Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
1999-02-26
2001-07-03
Sheehan, John (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C419S038000, C419S012000, C148S302000, C148S101000
Reexamination Certificate
active
06254659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a permanent magnet of the type SE—Fe—B that has the tetragonal phase SE
2
Fe
4
B as the principal phase, wherein SE is at least one rare earth element, including Y.
2. Description of the Prior Art
A magnet of the above general type is disclosed, for example, by in European Application 0 124 655 and in U.S. Pat. No. 5,230,751 that corresponds thereto. Magnets of the type SE—Fe—B exhibit the highest energy densities currently available. SE—Fe—B magnets manufactured by powder metallurgy contain approximately 90% of the hard-magnetic principal phase SE
2
Fe
14
B.
German Offenlegungsschrift 41 35 403 discloses a two-phase magnet, wherein the second phase can be a SE—Fe—Co—Ga phase.
European Application 0 583 041 likewise discloses a two-phase magnet, wherein second phase is composed of a SE—Ga phase.
U.S. Pat. No. 5,447,578 discloses a SE-transition metal-Ga phase.
Conventionally in the manufacture of these Se—Fe—B-magnets by combining Se—Fe—B base alloys with the composition close to the SE
2
Fe
14
B phase with a binder alloy with a lower melting temperature. The goal is thereby that the structure of the SE—Fe—B sintered magnets of SE
2
Fe
14
B base alloys is set with inter-granular binders, using optimally little binder alloy.
European Application 0 517 179 proposes the employment of binder alloys having the composition Pr
20
Dy
10
Co
40
B
6
Ga
4
Fe
rest
(in weight percent, this is Pr≈35, Dy≈20, Co≈28, B≈0.77, Ga≈3.5).
It has now turned out that the proportion of this binder alloy in the mixture of the base alloy must lie within 7-10 weight %. In this mixing range, sinter densities of approximately &rgr;>7.55 g/cm
3
are achieved only at sintering temperatures above 1090° C. These sinter densities roughly correspond to 99% of the theoretical density. Outside this mixing range, the sinterability, and thus the remanence that can be achieved are considerably influenced. The grain growth is highly activated in the magnets with a proportion of this binder alloy of more than 10 weight %, but the pores are not closed. The consequence is the formation of a structure with anomalously large grains (>50 &mgr;m) and with high porosity as well as with low sinter densities. Given lower proportions of binder alloy, the amount of the fluid phase is accordingly not adequate for the densification.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a permanent magnet of the type SE—Fe—B manufactured by powder metallurgy that exhibits an enhanced sinterability compared to the known magnets upon reduction of the proportion of binder alloy and also exhibits a very good remanence, and to also specify a method for the manufacture thereof.
The object is inventively achieved by a permanent magnet that additionally contains an iron-free and boron-free phase of the general formula SE
5
(Co, Ga)
3
as binder alloy, wherein SE is at least one rare earth element, including Y.
The inventive permanent magnet is expediently manufactured with a method having the following steps:
a
1
) a powder of a base alloy of the general formula
SE
2
T
4
B,
wherein SE is at least one rare earth element, including Y, and T is Fe or a combination of Fe and Co, whereby the Co part does not exceed 40 weight % of the combination of Fe and Co,
a
2
) and a powder of a binder alloy of the general formula
SE′
5
T
3
,
wherein SE′ is at least one rare earth element, including Y, and T is a combination of Co and Ga are mixed in a weight ratio of 99:1 to 90:10;
b) the mixture is compressed and, subsequently,
c) is sintered in a vacuum and/or in an inert gas atmosphere.
It has been shown that permanent magnets manufactured in this way exhibit very high remanences, and that the proportion of binder alloy compared to the proportion of the base alloy can be reduced to below 7 weight %. Further, the additional gallium-containing phase of the binder alloy exhibits especially good wetting properties.
REFERENCES:
patent: 5230751 (1993-07-01), Endoh et al.
patent: 5405455 (1995-04-01), Kusunoki et al.
patent: 5447578 (1995-09-01), Ozaki et al.
patent: 5595608 (1997-01-01), Takebuchi et al.
patent: 6045751 (2000-04-01), Buschow et al.
patent: 41 35 403 (1993-04-01), None
patent: 0 517 179 (1992-12-01), None
patent: 0 583 041 (1994-02-01), None
patent: 0 651 401 (1995-05-01), None
patent: 6-207203 (1994-07-01), None
Schrey Peter
Velicescu Mircea
Schiff & Hardin & Waite
Sheehan John
Vacuumschmeleze GmbH
LandOfFree
Rare earth - iron -boron permanent magnet and method for the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rare earth - iron -boron permanent magnet and method for the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rare earth - iron -boron permanent magnet and method for the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446461