JPH0663065B2 - 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 (Mn-Al-C) alloy magnet, and more particularly to a method for producing a Mn-Al-C alloy magnet for multipolar magnetization.

Prior art alloys for Mn-Al-C magnets contain 68 to 73 mass% (hereinafter simply referred to as%
Mn and (1 / 10Mn-6.6) to (1 / 3Mn-22.
2) Multi-component magnet alloys composed of 3% C and the balance Al, ternary system containing no additional elements other than impurities, and quaternary system containing a small amount of additional elements are known. It is a thing.

Similarly, Mn-Al-C alloy magnet is composed of face-centered tetragonal (tau phase ,, L1 ₀ type ordered lattice) of the tissue is primarily a ferromagnetic phase, which contains a C as the essential constituent elements A ternary system magnet containing no additional element other than impurities and a quaternary system 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 of manufacturing the 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 of 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.

The method for producing the Mn-Al-C alloy magnet for multipolar magnetization is 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
-Based alloy magnets obtained by warm free compression processing in the anisotropic direction (for example, JP-A-56-119762), and Mn-Al-C
There are known various types of plastic working (for example, Japanese Patent Laid-Open No. 58-192303-6) which give a compressive strain in the axial direction of a hollow body billet made of a system magnet alloy.

Problems to be Solved by the Invention The shape of the magnet for multi-pole magnetization is generally cylindrical, and the main magnetization is the magnetization as shown in FIG. FIG. 2 schematically shows the formation of a magnetic path inside the magnet when the inner peripheral surface of the cylindrical magnet is magnetized in multiple poles. Such magnetization is referred to as inner circumference magnetization here.

In the magnet obtained by various plastic workings that give a compressive strain in the axial direction of the hollow body-shaped billet made of the above-mentioned alloy for Mn-Al-C magnets, when the inner circumference is magnetized,
Although it is locally anisotropic in the direction along the magnetic path, when viewed as a whole, it is not anisotropic in the desired direction.
Further, according to the above-mentioned known method, the inner circumferential portion of the cylindrical magnet is anisotropic in the radial direction and the outer circumferential portion is anisotropic in the circumferential direction (the chord direction). During the process of changing from the radial direction to the circumferential direction (chordal direction), it is not an anisotropic structure along that direction, and it is necessary to perform plastic working at a higher temperature twice or more.

Means for Solving Problems In order to solve the problems described above, the present invention provides Mn-
A hollow body-shaped axisymmetric billet made of an Al-C magnet alloy is compressed in the axial direction of the billet at a temperature of 530 to 830 ° C, and the cross-sectional shape of the inner peripheral surface of the billet is changed by this compression processing. (2n + 2) prisms (n = 1,2,3 ...) are formed.

Action By this method, that is, by this compression processing, the cross-sectional shape of the inner peripheral surface of the billet is changed to (2n + 2) square (n = 1,2,3
...) to obtain an anisotropic magnet exhibiting high magnetic characteristics, which can be anisotropy along the magnetic path when the inner circumferential magnetization shown in FIG. 2 is applied. You can

Embodiment An embodiment of the present invention will be described below with reference to the drawings. According to the present invention, an axially symmetrical billet made of an alloy for Mn-Al-C magnets is subjected to compression processing in the axial direction of the billet at a temperature of 530 to 830 ° C to obtain a cross-sectional shape of the inner peripheral surface of the billet. (2n
+2) It is formed into a rectangular shape (n = 1,2,3 ...).

Thus, the billet having an axially symmetric shape made of an alloy for Mn-Al-C magnets has a cross-sectional shape of the inner peripheral surface of the billet (2n + 2) prism (n = 1,2) at a temperature of 530 to 830 ° C. , 3 ...) is compressed in the axial direction of the billet to obtain a magnet exhibiting high magnetic characteristics in the inner circumference magnetization shown in FIG.

The compression processing described above does not necessarily have to be continuous compression processing, and may be given by dividing into a plurality of times.

An example of the compression processing of the present invention described above will be described with reference to FIG. 1 in which the billet has a cylindrical shape and the cross-sectional shape of the inner peripheral surface of the billet after compression processing is square (when n = 1). FIG. 1a is a sectional view of the state before compression processing as seen from the axial direction of the billet. 1 is a cylindrical billet, 2 is an outer die, and this outer die 2 is a die for preventing the outer peripheral surface of the billet from being deformed by compression processing. FIG. 1b is a sectional view showing a state after compression processing. As shown in FIG. 1B, the inner diameter of the cylindrical billet becomes smaller as the compression process progresses, and a part of the inner peripheral surface comes into contact with the surface of the punch 3. By further performing the compression process, the compression process can be performed until the inner peripheral surface of the billet 1 almost contacts the surface of the punch 3 as shown in FIG.

Further, it is not necessary to perform the compression processing to the state shown in FIG. 1B, and even if the compression processing is finished at any time after a part of the inner peripheral surface of the billet 1 contacts the surface of the punch 3. Good.

The minimum inner diameter of the billet of the present invention before compression processing is the size in contact with the surface of the punch 3. In that case, the compression processing is performed in a state where a part of the inner peripheral surface of the billet 1 is already constrained by the surface of the punch 3 before the compression processing.

Further, in the above example, the outer peripheral surface of the billet 1 is already in contact with the inner surface of the outer mold 2 before being compressed, and thus the billet 1 is in a restrained state, but the outer diameter of the billet 1 is considerably larger than the inner diameter of the outer mold 2. It may be small and have some clearance. In this case, both the outer diameter and the inner diameter of the billet 1 increase with the progress of the compression process, and the outer peripheral surface of the billet 1 contacts the inner surface of the outer mold 2, and the state becomes substantially as shown in FIG. The following changes are similar to the changes described above.

