JP2005286176A - R-t-b-based sintered magnet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an R-T-B-based sintered magnet that can obtain a high coercive force even when the oxygen content of the sintered body of the magnet is low and, at the same time, has a wide sintering temperature range. <P>SOLUTION: The R-T-B-based sintered magnet is composed of a sintered body which is provided with main-phase crystal grains composed of an R<SB>2</SB>T<SB>14</SB>B phase (wherein, R is one, two, or more kinds of elements selected from among rare-earth elements and T is one, two, or more kinds of elements selected from among transition metal elements including Fe or Fe and Co), and a crystal boundary phase containing more R than the main-phase crystal grains do and contains Ta in the crystal boundary phase. It is desirable that the Ta exists in the crystal boundary phase as a Ta-Fe compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to R (R is one or more elements selected from rare earth elements), T (T is one or more elements selected from transition metal elements including Fe or Fe and Co) ) And B (boron) as main components.

Among sintered magnets, RTB-based sintered magnets are used in various applications because they are excellent in magnetic properties and the main component Nd is abundant and relatively inexpensive. Yes.
Research and development for improving the magnetic properties of the RTB-based sintered magnet has been vigorously conducted. For example, in JP-A-1-219143 (Patent Document 1), by adding 0.02 to 0.5 at% Cu to an R-T-B system sintered magnet, the magnetic properties are improved and the heat treatment conditions are improved. Has also been reported to improve. However, the method described in Patent Document 1 is insufficient to obtain high magnetic properties required for high performance magnets, specifically, high coercive force (Hcj) and residual magnetic flux density (Br). .
Here, the magnetic properties of the RTB-based sintered magnet obtained by sintering depend on the sintering temperature. On the other hand, on an industrial production scale, it is difficult to make the heating temperature uniform throughout the sintering furnace. Therefore, the R-T-B system sintered magnet is required to obtain desired magnetic characteristics even if the sintering temperature varies. Here, the temperature range in which the desired magnetic characteristics can be obtained is referred to as a sintering temperature range.

In order to increase the main phase ratio of the RTB-based sintered magnet and achieve high performance, it is necessary to reduce the amount of oxygen in the alloy. To that end, various restrictions are imposed on the process of manufacturing the magnet. That is, it is necessary to manage not to increase the amount of oxygen from the alloy to sintering. When sintering fine powder obtained with low oxygen, it is difficult to maintain the crystal grains in a fine state, and if the sintering temperature is slightly higher than the optimum sintering temperature, the crystal grains are easily Grain grows and magnetic properties, especially coercive force, decrease. This is due to the fact that it is in a very active state due to the small proportion of oxygen in the fine powder, which easily induces abnormal grain growth during sintering, and can suppress the growth of crystal grains. This is because the oxide is insufficient.
Therefore, in Japanese Patent Application Laid-Open No. 2002-75717 (Patent Document 2), a fine ZrB compound, NbB compound or Rb-B-based sintered magnet containing Co, Al, Cu, and further Zr, Nb or Hf is used. It is disclosed that the abnormal grain growth in the sintering process can be suppressed by uniformly dispersing and precipitating the HfB compound (hereinafter referred to as the MB compound).

JP-A-1-219143 JP 2002-75717 A Japanese Patent Publication No. 5-31807 Japanese Patent No. 3254229

According to Patent Document 2, the sintering temperature range is expanded by dispersing and precipitating the MB compound. However, in Example 3-1, disclosed in Patent Document 2, the sintering temperature range is as narrow as about 20 ° C. Therefore, it is desirable to further widen the sintering temperature range in order to obtain high magnetic characteristics in a mass production furnace or the like.
Accordingly, an object of the present invention is to suppress the growth of crystal grains and improve the magnetic properties, particularly the coercive force, in an RTB-based sintered magnet with a small amount of oxygen in which crystal grains are likely to grow. In addition, an object of the present invention is to provide an RTB-based sintered magnet having a high coercive force and a wide sintering temperature range.

