(19)
(11) EP 0 286 357 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
06.06.1990 Bulletin 1990/23

(43) Date of publication A2:
12.10.1988 Bulletin 1988/41

(21) Application number: 88303018.1

(22) Date of filing: 05.04.1988
(51) International Patent Classification (IPC)4H01F 41/02, H01F 1/08
(84) Designated Contracting States:
DE FR GB

(30) Priority: 06.04.1987 US 34862

(71) Applicants:
  • FORD MOTOR COMPANY LIMITED
    Brentwood, Essex CM13 3BW (GB)

    GB 
  • FORD FRANCE SOCIETE ANONYME
    F-92506 Rueil Malmaison Cedex (FR)

    FR 
  • FORD-WERKE AKTIENGESELLSCHAFT
    D-50725 Köln (DE)

    DE 

(72) Inventors:
  • Patel, Suresh G.
    Canton Michigan 48187 (US)
  • Hadjipanayis, George C.
    Manhattan, KS 66502 (US)
  • Christoduoulou, Christodoulos
    Pittsburgh PA 15206 (US)
  • Abbott, Edward H.
    Ann Arbor Michigan 48104 (US)
  • Erickson, Robert H.
    West Bloomfield Michigan 48003 (US)

(74) Representative: Messulam, Alec Moses et al
A. Messulam & Co. 24 Broadway
Leigh on Sea Essex SS9 1BN
Leigh on Sea Essex SS9 1BN (GB)


(56) References cited: : 
   
       


    (54) Multiphase permanent magnet of the Fe-B-MM type


    (57) A method is disclosed for producing a permanent magnet of the Fe-B-MM type, comprising: (a) preparing a metallic powder having a mean particle size of 2-5 microns and having a composition comprising, by atomic weight percent: 60-80% Fe, 1-8% Al, 6-10% B, .1-.43% oxygen, 0-5% Dy and/or 0-10% Ni, and 12-22% MM, where MM is a misch metal (preferably having at least four naturally occurring insoluble cerium earth metals with a least 20% of the misch metal consisting of cerium and lanthanum), the powder having essentially a multiphase crystalline structure dominated by at least two R₂Fe₁₄B phases; (b) aligning such powder in a magnetic field; (c) compacting the aligned powder into shapes; (d) sintering such shapes at a temperature and for a period of time (i.e., in the range of 1000-1100°C for .5-9 hours) to fuse the powder and increase the proportion of said R₂Fe₁₄B phases to at least 70% by volume of the shapes; and preferably (e) anealing the sintered shapes at a temperature (i.e., in the range of 550-650°C for 1-4 hours) to cause the shapes to consist essentially of at least two R₂Fe₁₄B phases comprising the matrix and the phase RFe₄B₄ and the R-rich phase residing essentially in the grain boundaries.





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