JPH0665743B2 - Method for producing manganese-aluminum-carbon alloy magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of 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 high-performance Mn-Al-C alloy magnet for multipolar magnetization. Is.

(Prior 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
Containing as an essential constituent element, 3 elements containing no additional element other than impurities and 4 containing a small amount of additional element
Multi-element alloy magnets containing elements or more are known and are collectively referred to.

In addition, as a method of manufacturing this Mn-Al-C alloy magnet,
In addition to those by casting and heat treatment, those including warm plastic working steps such as warm extrusion processing are known. Especially the latter
It 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 of manufacturing the Mn-Al-C alloy magnet for multipolar magnetization,
Uniaxial anisotropic polycrystalline Mn-Al- obtained by a known method such as isotropic magnet, compression processing, warm extrusion processing in advance.
A hollow body made of a C-based alloy magnet by warm free compression in the anisotropic direction (Japanese Patent Laid-Open No. 56-119762), and a pre-anisotropic polycrystalline Mn-Al-C-based alloy magnet By various plastic workings that give compressive strain in the axial direction of the billet (for example, JP-A-58-182206 to 1822)
No. 08) is known.

(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. 3 schematically shows formation of a magnetic path inside the magnet when the outer peripheral surface of the cylindrical magnet is magnetized in multiple poles. Such magnetization is referred to as outer circumference magnetization here.

In the magnets obtained by various plastic workings which give a compressive strain in the axial direction of the hollow-body-shaped billet made of the previously anisotropy polycrystalline Mn-Al-C alloy magnet,
When the above-mentioned outer peripheral magnetization is applied, it is locally anisotropy in the direction along the magnetic path, but when viewed as a whole, it is not anisotropy in the desired direction. Further, according to the above-mentioned known method, the outer peripheral portion of the cylindrical magnet is anisotropic in the radial direction and the inner peripheral portion is anisotropic in the circumferential direction (the chord direction). During the process of changing from the radial direction to the circumferential direction (chord 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, a method for producing a manganese-aluminum-carbon alloy magnet according to the present invention is a pre-anisotropic polycrystalline Mn-Al-C. A (2n + 2) prism (n = 1,2,3, ...) shaped billet consisting of a system alloy magnet,
A first step of compressing the billet in the axial direction at a temperature of 530 to 830 ° C. to form the outer peripheral surface of the billet into a circumferential surface shape; 2n + 2) a second step of magnetically polarizing each part of the outer peripheral surface of the billet after compression processing corresponding to the central part of each flat surface of the outer peripheral surface of the prismatic shape.

(Operation) By this method, that is, by forming the outer peripheral surface of the billet into a circumferential surface by compression processing and performing (2n + 2) pole magnetization after compression processing, the outer peripheral magnetization shown in FIG. 3 is performed. In this case, it is possible to anisotropy along the magnetic path, and it is possible to obtain an anisotropic magnet exhibiting high magnetic characteristics.

(Example) In the present invention, a (2n + 2) prism (n = 1,2,3, ...) Billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet is provided at 530 to 830C. By subjecting the billet to compression processing in the axial direction at the temperature, the outer peripheral surface of the billet is formed into a circumferential surface shape.

That is, a known Mn-Al-C magnet alloy, for example, 68
Or 73% by mass of Mn and (1 / 10Mn-6.6) or (1/3
Mn-22.2) A polycrystalline Mn-Al-C based alloy magnet which is made anisotropic by subjecting an alloy composed of C by mass% and the balance of Al to plastic working such as extrusion in a temperature range of 530 to 830 ° C. Obtainable. A typical one of the magnets described above is a uniaxial anisotropic magnet having an easy magnetization direction in the extrusion direction, which is obtained when the plastic processing is extruded, and then subjected to free compression processing in the extrusion direction after the extrusion processing. There are surface anisotropic magnets and the like. The anisotropy polycrystalline Mn-Al-
(2n + 2) prism (n = 1,2,3, ...) made of C alloy magnet
...)-shaped billet is subjected to compression processing in the axial direction of the billet so that the outer peripheral surface of the billet becomes a circumferential surface to obtain a magnet exhibiting high magnetic characteristics in the outer peripheral magnetization shown in FIG. be able to.

When the billet is composed of a polycrystalline Mn-Al-C alloy magnet (uniaxial anisotropic magnet) having an easy magnetization direction in the axial direction, the compressive strain in the axial direction in the compressing process is a logarithmic strain. 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 outer peripheral magnetization. .

