EP0237416B1 - Aimant permanent à base de terres rares - Google Patents

Aimant permanent à base de terres rares Download PDF

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Publication number
EP0237416B1
EP0237416B1 EP19870400473 EP87400473A EP0237416B1 EP 0237416 B1 EP0237416 B1 EP 0237416B1 EP 19870400473 EP19870400473 EP 19870400473 EP 87400473 A EP87400473 A EP 87400473A EP 0237416 B1 EP0237416 B1 EP 0237416B1
Authority
EP
European Patent Office
Prior art keywords
rare earth
alloy
weight
permanent magnet
based permanent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19870400473
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German (de)
English (en)
Other versions
EP0237416A1 (fr
Inventor
Ken Ohashi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shin Etsu Chemical Co Ltd
Original Assignee
Shin Etsu Chemical Co Ltd
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Filing date
Publication date
Application filed by Shin Etsu Chemical Co Ltd filed Critical Shin Etsu Chemical Co Ltd
Publication of EP0237416A1 publication Critical patent/EP0237416A1/fr
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Publication of EP0237416B1 publication Critical patent/EP0237416B1/fr
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C22C1/0441—Alloys based on intermetallic compounds of the type rare earth - Co, Ni
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered

Definitions

  • the present invention relates to a rare earth-based permanent magnet or, more particularly, to a rare earth-based permanent magnet prepared by the powder metallurgical method.
  • Nd-Fe-B magnets those on neodymium, iron and boron, referred to as the Nd-Fe-B magnets hereinbelow, are prominently highlighted in recent years by virtue of their outstandingly high magnetic properties in comparison with the rare earth-based permanent magnets of other types.
  • These Nd-Fe-B magnets are expected to be a material used in large quantities, especially, in electric motors for which more and more powerful permanent magnets are required from the standpoint of energy saving or when more compact but more powerful motors are desired.
  • Nd-Fe-B permanent magnets are the relatively large temperature dependency of the magnetic properties thereof so that the Nd-Fe-B magnets at an elevated temperature cannot exhibit the magnetic properties as high as at low or room temperature.
  • the Nd-Fe-B magnets have coefficients of temperature dependency of about -0.13%/°C and -0.6%/°C for the residual magnetization B, and coercive force ;H c , respectively.
  • the temperature dependency of the coercive force is considerably larger than that of the residual magnetization and should desirably be much smaller.
  • a coefficient of temperature dependency of -0.6 %/° C means that the coercive force of the magnet at 100 ° C is only about a half of the value at room temperature. This large temperature dependency is the reason for the relatively low upper limit of 50 to 70°C at the highest of the temperature range in which the Nd-Fe-B magnets can be practically used.
  • the temperature dependency in the coercive force of the magnets can be improved by the admixture of the magnet alloy with a so-called heavy rare earth element such as dysprosium and terbium, light metal element such as aluminium or transition metal element such as niobium and vanadium.
  • the magnetic properties of the Nd-Fe-B magnets could be improved when the metallographic structure of the magnet alloy be converted to the precipitation- hardening type although no successful results have yet been obtained by this means.
  • the principle of the former method by the additional alloying elements is to impart the Nd-Fe-B magnet with a further increased coercive force so that the magnet can retain a value of the coercive force still in an acceptable range even at an elevated terrtpera- ture to cause decrease in the coercive force.
  • This improvement in the coercive force is naturally obtained at the sacrifice of the residual magnetization B r .
  • aluminium, niobium and vanadium as an additional alloying element are each non-magnetic so that the addition thereof to the magnet alloy is necessarily accompanied by the decrease in the residual magnetization in proportion to the added amount of these elements or even larger.
  • the heavy rare earth elements such as dysprosium and terbium, have a magnetic moment aligned anti-parallel to that of the transition metal elements so that the decrease in the residual magnetization of the Nd-Fe-B magnets by the addition thereof is even larger than by the addition of aluminium, niobium or vanadium.
  • the neodymium-based permanent magnets of the high coercive force type in the prior art unavoidably have a greatly decreased residual magnetization in comparison with conventional Nd-Fe-B magnets.
  • the coercive force of the neodymium-based magnet is increased by the addition of the above mentioned additive elements such as the heavy rare earth elements, aluminium, niobium and the like because these additive elements have an effect to increase the anisotropic magnetic field of the Nd 2 Fe 14 B compound and to influence on the morphology at the proximity of the grain boundaries of the crystallites.
  • additive elements such as the heavy rare earth elements, aluminium, niobium and the like because these additive elements have an effect to increase the anisotropic magnetic field of the Nd 2 Fe 14 B compound and to influence on the morphology at the proximity of the grain boundaries of the crystallites.
  • the present invention provides a rare earth-based permanent magnet which is a sintered body of a powdery mixture comprising or, rather, essentially composed of:
  • the powdery mixture should preferably have a particle size distribution in the range from 2 to 811m.
  • the rare earth-based permanent magnet of the invention is a magnet prepared by the powder metallurgical process from a magnetic alloy powder which is characteristically a mixture of two kinds of alloys defined above.
  • a magnetic alloy powder which is characteristically a mixture of two kinds of alloys defined above.
  • the additive elements contributing to the increase of the coercive force are uniformly admixed beforehand with the principal magnet alloy of a light rare earth element, e.g.
  • the invention proposes that the alloying elements are divided into two groups which are separately converted into the first alloy for the principal magnetic constituent and the second alloy for the additive elements and these two alloys are concurrently pulverized or separately pulverized followed by mixing of the powders together to give a powdery mixture to be subjected to shaping and sintering.
  • the additive elements in the invention form the second alloy separately from the first alloy for the matrix phase of the magnet and the powdery mixture for the powder metallurgical process is formed of the particles of these two types of alloys. In the sintering procedure, accordingly, the additive elements diffuse into the particles of the matrix phase from the surface of the particles but never reach the core portions of the particles.
