JPH061742B2 - Alloy magnet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a permanent magnet, and particularly to a high-performance multi-purpose alloy using a polycrystalline manganese-aluminum-carbon (Mn-Al-C) alloy. The present invention relates to a method for manufacturing an Mn-Al-C alloy magnet for polar magnetization.

The (prior art) Mn-Al-C alloy magnet is composed mainly face-centered tetragonal (tau phase, L1 ₀ type ordered lattice) is a ferromagnetic phase of tissue, those containing C as the essential constituent elements There are known ternary alloy magnets containing no additional element other than impurities and quaternary alloy magnets containing a small amount of additive element, and these are collectively referred to.

In addition, as a method for manufacturing this Mn-Al-C alloy magnet, in addition to those by casting and heat treatment, there are those that include warm plastic working steps such as warm extrusion, and especially the latter have high magnetic properties, It is known as a method for producing an anisotropic magnet having excellent properties such as mechanical strength, weather resistance and machinability.

As a method for producing Mn-Al-C alloy magnet for multi-pole magnetization, an isotropic magnet, one by compression processing, uniaxially anisotropic polycrystalline Mn obtained by a known method such as warm extrusion processing in advance. -Al-C alloy magnets by warm free compression in the anisotropic direction (for example, JP-A-56-119762), and pre-anisotropic polycrystalline Mn-Al-C alloy magnets By various plastic workings that give a compressive strain in the axial direction of a hollow billet made of (for example, JP-A-58-182206 to 182).
No. 208) 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. 4 schematically shows formation of a magnetic path inside the magnet when the inner peripheral surface of the cylindrical magnet is magnetized in multiple poles, and the magnetic path is shown by a dotted line. Such magnetization is referred to as inner circumferential surface magnetization here.

In the axial direction of the hollow body-shaped billet made of the above-mentioned anisotropy polycrystalline Mn-Al-C alloy magnet, in the magnet obtained by various plastic workings that give compressive strain,
When the inner circumference is magnetized, it is locally anisotropic in the direction along the magnetic path, but when viewed as a whole, it is not anisotropic in the desired direction. Further, according to the above-mentioned conventionally known method, the inner peripheral portion of the cylindrical magnet is anisotropic in the radial direction and the outer peripheral portion thereof is anisotropic in the circumferential direction (the chord direction, the same hereinafter). In the course of changing the path from the radial direction to the circumferential direction, it is not an anisotropic structure along that direction,
Therefore, 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 a hollow body-shaped billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet. The problem is solved by performing compression processing in the axial direction and forming the hollow inner peripheral surface of the billet on the unevenness by this compression processing.

(Operation) The present invention provides the fourth method by the above method, that is, by forming the hollow inner peripheral surface of the billet into an uneven shape by compression processing.
It is possible to anisotropy along the magnetic path shown by the dotted line when the inner circumference is magnetized as shown in the figure, so that it is possible to obtain an anisotropic magnet exhibiting high magnetic characteristics.

(Examples) The present invention is a billet of a hollow body formed by pre-anisotropic polycrystal Mn-Al-C alloy magnet by compression processing in the axial direction at a temperature of 530 to 830 ℃. The inner peripheral surface of the hollow is formed on the uneven surface.

That is, a conventional alloy for Mn-Al-C magnets, for example, 68 to 73 mass% Mn and (1 / 10Mn-6.6) to (1 / 3Mn-22.2)
530 to 830 ℃ for alloys consisting of C in mass% and the balance Al
By performing plastic working such as extrusion in the temperature range of
Anisotropic polycrystalline Mn-Al-C alloy magnets can be obtained, and a typical example is a uniaxial magnet having an easy magnetization direction in the extrusion direction, which is obtained when plastic working is performed by extrusion. There are anisotropic magnets and plane anisotropic magnets obtained by performing free compression processing in the extrusion direction after the extrusion processing. In this way, a hollow body-shaped billet made of an anisotropic Mn-Al-C alloy magnet, if subjected to compression processing in the axial direction of the billet so that the hollow inner peripheral surface becomes uneven, A magnet having high magnetic characteristics can be obtained in the inner circumference magnetization shown in FIG.

In the above, when the billet is composed of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction in the axial direction of the hollow body, a so-called uniaxial anisotropic magnet, the compressive strain in the direction of the axis of symmetry in compression processing is The absolute value of logarithmic strain must be 0.05 or more. This is because the billet before compression processing is anisotropy in the direction that gives compressive strain, so the structure changes to the minimum in order to show high magnetic characteristics in inner circumference magnetization.
This is because a compressive strain of 0.05 is necessary.

Further, the billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic in the plane, and is a straight line parallel to the axial direction and the plane. In the case of a polycrystalline Mn-Al-C alloy magnet that is anisotropic in the plane containing the so-called plane anisotropic magnet, the billet before compression processing is already in the plane containing the radial direction and the chord direction. Although it exhibits high magnetic properties in all directions, it is possible to obtain a magnet exhibiting high magnetic properties in inner circumference magnetization by performing the compression processing of the present invention.

