KR20010017376A - Nonocomposite rare earth magnet and it manufacturing method - Google Patents

Abstract

PURPOSE: A rare earth based nanocomposite permanent magnet and its fabrication method are provided to give excellent magnetic properties by the magnetic coupling between the magnetically hard and soft phases. CONSTITUTION: The rare earth based nanocomposite permanent magnet has a structure consisting of a magnetically hard phase and a magnetically soft phase partly replaced with cobalt each finely dispersed in the other in a fineness. The rare earth based nanocomposite permanent magnet is Nd<SB POS="POST">3+y</SB>Fe<SB POS="POST">78.5-x</SB>Co<SB POS="POST">x</SB>Hf<SB POS="POST">0.5</SB>Ga<SB POS="POST">0.5</SB>B<SB POS="POST">18.5-y</SB> with the range of 3 ≤ x ≤ 7, 0 ≤ y ≤ 3 and with a particle diameter from 10 nm to 30 nm. To prepare the amorphous magnet, materials are melted and high-speed solidification of the alloy melt is performed with the range of 10<SP POS="POST">5</SP> and 10<SP POS="POST">6</SP> °C/sec. Heat treatment of the alloy to effect microcrystallization for a finely dispersed structure is performed about 610 and 740 °C during 5 or 20 minutes.

Description

Ultrafine rare earth permanent magnet composition and manufacturing method of permanent magnet using same {NONOCOMPOSITE RARE EARTH MAGNET AND IT MANUFACTURING METHOD}

The present invention relates to an Nd-Fe-B-based ultrafine grain rare earth permanent magnet composition having excellent magnetic properties by co-complexing ferromagnetic Nd ₂ Fe ₁₄ B and weak magnetic Fe ₃ B, and more particularly, to a method of preparing permanent magnets using the same. , By adding 3 ~ 7 atoms of cobalt to refine the ferromagnetic Nd ₂ Fe ₁₄ B and weak magnetic Fe ₃ B crystals, and evenly distribute the particle size to improve the interaction between the grains of N 2 magnetic particles. -Fe-B-based ultrafine grain rare earth permanent magnet composition and a permanent magnet manufacturing method using the same.

Permanent magnet material is mainly used as a component of the rotor of the drive motor. Traditionally, bar-ferrite or strontium ferrite permanent magnets, which are mainly made of hard magnet ferrite, are used. Can be mentioned. They are inexpensive but have good magnetic properties and are widely used in various general-purpose motors, small household motors, and automobile motors. However, in recent years, the electric and electronic products have become smaller and smaller, while the electric characteristics of the motor require more improved products. Therefore, there is a demand for a material having much superior magnetic properties of a permanent magnet that is a material of a rotor.

As a material for overcoming the limitations of the traditional permanent magnets, a rare earth permanent magnet material having improved both residual magnetization and intrinsic coercivity has been developed. In other words, the magnetic substance of the Nd ₂ Fe ₁₄ B compound is an intermetallic compound magnetic substance having iron (Fe) as a main element and a rare earth element niobium (Nd) as a secondary element. Due to the original characteristics of the crystal structure, the magnetic material has a large anisotropic energy as well as its large magnetization power, and its use is rapidly expanding as a new magnetic material. In recent years, such rare earth magnets are employed in high performance small motors. There is a tendency to be. However, these rare earth magnets have excellent magnetic properties but are expensive and cannot completely replace the conventional hard magnetic ferrites.

As an example of the technology for solving the above problems there is a Korean patent application (Application No. 95-66229) of the present inventors. As a result, a Nd-Fe-B based permanent magnet material having cobalt added to a ferromagnetic Nd ₂ Fe ₁₄ B, a weak magnetic Fe ₃ B, and α-Fe of 3 atoms or less and a method of manufacturing the same are proposed. In the magnetic material described above, the grain size of the two magnetic phases present in the material is controlled in the nanometer range and the grain boundary between the two magnetic grains is removed. Therefore, the magnetic moment between the two interfaces physically exchanges, and the coercive force and the magnetization force are improved according to the characteristics of the ferromagnetic and weak magnetic bodies, so that they have not only excellent magnetic properties but also Nd, a high rare earth element. Since the amount of used can be reduced, the price of the material can be lowered. However, in the magnetic material, it is difficult to control the grain size of each magnetic body to be less than 20 nm, and there is a problem in that excellent magnetic properties cannot be stably obtained because uniformity of the particle size distribution of each magnetic body cannot be achieved.

