JPH0338723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to permanent magnets, and more particularly to improvements in polycrystalline manganese-aluminum-carbon (Mn--Al--C) alloy magnets.

Mn-Al-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, Llo-type regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element, with no additives other than impurities. Ternary alloy magnets containing no elements and multi-element alloy magnets containing four or more elements containing a small amount of additional elements are known. Also, this Mn-Al-C
Based on the arrangement of the [001] axes of the face-centered tetragonal system, there are two types of alloy magnets: isotropic magnets and anisotropic magnets that have an easy magnetization direction in a specific direction or a specific plane. .

Anisotropic magnets used in the field of multipolar magnetization include radially anisotropic magnets that have an easy magnetization direction in a specific direction, and radially anisotropic magnets that have an easy magnetization direction in an arbitrary direction parallel to a specific plane. Oriental magnets are known.
The latter anisotropic magnet has the face-centered tetragonal [001]
It is a structure in which the axes are preferentially arranged in an arbitrary direction parallel to a specific plane compared to the perpendicular direction of the plane, and are not preferentially arranged in a specific direction within the plane ( (hereinafter referred to as a planar anisotropic magnet).

The shape of a magnet used in the field of multipolar magnetization is generally an axially symmetrical shape, and one example is a cylindrical shape. FIG. 1 schematically shows the formation of a magnetic path inside the magnet when the outer periphery of a cylindrical magnet is magnetized with multiple poles. In Figure 1, the broken line indicates the magnetic path, and the chordal direction (θ direction) with respect to one radial direction (r direction)
is also shown. As described above, the direction perpendicular to the radial direction (r direction) of the cylinder and the axial direction of the cylinder is defined as the chordal direction (θ direction).

As shown in FIG. 1, the magnetic path runs approximately in the radial direction at the outer periphery and approximately along the chord direction at the inner periphery. As mentioned above, when the shape of the magnet is cylindrical, the outer periphery refers to the part where the magnetic path runs approximately in the radial direction when the outer periphery is magnetized with multiple poles, and the inner periphery refers to the part where the magnetic path runs along the radial direction. refers to the part where the magnetic path runs approximately along the chord direction. The above-mentioned planar anisotropic magnet has an easy magnetization direction in any direction parallel to the plane, including the radial direction and the chordal direction, so it has excellent magnetic properties when it is magnetized on its outer periphery. However, when only the outer circumferential portion or the inner circumferential portion mentioned above is viewed, it is not necessarily a desirable anisotropic structure. In other words, when looking only at the outer circumference, it is better to have higher magnetic properties in the radial direction than in the chord direction, and when looking only at the inner circumference, it is better to have higher magnetic properties in the chord direction than in the radial direction. This can be said to be an anisotropic structure suitable for multi-pole magnetization around the outer periphery.

Furthermore, as mentioned above, Mn-Al-C alloy magnets are mainly composed of a face-centered tetragonal structure, which is a ferromagnetic phase, and the statistics of the [001] axis (easy axis of magnetization) of the face-centered tetragonal crystal described above. The surface anisotropic magnet has various anisotropic structures due to the difference in the distribution of the magnetic field, and the above-mentioned plane anisotropic magnet has the above-mentioned [001] axis aligned in any direction parallel to a specific plane within the magnet, perpendicular to that plane. They are arranged preferentially compared to the direction, and are arranged magnetically isotropically within the plane. From this, to put the above matter in other words, when looking only at the outer periphery, the [001] axes are arranged preferentially in the radial direction compared to the chord direction, or when looking only at the inner periphery, [001]
Satisfies at least one of arranging the axes preferentially in the chordal direction compared to the radial direction, and moreover preferentially arranging the axes in a direction parallel to a plane including the radial and chordal directions compared to the perpendicular direction of that plane. . Such a structure is an anisotropic structure suitable for peripheral multi-pole magnetization.

Based on the above-mentioned background, the present invention is an improvement of the Mn-Al-C alloy magnet by improving the planar anisotropic magnet and creating a permanent magnet with a new anisotropic structure suitable for multipolar magnetization. This is what we offer.

