JPS61166957A - Manufacture of manganese-aluminum-carbon alloy magnet - Google Patents

Abstract

PURPOSE:To obtain anisotropic magnet exhibiting high magnetic characteristic, by press working square columnar billet of polycrystalline Mn-Al-C alloy magnet made anisotropic previously at a prescribed temp. in billet axis direction, forming outer surface to circumferential shape and magnetizing the outer circumference. CONSTITUTION:Columnar billet of well-known Mn-Al-C magnet alloy is extruded at 530-830 deg.C range to round rod, and it is machined to (2n+2) square column (n=1, 2, 3,...) shape, e.g. regular square column billet 1. The billet 1 is press worked in axis direction thereof at 530-830 deg.C by using an outer mold 2 and punches 3, 4 to form outer surface of the billet 1 to circumferential state, and anisotropic structure suitable for outer circumferential magnetization is obtd. by shape variation of the billet 1. Next, outer circumference magnetization of 4 poles is applied to billet after press working to obtain anisotropic magnet exhibiting high magnetic characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a permanent magnet. More specifically, it relates to a method for manufacturing polycrystalline manganese-aluminum-carbon (Mn-A fl-C) alloy magnets, particularly for manufacturing high-performance Mn-A I2-C alloy magnets for multipolar magnetization. It is about the method.

(Prior art) Mn-A Q-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, Ll, regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element. Multi-element alloy magnets containing three elements containing no additional elements other than impurities and four or more elements containing a small amount of additional elements are known, and these are collectively referred to as magnets.

Further, as a method for manufacturing this Mn-A Q-C alloy magnet, there is known a method including a warm plastic working process such as warm extrusion process in addition to the method using casting and heat treatment. In particular, the latter method is known as a method for producing anisotropic magnets having excellent properties such as high magnetic properties, mechanical strength, weather resistance, and machinability.

The manufacturing method of the Mn-A Q-C alloy magnet for multipolar magnetization is a 5-isotropic magnet, a compression process, a uniaxially anisotropic multi-magnet obtained by a known method such as warm extrusion process, etc. Crystal M
n-A Q-C alloy magnet subjected to warm free compression processing in the anisotropic direction (Japanese Patent Laid-Open No. 119762/1983)
, and pre-anisotropic polycrystalline Mn-A Q-
Various types of plastic working that apply compressive strain in the axial direction of a hollow billet made of a C-based alloy magnet (for example, JP-A-58-182206 to 182208)
It has been known.

(Problems to be Solved by the Invention) The shape of a multipolar magnetized magnet is generally a cylindrical body, and the main magnetization is as shown in FIG. 3. FIG. 3 schematically shows the formation of a magnetic path inside the magnet when the outer peripheral surface of the cylindrical magnet is magnetized with multiple poles. Such magnetization is herein referred to as outer circumferential magnetization.

The previously anisotropic polycrystalline Mn-A n-
In magnets obtained by various types of plastic working that apply compressive strain in the axial direction of a hollow billet made of a C-based alloy magnet, when the above-mentioned outer periphery magnetization is applied, local magnetization occurs in the direction along the magnetic path. However, when looking at the whole, the anisotropy is not in the desired direction. In addition, the outer circumference of the cylindrical magnet is made anisotropic in the radial direction by the known method described above,
In the inner circumference, an anisotropic structure is obtained in the circumferential direction (chord direction), but as the magnetic path changes from the radial direction to the circumferential direction (chord direction), an anisotropic structure along that direction is obtained. Instead, it is necessary to perform plastic working at higher temperatures two or more times.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the method for manufacturing a manganese-aluminum-carbon alloy magnet of the present invention uses polycrystalline Mn-A I2- which has been made anisotropic in advance. (2n+2) prismatic column (n=t, L3y...) made of C-based alloy magnet
...)-shaped billet is compressed in the axial direction of the billet, and the outer circumferential surface of the billet is shaped into a circumferential surface by this compression process.

(Function) By this method, that is, by shaping the outer peripheral surface of the billet into a circular shape by compression processing.

When the outer periphery magnetization shown in FIG. 3 is applied, anisotropy can be achieved along the magnetic path, and an anisotropic magnet exhibiting high magnetic properties can be obtained.

(Example) The present invention uses polycrystalline Mn-A Q-
(2n+2) prismatic column (n=1.2,
3. ......) shaped billet, 530 to 83
By compressing the billet in the axial direction at a temperature of 0°C.

The outer peripheral surface of the billet is formed into a circular shape.

