JP6094612B2 - Method for producing RTB-based sintered magnet - Google Patents

Description

  The present invention relates to a method for producing an RTB-based sintered magnet.

  R-T-B sintered magnets (R is at least one of rare earth elements and always contains Nd, T is at least one kind of transition metal elements and always contains Fe), and has the highest performance among permanent magnets It is known as a magnet, and is used in various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and home appliances.

The RTB-based sintered magnet is mainly composed of a main phase composed of an R ₂ T ₁₄ B compound and a grain boundary phase located at the grain boundary portion of the main phase. The R ₂ T ₁₄ B compound as the main phase is a ferromagnetic material having high magnetization and forms the basis of the characteristics of the R—T—B system sintered magnet.

The _RTB -based sintered magnet has irreversible thermal demagnetization because the coercive force H _cJ (hereinafter simply referred to as “H _cJ ”) decreases at high temperatures. Therefore, especially when used for a motor for an electric vehicle, it is required to have a high _HcJ even under a high temperature.

In the R-T-B based sintered magnet, a part of the light rare earth element RL (mainly Nd and / or Pr) contained in R in the main phase R ₂ T ₁₄ B compound is converted to heavy rare earth element RH (mainly Dy and / or Tb) substituting H _cJ are known to be improved by, H _cJ with increasing substitution of heavy rare-earth element RH is improved.

However, when the light rare earth element RL in the R ₂ T ₁₄ B compound is replaced with the heavy rare earth element RH, the H _{cJ of the RTB} -based sintered magnet is improved, while the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ") decreases. In addition, heavy rare earth elements, especially Dy, have a problem that their supply is not stable and the price fluctuates greatly because of their low resource abundance and limited production area. Therefore, in recent years, it without lowering the B _r without using as much as possible the heavy rare-earth element RH from the user to improve the H _cJ are required.

In Patent Document 1, at least one metal element selected from Al, Ga, and Cu is limited to a specific range in which the amount of B is relatively smaller than that of an RTB-based alloy that has been generally used in the past. By containing M, the R ₂ T ₁₇ phase is generated, and the volume ratio of the transition metal rich phase (R ₆ T ₁₃ M) generated using the R ₂ T ₁₇ phase as a raw material is sufficiently ensured, so that Dy It is described that an RTB-based rare earth sintered magnet with a high coercive force can be obtained while suppressing the content of.

Further, as a means for improving the _{HcJ of the RTB} -based sintered magnet, a metal, an alloy, a compound or the like containing the heavy rare earth element RH is added to the RTB-based sintered magnet by a specific means. is supplied to the surface of the sintered magnet, the heavy rare-earth element RH is diffused inside the magnet by a heat treatment, by replacing the light rare-earth element RL in the outer shell of the R 2 _T 14 _B compound in the heavy rare-earth element RH, the B _r Various methods for improving _HcJ while suppressing the reduction have been proposed.

  For example, in Patent Document 2, a bulk body containing an R—Fe—B rare earth sintered magnet body and a heavy rare earth element RH (at least one selected from the group consisting of Dy, Ho, and Tb) is disposed in a processing chamber. Then, by heating them to 700 ° C. or more and 1000 ° C. or less, the heavy rare earth element RH is supplied to the surface of the R—Fe—B rare earth sintered magnet body from the bulk body while the heavy rare earth element RH is supplied to R—Fe—B. Discloses a method of diffusing into a rare earth sintered magnet body.

Furthermore, Patent Document 3 includes an RTB-based alloy containing 4 to 10% by mass of Dy and a high melting point compound (Al, Ga, Mg, Nb, Si, Ti, Zr having a melting point of 1080 ° C. or higher. High coercive force can be obtained without increasing the Dy concentration by mixing, molding and sintering any one oxide selected from the group, boride, carbide, nitride, or silicide). In addition, it is described that a decrease in magnetic properties such as magnetization (B _r ) due to the addition of Dy can be suppressed.

International Publication No. 2013/008756 International Publication No. 2007/102391 International Publication No. 2010/073533

In general, when an RTB-based sintered magnet is manufactured, a ferroboron alloy whose B content is not necessarily stable is used as a B raw material. In addition, since B is an element that is likely to vary in content during the manufacturing process and is difficult to analyze with high accuracy, it is extremely difficult to strictly manage it. Further, the present inventors have found that the smaller the amount of B, the greater the influence on the magnetic characteristics, and the slight fluctuation in the amount of B _{causes the} magnetic characteristics, particularly _HcJ, to fluctuate (decrease rapidly).

In the invention described in Patent Document 1, since the amount of B is limited to a specific range that is relatively small, as described above, H _cJ is increased due to slight fluctuations in the amount of B caused by the raw materials used and the manufacturing process. There is a problem that it fluctuates (decreases rapidly). Further, in Patent Document 1, since it is necessary to manufacture an RTB-based alloy having a new composition different from the conventional one, optimum conditions such as melting and casting conditions of the alloy, pulverizing conditions, sintering conditions, heat treatment conditions, etc. It is necessary to find all of these from scratch, and when each of these conditions is different from the current production conditions, it is necessary to change the conditions of each equipment each time a new R-T-B alloy is produced. There is a problem that man-hours and costs are increased during the production.

