KR20210038256A - Manufacturing method of sintered magnet - Google Patents

Abstract

According to an embodiment of the present invention, a manufacturing method of a sintered magnet includes steps of: manufacturing a mixture by mixing rare earth oxide, iron, boron, a reducing agent and heavy rare earth oxide; heating the mixture at a temperature of 800.C to 1100.C to synthesize magnet powder using a reduction-diffusion method; and sintering the magnet powder to manufacture the sintered magnet, wherein the heavy rare earth oxide includes Dy^2O^3, thereby greatly improving coercive force of an R-Fe-B-based sintered magnet.

Description

Manufacturing method of sintered magnet {MANUFACTURING METHOD OF SINTERED MAGNET}

The present invention relates to a method of manufacturing a sintered magnet, and more specifically, to a method of manufacturing an R-Fe-B-based sintered magnet.

NdFeB-based magnets are permanent magnets having a composition of neodymium (Nd), a rare earth element, and Nd ₂ Fe ₁₄ B, a compound of iron and boron (B), and have been used as a general-purpose permanent magnet for 30 years after being developed in 1983. These NdFeB-based magnets are used in various fields such as electronic information, automobile industry, medical equipment, energy, and transportation. In particular, in line with the recent light weight and miniaturization trend, it is used in products such as machine tools, electronic information devices, electronic products for home appliances, mobile phones, robot motors, wind power generators, small motors for automobiles and driving motors.

For the general manufacture of NdFeB-based magnets, a strip/mold casting or melt spinning method based on a metal powder metallurgy method is known. First, in the case of the strip/mold casting method, metals such as neodymium (Nd), iron (Fe), and boron (B) are melted through heating to produce an ingot, and the grain particles are coarsely pulverized. And, it is a process of manufacturing microparticles through a micronization process. By repeating this, magnetic powder is obtained, and an anisotropic sintered magnet is manufactured through pressing and sintering processes under a magnetic field.

In addition, in the melt spinning method, metal elements are melted, poured into a wheel rotating at a high speed, and then quenched, jet milled, pulverized, blended with a polymer to form a bonded magnet, or pressed to form a magnet. To manufacture.

However, all of these methods require a pulverization process, a long time is required in the pulverization process, and there is a problem that a process of coating the surface of the powder after pulverization is required.

Recently, attention has been paid to a method of manufacturing a magnetic powder by a reduction-diffusion method. For example, it is possible to prepare uniform NdFeB fine particles through a reduction-diffusion process of mixing _{Nd 2} O _{3, Fe, and B and reducing it to Ca.}

However, in the case of the process of obtaining a sintered magnet by sintering the magnet powder produced by the reduction-diffusion method, grain growth accompanies the sintering in a temperature range of 1000 to 1250 degrees Celsius, and the growth of such grains decreases the coercive force. It acts as a factor to make. In addition, during sintering, grain growth (more than 1.5 times the size of the initial powder) and abnormal grain growth (more than twice the size of the general grain size) occur during sintering, which greatly decreases the theoretical coercivity that the initial powder can have.

Therefore, as a method to suppress the growth of crystal grains during sintering, the HDDR (Hydrogenation, disproportionation, desorption and recombination) process, a method of reducing the size of the initial powder through jet mill grinding, and a triple point by adding an element capable of forming a secondary phase. There is a method of suppressing the movement of grain boundaries by forming.

However, although the coercive force of the sintered magnet can be secured to some extent through the various methods described above, the process itself is very complicated and the effect on suppressing grain growth during sintering is still insufficient. In addition, the microstructure is greatly changed due to grain migration, and thus another problem occurs, such as a decrease in properties of a sintered magnet and a decrease in magnetic properties due to an additional element.

In addition, in the magnetic powder manufactured by the reduction-diffusion method, a cleaning process in which by-products such as calcium oxide (CaO) remain in the particles and remove them is essentially required.

However, in this cleaning process, particles of the magnetic powder may be oxidized to form an oxide film on the surface. The oxide film not only interferes with the sintering of the magnet powder, but also promotes the columnar decomposition, which causes deterioration of physical properties of the sintered magnet such as coercivity.

Embodiments of the present invention have been proposed to solve the above problems, and to provide a method of manufacturing a sintered magnet capable of greatly improving the coercivity of an R-Fe-B-based sintered magnet.

