JPS63285911A - Permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve performance, and to reduce cost by specifying the crystal mean grain size of a magnet and limiting the concentration of carbon and oxygen contents in the magnet using a rare earth element, iron and boron as basic ingredients. CONSTITUTION:In a permanent magnet employing a rare earth element (where including Y), iron and boron as basic ingredients, crystal mean grain size ranges from 0.1mum to 100mum, carbon and oxygen contents respectively range from 400ppm to 1000ppm, and amorphous phase is not contained. For form such a permanent magnet, the basic ingredients are cooled so that the crystal mean grain size of the basic ingredients ranges from 0.1mum to 100mum, and thermally treated at a temperature of 250 deg.C or higher. Cooling is further accelerated and the crystal mean grain size is brought to 30mum or smaller, and the basic ingredients are thermally treated at a temperature of 250 deg.C or higher, crushed, and kneaded and bonded with a resin. The bonded basic ingredients are casted so that the crystal mean grain size ranges from 0.1mum to 100mum, and hot-worked at a temperature of 500 deg.C or higher, thus changing the basic ingredients into anisotropy. The hot-worked basic ingredients are further turned into anisotropy, and thermally treated at a temperature of 250 deg.C, thus acquiring the permanent magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a permanent magnet whose basic components are rare earth elements and boron of iron, and a method for manufacturing the same.

(Prior Art) Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from various household electrical appliances to peripheral terminal equipment for large computers.

With the recent demand for smaller and more efficient electrical products,
Permanent magnets are also required to have increasingly higher performance. Typical permanent magnets currently in use are alnico, hard ferrite, and rare earth-transition metal magnets. In particular, R-Co permanent magnets, which are rare earth-transition metal magnets, and R-
Since Fe-B permanent magnets can provide high magnetic performance, much research and development has been carried out on them.

Conventionally, there are methods for manufacturing these R-Fe-B permanent magnets as shown in the following documents.

(1) Sintering method based on powder metallurgy.

(Reference 1, Reference 2) (2) A quenched thin strip with a thickness of about 30 μm is made using a quenched ribbon manufacturing device used to produce an amorphous alloy, and the quenched thin section is made into a magnet using a resin bonding method. The quenched using the melt spinning method. Resin bonding method using thin pieces. (Reference 3, Reference 4
) (3) The quenched flakes used in method (2) above,
A method that performs mechanical alignment treatment using a two-step hot press method.

(Reference 4, Reference 5) Here, Reference 1: JP-A-59-46008; Reference 2: M
, Sagawa, S., Fuji imura, N., T.
ogawa, H., Yamamoto, and Y.
, Matsuura; J', A, ppI, Phys, V
ol, 55 (6) 15 Maroh 1984. p2
083° Document 3: JP-A-59-211549; Document 4: R,
W, Lee; APPI, Phys, Lett, Vo
l, 46 (8), 15APrif 1985. p7
90; Document 5: Japanese Unexamined Patent Publication No. 80-100402 Next, the above conventional method will be explained.

First, in the sintering method (1), an alloy ingot is produced by melting and casting, this ingot is crushed to a particle size of about 3 μm, kneaded with a binder, and press-formed in a magnetic field to complete a compact.

This compact is sintered in argon gas at a temperature of around 1100°C for 1 hour, and then heat treated at a temperature of around 600°C to improve its coercive force.

In the resin bonding method using quenched thin flakes by the melt spinning method described in (2,), first, the rotation speed of the quenched ribbon production equipment is optimized, and the R A ribbon-shaped thin piece of -Fe-B alloy with a thickness of 30 μm is produced. The crystal axes of the crystal grains in this flake are isotropically distributed and magnetically isotropic, and an isotropic magnet can be obtained by grinding to an appropriate particle size, kneading with resin, and press-molding. .

In the two-step hot pressing manufacturing method (3), the ribbon-folded quenched flakes used in (2) are pressed at around 700° C. in vacuum or inert gas at a pressure of ~1.4 ton/cmj. Next, 0.7 ton/cm at 700℃
- When pressed for several seconds to the initial thickness of 172 mm, the alloy becomes anisotropic and becomes dense and anisotropic R-Fe-
B magnets can be manufactured.

