JPH0639666B2 - Method for producing manganese-aluminum-carbon alloy magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a permanent magnet. More specifically, the present invention relates to a method for producing a polycrystalline manganese-aluminum-carbon system (Mn-Al-C system) alloy magnet, and particularly to a method for producing a Mn-Al-C system alloy magnet for multipolar magnetization. is there.

2. Description of the Related Art Mn-Al-C based magnet alloys are a general term for Mn-Al-C based magnet alloys and Mn-Al-C based alloy magnets. Mn-Al-C magnet alloy is 68 to 73 mass%
(Hereinafter simply expressed as%) Mn and (1/10 Mn-6.
6) to (1 / 3Mn-22.2)% of C and the balance of Al, and a ternary system alloy containing no additional element other than impurities and a quaternary or more multicomponent magnet alloy containing a small amount of additional element Are known and are generic terms. Similarly, M
n-Al-C alloy magnet is composed of mainly face-centered tetragonal (tau phase, L1 ₀ type ordered lattice) is a ferromagnetic phase of tissue are those containing C as essential constituent elements, in addition to impurities A ternary system magnet containing no additional element and a quaternary or more multi-component alloy magnet containing a small amount of additional element are known, and they are collectively referred to.

Further, as a method for producing this Mn-Al-C alloy magnet, a method including a warm plastic working step such as warm extrusion processing is known in addition to the method by casting and heat treatment. In particular, the latter is known as a method for producing an anisotropic magnet having excellent properties such as high magnetic properties, mechanical strength, weather resistance and machinability.

As a method for producing the Mn-Al-C alloy magnet for multipolar magnetization, an isotropic magnet, a compression processing method, or a uniaxially anisotropic polycrystalline Mn obtained by a known method such as warm extrusion processing in advance.
-Al-C alloy magnet by free warm compression in the anisotropic direction (Japanese Patent Laid-Open No. 56-119762), and a hollow billet shaft made of Mn-Al-C magnet alloy. Various plastic workings that give a compressive strain in the direction (for example, JP-A-58-182206 and JP-A-58-192303) are known.

Problems to be Solved by the Invention Various types of plastic working that give compressive strain in the axial direction of the hollow body billet made of the above-mentioned Mn-Al-C magnet alloy (especially JP-A-58-182206). )
That is, that is, polycrystalline Mn-A that has been anisotropy beforehand
In a method of performing compression processing in the axial direction of the billet in a state in which at least a part of the outer circumference and the inner circumference of the billet is made free in a billet having a hollow body made of an lC-based alloy magnet,
For example, a hollow billet made of a uniaxially anisotropic polycrystalline Mn-Al-C alloy magnet obtained by a known method such as extrusion is used. By subjecting the billet to the specific compression process described above, a magnet exhibiting excellent magnetic characteristics when multi-polarized is obtained. However, the above method requires at least two types of plastic working, extrusion processing and compression processing.The billet after extrusion has an easy magnetization direction in the extrusion direction, and it has excellent magnetic properties when it is magnetized in multiple poles by compression processing. A magnetic anisotropy structure is converted into a magnet exhibiting characteristics. In other words, the billet after extrusion has a uniaxial anisotropy that has a direction of easy magnetization in the axial direction of the billet, and has an anisotropic structure that is not suitable for multipolar magnetization. The magnetic properties in the circumferential direction are improved, and the magnetic anisotropy structure is converted into a magnet that exhibits excellent magnetic properties when magnetized in multiple poles.

A magnet with excellent magnetic properties when it is extruded by the above-mentioned method and once made into a uniaxial anisotropic magnet (anisotropic magnet that is not suitable for multi-pole magnetization) and then multi-polarized by compression. This is a wasteful manufacturing method in terms of magnetic characteristics.

The present invention aims to obtain excellent magnetic properties with a small amount of processing.

In order to achieve this object, the present invention provides manganese-
A hollow body-shaped billet made of an aluminum-carbon magnet alloy has a hollow cross-sectional shape of the hollow part of the container part at a temperature of 530 to 830 ° C., and the opening area of the container part is larger than that of the bearing part. Using, the extruding process is carried out in parallel with the axial direction of the billet and the extruding direction, and the hollow body-shaped billet is extruded by this extruding process.
After being stretched in the axial direction and the circumferential direction, the billet is compressed in the axial direction in a state where at least a part of the outer circumference and the inner circumference of the stretched billet is free.

