Patent US5527504A successfully refreshed from Google Patents.
US5527504A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Powder mixture for use in compaction to produce rare earth iron sintered permanent magnets
Assignee: Nippon Steel Corp
•
Filing: 1995-05-09
•
Granted: 1996-06-18
•
Expires: 2015-05-09
Abstract
Abstract To a fine R-Fe-B alloy powder comprised predominantly of 10-30 atomic % of R (wherein R stands for at least one elements selected from rare earth elements including yttrium), 2-28 atomic % of B, and 65-82 atomic % of Fe in which up to 50 atomic % of Fe may be replaced by Co, at least one boric acid ester compound such as tributyl borate is added as a lubricant in a proportion of 0.01%-2% by weight and mixed uniformly before, during, or after fine grinding of the alloy powder. The resulting powder mixture is compacted by compression molding in a magnetic field and the green compacts are sintered and aged. Compression molding can be performed continuously without need of mold lubrication, and the resulting magnets have improved magnet properties with respect to residual flux density, maximum energy product, and intrinsic coercive force.
Inventors
- 👤 Yoshihisa Kishimoto
- 👤 Nobushige Hiraishi
- 👤 Wataru Takahashi
- 👤 Masakazu Ohkita
- 👤 Naoyuki Ishigaki
- 👤 Yutaka Matsuura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:37
CPC Classifications
B; B22; B22F; B22F1/00; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/047; H01F1/053; H01F1/055; H01F1/057; H01F1/0571; H01F1/0575; H01F1/0577; Y; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
94 words
A process for producing R-Fe-B sintered permanent magnets, comprising compacting a powder mixture which consists essentially of a fine R-Fe-B alloy powder and at least one boric acid ester compound substantially uniformly mixed with the alloy powder, the R-Fe-B alloy powder being comprised predominantly of 10-30 atomic % of R (wherein R stands for at least one element selected from rare earth elements including yttrium), 2-28% of B, 65-82 atomic % of Fe, and 0 to 41 atomic % of Co, by compression molding to form green compacts, and sintering the resulting green compacts.
Claim 2
Dependent Claim
94 words
A process for producing R-Fe-B sintered permanent magnets, comprising compacting a powder mixture which consists essentially of a fine R-Fe-B alloy powder and at least one boric acid ester compound substantially uniformly mixed with the alloy powder, the R-Fe-B alloy powder being comprised predominantly of 10-30 atomic % of R (wherein R stands for at least one element selected from rare earth elements including yttrium), 2-28% of B, 65-82 atomic % of Fe, and 0 to 41 atomic % of Co, by compression molding to form green compacts, and sintering the resulting green compacts.
Claim 3
Dependent Claim
16 words
The process according to claim 1, wherein the compression molding is performed in a magnetic field.
Claim 4
Dependent Claim
20 words
The process according to claim 1, wherein the sintering is performed at a temperature between 1000° C. and 1100° C.
Claim 5
Dependent Claim
15 words
The process according to claim 1, which further comprises subjecting the sintered compacts to aging.
Claim 6
Dependent Claim
36 words
The process according to claim 1, wherein the boric acid ester compound is present in the powder mixture in a proportion of from 0.01% to 2% by weight based on the weight of the alloy powder.
Claim 7
Dependent Claim
36 words
The process according to claim 1, wherein the boric acid ester compound is present in the powder mixture in a proportion of from 0.1% to 1% by weight based on the weight of the alloy powder.
Claim 8
Dependent Claim
20 words
The process according to claim 1, further comprising preparing the alloy powder by crushing and finely grinding an alloy ingot.
Claim 9
Dependent Claim
64 words
The process according to claim 1, further comprising preparing the alloy powder by rapidly solidifying a molten alloy by the single roll or twin roll method to form a thin sheet or thin flakes which have a thickness of 0.05-3 mm and which consist of fine grains in the range of 3-30 μm, and crushing and finely grinding the thin sheet or thin flakes.
Claim 10
Dependent Claim
16 words
The process according to claim 8, wherein the crushing is performed by the hydrogenation crushing method.
Claim 11
Dependent Claim
22 words
The process according to claim 1, wherein the boric acid ester compound is mixed with the alloy powder before fine grinding thereof.
Claim 12
Dependent Claim
22 words
The process according to claim 1, wherein the boric acid ester compound is mixed with the alloy powder during fine grinding thereof.
Claim 13
Dependent Claim
22 words
The process according to claim 1, wherein the boric acid ester compound is mixed with the alloy powder after fine grinding thereof.
Claim 14
Dependent Claim
34 words
The process according to claim 1, wherein the alloy powder in the powder mixture has a composition of 10-25 atomic % of R, 4-26 atomic % of B, and 65-82 atomic % of Fe.
Claim 15
Dependent Claim
18 words
The process according to claim 13, wherein up to 50 atomic % of Fe is replaced by Co.
Claim 16
Dependent Claim
34 words
The process according to claim 1, wherein the alloy powder in the powder mixture has a composition of 10-20 atomic % of R, 4-24 atomic % of B, and 65-82 atomic % of Fe.
Claim 17
Dependent Claim
18 words
The process according to claim 15, wherein up to 50 atomic % of Fe is replaced by Co.
Claim 18
Dependent Claim
18 words
The process according to claim 1, wherein the alloy powder has an average particle diameter of 1-20 μm.
Claim 19
Dependent Claim
12 words
The process according to claim 1, wherein R consists essentially of Nd.
Claim 20
Dependent Claim
18 words
The process according to claim 1, wherein the powder mixture has a residual carbon content of ≦760 ppm.
Claim 21
Dependent Claim
21 words
The process according to claim 1, wherein the powder mixture has a residual flux density (Br) of at least 10 kG.
Claim 22
Dependent Claim
21 words
The process according to claim 1, wherein the powder mixture has an intrinsic coercive force (iHc) of at least 10 kOe.
Claim 23
Dependent Claim
22 words
The process according to claim 1, wherein the powder mixture has a maximum energy product (BH max) of at least 35 MGOe.
Claim 24
Dependent Claim
20 words
The process according to claim 1, wherein the powder mixture has a density of at least 4.3 g/cm 3 .
Claim 25
Dependent Claim
39 words
The process according to claim 2, wherein the at least one boric acid ester is present in amounts sufficient to permit rotation and alignment of magnetizable axes of the alloy powder during the compaction in the applied magnetic field.
Claim 26
Dependent Claim
21 words
The process according to claim 1, wherein the powder of the powder mixture has an average particle size of 1-20 μm.
Claim 27
Dependent Claim
38 words
The process according to claim 1, wherein the boric acid ester is a boric acid tri-ester compound obtained by esterification of boric acid or boric anhydride with one or more monohydric alcohols having 3 to 18 carbon atoms.
References Cited (Backward Citations)
US4264361A
Cited
JPS5763601A
Cited
JPS5946008A
Cited
JPS5964733A
Cited
US4597738A
Cited
USRE34838E
Cited
JPS63138706A
Cited
JPS63317643A
Cited
US4770273A
Cited
JPH0452203A
Cited
JPH04124202A
Cited
JPH04191302A
Cited
JPH04191392A
Cited
JPH04214804A
Cited
JPH04214803A
Cited
US5393445A
Cited
JPH05295490A
Cited
US5380179A
Cited
US5427734A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-06-18 | 1999-12-18 | 2000-06-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-06-18 | 2003-12-18 | 2004-06-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-06-18 | 2007-12-18 | 2008-06-18 | $7700.00 | Window Closed / Lapsed |