That is, a known Mn-A n-C magnet alloy, for example, 68 to 73% by mass of An and (1/10 Mn-6
, 6) or 1/3Mn-22, 2) Polycrystalline material made anisotropic by subjecting an alloy consisting of mass% C and the balance AQ to plastic working such as extrusion in a temperature range of 530 to 830°C. A Mn-AμmC alloy magnet can be obtained. Typical examples of the above magnets include a uniaxially anisotropic magnet with an easy magnetization direction in the extrusion direction, which is obtained when the plastic working described above is used as an extrusion process, and a magnet that is subjected to free compression processing in the extrusion direction after the extrusion process. There are planar anisotropic magnets obtained by (2n+2) prismatic column (n=1,2,3.-...
・By compressing a )-shaped billet in the axial direction of the billet so that the outer peripheral surface of the billet becomes circular, a magnet that exhibits high magnetic properties when magnetized at the outer periphery as shown in Fig. 2 is obtained. 6. When the billet is made of a polycrystalline Mn-A Q-C alloy magnet (-axis anisotropic magnet) having an easy magnetization direction in the axial direction, the axial direction in the compression process can be The compressive strain needs to be the absolute value of the logarithmic strain, which is O.OS or more. This is because the billet before compression processing is anisotropic in the direction of applying compressive strain, and a compressive strain of at least 0.05 is required for the structure to change so that it exhibits high magnetic properties when magnetized on the outer periphery. It is.

The billet has an easy magnetization direction parallel to a plane perpendicular to the axial direction, is magnetically isotropic within the plane, and is within a plane containing a straight line parallel to the axial direction and the plane. In the case of an anisotropic polycrystalline Mn-A Q-C alloy magnet (planar anisotropic magnet), the billet before compression processing already has all the shapes in the plane including the radial and chordal directions. However, by applying the compression process of the present invention, it is possible to obtain a magnet that exhibits high magnetic properties in the outer periphery magnetization.

The compression process described above does not necessarily have to be continuous compression process, and may be divided into multiple times. In addition, although the case of a -axis anisotropic magnet and a plane anisotropic magnet is shown as the above-mentioned billet, magnets having an easy magnetization direction in the radial direction, magnets having an easy magnetization direction in the circumferential direction, etc. may also be used. This means that the Mn-A 2-C alloy for magnets is subjected to some kind of plastic working in a predetermined temperature range.

An example of the above-described compression processing of the present invention will be described with reference to FIG. 1, assuming that the shape of the billet is a prism (in the case of n=1). FIG. 1(a) shows a cross-sectional view of the billet before compression processing, viewed from the axial direction. Reference numeral 1 denotes a square prism-shaped billet, and 2 denotes an outer mold for shaping the outer peripheral surface of the billet (in this case, since the billet is a solid body, the side surface) into a circular circumferential surface by compression processing. FIG. 1(b) is a sectional view taken in a direction perpendicular to FIG. 1(a). 3 and 4 are punches used to compress billet 1. Set the billet 1 in the state shown in Fig. 1, and use punches 3 and 4 to r-t?
'7) "01°°°l + 12 mm 98 ・The cross-sectional area of the rut 1 gradually increases until the side surface of the billet and the inner surface of the outer mold 2 come into contact. If compression processing is performed to this point, the billet The side surface is almost a circumferential surface.

In this case, the maximum size of the billet before compression processing is the size whose cross section is a square inscribed in the inner circle of the outer mold 2. In that case, the compression process is performed with a part of the outer peripheral surface (in this case, the side surface) of the billet 1 already constrained by the inner surface of the outer mold 2 before the compression process.

In this example, the billet is a solid body, but the billet may be a hollow body.

In the above example, the shape of the billet changes from a regular square prism to a substantially cylindrical shape.・These changes result in an anisotropic structure suitable for outer circumferential magnetization.

During the compression processing process, the portion where the outer circumferential surface is restrained earliest (the portion corresponding to the corner of the prism of the billet before processing) becomes a portion with an easy magnetization direction in the chord direction.

The part where the outer peripheral surface is finally restrained or the part where the outer peripheral surface is not restrained until the end (the central part of one plane of the side surface of the billet 1 before processing and the part furthest from the inner surface of the outer mold 2) is the radial direction. It has an easy magnetization direction. The portion between them is a portion where the direction of easy magnetization changes sequentially from the radial direction to the chordal direction. In this way, the shape of the billet 1 before compression processing can be determined depending on how many kinds of magnets are to be used in the outer periphery magnetization. That is, in the example described above, since it was a regular square prism, it had an anisotropic structure suitable for quadrupole magnetization. (
2n+2) It is a prismatic billet.

As mentioned above, the shape of the billet must be an even number of polygonal prisms, and when n = 1, it is for 4 poles, when n = 2, it is for 6 poles, etc. The smaller n is, the clearer the anisotropic structure according to the position described above is, but as n becomes larger, it becomes less clear.

(2n+2) prismatic column (n=1.2, 3...
The cross section of the billet shaped like ・・・・・・) is geometrically accurate (
2n+2) It does not have to be a square shape, and there is no problem even if there is some chamfering.

Polycrystalline Mn- whose billet has an easy magnetization direction in the axial direction
In the case of an AQ-C alloy magnet, as described above, the compressive strain needs to be 0.05 or more in terms of the absolute value of the logarithmic strain. However, in actual applications, if you want to keep a part of the magnet in the uniaxial anisotropy and maintain the easy magnetization direction, you can constrain the outer circumferential surface of a part of the billet to create an area where no compressive strain is applied locally. You can also use the method of making .

As described in the above example, one aspect of the present invention is that when compressing a billet in the axial direction, the outer circumferential surface of the billet is compressed using a mold or the like so that the outer circumferential surface of the billet becomes a circular surface. A magnet having an anisotropic structure that exhibits high magnetic properties when magnetized is obtained.

