EP0185439B1 - Permanent magnet alloy - Google Patents

Permanent magnet alloy Download PDF

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Publication number
EP0185439B1
EP0185439B1 EP85306148A EP85306148A EP0185439B1 EP 0185439 B1 EP0185439 B1 EP 0185439B1 EP 85306148 A EP85306148 A EP 85306148A EP 85306148 A EP85306148 A EP 85306148A EP 0185439 B1 EP0185439 B1 EP 0185439B1
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Prior art keywords
dysprosium
alloy
neodymium
coercive force
permanent magnet
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EP85306148A
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German (de)
French (fr)
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EP0185439A1 (en
Inventor
Kalathur S.V.L. Narasimham
Bao-Min Ma
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Crucible Materials Corp
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Crucible Materials Corp
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    • 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
    • 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

Definitions

  • This invention relates to permanent magnet alloys.
  • Permanent magnet alloys used in the production of permanent magnets for use in electric motors, and particularly electric motors used in household appliances and the like, are required to have good resistance to demagnetization at elevated temperatures for efficient motor operation.
  • the temperatures involved in these motor applications are typically within the range of 125 to 150°C.
  • To achieve high resistance to demagnetization good remanence (B r ) and coercive force (He;) values are required within this temperature range. It is further desired in applications such as permanent magnets used in electric motors for household appliance applications that the alloy of the magnet be relatively low cost.
  • a more specific object of the invention is to provide a permanent magnet alloy of low cost having a good combination of both remanence and coercive force within the temperature range of 125 to 150°C which increase in coercive force is achieved by an improved crystal anisotropy without decreasing remanence to below acceptable levels.
  • the permanent magnet alloy of the invention consists of, in weight percent, 1 to 10 dysprosium, 20 to 37 neodymium, with the total dysprosium and neodymium content being within the range of 30 to 38, 0.8 to 1.33 boron and balance iron and impurities usual in metal alloys.
  • the dysprosium content is from 2.5 to 6.5% and more preferred from 3 to 6%.
  • the single figure of the drawing is a graph illustrating the effect of the dysprosium content of a magnet alloy on the coercive force.
  • the following specific examples of the invention show with neodymium, iron, boron magnets the temperature effect on loss of coercive force. Also, the examples demonstrate that coercive force in magnet alloys of this type are increased by the addition of dysprosium as a rare earth element. They also show that increased dysprosium above the limits of the invention decreases remanence values to below acceptable levels. Consequently, it is critical with regard to achieving a combination of good remanence and coercive force within the required temperature range of 125 to 150°C to have the rare earth element content of the alloy comprise a combination of dysprosium and neodymium.
  • Dysprosium was added to the NdFeB alloy while maintaining the total rare earth content as 35.6% and 37.1%.
  • Tables II and III list the magnetic properties of the magnets.
  • dysprosium addition in combination with neodymium permits utilization of these magnets at elevated temperatures. Increasing the dysprosium further results in a decrease in B r which makes the magnets not have enough flux at the required temperature for the intended applications.
  • Table V shows the magnetic properties of a 10% Dy containing magnet.

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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)

Abstract

A permanent magnet alloy consisting of, in weight percent, 1 to 10 dysprosium, 20 to 37 neodymium, with the total dysprosium and neodymium content being within the range of 30 to 38, 0.8 to 1.33 boron and balance iron and impurities usual in metal alloys. This alloy is characterized by high resistance to demagnetization at elevated temperatures with the alloy content being of relatively low cost.

