JP2020107888A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

To provide a method for manufacturing an R-T-B based sintered magnet having high HcJ while reducing an amount of use of heavy rare earth RH and suppressing Br from lowering.SOLUTION: A method for manufacturing an R-T-B based sintered magnet comprises: a step of preparing an R-T-B based sintered magnet material having, as a main phase, R2Fe14B type compound crystal grains containing a light rare earth element RL as a main rare earth element R; a step of preparing diffusion source powder to be formed from powder of an alloy or compound containing a heavy rare earth element RH; a step of bringing at least part of the diffusion source powder into contact with at least part of the surface of the R-T-B based sintered magnet material; and a diffusion step of performing a thermal treatment for heating the R-T-B based sintered magnet material with the diffusion source powder put in contact therewith at a temperature of 800°C or higher and a sintering temperature of the R-T-B based sintered magnet material or lower for 30 hours or longer, thereby diffusing the heavy rare earth element RH included in the diffusion source powder from the surface of the R-T-B based sintered magnet material to inside.SELECTED DRAWING: None

Description

The present disclosure relates to a method for manufacturing an RTB-based sintered magnet.

The R-T-B system sintered magnet (R is a rare earth element, T is Fe or Fe and Co) having an R ₂ Fe ₁₄ B type compound as a main phase is known as the most high-performance magnet among permanent magnets. It is used for various motors such as voice coil motors (VCM) of hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and home electric appliances.

The RTB sintered magnet is mainly composed of a main phase composed of an R ₂ Fe ₁₄ B type compound and a grain boundary phase located in a grain boundary portion of the main phase. The main phase R ₂ Fe ₁₄ B type compound is a ferromagnetic material having a high saturation magnetization and an anisotropic magnetic field, and forms the basis of the characteristics of the RTB sintered magnet.

Since the intrinsic coercive force H _cJ (hereinafter, simply referred to as “H _cJ ”) of the _RTB -based sintered magnet decreases at high temperature, irreversible thermal demagnetization occurs. In order to avoid irreversible thermal demagnetization, when used for a motor or the like, it is required to maintain high H _cJ even at high temperatures.

It is known that in the RTB sintered magnet, H _cJ is improved when a part of R in the R ₂ Fe ₁₄ B type compound phase is replaced with a heavy rare earth element RH (Dy, Tb, etc.). There is. In order to obtain high _HcJ at high temperature, it is effective to add a large amount of heavy rare earth element RH to the RTB-based sintered magnet. However, the R-T-B based sintered magnet, replacing light rare-earth element RL as R a (Nd, Pr) in the heavy rare-earth element _RH, while _{the H cJ} is improved, the residual magnetic flux density _{B r} (hereinafter, simply " B _r )) is decreased. Further, the heavy rare earth element RH is a rare resource. For these reasons, it is required to reduce the amount of heavy rare earth element RH used.

Therefore, in recent years, in order to improve the _HcJ of the _RTB -based sintered magnet with a _{smaller amount} of the heavy rare-earth element RH, a heavy rare-earth element RH such as Tb or Dy is _added to the surface of the RTB-based sintered magnet. It is proposed to supply and diffuse the heavy rare earth element RH inside the magnet. As a result, a large amount of heavy rare earth element RH can be distributed in the outer shell of the main phase (near the grain boundary). It is possible to suppress a decrease in B _r by distributing the outer periphery of the main phase (grain boundary vicinity) heavy rare-earth element RH thin shell layer (RH concentrated layer), further, R-T-B based sintered Since the H _cJ generation mechanism of the binder magnet is a nucleation type (nucleation type), it is possible to distribute the thin shell layer of the heavy rare earth element RH in the outer shell of the main phase (near the grain boundary) to obtain the crystal magnetism of the entire crystal grain. The anisotropy is enhanced and the nucleation of the reverse domain is prevented, resulting in an improved H _cJ .

In Patent Document 1, by heating a powder containing Dy, Tb, etc. at a temperature lower than the sintering temperature in the state of being present on the surface of the sintered body, Dy, Tb, etc. are converted from the powder into a sintered body. The method of diffusion is described.

