JPS62143406A - Manufacture of manganese-aluminum-carbon alloy magnet - Google Patents

Abstract

PURPOSE:To obtain the desirable magnetic anisotropy by a method wherein a compression-processing is performed in the axial direction of a billet in such a manner that the compressive distortion of the outer circumferential part of the billet is made larger than that of the inner circumferential part in the state wherein a part of the outer and the inner circumference of the billet is made free. CONSTITUTION:A cylindrical billet 1 is obtained by performing cutting and machining operations on the rod obtained by conducting an extrusion-processing on an Mn-Al-C alloy. This billet 1 has the direction of axis of easy magnetization in parallel with the plane surface vertical to axial direction. Then, said billet 1 is inserted between punches 2 and 3, maintained at the temperature of 530-830 deg.C, and a compressive processing is performed thereon. As the end face of the punches 2 and 3 has a non- plane surface, the outer circumferential part of the billet has the compressive distortion larger than that of the inner circumferential part. Then, after a cutting process has been finished, the outer circumference of the billet is magnetized. As a result, the magnet having the magnetic characteristics suitable for an outer circumferential multipolar magnetization can be obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a permanent magnet, and in particular, to a method for producing a permanent magnet, and in particular to a method for producing a high-performance multi-polar magnet using a polycrystalline manganese-aluminum-carbon (Mn-mu-iC) alloy magnet. The present invention relates to a method of manufacturing a Mn-Ae-C alloy magnet for use in the manufacturing industry.

Conventional technology Mn-Ae-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, L, regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element. , ternary alloy magnets containing no additive elements other than impurities, and quaternary or higher multi-component alloy magnets containing a small amount of additive elements are known, and these are collectively referred to as magnets.

As for the manufacturing method, there are known methods including plastic working steps such as extrusion processing in addition to those using casting and heat treatment. In particular, the latter method is known as a method for producing anisotropic magnets having excellent properties such as high magnetic properties, mechanical strength, weather resistance, and machinability.

In addition, methods for producing multipolar magnetized alloy magnets using Mn-Ae-C alloy magnets include isotropic magnets, compression processing, and uniaxial anisotropy obtained by known methods such as extrusion processing. (The obtained magnet is called a plane anisotropic magnet.)

JP-A No. 66-119762), and one in which a hollow billet made of a polycrystalline Mn-Al-1 alloy magnet that has been made anisotropic in advance is subjected to a specific compression process (JP-A No. 58-182205). Public bulletin) is known.

Problems to be Solved by the Invention The previously anisotropic polycrystalline Mn
In the method in which a hollow billet made of a C-based alloy magnet is subjected to a specific compression process (in particular, JP-A-68-182205), polycrystalline Mn that has been made anisotropic in advance is used.
-A hollow billet made of Ae-C alloy magnet,
In a method in which the billet is compressed in the axial direction with at least a portion of the outer circumference and inner circumference of the billet free, the obtained magnet has an easy magnetization direction in the radial direction. This anisotropic structure is not necessarily a desirable anisotropic structure for use with multipolar magnetization on the outer or inner circumferential surface.

The present invention aims at obtaining a magnet with a desirable anisotropic structure.

In order to solve the problems that are more than just a means to solve the problems, the present invention provides a hollow body-shaped billet made of a polycrystalline Mn-M-e-C alloy magnet which has been made anisotropic in advance. The billet is compressed in the axial direction so that the compressive strain on the outer periphery of the billet is greater than the compressive strain on the inner periphery, with a portion of the outer periphery and inner periphery free.

Effect: In the specific compression process mentioned above, the compression process is performed in the axial direction of the billet so that the compression strain on the outer circumference of the billet is greater than the compression strain on the inner circumference, unlike conventional methods. A magnet having an easy magnetization direction in the radial direction at the outer circumference of the magnet and an easy magnetization direction in the circumferential direction at the inner circumference is obtained.

Example The present invention uses polycrystalline Mn-Ae- which has been made anisotropic in advance.
A hollow body-shaped billet made of a C-based alloy magnet has 530~
At a temperature of 830 °C, with at least a portion of the outer and inner circumferences of the billet free, the billet is compressed in the axial direction so that the compressive strain on the outer circumference of the billet is greater than the compressive strain on the inner circumference. It is something.

