JPH0311527B2 - - Google Patents

Description

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

Conventional structure and problems Mn-Al-C alloy magnets are mainly composed of face-centered tetragonal (τ phase, Ll ₀ type regular lattice), which is a ferromagnetic phase, and C is an essential constituent element. There are known ternary alloy magnets that contain no additive elements other than impurities, and multi-element alloy magnets that include quaternary or higher alloy magnets that contain small amounts of additive elements, and these are collectively referred to as magnets.

Furthermore, as a manufacturing method for this Mn--Al--C alloy magnet, there is known a method that includes a warm plastic working process such as warm extrusion, in addition to the method of casting and heat treatment. Especially the latter has high magnetic properties, mechanical strength,
It is known as a method for producing anisotropic magnets that have excellent properties such as weather resistance and machinability.

Methods for producing multipolar magnetized Mn-Al-C alloy magnets include isotropic magnets, compression processing, and uniaxially anisotropic polycrystals obtained in advance by known methods such as warm extrusion processing. It is known that Mn--Al--C alloy magnets are subjected to warm free compression processing in an anisotropic direction (combined processing method).

Compression processing provides high magnetic properties in the radial direction, but a relatively large processing rate is required, non-uniform deformation may occur, and the presence of undeformed bands is unavoidable. There are problems such as: With the combined processing method, high magnetic properties are obtained in all directions within the plane, including the radial and chordal directions, with small compressive strain. The magnet obtained by the composite processing method has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and includes a line perpendicular to the plane and a straight line parallel to the plane. It has a structure that is anisotropic in a plane (hereinafter, such a magnet will be referred to as a plane anisotropic magnet).

The shape of a multipolar magnetized magnet is generally a cylindrical body, and the main magnetization methods include magnetization as shown in FIGS. 1 and 2. FIG. 1 schematically shows the formation of a magnetic path (indicated by a broken line) inside the cylindrical magnet when the outer periphery of the cylindrical magnet is magnetized with multiple poles. Similarly, FIG. 2 shows a case where the inner circumference is multipole magnetized.
In this specification, the magnetization shown in FIG. 1 is referred to as outer circumference magnetization, and the magnetization shown in FIG. 2 is referred to as inner circumference magnetization.

As shown in Figure 2, in internal magnetization, the magnetic path runs along the radial direction at the inner periphery of the magnet, and along the chordal direction at the outer periphery. It can be said that this is not appropriate.As mentioned above, the shape of a multipolar magnetizing magnet is generally a cylindrical body, that is, a hollow body. The magnet obtained by the above-described compression processing method and composite processing method is a solid body (for example, a cylindrical body), and the manufacturing process of the magnet requires drilling after this.

Furthermore, since the above-mentioned compression processing method and composite processing method have a free compression processing step,
Assuming that the workpiece is a cylinder, if the ratio L ₀ /D ₀ between its diameter D ₀ and length L ₀ is too large, a problem will arise in which it will break due to buckling. This results in a restriction that the ratio L/D between the diameter D and length L of the workpiece after processing cannot be made too large. Therefore,
In order to obtain a long magnet (large L/D), it was necessary to stack several magnets. For example, as mentioned above, Mn-Al-C alloy magnets are
Due to its excellent mechanical strength and machinability, it can be used as a single rod for long outer circumferential magnetization, but with conventional manufacturing methods, Since it was not possible to obtain long magnets, it was necessary to process Mn-Al-C alloy magnets into cylinders and stack them together.

Purpose of the Invention As described above, the present invention makes it possible to simplify the drilling process of a magnet after plastic working, to obtain a magnet with a longer length than a method having a free compression process, and to have a planar anisotropic structure. It is an object of the present invention to provide a method for manufacturing a high-performance multi-pole magnetized Mn-Al-C alloy magnet having a structure other than that described above.

