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Rareearth magnet and making method therefor

A rare earth magnet and manufacturing method technology, applied in the direction of inductor/transformer/magnet manufacturing, magnetic materials, magnetic objects, etc., can solve the problems of insufficient improvement of magnet characteristics, changes in magnetic characteristics, low production efficiency, etc. The effect of improving magnetic properties and reducing oxygen content

Inactive Publication Date: 2007-11-28
PROTERIAL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] Compared with mechanical pulverization methods such as ball milling, the production efficiency of the hydrogen pulverization method is good, but there is a problem that when using the magnet powder obtained by the hydrogen pulverization method, the magnetic properties (especially the coercive force) are easily changed with the sintering conditions , but also easy to catch fire
[0011] However, according to the above-mentioned prior art, after the slurry-like R-Fe-B alloy powder is filled into the cavity of the pressing device, the production efficiency is low because it is necessary to carry out the pressing process while squeezing out the oil.
According to the conventional rare-earth magnet manufacturing method, coarse crystal particles are easily formed during the sintering process, so even when using magnet powder with a low oxygen concentration, there is still a problem that the magnet characteristics (coercive force) cannot be sufficiently improved

Method used

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  • Rareearth magnet and making method therefor
  • Rareearth magnet and making method therefor
  • Rareearth magnet and making method therefor

Examples

Experimental program
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Effect test

Embodiment approach 1

[0040] The R-Fe-B-based rare earth magnet in this embodiment has an average grain size of 3 μm to 9 μm, an oxygen concentration of 50 ppm to 4000 ppm by weight, and a nitrogen concentration of 150 ppm to 1500 ppm by weight. The "R-Fe-B-based rare earth magnet" here broadly includes a rare earth magnet in which a part of Fe is replaced by a metal such as Co and a part of B (boron) is replaced by C (carbon). The R-Fe-B series rare earth magnet has R-rich phase and B-rich phase (grain boundary phase) surrounded by R with a square crystal structure. 2 Fe 14 The organizational structure around the main phase composed of type B compounds. The structure of the R-Fe-B rare earth magnet is disclosed in US Patent No. 5,645,651.

[0041] A preferred embodiment of the method for producing such a rare earth magnet will be described in detail below.

[0042] First, R- Melt of Fe-B alloy. A part of Fe may be substituted with one or both of Co and Ni, and a part of B may be substituted w...

Embodiment 1

[0063] First, an alloy molten liquid composed of Nd+Pr (30.0% by mass)-Dy (1.0% by mass)-B (1.0% by mass)-Fe (the rest) is produced in a high-frequency melting furnace, and a water-cooled roll-type strip is used The casting method cools the above-mentioned molten liquid to produce a thin plate-shaped cast piece (flaky alloy) with a thickness of about 0.5 mm. The oxygen concentration of this flaky alloy was 150 mass ppm.

[0064] Next, the flake-shaped alloy was charged into a hydrogen furnace, and after the furnace was evacuated, hydrogen gas was supplied to the furnace for 2 hours to carry out hydrogen embrittlement. The hydrogen partial pressure in the furnace was 200 kPa. After absorbing hydrogen, the flakes will naturally collapse, and after that, dehydrogenation treatment is carried out by vacuumizing while heating. Argon gas was then introduced into the furnace and cooled to room temperature. When the alloy temperature is cooled to 20°C, it is taken out from the hydro...

Embodiment approach 2

[0082] A second embodiment of the present invention will be described below.

[0083] As in the above-mentioned embodiment, trying to suppress the oxygen content and obtain a high-performance R-Fe-B-based rare earth magnet, it is possible to increase the residual magnetic flux density B while maintaining a high coercive force. r . However, in the first embodiment described above, depending on the sintering conditions, the magnetic properties may be deteriorated (in particular, the coercive force may be lowered), and a sufficient sintered density may not be obtained. Such a problem remarkably exists when the amount of the rare earth element is small, for example, 32% by mass or less. In order to mass-produce the rare earth sintered magnet, the amount of the rare earth element in the magnet is preferably in the range of 29% by mass or more. And, considering the residual magnetic flux density B r and coercive force H cj , preferably in the range of 29.5 to 32% by mass. There...

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Abstract

Rare earth alloy powder having an oxygen content of 50 to 4000 wt. ppm and a nitrogen content of 150 to 1500 wt. ppm is compacted by dry pressing to produce a compact. The compact is impregnated with an oil agent and then sintered. The sintering process includes a first step of retaining the compact at a temperature of 700 DEG C. to less than 1000 DEG C. for a period of time of 10 to 420 minutes and a second step of permitting proceeding of sintering at a temperature of 1000 DEG C. to 1200 DEG C. The average crystal grain size of the rare earth magnet after the sintering is controlled to be 3 mum to 9 mum. This method reduces material powder in oxygen content so as to protect it against danger such as heat evolution / ignition and to improve a rare earth magnet in magnet characteristics.

Description

technical field [0001] The present invention relates to a rare-earth magnet and its manufacturing method, more specifically, to a high-performance rare-earth sintered magnet made from rare-earth alloy powder with reduced oxygen content. Background technique [0002] R-Fe-B series rare earth magnets (R is at least one element selected from yttrium (Y) and rare earth elements), mainly composed of R 2 Fe 14 The main phase formed by the B tetragonal compound, the R-rich phase containing a large amount of Nd and other rare earth elements, and the B-rich phase containing a large amount of B (boron). In the R-Fe-B series rare earth magnet, if the main phase R 2 Fe 14 The presence ratio of the tetragonal crystal compound of B can improve its magnetic properties. [0003] A minimum amount of R-rich phase is required for liquid phase sintering, but since R reacts with oxygen to produce R 2 o 3 Oxide, a part of R is consumed by unused parts during sintering. Therefore, only the ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01F1/08H01F1/06C22C38/00B22F9/04B22F3/00C22C33/02H01F1/055H01F1/057H01F41/02
CPCH01F41/0266H01F1/0577H01F1/0573H01F1/0557H01F41/02
Inventor 国吉太森本仁
Owner PROTERIAL LTD
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