JPS62247055A - Manufacture of manganese-aluminum-carbon alloy magnet - Google Patents

Abstract

PURPOSE:To obtain the titled alloy magnet showing high magnetic properties, by subjecting a billet of the titled polycrystalline alloy magnet which is previously made anisotropic to compression working so that compressive strain is higher in the outside peripheral part than in the inside peripheral part and further by subjecting the outside peripheral surface of the billet to compression forming into recessed and projecting shape. CONSTITUTION:The billet 1 of axially symmetric shape composed of the polycrystalline Mn-Al-C alloy magnet which is previously made anisotropic is subjected to compression working in the axial direction by the use of a punch 2 having a shape capable of preventing the center from spreading at the time of the compression working of the billet 1. At that time, the temp. is regulated to 530-830 deg.C. As the compression working proceeds, the outside peripheral surface of the billet 1 is nearly brought into contact with the internal surface of an outer die 4, while the inside peripheral surface is brought into contact with the surface of the punch 2. Then, further compression working is applied to the billet 1 by means of the punch 2, so that outside peripheral surface of the billet 1 is formed into recessed and projecting shape. In this way, the Mn-Al-C alloy magnet which shows high magnetic properties when subjected to outside peripheral magnetization can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing permanent magnets, and in particular to a method for manufacturing permanent magnets, in particular Mn magnets for multipolar magnetization using polycrystalline manganese-aluminum-carbon (Mn-1-C) alloy magnets. -Relates to a method for manufacturing a MLC alloy magnet.

Conventional technology Mn-Ml-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, Lo-type regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element, with no other impurities. Multi-component alloy magnets are known, including ternary alloy magnets that do not contain additive elements and quaternary or higher alloy magnets that contain additive elements.

In addition to casting and heat treatment, there are manufacturing methods that include plastic working processes such as extrusion, and the latter in particular has excellent properties such as high magnetic properties, mechanical strength, weather resistance, and machinability. It is known as a method for manufacturing anisotropic magnets.

In addition, methods for manufacturing multipolar magnets using Mn-Ml-1 alloy magnets include isotropic magnets, compression processing, and uniaxial anisotropy obtained by known methods such as extrusion processing. Polycrystalline M
An n-mul l-0 alloy magnet subjected to free compression processing in an anisotropic direction (for example, JP-A-66-119762)
, by various plastic working methods that apply compressive strain in the axial direction of a hollow billet made of a polycrystalline Mn-Ml-C alloy magnet that has been made anisotropic in advance (for example, JP-A-58
-182205. 58-182207゜58-18
No. 2208), and those in which a hollow billet made of a polycrystalline Mn-M1-0 alloy magnet that has been made anisotropic in advance and a billet made of a metal material are simultaneously compressed (for example, JP-A No. 2208), No. 59721) is known.

Problems to be Solved by the Invention Multi-pole magnetizing magnets are generally cylindrical in shape, and the main magnetization is as shown in FIG. Figure 6 schematically shows the formation of a magnetic path inside the magnet when the outer peripheral surface of a cylindrical magnet is magnetized with multiple poles. Pre-anisotropic polycrystalline Mn-mul
- For magnets obtained by various types of plastic working that apply compressive strain in the axial direction of a hollow body-shaped billet made of C-based alloy magnets, when the outer periphery is magnetized, the magnets are locally magnetized in the direction along the magnetic path. However, when looking at the whole, the anisotropy is not in the desired direction. Furthermore, according to the method described above, the outer circumference of the cylindrical magnet is anisotropic in the radial direction, and the inner circumference is anisotropic in the circumferential direction (chord direction, hereinafter the same), but the magnetic path In the middle of the change from the radial direction to the circumferential direction, the structure is not anisotropic along that direction, and it is necessary to perform plastic working at a higher temperature two or more times.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention provides an axially symmetrical billet made of a polycrystalline Mn-1-C alloy magnet which has been made anisotropic in advance. The billet is compressed so that the compressive strain on the outer circumferential portion is greater than the compressive strain on the inner circumferential portion, and the outer circumferential surface of the billet is shaped into an uneven shape by the compression process.

Operation By using the method described above, that is, by compressing so that the compressive strain on the outer circumference is larger than the compressive strain on the inner circumference, and further forming the outer circumferential surface of the billet into an uneven shape by compression, the billet is produced as shown in FIG. When the outer periphery is magnetized, anisotropy can be achieved along the magnetic path, and an anisotropic magnet exhibiting high magnetic properties can be obtained.

