Method of producing r-t-b sintered magnet

Abstract

To enable an appropriate use of solid recycled raw materials recovered during a manufacturing process.SOLUTION: A method of producing R-T-B sintered magnet includes: an alloy preparation step of preparing a raw material alloy for an R-T-B sintered magnet; a crushing step of producing alloy powder from the raw material alloy; a molding step of producing a powder compact from the alloy powder; and a sintering step of producing a sintered body from the powder compact. In the method, depending on a type of solid recycled raw materials recovered during a manufacturing process including the crushing step, the molding step and the sintering step and target oxygen concentration of an R-T-B sintered magnet to be produced, the raw material alloy produced using the solid recycled raw materials and / or the alloy powder mixed with remilled powder produced from the solid recycled raw materials is used.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for producing an RTB based sintered magnet. [Background technology]

[0002] An RTB type sintered magnet (R is a rare earth element and must contain at least one selected from the group consisting of Nd, Pr and Ce, T is at least one transition metal and must contain Fe, and B is boron) is represented by the formula RFe 14 It is composed of a main phase of a compound having a B-type crystal structure, a grain boundary phase located at the grain boundaries of this main phase, and a compound phase formed by the influence of trace additive elements and impurities. RTB-based sintered magnets have a high residual magnetic flux density B r (Hereinafter, simply "B r ") and high coercive force H cJ (Hereafter, simply "H cJ ") and have excellent magnetic properties, making them known as the highest performance magnets among permanent magnets. For this reason, RTB sintered magnets are used in a variety of motors in the automotive sector, including electric vehicles (EVs, HVs, PHVs), renewable energy sectors such as wind power generation, home appliances, and industrial sectors.

[0003] Rare earth RTB sintered magnets such as RTB sintered magnets are manufactured through the steps of preparing a raw alloy, preparing an alloy powder, press-molding the alloy powder to produce a compact, and sintering the compact. The alloy powder is manufactured, for example, by the following method.

[0004] First, a raw alloy is produced from molten metals of various raw metals by a method such as strip casting. The obtained raw alloy is subjected to a pulverization process to obtain raw alloy powder having a predetermined particle size distribution. This pulverization process usually includes a coarse pulverization process and a fine pulverization process, the former of which is carried out, for example, by a "hydrogen pulverization process" that utilizes the hydrogen embrittlement phenomenon. The latter of which is carried out, for example, by using an airflow pulverizer (jet mill). The sintered body obtained by the process of sintering the compact is then subjected to mechanical processing such as grinding and cutting to be divided into individual pieces.

[0005] Powder of alloy (auxiliary alloy) for adjusting composition is mixed with powder of raw alloy (main raw alloy) produced by a method such as strip casting. If solid recycled raw materials such as defective compacts generated in the powder molding process or RTB sintered magnets cracked or chipped in the sintering process can be used as auxiliary alloys, wasteful consumption of scarce resources can be reduced by recycling, and manufacturing costs can also be reduced. The solid recycled raw materials obtained during these manufacturing processes can be mixed with powder of raw alloy (strip cast alloy) through, for example, coarse crushing and fine crushing processes (in the case of defective compacts, the defective compacts are sintered and then coarse crushing and fine crushing processes).

[0006] Patent Document 1 discloses a method for producing a rare earth sintered magnet using a powder obtained by mixing a first fine powder (recycled raw material fine powder) and a second fine powder (new raw material fine powder). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2003-49234 A Summary of the Invention [Problem to be solved by the invention]

[0008] When the solid recycled raw material powder is mixed with the raw alloy powder, the magnetic properties of the final RTB sintered magnet are likely to vary, making it difficult to efficiently use the solid recycled raw material to produce an RTB sintered magnet with the desired magnetic properties.