In Patent Document 2 and Patent Document 3, a sintered magnet (Patent Document 3 is a sintered body) and an evaporation material containing Dy and the like (Patent Document 3 is a bulk body) are spaced apart via a net, A method is disclosed in which Dy or the like is diffused from the evaporation material into the sintered magnet by heating the sintering magnet and the evaporation material to a predetermined temperature.

In Patent Document 4, a plurality of RTB-based sintered magnet bodies and a plurality of RH diffusion sources containing Dy or the like are inserted into a processing chamber so as to be relatively movable and close to or in contact with each other, By heating the R-T-B based sintered magnet body and the former RH diffusion source while continuously or intermittently moving in the processing chamber, Dy and the like from the RH diffusion source are RT-. A method of diffusing into a B-based sintered magnet body is described.

JP, 2008-147634, A JP, 2008-171995, A International Publication No. 2007/102391 International Publication No. 2011/007758

However, according to the method described in Patent Document 1, the heavy rare-earth element RH accumulated on the surface of the sintered body diffuses into the inside of the sintered body at once, so that it is close to the central portion of the main phase in the surface layer region of the sintered body. Even so, the heavy rare earth element RH diffuses. Thus lowering the _{B r.} Further, since a large amount of heavy rare earth element RH is consumed in the surface layer region of the sintered body, it is possible to diffuse sufficient heavy rare earth element RH from the surface layer region of the magnet body to a region further inside (the central portion of the magnet). It will be difficult.

Further, according to the methods described in Patent Documents 2 to 4, the heavy rare earth element RH rapidly diffuses inside the sintered magnet after colliding with the surface. However, since the heavy rare earth element RH is sequentially supplied to the surface of the magnet, if an attempt is made to diffuse sufficient heavy rare earth element RH from the surface layer region of the sintered magnet to a further inner region (the central portion of the magnet), sintering will occur. A relatively thick shell layer of the heavy rare earth element RH may be formed in the main phase of the surface layer region of the magnet.

As described above, in the methods described in Patent Documents 1 to 4, in the surface layer region of the sintered magnet, the heavy rare earth element RH diffuses not only into the main phase outer shell (near the grain boundary) but also into the main phase, since there is a case where relatively thick heavy rare-earth element RH in the shell layer is formed, while always sufficiently suppress a decrease in B _r, it is hard to say that which improves the H _cJ.

Various embodiments of the present disclosure is to reduce the amount of heavy rare-earth RH, to provide a method of manufacturing a R-T-B based sintered magnet having a high H _cJ while suppressing a decrease in B _r.

In an exemplary embodiment, a method for manufacturing an RTB-based sintered magnet according to the present disclosure is a rare earth having a light rare earth element RL (RL is at least one selected from the group consisting of Nd, Pr, and Ce) as a main rare earth element. A step of preparing an RTB-based sintered magnet material (T is Fe or Fe and Co) having R ₂ Fe ₁₄ B type compound crystal grains contained as an element R as a main phase; and a heavy rare earth element RH (RH Is a step of preparing a diffusion source powder formed from a powder of an alloy or compound containing at least one selected from the group consisting of Tb, Dy and Ho, and a step of preparing a surface of the R-T-B based sintered magnet material. The step of bringing at least a portion of the diffusion source powder into contact with at least a portion, and the RTB-based sintered magnet material in a state where the diffusion source powder is in contact with the RTB-based sintered body at 800° C. or higher. Heat treatment is performed by heating the sintered magnet material at a temperature equal to or lower than the sintering temperature for 30 hours or more to transfer the heavy rare earth element RH contained in the diffusion source powder from the surface of the RTB-based sintered magnet material to the inside. And a diffusion step of diffusing.

In one embodiment, in the diffusion step, the RTB-based sintered magnet material in a state where the diffusion source powder is in contact is used at a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet material. Heat treatment is performed by heating for 30 hours or more and 45 hours or less.

In one embodiment, in the diffusion step, the RTB-based sintered magnet material in a state where the diffusion source powder is in contact is used at a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet material. Heat treatment is performed by heating for 35 hours or more and 40 hours or less.

In one embodiment, the diffusion source powder is RHM alloy powder (M is at least one selected from the group consisting of Nd, Pr, Ce, Cu, Ga, Fe, Co, Ni, and Al).

In one embodiment, the diffusion source powder contains Cu.

In one embodiment, the thickness of the RTB-based sintered magnet material in the thickness direction is 1 mm or more and 5 mm or less.