Further, according to Patent Document 1, although an _RTB -based sintered magnet having a higher H _cJ than that of the conventional one can be obtained, a high H _cJ required for use in an electric vehicle motor, a hybrid vehicle motor, or the like. The use of Dy is indispensable to satisfy the above. Therefore, in order to reduce the amount of Dy used, a method of supplying heavy rare earth elements from the surface of an RTB-based sintered magnet as disclosed in Patent Document 2 and diffusing it inside must be applied. I do not get.

However, when the method disclosed in Patent Document 2 is applied to the R-T-B rare earth sintered magnet of Patent Document 1, the squareness ratio H _k / H _cJ (hereinafter simply referred to as “H _k / H _cJ ”). H _k is a position at which J becomes a constant value with respect to the value of J _r [residual magnetization = B _r ] in the second quadrant of the J [magnetization magnitude] -H [magnetic field strength] curve. The value of H. In R-T-B based sintered magnets, 0.9 × J _r [0.9 × B _r ] is often used as a constant ratio value). was there.

Further, according to Patent Document 3, although a high coercive force can be obtained without increasing the Dy concentration, the amount of Dy contained in the RTB-based alloy is extremely large in the first place (in the RTB-based alloy). 4 to 10 wt%), it can not satisfy the user's request of improving H _cJ without lowering the no B _r using only possible heavy rare-earth element RH.

  Furthermore, in Patent Document 3, any one oxide, boride, carbide, nitride, or silicide selected from the group consisting of Al, Ga, Mg, Nb, Si, Ti, and Zr is used as the high melting point compound. However, oxygen, boron, carbon, nitrogen, silicon, and the like contained in these compounds remain in the magnet even after sintering, and may deteriorate the magnetic properties of the obtained magnet.

The present invention, without using as much as possible the heavy rare-earth element RH, providing a stable and inexpensive R-T-B based sintered magnet having a high H _cJ and high H _{k /} H _cJ while suppressing a decrease in B _r The purpose is to do.

The manufacturing method of the RTB system sintered magnet which concerns on aspect 1 of this invention is the following.
R: 27 to 35% by mass (R is at least one of rare earth elements and must contain Nd),
B: 0.9 to 1.0% by mass,
Ga: 0.15-0.6 mass%,
Remainder T (T is at least one of transition metal elements and must contain Fe)
And preparing an alloy powder containing inevitable impurities;
Preparing a powder of Ti hydride;
Mixing the alloy powder and Ti hydride powder so that Ti contained in 100% by mass of the mixed powder after mixing is 0.3% by mass or less to prepare a mixed powder;
Forming a mixed powder to prepare a molded body; and
A step of sintering the compact and preparing an R-T-B system sintered magnet material;
A step of heat-treating the RTB-based sintered magnet material;
including.

The manufacturing method of the RTB system sintered magnet which concerns on aspect 2 of this invention is the aspect 1,
In place of the step of heat-treating the RTB-based sintered magnet material,
Providing an RH diffusion source comprising a metal, alloy or compound containing Dy and / or Tb;
Supplying RH diffusion source Dy and / or Tb to the RTB-based sintered magnet material, and performing an RH supply diffusion treatment;
A step of heat-treating the RTB-based sintered magnet material after the RH supply diffusion treatment step;
It is characterized by including.

  In the aspect 1 or 2, the manufacturing method of the RTB system sintered magnet which concerns on aspect 3 of this invention is B: 0.91-1.0 mass%, It is characterized by the above-mentioned.

In any one of the aspects 1 to 3, the manufacturing method of the RTB-based sintered magnet according to the aspect 4 of the present invention includes:
R-T-B system sintered magnet
An R ₂ T ₁₄ B compound (R is at least one rare earth element and always contains Nd, T is at least one transition metal element and always contains Fe),
R ₆ T ₁₃ M compound (R is at least one rare earth element and always contains Nd, T is at least one transition metal element and always contains Fe, M is at least one of Ga, Al, Cu and Si) Is a type and must contain Ga)
Ti boride,
Have a coexisting organization.

The manufacturing method of the RTB system sintered magnet which concerns on aspect 5 of this invention is the aspect 4,
The area ratio of the R ₆ T ₁₃ M compound in an arbitrary cross section of the RTB-based sintered magnet is 1% or more.

The manufacturing method of the RTB system sintered magnet which concerns on aspect 6 of this invention is the aspect 5,
The area ratio of the R ₆ T ₁₃ M compound in an arbitrary cross section of the RTB-based sintered magnet is 2% or more.

According to the present invention, without using as much as possible the heavy rare-earth element RH, stable and inexpensive R-T-B based sintered magnet having a high H _cJ and high H _{k /} H _cJ while suppressing a decrease in B _r Can be offered at.

6 is a graph showing the relationship between the Ti content of the _RTB -based sintered magnet of Example 3 and _HcJ . It is a graph showing the relationship between the Ti content and the B _r of the R-T-B based sintered magnet of Example 3. It is a graph showing the relationship between the Ti content and H _k R-T-B based sintered magnet of Example 3. It is a graph showing the relationship between the Ti content and the _H k _{/ H cJ} of the R-T-B-based sintered magnet of Example 3. It is a graph which shows the relationship between Ti amount of the _RTB system sintered magnet of Example 4, and _HcJ . 6 is a photograph showing a FE-TEM structure observation result of an RTB-based sintered magnet of Example 5. FIG. It is a photograph which shows the diffraction pattern characterizing the crystal structure of the electron beam diffraction of the site | part a of FIG. It is a photograph which shows the diffraction pattern characterizing the crystal structure of the electron beam diffraction of the site | part b of FIG. It is a photograph which shows the diffraction pattern characterizing the crystal structure of the electron beam diffraction of the site | part c of FIG. Is a graph showing the X-ray diffraction pattern of TiB _2. It is a graph showing the X-ray diffraction pattern of Nd ₆ Fe ₁₃ Ga alloy.

