JPH09124372A - Production of magnet of rare earth element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnet of a rare earth element causing neither seizing nor cracking, capable of being sufficiently extruded, hardly deteriorating magnetic characteristics, by cold pressing powder of magnet alloy to prepare a compact, coating the whole surface of the compact with a lubricant and continuously carrying out hot pressing and extrusion. SOLUTION: An ingot obtained by casting a molten metal comprising a rare earth element, an iron-group element and boron is ground to give powder of magnet alloy having <=1,000μm particle diameter. The powder is cold pressed to give a compact. The whole surface of the compact is coated with a lubricant (e.g. graphite) and simultaneously hot-pressed and extruded. The treatment temperature is 600-900 deg.C and the pressure is 0.5-10ton/cm<2> . The process is shown in the figure. A container 4 is arranged in a space formed by a die 1, a lower punch 2 and an upper punch 3, the compact 5 coated with the lubricant is put in the space and hot pressed and extruded. An outer punch 6 is installed at the free end of the extrusion.

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 rare earth magnet. More specifically, the present invention relates to a method for producing a rare earth magnet having a multiple structure, which is useful for a magnet rotor used in a high-speed rotating state of a generator or an electric motor, and has excellent magnet damage prevention performance.

[0002]

2. Description of the Related Art Rare earth permanent magnets represented by the Nd-Fe-B system have been widely used in various fields because of their excellent magnetic properties. Rare earth magnets with such characteristics are usually cast from a molten alloy, the obtained ingot is crushed, then shaped and sintered in a magnetic field while oriented, and then subjected to the required heat treatment. Manufactured by magnetizing.

Further, a magnet having particularly high magnetic characteristics is an isotropic magnet in which a molten alloy is rapidly quenched to form a ribbon, and a powder obtained by crushing the alloy is hot-pressed to be magnetized. Alternatively, or after hot pressing, it is manufactured by hot working and then magnetizing to obtain an extremely large anisotropic magnet of maximum energy species. However, in the case of a rare earth magnet such as an Nd-Fe-B system up to now, in order to use it in a high-speed rotating portion such as a magnet rotor of a generator or an electric motor, the physical properties of the rare earth magnet are not limited to those produced by any manufacturing method. The strength is not sufficient, there is a risk of damage during rotation, there is a drawback that it is not necessarily practical.

This has particularly excellent magnetic properties,
For magnets made of powder from ultra-quenched ribbon,
It was a big problem in utilizing the excellent magnetic properties. For the purpose of compensating for the weakness in strength of the rare earth magnet typified by the Nd-Fe-B system, the magnet alloy is contained in a container made of a material having relatively large strength and excellent corrosion resistance. Hot pressing of powders and extrusion of magnets for multiple structuring have been proposed in the past, but these proposed methods require, for example, that the powder be enclosed in a container. However, there are problems such as industrial production problems, and burning of the magnet and the container, resulting in cracking of the magnet.

Therefore, the present invention solves the problems of the prior art as described above, does not cause seizure or cracks due to extrusion, allows sufficient extrusion, hardly deteriorates magnetic properties, and has a high-speed rotating portion. It is an object of the present invention to provide a new method capable of producing a multi-structured magnet excellent in breakage preventive property that can be used for such purposes.

[0006]

Means for Solving the Problems The present invention is, in order to solve the above problems, in the production of a multi-structure magnet by extruding a rare earth magnet containing a rare earth element, an iron group element and boron into a container, A rare earth magnet characterized in that a magnet alloy powder is cold-pressed to prepare a compact, a lubricant is applied to the entire surface of the compact, the compact is placed in a container, and hot pressing and extrusion are continuously performed. To provide a manufacturing method of.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that a rare earth magnet having a multi-structure is manufactured by extrusion into a container by the method as described above. However, in the composition of the rare earth magnet itself, the rare earth magnet is Element is Nd
(Neodymium), Ce, D
Various kinds of other rare earths such as y and Pr. Among them, it is considered as Nd, or Ce, Dy, etc. added to this Nd. The iron group element is typically Fe or Co, and a system composed of both is also exemplified. The composition ratio of rare earth element-iron group element-boron may be in a conventionally known range. Further, in order to improve not only magnetic performance but also corrosion resistance, workability, heat resistance, etc., Ga, Nb, Ni, Z
You may further contain elements, such as n, Pb, and Al.

In the present invention, the magnets having these compositions are first formed as alloy powder by cold pressing into a compact having a desired shape and size. In this case, as the alloy powder, one prepared by crushing an ingot obtained by casting a molten alloy of rare earth magnet constituent elements, crushing a thin band obtained by ultra-quenching, or the like is used. There is no strict limitation on the particle size, but in view of sinterability, magnetic properties, etc., it is generally 1000 μm or less, more preferably 100 to 8 μm.
Those having a diameter of about 00 μm are preferably used.