However, the problems to be solved by the embodiments of the present invention are not limited to the above-described problems and may be variously expanded within the scope of the technical idea included in the present invention.

A method of manufacturing a sintered magnet according to an embodiment of the present invention includes preparing a mixture by mixing a rare earth oxide, iron, boron, a reducing agent, and a heavy rare earth oxide; Heating the mixture at a temperature of 800°C to 1100°C to synthesize magnetic powder using a reduction-diffusion method; And sintering the magnet powder to manufacture a sintered magnet, wherein the heavy rare earth oxide includes Dy ₂ O ₃ .

The heavy rare earth oxide may be mixed in an amount of 3% by mass to 10% by mass relative to the mixture.

The rare earth oxide may include at least one _{of Nd 2} O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ and Eu ₂ O _3.

The sintered magnet is an R-Fe-B-based sintered magnet, and R may be Nd, La, Ce, Pr, Pm, Sm, or Eu.

The reducing agent may include at least one _{of Ca, CaH 2 and Mg.}

The manufacturing of the sintered magnet may include preparing a mixed powder by mixing the magnetic powder and the rare earth hydride powder, and sintering the mixed powder at 1000°C to 1100°C.

The method of manufacturing the sintered magnet may further include a heat treatment step after heating the sintered magnet to 500 to 800 degrees Celsius.

The manufacturing method of the sintered magnet may further include coating a heavy rare earth powder on the surface of the sintered magnet and performing heat treatment on the coated sintered magnet to diffuse the heavy rare earth element into grain boundaries.

According to embodiments of the present invention, a sintered magnet having high coercivity may be manufactured by adding a heavy rare earth oxide to prepare a magnet powder and sintering the magnet powder in a reduction-diffusion method.

1 is a BH curve graph for the sintered magnets of Example 1-1 and Example 1-2.
2 is a BH curve graph for the sintered magnets of Example 2-1 and Example 2-2.
3 is a BH curve graph for the sintered magnet of Comparative Example 1.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In addition, throughout the specification, when a certain part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

The method of manufacturing a sintered magnet according to an embodiment of the present invention includes preparing a mixture by mixing rare earth oxide, iron, boron, reducing agent, and heavy rare earth oxide, and heating the mixture at a temperature of 800 to 1100 degrees Celsius to reduce- And synthesizing the magnetic powder using a diffusion method, and sintering the magnetic powder to manufacture a sintered magnet. In this case, the heavy rare earth oxide includes Dy ₂ O ₃ .

The magnet powder synthesized by the reduction-diffusion method may be an R-Fe-B based magnet powder, and the sintered magnet manufactured by sintering the R-Fe-B based magnet powder may be an R-Fe-B based sintered magnet. .

Here, R refers to a rare earth element, and may be Nd, La, Ce, Pr, Pm, Sm, or Eu. That is, R described below means one of Nd, La, Ce, Pr, Pm, Sm, or Eu.

In this embodiment, the R-Fe-B-based magnet powder is produced through a reduction-diffusion method. In the reduction-diffusion method, a mixture is prepared by mixing rare earth oxides, iron, boron, and a reducing agent, and then the mixture is heated to reduce the rare earth oxides, and at the same time, _{the powder on R 2} Fe ₁₄ B is synthesized.

The rare earth oxide includes at least one of _{Nd 2} O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ and Eu ₂ O ₃ in correspondence with the rare earth element R. can do.

Since the reduction-diffusion method uses rare earth oxides as a raw material, the price is inexpensive, and a separate grinding process such as coarse grinding, hydrogen grinding, or jet mill or surface treatment process is not required.

In addition, in order to improve the magnetic performance of the sintered magnet, it is essential to refine the grains of the sintered magnet, and the size of the grains of the sintered magnet is directly related to the size of the initial magnet powder. In this case, the reduction-diffusion method has an advantage in that it is easier to manufacture magnetic powder having fine particles compared to other methods.

However, in the case of sintering the magnetic powder manufactured by the reduction-diffusion method, grain growth (more than 1.5 times the initial powder size) or abnormal grain growth (more than twice the size of normal grain size) may occur during the sintering process. There is a problem that the grain size distribution of the magnet is not uniform, and magnetic performance such as coercivity is deteriorated.

