JP2007162064A - Method of manufacturing magnetostriction material powder, and method of manufacturing magnetostrictor - Google Patents
Method of manufacturing magnetostriction material powder, and method of manufacturing magnetostrictor Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 45
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 68
- 239000001257 hydrogen Substances 0.000 claims abstract description 67
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- 230000000052 comparative effect Effects 0.000 description 9
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Abstract
Description
本発明は、磁歪材料粉末の製造方法に関し、前記製造方法により得られた磁歪材料粉末を用いた粉末冶金法による磁歪素子の製造方法に関する。 The present invention relates to a method for producing a magnetostrictive material powder, and relates to a method for producing a magnetostrictive element by powder metallurgy using the magnetostrictive material powder obtained by the production method.
例えば、Ｔｂ−Ｄｙ−Ｆｅ系金属間化合物等からなる磁歪材料（いわゆる超磁歪材料）は、従来のフェライト系磁歪材料等に比べて高い磁歪特性を有することから、近年、その需要は益々拡大する傾向にある。具体的な用途としては、リニアアクチュエータ、振動子、圧力トルクセンサ、振動センサ、ジャイロセンサ等である。リニアアクチュエータや振動子等に用いた場合、磁歪素子は、付与する磁界の変化に伴い寸法が変化し、駆動力を発生する。圧力トルクセンサ、振動センサ、ジャイロセンサ等に用いた場合、磁歪素子は、外部から加わる力の変化に伴い透磁率が変化し、これをセンシングすることで圧力、トルク、振動等が検出される。 For example, a magnetostrictive material (so-called super magnetostrictive material) made of a Tb—Dy—Fe intermetallic compound or the like has higher magnetostriction characteristics than a conventional ferrite magnetostrictive material, and therefore, the demand thereof has been increasing more and more in recent years. There is a tendency. Specific applications include linear actuators, vibrators, pressure torque sensors, vibration sensors, gyro sensors, and the like. When used in a linear actuator, a vibrator, or the like, the magnetostrictive element changes its size in accordance with the change in the applied magnetic field and generates a driving force. When used in a pressure torque sensor, vibration sensor, gyro sensor, or the like, the magnetostrictive element changes its magnetic permeability with a change in force applied from the outside, and pressure, torque, vibration, etc. are detected by sensing this.
このような磁歪材料の製造法としては、単結晶育成法が有効であることが従来から知られているが、単結晶育成法は極めて生産性が低く、形状の自由度も大幅に制限されるという欠点がある。そこで、単結晶育成法の欠点を改善し、低コストな製造を可能とするために、粉末冶金法による磁歪材料の製造が検討されている。粉末冶金法においては、基本的には、原料合金粉末を秤量及び混合し、所定の形状に加圧成形し、得られた成形体について焼結を行い、必要に応じて後加工処理を施すことにより磁歪材料が焼結体として製造される。 As a method for producing such a magnetostrictive material, it has hitherto been known that a single crystal growth method is effective, but the single crystal growth method is extremely low in productivity and the degree of freedom of shape is greatly limited. There is a drawback. Therefore, in order to improve the drawbacks of the single crystal growth method and enable low-cost production, production of magnetostrictive materials by powder metallurgy is being studied. In the powder metallurgy method, basically, the raw material alloy powder is weighed and mixed, pressed into a predetermined shape, the resulting molded body is sintered, and post-processing is performed as necessary. Thus, the magnetostrictive material is manufactured as a sintered body.
超磁歪材料を粉末冶金法により製造する方法としては、例えば、最終組成の合金を粉砕し、磁場中成形した後、Ａｒガス等の不活性ガス中で焼結する方法が提案されている（例えば、特許文献１等参照。）。しかしながら、最終組成の合金をそのまま粉砕して得られる原料粉末は磁場中での結晶の配向が悪く、磁歪値が低くなり、かつ焼結体密度が低くなるという不都合がある。 As a method for producing a giant magnetostrictive material by a powder metallurgy method, for example, a method is proposed in which an alloy having a final composition is pulverized, molded in a magnetic field, and then sintered in an inert gas such as Ar gas (for example, , See Patent Document 1). However, the raw material powder obtained by pulverizing the alloy having the final composition as it is has the disadvantages that the crystal orientation in the magnetic field is poor, the magnetostriction value is low, and the sintered body density is low.
この点を改善する手法としては、出発原料を、主相組成を与える原料粉末（例えばＴｂｙＤｙ１−ｙＦｅｚ（ただし、ｚ：１．７〜２．１））と、希土類リッチな原料粉末（（ＴｂｙＤｙ１−ｙ）２Ｆｅ）との２種類に分け、それぞれ粉砕した後、混合する方法が挙げられる。焼結体密度を高める観点では、前記希土類リッチな原料粉末を極力小さく粉砕することが望まれる。ただし、希土類リッチな合金粉末は展性及び延性に富むため、通常の機械的粉砕手法による微粉化は難しい。 In order to improve this point, the starting material is a raw material powder that gives the main phase composition (for example, Tb y Dy 1-y Fe z (where z is 1.7 to 2.1)) and a rare earth-rich raw material. There is a method in which the powder is divided into two types ((Tb y Dy 1-y ) 2 Fe), pulverized, and mixed. From the viewpoint of increasing the density of the sintered body, it is desired to pulverize the rare earth-rich raw material powder as small as possible. However, since rare earth-rich alloy powders are rich in malleability and ductility, it is difficult to pulverize them by a normal mechanical grinding method.
そこで、特許文献２等においては、希土類リッチな原料粉末をガスアトマイズ法等のような特殊な方法で粉砕し、粉砕後の２種類の粉末を混合した後にジェットミルで粉砕する技術が提案されている。具体的には、主相形成用合金粉末として、ＲＥＦｅ２なる組成の合金鋳塊を粉砕して得られる第一の粉末を用いる一方、液相組成合金粉末として、ガスアトマイズ法等によって調製された、前記ＲＥとＦｅの共晶組成を有する第二の粉末を用い、それらを混合せしめた後、微粉末と為し、磁場プレスにより圧粉体を形成した後、焼結している。
しかしながら、前記特許文献２に記載されるようにガスアトマイズ法を採用したとしても、ＲＥとＦｅの共晶組成を有するような希土類リッチな粉末を微粉砕することは難しい。例えば粒径５０μｍ程度の粗大な粉末しか得られないのが実際であり、したがって、焼結体密度の向上には限界がある。また、不活性ガス中でのガスアトマイズ法等はコストが高いという欠点がある。 However, even if the gas atomization method is employed as described in Patent Document 2, it is difficult to finely pulverize a rare earth-rich powder having an eutectic composition of RE and Fe. For example, only a coarse powder having a particle size of about 50 μm is actually obtained, and therefore there is a limit to improving the density of the sintered body. In addition, the gas atomization method in an inert gas has a drawback of high cost.