Then, a lubricant is applied to the entire surface of the obtained molded body. Inorganic or organic lubricants are considered as the lubricant, but graphite is exemplified as one of the preferable lubricants from the viewpoint of high temperature stability and the like. This lubricant should be applied to the entire surface of the molded body, and if only a part of it is applied, seizure occurs between the container and the magnet,
It cannot be extruded sufficiently. The magnet also tends to crack.

The molded body coated with the lubricant is placed in a predetermined container and hot pressed and extruded continuously. The container in this case has sufficient strength to prevent breakage, has a small resistance to hot deformation, is unlikely to cause seizure, and is also selected as having good corrosion resistance and workability according to the purpose of use. . Hot pressing and extrusion are performed by heating at about 600 to 900 ° C., but it is conceivable to heat the container itself. It is also preferable to carry out under vacuum or in an inert gas atmosphere such as Ar (argon). The pressure depends on the size and thickness of the container, but is set to about 0.5 to 10 ton / cm ² . It should be noted that the hot pressing and the extrusion process are continuously performed in the present invention. Cool down after hot pressing,
When heated and extruded again, the crystal grains of the magnet grow, increasing the deformation resistance and deteriorating the magnetic properties, especially iHc.
Is not preferable because it causes a large decrease in

In the extrusion process, it is preferable to apply pressure to the free end of extrusion in order to suppress cracking of the magnet. FIG. 1 shows an example of the steps of hot pressing and subsequent extrusion processing.
A container (4) is arranged in a space formed by the lower punch (2) and the upper punch (3), and a cold press in which a lubricant is applied to the entire surface of the container (4). The molded body (5) is charged and hot pressing is performed, and immediately thereafter, extrusion processing is performed while the container (4) and the magnet molded body (5) are continuously heated. At this time, in the example of FIG. 1, pressure is applied to the free extruding end by the outer punch (6).

As described above, the multi-structured magnet of the present invention, which is excellent in damage prevention performance, is manufactured. Therefore, examples will be shown below, and the embodiments of the present invention will be described in more detail.

[0013]

EXAMPLES Example Nd 30.5 wt%, Co 5.5 wt%, B 0.9 wt
%, Ga 0.6 wt%, Fe 62.5 wt%, and a powder produced by a super-quenching method from a molten alloy having a composition of 6% by weight. After applying graphite as a lubricant to the entire surface of this molded body, a cylindrical Inconel of the size and shape shown in FIG.
It was put in a container made of. After heating this container to 750 ° C., hot pressing was performed by the method shown in FIG. 1 and subsequently extrusion processing was performed.

Comparative Example 1 A molded body was prepared in the same manner as in Example 1. A lubricant was applied only to the upper and lower end surfaces of the molded body, and the molded body was placed in a container and hot pressed and extruded. Comparative Example 2 After hot pressing, it was once cooled to room temperature. After that, a lubricant was applied again to the upper end surface, heated to 750 ° C., and extruded. The other conditions were the same as in the example.
Table 1 shows the extrusion depth, the presence or absence of cracks, and the magnetic properties of the magnets obtained in the examples and comparative examples. When the extrusion process was performed without applying the lubricant to the entire surface of the molded body (Comparative Example 1), seizure occurred between the container and the magnet, and sufficient extrusion process could not be performed. Also, cracks occur in the magnet. Further, when hot pressing and extrusion processing are not continuously performed and heating is performed twice (Comparative Example 2), crystal grains grow and deformation resistance increases and magnetic characteristics deteriorate, particularly iHc significantly decreases. It was

[0015]

[Table 1]

On the other hand, in the examples of the present invention, neither seizure nor cracking occurred, sufficient extrusion processing was possible, and the magnetic characteristics were hardly deteriorated. With the obtained multi-structure magnet with the container, the magnet was not damaged even at high speed rotation of the electric motor.

[0017]

As described in detail above, according to the present invention, a multi-layer structure which is capable of sufficient extrusion without seizure or cracking, has almost no deterioration in magnetic properties, and has an excellent damage prevention performance at high speed rotation. It becomes possible to manufacture a rare earth oxide magnet.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view illustrating a method of the present invention.

FIG. 2 is a cross-sectional view illustrating a container.

[Explanation of symbols]

 1 die 2 lower punch 3 upper punch 4 container 5 molded body 6 outer punch 7 magnet

Claims (2)

[Claims] 1. In the production of a multi-structured magnet by extruding a rare earth magnet containing a rare earth element, an iron group element and boron into a container, a powder of a magnet alloy is cold pressed to produce a compact, and A method for producing a rare earth magnet, which comprises applying a lubricant to the entire surface, placing the molded body in a container, and continuously performing hot pressing and extrusion. 2. The production method according to claim 1, wherein the extrusion is performed while applying pressure to the free end of the extrusion.