JPH037746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a permanent magnet. More specifically, the present invention relates to a method of manufacturing an isotropic manganese-aluminum-carbon (Mn-Al-C based) alloy magnet.

Isotropic Mn-Al-C alloy for magnets is 71.0~
73.0% by weight (hereinafter simply expressed as %) of Mn and (1/
10 Mn-6.6) to (1/3 Mn-22.2)% C and the balance Al, ternary magnets containing no additive elements other than impurities, and quaternary or higher multi-component magnets containing small amounts of additive elements. There are several known alloys for this purpose, and these are collectively referred to as alloys. Similarly, isotropic Mn-Al-C
Alloy magnets are mainly composed of a face-centered tetragonal (τ phase, L1 ₀ type regular lattice) structure, which is a ferromagnetic phase, and include ternary systems that do not contain any additive elements other than impurities, and quaternary systems that contain small amounts of additive elements. Multi-component alloy magnets are known, and these are collectively referred to as magnets. In addition, as a manufacturing method for this isotropic Mn-Al-C alloy magnet, for example, a billet made of an isotropic Mn-Al-C alloy for magnets is heated in a temperature range of 830 to 900°C.
Quenched at cooling rate faster than 10℃/min, 480~750℃
When tempered for an appropriate time, Mn ₃ AlC or a similar face-centered cubic phase is precipitated in the form of fine grains or networks. Furthermore, it is known that plastic working is performed in a temperature range of 550 to 780°C. There is a difference between the cooling rate when quenching in the temperature range of 830 to 900°C at a cooling rate faster than 10°C/min and the magnetic properties after plastic working, and it is said that the faster the cooling rate, the higher the magnetic properties. Tend. If the shape of the billet is large (if it is a cylinder, the diameter is large and the length is long), it will be difficult to obtain a sufficiently fast cooling rate due to the mass effect, so the shape of the billet should be made as small as possible (if it is a cylinder, the diameter will be small). It is desirable to do so.

In order to obtain, for example, an isotropic manganese-aluminum-carbon alloy magnet with a long length and a large diameter using a known manufacturing method, if the above-mentioned plastic working is compression working, the diameter of the billet can be compared. Since the diameter can be made small, the cooling rate during quenching can be made sufficiently high, and a large diameter product can be obtained, but since it is a compression process, it is not possible to obtain a very long product. Furthermore, if the above-mentioned plastic working is used as a known extrusion process, a long piece can be obtained, but if the diameter of the magnet is increased, the diameter of the billet must be made larger, so the cooling during quenching described above is required. You won't be able to get the speed fast enough.

In view of the above, there has been a desire for a manufacturing method that can obtain a heat treatment effect equivalent to that of the known manufacturing method using compression processing, and that can also obtain a long magnet with a length equivalent to that of the known manufacturing method that uses extrusion processing.

The present inventor has discovered that isotropic manganese-aluminum-
A billet made of a carbon-based magnet alloy is made up of one or more parts that include an arbitrary cross section perpendicular to a specific direction within the billet, and the billet as a whole is partially plastically worked. ,
Furthermore, it has been found that the above-mentioned problems can be solved by applying such plastic working to the entire billet and applying compressive strain in a specific direction through this plastic working.

The present invention will be explained in detail below.

To simplify the explanation, as an example, the billet is assumed to be a cylinder, and the specific direction is assumed to be the axis of the cylinder. In known compression processing, the entire billet is plastically deformed at the same time.
As the length of the cylinder increases, it will buckle. Therefore, when the length of the cylinder is increased, if you plastically deform only the length that will not buckle from one end face of the cylinder and repeat this process toward the other end face, the entire cylinder will eventually become plastically deformed. Become. That is, consider a portion that is appropriately plastically deformed from one end face of the cylinder, and constrain the shape of the remaining portion by using a portion that does not undergo plastic deformation. In this way, after applying a predetermined plastic deformation to a specific part, a new plastic deformation is applied to the part that was not plastically deformed and is adjacent to the part that was plastically deformed earlier, and the remaining part and the part that was plastically deformed earlier are , the shape is constrained to prevent plastic deformation. By repeating the above-described partial plastic deformation operation up to the other end face, the entire billet is plastically deformed.

