JP2013093148A - Microwave furnace, porous body, and soft magnetic pressed powder core material - Google Patents
Microwave furnace, porous body, and soft magnetic pressed powder core material Download PDFInfo
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本発明は、マイクロ波加熱炉及びこの炉により製造される多孔質体、軟磁性圧粉コア材料に関する。 The present invention relates to a microwave heating furnace, a porous body produced by the furnace, and a soft magnetic powder core material.
マイクロ波加熱は従来、電子レンジに代表されるように、水分を含む食品の急速加熱・急速乾燥に主に用いられてきた。これまで、電子レンジにより加熱できるのは、誘電体のみと考えられてきたが、近年、金属なども粉末であれば加熱できることが解ってきた。マイクロ波による金属粉末加熱のメカニズムは主として、誘導加熱と磁性損失と磁気共鳴によるものである。通常の電子レンジタイプの炉の場合、金属粉末の加熱では、マイクロ波加熱の特徴である高速加熱ができないことがある。これは、大部分の金属粉末はマイクロ波の磁場によって加熱されやすく、電子レンジに代表されるマルチモードタイプの炉では、炉内の電磁界分布がランダムで、試料に充分な磁場が印加されない場合があるためである。 Conventionally, microwave heating has been mainly used for rapid heating and rapid drying of water-containing foods, as represented by microwave ovens. So far, it has been considered that only a dielectric can be heated by a microwave oven. However, in recent years, it has been understood that a metal or the like can be heated if it is a powder. The mechanism of the metal powder heating by microwave is mainly due to induction heating, magnetic loss and magnetic resonance. In the case of a normal microwave oven, high-speed heating, which is a feature of microwave heating, may not be performed when metal powder is heated. This is because most metal powders are easily heated by a microwave magnetic field, and in a multimode type furnace represented by a microwave oven, the electromagnetic field distribution in the furnace is random and a sufficient magnetic field is not applied to the sample. Because there is.
一方、シングルモードタイプの炉では、炉内で特定の電磁界モードのみのマイクロ波を伝搬させる。そのため、炉内に強電界域あるいは強磁界域を作ることができ、殆どの金属粉末を高速に加熱することができる。シングルモードタイプの炉は、金属粉末の加熱において極めて有用なツールである。しかしながら、一般に使用可能なマイクロ波の周波数は２.４５ＧＨｚであるため、従来のシングルモードタイプの炉は小型のサンプルの処理にしか対応できない。例えば特許文献１には、１０００ＭＨｚ前後の周波数の低いマイクロ波源を用いることで、より広いワークゾーンを確保できることが開示されている。 On the other hand, in a single mode type furnace, microwaves of only a specific electromagnetic field mode are propagated in the furnace. Therefore, a strong electric field region or a strong magnetic field region can be created in the furnace, and most metal powder can be heated at high speed. Single mode furnaces are extremely useful tools for heating metal powders. However, since the microwave frequency that can be generally used is 2.45 GHz, the conventional single-mode type furnace can only handle a small sample. For example, Patent Document 1 discloses that a wider work zone can be secured by using a microwave source having a low frequency of about 1000 MHz.
しかし上記特許文献のものでは、大型試料を加熱しようとして１０００ＭＨｚ前後の炉を使用する場合、設備も大規模化する。しかも単純に設備を大きくしても、大型試料が同程度の強度の電磁界域に収まるように電磁界の強度分布を広げることは困難である。特に複雑な形状であるリング状の試料を大型化する場合に、強い電磁場域から試料の一部がはみ出ることで加熱ムラが生じ易いという課題がある。 However, in the above-mentioned patent document, when a furnace of about 1000 MHz is used to heat a large sample, the facilities are also enlarged. Moreover, even if the equipment is simply enlarged, it is difficult to widen the electromagnetic field intensity distribution so that the large sample can be accommodated in the electromagnetic field region of the same intensity. In particular, when a ring-shaped sample having a complicated shape is enlarged, there is a problem that uneven heating tends to occur due to a part of the sample protruding from a strong electromagnetic field region.
