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Cast alloy used for production of rare earth magnet and method for producing cast alloy and magnet
| Details |
Inventors: Sasaki, Shiro; Hasegawa, Hiroshi; Hirose, Yoichi;
Assignee: Showa Denko K.K. (Tokyo, JP)
Primary Examiner: Sheehan; John
Assistant Examiner:
Attorney, Agent or Firm: Armstrong, Westerman, Hattori, McCleland & Naughton
The magnetic properties of rare earth magnet are improved by means of forming a novel structure of the cast alloy used for the production of a rare earth magnet, which contains from 27 to 34% by weight of at least one rare earth element (R) including yttrium, from 07 to 1.4% by weight of boron, and the balance being essentially iron and, occasionally any other transition element, and comprises an R.sub.2 T.sub.14 B phase, an R-rich phase and optionally at least one ternary phase except for the R.sub.2 T.sub.14 B phase and the R-rich phase. The novel structure is that the volume fraction (V) in percentage of said R.sub.2 T.sub.14 B phase and said at least one ternary phase is more than 138-1.6r (with the proviso that r is the content of R), the average grain size of the R.sub.2 T.sub.14 B phases is from 10 to 100 .mu.m and, further, the average spacing between the adjacent R-rich phases is from 3 to 15 .mu.m. The novel structure can be formed by by means of feeding alloy melt onto a rotary casting roll, cooling in a temperature range of from melting point to 1000.degree. C. at a cooling rate of 300.degree. C. per second or more, and further cooling in a temperature range of from 800 to 600.degree. C. at a cooling rate of 1.degree. C./second or less. |
|
DETAILED DESCRIPTION We claim: 1.
A cast alloy used for the production of a rare earth magnet, which: (a) contains from 27 to 34% by weight of at least one member selected from yttrium and rare earth elements, from 0.
7 to 1.
4% by weight of boron, and the balance being essentially iron and, optionally any other transition element, and (b) a R.
sub.
2 T.
sub.
14 B phase, an R-rich phase and optionally at least one ternary phase other than the R.
sub.
2 T.
sub.
14 B phase and the R-rich phase, characterized in that the volume fraction (V), in percent, of said R.
sub.
2 T.
sub.
14 B phase and said at least one ternary phase is more than 138-1.
6r, with the proviso that r is the content of R, the average grain size of the R.
sub.
2 T.
sub.
14 B phases is from 10 to 100 .
mu.
m is greater than the average spacing between the adjacent R-rich phases in a range from 3 to 15 .
mu.
m.
2.
A cast alloy used for the production of a rare earth magnet according to claim 1, which contains from 28 to 33% by weight of at least one rare earth element (R) including yttrium, from 0.
95 to 1.
1% by weight of boron, and the balance being essentially iron and, occasionally any other transition element, characterized in that the volume fraction (V') in percent of said R.
sub.
2 T.
sub.
14 B phase is in the range of from 138-1.
6r<V'<95, the average grain size of the R.
sub.
2 T.
sub.
14 B phases is from 10 to 50 .
mu.
m and, further, the average spacing between the adjacent R-rich phases is from 3 to 10 .
mu.
m.
3.
A cast alloy used for the production of a rare earth magnet according to claim 2, which contains from 30 to 32% by weight of at least one rare earth element (R) including yttrium, from 0.
95 to 1.
05% by weight of boron, and the balance being essentially iron and, occasionally any other transition element, characterized in that the volume fraction (V') in percent, of said R.
sub.
2 T.
sub.
14 B phase is in the range of from 138-1.
6r<V'<95, the average grain size of the R.
sub.
2 T.
sub.
14 B phases is from 15 to 35 .
mu.
m and, further, the average spacing between the adjacent R-rich phases is from 3 to 8
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