Structure of the Invention The present invention provides polycrystalline Mn that has been anisotropically made in advance.
- A solid body made of an Al-C alloy magnet, for example a cylindrical billet, is heated at a temperature of 530 to 830°C so that the cross-sectional shape of the hollow part of the bearing part, that is, the part that accommodates the billet after extrusion processing, is hollow. Extrusion processing is performed using a die in which the opening area of the container part, that is, the part that accommodates the billet before extrusion processing is smaller than the opening area of the bearing part, and the extrusion processing is performed with the axial direction of the solid body parallel to the extrusion direction. The method is characterized in that compressive strain is applied to the billet in the extrusion direction by extrusion processing. Furthermore, the present invention is characterized in that a portion of the billet that has been subjected to the extrusion process described above is subjected to a compression process in a direction parallel to the extrusion direction.

Since the cross-sectional shape of the hollow portion of the bearing portion is hollow, the solid billet becomes a hollow billet after extrusion processing.

The present invention changes the magnet structure into an anisotropic structure suitable for multipolar magnetization by extrusion processing using a die in which the opening area of the container part is smaller than the opening area of the bearing part, without using a free compression process. .

Furthermore, by compressing a portion of the extruded billet in a direction parallel to the extrusion direction, it is changed into an anisotropic structure more suitable for outer or inner circumference magnetization.

Description of Examples Known Mn-Al-C alloys for magnets, e.g. 68~
73% by weight (hereinafter simply expressed as %) of Mn and (1/10
Mn−6.6) to (1/3Mn−22.2)% C and balance Al
An anisotropic polycrystalline Mn-Al-C alloy magnet can be obtained by subjecting an alloy consisting of the following to plastic working such as extrusion processing in a temperature range of 530 to 830°C. Typical examples of the magnet include a uniaxially anisotropic magnet having an easy magnetization direction in the extrusion direction, which is obtained when the plastic working is performed by extrusion, and the above-mentioned planar anisotropic magnet.

The solid billet made of the above-mentioned anisotropic polycrystalline Mn-Al-C alloy magnet has a hollow cross-sectional shape of the bearing part, and the opening area of the container part is the opening area of the bearing part. By using a smaller die and extruding with the axial direction of the solid body parallel to the extrusion direction, compressive strain is applied to the billet in the extrusion direction, thereby making it possible to magnetize the outer or inner circumference. A magnet with high magnetic properties can be obtained by polar magnetization.

Here, the container section refers to a section that accommodates a billet before extrusion processing, and the bearing section refers to a section that accommodates a billet that has undergone extrusion processing. In addition, the opening area of the container section is the cross-sectional area of the hollow part of the container section when the die is cut through the container section perpendicular to the extrusion direction, and the opening area of the bearing section is the cross-sectional area of the hollow section of the container section when the die is cut through the extrusion direction through the bearing section. This is the cross-sectional area of the hollow part of the bearing part when cut in the direction of the bearing part. Further, the cross-sectional shape of the hollow portion of the bearing portion is the shape from which the opening area of the bearing portion is determined. In other words,
The opening area of the bearing portion is the cross-sectional shape of the hollow portion of the bearing portion. The fact that the hollow part of the bearing part is hollow means that the bearing part has an appropriate length in the extrusion direction, so that the hollow part of the bearing part is a hollow body.

As mentioned above, in order to apply compressive strain in the extrusion direction of the billet using a die in which the opening area of the container part is smaller than the opening area of the bearing part, it is necessary to move the billet parallel to the extrusion direction during extrusion processing, as described later. It is necessary to apply pressure from two directions. For example, compressive strain can be applied in the extrusion direction by applying pressure to the billet from two directions parallel to the extrusion direction and moving the billet from the container section to the bearing section under compressive load.

When the billet is made of a polycrystalline Mn-Al-C alloy magnet (uniaxially anisotropic magnet) having an easy magnetization direction in the axial direction of the solid body, the compressive strain is 0.05 as the absolute value of the logarithmic strain. The above is necessary.
This is because, as detailed in the examples, the billet before extrusion is anisotropic in the compression direction, and a compression of at least 0.05 is required to change the structure to a magnet with high magnetic properties in multipole magnetization. This is because strain is required.