In addition, the magnetic powder produced by the reduction-diffusion method requires a cleaning process to remove by-products such as calcium oxide (CaO) remaining in the particles, but an oxide film is formed due to oxidation of the magnetic powder particles during the cleaning process. Can be. This oxide film not only interferes with sintering of the magnet powder, but also promotes column phase decomposition, thereby deteriorating physical properties of the sintered magnet such as coercivity.

Accordingly, a method for increasing the coercivity of the sintered magnet is required, and in this embodiment, _{a heavy rare earth oxide including Dy 2} O ₃ is further added to the rare earth oxide, iron, boron, and a reducing agent to prepare a mixture, and the mixture is To synthesize R-Fe-B magnet powder.

Since _{the heavy rare earth oxide containing Dy 2} O ₃ is added, Dy having a large anisotropy coefficient is distributed inside the sintered magnet, so that the coercive force can be improved.

In addition, this embodiment _{has the feature of adding Dy 2} O ₃ in the step of manufacturing the magnetic powder by the reduction-diffusion method.

When Dy ₂ O ₃ is added in a subsequent sintering step, etc., since Dy ₂ O ₃ is difficult to phase decompose, it _{can remain as Dy 2} O ₃ and maintain a non-magnetic state. The remaining Dy ₂ O ₃ can act as a factor to reduce the residual magnetic flux density (Br) of the sintered magnet.

On the other hand, when Dy ₂ O ₃ is added in the step of synthesizing the magnetic powder by the reduction-diffusion method as in this example, Dy ₂ O ₃ added in the step in which the reduction of the raw material is performed is also It can be reduced to form a Dy-Fe-B phase. This not only becomes a factor capable of increasing the coercive force of the sintered magnet, but also does not have a large influence on the residual magnetic flux density of the sintered magnet.

In addition, in this embodiment, _{by adding Dy 2} O ₃ in the step of synthesizing the magnet powder by a reduction-diffusion method, it is intended to homogeneously distribute Dy resulting from _{Dy 2} O _{3 over the entire area of the sintered magnet manufactured afterwards.} do. The addition of Dy ₂ O ₃ is for improving the coercive force. If Dy _{from Dy 2} O ₃ exists locally in the sintered magnet, the effect may be insufficient. _{Adding Dy 2} O ₃ in the sintering step is highly likely to have Dy locally in the sintered magnet, but adding Dy ₂ O ₃ in the step of synthesizing the magnetic powder by the reduction-diffusion method as in this example , R-Fe-B magnet powder particles are added at the stage of synthesis, so even distribution of Dy is possible. That is, the effect of improving the coercivity can be further maximized.

Specifically, _{by adding Dy 2} O ₃ in the step of synthesizing the magnetic powder by the reduction-diffusion method, the coercive force of the sintered magnet can be increased by 5 to 15 kOe (Kiloersted), and thus has a coercive force of 20 to 30 kOe. A sintered magnet can be implemented.

In addition, since Dy is added in the step of synthesizing the magnetic powder by the reduction-diffusion method, it is preferable to add _{Dy 2} O _{3 in the form of an oxide that can be reduced.}

Meanwhile, the heavy rare earth oxide may be mixed in an amount of 3% by mass to 10% by mass relative to the mixture. When the heavy rare earth oxide is mixed in an amount of less than 3% by mass relative to the mixture, there may be a problem in that the coercive force is insufficiently improved due to insufficient Dy content. When the heavy rare earth oxide is mixed in an amount greater than 10% by mass relative to the mixture, there may be a problem in that the residual magnetic flux density of the sintered magnet is excessively decreased due to the addition of more than necessary.

Then, each step will be described in more detail below.

First, a mixture is prepared by mixing a rare earth oxide, iron, boron, a reducing agent, and a heavy rare earth oxide. Then, the mixture is heated to a temperature of 800 to 1100 degrees Celsius. R-Fe-B-based magnet powder is synthesized by reduction and diffusion of raw materials at a temperature of 800 to 1100 degrees Celsius.

