JPH0663064B2 - 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, it relates to a method for producing a polycrystalline manganese-aluminum-carbon system (Mn-Al-C system) alloy magnet, and more particularly to a method for producing a high-performance Mn-Al-C system alloy magnet for magnetizing multipoles. It is a thing.

ART Mn-Al-C alloy magnet is composed of mainly face-centered tetragonal (tau phase, L1 ₀ type ordered lattice) is a ferromagnetic phase of tissue, C
Is included as an essential constituent element, and ternary alloy magnets of quaternary system or more containing no additional element other than impurities and quaternary system or more containing a small amount of additive element are known. is there.

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 taken 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
A hollow body made of a system alloy magnet by warm free compression in an anisotropic direction (for example, Japanese Patent Laid-Open No. 56-119762) and a pre-anisotropic polycrystalline Mn-Al-C system alloy magnet. There are known various types of plastic working (for example, JP-A-58-182206-8) which give a compressive strain in the axial direction of the billet.

Problems to be Solved by the Invention The shape of a multi-pole magnetizing magnet is generally a cylindrical body, and the main magnetizing is magnetizing 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 compressive strain in the axial direction of the hollow body billet made of the previously anisotropy-crystallized polycrystalline Mn-Al-C alloy magnet, the inner circumferential magnetization is applied. In this case, locally anisotropy was made in the direction along the magnetic path, but when viewed as a whole, it was not anisotropy 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 the Problems In order to solve the problems described above, the present invention provides a hollow body-shaped axisymmetric billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet. Then, the billet is compressed in the axial direction at a temperature of 530 to 830 ° C, and the cross-section of the inner peripheral surface of the billet is formed into a (2n + 2) square (n = 1,2,3 ...) It is a thing.

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. The present invention provides a hollow body-shaped axisymmetric billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet.
By performing compression processing in the axial direction of the billet at a temperature of 30 ° C, the cross-sectional shape of the inner peripheral surface of the billet is (2n
+2) It is formed into a rectangular shape (n = 1,2,3 ...).

That is, a known alloy for Mn-Al-C magnets, for example, 68-
73 mass% Mn and (1 / 10Mn-6.6) to (1 / 3Mn-22.2)
An anisotropic polycrystal Mn-Al-C alloy magnet is obtained by subjecting an alloy composed of C by mass% and the balance Al to plastic working such as extrusion in the temperature range of 530 to 830C. Typical examples of the magnet include a uniaxial anisotropic magnet having an easy magnetization direction in the extruding direction, which is obtained when the plastic working is extruding, and a free compression process in the extruding direction after the extruding process. There are obtained plane anisotropic magnets and the like. The hollow body of the billet having the axially symmetric shape made of the anisotropic Mn-Al-C alloy magnet has a cross section of the inner peripheral surface of the billet of (2n + 2) square (n = 1, 2, (3 ...) By performing compression processing in the axial direction of the billet so as to obtain a magnet exhibiting high magnetic characteristics in the inner circumferential magnetization shown in FIG.

When the billet is composed of a polycrystalline Mn-Al-C alloy magnet (uniaxial anisotropic magnet) having an easy magnetization direction in the direction of the symmetry axis, the compressive strain is logarithmic strain in the direction of the symmetry axis in the compression processing. An absolute value of 0.05 or more is required. This is because the billet before compression processing is anisotropy in the direction of giving compressive strain, and at least 0.05 compressive strain is required for the structural change that shows high magnetic characteristics in inner circumference magnetization. is there.

The billet has an easy magnetization direction parallel to a plane perpendicular to the axis of symmetry, is magnetically isotropic in the plane, and is different in a plane including a straight line parallel to the axial direction and the plane. When it is composed of a polycrystalline Mn-Al-C alloy magnet (bianisotropic magnet) that is anisotropic, the billet before compression is already high in all directions in the plane including the radial direction and the chord direction. Although the magnetic properties are shown, by performing the compression processing of the present invention, it is possible to obtain a magnet having high magnetic properties in the inner circumference magnetization.