EXAMPLE The present invention is based on polycrystalline Mn-Ml- which has been anisotropic in advance.
530 on an axially symmetrical billet made of 1 series alloy magnet.
The billet is compressed at a temperature between 830° C. and 830° C. so that the compressive strain at the outer circumferential portion is larger than that at the inner circumferential portion, and the outer circumferential surface of the billet is shaped into an uneven shape by the compression process.

The compression process described above does not necessarily have to be continuous compression process, and may be divided into multiple times.

Similar to the prior art described above, when the billet is made of a polycrystalline Mn-Al-C alloy magnet (-axis anisotropic magnet) having an easy magnetization direction in the direction of the object axis, the compression during compression processing The strain must be 0.05 or more in absolute value of logarithmic strain. This is because the billet before compression processing is anisotropic in the direction of applying compressive strain, and the change in structure that exhibits high magnetic properties in multipole magnetization requires a minimum of 0-OS.
This is because a compressive strain of .

Next, concrete examples of compression processing are divided into a method in which the outer peripheral surface of the billet is molded into an uneven shape and a method in which compression processing is performed so that the compressive strain on the outer peripheral part is larger than the compressive strain on the inner peripheral part.
The axis-symmetric shape will be explained using a cylindrical body.

First, an example of forming the outer circumferential surface of a billet into an uneven shape by compression processing will be described with reference to FIG.

Fig. 1 (+L) shows a cross section of the billet before compression processing as seen from the axial direction, 1 is a cylindrical billet made of a polycrystalline Mn-Al-C alloy magnet that has been anisotropic in advance; A punch 2 prevents the billet 1 from spreading toward the center when the billet 1 is compressed and molded. 4 is an outer mold, which is a mold for molding. FIG. 1(b) shows the state after compression processing. As shown in (b), as the compression process progresses, the diameter of the cylindrical billet 1 increases, and a part of the outer peripheral surface comes into contact with the inner surface of the outer mold 4.
By further advancing the compression process, the outer circumferential surface of the billet 1 almost comes into contact with the inner surface of the outer mold 4, while the inner circumferential surface comes into contact with the surface of the punch 2, as shown in rb>. There is no need to compress the billet 1 to the state shown in (b).
After a part of the outer circumferential surface of the outer mold 4 comes into contact with the inner surface of the outer mold 4, the compression process may be finished at an appropriate time.

In other words, unevenness may be formed on the outer peripheral surface of the billet 1.

In this case, the maximum outer diameter of the billet 1 before compression processing is a size that touches the convex portion on the inner surface of the outer mold 4.

In this case, before the compression process, the billet 1 is subjected to the compression process in a state where a part of its outer circumferential surface is already restrained by the inner surface of the outer mold 4. An example of this case is shown in FIG. FIG. 2 is a cross section similar to FIG. 1, showing the state before compression processing. In the example shown in FIG. 2, the inner peripheral surface of the billet 1 is also already in contact with the punch 2 before compression processing.

As described above, since the unevenness exists on the inner surface of the outer mold 4, the billet 1 is formed with unevenness on the outer circumferential surface after compression processing. In the compression processing process, the part where the outer circumferential surface is constrained earliest (the concave part on the outer circumferential surface of the billet 1 after processing) is the part with the easy magnetization direction in the circumferential direction, and the part where the outer circumferential surface is constrained last or until the end. The portion where the outer circumferential surface is not constrained (the convex portion on the outer circumferential surface of the billet 1 after processing) becomes a portion having an easy magnetization direction in the radial direction. The easy magnetization direction of the intermediate portion changes sequentially from the circumferential direction to the radial direction.

In other words, in FIG. 1, the direction of easy magnetization gradually changes continuously from the outer circumference of the billet 1 in a direction along the curved surface of the recess on the outer circumference of the billet 1 formed by the convex portion on the inner surface of the outer mold 4. Therefore, the number of these uneven portions may be determined depending on whether or not the outer periphery is magnetized with the same polarity. In Figure 1, there are six convex portions on the outer peripheral surface of the billet 1 after processing. It becomes the pole part in magnetization.