In one embodiment, the step of bringing at least a part of the diffusion source powder into contact with at least a part of the surface of the RTB-based sintered magnet material is performed by It is a step of adhering at least a part of the diffusion source powder to at least a part of the surface.

The present disclosure reduces the amount of heavy rare-earth RH, it is possible to provide a manufacturing method of the R-T-B based sintered magnet having a high H _cJ while suppressing a decrease in B _r.

The present inventors have made a method described in Patent Document 1, for example, a state in which a diffusion source powder containing a heavy rare earth element RH is brought into contact with the surface of an RTB-based sintered magnet material, and the diffusion source powder is brought into contact with the surface. When the heavy rare earth element RH is diffused into the RTB-based sintered magnet material by heat treatment for heating the RTB-based sintered magnet, the surface layer of the RTB-based sintered magnet. In the region, it was investigated whether or not the heavy rare earth element RH could not be diffused into the main phase shell part (near the grain boundary).

Usually, the heating time in the diffusion step is such that as the heating time is lengthened (for example, 5 to 10 hours), diffusion of the heavy rare earth element RH into the main phase progresses in the surface layer region of the magnet. Therefore, conventionally, the more you increase the heating time, the heavy rare-earth element RH into the main phase inside the surface region of the magnet is diffused, thereby leading to decrease in B _r, many heavy rare-earth element RH in the further surface region It has been considered that when _consumed , it becomes difficult to diffuse sufficient heavy rare earth element RH to the central portion of the magnet, and improvement of H _cJ is hindered. However, as a result of the investigation, surprisingly, when the heating time is longer than 30 hours, the heavy rare earth element RH is not diffused inside the main phase, and the heavy rare earth element RH is diffused into the outer phase of the main phase (near the grain boundary). It turned out that it can be diffused. It was also found that the heavy rare earth element RH can be diffused from the surface layer region of the magnet to a region further inside (the central portion of the magnet). Although the detailed mechanism is unknown, the heavy rare earth element RH once diffused inside the main phase is inversely diffused to the grain boundary by heating for a long time, and the diffused heavy rare earth element RH is inversely diffused. It is considered that the particles diffused from the surface layer region of the magnet to the inner region through the grain boundary. It believed it was possible to thereby obtain a R-T-B based sintered magnet having a high H _cJ while suppressing a decrease in B _r. It was also found that this phenomenon does not occur in the methods of Patent Documents 2 to 4. It is considered that this is because, unlike Patent Document 1, the heavy rare earth element RH is successively newly introduced to the magnet surface.

In Patent Document 1, the diffusion time is described in a very wide range of 1 minute to 100 hours, but the examples are in the range of 5 hours to 20 hours, and the preferable range is 5 minutes to 8 hours, and particularly 10 minutes. It is stated to be from minutes to 6 hours. Further, although Patent Document 2 describes that the diffusion time is 48 hours and 60 hours, as described above, in the method described in Patent Document 2, the heavy rare earth element RH is successively newly introduced onto the magnet surface. , R-T-B based sintered magnet, the heavy rare earth element RH cannot be diffused into the main phase shell part (near the grain boundary) in the surface layer region.

In the present disclosure, the RTB-based sintered magnet before and during the diffusion step is referred to as an “RTB-based sintered magnet material”, and the RTB-based sintered magnet after the diffusion step is referred to. The binder magnet is simply referred to as "RTB-based sintered magnet". Further, in the present disclosure, the “surface layer region” refers to a region from the magnet surface to a depth of about 20 μm.

(Process of preparing R-T-B system sintered magnet material)
R-T-B having R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (RL is at least one selected from the group consisting of Nd, Pr and Ce) as a main rare earth element R as a main phase A sintered magnet material (T is Fe or Fe and Co) is prepared.

As the RTB-based sintered magnet material, known materials can be used. For example, it has the following composition.
Rare earth element R: 27.5 to 35.0 mass%,
B (some of B (boron) may be substituted with C (carbon)): 0.80 to 1.20% by mass,
Ga: 0 to 0.8 mass%,
Additive element M (at least one selected from the group consisting of Al, Cu, Zr, and Nb): 0 to 2% by mass,
T (T is Fe or Fe and Co) and inevitable impurities: balance.

