EP0242283A1 - Legierung auf Basis seltener Erden für Permanentmagnet - Google Patents

Legierung auf Basis seltener Erden für Permanentmagnet Download PDF

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Publication number
EP0242283A1
EP0242283A1 EP87400808A EP87400808A EP0242283A1 EP 0242283 A1 EP0242283 A1 EP 0242283A1 EP 87400808 A EP87400808 A EP 87400808A EP 87400808 A EP87400808 A EP 87400808A EP 0242283 A1 EP0242283 A1 EP 0242283A1
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EP
European Patent Office
Prior art keywords
rare earth
iron
permanent magnet
alloy
cobalt
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.)
Granted
Application number
EP87400808A
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English (en)
French (fr)
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EP0242283B1 (de
Inventor
Ken Ohashi
Toshikazu Yokoyama
Yoshio Tawara
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
Priority claimed from JP61084724A external-priority patent/JPS62241303A/ja
Priority claimed from JP61084723A external-priority patent/JPS62241302A/ja
Application filed by Shin Etsu Chemical Co Ltd filed Critical Shin Etsu Chemical Co Ltd
Publication of EP0242283A1 publication Critical patent/EP0242283A1/de
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Publication of EP0242283B1 publication Critical patent/EP0242283B1/de
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
    • H01F1/0557—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together sintered

