ／ｍ３に近く、従来の圧粉磁心の密度に劣らない値である。比抵抗は７２μΩｍで、鉄粉の比抵抗の７２０倍であり、従来の圧粉磁心より３割近く比抵抗が高い。磁束密度は１．７Ｔで、鉄粉の磁束密度２．２Ｔに近く、従来の圧粉磁心の密度に劣らない値である。鉄損は３６Ｗ／ｋｇで、磁気焼鈍した従来の圧粉磁心の８割程度である。また、２ｍの高さから圧粉磁心を落下させても、圧粉磁心は破壊しなかった。
Example This example is an example in which a dust core is manufactured by compression molding a collection of iron powders covered with fine particles of zinc oxide ZnO. As the iron powder, Atmel 300NH, which is an atomized pure iron powder of a product of Kobe Steel, Ltd., was used. Atmel 300NH is an atomized pure iron powder with a very small amount of manganese, phosphorus, and sulfur, and has high purity, so it has excellent magnetic properties and excellent compressibility from the shape of the powder. Further, as the organic zinc compound, with zinc caprylate Zn (C 7 H 15 COO) 2 ( e.g., product of Mitsuwa Chemicals Co., Ltd.). In addition, atomized iron powder consists of a shape which does not have a void | hole in iron powder itself like reduced iron powder.
First, 2.4 g of zinc caprylate was mixed in a container filled with 100 cc of n-butanol to prepare a dispersion. To this dispersion, 200 g of atomized pure iron powder was mixed to prepare a suspension. This suspension was filled in a mold. The mold has a shape in which a ring-shaped molded body having an outer diameter of 40 mm, an inner diameter of 25 mm, and a height of 6 mm is formed. Next, the mold was heated to 290 ° C. and left at 290 ° C. for 1 minute to thermally decompose zinc caprylate. After returning the mold to room temperature, pressure was applied to the iron powder in the mold at a pressure increase rate of 10 MPa / min to form a dust core. The pressurization was stopped when the repulsive force received by the press machine became maximum, and a dust core was produced. When 2.4 g of zinc caprylate is thermally decomposed and covered with 200 g of iron powder and covered with zinc oxide fine particles, the volume ratio of the zinc oxide fine particles to the powder magnetic core is as small as 0.3%.
Next, the manufactured dust core was observed and analyzed. The dust core was cut into two in the thickness direction, and the cut surface was observed with an electron microscope. The electron microscope used was an ultra-low acceleration voltage SEM from JFE Techno-Research Corporation. This apparatus is capable of observation with an extremely low acceleration voltage from 100 V, and has a feature that the sample can be directly observed without forming a conductive film on the sample.
First, a secondary electron beam between 900-1000 V of the reflected electron beam was taken out, image processing was performed, and the cut surface was observed. It was confirmed that granular fine particles having various sizes ranging from 5 to 60 nm completely filled the gaps of the magnetic powder, and voids having a size of 4 nm or less were randomly formed in many places. . In addition, there are 30-40 granular fine particles of various sizes where the adjacent iron powder is closest, and 50-100 granular fine particles of various sizes are present where the iron powder is surrounded. Were present. Next, the energy and intensity of characteristic X-rays were subjected to image processing, and the types of elements constituting the particulate particles and their distribution states were analyzed. It was confirmed that both zinc atoms and oxygen atoms were uniformly dispersed and there was no particular uneven distribution, and that the zinc oxide granular fine particles filled the gaps in the iron powder evenly. FIG. 1 schematically shows an enlarged view of a part of the cut surface. 1 is iron powder and 2 is fine particles of zinc oxide.
Next, the powder density, specific resistance, magnetic flux density, and iron loss were measured for the powder magnetic core. The green compact density was calculated from these values by measuring the dimensions and weight of the sample. The specific resistance was measured by the four probe method. The magnetic flux density is a magnetic flux density B at a magnetic core size of 10 kA / m, using a coil with a powder core having a formal coated conductor having a diameter of 0.6 mm on the primary side and 100 turns on the primary side and 20 turns on the secondary side. evaluated. The iron loss is obtained by using a coil having a powder core having 40 turns of a formal coated conductor having a diameter of 0.6 mm on the primary side and 40 turns on the secondary side, and a frequency of 200-10 kHz and a magnetic flux density B of 0.2 T. Measurement was performed using a magnetic property measuring apparatus manufactured by Sumitomo Metal Technology Co., Ltd. In addition, the numerical value of the iron loss was represented by a value with an excitation frequency of 5 kHz and an excitation magnetic flux density of 0.2T.
The density of the dust core is 7.56 kg / m 3, which is close to the iron density of 7.87 kg / m 3 , which is not inferior to the density of the conventional dust core. The specific resistance is 72 μΩm, which is 720 times the specific resistance of iron powder, and is nearly 30% higher than the conventional dust core. The magnetic flux density is 1.7T, which is close to the magnetic flux density of 2.2T of iron powder and is not inferior to the density of the conventional dust core. The iron loss is 36 W / kg, which is about 80% of a conventional magnetically annealed dust core. Moreover, even if the dust core was dropped from a height of 2 m, the dust core was not broken.