As described in the above example, the present invention is capable of magnetizing the outer periphery by compressing the billet in the axial direction using a mold or the like so that the outer periphery of the billet becomes uneven. A magnet having an anisotropic structure exhibiting high magnetic properties is obtained when subjected to the following steps.

Next, a specific example of compression processing so that the compressive strain on the outer circumference becomes larger than the compressive strain on the inner circumference will be explained using Fig. 4. Fig. 4 shows the direction perpendicular to Fig. 1. This shows a cross section of the state before processing when viewed from above. 1 is billet, 2.3
is the punch, and 4 is the outer mold. As shown in FIG. 4, the surfaces of the punches 2 and 3 that contact the billet 1 (punch end surfaces) are not flat surfaces but sloped surfaces. By applying pressure to the billet 1 in the axial direction using the punches 2 and 3, the billet 1 is compressed in the axial direction. The height of the outer periphery of the billet 1 after compression processing is smaller than the height of the inner periphery. In other words, the billet 1 is compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet 1 is greater than the compressive strain on the inner circumferential portion. Compressive strain refers to strain in the axial direction of billet 1.

Next, a specific example of compressing so that the compressive strain of another outer peripheral part is larger than the compressive strain of the inner peripheral part will be explained using FIG. . FIG. 6 shows a cross section before processing, similar to FIG. 4. As shown in Fig. 6, the difference from Fig. 4 is that the punch end faces of punches 2 and 3 are flat, and the height of the outer periphery of the billet 1 before compression processing is greater than the height of the inner periphery. be. After processing, the billet 1 has a substantially cylindrical shape, and the height of the outer circumferential portion of the billet 1 and the height of the inner circumferential portion of the billet 1 substantially match. In this case as well, the billet 1 is compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet 1 is greater than the compressive strain on the inner circumferential portion.

As mentioned above, by making the end face of billet 1 an inclined face or the end face of punch 2.3 an inclined face, in this particular compression process, the compressive strain at the outer circumference of billet 1 is lower than the compressive strain at the inner circumference. Compression processing can be performed in the axial direction of the billet 1 to increase its size.

Even in a combination of the above two examples, the billet 1 can be compressed in the axial direction so that the compressive strain on the outer circumferential portion of the billet 1 is larger than the compressive strain on the inner circumferential portion.

That is, this is a method of compressing the billet 1 shown in FIG. 6 using a mold consisting of the punch 2.3 and the outer mold 4 shown in FIG.

In the above example, the punch 2.3 end face or billet 1
The end surface was a sloped surface, but there were also stepped surfaces (stepped shape),
There are flat surfaces + inclined surfaces, or a combination of the above, and the end surface of the billet can be punched or punched to make it uneven. What is necessary is to compress the billet 1 in the axial direction so that the compressive strain on the outer circumference of the billet 1 is greater than the compressive strain on the inner circumference.

In the above-described specific example of the compression process, the shape of the billet 1 is cylindrical, but the same applies to a cylindrical body.

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 above 780°C, the magnetic properties deteriorated considerably. A more desirable temperature range was from seo to 760'C.

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

Example 1 (Figure 6) Blend composition: 69.6% Mn, 2J3% Mn 1.0.6
% C and O-7% N1 melted and cast, diameter 60 city,
A cylindrical billet 1 having a length of 40 mm was produced.

After holding this billet 1 at 1100°C for 2 hours, 8
After air-cooling to 00'C, holding at 600'C for 30 minutes, heat treatment was performed by cooling to room temperature.

Next, extrusion processing was performed at a temperature of 720° C. through a lubricant. Billet 1 after extrusion had a diameter of 32 mm and a length of 9801 m. The extruded rod was cut and machined to an outer diameter of 24! IIm, inner diameter 18ffll11. A billet 1 having an outer circumference length of 25fflm and an inner circumference length of 2oImm and having an inclined end surface was produced. This billet 1 has a third
Compression processing was performed at a temperature of 680°C using a lubricant using a mold consisting of punches 2 and 3 and an outer mold 4 as shown in the figure and Fig. 6! -ta. Figure 3 is a cross-sectional view of gold similar to Figure 1, (inner diameter of outer mold 4) Dk = 30m
m, XAzl 5mn+, (radius of convex part of outer mold 4)
R1=3 mm, the punch diameter is 1801 m, and there are 8 convex portions on the inner surface of the outer mold 4. 2 and 3 are punches having outer circumferential surfaces that fit together with the uneven surface of the outer mold 4, and can be moved in the vertical direction in the figure. Using such a mold, compression processing was performed until the cavity in the mold was almost completely eliminated.