The present invention has almost the same composition as a conventional RTB-based sintered magnet (including R, B, Ga, Fe and the like, and has a higher B content than the sintered magnet of Patent Document 1 [0.9 to 1. A predetermined amount of Ti hydride powder (hereinafter referred to as “Ti hydride powder”) is added to the alloy powder of 0 mass%] composition). Thereby, it is possible to provide a R-T-B based sintered magnet having no, while suppressing a decrease in _{B r} high _{H cJ} and high _H k _{/ H cJ} be used as much as possible the heavy rare-earth element RH.

Although the reason is not clear with the R-T-B based sintered magnet is high while suppressing the decrease in B _r H _cJ and high H _{k /} H _cJ according to the invention, the addition of Ti hydride powder, sintering And / or heat treatment is caused by the generation of R ₆ T ₁₃ M compound (typically Nd ₆ Fe ₁₃ Ga compound) and Ti boride (typically TiB ₂ compound). Conceivable.

According to the present invention, since alloy powder having a composition almost the same as that of a conventional _RTB -based sintered magnet is used, _HcJ does not fluctuate greatly (abruptly decreases) due to slight fluctuations in the amount of B. . Further, no new alloy or new process is required, and the existing manufacturing conditions can be basically applied as they are. Therefore, it becomes possible to provide a sintered magnet having a high _HcJ equivalent to or higher than that of the sintered magnet of Patent Document 1 more stably and inexpensively than Patent Document 1.

In addition, the _RTB -based sintered magnet according to the present invention can suppress a decrease in H _k / H _cJ due to the RH supply diffusion treatment. Although the reason for this is not clear, as described above, the addition of Ti hydride powder results in the formation of R ₆ T ₁₃ M compound and Ti boride during sintering and / or heat treatment. It is thought that there is.

On the other hand, in Patent Document 3, a high melting point compound (any one oxide, boride, carbide, nitride, or silicide selected from the group consisting of Al, Ga, Mg, Nb, Si, Ti, and Zr) is used. ), Oxygen, boron, carbon, nitrogen, silicon, etc. contained in the magnet may remain in the magnet even after sintering, and may deteriorate the magnetic properties of the obtained magnet. The powder is decomposed into Ti and H ₂ (hydrogen) in the sintering process, and hydrogen is released from the magnet into the sintering furnace and finally discharged out of the sintering furnace. Therefore, there is almost no possibility of deteriorating the magnetic characteristics.

Thus, according to the present invention, without using as much as possible the heavy rare-earth element RH has a sintered magnet and equal or higher H _cJ of Patent Document 1, and high while suppressing the decrease in B _r H An _RTB -based sintered magnet having _{k 2} / H _cJ can be provided stably and inexpensively.

  The present invention will be described below. In the following description, as described in Patent Document 2, the heavy rare earth element RH of the RH diffusion source is supplied to the surface of the R-T-B system sintered magnet material, and RH is supplied to the R-T-B system sintered magnet material. The process of diffusing inside is called “RH supply diffusion process”. In addition, the diffusion of RH into the RTB-based sintered magnet material without performing the supply of RH after the RH supply diffusion process is referred to as “RH diffusion process”. Furthermore, the heat treatment applied to the sintered RTB-based sintered magnet material and the heat treatment applied after the RH supply diffusion treatment or the RH diffusion treatment are simply referred to as “heat treatment”. Further, the RTB-based sintered magnet before the heat treatment is referred to as “RT-B-based sintered magnet material”, and the RTB-based sintered magnet after the heat treatment is referred to as the “RT-B-based sintered magnet”. It is called a “sintered magnet”.

[1] Manufacturing method of RTB-based sintered magnet (1) Step of preparing alloy powder In the step of preparing alloy powder, the composition of the alloy powder is as follows.
R: 27-35% by mass,
B: 0.9 to 1.0% by mass,
Ga: 0.15-0.6 mass%,
The balance T and inevitable impurities are contained.
In the composition, the R-T-B based sintered magnet content with high H _cJ and high H _{k /} H _cJ while suppressing lowering of the lower limit less than or exceeds the upper limit B _r of the range of each element You may not be able to get it. B is more preferably 0.91 to 1.0% by mass. Ga is preferably 0.2 to 0.6 mass%, more preferably 0.3 to 0.6 mass%, further preferably 0.4 to 0.6 mass%, and 0.4 to 0.5 mass%. Most preferred.

  R is at least one kind of rare earth elements and necessarily contains Nd. Examples of rare earth elements other than Nd include Pr. Further, at least one of a small amount of Dy, Tb, Gd and Ho may be contained. The content of at least one of Dy, Tb, Gd, and Ho is preferably 1.0% by mass or less of the entire RTB-based sintered magnet. A part of B can be replaced by C. T is at least one of transition metal elements and must contain Fe. Examples of transition metal elements other than Fe include Co. Further, a small amount of V, Cr, Mn, Ni, Zr, Nb, Mo, Hf, Ta, W, or the like may be contained.

  Cu and Al may be contained as an element other than the above. Cu and Al may be positively added for the purpose of improving magnetic properties, etc., or materials inevitably introduced in the manufacturing process of raw materials and alloy powders may be utilized (Cu and Al are used as impurities). You may use the raw material to contain). The contents of Cu and Al (the total amount added positively and the amount mixed as an inevitable impurity) are each preferably 0.5% by mass or less.

