Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1997-02-11
1998-03-31
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148105, H01F 1058
Patent
active
057333840
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention relates to the field of metallurgical process technology and is concerned with a process for the production of hard-magnetic parts from Sm.sub.2 --(Fe,M).sub.17 --C.sub.y -base work materials with interstitial insertions or inclusions, where M designates gallium and/or at least one metallic element serving to stabilize a rhombohedral 2:17 structure.
The process is applicable, for instance, for the production of hard-magnetic parts based on interstitial Sm.sub.2 Fe.sub.17 C.sub.y -compounds.
b) Description of the Related Art
Owing to their advantageous intrinsic properties (high Curie temperature, saturation polarization and anisotropic field strength), Sm.sub.2 Fe.sub.17 X.sub.y compounds with interstitial inclusions, where X=carbon or nitrogen, have very good preconditions for application as permanent magnet materials (J. M. Coey and H. Sun, J. Magn. Magn. Mater. 87 (1990) L 251).
While nitrogen can be included in such work materials only by way of a gas-solid reaction up to y=3, carbon can be included via this reaction or by melt-metallurgical processes. The Sm.sub.2 Fe.sub.17 X.sub.y compounds produced by the gas phase reaction are unstable at temperatures above 600.degree. C. (B.-P. Hu and G.-C. Liu, Solid State Commun. 79 (1991) 785; C. Kuhrt, M. Katter, K. Schnitzke and L. Schultz, Appl. Phys. Letters 60 (1992) 2029). Therefore, it is not possible to use heat treatments to achieve a greater density, e.g., the powder sintering applied in Nd--Fe--B permanent magnets.
The Sm.sub.2 Fe.sub.17 C.sub.y carbon compounds are unstable when y>1. The carbon content of Sm.sub.2 Fe.sub.17 C.sub.y can be increased to y>1 by substituting gallium for iron as a precondition for improving the interstitial characteristics, since the gallium addition stabilizes the rhombohedral 2:17 structure of the compound which is necessary for good magnetic properties (B.-G. Shen, L.-S. Kong, F.-W. Wang and L. Cao, Appl. Phys. Letters 63 (1993) 2288).
A hard-magnetic iron rare-earth metal alloy with a ThMn.sub.12 structure is known from DE 41 33 214 A1. During production of this alloy, the starting powder must be heat-treated in N.sub.2 gas or nitrogen-containing gases in order to obtain the hard-magnetic phase. The nitrides which occur in this process have inadequate thermal stability, so that the powders must generally be fixed in wax according to a magnetic field orientation to avoid compaction at higher temperatures.
It is also known to produce quick-solidifying strips, e.g., from Sm.sub.2 Fe.sub.15 Ga.sub.2 C.sub.2, directly from the melt. However, there was no indication of any method for the further processing of this material to produce magnets such as the hot pressing and hot deformation methods applied for quick-solidifying Nd--Fe--B materials (R. W. Lee, Appl. Phys. Letters 46 (1985)
SUMMARY OF THE INVENTION
The object of the invention is to provide a process for technologically controllable, economic production of hard-magnetic parts from Sm.sub.2 --(Fe,M).sub.17 --C.sub.y -base work materials with interstitial inclusions, where M designates gallium and/or at least one metallic element serving to stabilize a rhombohedral 2:17 structure.
This object is met, according to the invention, by the production process described in the patent claims.
The process is characterized in that x>0.1 and 3.gtoreq.y.gtoreq.0; mill; 650.degree. C. to 900.degree. C. for partial or complete recrystallization; and magnetic powder is compacted to form magnet bodies by means of a hot pressing processing in a temperature range from 650.degree. C. to 900.degree. C.
The magnet bodies obtained in this way have an isotropic magnetic behavior and can subsequently be provided, according to the invention, with a preferred magnetic orientation by means of a hot deformation process at a temperature ranging from 650.degree. C. to 900.degree. C. and at a pressure of more than 200 MPa.
In accordance with a first embodiment of the process according to the invention, samarium can b
REFERENCES:
patent: 4192696 (1980-03-01), Menth et al.
patent: 5007972 (1991-04-01), Kumar et al.
Journal of Applied Physics, vol. 75, No. 10, B. Shen et al., "A Novel Hard Magnetic Material For Sintering Permanent Magnets", pp. 6253-6255, May 1994.
Jouranal of Applied Physics, vol. 75, No. 1,L. Kohg et al., "High Coercivty Sm-Fe-C compounds with Th2Zn17 Structure By Melt Quenching", pp. 6250-6252, May 1994.
Applied Physics Letters, vol. 68, No. 1, Cao et al., "Highly Coercive Sm2Fe15Ga2C2 Mgnets Made By Intense Ball Milling", pp. 129-131, Jan. 1996.
Cao Lei
Handstein Axel
Mueller Karl-Hartmut
Neu Volker
Schultz Ludwig
Institut fuer Festkoerper-und Werkstofforschung
Sheehan John
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