The billet is a polycrystalline Mn-Al- having an easy magnetization direction parallel to a plane perpendicular to the axial direction of the solid body.
In the case of C-based alloy magnets (planar anisotropic magnets), the billet before extrusion is, as mentioned above,
It exhibits high magnetic properties in all directions within the plane, including the radial direction and chordal direction, but by applying the extrusion process described above, it is possible to obtain a magnet that exhibits high magnetic properties in multipolar magnetization. .

The billet, which has been extruded using a die in which the opening area of the container part is smaller than the opening area of the bearing part, is further compressed by compressing a part of the billet in a direction parallel to the extrusion direction. The magnetic properties in the radial direction are improved in the areas treated with .

An example of the above-mentioned plastic working will be explained assuming that the shape of the billet is a cylinder. The first method is to use a cylindrical billet with the axial direction of the cylinder parallel to the extrusion direction, the cross-sectional shape of the hollow part of the bearing part being hollow, and the opening area of the container part being smaller than the opening area of the bearing part. This method involves extrusion processing and applying compressive strain in the extrusion direction.

FIG. 3 shows a cross-sectional view of a portion of the die. Third
Figure 3a shows the state before extrusion, and Figure 3b shows the state after extrusion. 1 is billet.
Reference numerals 2 and 3 denote die constituent members, which have a structure that does not move relative to each other during extrusion processing, and are fixed. 4 and 5 are punches, each of which is attached to a hydraulic cylinder or the like.

The part 6 is a container part, which accommodates the billet before extrusion processing. The part 7 is a bearing part, which accommodates the billet after extrusion processing. The opening area of the container part is the cross-sectional area of the cavity 6 (perpendicular to the extrusion direction), which is almost the same as the cross-sectional area of the billet at a, and the opening area of the bearing part is the cross-sectional area of the cavity 7 (perpendicular to the extrusion direction). vertically) and almost coincides with the cross-sectional area of the billet at b.

In FIG. 3, since both the container part and the bearing part are circular with the extrusion shaft as the center, to paraphrase the above, the opening area of the container part is the area of a circle whose diameter is the diameter of the container part. Similarly, the opening area of the bearing section is a ring-shaped area defined by the outer diameter and inner diameter of the bearing section, and is hollow. For example, if the diameter of the container part is 20 mm, the outer diameter of the bearing part is 32 mm, and the inner diameter is 15 mm, the opening area of the container part is about 314 mm ² and the opening area of the bearing part is about 627 mm ² . Further, the cross-sectional shape of the hollow portion of the bearing part is a ring shape with an outer diameter of 32 mm and an inner diameter of 15 mm. In other words, the fact that the hollow part of the bearing part is hollow means that when the billet is housed in the bearing part and cut perpendicularly to the extrusion direction, as shown in FIG. There is a billet 1 on the outside of it, and a die 3 on the outside of it.

The extrusion method will be explained using FIG. 4. The structure of the dice etc. shown in FIG. 4 is the same as that of FIG. 3. First, as shown in a, the cylindrical billet 1' is housed in the bearing part. By pressurizing the billet using the punch 5, it becomes as shown in b. Next, as shown in c, the billet 1 is accommodated in the container part 6, and the billet is moved in the direction from the container part toward the bearing part while being pressurized by the punches 4 and 5, so that the state shown in d is obtained. When the billet 1' housed in the bearing section is taken out and a new billet is housed in the container section 6, the state shown in c is obtained. Thereafter, extrusion processing is performed by repeating this process.

The above steps a to b are not extrusion processing steps of the present invention, because the opening area of the container part is smaller than the opening area of the bearing part, and in addition, in the die shown in Fig. 4, the opening area increases sequentially from the container part to the bearing part. Since the conical part 8 has a conical part 8 extending to the bottom, this step is to fill the hollow part of the conical part mainly with billet.

As described above, by moving the billet from the container section toward the bearing section while pressurizing the billet with the punches 4 and 5, the billet is subjected to compressive strain in the extrusion direction.

