JP6503960B2 - Method of manufacturing RTB based sintered magnet - Google Patents

Description

The present invention relates to a method for producing an RTB-based sintered magnet (R is a rare earth element, T is Fe or Fe and Co) having an R ₂ T ₁₄ B type compound as a main phase.

An RTB-based sintered magnet having an R ₂ T ₁₄ B-type compound as a main phase is known as the highest performance magnet among permanent magnets, and is used as a voice coil motor (VCM) of a hard disk drive or It is used for various motors such as motors for hybrid vehicles and household appliances.

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

The RTB-based sintered magnet is known to improve H _cJ when a part of R in the R ₂ T ₁₄ B type compound phase is replaced with the heavy rare earth element RH (Dy, Tb) . 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, in the R-T-B based sintered magnet, when the light rare earth element RL (Nd, Pr) is replaced by the heavy rare earth element RH as R, H _cJ is improved while the residual magnetic flux density B _r (hereinafter simply referred to as “ There is a problem that B _r "is reduced. In addition, since the heavy rare earth element RH is a scarce resource, it is required to reduce its use amount.

In recent years, to improve the H _cJ of the R-T-B based sintered magnets have been studied with less heavy rare-earth element RH so as not to reduce the B _r. For example, as a method of supplying and diffusing heavy rare earth element RH to an RTB-based sintered magnet effectively, Patent Documents 1 to 4 disclose that RH oxides or RH fluorides and alloys of various metals M or M are used. By heat treating the mixed powder on the surface of the R-T-B based sintered magnet, RH and M are efficiently absorbed by the R-T-B based sintered magnet, and R-T-B is obtained. A method is disclosed to increase the H _{cJ of a} sintered sintered system.

  Patent Document 1 discloses that a mixed powder of a powder containing M (wherein M is one or more selected from Al, Cu, and Zn) and a powder of RH fluoride is used. Further, in Patent Document 2, RTMAH (where M is one or more selected from Al, Cu, Zn, In, Si, P, etc., which is a liquid phase at a heat treatment temperature, A is boron or carbon, H It is disclosed to use a powder of an alloy consisting of hydrogen, and it is disclosed that a mixed powder of a powder of this alloy and a powder such as RH fluoride may be used.

  In Patent Document 3 and Patent Document 4, powder or M1 M2 alloy (M1 and M2) of RM alloy (wherein R is a rare earth element and M is one or more selected from Al, Si, C, P, Ti, etc.) Is a partial mixture of RH oxide with RM alloy or M1M2 alloy during heat treatment by using a mixed powder of at least one powder selected from Al, Si, C, P, Ti, etc., and RH oxide. It is disclosed that it is possible to reduce to introduce more R into the magnet.

JP 2007-287874 A Unexamined-Japanese-Patent No. 2007-287875 JP, 2012-248827, A JP, 2012-248828, A

The methods described in Patent Documents 1 to 4 are remarkable in that more RH can be diffused into the magnet. However, according to these methods, RH present on the magnet surface can not be effectively linked to the improvement of H _cJ , and there is room for improvement. Particularly in Patent Document 3, although a mixed powder of RM alloy and RH oxide is used, the improvement of H _cJ by diffusion of the RM alloy itself is large and the effect of using RH oxide is slight, as far as the example is seen. It seems that the reduction effect of the RH oxide by the RM alloy is not exhibited so much.

The present invention has been made in view of the above circumstances, and reduces the amount of RH present on the surface of the magnet and effectively diffuses the inside of the magnet, thereby making the _RTB -based _burnout having high H _cJ. It is an object of the present invention to provide a method of manufacturing a magnet.

  The method for producing an RTB-based sintered magnet according to the present invention is, in an exemplary embodiment, an RLM alloy (RL is Nd and / or Pr, M, etc.) on the surface of the prepared RTB-based sintered magnet. Is a sintered R-T-B based magnet in the presence of at least one powder of Cu, Fe, Ga, Co, Ni) and a powder of RH oxide (RH: Dy and / or Tb) Heat treatment below the sintering temperature of The RLM alloy contains at least 65 atomic% of RL, and the melting point thereof is equal to or less than the temperature of the heat treatment, the powder of RLM alloy and the powder of RH oxide, RLM alloy: RH oxide = 9.6: 0.4-5 Heat treatment is performed with the mass ratio of 5 on the surface of the R-T-B-based sintered magnet.