本発明の目的は、リング状の大型試料を加熱する際の加熱ムラを抑制することにある。 An object of the present invention is to suppress heating unevenness when a ring-shaped large sample is heated.
被加熱体が収容される内部空間を有する加熱部と、前記内部空間へマイクロ波を照射するマグネトロンとを備えたマイクロ波加熱炉において、前記加熱部は、金属製の円筒形状の外側導体と、前記内部空間を介して前記外側導体の内部に設けられた金属製の円柱又は円筒形状の内側導体とを備えることを特徴とする。 In a microwave heating furnace including a heating unit having an internal space in which an object to be heated is accommodated, and a magnetron that irradiates the internal space with microwaves, the heating unit includes a metal cylindrical outer conductor, A metal columnar or cylindrical inner conductor provided inside the outer conductor via the inner space.
本発明によれば、リング状の大型試料を加熱する際の加熱ムラを抑制することができる。 According to the present invention, heating unevenness when heating a ring-shaped large sample can be suppressed.
導波管によって導波される電磁界は、ＴＥＭ（transverse electromagnetic）モード、ＴＥ（transverse electric）モード、ＴＭ（transverse magnetic）モードに分けることができる。マイクロ波の伝搬方向をｚ方向とすると、各モードにおける電界Ｅzと磁界Ｈzは次のようになる。
ＴＥＭモード：Ｅz＝Ｈz＝０
ＴＥモード：Ｅz＝０，Ｈz≠０
ＴＭモード：Ｅz≠０，Ｈz＝０
The electromagnetic field guided by the waveguide can be divided into a TEM (transverse electromagnetic) mode, a TE (transverse electric) mode, and a TM (transverse magnetic) mode. If the propagation direction of the microwave is the z direction, the electric field E z and the magnetic field H z in each mode are as follows.
TEM mode: E z = H z = 0
TE mode: E z = 0, H z ≠ 0
TM mode: E z ≠ 0, H z = 0
従来のシングルモードタイプの炉では、一般に矩形導波管を用い、例えばＴＥ10モードにより形成される強磁界域あるいは強電界域を試料の加熱に利用する。例えば断面積８０mm×８０mmの導波管で形成される強磁界域あるいは強電界域を利用すると、加熱ムラを抑制しながら処理できる試料の大きさはおよそ２０mm×２０mm×２０mm程度である。 In a conventional single mode type furnace, a rectangular waveguide is generally used. For example, a strong magnetic field region or a strong electric field region formed by the TE 10 mode is used for heating the sample. For example, when a strong magnetic field region or a strong electric field region formed by a waveguide having a cross-sectional area of 80 mm × 80 mm is used, the size of a sample that can be processed while suppressing heating unevenness is approximately 20 mm × 20 mm × 20 mm.
本発明では、従来、マイクロ波の伝送方法として利用されている同軸ケーブルのケーブル内に分布する電磁界を加熱炉として応用する。同軸ケーブルは従来、受信アンテナなどの信号の送電線などに用いられ、加熱炉などの大出力のエネルギ送電に用いられることは無い。一般の同軸ケーブルは、中心導線の周りにそれを支持するポリエチレンなどの絶縁物で覆われ、さらにその外部が導体で覆われている。 In the present invention, an electromagnetic field distributed in a coaxial cable that has been conventionally used as a microwave transmission method is applied as a heating furnace. Conventionally, a coaxial cable is used for a signal transmission line such as a receiving antenna, and is not used for high-power energy transmission such as a heating furnace. A general coaxial cable is covered with an insulator such as polyethylene that supports the central conductor around the center conductor, and the outside is covered with a conductor.
