JPH0673327B2 - Method for producing manganese-aluminum-carbon alloy magnet - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a permanent magnet, and more particularly, to a high-performance multi-pole magnetized with a polycrystalline manganese-aluminum-carbon (Mn-Al-C) alloy magnet. For manufacturing Mn-Al-C alloy magnet for use in automobiles.

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 a ternary alloy magnet containing no additional element other than impurities and a quaternary or more multi-component alloy magnet containing a small amount of additional element are known, and these are collectively referred to. .

As a manufacturing method thereof, a method including a plastic working step such as 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.

Further, as a method for producing an alloy magnet for multipolar magnetization using an Mn-Al-C alloy magnet, an uniaxial anisotropy obtained by a known method such as an isotropic magnet, a compression processing method or an extrusion processing method is used. Polycrystal
An Mn-Al-C alloy magnet by free compression processing in the anisotropic direction (the obtained magnet is called a bi-anisotropic magnet.
No. 56-119762), a part of a billet made of a plane anisotropic magnet that is compression-processed (JP-A-58-188103), and a pre-anisotropic polycrystalline Mn-Al-C alloy. It is known that a hollow billet made of a magnet is subjected to specific compression processing (for example, JP-A-58-182206 to 58-182208).

Problems to be Solved by the Invention One in which a part of the billet composed of the plane anisotropic magnet described above is subjected to compression processing (Japanese Patent Laid-Open No. 58-188103) or pre-anisotropic polycrystalline Mn-Al-C. Pre-anisotropic polycrystal Mn-, which is disclosed in a hollow-body billet made of a system alloy magnet and subjected to a specific compression process (for example, JP-A-58-182206 to 58-182208) In the method of compressing the inner peripheral portion of the billet made of an Al-C alloy magnet in the axial direction of the billet, a portion having the compression process has an easy magnetization direction in the radial direction. Some amount of compressive strain at the time of processing is required,
The magnet has a large step.

The present invention aims to increase the magnetic characteristics in the radial direction even with the same amount of compressive strain.

Means for Solving the Problems In order to solve the above problems, the present invention provides only the inner peripheral portion of a billet composed of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction parallel to a specific plane. In addition, the billet is subjected to compression working in a direction (axial direction) perpendicular to the specific plane so that the compressive strain of the innermost peripheral portion of the billet becomes larger than the compressive strain of the outer portion thereof.

Action By the above-mentioned method, that is, in the above-mentioned compression processing on the inner circumference of the billet, the billet is compressed in the axial direction so that the compression strain of the innermost circumference is larger than the compression strain of the outer part. By performing processing, unlike the known methods up to now, the radial magnetic characteristics are increased even with the same amount of compressive strain, and the amount of compressive strain can be reduced.

Example The present invention provides a billet composed of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction parallel to a specific plane, and a billet 530-8.
At a temperature of 30 ° C, only in the inner circumference of the billet, the direction perpendicular to the specific plane of the billet (axis) so that the compression strain of the innermost circumference of the billet is larger than the compression strain of the outer part. Direction).

Further, in the present invention, the billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction, and is magnetically isotropic in the plane, and includes a straight line parallel to the axial direction and the plane. It is a polycrystalline manganese-aluminum-carbon based alloy magnet that is anisotropic in the plane.

Most of the production method of the present invention is based on the above-mentioned known technique (Japanese Patent Laid-Open No.
-188103 or JP-A-58-182206 or 58-18220
This method is almost the same as the method disclosed in Japanese Patent No. 8).

The compression processing of the above-mentioned known technology is one in which only the inner peripheral portion of the billet is simply compressed in the axial direction of the billet.

On the other hand, the compression processing of the present invention, in the compression processing described above, further performs compression processing in the axial direction of the billet so that the compression strain of the innermost peripheral portion of the billet is larger than the compression strain of the portion outside thereof. is there. In other words, only the inner peripheral portion of the billet is compression-processed so that the innermost peripheral portion of the billet has the largest compressive strain.

A specific example of this compression processing will be described assuming that the billet shape is a cylindrical body. FIG. 1 shows a cross section in a state before processing in a. 1 is a billet, 2 is a restraining die, 3 is a movable punch, 4
Is the lower mold. As shown in FIG. 1a, the point different from the above-mentioned known technique is that the surface of the movable punch 3 that contacts the billet (the punch end surface) is not a flat surface but an inclined surface. By using the movable punch 3 to pressurize the billet 1 in the axial direction, only the inner peripheral portion of the billet is compressed in the axial direction to the state shown in FIG. 1b. As shown in FIG. 1b, the height of the innermost peripheral portion of the billet after compression processing is smaller than the height of the outer portion thereof. In other words, only the inner peripheral portion of the billet is compressed in the axial direction of the billet so that the compressive strain of the innermost peripheral portion of the billet is larger than the compressive strain of the outer portion. Compressive strain means strain in the axial direction of the billet.

