JPH0680607B2 - 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 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 magnets for automobiles.

2. _{Description of the Related} Art Mn-Al-C alloy magnets are mainly composed of a face-centered tetragonal crystal (τ phase, L _{1 O} type ordered lattice) that is a ferromagnetic phase, and contain C as an essential constituent element. A ternary system 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 they are collectively referred to.

As a manufacturing method thereof, there is known a method including a plastic working step such as extrusion processing in addition to 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 multi-pole magnetization using an Mn-Al-C alloy magnet, an isotropic magnet, a method by compression processing (registration number 1011473), or a known method such as extrusion processing is used. The obtained uniaxially anisotropic polycrystalline Mn-Al-C alloy magnet was subjected to free compression processing in the anisotropic direction (the obtained magnet is referred to as a plane anisotropic magnet. JP-A-56-119762) Gazette), a part of a billet made of a plane anisotropic magnet that is compression-processed (JP-A-58-188103), and a hollow made of a pre-anisotropic polycrystalline Mn-Al-C alloy magnet. There is known a body-shaped billet that is subjected to specific compression processing (for example, JP-A-58-182206 to 58-182208).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention One part of the billet composed of the above-mentioned plane anisotropic magnet is compression-processed (Japanese Patent Laid-Open No. 58-1880103) or pre-anisotropic polycrystalline Mn-Al-C Pre-anisotropic polycrystal Mn-, which is disclosed in a hollow body-shaped billet made of a system alloy magnet and subjected to specific compression processing (for example, JP-A-58-182206 to 58-182208) In the method of performing compression processing in the axial direction of the billet on the outer peripheral portion of the billet made of an Al-C alloy magnet, a portion having the compression processing has an easy magnetization direction in the radial direction,
The distribution of the magnetic characteristics of the processed portion is not necessarily suitable for the outer peripheral multipole magnetization. That is, when only the outer peripheral portion of the billet is compression-processed and the outer periphery is magnetized in multiple poles, it is desirable that the outermost peripheral portion has the strongest distribution of magnetic characteristics in the radial direction of the processed portion.

The present invention aims to obtain a magnet having a good distribution of magnetic properties.

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

Action According to the method described above, that is, in the compression processing on the outer peripheral portion of the billet, the compression processing is performed in the axial direction of the billet so that the compression strain of the outermost peripheral portion of the billet is larger than the compression strain of the inner portion. By applying the method, the distribution of the magnetic characteristics in the radial direction inside the magnet becomes suitable for the outer circumferential multipole magnetization, and the magnetic characteristics of the magnet are improved, unlike the known methods.

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 530 to 830.
At a temperature of ℃, the billet is compressed in the direction perpendicular to the specific plane (axial direction) so that the compressive strain of the outermost part of the billet is larger than the compressive strain of the inner part. It is to be processed.

Further, the billet has an easy magnetization direction parallel to a plane perpendicular to the axial direction, and is magnetically isotropic in the plane, and in a plane including a straight line parallel to the axial direction and the plane. It is an anisotropic polycrystalline manganese-aluminum-carbon alloy magnet.

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).

In the compression processing of the above-mentioned known technology, only the outer 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 is, in the compression processing described above, further subjected to compression processing in the axial direction of the billet so that the compression strain of the outermost peripheral portion of the billet is larger than the compression strain of the portion inside thereof. . In other words, only the outer peripheral portion of the billet is compression-processed so that the compressive strain in the outermost peripheral portion of the billet is maximized.

A specific example of this compression processing will be described assuming that the billet shape is a cylindrical body. FIG. 1A shows a cross section before processing. 1 is a billet, 2 is a fixed punch, 3 is a movable punch, and 4 is a lower die. 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 this movable punch 3 to pressurize the billet 1 in the axial direction, only the outer peripheral portion of the billet is compressed in the axial direction to the state shown in FIG. 1b. Figure 1b
As shown in (4), the height of the outermost peripheral portion of the billet after processing is smaller than the height of the inner portion. In other words, so that the compressive strain of the outermost peripheral part of the billet is larger than the compressive strain of the part inside it, in the axial direction of the billet,
This means that only the outer peripheral part of the billet was subjected to compression processing.
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 point different from FIG. 1 is that the punch end surface of the movable punch 3 is a flat surface, and the height of the outermost peripheral portion of the billet before compression processing is larger than the height of the portion inside thereof. That is.
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 outermost peripheral portion of the billet and the height of the portion inside 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 outermost peripheral portion of the billet becomes larger than the compression strain of the inner 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 58-18220
Almost the same as the compression processing shown in (No. 8), but by making the billet end surface an inclined surface or the punch end surface an inclined surface, in this specific compression processing, only the outer peripheral portion of the billet has the maximum billet. It is possible to perform compression processing in the axial direction of the billet so that the compression strain of the outer peripheral part is larger than the compression strain of the inner part than that, and the difference between the compression strain of this outermost peripheral part and the part inside it By changing the distribution, the distribution of the magnetic characteristics in the magnet in the radial direction can be made suitable for the outer peripheral multipole magnetization.

Even with the combination of the above two examples, compression processing can be performed in the axial direction of the billet so that the compression strain of the outermost peripheral portion of the billet is larger than the compression strain of the inner portion. That is, it is a method of compressing the billet (the billet end surface 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 outermost peripheral portion of the billet becomes larger than the compression strain of the portion inside thereof. As a result, the distribution of the magnetic properties in the radial direction of the processed portion of the magnet can be made suitable for the outer peripheral multipole magnetization. The greater the difference between the compressive strain at the outermost peripheral portion and the compressive strain at the inner portion of the outermost peripheral portion, the higher the radial magnetic characteristics of the machined portion of the magnet become at the outermost peripheral portion.