As mentioned earlier, heavy rare earth oxides include Dy ₂ O ₃ , and rare earth oxides include Nd ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ and Eu It may contain at least one of ₂ O _3. The reducing agent may include at least one _{of Ca, CaH 2 and Mg.}

The heavy rare earth oxide is preferably mixed in a powder form, and the size of the powder may be 1 to 5 micrometers.

The molar ratio of rare earth oxides, boron and iron may be between 1:14:1 and 1.5:14:1. Rare earth oxides, boron, and iron are _{raw materials for producing R 2} Fe ₁₄ B magnet powder, and when the above molar ratio is satisfied, R ₂ Fe ₁₄ B magnet powder can be produced with a high yield. If the molar ratio is less than 1:14:1, there _{is a problem in that the composition of the R 2} Fe ₁₄ B column phase is distorted and the R-rich grain boundary phase is not formed.If the molar ratio is greater than 1.5:14:1, the amount of rare earth elements is excessive. Thus, there may be a problem in that the reduced rare earth element remains, and the remaining rare earth element is _{changed to R(OH) 3} or RH _2.

The heating is for synthesis, and may be performed for 10 minutes to 6 hours at a temperature of 800 degrees Celsius to 1100 degrees Celsius in an inert gas atmosphere. If the heating time is less than 10 minutes, the powder cannot be sufficiently synthesized, and if the heating time is more than 6 hours, the size of the powder becomes coarse and there may be a problem in which primary particles are aggregated.

The magnetic powder thus prepared may be _{R 2} Fe _{14 B.} In addition, the size of the manufactured magnetic powder may be in the range of 0.3 micrometers to 10 micrometers. In addition, the size of the magnetic powder manufactured according to an embodiment may be 0.3 micrometers to 5 micrometers.

_{That is, the R 2} Fe ₁₄ B magnet powder may be formed by heating the raw material at a temperature of 800 to 1100 degrees Celsius _{, and the R 2} Fe ₁₄ B magnet powder is a neodymium magnet and exhibits excellent magnetic properties.

Typically, _{in order to form R 2} Fe ₁₄ B magnet powder such as _{Nd 2} Fe ₁₄ B, the raw material is melted at a high temperature of 1500 to 2000 degrees Celsius and then rapidly cooled to form a mass of raw material, and the mass is coarsely pulverized and hydrogenated. Crushing or the like is performed to obtain R ₂ Fe ₁₄ B magnet powder. However, in the case of such a method, a high temperature temperature for melting the raw material is required, and a process of cooling and pulverizing the raw material is required, so that the process time is long and complicated. In addition, a _{separate surface treatment process is required for the coarsely pulverized R 2} Fe ₁₄ B magnet powder in order to enhance corrosion resistance and improve electrical resistance.

However, in the case of manufacturing R-Fe-B magnet powder by the reduction-diffusion method as in this embodiment, R ₂ Fe ₁₄ B magnet powder is formed by reduction and diffusion of the raw materials at a temperature of 800 to 1100 degrees Celsius. . In this step, since the size of the magnetic powder is formed in units of several micrometers, a separate grinding process is not required.

In addition, in the case of the process of obtaining a sintered magnet by sintering the magnetic powder afterwards, when sintering is performed in a temperature range of 1000 to 1100 degrees Celsius, crystal grain growth is necessarily accompanied, and the growth of such grains acts as a factor for reducing the coercive force. Since the size of the crystal grains of the sintered magnet is directly related to the size of the initial magnet powder, if the average size of the magnet powder is controlled to be 0.3 micrometers to 10 micrometers, like the magnet powder according to an embodiment of the present invention, the coercive force is then Improved sintered magnets can be manufactured.

In addition, it is possible to control the size of the alloy powder produced by adjusting the size of the iron powder used as a raw material.

However, in the case of manufacturing the magnetic powder by the reduction-diffusion method, by-products such as calcium oxide or magnesium oxide may be generated during the manufacturing process, and a cleaning step of removing the magnetic powder may be required.

In order to remove such by-products, a washing step in which the produced magnetic powder is immersed in an aqueous solvent or a non-aqueous solvent and washed is followed. This cleaning can be repeated two or more times.

The aqueous solvent may include deionized water (DI water), and the non-aqueous solvent may include at least one of methanol, ethanol, acetone, acetonitrile, and tetrahydrofuran.