Definitions

  • the present invention relates to a rare earth-based alloy for permanent magnet having excellent magnetic properties and suit­able as a component of various kinds of electric and electronic in­struments.
  • Various kinds of rare earth-based permanent magnet alloys have been developed hitherto and are under production in large quantities including the samarium-cobalt magnet alloys of the chemical composition SmCo5.
  • the magnetic properties of the per­manent magnets of this type are so excellent that the maximum energy product (BH) max thereof exceeds 20 MGOe in the magnets manufactured under experimental conditions or is constantly in the range from 16 to 18 MGOe in the magnets manufactured as in­dustrial products. Accordingly, these permanent magnets are widely used in a variety of applications such as speakers, electric motors, metering instruments and the like in which the perma­nent magnets are required to exhibit high performance.
  • the only permanent magnet based on a rare earth-iron binary compound so far report­ed is the magnet in a metastable phase prepared by the quenched thin-film method disclosed by Croat, et al. in IEEE Transactions on Magnetics, volume MAG 18, page 1442 (November, 1982).
  • the quenched thin-film magnet prepared by this method is isotropic and based on a metastable phase so that the magnet is not free from the problem of low stability so that the magnets of this type are not in practical use.
  • neodymium-iron-­boron magnets formed of a ternary compound of a chemical compo­sition of the formula R2F14B, they are promising as a high-per­formance permanent magnet since the base components are inex­pensive neodymium and iron and the magnetic properties thereof are even better than those of the samarium-cobalt magnets.
  • These neodymium-iron-boron magnets are, however, not free from a very serious problem that they are highly susceptible to rusting so that the magnets cannot be used practically without providing a protective coating. This disadvantage can hardly be overcome and no practical solution of the problem has yet been obtained to give a possibility of industrial production of the magnets of this type.
  • An object of the present invention is therefore to provide a rare earth-based permanent magnet having magnetic properties equivalent to or even better than those of the samarium-cobalt permanent magnets without using or by decreasing the amount of expensive cobalt as well as to provide a rare earth-based alloy as a base material of such a permanent magnet.
  • the permanent magnet alloy of the present invention consists essentially of:
  • the permanent magnet of the invention is a sintered body of a powder of the above defined rare earth-based alloy hav­ing magnetic anisotropy.
  • the inventors have conducted ex­tensive investigations on a third additive element to be added to the rare earth-iron binary magnet alloys and arrived at discover­ies that addition of titanium would give a quite satisfactory result and a hitherto unknown ternary intermetallic compound of sama­rium, titanium and iron can exist in a bulky form by the optimi­zation of the amount of substitution of titanium for the rare earth element or, in particular, samarium.
  • a ternary alloy of sa­marium, titanium and iron was prepared in such a proportion as to correspond to the formula of SmTiFe10 and the alloy was subjected to the measurement of the magnetization as a function of tempera­ture and X-ray diffractometry to give the results shown in FIG­URES 1 and 2, respectively.
  • crys­tallographic indices approximately corresponding to those of the tetragonal crystalline structure can be allotted to the peaks in the X-ray diffractometric diagram of the ternary ally and the temper­ature dependency of the magnetization thereof is also close to that of a single-phase alloy leading to a conclusion that the ternary compound of samarium, titanium and iron is imparted with stabi­lity as a result of introduction of titanium into the samarium-iron binary alloy.
  • the further continued investigations have led to con­firmation that the above described unique phenomenon is held also for the rare earth elements in general other than samarium including yttrium.
  • the present invention provides, as an embodiment, a ternary alloy composed of (a) from 12 to 45% by weight of a rare earth element or a combination of rare earth elements; (b) from 0.1 to 10% by wieght of titanium; and (c) the balance of iron including unavoidable impurities.
  • the magnet alloy can be obtained by melting the component metals together and the alloy is finely pulverized followed by the powder metallurgical processing of the powder by compression molding and sintering.
  • the ternary compound When the amount of the rare earth component in the alloy formulation is outside the above specified range, the ternary compound would be less stable and, therefore, any amounts thereof smaller than 12% by weight and larger than 45% may result in a disadvantageously rapid de­crease in the coercive force i H c and saturation magnetization 4 ⁇ M s , respective-ly.
  • the above mentioned range for titanium is also critical because the ternary compound is less stable when the amount of titanium is smaller than 0.1% by weight while the frac­tion of the phase of the ternary compound is decreased when the amount of titanium is larger than 10% by weight.
  • the rare earth element here implied include the so-called lanthanoid elements having atomic munbers of 57 to 71 and yttrium. Any of these rare earth elements can be used either singly or as a combination of two kinds or more according to need.
  • the rare earth-based permanent magnet of the invention prepared of the ternary alloy contains the stable phase of the ter­nary compound as a result of the introduction of titanium so that the Curie point thereof is about 310°C when the rare earth ele­ment is samarium which is much higher than 120°C of the Sm2Fe17 phase.
  • the saturation magnetization is also greatly increased so that the thus obtained permanent magnet has very high magnetic properties.
  • the rare earth-titanium-­iron permanent magnet of the invention can be imparted with magnetic anistropy by the powder metallurgical method so that the overall magnetic performance of the inventive permanent magnet can be almost equivalent to or even better than the sama­rium-cobalt based magnets.
  • the inventive permanent mgnet is highly cor­rosion-resistant and free from rusting in clear contrast to the neo­dymium-iron based magnets. Accordingly, the inventive perma­nent magnets can be used in practical applications without any pr­tective coating on the surface although the corrosion resistance thereof can of course be further increased by a protective coating or surface treatment by forming a resinous layer or a metallic layer formed by electrolytic or electroless plating, vacuum vapor deposi­tion, sputtering or ion plating.
  • the ternary alloy can be processed into a thin film having a high coercive force by the quenched thin-film method and the thin film can be finely pulverized into fine particles of which magnetically isotropic permanent magnets can be prepared. It is of course that the magnetically anisotropic sintered magnet is pul­verized into fine particles of which anisotropic plastic magnets can be prepared.
  • the permanent magnet of the ternary alloy of samarium, titanium and iron has a Curie point of about 310°C. Although this Curie point is well within the practically ac­ceptable range, it is of course desirable to have a higher Curie point when comparison is made with the SmCo5 permanent mag­nets having a Curie point at about 740°C.
  • the in­ventors have further continued extensive investigations and arriv­ed at a discovery that a magnetic alloy suitable for the purpose can be obtained when a solid solution is formed of the above described ternary compound of rare earth, titanium and iron with cobalt.
  • an increase by about 40 to 100°C can be obtained in the Curie point of the ternary alloy when 10 atomic % of iron in the alloy is replaced with cobalt although the increment depends on the kind of the rare earth element.
  • the Curie point T c is increased approximately linearly with the increase in the amount of replace­ment of iron with cobalt up to 50% replacement by weight but thereafter the increment in the Curie point is relatively small with further increased replacement of iron with cobalt to finally level off.
  • the saturation magnetization of the magnet is in­creased as a trend though dependent on the kind of the rare earth element by the substitution of cobalt for a part of iron in the ter­nary magnet alloy of rare earth, titanium and iron to level off with increase of the proportion of cobalt relative to iron.
  • Metals of samarium, titanium and iron each having a purity of 99.9% were taken by weighing in the proportion indicated in Table 1 below and melted together in a high-frequency induction furnace. The melt was cast into a water-cooled, copper-made cast­ing mold to form an ingot of the alloy. The ingot was crushed and then pulverized in a jet mill using nitrogen gas as the ject gas to give a fine powder having an average particle diameter in the range from 2 to 10 ⁇ m.
  • the powder was compression-molded under a pressure of 1.5 tons/cm2 with the particles oriented in a static magnetic field of 15 KOe into a green body, which was sintered by heating in an atmosphere of argon gas for 1 hour at a temperature in the range form 1000 to 1200 °C and then subjected to thermal aging for 4 hours at a temperature in the range from 500 to 900 °C followed by quenching.
  • Table 1 also includes the results of the magnetic measurement of a sintered body of a samarium-iron al­ loy corresponding to SmFe5 (No. 4) prepared in the same manner as above. As is shown in the table, this comparative sintered body had only negligibly small values of coercive force and maximum energy product.
  • Magnetically anisotropic sintered permanent magnets No. 1 to No. 4 were prepared each in the same manner as in Example 1 except that the magnetic alloy was prepared from metals of neody­mium, titanium, iron and cobalt each having a purity of 99.9% taken by weighing in the proportion indicated in Table 3.
  • Magnetically anisotropic sintered permanent magnets No. 1 and No. 2 were prepared in the same manner as in the preceding examples from metals of samarium, cerium, titanium, iron and co­balt taken by weighing in the proportion indicated in Table 4 below. These sintered permanent magnets were subjected to the measurement of the magnetic properties to give the results shown in the table.