In a preferred embodiment, the amount of RH element in the powder to be present on the surface of the RTB-based sintered magnet is 0.03 to 0.35 mg per 1 mm ^{2 of the} magnet surface.

  In one embodiment, the powder of the RLM alloy and the powder of the RH oxide are in a mixed state on the surface of the R-T-B-based sintered magnet.

  In one preferred embodiment, the content of RL in the RLM alloy is over 85 at%.

  In the embodiment, the step of performing the heat treatment is a step of melting the RLM alloy, and the RH oxide in the RH oxide is reduced by the RTB based reduction by reducing the RH oxide with the molten RLM alloy. And d) diffusing into the interior of the magnet.

According to the embodiment of the present invention, the RLM alloy can reduce the RH oxide with higher efficiency than in the past to diffuse the RH into the R-T-B-based sintered magnet, so the RH less than the prior art can be obtained. The amount of H _cJ can be improved more than in the prior art.

  The manufacturing method of the RTB-based sintered magnet (R is a rare earth element, T is Fe or Fe and Co, B is boron) in the embodiment of the present invention is on the surface of the RTB-based sintered magnet. Powder of RLM alloy (RL is Nd and / or Pr, M is one or more selected from Cu, Fe, Ga, Co, Ni) and powder of RH oxide (RH is Dy and / or Tb) It includes the step of heat treatment at a temperature not higher than the sintering temperature of the R-T-B-based sintered magnet. The RLM alloy contains 65 atomic% or more of RL, and the melting point thereof is equal to or less than the temperature of the heat treatment. The heat treatment described above is a powder of RLM alloy and a powder of RH oxide, the surface of R-T-B based sintered magnet with a mass ratio of RLM alloy: RH oxide = 9.6: 0.4-5: 5. To be present in

The inventor of the present invention is a diffusion aid for reducing RH oxide on the surface of _RTB -based sintered magnet and reducing RH oxide during heat treatment as a method of improving H _cJ by effectively using less RH. It was thought that the method of making it exist and heat-treating was effective. As a result of the inventor's investigation, it is an alloy (RLM alloy) of a specific combination of RL and M, which contains 65 atomic% or more of RL and whose melting point is equal to or less than the heat treatment temperature It was found that the reduction ability of RH oxide is excellent. In the present specification, a substance containing RH is referred to as a “diffusing agent”, and a substance that reduces the RH of the diffusing agent to a state capable of diffusing is referred to as a “diffusion aid”.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

[R-T-B based sintered magnet base material]
First, in the present invention, an RTB-based sintered magnet base material to be diffused of the heavy rare earth element RH is prepared. In this specification, the RTB-based sintered magnet to which the diffusion of the heavy rare earth element RH is to be subjected may be strictly referred to as RTB-based sintered magnet base material for the sake of easy understanding. The term "R-T-B-based sintered magnet" is intended to include such "R-T-B-based sintered magnet base material". A publicly known thing can be used for this RTB-based sintered magnet base material, and it has the following composition, for example.
Rare earth element R: 12 to 17 atomic%
B (part of B (boron) may be substituted by C (carbon)): 5 to 8 atomic%
Selected from the group consisting of the additive elements M ′ (Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi At least one kind): 0-2 atomic%
T (a transition metal element mainly composed of Fe and may contain Co) and unavoidable impurities: balance

  Here, the rare earth element R is mainly the light rare earth element RL (Nd and / or Pr), but may contain a heavy rare earth element. In the case of containing a heavy rare earth element, it is preferable to include at least one of Dy and Tb which are heavy rare earth elements RH.

  The R-T-B-based sintered magnet base material of the above composition is manufactured by any manufacturing method.

