JPH06251917A - Rare earth element permanent magnet - Google Patents

Abstract

PURPOSE:To avoid the crazing and cracking in the title rare earth element permanent magnet by a method wherein the title magnet comprising R, Fe, B, Ca as the material basic components manufactured by hot working and heat treatment after molding step has R6Fe11Ga3 phase as the composing phase while containing the alloy composition in a specific composition region. CONSTITUTION:The rare earth element permanent magnet to be manufactured by hot rolling step after melting down and molding step of an alloy using R (R represents rare earth element mainly comprising Pr, Nd) Fe, B, Ga as the material basic components and further heat treatment has R6Fe11Ga3 phase as a composing phase. Furthermore, when the alloy composition is represented by RxFeyBzGa100-x-y-z in atomic ratio, the earth element is to be in the composition region of x>=15, y-14z>0, z>=4, 100-x-y-z<2. In such a constitution, the title rare earth element permanent magnet having high performances and excellent corrosion resistance can be manufactured at low cost.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R (where R is Pr,
The present invention relates to a rare earth permanent magnet containing Nd as a main component, Fe, B, and Ga as raw material basic components.

[0002]

2. Description of the Related Art R-Fe-B system permanent magnets have been much researched and developed since the announcement in 1983 as permanent magnets having extremely high coercive force and energy product.

Conventionally, there are the following methods for producing these R—Fe—B type high-performance anisotropic permanent magnets.

(1) First, Japanese Patent Laid-Open No. 59-46008 and M. Sagaw
a, S.Fujimura, N.Togawa, H.Yamamoto and Y.Matsuura; JA
In ppl.Phys.Vol.55 (6), 15 March 1984, p2083, etc., 8 to 30% of R (where R is at least one rare earth element including Y) and 2 to 28% of B in atomic percentage are described. It is disclosed that a permanent magnet characterized by being a magnetic anisotropic sintered body composed of Fe and the balance Fe is manufactured by sintering based on the powder metallurgy method.

In this sintering method, an alloy ingot is produced by melting and casting and crushed to obtain a magnetic powder having an appropriate particle size (several μm). The magnetic powder is kneaded with a binder, which is a molding aid, and press-molded in a magnetic field to form a molded body. The compact is sintered in argon at a temperature of about 1100 ° C. for about 1 to 5 hours and then rapidly cooled to room temperature. 600 ° C after sintering
The permanent magnet further improves the coercive force by heat treatment at the temperature around.

Regarding the heat treatment of this sintered magnet, Japanese Patent Laid-Open No. 61-217540, Japanese Patent Laid-Open No. 62-165305, etc.
The effect of multi-step heat treatment is disclosed.

(2) JP-A-59-211549 and RWLee; A
Vol. 46 (8), 15 April 1985, p790, ppl.
Fe-B magnets are disclosed. This permanent magnet is manufactured by a quenching ribbon production apparatus used for producing an amorphous alloy, by making a quenching thin piece having a thickness of about 30 μm, kneading the thin piece with a resin and press-molding.

(3) JP-A-60-100402 and RWLee; Ap
In Pl. Phys. Lett. Vol. 46 (8), 15 April1985, p790, the quenched flakes used in the method of (2) above are prepared by a method called a two-step hot pressing method in vacuum or in an inert atmosphere. It is disclosed to obtain a dense and anisotropic R-Fe-B magnet.

(4) Japanese Patent Laid-Open No. 64-704 discloses R, Fe,
After melting and casting an alloy containing B and Cu as basic components, the cast ingot is subjected to hot working at a temperature of 500 ° C. or higher to refine the crystal grains and to orient the crystal axes in a specific direction. A method for producing a rare earth permanent magnet by a so-called casting / hot working method, which is characterized by magnetically anisotroping a cast alloy, is disclosed. Further, Japanese Patent Application Laid-Open No. 1-175206 discloses a rare earth-iron-based magnet by a casting / hot working method in which Al 15 atomic% or less, Cu 6 atomic% or less, and Ga 6 atomic% or less are added. Further, in JP-A-4-105305, the main phase R ₂ Fe ₁₄ B phase and the second phase R- (Ga,
A rare earth permanent magnet made of an In, Sn) -based low melting point phase by a casting / hot working method is disclosed.

[0010]

The conventional methods for manufacturing R-Fe-B based permanent magnets (1) to (4) above have the following drawbacks.

The method for producing a permanent magnet of (1) requires that the alloy be made into a powder. However, since the R-Fe-B type alloy is very active in oxygen, if it is made into a powder. Oxidation becomes excessive, and the oxygen concentration in the sintered body will inevitably increase.

When molding the powder, it is necessary to use a molding aid, such as zinc stearate, which has been removed beforehand in the sintering process. However, it remains in the form of carbon in the magnet body, and this carbon remarkably deteriorates the magnetic performance of the R-Fe-B magnet, which is not preferable.