本発明では、例えば２.４５ＧＨｚのシングルモードタイプの定在波炉で、外側導体３と内側導体４の各々の中心軸が同軸となるようにこれらの導体を配置することで、内側導体４に対して軸対称に発生する強磁界域あるいは強電界域の何れかを試料の加熱に利用する。電磁界の強度分布は軸対称になり、リング状の試料であっても電磁界が集中するトロイダル状の領域に試料を収容することができるので、加熱ムラを抑制しつつ迅速に加熱することができる。試料を大きくする場合は、外側導体３と内側導体４の径方向寸法を調節することで、試料が同程度の電磁界域に配置されるように調節することができる。これによれば、従来の矩形導波管を用いたシングルモード炉では処理できなかった複雑なリング状の大型試料であっても加熱ムラを抑制しつつ迅速に加熱することができる。 In the present invention, for example, in a single-mode type standing wave furnace of 2.45 GHz, these conductors are arranged so that the central axes of the outer conductor 3 and the inner conductor 4 are coaxial with each other. On the other hand, either a strong magnetic field region or a strong electric field region generated in an axial symmetry is used for heating the sample. The intensity distribution of the electromagnetic field is axisymmetric, and even a ring-shaped sample can be stored in a toroidal region where the electromagnetic field is concentrated, so that heating can be performed quickly while suppressing uneven heating. it can. When enlarging a sample, it can adjust so that a sample may be arrange | positioned in the electromagnetic field area of the same grade by adjusting the radial direction dimension of the outer side conductor 3 and the inner side conductor 4. FIG. According to this, even a complex ring-shaped large sample that could not be processed by a single mode furnace using a conventional rectangular waveguide can be heated quickly while suppressing uneven heating.
なお、本発明において、リング状とは試料が必ずしも周方向につながっていなくてもよく、試料の中心軸を通る断面で試料を切断した際の試料の断面積が場所によって異なっていても良い。また、加熱とは、粉体を成型するための焼結や、成型体の歪みを除去する焼鈍等を示す。 In the present invention, the ring shape does not necessarily mean that the sample is connected in the circumferential direction, and the cross-sectional area of the sample when the sample is cut along a cross section passing through the central axis of the sample may differ depending on the location. Further, heating refers to sintering for molding powder, annealing for removing distortion of the molded body, and the like.
加熱炉の概略を図１に示す。本加熱炉のマイクロ波供給源は２.４５ＧＨｚのマグネトロン１である。加熱部１３は外側導体３、内側導体４、反射体６等から構成される。マグネトロン１から加熱部１３まで、マイクロ波をＴＭ又はＴＥＭモードで伝送する。マグネトロン１から発振されたマイクロ波は、接続導波管２を経由し、加熱部１３に供給される。一般に、情報通信に使用される同軸ケーブルは円筒形状の外側導体がφ５mm程度、内部導体がφ１.５mm程度であるが、本発明の炉は、外側導体３がφ１００mm以上の外径を有する。円筒形状の外側導体３の内部に、外側導体３よりも径の小さい円柱又は円筒形状の内側導体４が設けられ、両者の間は試料（被加熱体）５を設置するため自由空間となっている。外側導体３と内側導体４は共に金属製であり、電気的に絶縁されている。内側導体４はアタッチメントとして、処理する試料５の寸法によりその径を任意に変更することが可能である。外側導体３の内径Ｄと内側導体４の外径ｄの比（内径Ｄ／外径ｄ）は、試料５の支持冶具８や断熱材スペース、炉内電磁界分布を勘案し、１.０５〜３.３３の範囲で与えられる。 An outline of the heating furnace is shown in FIG. The microwave supply source of the heating furnace is a 2.45 GHz magnetron 1. The heating unit 13 includes an outer conductor 3, an inner conductor 4, a reflector 6, and the like. Microwaves are transmitted from the magnetron 1 to the heating unit 13 in TM or TEM mode. The microwave oscillated from the magnetron 1 is supplied to the heating unit 13 via the connection waveguide 2. In general, a coaxial cable used for information communication has a cylindrical outer conductor of about φ5 mm and an inner conductor of about φ1.5 mm. In the furnace of the present invention, the outer conductor 3 has an outer diameter of φ100 mm or more. A cylindrical or cylindrical inner conductor 4 having a diameter smaller than that of the outer conductor 3 is provided inside the cylindrical outer conductor 3, and a sample (heated body) 5 is placed between the two to form a free space. Yes. Both the outer conductor 3 and the inner conductor 4 are made of metal and are electrically insulated. The diameter of the inner conductor 4 can be arbitrarily changed depending on the size of the sample 5 to be processed as an attachment. The ratio of the inner diameter D of the outer conductor 3 to the outer diameter d of the inner conductor 4 (inner diameter D / outer diameter d) is 1.05 considering the support jig 8 of the sample 5, the heat insulating material space, and the electromagnetic field distribution in the furnace. It is given in the range of 3.33.