  In the step of preparing the alloy powder, the raw materials of each element are weighed so as to have the above-described composition, and the powder is formed by a known manufacturing method. For example, an alloy is produced by a strip casting method, and the obtained alloy is made into a coarsely pulverized powder by a hydrogen pulverization method. Alternatively, the coarsely pulverized powder is finely pulverized by a jet mill or the like to obtain a finely pulverized powder. The alloy powder may be either a coarsely pulverized powder or a finely pulverized powder.

(2) Step of preparing a powder of Ti hydride A commercially available Ti hydride powder can be used. The particle size of the commercially available Ti hydride powder is about 50 μm at D50, which is a volume center value obtained by measurement by, for example, an air flow dispersion type laser diffraction method. Ti hydride powder is a very stable substance compared to the state of metal (Ti metal), and it can be pulverized with a jet mill or the like, so commercially available Ti hydride powder is finely pulverized with a jet mill or the like. However, even if it becomes finely pulverized powder (D50 or less at D50), it has an advantage that it can be handled relatively safely.

Further, as described above, in Patent Document 3, a high melting point compound (any one oxide selected from the group consisting of Al, Ga, Mg, Nb, Si, Ti, Zr, boride, carbide, nitride) Oxygen, boron, carbon, nitrogen, silicon, etc. contained in the silicide) may remain in the magnet even after sintering, and may deteriorate the magnetic properties of the resulting magnet. The Ti hydride powder to be decomposed into Ti and H ₂ (hydrogen) in the sintering process, and hydrogen is released from the magnet into the sintering furnace and finally discharged out of the sintering furnace. Therefore, there is an advantage that there is almost no possibility of deteriorating the magnetic characteristics. Further, this can suppress an increase in oxygen content, carbon content, and nitrogen content of the R-T-B system sintered magnet, for example, an oxygen content of 2000 ppm or less, a carbon content of 1500 ppm or less, and a nitrogen content. An RTB-based sintered magnet having an amount of 1000 ppm or less can be produced, and the magnetic properties can be further improved.

(3) Step of preparing mixed powder The alloy powder and Ti hydride powder prepared as described above are mixed and mixed so that Ti contained in 100% by mass of the mixed powder after mixing is 0.3% by mass or less. Powder and eggplant. The R-T-B based sintered to Ti contained in the mixed powder 100 mass% after mixing has a high _{H cJ} and high _H k _{/ H cJ} while suppressing a decrease in _{B r} exceeds 0.3 mass% A magnet cannot be obtained. The mixing amount of Ti is preferably 0.05 to 0.3% by mass, more preferably 0.12 to 0.3% by mass, further preferably 0.18 to 0.3% by mass, and 0.22 to 0.3%. Mass% is most preferred. The mixing is preferably performed by mixing an alloy powder made of coarsely pulverized powder and (unground) Ti hydride powder, and then finely pulverizing with a jet mill or the like. Prepare a mixed powder consisting of finely pulverized powder of alloy powder and Ti hydride powder by adding fine powder after mixing and without adding new processes in the same process as before. Can do. Of course, the alloy powder and Ti hydride powder may be separately pulverized and then mixed by a known mixing means to prepare a mixed powder. In this case, the mixing may be either dry or wet.

(4) Step of preparing a formed body The mixed powder is formed into a formed body. Molding is performed by known molding means. For example, a dry molding method in which a dry alloy powder is supplied into a mold cavity and molded in a magnetic field, or a slurry containing the alloy powder is injected into a mold cavity and a slurry dispersion medium is discharged while the alloy is discharged. A wet molding method for molding powder in a magnetic field can be applied.

(5) Step of preparing an RTB-based sintered magnet material The sintered compact is sintered to form an RTB-based sintered magnet material (sintered body). Sintering is performed by a known sintering means. For example, a sintering temperature of 1000 ° C. to 1180 ° C., a sintering time of about 1 to 10 hours, a method of sintering in a vacuum atmosphere or an inert gas (such as helium or argon) can be applied.

(6) The process which heat-processes to a RTB system sintered magnet raw material The said RTB system sintered magnet raw material is heat-processed, and it is set as an RTB system sintered magnet. Known conditions can be applied to the heat treatment temperature, time, atmosphere, and the like. For example, a heat treatment (one-step heat treatment) only at a relatively low temperature (400 ° C. or more and 600 ° C. or less) or a heat treatment at a relatively high temperature (700 ° C. or more and a sintering temperature or less (eg, 1050 ° C. or less)) Conditions such as heat treatment (two-stage heat treatment) at a low temperature (400 ° C. or more and 600 ° C. or less) can be employed. As preferable conditions, heat treatment is performed at 730 ° C. or more and 1020 ° C. or less for about 5 minutes to 500 minutes, and after cooling (room temperature or after cooling to 440 ° C. or more and 550 ° C. or less), further at 440 ° C. or more and 550 ° C. or less for 5 minutes to 500 minutes. Heat treatment to some extent is mentioned. The heat treatment atmosphere is preferably a vacuum atmosphere or an inert gas (such as helium or argon).

When the RH supply diffusion treatment is performed to further improve the _HcJ of the R-T-B system sintered magnet, the following process is performed instead of the process of heat-treating the R-T-B system sintered magnet material. carry out.

