JPH11256203A - Forming die for high orientation rare earth metal sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming die, in which a high orientation rare earth metals sintered magnet (further desiarably, the large scaled magnet) suitable to a wiggler for corpuscular ray accelerator can stably be manufactured. SOLUTION: This forming die for a high orientation rare earth metal sintered magnet is composed of a ferromagnetic die member which forms the long side or large diameter A and the short side or small diameter B of a cavity and a non-magnetic die member which forms the short side or small diameter B and thickness C of the cavity and (A>=B>C) so as to generate a parallel magnetic field in which the inclination of lines of magnetic force at the time of impressing the magnetic field passing through a plane (reference plane) formed with the long side or large diameter A and the short side or small diameter B of the cavity is within 3 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for extracting radiation from a particle accelerator, such as a wiggler magnet.
The present invention relates to a molding die for a highly oriented rare earth sintered magnet useful for RI (nuclear magnetic resonance imaging) and the like.

[0002]

2. Description of the Related Art In an apparatus for extracting radiation from a particle beam accelerator such as a free electron laser or synchrotron radiation, a large number of permanent magnets are continuously arranged and used. In this type of device, a plurality of permanent magnets called wiggler or undulator are continuously arranged on both sides of the electron beam path, and each permanent magnet generally has an opposite polarity to an adjacent one and an opposite one. There is a device configured to apply a periodic magnetic field in a direction perpendicular to a traveling direction of a passing electron beam. Alternatively, there is a so-called hybrid type combined with a yoke such as permendur or permalloy. One example of a wiggler is shown in FIG. Dozens of pairs of magnets magnetized so that magnetic flux enters and exits perpendicularly to the plane formed by the long side a and the short side b of the plate (hereinafter referred to as ab plane) are arranged with N and S poles alternately arranged. Have been. The electron beam travels while being bent in the alternating magnetic field, and emits radiation of a specific wavelength. Permanent magnets used for such applications are required to have high magnetic properties, and Sm-Co-based and Nd-Fe-B-based anisotropic rare earth permanent magnets are used. In general, a wiggler or the like having a relationship of a ≧ b> c among the long side or long diameter a, the short side or short diameter b, and the thickness c is used. Strict specifications are required for permanent magnets used in wiggler for particle beam accelerators, etc., such that the inclination angle of the magnetization direction with respect to the normal to the reference plane of assembly is within 3 degrees, preferably within 2 degrees. When the tilt angle of the magnetization direction exceeds 3 degrees, a magnetic field component that is not perpendicular to the traveling direction of the electron beam is generated, and the effective component is reduced by that amount. There is a problem that the wavelength of light fluctuates. Therefore, it is required that the tilt angle of the magnetization direction be uniformly distributed within 3 degrees, more preferably within 2 degrees with respect to the normal line in the ab plane (reference plane) of the permanent magnet.