The above-mentioned compression processing does not necessarily have to be continuous compression processing, and may be given by dividing it into a plurality of times. The billet described above is a uniaxial anisotropic magnet or a plane anisotropic magnet, but a magnet having an easy magnetization direction in the radial direction, a magnet having an easy magnetization direction in the circumferential direction, or the like may be used. Means that the Mn-Al-C magnet alloy has been subjected to some plastic working in a predetermined temperature range.

An example of the compression processing of the present invention will be described below with reference to FIG. 1 in which the billet has a cylindrical body.

FIG. 1 (a) is a sectional view of the state before compression processing as seen from the axial direction of the billet. Reference numeral 1 is a cylindrical billet, and 2 is an outer die, which is a die for restraining the outer peripheral surface of the billet 1 during compression processing. Reference numeral 3 is a punch, and as shown in the figure, its cross section has a predetermined uneven shape. Similarly, Fig. (B) shows a state after processing. The inner diameter of the cylindrical billet 1 shrinks as the compression processing progresses, a part of the inner peripheral surface contacts the convex portion of the punch 3, and the compression processing further progresses. As a result, the inner peripheral surface of the billet 1 becomes substantially the outer surface shape of the punch 3 as shown in the figure. The compression is
(b) It is not necessary to carry out the process shown in the figure
After a part of the inner peripheral surface of the punch 3 comes into contact with the punch 3, the compression processing may be finished at an appropriate time. In other words, irregularities may be formed on the inner peripheral surface of the billet 1. Further, in the above-mentioned example, the outer peripheral surface of the billet 1 and the outer die 2 have already been compressed.
Although the inner surface of was almost in contact, it does not have to be in contact. That is, the outer diameter of the billet 1 may be considerably smaller than the diameter of the cavity of the outer mold 2. In this case, as the compression processing progresses, the outer diameter of the billet 1 increases and the inner diameter decreases, and the outer peripheral surface of the billet 1 eventually contacts the inner surface of the outer mold 2. After that, it is the same as the change described above. On the other hand, the inner diameter of the billet 1 is the size that contacts the convex portion of the punch 3 at the minimum. If the billet 1 and the outer mold 2 are already in contact with each other before the compression processing, the compression processing is performed with a part of the inner peripheral surface of the billet 1, that is, a portion in contact with the convex portion of the punch 3 being restrained. Is applied.

As described above, in the compression process, since the surface of the punch 3 is provided with unevenness, the billet 1 is provided with unevenness on the inner peripheral surface thereof. In the billet compression process, the part where the inner peripheral surface was constrained first, that is, the recessed part of the inner peripheral surface of the billet after processing became the part having the easy magnetization direction in the circumferential direction, and finally the inner peripheral surface was restricted. The part or the part where the inner peripheral surface is not constrained to the end, that is, the concave part of the inner peripheral surface of the billet after processing is a part having the easy magnetization direction in the radial direction. The easy magnetization direction of the intermediate portion is a portion that gradually changes from the circumferential direction to the radial direction. In other words, the first
In the drawing, the easy magnetization direction continuously changes from the inner peripheral surface of the billet 1 in a direction along the curved surface of the concave portion of the inner peripheral surface of the billet 1 formed by the convex portion of the punch 3.

Therefore, depending on how many poles are magnetized in the inner circumference magnetization,
The number of uneven portions may be determined. In Fig. 1, since there are 6 convex portions on the inner peripheral surface of the billet 1 after processing, the magnet has an anisotropic structure suitable for 6-pole magnetization, and the portion corresponding to the convex portion after processing is the inner peripheral surface. It becomes the pole part in magnetization.

Polycrystalline Mn whose billet has an easy magnetization direction in its axial direction
In the case of the -Al-C alloy magnet, the compressive strain must be 0.05 or more in absolute value of logarithmic strain as described above. However, in actual application, if you want to preserve the easy magnetization direction 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. Areas may be created.

As described above, according to the present invention, when the billet is compressed in the axial direction, the inner peripheral surface of the billet is formed and compressed by using a mold having an outer surface having irregularities to form an inner peripheral surface. 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 is possible, processing could be performed in the temperature range of 530 to 830 ° C, but in the temperature range of higher than 780 ° C, the magnetic properties are considerably deteriorated, and a more preferable temperature range is 560 to 760. It was ℃.

Next, the present invention will be described more specifically with reference to numerical examples.