[Diffusion aid]
As a diffusion aid, powder of RLM alloy is used. As RL, a light rare earth element having a high effect of reducing RH oxide is suitable. Further, RL is also sometimes M also has the effect of diffused into the magnet to improve the H _cJ, tends to reduce the spread easily B _r to the main phase crystal grains inside the element should be avoided. From the viewpoint of the high effect of reducing the RH oxide and the difficulty of diffusion into main phase grains, RL is at least one selected from Nd and / or Pr, and M is Cu, Fe, Ga, Co, and Ni. Do. Among them, it is preferable to use Nd-Cu alloy or Nd-Fe alloy because the reduction ability of RH oxide by Nd is exhibited effectively. Further, the RLM alloy uses an alloy containing 65 atomic% or more of RL and having a melting point not higher than the heat treatment temperature. The RLM alloy preferably contains more than 85 atomic percent of RL. The RLM alloy having such a large content ratio of RL has a high ability to reduce RH oxide and the melting point is equal to or less than the heat treatment temperature. Therefore, when an RLM alloy having such a large content ratio of RL is used, it melts at the time of heat treatment and efficiently reduces the RH oxide. As a result, it is possible to diffuse the reduced RH at a higher rate into the R-T-B-based sintered magnet and improve the _HcJ of the R-T-B-based sintered magnet efficiently even with a small amount. The particle size of the RLM alloy powder is preferably 500 μm or less.

[Diverging agent]
As a diffusing agent, powder of RH oxide (RH is Dy and / or Tb) is used. According to the study of the inventor, the particle size of the RH oxide powder is preferably 100 μm or less.

[Diffusion heat treatment]
Any method may be used to cause the RLM alloy powder and the RH oxide powder to be present on the surface of the R-T-B sintered magnet. For example, a method of dispersing RLM alloy powder and RH oxide powder in a solvent such as pure water or an organic solvent, and immersing the RTB-based sintered magnet in this and pulling it up, or a powder of RLM alloy The method of mixing the powder of RH oxide with a binder and a solvent, producing a slurry, and apply | coating this slurry on the surface of a RTB type | system | group sintered magnet, etc. are mentioned. The binder and the solvent are removed from the surface of the R-T-B-based sintered magnet by thermal decomposition or evaporation at a temperature not higher than the melting point of the diffusion aid in the temperature raising process of the subsequent heat treatment (diffusion heat treatment) There is no particular limitation, as long as it is sufficient. Examples of the binder include polyvinyl alcohol and ethyl cellulose. Further, the powder of RLM alloy and the powder of RH oxide may be present on the surface of the R-T-B-based sintered magnet in the state of mixing them, or may be separately present. When these powders are separately present, it is preferable to first allow RLM alloy powder to be present on the surface of the RTB-based sintered magnet and then allow RH oxide powder to be present on the upper surface thereof. In the method of the present invention, since the melting point of the RLM alloy is equal to or lower than the heat treatment temperature, it melts during heat treatment, whereby the reduced RH diffuses inside the RTB-based sintered magnet. It becomes easy to do. Therefore, before the RLM alloy powder and the RH oxide powder are present on the surface of the R-T-B-based sintered magnet, the surface of the R-T-B-based sintered magnet may be specially pickled, etc. There is no need to carry out a cleaning process. Of course, it does not exclude that such cleaning treatment is performed. In addition, even if the surface of the RLM alloy powder particles is somewhat oxidized, the effect of reducing the RH oxide is hardly affected.

  The abundance ratio of RLM alloy and RH oxide in the powder state on the surface of the R-T-B sintered magnet (before heat treatment) is RLM alloy: RH oxide = 9.6: 0.4 to 5 in mass ratio : 5. More preferably, the abundance ratio is RLM alloy: RH oxide = 9.5: 0.5 to 6: 4. The present invention does not necessarily exclude the presence of a powder (third powder) other than RLM alloy and RH oxide powder on the surface of the RTB-based sintered magnet, but the third powder is RH oxidized. Care must be taken not to inhibit the diffusion of the RH in the substance into the interior of the RTB-based sintered magnet. It is desirable that the mass ratio of the “RLM alloy and RH oxide” powder to the whole of the powder present on the surface of the RTB-based sintered magnet be 70% or more.

According to the present invention, it is possible to efficiently improve the _HcJ of the _RTB -based sintered magnet with a small amount of RH. The amount of the RH element in the powder to be present on the surface of the R-T-B based sintered magnet is preferably 0.03 to 0.35 mg per 1 mm ² of the magnet surface, and 0.05 to 0.25 mg. Is more preferred.