ＴＥ、ＴＭ、ＴＥＭモードの電界（磁界）分布を図２（ａ）〜（ｃ）に示す。（ａ）ＴＥモードと（ｂ）ＴＭモードについては、Ｚ軸に沿って導体中央を切断した断面の電界（磁界）分布を示し、（ｃ）ＴＥＭモードについては、導体の斜視図における電界（磁界）分布を示す。図中の破線内が最も電界（磁界）の強度が高い。電界と磁界とは導体中の同じ位置で強度が大きくならず、Ｚ方向にいくらかシフトするが、強度分布は同様の傾向を示す。加熱炉内では、マイクロ波の電波モードはＴＭモードあるいはＴＥＭモードとする。ＴＥモードでは、内側導体の近傍の電磁界の強度が大きくなり、外側導体に近づくほど強度が弱くなるので、試料５に効率的にマイクロ波を照射することができない。ＴＭ又はＴＥＭモードにすることで電磁界の分布はトロイダル状になり、外側導体３と内側導体４間の試料５を強電場あるいは強磁場域に置くことができる。 The electric field (magnetic field) distribution in the TE, TM, and TEM modes is shown in FIGS. For (a) TE mode and (b) TM mode, the electric field (magnetic field) distribution of the cross-section cut along the Z axis is shown, and for (c) TEM mode, the electric field (magnetic field) in the perspective view of the conductor. ) Show the distribution. The intensity of the electric field (magnetic field) is highest in the broken line in the figure. The electric field and the magnetic field do not increase in strength at the same position in the conductor and shift somewhat in the Z direction, but the intensity distribution shows the same tendency. In the heating furnace, the microwave radio wave mode is set to TM mode or TEM mode. In the TE mode, the strength of the electromagnetic field in the vicinity of the inner conductor increases, and the strength decreases as the outer conductor is approached. Therefore, the sample 5 cannot be efficiently irradiated with microwaves. By setting the TM or TEM mode, the electromagnetic field distribution becomes toroidal, and the sample 5 between the outer conductor 3 and the inner conductor 4 can be placed in a strong electric field or a strong magnetic field region.
炉内の電磁界分布は、試料５および断熱材１０、炉壁の誘電率、電気抵抗等に影響を受ける。マイクロ波を照射すると、試料５および断熱材１０、炉壁の誘電率も変化するため、炉内の電磁界分布も変化する。電磁界分布が変化した場合、試料５が所望の強電界域あるいは強磁界域から外れ、効率的な加熱ができない場合がある。この場合、炉終端部の反射体６を、筒形状の加熱部１３の軸方向に移動させる。これにより、炉内の空間の体積を増減させて電磁界分布も移動させることができ、試料５を強電界域あるいは強磁界域に置くことができる。反射体６の移動ストロークは、炉内に形成される定在波の１／８以上、好ましくは１／４波長以上とすることで、ほぼ実用的な加熱温度範囲において電磁界分布が変化しても、その分布を補正することが可能となる。 The electromagnetic field distribution in the furnace is affected by the sample 5, the heat insulating material 10, the dielectric constant of the furnace wall, the electrical resistance, and the like. When microwave irradiation is performed, the dielectric constants of the sample 5, the heat insulating material 10, and the furnace wall also change, so that the electromagnetic field distribution in the furnace also changes. When the electromagnetic field distribution changes, the sample 5 may deviate from the desired strong electric field region or strong magnetic field region, and efficient heating may not be possible. In this case, the reflector 6 at the furnace end is moved in the axial direction of the cylindrical heating unit 13. Thereby, the volume of the space in the furnace can be increased or decreased to move the electromagnetic field distribution, and the sample 5 can be placed in a strong electric field region or a strong magnetic field region. The moving stroke of the reflector 6 is set to 1/8 or more of the standing wave formed in the furnace, preferably 1/4 wavelength or more, so that the electromagnetic field distribution changes in a practical temperature range. It is possible to correct the distribution.