By the above-described method, that is, after performing the above-mentioned specific extrusion processing, by performing the above-mentioned specific compression processing, after performing the publicly known extrusion processing until now, and then performing the above-mentioned specific compression processing Even if the total plastic working amount is small, it is possible to obtain a magnet exhibiting excellent magnetic properties when magnetized in multiple poles.

Example The present invention is a hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy, has a hollow cross-sectional shape of the container portion at a temperature of 530 to 830 ° C., and has an opening area of the container portion. Using a die larger than the opening area of the bearing part, the billet is extruded in parallel with the axial direction and the extruding direction, and the hollow billet is stretched in the axial direction and the circumferential direction by this extruding process. Further, compression processing is performed in the axial direction of the billet in a state where at least a part of the outer circumference and the inner circumference of the expanded billet is free.

By subjecting the above-mentioned extrusion process to Mn-Al which has been previously anisotropy by known extrusion processes.
By the method of obtaining a -C alloy magnet, a magnet exhibiting excellent magnetic characteristics can be obtained when multipolar magnetization is performed even if the amount of strain during compression processing is small.

The above-mentioned extrusion processing and compression processing do not necessarily have to be continuous plastic processing, and may be given by dividing into multiple times.

An example of the extrusion processing of the present invention described above will be described with reference to FIG. 1 in which the billet has a cylindrical shape. FIG. 1a is a sectional view of a part of the die showing a state before extrusion,
Similarly, FIG. 1b shows the state after extrusion. 1 is a billet, 2 is a mandrel, 3 is a die, and 4 and 5 are punches. The mandrel 2 and the dice 3 form a dice. In FIG. 1, 6 is a container part, which is a part for accommodating the billet 1 before extrusion, and 7 is a bearing part, which is a part for accommodating the billet 1 after extrusion. 8 is a conical part. The opening area of the container portion 6 is the cross-sectional area of the cavity of the container portion 6 (perpendicular to the extrusion direction), which is substantially the same as the cross-sectional area of the billet 1 in FIG. , The cross-sectional area of the cavity of the bearing portion 7 (perpendicular to the extrusion direction), which is substantially the same as the cross-sectional area of the billet 1 in FIG.

In FIG. 1, since both the container portion 6 and the bearing portion 7 are circular with the extruding shaft as the center, in other words, the opening area of the container portion 6 is a ring shape defined by the outer diameter and the inner diameter of the container portion 6. Area. The cross-sectional shape of the hollow portion of the container portion 6 is the above-mentioned ring shape and is hollow. Similarly, the opening area of the bearing portion 7 is a ring-shaped area formed by the outer diameter and the inner diameter of the bearing portion 7. For example, the outer diameter of the container portion 6 is 40 mm, the inner diameter is 20 mm,
When the outer diameter of the bearing portion 7 is 50 mm and the inner diameter is 40 mm, the opening area of the container portion 6 is about 942 mm ² , and the opening area of the bearing portion 7 is about 707 mm ² . The cross-sectional shape of the hollow portion of the container portion 6 is a ring shape having an outer diameter of 40 mm and an inner diameter of 20 mm. In other words, the hollow portion of the container portion 6 has a hollow cross-sectional shape, that is, when the billet 1 is housed in the container portion 6 as shown in FIG. There is a die constituent member (mandrel 2) in the part, the billet 1 is further outside thereof, and the die constituent member (die 3) is further outside thereof.

An example of the extrusion processing method will be described with reference to FIG. First, as shown in FIG. 2A, the cylindrical billet 1'is housed in the container portion 6. By pressing the billet 1'with the punch 4, the state shown in FIG. 2b is obtained. Next, as shown in FIG. 2c, the billet 1 is newly accommodated in the container portion 6, and the punch 4 is used to pressurize the billet 1 in the same manner as described above, whereby the state shown in FIG. 2d is obtained. . Thereafter, extrusion processing is performed by repeating this.

As another extrusion processing method, in the state shown in FIG.
While pressing the billet 1 with the punches 4 and 5, the billet 1 is moved in the direction from the container portion 6 to the bearing portion 7 (in FIG. 2, the state of the billet 1 is changed from FIG. 2c to FIG. 2d). ) There is a method of performing extrusion processing.

In Fig. 2a, the shape of the cylindrical billet 1'has a shape with an appropriate clearance in order to facilitate the insertion of the cylindrical billet 1'in the container portion 6, but the cross section of the cylindrical billet 1 '(axial direction And a cross-sectional shape of the hollow portion of the container portion 6 (the shape of the hollow portion when the die is cut along a plane perpendicular to the extrusion direction) are ring-shaped.

