Patent Number: 6,254,694

Title: R-T-B-based, permanent magnet, method for producing same, and permanent magnet-type motor and actuator comprising same

Abstract: An R--T--B-based, permanent magnet with improved resistance to the deterioration of magnetic properties by working, electroplating, etc. and to their change with time, wherein R is one or more of rare earth elements including Y, and T is Fe, part of which may be substituted by Co, has (a) a corrosion-resistant film layer having an average thickness of 5 .mu.m or more on a surface of a sintered magnet having a composition consisting essentially of 20-45 weight % of R, 15 weight % or less of Co, 0.5-6 weight % of B, and 10 weight % or less of M selected from the group consisting of Al, Si, Nb, Mo, V, Mn, Sn, Ni, Zn, Ti, Cr, Ta, W, Ge, Zr, Hf and Ga, the balance being substantially Fe and inevitable impurities, and (b) a layer richer in rare earth elements than a main phase of R.sub.2 Fe.sub.14 B beneath the corrosion-resistant film layer.

Inventors: Hasegawa; Motohisa (Kumagaya, JP), Sasaki; Takashi (Fukaya, JP)

Assignee: Hitachi Metals, Ltd.

International Classification: H01F 41/02 (20060101); H02K 1/00 (20060101); H02K 1/02 (20060101); H01F 001/057 ()

Expiration Date: 07/03/2018