マイクロ波中では、熱電対は先端に電界集中して放電しやすいため、マイクロ波プロセスでの温度測定に熱電対は不適である。マイクロ波プロセスでは、放射温度計により試料５の温度が測定される。反射体６には、放射温度計測用ポート９が設けられている。反射体６は炉の中心軸を回転軸として、円周方向に自由に回転できるように構成されることで、試料５の任意の位置の温度を計測することができる。なお、粉末を焼結したい場合は後述するように試料５を容器として試料内に粉末をセットする。炉の設置方向を反射体６が炉上部になる方向に設置すると、粉末をこぼさずに粉末表面の温度を放射温度計で直接測定することができる。 In a microwave, since a thermocouple is likely to discharge due to electric field concentration at the tip, the thermocouple is not suitable for temperature measurement in a microwave process. In the microwave process, the temperature of the sample 5 is measured by a radiation thermometer. The reflector 6 is provided with a radiation temperature measurement port 9. The reflector 6 is configured to be freely rotatable in the circumferential direction with the central axis of the furnace as the rotation axis, so that the temperature at an arbitrary position of the sample 5 can be measured. If the powder is to be sintered, the powder is set in the sample using the sample 5 as a container as described later. When the installation direction of the furnace is set in a direction in which the reflector 6 becomes the upper part of the furnace, the temperature of the powder surface can be directly measured with a radiation thermometer without spilling the powder.
炉は同心円状であり、電磁界も同心円状に発生させることができるため、例えば、圧粉コア材料などのリング状の製品を効率的に加熱することができる。特に、非晶質材などでは加熱により結晶化した際、電界あるいは磁界の振動方向に対して配向するように組織を制御することが可能である。 Since the furnace is concentric and electromagnetic fields can be generated concentrically, for example, a ring-shaped product such as a dust core material can be efficiently heated. In particular, when an amorphous material or the like is crystallized by heating, the structure can be controlled so as to be oriented with respect to the vibration direction of an electric field or a magnetic field.
一般に強磁性体に電磁界が印加されると、渦電流損失とヒステリシス損失による発熱が生じるが、ＧＨｚ帯の電磁界では磁壁の移動が追随しないため、ヒステリシス損失の影響は非常に小さくなる。しかし、ＧＨｚ帯であっても材料系と周波数によっては、磁気共鳴が生じ発熱する場合がある。磁気共鳴周波数は材料の微細構造の影響を受ける。特にひずみが加わり結晶構造の対称性が大きく変化した個所では、磁気共鳴が集中し、局所加熱が起きる可能性がある。鉄系の圧粉コア材料をプレス成形した後に、ひずみ除去するために本発明の炉を用いると、上記のようなヒータ加熱とは異なるメカニズムにより製品が加熱されるため、従来のヒータ加熱よりも優れた磁気特性を発現する。 In general, when an electromagnetic field is applied to a ferromagnetic material, heat is generated due to eddy current loss and hysteresis loss. However, in the GHz band electromagnetic field, domain wall movement does not follow, so the influence of hysteresis loss is very small. However, even in the GHz band, depending on the material system and frequency, magnetic resonance may occur and heat may be generated. The magnetic resonance frequency is affected by the microstructure of the material. In particular, magnetic resonance concentrates and local heating may occur at a location where the symmetry of the crystal structure changes greatly due to strain. When the furnace of the present invention is used to remove strain after press forming iron-based dust core material, the product is heated by a mechanism different from the heater heating as described above. Excellent magnetic properties.