In recent years, when manufacturing a high-performance RTB-based sintered magnet, a mixing method in which alloy powders having different compositions are mixed and sintered has been proposed (for example, Japanese Patent Publication No. 5-31807 (Patent Document). 3), Japanese Patent No. 3254229 (Patent Document 4)). This mixing method typically includes an R ₂ T ₁₄ B intermetallic compound (R is one or more elements selected from rare earth elements, T is a transition metal element including Fe or Fe and Co). An alloy for forming a main phase mainly composed of one or more selected elements) and an alloy for forming a grain boundary phase existing between the main phases are mixed. Here, the main phase forming alloy is sometimes referred to as a low R alloy because the R content is relatively small. On the other hand, an alloy for forming a grain boundary phase is sometimes called a high-R alloy because of its relatively high R content.
When the present inventor contains Ta in a high R alloy and obtains an R-T-B sintered magnet by using a mixing method, it is effective for improving the coercive force and widening the sintering temperature range. I found.

The present invention is based on the above knowledge, and R ₂ T ₁₄ B phase (R is one or more elements selected from rare earth elements, T is selected from transition metal elements including Fe or Fe and Co) Comprising a main phase crystal grain composed of one or more kinds of elements) and a grain boundary phase containing more R than the main phase crystal grain, and comprising a sintered body containing Ta in the grain boundary phase. It is a characteristic R-T-B system sintered magnet.
In the present invention, it is important that Ta in the grain boundary phase exists as a Ta—Fe compound. Since this Ta—Fe compound has a high melting point, the coarsening of the main phase crystal grains in the sintering process can be suppressed. As a result, the sintered structure becomes fine and the coercive force can be improved.

In the present invention, the effect of improving the coercive force by containing Ta in the high R alloy is effective when the oxygen content in the sintered body is as low as 2000 ppm or less.
In the RTB-based sintered magnet of the present invention, R: 25 to 35 wt%, B: 0.5 to 4.5 wt%, and one or two of Al and Cu are 0.02 to 0.02. It is desirable that the composition be 6 wt%, Ta: 0.1 to 2.0 wt%, Co: 4 wt% or less (not including 0), and the balance substantially consisting of Fe.

The present invention provides a method for producing the above RTB-based sintered magnet. This production method comprises R ₂ T ₁₄ B compound (R is one or more elements selected from rare earth elements, T is one or two elements selected from transition metal elements including Fe, Fe and Co) or more elements) and the main phase crystal grains consisting of a main phase method for producing a grain from a sintered body and a grain boundary phase rich in R R-T-B based sintered magnet, R ₂ A compact formed of a low R alloy powder mainly composed of a T ₁₄ B compound and a high R alloy powder having a larger amount of R than the low R alloy powder and mainly containing R and T and containing Ta is prepared. The molded body is sintered.

  According to the RTB-based sintered magnet of the present invention, a high coercive force can be obtained by forming a fine crystal structure even when the sintered body has a low oxygen content. Moreover, according to the RTB-based sintered magnet of the present invention, it has a wide sintering temperature range.

<Organization>
First, the structure of the RTB-based sintered magnet, which is a feature of the present invention, will be described.
The present invention is characterized in that Ta is present in the grain boundary phase in the sintered body structure. In particular, this Ta is present in the grain boundary phase as a Ta—Fe compound. The Ta—Fe compound has a high melting point of Fe ₂ Ta at 1775 ° C. and FeTa at 1875 ° C. Thus, when the high melting point compound exists in the grain boundary phase, coarsening of the main phase crystal grains in the sintering process can be suppressed, and as a result, the structure after sintering can be made fine. As a result, a high coercive force can be obtained.