On the other hand, to remove by-products, ammonium salt or acid may be dissolved in an aqueous or non-aqueous solvent, and specifically, _{at least one of NH 4} NO ₃ , NH ₄ Cl and ethylenediaminetetraacetic acid (EDTA) may be dissolved. I can.

However, the magnetic powder particles produced in the cleaning process are exposed to oxygen in the aqueous solution, and the surface oxidation of the magnetic powder particles produced by oxygen remaining in the aqueous solution is performed, and an oxide film may be formed on the surface. The oxide film not only interferes with the sintering of the magnet powder, but also promotes the columnar decomposition, which is a cause of deteriorating physical properties of the sintered magnet such as coercivity.

Accordingly, in the present embodiment, _{a heavy rare earth oxide containing Dy 2} O ₃ was added and the coercivity was improved through this, thereby compensating for the reduction in coercivity as described above.

Thereafter, the step of sintering the R-Fe-B-based magnet powder that has undergone the synthesis step and the washing step as described above is followed.

A mixed powder can be prepared by mixing R-Fe-B magnetic powder and rare earth hydride powder.

The rare earth hydride powder is preferably mixed in an amount of 3 to 15% by mass relative to the mixed powder.

If the content of the rare earth hydride powder is less than 3% by mass, there is a problem in that sufficient wetting between the particles is not provided and sintering is not performed well, and the role of suppressing the columnar decomposition of R-Fe-B is not sufficiently performed. I can. In addition, when the content of the rare earth hydride powder is more than 15% by mass, the volume ratio of the R-Fe-B column in the sintered magnet decreases, resulting in a decrease in the residual magnetization value, and there may be a problem in that particles grow excessively due to liquid phase sintering. have. When the size of the crystal grains increases due to the overgrowth of the particles, the coercivity decreases because it is vulnerable to magnetization reversal.

Next, the mixed powder may be heated at a temperature of 700 degrees Celsius to 900 degrees Celsius. In this step, the rare earth hydride is separated into rare earth metal and hydrogen gas, and hydrogen gas is removed. That is, for example, when the rare earth hydride powder is NdH ₂ , NdH ₂ is separated into Nd and H ₂ gas, and H ₂ gas is removed. That is, heating at 700 to 900 degrees Celsius is a process of removing hydrogen from the mixed powder. In this case, heating may be performed in a vacuum atmosphere.

Next, the heated mixed powder is sintered at a temperature of 1000 to 1100 degrees Celsius. At this time, the step of sintering the heated mixed powder at a temperature of 1000 degrees to 1100 degrees Celsius may be performed for 30 minutes to 4 hours. This sintering process can also be performed in a vacuum atmosphere.

More specifically, the mixed powder heated at 700 to 900 degrees Celsius is put into a graphite mold, compressed, and oriented by applying a pulsed magnetic field to prepare a molded body for a sintered magnet. The sintered magnet is manufactured by heat-treating the molded body for a sintered magnet at 300 to 400 degrees Celsius in a vacuum atmosphere and then sintering at a temperature of 1000 to 1100 degrees Celsius.

In this sintering step, liquid phase sintering by rare earth elements is induced. That is, between the R-Fe-B-based magnet powder produced by the conventional reduction-diffusion method and the added rare-earth hydride powder, liquid phase sintering occurs by the rare-earth element. Through this, R-rich and ROx phases are formed in the grain boundary area inside the sintered magnet or the grain boundary area of the columnar grains of the sintered magnet. The thus formed R-Rich region or ROx phase improves the sinterability of the magnetic powder and prevents the decomposition of the columnar particles in the sintering process for manufacturing a sintered magnet. Therefore, it is possible to stably manufacture a sintered magnet.

The manufactured sintered magnet has a high density and may have a size of 1 micrometer to 10 micrometers.

Next, in order to further improve coercivity, a heat treatment step may be followed after heating the sintered magnet to 500 to 800 degrees Celsius in a vacuum atmosphere.

Meanwhile, a grain boundary diffusion process (GBDP) may be performed on the sintered magnet.