The compression process in the next step and the method of applying a compressive strain to a part of the billet 1 in the axial direction of the billet 1 are the same as those of the above-mentioned known technique (Japanese Patent Laid-Open No. 58-182206).

Regarding the temperature range in which the plastic working (extrusion processing and compression processing) as described above is possible, the working could be performed in the temperature range of 530 to 830 ° C, but at the temperature exceeding 780 ° C, the magnetic properties were considerably deteriorated. A more desirable temperature range was 560 to 760 ° C.

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

Example 1 69.5% of Mn, 29.3% of Al, 0.
5% C and 0.7% Ni are melt-cast and the outer diameter is 30 m
A cylindrical billet having an m, an inner diameter of 10 mm and a length of 20 mm was produced. After holding this billet at 1100 ° C. for 2 hours,
After air-cooling to 00 ° C., holding at 600 ° C. for 30 minutes, heat treatment of allowing to cool to room temperature was performed.

Next, extrusion processing as shown in FIG. 1 was performed at a temperature of 720 ° C. through a lubricant. In Fig. 1, the outer diameter of the container part of the die is 30 mm, the inner diameter is 10 mm, the outer diameter of the bearing part is 40 mm, the inner diameter is 35 mm, and X is 20 mm.
Is. The billet after extrusion has an outer diameter of 40 mm and an inner diameter of 35.
mm and the length was 42.7 mm. Next, this cylindrical billet is cut and cut to have an outer diameter of 40 mm, an inner diameter of 35 mm, and a length of 20.
mm billet. Next, through a lubricant, free compression processing was performed in the axial direction of the cylindrical billet. The compression temperature was 680 ° C., and the length of the cylindrical billet was compressed to 10 mm.

The compression processed billet has an outer diameter of 50 mm and an inner diameter of 42
As a cylindrical magnet having a length of 10 mm and a length of 10 mm, the inner peripheral surface was magnetized with 30 poles. For the magnetization, a 2000 μF oil condenser was used and pulsed at 1500 V. The surface magnetic flux density on the outer peripheral surface was measured with a Hall element. For comparison, Mn, Al, C having the same composition as the composition described above
And Ni were melt-cast to produce a cylindrical billet having a diameter of 60 mm and a length of 20 mm. The billet was held at 1100 ° C. for 2 hours and then heat-treated by allowing it to cool to room temperature. Next, a known extrusion process up to a diameter of 40 mm was performed at a temperature of 720 ° C. through a lubricant. This extruded rod is cut to a length of 20 mm and cut to give an outer diameter of 40 mm, an inner diameter of 35 mm and a length of 2
A 0 mm cylindrical billet was produced. Next, this billet was subjected to the same free compression processing as the above-described compression processing, and was further cut into a cylindrical shape in the same manner as described above, 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.

Further, the magnet magnetized previously according to the present invention was compression-processed only at the inner peripheral portion of the billet at a temperature of 680 ° C. using a mold as shown in FIG. FIG. 3a shows a state before processing, and FIG. 3b shows a state after processing. 9 is the lower mold, 10
Is a restraining die, and 11 is a movable punch. The billet 1 is fixed and restrained by the lower die 9 and the restraining die 10, and the billet 1 is pressed by the movable punch 11, so that only the inner peripheral portion of the billet is compressed as shown in FIG. 3b. The die punch 11 used here has a diameter of 47 mm. The length of the inner peripheral portion of the billet after compression processing was 7 mm. After machining, the billet after machining was made to have an inner diameter of 42 mm, magnetized in the same manner as above, and the surface magnetic flux density values before and after this local compression were compared.
kG increased.

Example 2 69.4% of Mn, 29.3% of Al, 0.
5% C, 0.7% Ni and 0.1% Ti were melted and cast to prepare a cylindrical billet having an outer diameter of 20 mm, an inner diameter of 5 mm and a length of 20 mm. The billet was held at 1100 ° C. for 2 hours, then air-cooled to 600 ° C., held at 600 ° C. for 30 minutes, and then heat-treated to cool to room temperature.