Another method for manufacturing a micro-rare earth magnetic material in which ferromagnetic materials (Nd ₂ Fe ₁₄ B) and weak magnetic materials (Fe ₃ B and α-Fe) coexist and is applied. There is a Korean patent application (Application No. 95-68462) of the present inventor to reduce the grain size and improve the magnetic properties. However, this method is inconvenient in that it is not possible to achieve uniformity of the particle size distribution of the magnetic substance and also to apply a new magnetic field.

In order to solve the above problems, the present inventors have found that, when an appropriate amount of cobalt is added, the crystallization temperature of the ferromagnetic and weak magnetic phases can be controlled. The discovery of this possibility has led to the completion of the present invention.

Therefore, in the present invention, cobalt is contained in 3 to 7 atoms, and thus the fine particles and particle size distribution of the ferromagnetic substance (Nd ₂ Fe ₁₄ B) and the weak magnetic substance (Fe ₃ B) are promoted to activate the interaction between the grains of the magnetic substance. An object of the present invention is to provide an Nd-Fe-B-based ultrafine grain rare earth permanent magnet composition having excellent magnetization and coercivity.

In addition, the present invention, by the heat treatment at a predetermined temperature using the permanent magnet composition to achieve a fine particle size and particle size distribution of each magnetic material to produce an Nd-Fe-B-based ultrafine grain rare earth permanent magnet excellent in residual magnetization and coercivity The purpose is to provide a method.

In order to achieve the above object, the present invention has a composition of Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y , wherein the ferromagnetic phase Nd ₂ Fe ₁₄ B and the weak magnetic phase Fe ₃ B coexist and complex It provides a Nd-Fe-B-based ultrafine grain rare earth permanent magnet composition having a crystal grain size of 10 ~ 30nm in each magnetic phase. Where x and y are in the range of 3 ≦ x ≦ 7 and 0 ≦ y ≦ 3.

In addition, the present invention dissolves the base material having a composition of Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y (where x and y are in the range of 3≤x≤7, 0≤y≤3) After quenching at a cooling rate of 10 ⁵ ~ 10 ⁶ ℃ / sec to form an amorphous magnetic material, Nd-Fe-B-based ultrafine grain rare earth including heat treatment for 5 to 20 minutes in the temperature range of 610 ~ 740 ℃ It provides a permanent magnet manufacturing method.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Permanent magnet composition according to the present invention using a low content of Nd as a ferromagnetic Nd ₂ Fe ₁₄ B phase, as well as a weak magnetic phase α-Fe and Fe ₃ based on iron (Fe) showing the highest magnetizing power By coexisting B at the same time to generate the exchange coupling (exchange coupling) to maximize the residual magnetization force and intrinsic coercivity to reach the usable range, so as to secure excellent magnetic properties Maximization of exchange interactions is necessary.

The maximization of this exchange interaction is achieved by crystallizing each crystal phase when Nd ₂ Fe ₁₄ B and Fe ₃ B crystal phases are formed by heat treatment of a melt of Nd-Fe-B-based magnetic material into an amorphous magnetic material using a rapid cooling technique. This is made possible by controlling the crystallization temperature and controlling the grain growth rate of each phase accordingly. In other words, by appropriately controlling the grain growth rate of each magnetic material in the heat treatment step, it is possible to maximize the exchange interaction by minimizing the particle size and uniformity of the particle size distribution of each magnetic material.

However, when the amorphous magnetic body obtained by conventional quenching and solidification is heat-treated in the range of 600 to 750 ° C, a weak magnetic Fe ₃ B grain is formed in the temperature range of 585 to 615 ° C, and Nd ₂ Fe ₁₄ B is a ferromagnetic material. Since the grains are produced at 630 ~ 655 ℃ and grow over time, it is difficult to simultaneously secure the particle size distribution and uniform particle size distribution of each magnetic material.