(7) Step of Preparing RH Diffusion Source The step of preparing an RH diffusion source made of a metal, alloy or compound containing Dy and / or Tb is disclosed in a known RH supply diffusion process such as Patent Document 2 Can be applied.

(8) Step of performing RH supply diffusion treatment The step of performing RH supply diffusion treatment of supplying and diffusing Dy and / or Tb of the RH diffusion source to the R-T-B system sintered magnet material is described in Patent Document 2 above. A process disclosed in a known RH supply diffusion process can be applied. The RH supply / diffusion treatment may be a method in which heavy rare earth element RH is supplied from the RH diffusion source to the surface of the R-T-B system sintered magnet material and diffused inside as in Patent Document 2, or RH A metal, alloy, compound, etc., containing the R-T-B system is preliminarily present on the surface of the R-T-B system sintered magnet material by film formation (dry process or wet process) or coating, and then heat-treated. A method of diffusing inside the magnet material may also be used.

RH diffusion treatment may be performed for the purpose of further diffusing Dy and / or Tb supplied to the inside of the RTB-based sintered magnet material by the RH supply diffusion treatment. In the RH diffusion process, after the RH supply diffusion process is performed, heating is performed without newly supplying Dy and / or Tb from the RH diffusion source. For example, when the RH diffusion process is performed after the RH supply diffusion process is performed, preferably 700 ° C. or more and 1000 ° C. or less, more preferably, under the condition that Dy and / or Tb is not newly supplied from the RH supply source. It implements at 800 degreeC or more and 950 degrees C or less. Alternatively, when only the R-T-B system sintered magnet material is recovered after the RH supply diffusion treatment, the vacuum or inertness below atmospheric pressure with respect to the R-T-B system sintered magnet material In a gas atmosphere, it is preferably performed at 700 ° C. or higher and 1000 ° C. or lower, more preferably 800 ° C. or higher and 950 ° C. or lower. The treatment time is, for example, about 10 minutes to 24 hours, more preferably about 1 hour to 6 hours. The diffusion of Dy and / or Tb occurs inside the RTB-based sintered magnet material by the RH diffusion treatment, and Dy and / or Tb supplied near the surface layer is further diffused deeply, and H _cJ is _reduced as a whole magnet. Can be increased.

(9) Process for heat-treating R-T-B system sintered magnet material R-T-B system sintered magnet after RH supply diffusion process (the RH diffusion process may be performed after RH supply diffusion process) The material is heat treated to form an R-T-B sintered magnet. This heat treatment is the same as the heat treatment (6).

[2] R-T-B system sintered magnet As described above, by adding Ti hydride powder, sintering and / or heat treatment (including RH supply diffusion treatment and heat treatment instead of heat treatment step) , An R ₆ T ₁₃ M compound (typically an Nd ₆ Fe ₁₃ Ga compound) and a boride of Ti (typically a TiB ₂ compound) are produced. That is, the RTB-based sintered magnet obtained by the method for manufacturing an RTB-based sintered magnet of the present invention includes an R ₂ T ₁₄ B compound, an R ₆ T ₁₃ M compound, and a Ti boron. Have a coexisting organization.

In the R ₂ T ₁₄ B compound, R is at least one of rare earth elements and necessarily contains Nd. Examples of rare earth elements other than Nd include Pr. Further, at least one of a small amount of Dy, Tb, Gd and Ho may be contained. T is at least one of transition metal elements and must contain Fe. Examples of transition metal elements other than Fe include Co. A part of B can be replaced by C.

In the R ₆ T ₁₃ M compound, R is at least one of rare earth elements and necessarily contains Nd. Examples of rare earth elements other than Nd include Pr. Further, at least one of a small amount of Dy, Tb, Gd and Ho may be contained. T is at least one of transition metal elements and must contain Fe. Examples of transition metal elements other than Fe include Co. M is mainly Ga. The R ₆ T ₁₃ M compound is typically an Nd ₆ Fe ₁₃ Ga compound. The R ₆ T ₁₃ M compound has a La ₆ Co ₁₁ Ga ₃ type crystal structure. The R ₆ T ₁₃ M compound may be an R ₆ T _13-α M _{1 + α} compound (α is typically 2 or less) depending on the state. In addition, even when only Ga is used as M, in the case where Al, Cu, and Si are contained in the RTB-based sintered magnet, R ₆ T _13-α (Ga _1−x−yz Cu _x Al _y Si _z ) _{1 + α} .

The RTB-based sintered magnet obtained by the method for manufacturing an RTB-based sintered magnet of the present invention includes an R ₆ T ₁₃ M compound in an area ratio of 1% or more in an arbitrary cross section. ing. Furthermore, when it has higher H _cJ , the R ₆ T ₁₃ M compound is contained in an area ratio of 2% or more. The area ratio of R 6 _T 13 _M compound, as shown in Examples described later, the reflection electron image by an arbitrary cross section of FE-SEM of the R-T-B-based sintered magnet (field emission scanning electron microscope) The (BSE image) image can be obtained by analyzing with a commercially available image analysis software. In the present specification, “arbitrary cross section” means, for example, a reasonable expectation that typical characteristics of the RTB-based sintered magnet according to the present invention are shown as a cross section including the central portion. It means any cross section selected on the basis, and does not include a cross section arbitrarily selected such that the features of the present invention are not shown.