The most commonly used magnet shape in the field of multipolar magnetization is a cylindrical shape. Therefore, the permanent magnet of the present invention will be explained assuming that the magnet has a cylindrical shape.

The permanent magnet of the present invention is an anisotropic magnet, but it is a permanent magnet with a novel anisotropic structure that cannot be easily assumed from the conventional general concept of anisotropic magnets. Anisotropic magnets known so far include uniaxial anisotropy, which has high magnetic properties in one specific direction, radial anisotropy, which is used in the field of multipolar magnetization, and the above-mentioned surface anisotropy. etc. are known. The above three types of anisotropy are explained assuming that the shape of the magnet is cylindrical.In uniaxial anisotropy, for example, the easy magnetization direction is in the axial direction of the cylinder, and the easy magnetization direction is present in any part of the magnet. is parallel to the axial direction of the cylinder. With radial anisotropy, for example, a cylindrical body has an easy magnetization direction parallel to the radial direction, and the easy magnetization direction is parallel to the radial direction in any part within the magnet. In addition, in plane anisotropy, for example, the direction of easy magnetization is parallel to the plane perpendicular to the axial direction of the cylinder,
Within the plane, the particles are not preferentially arranged in a specific direction within the plane, and therefore are magnetically isotropic within the plane. Moreover, every part within the magnet has the above-described structure.

On the other hand, the permanent magnet of the present invention does not have the same structure in every part of the magnet, but is roughly divided into two parts (the outer circumferential part and the inner circumferential part). Two types of such anisotropic structures can be considered to exist within a single magnet.

The permanent magnet of the present invention has radial anisotropy or plane anisotropy at the outer circumference, and chordwise anisotropy or plane anisotropy at the inner circumference. Furthermore, the structure is such that neither the outer circumferential portion nor the inner circumferential portion has surface anisotropy.

From the above, the permanent magnet of the present invention is divided into three types, the first type is one in which the outer circumference is radially anisotropic and the inner circumference is chordwise anisotropic;
The second type has radial anisotropy on the outer periphery and plane anisotropy on the inner periphery, and the third type has plane anisotropy on the outer periphery and chordal anisotropy on the inner periphery. It is directional. Here, chordwise anisotropy (θ-direction anisotropy) is an anisotropic structure similar to radial anisotropy. The direction of easy magnetization is parallel to the chordal direction (theta direction) in any part of the magnet. In other words, the direction of easy magnetization is along the tangential direction of the circumference.

Earlier, I expressed that two different types of anisotropic structures can be considered to exist within one magnet, but on the other hand, if you look at it in another way, the above-mentioned planar anisotropic magnet is magnetically equivalent. A structure that is magnetically anisotropic on at least one of the outer peripheral part or the inner peripheral part on a plane that is tropic, and the outer peripheral part is anisotropic in the radial direction,
The permanent magnet of the present invention has a structure in which the inner peripheral portion is anisotropic in the chord direction. For example, in the first type described above, the outer circumferential portion is anisotropic in the radial direction, and the inner circumferential portion is anisotropic in the chordal direction.

Since the permanent magnet of the present invention has an anisotropic structure as described above, when multipolar magnetization is applied to the outer periphery as shown in FIG. It shows the characteristics.

This is because when multi-polar magnetization is applied to the outer periphery as shown in Figure 1, the [001] axes are arranged along the magnetic path in consideration of the formation of the magnetic path.
If you look at it this way, you can think of plane anisotropy as a wasteful anisotropic structure because the [001] axis is arranged equally in directions that are not along the direction of the magnetic path. You can also do it.

Generally, the preferential orientation state of crystal orientation in a polycrystalline body is expressed by polar density P. Since the τ phase is a tetragonal system, the orientation of the [001] axis can be understood as a (001) polar density distribution. The (001) polar density in a certain orientation of a polycrystal is measured as the ratio of the integrated intensity of (00n) plane diffraction when the X-ray diffraction normal is placed in that orientation to that of an isotropic material. In an isotropic magnet, the polar density is 1 for all three-dimensional orientations. In other words, the permanent magnet of the present invention has P>1 in a specific direction parallel to a specific plane within the magnet, and P<1 in a direction perpendicular to that plane. In the first type, if the inside of the magnet is the outer circumference of the magnet, the specific direction is the radial direction (r direction), and if the inside of the magnet is the inner circumference, the specific direction is the string direction. direction (θ direction). In the second type, if the inside of the magnet is the outer circumference of the magnet, the specific direction is the radial direction (r direction) (this is the same as the first type), and the inner circumference of the magnet is the same as the first type. Then, the above-mentioned specific direction is an arbitrary direction. In the third type, if the inside of the magnet is the outer circumference of the magnet, the specific direction is any direction, and if the inner circumference of the magnet is the inner circumference, the specific direction is the chordal direction (θ direction). It is.