また、前記希土類リッチな合金粉末における遷移金属Ｆｅの一部をＣｏ又はＮｉで置換することにより、機械粉砕し易い状態とする技術も知られているが、Ｃｏは磁気異方性が大きくなるため磁歪特性を低下させ、Ｎｉはキュリー温度を低下させるという問題がある。また、Ｃｏ及びＮｉのいずれも高価であるというデメリットもある。 In addition, there is known a technique that makes part of the transition metal Fe in the rare earth-rich alloy powder partly replaced with Co or Ni to make it easy to mechanically pulverize, but Co has a large magnetic anisotropy. There is a problem that the magnetostrictive characteristics are lowered, and Ni lowers the Curie temperature. Moreover, there is a demerit that both Co and Ni are expensive.
そこで本発明はこのような従来の実情に鑑みて提案されたものであり、特殊な粉砕法を用いることなく密度の高い焼結体を得ることができ、しかも得られる焼結体において磁歪特性の低下を抑えることが可能な磁歪材料粉末の製造方法を提供することを目的とする。また、本発明は、前記磁歪材料粉末の製造方法により得られた磁歪材料粉末を用いた磁歪素子の製造方法を提供することを目的とする。 Therefore, the present invention has been proposed in view of such a conventional situation, and a high-density sintered body can be obtained without using a special pulverization method, and the obtained sintered body has magnetostrictive characteristics. It is an object of the present invention to provide a method for producing a magnetostrictive material powder capable of suppressing the decrease. Another object of the present invention is to provide a method for producing a magnetostrictive element using the magnetostrictive material powder obtained by the method for producing a magnetostrictive material powder.
前述の目的を達成するために、本発明に係る磁歪材料粉末の製造方法は、水素吸蔵処理が施された（ＴｂｙＤｙ１−ｙ）２Ｆｅ（ただし、０≦ｙ≦１である。）で表される原料粉末Ｂを真空中で加熱保持する脱水素工程と、前記脱水素工程後、前記原料粉末ＢをＴｂｖＤｙ１−ｖＦｅｗ（ただし、０≦ｖ≦１であり、１．７≦ｗ≦２．１である。）で表される原料粉末Ａと混合し、ＴｂｘＤｙ１−ｘＦｅｚ（ただし、０．２７≦ｘ≦０．３５であり、１．２７≦ｚ≦２．１である。）で表される磁歪材料粉末を得る混合工程とを有することを特徴とする。 In order to achieve the above-described object, the method for producing a magnetostrictive material powder according to the present invention has been subjected to hydrogen storage treatment (Tb y Dy 1-y ) 2 Fe (where 0 ≦ y ≦ 1). And after the dehydrogenation step, the raw material powder B is converted to Tb v Dy 1-v Fe w (where 0 ≦ v ≦ 1 and 1 0.7 ≦ w ≦ 2.1.) And mixed with a raw material powder A represented by Tb x Dy 1-x Fe z (where 0.27 ≦ x ≦ 0.35 and 1.27 ≦ z ≦ 2.1.) and a mixing step for obtaining a magnetostrictive material powder represented by the following formula.
また、本発明に係る磁歪素子の製造方法は、前記製造方法により得られた磁歪材料粉末を磁場中成形し、焼成することを特徴とする。 The magnetostrictive element manufacturing method according to the present invention is characterized in that the magnetostrictive material powder obtained by the above manufacturing method is molded in a magnetic field and fired.
出発原料として用いる原料粉末のうち、（ＴｂｙＤｙ１−ｙ）２Ｆｅで表される希土類リッチな原料粉末Ｂについては、水素吸蔵処理により脆化させ、通常の機械粉砕により粉砕可能な状態とする。このことにより（ＴｂｙＤｙ１−ｙ）２Ｔで表される原料粉末の微粉砕が実現され、これを原料粉末Ａ等と混合することで、密度の高い焼結体（磁歪素子）の作製に好適な磁歪材料粉末が得られる。 Among the raw material powders used as starting raw materials, the rare earth-rich raw material powder B represented by (Tb y Dy 1-y ) 2 Fe is embrittled by hydrogen storage treatment and pulverized by ordinary mechanical pulverization. To do. As a result, fine pulverization of the raw material powder represented by (Tb y Dy 1-y ) 2 T is realized, and this is mixed with the raw material powder A or the like to produce a high-density sintered body (magnetostrictive element). Can be obtained.
ところで、前記水素吸蔵処理により（ＴｂｙＤｙ１−ｙ）２Ｔで表される原料粉末Ｂ中に水素が含まれることになるが、この水素は、結晶成長を抑制し、磁歪特性を低下させる原因となる。そこで、原料粉末Ｂから水素を除去する必要がある。例えば熱処理により水素を強制的に放出させることが考えられるが、通常の熱処理により原料粉末Ｂから水素を放出させることは難しい。また、水素量を充分に低減させるためには熱処理を高温で行えばよいものの、原料粉末Ｂは融点が低いため、加熱温度を高めると原料粉末Ｂが溶融することがある。 By the way, although hydrogen is contained in the raw material powder B represented by (Tb y Dy 1-y ) 2 T by the hydrogen storage treatment, this hydrogen suppresses crystal growth and lowers magnetostriction characteristics. Cause. Therefore, it is necessary to remove hydrogen from the raw material powder B. For example, it is conceivable to forcibly release hydrogen by heat treatment, but it is difficult to release hydrogen from the raw material powder B by normal heat treatment. In order to sufficiently reduce the amount of hydrogen, heat treatment may be performed at a high temperature. However, since the raw material powder B has a low melting point, the raw material powder B may melt when the heating temperature is increased.