Recently, a particle beam accelerator having a larger capacity is desired. In such a case, a large permanent magnet is required. Shaped and used. However, when a large-shaped anisotropic permanent magnet is manufactured by bonding a plurality of block magnets with an adhesive, there are the following problems. Since the adhesive is interposed between the block magnets to form a magnetic gap, the magnetic flux density decreases at that portion, the magnetic characteristics become non-uniform as a whole, and the performance of the device using the same decreases. I will. When a large anisotropic permanent magnet is incorporated into a free electron laser or the like, it is placed in an environment where high vacuum and ultraviolet light are present. Is often degraded because it is destroyed. Furthermore, the work of assembling and joining a plurality of block magnets with an adhesive is complicated, requiring a lot of time for this work, and making it difficult to supply uniform quality. Sintered magnets are manufactured by molding and sintering magnet materials. Warping may occur due to shrinkage due to the sintering of the molded body. Is big. The reason for this is that in the conventional method of magnetic field orientation in a molding die, firstly, there is unevenness in the density of the molding due to uneven pressure distribution in the molding, and secondly, in the molding die. This is because there is non-uniformity of the degree of orientation due to non-uniformity of the magnetic field for orientation in the inside. To explain the second reason in detail, conventional molding dies are often made of an integral body of a ferromagnetic material such as tool steel due to requirements for strength and rigidity, and therefore, near the end of the molding cavity, This is because, due to the difference in magnetic permeability between the mold and the molded body, the magnetic flux easily passes through the mold rather than the molded body. As described above, molding in a magnetic field with a conventional molding die was not suitable for a wiggler magnet or the like. Therefore, a container made of a non-magnetic material, a pair of upper and lower punches made of a magnetic material provided so as to penetrate the container to pressurize the powder given as a molding material in the container, Two coils wound around each of the upper and lower punches to apply a magnetic field to the powder inserted therebetween, and the container to apply hydrostatic pressure to the powder to be applied with the magnetic field (Japanese Patent Application Laid-Open No. Sho 62-64498) has been proposed which relates to a wet rubber press in a magnetic field having pores for water supply opened on the side surface. Cold isostatic pressing (Cold Iso
static Pressing, abbreviated as CIP).
In the example of the publication, the relationship between the X-ray diffraction intensity of the (002) plane and the tilt angle with respect to the direction of application of the magnetic field is shown, and shows a relatively improved tilt angle of the magnetization direction.

[0004]

In the above-mentioned method using a wet rubber press in a magnetic field, the upper and lower punches made of a magnetic material are indispensable, so that the pressing force in the rubber press is not isotropic, and a side pressure is applied. Therefore, there is a problem that not only the end of the molded body is deformed, but also the inclination of the magnetization direction is affected. Further, the molding die is required to have sufficient strength to withstand the pressure received from the inside of the CIP. Further, sufficient electrical insulation is required to install the coil in the CIP device, and technical and safety aspects are required. However, there is a problem that significant difficulties are involved. Furthermore, even the permanent magnets thus obtained have not yet been realized which satisfy the above-mentioned characteristics required by a wiggler for a particle accelerator. The reason for this is that the configuration of the invention described in Japanese Patent Application Laid-Open No. 62-64498 is practically limited to a method called a vertical magnetic field press in which the press direction and the applied magnetic field direction are parallel. However, it cannot be expected to some extent. In general, in the molding step of anisotropic rare earth sintered magnets, when the magnetic powder is filled into a mold and pressed, the magnetic powder has a flat shape, so that the longitudinal direction of the magnetic powder is substantially perpendicular to the pressing direction. Tends to align. Therefore, when manufacturing a high-performance rare-earth sintered magnet, a manufacturing method in which a magnetic field is applied in a direction perpendicular to the direction of pressure called transverse magnetic field pressing and molding in a magnetic field can obtain a higher degree of orientation. Preferred. As described above, in the conventional molding die, the inclination angle of the magnetization direction is 3 degrees.
It is difficult to manufacture a rare earth sintered magnet having a high degree of orientation within a degree, and there has been a demand for a molding die capable of realizing the rare earth sintered magnet having a high degree of orientation. Therefore, an object of the present invention is to provide a molding die capable of stably producing a highly oriented rare earth sintered magnet (more preferably, a large one) suitable for, for example, a wiggler for a particle beam accelerator.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a ferromagnetic mold member for forming a long side or a long diameter A and a short side or a short diameter B of a cavity and a short side or a short diameter of the cavity. B and a non-magnetic mold member (A ≧ B> C) forming a thickness C, wherein the dimension of the non-magnetic mold member along the direction of the thickness C of the cavity is substantially the same as the thickness C of the cavity. And the protrusion along the short side or short diameter B direction of the cavity is formed to be larger than the short side or short diameter B of the cavity, and the ferromagnetic mold member is The ferromagnetic metal mold, which is disposed so as to sandwich the projecting portion of the non-magnetic mold member and face each other, and which has the tip of the projecting portion of the non-magnetic mold member sandwiching the projecting portion. Key than both ends of the mold By arranging them so as to protrude to the side of the cavity and face each other, the inclination of the magnetic field lines when a magnetic field is applied through a plane (reference plane) formed by the long side or long diameter A and the short side or short diameter B of the cavity is set. This is a molding die for a rare earth sintered magnet with a high degree of orientation, which generates a parallel magnetic field within 3 degrees. With the mold of the present invention,
There is a relationship of a ≧ b> c between the long side or long diameter a, the short side or short diameter b, and the thickness c, and a flat shape magnetized in the thickness c direction is formed by the above a and b. The inclination angle of the magnetization direction with respect to the normal line of the plane (reference plane) to be formed is within 3 degrees, and the surface magnetic flux density (Bo) of the pole face is 3.5 kG or more when magnetized with a pulse magnetic field of 25 kOe. A rare earth sintered magnet with a degree of orientation can be obtained. The high-orientation rare earth sintered magnet may have a tapered shape in which the thickness c changes continuously. Further, the high-orientation rare earth sintered magnet is Sm
-Co magnet or R-TM-B magnet (R is Nd, D
one or more rare earth elements represented by y or the like;
M is composed of Fe or Fe and Co), and the R-TM-B-based magnet may further contain 13% by weight or less of Ga, Si, Al and the like. The cavity of the molding die of the present invention is filled with the raw material powder for a rare earth sintered magnet, and a parallel magnetic field is applied in which the inclination of the line of magnetic force when applying a magnetic field passing through the reference surface of the cavity of the molding die is within 3 degrees. While being compacted in a magnetic field, a compact having a tilt angle of the magnetization direction with respect to the normal of the reference plane within 3 degrees is obtained, and the compact is sintered and heat-treated to obtain the highly oriented rare earth sintered magnet. can get. Molding mold of the present invention,
A horizontal magnetic field press method in which a magnetic field is applied in a direction perpendicular to the press direction is employed. FIG. 2 shows an example of a molded body obtained by using the molding die of the present invention. (A) is a molded article obtained by using the molding die of the present invention, (b) is (a)
Shows a higher density molded product obtained by further applying CIP to the molded product of Example 1.