Ti borides are typically TiB ₂ compounds. A TiB compound may be present together with the TiB ₂ compound. In the example of Patent Document 3, when the high melting point compound is TiC, TiC reacts with B in the material of the RTB-based rare earth permanent magnet during the sintering to produce TiB _2. It is described that it exists at the grain boundary. However, C (carbon) separated from TiC remains in the magnet even after sintering, and may deteriorate the magnetic properties of the obtained magnet. Further, in Examples of Patent Document 3 for Ga content is 0.08 mass%, considered the R _{6 T} 13 _M compound is hardly generated. Therefore, in Patent Document 3, an R-T-B system sintering having a structure in which an R ₂ T ₁₄ B compound, an R ₆ T ₁₃ M compound, and a boride of Ti coexist as in the present invention. It seems that no magnet was obtained.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
The raw materials of each element were weighed so as to have the alloy compositions shown in A and B of Table 1, and an alloy was produced by a strip casting method. Each obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. The composition of the mixed powder after mixing with the coarsely pulverized powder of the alloy A was the sample No. Mixing the mixed powder with TiH ₂ so as to have the composition shown in 2-6 was prepared (mixed powder of coarsely pulverized powder). Sample No. 1 is a coarsely pulverized powder of alloy A; 7 is a coarsely pulverized powder of Alloy B, and none of them is mixed with TiH ₂ . Sample No. 2-6 mixed powder and sample no. The coarsely pulverized powders Nos. 1 and 7 were each finely pulverized by a jet mill, and sample No. 1 having a particle diameter D50 (volume center value obtained by measurement by airflow dispersion type laser diffraction method, the same applies hereinafter) of 4.2 μm was obtained. 2-6 mixed powder (mixed powder of finely pulverized powder) and sample no. 1 and 7 finely pulverized powders were prepared.

Sample No. 2-6 mixed powder and sample no. The finely pulverized powders 1 and 7 were measured with a perpendicular magnetic field molding device (transverse magnetic field molding device) at a magnetic field strength of 0.8 MA / m, a pressure of 49 MPa (0.5 ton / cm ² ), a thickness of 12 mm × width 26 mm × length 55 mm (width). After molding two molded bodies each having a magnetic field application direction), the obtained molded bodies were sintered at 1030 ° C. for 4 hours. 2-6 mixed powder and sample no. Two RTB-based sintered magnet materials (hereinafter referred to as “RTB-based sintered magnet material of sample No. **”) based on the finely pulverized powders 1 and 7 were prepared. did.

Sample No. In order to measure the magnetic properties of the R-T-B system sintered magnets Nos. 1 to 7, sample Nos. 1 to 7 of each of the R-T-B system sintered magnet materials is subjected to a heat treatment for 3 hours at a temperature of 880 ° C. in a vacuum atmosphere, and after cooling, further at 500 ° C. for 2 hours, Heat treatment was performed in a vacuum atmosphere. The obtained sample No. RTB-based sintered magnets based on 1-7 RTB-based sintered magnet materials (hereinafter referred to as “Sample No. ** RTB-based sintered magnets”). Were cut and ground, and processed into a thickness of 7.0 mm × width of 7.0 mm × length of 7.0 mm. Sample No. after processing The magnetic properties of 1 to 7 RTB-based sintered magnets were measured with a BH tracer. Table 3 shows the measurement results. In H _k / H _cJ , H _k is the second quadrant of the J (magnetization magnitude) -H (magnetic field strength) curve, and J is 0.9 × J _r (J _r is the residual magnetization, J The value of H at the position where _r = B _r ) (hereinafter the same).

As shown in Table 3, RTB-based sintered magnets (sample Nos. ₂ to 6, examples of the present invention) obtained by mixing, forming, sintering, and heat-treating TiH ₂ to alloy powders do not mix TiH ₂ powder ( It can be seen that _HcJ is greatly improved as compared with Sample No. 1, Comparative Example). It can also be seen that _HcJ is particularly improved when the amount of Ti contained in 100% by mass of the mixed powder is in the range of _0.22 to _0.27 . Furthermore, _{B r} is not very large decrease in _{B r} for enhancing the effect of _{H cJ} although slightly lowered by the addition of TiH _2. That, _{H cJ} is improved while suppressing a decrease in _{B r.} Furthermore, H _k / H _cJ has a high value of 0.98 for all samples. Sample No. 7 is a reproduction example of Patent Document 1, and the amount of B is lower than other samples (0.88% by mass). As shown in Table 3, the sample No. before the RH supply diffusion treatment. 7 of the R-T-B based sintered magnet H _cJ and B _r is approximately is the same the as the present invention, in the R-T-B based sintered magnet according to Patent Document 1, using raw materials and manufacturing There is a problem that _HcJ largely fluctuates (abruptly decreases) due to a slight fluctuation of the B amount caused by the process.