The second method is a method in which the billet obtained in the first method (the billet subjected to the extrusion process described above) is further compressed into a portion of the billet in a direction parallel to the extrusion direction. An example is shown in FIG. FIG. 5 is a sectional view of the mold, where a shows the state before processing and b shows the state after processing. In FIG. 5, the punch 10 is attached to a hydraulic cylinder or the like, and the lower die 12 is fixed to a surface plate or the like. First, the billet 9 is placed on the lower mold 12, and the restraining mold 11 is set so as to cover the billet 9 (as shown in a). The state shown in a is that the punch 10 is placed in the restraining mold 11 and brought closer to the billet 9. The processing is performed by pressurizing only the inner circumference of the billet 9 with the punch 10, and the state shown in b is obtained. Become. In this case, 11 and 12 should not move relative to each other.
It is necessary to fix it to 12. Note that the billet 9 is a billet subjected to the extrusion process described above.
In the above example, a part of the billet was used as the inner periphery, but other methods include making it the outer periphery, such as reversing the parts to be machined and the parts not to be machined in the above example. For each, you can choose the appropriate part for each.

Regarding the possible temperature range of plastic working as mentioned above, it was possible to perform it in the temperature range of 530 to 830℃, but
At temperatures above 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.

A cylindrical billet with a diameter of 60 mm and a length of 60 mm was created by melting and casting a mixture of 69.5% Mn, 29.3% Al, 0.5% C, and 0.7% Ni. 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 35 mm was performed at a temperature of 720°C via a lubricant. Furthermore, extrusion processing up to a diameter of 21 mm was performed at a temperature of 680°C using a lubricant.

This extruded rod was cut to a length of 40 mm and machined to produce several cylindrical billets with a diameter of 20 mm and a length of 40 mm. Next, extrusion processing was performed at a temperature of 680° C. using a die as shown in FIG. 3 through a lubricant.
The extrusion method is the above-mentioned method explained using FIG. In addition, the diameter of the container part of the die is 20 mm.
The outer diameter of the bearing part is 30mm, the inner diameter is 10mm,
x is 20mm. During extrusion, that is, in Fig. 3, four billets existing in the conical part 8 were prepared, each billet was cut into a thickness of 1 mm perpendicular to the extrusion direction, and the billets were given the same compressive strain. They were superimposed to prepare a sample.

A cube with a side of about 4 mm was cut out from this sample,
We performed magnetic measurements. Note that each side was parallel to the axial direction, radial direction, and chord direction. Figure 6 shows the values of the residual magnetic flux density Br versus the compressive strain _εz . As shown in FIG. 6, when ε _z is 0.05, Br in the chordal direction becomes larger than Br in the axial direction, and as ε _z becomes even larger, Br in the chordal direction further increases. As can be seen from this figure, the change in the direction of easy magnetization from the axial direction to the chordal direction progresses significantly in the range of ε _z up to 0.05.

Furthermore, the extruded billet (outer diameter 30 mm, inner diameter 10 mm, length 20 mm) after the extrusion process according to the present invention was machined to create a cylindrical magnet with an outer diameter of 28 mm and an inner diameter of 14 mm, as shown in Figure 2. The inner periphery is multi-pole magnetized. The number of poles was 4, and a 2000μF oil capacitor was used for magnetization, and pulse magnetization was performed at 1500V.
The surface magnetic flux density of the inner circumference was measured using a Hall element.

For comparison, the extruded rod of 21 mm was cut into a length of 20 mm and machined to produce a cylindrical billet with a diameter of 20.5 mm and a length of 20 mm. Apply this via lubricant
Free compression was performed in the axial direction of the cylinder at a temperature of 680°C. The length of the billet after processing was 10 mm. The processed billet was a planar anisotropic magnet, which was cut into a cylinder in the same manner as described above, and the surface magnetic flux density after magnetization 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 1.2 times that of both anisotropic magnets.