The green body after press molding with the addition of a molding aid is called a green body, which is very brittle and difficult to handle. Therefore, it takes a great deal of time to neatly put them side by side in the sintering furnace, which is a big drawback.

Because of these drawbacks, generally speaking, not only expensive equipment is required for producing an R--Fe--B system sintered magnet, but also the production method thereof has a low production efficiency, Eventually, the manufacturing cost of the magnet increases. Therefore, it is not possible to take advantage of the advantages of the R-Fe-B magnets, which have relatively low raw material costs.

Next, in the manufacturing methods of the permanent magnets of (2) and (3), a vacuum melt spinning device is used, but this device is currently very poor in productivity and expensive.

Since the permanent magnet of (2) is isotropic in principle, it has a low energy product, the squareness of the hysteresis loop is poor, and it is disadvantageous in terms of temperature characteristics and use.

The method (3) for manufacturing a permanent magnet is a unique method in which hot pressing is used in two steps.
It cannot be denied that it is inefficient considering mass production.

Further, in this method, the crystal grains are remarkably coarsened at a high temperature, for example, at 800 ° C. or higher, which causes the coercive force iHc
Becomes extremely low, and it does not become a practical permanent magnet.

The method of manufacturing a permanent magnet of (4) does not include a powder process and requires only one step of hot working, so that the manufacturing process is most simplified, but the performance is (1)- There was a problem that it was slightly inferior to (3). Although the addition of Ga improves the magnetic properties, this is not always the case as R-Ga as the second phase as described in JP-A-4-105305.
It is not obtained in the presence of the low melting point phase of the system, and even in the presence of such a second phase, there are large variations in the magnetic properties, especially the coercive force, and the coercive force remains quite low depending on the sample. The case was seen.

The present invention solves the drawbacks of the casting / hot rolling method, and an object of the invention is to provide a high-performance and low-cost method for producing a rare earth permanent magnet. It is in.

[0021]

According to the present invention, R (where R is a rare earth element containing Pr, Nd as a main component), Fe, B, G is used.
A rare earth permanent magnet obtained by melting / casting an alloy containing a as a raw material basic component, hot rolling, and further heat-treating the rare earth permanent magnet having a R ₆ Fe ₁₁ Ga ₃ phase as a constituent phase. It is a permanent magnet.

Further, the alloy composition has an atomic ratio of R _x Fe _y B _z G
When expressed as a _100-xyz , the rare earth permanent magnet is characterized by having a composition range of x ≧ 15 y-14z> 0 z ≧ 4 100-x−y−z <2.

[0023]

First, the R ₆ Fe ₁₁ Ga ₃ phase will be described. The presence or absence of this phase in the magnet structure can be easily determined by observing the structure with a polarization optical microscope. This is because it shows a very strong reflection for a specific polarized light. With respect to Sample No. 1 in Table 1 described later, composition analysis by EPMA of the phase confirmed by a polarization optical microscope was performed. As a result, this phase is approximately Pr30at%, F
It was found that the composition was composed of e54 at% and Ga14 at% and other trace elements, and the atomic ratio of Pr, Fe and Ga was approximately 6: 11: 3. According to F. Weitzer et al., Pr-Fe-G
In the study on the ternary alloy of a, R _{6 of} tetragonal compound
The existence of the Fe ₁₁ Ga ₃ phase has been confirmed (F. Weitzer et.
al; J. Less-Common Met. 167 (1990) 135), and it was found that this phase also exists in the magnet by the casting / hot working method as in the present invention.

R-Fe-B-Ga with R ₆ Fe ₁₁ Ga ₃ phase
In the system magnet, good magnetic characteristics, especially high coercive force can be obtained. It is considered that such improvement of the magnetic characteristics according to the present invention is due to the following effects.