As described above, in the present invention, plastic deformation is always applied to only a portion of the billet, and the surface of the portion that is not to be plastically deformed is, of course, processed from the outside to restrain it from plastic deformation. However, even if the billet is not restrained by an external force, a method may be used in which the billet is locally heated to create parts that are plastically deformed and parts that are not deformed due to the difference in deformation resistance within the billet. Furthermore, the above-mentioned portion does not refer to a certain portion within the billet. During plastic working, the billet must always be divided into two parts: a plastically deformed part and a non-plastically deformed part.

In the above explanation, the part that is plastically deformed is one part within the billet, but even if this part is divided into two or more parts, the part that is not plastically deformed is always in the billet during plastic working. It only needs to exist within. There are methods in which the portion to be plastically deformed within the billet is continuously changed with respect to time, and methods in which it is not changed, but the above explanation is a method in which the portion is not changed continuously.

One method of plastic deformation is extrusion using a die in which the opening area of the container portion is smaller than the opening area of the bearing portion. In this case, the specific direction becomes the extrusion direction. Compressive strain is applied to the billet in the extrusion direction through extrusion. Here, the opening area of the container section is the cross-sectional area of the container section when the die is cut along a plane that passes through the container section and is perpendicular to the extrusion direction. This is the cross-sectional area of the bearing section when cut along a plane that passes through the section and is perpendicular to the extrusion direction. Further, the container section is a section that accommodates the billet to be subjected to plastic working, and the bearing section is a section that accommodates the billet that has undergone predetermined plastic deformation. For example, in the die shown in Figure 3, the opening area of the container section is the area of a circle with a diameter Dc, and the opening area of the bearing section is the area of the circle with a diameter Dc.
It is the area of the circle Db. Although the shape of the opening is solid in the above example, it may be hollow, for example, ring-shaped. What is required is that the above-mentioned relationship be established between the opening area of the container portion and the opening area of the bearing portion, and that compressive strain be applied to the billet after extrusion in the extrusion direction.

According to the present invention, when a known isotropic Mn-Al-C magnet alloy is extruded at a temperature of 550 to 780°C 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 apply compressive strain in the extrusion direction by extrusion processing.

In order to apply compressive strain to the billet in the extrusion direction by extrusion using a die in which the opening area of the container part is smaller than the opening area of the bearing part, two It must be possible to apply pressure to the billet from any direction. On the other hand, in the extrusion process of general metal materials or the extrusion process used in the production method of known Mn-Al-C alloy magnets, a die is used in which the opening area of the container part is larger than the opening area of the bearing part. It is a process that stretches in the direction of
During extrusion, it is sufficient to be able to apply pressure to the billet from at least one direction of extrusion.

Here, both processes will be referred to as extrusion processing.
For example, when extruding a billet made of a Mn-Al-C alloy magnet, in other words when moving the billet from the container part to the bearing part, in the latter method, the billet is moved from at least the upper part of the container part in the extrusion direction with a punch. Machining can be done by applying pressure, but in the former method, for example, pressure is applied from above the container part with a punch (5 in Figure 3) and from below the bearing part with a punch (6 in Figure 3). By applying pressure, it is necessary to bring the billet into a pressurized state by the upper and lower punches, and to move these punches in a direction from the container section toward the bearing section relative to the die. In other words, the billet moves from the container section toward the bearing section while being pressurized. As a result, compressive strain is applied to the billet in the extrusion direction during the extrusion process.

Next, one method of implementing the present invention using an extrusion processing method will be explained with reference to FIG.

A is a state in which there is no billet in the die 1. Here, 2 is a container part, 3 is a bearing part, 4 is a conical part, and 5 and 6 are punches having diameters that are large enough to fit into the container part 2 and the bearing part 3, respectively.