<Chemical composition>
Next, a desirable chemical composition of the RTB-based sintered magnet according to the present invention will be described. The chemical composition here refers to the chemical composition after sintering.
The RTB-based sintered magnet of the present invention contains 25 to 35 wt% of R.
Here, R has a concept including Y, and one or two selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, and Y More than a seed element. When the amount of R is less than 25 wt%, the generation of R ₂ T ₁₄ B crystal grains that are the main phase of the R—T—B system sintered magnet is not sufficient. For this reason, α-Fe or the like having soft magnetism is precipitated, and the coercive force is remarkably lowered. On the other hand, when the amount of R exceeds 35 wt%, the volume ratio of R ₂ T ₁₄ B crystal grains constituting the main phase is lowered, and the residual magnetic flux density is lowered. On the other hand, when the amount of R exceeds 35 wt%, R reacts with oxygen, and the amount of oxygen contained increases, and as a result, the R-rich phase effective for the generation of coercive force decreases and the coercive force decreases. Therefore, the amount of R is set to 25 to 35 wt%. A desirable amount of R is 28 to 33 wt%, and a more desirable amount of R is 29 to 32 wt%.
Since Nd is abundant in resources and relatively inexpensive, it is preferable that the main component as R is Nd. Further, the inclusion of Dy is effective in improving the coercive force because it increases the anisotropic magnetic field. Therefore, it is desirable that Nd and Dy are selected as R and the total of Nd and Dy is 25 to 35 wt%. In this range, the amount of Dy is preferably 0.1 to 8 wt%. It is desirable to determine the amount of Dy within the above range depending on which of the residual magnetic flux density and the coercive force is important. That is, when it is desired to obtain a high residual magnetic flux density, the Dy amount is preferably 0.1 to 3.5 wt%, and when a high coercive force is desired, the Dy amount is desirably 3.5 to 8 wt%.

  The RTB-based sintered magnet of the present invention contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. However, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit is 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.

  The RTB-based sintered magnet of the present invention can contain one or two of Al and Cu in the range of 0.02 to 0.6 wt%. By containing one or two of Al and Cu within this range, it is possible to increase the coercive force, corrosion resistance, and temperature characteristics of the obtained rare earth permanent magnet. In the case of adding Al, a desirable amount of Al is 0.03 to 0.3 wt%, and a more desirable amount of Al is 0.05 to 0.25 wt%. In addition, in the case of adding Cu, the amount of Cu is 0.3 wt% or less (excluding 0), desirably 0.15 wt% or less (not including 0), and the more desirable amount of Cu is 0.03 to 0 0.08 wt%.

  The RTB-based sintered magnet of the present invention contains 0.1 to 2.0 wt% of Ta. When reducing the oxygen content in order to improve the magnetic properties of the RTB-based sintered magnet, Ta exerts the effect of suppressing the abnormal growth of crystal grains during the sintering process. Make the tissue uniform and fine. Therefore, the effect of Ta becomes remarkable when the amount of oxygen is low. A desirable amount of Ta is 0.2 to 1.7 wt%, and a more desirable amount is 0.3 to 1.5 wt%.

  The RTB-based sintered magnet of the present invention has an oxygen content of 2000 ppm or less. When the amount of oxygen is large, the oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated. Therefore, in the present invention, the amount of oxygen contained in the sintered body is set to 2000 ppm or less, desirably 1500 ppm or less, and more desirably 1000 ppm or less. However, when the oxygen amount is simply reduced, the oxide phase having the effect of suppressing grain growth is insufficient, and grain growth easily occurs in the process of obtaining a sufficient density increase during sintering. Therefore, in the present invention, a predetermined amount of Ta, which exhibits the effect of suppressing abnormal growth of main phase crystal grains during the sintering process, is contained in the R-T-B system sintered magnet, particularly in the grain boundary phase. However, even if Ta is present in the main phase crystal grains, the effect of the present invention is not hindered.

  The RTB-based sintered magnet of the present invention contains Co of 4 wt% or less (not including 0), preferably 0.1 to 2.0 wt%, more preferably 0.3 to 1.0 wt%. . Co forms the same phase as Fe, but is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.

<Manufacturing method>
Next, the suitable manufacturing method of the RTB system sintered magnet by this invention is demonstrated.
In the present embodiment, the R-T according to the present invention is made using an alloy mainly composed of R ₂ T ₁₄ B crystal grains (low R alloy) and an alloy containing more R than the low R alloy (high R alloy). -It shows about the method of manufacturing a B type sintered magnet.
A low R alloy and a high R alloy are obtained by strip casting the raw metal in a vacuum or an inert gas, preferably in an Ar atmosphere. As the raw material metal, rare earth metals or rare earth alloys, pure iron, ferroboron, and alloys thereof can be used. The obtained raw material alloy is subjected to a solution treatment as necessary when there is solidification segregation. The conditions may be maintained for 1 hour or longer in a region of 700 to 1500 ° C. in a vacuum or Ar atmosphere.