The rare earth element R mainly contains a light rare earth element RL, but may contain a heavy rare earth element RH (RH is at least one selected from the group consisting of Tb, Dy and Ho).

The RTB based sintered magnet material having the above composition is manufactured by any known manufacturing method. The RTB-based sintered magnet material may be as-sintered or may be subjected to cutting or polishing.

Further, the RTB sintered magnet material preferably has a dimension in the thickness direction of 1 mm or more and 5 mm or less. For example, when the magnet has a rectangular shape and has a size of 4 mm×4 mm×2 mm, 2 mm is the thickness direction. When the dimensions are the same, for example, 2 mm×2 mm×2 mm, 2 mm is the thickness direction. If the dimension in the thickness direction is less than 1 mm, cracks and cracks may occur due to insufficient strength, and if it exceeds 5 mm, the heavy rare earth element RH sufficient to reach the central portion of the R-T-B based sintered magnet material is obtained. Can be difficult to spread. Further, the thickness direction does not necessarily have to be the magnetization direction, and a direction different from the thickness direction may be the magnetization direction.

(Process of preparing diffusion source powder)
A diffusion source powder formed from an alloy or compound powder containing a heavy rare earth element RH (RH is at least one selected from the group consisting of Tb, Dy and Ho) is prepared.

The diffusion source powder is, for example, a RHM alloy powder (M is at least one selected from the group consisting of Nd, Pr, Ce, Cu, Ga, Fe, Co, Ni, and Al).

The method for producing the RHM alloy powder is not particularly limited. The alloy ribbon may be prepared by a roll quenching method, and the alloy ribbon may be crushed by a known atomizing method such as a centrifugal atomizing method, a rotating electrode method, a gas atomizing method, or a plasma atomizing method. May be. You may grind the ingot produced by the casting method. Typical examples of the RHM alloy powder are DyFe alloy powder, DyAl alloy powder, DyCu alloy powder, TbFe alloy powder, TbAl alloy powder, TbCu alloy powder, DyFeCu alloy powder, TbCuAl alloy powder, TbNdPrCu alloy powder, TbNdCePrCu alloy powder, TbNdGa alloy. Powder, TbNdPrGaCu alloy powder, and the like. Further, the RHM alloy powder preferably contains Cu. By containing Cu, it is possible to diffuse sufficient heavy rare earth element RH from the surface layer region of the R-T-B based sintered magnet material to a further inner region (center portion of the magnet). The particle size of the RHM alloy powder is, for example, 500 μm or less, and the small one is about 10 μm.

The compound of the heavy rare earth element RH is at least one selected from RH fluorides, RH oxyfluorides, and RH oxides, and these are collectively referred to as RH compounds. The RH oxyfluoride may be contained in the RH fluoride as an intermediate substance in the production process of the RH fluoride. The particle size of many available RH compound powders is 20 μm or less, typically 10 μm or less in the size of agglomerated secondary particles, and the small one is about several μm in primary particles.

(Step of contacting at least a part of the diffusion source powder with at least a part of the surface of the RTB-based sintered magnet material)
At least a part of the diffusion source powder is brought into contact with at least a part of the surface of the R-T-B based sintered magnet material. The method of bringing the diffusion source powder into contact with the surface of the RTB-based sintered magnet material is not particularly limited. Any method may be used as long as at least a part of the diffusion source powder can be attached to at least a part of the surface of the RTB-based sintered magnet material. For example, a spray method, a dipping method, coating with a dispenser, etc. may be mentioned. Also, by applying a pressure sensitive adhesive to the surface of the R-T-B type sintered magnet material, and by applying a diffusion source powder to the surface of the R-T-B type sintered magnet material with the pressure sensitive adhesive attached, Good. For example, a so-called fluidized bed coating process may be used in which an RTB-based sintered magnet material coated with an adhesive is immersed in a fluidized diffusion source powder. Hereinafter, an example of applying the fluidized-bed method will be described.

