KR101195450B1 - The method for preparation of R-Fe-B type rare earth magnet powder for bonded magnet, R-Fe-B type rare earth magnet powder thereby and the method for preparation of bonded magnet using the magnet powder, bonded magnet thereby - Google Patents

Abstract

The present invention relates to a method for preparing R-Fe-B rare earth magnetic powder with improved magnetic properties and to a R-Fe-B based rare earth magnetic powder prepared according to the present invention, and more particularly, a process occurring in a rare earth sintered magnet manufacturing process. Coarsely crushing the R-Fe-B-based rare earth sintered magnet scrap recovered from scrap, defective or discarded products (step 1); A hydrogenation process step (step 2) of charging the pulverized product of step 1 to a tube furnace and then filling hydrogen in a vacuum state and increasing the temperature from 200 to 300 ° C. at the temperature of the tube; Phase decomposition process step (step 3) of increasing the temperature to 700 to 900 ℃ temperature in the tube in the same hydrogen atmosphere as in step 2; Hydrogen discharge process step (step 4) to exhaust the hydrogen pressure in the tube furnace at 340 to 10 ^-1 torr or less for 1 to 30 minutes at the same temperature as step 3; R-Fe-B rare earth with improved magnetic properties, characterized in that it comprises a recombination process step (step 5) of performing a vacuum evacuation of hydrogen pressure in the tube furnace to 10 ^-1 to 10 ^-5 torr after performing step 4 The present invention relates to a method for preparing magnetic powder and an R-Fe-B rare earth magnetic powder prepared by the above method.

Description

R-Frequency-based rare earth magnetic powder for bond magnets, a magnetic powder prepared by the same, and a method for producing a bonded magnet using the magnetic powder, and a bonded magnet produced by the same {The method for preparation of R? FE-? Rare type rare earth magnet powder for bonded magnet, R-Fe-B type rare earth magnet powder thereby and the method for preparation of bonded magnet using the magnet powder, bonded magnet

The present invention relates to a method for preparing a R-Fe-B rare earth magnetic powder for bond magnets having improved magnetic properties, and a R-Fe-B rare earth magnetic powder prepared accordingly.

The present invention also relates to a method for producing a R-Fe-B rare earth bonded magnet using the R-Fe-B based rare earth magnetic powder and an R-Fe-B bonded magnet prepared accordingly.

Recently, the energy reduction and environmentally friendly green growth projects have emerged as a new issue, and the automobile industry is using hybrid cars using internal combustion engines using fossil raw materials in combination with motors or hydrogen, an environmentally friendly energy source, as alternative energy. There is an active research on fuel cell vehicles that drive a motor by generating. Since these environmentally friendly cars are driven by electric energy, permanent magnet motors and generators are inevitably employed. In terms of magnetic materials, the rare earth permanent magnets, which exhibit superior light magnetic performance in order to further improve energy efficiency, are used. Technical demand is on the rise. In addition, other aspects for improving fuel efficiency of automobiles should be realized in light weight and miniaturization of automotive parts. For example, in the case of motors, ferrites, which were previously used as permanent magnets, were changed in addition to the design of the motors to realize light weight and miniaturization. It is essential to replace rare earth permanent magnets that show better magnetic performance than ferrite.

However, since rare earth permanent magnets use expensive rare earth elements as their main raw materials, the manufacturing cost is higher than that of ferrite magnets. Therefore, the rare earth magnets not only increase the price of the motor but also increase the reserves of rare earth elements compared to other metals. Due to the poor resource limitations, in order to expand the field of application of rare earth magnets and to solve the problem of smooth supply and demand, it is necessary to invent a low-cost magnet manufacturing method by recycling discarded rare earth magnets.