Also, Liquid dynamic compac
An alloy that exhibits a coercive force in a bulk state is also produced by the ion method (hereinafter referred to as the LDC method). (Reference 6) Reference 13: T, S, Chin et al., J, Apl) 1°Ph
ys, 59 (4) + 15 February1
98B, p1297 [Problems to be solved by the invention] Although it is possible to manufacture permanent magnets whose basic components are rare earth elements, iron, and boron using the conventional techniques described above, these manufacturing methods have the following drawbacks. are doing.

For the sintering method (1), it is essential to turn the alloy into powder, but in the case of R-Fe-B magnet alloys, the powder is highly active against oxygen, so it is used in the sintering method. Powder must be strictly controlled, and expensive equipment such as an inert gas atmosphere is required.

In addition, in the sintering method, there are problems such as carbon in the binder having a negative impact on magnetic performance and problems such as poor handling of the molded body called green body, which reduces production efficiency. It is difficult to say that this is a method that can fully take advantage of low raw material costs.

Furthermore, the methods (2) and (3) are interesting and change the concept of conventional permanent magnet manufacturing, but the production speed is about 10＠℃/s.
It requires very rapid cooling such as e c, and its structure contains not only a crystalline phase but also an amorphous phase, so it has poor thermal stability and cannot be hot-processed for anisotropy. A major disadvantage is that the process must be carried out in a short period of time to prevent crystallization, which is a problem caused by productivity.

The LDC method also has problems such as expensive equipment and poor production efficiency.

The present invention solves the above-mentioned drawbacks of the prior art, and its purpose is to provide a high-performance, low-cost rare earth-iron permanent magnet and a method for manufacturing the same.

[Means for solving problems]

The permanent magnet of the present invention is a magnet whose basic components are rare earth elements (including Y), iron, and boron, and has an average crystal grain size of 0.1 μm or more and 100 μm or less, and contains carbon and oxygen. 400ppm or less, 11000p each
It is a permanent magnet characterized by p or less.

Therefore, the first method for producing a permanent magnet is a method for producing a magnet whose basic components are rare earth elements (including Y), iron, and boron, in which the average crystal grain size is 0.1 μm or more and 100 μm or less. This is a method for producing a permanent magnet, which is characterized by cooling the magnet so that the permanent magnet is cooled, and then performing a heat treatment at 250° C. or higher.

The second method of manufacturing the permanent magnet is to further speed up the cooling in the first manufacturing method to achieve a diameter of 30 μm or less, and then
This method of producing a permanent magnet is characterized in that the magnet is heat treated at a temperature of 50° C. or higher, then pulverized, kneaded with a resin, and bonded.

A third method for manufacturing a permanent magnet is to make the magnet anisotropic by hot working at a temperature of 500° C. or higher after casting in the first manufacturing method. It's a method.

Furthermore, a fourth method for manufacturing a permanent magnet is a method for manufacturing a permanent magnet, which is characterized in that, after the hot working in the second manufacturing method, heat treatment is performed at 250° C. or higher.

[Effect]

A preferred composition of the permanent magnet used in the present invention, which has rare earth elements, iron, and boron as basic components, is 8 to 30 at. % of rare earth elements, 2 to 28 at. % of boron, and the balance is iron.

Rare earth elements include YlLalCe, PrtNdlP
m, Sm1Eu1Gds Tbs DVN HON E
rN Tm1Ybt Lu is used, but especially Nd,
Pr is preferred. Moreover, two or more types of these rare earth elements may be included. In addition to the basic components mentioned above, impurities unavoidable in the manufacturing process may be included, such as cobalt to improve the Curie temperature and temperature characteristics, and A1, CrsMosKai, Nbt Tas to improve the coercive force. Zrs
Hfs Ti, etc. may also be included.