[0009] The embodiments of the present disclosure provide a method for producing an RTB based sintered magnet that can solve the above problems. [Means for solving the problem]

[0010] In a non-limiting exemplary embodiment, the method for producing an RTB based sintered magnet according to the present disclosure includes an alloy preparation step of preparing a raw material alloy for an RTB based sintered magnet, a crushing step of producing an alloy powder from the raw material alloy, a compacting step of producing a powder compact from the alloy powder, and a sintering step of producing a sintered body from the powder compact, and uses the raw material alloy produced using the solid recycled raw material and / or the alloy powder mixed with re-milled powder produced from the solid recycled raw material depending on the type of solid recycled raw material recovered during the production steps including the crushing, compacting, and sintering steps, and the target oxygen concentration of the RTB based sintered magnet to be produced. Effect of the Invention

[0011] According to the embodiments of the present disclosure, depending on the type of solid recycled raw materials recovered during the manufacturing process and the target oxygen concentration of the RTB-based sintered magnet to be produced, a raw material alloy made from the solid recycled raw materials or an alloy powder mixed with re-milled powder made from the solid recycled raw materials is used, thereby suppressing fluctuations in the magnetic properties of the RTB-based sintered magnet finally obtained, and it is possible to efficiently utilize the solid recycled raw materials to manufacture RTB-based sintered magnets with the desired magnetic properties. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic example of a "recovery" step in the production process of an RTB based sintered magnet. [Diagram 2] FIG. 2 is a flowchart showing the main steps in the method for producing an RTB based sintered magnet of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As a result of the inventor's investigation, it was found that the main cause of the variation in the magnetic properties of the finally obtained RTB-based sintered magnet is the variation in the oxygen concentration in the solid recycled raw material recovered in the process of manufacturing various types of RTB-based sintered magnets, depending on the type and the process stage at which it is recovered. The solid recycled raw material may contain oxygen at a concentration of, for example, about 900 to 7000 ppm. Since the powder re-milling is obtained by crushing the solid recycled raw material, the solid recycled raw material can be efficiently reused. However, the obtained powder re-milling contains the same level of oxygen as the solid recycled raw material, and the presence of such a concentration of oxygen affects the performance of the finally obtained RTB-based sintered magnet. In contrast, the raw material alloy produced using the solid recycled raw material can recover oxygen as slag when the solid recycled raw material is melted, so the oxygen level of the finally obtained raw material alloy is low, regardless of the amount of oxygen in the solid produced raw material. However, the raw material alloy produced using the solid recycled raw material is not as efficient as the case of producing the powder re-milling, since it is necessary to melt the solid recycled raw material. Therefore, depending on the type of solid recycled raw materials recovered during the manufacturing process and the target oxygen concentration of the RTB-based sintered magnet to be produced, a raw material alloy made from the solid recycled raw materials or an alloy powder mixed with re-milled powder made from the solid recycled raw materials can be used, making it possible to efficiently utilize the solid recycled raw materials to produce RTB-based sintered magnets with the desired magnetic properties.

[0014] The method for producing an RTB based sintered magnet according to the present disclosure reuses cracks, chips, etc. of the compacts and sintered bodies recovered during the manufacturing process of an RTB based sintered magnet.

[0015] Fig. 1 is a diagram showing a schematic example of a "recovery" step in the production process of an RTB based sintered magnet. In the example of Fig. 1, the production of an RTB based sintered magnet proceeds by sequentially carrying out the following steps.

[0016] First, the raw alloy is delivered through the alloy delivery service. The raw alloy is embrittled by hydrogen treatment and crushed roughly (coarse grinding). It is then finely ground using a jet mill or similar device. The powder produced by fine grinding is molded using a press in a magnetic field or similar device to obtain a powder compact. The powder compact is sintered in a sintering furnace to obtain a sintered body (RTB sintered magnet material). After heat treatment to improve the magnetic properties, the product is mechanically processed, such as cut and polished, to obtain an RTB sintered magnet with the desired shape and size. The product is then surface-treated, such as plated, and inspected before being shipped.

[0017] Before and after each of these processes, solids that are not used in products due to cracks, cracks, chips, dimensional defects, coating defects, etc. are collected as solid recycled raw materials. Here, the cracks are cracks in the molded body that occur due to uneven density of the molded body during molding, or strong stress when the molded body is removed from the mold. The cracks and chips are cracks and chips in the sintered body that occur due to poor shrinkage due to sintering or heat treatment, or contact between sintered bodies during processing. The dimensional defect is a dimensional defect in the sintered body after processing that occurs when processing to the target dimension is not possible due to a problem with the processing device. The coating defect is a coating defect in the sintered body after painting that occurs when painting is performed with foreign matter attached to the magnet surface. The appearance defect is a defect in the RTB-based sintered magnet that occurs when the RTB-based sintered magnet obtained through each manufacturing process is finally inspected for defects due to these cracks, cracks, chips, dimensional defects, coating defects, etc. These cracks, cracks, chips, dimensional defects, coating defects, appearance defects, etc. can be confirmed by human visual inspection or by using inspection equipment. They may also be confirmed by an automatic inspection device instead of humans. In addition, it is preferable to sinter the defective compacts and recover them as solid recycled raw materials, and it is preferable to peel off the coating from the defective coated products and recover them as solid recycled raw materials. Such solid recycled raw materials can be used to make raw alloys, or can be stored as powdered auxiliary alloys (remilled powder) divided into multiple packs in a predetermined weight unit.