After cutting the processed billet 1 to an outer diameter of 27 mm, the outer periphery was magnetized with eight poles. Magnetization was carried out using a 2000 μF oil capacitor and pulsed magnetization at 16 oOv. The surface magnetic flux density on the outer peripheral surface was measured using a Hall element.

For comparison, the extruded rod described above was cut and machined to produce a cylindrical virest having a diameter of 24 aIm and a length of 201!1 fl. This billet was subjected to free compression processing at a temperature of aso'c in the axial direction of the cylinder to a length of 2Qmfl.

After cutting the processed billet in the same manner as described above, it was magnetized and the surface magnetic flux density was measured.

Comparing the values of the surface magnetic flux density of both of the above, the value of the magnet obtained by the method of this example was about 1.7 times that of the magnet produced for comparison.

Example 2 (Figure 4) Mixture composition: 69.4% Mn, 29.3% Mn 110
．． Cylindrical billet 1 of diameter somm and length aomm (melting and casting of 6% C, O7% NIL and 0.1% Ti)
was created. This billet 1 was subjected to the same heat treatment as in Example 1. Then, through a lubricant, at a temperature of 720 °C,
Extrusion processing was performed. Bin 1 after extrusion has a diameter of 32 mm.
+nm, and the length was 98ffllll+. This extruded rod was cut and machined to have an outer diameter of 24 mm and an inner diameter of 1 mm.
Billet 1 having a length of 801 m and a length of 20 mm was produced. This billet 1 was molded into the mold shown in FIGS. 3 and 4 (each dimension is the same as the mold used in Example 1, and the inclination angle α is 1.
It is 0°. ) using a lubricant at 680'C.
Compression processing was performed at a temperature of . Processing was performed until the cavity in the mold was almost completely eliminated.

After cutting the processed billet 1 to an outer diameter of 27 mm in the same manner as in Example 1, the outer periphery was magnetized with 8 poles, and the surface magnetic flux density was measured.

For comparison, the extruded rod described above was cut and machined to produce a cylindrical billet 1 with a diameter of 24 mm and a length of 20 ml. This billet 1 was subjected to free compression processing in the axial direction of the cylinder at a humidity of 680° C. to a length of IQffllll+.

After cutting the processed billet 1 in the same manner as described above, it was magnetized and the surface magnetic flux density was measured.

Comparing the values of the surface magnetic flux density of both of the above, the value of the magnet obtained by the method of this example was about 1.7 times that of the magnet produced for comparison.

Example 3 The extruded rod obtained in Example 1 was cut and machined to an outer diameter of 24 mm.
Cylindrical billet with ff1m, inner diameter 18mm, and length 20 capes (
Billet X) was produced.

Furthermore, the same extruded rod was cut and machined to create a diameter of 23 m.
A cylindrical billet with a length of 35 mm and a length of 35 mm was prepared, and was subjected to free compression in the axial direction of the billet at a temperature of 680'C via a lubricant. The length of the billet after processing was 20 mm. After processing, the billet (planar anisotropic magnet) is cut to have an outer diameter of 24 mm, an inner diameter of 1B+11ff+, and a length of 20 mm.
A cylindrical billet (billet Y) was produced.

These billets)
Compression processing was performed at a temperature of 0°C until the cavity in the mold was almost eliminated.

After cutting the processed billet to an outer diameter of 27 inches in the same manner as in Example 1, the outer periphery was magnetized with 8 poles, and the surface magnetic flux density was measured.

For comparison, the extruded rod described above was cut and machined to produce a cylindrical billet with a diameter of 24111 m and a length of 20 m1. This billet was subjected to free compression processing in the axial direction of the cylinder up to a length of 10 mm at a temperature of 6BO"C. The processed billet was cut in the same manner as described above, and then magnetized and the surface magnetic flux density was measured.

Comparing the above surface magnetic flux density values, the value of the magnet obtained in Example 3 shows almost no difference between billet x and billet Y, and is about 1. It was 8 times more.