  The heat treatment is performed in the state where the RLM alloy powder and the RH oxide powder are present on the surface of the RTB-based sintered magnet. In addition, since the powder of the RLM alloy is melted after the start of the heat treatment, it is not necessary to always maintain the “powder” state during the heat treatment of the RLM alloy. The atmosphere of the heat treatment is preferably a vacuum or an inert gas atmosphere. The heat treatment temperature is equal to or lower than the sintering temperature (specifically, for example, 1000 ° C. or lower) of the RTB-based sintered magnet and is higher than the melting point of the RLM alloy. The heat treatment time is, for example, 10 minutes to 72 hours. Moreover, you may heat-process for the magnetic characteristic improvement for 10 minutes-72 hours at 400-700 degreeC further as needed after the said heat processing.

[Experimental Example 1]
First, R-T of composition ratio Nd = 13.4, B = 5.8, Al = 0.5, Cu = 0.1, Co = 1.1, balance = Fe (atomic%) by a known method A B-based sintered magnet was produced (sintering temperature: 1050 ° C., heat treatment temperature after sintering: 500 ° C.). By machining this, an RTB-based sintered magnet base material of 6.9 mm × 7.4 mm × 7.4 mm was obtained. Magnetic properties of the obtained R-T-B based sintered magnet base material where a measured by B-H tracer, H _cJ is 1035kA / m, B _r was 1.45 T. As described later, since the magnetic properties of the RTB-based sintered magnet after heat treatment are measured after the surface of the RTB-based sintered magnet is removed by machining, RT In accordance with this, the surface was further removed by 0.2 mm each by machining, and the size was measured as 6.5 mm × 7.0 mm × 7.0 mm. In addition, when the amount of impurities of the RTB-based sintered magnet base material was separately measured by a gas analyzer, it was 760 mass ppm for oxygen, 490 mass ppm for nitrogen, and 905 mass ppm for carbon.

Next, a diffusion aid having the composition shown in Table 1 was prepared. The powder particle size of the diffusion aid was adjusted to 150 μm or less by grinding an alloy ribbon produced by the ultra-quenching method with a coffee mill. The mixing ratio of the obtained diffusion aid powder and the diffusion agent, Tb ₄ O ₇ powder or Dy ₂ O ₃ powder with a particle size of 20 μm or less, polyvinyl alcohol and pure water, the diffusion aid and the diffusion agent become as shown in Table 1 Mixed to obtain a slurry. The amount of RH per 1 mm ² of the R-T-B-based sintered magnet surface (diffusion surface) is shown on two faces of 7.4 mm × 7.4 mm of the R-T-B-based sintered magnet base material. It applied so that it might become a value of 1. Hereinafter, the melting point of the diffusion aid in the present example is a value shown in the binary phase diagram of RLM. The R-T-B-based sintered magnet base material coated with the slurry was placed on a Mo plate, housed in a processing vessel, and covered. (This lid does not prevent the gas from flowing in and out of the container.) This was housed in a heat treatment furnace, and heat treatment was performed at 900 ° C. for 4 hours in an Ar atmosphere of 100 Pa. The heat treatment was performed while raising the temperature while evacuating from room temperature, and was performed under the above conditions after the atmospheric pressure and temperature reached the above conditions. Thereafter, the temperature was lowered to room temperature and then the Mo plate was taken out to recover an RTB-based sintered magnet. The recovered R-T-B-based sintered magnet was returned to the processing vessel and housed again in the heat treatment furnace, and heat treatment was performed for 2 hours at 500 ° C. in a vacuum of 10 Pa or less to improve the magnetic properties. This heat treatment was also performed while raising the temperature while evacuating from room temperature, and was performed under the above conditions after the atmospheric pressure and temperature reached the above conditions. After that, the temperature was once lowered to room temperature, and then the RTB-based sintered magnet was recovered.

The surface of the resulting RTB-based sintered magnet was removed by machining by 0.2 mm each to obtain samples 1 to 11, 30 and 31 of 6.5 mm × 7.0 mm × 7.0 mm. . The magnetic properties of the obtained samples 1 to 11, 30 and 31 were measured by the B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 2.