  Next, sample No. One of two R-T-B sintered magnet materials 1 to 7 was cut and ground, and processed into a thickness of 7.4 mm, a width of 7.4 mm, and a length of 7.4 mm. Sample No. after processing For each of the 1-7 RTB-based sintered magnet materials, on the Mo plate, an RH diffusion source made of plate-like Dy metal, a holding member, an RTB-based sintered magnet material, and a holding member Seven types of laminates were prepared by laminating in order of RH diffusion sources made of plate-like Dy metal. The holding member was a plain weave wire mesh made of Mo. The seven types of laminates were charged into a heat treatment furnace and subjected to RH supply diffusion treatment at a temperature of 880 ° C. for 5.5 hours in a vacuum atmosphere at a pressure of 0.1 Pa. Thereafter, the inside of the furnace was cooled, and sample No. Only 1 to 7 RTB-based sintered magnet materials were taken out. Sample No. after RH supply diffusion treatment 1 to 7 RTB-based sintered magnet materials are subjected to RH diffusion treatment at a temperature of 880 ° C. for 5 hours in a vacuum atmosphere, and after cooling, heat treatment is performed at 500 ° C. for 2 hours in a vacuum atmosphere, No. 1 to 7 RTB-based sintered magnets were obtained. The obtained sample No. The entire surface of the 1-7 RTB-based sintered magnets was ground by 0.2 mm and processed to a thickness of 7.0 mm, a width of 7.0 mm, and a length of 7.0 mm. Sample No. after processing The magnetic characteristics of 1 to 7 RTB-based sintered magnets were measured by a pulse BH tracer. Table 4 shows the measurement results.

As shown in Table 4, RTB-based sintering was performed by subjecting an RTB-based sintered magnet material obtained by mixing, molding, and sintering TiH ₂ to an alloy powder to RH supply diffusion treatment, RH diffusion treatment, and heat treatment. It can be seen that the magnets (samples Nos. ₂ to 6, examples of the present invention) have higher H _cJ than those not mixed with the TiH ₂ powder (sample No. 1, comparative example). Further, decrease in _{B r} and _H k _{/ H cJ} even after RH supply diffusion process is small, it can be seen that a high _{B r} and high _H k _{/ H cJ.} On the other hand, Sample No. In the R-T-B system sintered magnet of _{No. 7,} H _k / H _cJ is significantly reduced as compared to before RH supply diffusion.

Example 2
The raw materials of each element were weighed so that the alloy composition shown in C of Table 5 was obtained, and an alloy was produced by a strip casting method. The obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. TiH ₂ was mixed with the coarsely pulverized powder of the obtained alloy C so that the composition of the mixed powder after mixing had the composition shown in Table 6. 8-11 mixed powder (mixed powder of coarsely pulverized powder) was prepared. Sample No. Each of the mixed powders 8 to 11 was finely pulverized by a jet mill, and sample No. 8 having a particle diameter D50 of 4.2 μm was obtained. 8-11 mixed powder (mixed powder of finely pulverized powder) was prepared.

  Sample No. The mixed powders 8 to 11 were molded and sintered by the same method as in Example 1, and Sample No. Two RTB-based sintered magnet materials based on 8-11 mixed powders were prepared. Sample No. In order to measure the magnetic properties of the R-T-B type sintered magnets 8-11, sample Nos. The same heat treatment and processing as in Example 1 were performed on one of two of the 8 to 11 RTB-based sintered magnet materials. The obtained sample No. The magnetic properties of 8-11 RTB-based sintered magnets were measured with a BH tracer. Table 7 shows the measurement results.

  In this example, the composition and B content (0.95 to 0.93), Ga content (0.4 to 0.2) and Co content (0.5 to 2.0) of the alloy A of Example 1 ) Is a different example. As shown in Table 7, excellent magnetic properties are obtained, though slightly inferior to the magnetic properties of the RTB-based sintered magnet based on the alloy A.

  Next, sample No. After processing one of two R-T-B type sintered magnet materials 8 to 11 into the same shape as in Example 1, the RH supply diffusion process and the RH diffusion process are performed in the same manner as in Example 1. And heat treatment was performed. The obtained sample No. 8 to 11 RTB-based sintered magnets were processed in the same manner as in Example 1, and then magnetic characteristics were measured with a pulsed B-H tracer. Table 8 shows the measurement results.

As Table 8, mixed TiH ₂ in alloy powder, the R-T-B-based sintered magnet subjected to RH supply diffusion process to R-T-B based sintered magnet material molded and sintered, the B _r it can be seen to have a high _{H cJ} and high _H k _{/ H cJ} while suppressing lowering.

Example 3
The raw materials of each element were weighed so as to have the alloy compositions shown in D to F of Table 9, and an alloy was produced by a strip casting method. Each obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. TiH ₂ was mixed with the coarsely pulverized powders of the obtained alloys D to F so that the composition of the mixed powder after mixing was the composition shown in Table 10. A mixed powder (mixed powder of coarsely pulverized powder) of 13 to 15, 17 to 20, and 22 to 25 was prepared. Sample No. 12 is a coarsely pulverized powder of Alloy D; 16 is a coarsely pulverized powder of Alloy E, Sample No. 21 is a coarsely pulverized powder of the alloy F, and none of them is mixed with TiH ₂ . Each of the mixed powder and coarsely pulverized powder was finely pulverized by a jet mill, and sample No. 4 having a particle diameter D50 of 4.2 μm was obtained. 13-15, 17-20, 22-25 mixed powder (mixed powder of finely pulverized powder) and sample no. 12, 16 and 21 finely divided powders were prepared.

  Sample No. 13-15, 17-20, 22-25 mixed powder and sample No. The finely pulverized powders Nos. 12, 16 and 21 were molded and sintered in the same manner as in Example 1. 13-15, 17-20, 22-25 mixed powder and sample No. An RTB-based sintered magnet material based on 12, 16, and 21 finely pulverized powders was prepared.

