JPS58182206A - Preparation of manganese-aluminum-carbon alloy magnet - Google Patents

Abstract

PURPOSE:To obtain a magnet having high magnetic characteristics in the diametric direction with small compressive stress by a method wherein a hollow steel piece of magnet made of alloy of polycrystalline Mn-Al-C system that has been made anisotropic is compressed in the axial direction at the preselected temperature in such a manner as to make free at least part of its internal and external peripheries. CONSTITUTION:A known alloy of Mn-Al-C system for preparing a magnet is extrusion-processed at 530-830 deg.C to obtain a uniaxial or facial anisotropic magnet. A hollow steel body 1 of the magnet is compression-processed at the temperature range of 530-830 deg.C in such a state that at least part of the internal and external peripheries thereof is set free. In the case of the uniaxial anisotropic magnet, compressive stress must be 0.05 or more at the logarithmic value. With this construction, the magnets of both the anisotropic types display high magnetic characteristics in the diametric direction and the part locally compression- processed has higher magnetic characteristics in the diametric direction, so that flaws such as uneven transformation or a permanent band can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a permanent magnet. More specifically, polycrystalline manganese-aluminum-carbon system (
The present invention relates to a method for manufacturing a Mn-A11-C alloy magnet, and provides a method for manufacturing a particularly high-performance Mn-A11-C alloy magnet for multipolar magnetization.

Mn-A/-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, LIo-type regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element, with no additives other than impurities. Multi-component alloy magnets are known, including ternary alloy magnets containing no elements and quaternary or higher alloy magnets containing a small amount of additional elements.

Furthermore, as a manufacturing method of this Mn-M1-0 alloy magnet, in addition to the method of casting and heat treatment, methods including a warm plastic working process such as warm extrusion are known. In particular, the latter is known as a method for producing anisotropic magnets having excellent properties such as high magnetic properties, mechanical strength, 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. Mn-A7! -C alloy magnets subjected to warm free compression processing in an anisotropic direction (combined processing method) are known.

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 first chord direction with small compressive strain. A magnet obtained by a composite processing method has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and has a direction perpendicular to the plane and a direction parallel to the plane. It has a structure that is anisotropic within a plane that includes straight lines (hereinafter, such a magnet will be referred to as a planar 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 to 3. FIG. 1 schematically shows the formation of a magnetic path (indicated by a broken line) inside the cylindrical magnet when the cylindrical magnet is magnetized with multiple poles in the radial direction. Similarly, FIG. 2 shows a case where the outer periphery of a cylindrical magnet is magnetized with multiple poles.

FIG. 3 shows a case where the inner circumference is multi-pole magnetized.

In this specification, the magnetization shown in FIG. 1 is referred to as radial magnetization, the magnetization in FIG. 2 is referred to as outer circumference magnetization, and the magnetization in FIG. 3 is referred to as inner circumference magnetization.

As shown in FIG. 1, in radial magnetization, the magnetic path is substantially along the radial direction, and it can be said that the structure of the above-mentioned planar anisotropic magnet is not necessarily appropriate. On the other hand, pressure wire machining provides high magnetic properties in the radial direction, but as mentioned above, it requires a relatively large machining rate, non-uniform deformation may occur, and the There were problems such as the fact that its existence was unavoidable.

The present inventors applied 63 mm to a hollow billet made of a polycrystalline Mn-1-c alloy magnet that had been made anisotropic in advance.
It has been found that the above-mentioned problems can be solved by compressing the hollow body in the axial direction at a temperature of 0 to 830° C. while leaving at least a portion of the outer and inner circumferences of the billet free.

That is, the known Mn-A7! - Alloy for C-based magnets,
For example, 68-73% by weight of Mn and (1/10Mn-5,
e) An alloy consisting of ~(+/3Mn -22,2)% by weight of C and the balance of mulch was made anisotropic by performing plastic working such as extrusion in a temperature range of 530 to 830'C. A polycrystalline Mn-kl-C alloy magnet can be obtained. 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 hollow billet made of the anisotropic polycrystalline Mn-Ml-C alloy magnet is compressed in the axial direction of the hollow body, with at least a portion of the outer circumference and inner circumference of the billet free. By applying this, it is possible to obtain a magnet having high magnetic properties in multipolar magnetization. Note that the term "hollow body" as used herein refers to a billet in which a hollow portion exists along a certain arbitrary direction (axial direction), and the simplest shape is a cylinder.

