JPH05291068A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a permanent magnet high in productivity with a cheap equipment by a method wherein the surface of a magnet material is plated with metal and then subjected to plastic working in the air. CONSTITUTION:Alloy powder, composed 30wt.% Nd, 30wt.% Co, 0.9wt.% B, and of rare earth magnet material as the remainder, is compressed in an atmosphere of Ar at a temperature of 600-900 deg.C into a thick-walled ring-shaped powder-compressed molded body 10. The molded body 10 is plated with Ni and then subjected to plastic working in the air at 600 to 900 deg.C through a ring rolling method. Since the surface of the magnet material 10 is placed with metal, it can be subjected to ring rolling working in the air. Even if an upset working method is employed as a plastic working method, the magnet material 10 can be subjected to plastic working in the air if it is plated with metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a permanent magnet.

[0002]

2. Description of the Related Art In rare earth magnets represented by R-Fe-B (R is a La-based rare earth element), (a) a base alloy is melted and cast into a mold to form an ingot, which is crushed. To form ultra-fine powder, which is then compacted and sintered in a magnetic field to form an anisotropic magnet, and (b) the melt of the base alloy is rapidly quenched into a ribbon, which is roughly crushed. There is a super-quenching magnet that is magnetically anisotropic by plastically working an isotropic magnetic material made by compacting powder.

These anisotropic rare earth magnets have high magnetic properties, and if they can be applied to a small motor for OA and FA, they are extremely useful for downsizing and weight saving of the motor.

In order to apply this rare earth magnet to a motor,
It is most desirable to use this as a ring-shaped magnet that is magnetically anisotropic in the radial direction, but in the case of the above-mentioned sintered magnet, it is difficult to apply a magnetic field in the radial direction when molding and sintering the powder in the magnetic field. There's a problem.

On the other hand, in the latter case of the ultra-quenching magnet, it is possible to maximize the anisotropy even in the above-mentioned ring-shaped magnet because the anisotropy is achieved by plastic deformation without the need for forming in a magnetic field. There is.

Here, as a method of magnetically anisotropy by plastic deformation, there is a method of extruding a magnet material backward using a die and a punch. In this method, the thickness is a thin ring shape having a certain thickness or less. It is difficult to mold the magnet, and it is necessary to perform grinding after that in order to obtain a desired ring-shaped magnet having a thin wall thickness.

However, the rare earth magnet is a difficult-to-machine material and is difficult to machine, and in some cases causes a machining crack.

When such a grinding process is performed,
The number of manufacturing steps is increased, and the cost of the rare earth magnet is increased.

Therefore, the inventor of the present invention has filed an earlier patent application (Japanese Unexamined Patent Application Publication No.
173239), the magnet material is once preformed into a thick ring shape, and while being pressed by a pair of roll tools, the ring shaped preform is continuously plastically deformed by the rotation of these roll tools, A processing method to reduce the wall thickness was proposed.

According to this method, the wall thickness is very thin (for example, the wall thickness is about t = 0.05d with respect to the diameter d), the dimensional accuracy is good, and the surface texture is clean, and It is possible to easily obtain a ring-shaped molded body in which finishing processing such as grinding processing can be omitted.

However, since the rare earth magnet contains an active rare earth element, there is a problem that when it is processed in a heated state in the atmosphere, it is significantly oxidized and the magnetic characteristics are deteriorated or defects occur during processing. In both cases of ring rolling and backward extrusion using a roll tool, processing must be performed in a non-oxidizing atmosphere, in which case expensive equipment is required and productivity is poor,
The manufacturing cost of the magnet increases.

Although the anisotropic rare earth magnet has been described above as an example, such a problem is a problem that can generally occur in the production of a permanent magnet having an active element.

[0013]

The present invention has been made to solve the above problems, and its gist is to form a magnet material containing an active element into a predetermined shape by plastic working. This is to plastically process the magnet material in the atmosphere while the surface of the magnet material is plated with metal.

The present invention is characterized in that the surface of a magnet material is metal-plated and then a predetermined plastic working is carried out in the atmosphere. It has been confirmed that the magnet material containing the element is prevented from being oxidized and a good molded product can be obtained. According to the present invention, a permanent magnet can be manufactured with good productivity with inexpensive equipment.

Further, according to the present invention, after plastic working of the magnet material, a secondary effect that plating for rust prevention, electrodeposition treatment, etc. can be omitted can be obtained.

Conventionally, in the manufacturing process of a permanent magnet containing an active element, a plating treatment for rust prevention is performed after plastic working. However, in the present invention, the surface of the magnet material is preliminarily metal-plated, so that it may be plastic. It is possible to omit the above-mentioned plating treatment for rust prevention after processing.