Most of the manufacturing method of the present invention is based on the above-mentioned known technology (Japanese Unexamined Patent Publication No.
8-182205).

In the compression processing of the known technique, compression processing is performed in the axial direction of the billet with at least a portion of the outer periphery and inner periphery of the billet free.

On the other hand, in the compression processing of the present invention, in addition to the compression processing described above, compression processing is further performed in the axial direction of the billet so that the compression strain at the outer peripheral portion of the billet is larger than the compression strain at the inner and peripheral portions.

Similar to the above-mentioned known technology, the above-mentioned billet has a polycrystalline Mn-m e-c having an easy magnetization direction in the axial direction of the hollow body.
In the case of a magnet made of a series alloy magnet (-axis anisotropic magnet), the compressive strain during compression processing must be 0.05 or more in terms of the absolute value of the logarithmic strain. This is because the billet before compression processing is anisotropic in the direction of applying compressive strain, and the change in structure that exhibits high magnetic properties in multipole magnetization requires at least zero
．． This is because a compressive strain of 0.05 is required.

Further, in the present invention, the billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is parallel to the axial direction and the plane. The magnet becomes a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing straight lines.

A specific example of this compression υ loe is shown below. The first method is to perform free compression in the axial direction of a cylindrical billet using a mold shown in FIG. Figure 1 is (a)
shows the cross section before processing. 1 is billet, 2 and 3 are punch. As shown in FIG. 1(a), the difference from the prior art is that the surfaces of punches 2 and 3 that contact the billet (punch end surfaces) are not flat surfaces but are sloped surfaces (angle of inclination α). . This punch 2 and punch 3
By applying pressure in the axial direction of the billet 1 using a compressor, the billet is compressed in the axial direction and becomes the state shown in FIG. 1(b). As shown in FIG. 1(b), the height of the outer peripheral part of the billet after compression processing is smaller than the height of the inner peripheral part.

In other words, the billet was compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet was greater than the compressive strain on the inner circumferential portion.

Compressive strain refers to strain in the billet's axial direction.

Another typical compression processing example of the first method will be described assuming that the cross-sectional shape of the billet is ring-shaped. FIG. 2 (+L) shows a cross section before processing, similar to FIG. 1. Figure 2 (&
), the difference from FIG. 1 is that the punch end faces of punches 2 and 3 are flat, and the height of the outer periphery of the billet before processing is greater than the height of the inner periphery. FIG. 2(b) shows the state after processing. The billet after processing has a substantially cylindrical shape, and the height of the outer circumferential portion of the billet and the height of the inner circumferential portion of the billet are approximately the same. In this case as well, the billet was compressed in the axial direction so that the compressive strain at the outer circumferential portion of the billet was greater than the compressive strain at the inner circumferential portion.

The second method is a method in which a portion of the billet that has been subjected to free compression, which is advantageous in the first method, is compressed in the axial direction, and this method is the same as the above-mentioned known technique.

The third method is to perform free compression processing (compression processing 1, first method) in the axial direction of the billet so that the compression strain on the outer circumference of the billet is larger than the compression strain on the inner circumference, and then
With the outer circumference of the billet constrained and the inner circumference free, compression processing is performed in the axial direction of the billet (compression processing 2
) An example of this series of compression processing is shown in Fig. 3. FIG. 3(a) shows a cross section before processing. 1 is a billet, 2.3 is a punch, and 4 is an outer mold. Figure 3 (
As shown in a), the difference from the prior art is that the punch end faces of punches 2 and 3 are not flat but sloped. By applying pressure in the axial direction of the billet 1 using the punches 2 and 3, the billet is compressed in the axial direction and is in the state shown in FIG. 1(b) (
Compression processing 1 is completed), and if you perform further compression processing, the third
The result is as shown in Figure (C). The height of the outer periphery of the billet after compression processing is smaller than the height of the inner periphery. In other words, in this case as well, the billet was compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet was greater than the compressive strain on the inner circumferential portion.