Next, extrusion processing as shown in FIG. 1 was performed at a temperature of 720 ° C. through a lubricant. In FIG. 1, the outer diameter of the container portion of the die is 20 mm, the inner diameter is 5 mm, the outer diameter of the bearing portion is 30 mm, the inner diameter is 26 mm, and X is 20 mm. The billet after extrusion has an outer diameter of 30 mm and an inner diameter of 26 m.
The length was 33.5 mm. Next, this cylindrical billet is freely compressed in the axial direction of the cylindrical billet using a mold as shown in Fig. 4 through a lubricant, and then the outer peripheral surface of the billet is constrained and the inner circumference is free. 68
The cylindrical billet was compressed to a length of 16 mm at a temperature of 0 ° C. In FIG. 4, FIG. 4a shows a state before working, and FIG. 4b shows that the diameter of the billet 1 increases as the working progresses, and the outer peripheral surface of the billet 1 becomes the inner surface of the outer die 12. FIG. 4c shows a state when they come into contact with each other (the outer peripheral surface of the billet 1 is restrained by this), and FIG. 4c shows a state after compression processing. The inner diameter of the outer mold 12 of the used mold is 34
mm.

This compression billet has an outer diameter of 33 mm and an inner diameter of 27
As a cylindrical magnet having a length of 16 mm and a length of 16 mm, the outer peripheral surface was magnetized with 24 poles. The magnetization was pulse-magnetized at 1500 V using a 2000 μF oil condenser. The surface magnetic flux density on the outer peripheral surface was measured with a Hall element. For comparison,
Mn, Al, C, N having the same composition as the composition described above
i and Ti were melted and cast to form a cylindrical billet having a diameter of 50 mm and a length of 20 mm. This billet is 2 at 1100 ℃
After holding for a time, a heat treatment of cooling to room temperature was performed. Then, a known extrusion process up to a diameter of 30 mm was performed at a temperature of 720 ° C. through a lubricant. This extruded rod has a length of 33.5
cut into mm and cut, outer diameter 30mm, inner diameter 26mm,
A cylindrical billet having a length of 33.5 mm was produced. Next, this billet was subjected to the same compression processing as the above-mentioned compression processing, and was further cut into a cylindrical shape in the same manner as described above, 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.

Further, the magnet magnetized previously according to the present invention was compression-processed only at the inner peripheral portion of the billet at a temperature of 680 ° C. using a mold as shown in FIG. In FIG. 5, FIG. 5a shows a state before processing, and FIG. 5b shows a state after processing.
Reference numeral 9 is a lower die, 13 is a fixed punch, and 14 is a movable punch. The billet 1 is fixed and constrained by the lower die 9 and the fixing punch 13, and only the outer peripheral portion of the billet is compressed by pressing the billet 1 with the movable punch 14. The diameter of the punch 13 (the inner diameter of the punch 14) is 30 mm. The outer peripheral length after compression processing is 10
It was mm. The billet after processing is cut to an outer diameter of 33
When the value of surface magnetic flux density was compared before and after this local compression processing, it was 0.2 kG higher after processing.

Example 3 Mn, Al, C and Ni having the same blending composition as in Example 1 were melt cast to prepare a cylindrical billet having an outer diameter of 40 mm, an inner diameter of 30 mm and a length of 20 mm. The billet was held at 1100 ° C. for 2 hours, then air-cooled to 600 ° C., held at 600 ° C. for 30 minutes, and then heat-treated to cool to room temperature.

Next, extrusion processing as shown in FIG. 1 was performed at a temperature of 720 ° C. through a lubricant. In FIG. 1, the outer diameter of the container part of the die is 40 mm, the inner diameter is 30 mm, the outer diameter of the bearing part is 30 mm, the inner diameter is 20.8 mm, and X is 2
It is 0 mm. The billet after extrusion had an outer diameter of 30 mm, an inner diameter of 20.8 mm and a length of 30 mm. Next, this cylindrical billet was subjected to free compression processing using a mold as shown in FIG. 4 through a lubricant, and then the outer peripheral surface of the cylindrical billet was restrained and the inner circumference was made free. A compression process was performed at a temperature of 680 ° C. to a cylindrical billet length of up to 20 mm. In FIG. 4, the inner diameter of the outer mold 12 is 34 mm.

