JP2928494B2 - Rare earth sintered magnet and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-piece anisotropic rare earth sintered magnet having a sintered joint, and a high magnetic anisotropy in a desired direction without being restricted by magnetic anisotropy conditions. The present invention relates to a rare-earth sintered magnet capable of enlarging and forming a magnetically anisotropic region having characteristics and a method of manufacturing the same.

[0002]

2. Description of the Related Art Recently, many permanent magnets are continuously arranged and used in an accelerator of a free electron laser or a synchrotron radiation device. In this type of accelerator, etc., a plurality of permanent magnets are continuously arranged on both sides of the electron beam path, and each permanent magnet is configured such that the adjacent magnets and the opposed magnets have opposite polarities. In some cases, a transverse periodic magnetic field is applied to a rotating electron beam. Alternatively, there is a so-called hybrid type combined with permalloy or the like.

[0003] Permanent magnets used in accelerators and the like are required to have high magnetic properties, and are required to be Sm-Co based or Nd-Fe-B.
A series of anisotropic rare earth magnets are used. These permanent magnets are generally produced by molding a magnet material powder and then sintering.When molding with a mold, a magnetic field applying means is provided on the outer periphery of the mold to make the molded body anisotropic. Has been granted. However, in order to effectively apply a magnetic field to the entire molded body,
The molded body could not be made too large, and the permanent magnet could not be manufactured in a large shape.

In recent years, accelerators and the like having a higher capacity have been demanded. In such a case, a large permanent magnet is required. Shaped and used.

[0005]

That is, in the conventional rare earth sintered magnet, there is a problem that the dimension that can be made magnetically anisotropic is limited by the magnetic field applying means employed in the molding process.

Conventionally, when an anisotropic permanent magnet is manufactured in a large shape, a plurality of block magnets are bonded with an adhesive, so that the following problem arises.

When a large anisotropic permanent magnet formed by bonding a plurality of block magnets with an adhesive is incorporated in a free electron laser or the like, it is placed in an environment where high vacuum and ultraviolet light exist. In many cases, the polymer structure of the agent is degraded by destruction of its polymer structure by a photochemical reaction caused by ultraviolet rays.

Further, the work of assembling and joining into a large anisotropic permanent magnet shape using a plurality of anisotropic block magnets and an adhesive is complicated, requires a lot of work time, and has a uniform quality. Is often difficult to supply.

Therefore, an object of the present invention is to provide a monolithic sintered body having a sintered joint, and a magnetic anisotropic region having sufficiently high magnetic characteristics without being restricted by magnetic anisotropy means. Is to provide a rare earth sintered magnet that can be formed in a desired direction and a method of manufacturing the same.

[0010]

According to the present invention, which has achieved the above objects, the present invention provides a method of filling a cavity in a mold provided for imparting magnetic anisotropy with alloy powder for a rare earth sintered magnet, and forming a magnetic field. Preforming in the presence and forming a preformed body having magnetic anisotropy, and then forming a plurality of the preformed bodies at a pressure higher than the preforming pressure after alignment to obtain an aggregated molded body, A method for manufacturing a rare earth sintered magnet, characterized in that a portion corresponding to a joint between the preforms is sintered and joined by sintering the compact.

Further, the present invention provides a SmCo ₅ sintered magnet,
Sm ₂ Co ₁₇ based sintered magnet, (Sm, Ce) ₂ Co ₁₇ based sintered magnet, Nd or Nd and Dy as main components, Fe and B
A rare earth-sintered magnet made of any one of the rare earth-Fe-B based sintered magnets containing Co as needed, having a magnetic anisotropy and being sintered. It is a rare earth sintered magnet characterized by having.

According to the present invention, a plurality of preforms are aligned using a preform which is sufficiently magnetically anisotropic as a basic unit, and then a pressure higher than the preforming pressure is applied. By doing so, the portion corresponding to the joint between the preforms is also sintered and joined. Therefore, the magnetic anisotropy region can be enlarged in a desired direction without being restricted by the anisotropy condition such as a magnetic field applying unit.