Theoretically, the residual magnetic flux density of the permanent magnet is determined by the conditions of the saturation magnetic flux density of the columnar, the degree of anisotropy of crystal grains, the density of the magnet, and the like. Because of this, it is beneficial to improve the efficiency and performance of the device in various applications. In addition, among the magnetic characteristics of permanent magnets, coercive force plays a role in maintaining the intrinsic performance of permanent magnets in response to the environment in which magnets are demagnetized, such as heat, opposite magnetic fields, and mechanical impacts. Not only can be used for high temperature applications, high output devices, etc., but also because the magnet can be manufactured thinly, the weight is reduced and the economic value is increased. As a permanent magnet material exhibiting such excellent magnetic performance, R-Fe-B-based rare earth magnets are known, but since these magnets contain expensive rare earth elements, the unit cost is about 10 to 20 than that of ferrite magnets, which are general permanent magnet materials. There is a problem in that the cost increase of the motor increases as the rare earth magnet is adopted.

However, R-Fe-B-based rare earth magnets are manufactured in the form of sintered magnets or bond magnets using R-Fe-B alloys as starting materials. Rare-earth sintered magnets are manufactured by general powder metallurgy process and processing. Is generating about 30 to 40% of scrap in 2008 (58,000 tonnes / year × 0.35 = 20,300 tonnes / year), but these rare earth magnet scraps are rarely reused and are rarely recycled. The process of extraction and use requires additional process costs for recycling.

Accordingly, attempts have been made to recycle low-cost rare earth bond magnet powders using low-cost starting materials such as process scraps generated in the rare earth sintered magnet manufacturing process, rare earth sintered magnet products recovered from defective or discarded products, and the like. According to the conventional techniques utilized in this field, these rare earth scraps are pulverized into powders of 50 to 500 µm in size to form powders, and then kneaded with thermosetting resins such as epoxy and the like. The rare earth bond magnets undergo a curing process in the range of 100 to 150 ° C. It will go through the process of manufacturing.

However, when the rare earth powder and the bonded magnet are manufactured by such a process, magnetic defects such as oxidation or mechanical residual stress occur during the grinding process, and consequently, the coercivity decreases in inverse proportion to the powder particle size, particularly in the range of 100 to 150 ° C. Through the hardening process, the magnetic defect effect of the surface is further increased, resulting in a quality problem of unstable characteristics.

Thus, the present invention is a process scrap generated during the rare earth sintered magnet production process to manufacture R-Fe-B-based powders for bond magnets that are widely used in various industries such as home appliances, IT, and medical fields as well as the automotive field ( Using low cost starting materials such as scrap, scrap or rare earth sintered magnet products recovered from discarded products, the HDDR process can be used to stably control the hydrogen release reaction rate during hydrogen release and recombination, or to repeat the hydrogenation and release reaction. By uniformly controlling the microcrystal structure by performing the process to prepare a powder for rare earth bond magnets to produce R-Fe-B-based powder of excellent magnetic performance, stable production and uniform quality.

It is an object of the present invention to provide a method for preparing R-Fe-B rare earth magnetic powder having improved magnetic properties and R-Fe-B rare earth magnetic powder prepared accordingly.

In addition, another object of the present invention is to provide a method for producing a bonded magnet using the R-Fe-B-based rare earth magnetic powder and the bond magnet prepared accordingly.

In order to achieve the above object, the present invention comprises the steps of coarsely crushing the R-Fe-B-based rare earth sintered magnet recovered from the scrap, defective or discarded products generated in the rare earth sintered magnet manufacturing process; A hydrogenation process step of charging the pulverized product of the above step into a tube furnace, filling hydrogen in a vacuum state, and increasing the temperature from room temperature to 300 ° C; Phase decomposition step of increasing the temperature to 700 to 900 ℃ temperature in the tube in the same hydrogen atmosphere as the step; Hydrogen discharge process step of exhausting the hydrogen pressure in the tube furnace for 1 to 30 minutes at the same temperature as the above step to 340 to 10 ^-1 torr or less; After the step of performing a recombination process step of evacuating the hydrogen pressure to a pressure of 10 ^-1 to 10 ^-5 torr and the method for producing a magnetic powder with improved magnetic properties R-Fe-B rare earth magnetic powder characterized by It provides a R-Fe-B-based rare earth magnetic powder prepared.