This compression billet has an outer diameter of 33 mm and an inner diameter of 22
As a cylindrical magnet having a length of 20 mm and a length of 20 mm, 12 poles were radially magnetized from the outer peripheral surface and the inner peripheral surface as shown in FIG. FIG. 6 schematically shows the formation of a magnetic path (indicated by a broken line in the drawing) inside the magnet when magnetized in a radial direction of the cylindrical magnet. As shown in FIG. 6, the magnetic path is substantially along the radial direction of the magnet. The magnetization was pulse-magnetized at 1500 V using a 2000 μF oil condenser.
The surface magnetic flux density on the outer peripheral surface was measured with a Hall element. For comparison, Mn and A having the same composition as the composition described above are used.
l, C and Ni are melt-cast, diameter 60mm, length 20mm
The cylindrical billet of was produced. This billet is 1100 ℃
After being held for 2 hours at room temperature, a heat treatment of allowing to cool to room temperature was performed. Then, through the lubricant, at a temperature of 720 ° C., a diameter of 40
Known extrusion processes up to mm were performed. This extruded rod has a length of 3
Cut to 0mm and cut to have an outer diameter of 30mm and an inner diameter of 20.
A cylindrical billet having a length of 8 mm and a length of 30 mm was produced. Next, this billet was subjected to the same compression processing as the above-mentioned compression processing, and was further cut into a cylindrical shape in the same manner as described above, 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.

Further, the magnet magnetized previously according to the present invention was compression-processed only at the inner peripheral portion of the billet at a temperature of 680 ° C. using a mold as shown in FIG. The diameter of the punch 13 (the inner diameter of the punch 14) is 27 mm. The outer peripheral length after compression processing was 15 mm. After machining, the billet was machined to have an outer diameter of 33 mm, magnetized in the same manner as above, and the surface magnetic flux density values before and after this local compression were compared. It became high.

Example 4 Mn, Al, C and Ni having the same composition as in Example 1 were melt-cast and a cylindrical billet having a diameter of 50 mm and a length of 20 mm was produced. The billet was held at 1100 ° C. for 2 hours and then heat-treated by allowing it to cool to room temperature.

Then, a known extrusion process up to a diameter of 30 mm was performed at a temperature of 720 ° C. through a lubricant. The extruded rod is cut into a length of 20 mm and cut to have an outer diameter of 30 mm, an inner diameter of 10 mm, and a length of 20.
A cylindrical billet (billet A) of mm was prepared. Further, the extruded rod was cut into a length of 20 mm and cut into a cylindrical billet (billet B) having a diameter of 29 mm and a length of 40 mm. This billet B was subjected to free compression processing in the axial direction of the billet at a temperature of 660 ° C via a lubricant. The length of the billet after processing was 20 mm. The billet (plane anisotropic magnet) after this working was cut into a cylindrical billet (billet B) having an outer diameter of 30 mm, an inner diameter of 10 mm and a length of 20 mm, similarly to the billet A. Next, as in Example 1, the billet A and the billet B were extruded through a lubricant at a temperature of 720 ° C. using a die as shown in FIG. In Fig. 1, the outer diameter of the container part of the die is 30 mm, the inner diameter is 10 mm, and the outer diameter of the bearing part is 4 mm.
The inner diameter is 0 mm, the inner diameter is 35 mm, and the X is 20 mm. The billet after extrusion has an outer diameter of 40 mm, an inner diameter of 35 mm and a length of 42.
It was 7 mm. Next, the length of each of these cylindrical billets was set to 20 mm, and the length of each cylindrical billet was freely compressed to 10 mm at a temperature of 680 ° C. through a lubricant.

The billets that have been subjected to this compression processing have an outer diameter of 50 mm,
As a cylindrical magnet having an inner diameter of 42 mm and a length of 10 mm, the inner peripheral surface was magnetized with 30 poles. The magnetization was pulse-magnetized at 1500 V using a 2000 μF oil condenser. The surface magnetic flux density of the inner peripheral surface was measured with a Hall element, and
It was compared with the magnet of the present invention obtained in.

Comparing the values of the following two (the magnet of the present invention using billet A and billet B and the magnet of the present invention obtained in Example 1), the value of the surface magnetic flux density of the magnet obtained in Example 4 was The magnet produced by using the billet A of the magnet produced in Example 1 was about 1.2 times, and the magnet produced by the billet B was about 1.3 times.

Further, the magnet magnetized previously according to the present invention was compression-processed only at the inner peripheral portion of the billet at a temperature of 680 ° C. using a mold as shown in FIG. The punch 11 has a diameter of 46 mm. The inner peripheral length after compression processing was 7 mm. After machining, the billet is machined to an inner diameter of 42 mm and magnetized in the same manner as above, before this local compression processing.
When the values of the surface magnetic flux densities were compared later, the values after processing were higher by 0.2 kG.

As described above, regarding the composition of the Mn-Al-C based magnet alloy, N
Only the i-added quaternary system and the Ni- and Ti-added quinary system are shown. However, a known ternary system which is a basic composition of the Mn-Al-C alloy magnet or a known additive element other than the above Regarding the multi-component system, although a slight difference was found in the magnetic characteristics of the magnet after plastic working (extrusion processing + compression processing), the improvement in magnetic characteristics as described above was recognized by the known method of extrusion processing.