A characteristic feature of the present invention is that Ta is added from a high R alloy. As described in the section of <structure>, this adds Ta from a high R alloy to generate a Ta-Fe compound in the grain boundary phase and suppress abnormal growth of crystal grains.
If the low R alloy is mainly composed of R ₂ T ₁₄ B crystal grains, it is not necessary to limit the composition thereof, but R is 25 to 35 wt%, B is 0.5 to 4.5 wt%, and the balance The composition of T may be used. The high R alloy may have a composition of 30 to 65 wt% R, 0 to 5 wt% B, and the balance T.
In addition to R, T, and B, the low R alloy can contain Cu and Al. At this time, the low R alloy constitutes an R-Cu-Al-T (Fe) -B alloy. Further, the high R alloy can contain Cu, Co and Al in addition to R and T (Fe). At this time, the high R alloy constitutes an R-Cu-Co-Al-Ta-T alloy.

  After the low R and high R alloys are made, each of these master alloys is ground separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, each mother alloy is coarsely pulverized until the particle size becomes about several hundred μm. Coarse pulverization can be performed in an inert gas atmosphere using mechanical means such as a stamp mill, a jaw crusher, and a brown mill. Further, coarse pulverization can be performed by occluding hydrogen without using mechanical means. Furthermore, after hydrogen storage, coarse pulverization can be performed by mechanical means. Which method is used depends on the form of the master alloy. It is desirable to dehydrogenate after hydrogen storage. This is because hydrogen is an impurity for the RTB-based sintered magnet.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. In the fine pulverization, a jet mill is mainly used, and a coarsely pulverized powder having a particle size of about several hundreds of μm is pulverized until the average particle size becomes 3 to 5 μm. The jet mill opens a high-pressure non-oxidizing gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, This is a method of crushing by generating a collision with a target or a container wall.

  When the low R alloy and the high R alloy are separately pulverized in the fine pulverization step, the finely pulverized low R alloy powder and high R alloy powder are mixed in a nitrogen atmosphere. The mixing ratio of the low R alloy powder and the high R alloy powder may be about 80:20 to 97: 3 by weight. Similarly, the mixing ratio when the low R alloy and the high R alloy are finely pulverized together may be about 80:20 to 97: 3 by weight. By adding about 0.01 to 0.3 wt% of an additive such as zinc stearate at the time of fine pulverization, a fine powder having high orientation during molding can be obtained.

  Next, the mixed powder composed of the low R alloy powder and the high R alloy powder is pressure-molded in a state where the crystal axis is oriented by applying a magnetic field. The forming in the magnetic field may be performed at a pressure of 70 to 150 MPa in a magnetic field of 940 to 1400 kA / m.

  After molding in a magnetic field, the compact is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, a particle size, and a particle size distribution difference, what is necessary is just to sinter at 1000-1100 degreeC for about 1 to 5 hours.

  After sintering, the obtained sintered body can be subjected to an aging treatment. The aging treatment is important for controlling the coercive force. When the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment at around 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by the heat treatment at around 600 ° C., the aging treatment at around 600 ° C. is preferably performed when the aging treatment is performed in one stage.

Next, the present invention will be described in more detail with specific examples. In the following, the RTB-based sintered magnet according to the present invention will be described by dividing it into Example 1 to Example 2. However, since the prepared raw material alloy and each manufacturing process are common, this point is first introduced. Let me explain.
1) Raw material alloys Low R alloys and high R alloys having the compositions shown in Table 1 were prepared by strip casting.
2) Pulverization process After occluding hydrogen at room temperature, a hydrogen pulverization process was performed in which dehydrogenation was performed in an Ar atmosphere at 600 ° C. for 1 hour.
In order to obtain high magnetic properties, in this experiment, the atmosphere of each process from hydrogen treatment (recovery after pulverization) to sintering (put into the sintering furnace) to suppress the amount of oxygen in the sintered body to 2000 ppm or less Is suppressed to an oxygen concentration of less than 100 ppm. Hereinafter, it is referred to as an oxygen-free process.