In the plane where the billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction, is magnetically isotropic in the plane, and includes a straight line parallel to the axial direction. If it is composed of an anisotropic polycrystalline Mn-Al-C alloy magnet (plane anisotropic magnet), the billet before compression processing is already in all directions in the plane including the radial direction and the chord direction. However, by performing the compression processing of the present invention, it is possible to obtain a magnet exhibiting high magnetic characteristics in outer peripheral magnetization.

The compression processing described above does not necessarily have to be continuous compression processing, and may be given in multiple divisions. Although the billet described above is a uniaxial anisotropic magnet or a plane anisotropic magnet, it may be a magnet having an easy magnetization direction in a radial direction, a magnet having an easy magnetization direction in the circumferential direction, or the like. Means that the Mn-Al-C alloy magnet alloy has been subjected to some plastic working 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 with the billet shape as a prism (when n = 1). FIG. 1 (a) shows a sectional view of the state before compression processing as seen from the axial direction of the billet. Reference numeral 1 is a regular quadrangular prism-shaped billet, 2 is an outer mold, and is a mold for molding the outer peripheral surface of the billet (in this case, the side surface of the billet is a solid body) into a circumferential surface by compression processing. FIG. 1 (b) is a sectional view taken in a direction perpendicular to (a). 3 and 4 are punches used to compress the billet 1. When the billet 1 is set in the state shown in FIG. 1 and the punches 3 and 4 are used to perform compression processing in the axial direction of the billet 1, the cross-sectional area of the billet 1 gradually increases, and the side surface of the billet and the outer die 2 Can be done until the inner surfaces of the contact. If compression processing is performed up to this point, the side surface of the billet becomes a substantially circumferential surface.

In this case, the maximum size of the billet before compression processing is a size having a cross section of a square inscribed in the circle on the inner surface of the outer mold 2. In that case, before the compression processing, the compression processing is performed with a part of the outer peripheral surface (in this case, the side surface) of the billet 1 being constrained by the inner surface of the outer mold 2.

Although the billet is a solid body in this example, the billet may be a hollow body.

In the above example, the change in shape of the billet is from a regular square prism to a substantially circular cylinder. Due to such a change, an anisotropic structure suitable for outer peripheral magnetization is obtained. In the compression process, the part where the outer peripheral surface is constrained earliest (the part that hits the corner of the prism of the billet before processing) has the direction of easy magnetization in the chord direction, and the part where the outer peripheral surface is constrained or the last part The portion where the outer peripheral surface is not restrained (the central portion of one plane of the side surface of the billet 1 before processing and the portion farthest from the inner surface of the outer die 2) has the 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 1 before compression processing may be determined depending on how many poles are magnetized in the outer peripheral magnetization. In other words, in the above-mentioned example, since it is a square prism, it has an anisotropic structure suitable for quadrupole magnetization. As described above, the billet having a (2n + 2) prismatic shape needs to have an even number of polygonal pillars as described above. When n = 1, it is for 4 poles, and when n = 2, it is 6 poles.
It becomes something like ………. 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 section of the (2n + 2) prism (n = 1,2,3, ...) shaped billet in the present invention does not need to be a geometrically accurate (2n + 2) prism, even if there is some chamfering. No problem.

Polycrystalline Mn-Al with billet having easy magnetization in the axial direction
In the case of a -C alloy magnet, the compressive strain is required to be 0.05 or more in absolute value of logarithmic strain as described above. However, in an actual application, if you want to keep the easy magnetization direction while keeping a part of the magnet as uniaxial anisotropy, restrict the outer peripheral surface of the part of the billet to a region where no compressive strain is locally applied. It may be a method of making.

As described in the above example, when the compression processing is performed in the axial direction of the billet, the outer circumference of the billet is molded and compressed by using a mold etc. It is intended to obtain a magnet having an anisotropic structure that exhibits high magnetic properties when magnetized.

Regarding the temperature range in which compression processing as described above is possible,
Processing was possible in the temperature range of 530 to 830 ° C, but at temperatures above 780 ° 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 69.5% by mass (hereinafter simply expressed as%) of Mn, 29.3 in the compounding range
% Al, 0.5% C and 0.7% Ni by melt casting, diameter
A cylindrical billet having a length of 60 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. Next, through a lubricant, extrusion processing was performed at a temperature of 720 ° C. to a diameter of 45 mm. Further, extrusion processing was performed at a temperature of 680 ° C through a lubricant to a diameter of 28 mm. This extruded rod was cut into a length of 20 mm and cut to produce a regular square pole billet having a side of 18 mm and a length of 20 mm. 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. Using such a die, compression processing was performed to a height of 9.2 mm.