Regarding the permanent magnet of the present invention prototyped by the inventors, (001) between both directions (specific direction and perpendicular direction)
The difference in polar density was more than 3 times for all samples. Also, (001) in the direction parallel to the plane
When the polar density is set in any direction, the change is about 10% or less, which is the degree of general accuracy in X-ray diffraction intensity measurement. The ratio with respect to the magnetic field direction is 1.1 or more, but increasing the ratio is advantageous in terms of magnetic properties.

The permanent magnet of the present invention is one in which the [001] axes are arranged preferentially in a specific direction at the outer periphery, the inner periphery, or both within a plane in which the [001] axes are arranged in the same manner as in the above-mentioned plane anisotropic magnet. It is. In terms of magnetic properties, the question is whether to have radial (r-direction) anisotropy at the outer circumference or chordal (θ-direction) anisotropy at the inner circumference. For the permanent magnet of the present invention, the ratio of the residual magnetic flux density in the radial direction and the chordal direction was 1.1 or more.

The permanent magnet of the present invention is made of a known Mn-Al-C alloy for magnets, for example, 68 to 73% by weight of Mn and (1/10
A uniaxial, homogeneous, fine [001 [After forming a fiber structure, for example, one manufacturing method is to perform free compression processing in the axial direction to obtain a planar anisotropic magnet, and further perform compression processing on a portion of the magnet in a direction parallel to the free compression processing. It can be obtained by Another manufacturing method is to create a uniaxial, homogeneous, fine [001] fiber structure, and then extrude it using a die in which the opening area of the container part is smaller than the opening area of the bearing part, and in addition, in the extrusion process, By making the direction parallel to the axial direction, applying compressive strain in the extrusion direction, and applying the extrusion process to the magnet obtained by further applying compression process to a part of the magnet in a direction parallel to the axial direction. Obtainable.

Next, the present invention will be explained with reference to examples.

In the blended composition, 69.5% by weight of Mn, 29.3% by weight of Al,
A cylindrical billet having a diameter of 80 mm and a length of 60 mm was prepared by melting and casting 0.5% by weight of C and 0.7% by weight of Ni in the atmosphere. This billet was held at 1100° C. for 2 hours, and then heat-treated by allowing it to cool to room temperature. Next, extrusion processing up to a diameter of 45 mm was performed at a temperature of 720°C via a lubricant. Furthermore, extrusion processing up to a diameter of 31 mm was performed at a temperature of 680°C using a lubricant. This extruded rod was cut to a length of 20 mm and machined to create an outer diameter of 30 mm.
A cylindrical billet with an inner diameter of 10 mm and a length of 20 mm was prepared.

Next, this cylindrical billet was extruded at a temperature of 680° C. using a die as shown in FIG. 2 through a lubricant. Figure 2 a shows the state before processing, and b
is the state after processing. In FIG. 2, 1 is the billet described above, 2 and 3 are die constituent members, and 4 and 5 are
is punch. The part 21 is the container part, and has an outer diameter of 30 mm and an inner diameter of 10 mm. The part 22 is a conical part. The part 23 is the bearing part, and has an outer diameter of 63.2 mm, an inner diameter of 49 mm, and x is 40 mm. The opening area of the container part of this die is the outer diameter
The cross-sectional area of a ring with an outer diameter of 63.2 mm and an inner diameter of 49 mm is the cross-sectional area of a ring with an outer diameter of 63.2 mm and an inner diameter of 49 mm. After processing, the billet has an outer diameter of
It was 63.2mm, inner diameter 49mm, and length 10mm.