The absolute value of the logarithmic strain must be o, 06 or more.

This is because, as detailed in the examples, the billet before compression processing is anisotropic in the compression direction, and when multipole magnetized, the structure changes to a magnet with high magnetic properties at least 0.
This is because a compressive strain of 0.06 is required.

As a known technique, there is an example in which a prismatic magnet with -axis anisotropy is subjected to warm compression in the axial direction, but in that case, the entire surface of a pair of side surfaces is initially restricted by a horizontal mold, and free compression is performed. isn't it. The purpose is also to change the direction of easy magnetization from uniaxial anisotropy to uniaxial direction perpendicular to it. Converting the direction of easy magnetization to one direction using the known technique requires processing of about 60 to 70% or more, which is about 0.9 in absolute value of logarithmic strain.
This is a large value of ~1.2 or more. Furthermore, there is a method (the above-mentioned composite processing method) of performing warm free compression processing in the axial direction of a magnet with -axis anisotropy, but the magnet obtained by this method is the above-mentioned plane anisotropic magnet. On the other hand, the present invention provides, for example, a billet to be subjected to free compression processing in the form of a hollow body, and by compression processing with the outer and inner peripheries free, a planar anisotropic magnet can be obtained in multipolar magnetization. A magnet exhibiting better magnetic properties is obtained.

When the billet is made of a polycrystalline Mn-Ml-C alloy magnet (planar anisotropic magnet) having an easy magnetization direction parallel to a plane perpendicular to the axial direction of the hollow body, the billet before compression processing As mentioned above, shows high magnetic properties in all directions in the plane including the radial direction and the chordal direction, but by applying the compression process in the axial direction of the hollow body, it is possible to A magnet exhibiting higher magnetic properties can be obtained.

The magnetic properties of the above-mentioned compression processing are better improved by performing the compression processing in a plurality of times with the plastic processing stopped, rather than continuous processing.

By further compressing a portion of the billet that has been subjected to the compression processing in the axial direction, the compressed portion becomes a magnet that exhibits higher magnetic properties in the radial direction. In addition, by further compressing the compressed billet in the axial direction with the outer periphery of the billet constrained and with at least a portion of the inner periphery free, it exhibits higher magnetic properties in the radial direction. Becomes a magnet. Furthermore, after the above-mentioned compression processing, the compressed billet is compressed in the axial direction while the outer periphery is constrained and at least a part of the inner periphery is free. The processed portion becomes a magnet with higher magnetic properties in the radial direction. In the compression processing described above, there are two methods: applying compressive strain all at once and applying it in multiple steps.

In a method in which the compressed billet is further compressed in the axial direction with the outer periphery of the billet constrained and at least a portion of the inner periphery free, the billet is magnetized in the axial direction of the hollow body. In the case of a polycrystalline Mn-Ml-C alloy magnet (-axis anisotropic magnet) having an easy direction, the axial direction is set with the outer periphery constrained and at least a part of the inner periphery free. At the end of the compression process, the billet must be subjected to a compression strain of 0.06 or more in terms of the absolute value of logarithmic strain in the axial direction. In other words, let εzf be the amount of compressive strain during the compression process, and let εzf be the amount of compressive strain during the compression process with the outer periphery constrained and at least a portion of the inner periphery free.
2r, it is necessary to make the sum of ε2f and εzr equal to or greater than o,06.

An example of the above-mentioned compression processing will be explained assuming that the shape of the billet is cylindrical. The first method is to perform free compression in the axial direction of a cylindrical billet.

The second method is a method in which a part of the cylindrical billet obtained by the first method and subjected to free compression is compressed in the axial direction, an example of which is shown in FIG. FIG. 4(a) shows the state before compression processing is applied to a part of the cylindrical billet. Figure 4 (2
L) shows a cross section of the mold. In ', the billet 1 is fixed and restrained by the restraining mold 2 and the lower mold 3, and the movable punch 4 can press only the inner periphery of the billet. ing.

By compressing the billet with the punch 4, the state shown in FIG. 4 (bl) is achieved, and only the inner peripheral portion of the billet is compressed.