In the above-mentioned example, the change in the cross-sectional shape of the inner peripheral surface of the billet is from circular to almost square (there may be R with a chamfer at each corner). It has an anisotropic structure suitable for magnetism. In the compression process, the part where the inner peripheral surface is constrained earliest becomes the part having the easy magnetization direction in the chord direction, and the part where the inner peripheral surface is restricted at the end or the part where the inner peripheral surface is not restricted until the end is It has an easy magnetization direction in the radial direction.
The portion between them is a portion in which the easy magnetization direction sequentially changes from the radial direction to the chord direction. In this way, the shape of the billet after compression processing may be determined depending on how many poles are magnetized in the inner circumference magnetization. That is, in the above-mentioned example, since the sectional shape of the inner peripheral surface of the billet after compression processing is substantially square, it has an anisotropic structure suitable for quadrupole magnetization. The cross-sectional shape of the inner peripheral surface of the billet after compression processing is (2n + 2) square (n =
As described above, it is necessary that the inner circumferential magnetization has an even number of poles and an even polygonal cross-sectional shape. When n = 1, 4 poles are used, and when n = 2, 6 poles are used. The smaller n is, the clearer the anisotropic structure due to the above-mentioned position becomes, but the larger n becomes, the more unclear it becomes.

The (2n + 2) polygon (n = 1,2,3 ...) in the present invention does not need to be a geometrically accurate (2n + 2) polygon, and there is no problem even if some chamfering etc. .

As described in the above example, in the present invention, when the billet is compressed in the axial direction, the cross-sectional shape of the billet inner peripheral surface is (2n + 2) square (n = 1, 2,3
..) to obtain a magnet having an anisotropic structure that exhibits high magnetic characteristics when subjected to inner circumference magnetization.

Regarding the temperature range in which compression processing as described above is possible,
Processing was possible in the temperature range of 530-830 ℃, but 780
At temperatures above ° C, the magnetic properties deteriorated considerably. A more desirable temperature range was 560 to 760 ° C.

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

Example 1 69.4% Mn, 29.3% Al, 0.5% C, 0.7% in the composition
Ni and 0.1% Ti are melt cast, outer diameter 30mm, inner diameter 24m
A cylindrical billet having a length of m and a length of 20 mm was produced. After holding this billet at 1100 ℃ for 2 hours, air-cool it to 600 ℃,
After holding it for 30 minutes at 30 ° C., it was heat-treated to cool to room temperature. Using this billet, compression processing was performed using the mold shown in FIG. In FIG. 1, the inner diameter of the outer mold 2 is
At 30 mm, the length of one side of the punch 3 square is 14 mm.
Using this mold, compression processing up to a height of 10 mm was performed.

The billet after compression processing was machined to an inner diameter of 15 mm except for the four corners of the inner surface, and magnetized with four poles on the inner circumference. For the magnetization, a 2000 μF oil condenser was used and pulsed at 1500 V. The surface magnetic flux density of the inner peripheral surface was measured with a Hall element. The peak value at each magnetic pole was 2.3 to 2.4 KG.

As a result of magnetic torque measurement, the magnets obtained by the method of the present invention obtained in the above examples show that, as described above, the easy magnetization direction is along the port direction at the side portion of the inner peripheral surface of the billet after compression processing. , In the middle, along the radial direction, between them was found to change continuously from the radial direction to the chordal direction (circumferential direction).

EFFECTS OF THE INVENTION As described in the examples, the present invention provides a hollow body-shaped axisymmetric billet made of an alloy for Mn—Al—C magnets at a temperature of 530 to 830 ° C. in the axial direction of the billet. A magnet that exhibits high magnetic properties when subjected to inner circumference magnetization by performing compression processing and shaping the cross-sectional shape of the inner circumference of the billet into a (2n + 2) polygonal shape (n = 1,2,3 ...) Is what you get.

Compared with the magnet obtained by the known method, the magnet obtained by the method of the present invention shows superior magnetic characteristics to the magnet obtained by the known method when subjected to inner circumferential magnetization, and further At least two or more plastic workings were required to obtain a structure in which the peripheral portion has the easy magnetization direction in the radial direction, and the outer peripheral portion has the easy magnetization direction in the circumferential direction (chord direction). The method of the invention can at least once yield a magnet with a more desirable anisotropic structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold used for compression processing of an embodiment of the present invention, showing a change in cross-sectional shape of a billet before and after compression processing, and FIG. 2 is a multi-pole on the inner peripheral surface of a cylindrical magnet. It is a figure which shows typically formation of the magnetic path inside a magnet when magnetized. 1 ... Billet, 2 ... External type, 3 ... Punch

Claims (2)

[Claims] 1. An axisymmetric hollow body-shaped billet made of a manganese-aluminum-carbon alloy magnet and having a cylindrical hollow portion is compressed at a temperature of 530 to 830 ° C. in the axial direction of the billet. Then, the hollow part of the billet is (2n + 2)
First step of forming into a prism (n = 1, 2, 3 ...) And (2n + 2) of the billet formed in the first step
The second pole that is pole-polarized in the middle of one plane of the side surface of the hollow portion of the prismatic shape
And a method for manufacturing a manganese-aluminum-carbon alloy magnet. 2. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, wherein the compression working is carried out with a part of the inner peripheral surface of the billet being constrained. .