The first effect is that the ferromagnetic phase, which can be a nucleus of magnetization reversal in the grain boundary phase portion, disappears. In the conventional R-Fe-B-Ga-based magnet, there were scattered ferromagnetic phases with low coercive force such as α-Fe or R ₂ Fe _{17 in} the grain boundary phase portion. Such a ferromagnetic phase becomes the nucleus of the magnetization reversal, so that the coercive force is drastically reduced. But R
_{When the 6} Fe ₁₁ Ga ₃ phase is formed, such a ferromagnetic phase disappears. The R ₆ Fe _{1 1} Ga ₃ phase rarely exerts a magnetic effect on the main phase as a nucleus of magnetization reversal, and it is considered that a good coercive force is obtained. The second effect is to promote the separation of the main phase crystal grains from each other and to suppress the grain growth of the main phase crystal grains. As will be seen in Examples described later, when the R ₆ Fe ₁₁ Ga ₃ phase does not exist at the grain boundary, there are many portions where the main phase grains are in contact with each other.
In such a portion, the magnetization reversal becomes easy and the coercive force is lowered. On the other hand, when the R ₆ Fe ₁₁ Ga ₃ phase exists uniformly dispersed in the grain boundary phase portion, the main phases are magnetically isolated well by this phase, and therefore the magnetization reversal is caused. It is thought that the high coercive force can be realized because it becomes less likely to occur. Judging from the microstructure photograph, when the R ₆ Fe _{1 1} Ga ₃ phase was present as the final magnet structure, the crystal grain size of the main phase was smaller than when the R ₆ Fe ₁₁ Ga ₃ phase was not present. ing. It is unclear whether the R ₆ Fe ₁₁ Ga ₃ phase directly contributes to the refinement of the crystal grain size of the main phase, but as a result, fine main phase grains are obtained and a high coercive force is realized. It

As described above, the presence of the R ₆ Fe ₁₁ Ga ₃ phase as a constituent phase in the magnet structure makes it possible to obtain high magnetic characteristics. However, by appropriately selecting the alloy composition, it is possible to significantly suppress the cracking / cracking of the rolled material during hot rolling, and it is possible to realize a high yield and reduce costs. The occurrence of cracks and cracks in the rolled material during hot rolling is due to the rare earth element R content of 15
It becomes violent when it becomes less than atomic%. It is considered that this is because the abundance ratio of the R-rich phase, which is in a liquid state at the hot rolling temperature at the grain boundary, becomes small, and a sufficient amount of liquid phase is not obtained to easily perform the semi-melt processing. Also Ga
The addition amount of has a great influence on the occurrence of cracks and cracks. Specifically, if the addition amount is 2 atomic% or more, the amount of cracks increases significantly. The reason for this is not clear, but it is thought that the cracks easily develop due to shear stress during rolling. Regarding the amount of Fe in the alloy composition, the composition range is such that all Fe is not consumed in the main phase because the R ₆ Fe ₁₁ Ga ₃ phase is present as a grain boundary phase, specifically, y-14z> 0. is necessary. If the amount of B is less than 4 atomic%, the amount of main phase will be insufficient and satisfactory magnetic properties will not be obtained.

Further, the generation of cracks / cracks increases the concentration of oxygen present in the magnet, which adversely affects the corrosion resistance.
Japanese Patent Laid-Open No. 4-62903 discloses that the corrosion resistance deteriorates when the oxygen concentration in the magnet exceeds 1500 ppm, but if cracks or cracks occur, oxidation proceeds from there and the oxygen concentration increases. Corrosion resistance deteriorates beyond 1500ppm. Therefore, by setting the alloy composition in the composition range as in the present invention, it is possible to obtain a secondary effect that good corrosion resistance can be secured.

The hot rolling conditions may be those already known in the above-mentioned patents and the like. Specifically, it is desirable that the temperature is not less than the recrystallization temperature of the main phase, and in the case of the alloy of the present invention, it is preferably not less than 500 ° C.

The heat treatment conditions after hot working are R ₆ Fe ₁₁ Ga ₃
It is desirable to carry out under the condition that a phase can be formed, and specifically it is desirable to carry out heat treatment in the temperature range of 400 to 800 ° C. Furthermore, 800-110 prior to this heat treatment
It is preferable to perform a two-step heat treatment in which the heat treatment is performed at a temperature of 0 ° C.

Next, examples of the present invention will be described.

[0031]

【Example】

(Example 1) An alloy having the composition shown in Table 1 was melted in an argon atmosphere using a high frequency induction heating melting furnace, and then cast in a mold. 99.9% as raw material for rare earth, iron and copper
Of the above-mentioned purity, and a ferroboron alloy was used as boron.

Next, the cast ingot was placed in an iron capsule, deaerated and sealed. Degree of processing at 950 ℃
30% hot rolling is performed 4 times in air, and finally the workability is 7
I made it 6%.

During hot rolling, the easy axis of magnetization of the main phase (R ₂ Fe ₁₄ B phase) was oriented so as to be parallel to the pushing direction of the alloy.

After this, 1025 ° C. × 20 in an argon atmosphere
A two-stage heat treatment of h + 500 ° C. × 6 h was performed.

When the structure at this time was observed by an optical microscope with polarized light, R ₆ Fe ₁₁ G was observed as a grain boundary phase other than the main phase.
Both what does and does not a _3-phase is present is observed. Here, a schematic diagram of the typical structure observation results of both is shown in FIG.
And shown in FIG. Figure 1 shows R ₆ Fe ₁₁ Ga ₃ as the grain boundary phase.
Due to the existence of phases, the separation of the main phases is promoted and the grain size is small. Figure 2 shows R ₆ Fe as the grain boundary phase.
_This structure has no ₁₁ Ga ₃ phase, the main phases are not well isolated from each other, and the main phase grain size is coarse.