そこで本発明では真空中で加熱して、原料粉末Ｂから水素を放出させる。このことにより、原料粉末Ｂが溶融しないような比較的低温にて水素を効率的に放出させることが可能となる。結果として、この原料粉末Ｂを含む磁歪材料粉末を用いた磁歪素子において、高い磁歪特性が実現される。 Therefore, in the present invention, hydrogen is released from the raw material powder B by heating in vacuum. This makes it possible to efficiently release hydrogen at a relatively low temperature so that the raw material powder B does not melt. As a result, high magnetostriction characteristics are realized in the magnetostrictive element using the magnetostrictive material powder containing the raw material powder B.
また、本発明に係る磁歪材料粉末の製造方法においては、前記脱水素工程における加熱温度を、４５０℃以上、前記原料粉末の共晶温度未満とすることが好ましい。 Moreover, in the manufacturing method of the magnetostrictive material powder which concerns on this invention, it is preferable that the heating temperature in the said dehydrogenation process shall be 450 degreeC or more and less than the eutectic temperature of the said raw material powder.
前記脱水素処理時の加熱温度が低いと脱水素に長時間を要するため、脱水素処理における加熱温度は４５０℃以上とする。ただし、（ＴｂｙＤｙ１−ｙ）２Ｔで表される原料粉末Ｂの溶融を防ぐため、加熱温度は当該原料粉末Ｂの共晶温度未満とする。以上のように、脱水素処理時の加熱温度を適正な範囲内とすることで、（ＴｂｙＤｙ１−ｙ）２Ｔ中の水素量の低減効果が確実に発揮される。 If the heating temperature at the time of the dehydrogenation is low, it takes a long time for the dehydrogenation. However, (Tb y Dy 1-y ) to prevent melting of the raw material powder B represented by 2 T, the heating temperature is set to the eutectic than the temperature of the raw material powder B. As described above, the heating temperature during the dehydrogenation process With the proper range, (Tb y Dy 1-y ) the effect of reducing the amount of hydrogen in 2 T is reliably exhibited.
本発明によれば、超磁歪材料粉末を作製するに際し、特殊な粉砕法を用いることなく希土類リッチな原料粉末Ｂを微粉化することができる。そして、得られる磁歪材料粉末を用いることで、密度の高い焼結体を得ることができ、しかも、得られる焼結体において磁歪特性の低下を抑えることが可能である。したがって、製造コストを抑えながら磁歪特性等の特性に優れた磁歪素子を製造することが可能である。 According to the present invention, when producing a giant magnetostrictive material powder, the rare earth-rich raw material powder B can be pulverized without using a special grinding method. By using the obtained magnetostrictive material powder, it is possible to obtain a sintered body having a high density, and it is possible to suppress a decrease in magnetostrictive characteristics in the obtained sintered body. Therefore, it is possible to manufacture a magnetostrictive element having excellent characteristics such as magnetostrictive characteristics while suppressing manufacturing costs.
以下、本発明を適用した磁歪材料粉末の製造方法及び磁歪素子の製造方法について、詳細に説明する。 Hereinafter, a method for producing a magnetostrictive material powder and a method for producing a magnetostrictive element to which the present invention is applied will be described in detail.
先ず、粉末冶金法により製造される磁歪素子について説明する。粉末冶金法においては、磁歪素子は、例えば一般式ＴｂｘＤｙ１−ｘＦｅｚ（ただし、０．２７≦ｘ≦０．３５であり、１．７≦ｚ≦２．１である。）で表される磁歪材料粉末（原料組成物）を焼結することによって焼結体として得られる。磁歪材料粉末は、ＴｂｖＤｙ１−ｖＦｅｗ（ただし、０≦ｖ≦１であり、１．７≦ｗ≦２．１である。）で表される原料粉末Ａと、（ＴｂｙＤｙ１−ｙ）２Ｆｅ（ただし、０≦ｙ≦１である。）で表される原料粉末Ｂとを少なくとも含むものである。 First, a magnetostrictive element manufactured by a powder metallurgy method will be described. In the powder metallurgy method, the magnetostrictive element is, for example, a general formula Tb x Dy 1-x Fe z (where 0.27 ≦ x ≦ 0.35 and 1.7 ≦ z ≦ 2.1). It is obtained as a sintered body by sintering the represented magnetostrictive material powder (raw material composition). The magnetostrictive material powder includes a raw material powder A represented by Tb v Dy 1-v Fe w (where 0 ≦ v ≦ 1 and 1.7 ≦ w ≦ 2.1), and (Tb y Dy 1-y ) 2 Fe (provided that 0 ≦ y ≦ 1) and at least the raw material powder B.
ＴｂｘＤｙ１−ｘＦｅｚで表される合金のうち、ｚ＝２であるＲＴ２ラーベス型金属間化合物は、キュリー温度が高く、磁歪値が大きいため、磁歪素子に適する。ここで、ｚが１．７未満では、焼結後の熱処理でＲＴ相が析出して磁歪値が低下する。また、ｚが２．１を上回ると、ＲＴ３相又はＲＴ６相が多くなり、磁歪値が低下する。したがって、ＲＴ２相を多くするために、ｚは１．７≦ｚ≦２．１の範囲が好ましい。 Of the alloys represented by Tb x Dy 1-x Fe z , the RT 2 Laves-type intermetallic compound with z = 2 has a high Curie temperature and a large magnetostriction value, and therefore is suitable for a magnetostrictive element. Here, when z is less than 1.7, the RT phase is precipitated by the heat treatment after sintering, and the magnetostriction value is lowered. Moreover, when z exceeds 2.1, the RT 3 phase or the RT 6 phase increases, and the magnetostriction value decreases. Therefore, in order to increase the RT 2 phase, z is preferably in the range of 1.7 ≦ z ≦ 2.1.
ＴｂｘＤｙ１−ｘＦｅｚで表される合金において、０．２７≦ｘ≦０．３５とすることで、飽和磁歪定数が大きく、大きな磁歪値が得られる。ここで、ｘが０．２７未満では室温以下では十分な磁歪値を示さず、逆に０．３５を越えると室温付近では十分な磁歪値を示さない。 In an alloy represented by Tb x Dy 1-x Fe z , With 0.27 ≦ x ≦ 0.35, the saturation magnetostriction constant is large, a large magnetostriction value can be obtained. Here, when x is less than 0.27, a sufficient magnetostriction value is not exhibited at room temperature or lower, whereas when it exceeds 0.35, a sufficient magnetostriction value is not exhibited near room temperature.
