JPH061741B2 - Alloy magnet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a permanent magnet, and more particularly to a multi-pole magnetizing method using a polycrystalline manganese-aluminum-carbon (Mn-Al-C system) alloy. The present invention relates to a manufacturing method of a magnet.

(Prior Art) Mn-Al-C alloy magnets have 68 to 73 mass% (hereinafter simply referred to as%
) And (1 / 10Mn-6.6) to (1 / 3Mn-22.2)% C and the balance Al, 3 elements that do not contain additional elements other than impurities, and 4 elements that contain a small amount of additional elements. Alloys for multi-element elementary magnets of the series and above are known and are collectively referred to. Similarly, the Mn-Al-C alloy magnet is mainly composed of a face-centered tetragonal (τ phase, L ₀ -type ordered lattice) structure that is a ferromagnetic phase, and contains three elements including no additional element other than impurities and Quaternary or higher multi-component alloy magnets containing a small amount of additional elements are known, and they are collectively referred to.

In addition, as a method for manufacturing this Mn-Al-C alloy magnet, in addition to those by casting and heat treatment, there are those that include warm plastic working steps such as warm extrusion, and especially the latter have high magnetic properties, It is known as a method for producing an anisotropic magnet having excellent properties such as mechanical strength, weather resistance and machinability.

As a method for producing Mn-Al-C alloy magnet for multi-pole magnetization, an isotropic magnet, one by compression processing, uniaxially anisotropic polycrystalline Mn obtained by a known method such as warm extrusion processing in advance. -Al-C alloy magnets by warm free compression in the anisotropic direction (for example, JP-A-56-119762) and hollow billets made of Mn-Al-C alloy alloys. By various types of plastic working that give a compressive strain in the axial direction
58-192303 to 192306) are known.

(Problems to be Solved by the Invention) The shape of a multi-pole magnetizing magnet is generally a cylindrical body, and the main magnetizing is magnetizing as shown in FIG. FIG. 5 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 axial direction of the hollow body-shaped billet made of the above-mentioned Mn-Al-C magnet alloy, in the magnet obtained by various plastic workings that give compressive strain, when the outer peripheral magnetization is applied, locally Has anisotropy in the direction along the magnetic path, but when viewed as a whole, it does not anisotropy 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, the same applies hereinafter). While the magnetic path is changing from the radial direction to the circumferential 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 as described above, the present invention provides Mn-A
This is characterized in that an axially symmetric billet made of an alloy for lC-based magnets is compressed in the axial direction, and the outer peripheral surface is formed on the unevenness by this compression processing.

(Operation) By the above method, that is, by forming the outer peripheral surface of the billet into an uneven shape by compression processing, anisotropy is achieved along the magnetic path when the outer peripheral magnetization shown in FIG. 5 is applied. It is possible to obtain an anisotropic magnet exhibiting high magnetic properties.

(Example) The present invention is a billet having an axially symmetric shape made of an alloy for Mn-Al-C magnets, and compressed at a temperature of 530 to 830 ° C in the axial direction of the billet so that the outer peripheral surface becomes uneven. By applying the above, it is possible to obtain a magnet exhibiting high magnetic characteristics in the outer peripheral magnetization shown in FIG.

The compression process described above does not necessarily have to be a continuous compression process, and may be given in multiple divisions.

An example of the compression processing of the present invention described above will be described with reference to the drawings, assuming that the billet has a cylindrical shape.

FIG. 1 (a) shows a cross-sectional view of the billet before compression processing as seen from the direction of the symmetry axis of the billet. Reference numeral 1 is a cylindrical billet, and 2 is an outer mold, which is a mold for molding. Fig. 1
Similarly, (b) shows the state after processing. As shown in FIG. 2B, the diameter of the cylindrical billet 1 increases with the progress of compression processing, and a part of the outer peripheral surface comes into contact with the outer die 2. When compression processing is further advanced, compression processing is performed until the outer peripheral surface of the billet 1 almost contacts the inner surface of the outer mold 2. It is not necessary to perform compression processing to the state shown in FIG. 7B, and even if compression processing is finished at any time after a part of the outer peripheral surface of the billet 1 contacts the inner surface of the outer mold 2. Good. The point is that irregularities may be formed on the outer peripheral surface of the billet.

In this case, the diameter of the billet 1 before compression processing is the maximum size in contact with the convex portion on the inner surface of the outer mold 2. In that case,
Before the compression processing, part of the outer peripheral surface of the billet 1 has an outer diameter of 2
It will be compressed while being constrained by the inner surface of the.

Another typical example of the compression processing of the present invention will be described with reference to FIG. 2 with a billet having a cylindrical body. Figure 2 shows the first
The cross section of the outer mold is shown as in the figure, and the big difference in FIG. 1 is that the core 3 exists in the center. In this example, the core 3 has a diameter approximately equal to the inner diameter of the billet 1.
The core 3 is always present in the center during the compression process, and the billet 1 is formed by performing the compression process.
To prevent the inner diameter of the core from becoming smaller than the diameter of the core 3.

Further, in this example, a part of the outer peripheral surface of the cylindrical billet is already in contact with the outer mold 2 before compression processing, and is in a restrained state.