In addition, the present invention comprises the steps of grinding the R-Fe-B-based rare earth magnetic powder; Kneading the thermosetting or thermoplastic resin to the ground powder to form a mixture; And forming a bonded magnet by molding the kneaded mixture, and a method of preparing an R-Fe-B rare earth bond magnet by a molding method, and the R-Fe-B based rare earth bond magnet manufactured according to the forming method. To provide.

The manufacturing method of the R-Fe-B-based rare earth magnetic powder with improved magnetic properties according to the present invention is performed by separating the hydrogen release process and the recombination process during the HDDR process using a low-cost starting material and controlling the hydrogen gas emission. Since the size of the powder is fine and uniform composition is used to improve the magnetic properties, it can be usefully used in the manufacture of inexpensive permanent magnet powder in automobiles, home appliances, IT and medical industries.

1 is a SEM photograph of the rare earth sintered magnet scrap fracture surface,
2 is a SEM photograph of the rare earth magnetic powder fracture surface prepared in accordance with an embodiment of the present invention.

The present invention

Coarsely pulverizing the R-Fe-B-based rare earth sintered magnet scrap recovered from the process scrap, defective or scrapped products generated in the rare earth sintered magnet manufacturing process (step 1);

A hydrogenation process step (step 2) of charging the pulverized product of the step 1 into a tube furnace and then filling hydrogen in a vacuum state and increasing the temperature to 200 to 300 ° C .;

Phase decomposition process step (step 3) of increasing the temperature to 700 to 900 ℃ in the tube in the same hydrogen atmosphere as in step 2;

Hydrogen discharge process step (step 4) to exhaust the hydrogen pressure in the tube furnace at 340 to 10 ^-1 torr or less for 1 to 30 minutes at the same temperature as step 3;

R-Fe-B rare earth with improved magnetic properties, characterized in that it comprises a recombination process step (step 5) of performing a vacuum evacuation of hydrogen pressure in the tube furnace to 10 ^-1 to 10 ^-5 torr after performing step 4 Provided is a method for producing a magnetic powder.

Hereinafter, a method for preparing the R-Fe-B rare earth magnetic powder according to the present invention will be described in detail step by step.

In the manufacturing method of the R-Fe-B rare earth magnetic powder according to the present invention, step 1 is an R-Fe-B rare earth sintered magnet recovered from scrap, defective or discarded products generated in the rare earth sintered magnet manufacturing process Coarse grinding is a step.

Since the rare earth sintered magnet scrap used as the starting material in this step has already been manufactured through the sintering process, it has a microstructure in which the main phase R ₂ Fe ₁₄ B phase and the auxiliary phase R-rich phase are uniformly distributed. It does not contain phosphorus α-Fe and does not undergo a separate homogenization process.

In the present specification, R is a rare earth element, which is a generic name of 17 elements of the periodic table, includes scandium, yttrium, and lanthanide elements, and may include an actinium group element.

In the coarse grinding of Step 1, the R-Fe-B-based rare earth sintered magnet scrap is preferably pulverized to 0.1 to 5,000 μm. If the sintered magnet scrap is coarsely pulverized to less than 0.1 μm, there is a problem that the powder surface area is increased so that it is excessively exposed to oxygen during the HDDR process, and if it exceeds 5,000 μm, the volume expansion due to the phase change during the HDDR process and There is a problem that cracks occur in the powder due to shrinkage.

Step 2 of the present invention is a hydrogenation process step of charging the pulverized product obtained in step 1 into a tube furnace and filling with hydrogen in a vacuum state and heating the tube furnace by increasing the temperature from 200 to 300 ° C. .

If the temperature is less than 200 ° C., there is a problem in that hydrates of R ₂ Fe ₁₄ BH _x + RH _x are not sufficiently formed, and if it exceeds 300 ° C., excess energy is consumed in terms of energy efficiency. There may be. In addition, as the pressure of the hydrogen gas increases, the reaction temperature that combines with hydrogen increases, thereby reducing the temperature for stably forming hydrogen compounds.

In the vacuum state of Step 2, it is preferable to maintain hydrogen at 2 × 10 ⁻⁵ torr or less and then charge hydrogen to 0.3 to 2.0 atm. If the hydrogen pressure is less than 0.3 atm, there is a problem that the HDDR process reaction does not occur sufficiently, and when the hydrogen pressure exceeds 2.0 atm, a separate equipment for handling the high-pressure hydrogen gas has to be constructed, thereby increasing the process cost. .