The fluidized dipping method has been widely used in the field of powder coating, and the heated coating material is dipped in the fluidized thermoplastic powder coating material to heat the surface of the coating material. Is a method of fusing. In this example, in order to apply the fluidized-bed method to a magnet, the above-mentioned diffusion source powder is used in place of the thermoplastic powder coating material, and an R-T-B system in which a pressure-sensitive adhesive is applied instead of the heated coating material. Use a sintered magnet material. Any method may be used for flowing the diffusion source powder. For example, as one specific example, a method of using a container provided with a porous partition wall in the lower part will be described. In this example, the diffusion source powder is put in a container, and a gas such as the atmosphere or an inert gas is injected into the container by applying pressure from the lower part of the partition wall, and the diffusion source powder above the partition wall is floated by the pressure or air flow. Can be fluidized.

The diffusion source powder is burnt in the RTB system by immersing (or placing or passing) the RTB system sintered magnet material coated with an adhesive in the diffusion source powder flowing inside the container. Attach it to the magnet material. The time for immersing the RTB-based sintered magnet material coated with the adhesive is, for example, about 0.5 to 5.0 seconds. By using the fluidized dipping method, the diffusion source powder is flown (stirred) in the container, so that relatively large powder particles are unevenly attached to the magnet surface, or conversely, relatively small powder particles are separated and the magnet surface It is suppressed that it adheres to. Therefore, the diffusion source powder can be more uniformly adhered to the RTB-based sintered magnet material.

(Diffusion process)
The heat treatment is performed by heating the RTB-based sintered magnet material in a state in which the diffusion source powder is in contact with the sintered material of the RTB-based sintered magnet material at a temperature of 800° C. or higher for 30 hours or more. The heavy rare earth element RH contained in the diffusion source powder is diffused from the surface of the RTB-based sintered magnet material to the inside. When the heating temperature is 800° C. or lower, the amount of the liquid phase containing the heavy rare earth element RH is too small and diffusion into the inside of the _RTB -based sintered magnet is insufficient, so that high H _cJ cannot be obtained. may, abnormal grain growth exceeds the sintering temperature occurs, there is a possibility that the B _r and H _cJ is reduced significantly. The heating temperature is preferably 850° C. or higher and 950° C. or lower. Higher H _cJ can be obtained. The heat treatment can be performed using a known heat treatment device.

As described above, by performing the heating time for 30 hours or more, the heavy rare earth element RH can be diffused into the main phase shell portion (near the grain boundary) in the surface layer region of the RTB sintered magnet. The heavy rare earth element RH can be diffused from the surface layer region of the magnet to a region further inside (the central portion of the magnet). Thus, it is possible to obtain the R-T-B based sintered magnet having a high H _cJ while suppressing a decrease in B _r.

The heating time in the diffusion step of the present disclosure has a starting point when the temperature of the RTB-based sintered magnet material reaches a set temperature (for example, when the set temperature is 920° C., it becomes 920° C.). The end point is when the temperature becomes lower than the set temperature by more than 20° C. (for example, when the set temperature is 920° C., the temperature becomes less than 900° C.). When the heat treatment is performed twice or more, the total time may be 30 hours or more. The temperature of the RTB-based sintered magnet material can be measured, for example, by attaching a thermocouple to the magnet material. The heating time is preferably 30 hours or longer and 45 hours or shorter, and more preferably 35 hours or longer and 40 hours or shorter.

The RTB-based sintered magnet after the diffusion step may be subjected to a second heat treatment for the purpose of improving magnetic properties. As the conditions such as temperature and time in the second heat treatment, known conditions as heat treatment conditions for the sintered magnet (for example, 500° C. for 3 hours) can be adopted. Further, the final adjustment of the magnet size may be performed by machining such as grinding. In this case, it may be performed before or after the second heat treatment.

The present disclosure will be described in more detail by way of examples, but the present disclosure is not limited thereto.

Experimental example 1
(Process of preparing R-T-B system sintered magnet material)
Each element is weighed and cast by the strip casting method so that the RTB sintered magnet material has a composition of 1-A in Table 1, and a flaky raw material alloy having a thickness of 0.2 to 0.4 mm. Got The obtained flaky raw material alloy was pulverized with hydrogen and then subjected to a dehydrogenation treatment of heating in vacuum to 550° C. and then cooling to obtain coarsely pulverized powder. Next, zinc stearate as a lubricant was added to the obtained coarsely pulverized powder in an amount of 0.04% by mass relative to 100% by mass of the coarsely pulverized powder, and the mixture was mixed. After dry pulverization in a nitrogen stream, finely pulverized powder (alloy powder) having a particle size D ₅₀ of 4 μm was obtained. The particle diameter D ₅₀ is a volume center value (volume-based median diameter) obtained by a laser diffraction method using an air flow dispersion method.