EFFECTS OF THE INVENTION As described in the examples, according to the present invention, a hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy has a hollow cross-sectional shape of a hollow portion of a container portion at a temperature of 530 to 830 ° C. And, using a die in which the opening area of the container part is larger than the opening area of the bearing part, extrusion processing is performed by making the extrusion direction parallel to the axial direction of the billet,
By this extrusion, the hollow billet is stretched in the axial direction and the circumferential direction, and then, in a state where at least a part of the outer circumference and the inner circumference of the billet after the expansion is free, the billet is axially moved. A magnet that exhibits high magnetic characteristics when subjected to multi-pole magnetization by performing compression processing is obtained.

By this method, that is, after performing the above-mentioned specific extrusion processing, by performing the compression processing with the above-mentioned characteristics, after performing the known extrusion processing until now, the total is more than the method of performing the specific compression processing. A magnet exhibiting excellent magnetic characteristics can be obtained when magnetized in multiple poles, even if the plastic working amount is small.

[Brief description of drawings]

1A and 1B are partial sectional views of a mold showing an example of extrusion processing of the present invention, and FIGS. 2A to 2D are partial sectional views of a mold showing an example of extrusion method of the present invention, 3a, 3b, 4a-c
5a and 5b are sectional views of a part of a die showing an example of the compression processing of the present invention, and FIG. 6 shows the inside of a magnet when multi-pole magnetized in the radial direction of a cylindrical magnet. It is a figure which shows formation of a magnetic path typically. 1, 1 '... Billet, 2 ... Mandrel, 3 ... Die, 4, 5 ... Punch, 6 ... Container part, 7 ... Bearing part, 8 ... Conical part, 9 ... Lower mold, 10 ...... Restraint mold, 11 ...... Movable punch, 12 ...... Outer mold, 13 ......
Fixed punch, 14 ... Movable punch.

Claims (4)

[Claims] 1. A hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy, having a hollow cross-sectional shape of a hollow portion of a container portion at a temperature of 530 to 830 ° C.,
Using a die whose opening area of the container is larger than that of the bearing, extruding is performed with the axial direction of the billet parallel to the extruding direction. After stretching in the direction,
A method for producing a manganese-aluminum-carbon alloy magnet, further comprising compressing the billet in the axial direction in a state where at least a part of the outer circumference and the inner circumference of the expanded billet is free. 2. A hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy, having a hollow cross section at a temperature of 530 to 830 ° C.
Using a die whose opening area of the container part is larger than the opening area of the bearing part, extrusion processing is performed by making the extrusion direction parallel to the axial direction of the billet, and the hollow body-shaped billet is formed by the extrusion processing in the axial direction. After being stretched in the circumferential direction, further, at least a part of the outer circumference and the inner circumference of the billet after the stretching is subjected to compression processing in the axial direction of the billet, and then a part of the billet after the compression is A method for producing a manganese-aluminum-carbon alloy magnet, which comprises compressing the billet in the axial direction. 3. A hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy, wherein the hollow portion of the container portion has a hollow cross section at a temperature of 530 to 830 ° C.,
Using a die whose opening area of the container part is larger than that of the bearing part, the billet is extruded with the axial direction parallel to the extruding direction, and the hollow billet is extruded by the extruding process. After being stretched, the billet is compressed in the axial direction in a state where at least a part of the outer circumference and the inner circumference of the billet after the stretching is freed, and thereafter, the outer circumference of the billet after the compression is constrained and at least A method for producing a manganese-aluminum-carbon alloy magnet, which comprises subjecting a billet to axial compression while leaving a part of the inner periphery free. 4. A hollow body-shaped billet made of a manganese-aluminum-carbon magnet alloy, having a hollow cross section at a temperature of 530 to 830 ° C.
Using a die whose opening area of the container part is larger than that of the bearing part, the billet is extruded with the axial direction parallel to the extruding direction, and the hollow billet is extruded by the extruding process. After being stretched, the billet is compressed in the axial direction with at least a part of the outer and inner circumferences of the billet being stretched, and then the outer periphery of the billet after compression is constrained. , And at least a part of the inner circumference of the billet is compressed in the axial direction of the billet, and then a part of the billet after compression is further compressed in the axial direction of the billet. -Aluminum-Carbon-based alloy magnet manufacturing method.