The inventors of the present invention have conducted intensive studies and, as a result, have attempted to solve the problem of the conventional molding die for rare earth sintered magnets by using the transverse magnetic field pressing method to eliminate the non-uniformity of the magnetic field at the end of the cavity. The configuration of the molding die shown in FIG. In the configuration of the molding die, the parallel magnetic field can be formed in the cavity when the dimensional relationship such that L> l is obtained by projecting a mold member made of a nonmagnetic material constituting a part of the cavity. I learned. That is, the mold shown in FIG. 1 is composed of a ferromagnetic mold member forming the long side or major axis A and a short side or minor axis B of the cavity and a nonmagnetic mold forming the short side or minor axis B and the thickness C of the cavity. And a mold member (A ≧ B> C). The dimension of the nonmagnetic mold member along the direction of the thickness C of the cavity is substantially the same as the thickness C of the cavity, and the dimension of the non-magnetic mold member along the short side of the cavity or the direction of the minor axis B is the short side of the cavity or It has a protruding portion formed to be larger than the minor diameter B. The ferromagnetic mold member is disposed so as to sandwich the projecting portion of the non-magnetic mold member and face each other, and the tip of the projecting portion of the non-magnetic mold member is protruded from the ferromagnetic mold member. By arranging the ferromagnetic mold member sandwiching the portion so as to protrude toward the cavity from both end positions and face each other, the cavity is formed with the long side or long diameter A and the short side or short diameter B. A magnetic field anisotropic mold capable of generating a parallel magnetic field with a tilt angle of a magnetic field line of 3 degrees or less when a magnetic field is applied through a plane (reference plane) can be realized.