[0018] In this way, the various solid recycled raw materials obtained during the manufacturing process are either used to make the raw alloy (strip cast alloy) (1) or mixed with the raw alloy powder as powder remilling (auxiliary alloy) and used (2).

[0019] In the embodiments of the present disclosure, the solid recycled raw materials are not only reused in the production of RTB sintered magnets by remilling them into powder and mixing them with raw alloy powder (main raw alloy), but are also used to produce the raw alloy. Whether the solid recycled raw materials are used to mix with the alloy powder or to produce the raw alloy is determined depending on the type of solid recycled raw material and the target oxygen concentration of the RTB sintered magnet to be produced.

[0020] The method for producing the RTB based sintered magnet of this embodiment will now be described.

[0021] The method for producing an RTB based sintered magnet of this embodiment is as shown in the flow chart of FIG. an alloy preparation step (S10) of preparing a raw material alloy for an RTB sintered magnet; A pulverization step (S12) of producing alloy powder from the raw alloy; a compacting step (S14) of producing a powder compact from the alloy powder; a sintering step (S16) of producing a sintered body from the powder compact; Includes.

[0022] In the manufacturing method of the RTB based sintered magnet of this embodiment, as described in the block designated by reference symbol S18, a raw material alloy produced using the solid recycled raw material and / or the alloy powder mixed with re-milled powder produced from the solid recycled raw material is used depending on the type of solid recycled raw material recovered during the manufacturing process, including the crushing step (S14), the molding step (S18), and the sintering step (S16), and the target oxygen concentration of the RTB based sintered magnet to be manufactured.

[0023] As mentioned above, the solid recycled raw materials can be used to make raw alloys, and can also be used as powder re-milling. The target oxygen concentration of RTB sintered magnets manufactured by reusing the solid recycled raw materials recovered during the manufacturing process (hereinafter sometimes referred to as "magnets using solid recycled raw materials") varies depending on the required magnetic properties. In other words, the target oxygen concentration varies depending on the type of RTB sintered magnet.

[0024] Although it may vary depending on the defective rate of the manufacturing process, the "magnet using solid recycled raw materials" may contain, for example, about 3 mass% of solid recycled raw materials. In this embodiment, even if there are multiple solid recycled raw materials with the same composition and oxygen concentration, it is determined whether to use those solid recycled raw materials to make a raw alloy or to make a powder re-milled product depending on the type of magnet using solid recycled raw materials, in other words, depending on the target oxygen concentration.

[0025] In this embodiment, the recovered solid recycled raw material can be reused after being sintered. For example, the defective compacts are not mixed with the raw alloy powder as they are, but are re-milled into powder through sintering and crushing processes.

[0026] The solid recycled raw materials recovered in the manufacturing process of RTB-based sintered magnets contain oxygen at a concentration of about 900 to 7000 ppm. Even after the solid recycled raw materials are pulverized by performing a process such as hydrogen pulverization, the same level of oxygen concentration is maintained. In contrast, the oxygen concentration contained in general raw material alloys is 100 to 200 ppm. Therefore, when manufacturing an RTB-based sintered magnet with a relatively low target oxygen concentration, it is desirable to lower the mixing ratio when mixing the powder remilled from the solid recycled raw materials with the normal raw alloy powder. In other words, when the target oxygen concentration is equal to or lower than a first set value (e.g., 1500 ppm), it is desirable to set the ratio of the solid recycled raw materials used to prepare the powder remilled in the total solid recycled raw materials contained in the RTB-based sintered magnet to less than a second set value (e.g., 10%).