Another example of the third method will be described assuming that the cross-sectional shape of the billet is ring-shaped. 1. FIG. 4(a) shows a cross-section of the billet before processing, similar to FIG. 3. As shown in Figure 4 (&), the third
The difference from the figure is that the punch end faces of punches 2 and 3 are flat, and the height of the outer circumference of the billet processed mT is greater than the height of the inner circumference. FIG. 4(b) shows the state after compression processing 1. The billet after processing has a substantially cylindrical shape, and the height of the outer circumferential portion of the billet and the height of the inner circumferential portion of the billet are approximately the same. In this case as well, the billet was compressed in the axial direction so that the compressive strain at the outer circumferential portion of the billet was greater than the compressive strain at the inner circumferential portion.

Further, when compression processing is performed, the state shown in FIG. 4(C) is obtained.

The fourth method is a method in which a part of the billet obtained in the third method is further compressed in the axial direction, and this method is the same as the above-mentioned known technique.

As described above, the present invention is based on the above-mentioned known technology (Japanese Unexamined Patent Publication No. 5
This is almost the same as the compression process shown in Japanese Patent No. 8-182205), but by making the billet end surface an inclined surface or the punch end surface an inclined surface, in this particular compression process, the compressive strain on the outer periphery of the billet can be reduced. The billet can be compressed in the axial direction so that the compressive strain is greater than the compressive strain on the inner circumference, and as a result, the outer circumference of the magnet has an easy magnetization direction in the radial direction, and the inner circumference has an easy magnetization direction in the circumferential direction. An anisotropic structure with an easy direction is obtained, and a magnet suitable for peripheral multi-pole magnetization can be obtained.

Even in a combination of the above two examples, the billet can be compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet is larger than the compressive strain on the inner circumferential portion. In other words, using the mold shown in Fig. 1 (the punch end face is an inclined face), the billet shown in Fig. 2 (the billet end face is an inclined face) is used.
This is a method of compression processing.

In the above example, the punch end face or billet end face was a sloped face, but there are also stepped faces (stepped shapes), flat + sloped faces, or a combination of the above, and the punch or billet end face that has an uneven shape has both sides. But it can be one-sided. What is necessary is to compress the billet in the axial direction so that the compressive strain on the outer circumference of the billet is greater than the compressive strain on the inner circumference. This creates an anisotropic structure in which the outer periphery of the magnet has an easy magnetization direction in the radial direction, and the inner periphery has an easy magnetization direction in the circumferential direction, resulting in an anisotropic magnet suitable for outer periphery multipole magnetization. It will be done.

Regarding the possible temperature range of compression processing as mentioned above,
Processing was possible in the temperature range of 530 to 830°C, but at temperatures exceeding 780°C, the magnetic properties decreased by 9 degrees. The most desirable temperature range was 560 to 76oC.

Next, more specific embodiments of the present invention will be described.

Example 1 Blending composition: 69.5% Mn, 29-3% Aero,
6% C and 0.7% Ni were melted and cast to produce a cylindrical billet with a diameter of 50 layers R1 and a length of 4QMll.

After holding this billet at 1100℃ for 2 hours,
After cooling with air to 600°C for 30 minutes, heat treatment was performed by cooling to room temperature.

Extrusion processing up to a diameter of 32 mm was carried out at a temperature of 720° C. via a lubricant. The extruded rod was cut and machined to produce a billet having an outer diameter of 30 mm, an inner diameter of 16 mm, an outer circumference length of 25 mm, an inner circumference length of 20 mm, and both end faces having sloped surfaces.

Next, using a mold as shown in Figure 2, the outer and inner peripheries of the billet are made free using a lubricant.
Compression processing up to a length of 12 fl was performed at a temperature of 680°C.

After cutting this billet to an outer diameter of 40 fl, the outer peripheral surface was magnetized with 24 poles. For magnetization, a 2000 μF oil capacitor was used, and pulse magnetization was performed at 16 oov.

The surface magnetic flux density on the outer peripheral surface was measured using a Hall element.

For comparison, the extruded rod described above was cut and machined to have an outer diameter of 30 ffff, an inner diameter of 16 mm, and a length of 22.5 mm.
I made my cylindrical billet. Using a lubricant and using the same mold as above, compression working was performed up to a length of 12 mm. Furthermore, it was cut and magnetized in the same manner as above, and the surface magnetic flux density was measured.

Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the magnet produced for comparison.