Phase analysis of the hydrogenated compound prepared as a result of the above step 1 according to the present invention using an X-ray analyzer (X-Ray Diffractometer, XRD), the scrap used in the present invention is R ₂ Fe ₁₄ B + R- It is composed of a rich phase, when heated to increase the temperature to more than 200 ℃ in a hydrogen gas atmosphere it can be seen that the hydrogenated bonds are formed as a hydrogen compound of R ₂ Fe ₁₄ BH _x + RH _x .

Step 3 of the present invention is a phase decomposition process step of increasing the temperature to a tube from 700 to 900 ℃ in the same hydrogen atmosphere as in step 2.

The phase decomposition step is a step for realizing the micronization and anisotropy of the particles, after the hydrogenation step of step 2, the hydrogenated phase powder of R ₂ Fe ₁₄ BH _x + RH _x into the tube at the same hydrogen pressure as the hydrogenation step When the internal temperature is increased to 700 to 900 ° C, the hydrogenated phase powder further absorbs hydrogen to cause phase decomposition into three phases completely different from the phases constituting the initial scrap as shown in Scheme 1 below.

[Reaction Scheme 1]

R ₂ Fe ₁₄ BH _x + RH _x + H ₂ → α-Fe + Fe ₂ B + RH _x

If the temperature is less than 700 ℃ there is a problem that phase decomposition does not occur, if the temperature exceeds 900 ℃ there is a problem to grow the crystal grains of the decomposition phase to reduce the magnetic properties. If the phase decomposition process is not performed completely, there may be a problem that the coercive grains of the initial master alloy is continuously present to decrease the coercive force of the permanent magnet powder. Variables that determine the phase decomposition process include reaction temperature, time, and hydrogen gas pressure, and the optimum conditions of the reaction variables vary according to the contamination of impurities such as the initial scrap component and oxygen.

Step 4 of the present invention is a hydrogen discharge process step of exhausting the hydrogen pressure in the tube furnace to 380 to 0.1 torr at the same temperature as in step 3.

In the hydrogen release process, as the hydrogen is released from the α-Fe + Fe ₂ B + RH _x decomposition phase powder in which phase decomposition is completed in step 3, an initial R ₂ Fe ₁₄ B recrystallized nucleus is formed inside the powder according to Scheme 2 below. do.

Scheme 2

α-Fe + Fe ₂ B + RH _x → R ₂ Fe ₁₄ B + R-rich phase + H ₂

If the hydrogen pressure in the tube furnace is less than 0.1 torr, there is a problem that the nucleus of the R ₂ Fe ₁₄ B recrystallized phase grows coarsely, and when it exceeds 380 torr (0.5 atm), hydrogen is not released enough to R ₂ There is a problem that the nucleus of Fe ₁₄ B recrystallization is not sufficiently formed. In addition, similar to the reason for the limitation of the hydrogen pressure, when the exhaust time is less than 1 minute, there is a problem that the nucleus of R ₂ Fe ₁₄ B recrystallization phase is not sufficiently formed, and when it exceeds 30 minutes, the formed nuclei grow coarsely. There is a problem.

Finally, step 5 of the present invention is a recombination process step of evacuating hydrogen by lowering the hydrogen pressure in the tube to 10 ^-5 to 10 ^-1 torr after performing the hydrogen discharge process step.

The recombination process step is R ₂ Fe ₁₄ B in the step of growing the nucleus on the recrystallization to complete the recombination, so the hydrogen pressure is fully recombined image is formed in the 10 ^-5 torr, it is not necessary to vacuum evacuated to less, ^10- If it exceeds ¹ torr, there is a problem that the decomposed phase remains and the magnetic properties are deteriorated.