The grain boundary diffusion process is a process of distributing heavy rare earth elements such as Dy along the grain boundaries of the crystal grains of the R-Fe-B sintered magnet, and can increase the coercive force without reducing the residual magnetization. During the heat treatment process for grain boundary diffusion, heavy rare earth elements are substituted by Nd on the Nd-rich phase and diffuse along the grain boundaries of the grains. This diffusion results in the formation of a shell structure with a high content of heavy rare earth elements around the grains.

However, in the case of the intergranular diffusion process using Dy, there is a difference in the concentration of Dy according to the depth of the sintered magnet, so there is a limit in increasing the coercive force. _{However, as in the present embodiment, when Dy 2} O ₃ is added in the step of synthesizing the magnetic powder by the reduction-diffusion method, the difference in concentration of Dy according to this depth can be minimized.

In other words, for a sintered magnet in which Dy is evenly distributed in this way, if Dy is further diffused on the grain boundary of the grain through the grain boundary diffusion process, the coercive force can be further improved, and the grain boundary diffusion process using Dy can have disadvantages. It can be supplemented.

The grain boundary diffusion process may include, specifically, coating a heavy rare earth powder on a surface of the sintered magnet, and performing heat treatment on the coated sintered magnet to grain boundary diffusion of the heavy rare earth element.

The step of coating the heavy rare earth powder on the surface of the sintered magnet may include mixing the heavy rare earth powder with a solvent and then applying the heavy rare earth powder to the surface of the sintered magnet. Anhydrous alcohol may be used as the solvent, but is not limited thereto.

Thereafter, heat treatment is performed on the sintered magnet coated with the heavy rare earth powder, so that the heavy rare earth element can be diffused into the grain boundaries of the sintered magnet.

The heat treatment may include a first heat treatment heated to 790 degrees Celsius to 910 degrees Celsius, and a second heat treatment heated to 450 degrees Celsius to 550 degrees Celsius. This is because the diffusion action of diffusing the heavy rare earth elements contained in the heavy rare earth powder onto the surface of the sintered magnet proceeds smoothly in this temperature range.

The heavy rare earth powder may include at least one of Dy and Tb, but it is more preferable to include Dy.

Then, in the following, a method of manufacturing a sintered magnet according to an embodiment of the present invention will be described through specific examples.

Example 1-1: Dy ₂ O ₃ 3% by mass

Nd ₂ O ₃ 15.46g, Fe 31.71g, B 0.52g, Co 0.51g, Cu 0.14g, Al 0.18g were mixed using a ball mill to prepare a mixture, and Dy ₂ O ₃ powder compared to the mixture It was added at 3% by mass, and 6.1 g of Ca was further mixed.

The mixture is put in a stainless steel container of any shape and pressed, and reacted in an inert gas (Ar) atmosphere at 900°C to 920°C for 30 minutes to 3 hours in a tube electric furnace. Thereafter, the reactants are coarsely pulverized with an automatic grinder.

Next, a washing step is performed to remove Ca and CaO, which are reduction by-products. After uniformly mixing 30 g to 35 g of NH ₄ NO ₃ with the synthesized powder, immerse in ~200 ml of methanol, and alternately perform a homogenizer and ultrasonic cleaning (ultra sonic) once or twice for effective cleaning. Next, it is washed with acetone, acid washed with a solution of acetic acid in methanol, and final washed with methanol. Then, vacuum drying to obtain a single-phase Nd-Fe-B magnet powder.

Thereafter, 6% by mass of NdH ₂ was added to the magnet powder, mixed, and compression-molded by putting it in a graphite mold, and the powder was oriented by applying a pulsed magnetic field of 5T or more to prepare a molded body for a sintered magnet.

Thereafter, the compact was heated in a vacuum sintering furnace at a temperature of 1065 degrees Celsius for 2 hours to perform sintering, thereby manufacturing a sintered magnet. The composition of the prepared Nd-Fe-B-based sintered magnet is Nd _2.12 Dy _0.22 Fe _13.1 B _1.1 Co _0.2 Cu _0.05 Al _0.15 .

Example 1-2: Dy ₂ O ₃ 3% by mass

For the same raw material as in Example 1-1, magnetic powder was synthesized and washed in the same manner as in Example 1-1. Thereafter, the same sintering process as in Example 1-1 was performed, except for heating at a temperature of 1040 degrees Celsius for 4 hours.