Furthermore, only the outer circumferential portion of the billet was compressed using a mold as shown in FIG. 5 at a temperature of 680'C. FIG. 5(a) shows the state before processing, and FIG. 5(b) shows the state after processing. 5 is a fixed punch, 6 is a movable punch, and 7 is a lower die. The fixing punch 5 and the lower mold 7 fix and restrain the billet, and the movable punch 6 pressurizes the billet 1 to form the sixth
The state shown in Figure (b) is reached, whereby only the outer peripheral portion of the billet is compressed. Note that the diameter of the punch 5 (inner diameter of the punch 6) is 35111111. The length of the outer periphery after compression processing was 8 mm. The processed billet was machined to an outer diameter of 40 MM and magnetized in the same manner as above.
Comparing the values of the surface magnetic flux density before and after this compression processing, the surface magnetic flux density was higher by 2 kG after processing.

Example 2 The blend composition is 69.4% Mn and 29.3% Ae.

A cylindrical billet having a diameter of 50 mm and a length of 40 mm was prepared by melting and casting 0.5% C, 0.7% Ni, and 0.1% Ti. This billet was subjected to the same heat treatment as in Example 1. Then, through lubricant, at a temperature of 720°C, a diameter of 32
We performed extrusion processing up to the size.

The extruded rod was cut and machined to have an outer diameter of 3011M.

A cylindrical billet with an inner diameter of 16ffff and a length of 26 mm was produced. Next, using a mold as shown in Figure 1, the outer and inner circumferences of the cylindrical billet are made free using a lubricant, and the inner circumference of the cylindrical billet is heated at a temperature of 680°C. Compression processing was performed up to a length of 16 mm. In FIG. 1, the inclination angle α of the punch end face is 100.

This billet was cut to an outer diameter of 4071 ff, and the outer circumference was magnetized with 24 poles in the same manner as in Example 1, and the surface magnetic flux density was measured. For comparison, the extruded rod was cut and machined to have an outer diameter of 30 mm and an inner diameter of 16 mm.

A cylindrical billet with a length of 25 mm was produced. Compression processing up to a length of 15 mm was performed using the mold used in Example 1 via a lubricant. Furthermore, after cutting in the same manner as described above, it was magnetized and the surface magnetic flux density was measured.

Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the magnet produced for comparison.

Furthermore, in the same manner as in Example 1, only the outer circumferential portion of the previously magnetized magnet of the present invention was compressed to a length of up to 7 wings. The processed billet was cut to an outer diameter of 40 mm and magnetized in the same manner as above, and when comparing the surface magnetic flux density values before and after this compression processing, it was found that the value after processing was 2 kG higher. .

Example 3 The extruded rod obtained in Example 1 was cut and machined to have an outer diameter of 30 ffff, an inner diameter of 16 mm, an outer periphery length of 26 mm, and an inner periphery length of 20 ffff, with both end surfaces having a stepped shape. A billet with a diameter of 23mm at the border of the attached part was produced.

The same compression process as in Example 1 was performed using this billet. The length of the billet after processing was 12 mm. This billet was cut to an outer diameter of 40ffllr, and Example 1
After magnetizing the outer periphery of 24 poles in the same way as above, measure the surface magnetic flux density,
A comparison was made with the magnet produced for comparison in Example 1.

Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.3 times that of the magnet produced for comparison.

Further, in the same manner as in Example 1, only the outer peripheral portion of the magnet of the present invention, which had just been magnetized, was compressed to a length of up to 8 mm. After cutting the billet after processing to a total outer diameter of 4 Q Ml, it was magnetized in the same manner as above, and when comparing the surface magnetic flux density values before and after this compression processing, the value after processing was 0.2 kG higher. became.

Example 4 The extruded rod obtained in Example 2 was cut and machined to produce two cylindrical fillets with an outer diameter of 30 mm, an inner diameter of 16 mm, and a length of 2571 ff. Next, the outer and inner peripheries of the cylindrical billet were made free using a mold as shown in Fig. 6 using a lubricant, and the length of the inner periphery of the cylindrical billet was heated at a temperature of 680°C. Compression processing was performed up to 17 mm. In FIG. 6, the diameter of the stepped portion on the end face of the punch is 30 holes, and one step is 2.5 mm.

After cutting this billet to an outer diameter of 40mm, Example 1
The outer periphery of 24 poles was magnetized in the same manner as above, and the surface magnetic flux density was measured and compared with the magnet prepared for comparison in Example 2:c.

Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.3 times that of the magnet produced for comparison.