The third method is to perform free compression processing in the axial direction of a cylindrical billet, and then perform compression processing with the outer periphery of the cylindrical billet constrained and the inner periphery free. An example of compression processing is shown in FIG. Figure (a) shows the state before free compression processing, with the upper and lower movable punches 6.6
By pressurizing the billet 1 and performing free compression processing, the billet, which has a large diameter, comes into contact with the inner wall of the outer mold 7, resulting in a state as shown in (bl).As a result, the outer periphery of the billet is restrained. This corresponds to compression processing in a state where the outer periphery is constrained and the inner periphery is free.Proceeding with compression processing with the inner periphery free is equivalent to compression processing with the outer periphery constrained and the inner periphery free. If the hollow body is a cylinder, the outer periphery refers to the outer surface of the cylinder, and the inner periphery refers to the inner surface of the cylinder.

The fourth method is to further compress a portion of the cylindrical billet obtained in the third method in the axial direction, an example of which is shown in FIG. In Fig. 4 (lL), if 1 is the billet obtained by the third method, Fig. 4 (bli) is the state in which only the inner circumference of the billet has been compressed. Although the outer periphery is used as the outer periphery, another method is to use the outer periphery, and for special purposes, the appropriate part may be used.

In the above example, the plastic working that applies compressive strain in the axial direction of the hollow body while leaving at least part of the outer periphery and inner periphery of the billet free is defined as 'free compression working'. In free compression processing, the entire outer and inner circumferences of the billet are left free. On the other hand, in actual applications, if it is desired to preserve the easy magnetization direction of a part of the magnet with the same anisotropy as before the plastic working of the present invention, by restraining the outer and inner peripheries of a part of the billet, it is possible to Therefore, it is best to use a method that does not apply compressive strain in the axial direction.

Regarding the possible temperature range of compression processing as mentioned above,
Processing was possible in the temperature range of 630 to 830'C, but the magnetic properties deteriorated considerably at temperatures exceeding 780'C.A more desirable temperature range is 56Q to 760'C.
It was C.

The present invention will be explained in detail below using examples.

Example 1 Mn of 69.6% by weight (hereinafter simply expressed as %) in the blended composition
, 29.3% Mul, 0.5% C and 0.7% N
i was melted and cast to produce a cylindrical billet with a diameter of 70 mm and a length of 60 mm. This billet is 11o.

After being held at ℃ for 2 hours, heat treatment was performed by allowing it to cool to room temperature. Then 45m in diameter at 720'C through lubricant.
Extrusion processing up to In was performed. Further through lubricant 6
Extrusion processing up to a diameter of 3111 m was carried out at a temperature of 80°C. This extruded rod was cut to a length of 2 omm and machined to produce several cylindrical billets with an outer diameter of 3QIIIm, an inner diameter of 2Qff1m, and a length of 2om. Using these billet NC lubricants, the compressive strain was changed at a temperature of 680° C., and four free compression processes were performed in the axial direction.

A cubic sample with a side of about 4 mm was cut out from the processed billet and its magnetic properties were measured. Note that each side is in the axial direction.

It was made to be parallel to the radial direction and chord direction.

FIG. 6 shows the change in residual magnetic flux density (Br) with respect to compressive strain (ε2).

As shown in FIG. 6, when ε2 is O and OS, Br in the radial direction is larger than Br in the axial direction, and as ε2 becomes further larger, Br in the radial direction further increases.

As can be seen from this figure, the direction of easy magnetization is changed from the axial direction to the direction 82. ,. It progresses markedly in the range up to 6. As shown in FIG. 6, compared to the known compression process, it exhibits high magnetic properties with a very small compressive strain. In other words, compression processing requires large compressive strain to obtain high magnetic properties in the radial direction, but according to the method of the present invention, a magnet with high magnetic properties can be obtained with small compressive strain. .

Furthermore, the billet processed with εz=0.69 has an outer diameter of 3
A cylindrical magnet with an inner diameter of 25 mm and a length of 10 ml was machined, and the inner circumference was magnetized as shown in FIG.

The number of poles was 18, and the magnetization was pulsed at 1500V using a 2000 μF oil capacitor. The surface magnetic flux density of the inner circumference was measured using a Hall element.

For comparison, the extruded rod with a diameter of 31 mm was
A cylindrical billet having a diameter of somm and a length of 20mm was produced by cutting to a length of 0ff1m and machining. This was subjected to free compression processing in the axial direction of the cylinder at a temperature of 680° C. via a lubricant. Note that the compressive strain (5) was set to 0.69. The processed billet was cut into a cylinder using a planar anisotropic magnet 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 is about 1.2 of that of the plane anisotropic magnet.
It was double that.