Hydrogen emission process and recombination process step of HDDR process is a key step in which R ₂ Fe ₁₄ B phase is recombined into fine grains to obtain enhanced coercivity, and the reaction rate is constant because it is almost continuous and is completed in a very short time. Failure to control results in non-uniform particle size distribution or uneven distribution of recombined R ₂ Fe ₁₄ B + R-rich phases depending on reaction conditions, reducing coercive force of the R-Fe-B rare earth magnetic powder There is. 1 is a fracture surface photograph of the rare earth sintered magnet scrap used as a starting material, it can be seen that the grain size is several tens of micrometers, Figure 2 is a fracture surface photograph of the rare earth magnetic powder prepared according to the method of the present invention is several hundred nm size It can be seen that the finer.

The present invention also provides an R-Fe-B rare earth magnetic powder prepared according to the HDDR process.

The magnetic powder is recombination is formed according to the reaction formula 2 after the phase decomposition of the reaction formula 1, and as a result, the grain size of the main phase R ₂ Fe ₁₄ B phase hundreds of micrometers to several mm after the reaction of the HDDR reaction Grain refinement occurs at the nm level, which corresponds to a grain size approaching the terminal sphere size (200-300 nm) of R ₂ Fe ₁₄ B.

In addition, the present invention comprises the step of forming a powder by grinding the R-Fe-B-based rare earth magnetic powder prepared by the method for producing the R-Fe-B-based rare earth magnetic powder (step A);

Kneading the thermosetting resin or thermoplastic resin with the powder of step A to produce a mixture (step B); And

It provides a method of producing a R-Fe-B-based rare earth bond magnet by the molding method comprising the step (step C) of forming a compressed or injection-bonded magnet by molding the mixture of step B.

Step A of the present invention is a step of grinding the R-Fe-B-based rare earth magnetic powder to 50 to 500 ㎛ using a conventional mill. If the particle size after grinding of the magnetic powder is less than 50 μm, there is a problem in that the surface area is increased, thereby deteriorating characteristics due to oxidation during the manufacture of the magnet, and when it exceeds 500 μm, a small magnet may be manufactured. There is a problem in that the fluidity is lowered and the molding density is lowered.

Step B of the present invention is a step of kneading and mixing a thermosetting or thermoplastic synthetic resin into the magnetic powder ground in step 1 to produce a compound.

The choice of the synthetic resin is determined by the method of manufacturing the bonded magnet, and in the case of the compressed bond magnet, thermosetting resins such as epoxy resin, phenol resin, and urea resin are suitable, and in the case of injection bond magnet, nylon resin, etc. Thermoplastic resin of is preferable.

In general, the manufacturing method of the high-density magnet has an advantage of the manufacturing method of the compression method, the thermosetting resin added during the production of the compressed bond magnet is added in 2.0 to 3.0% by weight based on the total bond magnet weight. If the amount is less than 2.0% by weight, there is a problem that the bonding strength is lowered because the resin does not completely apply the powder, and when more than 3.0% by weight, the molding density of the magnet is low.

Step C of the present invention is a step of forming a bond magnet by molding the mixture of step B.

Through step C, the mixture of step B may be formed using a conventional molding method, for example, compression molding or injection molding, to form an R-Fe-B rare earth bonded magnet having an improved magnetic force having a desired shape.

In addition, the present invention provides a R-Fe-B-based rare earth bonded magnet prepared according to the method for producing a R-Fe-B-based rare earth bonded magnet by the molding method.

According to the present invention, by using the R-Fe-B-based rare earth magnetic powder to prepare a bond magnet, the conventional rare earth magnetic powder scrap is pulverized and then kneaded with a thermosetting resin and molded, and cured at 100 to 150 ℃ Quality caused by the reduction of coercive force due to magnetic defects such as oxidation or mechanical residual stress in the grinding step of the bonded magnets and the increase of the magnetic defect effect of the surface during the curing process in the range of 100 to 150 ℃ The occurrence of problems is reduced.

Hereinafter, the present invention will be described in detail by Examples and Experimental Examples. However, the following Examples and Experimental Examples are only for illustrating the present invention, and the scope of the present invention is not limited by the following Examples and Experimental Examples.