  • the concentration of the additive elements is inhomogeneous in the inventive magnet as sintered. Namely, the concentration is high only at the surface of the matrix particles while the additive elements are substantially absent in the core portion of the matrix particles exhibiting a great influence on the anisotropic magnetic field and morphology at or in the vicinity of the grain boundaries even when the overall amount of the additive elements is so low that the residual magnetization of the magnet is little affected and consequently the magnet has a high maximum energy product (BH) max .
  • BH maximum energy product
  • the first alloy which is pulverized and mixed with a powder of the second alloy, is a ternary alloy composed of a light rare earth element, iron and/or cobalt and boron.
  • the light rare earth element here implied as the first component of the first alloy includes the rare earth elements having an atomic number of 57 to 62, i.e. lanthanum to samarium, but it is preferably neodymium or praseodymium although combinations of these two elements without or with a minor amount of the other light rare earth elements can be used equally.
  • at least 50% by weight of the light rare earth component should be neodymium, praseodymium or a combination of the two. Neodymium is preferred.
  • the amount of the light rare earth element or elements in the first alloy should be in the range from 25 to 35% by weight.
  • the second component in the first alloy is boron, of which the content in the first alloy should be in the range from 0.7 to 1.5% by weight.
  • the balance of the above mentioned light rare earth elements and boron in the first alloy is iron, cobalt or a combination thereof although iron is preferred mainly for the economical reason while replacement of a part of iron with cobalt has an effect of increasing the Curie point of the magnet contributing to the improvement of the reversible temperature coefficient.
  • the amount of this third component, i.e. iron and/or cobalt, in the first alloy should accordingly be in the range from 63.5 to 74.3% by weight including unavoidable impurity elements, the amount of which should be as small as possible.
  • the second alloy which is pulverized and mixed with the powder of the first alloy, is a binary alloy composed of a heavy rare earth element and an alloying element selected from the group consisting of aluminium, niobium, zirconium, vanadium, tantalum and molybdenum.
  • the heavy rare earth element here implied is an element having an atomic number of 64 to 71, i.e. gadolinium to lutetium, and terbium, dysprosium and holmium are preferred, of which dysprosium is more preferable.
  • These heavy rare earth elements are preferred to the light rare earth elements, e.g.
  • R a rare earth element
  • Nd 2 Fe 14 B a rare earth element
  • the above mentioned six kinds of alloying elements can exhibit an effect of increasing the coercive force of the magnet even in an unalloyed condition while alloying thereof with a heavy rare earth element may have a synergistic effect. It is noteworthy that the alloy is more resistant against oxidation than the heavy rare earth element alone.
  • the amount of the heavy rare earth element or elements in the second alloy should be in the range from 30to 86% by weight, the balance, i.e.
  • the alloy from 70 to 14% by weight, being one or a combination of the above mentioned alloying elements including unavoidable impurity elements, the amount of which should be as small as possible.
  • the alloy can be pulverized with great difficulties due to the increased tenacity of the alloy.
  • the alloy would be more susceptible to oxidation.
  • the most preferred is an alloy of dysprosium and aluminium, which should have a composition of DyA1 2 in the so-called Laves phase. This is because the Laves phase of the DyA1 2 alloy is brittle and can be easily pulverized and the powder thereof is little susceptible to oxidation in addition to the relatively large effect on the magnet properties by the addition thereof.
  • the elementary materials forming the first or the second alloy should be melted together to prepare the first and second alloys separately.
  • the method for the preparation of the alloy can be conventional without particular limitations.
  • the two alloys may be separately pulverized into powders which are weighed and mixed together subsequently. It is, however, a convenient way that each of the alloys in the form of an ingot is crushed into coarse granules having a particle size distribution of, for example, 10 to 500 1 1m which should be mixed with the granules of the other alloy in a calculated proportion followed by concurrent fine pulverization so that the pulverization and mixing can be performed in one step.
  • the fine powder of the two alloys should have a particle size distribution in the range from 1 to 10 ⁇ m or, preferably, from 2 to 8 ⁇ m.
  • the thus prepared mixed powder should be composed of from 90 to 99.9 parts by weight of the first alloy and from 10 to 0.1 part by weight of the second alloy.
  • the amount of the second alloy is smaller than 0.1 part by weight in 100 parts by weight of the mixed powder, no sufficient improvement can be obtained in the coercive force of the resultant sintered magnet.
  • the amount of the second alloy is too large, on the other hand, the residual magnetization of the sintered magnet would be unduly decreased.
  • a first alloy ingot was prepared by melting together, in a high frequency induction furnace under an inert atmosphere, metallic neodymium having a purity of 99.4%, iron having a purity of 99.5% and boron having a purity of 99.5% in such a proportion that the alloy was composed of 34.0% of neodymium, 64.9% of iron and 1.1 % of boron.
  • a second alloy ingot was prepared from metallic dysprosium having a purity of 99.4% and aluminium having a purity of 99.9% in a weight proportion of 75.1% dysprosium and 24.9% aluminium.
  • each of the alloy ingots was crushed in a disc mill separately from the other into granules having a fineness to pass a screen of 20 meshes by the Tyler standard.
  • the granules of the first alloy were admixed with the granules of the second alloy in four different weight proportions as indicated in Table 1 below and each of the mixtures as well as the granules of the first alloy alone for comparative purpose was finely pulverized in a jet mill using nitrogen as the ject gas into a powder having an average particle diameter of 3.0 ⁇ m.
  • the powder was molded into a shaped body in a magnetic field of 10 kOe under a compressive pressure of 1.5 tons/cm 2 into a green body which was subjected to sintering at 1050°Cfor 1 hour in an atmosphere of argon followed by aging at 550°C for 1 hour and then quenching with a cold inert gas.
  • Table 1 shows the residual magnetization B r and coercive force i H c of the prepared sintered magnets. It is understood from these results that the addition of the second alloy to the first alloy was very effective in increasing the coercive force of the magnets with little adverse influence on the residual magnetization of the magnets.
  • Example 5 The experimental procedure in each of the experiments (Experiments No. 1 to No. 5) was substantially the same as in Example 1 excepting modifications in the compositions of the first and second alloys and the mixing ratio thereof.
  • the first alloy was composed of of 31 % neodymium, 68% iron and 1 % boron as prepared using the same materials as used in Example 1.
  • the second alloy was one of the four alloys having compositions of:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)