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 produce a cylindrical billet having a diameter of 60 mm and a length of 40 mm. The billet was kept at 1100 ° C. for 2 hours, air-cooled to 600 ° C., kept at 600 ° C. for 30 minutes, and then allowed to cool to room temperature.

Using this billet, extrusion processing was performed at a temperature of 720 ° C. 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.

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 diameter of the punch 2 (the inner diameter of the punch 3) is 24 mm. The length of the billet boundary portion (24 mm diameter portion) after processing was 15 mm. After cutting the billet after processing to an outer diameter of 30 mm, the outer peripheral surface was magnetized with 24 poles. For the magnetization, an oil condenser of 2000 μF was used and pulsed at 1500 V. The surface magnetic flux density on the outer peripheral surface was measured with a Hall element.

For comparison, using the billet having the above-mentioned plane anisotropic structure, the die shown in FIG. 2 was used, and only the outer peripheral portion was compression-processed through the lubricant in the same manner as described above. The diameter of the fixing punch 2 is 24 mm. The length of the outer peripheral portion of the billet after processing was 15 mm. 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 2 Using the billet composed of the plane-anisotropic magnet obtained in Example 1, the center portion of the billet was pressed with a punch having a diameter of 16 mm at a temperature of 680 ° C. through a lubricant to give an outer diameter. 37
A billet having a diameter of 16 mm, an inner diameter of 16 mm, and a length of 20 mm was produced. The processed magnet had an easy magnetization direction in the circumferential direction (circumferentially anisotropic magnet). This billet was subjected to compression processing only on the outer peripheral portion using the mold shown in FIG.

The billet after processing was cut to have an outer diameter of 30 mm, and then outer peripheral magnetization of 24 poles was performed in the same manner as in Example 1, and the surface magnetic flux density was measured.

For comparison, the billet formed of the circumferentially anisotropic magnet was subjected to compression processing only on the outer 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 cut to a diameter of 24 m
A cylindrical billet having a length of m and a length of 40 mm was produced and, similarly to Example 1, a surface compression magnet having a length of 20 mm was produced by free compression processing. By cutting this magnet, the outer diameter is 34 mm, the inner diameter is 10 mm,
A billet having a shape as shown in FIG. 2 having a length of 20 mm at the outermost peripheral portion and a length of 15 mm at a position of 24 mm in diameter was produced. Next, this billet is compressed with a lubricant as shown in FIG. 2 only at the outer peripheral portion of the billet at a temperature of 680 ° C. through a lubricant to a length of the outer peripheral portion of the billet of up to 10 mm. went. In FIG. 2, the inner diameter of the movable punch is 24 mm.

The billet after processing was cut to have an outer diameter of 30 mm, and then outer peripheral magnetization of 24 poles was performed in the same manner as in Example 1 to measure the surface magnetic flux density.

For comparison, the above-mentioned plane anisotropic magnet was subjected to a cutting process to produce a cylindrical billet having an outer diameter of 34 mm, an inner diameter of 10 mm and a length of 17.5 mm. Next, only the outer peripheral portion was compression processed in the same manner as above via a lubricant. The outer 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 above, regarding the composition of the Mn-Al-C system alloy magnet, only the quaternary system of Ni addition and the quinary system of Ni and Ti additions are shown, but the basic composition of the Mn-Al-C alloy magnet 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.

Polycrystalline Mn-Al- with easy magnetization direction parallel to a specific plane
An example using a plane anisotropic magnet or a circumferential anisotropic magnet as the C-based alloy magnet has been shown, but a diameter anisotropic magnet, a magnet having a composite structure obtained by the above-mentioned known technique (for example, in the outer peripheral portion with a diameter anisotropic The same was true for the inner peripheral portion using (circumferential anisotropy).

Further, the examples of the billet and the end face of the punch are inclined faces, but the magnetic properties are improved in comparison with the conventional compression processing even in the stepped stepped form and the plane + inclined face or the above combination. . Further, the same surface was formed on both end faces.

EFFECTS OF THE INVENTION The present invention, as described in the embodiments, in a billet composed of a polycrystalline Mn-Al-C alloy magnet having an easy magnetization direction parallel to a specific plane, only on the outer periphery of the billet, A magnet that exhibits high magnetic characteristics when multi-pole magnetized on the outer circumference by performing compression processing in the axial direction of the billet so that the compression strain of the outermost circumference is larger than the compression strain of the inner part than that. I will get it.

By this method, the distribution of the magnetic characteristics in the radial direction inside the magnet can be made suitable for outer peripheral multi-pole magnetization, and the difference between the compressive strain at the outermost peripheral portion and the compressive strain at the inner portion is increased The more you do it, the greater the effect.

[Brief description of drawings]

FIG. 1 and FIG. 2 are sectional views of a part of a mold showing an example of compression processing of the present invention. 1 ... Billet, 2 ... Fixed punch, 3 ... Movable punch, 4 ... Lower mold.

Claims (4)

[Claims] 1. A billet made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction parallel to a specific plane, at the temperature of 530 to 830 ° C., only at the outer peripheral portion of the billet, the outermost circumference of the billet. Manganese-aluminum-carbon alloy characterized by performing compression working in a direction (axial direction) perpendicular to the specific plane of the billet so that the compressive strain of the portion becomes larger than the compressive strain of the inner portion. 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. .