JPH0663069B2 - Method for producing manganese-aluminum-carbon alloy magnet - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a permanent magnet, and more particularly to Mn- for magnetizing multipoles using a polycrystalline manganese-aluminum-carbon (Mn-Al-C) alloy magnet. The present invention relates to a method for manufacturing an Al-C alloy magnet.

Prior art alloys for Mn-Al-C magnets contain 68 to 73 mass% (hereinafter simply referred to as%
Mn and (1 / 10Mn-6.6) to (1 / 3Mn-22.
2) Multi-component magnet alloys composed of 3% C and the balance Al, ternary system containing no additional elements other than impurities, and quaternary system containing a small amount of additional elements are known. It is a thing. Similarly, Mn-Al-C alloy magnet, face-centered tetragonal predominantly ferromagnetic phase (tau phase, L1 ₀ type ordered lattice)
It is known that there are ternary alloy magnets of ternary system or more containing ternary system containing no additional element other than impurities and quaternary system containing a small amount of additional element, These are generic names.

Conventionally, the manufacturing method is such that the outer periphery of a hollow body billet made of an alloy for Mn-Al-C magnets is constrained by an outer mold,
A punch having a flat compression surface was used for compression processing (Japanese Patent Laid-Open No. 192306/58).

Problems to be Solved by the Invention According to the above-described conventional manufacturing method, the billet is subjected to substantially the same compressive strain both in the billet and the outer peripheral portion thereof. It becomes a substantially straight line in the radial direction like the line A.

Therefore, in this state, even if S and N are magnetized on the outer circumference or the inner circumference as shown in the figure, the ideal semi-circular B line which is the ideal easy magnetization direction array is too much. Since the arrangement of the easy magnetization direction is different, a strong magnetic force could not be obtained even when the magnetizing work was performed.

Therefore, in the above-mentioned conventional example, as shown in FIG.
Before the magnetizing of N, the inner peripheral portion of the compressed billet is compressed again to bring the easy magnetization direction array to a substantially semicircular shape as shown by line B in FIG. 6 of the present application, and then to the inner periphery. I was supposed to do the magnetization work.

However, in the conventional case, in order to obtain such a substantially semi-circular easy direction alignment, the inner circumference or the outer circumference of the billet must be compressed again after the compression of the billet, resulting in poor workability. It was

Therefore, an object of the present invention is to make it possible to easily obtain a substantially semi-circular array of easy magnetization directions in the case of magnetizing S and N on the outer peripheral portion of the billet.

In order to achieve this object, the present invention provides manganese-
A hollow body-shaped billet made of an alloy for aluminum-carbon magnets is configured to be compressed by axially pressing it with a punch in a mold, and the punch has a compression surface for axially compressing the billet from an end portion. , A projecting portion projecting inward from the central portion of the compression surface, the compression surface,
The billet has an inclination that approaches the end of the billet from the inner peripheral portion toward the outer peripheral portion, and the billet is formed by this inclined compression surface at a temperature of 530 to 830 ° C., and the compressive strain of the outer peripheral portion is The outer peripheral surface of the billet is molded into an uneven shape by performing compression processing so as to be larger than the compressive strain, and then forming the uneven shape of the mold.

With the above configuration, when a hollow body billet made of an alloy for manganese-aluminum-carbon magnets is axially compressed by a punch, the compression surface of the punch has an end portion of the billet from the inner peripheral portion toward the outer peripheral portion. Since the billet has an inclination that approaches the part, the compressive strain of the outer peripheral part of the billet becomes larger than the compressive strain of the inner peripheral part, and the billet outer peripheral surface is compressed by the compression surface of the punch in the axial direction. It comes to be pressed against the inner surface of the uneven mold and receives a compressive force.As a result, a roughly semi-circular easy magnetization direction array is easily formed by one compression on the outer periphery of the compressed billet. Formed on the billet periphery
When S and N are magnetized, a strong magnetic force will be obtained.