以下、本発明の実施例について説明する。 Examples of the present invention will be described below.
本実施例では、鋳鉄粉末の多孔質体を焼結した。粉末の平均粒径を１５０μｍ程度とした。炉の外側導体３の内径をφ１００mmとし、内側導体４の外径をφ７０mmとした。ここで試料（被加熱体）５は、断熱材１０と、断熱材１０上面の溝に充填された鋳鉄粉末１１と、蓋１２から構成される。断熱材１０はＣを０.５％含む低密度Ａｌ2Ｏ3で形成され、外径φ９５mm／内径φ６５mm×厚さ２０mmである。この上面に、外径φ８５mm、内径φ７５mm、深さ７mmの溝が形成され、この溝に鋳鉄粉末１１をタッピングにより充填した。溝に充填された鋳鉄粉末１１の見掛け密度はおよそ３ｇ／mm3である。粉末を焼結する場合は、試料５と支持冶具８とが粉末の支持部材となる。 In this example, a porous body of cast iron powder was sintered. The average particle size of the powder was about 150 μm. The inner diameter of the outer conductor 3 of the furnace was φ100 mm, and the outer diameter of the inner conductor 4 was φ70 mm. Here, the sample (object to be heated) 5 includes a heat insulating material 10, cast iron powder 11 filled in a groove on the upper surface of the heat insulating material 10, and a lid 12. The heat insulating material 10 is made of low-density Al 2 O 3 containing 0.5% of C, and has an outer diameter of 95 mm / inner diameter of 65 mm × thickness of 20 mm. A groove having an outer diameter of φ85 mm, an inner diameter of φ75 mm, and a depth of 7 mm was formed on the upper surface, and the cast iron powder 11 was filled into the groove by tapping. The apparent density of the cast iron powder 11 filled in the groove is about 3 g / mm 3 . In the case of sintering powder, the sample 5 and the support jig 8 are powder support members.
図３は炉内の試料５の構造を説明する図であり、粉末を試料５内に充填し、試料５を炉内にセッティングした状態を示す。鋳鉄粉末１１を充填した断熱材１０には、断熱材１０と同材質の断熱材を蓋１２として載せた。試料温度を放射温度計で測定する際に、放射温度計の視野を確保するため、蓋１２には約３０°間隔で放射温度計測用の貫通穴７を設けた。 FIG. 3 is a diagram for explaining the structure of the sample 5 in the furnace, and shows a state in which the powder is filled in the sample 5 and the sample 5 is set in the furnace. On the heat insulating material 10 filled with the cast iron powder 11, a heat insulating material of the same material as the heat insulating material 10 was placed as a lid 12. When the sample temperature was measured with a radiation thermometer, the lid 12 was provided with through-holes 7 for measuring the radiation temperature at intervals of about 30 ° in order to ensure the field of view of the radiation thermometer.