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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)
EP87400808A 1986-04-12 1987-04-09 Legierung auf Basis seltener Erden für Permanentmagnet Expired - Lifetime EP0242283B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP84724/86 1986-04-12
JP61084724A JPS62241303A (ja) 1986-04-12 1986-04-12 希土類永久磁石
JP61084723A JPS62241302A (ja) 1986-04-12 1986-04-12 希土類永久磁石
JP84723/86 1986-04-12

Publications (2)

Publication Number Publication Date
EP0242283A1 true EP0242283A1 (de) 1987-10-21
EP0242283B1 EP0242283B1 (de) 1990-11-07

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Family Applications (1)

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EP87400808A Expired - Lifetime EP0242283B1 (de) 1986-04-12 1987-04-09 Legierung auf Basis seltener Erden für Permanentmagnet

Country Status (2)

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EP (1) EP0242283B1 (de)
DE (1) DE3765980D1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0386286A1 (de) * 1987-09-17 1990-09-12 Shin-Etsu Chemical Co., Ltd. Auf Seltenerdeisen basierender Dauermagnet
DE102013009940A1 (de) * 2013-06-13 2014-12-18 Hochschule Aalen Magnetisches Material, seine Verwendung und Verfahren zu dessen Herstellung

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4221613A (en) * 1978-02-03 1980-09-09 Namiki Precision Jewel Co., Ltd. Rare earth-cobalt system permanent magnetic alloys and method of preparing same

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4221613A (en) * 1978-02-03 1980-09-09 Namiki Precision Jewel Co., Ltd. Rare earth-cobalt system permanent magnetic alloys and method of preparing same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 85, no. 18, November 1, 1976, Columbus, Ohio, USA TOKYO SHIBAURA ELECTRIC CO., "Sintered alloy permanent magnets" page 903, column 1, abstract no. 136255z; & JP-A-51 047 296 (TOKYO SHIBAURA ELECTRIC CO) 22 APRIL 1976 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0386286A1 (de) * 1987-09-17 1990-09-12 Shin-Etsu Chemical Co., Ltd. Auf Seltenerdeisen basierender Dauermagnet
DE102013009940A1 (de) * 2013-06-13 2014-12-18 Hochschule Aalen Magnetisches Material, seine Verwendung und Verfahren zu dessen Herstellung

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Publication number Publication date
EP0242283B1 (de) 1990-11-07
DE3765980D1 (de) 1990-12-13

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