前述の磁歪素子は、粉末冶金法により製造される。以下、本発明の磁歪材料粉末の製造方法及び磁歪材料粉末を用いた粉末冶金法による磁歪素子（焼結体）の製造方法について、図１を参照しながら説明する。 The aforementioned magnetostrictive element is manufactured by powder metallurgy. Hereinafter, a method for producing a magnetostrictive material powder of the present invention and a method for producing a magnetostrictive element (sintered body) by a powder metallurgy method using the magnetostrictive material powder will be described with reference to FIG.
磁歪素子の粉末冶金法による製造においては、例えば、３種類の原料Ａ，Ｂ，Ｃをそれぞれ前処理した後、秤量・混合し、粉砕処理して得た磁歪材料粉末を、成形、焼成（焼結）等の工程を経て最終的な製品とされる。 In the production of a magnetostrictive element by powder metallurgy, for example, three types of raw materials A, B, and C are pretreated, weighed, mixed, and pulverized to produce a magnetostrictive material powder that is molded, fired (fired). The final product is obtained through processes such as
本実施形態で用いる原料の一部である原料Ａは、ＴｂｖＤｙ１−ｖＦｅｗ（ただし、０≦ｖ≦１であり、１．７≦ｗ≦２．１である。）なる組成を有するものである。先ず、Ａ原料として、前記組成となるようにＴｂ及び／又はＤｙ、Ｔ等を秤量し、例えばＡｒガスの不活性雰囲気中で溶融して合金を作製する。この合金を、１１５０℃〜１２５０℃程度の温度で熱処理する。前記熱処理により、合金作製時の各金属元素の濃度分布を一様にし、また、析出した異相を消滅させることができる。次に、例えばブラウンミル等の機械的粉砕手法により、平均粒径で５〜２０μｍ程度まで粉砕処理することで、原料粉末Ａが得られる。 The raw material A which is a part of the raw material used in the present embodiment has a composition of Tb v Dy 1-v Fe w (where 0 ≦ v ≦ 1 and 1.7 ≦ w ≦ 2.1). It is what you have. First, Tb and / or Dy, T, etc. are weighed as the A raw material so as to have the above composition, and melted in an inert atmosphere of Ar gas, for example, to produce an alloy. This alloy is heat-treated at a temperature of about 1150 ° C to 1250 ° C. By the heat treatment, the concentration distribution of each metal element at the time of producing the alloy can be made uniform, and the precipitated foreign phase can be eliminated. Next, the raw material powder A is obtained by pulverizing to an average particle diameter of about 5 to 20 μm by a mechanical pulverization method such as a brown mill.
原料の一部である原料粉末Ｂは、（ＴｂｙＤｙ１−ｙ）２Ｆｅ（ただし、０≦ｙ≦１である。）なる組成を有するものであり、水素吸蔵工程及び脱水素工程が施されたものである。先ず、Ｂ原料として、前記組成となるように、Ｔｂ及び／又はＤｙ、Ｆｅ等を秤量し、例えばＡｒガスの不活性雰囲気中で溶融して合金を作製し、機械的粉砕手法により粗粉砕する。 The raw material powder B, which is a part of the raw material, has a composition of (Tb y Dy 1-y ) 2 Fe (where 0 ≦ y ≦ 1), and is subjected to a hydrogen storage step and a dehydrogenation step. It has been done. First, Tb and / or Dy, Fe, etc. are weighed as raw material B so as to have the above-mentioned composition, for example, melted in an inert atmosphere of Ar gas to produce an alloy, and coarsely pulverized by a mechanical pulverization technique .
次に、水素吸蔵処理を行い、原料粉末Ｂの結晶格子中に水素原子を進入させ、又は水素化物とする。水素吸蔵処理は、原料粉末Ｂを水素雰囲気中又は水素ガスと不活性ガス（例えばＡｒガス）との混合ガス雰囲気中に所定時間加熱保持すればよい。水素吸蔵処理の際、水素ガスと不活性ガス（例えばＡｒガス）との混合ガス雰囲気とすることが好ましく、また、温度は１００℃〜２００℃程度とすることが好ましい。 Next, hydrogen storage treatment is performed to allow hydrogen atoms to enter the crystal lattice of the raw material powder B or to obtain a hydride. In the hydrogen occlusion treatment, the raw material powder B may be heated and held for a predetermined time in a hydrogen atmosphere or in a mixed gas atmosphere of hydrogen gas and an inert gas (for example, Ar gas). In the hydrogen storage treatment, a mixed gas atmosphere of hydrogen gas and inert gas (for example, Ar gas) is preferably used, and the temperature is preferably about 100 ° C. to 200 ° C.
原料粉末Ｂに水素を吸蔵させることにより、歪みが生じ、その内部応力によって割れが生ずる。この割れ又は水素吸蔵後の機械的粉砕により原料粉末Ｂはさらに微粉砕される。原料粉末Ｂは、細かく粉砕されることで焼結時に焼結助剤として働き、密度の高い焼結体を与える。さらに、Ｔｂ、Ｄｙ等の希土類元素は酸化されやすいために、わずかな酸素があっても表面に融点の高い酸化膜を形成して焼結の進行を抑制するが、水素を吸蔵することで、酸化され難くなるという利点もある。 By causing the raw material powder B to occlude hydrogen, distortion occurs and cracks occur due to the internal stress. The raw material powder B is further finely pulverized by this cracking or mechanical pulverization after hydrogen storage. The raw material powder B is finely pulverized to serve as a sintering aid during sintering, thereby giving a dense sintered body. Furthermore, since rare earth elements such as Tb and Dy are easily oxidized, an oxide film having a high melting point is formed on the surface even if there is a slight amount of oxygen to suppress the progress of sintering, but by storing hydrogen, There is also an advantage that oxidation is difficult.