Next, another typical example of the compression processing of the present invention will be described assuming that the billet has a ring-shaped cross section.
Similar to the figure, a cross section before processing is shown. As shown in FIG. 2a, the difference from FIG. 1 is that the punch end surface of the movable punch 3 is a flat surface, and the height of the innermost peripheral portion of the billet before compression processing is higher than the height of the outer portion thereof. That's a big thing.
FIG. 2b shows the state after processing. The processed portion of the billet after processing has a substantially cylindrical shape, and the height of the innermost peripheral portion of the billet and the height of the portion outside thereof are substantially the same. In this case as well, compression processing is performed in the axial direction of the billet so that the compression strain of the innermost peripheral portion of the billet is larger than the compression strain of the outer portion thereof.

As described above, the present invention is based on the above-mentioned known technique (JP-A-58).
-188103 or JP-A-58-182206 or 58-1822
08), but by making the billet end face an inclined surface or the punch end face an inclined surface, it is possible to make the billet only inside the billet in this specific compression process. It is possible to perform compression processing in the axial direction of the billet so that the compression strain of the innermost circumference is larger than the compression strain of the outer part, and this allows the same compression strain amount as compared to the conventional methods. High magnetic properties can be obtained in the radial direction.

Even by combining the above two examples, it is possible to perform compression processing in the axial direction of the billet so that the compression strain of the innermost peripheral portion of the billet is larger than the compression strain of the outer portion thereof. That is, there is a method of compressing the billet (the end surface of the inner peripheral portion of the billet is an inclined surface) shown in FIG. 2 using the mold shown in FIG. 1 (the punch end surface is an inclined surface).

In the above example, the punch end surface or billet end surface was an inclined surface, but there are other steps such as a stepped surface (stepped shape), a plane + inclined surface, or a combination of the above. However, it may be one side. What is necessary is to perform compression processing in the axial direction of the billet so that the compression strain of the innermost peripheral portion of the billet is larger than the compression strain of the outer portion. As a result, magnetic properties higher in the radial direction can be obtained with the same amount of compressive strain than in the conventional methods. The greater the difference between the compressive strain in the innermost peripheral portion and the compressive strain in the outer peripheral portion, the greater the effect.

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 69.5% Mn, 29.3% Al, 0.5% C and 0.7
% Ni was melted and cast to form a cylindrical billet having a diameter of 50 mm and a length of 40 mm. The billet was held at 1100 ° C. for 2 hours, air-cooled to 600 ° C., held at 600 ° C. for 30 minutes, and then heat-treated to cool to room temperature.

Next, extrusion processing was performed at a temperature of 720 ° C. through a lubricant. The billet after processing had a diameter of 32 mm and a length of 98 mm. This extruded rod is cut and cut to have a diameter of 24 mm,
A cylindrical billet having a length of 40 mm was produced. Next, free compression processing was performed to a length of 20 mm at a temperature of 680 ° C. through a lubricant. The billet after processing is a plane anisotropic magnet.

This billet was cut to produce a cylindrical billet having an outer diameter of 34 mm, an inner diameter of 16 mm and a length of 20 mm. Next, using a mold as shown in FIG. 1, only the outer peripheral portion of the billet was compression processed at a temperature of 680 ° C. The punch 3 has a diameter of 24 mm and the inclination angle α is 20 °. Boundary after processing (diameter 24 mm
The part) was 15 mm in length. After machining the billet after processing to an inner diameter of 18 mm, the inner peripheral surface was magnetized with 24 poles. Use a 2000 μF oil condenser for magnetization.
Pulse magnetized at 00V. The surface magnetic flux density on the inner peripheral surface was measured with a Hall element.

For comparison, the above-mentioned bi-anisotropic structure billet (outer diameter
A cylindrical billet having a diameter of 34 mm, an inner diameter of 16 mm, and a length of 20 mm was subjected to compression processing only on the inner peripheral portion using the mold shown in FIG. The movable punch 3 has a diameter of 24 mm. The length of the inner circumference of the billet after processing is 15 mm
Met. Further, after cutting in the same manner as above, it was 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.

Example 2 The billet composed of the bi-anisotropic magnet obtained in Example 1 was passed through a lubricant at a temperature of 680 ° C. and the center of the billet had a diameter of 1
By pressing with a 6 mm punch, outer diameter 37 mm, inner diameter 1
The billet is 6mm long and 20mm long. The billet after processing has an easy magnetization direction in the circumferential direction (the same anisotropic magnet). This billet was subjected to compression processing only on the inner peripheral portion using the mold shown in FIG.