Example 2-1: Dy ₂ O ₃ 6% by mass

Nd ₂ O ₃ 11.67g, Fe 31.71g, B 0.52g, Co 0.51g, Cu 0.14g, Al 0.18g were mixed using a ball mill to prepare a mixture, and Dy ₂ O ₃ powder compared to the mixture It was added at 6% by mass, and 5.32 g of Ca was further mixed.

Thereafter, magnetic powder synthesis, washing and sintering were performed in the same manner as in Example 1-1. The composition of the prepared Nd-Fe-B-based sintered magnet is Nd _1.9 Dy _0.44 Fe _13.1 B _1.1 Co _0.2 Cu _0.05 Al _0.15 .

Example 2-2: Dy ₂ O ₃ 6% by mass

For the same raw material as in Example 2-1, magnetic powder was synthesized and washed in the same manner as in Example 2-1. Thereafter, the same sintering process as in Example 2-1 was carried out, except that it was heated at a temperature of 1040 degrees Celsius for 4 hours.

Comparative Example 1: Dy ₂ O ₃ Not added

Nd ₂ O ₃ 17.06g, Fe 31.7g, B 0.52g, Co 0.51g, Cu 0.14g, Al 0.18g were mixed using a ball mill to prepare a mixture, and Ca 6.1g was further mixed . No Dy ₂ O ₃ powder was added.

Thereafter, magnetic powder synthesis, washing and sintering were performed in the same manner as in Example 1-1. The composition of the prepared Nd-Fe-B-based sintered magnet is Nd _2.34 Fe _13.1 B _1.1 Co _0.2 Cu _0.05 Al _0.15 .

Evaluation Example 1: B-H curve graph

BH curve graphs for the sintered magnets of Examples 1-1 and 1-2 are shown in FIG. 1, and BH curve graphs for the sintered magnets of Examples 2-1 and 2-2 are shown in FIG. The graph of the BH curve for the sintered magnet of Comparative Example 1 is shown in FIG. 3.

_{1 to 3, when Dy 2} O ₃ was added as in Example 1-1, Example 1-2, Example 2-1, and Example 2-2, Comparative Example 1 was not Compared to the case, it was confirmed that the coercive force value increased by about 5 to 15 kOe.

In particular, _{the sintered magnets of Example 2-1 and Example 2-2, in which the amount of Dy 2} O ₃ added was relatively large, showed that the coercive force was further increased compared to the sintered magnets of Example 1-1 and Example 1-2. Confirmed.

In addition, when the sintering temperature was increased to 1065 degrees Celsius for the same raw material, it was confirmed that the residual magnetic flux density slightly increased.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

Claims (8)

Preparing a mixture by mixing a rare earth oxide, iron, boron, a reducing agent, and a heavy rare earth oxide;
Heating the mixture at a temperature of 800°C to 1100°C to synthesize magnetic powder using a reduction-diffusion method; And
Including the step of sintering the magnet powder to produce a sintered magnet,
The heavy rare earth oxide is a method of manufacturing a sintered magnet containing _{Dy 2} O _3. In claim 1,
The heavy rare earth oxide is a method of manufacturing a sintered magnet in which 3% by mass to 10% by mass is mixed with respect to the mixture. In claim 1,
The rare earth oxide is Nd ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ and Eu ₂ O _{3 A} method of manufacturing a sintered magnet comprising at least one of. In claim 1,
The sintered magnet is an R-Fe-B-based sintered magnet,
The R is Nd, La, Ce, Pr, Pm, Sm or Eu in the manufacturing method of the sintered magnet. In claim 1,
The reducing agent is a method of manufacturing a sintered magnet containing at least one _{of Ca, CaH 2 and Mg.} In claim 1,
The manufacturing of the sintered magnet includes preparing a mixed powder by mixing the magnetic powder and the rare earth hydride powder, and sintering the mixed powder at 1000 degrees to 1100 degrees Celsius. In claim 1,
The method of manufacturing a sintered magnet further comprising a heat treatment step after heating the sintered magnet to 500 to 800 degrees Celsius. In claim 1,
The method of manufacturing a sintered magnet further comprising coating a heavy rare earth powder on the surface of the sintered magnet and performing heat treatment on the coated sintered magnet to diffuse the heavy rare earth element into grain boundaries.

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