本発明では、原料粉末Ｂ中の水素量を低減する目的で、水素吸蔵処理に引き続いて、原料粉末Ｂを真空中で所定時間加熱保持する脱水素処理を行う。なお、ここで真空とは、例えば減圧により圧力１０−２Ｔｏｒｒ以下とすることを言うものとする。真空中で加熱することにより、先の水素吸蔵処理により原料粉末Ｂに取り込まれた水素が効率よく放出（脱水素）される。希土類リッチな組成を持つ原料粉末Ｂは融点が低いため、脱水素処理での加熱による溶融が懸念されるが、脱水素処理を真空中で行うことで、原料粉末Ｂの融点より低い温度域にて水素を効率よく放出させることができる。したがって、原料粉末Ｂの溶融を起こすことなく原料粉末Ｂ中の水素量を限りなくゼロに近づけることができる。なお、原料Ａ〜Ｃの混合粉末を磁場中成形した後、焼結時に原料粉末Ｂ中の水素を放出させることも考えられるが、この場合には脱水素が効率よく進まず、磁歪特性の低下を招く。また、常圧下での脱水素処理は、水素が放出されにくいため磁歪特性を低下させ、脱水素の効率を高める目的で加熱温度を高温とすると、融点の低い原料粉末Ｂが溶融することがあり、好ましくない。 In the present invention, for the purpose of reducing the amount of hydrogen in the raw material powder B, a dehydrogenation treatment in which the raw material powder B is heated and held in a vacuum for a predetermined time is performed following the hydrogen storage treatment. Here, the vacuum means that the pressure is reduced to 10 −2 Torr or less by reducing pressure, for example. By heating in vacuum, the hydrogen taken into the raw material powder B by the previous hydrogen storage treatment is efficiently released (dehydrogenated). Since the raw material powder B having a rare earth-rich composition has a low melting point, there is a concern about melting due to heating in the dehydrogenation process. However, by performing the dehydrogenation process in a vacuum, the temperature is lower than the melting point of the raw material powder B. Thus, hydrogen can be released efficiently. Therefore, the amount of hydrogen in the raw material powder B can be made as close to zero as possible without causing the raw material powder B to melt. In addition, after forming the mixed powders of the raw materials A to C in a magnetic field, it may be possible to release hydrogen in the raw material powder B during sintering. In this case, however, dehydrogenation does not proceed efficiently, and the magnetostrictive characteristics are deteriorated. Invite. In addition, the dehydrogenation treatment under normal pressure may cause the raw material powder B having a low melting point to melt when the heating temperature is increased for the purpose of reducing magnetostriction characteristics and increasing the dehydrogenation efficiency because hydrogen is not easily released. It is not preferable.
脱水素処理における加熱温度は、４５０℃以上、原料粉末Ｂである（ＴｂｙＤｙ１−ｙ）２Ｆｅの共晶温度未満とすることが好ましい。加熱温度が低すぎると脱水素に長時間を要することから、加熱温度は４５０℃以上とする。一方、加熱温度を高温とすれば、脱水素処理に要する時間を短縮できるものの、原料粉末Ｂの共晶温度（例えば８６０℃程度）を上回ると原料粉末Ｂの溶融を引き起こす。したがって、脱水素処理の際の温度範囲は４５０℃以上、原料粉末Ｂの共晶温度未満とする。また、より好ましい加熱温度は、５５０℃以上、７５０℃以下の範囲である。加熱温度を５５０℃以上とすることで原料粉末Ｂの水素量をより効率的に低減することができる。また、７５０℃以下とすることで、原料粉末Ｂの溶融を確実に防止することができる。 The heating temperature in the dehydrogenation treatment is preferably 450 ° C. or higher and lower than the eutectic temperature of (Tb y Dy 1-y ) 2 Fe that is the raw material powder B. If the heating temperature is too low, it takes a long time for dehydrogenation, so the heating temperature is set to 450 ° C. or higher. On the other hand, if the heating temperature is set high, the time required for the dehydrogenation treatment can be shortened, but if the eutectic temperature of the raw material powder B (for example, about 860 ° C.) is exceeded, the raw material powder B is melted. Therefore, the temperature range during the dehydrogenation treatment is set to 450 ° C. or higher and lower than the eutectic temperature of the raw material powder B. A more preferable heating temperature is in the range of 550 ° C. or higher and 750 ° C. or lower. By setting the heating temperature to 550 ° C. or higher, the amount of hydrogen in the raw material powder B can be more efficiently reduced. Moreover, melting | fusing of the raw material powder B can be reliably prevented by setting it as 750 degrees C or less.
原料粉末Ｃは、Ｆｅを水素ガス雰囲気中で酸素を除去する還元処理を行うことにより得られる。 The raw material powder C can be obtained by performing a reduction treatment for removing oxygen from Fe in a hydrogen gas atmosphere.
以上のような原料粉末Ａ〜Ｃを所定量秤量・混合し、粉砕処理することで、磁歪材料粉末が得られる。この磁歪材料粉末を磁場中で成形して成形体を作製する。このとき、例えば昇華性有機化合物等を成形助剤として用い、効率的な成形を可能とするようにしてもよい。成形は、所定形状のキャビティを有する金型内に磁歪材料粉末（前記原料Ａ、原料Ｂ及び原料Ｃを混合したもの）を充填し、加圧することにより行う。 Magnetostrictive material powder can be obtained by weighing and mixing a predetermined amount of the above raw material powders A to C, followed by pulverization. The magnetostrictive material powder is molded in a magnetic field to produce a molded body. At this time, for example, a sublimable organic compound or the like may be used as a molding aid to enable efficient molding. The molding is performed by filling a mold having a cavity with a predetermined shape with a magnetostrictive material powder (mixed raw material A, raw material B and raw material C) and pressurizing it.
前記により成形された成形体を焼結炉内に入れ、所定の条件で熱処理し、焼成（焼結）を行うことにより、焼結体（磁歪素子）を作製する。焼成は、成形体を焼結炉に入れた後に所定温度まで昇温する昇温過程、所定の温度（安定温度）をほぼ一定に保持する過程、及び降温過程を経ることにより行われる。 The molded body molded as described above is placed in a sintering furnace, heat-treated under predetermined conditions, and fired (sintered) to produce a sintered body (magnetostrictive element). Firing is performed by going through a temperature raising process in which the molded body is heated to a predetermined temperature after being placed in a sintering furnace, a process in which the predetermined temperature (stable temperature) is kept substantially constant, and a temperature lowering process.