The billet after compression processing was cut into a diameter of 29 mm and magnetized with 4 poles. The magnetization was pulse-magnetized at 1500V using a 2000 μF oil condenser. The surface magnetic flux density of the outer peripheral surface was measured with a Hall element. 23m diameter for comparison
A cylindrical billet of m and 20 mm in height 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 9.2 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.

Example 2 A square-shaped billet having a side length of 18 mm and a length of 20 mm obtained in Example 1 was cut to form a square cavity having a side length of 8 mm, and a hollow body billet was produced. Using this billet, compression processing was performed using the mold shown in FIG. The dimensions of each part of the outer mold 2 are the same as those shown in FIG. 5 is a core, and the length of one side is 8 mm. Using such a die, compression processing was performed to a height of 8 mm.

The billet after compression processing was cut to an outer diameter of 29 mm, magnetized on the outer periphery in the same manner as in Example 1, and the surface magnetic flux density was measured. The same as the magnet obtained by the method of the present invention obtained in Example 1 The value of the surface magnetic flux density was shown.

As for the magnets obtained by the method of the present invention obtained in Examples 1 and 2, as a result of magnetic torque measurement, as described above, the easy magnetization direction was along the chord direction at the side of the billet before compression processing. , In the middle, along the radial direction, between them, it was found to change continuously from the radial direction to the chordal direction (circumferential direction).

(Effects of the Invention) According to the present invention, as described in the embodiments, a (2n + 2) prism (n = 1,2,3, n) made of a pre-anisotropic polycrystalline manganese-aluminum-carbon alloy magnet is used. ......)
-Shaped billet is subjected to compression processing in the axial direction of the billet to form the outer peripheral surface of the billet into a circumferential surface shape, and the central portion of each flat surface of the (2n + 2) prismatic outer peripheral surface of the billet before compression processing. By magnetizing each part of the outer peripheral surface of the billet after compression processing corresponding to the above, a magnet exhibiting high magnetic characteristics is obtained.

Compared with the magnet obtained by the known method, the magnet obtained by the method of the present invention, when subjected to outer circumference magnetization,
It exhibits better magnetic characteristics than the magnets by the known method, and the magnets have an easy magnetizing direction in the radial direction by the known method, and an easily magnetizing direction in the circumferential direction (chord direction) at the inner peripheral portion. However, the method of the present invention has an effect that a magnet having a desired anisotropic structure can be obtained at least once by the method of the present invention.

[Brief description of drawings]

1 (a) and 1 (b) are a horizontal cross-sectional view and a vertical cross-sectional view, respectively, of a mold used in the compression processing of the first embodiment of the present invention.
FIG. 3 is a cross-sectional view of a mold used in the compression processing of the second embodiment of the present invention, and FIG. 3 shows the formation of magnetic paths inside the magnet when the outer peripheral surface of the cylindrical magnet is magnetized with multiple poles. It is the figure shown typically. 1 …… Billet, 2 …… Outer mold, 3,4 …… Punch, 5 ……
Core.

Claims (4)

[Claims] 1. Pre-anisotropic polycrystalline manganese-
A (2n + 2) prism (n = 1,2,3, ...) shaped billet made of an aluminum-carbon alloy magnet is subjected to compression processing in the axial direction of the billet at a temperature of 530 to 830 ° C. The outer peripheral surface is formed into a circular surface shape, and further, there is a pole on each part of the outer peripheral surface of the billet after compression processing corresponding to the center part of each flat surface of the (2n + 2) prismatic outer peripheral surface of the billet before compression processing. A method of manufacturing a manganese-aluminum-carbon alloy magnet, which comprises magnetizing. 2. The billet is composed of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction, and the compressive strain is 0.05 or more in absolute value of logarithmic strain. The method for producing a manganese-aluminum-carbon alloy magnet according to item (1). 3. A billet has a straight line which has a direction of easy magnetization parallel to a plane perpendicular to the axial direction, is magnetically isotropic in the plane, and is parallel to the axial direction and the plane. The method for producing a manganese-aluminum-carbon based alloy magnet according to claim (1), characterized by comprising a polycrystalline manganese-aluminum-carbon based alloy magnet which is anisotropic in the plane containing the magnet. 4. The manganese-aluminum-carbon alloy magnet according to claim 1, wherein the compression processing is performed with a part of the outer peripheral surface of the billet being constrained. Production method.