3) Grinding step A low R alloy and a high R alloy which have been subjected to hydrogen storage treatment, and further additives are mixed. The type of the additive is not particularly limited, and any additive that contributes to improvement in grindability and orientation during molding may be appropriately selected. In this example, zinc stearate is added in an amount of 0.05 to 0. 1 wt% was mixed. The additive may be mixed for about 5 to 30 minutes using, for example, a Nauter mixer.
Thereafter, fine grinding was performed using a jet mill until the alloy powder had an average particle size of about 4.0 μm.
Of course, the mixing step and the fine pulverization step of the low R alloy, the high R alloy and the additive are both performed by an oxygen-free process.

  Before fine pulverization, a plurality of types of high R alloys can be prepared and mixed so as to have a desired composition (particularly, Ta amount). The mixing in this case may be performed only for about 5 to 30 minutes using, for example, a Nauta mixer.

4) Molding step The obtained fine powder is molded in a magnetic field. Specifically, molding was performed at a pressure of 120 MPa in a magnetic field of 1200 kA / m to obtain a molded body. This step was also performed by an oxygen-free process.
5) Sintering and aging process This compact was sintered at 1020 to 1080 ° C for 4 hours in a vacuum and then rapidly cooled. Next, the obtained sintered body was subjected to a two-stage aging treatment of 800 ° C. × 1 hour and 540 ° C. × 1 hour (both in an Ar atmosphere).

Using the low R alloys A1 to A2 and the high R alloys B1 to 4 shown in Table 1, the final compositions shown in Table 2 were blended. Thereafter, each mixture was subjected to hydrogen pulverization treatment and then pulverized in a jet mill. Then, after forming in a magnetic field, sintering was performed at 1020 ° C., 1050 ° C. and 1080 ° C. (held for 4 hours), and the obtained sintered body was subjected to a two-stage aging treatment.
About the obtained RTB system sintered magnet, the residual magnetic flux density (Br), the coercive force (HcJ), and the squareness ratio (Hk / HcJ) were measured with a BH tracer. Hk is the external magnetic field strength when the magnetic flux density is 90% of the residual magnetic flux density in the second quadrant of the magnetic hysteresis loop. Moreover, about the obtained RTB system sintered magnet, the amount of oxygen contained in the sintered body was measured. The results are shown in Table 2.

  In this example, in order to obtain high magnetic properties, the oxygen content of the sintered body was reduced to 1000 ppm or less by an oxygen-free process, and the average particle size of the pulverized powder was as fine as 4.0 μm. Accordingly, abnormal grain growth is likely to occur during the sintering process. FIG. 1 shows the relationship between the sintering temperature, the residual magnetic flux density (Br), the coercive force (HcJ), and the squareness ratio (Hk / HcJ).

As shown in Table 2 and FIG. 1, it can be seen that the sintered magnet obtained by adding Ta to the high R alloy has a higher coercive force (HcJ) than the sintered magnet not containing Ta.
In addition, among the magnetic properties, the squareness ratio (Hk / HcJ) tends to decrease most rapidly due to abnormal grain growth. That is, the squareness ratio (Hk / HcJ) is an index that can grasp the tendency of abnormal grain growth. Therefore, if the sintering temperature range in which the squareness ratio (Hk / HcJ) of 90% or more is obtained is defined as the sintering temperature range, the sintering temperature range of the sintered magnet not added with Ta is zero. In contrast, a sintered magnet obtained by adding Ta to a high R alloy has a squareness ratio (Hk / HcJ) of 90% or more at 1020 to 1080 ° C. That is, the sintering temperature width of the sintered magnet to which 0.50% of Ta is added is 60 ° C. or more.
An SEM (scanning electron microscope, 1000 times) image of a fracture surface of a sintered magnet having a sintering temperature of 1080 ° C. is shown, but Ta is reduced to 0. 0 as compared with a sintered magnet not containing Ta (FIG. 2A). It can be seen that the sintered magnet containing 50 wt% (FIG. 2B) shows a finer crystal structure.