For this reason, according to the present invention, it is possible to obtain a larger one, the shortest side of which is 5 mm or more,
In addition, a large anisotropic rare earth sintered magnet having a weight of 500 g or more can be provided. Here, the reason why the shortest side of the rare earth sintered magnet is set to 5 mm or more is that if it is less than 5 mm, the strength is weak and it is difficult to handle. Further, the reason why the weight is set to 500 g or more is that there is a limit near the point where it is impossible to produce an integrated anisotropic rare earth sintered magnet in the related art. Further, the weight of the permanent magnet is 1000 g or more, 1500 g or more,
2000 g or more, or 2500 g or more.

In the present invention, if at least one side of the molding die and the molded body is provided with a taper, the die can be easily removed.

The present invention is suitable for the case where pressure molding is performed in a direction perpendicular to the direction of an applied magnetic field passing through the cavity.

The large magnets made according to the present invention have no mechanical seams and have sintered joints. Therefore, the magnetic properties are substantially uniform as a whole, and for example, when used in a free electron laser accelerator, the accelerator has good durability performance.

As the rare earth sintered magnet of the present invention, for example, SmCo ₅ system, Sm ₂ Co ₁₇ system, (Sm, Ce) ₂
Co ₁₇ system, Nd-Fe-B system, (Nd, Dy) -Fe-
Any one of the B type is mentioned. For rare earth sintered magnets, for example, in applications where radiation is present, there is little concern about a decrease in magnetic flux density due to radiation irradiation.
Since the irreversible demagnetization rate, which is evaluated by heating to about ° C and then cooling to room temperature, is small, the Curie temperature is high, and the coercive force is high, it is advantageous in terms of permeance coefficient.

The permeance coefficient P is the magnetic flux density B at the operating point on the demagnetization curve representing the magnetic properties of the anisotropic permanent magnet.
d and the coercive force Hd are calculated by the ratio Bd / Hd, and P
= Bd / μo Hd [μo is a magnetic constant (vacuum magnetic permeability)].

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments.

Example An SmCo ₅ -based sintered magnet alloy comprising 38% by weight of Sm and the balance Co was produced by arc melting and cast into an ingot. The obtained ingot was put into a stamp mill for 35.
The mixture was coarsely pulverized until passing through a mesh, and finely pulverized by a ball mill for 3 hours.

Next, the obtained fine powder was cross-section 23 mm × 2
A cavity of a mold having a molding space of 4 mm is filled, and 0.7 t in a vertical direction in a state where a substantial parallel magnetic field of 8000 Oe is applied in a substantially horizontal direction to impart anisotropy.
/ Cm ² was applied to perform preforming to form a block having a height of 76 mm.

When extracting the preformed block from the molding die, a hydraulic press with lifting is used.
The upper punch was lifted 3/100 mm upward to prevent cracks and other defects from occurring in the block. This is because the pressure applied in the preforming is extremely small, so that the density and strength of the block become insufficient, and if the weight of the upper punch is added during die cutting, the block may collapse.

Next, the preformed blocks prepared above were aligned in a direction substantially parallel to the direction of magnetic anisotropy, and five blocks were continuously aligned and sealed in a vinyl chloride bag having a thickness of 0.1 mm. In this case, the air in the bag was removed, and the adjacent surfaces of the five blocks were brought into close contact with each other.
A pressure of t / cm ² was applied to obtain a collective molded body. As a result of grinding the upper and lower surfaces of the collective molded body by 0.8 mm surface grinding, no joint was observed between adjacent blocks.

This is because the density of the block obtained by the preforming is low, so that the surface roughness of the block is relatively large, and when cold isostatic pressure is applied, between the adjacent blocks,
It is presumed that the fine powders are entangled with each other and diffused in units of powder particles.

The above aggregated body is sintered at 1150 ° C. × 1 hour in an Ar gas atmosphere, then held at 950 ° C. × 1.5 hour in the same atmosphere, and then slowly cooled at 1.3 ° C./min. Then, heat treatment was performed at 790 ° C. by cooling in an Ar gas stream.