< Example  1>

Preparation of R-Fe-B Rare Earth Magnetic Powders of the Present Invention

R-Fe-B rare earth sintered magnet products recovered from scrap, defective or discarded products produced in the process of manufacturing rare earth sintered magnets as starting materials are coarsely pulverized to about 0.1 μm to 5 mm in size into a tube (Model name: H1000 -T, manufacturer: Dongwon Systems / Korea), and maintained the initial vacuum to 2 × 10 ^-5 torr or less, and then filled with hydrogen gas to 1.0 atm, the temperature was increased from room temperature to 300 ℃ to proceed the hydrogenation process. In the same hydrogen atmosphere, the temperature in the furnace was increased to 810 ° C. for 15 minutes (Example 1-1), 30 minutes (Example 1-2), and 60 minutes (Example 1-3), respectively. The phase decomposition process was completely completed with α-Fe + Fe ₂ B + NdH _X.

After the phase decomposition process was completed, the hydrogen discharge process and the recombination process were separately separated in the hydrogen release control at the same temperature in the furnace, and in the hydrogen release process, the hydrogen pressure in the tube furnace was maintained at 200 torr for 5 minutes. The recombination process was completed while evacuating to 10 ^-5 torr again.

< Example  2>

R- of the present invention Fe -B-based rare earth magnetic powder Ⅱ

The hydrogen pressure in the tube furnace of the hydrogenation step and the phase decomposition step is 0.3 atm, and the holding time is 60 minutes (Example 2-1), 120 minutes (Example 2-2), and 180 minutes (Example 2-3). R-Fe-B-based rare earth magnetic powder was prepared in the same manner as in Example 1 except that

< Example  3>

R- Fe -B-based rare earth bonded magnet

After grinding the powder of Example 2-3 to 50 to 500 ㎛ size, 2.0 to 3.0% by weight of an epoxy resin was added to prepare a mixture. Thereafter, the mixture was molded using a conventional molding machine to prepare an R-Fe-B-based rare earth bonded magnet of a desired form.

&Lt; Comparative Example 1 &

Sintered Magnet Scrap scrap ) Preparation of Powder

As a starting material, the rare earth sintered magnet product recovered from a process scrap, a defective product or a discarded product generated in the rare earth sintered magnet manufacturing process was pulverized to a size of 50 to 150 μm by a hand mill method.

< Comparative example  2>

Preparation of Bond Magnet Using Powder of Comparative Example 1

2.0 to 3.0 wt% of the epoxy resin was added to the ground powder of Comparative Example 1 to prepare a mixture. Thereafter, the mixture was molded using a conventional molding machine to prepare an R-Fe-B-based rare earth bonded magnet of a desired form.

< Experimental Example  1>

Magnetic Force Characterization of Rare Earth Magnetic Powders According to the Present Invention

The rare earth magnetic powder prepared according to Examples 1 and 2 was pulverized to 50 to 150 μm in size and then aligned in a non-aligned or 1 T magnetic field using a sample vibration magnetometer (model name: EM7-HV, manufacturer: Lake Shore / USA). After the magnetic properties were measured, these are shown in Table 1.

division Phase decomposition process condition Self Alignment Residual magnetic flux density
Br (kGe) Coercivity
iHc (kOe) Hydrogen pressure (atm) Time (min) Example 1-1 1.0 15 radish 7.20 9.12 U 7.22 9.30 Sealing Example 1-2 1.0 30 radish 7.16 10.57 U 7.19 10.73 Example 1-3 1.0 60 radish 7.12 12.05 U 7.20 12.10 Example 2-1 0.3 60 radish 7.11 6.80 U 11.45 6.25 Example 2-2 0.3 120 radish 7.21 8.12 U 11.40 7.68 Example 2-3 0.3 180 radish 7.20 8.50 U 11.43 8.01

Through Table 1, it can be seen that the magnetic properties of the powder increase with the change of holding time under constant hydrogen pressure during the phase decomposition process step, and it can be seen that the magnetic field has a higher value when aligned. In addition, comparing Example 1-3 with Example 2-1, it was found that the magnetic properties were increased when the hydrogen pressure in the tube furnace was 0.3 atm when the holding time of the phase decomposition process step was the same. From this, a rare earth magnetic powder having optimum magnetic properties can be obtained by an efficient process in which the hydrogen pressure and the holding time parameters of the phase decomposition step are adjusted.