The billet after processing was machined to have an inner diameter of 18 mm, and then the inner circumference was magnetized with 24 poles in the same manner as in Example 1 to measure the surface magnetic flux density.

For comparison, the billet made of the same anisotropic magnet as described above was subjected to compression processing only on the inner peripheral portion using the mold shown in FIG. Further, after cutting the same as the above, it was 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.

Example 3 69.4% Mn, 29.3% Al, 0.5% C, 0.7% in the composition
Ni and 0.1% Ti are melt-cast, diameter 50mm, length 40mm
The cylindrical billet of was prepared and subjected to the same heat treatment as in Example 1. Next, extrusion processing was performed at a temperature of 720 ° C. through a lubricant. The billet after processing had a diameter of 32 mm and a length of 98 mm. This extruded rod is cut and machined to a diameter of 24
A cylindrical billet having a length of 40 mm and a length of 40 mm was produced, and a plane anisotropic magnet having a length of 20 mm was produced by free compression as in Example 1. This billet is machined to an outer diameter of 34 mm and an inner diameter of 16
mm, length of innermost part 20 mm, diameter 24 mm, position 15 mm
The shape is as shown in FIG. Next, using a mold as shown in FIG. 2 through a lubricant, only the inner peripheral portion of the billet was heated to a temperature of 680 ° C., and the inner peripheral portion of the billet had a length of 10 m.
Compressed up to m. In FIG. 2, the inner diameter of the movable punch is 24 mm.

The billet after processing was cut to have an inner diameter of 18 mm, and then the inner circumference was magnetized with 24 poles in the same manner as in Example 1, and the surface magnetic flux density was measured.

For comparison, the above-described plane anisotropic magnet was cut to form a cylindrical billet having an outer diameter of 34 mm, an inner diameter of 16 mm and a length of 17.5 mm. Next, only the inner peripheral portion was compression-processed via a lubricant in the same manner as described above. The inner peripheral length of the billet after processing is 10 mm
Met. Further, after cutting the same as the above, it was 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.

As described above, regarding the composition of the Mn-Al-C alloy magnet, only the quaternary system with Mi addition and the quinary system with Ni and Ti additions are shown. Although a slight difference was observed in the magnetic characteristics of the magnet in a certain ternary system as well, the improvement in magnetic characteristics as described above was recognized by the known compression processing method.

An example in which a plane anisotropic magnet or a circumferential anisotropic magnet is used as the Mn-Al-C alloy magnet that has been anisotropy in advance has been shown, but a diameter anisotropic magnet, an anisotropic magnet having a composite structure (for example, an outer peripheral portion). It was also the same when using (for example, those having circumferential anisotropy and those having a diameter anisotropic structure at the inner circumferential portion).

Furthermore, although examples of the billet and punch end surfaces are inclined surfaces are shown, the improvement of the magnetic characteristics was recognized in comparison with the conventional compression processing even with the stepped stepped shape and the plane + inclined surface or the above combination. . In addition, there was no great difference between the uneven end faces on one side or both sides.

EFFECTS OF THE INVENTION As described in the embodiments, the present invention provides a billet made of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction parallel to a specific plane, and only the inner peripheral portion of the billet has a billet. By performing compression processing in the axial direction of the billet so that the compressive strain of the innermost peripheral part of is larger than the compressive strain of the outer part, even if the same compressive strain amount is applied in the radial direction as compared with the conventional methods. High magnetic properties can be obtained.
The greater the difference between the compressive strain in the innermost peripheral portion and the compressive strain in the outer peripheral portion, the greater the effect.

[Brief description of drawings]

FIG. 1 and FIG. 2 are partial cross-sectional views of a mold showing an example of the compression processing of the present invention. 1 ... Billet, 2 ... Restraint die, 3 ... Movable punch,
4 ... Lower mold.

Claims (4)

[Claims] 1. A billet composed of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction parallel to a specific plane, and at the temperature of 530 to 830 ° C., only the innermost portion of the billet has the maximum billet. Manganese-aluminum-carbon characterized in that compression processing is performed in a direction (axial direction) perpendicular to the specific plane of the billet so that the compression strain of the inner peripheral portion is larger than the compression strain of the outer portion. -Based alloy magnet manufacturing method. 2. A billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction, and is magnetically isotropic in the plane, and a straight line parallel to the axial direction and the plane. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, comprising a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in the plane containing the magnet. 3. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, wherein the billet is a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction parallel to the radial direction. . 4. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, wherein the billet is a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction parallel to the circumferential direction. .