When R-Fe-B magnets are classified based on their coercive force mechanism,
In the prior art, the sintering method (1) is the nucleage type, and the quenching methods (2) and (3) are the pinning method. Stated in phase terms, the sintering method consists of only a crystalline phase, and the quenching method includes an amorphous phase that becomes a pinning site. In terms of grain size, it is around 10 μm in the sintering method, and 0.1 μm in the quenching method. Generally, in the nucreation model, the main phase (
In the case of rare earth-iron-borrow system, R* Fe+, B phase,
It is said that the cause of coercive force generation is that R is a rare earth element) approaches the critical radius of a single magnetic domain and does not easily generate a reverse magnetic domain. However, although the critical radius of the R;Fe;aB phase is on the order of submicrons, the grain size of the sintered magnet is about 10 μm. In the case of the sintering method, this
Since the cast ingot is first pulverized, the surface area increases significantly and the oxygen concentration increases at that stage, making it impossible to create a sintered body with a particle size close to the critical radius.

In other words, as long as the magnet complies with the coercive force of the Nucleage Shuki model, you can obtain sufficient coercive force by increasing the cooling rate during casting than usual, without having to go through the process of crushing and sintering the casting ingot. R* to the possible particle size
The FeI'aB phase can be controlled. This method makes it possible to obtain coercive force in the bulk state, and is free from productivity problems such as difficulty in powder management. Furthermore, even though the cooling rate is faster than usual, there is no need to form an amorphous phase as in the conventional rapid cooling method, and the structure consists only of crystalline materials, so hot working for anisotropy can also be done at high temperatures. It can be done stably and with high productivity.

With magnets produced using conventional sintering methods, it was not possible to crush the finished magnets into resin-bonded magnets. This is due to mechanical strain caused by crushing and too large crystal grains. However, if the particle size is controlled by changing the cooling rate using the present invention, the particle size of resin-bonded magnet powder (several to several tens of μm) can be reduced.
m), it is possible to create a powder that has coercive force,
It becomes possible to create resin-bonded magnets that follow the nu-creation model.

As mentioned above, R- follows the nu-creation model.
In order to obtain coercive force in a Fe-B based magnet in a bulk underground state, its crystal grains must be appropriate. That is,
Even after hot working with an average grain size of over 100 μm upon cooling, the coercive force is still not sufficient for a rare earth magnet.
, 0.1 μm or less is below the critical radius of a single magnetic domain, so the average grain size must be 0.1 μm or more and 100 μm or less. These particle size controls can be accomplished by adjusting the mold material and heat capacity of the mold, or by using cooling rolls at low speeds that do not form an amorphous phase.

The heat treatment after cooling is necessary to diffuse the Fe phase that exists as primary crystals in the cast alloy to form a magnetically soft phase, and of course, the same heat treatment is also required after hot working. This has the effect of improving its magnetic properties.

Hot working at a temperature of 500°C or higher has the effect of orienting the crystal axes of the crystal grains to make them anisotropic, and also has the effect of making the crystal grains finer, significantly improving magnetic performance. . Setting the upper limit of the particle size to 30 μm or less by further increasing the cooling rate is effective in producing powder that has a coercive force when producing a resin bonded magnet by pulverization.

Next, embodiments of the present invention will be described.

〔Example〕

(Example 1) Table 1 shows the composition of a permanent magnet alloy whose basic components are various rare earth elements and iron boron used in this example.

First, an alloy with a desired composition is melted in an Ar atmosphere using a low-frequency melting furnace, and cast into various molds at 100.0°C.
After that, the jointed alloy was taken out. At this time, the rare earth metal used was one with a purity of 95% (impurities were mainly other rare earth metals), the transition metal used was one with a purity of 99.9% or more, and the boron used was a ferroboron alloy. .

These cast alloys are then heat treated at 250°C or higher (10
00° C. for 24 hours), cutting and grinding were performed to obtain a permanent magnet.

Table 2 shows the magnetic performance and average grain size of each composition when cast using an iron mold.

Further, FIG. 1 shows the relationship between the average grain size (μm) after molding and the coercive force iHc after hot pressing for samples using compositions No. 3, No. 4, and No. 4 in Table 1. At this time, the grain size was controlled using various molds such as water-cooled copper molds, iron molds, and ceramic molds, and by applying vibration to the molds. This result shows that a permanent magnet with high coercive force can be obtained by casting with controlled particle size.

