Solid material comminution or disintegration – Processes – Miscellaneous
Reexamination Certificate
1999-10-06
2001-06-19
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
Miscellaneous
Reexamination Certificate
active
06247660
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for hydrogen-pulverizing a rare earth metal-based magnetic material for producing an alloy powder for a permanent magnet made from, for example, R (which is at least one of rare earth elements including Y), B and Fe as main components, and to a hydrogen pulverizing case used in the hydrogen pulverizing process.
2. Description of the Related Art
The conventional pulverization of such a type of a magnetic material is carried out in the following manner: An alloy ingot having a preselected composition corresponding to that of a rare earth metal-based magnet to be produced, is embrittled by occluding hydrogen (H
2
) thereinto in a hydrogen gas (H
2
) atmosphere by utilizing an H
2
occluding property of the alloy ingot, thereby producing a coarse powder of rare earth metal-based magnetic material efficiently and in a short time.
In the conventional hydrogen pulverization of the rare earth metal-based magnetic material, however, the magnetic material is embrittled with occlusion of hydrogen, and risen in temperature up to 300° C. to 350° C. by an exothermic reaction during occlusion of hydrogen. Thereafter, to enhance the oxidation resistance of the magnetic material pulverized, it is necessary to further heat the magnetic material to 400° C. to 600° C. in vacuum or in an inert atmosphere to release a portion of occluded hydrogen. However, even if the hydrogen is released, the rare earth metal-based magnetic material is active and liable to be oxidized at a high temperature. For this reason, it is necessary to cool the magnetic material to a level on the order of 20° C. to 30° C. by an inert gas such as argon gas and then remove the cooled magnetic material into the atmosphere. Particularly, a rare earth metal-based magnetic material produced by a strip casting process which will be described hereinafter is in the form of flakes and hence, has a large surface after pulverization, as compared with a material produced in a mold-casting process. Unless the rare earth metal-based magnetic material is removed after being cooled reliably to the level on the order of 20° C. to 30° C., there is a possibility that a firing occurs. When the rare earth metal-based-magnetic material in the form of the flakes produced by the strip casting process is placed into a pulverizing container, the flakes are placed one onto another and for this reason, an inner part of the material in the container is more difficult to cool, as compared with a rare earth metal-based magnetic material in the form of an ingot produced by a mold-casting process. Therefore, in the hydrogen pulverizing process governed by the thermal treatment of such heating and cooling, it is a subject for enhancing the productivity to conduct the heating and cooling in a short time.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a process for hydrogen-pulverizing a rare earth metal-based magnetic material, wherein the above subject is solved, and the heating and cooling can be performed in a short time, thereby providing an extremely excellent productivity, and to provide a hydrogen pulverizing case suitable for use in such hydrogen pulverizing process.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a case for hydrogen-pulverizing a rare earth metal-based magnetic material accommodated in the case with hydrogen occluded in the magnetic material, the case comprising a case body which is formed of a material having a heat conductivity of 1 W/cm·deg or more.
According to a second aspect and feature of the present invention, in addition to the first feature, the case body is formed of a material having a heat conductivity of 2.35 W/cm·deg or more.
According to a third aspect and feature of the present invention, in addition to the second feature, the case body is formed of copper or a copper alloy.
According to a fourth aspect and feature of the present invention, there is provided a case for hydrogen-pulverizing a rare earth metal-based magnetic material accommodated in the case with hydrogen occluded in the magnetic material, the case comprising a case body which is formed of a material having a heat conductivity of 1 W/cm·deg or more, and at least one heat-transferring/releasing member mounted in the case body and each formed of a material having a heat conductivity of 1 W/cm·deg or more.
According to a fifth aspect and feature of the present invention, in addition to the fourth feature, the case body and/or the heat-transferring/releasing member is formed of a material having a heat conductivity of 2.35 W/cm·deg or more.
According to a sixth aspect and feature of the present invention, in addition to the fifth feature, the case body and/or the heat-transferring/releasing member is formed of copper or a copper alloy.
According to a seventh aspect and feature of the present invention, in addition to the fourth feature, the heat-transferring/releasing member is a heat-transferring/releasing fin.
According to an eighth aspect and feature of the present invention, in addition to the fourth feature, the heat-transferring/releasing member is a rod-like member spanned between sidewalls of the case body.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the rod-like member is a hollow pipe mounted between the opposite sidewalls of the case and having, at opposite ends, openings which are in communication with the outside air.
According to a tenth aspect and feature of the present invention, in addition to the fourth feature, the heat-transferring/releasing member is mounted at such a level that it is embedded in the rare earth metal -based magnetic material.
According to an eleventh aspect and feature of the present invention, there is provided a case for hydrogen-pulverizing a rare earth metal-based magnetic material accommodated in the case with hydrogen occluded in the magnetic material, the case comprising a case body, and at least one heat-transferring/releasing member comprising a hollow pipe mounted between the opposite sidewalls of the case and having, at opposite ends, openings which are in communication with the outside air, the heat-transferring/releasing member being mounted in the case body at such a level that it is embedded in the magnetic material in the case body.
According to a twelfth aspect and feature of the present invention, in addition to the first feature, the case body is placed within a reinforcing bottom frame which is formed of a material having a heat conductivity of 1 W/cm·deg or more and surrounding the entire bottom of the case body.
According to a thirteenth aspect and feature of the present invention, in addition to the twelfth feature, the case body and/or the reinforcing bottom frame is formed of a material having a heat conductivity of 2.35 W/cm·deg or more.
According to a fourteenth aspect and feature of the present invention, in addition to the thirteenth feature, the case body and/or the reinforcing bottom frame is formed of copper or a copper alloy.
According to a fifteenth aspect and feature of the present invention, in addition to the fourteenth feature, the case body is placed within a reinforcing bottom frame formed of a material having a heat conductivity of 1 W/cm·deg or more and surrounding the entire bottom of the case body.
According to a sixteenth aspect and feature of the present invention, in addition to the fifteenth feature, the case body and/or the reinforcing bottom frame is formed of a material having a heat conductivity of 2.35 w/cm·deg or more.
According to a seventeenth aspect and feature of the present invention, in addition to the sixteenth feature, the case body and/or the reinforcing bottom frame is formed of copper or a copper alloy.
According to an eighteenth aspect and feature of the present invention, in addition to the first feature, a reinforcing portion having a reinforcing member wrapped in an upper end edge of each of s
Imai Yasuhiko
Okayama Katsumi
Oota Akiyasu
Tokuhara Koki
Tsujimoto Akihito
Armstrong Westerman Hattori McLeland & Naughton LLP
Rosenbaum Mark
Sumitomo Special Metals Co. Ltd.
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