Next, the planar anisotropic magnet produced under the same conditions as above was cut to a diameter of 20 mm, and extruded under the same conditions as above. Using four extruded billets, we cut them into outer diameter 28mm, inner diameter 14mm, and length 20mm.
When a cylindrical magnet was prepared, magnetized and measured in the same manner as described above, there was no significant difference in characteristics from the magnet obtained earlier by the method of the present invention.

Next, a billet subjected to the extrusion process of the present invention described above (before the extrusion process of the present invention is a magnet made axially anisotropic), the dimensions of the billet are an outer diameter of 30 mm, an inner diameter of 10 mm, and a length of 20 mm. ) was machined to an outer diameter of 29 mm,
A cylindrical billet with an inner diameter of 11 mm and a length of 10 mm was prepared, and only the inner peripheral portion of the billet was compressed in the axial direction of the cylinder at a temperature of 680° C. in the state shown in FIG. The diameter of the punch 10 shown in Figure 5 is 18
mm, and was compressed by aligning the center of the billet with the center of the punch. The length of the inner circumference of the billet after processing was 8 mm. This billet was machined to produce a cylindrical magnet with an outer diameter of 28 mm and an inner diameter of 14 mm. The surface magnetic flux density after magnetization was measured in the same manner as above.

When compared with the value of the above-mentioned planar anisotropic magnet, the value of the surface magnetic flux density of the locally compressed magnet was about 1.4 times that of the planar anisotropic magnet.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a magnet that exhibits excellent magnetic properties in multipolar magnetization. Furthermore, the method of the present invention makes it possible to simplify the hole-drilling process after plastic working, and also to manufacture a magnet with a long length, compared to the case of using a composite working method or the like.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the formation of a magnetic path inside the magnet when the outer circumference of a cylindrical magnet is magnetized with multiple poles. A diagram schematically showing the formation of a magnetic path inside a magnet when magnetized, FIG. 3 is a cross-sectional view of a part of a mold showing an example of the extrusion process of the present invention, and FIG. 4 is a diagram showing the extrusion method. FIG. 5 is a cross-sectional view of a part of the mold showing an example of plastic working of the present invention, and FIG. 6 shows the residual magnetic flux density Br versus compressive strain ε _z in the example. It is a figure showing a change. 1, 1'... billet, 4, 5... punch, 6
... Container part, 7 ... Bearing part, 8 ... Conical part, 9 ... Billet, 10 ... Punch, 1
1...Restriction mold, 12...Lower mold.

Claims (1)

[Claims] 1. A solid billet made of a pre-anisotropic polycrystalline manganese-aluminum-carbon alloy magnet is heated at a temperature of 530 to 830°C so that the cross-sectional shape of the hollow part of the bearing part is hollow. Using a die in which the opening area of the container part is smaller than the opening area of the bearing part, extrusion processing is performed with the axial direction of the solid body parallel to the extrusion direction, and the extrusion direction of the billet is Manganese-aluminum- characterized by imparting compressive strain to
Manufacturing method for carbon-based alloy magnets. 2. The billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the solid body, and the compressive strain is applied to an absolute value of logarithmic strain of 0.05 or more. A method for producing a manganese-aluminum-carbon alloy magnet according to scope 1. 3. The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the solid body, is magnetically isotropic within the plane, and has a direction perpendicular to the plane and the specific plane. A method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing straight lines parallel to the plane. 4. A solid 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, and the cross-sectional shape of the hollow part of the bearing part is hollow, and the shape of the container part is Using a die whose opening area is smaller than that of the bearing part, extrusion processing is performed with the axial direction of the hollow body parallel to the extrusion direction, and after applying compressive strain in the extrusion direction of the billet by the extrusion processing. A method for producing a manganese-aluminum-carbon alloy magnet, further comprising subjecting a portion of the billet to compression processing in a direction parallel to the extrusion direction. 5. The billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the solid body, and the compressive strain is applied to an absolute value of logarithmic strain of 0.05 or more. A method for producing a manganese-aluminum-carbon alloy magnet according to Scope 4. 6. The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the solid body, is magnetically isotropic within the plane, and has a direction perpendicular to the plane and the specific plane. 5. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 4, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing a straight line parallel to .