First, as shown in b, a billet 7 of an appropriate length is accommodated in the bearing part 2. By pressurizing the billet with the punch 6, it is brought into the state shown in c. The preparatory process is completed above, and the extrusion process of the present invention can be started next. This preparatory process is carried out by extrusion processing of general metal materials or known Mn-
This is similar to the extrusion process used in the manufacturing method of Al-C alloy magnets, and is an extrusion process in which the bearing part in the present invention is a container part, and the container part is a bearing part.

Next, as shown in FIG. 1d, a new billet 8 is placed in the container section 2, and while pressurizing this billet 8 using the punches 5 and 6, the punch 5 is moved into the container relative to the die. By moving it in the direction from the part toward the bearing part (in the direction of the arrow in FIG. 1d), the state shown in e is obtained. Next, remove the billet 7 housed in the bearing part and place a new billet 9 in the container part.
(Fig. 1 f). This state is the same as the state shown in FIG. 1d, and by repeating the above-described method, a billet that is compressively strained in the extrusion direction can be obtained.

Next, an example of another method will be explained. This method does not require the above-mentioned preparatory steps.
First, as shown in FIG. 2a, a billet 10 having a diameter large enough to fit into the container part is accommodated from the container part to the bearing part, so that the punch 5 does not move relative to the die. By pressing the billet 10 with the punch 6 while fixing it to the position shown in b, the billet 10 is brought into the state shown in b. Next, the punch 6 is moved in the extrusion direction with a small force (a force that does not cause the billet to undergo plastic processing), and the punch 5 is moved to the punch 6.
It is moved by an arbitrary distance, for example, about 10 mm, relative to the die in the extrusion direction. This result c
The situation will be as shown in . Next, while fixing the punch 5 so that it does not move relative to the die,
The billet is pressurized using the punch 6 so that the space surrounded by the die and the punches 5 and 6 is sufficiently filled mainly with the billet, ie, the state shown in d. Below, Figure 2 c, d
Extrusion processing can be performed by repeating the same conditions as above.

Here, the former extrusion method of the present invention corresponds to the above-mentioned method of continuously changing the plastically deformed portion with respect to time, and the latter method corresponds to the method of not continuously changing the portion to be plastically deformed. Further, the former series of steps can be divided into a preparatory step and one extrusion method of the present invention, and the latter series consists of only one extrusion method of the present invention. Here, the method of continuously changing the part to be plastically deformed over time and the method of not changing it have been explained completely separately, but when plastically working one billet, these two methods may be combined. What is required is that the billet is subjected to compressive strain in the direction of extrusion after extrusion. As a result, it is possible to obtain a long outer circumference or inner circumference magnetization magnet.

Regarding the possible temperature range of this extrusion process,
Although processing was possible in the temperature range of 550 to 780℃,
A more desirable temperature range was 600 to 760°C.

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

Example 1 Blend composition: 72% Mn, 27% Al and 1% C
was melted and cast to produce a cylindrical billet with a diameter of 18 mm and a length of 120 mm. This billet was held at 1150°C for 2 hours and then cooled at a cooling rate faster than 10°C/min.
Heat treatment was performed at 700°C for 30 minutes.

Next, extrusion processing was performed using a lubricant at a temperature of 720° C. according to the method shown in FIG. The die used here has a die half angle α of 15° in Figure 3.
Dc=18mm, Db=30mm. The diameter of the sample after processing is 30 mm and the length is 43 mm. After processing, the sample was made into an outer diameter of 28 mm, an inner diameter of 10 mm, and a length of 40 mm.
20 pole magnetization was applied. The magnetization was pulsed at 1500V using a 2000μF oil capacitor. When the surface magnetic flux density at the outer periphery was measured using a Hall element,
The peak value at each magnetic pole was 1.7-1.8KG.

For comparison, the above-mentioned cast billet was made with a length of 20 mm.
It was cut into pieces and subjected to the same heat treatment as described above. Next, free compression processing was performed at a temperature of 720°C via a lubricant. The compressive strain was set to be the same as in Example 1. The sample after compression processing has an outer diameter of 28 mm and an inner diameter of 10 mm.
Magnetization and measurement were carried out in the same manner as described above, with a length of 7 mm and a length of 7 mm. The peak value at each magnetic pole is 1.7~1.8KG
, and no difference in magnetic properties from the magnet obtained in Example 1 was observed.