In the case of performing the above heat treatment, the aggregated molded product shrinks, and if the aggregated molded product cannot shrink smoothly with respect to its support surface, cracks or warpage will occur. Therefore, a large number of spherical rotating bodies were placed on the support surface, and the collectively formed body was placed thereon. The rotating body must have sufficient heat resistance so as not to be denatured during sintering, and must not react with the collectively formed body during sintering. Therefore, a material made of ceramic such as alumina and coated with BN on the surface was used.

The size of the rotator was 18 mm in diameter, and the occupancy of many rotators in the plane was about 70%. Then, when the collective molded body is shrunk and deformed by the heat treatment, the rotating body that supports it is rotated, so that the shrinkage is performed smoothly, and the sintered body is less likely to crack or warp. In addition, you may enable it to slide on a rotating body, without rotating the rotating body which supports a collective molded body.

As a comparative example, the magnet powder was 3.5 t / c.
A block magnet obtained by sintering a molded body molded in m ² under the above conditions was subjected to surface grinding, and a plurality of the magnets were bonded with an adhesive. The adhesive magnet of this comparative example and the sintered magnet of the above example were magnetized with a pulse magnetic field of 25 kOe. Then, while maintaining an interval of 0.5 mm from the magnetized surface of each permanent magnet, the surface magnetic flux density on the N pole side was measured by a Siemens FA-22E probe. The sintered magnet of the above example exhibited a value of 2500 G or more over the entire surface on the N-pole side, and the portion corresponding to the joint of the preformed block was sintered and integrated.

On the other hand, in the case of the comparative example, a decrease in the surface magnetic flux density corresponding to the bonded portion was observed.

Instead of the SmCo ₅ -based anisotropic sintered magnet of the above embodiment, the composition of the Sm ₂ Co ₁₇ -based and Nd—Fe—B-based anisotropic sintered magnet was selected. When an integrated anisotropic sintered magnet was produced in substantially the same manner, the portion corresponding to the joint between the preformed blocks was also integrally joined and sintered by powder metallurgy.

In the above-mentioned embodiment, the case where five preformed blocks are used for sintering is shown. However, by using a larger number of preformed blocks, a rare earth element having a larger size and a larger anisotropy can be obtained. A sintered magnet can be made.

Further, the rare earth sintered magnet of the present invention is not limited to a rectangular parallelepiped, but may be formed in any shape having a flat surface.

Further, it is not necessary to join all the preformed blocks so that the directions of magnetic anisotropy are the same. For example, the directions of magnetic anisotropy are sequentially changed like an accelerator of a free electron laser. The present invention can be applied to a joined large magnet.

[0034]

According to the present invention, a molded article having a sufficiently magnetic anisotropy is used as a basic unit to keep the molded articles in close contact with each other without using an adhesive as in the prior art.
Subsequently, by sintering, it is possible to obtain a rare earth sintered magnet in which the joint portions of the formed bodies are integrated by powder metallurgy. Therefore, it is extremely useful that the magnetic anisotropy region can be enlarged and formed in a desired direction without being restricted by the magnetic anisotropy condition.

Claims (2)

(57) [Claims] A cavity in a mold provided for imparting magnetic anisotropy is filled with alloy powder for a rare earth sintered magnet and preformed in the presence of a magnetic field to impart magnetic anisotropy. And then align a plurality of the preforms
Molded at a pressure higher than the rear preforming pressure to obtain an aggregate formed body, said preformed by sintering said set shaped body
A method for manufacturing a rare earth sintered magnet , characterized in that a portion corresponding to a joint between the bodies is sintered and joined . 2. SmCo ₅ based sintered magnet, Sm ₂ Co ₁₇ based magnet
Sintered magnet, (Sm, Ce) ₂ Co ₁₇ based sintered magnet, main component
Is composed of Nd or Nd and Dy and Fe and B
Of rare earth-Fe-B based sintered magnets containing Co according to
A rare earth sintered magnet comprising any one of the above,
Features anisotropic and sintered joints
Rare earth sintered magnet.