Example 4 The extruded rod obtained in Example 1 was cut and processed to have a diameter of 1
A billet having a length of 6m+n and a length of 20III11 was produced. This billet was compressed using a mold as shown in Figures 3 and 4 at a humidity of 680°C with a lubricant until the cavity in the mold was almost eliminated. . Here, in the center of the punch 2.3 of the mold used, there is a stepped part that fits together (φ1B of the mold used in Example 3).
The other dimensions are the same as the mold used in Example 3.

After cutting the processed billet to an outer diameter of 27 mm in the same manner as in Example 1, the outer periphery was magnetized with 8 poles, and the surface magnetic flux density was measured.

For comparison, the extruded rod described above was cut and machined to produce a cylindrical billet with a diameter of 24 mm and a length of 20111111. This billet was subjected to free compression processing to a length of 10 mm in the axial direction of the cylinder at a temperature of 680°C. After cutting the processed billet in the same manner as described above, it was magnetized and the surface magnetic flux density was measured.

Comparing the values of the surface magnetic flux density of both of the above, the value of the magnet obtained by the method of this example was about 1.7 times that of the magnet produced for comparison.

In the magnets obtained by the method of the present invention obtained in Examples 1.2.3 and 4, as a result of magnetic torque measurement, the direction of easy magnetization continuously changes from the radial direction to the circumferential direction along the surface of the recessed part, as described above. It was confirmed that

The above has only shown the composition of the Mn-Ml-C alloy magnet, but the basic composition of the Mn-Ml-C alloy magnet is the ternary system or the known composition containing additive elements other than the above. Although some differences were observed in the magnetic properties of the magnets after plastic working for the multi-component system, the above-mentioned improvement in magnetic properties was observed compared to the conventional method.

Although we have shown examples using uniaxial anisotropic magnets and planar anisotropic magnets as Mn-Ml-C alloy magnets that have been made anisotropic in advance, it is also possible to use radially anisotropic magnets, single-turn anisotropic magnets, etc. It was the same.

Further, regarding the shapes of the billet and punch end faces, although an example of an inclined surface is shown, a stepped shape, a flat surface + an inclined surface, or a combination of the above may also be used.

Effects of the Invention As is clear from the detailed explanation above, the present invention provides an axially symmetrical billet made of a polycrystalline Mn-Ml-C alloy magnet that has been made anisotropic in advance. A method for manufacturing a magnet that exhibits high magnetic properties when the billet is compressed so that it becomes larger than the compressive strain, and then the outer circumference is magnetized by forming uneven portions on the outer peripheral surface of the billet by compression processing, and the present invention Comparing the magnet produced by this method with the magnet produced by the conventional method, it was found that when the outer periphery is magnetized, it has superior magnetic properties than the magnet produced by the conventional method, and that the outer periphery of the magnet has an easy magnetization direction in the radial direction. Furthermore, in order to obtain a structure with an easy magnetization direction in the circumferential direction at the inner periphery, the conventional method required plastic working at least twice, but the method of the present invention requires only one plastic working, making it even more effective. A magnet having a desirable anisotropic structure can be obtained.

[Brief explanation of drawings]

1 to 6 are cross-sectional views of a mold part used in an embodiment of the present invention, and FIG. 6 is a diagram schematically showing a magnetic path caused by multi-pole magnetization on the outer periphery of a cylindrical magnet. 1... Billet, 2.3... Punch,
4...External shape, α...Inclination angle. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure (α) Cb) Figure 23 Figure 4 Figure 5

Claims (4)

[Claims] (1) An axially symmetrical billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance is heated at a temperature of 530 to 830°C, so that the compressive strain at the outer circumference is larger than that at the inner circumference. A method for manufacturing a manganese-aluminum-carbon alloy magnet, which comprises compressing the billet so that the billet has an uneven shape, and then molding the outer peripheral surface of the billet into an uneven shape. (2) The billet has an easy magnetization direction in the direction of the symmetrical axis, and the compressive strain during compression processing is 0.0 as the absolute value of the logarithmic strain.
A method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim (1), wherein the manganese-aluminum-carbon alloy magnet has a carbon content of 0.05% or more. (3) The billet has a direction of easy magnetization parallel to a plane perpendicular to the object axis, is magnetically isotropic within the plane, and has a straight line parallel to the direction of the object axis and the plane. A method for producing a manganese-aluminum-carbon alloy magnet according to claim (1), which is anisotropic in a plane containing the magnet. (4) The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim (1), wherein the compression processing is performed with a portion of the outer periphery of the billet being restrained.