Table 2 shows the magnetic properties of the rolled magnets having the alloy compositions shown in Table 1 and the presence / absence of the R ₆ Fe ₁₁ Ga ₃ phase judged from the results of observation with an optical microscope. The magnetic characteristics in this case were measured by a BH tracer with a maximum applied magnetic field of 25 kOe after the sample was magnetized with a pulsed magnetic field of 40 kOe.

[0037]

[Table 1]

[0038]

[Table 2]

As described above, R ₆ Fe ₁₁ Ga _{3 is used} as the constituent phase.
R-Fe-B-Ga permanent magnets with phases have high magnetic characteristics,
In particular, a high coercive force can be realized.

Example 2 Alloys having the compositions shown in Table 3 were melted and cast, and then rolled under the same conditions as in Example 1.

After the completion of rolling, the material was cooled and the rolled material was taken out from the iron capsule. The cross section including the rolling direction and the rolling direction of the obtained rolled material was observed, and the presence or absence of cracks / cracks was visually evaluated. The results are shown in Table 4.

Regarding the obtained rolled material, 1025 ° C. × 20 h + 500
A two-stage heat treatment of ℃ × 6h was applied to obtain a magnet sample. The R ₆ Fe ₁₁ Ga ₃ phase was confirmed as a constituent phase in all the magnet structures. The magnetic properties measured for these samples are also shown in Table 4. In this case, the magnetic characteristics of the sample
After magnetizing with a pulsed magnetic field of 40kOe, the maximum applied magnetic field is 25kOe.
Measured by BH tracer.

[0043]

[Table 3]

[0044]

[Table 4]

As described above, x ≧ 15, y-14z> 0,
By hot rolling an alloy in the composition range of z ≧ 4, 100−x−y−z <2, it is possible to obtain a rare earth permanent magnet having no cracks and good magnetic properties.

The oxygen concentration in the sample was measured for the same magnets as in Table 4 above. The measurement results are shown in Table 5. Also, each magnet sample is cut and polished into a desired shape, and the magnet surface is coated with an epoxy resin to a film thickness of 20 μm by a spray method, and then a corrosion resistance test is performed at a temperature of 60
Corrosion resistance was evaluated by observing the appearance and observing under atmospheric conditions of 90 ° C. and 90% humidity. The results are also shown in Table 5.

[0047]

[Table 5]

As described above, x ≧ 15, y-14z> 0, z ≧ 4, 10 in which no cracks or cracks occur in the rolled material.
In the alloy having a composition range of 0-x-yz- <2, the oxygen concentration is suppressed to be low, and as a result, good corrosion resistance is realized. On the other hand, the oxygen concentration of the magnet sample with cracks / cracks exceeds 1500 ppm,
Corrosion resistance is also deteriorated.

[0049]

According to the present invention, as described above, R, Fe,
It is manufactured by subjecting B and Ga to the raw material basic components and subjecting to hot working and heat treatment after casting, and R ₆ F as a constituent phase.
In the rare earth permanent magnet having the e ₁₁ Ga ₃ phase, high magnetic characteristics, especially high coercive force can be obtained. Further, the alloy composition is x ≧ 15, y-14z> 0, z ≧ 4, 100-x−y−z
When the composition range is <2, it is possible to manufacture a rare earth permanent magnet having no cracks / cracks, excellent mass productivity, and good corrosion resistance. Therefore, the advantage of the casting / hot working method that the high performance can be obtained at a low cost is further promoted as compared with the conventional sintering method and melt spinning method.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a rolled magnet structure in which an R ₆ Fe ₁₁ Ga ₃ phase exists.

FIG. 2 is a schematic view of a rolled magnet structure in which an R ₆ Fe ₁₁ Ga ₃ phase does not exist.

[Explanation of symbols]

1 R ₂ Fe ₁₄ B phase 2 R-rich phase 3 R ₆ Fe ₁₁ Ga ₃ phase

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Seiji Ihara 3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Co., Ltd. (72) Inventor Koji Akioka 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Within the corporation

Claims (2)

[Claims] 1. An alloy containing R (where R is a rare earth element containing Pr, Nd as a main component), Fe, B, and Ga as a raw material basic component is melted and cast, followed by hot rolling and further heat treatment. A rare earth permanent magnet obtained by the above method, having an R ₆ Fe ₁₁ Ga ₃ phase as a constituent phase. 2. The alloy composition has an atomic ratio of R _x Fe _y B _z Ga.
The rare earth permanent magnet according to claim 1, wherein when expressed as _100-xyz , x ≧ 15 y-14z> 0 z ≧ 4 100-x−y−z <2.