Claims (7)

1. Aimant permanent à base de terres rares, formé d'un corps fritté qui est constitué d'un mélange pulvérulent comprenant:
a) 90 à 99,9 parties en poids d'un premier alliage contenant 25 à 35% en poids d'un élément léger des terres rares et 0,7 à 1,5% en poids de bore, le reste étant du fer, du cobalt ou une combinaison de fer et de cobalt; et
b) 10 à 0,1 partie en poids d'un second alliage contenant de 30 à 86% en poids d'un élément lourd des terres rares, le reste étant un élément choisi dans le groupe constitué par l'aluminium, le niobium, le zirconium, le vanadium, le tantale et le molybdène.
2. Aimant permanent à base de terres rares selon la revendication 1, dans lequel l'élément léger des terres rares est choisi dans le groupe constitué par le lanthane, le cérium, le praséodyme, le néodyme et le samarium.
3. Aimant permanent à base de terres rares selon la revendication 1, dans lequel l'élément lourd des terres rares est choisi dans le groupe constitué par le gadolinium, le terbium, le dysprosium, l'holmium, l'erbium, le thulium, l'ytterbium et le lutétium.
4. Aimant permanent à base de terres rares selon la revendication 1, dans lequel au moins 50% en poids de l'élément léger des terres rares compris dans le premier alliage est le néodyme, le praséodyme ou une combinaison de ces éléments.
5. Aimant permanent à base de terres rares selon la revendication 1, dans lequel au moins 50% en poids de l'élément lourd des terres rares compris dans le second alliage est le terbium, le dysprosium, l'holmium ou une combinaison de ces éléments.
6. Aimant permanent à base de terres rares selon la revendication 1, dans lequel le second alliage est un alliage de dysprosium et d'aluminium.
7. Aimant permanent à base de terres rares selon la revendication 1, dans lequel le mélange pulvérulent présente une répartition granulométrique dans la gamme de 2 à 8 µm.
EP19870400473 1986-03-06 1987-03-04 Aimant permanent à base de terres rares Expired EP0237416B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP49245/86 1986-03-06
JP61049245A JPH07105289B2 (ja) 1986-03-06 1986-03-06 希土類永久磁石の製造方法

