Permanent magnet

Details Permanent magnet Permanent magnet

1990-11-29

1993-04-06

Sheehan, John P.

Metal treatment

Stock

Magnetic

420 83, 420121, 75244, H01F 1053

Patent

active

052000010

ABSTRACT:
An anisotropic sintered permanent magnet consists essentially of 12 to 18 at % R, wherein R represents Pr, Nd, Dy, Tb and other rare earth element or elements contained as inevitable impurities provided that 0.8.ltoreq.(Pr+Nd+Dy+Tb)/R.ltoreq.1.0, 5 to 9.5 at % B, 2 to 5 at % Mo, 0.01 to 0.5 at % Cu, 0.1 to 3 at % Al, and balance being Fe. B(x) and Mo(y) are (x-4.5).ltoreq.y.ltoreq.(x-3.0), and part of Fe may be replaced by Co to be 3-7 at % Co. Up to 90 at % of Mo may be replaced by V. The magnet is characterized by main tetragonal R.sub.2 (Fe, Mo).sub.14 B or R.sub.2 (Fe, Co, Mo).sub.14 B phase and boundary phase of (Fe, Mo)-B, or (Fe, Co, Mo)-B and R.sub.m (Fe, Co, Mo).sub.n where m
=1/2 to 3/1. B-rich phase Nd.sub.1+.epsilon. Fe.sub.4 B.sub.4 disappears. Dy and/or Tb linearly increase iHc. High coercivity and maximum energy product are obtained: iHc.gtoreq.15 kOe (or 21 kOe) and (BH)max.gtoreq.20 MGOe (or 28 MGOe) with high corrosion resistance and high pulverizability of alloy.

REFERENCES:
patent: 4773950 (1983-09-01), Fujimura et al.
patent: 4814139 (1989-03-01), Tokunaga et al.
M. Endoh et al., "Magnetic Properties and Thermal Stabilities of Ga Substituted ND-Fe-Co-B Magnets", IEEE Trans. on Magnetics, vol. MAG-23, No. 5, p. 2290 (Sep. 1987).
X. Shen et al., "The effect of molybdenum on the magnetic properties of the ND-Fe-Co-B system", J. Appl. Phys., 61 (8), p. 3433 (1987).
Liu Guozeng et al., "Effect of Mo Addition on the Magnetic Properties and Thermal Stability of Sintered (PrNd)-Fe-Co-Al-B Magnet", AG-23, paper distributed at Kyoto, Japan in May 1989.
IEEE Transactions of Magnetics, vol. 25, No. 5, Sep. 1989, N.Y. US, pp. 3770-3772; W. Rodewald & P. Schrey: "Structural and Magnetic Properties of Sintered Nd14.4Fe67.0-xCo11.8MoxB6.8 Magnets".
Patent Abstracts of Japan, vol. 12, No. 82 (C-481)(2929) Mar. 15, 1988, and JP-A-62 218543 (Seiko) Sep. 25, 1987.
Proc. 8th Int. Workshop of Rare Earth Magnets 1985 BG pp. 541-552, A. Maocai et al. "Effects of Additive Elements of Magnetic Properties of Sintered Nd-B-Fe Magnet".
IEEE Transactions on Magnetics, vol. 26, No. 5, Sep. 1990, N.Y. US, 1960-1962, S. Hirosawa et al.: "High Coercivity Nd-Fe-B Type Permanent Magnets With Less Dysprosium".

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