JPH0642408B2 - 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 structure (τ phase, L ₁₀ type ordered lattice) that is a ferromagnetic phase, and have a C
Containing as an essential constituent element, a ternary system containing no additional element other than impurities, and a small amount of additional element containing 4
Multi-component alloy magnets of the original type and above are known, and are collectively referred to as these.

As a manufacturing method thereof, a method including a plastic working step such as extrusion processing is known in addition to the method of casting and heat treatment. Particularly, the latter is known as a method for producing an anisotropic magnet having excellent magnetic properties, mechanical strength, weather resistance and machinability.

Further, as a method for manufacturing an alloy magnet for multi-pole magnetization using an Mn-Al-C alloy magnet, an isotropic magnet, a compression processing method,
Uniaxially anisotropic polycrystalline Mn-A obtained by a known method such as extrusion
lC alloy magnet by free compression processing in the anisotropic direction (the obtained magnet is referred to as a plane anisotropic magnet.
No. 119762) and a part of a billet composed of a uniaxial anisotropic magnet, which is subjected to compression processing (Japanese Patent Laid-Open No. 58-2).
No. 06105) is known.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention A billet made of a uniaxially anisotropic magnet described above, which is subjected to compression processing (Japanese Patent Laid-Open No. 58-206105), is made of a uniaxially anisotropic magnet. In the method of compressing the billet inside the billet in the axial direction of the billet, it is possible to obtain the one having the easy magnetization direction in the radial direction in the compressed portion. Since it is necessary to some extent, the step generated on the magnet is relatively large.

An object of the present invention is to obtain a magnet having large magnetic characteristics even with the same amount of compressive strain.

Means for Solving the Problems In order to solve the above problems, the present invention is directed to polycrystalline Mn-Al- having a direction of easy magnetization parallel to a specific one direction (axial direction).
The absolute value of the logarithmic strain in the axial direction of the billet is 0.05 so that the compressive strain of the innermost part of the billet is larger than the compressive strain of the outer part only in the inner part of the billet made of C-based alloy magnets. The compression processing is performed to give the above compression strain.

Action According to the method described above, that is, in the compression processing on the inner circumference of the billet described above, the logarithm in the axial direction of the billet is set so that the compression strain of the innermost circumference of the billet is larger than the compression strain of the outer part. Absolute value of strain 0.05
By giving the above-mentioned compressive strain, the magnetic characteristics in the radial direction are increased even if the same compressive strain amount is used, and the compressive strain amount can be reduced, unlike the conventional methods of performing compressive processing.

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 one direction (axial direction), at a temperature of 530 to 830 ° C, and an inner peripheral portion of the billet. In order to make the compression strain of the innermost part of the billet larger than the compression strain of the outer part, the compression process that gives a compression strain of 0.05 or more in the absolute value of the logarithmic strain in the axial direction of the billet is performed. Is.

Most of the production methods of the present invention are based on the above-mentioned known technology (Japanese Patent Laid-Open No. Sho 5).
The method is substantially the same as the method disclosed in Japanese Patent Laid-Open No. 8-206105).

In the compression processing of the above-mentioned known technology, only the inner peripheral portion of the billet is 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.

Similar to the above-mentioned known technique, the compression strain at the time of compression processing is required to be 0.05 or more in absolute value of logarithmic strain. 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 structural changes that show high magnetic characteristics in multipolar magnetization. Is.

A specific example of this compression processing will be described assuming that the billet shape is a cylindrical body. FIG. 1 (a) shows a cross section before processing. 1 is a billet, 2 is a restraining die, 3 is a movable punch, 4
Is the lower mold. As shown in FIG. 1 (a), a 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 and the state shown in FIG. 1 (b) is obtained. Fig. 1 (b)
As shown in FIG. 5, 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, in the present invention, another typical example of compression processing will be described in which the billet has a ring-shaped cross-sectional shape. FIG. 2 (a) shows a cross-section before processing as in FIG. As shown in Fig. 2 (a), the point different from Fig. 1 is that the punch end face 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 that of the portion outside thereof. It is bigger than that. FIG. 2 (b) 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 (Japanese Patent Laid-Open Publication No.
8-206105), which is almost the same as the compression processing shown in (8-206105), but by making the billet end surface an inclined surface or the punch end surface an inclined surface, only the inner peripheral portion of the billet in this specific compression processing, It is possible to perform compression processing in the axial direction of the billet so that the compressive strain of the innermost part of the billet is larger than the compressive strain of the part on the outer side, which allows the same compressive strain as compared with the conventional methods. High magnetic properties can be obtained in the radial direction even with the amount.