Zinc stearate as a lubricant was added to the finely pulverized powder in an amount of 0.05% by mass relative to 100% by mass of the finely pulverized powder, and the mixture was molded in a magnetic field to obtain a molded body. A so-called orthogonal magnetic field molding device (transverse magnetic field molding device) in which the magnetic field applying direction and the pressurizing direction are orthogonal to each other was used as the molding device.

The obtained molded body was sintered for 4 hours (a temperature at which sufficient densification by sintering was sufficient was selected), and a plurality of RTB-based sintered magnet materials (No. 1-A) were prepared. The density of the obtained RTB-based sintered magnet material was 7.5 Mg/m ³ or more. The results of the components of the obtained RTB-based sintered magnet material are shown in Table 1. In addition, each component in Table 1 was measured using the high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, as a result of measuring the oxygen content of the sintered body by a gas melting-infrared absorption method, it was confirmed that the oxygen content was around 0.1 mass %. In addition, No. The 1-A RTB-based sintered magnet material was cut and cut to obtain a rectangular parallelepiped of 4.4 mm x 10.0 mm x 11.0 mm (a plane of 10.0 mm x 11.0 mm is perpendicular to the orientation direction). In the plane, the 4.4 mm direction is the thickness direction and is the orientation direction).

(Process of preparing diffusion source powder)
No. of Table 2 A diffusion source powder was prepared by preparing an alloy powder having a composition shown in 1-a by an atomizing method. The particle size of the obtained diffusion source powder was 106 μm or less.

(Step of contacting at least a part of the diffusion source powder with at least a part of the surface of the RTB-based sintered magnet material)
Next, in Table 1, No. An adhesive was applied to the entire surface of the 1-A RTB-based sintered magnet material. As an application method, an RTB-based sintered magnet material was heated to 60° C. on a hot plate, and then an adhesive was applied to the RTB-based sintered magnet material by a spray method. PVP (polyvinylpyrrolidone) was used as an adhesive.

Next, with respect to the RTB-based sintered magnet material (No. 1-A) coated with an adhesive, the No. The diffusion source powder of 1-a was attached. As the adhesion method, the diffusion source powder was spread in a container, and the diffusion source powder was adhered to the entire surface of the R-T-B based sintered magnet material coated with the pressure-sensitive adhesive in the container.

(Diffusion process)
Using a tubular flow furnace, the RTB-based sintered magnet material in a state in which the diffusion source powder (No. 1-a) was in contact was heated at 920° C. for 36 hours in reduced pressure argon controlled to 200 Pa. Heat treatment (diffusion treatment) was performed. Further, the RTB-based sintered magnet after the diffusion treatment was subjected to a second heat treatment of heating at 490° C. for 6 hours to obtain an RTB-based sintered magnet (No. 1-1). In addition, except that the heating time in the diffusion process was changed from 36 hours to 10 hours. An RTB-based sintered magnet (No. 1-2) was produced in the same manner as the RTB-based sintered magnet of 1-1. The magnetic characteristics of the obtained RTB-based sintered magnets (No. 1-1 and No. 1-2) were measured by a BH tracer. The _{B r} and _{H cJ} of each sample was measured. The results are shown in Table 3.

As shown in Table 3, by heating time 36 hours, while suppressing a decrease in B _r, a high H _cJ are achieved.

No. 1-1 (Example of the present invention) and No. A cross section near the magnet surface of 1-2 (Comparative Example) was observed with a scanning electron microscope (SEM: JCM-6000 manufactured by JEOL Ltd.) to confirm a concentrated layer of Tb in the main phase crystal grains. As a result, in the example of the present invention (No. 1-1), in the surface layer region of the R-T-B system sintered magnet, a thin char phase (RH concentration) of the heavy rare earth element RH(Tb) is present in the outer shell of the main phase. However, in the comparative example (No. 2-1), in the surface layer region of the RTB-based sintered magnet, it is possible to reach a position close to the central portion of the main phase. It was also confirmed that the heavy rare earth element RH(Tb) was diffused.

In addition, No. 1-1 and No. When the amount of Tb in the central portion of the magnet No. 1-2 was measured, No. In No. 1-1, Tb was measured, whereas in No. 1-1. 1-2, Tb was not measured.

