JPH0663063B2 - Method for producing manganese-aluminum-carbon alloy magnet - Google Patents

Description

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

Prior art alloys for Mn-Al-C magnets contain 68 to 73 mass% (hereinafter simply referred to as%
Mn and (1 / 10Mn−6.6) to (1 / 3Mn−22.
2) Multi-component magnet alloys composed of 3% C and the balance Al, ternary system containing no additional elements other than impurities, and quaternary system containing a small amount of additional elements are known. It is a thing.

Similarly, 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 are those containing C as essential constituent elements, 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 these are collectively referred to.

Further, as a method of manufacturing the Mn-Al-C alloy magnet, a method including a warm plastic working step such as warm extrusion processing is known in addition to the method of 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.

The method for producing the Mn-Al-C alloy magnet for multipolar magnetization is an isotropic magnet, a compression processing method, or a uniaxially anisotropic polycrystalline Mn obtained by a known method such as warm extrusion processing in advance. -Al-C
-Based alloy magnets subjected to warm free compression in the anisotropic direction (for example, Japanese Patent Laid-Open No. 56-119762), and Mn-Al-C
There are known various types of plastic working (for example, Japanese Unexamined Patent Publication No. 58-192303-6) that give a compressive strain in the axial direction of a hollow body billet made of a system magnet alloy.

Problems to be Solved by the Invention The shape of a magnet for multi-pole magnetizing is generally cylindrical, and the main magnetizing is magnetizing as shown in FIG. FIG. 3 schematically shows the formation of magnetic paths 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 magnet obtained by various plastic workings that give compressive strain in the axial direction of the hollow body billet made of the alloy for Mn-Al-C based magnets, when the outer peripheral magnetization is applied, the magnet is locally magnetized. Although it is anisotropic in the direction along the road, when viewed as a whole, it is not anisotropic 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 (chordal 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, the present invention provides Mn-
For an axisymmetric billet made of Al-C magnet alloy,
At a temperature of 530 ~ 830 ℃, compression processing in the axial direction of the billet,
By this compression processing, the cross-sectional shape of the outer peripheral surface of the billet is formed into a (2n + 2) polygonal shape (n = 1,2,3 ...).

Action By this method, that is, by this compression processing, the cross-sectional shape of the billet outer peripheral surface is changed to (2n + 2) square (n = 1,2,3
..), it is possible to anisotropy along the magnetic path when the outer peripheral magnetization shown in FIG. 3 is applied, and an anisotropic magnet exhibiting high magnetic characteristics can be obtained. it can.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. According to the present invention, an axially symmetric billet made of an alloy for Mn-Al-C magnets is subjected to compression processing in the axial direction of the billet at a temperature of 530 to 830 ° C to change the cross-sectional shape of the outer peripheral surface of the billet ( 2n
+2) It is formed into a rectangular shape (n = 1,2,3 ...).

Thus, the billet having an axially symmetric shape made of an alloy for Mn-Al-C magnets has a cross-sectional shape of the outer peripheral surface of the billet having a (2n + 2) polygonal shape (n = 1, 2, (3 ...) By performing compression processing in the axial direction of the billet, it is possible to obtain a magnet exhibiting high magnetic characteristics in the outer peripheral magnetization shown in FIG.

The compression processing described above does not necessarily have to be continuous compression processing, and may be given by dividing into a plurality of times.

An example of the above-described compression processing of the present invention will be described with reference to FIG. 1 in which the billet has a cylindrical shape and the sectional shape of the billet after compression processing is square (when n = 1). First
FIG. 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, 2 is an outer mold, and this outer mold 2 is a mold for forming the outer peripheral surface of the billet (in this case, the side surface of the billet is a solid body) into a square shape by compression processing. . FIG. 1b is a sectional view showing a state after compression processing. As shown in FIG. 1B, the diameter of the cylindrical billet increases as the compression process progresses, and a part of the outer peripheral surface (side surface) comes into contact with the inner surface of the outer mold 2. By further compressing, FIG. 1b
As shown in, the compression processing can be performed until the outer peripheral surface (side surface) of the billet 1 almost contacts the inner surface of the outer mold 2.

Further, it is not necessary to perform compression processing to the state shown in Fig. 1b, and after a part of the outer peripheral surface (side surface) of the billet 1 contacts the inner surface of the outer mold 2, the compression processing ends at any time. You may.

The maximum diameter of the billet of the present invention before compression processing is the outer die 2
It is the size that touches (inscribes) the inner surface of. In that case, before the compression processing, the compression processing is performed with a part of the outer peripheral surface (side surface) of the billet 1 already constrained by the inner surface of the outer mold 2.

Another typical example of the compression processing of the present invention will be described with reference to FIG. 2 in which the billet has a cylindrical shape. As in FIG. 1, FIG. 2 shows a before compression processing and b shows after compression processing. A significant difference from FIG. 1 is that the billet 11 is a cylindrical body and the punch 13 is present in the hollow portion. In this example, the punch 13 has a diameter approximately equal to the inner diameter of the billet 11.
Shows an example of using. The punch 13 always exists in the center during the compression process, and the billet is formed by the compression process.
Prevent the inner diameter of 11 from becoming smaller than the diameter of the punch 13. Further, in the example of FIG. 2, a part of the outer peripheral surface of the cylindrical billet is already in contact with the outer die 12 before the compression processing, and is in a restrained state.