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. Further, although the uniaxial anisotropic magnet and the plane anisotropic magnet have been shown as the billet, a magnet having an easy magnetization direction in a radial direction, a magnet having an easy magnetization direction in the circumferential direction, and the like may be used. That is, some plastic working is applied to the Mn-Al-C magnet alloy in a predetermined temperature range.

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 comes into contact with 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. .

When the billet is made of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction in the axial direction of the cylindrical body, the compressive strain must be 0.05 or more in absolute value of logarithmic strain as described above. However, in an actual application, if you want to preserve the direction of easy magnetization while keeping a part of the magnet as uniaxial anisotropy, constrain the inner peripheral surface of the part of the billet so that no compressive strain is locally applied. A method of creating a region may be used.

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, 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 69.5% by mass (hereinafter simply referred to as%) of Mn, 29.3 in the composition of the composition
% Al, 0.5% C and 0.7% Ni melt-cast, diameter 70
A cylindrical billet having a length of 50 mm and a length of 50 mm was produced. After holding this billet at 1100 ° C. for 2 hours, it was heat-treated by allowing it to cool to room temperature. Then through the lubricant at a temperature of 720 ℃ diameter 50 mm
Was extruded. 680 ℃ through lubricant
Extrusion processing was performed at a temperature of up to 31 mm in diameter. This extruded rod is cut to a length of 20 mm and cut to form an outer diameter of 30 mm and an inner diameter of 24
A cylindrical billet having a length of 20 mm and a length of 20 mm was produced. 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 30 mm, and the punch 3
The length of one side of the square is 14 mm. Using such a mold, compression processing was performed to a height of 10 mm.

The billet after compression processing was machined to an inner diameter of 15 mm except the four corners of the inner peripheral surface, and magnetized with four poles on the inner peripheral surface. 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. For comparison, a cylindrical billet having a diameter of 18 mm and a height of 20 mm was freely compressed in the axial direction of the cylinder at a temperature of 680 ° C. The height of the billet after compression processing was 10 mm. The billet after processing was a plane anisotropic magnet, cut and magnetized in the same manner as described 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 1.6 times that of the surface anisotropic magnet.

The magnet obtained by the method of the present invention obtained in the above example, as a result of the magnetic torque measurement, as described above, the easy magnetization direction is along the radial direction at the side portion of the inner peripheral surface of the billet after compression processing, It was found that it was along the chord direction in the middle, and between them was continuously changing from the radial direction to the chord direction (circumferential direction).

EFFECTS OF THE INVENTION As described in the embodiments, the present invention provides a hollow body-shaped axisymmetric billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet at a temperature of 530 to 830 ° C. When the inner circumference is magnetized by performing compression processing in the axial direction of the billet and shaping the cross-sectional shape of the inner circumference of the billet into a (2n + 2) square (n = 1,2,3 ...) It is intended to obtain a magnet exhibiting extremely high magnetic characteristics.

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 die used for compression processing according to 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 attached to an inner peripheral surface of a cylindrical magnet. It is a figure which shows typically formation of the magnetic path inside a magnet when magnetizing. 1 ... Billet, 2 ... External type, 3 ... Punch

Claims (4)

[Claims] 1. Pre-anisotropic polycrystalline manganese-
An axisymmetric hollow body-shaped billet having a cylindrical hollow portion made of an aluminum-carbon alloy magnet was heated at 530 to 830 ° C.
At the temperature of, the billet is compressed in the axial direction to form a hollow part of the billet into a (2n + 2) prism (n = 1, 2, 3).
Manganese-having a first step of magnetizing the billet formed in the first step and a second step of magnetizing the billet in the middle of one plane of the side surface of the hollow part of the (2n + 2) prism A method for manufacturing an aluminum-carbon alloy magnet. 2. A billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having a direction of easy magnetization in the direction of the axis of symmetry, and the compression strain in compression processing is 0.05 or more in absolute value of logarithmic strain. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1. 3. A billet has a straight line which has a direction of easy magnetization parallel to a plane perpendicular to the axis of symmetry, is magnetically isotropic in the plane, and is parallel to the axial direction and the plane. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, which is composed of a polycrystalline manganese-aluminum-carbon alloy magnet which is anisotropic in a plane including the magnet. 4. 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. .