As can be seen from Table 2, R-T-B based sintered magnet according to the manufacturing method of the present invention is H _cJ is greatly improved without the B _r decreases, 900 ° C. of the melting point of the RLM alloy heat treatment temperature The improvement of H _cJ of sample 1 which is more than sample 1 and the content of RL of RLM alloy is less than specified in the present invention is an example of the present invention (samples 2 to 5, samples 8 to 8) using the same diffusing agent 11, it turned out that it did not reach to samples 30 and 31).

From this, it is the RLM alloy whose content ratio of RL which is a diffusion aid is within the scope of the present invention that _{HcJ of the RTB} -based sintered magnet is greatly improved by the manufacturing method of the present invention. Is melted at the heat treatment temperature to reduce the RH oxide, and the reduced RH diffuses inside the magnet through grain boundaries, which is considered to contribute to the improvement of H _cJ efficiently.

[Experimental Example 2]
A slurry was prepared by mixing a Nd ₈₇ Cu ₁₃ and Tb ₇₄ Cu ₂₆ (atomic%) diffusion aid and Tb ₄ O ₇ powder (diffusing agent) so that the mixing ratio was as shown in Table 3. Samples 12 to 20 were obtained in the same manner as in Experimental Example 1. Incidentally, the sample 20 using the Tb ₇₄ Cu ₂₆ as a diffusion aid was applied to the same coating amount of the slurry and sample 3 is the same mixing mass ratio of the diffusing agent and diffusion aid. The magnetic properties of the obtained samples 12 to 20 were measured by the B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 4. In each table, the conditions and the measurement results of the sample 3 are shown as the comparative examples.

As can be seen from Table 4, R-T-B based sintered magnet (Sample 3,14～16) by the manufacturing method of the present invention is H _cJ is greatly improved without the B _r is decreased, the present invention It was found that the sample 12 having a larger amount of RH oxide and the same RH amount per 1 mm ^{2 of the} diffusion surface than the mixed mass ratio specified in the above does not have the improvement of H _{cJ according to} the present invention. Also, even though the sample 13 amounts RH per diffusion surface 1 mm ² is larger than the sample 3,14～16, since many RH oxides than mass mixing ratio defined in the present invention, improvement in H _cJ is It did not reach the present invention. In addition, Sample 17 containing less RH oxide (not mixed with RH oxide) than the mixing mass ratio specified in the present invention, Sample 18 containing only RH oxide, and only RH oxide per 1 mm ² of the diffusion surface It was found that the improvement of H _cJ did not reach to the present invention also for the sample 19 having a larger amount of RH than the example of the present invention. In addition, although _HcJ is improved to the same extent as in the example of the present invention in the sample 20 using the RHM alloy as the diffusion aid, the RH amount per 1 mm ^{2 of the} diffusion surface is equal to The effect of improving H _cJ by a small amount of RH is not obtained, which is much larger than the example. That is, only when RLM alloy and RH oxide specified in the present invention are mixed and used at the mixing mass ratio specified in the present invention, RLM alloy efficiently reduces RH oxide and RH is sufficiently reduced. It was found that _HcJ could be greatly improved with a small amount of RH by diffusing into the _RTB -based sintered magnet base material.

[Experimental Example 3]
A slurry was prepared by mixing a diffusion aid having a composition of Nd ₈₇ Cu ₁₃ (atomic%) and Tb ₄ O ₇ powder (a diffusion agent) so that the diffusion aid: the diffusion agent was 8: 2, Table 5 Samples 21 to 23 were obtained in the same manner as in Experimental Example 1 except that the heat treatment was performed under the conditions shown in Table 2. The magnetic properties of the obtained samples 21 to 23 were measured by a B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 6.

As can be seen from Table 6, the H _cJ without even when subjected to heat treatment at various heat treatment conditions shown in Table 5, in the R-T-B-based sintered magnet according to the manufacturing method of the invention in which B _r drops It turned out that it improves greatly.

[Experimental Example 4]
Samples 24 to 27 are the same as Sample 3 except that the RTB-based sintered magnet base material has the composition, sintering temperature, amount of impurities, and magnetic properties shown in Samples 24 to 27 in Table 7. I got The magnetic properties of the obtained samples 24 to 27 were measured by a B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 8.