以上の結果から次のことがわかる。第一に、密度が鉄粉の密度に近く、磁束密度が鉄粉の磁束密度に近いため、鉄粉を覆う金属酸化物の微粒子の存在が、鉄粉の再配列に貢献している。第二に、比抵抗が鉄粉の７２０倍もあり、様々な大きさの金属酸化物の微粒子が稠密構造で鉄粉を覆い、鉄粉の絶縁化に貢献している。第三に、鉄損が焼鈍処理を行った従来の圧粉磁心に比べ低下し、鉄粉に加工歪が存在しないことを裏付けている。これによって、磁気焼鈍の処理が不要になることが裏付けられた。従って、本発明の圧粉磁心の製造方法によれば、従来の圧粉磁心より著しく安価な圧粉磁心が製造できる。
以上に説明したように、鉄粉の平均粒径より３桁も小さく、鉄粉より硬度が低い金属酸化物の微粒子で鉄粉を覆い、この鉄粉の集まりに徐々に増大する圧縮応力を加えると、次の現象が起こることが裏付けられた。圧縮時に鉄粉同士が接触しないため、鉄粉の移動が容易になり、鉄粉が微粒子を伴って移動し、鉄粉が再配列する。また、酸化亜鉛の微粒子が圧粉磁心に占める体積割合は、０．３％と極めて少ない。これによって、圧粉磁心の密度と磁束密度とが高まった。次に、大きさが数ナノ程度になるまで微粒子の破壊が進み、鉄粉が様々な大きさからなる微粒子で隙間なく覆われ、空孔が数ナノの大きさに縮減される。これによって、圧粉磁心の絶縁抵抗が増大した。さらに、圧粉磁心を構成する鉄粉に加工歪が存在しないため、鉄損が低下した。また、全ての微粒子同士が摩擦接合するとともに、鉄粉の表面に微粒子が摩擦接合するため、圧粉磁心は必要な機械的強度を持った。
From the above results, the following can be understood. First, since the density is close to the density of the iron powder and the magnetic flux density is close to the magnetic flux density of the iron powder, the presence of metal oxide fine particles covering the iron powder contributes to the rearrangement of the iron powder. Second, the resistivity is 720 times that of iron powder, and metal oxide fine particles of various sizes cover the iron powder in a dense structure, contributing to the insulation of the iron powder. Thirdly, the iron loss is lower than that of the conventional dust core subjected to the annealing treatment, which confirms that there is no processing strain in the iron powder. This proved that the magnetic annealing treatment is not necessary. Therefore, according to the method for manufacturing a dust core of the present invention, a dust core that is significantly less expensive than a conventional dust core can be manufactured.
As described above, the iron powder is covered with metal oxide fine particles that are three orders of magnitude smaller than the average particle diameter of the iron powder and lower in hardness than the iron powder, and a gradually increasing compressive stress is applied to the aggregate of the iron powder. It was confirmed that the following phenomenon occurred. Since the iron powders do not come into contact with each other at the time of compression, the movement of the iron powder becomes easy, the iron powder moves with the fine particles, and the iron powder rearranges. Further, the volume ratio of the zinc oxide fine particles to the powder magnetic core is as extremely low as 0.3%. As a result, the density of the dust core and the magnetic flux density increased. Next, the destruction of the fine particles proceeds until the size reaches several nanometers, the iron powder is covered with fine particles having various sizes without gaps, and the pores are reduced to a size of several nanometers. This increased the insulation resistance of the dust core. Furthermore, since there was no processing strain in the iron powder constituting the dust core, the iron loss was reduced. Moreover, since all the fine particles were friction-bonded and the fine particles were friction-bonded to the surface of the iron powder, the dust core had the necessary mechanical strength.
１ 鉄粉 ２ 酸化亜鉛の微粒子
1
Claims (4)
The method for manufacturing a dust core according to claim 1, wherein the metal oxide is any metal oxide made of copper oxide CuO or zinc oxide ZnO. .
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| JP2021082717A (en) * | 2019-11-19 | 2021-05-27 | 小林 博 | Method for manufacturing powder magnetic core obtained by connecting soft magnetic powders with friction bonding of aluminum oxide fine particles by insulating soft magnetic powder with aggregate of aluminum oxide powders |
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| JP2021082717A (en) * | 2019-11-19 | 2021-05-27 | 小林 博 | Method for manufacturing powder magnetic core obtained by connecting soft magnetic powders with friction bonding of aluminum oxide fine particles by insulating soft magnetic powder with aggregate of aluminum oxide powders |
| JP7253202B2 (en) | 2019-11-19 | 2023-04-06 | 博 小林 | A method for producing a powder magnetic core, in which soft magnetic flat powder is insulated with a group of aluminum oxide fine particles, and the soft magnetic flat powder is bonded by friction bonding of the aluminum oxide fine particles. |
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