In this regard, the inventors of the present invention have found that the addition of three atoms or more of cobalt to the rare earth-based magnetic material makes it possible to control the crystallization temperature of each of the magnetic bodies, and came up with the present invention. In detail, the crystallization temperature of each magnetic material is different depending on the amount of Co added. The more the amount is added, the higher the Fe ₃ B grain formation temperature (crystallization temperature) is adjusted to 585 → 610 ° C. and the ferromagnetic material is The formation temperature of Nd ₂ Fe ₁₄ B grains is controlled down to 655 → 630 ° C. Therefore, when more than 3 atoms of Co are added, the ferromagnetic Nd ₂ Fe ₁₄ B can be produced while suppressing the grain growth of the weak magnetic Fe ₃ B during the heat treatment of the amorphous magnetic material, thereby minimizing the grain size of each phase. However, since the particle size distribution can be uniform, the average particle size distribution of each phase can be narrowed, thereby maximizing the interaction effect between the grains of Fe ₃ B and Nd ₂ Fe ₁₄ B.

Therefore, the composition of the present invention has a compositional formula of Nd-Fe-B-based Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y (where x and y are reactors 3≤x≤7, 0≤ a y≤3 range), if the rapid cooling these compositions saeroeun heat treatment under the following specific conditions were formed of an amorphous magnetic material, that the crystal grain size in the range of 10 ~ 30nm grain size distribution uniform ferromagnetic Nd ₂ Fe ₁₄ B and stands for Co-complex of adult Fe ₃ B is formed.

As described above, the present invention requires that at least 3 atoms of Co be added in order to maximize the interaction between the magnetic materials. Preferably, 3 to 7 atoms are added. This is because if Co is added less than 3 atoms, the grain size is not refined, and if it exceeds 7 atoms, the price of materials increases, the overall manufacturing process becomes difficult, and the heat treatment temperature also increases.

On the other hand, it is more preferable to limit the amount of Co added to 3 to 5 atoms, which is not only increases the price of the material when the amount of Co added exceeds 5 atoms, but also lowers magnetic properties, particularly residual magnetic flux density. Because there is a tendency.

In addition, according to the present invention, in a magnetic body having a composition of Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y (where x and y are in the range of 3≤x≤7, 0≤y≤3) The volume fraction of ferromagnetic Nd ₂ Fe ₁₄ B and weak magnetic Fe ₃ B is important for the magnetic properties of the material. The volume fraction is determined by the amount of boron (B) added, the cooling rate during quenching and subsequent heat treatment conditions. In the present invention, the volume fraction of the ferromagnetic Nd ₂ Fe ₁₄ B and the weak magnetic Fe ₃ B is Nd. ₂ Fe ₁₄ B: It is preferable that Fe ₃ B = (20-30 volume): (70-80 volume). This is an emergency weak-magnetic material is Fe if the volume fraction of the ₃ B exceeds the above is caused a sharp decrease in the coercive force, the ferromagnetic an Nd ₂ Fe ₁₄ B when the volume fraction exceeds the coercivity of the rise, but a sharp decrease in the residual magnetic flux density Because it can cause.

In addition, the grain size of each of the ferromagnetic and weak magnetic particles precipitated in the magnetic body having the composition of the present invention is limited to 10 to 30 nm, but in order to ensure excellent magnetic properties, the size is limited to 10 to 20 nm and the particle size distribution is uniform. It is preferable to. The grain size and the particle size distribution of the ferromagnetic and weak magnetic bodies present in the magnetic composition of the present invention are important factors for the magnetic properties affecting the interaction between the magnetic grains. The crystal grain size and its particle size distribution of each magnetic body are generally affected by the heat treatment conditions. In other words, if the heat treatment temperature is high or the heat treatment time is long, the grains of the magnetic phases may be large and the residual magnetic flux density may be reduced. Therefore, an appropriate heat treatment condition should be selected. However, as described above, since the formation temperatures of the ferromagnetic Nd ₂ Fe ₁₄ B grains and the formation temperatures of the weak magnetic Fe ₃ B grains are different, it is difficult to attain both the grain size of each magnetic body and the uniformity of the particle size distribution at the same time. .

Therefore, in the present invention, by adding 3 to 7 atoms of Co, which can control the formation temperature of the grains of each magnetic body, the crystal grain size of each magnetic body is not only refined, but also the uniformity of the particle size distribution is characterized.

Hereinafter, the permanent magnet manufacturing method of the present invention will be described in detail.

First, the rare earth composition of the present invention having a composition of Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y (where x and y are in the range of 3≤x≤7, 0≤y≤3) Is melted by induction melting, plasma arc melting, etc. to make a molten metal and then quenched in a rapid cooling apparatus to prepare a quenching magnetic material amorphous in the form of ribbon or powder.