This billet was further compressed only at the outer periphery in the axial direction of the cylinder at a temperature of 680°C in the state shown in Figure 3. In FIG. 3a, 11 is the billet after the above-mentioned processing, 6 is a movable punch, 7 is a fixing punch, and 8 is a lower mold, and the inner diameter of the movable punch 6 is 56 mm. Fix the billet 11 with the lower die 8 and the fixing punch 7, and align the center of the billet 11 with the punch 6.
Only the outer periphery of the billet 11 was compressed using the punch 6, with the center of the billet 11 substantially aligned with the center of the billet 11. Figure 3b
indicates the state after processing. The length of the billet after processing was 8 mm at the outer circumference and 10 mm at the inner circumference. This billet was machined to an outer diameter of 62 mm and an inner diameter of 50 mm, and the outer circumference was magnetized with 30 poles. The magnetization was pulsed at 1500V using a 2000μF oil capacitor. The surface magnetic flux density at the outer periphery was measured using a Hall element.

A cylindrical magnet having an outer diameter of 62 mm, an inner diameter of 50 mm, and a length of 8 mm at the outer periphery and 10 mm at the inner periphery was produced in the same manner as described above. The outer periphery (8 mm long part) and the inner periphery (10 mm long part) of this magnet are parallel to the radial direction (r direction), chordal direction (θ direction), and axial direction, respectively. A total of 6 pieces were cut out, 3 pieces from each body. The length of each side was 2 mm in the radial direction, 4 mm in the chordal direction, and 5 mm in the axial direction.
The above three pieces are overlapped and each side is 6mm,
The magnetic properties of the samples in each direction were measured using rectangular bodies of 4 mm and 5 mm.

In the chord direction of the inner circumference, Br=5.9kG, Hc=
2.7kOe, (BH) _nax = 6.2MG・Oe, and in the radial direction, Br = 3.1kG, Hc = 2.3kOe, (BH) _nax =
2.0MG・Oe, Br=2.6kG in the axial direction, Hc=
1.9kOe, (BH) _nax = 1.4MG・Oe, or in the chord direction of the outer circumference Br = 3.0kG, Hc = 2.0kOe, (BH) _na
x = 1.7MG・Oe, and in the radial direction, Br = 5.6kG,
Hc=2.5kOe, (BH) _nax =5.4MG・Oe, axial direction Br=2.6kG, Hc=1.9kOe, max=1.4MG・Oe
It was hot.

As described above, the magnet is of the first type, and is anisotropic in the chordal direction at the inner circumference, and anisotropic in the radial direction at the outer circumference.

For comparison, the length of the extruded rod with a diameter of 45 mm was
A cylindrical billet with a diameter of 45 mm and a length of 20 mm was produced by cutting it into 20 mm pieces. Next, the cylindrical billet was subjected to free compression processing in the axial direction of the cylinder at a temperature of 680°C using a lubricant. The length of the billet after processing was 10 mm. This billet was a planar anisotropic magnet, which was cut into a cylindrical shape with an outer diameter of 62 mm and an inner diameter of 50 mm, and was magnetized and measured in the same manner as described above.

The diameter of the planar anisotropic magnet obtained by the same method as above is approx.
A cube with sides of 5 mm was cut out from around 55 mm.
Note that each side was made parallel to the radial direction, chord direction, and axial direction. Magnetic measurements of cubic samples were carried out. The magnetic properties are Br= in the radial and chordal directions.
4.6kG, Hc = 2.8kOe, (BH) _nax = 40MG・Oe. On the other hand, in the axial direction, Br=2.6kG, Hc=
2.0kOe, (BH) _nax = 1.4MG・Oe.

Comparing the surface magnetic flux density values of the permanent magnet of the present invention and the planar anisotropic magnet, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention is approximately 1.4 that of the planar anisotropic magnet. This was an extremely excellent permanent magnet for multi-pole magnetization on the outer periphery.

The magnet of the present invention described above is a first type of magnet in which the outer circumference is radially anisotropic and the inner circumference is chordwise anisotropic; An example of obtaining the second type in which the peripheral portion has planar anisotropy will be described below.

The planar anisotropic magnet prepared for the comparison described above was cut into a cylindrical shape with an outer diameter of 63.2 mm, an inner diameter of 49 mm, and a length of 10 mm. Only the outer periphery was processed at a temperature of ℃. The length of the billet after processing is 8 mm at the outer circumference and 8 mm at the inner circumference.
It was 10mm.

As a result of cutting out a material similar to the first type magnet from this magnet and measuring its characteristics, in the chord direction of the outer circumference, Br = 3.0KG, Hc = 2.0KOe, (BH) _nax =
1.7MG・Oe, and in the radial direction, Br=5.6KG,
Hc = 2.5KOe, (BH) _nax = 5.4MG・Oe, in the axial direction, Br = 2.6KG, Hc = 1.9KOe, (BH) _nax =
It was 1.4MG・Oe. On the other hand, in the chordal and radial directions of the inner circumference, Br=4.6KG, Hc=2.8KOe,
(BH) _nax = 4.0MG・Oe, and in the axial direction, Br
=2.6KG, Hc=2.0KOe, (BH) _nax =1.4MG・Oe
It was hot.

This magnet is the second type of permanent magnet of the present invention, and when comparing the value of the surface magnetic flux density of the magnet of the present invention and the surface anisotropic magnet prepared previously, the value of the surface magnetic flux density of the present invention is found to be , about 1.3 of that of a planar anisotropic magnet
Although it was slightly inferior to the first type, it was an extremely excellent permanent magnet for internal magnetization.

Next, there is a method for manufacturing a third type of magnet in which the outer circumference has planar anisotropy and the inner circumference has chordwise anisotropy, but this is almost the same as the method for manufacturing the first type of magnet. The only difference is the compression length of the final outer periphery. The first type of magnet was compressed to an outer circumference of 8 mm, but the third type of magnet was compressed to an outer circumference of 9 mm.

The magnetic properties of this magnet in each direction were measured using the same method as described above. In the radial and chordal directions of the outer circumference,
Br=4.5KG, Hc=2.8KOe, (BH) _nax =3.9MG・
Oe, and in the axial direction, Br=2.6KG, Hc=
1.9KOe, (BH) _nax = 1.4MG・Oe. On the other hand, in the chord direction of the inner circumference, Br = 5.9KG, Hc =
2.7KOe, (BH) _nax = 6.2MG・Oe, and in the radial direction, Br = 3.1KG, Hc = 2.3KOe, (BH) _nax =
2.0MG・Oe, and in the axial direction, Br=2.6KG,
Hc = 1.9KOe, (BH) _nax = 1.4MG・Oe.

This magnet is the third type of magnet of the present invention, and when comparing the surface magnetic flux density values of this permanent magnet and a planar anisotropic magnet prepared for comparison, the value of the surface magnetic flux density of the present invention is as follows. Approximately that of a planar anisotropic magnet
1.3 times, and was an extremely excellent permanent magnet for outer periphery magnetization with almost the same characteristics as the second type.

As described above, the permanent magnet of the present invention has an anisotropic structure that is more suitable for peripheral multi-pole magnetization than a plane anisotropic magnet, and thus has superior magnetic properties. It is a permanent magnet.

[Brief explanation of drawings]

Fig. 1 is a film diagram showing the formation of a magnetic path inside the magnet when the outer periphery of a cylindrical magnet is subjected to multipolar magnetization, and Figs. 2 and 3 are examples of the present invention. FIG. 2 is a cross-sectional view of a part of a mold used to obtain a permanent magnet. 1... billet, 4, 5... punch, 21...
Container part, 22... Conical part, 23... Bearing part, 6... Movable punch, 7... Fixing punch, 8... Lower mold.

Claims (1)

[Scope of Claims] 1. A polycrystalline manganese-aluminum-carbon alloy magnet mainly composed of a face-centered tetragonal structure, wherein the shape of the magnet is axially symmetric, and the [001 ] The axes are preferentially arranged in an arbitrary direction parallel to a plane perpendicular to the axis, compared to the axial direction, and only the outer periphery within the plane is magnetically anisotropic in the radial direction. A permanent magnet that satisfies at least one of the following conditions: or, only the inner circumference is magnetically anisotropic in the string direction.