前記焼成の最初の段階において、水素を含む雰囲気中で焼成を行うことが好ましい。水素を含む雰囲気中で前記焼成を行うことで、得られる焼結体の焼結密度を向上することができる。この場合、前記水素を含む雰囲気における水素濃度は任意であるが、低圧成形で十分に高い焼結密度を得るためには、水素濃度３５容積％以上とすることが好ましく、５０容積％以上とすることがより好ましい。 In the first stage of the firing, it is preferable to perform the firing in an atmosphere containing hydrogen. By performing the firing in an atmosphere containing hydrogen, the sintered density of the obtained sintered body can be improved. In this case, the hydrogen concentration in the atmosphere containing hydrogen is arbitrary, but in order to obtain a sufficiently high sintered density by low-pressure molding, the hydrogen concentration is preferably 35% by volume or more, and 50% by volume or more. It is more preferable.
前記水素を含む雰囲気とする場合、水素ガスと不活性ガスとを混合した混合ガスを炉内に導入する。不活性ガス、例えばＡｒガスは希土類元素（Ｒ）を酸化することがなく、水素ガスと混合することにより還元作用を有する雰囲気を得ることができる。希土類元素Ｒは、酸素と極めて容易に反応し、安定な希土類酸化物を形成する。前記希土類酸化物は、実用となるような磁気特性は示さず、したがって前記希土類酸化物の形成は焼結体の磁気特性を大きく低下する要因となる。このような観点からも、前記焼成の際に水素雰囲気とすることが好ましい。なお、酸化を防ぐ雰囲気としては、不活性ガス雰囲気とすることも考えられるが、不活性ガスのみでは完全に酸化を防ぐことは難しく、水素を含む還元雰囲気とすることが好ましい。 In the case of an atmosphere containing hydrogen, a mixed gas in which hydrogen gas and inert gas are mixed is introduced into the furnace. An inert gas such as Ar gas does not oxidize the rare earth element (R), and an atmosphere having a reducing action can be obtained by mixing with hydrogen gas. The rare earth element R reacts very easily with oxygen to form a stable rare earth oxide. The rare earth oxide does not exhibit practical magnetic properties, and therefore the formation of the rare earth oxide is a factor that greatly reduces the magnetic properties of the sintered body. From this point of view, it is preferable that a hydrogen atmosphere is used in the firing. An atmosphere for preventing oxidation may be an inert gas atmosphere, but it is difficult to completely prevent oxidation with only an inert gas, and a reducing atmosphere containing hydrogen is preferable.
前記水素を含む雰囲気とするのは、焼成の前半、例えば昇温過程である。前記焼成により製造する磁歪材料がテルビウム系超磁歪材料の場合、８２０℃〜１２００℃の区間（昇温過程）を前記水素を含む雰囲気として焼成を行う。 The atmosphere containing hydrogen is the first half of firing, for example, the temperature raising process. When the magnetostrictive material produced by the firing is a terbium-based giant magnetostrictive material, the firing is performed with the section of 820 ° C. to 1200 ° C. (temperature raising process) as an atmosphere containing hydrogen.
昇温過程に続いて、例えば焼成の際の到達温度に到達後、１１５０℃〜１２５０℃の温度範囲で所定時間保持し、焼成を行えばよい。ただし、あまり温度が低いと焼結体の密度が十分に上昇せず、成形の際に成形圧を高く設定する必要が生ずるため、１２５０℃以上の温度で前記真空中での焼成を行うことが好ましい。このときの雰囲気は非酸化性雰囲気がよく、具体的には不活性ガス、水素ガス又は不活性ガスと水素ガスの混合ガスとすることが好ましい。保持時間は、１〜１０時間の範囲で適宜選択すればよい。 Subsequent to the temperature raising process, for example, after reaching the temperature reached during firing, the temperature may be maintained within a temperature range of 1150 ° C. to 1250 ° C. for a predetermined time to perform firing. However, if the temperature is too low, the density of the sintered body will not increase sufficiently, and it will be necessary to set the molding pressure high during molding, so firing in the vacuum at a temperature of 1250 ° C. or higher can be performed. preferable. The atmosphere at this time is preferably a non-oxidizing atmosphere, and specifically, an inert gas, hydrogen gas, or a mixed gas of an inert gas and hydrogen gas is preferably used. The holding time may be appropriately selected within the range of 1 to 10 hours.
前記焼成により得られた焼結体に対し時効処理を行い、必要に応じて焼結体を所定サイズに切断することで、磁歪素子を得ることができる。 A magnetostrictive element can be obtained by performing an aging process with respect to the sintered compact obtained by the said baking, and cutting a sintered compact into a predetermined size as needed.
以上のように、水素吸蔵処理を施した原料粉末Ｂに真空中、適正な加熱温度にて加熱保持する脱水素処理を行うことで、特殊な粉砕法を用いることなく微細な原料粉末Ｂが得られる。これを含む磁歪材料粉末を用いることで、焼結体（磁歪素子）の高密度化が実現されるとともに、原料粉末Ｂ中の水素に起因する結晶成長抑制の問題が解消され、得られる焼結体（磁歪素子）において優れた磁歪特性が実現される。 As described above, a fine raw material powder B can be obtained without using a special pulverization method by performing a dehydrogenation treatment in which the raw material powder B subjected to the hydrogen storage treatment is heated and held in vacuum at an appropriate heating temperature. It is done. By using a magnetostrictive material powder containing this, a high density of the sintered body (magnetostrictive element) is realized, and the problem of suppressing crystal growth caused by hydrogen in the raw material powder B is solved, and the obtained sintering Excellent magnetostrictive characteristics are realized in the body (magnetostrictive element).
次に、本発明の具体的な実施例について、実験結果を基に説明する。 Next, specific examples of the present invention will be described based on experimental results.
＜実験１：真空又はＡｒガス（常圧）条件での材料中水素量の推移＞
Ｂ原料としてのＤｙ２Ｆｅ合金に、１５０℃で１時間、水素を吸蔵させ、水素吸蔵処理を行った。水素吸蔵処理後の粉末を真空中又はＡｒガス（常圧）中、所定温度で６時間保持し、脱水素を行った。以上の方法に従い、加熱温度を０〜１０００℃の範囲内で変化させ、脱水素後のＤｙ２Ｆｅ合金に含まれる水素量を測定した。結果を図２に示す。
<Experiment 1: Transition of hydrogen content in material under vacuum or Ar gas (normal pressure) conditions>
Hydrogen was occluded by allowing the Dy 2 Fe alloy as the B raw material to occlude hydrogen at 150 ° C. for 1 hour. The hydrogen-absorbed powder was held in vacuum or Ar gas (normal pressure) at a predetermined temperature for 6 hours for dehydrogenation. According to the above method, the heating temperature was changed within the range of 0 to 1000 ° C., and the amount of hydrogen contained in the Dy 2 Fe alloy after dehydrogenation was measured. The results are shown in FIG.