As described above, the unevenness is present on the inner surface of the outer mold 2, so that the billet 1 is unevenly formed on the outer peripheral surface after the compression processing.

In the compression process, the part where the outer peripheral surface is constrained first (the recess on the outer peripheral surface of the billet after processing) has a magnetic easy direction in the circumferential direction, and finally the part where the outer peripheral surface is constrained or the outer periphery to the end. The portion where the surface is not restricted (the convex portion on the outer peripheral surface of the billet after processing) is a portion having the easy magnetization direction in the radial direction. The easy magnetization direction of the intermediate portion is a portion that gradually changes from the circumferential direction to the radial direction. In other words, in FIG. 1, the easy magnetization direction gradually and continuously changes from the outer peripheral portion of the billet 1 in the direction along the curved surface of the concave portion on the outer peripheral surface of the billet formed by the convex portion on the inner surface of the outer mold 2. Therefore, the number of the uneven portions is determined depending on how many poles are magnetized in the outer circumference magnetization. In FIG. 1, since there are six convex portions on the outer peripheral surface of the billet after processing, the magnet has an anisotropic structure suitable for 6-pole magnetization, and the portion corresponding to the convex portion after processing is the same as in the outer peripheral magnetization. It becomes the pole part.

As described above, according to the present invention, when the billet is compressed in the axial direction, the outer circumference is magnetized by using an outer die (mold) and the like so that the outer circumferential surface of the billet becomes uneven. It is intended to obtain a magnet having an anisotropic structure that exhibits high magnetic properties when applied.

For the temperature range in which such compression processing is possible, see 530
Can be processed in the temperature range of 830 to 830 ℃, but 780
At temperatures above ° C, the magnetic properties are significantly reduced. A more desirable temperature range was 560 to 760 ° C.

Next, the present invention will be described more specifically.

Example 1 69.4% Mn, 29.3% Al, 0.5% C, 0.7%
Ni and 0.1% Ti are melt-cast, diameter 18mm, 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 that temperature for 30 minutes, and then heat-treated by allowing it to cool to room temperature. The billet thus produced was compression-processed using the mold (outer mold) shown in FIGS. 3 and 4. FIG. 3 is a sectional view of the outer mold similar to FIG. In FIG. 3, (inner diameter of outer mold 2) D _K = 30 mm, X _A = 15 mm, (curvature radius of convex portion of outer mold 2)
R _S = 3 mm, and there are 8 convex portions on the inner surface of the outer mold 2. Fourth
The figure shows a cross-sectional view from the direction orthogonal to FIG. Punches 4 and 5 have an outer peripheral surface that fits with the uneven surface of the outer mold 2 and can move in the vertical direction in the drawing. Using such an outer mold 2, the billet 1 was compressed to a height of 8.5 mm.

The billet 1 after compression processing is cut to a diameter of 27 mm, and
The outer circumference of the pole was magnetized. The magnetization was pulsed at 1500 V using an oil condenser of 200 μF. When 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.

Specific Example 2 The same compounding composition as in Specific Example 1 was melt cast to produce a cylindrical billet having an outer diameter of 24 mm, an inner diameter of 18 mm and a length of 20 mm. The billet was heat-treated under the same conditions as in Example 1. Using this billet, compression processing was performed using the outer diameter shown in FIG. The dimensions of each part of the outer mold 2 are the same as those shown in FIG. 3, and the diameter of the core 3 is 18 mm. Using such an outer die, compression processing up to a height of 11.5 mm was performed.

The billet after compression processing was cut into an outer die of 27 mm in the same manner as in Example 1, 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.

As a result of the magnetic torque measurement, the magnets obtained by the methods of the present invention obtained in Examples 1 and 2 showed that the easy magnetization direction was gradually changed from the radial direction to the circumferential direction along the surface of the recess as described above. Was confirmed.

(Effects of the Invention) As described in detail above, the present invention provides a billet having an axially symmetric shape made of an alloy for Mn-Al-C magnets, which is subjected to compression processing in the axial direction thereof, and at the same time, the outer peripheral surface of the pellet is uneven. By forming the magnet into a shape, it is possible to obtain a magnet exhibiting high magnetic characteristics when the outer circumference is magnetized.

Compared with the magnet obtained by the conventional method, the magnet obtained by the method of the present invention is
A structure that shows superior magnetic characteristics to the magnet by the conventional method, and further has a magnetized direction in the outer peripheral portion of the magnet in the radial direction and a magnetized direction in the circumferential direction at the inner peripheral portion of the magnet by the conventional method. However, the method of the present invention requires only at least once, and it is possible to obtain a magnet having an anisotropic structure more desirable than in the past.

[Brief description of drawings]

1 to 4 are cross-sectional views of an outer die used for compression processing of an embodiment of the present invention, and FIG. 5 is a diagram schematically showing a magnetic path by multi-pole magnetization of a cylindrical magnet. 1 ... Billet, 2 ... Outer mold, 3 ... Core, 4,5 ... Punch.

Claims (2)

[Claims] 1. An outer peripheral surface is formed into an uneven shape by compressing an axially symmetrical billet made of a manganese-aluminum-carbon alloy magnet at a temperature of 530 to 830 ° C. in the axial direction. And method for manufacturing alloy magnets. 2. The method for producing an 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.