From the above results, according to the present invention, it is possible to obtain a magnet with magnetic properties equivalent to those obtained by compression processing, and also to obtain a magnet having a long length and a large diameter.

Example 2 A mixture of 71.4% Mn, 26.8% Al, 1% C, 0.7% Ni and 0.1% Ti was melted and cast, and the diameter
A cylindrical billet with a diameter of 15 mm and a length of 150 mm was prepared. After holding this billet at 1150℃ for 2 hours,
Heat treatment was performed by cooling at a cooling rate faster than 1 minute and holding at 700°C for 30 minutes. then 720 through lubricant
Extrusion processing was carried out according to the method shown in FIG. 2 at a temperature of .degree. The dice used here are α=20° and Dc=15.
mm, Db=28mm.

The diameter of the sample after processing is 28 mm and the length is 43 mm.
The processed sample had an outer diameter of 26 mm, an inner diameter of 10 mm, and a length of 40 mm, and was magnetized with 20 poles on the outer periphery. The peak value at each magnetic pole was 1.8-1.9KG. Magnetization and measurement methods are as follows.
This is the same as in Example 1.

Example 3 A mixture of 71.4% Mn, 26.8% Al, 1% C, 0.7% Ni and 0.1% Ti was melted and cast, and the diameter
A cylindrical billet with a diameter of 18 mm and a length of 100 mm was prepared. After holding this billet at 1150℃ for 2 hours,
Heat treatment was performed by cooling at a cooling rate faster than 1 minute and holding at 700°C for 30 minutes. The billet was held so that it could be compressed in the axial direction. The billet was then locally heated to 720°C by approximately 20 mm along its length. While applying a compressive load to the billet, the entire billet is compressed by moving the heating part along the entire length of the billet, and the length of the billet after processing is 50mm and the diameter is 23mm. I made it 27mm. The processed sample had an outer diameter of 22 mm, an inner diameter of 8 mm, and a length of 45 mm, and was magnetized with 18 poles on the outer periphery. The pix value at each magnetic pole is
It was 1.8~1.9KG. The magnetization and measurement methods are the same as in Example 1.

As described in the examples, the present invention provides a billet made of an isotropic manganese-aluminum-carbon alloy for magnets with a portion (one or more By applying plastic working to a part of the billet, and applying such plastic working to the entire billet, compressive strain is applied to the billet in a specific direction. It is possible to obtain an isotropic Mn--Al--C based alloy magnet which has the same heat treatment effect as the known manufacturing method using compression processing, and also has a long length equivalent to that of the known manufacturing method using extrusion processing. The magnet obtained by the present invention can be applied to many fields such as motors, generators, and meters as a magnet for magnetizing the outer or inner circumference.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an extrusion method in an embodiment of the present invention, FIG. 2 is a process diagram showing an extrusion method in another embodiment, and FIG. 3 is a longitudinal sectional view of the main part of a die. 1...Dice, 2...Container part, 3...Bearing part, 4...Conical part, 5, 6...Punch.

Claims (1)

[Scope of Claims] 1. A billet made of an isotropic manganese-aluminum-carbon alloy for magnets, at a temperature of 550 to 780°C, including an arbitrary cross section perpendicular to a specific direction within the billet, 1 By applying plastic working to a part of the billet, the billet is made up of two or more parts, and the plastic working is applied to the entire billet, and this plastic working applies compressive strain to the billet in a specific direction. 1. A method for producing an isotropic manganese-aluminum-carbon alloy magnet, characterized by comprising: 2. The isotropic manganese according to claim 1, wherein the plastic working is extrusion using a die in which the opening area of the container part is smaller than the opening area of the bearing part, and the specific direction is the extrusion direction. A method for producing an aluminum-carbon alloy magnet.