脱水素処理を常圧で行った場合、１０００℃程度に高温加熱してもなお材料中に１０００ｐｐｍ程度の多量の水素が残留している。脱水素処理時の加熱温度をさらに高温として水素を強制的に放出させることも考えられるが、前記Ｂ原料の融点は低いため、溶融が懸念される。これに対し、真空中での脱水素処理は、原料粉末Ｂが溶融しないような低温で水素量の低減（３００ｐｐｍ程度）を実現している。 When the dehydrogenation treatment is performed at normal pressure, a large amount of hydrogen of about 1000 ppm remains in the material even when heated at a high temperature of about 1000 ° C. Although it is conceivable to forcibly release hydrogen by further increasing the heating temperature during the dehydrogenation treatment, there is concern about melting because the melting point of the B raw material is low. In contrast, the dehydrogenation process in vacuum achieves a reduction in hydrogen content (about 300 ppm) at a low temperature so that the raw material powder B does not melt.
＜実験２：真空中での脱水素処理における温度と真空度の関係＞
実験２においては、実験１と同様にして水素吸蔵処理を施した後のＢ原料（Ｄｙ２Ｆｅ合金）粉末を密閉容器に入れ、真空中、昇温速度５℃／分にて昇温して脱水素処理を行った。そして、各温度における密閉容器内の真空度を測定した。結果を図３に示す。密閉容器内の真空度は原料粉末Ｂから放出される水素量に応じて変動し、真空度の劣化は原料粉末Ｂから水素が放出されていること意味する。
<Experiment 2: Relationship between temperature and degree of vacuum in vacuum dehydrogenation>
In Experiment 2, the raw material B (Dy 2 Fe alloy) powder after hydrogen storage treatment as in Experiment 1 was put in a sealed container and heated at a heating rate of 5 ° C./min in a vacuum. Dehydrogenation treatment was performed. And the vacuum degree in the airtight container in each temperature was measured. The results are shown in FIG. The degree of vacuum in the sealed container varies according to the amount of hydrogen released from the raw material powder B, and the deterioration of the degree of vacuum means that hydrogen is released from the raw material powder B.
図３によると、水素の放出量は４５０℃近辺から急激に増加し、５００℃近辺でピークとなる。さらに温度を上げていくと徐々に収束していき、原料粉末Ｂの共晶温度未満で充分に水素を除去できることがわかる。また、脱水素を効率的に行うには、４５０℃以上とすることが好ましいことがわかる。 According to FIG. 3, the amount of hydrogen released increases rapidly from around 450 ° C. and peaks around 500 ° C. As the temperature is further increased, it gradually converges and it can be seen that hydrogen can be sufficiently removed below the eutectic temperature of the raw material powder B. It can also be seen that the temperature is preferably set to 450 ° C. or higher for efficient dehydrogenation.
＜実験３：真空中での脱水素処理による効果の確認＞
（実施例）
Ｔｂ０．４Ｄｙ０．６Ｆｅ１．９３合金（Ａ合金）を１１５０℃でアニールし、ブラウンミルを用いて粉砕し、Ａ原料とした。Ｂ原料としてのＤｙ２Ｆｅ合金に、１５０℃で１時間、水素を吸蔵させ、水素吸蔵処理を行った。水素吸蔵処理後の粉末を真空中、所定温度で６時間保持し、脱水素を行った。その後、２ｍｍのメッシュを通してＢ原料とした。さらに、粒径５μｍのＦｅ粉を水素還元し、Ｃ原料とした。前記Ａ原料、Ｂ原料、及びＣ原料を最終組成（Ｔｂ０．３４Ｄｙ０．６６Ｆｅ１．８７２）となるように秤量・混合し、アトマイザーで粉砕して磁歪材料粉末を得た。この磁歪材料粉末を１ｔ／ｃｍ２〜８ｔ／ｃｍ２の圧力で成形した。
<Experiment 3: Confirmation of effect by dehydrogenation in vacuum>
(Example)
Tb 0.4 Dy 0.6 Fe 1.93 alloy (A alloy) was annealed at 1150 ° C. and pulverized using a brown mill to obtain A raw material. Hydrogen was occluded by allowing the Dy 2 Fe alloy as the B raw material to occlude hydrogen at 150 ° C. for 1 hour. The powder after the hydrogen storage treatment was held in vacuum at a predetermined temperature for 6 hours for dehydrogenation. Thereafter, the raw material B was passed through a 2 mm mesh. Furthermore, Fe powder having a particle size of 5 μm was reduced with hydrogen to obtain a C raw material. The A raw material, the B raw material, and the C raw material were weighed and mixed so as to have a final composition (Tb 0.34 Dy 0.66 Fe 1.872 ), and pulverized with an atomizer to obtain a magnetostrictive material powder. The magnetostrictive material powder was molded under a pressure of 1t / cm 2 ~8t / cm 2 .
次いで、成形した成形体を焼成し、磁歪素子を作製した。焼成に際しては、先ず、Ａｒ雰囲気として昇温を開始し、８２０℃に到達した時点で水素を導入した。さらに昇温を続け、焼結の到達温度１２００℃に到達した後、３５分経過した時点でＡｒ雰囲気に切り換え、さらに３時間温度を維持し、降温して焼結体（磁歪素子）を得た。 Next, the molded body was fired to produce a magnetostrictive element. In firing, first, the temperature was raised as an Ar atmosphere, and hydrogen was introduced when the temperature reached 820 ° C. The temperature was further increased, and after reaching the sintering temperature of 1200 ° C., when 35 minutes had passed, the atmosphere was switched to an Ar atmosphere, and the temperature was further maintained for 3 hours, and the temperature was lowered to obtain a sintered body (magnetostrictive element). .
（比較例１）
原料粉末Ｂを得る際の脱水素処理をＡｒガス（常圧）下で行ったこと以外は、前記実施例と同様にして焼結体を作製した。
(Comparative Example 1)
A sintered body was produced in the same manner as in the above example, except that the dehydrogenation treatment for obtaining the raw material powder B was performed under Ar gas (normal pressure).