Regarding the possible temperature range of compression processing as mentioned above,
Processing was possible in the temperature range of 530 to 830°C, but at temperatures exceeding 780°C, the magnetic properties deteriorated considerably. A more desirable temperature range was 560 to 760°C.

Next, more specific embodiments of the present invention will be described.

Example 1 69.5% by mass (hereinafter simply expressed as %) of Mn in the blending area
, 29.3% II, 0.5% C and 0.7% Ni were melted and cast to produce a cylindrical billet with a diameter of 60 m and a length of 50+ am. This billet was held at 1100° C. for 2 hours, and then heat-treated by allowing it to cool to room temperature.

Then, through lubricant, at a temperature of 720°C, a diameter of 45rra
Extrusion processing was performed up to. Further through lubricant 68
Extrusion processing up to a diameter of 28 aa was carried out at a temperature of 0°C.

This extruded rod was cut to a length of 20 m and machined to produce a regular square prism billet with a negative side of 18 m and a length of 20 cm.

This billet was compressed using the mold shown in Figure 1.6 In Figure 1, the inner diameter of the outer mold 2 was 30 mm.
■It is. Using a mold like this, the height was 9.2 mm.
Compression processing was performed to +.

After compression processing, the billet was cut to a diameter of 29 m, and
The outer circumference of the pole was magnetized. The magnetization was pulsed at 1500V using a 2000μF oil capacitor. The surface magnetic flux density of the outer peripheral surface was measured using a Hall element. For comparison, a cylindrical billet with a diameter of 23 mm and a height of 20+ m was heated to 680°C.
Free compression processing was performed in the axial direction of the cylinder at a temperature of . The height of the billet after compression processing was 9.2 mm. The processed billet was a planar 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 is approximately 1.6 of that of the one-plane anisotropic magnet.
It was double that.

Example 2 A square prism billet with a side of 18+m and a length of 20mm obtained in Example 1 was cut to create a square cavity with a side of 8m inside to produce a hollow billet. This billet was compressed using a mold shown in FIG. The dimensions of each part of the outer mold 2 are the same as those shown in FIG. 5 is a core, and the length of the negative side is 8 m.

Using such a mold, compression processing was performed up to a height of 8 m.

After compression processing, the billet is cut to an outer diameter of 29m+,
When the outer periphery was magnetized in the same manner as in Example 1 and the surface magnetic flux density was measured, the surface magnetic flux density value was almost the same as that of the magnet obtained by the method of the present invention obtained in Example 1.

The magnets obtained by the method of the present invention obtained in Example 1 and Example 2 are the results of magnetic torque measurement.

As mentioned above, the direction of easy magnetization is along the chordal direction in the part of the billet before compression processing, along the radial direction in the middle,
It was found that there was a continuous change between them from the radial direction to the chordal direction (circumferential direction).

(Effects of the Invention) According to the present invention, as described in the examples, a (2n+2) prismatic column (n=1°2.3
．． )-shaped billet is subjected to compression processing in the axial direction of the billet, and the outer circumferential surface of the billet is shaped into a circumferential surface by this compression processing, and the outer circumference is magnetized. A magnet exhibiting high magnetic properties is obtained.

When compared with magnets obtained by known methods, the magnets obtained by the method of the present invention have the following characteristics:
It exhibits better magnetic properties than magnets produced by known methods, and furthermore, by known methods, the outer periphery of the magnet has an easy magnetization direction in the radial direction, and the inner periphery has an easy magnetization direction in the circumferential direction (chord direction). In order to obtain a structure having a structure having an anisotropic structure, it is necessary to carry out plastic working at least twice, but the method of the present invention has the advantage that a magnet having a more desirable anisotropic structure can be obtained by performing plastic working at least once.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a cross-sectional view and a vertical cross-sectional view of a mold used in compression processing according to the first embodiment of the present invention, respectively;
Fig. 2 is a cross-sectional view of a mold used in compression processing according to the second embodiment of the present invention, and Fig. 3 shows the magnetic path inside the cylindrical magnet when multipolar magnetization is applied to the outer peripheral surface of the cylindrical magnet. FIG. 3 is a diagram schematically showing the formation. 1... billet, 2... outer mold, 3,4
... Punch, 5 ... Core. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 1 (b) Figure 2 Figure 3~

Claims (4)

[Claims] (1) (2n+2) prismatic (n
A billet having a shape of A method for producing a manganese-aluminum-carbon alloy magnet, the method comprising forming it into a shape. (2) the billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction;
The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim (1), wherein the compressive strain is 0.05 or more as an absolute value of the logarithmic strain. (3) A plane in which the billet has an easy magnetization direction parallel to a plane perpendicular to the axial direction, is magnetically isotropic within the plane, and includes a straight line parallel to the axial direction and the plane. Polycrystalline manganese-aluminum is anisotropic within
A method for producing a manganese-aluminum-carbon alloy magnet according to claim (1), characterized in that the magnet is made of a carbon alloy magnet. (4) The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim (1), wherein the compression processing is performed with a part of the outer circumferential surface of the billet being restrained. .