[0027] In addition, when the solid recycled raw material is used to prepare the powder re-milled, it is preferable to prepare a coarsely pulverized powder by hydrogen treatment. The pulverization process may include, for example, a process of preparing a coarsely pulverized powder of the raw alloy by hydrogen treatment, mixing the coarsely pulverized powder of the solid recycled raw material with the coarsely pulverized powder of the raw alloy to prepare a mixed powder, and then finely pulverizing the mixed powder to prepare the alloy powder.

[0028] In the alloy preparation step, it is preferable to melt the solid recycled raw material together with other raw material alloys to prepare a molten alloy, and then cool the molten alloy to prepare the raw material alloy. This is because, when producing a high-performance magnet in which the target oxygen concentration is equal to or less than a first set value (e.g., 1500 ppm), it is possible to tolerate a decrease in efficiency compared to the case of using powder re-milling. Such a raw material alloy is, for example, an alloy produced by a strip cast method.

[0029] On the other hand, when the target oxygen concentration exceeds a first set value (e.g., 1500 ppm), it is preferable to set the ratio of the solid recycled raw materials used to prepare the powder refining to the total solid recycled raw materials contained in the RTB sintered magnet to a second set value (e.g., 10%) or more. This is because the efficiency of preparing the powder refining from the solid recycled raw materials recovered during the manufacturing process is lower than the efficiency of using the solid recycled raw materials to prepare the raw alloy.

[0030] To realize the above-mentioned recycling, it is desirable to classify and store the solid recycled raw materials into multiple groups based on data including composition information such as oxygen concentration. If such classification is performed, it is possible to determine whether the solid recycled raw materials being stored will be used to make raw alloys or to make powder re-milling depending on the group to which they belong.

[0031] The present embodiment will now be described in more detail.

[0032] First, this embodiment will be described taking as an example the production of an RTB based sintered magnet having the following composition. R: 26.5mass% or more and 35mass% or less, B: 0.80mass% or more and 1.20mass% or less, Ga: 1.2 mass% or less (including 0 mass%) Cu: 1.2 mass% or less (including 0 mass%) O: 2000ppm or less T: Contains 60 mass% or more.

[0033] Here, each composition range will be explained. (R:26.5~35mass%) R is a rare earth element, and must contain at least one selected from the group consisting of Nd, Pr, and Ce. If R is less than 26.5 mass%, the liquid phase is not sufficiently generated during the sintering process, and it may be difficult to sufficiently densify the sintered body. On the other hand, if R exceeds 35 mass%, grain growth occurs during sintering, and H cJThe content of R is preferably 29.5 to 33.0 mass%. If the content of R is within this range, a higher B r can be obtained. (B: 0.80~1.20mass%) When B is less than 0.80 mass%, B r On the other hand, if B exceeds 1.20 mass%, H cJ The B content is preferably 0.88 to 0.90 mass%. If the B content is within this range, a higher H cJ is obtained. (Ga: 0-1.2 mass%) The Ga content is preferably 0 to 1.2 mass%, and more preferably 0.2 to 0.7 mass%. When the Ga content is in this range, the higher H cJ is obtained. (Cu: 0-1.2 mass%) The Cu content is preferably 0 to 1.2 mass%, more preferably 0.05 to 0.50 mass%. When the Cu content is within this range, a higher H cJ is obtained. (T:60mass% or more) T is at least one transition metal element and necessarily includes Fe.

[0034] If the T content in the sintered magnet is less than 60 mass%, the magnetic properties may be significantly degraded. The T content is preferably 61.5 to 69.5 mass%. Furthermore, when the total amount of T is taken as 100 mass%, 10 mass% or less of this can be substituted with Co. For example, 90 mass% of the total amount of T can be Fe and 10 mass% can be Co. Furthermore, the total amount of T (100 mass%) may be Fe. The inclusion of Co can improve corrosion resistance, but if the amount of Co substituted exceeds 10 mass% of Fe, high B r may not be obtained.

[0035] The RTB based sintered magnet of the present disclosure may further contain other elements.

[0036] After the alloy for RTB sintered magnets (raw material alloy) is prepared, the raw material alloy is roughly crushed by, for example, a hydrogen crushing method.

[0037] An alloy ingot can be obtained by an ingot casting method in which a metal or alloy previously adjusted to have the above-mentioned composition is melted and poured into a mold to solidify. Alternatively, the alloy can be produced by a strip casting method in which a molten metal or alloy previously adjusted to have the above-mentioned composition is brought into contact with a single roll, twin rolls, rotating disk, or rotating cylindrical mold, etc., and quenched to produce a rapidly solidified alloy. Alternatively, flake-shaped alloys can be produced by other quenching methods, such as centrifugal casting.