Table 1 Table 2 (Example 2) The composition of the permanent magnet alloy shown in Table 3 was cast using a water-cooled copper mold in the same manner as in Example 1, and then hot pressed at 1000°C to anisotropically It became sexualized.

Table 4 shows the average grain size and magnetic performance when heat treated at the casting stage and the average grain size and magnetic performance after hot pressing.

Also, No. 11 and No. 13. Table 5 shows the magnetic properties of samples No. 14 when they were heat-treated at 1000° C. for 24 hours after hot pressing.

Table 3 Table 4 Table 5 As is clear from the results, it can be seen that hot working reduces the grain size and significantly improves the magnetic performance.

It is also seen that heat treatment improves magnetic performance.

(Example 3) Pr+tFe7* which had the highest performance in Example 2
Ba compositions were prepared using conventional sintering methods and ribbons cooled by twin rolls at a roll rotation speed of 10 m/s using the present invention. In the sintering method, the cast ingot is
Mechanically pulverize using a stamp mill or ball mill, 1
After magnetic field forming at 5KOe, sintering was performed at a temperature of 1000° C. for 1.5 hours. At this stage (BM)max=25.4MG
Oes 1Hc=10.4KOe. After crushing this again to make the average particle size 20 μm, 2 wt% of epoxy resin was added, and after magnetic field molding at 15 KOe again, 15
A resin-bonded magnet was cured at a temperature of 0°C.

In the rapid cooling method using the present invention, twin rolls with a radius of 30 mm (
10m/chrome-plated copper roll)
The molten metal having the composition was injected with Ar gas and rapidly cooled to form a ribbon. At this time, the ribbon thickness was about 50 μm. This was annealed at 700° C. for 1.5 hours, pulverized to an average particle size of 20 μm in the same manner as in the sintering method, and bonded with the same epoxy resin to produce a resin-bonded magnet.

The results are shown in Table 6.

Table 6: After sintering and pulverization, the coercive force is drastically reduced.1 However, by using the present invention, it is possible to produce resin-bonded magnets even if the conventional quenching method (roll speed of 20 m/s or more) is not as fast. I understand. The resulting magnet's cut curve was of the New Creation type, with a steep rise.

〔Effect of the invention〕

As described above, according to the permanent magnet of the present invention and its manufacturing method, a sufficient coercive force can be obtained from a bulk magnet without going through the steps of crushing and sintering, and the manufacturing process can be significantly simplified. ,
It becomes possible to manufacture low-cost, high-performance permanent magnets. Furthermore, by adjusting the particle size, it is also possible to manufacture resin-bonded magnets consisting only of crystalline phases.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the coercive force iHc after hot pressing and the average grain size after casting in Examples of the present invention. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Tsutomu Mogami and 1 other person: /nee, -!

Claims (5)

[Claims] (1) In a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the average crystal grain size is 0.1μ.
m or more and 100 μm or less, carbon and oxygen content are 400 ppm or less and 1000 ppm or less, respectively, and does not contain an amorphous phase. (2) In a method for manufacturing a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cooled to a temperature of 250°C so that the average crystal grain size becomes 0.1 μm or more and 100 μm or less. A method for producing a permanent magnet, characterized by performing heat treatment at a temperature above. (3) In a method for manufacturing a magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cooled to have an average crystal grain size of 0.1 μm or more and 30 μm or less, and then cooled to 250°C or more. A method for producing a permanent magnet, characterized in that the permanent magnet is subjected to heat treatment at a temperature of , and then pulverized, kneaded with resin, and bonded. (4) In a method for manufacturing a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cast so that the average crystal grain size is 0.1 μm or more and 100 μm or less, and then heated at 500°C. A method for producing a permanent magnet, characterized in that it is made anisotropic by hot working at a temperature above. (5) In a method for manufacturing a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cast so that the average crystal grain size is 0.1 μm or more and 100 μm or less, and then heated at 500°C. A method for producing a permanent magnet, which comprises making it anisotropic by hot working at a temperature above, and then heat treating at a temperature above 250°C.