In the above two examples, the outer peripheral surface (or side surface) of the billet
The cross-sectional shape changes from circular to almost square (R may have chamfers at each corner). Due to such changes, it is possible to have an anisotropic structure suitable for outer circumference magnetization. become. In the compression process, the part where the outer peripheral surface is constrained earliest becomes the part having the easy magnetization direction in the chord direction, and the part where the outer peripheral surface (or side surface) is restricted at the end or the part where the outer peripheral surface is not restricted until the end. The portion (corresponding to the corner of the prism after processing) 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 after compression processing may be determined depending on how many poles are magnetized in the outer peripheral magnetization. That is,
In the above-described example, the outer peripheral surface (or side surface) of the billet after compression processing has a substantially square cross-sectional shape, so that the billet has an anisotropic structure suitable for 4-pole magnetization. The cross-sectional shape of the outer peripheral surface of the billet after compression processing is (2n + 2) square (n = 1,2,3 ...)
As described above, it is necessary that the outer peripheral magnetization has an even number of poles and has an even polygonal cross-sectional shape.
When n = 1, 4 poles are used, and when n = 2, 6 poles are used. 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 (2n + 2) polygon (n = 1,2,3 ...) in the present invention does not need to be a geometrically accurate (2n + 2) polygon, and there is no problem even if some chamfering etc. .

As described in the above example, in the present invention, when the billet is compressed in the axial direction, the cross-sectional shape of the outer peripheral surface of the billet is a (2n + 2) square (n = 1,2,3 ... (2) is shaped and compressed to obtain a magnet having an anisotropic structure that exhibits high magnetic characteristics when the outer circumference is magnetized.

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 69.4% Mn, 29.3% Al, 0.5% C, 0.7% in the composition
Ni and 0.1% Ti are melt-cast, diameter 22mm, length 20mm
The cylindrical billet of was produced. 2 this billet at 1100 ℃
After holding for a time, it was air-cooled to 600 ° C., held at 600 ° C. for 30 minutes, and then heat-treated by allowing it to cool to room temperature. Using this billet, compression processing was performed using the mold shown in FIG. In FIG. 1, the length of one side of the square inside the outer mold 2 is 28 mm. Using this mold, compression processing was performed to a height of 9.7 mm.

The billet after compression processing was cut at the four corners to a diameter of 30 mm, and magnetized with 4 poles on the outer circumference. For the magnetization, a 2000 μF oil condenser was used and pulsed at 1500 V. The surface magnetic flux density of the outer peripheral surface was measured with a Hall element. The peak value at each magnetic pole was 2.3 to 2.4 KG.

Example 2 The same compounding composition as in Example 1 was melt cast and the outer diameter was 22 mm and the inner diameter was
A cylindrical billet having a length of 14 mm and a length of 20 mm was produced. This billet was heat-treated under the same conditions as in Example 1. 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. The punch 13 has a diameter of 14 mm. Using such a mold, compression processing was performed to a height of 7.2 mm.

Similarly to Example 1, the billet after compression processing was cut at the four corners to an outer diameter of 30 mm, magnetized on the outer periphery, and the surface magnetic flux density was measured. The peak value at each magnetic pole was not much different from that of the magnet obtained in Example 1.

The magnets obtained by the method of the present invention obtained in Example 1 and Example 2 were measured by magnetic torque. As a result, as described above, the easy magnetization direction was along the radial direction at the side of the billet after compression processing, It was found that it was along the chord direction in the middle, and between them was continuously changing from the radial direction to the chord direction (circumferential direction).

EFFECTS OF THE INVENTION As described in the examples, the present invention provides an axisymmetric billet made of an alloy for Mn—Al—C magnets with 530 to 830.
At the temperature of ℃, the cross-sectional shape of the billet outer surface compressed in the axial direction of the billet is (2n + 2) square (n = 1,2,3
..) to obtain a magnet exhibiting high magnetic characteristics when the outer circumference is magnetized.

When compared with the magnet obtained by the known method, the magnet obtained by the method of the present invention shows superior magnetic characteristics to the magnet obtained by the known method when subjected to the outer circumferential magnetization, and further, the outer peripheral portion of the magnet by the known method. Has a direction of easy magnetization in the radial direction and a structure having a direction of easy magnetization in the circumferential direction (chord direction) in the inner peripheral portion thereof requires plastic working at least twice. According to the method (1), a magnet having a more desirable anisotropic structure can be obtained at least once.

[Brief description of drawings]

1A and 1B and 2A and 2B are cross-sectional views of a mold used in compression processing according to an embodiment of the present invention, showing changes in cross-sectional shape of a billet before and after compression processing, and FIG. FIG. 6 is a diagram schematically showing formation of a magnetic path inside the magnet when the outer peripheral surface of the cylindrical magnet is multi-pole magnetized. 1,11 …… Billet, 2,12 …… Outer mold, 13 …… Punch

Claims (2)

[Claims] 1. An axisymmetric billet made of a manganese-aluminum-carbon alloy magnet is provided at 530 to 830.degree.
At the temperature of, the billet is compressed in the axial direction, and the cross-sectional shape of the outer peripheral surface of the billet is a (2n + 2) polygon (n =
Manganese having a first step of forming into a 1,2,3, ...) shape and a second step of polarizing the corners of the (2n + 2) square outer peripheral surface of the billet formed in the first step. −
A method for manufacturing an aluminum-carbon alloy magnet. 2. The method for producing a manganese-aluminum-carbon based alloy magnet according to claim 1, wherein the compression processing is carried out with a part of the outer peripheral surface of the billet being constrained.