[0038] In the embodiment of the present disclosure, it is preferable to use an alloy manufactured by a quenching method such as a strip casting method. The thickness of the alloy manufactured by the quenching method is usually in the range of 0.03 mm to 1 mm, and it is in a flake shape. By subjecting the obtained alloy to hydrogen pulverization, the size of the hydrogen pulverized powder (coarsely pulverized powder) can be, for example, 1.0 mm or less. The coarsely pulverized powder thus obtained is pulverized, for example, by a jet mill. Jet mill pulverization is performed in an inert atmosphere such as nitrogen. Pulverization may be performed, for example, by a jet mill in a humidified atmosphere.

[0039] In this embodiment, the target oxygen concentration is 2000 ppm or less, which exceeds the first set value (1500 ppm). Therefore, the ratio of the solid recycled raw material used to prepare the remilled powder to the entire solid recycled raw material contained in the RTB sintered magnet is set to a second set value (e.g., 20%) or more. Specifically, when the above-mentioned jet mill pulverization is performed, or to the raw alloy powder after the jet mill pulverization, a powder (remilled powder) obtained from the solid recycled raw material having an oxygen concentration of, for example, about 5000 ppm is mixed. The mixing ratio is determined, for example, so that the ratio of the solid recycled raw material used to prepare the remilled powder to the entire recycled raw material contained in the RTB sintered magnet is 10 to 30%.

[0040] The fine powder used to produce the RTB sintered magnet may contain, as the raw material alloy powder, not only one type of raw material alloy (single raw material alloy), but also two or more types of raw material alloy powder.

[0041] Next, a powder compact is produced from the fine powder by pressing in a magnetic field, and then the powder compact is sintered. In the case of pressing in a magnetic field, it is preferable to form the powder compact by pressing in an inert gas atmosphere or by wet pressing from the viewpoint of suppressing oxidation. In particular, in wet pressing, the surface of the particles constituting the powder compact is covered with a dispersant such as an oil agent, and contact with oxygen or water vapor in the air is suppressed. Therefore, it is possible to prevent or suppress the particles from being oxidized by the air before, during, or after the pressing process. Therefore, it is easy to control the oxygen content within a predetermined range. When performing wet pressing in a magnetic field, a slurry is prepared by mixing the fine powder with a dispersion medium, and the slurry is supplied to a cavity in a mold of a wet pressing device and press-molded in a magnetic field.

[0042] The thus obtained molded body is sintered to obtain an RTB sintered magnet material. The molded body is preferably sintered at a temperature in the range of 950°C to 1150°C. To prevent oxidation due to sintering, residual gas in the atmosphere may be replaced with an inert gas such as helium or argon. The obtained sintered body (RTB sintered magnet) may be subjected to a heat treatment. Known conditions for the heat treatment, such as the heat treatment temperature and heat treatment time, may be adopted. The RTB sintered magnet may be prepared using a known method, such as the PLP (Press-Less Process) method described in JP-A-2006-19521, without carrying out the above-mentioned molding.