As can be seen from Table 8, even when various RTB-based sintered magnet base materials shown in Table 7 are used, the RTB-based sintered magnet according to the manufacturing method of the present invention has B _r. It was found that H _cJ is greatly improved without decreasing.

[Experimental Example 5]
Samples 28 and 29 were prepared in the same manner as in Experimental Example 1 except that a diffusion aid and Tb ₄ O ₇ powder (diffusing agent) shown in Table 9 were mixed to obtain a mixing ratio shown in Table 9 to prepare a slurry. Obtained. The magnetic properties of the obtained samples 28 and 29 were measured by the B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 10. In each table, conditions and measurement results of sample 3 are shown as an example of comparison object.

As can be seen from Table 10, it is found that the improvement in H _cJ of neither of Samples 28 and 29 _{falls below} the present invention. Since the diffusion aid Cu is also capable of reducing the melting point is higher RH oxide than the heat treatment temperature itself no ability to enhance H _cJ diffuse, H _cJ was hardly improved. Further, Al also has little effect of reducing RH oxide, and it is _{considered that} the improvement of H _cJ of sample 29 is due to Al itself diffused into the R-T-B-based sintered magnet. That is, it is considered that _Br is lowered by the diffusion of Al that easily reacts with the main phase crystal grains to the inside of the main phase crystal grains.

[Experimental Example 6]
The diffusion aid was left to stand in a normal temperature atmosphere for 50 days to prepare a diffusion aid with the surface oxidized. A sample 32 was produced in the same manner as the sample 5 except this point. In addition, as for the diffusion adjuvant after leaving-to-stand for 50 days, the oxygen content which was 1800 ppm before leaving-to-stand rose to 6600 ppm.

The R-T-B based sintered magnet base material was left in an atmosphere with a relative humidity of 90% and a temperature of 60 ° C. for 100 hours to generate many red rusts on the surface. A sample 33 was produced in the same manner as the sample 5 except that such an RTB-based sintered magnet base material was used. The magnetic properties of the obtained samples 32 and 33 were measured by a B-H tracer, and the change amounts of H _cJ and B _r were determined. The results are shown in Table 11. Table 11 also shows the results of sample 5 as a comparison.

It was found from Table 11 that even if the surfaces of the diffusion aid and the _RTB -based sintered magnet base material were oxidized, the improvement of H _cJ was hardly affected.

The method for producing an RTB-based sintered magnet according to the present invention can provide an _RTB -based sintered magnet in which H _cJ is improved by using less heavy rare earth elements RH.

Claims (4)

Preparing an RTB-based sintered magnet;
A powder of RLM alloy (RL is Nd and / or Pr, M is one or more selected from Cu, Fe, Ga, Co, Ni) on the surface of the RTB-based sintered magnet, and RH oxide ( Performing a heat treatment at a temperature equal to or lower than the sintering temperature of the R-T-B-based sintered magnet in the presence of RH and a powder of Dy and / or Tb);
Including
The RLM alloy contains 65 atomic% or more of RL, and the melting point of the RLM alloy is equal to or less than the temperature of the heat treatment,
In the heat treatment, the RLM alloy powder and the RH oxide powder are sintered at the mass ratio of RLM alloy: RH oxide = 9.6: 0.4-5: 5. Done on the surface of the magnet ,
In the step of performing the heat treatment, the step of melting the RLM alloy, and the step of reducing the RH oxide with the molten RLM alloy to reduce the RH in the RH oxide by the RTB-based sintered magnet And D. diffusing into the interior . The mass of the RH element contained in the powder of the RH oxide on the surface of the RTB-based sintered magnet is 0.03 to 0.35 mg per 1 mm ^{2 of the} surface. The manufacturing method of the RTB-based sintered magnet.   The R-T-B-based sintered material according to claim 1 or 2, wherein the RLM alloy powder and the RH oxide powder are mixed on the surface of the R-T-B-based sintered magnet. Method of manufacturing a magnet   The method for producing an RTB-based sintered magnet according to any one of claims 1 to 3, wherein the content of RL in the RLM alloy is over 85 at%.