焼結条件は、雰囲気をＮ2ガス、目標温度を１０５０〜１０６０℃とした。また、初期マイクロ波出力を１ｋＷとし、加熱状況を見ながら出力を調整した。試料５には強電場が印加されるよう初期位置を反射体の初期位置を調整した。温度の測定は放射温度計により行い、設定放射率は１.０とした。加熱処理中、温度上昇が緩慢になった場合は反射体６を移動し、昇温速度が最大となるよう制御した。１０００℃以上に加熱されたとき、反射体６を周方向に回転させ、１２点の試料位置で温度を測定し、温度差が±２０℃程度であることを確認した。また、比較のため、同様の断熱材にセッティングした鋳鉄粉末を通常のマルチモード炉により焼結した。 The sintering conditions were an atmosphere of N 2 gas and a target temperature of 1050 to 1060 ° C. Moreover, the initial microwave output was set to 1 kW, and the output was adjusted while observing the heating state. The initial position of the reflector was adjusted so that the sample 5 was applied with a strong electric field. The temperature was measured with a radiation thermometer, and the set emissivity was 1.0. During the heat treatment, when the temperature rise slowed, the reflector 6 was moved and controlled so that the rate of temperature rise was maximized. When heated to 1000 ° C. or higher, the reflector 6 was rotated in the circumferential direction, the temperature was measured at 12 sample positions, and it was confirmed that the temperature difference was about ± 20 ° C. For comparison, cast iron powder set on the same heat insulating material was sintered in a normal multimode furnace.
焼結時の加熱時の昇温状況と、焼結結果を表１に示す。一般のマルチモード炉での加熱と比較すると、本実施例の炉は１.０ｋＷの低い出力でも目標温度に達し、一般のマルチモード炉の約５倍の加熱速度を得た。本実施例の炉で焼結したリングは、焼結による収縮が殆どなく、ほぼ充填した形状のまま焼結させることができた。加熱後の試料は充分ハンドリングでき、リング全周にわたり良好な焼結状態であった。一方、マルチモード炉で焼結した試料では加熱ムラが激しく、試料の一部は溶融により凝集し、リング状の製品が得られなかった。本実験により、本実施例の炉は低出力でかつ効率的に粉末を焼結することができることが確認された。 Table 1 shows the temperature rise during heating during sintering and the sintering results. Compared to heating in a general multimode furnace, the furnace of this example reached the target temperature even at a low power of 1.0 kW, and a heating rate about 5 times that of a general multimode furnace was obtained. The ring sintered in the furnace of this example was hardly shrunk by sintering, and could be sintered in a substantially filled shape. The sample after heating could be handled sufficiently and was in a good sintered state over the entire circumference of the ring. On the other hand, in the sample sintered in the multimode furnace, the heating unevenness was severe, and a part of the sample was agglomerated by melting, and a ring-shaped product was not obtained. From this experiment, it was confirmed that the furnace of this example can sinter the powder efficiently with low power.
マイクロ波で粉末を焼結させると、粉末の接触部分のみ反応するため、焼結させても体積が減少しにくい。つまり、粉末間の空隙が残ったままの多孔質焼結体を生成することができるので、その焼結体に金属等を含侵させる場合は含侵率を高めることができる。 When the powder is sintered with microwaves, only the contact portion of the powder reacts, so that the volume is difficult to decrease even if the powder is sintered. That is, since a porous sintered body can be produced with the voids between the powders remaining, the impregnation rate can be increased when the sintered body is impregnated with metal or the like.
本実施例では、鉄系の圧粉コアを焼鈍した。試料原料は純鉄粉末とし、その表面にリン酸コートを施し、圧粉成形圧を１２００ＭＰａとして外径φ８０mm／内径φ６０mm×厚さ５mmの圧粉コアを作製した。作製した軟磁性圧粉コア材料は、本実施例の炉と通常のヒータ加熱炉により焼鈍処理をし、それぞれ磁性特性を評価した。 In this example, an iron-based dust core was annealed. The raw material of the sample was pure iron powder, and the surface thereof was coated with phosphoric acid, and a dust core with an outer diameter of φ80 mm / inner diameter of φ60 mm × thickness of 5 mm was prepared with a compacting pressure of 1200 MPa. The produced soft magnetic powder core material was annealed by the furnace of this example and a normal heater heating furnace, and the magnetic properties were evaluated.