Further, in the same manner as in Example 1, only the outer peripheral portion of the magnet of the present invention, which had just been magnetized, was compressed to a length of up to 8 mm. A billet was machined to an outer diameter of 40 MM, magnetized in the same manner as described above, and when the surface magnetic flux density values were compared before and after the compression process, the value after the process was 0.2 kG higher.

Example 5 The extruded rod obtained in Example 1 was cut and machined to have an outer diameter of 30 mm, an inner diameter of 16 mm, an outer circumference length of 26 mm, and an inner circumference length of 20 mm, with both end surfaces being inclined surfaces. Next, using a mold as shown in Fig. 4, the outer and inner circumferences of the billet were made free using a lubricant.
Compression processing up to a length of 157ffff was performed at a temperature of 0°C. In Fig. 4, the inner diameter of the outer mold 4 is 34MM.
It is.

After cutting this billet to an outer diameter of 33M, Example 1
The outer periphery of the 24-pole was magnetized in the same manner as above, and the surface magnetic flux density was measured.

For comparison, the extruded rod described above was cut and machined to produce a cylindrical billet having an outer diameter of 30 mm, an inner diameter of 16 mm, and a length of 22.5 mm. Next, through a lubricant, compression processing was performed to a length of about 16 mm in the same manner as described above, cutting was performed, magnetization was performed, and the surface magnetic flux density was measured.

Comparing the above two values, it was found that the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the magnet produced for comparison. As in Example 1, only the outer peripheral portion of the magnet was compressed. The diameter of the punch 6 was 29 mm, and the length of the outer circumference was 10 mm. After cutting the processed billet to an outer diameter of 33 mm, it was magnetized in the same manner as above, and when comparing the surface magnetic flux density before and after compression processing, the value after processing was 0.2 kG. It got expensive.

Example 6 The extruded rod obtained in Example 1 was cut and machined to have an outer diameter of 3QM11. A cylindrical billet with an inner diameter of 16 and a length of 25 was produced. Next, the outer and inner peripheries of the billet were made free using a mold as shown in Figure 3 using a lubricant, and the length of the outer periphery of the billet was reduced to 13 mm at a temperature of 680°C. - Compression processing was performed up to 3 fights. In Fig. 1, the inclination angle α of the punch end face is 100, and the inner diameter of the outer die 4 is 3.
There are 4 friends.

After cutting the compressed billet to an outer diameter of 33 mm, the outer circumference was magnetized with 24 poles in the same manner as in Example 1, the surface magnetic flux density was measured, and a billet was prepared for comparison in Example 5. compared to magnets.

Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the magnet produced for comparison.

Further, in the same manner as in Example 1, only the outer circumferential portion of the previously magnetized magnet of the present invention was compressed to a length of up to 10 mm. After cutting the processed billet into an outer diameter of 33 silk,
Magnetized in the same way as above, and comparing the surface magnetic flux density values before and after this compression processing, the value after processing is 0.2 k G
It got expensive.

As mentioned above, regarding the composition of the Mn-Ae-C alloy magnet, N
Although only the quaternary system with i addition and the quinary system with Ni and Ti additions are shown, the ternary system, which is the basic composition of Mn-Ae-C alloy magnets, or the multi-component system with addition elements other than those mentioned above are shown. Although some differences were observed in the magnetic properties of the magnets, improvements in the magnetic properties as described above were observed compared to the known compression processing method.

Although we have shown an example in which a uniaxial anisotropic magnet is used as an Mn-Ae-C alloy magnet that has been made anisotropic in advance, a planar anisotropic magnet,
The same result was obtained even when a diameter anisotropic magnet was used.

Furthermore, regarding the compression processing of a portion of the billet, only the example in which only the outer circumference of the billet is compressed is shown, but it is also possible to compress only the inner circumference, but in this case, the entire magnet is magnetized in the radial direction. This is effective when you want to have an easy direction.

Furthermore, regarding the shape of the billet and punch end faces, we have shown examples of inclined surfaces and stepped shapes, but even flat surfaces, inclined surfaces, or a combination of the above can improve magnetic properties compared to conventional compression processing. Admitted. Further, the uneven end face may be one end face or both end faces.