[0043] As described above, the present disclosure includes the methods for producing RTB based sintered magnets described in the following items. [Item 1] an alloy preparation step of preparing a raw material alloy for an RTB sintered magnet; a pulverization step of producing an alloy powder from the raw alloy; a compacting step of producing a powder compact from the alloy powder; a sintering step of producing a sintered body from the powder compact; Including, The method for producing an RTB based sintered magnet uses the raw material alloy produced using the solid recycled raw material and / or the alloy powder mixed with re-milled powder produced from the solid recycled raw material, depending on the type of solid recycled raw material recovered during the production process including the crushing, molding, and sintering processes, and the target oxygen concentration of the RTB based sintered magnet to be produced. [Item 2] when the target oxygen concentration is equal to or lower than a first set value, a ratio of the solid recycled raw material used for preparing the powder re-milled product to the total amount of the solid recycled raw material contained in the RTB based sintered magnet is set to be less than a second set value; 2. The method for producing an RTB based sintered magnet according to item 1, wherein, when the target oxygen concentration exceeds the first set value, a ratio of the solid recycled raw material used for preparing the re-milled powder to the total amount of the solid recycled raw material contained in the RTB based sintered magnet is set to be equal to or greater than the second set value. [Item 3] the first set value is 1500 ppm; 3. The method for producing an RTB based sintered magnet according to item 2, wherein the second set value is 10%. [Item 4] 4. The method for producing an RTB sintered magnet according to any one of items 1 to 3, wherein the alloy preparation step includes a step of melting the solid recycled raw material together with other raw material alloys to prepare a molten alloy, and cooling the molten alloy to prepare a raw material alloy. [Item 5] 5. The method for producing an RTB sintered magnet according to item 4, wherein the raw material alloy is a strip cast alloy. [Item 6] 6. The method for producing an RTB sintered magnet according to any one of items 1 to 5, wherein when the solid recycled raw material is used to produce the re-milled powder, coarse pulverized powder is produced by a hydrogen treatment. [Item 7] The grinding step comprises: preparing a coarsely pulverized powder of the raw alloy by hydrogen treatment; mixing the coarsely pulverized powder of the solid recycled raw material with the coarsely pulverized powder of the raw alloy to prepare a mixed powder, and then pulverizing the mixed powder to prepare the alloy powder; 7. A method for producing an RTB based sintered magnet according to item 6, comprising: [Industrial Applicability]

[0044] The method of producing an RTB based sintered magnet according to the present disclosure can be widely used in the field of producing RTB based sintered magnets that contain rare resource elements in the raw material alloy.

Claims

1. an alloy preparation step of preparing a raw material alloy for an RTB-based sintered magnet; a pulverization step of producing an alloy powder from the raw alloy; a compacting step of producing a powder compact from the alloy powder; a sintering step of producing a sintered body from the powder compact; Including, The method for producing an R-T-B based sintered magnet uses the raw alloy produced using the solid recycled raw material and / or the alloy powder mixed with re-milled powder produced from the solid recycled raw material, depending on the type of solid recycled raw material recovered during the production process including the pulverization, molding, and sintering processes, and the target oxygen concentration of the R-T-B based sintered magnet to be produced, and determines whether the solid recycled raw material will be used to mix with the alloy powder or to produce the raw alloy.

2. The method for producing an RTB based sintered magnet according to claim 1, wherein the raw material alloy is produced using the solid recycled raw material.

3. 2. The method for producing an RTB based sintered magnet according to claim 1, wherein the alloy powder is a mixture of re-milled powder produced from the solid recycled raw material.

4. The method for producing an R-T-B based sintered magnet according to claim 1, wherein the alloy powder is a mixture of the raw alloy produced using the solid recycled raw material and re-milled powder produced from the solid recycled raw material.

5. when the target oxygen concentration is equal to or less than a first set value, a ratio of the solid recycled raw material used to prepare the powder re-milled to the total amount of the solid recycled raw material contained in the R-T-B based sintered magnet is set to be less than a second set value; 5. The method for producing an R-T-B based sintered magnet according to claim 1, wherein, when the target oxygen concentration exceeds the first set value, a proportion of the solid recycled raw material used to prepare the powder re-milled to account for the total amount of the solid recycled raw material contained in the R-T-B based sintered magnet is set to be equal to or greater than the second set value.

6. the first set value is 1500 ppm; 6. The method for producing a sintered RTB based magnet according to claim 5, wherein the second set value is 10%.

7. 2. The method for producing an R-T-B based sintered magnet according to claim 1, wherein the alloy preparation step includes the steps of melting the solid recycled raw material together with other raw material alloys to prepare a molten alloy, and cooling the molten alloy to prepare a raw material alloy.

8. 8. The method for producing an RTB based sintered magnet according to claim 7, wherein the raw material alloy is a strip cast alloy.

9. The method for producing an RTB based sintered magnet according to any one of claims 1 to 8, wherein when the solid recycled raw material is used to produce the powder re-milled, coarsely pulverized powder is produced by hydrogen treatment.

10. The pulverization step includes: preparing a coarsely pulverized powder of the raw alloy by hydrogen treatment; a step of mixing the coarsely pulverized powder of the solid recycled raw material with the coarsely pulverized powder of the raw alloy to prepare a mixed powder, and then finely pulverizing the mixed powder to prepare the alloy powder; The method for producing a sintered RTB based magnet according to claim 9, comprising:

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