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 innermost peripheral portion of the billet is larger than the compression strain of the outer portion thereof. That is, this 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 stepped surfaces (stepped shape), 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,
Machining could be performed in the temperature range of 530 to 830 ° C, but the magnetic properties were considerably deteriorated at a temperature exceeding 780 ° C. A more desirable temperature range is 560 to 760 ° C.
Met.

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 prepare a cylindrical billet having a diameter of 60 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 allowed to cool to room temperature. 720
Extrusion with a diameter of up to 36 mm was carried out at a temperature of ° C. The extruded rod was cut and cut to form a cylindrical billet having an outer diameter of 34 mm, an inner diameter of 16 mm and a length of 20 mm.

Next, only the outer peripheral portion of the billet was compression processed at a temperature of 680 ° C. using a mold as shown in FIG. 1 through a lubricant. The punch 3 has a diameter of 24 mm and the angle of inclination is
(a) is 20 °. The length of the boundary (portion having a diameter of 24 mm) after processing was 15 mm.

The billet after processing was cut into an inner diameter of 18 mm, and then the inner peripheral surface was magnetized with 24 poles. For the magnetization, a 2000 μF oil condenser was used, and pulse magnetization was performed at 1500V. The surface magnetic flux density on the inner peripheral surface was measured with a Hall element.

For comparison, the extruded rod described above is cut and machined,
A cylindrical billet having an outer diameter of 34 mm, an inner diameter of 16 mm, and a length of 20 mm was prepared, and only the inner peripheral portion was compression-processed using the mold shown in FIG. The movable punch 3 has a diameter of 24 mm. The length of the inner peripheral portion of the billet after processing was 15 mm. 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 69.4% Mn, 29.3% Al, 0.5% C, 0.7% in the composition
Ni and 0.1% Ti are melt-cast, diameter 60 mm, length 4
A 0 mm cylindrical billet was produced and subjected to the same heat treatment as in Example 1. At a temperature of 720 ° C., extrusion processing up to a diameter of 36 mm was performed. By cutting and cutting this extrusion rod,
A billet having an outer diameter of 34 mm, an inner diameter of 16 mm, a length of the innermost peripheral portion of 20 mm, and a diameter of 24 mm and a length of 15 mm was formed as shown in FIG.

Next, using a die as shown in FIG. 2, through a lubricant, only the inner peripheral portion of the billet is compressed at a temperature of 680 ° C. and the inner peripheral portion of the billet is compressed to a length of 10 mm. went. In FIG. 2, the inner diameter of the movable punch is 24 mm.

Example 1 after cutting the billet after processing to an inner diameter of 18 mm
In the same manner as above, the inner circumference of 24 poles was magnetized, and the surface magnetic flux density was measured.

For comparison, the extruded rod described above was cut and cut to produce 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 length of the inner peripheral portion of the billet after processing was 10 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.

As mentioned above, regarding the composition of the Mn-Al-C alloy magnet, only the quaternary system of Ni addition and the quaternary system of Ni and Ti additions are shown, but the basic composition of the Mn-Al-C alloy magnet is 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.

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, there was no great difference between the uneven end faces on one end face and both end faces.

EFFECTS OF THE INVENTION As described in the examples, the present invention provides a billet composed of a polycrystalline Mn-Al-C alloy magnet having a uniaxially anisotropic structure, only the inner peripheral portion of the billet, and the innermost periphery of the billet. The absolute value of logarithmic strain is set in the axial direction of the billet so that the compressive strain of the part is larger than the compressive strain of the outer part.
It is subjected to compression processing that gives a compression strain of 0.05 or more. As a result, higher magnetic properties can be obtained in the radial direction even with the same amount of compressive strain compared to the conventional methods, and the difference between the compressive strain at the innermost peripheral portion and the compressive strain at the outer side portion can be increased. 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 (1)

[Claims] 1. A billet made of a polycrystalline manganese-aluminum-carbon alloy magnet having a direction of easy magnetization parallel to a specific one direction, at a temperature of 530 to 830 ° C., and the innermost portion of the billet only inside the billet. In the direction parallel to the specific direction of the billet so that the compressive strain of the peripheral part is larger than that of the outer part, perform compression processing to give a compressive strain of 0.05 or more in absolute value of logarithmic strain. A method for producing a manganese-aluminum-carbon alloy magnet, comprising: