JPH0638367B2 - permanent magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a permanent magnet, and more particularly, to a polycrystalline manganese-aluminum-carbon system (Mn-Al-C).
System) alloy magnets.

(Prior Art) An Mn-Al-C alloy magnet is mainly composed of a face-centered tetragonal structure (τ phase, L1 _{0 type} ordered lattice) which is a ferromagnetic phase, and contains C as an essential constituent element. There are known ternary alloy magnets containing no additional element other than impurities and quaternary or more multi-component alloy magnets containing a small amount of additional elements. Also this Mn
-Al-C alloy magnets are mainly composed of a face-centered tetragonal structure, which is a ferromagnetic phase, and are isotropic due to the difference in the statistical distribution of the [001] axis (easy axis of magnetization) of the face-centered tetragonal crystal. A magnetic magnet and an anisotropic magnet having various anisotropic structures (for example, an anisotropic magnet having an easy magnetization direction in a specific direction or in a specific plane) are known.

As anisotropic magnets used in the field of multi-pole magnetization, radial anisotropic magnets having an easy magnetization direction in a specific direction, anisotropic magnets having an easy magnetization direction in an arbitrary direction parallel to a specific plane. Magnetic magnet (plane anisotropic magnet, JP-A-56-111203) and an easy magnetization direction in a specific direction within the specific plane, and an easy magnetization direction in the radial direction at the inner peripheral portion Or an anisotropic magnet satisfying at least one of the directions of having an easy magnetization direction in the chordal direction at the outer peripheral portion (Japanese Patent Laid-Open No. Sho 61-96).
No. 58-189355) is known.

(Problems to be Solved by the Invention) The shape of a magnet used in the field of multi-pole magnetization is generally axisymmetric, and a cylindrical body is an example. FIG. 2 schematically shows the formation of a magnetic path inside the magnet when the inner circumference of the cylindrical magnet is multi-pole magnetized (inner circumference magnetized). In the figure, the broken line indicates the magnetic path, and also indicates the chord direction (θ direction) with respect to one radial direction (γ direction). As described above, the direction orthogonal to the radial direction of the cylinder (γ direction) and the axial direction of the cylinder are the chord directions (θ direction).

As shown in FIG. 2, the magnetic path changes along the radial direction at the inner peripheral portion and along the chordal direction at the outer peripheral portion, and changes from the radial direction to the chordal direction at the intermediate portion between the outer peripheral portion and the inner peripheral portion. is doing. As described above, in the case where the magnet has a cylindrical shape, the inner peripheral portion means the portion where the magnetic path is substantially along the radial direction,
The outer peripheral portion refers to a portion where the magnetic path is substantially along the chord direction, and the intermediate portion refers to a portion where the magnetic path sequentially changes from the radial direction to the chord direction.

In the anisotropic magnet satisfying at least one of the inner peripheral portion having the easy magnetization direction in the radial direction and the outer peripheral portion having the easy magnetization direction in the chord direction, an anisotropic structure satisfying both Even if it is an anisotropic magnet having the above, it does not have an anisotropic structure suitable for the above-mentioned inner peripheral intermediate portion (the portion where the magnetic path sequentially changes from the radial direction to the chord direction).

(Means for Solving the Problems) In order to solve the problems described above, the permanent magnet of the present invention has an easy magnetization direction in the radial direction at the inner peripheral portion and an easy magnetization direction in the chord direction at the outer peripheral portion. Having a direction, and having a novel anisotropic structure having a region where the easy magnetization direction sequentially changes from the radial direction to the chordal direction as a third portion (intermediate portion) at the boundary between the outer peripheral portion and the inner peripheral portion. Is.

(Operation) As described above, since the third portion (intermediate portion) is included,
When the inner circumferential magnetization shown in FIG. 2 is applied, the anisotropic magnet exhibits excellent magnetic characteristics.

(Example) The present invention satisfies at least one of the inner peripheral portion having the easy magnetization direction in the radial direction and the outer peripheral portion having the easy magnetization direction in the chord direction based on the background described above. The present invention provides a permanent magnet having a novel anisotropic structure, which is an improved anisotropic magnet and is suitable for multi-pole magnetization, by improving the Mn-Al-C alloy magnet.

Since the shape of a magnet used in the field of multi-pole magnetization is generally an axially symmetrical shape, the permanent magnet of the present invention will be described with reference to FIG.

In the anisotropic magnets known so far, the inner peripheral portion has the easy magnetization direction in the radial direction and the outer peripheral portion has the easy magnetization direction in the chord direction. A third portion (intermediate portion) has a region where the easy magnetization direction sequentially changes from the radial direction to the chordal direction at the boundary between the portion and the inner peripheral portion.

FIG. 1 shows a view of the permanent magnet of the present invention viewed from the direction of the axis of symmetry. For the sake of explanation, each part is divided into broken lines to schematically represent each region. Reference numeral 1 denotes an inner peripheral portion in which the easy magnetization direction is along the radial direction. In the middle part, 2 is a part in which the direction of easy magnetization changes from the chordal direction to the radial direction as it approaches the center, and refers to only the part in the vicinity of the surface of each recess, and all the concentric parts. Not of.
Reference numeral 3 denotes a peripheral portion where the easy magnetization direction is along the chord direction, and like the intermediate portion 2, does not refer to all concentric portions. In other words, in the permanent magnet of the present invention,
Looking at the change of the easy magnetization direction toward the outer circumference of the magnet along the surface of the recess on the inner peripheral surface, first in the vicinity of the surface of the recess, the innermost peripheral portion (closest to the center, part) is parallel to the radial direction. That is, the distance gradually changes toward the chord direction toward the outside, and changes so as to be parallel to the chord direction at the portion closest to the outer periphery of the recess. Although it is schematically divided into three parts in FIG. 1, it is continuously changed as described above.

In the example shown in FIG. 1, since there are six convex portions on the inner peripheral surface,
It has an anisotropic structure suitable for being used by magnetizing the inner circumference with 6 poles. That is, the number of convex portions changes according to the number of poles. The position of the pole when the inner circumference is magnetized is the convex portion on the inner circumference.

Since the permanent magnet of the present invention has the anisotropic structure as described above, it exhibits excellent magnetic characteristics when subjected to inner circumferential magnetization as shown in FIG.

When multi-pole magnetized on the inner circumference as shown in FIG. 2, it has a structure in which the face-centered tetragonal [001] axis (easy axis of magnetization) is arranged along the magnetic path. Is.

In general, the state of preferential orientation of crystal orientation in a polycrystal is represented by the pole density P. Since the τ phase is tetragonal, [00
The 1) axis orientation can be understood as a (001) pole density distribution. The (001) pole density in a certain orientation of a polycrystal is measured as the ratio of the integrated intensity of the (00n) plane diffraction when the X-ray diffraction line is placed in that orientation to that in the case of an isotropic material. In isotropic magnets, the pole 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 in the magnet, and P <1 in the direction perpendicular to that plane.

Regarding the permanent magnet of the present invention prototyped by the inventor, the difference in the (001) pole density between both directions (specific direction and perpendicular direction) was three times or more for all the samples. Further, the (001) pole density in the direction parallel to the plane is 1.1 or more in the ratio of the specific direction and the direction perpendicular to the specific direction, but it is advantageous in terms of magnetic properties to increase the ratio.

The permanent magnet of the present invention is one in which the plane anisotropic magnets are preferentially arranged in a specific direction at the outer peripheral portion, the intermediate portion and the inner peripheral portion within the plane in which the [001] axes are arranged in the same manner. Is. In terms of magnetic properties, the inner circumferential portion has radial (γ direction) anisotropy, the outer circumferential portion has chord direction (θ direction) anisotropy, and the middle portion has radial direction to chordwise anisotropic direction. Changes. With respect to the permanent magnet of the present invention prototyped by the inventors, the ratio of the residual magnetic flux density in the specific direction to the direction orthogonal thereto was 1.1 or more.

The permanent magnet of the present invention is a known alloy for Mn-Al-C magnets, for example, 68% by weight to 73% by weight (hereinafter referred to simply as%).
Of Mn and (1 / 10Mn-6.6) to (1 / 3Mn-22.2)% C and the balance of
An alloy made of Al is formed into a uniaxial homogeneous fine [001] fiber structure by a known method such as extrusion in a temperature range of 530 to 830 ° C, and, for example, one manufacturing method is compression processing in the axial direction. It can be obtained by forming the inner peripheral surface of the sample on the concavo-convex portion by applying and compression processing.

Next, specific examples of the present invention will be described.

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 70 mm and a length of 50 mm. After holding this billet at 1100 ° C. for 2 hours, it was heat-treated by allowing it to cool to room temperature. Next, through a lubricant, extrusion processing was performed at a temperature of 720 ° C. to a diameter of 45 mm. Further through the lubricant a diameter of 3 at a temperature of 680 ° C
Extrusion processing up to 1 mm was performed. This extruded rod is 20 mm long
Cut into pieces, cut and processed, outer diameter 30 mm, inner diameter 24 mm, length 20
A cylindrical billet of mm was produced. With this billet,
Compression processing was performed using the mold shown in FIGS. 3 and 4. In Fig. 3, D _K (outer diameter 5 inner diameter) = 30 mm, X _A
= 8 mm, R _S (R of punch protrusion) = 2.5 mm, D _P (punch diameter) = 16 _Z , and there are 8 punch protrusions. FIG. 4 shows a sectional view taken in a direction orthogonal to FIG. In the figure, 4 is a billet, 5 is an outer mold, and 6 and 7 are punches, which have a surface in which uneven surfaces are engaged with each other and can be moved in the vertical direction of the figure. Using such a die, compression processing was performed to a height of 12 mm.

The billet after compression processing was cut to an inner diameter of 20 mm and magnetized with an inner circumference of 8 poles. The magnetization was pulsed at 1500 V using a 2000 μF oil condenser. The surface magnetic flux density of the inner peripheral surface was measured with a Hall element. 18m diameter for comparison
A cylindrical billet of m and 20 mm in length was freely compressed in the axial direction of the cylinder at a temperature of 680 ° C. The height of the billet after compression processing was 12 mm. The billet after processing was a surface anisotropic magnet, which was cut and magnetized in the same manner as described above, 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 1.6 times that of the surface anisotropic magnet.

From the outer and inner circumferences of the permanent magnet of the present invention obtained by the same method as described above, a cube having a side of 3 mm and each side parallel to the axial direction, the radial direction and the chord direction was cut out, and the magnetism in each direction was cut. The properties were measured.

In the chord direction of the outer circumference, Br = 5.9kG, Hc = 2.7kOe, (BH) max ＝
6.2MG Oe, and in the radial direction, Br = 3.1kG, Hc = 2.3kOe,
(BH) max = 2.0MG ・ Oe, Br = 2.6kG, Hc = 1.9kOe, Axial direction
(BH) max = 1.4MG ・ Oe, and Br = 3.0kG, Hc = 2.0 in the inner circumference
kOe, (BH) max ＝ 1.7MG ・ Oe, and radial direction Br ＝ 5.6k
G, Hc = 2.5kOe, (BH) max = 5.4MG ・ Oe, axial direction Br = 2.6k
G, Hc = 1.9 kOe, (BH) max = 1.4 MG · Oe.

Further, as a result of measuring the magnetic torque, it was found that the portion of the inner peripheral surface of the magnet near the recess had an easy magnetization direction substantially along the surface of the recess.

(Effect of the Invention) According to the present invention, it is possible to obtain a permanent magnet exhibiting excellent magnetic properties because it has an anisotropic structure suitable for inner circumferential multipole magnetization.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing the classification of permanent magnets according to an embodiment of the present invention by the difference in anisotropic structure, and FIG. 2 is a diagram showing a case where multi-pole magnetization is applied to the inner peripheral surface of a cylindrical magnet. FIGS. 3 and 4 are schematic cross-sectional views of a mold used to obtain the permanent magnet of the present invention in Examples, showing the formation of a magnetic path inside the magnet. 1 ... inner peripheral part, 2 ... middle part, 3 ... outer peripheral part, 4 ... billet, 5 ... outer mold, 6,7 ... punch.

Claims (1)

[Claims] 1. A polycrystalline manganese-aluminum-carbon alloy magnet mainly composed of a face-centered tetragonal structure, wherein the shape of the magnet is axisymmetric, and the face-centered tetragonal [001] axis is used. Are preferentially arranged in an arbitrary direction parallel to a plane perpendicular to the axis in comparison with the axial direction, and moreover, the inner peripheral portion in the plane is magnetically anisotropic in the radial direction. , The outer peripheral portion is magnetically anisotropic in the chord direction, and the magnetic anisotropy direction is gradually increased from the chord direction toward the radial direction as the center portion is closer to the center as an intermediate portion between the outer peripheral portion and the inner peripheral portion. A permanent magnet having a region that changes to.