Description

  • This invention relates to permanent magnet alloys.
  • Permanent magnet alloys used in the production of permanent magnets for use in electric motors, and particularly electric motors used in household appliances and the like, are required to have good resistance to demagnetization at elevated temperatures for efficient motor operation. The temperatures involved in these motor applications are typically within the range of 125 to 150°C. To achieve high resistance to demagnetization good remanence (Br) and coercive force (He;) values are required within this temperature range. It is further desired in applications such as permanent magnets used in electric motors for household appliance applications that the alloy of the magnet be relatively low cost.
  • It is known that permanent magnet alloys of neodymium, iron, boron have remanence values sufficiently high for the purpose and these are relatively inexpensive alloys; however, at the typical service temperatures of 125 to 150°C magnets of these alloys are characterized by a loss of coercive force to below the level suitable for the purpose. Coercive force is known to be increased by increasing the crystal anisotropy or the anisotropy field (HA).
  • It is accordingly a primary object of the present invention to provide a low-cost permanent magnet.alloy that may be used in the manufacture of magnets having high resistance to demagnetization at elevated temperatures within the range of 125 to 150°C.
  • A more specific object of the invention is to provide a permanent magnet alloy of low cost having a good combination of both remanence and coercive force within the temperature range of 125 to 150°C which increase in coercive force is achieved by an improved crystal anisotropy without decreasing remanence to below acceptable levels.
  • The permanent magnet alloy of the invention consists of, in weight percent, 1 to 10 dysprosium, 20 to 37 neodymium, with the total dysprosium and neodymium content being within the range of 30 to 38, 0.8 to 1.33 boron and balance iron and impurities usual in metal alloys. Preferably the dysprosium content is from 2.5 to 6.5% and more preferred from 3 to 6%.
  • The invention will be more particularly described with reference to the accompanying drawing taken in conjunction with the following description and specific examples.
  • The single figure of the drawing is a graph illustrating the effect of the dysprosium content of a magnet alloy on the coercive force.
  • It is known generally that coercive force (He;) is increased by increases in the crystal ansotropy (HA). It has been discovered, in accordance with the present invention, that generally with magnet alloys of iron and boron with a neodymium content of approximately 33% the H" in kilo oersteds is 150*; with similar alloys having dysprosium as the rare earth element the HA values in kilo oersteds are approximately 314. It may be seen, therefore, that by the use of dysprosium in rare earth, iron, boron alloys the crystal anisotropy is improved to in turn increase the coercive force. In addition, however, it has been determined that the use of dysprosium in alloys of this type decreases remanence (Br.
  • The following specific examples of the invention show with neodymium, iron, boron magnets the temperature effect on loss of coercive force. Also, the examples demonstrate that coercive force in magnet alloys of this type are increased by the addition of dysprosium as a rare earth element. They also show that increased dysprosium above the limits of the invention decreases remanence values to below acceptable levels. Consequently, it is critical with regard to achieving a combination of good remanence and coercive force within the required temperature range of 125 to 150°C to have the rare earth element content of the alloy comprise a combination of dysprosium and neodymium.
  • An alloy of Nd (33%) B (1%) Fe (66%) in weight percent was melted, crushed to about 1 to 10 11m particle size. The fine powder was oriented in a magnetic field and pressed. The pressed part was sintered over a temperature range of 1000°C-1100°C and cooled. The sintered magnet had the intrinsic coercive force at the indicated temperatures in Table I.
    Figure imgb0001
    The remanance of the magnet varied from 12,100 Gauss** to 10,738 Gauss** from 20° to 145°C. The loss of intrinsic coercive force to below 6,000 Oersted at 94°C makes this magnet not applicable for motors.
  • Dysprosium was added to the NdFeB alloy while maintaining the total rare earth content as 35.6% and 37.1%. Tables II and III list the magnetic properties of the magnets.
    Figure imgb0002
    Figure imgb0003
    Figure imgb0004
  • As can be seen from Tables 11 and 111 and Figure 1 adding dysprosium increases the coercive force rapidly at room temperature. The temperature dependence of the coercive force of a 3% Dy containing alloy and 6% Dy containing alloy is given in Table IV.
    Figure imgb0005
  • As can be seen from Table IV, dysprosium addition in combination with neodymium permits utilization of these magnets at elevated temperatures. Increasing the dysprosium further results in a decrease in Br which makes the magnets not have enough flux at the required temperature for the intended applications. Table V shows the magnetic properties of a 10% Dy containing magnet.
    Figure imgb0006

Claims (3)

1. A permanent magnetic alloy of the REFeB- type characterised in consisting of, in weight percent, 1 to 10 dysprosium, 20 to 37 neodymium, with the total dysprosium and neodymium content being within the range of 30 to 38, 0.8 to 1.33 boron and balance iron and impurities usual in metal alloys and having good coercive force at elevated temperature.
2. An alloy according to Claim 1 wherein dysprosium is present in an amount of from 2.5 to 6.5%.
3. An alloy according to Claim 1 or 2, wherein dysprosium is present in an amount of from 3 to 6%.
EP85306148A 1984-12-10 1985-08-30 Permanent magnet alloy Expired EP0185439B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85306148T ATE43932T1 (en) 1984-12-10 1985-08-30 PERMANENT MAGNET ALLOY.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US67973984A 1984-12-10 1984-12-10
US679739 1984-12-10

Publications (2)

Publication Number Publication Date
EP0185439A1 EP0185439A1 (en) 1986-06-25
EP0185439B1 true EP0185439B1 (en) 1989-06-07

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ID=24728160

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EP85306148A Expired EP0185439B1 (en) 1984-12-10 1985-08-30 Permanent magnet alloy

Country Status (5)

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EP (1) EP0185439B1 (en)
JP (1) JPS61139641A (en)
AT (1) ATE43932T1 (en)
CA (1) CA1273231A (en)
DE (1) DE3570942D1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4837109A (en) * 1986-07-21 1989-06-06 Hitachi Metals, Ltd. Method of producing neodymium-iron-boron permanent magnet
EP0277416A3 (en) * 1987-02-04 1990-05-16 Crucible Materials Corporation Permanent magnet alloy for elevated temperature applications
JP2001332410A (en) * 2000-05-22 2001-11-30 Seiko Epson Corp Magnet powder, method for producing magnet powder, and bonded magnet

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0108474A2 (en) * 1982-09-03 1984-05-16 General Motors Corporation RE-TM-B alloys, method for their production and permanent magnets containing such alloys

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES533292A0 (en) * 1981-06-16 1985-04-16 Proyectos Magneticos S A Proma PROCEDURE FOR THE MANUFACTURE OF AN ALLOY THAT HAS PERMANENT MAGNETIC PROPERTIES AT ROOM TEMPERATURE
JPS59163802A (en) * 1983-03-08 1984-09-14 Sumitomo Special Metals Co Ltd Permanent magnet material
JPS59204209A (en) * 1983-05-06 1984-11-19 Sumitomo Special Metals Co Ltd Isotropic permanent magnet and manufacture thereof
JPS59215460A (en) * 1983-05-21 1984-12-05 Sumitomo Special Metals Co Ltd Permanent magnet material and its production

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0108474A2 (en) * 1982-09-03 1984-05-16 General Motors Corporation RE-TM-B alloys, method for their production and permanent magnets containing such alloys

Also Published As

Publication number Publication date
JPS61139641A (en) 1986-06-26
DE3570942D1 (en) 1989-07-13
ATE43932T1 (en) 1989-06-15
CA1273231A (en) 1990-08-28
EP0185439A1 (en) 1986-06-25

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