Next, the outer diameter somm and the inner diameter 201nf11. When subjecting a cylindrical billet with a length of 20 ml to free compression in the axial direction of the cylinder, first give εZ = 0.41, then stop the plastic working for 16 seconds, and then compress the billet at 680°C again to a total compression strain of 0.69. Free compression processing was carried out at temperature. The processed billet was cut into a cylinder in the same manner as described above, and the surface magnetic flux density after magnetization was measured. It increased by 0.2 kG compared to the one that was continuously subjected to free compression processing.

The cylindrical magnet, which has been continuously subjected to free compression processing and magnetized, is
Only the inner peripheral portion was compressed using a mold as shown in the figure.

In FIG. 4, the diameter of the punch 4 is 3Qml11.

The length of the inner peripheral portion of the billet after processing was 8 mm. After processing, the billet is cut to an outer diameter of 3em and an inner diameter of 25mm.
After magnetization in the same manner as described above, the surface magnetic flux density was measured. By compressing only the inner peripheral portion of the billet, the value of the surface magnetic flux density increased by 0.2 kG.

Actually, on the flow side 2, the extruded rod with a diameter of 31 mm obtained in Example 1 was
A cylindrical billet with an outer diameter of 24 m, an inner diameter of 12 ml, and a length of 2 omm was produced by cutting the billet into 2 mm. Next, after free compression in the axial direction of the cylinder at a temperature of 680°C using lubricant in the state shown in Figure 6, the billet is compressed with the outer periphery constrained and the inner periphery free. did. Furthermore, the 6th
In the figure, the inner diameter of the outer mold 7 is 3 omm. The billet after processing had an outer diameter of 30 mm and a length of 1-omm. After processing, the billet has an outer diameter of 28,111 m and an inner diameter of 14 m.
0 and was subjected to radial magnetization as shown in FIG. The number of poles was six, and the magnetization conditions and measurements were the same as in Example 1.

For comparison, a planar anisotropic magnet produced in the same manner as in Example 1 was machined to have an outer diameter of 28 mm and an inner diameter of 14 tnm, and was magnetized in the same manner as described above for comparison.

Comparing the above two values, 1. The value of the surface magnetic flux density of the magnet obtained by the method of the present invention is about 1.3 that of the plane anisotropic magnet.
It was double that.

The single-magnetized cylindrical magnet obtained according to the present invention was further compressed at a temperature of 680'C only on the outer circumference using a mold as shown in FIG. In Figure 7, h(a) shows the state before processing, (bl shows the state after compression processing was applied only to the outer periphery. 8 is the lower die, 9 is the fixing punch, and 10 is the movable one. The outer diameter of punch 9 (inner diameter of punch 10) is 2.
It is 0mm. The length of the outer circumference of the billet after processing is sm
It was m. After processing, the billet is cut to an outer diameter of 25
3 mm and an inner diameter of 14 mm, magnetized in the same manner as above, and when the 1-surface magnetic flux density was measured, it increased by 0.2 A)G.

Example 3 Plane anisotropic magnet (outer diameter 4
Two cylindrical billets (2 mm in diameter and 10 mm in length) were cut into an outer diameter of 301 ntll and an inner diameter of 20 tnm.

A cylindrical billet with a length of 20 mm was produced. This was subjected to free compression processing in the axial direction at a temperature of 660'C via a lubricant. The length of the billet after processing was 10 mm. After processing, the billet is cut to an outer diameter of 36mm and an inner diameter of 25mm.
A cylindrical magnet with a length of IQmfl and a length of IQmfl was magnetized on the inner circumference in the same manner as in Example 1. The magnetization conditions and measurement method are the same as in Example 1. When compared with the magnet produced by the method of the present invention obtained in Example 1, no significant difference was observed in the value of surface magnetic flux density.

As described in the examples, the present invention provides a hollow billet made of a polycrystalline Mn-Ml-C alloy magnet that has been made anisotropic in advance, with at least part of the outer and inner circumferences of the billet free. By compressing the hollow body in the axial direction in this state, a magnet exhibiting excellent magnetic properties in multipolar magnetization is obtained.