Effects of the Invention As described in the examples, the present invention provides a hollow billet made of a polycrystalline Mn-Ae-C alloy magnet that has been made anisotropic in advance, and at least a portion of the outer and inner circumferences of the billet. By compressing the billet in the axial direction so that the compressive strain on the outer periphery of the billet is greater than the compressive strain on the inner periphery in the free state, high magnetic properties can be achieved when the outer periphery is multipole magnetized. The magnet shown is obtained.

With this method, the outer circumference of the magnet has an easy magnetization direction in the radial direction, and the inner circumference has an easy magnetization direction in the circumferential direction,
A magnet having an easy magnetization direction in the circumferential direction can be obtained at the inner circumference.

[Brief explanation of drawings]

1 to 6 are sectional views of a part of a mold showing an example of compression processing according to the present invention. 1...Billet, 2,3...Punch, 4.
...Outer mold, 5...Fixing punch, 6...
...Movable pump, 7...Lower mold. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (S Cb) Figure 2 (Kuji Figure 5 (S) Cb)

Claims (12)

[Claims] (1) A state in which a hollow body-shaped billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance is kept free at least part of the outer and inner circumferences of the billet at a temperature of 530 to 830°C. A method for manufacturing a manganese-aluminum-carbon alloy magnet, characterized in that the billet is compressed in the axial direction so that the compressive strain is greater than the compressive strain at the outer periphery of the billet. (2) The billet has a direction of easy magnetization in the axial direction of the hollow body, and the compressive strain is 0.0 as the absolute value of the logarithmic strain.
Manganese according to claim 1, which is 05 or more.
A method for producing an aluminum-carbon alloy magnet. (3) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is a straight line parallel to the axial direction and the plane. 2. A method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing the . (4) A state in which a hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance is heated at a temperature of 530 to 830°C, with at least a portion of the outer periphery and inner periphery of the billet free. The manganese-aluminum material is characterized in that the billet is compressed in the axial direction so that the compressive strain at the outer circumference of the billet is greater than the compressive strain at the inner circumference, and then a part of the billet is further compressed. -Production method of carbon-based alloy magnet. (5) With the billet having an easy magnetization direction in the axial direction of the hollow body and with at least a portion of the outer circumference and inner circumference of the billet being free, the compressive strain on the outer circumference of the billet is equal to that on the inner circumference. The compressive strain in the axial direction of the billet is greater than the compressive strain, so that the absolute value of the logarithmic strain is 0.
．． 5. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 4, wherein the magnet is 0.05 or more. (6) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is a straight line parallel to the axial direction and the plane. 5. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 4, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing the . (7) A hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance, at a temperature of 530 to 830°C, with at least a portion of the outer circumference and inner circumference free; The billet is compressed in the axial direction so that the compressive strain on the outer periphery of the billet is greater than the compressive strain on the inner periphery, and the outer periphery of the billet is constrained, while at least a portion of the inner periphery is free. A method for manufacturing a manganese-aluminum-carbon alloy magnet, which comprises compressing a billet in the axial direction. (8) The billet has a direction of easy magnetization in the axial direction of the hollow body, and furthermore, when the compression process is completed, a compressive strain in the axial direction is applied to the billet by an absolute value of logarithmic strain of 0.05 or more. Manganese-aluminum- according to item 7
Manufacturing method for carbon-based alloy magnets. (9) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is a straight line parallel to the axial direction and the plane. 8. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 7, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing the . (10) A hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance, at a temperature of 530 to 830°C, with at least a portion of the outer and inner circumferences of the billet free. Then, the billet is compressed in the axial direction so that the compressive strain on the outer periphery of the billet is greater than the compressive strain on the inner periphery, and furthermore, while the outer periphery of the billet is constrained, at least a part of the inner periphery is free. 1. A method for manufacturing a manganese-aluminum-carbon alloy magnet, which comprises compressing the billet in the axial direction, and then compressing a portion of the billet in the axial direction of the billet. (11) The billet has an easy magnetization direction in the axial direction of the hollow body, and is compressed in the axial direction of the billet while the outer periphery of the billet is restrained and at least a part of the inner periphery is free. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 10, wherein compressive strain in the axial direction is applied at the end of the process by 0.05 or more in absolute value of logarithmic strain. (12) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is a straight line parallel to the axial direction and the plane. Claim 1 consisting of a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing
A method for producing a manganese-aluminum-carbon alloy magnet according to item 0.