焼鈍条件は、雰囲気を大気中、ヒータ加熱では目標温度を５５０℃、保持時間を１０minとした。マイクロ波加熱では目標温度５００℃、保持時間０minとした。マイクロ波加熱では放射温度計で温度を測定し、放射率は１.０とした。本実施例のマイクロ波で加熱する際は、断熱材１０は使用せず、ＳｉＯ2製の支持冶具８の上に圧粉コアを直接置いた。圧粉コアには強磁場が印加されるよう初期位置を調整した。マイクロ波の出力は約５００Ｗとし、目標温度に到達後に直ちに出力を切り炉を冷却した。本実施例の炉の外側導体の内径はφ１００mmとし、内部導体の外径はφ７０mmとした。コア材料は、鉄系結晶材料または非晶質材料、あるいは結晶と非晶質が混ざりあったものでも良い。 As for the annealing conditions, the atmosphere was air, the target temperature was 550 ° C., and the holding time was 10 minutes for heater heating. In microwave heating, the target temperature was 500 ° C. and the holding time was 0 min. In microwave heating, the temperature was measured with a radiation thermometer, and the emissivity was set to 1.0. When heating with the microwave of the present embodiment, the heat insulating material 10 was not used, and the dust core was directly placed on the support jig 8 made of SiO 2 . The initial position was adjusted so that a strong magnetic field was applied to the dust core. The output of the microwave was about 500 W, and immediately after reaching the target temperature, the output was turned off and the furnace was cooled. The inner diameter of the outer conductor of the furnace of this example was 100 mm, and the outer diameter of the inner conductor was 70 mm. The core material may be an iron-based crystal material or an amorphous material, or a mixture of crystal and amorphous.
マイクロ波およびヒータ加熱後の各圧粉コアの（４００Ｈｚにおける）磁気特性評価結果を表２に示す。渦電流損（渦損）の比較では、マイクロ波加熱とヒータ加熱に大きな差は認められないが、ヒステリシス損（ヒス損）の比較では、マイクロ波加熱の方が損失は小さかった。マイクロ波を用いて磁場中で加熱すると、従来のヒータ加熱と異なるメカニズムで加熱されるため、ひずみ除去効果が発揮される。また、本実施例の炉を使用した場合、焼鈍処理に要する時間は約３分程度であり、ヒータ加熱の１／１０以下であり、処理工程の短縮においても有効である。 Table 2 shows the magnetic property evaluation results (at 400 Hz) of the powder cores after heating with the microwave and the heater. In the comparison of eddy current loss (eddy loss), there is no significant difference between microwave heating and heater heating, but in the comparison of hysteresis loss (hist loss), the loss was smaller in microwave heating. When heated in a magnetic field using microwaves, the effect of removing strain is exhibited because it is heated by a mechanism different from conventional heater heating. Further, when the furnace of the present embodiment is used, the time required for the annealing process is about 3 minutes, which is 1/10 or less of the heater heating, which is effective in shortening the processing process.
１ マグネトロン
２ 接続導波管
３ 外側導体
４ 内側導体
５ 試料（被加熱体）
６ 反射体
７ 貫通穴
８ 支持冶具
９ 放射温度計測用ポート
１０ 断熱材
１１ 鋳鉄粉末
１２ 蓋
１３ 加熱部
DESCRIPTION OF SYMBOLS 1 Magnetron 2 Connection waveguide 3 Outer conductor 4 Inner conductor 5 Sample (to-be-heated body)
6 Reflector 7 Through-hole 8 Support jig 9 Radiation temperature measurement port 10 Heat insulating material 11 Cast iron powder 12 Lid 13 Heating part
Claims (9)
前記加熱部は、金属製の円筒形状の外側導体と、前記内部空間を介して前記外側導体の内部に設けられた金属製の円柱又は円筒形状の内側導体とを備えることを特徴とするマイクロ波加熱炉。 In a microwave heating furnace including a heating unit having an internal space in which an object to be heated is accommodated, and a magnetron that irradiates the internal space with microwaves,
The heating section includes a metal cylindrical outer conductor and a metal columnar or cylindrical inner conductor provided inside the outer conductor via the inner space. heating furnace.
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