The present invention is particularly suitable as a method for producing an anisotropic rare earth magnet. The rare earth magnet contains an active rare earth element, and in the case of an ultra-quenched magnet, plastic working is necessary to give magnetic anisotropy.

Therefore, if the present invention is applied to the production of such a rare earth magnet, a good magnet compact can be produced at low cost and with good productivity.

When applying the present invention as a method for producing a rare earth magnet, (a) a step of compressing the powder of the rare earth magnet at a temperature of 600 to 900 ° C. in a non-oxidizing atmosphere to obtain a green compact. , (B) a magnet is manufactured through a step of performing metal plating on the surface of the green compact and a step of (c) plastically processing the metal-plated green compact at a temperature of 600 to 900 ° C. in the atmosphere. It is better to do

As the plastic working method, it is possible to employ the above-mentioned backward or forward extrusion processing, ring rolling processing, and other processing methods.

[0021]

EXAMPLES In order to further clarify the characteristics of the present invention, examples thereof will be described in detail below. [Example 1] An alloy powder of a rare earth magnet having a composition of 30Nd-3Co-0.9B-remaining Fe (numerical values represent% by weight) was compressed at 780 ° C in an Ar atmosphere, and as shown in Fig. 1. 75 mmφ (outer diameter) x 64 mmφ (inner diameter) x 30
A thick powder molding (magnet material) 10 having a thickness of mm (height) was obtained.

Ni powder (Sample B in Table 1) and Cr plating (Sample C in Table 1) were applied to the green compact 10 with a thickness of 40 μm, respectively, and then the green compact 10 was plated. Was subjected to plastic working in the atmosphere by the ring rolling method.

FIG. 2 shows a method of plastic working by this ring rolling. In the figure, 12 and 14 are roll tools, and 16 is a roll tool for height regulation.

In this method, the ring-shaped powder compact 10 heated to 800 ° C. is compressed by the roll tools 12 and 14, and the roll tools 12 and 14 are rotated to continuously plasticize the powder compact 10. It is deformed and its thickness is gradually reduced.

Finally, 120 mmφ (outer diameter) × 1
13.5 mmφ (inner diameter) × 30 mm (height) molded body 1
Then, the molded body 11 was magnetized in the radial direction according to a conventional method, and the magnetic characteristics of the obtained anisotropic rare earth magnet were measured. The results are shown in Table 1.

For comparison, the same treatment was carried out on the one not subjected to the above-mentioned plating treatment (Sample A in Table 1). As a result, cracks due to oxidation occurred during plastic working, and a sound magnet was obtained. There wasn't. The magnetic properties are shown in Table 1.

[0027]

[Table 1]

From these results, it can be seen that by applying metal plating to the surface of the magnet material, a magnet with good magnetic properties can be obtained even when ring rolling is performed in the atmosphere.

Example 2 An alloy powder having the same composition as in Example 1 was compressed under the same conditions as in Example 1 into a solid disk shape of 37 mmφ × 15 mm (height) as shown in FIG. After molding, the surface of the green compact 18 was plated with Ni (Sample B) and Cr (Sample C) with a thickness of 60 μm.

Next, these metal-plated green compacts 18 were upset in the atmosphere to obtain 62 mm.
The formed body 20 of φ × 9.7 mm (height) was plastically processed.

After that, the molded body 20 was magnetized, and the magnetic characteristics of the obtained magnet were measured. The results are shown in Table 2.

For comparison, in the present example, the magnetic property of the obtained magnet was measured for the sample not subjected to the plating treatment (Sample A) by the same procedure. The results are also shown in Table 2.

[0033]

[Table 2]

From the results shown in Table 2, it is understood that even when the upset process is adopted as the plastic working method, the plastic working in the atmosphere can be performed by subjecting the magnet material to the metal plating treatment.

The embodiment of the present invention has been described in detail above, but this is merely an example, and the present invention can be implemented in a mode in which various modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the invention. is there.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of an embodiment method of the present invention.

FIG. 2 is an explanatory view of a ring rolling working method as a plastic working method adopted in the embodiment.

FIG. 3 is a process explanatory diagram of a method according to another embodiment of the present invention.

[Explanation of symbols]

 10,18 Magnet material 12,14 Roll tool

Claims (2)

[Claims] 1. When the magnet material containing an active element is plastically processed into a predetermined shape, the magnet material is plastically processed in the atmosphere while the surface of the magnet material is metal-plated. Method for manufacturing a permanent magnet. 2. A step of: (a) compressing rare earth magnet powder in a non-oxidizing atmosphere at a temperature of 600 to 900 ° C. to obtain a powder compact, and (b) metal-plating the surface of the powder compact. A method for producing a permanent magnet, which comprises a step of: (c) a step of plastically processing the metal-plated powder compact at a temperature of 600 to 900 ° C. in the atmosphere.