[0007] The inclination of the magnetization direction with respect to the normal line of the reference plane of the highly oriented rare earth sintered magnet manufactured using the mold of the present invention can be measured by using a measuring device combined with a Helmholtz coil. The above-mentioned Japanese Patent Application Laid-Open No. 62-6 / 1987
No. 4498, a method of obtaining a tilt angle with respect to the direction of application of a magnetic field using the diffracted X-ray intensity of the (002) plane, or an X-ray diffraction method. It can also be measured by such a method. In addition, a method of arranging three search coils of x, y, and z and applying a computer to process the magnetic flux detected by an integrating magnetometer by applying the principle of a VSM (vibrating sample magnetometer) is also a highly accurate method. Is the law.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Sm 38% by weight percentage
The permanent magnet alloy of SmCo ₅ balance consisting Co were prepared by arc melting. Next, it was coarsely pulverized to 35 mesh through with a stamp mill and finely pulverized with a ball mill for 3 hours. The magnetic powder thus obtained is filled in a cavity having a sectional size of 69 cm × 45 cm of the molding die shown in FIG. 1, and a magnetic field of 20 kOe is applied thereto until the height of the molded body becomes 16 cm while applying a parallel magnetic field of 20 kOe. It was preformed by a uniaxial press with lifting at a pressure of 0.7 ton / cm ² . afterwards,
It was transferred to a rubber mold made of latex rubber having a cross-sectional dimension of 69 cm x 45 cm. At this time, the strength of the preform was sufficient to prevent it from breaking even in a drop test.
No special handling was required. Next, the preform in a rubber mold was CIPed at 4 tons / cm ² to a height of 14 cm. Next, the CIPed 1140 ° C
For 1 hour in an argon gas atmosphere, and then
Heat treatment was performed at 00 ° C. for 1 hour in an argon gas atmosphere.
At this time, the CIPed test piece had reached a sufficient density, and shrinkage after sintering was so small as to be negligible. Therefore, in this case, it was sufficient to remove the oxide film on the surface.

(Comparative Example 1) For comparison, in order to examine the case where only CIP was applied without preforming, 70 cm × 4
Fill a rubber mold of latex rubber having a cross-sectional dimension of 6 cm, and apply CI at 4 ton / cm ² until the height becomes 16 cm.
P. The compact was taken out and sintered and heat-treated under the same conditions as described above. Since the test piece was deformed at the end, it had to be ground to a final size of 69 cm × 45 cm × 14 cm.

Using the specimens obtained in Example 1 and Comparative Example 1 as test pieces, the X-ray diffraction intensity distribution of the (002) plane with respect to the magnetic field application direction (magnetization direction) for both test pieces is shown in FIG.
Shown in The vertical axis indicates the relative intensity with respect to the maximum diffraction intensity.
From this figure, it can be seen that in the case of Comparative Example 1, the orientation was disordered and the distribution became gentle, whereas in the case of Example 1, the distribution was sharp. Table 1 shows the magnetic characteristics. In Table 1, the values in the upper row are the magnetic properties of those obtained from the upper side of the test piece, the values of interruption are the magnetic properties of those obtained from the center of the test piece, and the values in the lower row are those obtained from the lower side of the test piece. Shows magnetic properties. From Table 1, it can be seen that Comparative Example 1 has a large variation in magnetic properties and a low absolute value, whereas Example 1 provides a rare-earth sintered magnet with a small variation and a large absolute value. Further, when the inclination angle of the magnetization direction with respect to the normal line of the reference plane was measured, it was 0.7 degrees in Example 1 and 5.4 degrees in Comparative Example 1.

[0012]

[Table 1]

(Embodiment 2) The preforming pressure is set to 0.4 to 1
A test piece was prepared under the same conditions as in Example 1 except that the test piece was changed to 0 ton / cm ² . After removing the oxide film on the surface in order to examine the uniformity of orientation, pulse magnetization was performed with a pulse magnetic field of 25 kOe, and then FA-22 manufactured by Siemens Co., Ltd.
Using the E probe, the surface magnetic flux density Bo of the test piece surface
Was measured. FIG. 4 shows the distribution of Bo. The measurement point is the N pole face of the test piece. From this figure, it can be seen that, when it exceeds 4 tons / cm ² , the surface magnetic flux density drops below 3.5 kG. Furthermore, FIG. 4 shows that when the preforming pressure is 0.4 to 4 ton / cm ² , the uniformity of the Bo distribution is good and preferable.