Specific Example 1 69.5% by mass of compounded composition (hereinafter simply referred to as%) of Mn, 29.3
% Al, 0.5% C and 0.7% Ni by melt casting, diameter
A cylindrical billet having a length of 70 mm and a length of 50 mm was produced. After holding this billet at 1100 ° C for 2 hours, it was left to cool to room temperature and then heat-treated at a temperature of 720 ° C through a lubricant to a diameter of 45 m.
Extrusion processing up to m was performed. 680 through the lubricant
Extruded rods up to 31 mm in diameter at a temperature of ℃ were cut into 20 mm long extruded rods and cut to an outer diameter of 30 mm and an inner diameter of 24 m.
A cylindrical billet having a length of m and a length of 20 mm was produced. This billet was compressed to a height of 12 mm using the mold shown in FIGS. 2 and 3. Note that FIG. 2 is a sectional view of a mold similar to FIG. In the figure, D _K outer diameter 2 inner diameter = 30 m
m, X _A = 8 mm, the radius of curvature of the convex portion of the punch 3 R _S = 2.5 mm, the diameter of the punch 3 D _P = 16 mm, and the punch 3 has 8 convex portions. Further, FIG. 3 shows the center and cross-sectional view of FIG. 2, and 3 and 4 are punches, which have a surface to which the uneven portion fits, and can move in the vertical direction of the figure.

The billet after compression processing to the above height of 12 mm up to an inner diameter of 20 mm,
It was machined and magnetized with 8 tracks. Magnetization is 2000μF
It was pulse-magnetized at 1500 V using the oil condenser of No. 1. The surface magnetic flux density of the inner peripheral surface was measured with a Hall element. For comparison, a cylindrical billet with a diameter of 18 mm and a length of 20 mm is freely compressed in the direction of the cylinder axis at a temperature of 680 ° C. to make a surface anisotropic magnet with a height of 12 mm, and cut in the same manner as the above specific example. , Magnetized,
The surface bundle density was measured.

Comparing the above measured values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention is about that of the surface anisotropic magnet of the comparative example.
It was 1.6 times.

Example 2 The extruded rod having a diameter of 31 mm obtained in Example 1 was further extruded through a lubricant at a temperature of 680 ° C. to form an extruded rod having a diameter of 22 mm. The extruded rod was cut into a length of 40 mm to form a billet at 680 ° C. Free compression processing was performed at a temperature of up to 20 mm in the axial direction of the cylinder. The billet after processing is a plane anisotropic magnet. By cutting this billet, the outer diameter is 30 mm and the inner diameter is 24 m.
A cylindrical billet having a height of m and a height of 24 mm was produced. Using this billet, the same compression processing as in Example 1 was performed, and the billet after processing was cut to an inner diameter of 20 mm. Further, when the surface magnetic flux density was measured by performing inner circumferential magnetization similar to that in Example 1, the value was not much different from that of the magnet obtained by the method of the present invention obtained in Example 1.

As a result of the magnetic torque measurement, the magnets obtained by the methods of the present invention obtained in Examples 1 and 2 showed that the direction of easy magnetization was such that the concave portion of the inner peripheral surface was continuously and gradually increased from the radial direction to the circumferential direction along the surface. It was confirmed that it was changing.

(Effects of the Invention) As is clear from the above description, the present invention compresses a hollow billet made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet in its axial direction. By forming the inner peripheral surface of the billet in a concavo-convex shape by doing so, a magnet exhibiting high magnetic characteristics when the inner peripheral is magnetized is obtained.

Compared with the magnet obtained by the conventional method, the magnet obtained by the method of the present invention, when subjected to inner circumference magnetization,
In order to obtain a magnet exhibiting superior magnetic characteristics to the magnet by the conventional method, the inner peripheral surface of the magnet further has the easy magnetization direction in the radial direction, and the outer peripheral portion having the easy magnetization direction in the circumferential direction, Although the conventional method requires plastic working at least twice or more, the present invention requires only once, and a magnet having a more desirable anisotropic structure than the conventional method can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a mold used for compression processing of an embodiment of the present invention, FIGS. 2 to 3 are sectional views of an example of a mold used in the present invention, and FIG. 4 is an inner circumference of a cylindrical magnet. It is a figure which shows schematically the magnetic path at the time of carrying out multi-pole magnetization to the surface. 1 ... Billet, 2 ... Outer mold, 3, 4 ... Punch.

Claims (5)

[Claims] 1. Pre-anisotropic polycrystalline manganese-
A hollow body-shaped billet made of an aluminum-carbon alloy magnet is compressed at a temperature of 530 to 830 ° C. in the axial direction to form an inner peripheral surface of the billet in an uneven shape. Manufacturing method. 2. The billet according to claim 1, wherein the billet has an easy magnetization direction in the axial direction of the hollow body, and the compression strain due to compression processing is 0.05 or more in absolute value of logarithmic strain. The method for producing an alloy magnet according to the item 1). 3. The billet has an easy magnetization direction parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic in the plane, and is parallel to the axial direction and the plane. The method for producing an alloy magnet according to claim (1), which is anisotropic in a plane including a straight line. 4. The method according to claim 1, wherein the compression processing is performed with a part of the inner peripheral surface of the billet being constrained.
The method for producing an alloy magnet according to the item (1). 5. The method for producing an alloy magnet according to claim 1, wherein the compression processing is performed with the outer peripheral surface of the billet being constrained.