Experimental example 2
No. 1 of the first embodiment. A 1-A RTB sintered magnet material was prepared. Then, in Table 3, No. Diffusion source powders were prepared by making alloy powders having compositions shown in 2-a to 2-e by an atomizing method. The particle size of the obtained diffusion source powder was 106 μm or less.

Next, heat treatment (diffusion treatment) was performed in the same manner as in Example 1 except that the heating time shown in Table 5 was used. Furthermore, the RTB-based sintered magnet after the diffusion treatment is subjected to the second heat treatment in the same manner as in Example 1, and the RTB-based sintered magnet (No. 2-1 to 2-11). Got Magnetic properties of the obtained R-T-B based sintered magnet (No.2-1~2-11) the by B-H tracer was measured _{B r} and _{H cJ.} The results are shown in Table 5.

As shown in Table 5, examples of the present invention and comparative examples (No. 2-1 and 2-2, No. 2-3 and 2-) using the same RTB-based sintered magnet material and diffusion source powder. 4, No. 2-5 and 2-6, Nanba2-7 and 2-8, when compared respectively it No.2-9 and 2-9), both decrease toward the present invention examples of _{B r} While high H _cJ is obtained. In addition, No. 2-9 (heating time: 38 hours) and No. 2-11 (heating time: 45 hours) has the same magnetic characteristic level when compared with the examples of the present invention. Therefore, the heating time is preferably 30 hours or more and 45 hours or less, and more preferably 30 hours or more and 40 hours or less.

The RTB-based sintered magnet obtained according to the present disclosure is used in various types of motors such as voice coil motors (VCM) for hard disk drives, electric vehicle (EV, HV, PHV, etc.) motors, industrial equipment motors, and the like. It can be suitably used for home electric appliances and the like.

Claims (7)

R-T-B having R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (RL is at least one selected from the group consisting of Nd, Pr and Ce) as a main rare earth element R as a main phase Of preparing a system-based sintered magnet material (T is Fe or Fe and Co),
Providing a diffusion source powder formed from an alloy or compound powder containing a heavy rare earth element RH (RH is at least one selected from the group consisting of Tb, Dy and Ho);
Contacting at least a portion of the diffusion source powder with at least a portion of the surface of the RTB-based sintered magnet material,
A heat treatment for heating the RTB-based sintered magnet material in a state where the diffusion source powder is in contact with the RTB-based sintered magnet material at a temperature of 800° C. or higher and a temperature not higher than the sintering temperature of the RTB-based sintered magnet material for 30 hours or more. And a diffusion step of diffusing the heavy rare earth element RH contained in the diffusion source powder from the surface of the RTB-based sintered magnet material to the inside,
The manufacturing method of the RTB type|system|group sintered magnet containing. In the diffusion step, the RTB-based sintered magnet material in a state where the diffusion source powder is in contact with the RTB-based sintered magnet material is at a temperature not higher than the sintering temperature of the RTB-based sintered magnet material for 30 hours or more and 45 hours. The method for producing an RTB-based sintered magnet according to claim 1, wherein a heat treatment of heating is performed below. In the diffusion step, the RTB-based sintered magnet material in a state where the diffusion source powder is in contact with the RTB-based sintered magnet material is at a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet material for 35 hours or more and 40 hours. The method for producing an RTB-based sintered magnet according to claim 1, wherein a heat treatment of heating is performed below. The diffusion source powder is a RHM alloy powder (M is at least one selected from the group consisting of Nd, Pr, Ce, Cu, Ga, Fe, Co, Ni, and Al). The method for manufacturing an RTB-based sintered magnet according to any one of claims. The method for producing an RTB-based sintered magnet according to claim 1, wherein the diffusion source powder contains Cu. The method for manufacturing an RTB-based sintered magnet according to claim 1, wherein a dimension of the RTB-based sintered magnet material in a thickness direction is 1 mm or more and 5 mm or less. The step of bringing at least a part of the diffusion source powder into contact with at least a part of the surface of the RTB-based sintered magnet material includes at least a part of the surface of the RTB-based sintered magnet material. The method for producing an RTB-based sintered magnet according to claim 1, which is a step of adhering at least a part of the diffusion source powder to.