  No. in Table 2 When the structure of the sintered magnet 8 was observed with a TEM (transmission electron microscope), as shown in FIG. 3, it was surrounded by a white dotted line inside the grain boundary phase (triple point) surrounded by a black dotted line. The presence of Ta-Fe compound was confirmed in the region. Therefore, the presence of this Ta-Fe compound is considered to be the reason why the coercive force of the sintered magnet obtained by adding Ta to the high R alloy is improved and the sintering temperature range is wide.

  A sintered magnet obtained by adding Ta to a high R alloy tends to improve the coercive force (HcJ) as the amount of Ta increases. However, even in a sintered magnet with a high R alloy addition, when the Ta addition amount is increased to 2.5 wt%, the residual magnetic flux density (Br) becomes lower than that with a Ta-free additive magnet. On the other hand, if the amount of Ta is less than 0.1 wt%, the effect of improving the coercive force is not sufficient. Therefore, it can be seen that the amount of Ta is preferably in the range of 0.1 to 2.0 wt%.

  An R-T-B sintered magnet was obtained in the same manner as in Example 1 except that the alloy shown in Table 1 was used so that the final composition shown in Table 3 was obtained. Similarly, the magnetic characteristics were measured. The results are also shown in Table 3.

  As shown in Table 3, it can be seen that the coercive force (HcJ) can be improved by increasing the amount of Al and the amount of Cu. It can also be seen that the coercive force (HcJ) can be improved by increasing the amount of Dy. Therefore, according to the present invention, in addition to the effect of improving the coercive force (HcJ) due to the presence of the Ta-Fe compound in the grain boundary phase, the coercive force (HcJ) is particularly adjusted by adjusting the amounts of Al, Cu and Dy. R-T-B system sintered magnet having a high C can be obtained. Furthermore, it can be seen that the magnetic characteristics fluctuate by increasing / decreasing the R (Nd + Dy) amount and the B amount.

It is a graph which shows the relationship between the sintering temperature in Example 1, residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk / HcJ). 2 is a SEM (scanning electron microscope, 1000 times) image of a fractured surface of an RTB-based sintered magnet in Example 1. FIG. 2 is a TEM (transmission electron microscope) image of an RTB-based sintered magnet in Example 1. FIG.

Claims (5)

From the R ₂ T ₁₄ B phase (R is one or more elements selected from rare earth elements, T is one or more elements selected from transition metal elements including Fe or Fe and Co) An R-T-B system firing comprising: a main phase crystal grain, and a grain boundary phase containing more R than the main phase crystal grain, and comprising a sintered body containing Ta in the grain boundary phase. Magnet.   The RTB-based sintered magnet according to claim 1, wherein Ta is present as a Ta—Fe compound in the grain boundary phase.   The RTB-based sintered magnet according to claim 1 or 2, wherein the oxygen content is 2000 ppm or less.   R: 25-35 wt%, B: 0.5-4.5 wt%, one or two of Al and Cu are 0.02-0.6 wt%, Ta: 0.1-2.0 wt%, Co: The RTB-based sintered magnet according to any one of claims 1 to 3, which has a composition of 4 wt% or less (excluding 0) and the balance substantially consisting of Fe. From R ₂ T ₁₄ B compound (R is one or more elements selected from rare earth elements, T is one or more elements selected from transition metal elements including Fe or Fe and Co) An R-T-B system sintered magnet made of a sintered body comprising a main phase crystal grain and a grain boundary phase containing more R than the main phase crystal grain,
Molding composed of a low R alloy powder mainly composed of the R ₂ T ₁₄ B compound, and a high R alloy powder having a larger amount of R than the low R alloy powder and mainly composed of R and T and containing Ta. Producing a body;
And a step of sintering the molded body. A method for producing an RTB-based sintered magnet.

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