Example 3 31.7% by weight of Nd
Dy 4.0%, B (boron) 1.1%, Co 1%, Ga
A powder was prepared in the same manner as in Example 1 except that an alloy for a Nd-Fe-B-based sintered magnet consisting of 0.8% and the balance Fe was used.
The obtained powder was converted into a cross section of 24.5 mm ×
It was filled into a mold having a molding space of 120 mm to form a preformed block having a height of 95 mm. A hydraulic press with lifting was used in the same manner as in Example 1. Next, the obtained preformed block was subjected to CIP in the same manner as in Example 1.
did. The obtained CIP compact is placed on a large number of Nd ₂ O ₃ spheres (φ10 mm) placed on a support table and placed at 1090 ° C.
Sintering was performed in an argon gas atmosphere for × 1 hour. The reason for placing the CIP compact on the sphere is to prevent deformation due to shrinkage during sintering. After sintering, the sample was cooled in a furnace to room temperature, heated again at 900 ° C. for 2 hours, and continuously cooled at a cooling rate of 1.5 ° C./min. After cooling to room temperature, aging treatment (heat treatment) was performed at 580 ° C., but no cracks were found. Next, a test piece was cut out in the same manner as in Example 1 and the magnetic properties were measured. Br = 10900 G, _B H
_C = 23800 Oe, (BH) max = 28.7 MGOe
Was obtained. In addition, the tilt angle of the magnetization direction was within 0.9 degrees in any of the ab planes, and a film having extremely excellent uniformity was obtained.

[0015]

By using the mold of the present invention, it is possible to stably produce a highly oriented rare earth sintered magnet which satisfies the strict requirement of a high orientation degree that the inclination angle of the magnetization direction with respect to the normal line of the reference plane is within 3 degrees. It can be manufactured, and is extremely useful for manufacturing, for example, a wiggler for a particle beam accelerator or a nuclear magnetic resonance imaging (MRI).

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of a mold of the present invention.

FIG. 2 is a view showing a molded article (a) obtained by using the mold of the present invention and a molded article (b) obtained by subjecting the molded article of (a) to CIP.

FIG. 3 is a diagram illustrating an example of a correlation between a diffraction X-ray intensity of a (002) plane and a tilt angle with respect to a magnetization direction.

FIG. 4 is a diagram showing an example of a correlation between a preforming pressure and a Bo distribution.

FIG. 5 is a diagram illustrating a wiggler.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 41/02 H05H 13/04 F H05H 13/04 H01S 3/30 A // H01S 3/30 B22F 3/02 B

Claims (1)

[Claims] 1. A ferromagnetic mold member forming a long side or major axis A and a short side or minor axis B of a cavity and a non-magnetic mold member (A) defining a short side or minor axis B and a thickness C of a cavity. ≧ B> C), the dimension of the non-magnetic mold member along the direction of the thickness C of the cavity is substantially the same as the thickness C of the cavity, and the short side of the cavity or the direction of the short diameter B Has a protruding portion having a dimension along the shorter side or the shorter diameter B of the cavity, and the ferromagnetic mold member sandwiches the protruding portion of the nonmagnetic mold member and has a relative position. And the tip of the protruding portion of the non-magnetic mold member protrudes more toward the cavity than both end positions of the ferromagnetic mold member sandwiching the protruding portion. To face Thereby, a parallel magnetic field is generated in which the inclination angle of the magnetic field lines when applying a magnetic field passing through a plane (reference plane) formed by the long side or long diameter A and the short side or short diameter B of the cavity is within 3 degrees. A molding die for a highly oriented rare earth sintered magnet, characterized by the following features.