Example FIG. 1 and FIG. 5 are sectional views showing the state before compression processing as seen from the axial direction and the front direction of the billet 1, where 1 is Mn-Al-C.
A cylindrical billet made of an alloy for system magnets, 2 and 3 are punches, and their compression surfaces 2a and 3a are inclined toward the end of the billet 1 from the inner peripheral portion toward the outer peripheral portion. Also compression surface
The projecting portion 2b projecting from the central portion of 2a penetrates the hollow portion of the billet 1 and projects into the recess 3b of the punch 3. Reference numeral 4 is a mold, and the inner surface 4a thereof is uneven. FIG. 2 shows the state after compression processing. As shown in FIG. 2, the diameter of the cylindrical billet 1 increases with the progress of compression processing by the punch 2, and a part of the outer peripheral surface comes into contact with the inner surface 4a of the mold 4, As the compression processing is further advanced, the outer peripheral surface of the billet 1 comes into contact with the inner surface of the mold 4 and becomes uneven as shown in FIG. 2, while the inner peripheral surface contacts the surface of the punch 2. . Note that it is not necessary to perform compression processing to the state shown in FIG. 2, and after a part of the outer peripheral surface of the billet 1 contacts the inner surface 4a of the mold 4, the compression processing may be terminated at an appropriate time. . In other words, irregularities may be formed on the outer peripheral surface of the billet 1.

In this case, the maximum outer diameter before billet compression processing is the size in contact with the convex portion 4a on the inner surface of the mold 4. In this case, before the compression processing, the compression processing is performed with a part of the outer peripheral surface of the billet 1 already constrained by the convex portion of the inner surface 4a of the mold 4. An example of this case is shown in FIG. FIG. 3 is a sectional view similar to FIG. 1 and shows a state before compression processing.
In the example shown in FIG. 3, the inner peripheral surface of the billet 1 is also in contact with the protruding portion 2b of the punch 2 before the compression processing.

As described above, since the billet 1 has the unevenness on the inner surface 4a of the mold 4, the unevenness is formed on the outer peripheral surface of the billet 1 after the compression processing. In the compression processing process, the portion where the outer peripheral surface is constrained earliest (the recessed portion of the outer peripheral surface of the billet 1 after processing) is the portion where the easy magnetization direction array is formed in the circumferential direction, and finally the portion where the outer peripheral surface is constrained. Alternatively, a portion where the outer peripheral surface is not constrained to the end (a convex portion on the outer peripheral surface of the billet 1 after processing) is a portion having an easy magnetization direction in the radial direction. The direction of easy magnetization in the middle portion is a portion that sequentially changes from the circumferential direction to the radial direction. In other words, as shown by the line B in FIG.
In the figure, an easy magnetization direction array is formed in a direction along the curved surface of the concave portion of the outer peripheral surface of the billet 1 formed by the convex portion of the inner surface 4a of the mold 4. Therefore, the number of the uneven portions may be determined depending on how many poles are magnetized in the outer circumference magnetization. In FIG. 1, the convex portion on the outer peripheral surface of the billet 1 after processing is 6
Therefore, it becomes a magnet having an anisotropic structure suitable for 6-pole magnetization, and the portion corresponding to the convex portion after processing becomes the pole portion in the outer peripheral magnetization (the one in FIG. 6 has 8-pole magnetization). Things).

As described in the above example, according to the present invention, when the billet 1 is compressed in the axial direction, the billet 1 is molded and compressed using the punch 2, the mold 4, etc. so that the outer peripheral surface of the billet 1 becomes uneven. As a result, a magnet having an anisotropic structure that exhibits high magnetic characteristics when subjected to outer circumference magnetization is obtained.

Further, in the present embodiment, the compression processing is performed so that the compression strain of the outer peripheral portion of the billet 1 becomes larger than the compression strain of the inner peripheral portion. Next, this point will be described with reference to FIG. FIG. 5 shows a cross section in a state before processing as seen from the direction perpendicular to FIG. 1 (front direction). 1 is a billet, 2 and 3 are punches, and 4 is a mold. As shown in FIG. 5, the compression surface in contact with the ends of the billet 1 of punch 2 and punch 3.
2a and 3a are inclined surfaces that approach the end of the billet 1 from the inner peripheral portion toward the outer peripheral portion as described above. Therefore, the height of the outer peripheral portion of the billet 1 after compression processing is smaller than the height of the inner peripheral portion. That is, the billet 1 should have a compressive strain greater than that of the inner periphery of the billet 1.
This means that compression processing has been performed in the axial direction of. Compressive strain refers to strain in the axial direction of the billet 1.