Comparing with magnets obtained by known methods and those obtained by compression processing, the present invention shows high magnetic properties with small compressive strain, and there are no problems such as non-uniform deformation or non-deformation zones, making it possible to use the composite processing method. In comparison with a planar anisotropic magnet, higher characteristics can be obtained than when magnetized with multiple poles.

The permanent magnet obtained by the present invention is a high-performance magnet suitable for multipolar magnetization, and is suitable for use in motors and generators.

It can be applied to many fields such as meters.

[Brief explanation of the drawing]

Figure 1 schematically shows the formation of a magnetic path inside the magnet when a cylindrical magnet is multipole magnetized in the radial direction. Figure 3 schematically shows the formation of a magnetic path inside a magnet when the inner circumference of a cylindrical magnet is magnetized with multiple poles. Figures 4 and 6 are cross-sectional views of a part of a mold showing an example of plastic working according to the present invention, and Figure 6 shows the residual magnetic flux density ( Br)
FIG. 7 is a sectional view of a part of a mold showing an example of plastic working of the present invention. 1...Billet, 2...Restriction mold, 3
...Lower die, 4...Movable punch, 6.6
...Punch, 7...External mold, 8...
・・Lower mold, 9・・Fixing punch, 1o・・・・
・・Movable punch. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3

Claims (1)

[Scope of Claims] (1) A hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet which has been made anisotropic in advance is heated at a temperature of 630 to 830°C at least on the outer and inner peripheries of the billet. A method for manufacturing a manganese-aluminum-carbon alloy magnet, which comprises compressing a hollow body in the axial direction while leaving a portion free. (2) The billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the hollow body, and the compression process is performed with an absolute value of logarithmic strain of 0.05 or more. A method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 1. (3) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, and is magnetically isotropic within the plane, and has a direction parallel to the axial direction and the 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. (4) A hollow billet made of a pre-anisotropic polycrystalline manganese-aluminum-carbon alloy magnet was heated at a temperature of 630 to 830'C, with at least part of the outer and inner circumferences of the billet free. 1. A method for producing a ma/gan-aluminum-carbon alloy magnet, which comprises compressing the hollow body in the axial direction in the state, and then compressing a portion of the billet in the axial direction of the hollow body. (6) The billet may be a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the hollow body, or a state in which at least a portion of the outer periphery and inner periphery of the billet is free. 5. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 4, wherein the compression working is performed at a feed material value of logarithmic strain of 0.06 or more. (6) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is parallel to the axial direction and the 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 including straight lines. (7) A hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance, at a temperature of 530 to 830°C, with at least a portion of the outer and inner circumferences of the billet free. The billet is compressed in the axial direction of the hollow body, and is further compressed in the axial direction of the hollow body while the outer periphery of the billet is constrained, and at least a part of the inner periphery is left free. A method for manufacturing a manganese-aluminum-carbon alloy magnet. (8) The billet is made of a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the hollow body, and when the compression process is completed, the compressive strain in the axial direction is reduced to the absolute logarithmic strain. 8. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 7, wherein the magnet is applied in a value of 0.06 or more. (9) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is parallel to the axial direction and the plane. 8. The method for manufacturing a manganese-aluminum-carbon alloy magnet according to claim 7, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing a straight line. (l(g) At least a portion of the outer and inner circumference of the billet is freed at a temperature of 630 to 830'C to a hollow billet made of a polycrystalline manganese-aluminum-carbon alloy magnet that has been made anisotropic in advance. The hollow body was compressed in the axial direction while the billet was in a state of rear,
A method for manufacturing a manganese-aluminum-carbon alloy magnet, which comprises compressing a portion of a billet in the axial direction of a hollow body. (11) The billet is not a polycrystalline manganese-aluminum-carbon alloy magnet having an easy magnetization direction in the axial direction of the hollow body, and moreover, while the outer periphery of the billet is restrained, at least a part of the inner periphery is free. The production of a manganese-aluminum-carbon alloy magnet according to claim 10, wherein the compression processing in the state of Law. (12) The billet has a direction of easy magnetization parallel to a plane perpendicular to the axial direction of the hollow body, is magnetically isotropic within the plane, and is parallel to the axial direction and the plane. 11. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 10, which comprises a polycrystalline manganese-aluminum-carbon alloy magnet that is anisotropic in a plane containing straight lines.