As described above, the rapid cooling rate affects the volume fraction of each magnetic body constituting the magnetic body composition. That is, with increasing cooling rate stands, and results in a magnetic material is Fe ₃ B amount is excessive by an abrupt decrease in the coercive force, and to the contrary steel magnetic material Nd ₂ Fe ₁₄ B amount is excessive, resulting in a rapid decrease in the residual magnetic flux density. Therefore, in the present invention, the cooling rate is preferably limited to 10 ⁵ ~ 10 ⁶ ℃ / sec. The amorphous magnetic material prepared by quenching as described above may be heat-treated in a heat treatment furnace in a vacuum atmosphere to obtain a final composite magnetic compound.

As the heat treatment proceeds, as described above, Fe ₃ B grains, which are weak magnetic bodies, are produced at 585 to 615 ° C., and ferromagnetic Nd ₂ Fe ₁₄ B grains are then started to be formed in the range of 630 to 655 ° C. However, when Co is added to 3 to 7 atoms that can control the crystallization temperature of each magnetic material, the formation temperature (crystallization temperature) of the weak magnetic material is controlled toward a higher temperature as the amount of the added content increases (585 → 610 ° C). ), The production temperature of the ferromagnetic material can be adjusted down to 655 → 630 ℃. At this time, the exact value of the crystallization temperature may vary depending on the manufacturing conditions and manufacturing facilities. Therefore, in the present invention, by adding Co-rules 3 to 7 atoms, the ferromagnetic Nd ₂ Fe ₁₄ B can be produced while suppressing the grain growth of the weak magnetic material Fe ₃ B during the heat treatment, thereby minimizing the grain size of each phase as well as the particle size. Uniform distribution can be achieved.

Considering the above point, in the present invention, the heat treatment is preferably carried out for 5 to 20 minutes at a temperature of 610 ~ 740 ℃, which is the growth of grain size when the heat treatment temperature exceeds 740 ℃ or heat treatment time exceeds 20 minutes This is because the residual magnetic flux density deteriorates, and if the heat treatment temperature is less than 610 ° C. or less than 5 minutes, the complete crystallization of the amorphous magnetic material does not occur, which is not suitable for forming an ultrafine composite phase.

On the other hand, it is most preferable that the heat treatment is performed for 5 minutes at 660 ~ 690 ℃ in order to form the critical grain size that the interaction occurs most smoothly.

Hereinafter, the present invention will be described in detail through examples.

(Example 1)

_{Nd 4 Fe 76.5 Hf 0.5 Ga 0.5} B 18.5, Nd 4 Fe 73.5 Co 3 Hf 0.5 Ga 0.5 B 18.5, Nd 4 Fe 72.5 Co 4 Hf 0.5 Ga 0.5 B 18.5 and Nd ₄ Fe _72.5 magnetic material Co5Hf _0.5 Ga _0.5 B _18.5 Composition The compound was dissolved by plasma arc and then re-dissolved several times to obtain a uniform composition.

The molten alloy was ingot made, re-dissolved in an induction furnace, and then sprayed on a quench rotor rotating at high speed to produce an amorphous magnetic ribbon. At this time, the rotational speed of the surface of the rotating body was 24 m / sec.

As a result of analyzing the ribbon prepared as described above by X-ray diffraction test, it was confirmed that the entire amount of amorphous tissue was produced. In addition, by measuring the crystallization temperature of the Fe ₃ B and Nd ₂ Fe ₁₄ B phase through the thermo-magnetic analyzer (Thermo-magnetic analyzer), and the change of the crystallization temperature of each phase according to the change of Co content Table 1 shows. In addition, the amorphous magnetic ribbon prepared as described above was subjected to heat treatment in a vacuum heat treatment furnace. At this time, the initial vacuum was 4 × 10 ^-6 Torr or less and heated to the desired temperature, the specified heat treatment temperature was fixed at 680 ℃ and the heat treatment time was 10 minutes. And the volume fraction of the Fe ₃ B and Nd ₂ Fe ₁₄ B phase through the Mossbauer spectroscopy spectroscopic analysis of the heat-treated magnetic ribbon is shown in Table 1 below.