That is, in this embodiment, when the hollow body billet 1 made of a manganese-aluminum-carbon magnet alloy is axially compressed by the punches 2 and 3, the compression surfaces of the punches 2 and 3 are compressed.
Since 2a and 3a have a slope approaching the end of the billet 1 from the inner peripheral part toward the outer peripheral part, the billet 1 has a larger compressive strain at the outer peripheral part than the compressive strain at the inner peripheral part. Due to the axial compression of the billet 1 by the compression surfaces 2a, 3a of 2, 3, the outer peripheral surface of the billet 1 is pressed against the inner surface 4a of the uneven mold 4 to receive the compression force, As a result, a substantially semicircular easy magnetization direction array is easily formed on the outer peripheral portion of the billet 1 after compression by one-time compression as shown by line B in FIG. By magnetizing N, a strong magnetic force can be obtained.

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

69.5% Mn, 29.3% Al, 0.5% C and 0.7% in the composition
Ni was melted and cast to prepare a billet 1 having an outer diameter of 24 m, an inner diameter of 18 mm, an outer peripheral length of 25 mm, and an inner peripheral length of 20 mm with an inclined end surface. The billet 1 was kept at 1100 ° C. for 2 hours, air-cooled to 600 ° C., kept at 600 ° C. for 30 minutes, and then heat-treated to be released to room temperature.

Next, compression processing was performed at a temperature of 680 ° C. through a lubricant using the punch 2 and the mold 4 shown in FIGS. 4 and 5. FIG. 4 is a sectional view of the mold 4 similar to FIG.
(Inner diameter of die 4) DK = 30 mm, X _A = 15 mm (radius of convex portion of die 4), R _S = 3 mm, punch diameter is 18 mm, die 4
There are eight convex portions on the inner surface 4a. Punches 2 and 3 each have an outer peripheral surface that fits with the uneven surface of the mold 4 and can move in the vertical direction in the drawing. Using such punch 2 and die 4, compression processing was performed until the cavity in the die 4 was almost eliminated.

After machining the billet 1 after processing to an outer diameter of 27 mm, it was magnetized to 8 poles as shown in FIG. For the magnetization, an oil condenser of 2000 μF was used and pulsed at 1500 V.
The surface magnetic flux density on the outer peripheral surface was measured with a Hall element.

For comparison, Mn, Al, C, and Ni having the above-described composition were melted and cast to prepare a cylindrical billet 1 having a diameter of 24 mm and a length of 20 mm. This billet 1 was subjected to free compression processing at a temperature of 680 ° C. in the axial direction of the cylinder to a length of up to 20 mm. The billet 1 after processing was cut in the same manner as described above, magnetized, and the surface magnetic flux density was measured.

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

As described above, according to the present invention, when a hollow billet made of a manganese-aluminum-carbon magnet alloy is axially compressed by a punch, the compression surface of the punch has an inner peripheral portion and an outer peripheral portion. Since the billet has an inclination that approaches the end of the billet, the compression strain of the billet becomes larger than the compression strain of the inner periphery, and due to the compression of the billet in the axial direction by the compression surface of the punch, The outer peripheral surface of the billet comes into pressure contact with the inner surface of the uneven mold and receives a compressive force. As a result, the outer peripheral portion of the billet after compression has a substantially semicircular magnetic easy direction array. It is easily formed by one-time compression, and a strong magnetic force can be obtained by magnetizing S and N on the outer periphery of the billet.

[Brief description of drawings]

1 to 4 are plan sectional views of an outer die used in an embodiment of the present invention, FIG. 5 is a front sectional view thereof, and FIG. 6 is a schematic view of a magnetic path by outer peripheral multipole magnetization in a cylindrical magnet. FIG. 1 …… Billet, 2,3 …… Punch, 2a, 3a …… Compressed surface, 4
…… Mold, 4a …… Inside, α …… Inclination angle.

Claims (2)

[Claims] 1. A hollow-body billet made of a manganese-aluminum-carbon magnet alloy is compressed by axially pressing it with a punch in a mold. Has a compression surface that compresses in the direction, and a protrusion that protrudes inward from the center of the compression surface toward the billet. The compression surface approaches the end of the billet from the inner periphery to the outer periphery. The billet has an inclination, and the billet is compressed by the inclined compression surface at a temperature of 530 to 830 ° C. so that the compression strain of the outer peripheral portion is larger than the compression strain of the inner peripheral portion, and the inner surface of the mold is further processed. A method for manufacturing a manganese-aluminum-carbon alloy magnet, in which the outer peripheral surface of the billet is formed into an uneven shape by making the uneven shape. 2. The method for producing a manganese-aluminum-carbon alloy magnet according to claim 1, wherein the compression processing by punching is performed with a part of the outer periphery of the billet being constrained.