< Experimental Example  2>

Magnetic Property Analysis of Rare Earth Sintered Magnet Scrap Powder

The magnetic properties of the rare earth sintered magnet scrap powder not subjected to the HDDR process of the present invention were measured using a sample vibration magnetometer (model name: EM7-HV, manufacturer: Lake Shore / USA) in an unaligned or 1 T magnetic field, and then measured magnetic properties. This is shown in Table 2.

division Lush sorting Residual magnetic flux density,
Br (kGe) Coercivity,
iHc (kOe) Comparative Example 1 radish 6.00 8.01 U 11.89 5.74

Table 2 shows that the rare earth sintered magnet scrap powder has a high coercive force but a low residual magnetic flux density when it is unaligned, and a high coercive force when the aligned magnetic field is high but a low coercive force.

< Experimental Example  3>

Magnetic Force Characterization of Bond Magnets

Magnetic properties of the R-Fe-B rare earth bond magnets prepared according to Example 3 were measured using a BH tracer (BH tracer, PERMAGRAPH L, Magnet physik / Germany), which were measured using the same apparatus. The magnetic properties of the bonded magnets were compared, and the results are shown in Table 2 below.

division Bond Magnet Manufacturing Conditions Residual magnetic flux density
Br (kGe) Coercivity
iHc (kOe) Used powder Epoxy content (% by weight) Density (g / cc) Experimental Example 3-1 Example 2-3 2.5 6.0 5.18 10.67 Experimental Example 3-2 Comparative Example 1-1 2.5 6.0 3.45 2.46

Through the above Table 3, in the case of the bonded magnet using the rare earth magnetic powder prepared through the HDDR process of the present invention, there is no significant difference in residual magnetic flux density when compared with the rare earth magnetic powder prepared by immediately crushing the sintered magnet scrap. On the side, it can be seen that it has a remarkably high magnetic force. It can be seen that magnetic defects such as oxidation or mechanical residual stress occurs during sintered magnet scrap grinding, and as a result, the coercive force is reduced.

Claims (7)

Coarsely pulverizing the R-Fe-B-based rare earth sintered magnet scrap recovered from the process scrap, defective or scrapped products generated in the rare earth sintered magnet manufacturing process (step 1);
A hydrogenation process step (step 2) of charging the pulverized product of step 1 to a tube furnace and then filling hydrogen in a vacuum state and increasing the temperature from 200 to 300 ° C. at the temperature of the tube;
Phase decomposition process step (step 3) of increasing the temperature to 700 to 900 ℃ in the tube in the same hydrogen atmosphere as in step 2;
Hydrogen discharge process step (step 4) to form the nucleus of the R-Fe-B-based recrystallization by exhausting the hydrogen pressure in the tube furnace at 340 to 10 ^-1 torr or less at the same temperature as in step 3 for 1 to 30 minutes;
R-Fe-B rare earth with improved magnetic properties, characterized in that it comprises a recombination process step (step 5) of performing a vacuum evacuation of hydrogen pressure in the tube furnace to 10 ^-1 to 10 ^-5 torr after performing step 4 Method for producing magnetic powder.
The method of claim 1, wherein the coarsely pulverized in step 1 is a method for producing magnetic powder with improved magnetic properties, characterized in that the crushed rare earth sintered magnet to 0.1 ㎛ to 5,000 ㎛.
The method of claim 1, wherein the vacuum state of the step 2 is 2 × 10 ^-5 torr or less.
The method of claim 1, wherein the hydrogen of step 2 is charged to 0.3 to 2.0 atm.
delete Grinding the R-Fe-B-based rare earth magnetic powder prepared according to claim 1 to form a powder (step 1);
Mixing the thermosetting or thermoplastic synthetic resin with the powder of step 1 to produce a mixture (step 2); And
Forming a mixture of the step 2 by compression or injection to form a bonded magnet (step 3) comprising the method of manufacturing a R-Fe-B rare earth bonded magnet by the molding method.
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