Changes in Crystallization Temperature and Volume Fraction of Magnetic Materials with Co Addition Alloy composition Crystallization Temperature (℃ Volume fraction () Fe ₃ B Nd ₂ Fe ₁₄ B Fe ₃ B Nd ₂ Fe ₁₄ B Nd ₄ Fe _76.5 Hf _0.5 Ga _0.5 B _18.5 598 646 79 21 Nd ₄ Fe _73.5 Co ₃ Hf _0.5 Ga _0.5 B _18.5 599 641 72.4 27.6 Nd ₄ Fe _72.5 Co ₄ Hf _0.5 Ga _0.5 B _18.5 603 638 72 28 Nd ₄ Fe _72.5 Co5Hf _0.5 Ga _0.5 B _18.5 608 635 71.6 28.4

As shown in Table 1, it can be seen that the crystallization temperature of the ferromagnetic phase Nd ₂ Fe ₁₄ B crystals is down-regulated and the crystallization temperature of the weak magnetic phase Fe ₃ B crystals is up-regulated as the amount of Co is increased. In addition, although the volume fraction change of each magnetic phase according to the addition of Co is measured slightly, it can be seen that there is no significant difference in view of the range.

(Example 2)

The magnetic compound of the same composition as in Example 1 was rapidly cooled in the same manner to prepare an amorphous magnetic ribbon. The prepared amorphous magnetic ribbon was heat-treated in a vacuum heat treatment furnace in the same manner as in Example 1. However, the heat treatment temperature was performed at different temperatures, the heat treatment time was applied to 10 minutes the same regardless of the composition. And the magnetic properties of the heat-treated magnetic ribbon heat-treated as described above using a vibrating sample magnetometer (vibrating sample magnetometer) was measured, and the average value of the results of measuring the specimen three times of each condition is shown in Table 2 below.

As shown in Table 2, it can be seen that the magnetic properties are generally improved by adding Co. However, it can be seen that the inventive steel containing more than 3 atoms of Co exhibits better magnetic properties at the same heat treatment temperature than that of comparative steel containing less than 3 atoms of Co. Particularly, in the inventive steel, when the heat treatment temperature is 680 ° C., it shows the best magnetic property, which indicates that the critical grain size, that is, the most active grain size in the vicinity of the temperature, is a result of proper formation.

Therefore, as described above, in the present invention, by controlling the amount of Co added to 3 to 7 atoms, not only the grain size of the ferromagnetic and weak magnetic particles can be refined, but also the uniformity of the particle size distribution can be achieved. It can be seen that there is a useful effect in the production of Nd-Fe-B-based ultrafine rare-earth magnetic material having excellent magnetic properties.

Claims (7)

Nd _{3 + y} Fe _78.5-x Co _x Hf _0.5 Ga _0.5 B _18.5-y , ferromagnetic Nd ₂ Fe ₁₄ B and the weak magnetic phase Fe ₃ B co-composite complex, the crystal grain size of each magnetic material 10 ~ 30nm Nd-Fe-B Ultrafine Grain Rare Earth Permanent Magnet Composition Where x and y are in the range of 3 ≦ x ≦ 7 and 0 ≦ y ≦ 3. The composition of claim 1, wherein x is in the range of 3 ≦ x ≦ 5. The composition according to claim 1 or 2, wherein the sizes of the magnetic bodies Nd ₂ Fe ₁₄ B and Fe ₃ B grains are 10-20 nm, respectively. The method of claim 3, wherein the Nd ₂ Fe ₁₄ B and Fe ₃ B are mixed with Nd ₂ Fe ₁₄ B: Fe ₃ B = (20 ~ 30 volume): (70 ~ 80 volume) volume ratio Composition _{Nd 3 + y Fe 78.5-x} Co x Hf 0.5 Ga 0.5 B 18.5-y after dissolving the base material having the composition (where, x and y are atom 3≤x≤7, 0≤y≤3 range) 10 ^5-10 Method of producing an Nd-Fe-B-based ultrafine grain rare earth permanent magnet comprising quenching at a cooling rate of ⁶ ℃ / sec to form an amorphous magnetic material, and heat-treating the magnetic material at a temperature range of 610 ~ 740 ℃ for 5 to 20 minutes The method of claim 5, wherein in the composition formula x is in the range 3≤x≤5 manufacturing method of a permanent magnet The method of claim 5, wherein the amorphous magnetic material is heat-treated for 10 minutes at a temperature of 670 ~ 690 ℃, permanent magnet manufacturing method