（比較例２）
Ｂ原料としてのＤｙ２Ｆｅ合金中、Ｆｅの一部をＣｏ又はＮｉで置換し、水素吸蔵処理及び脱水素処理に代えて機械的に粉砕した。また、焼成雰囲気をＡｒ雰囲気とした。これらの点以外は、前記実施例と同様にして焼結体を作製した。
(Comparative Example 2)
In the Dy 2 Fe alloy as the B raw material, a part of Fe was replaced with Co or Ni, and mechanically pulverized instead of hydrogen storage treatment and dehydrogenation treatment. The firing atmosphere was an Ar atmosphere. Except for these points, a sintered body was produced in the same manner as in the above example.
（比較例３）
焼成雰囲気を水素雰囲気としたこと以外は、前記比較例２と同様にして焼結体を作製した。
(Comparative Example 3)
A sintered body was produced in the same manner as in Comparative Example 2 except that the firing atmosphere was a hydrogen atmosphere.
（比較例４）
Ｂ原料を得る際、水素吸蔵処理及び脱水素処理に代えて、不活性ガス中でガスアトマイズとすることによりＢ原料を粉砕した。前記Ａ原料、Ｂ原料、及びＣ原料を最終組成（Ｔｂ０．３４Ｄｙ０．６６Ｆｅ１．８７２）となるように秤量・混合し、ジェットミルで粉砕して磁歪材料粉末を得た。これらの点以外は、前記実施例と同様にして焼結体を作製した。
(Comparative Example 4)
When the B raw material was obtained, the B raw material was pulverized by gas atomization in an inert gas instead of the hydrogen storage treatment and dehydrogenation treatment. The A raw material, the B raw material, and the C raw material were weighed and mixed so as to have a final composition (Tb 0.34 Dy 0.66 Fe 1.872 ), and pulverized with a jet mill to obtain a magnetostrictive material powder. Except for these points, a sintered body was produced in the same manner as in the above example.
（比較例５）
比較例５では、原料組成物を原料Ａ〜Ｃに分けなかった。すなわち、最終組成（Ｔｂ０．３４Ｄｙ０．６６Ｆｅ１．８７２）の合金をジェットミルにより粉砕して磁歪材料粉末としたこと以外は、前記実施例と同様にして焼結体を作製した。
(Comparative Example 5)
In Comparative Example 5, the raw material composition was not divided into the raw materials A to C. That is, a sintered body was produced in the same manner as in the above example except that an alloy having a final composition (Tb 0.34 Dy 0.66 Fe 1.872 ) was pulverized by a jet mill to obtain a magnetostrictive material powder.
得られた各焼結体について、焼結密度Ｄｔ（％）を測定した。また、各焼結体について、磁歪特性〔磁歪値（Ｈ＝０．４ｋＯｅ）及び磁歪値（Ｈ＝１ｋＯｅ）〕を測定した。結果を表１に示す。 The sintered density Dt (%) was measured for each obtained sintered body. Further, the magnetostriction characteristics [magnetostriction value (H = 0.4 kOe) and magnetostriction value (H = 1 kOe)] of each sintered body were measured. The results are shown in Table 1.
表１から明らかなように、水素吸蔵処理を施した原料Ｂに脱水素処理を行うことにより、密度の高い焼結体が得られており、焼結密度９５％が達成されている。また、脱水素処理を真空中で実施した実施例は、常圧で実施した比較例１に比べて高い磁歪特性を実現している。なお、水素吸蔵処理を施し真空中で加熱保持する脱水素処理を行った後のＢ原料（実施例）と、不活性ガス中でガスアトマイズにより粉砕した後のＢ原料（比較例４）とについて、顕微鏡写真を比較したところ、実施例の原料粉末Ｂの表面には無数のクラックが入っており、機械粉砕可能な状態であることが確認された。 As is apparent from Table 1, by performing the dehydrogenation treatment on the raw material B that has been subjected to the hydrogen storage treatment, a sintered body having a high density is obtained, and a sintered density of 95% is achieved. Moreover, the Example which implemented the dehydrogenation process in the vacuum has implement | achieved the high magnetostriction characteristic compared with the comparative example 1 implemented by the normal pressure. In addition, about the B raw material (Example) after performing the hydrogen storage process and performing the dehydrogenation process which heat-maintains in a vacuum, and the B raw material (Comparative example 4) after grind | pulverizing by gas atomization in inert gas, As a result of comparing the micrographs, it was confirmed that the surface of the raw material powder B of the examples had innumerable cracks and was in a state capable of being mechanically pulverized.
Claims (4)
前記脱水素工程後、前記原料粉末ＢをＴｂｖＤｙ１−ｖＦｅｗ（ただし、０≦ｖ≦１であり、１．７≦ｗ≦２．１である。）で表される原料粉末Ａと混合し、ＴｂｘＤｙ１−ｘＦｅｚ（ただし、０．２７≦ｘ≦０．３５であり、１．２７≦ｚ≦２．１である。）で表される磁歪材料粉末を得る混合工程とを有することを特徴とする磁歪材料粉末の製造方法。 A dehydrogenation step in which the raw material powder B represented by (Tb y Dy 1-y ) 2 Fe (where 0 ≦ y ≦ 1) subjected to hydrogen storage treatment is heated and held in vacuum;
After the dehydrogenation step, the raw material powder B is represented by Tb v Dy 1-v Fe w (where 0 ≦ v ≦ 1 and 1.7 ≦ w ≦ 2.1). To obtain a magnetostrictive material powder represented by Tb x Dy 1-x Fe z (where 0.27 ≦ x ≦ 0.35 and 1.27 ≦ z ≦ 2.1). A process for producing a magnetostrictive material powder, comprising the steps of:
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102351142A (en) * | 2011-07-14 | 2012-02-15 | 辽宁石油化工大学 | Reversible hydrogen storage method based on magnetostriction |
| CN114570934A (en) * | 2022-02-28 | 2022-06-03 | 中国特种设备检测研究院 | Magnetostrictive powder and preparation method of magnetostrictive coating |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102351142A (en) * | 2011-07-14 | 2012-02-15 | 辽宁石油化工大学 | Reversible hydrogen storage method based on magnetostriction |
| CN114570934A (en) * | 2022-02-28 | 2022-06-03 | 中国特种设备检测研究院 | Magnetostrictive powder and preparation method of magnetostrictive coating |
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