Publications (2)

Publication Number Publication Date
EP0237416A1 EP0237416A1 (fr) 1987-09-16
EP0237416B1 true EP0237416B1 (fr) 1989-11-08

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EP19870400473 Expired EP0237416B1 (fr) 1986-03-06 1987-03-04 Aimant permanent à base de terres rares

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EP (1) EP0237416B1 (fr)
JP (1) JPH07105289B2 (fr)
DE (1) DE3760962D1 (fr)

Families Citing this family (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1336866C (fr) * 1986-08-04 1995-09-05 Setsuo Fujimura Aimant comportant des metaux du groupe des terres rares, a excellente resistance a la corrosion
EP0265006A1 (fr) * 1986-10-13 1988-04-27 Koninklijke Philips Electronics N.V. Méthode de fabrication d'un aimant permanent
US5000800A (en) * 1988-06-03 1991-03-19 Masato Sagawa Permanent magnet and method for producing the same
GB2232165A (en) * 1989-03-22 1990-12-05 Cookson Group Plc Magnetic compositions
BE1007857A3 (nl) * 1993-12-06 1995-11-07 Philips Electronics Nv Permanente magneet op basis van re-fe-b.
US6319336B1 (en) 1998-07-29 2001-11-20 Dowa Mining Co., Ltd. Permanent magnet alloy having improved heat resistance and process for production thereof
EP0994493B1 (fr) * 1998-10-14 2003-09-10 Hitachi Metals, Ltd. Aimant permanent fritté du type R-T-B
WO2002061769A1 (fr) 2001-01-30 2002-08-08 Sumitomo Special Metals Co., Ltd. Procede de preparation d'un aimant permanent
CN1306527C (zh) 2001-12-18 2007-03-21 昭和电工株式会社 用于稀土磁体的合金薄片及其生产方法、用于稀土烧结磁体的合金粉末、稀土烧结磁体、用于结合磁体的合金粉末和结合磁体
JP2005286176A (ja) * 2004-03-30 2005-10-13 Tdk Corp Ｒ−ｔ−ｂ系焼結磁石及びその製造方法
US8123832B2 (en) 2005-03-14 2012-02-28 Tdk Corporation R-T-B system sintered magnet
EP2178096B1 (fr) * 2007-07-27 2015-12-23 Hitachi Metals, Ltd. AIMANT FRITTÉ À BASE DE TERRE RARE-Fe-B
JP2010263172A (ja) 2008-07-04 2010-11-18 Daido Steel Co Ltd 希土類磁石およびその製造方法
US8480815B2 (en) * 2011-01-14 2013-07-09 GM Global Technology Operations LLC Method of making Nd-Fe-B sintered magnets with Dy or Tb
CN104347218A (zh) * 2014-10-30 2015-02-11 浙江鑫盛永磁科技有限公司 一种新型烧结钕铁硼永磁体及其制备方法
FR3030866B1 (fr) 2014-12-18 2021-03-12 Commissariat Energie Atomique Aimant permanent fritte
FR3044161B1 (fr) 2015-11-25 2019-05-03 Commissariat A L'energie Atomique Et Aux Energies Alternatives Aimant permanent fritte
CN107275029B (zh) * 2016-04-08 2018-11-20 沈阳中北通磁科技股份有限公司 一种用钕铁硼废料生产的高性能钕铁硼永磁铁及制造方法
CN110483031A (zh) * 2019-08-21 2019-11-22 南通成泰磁材科技有限公司 耐高温的永磁铁氧体磁性材料及其制备方法

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1315571C (fr) * 1982-08-21 1993-04-06 Masato Sagawa Materiaux magnetiques et aimants permanents
CA1316375C (fr) * 1982-08-21 1993-04-20 Masato Sagawa Materiaux magnetiques et aimants permanents
JPH0778269B2 (ja) * 1983-05-31 1995-08-23 住友特殊金属株式会社 永久磁石用希土類・鉄・ボロン系正方晶化合物
JPS6032306A (ja) * 1983-08-02 1985-02-19 Sumitomo Special Metals Co Ltd 永久磁石
DE3587977T2 (de) * 1984-02-28 1995-05-18 Sumitomo Spec Metals Dauermagnete.
US4767450A (en) * 1984-11-27 1988-08-30 Sumitomo Special Metals Co., Ltd. Process for producing the rare earth alloy powders
JP2537189B2 (ja) * 1985-10-25 1996-09-25 株式会社東芝 永久磁石

Also Published As

Publication number Publication date
JPS62206802A (ja) 1987-09-11
EP0237416A1 (fr) 1987-09-16
DE3760962D1 (en) 1989-12-14
JPH07105289B2 (ja) 1995-11-13

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