Sample No. In order to measure the magnetic properties of 12 to 25 RTB-based sintered magnets, The same heat treatment and processing as in Example 1 were performed on 12 to 25 RTB-based sintered magnet materials. The obtained sample No. The magnetic properties of 12-25 RTB-based sintered magnets were measured with a BH tracer. The measurement results are shown in FIGS. Figure 1 is the horizontal axis the amount of Ti, the vertical axis indicates the measurement result of H _cJ, 2 weight abscissa Ti, the vertical axis indicates the measurement results of B _r, 3 horizontal axis Ti amount, vertical axis shows the measurement result of _{H k,} 4 weight abscissa Ti, the vertical axis shows the measurement results of the _H k _{/ H cJ.} In FIG. 1 to FIG. 12-15, the triangle plot shows sample no. 16-20, the rhombus plot is Sample No. 21 to 25 are shown.

In this example, the B content of the alloy is changed. As shown in FIG. 1, an RTB-based sintered magnet obtained by mixing, forming, sintering and heat-treating TiH ₂ to an alloy powder (Sample Nos. 13 to 15, 17 to 20, 22 to 25, examples of the present invention). It can be seen that _HcJ is greatly improved in any B amount as compared with those in which TiH ₂ powder is not mixed (sample Nos. 12, 16, and 21, comparative example). It can also be seen that _HcJ is particularly improved when the amount of Ti contained in 100% by mass of the mixed powder is in the range of _0.18 to _0.25 .

Further, as shown in FIG. 2, R-T-B based sintered magnet according to the present invention is not so large reduction in B _r for enhancing the effect of H _cJ although B _r drops. That, _{H cJ} is improved while suppressing a decrease in _{B r.} Furthermore, higher as _{H k} shown in FIG. 3, as _H k _{/ H cj} shown in FIG. 4 has a high value exceeding 0.95 none of the samples.

Example 4
Ti contained in 100% by mass of the mixed powder after mixing in the coarsely pulverized powder of the alloy E of Example 3 is 0 to 0.3 (TiH ₂ is 0 to 0.31, TiO ₂ is 0 to 0.18). Each powder of TiH ₂ , TiO ₂ , TiB ₂ , TiC and TiN is mixed so as to become R-T-B system sintering by pulverization, molding, sintering and heat treatment in the same manner as in Example 1. A magnet was obtained. H _{cJ of the} obtained _RTB -based sintered magnet was measured with a BH tracer. The measurement results are shown in FIG. FIG. 5 shows the measurement results of Ti amount on the horizontal axis and _{HcJ on} the vertical axis, the round plot is TiH ₂ , the triangle plot is TiO ₂ , the diamond plot is TiB ₂ , the square plot is TiC, and x This plot shows the case where TiN is mixed.

As shown in FIG. 5, it can be seen that _HcJ is greatly improved when TiH ₂ is mixed. As described above, oxygen, boron, carbon, nitrogen, and the like contained in TiO ₂ , TiB ₂ , TiC, and TiN may remain in the magnet even after sintering, which may deteriorate the magnetic properties of the obtained magnet. is there. TiH ₂ used in the present invention is decomposed into Ti and H ₂ (hydrogen) in the sintering process, and hydrogen is released from the magnet into the sintering furnace and finally discharged out of the sintering furnace. Therefore, there is almost no possibility of deteriorating the magnetic characteristics.

Example 5
Sample No. of Example 3 The 18 R-T-B system sintered magnets were subjected to structure observation by FE-TEM (field emission transmission electron microscope, HF-2100, manufactured by Hitachi High-Technologies Corporation). The result (DF-STEM image) is shown in FIG. Moreover, the composition analysis by EDS (energy dispersive X-ray spectroscopy) was performed about site | part a, b, and c shown in FIG. The results are shown in Table 13. In addition, about the site | part a and b, the analysis of B is not performed. Moreover, the diffraction pattern characterizing the crystal structure of electron diffraction was image | photographed about part a, b, and c. The results are shown in FIGS. 7 is a diffraction pattern of a part a, FIG. 8 is a part b, and FIG. 9 is a diffraction pattern of the part c.

Further, in order to identify the compound, a composition analysis was performed by EDS in the same manner as described above for a standard sample of an R ₆ T ₁₃ M compound and a boride of Ti. The results are shown in Table 14. As a standard sample of Ti boride, commercially available TiB ₂ was used. First, as a precaution, commercially available TiB ₂ was X-ray diffracted by an X-ray diffractometer, and it was confirmed that there was no doubt a TiB ₂ compound. The result of X-ray diffraction is shown in FIG. As a standard sample of the R ₆ T ₁₃ M compound, Nd is used as R, Fe is used as T, and Ga is used as M. Nd: 52.1, which is a theoretical value of mass% of the Nd ₆ Fe ₁₃ Ga compound, Fe: Nd, Fe, and Ga were weighed and dissolved so as to be 43.7 and Ga: 4.2 to prepare an alloy. Table 15 shows the analysis results of the obtained alloy. It was confirmed that no doubt _Nd 6 _Fe 13 Ga compound of measuring the X-ray diffraction of the alloy _La 6 _Co 11 Ga ₃ type crystal structure. The result of X-ray diffraction is shown in FIG.

From the result of the composition analysis by EDS of the site a in Table 13 and the result of the diffraction pattern characterizing the crystal structure of electron beam diffraction of the site a shown in FIG. 7, it was confirmed that the site a was an Nd ₂ Fe ₁₄ B compound.

From the results of the diffractogram characterizing the crystalline structure of the electron diffraction sites b shown in composition analysis results and 8 of Tables 13 15, part b was identified as Nd 6 _Fe 13 _Ga compound. That is, although the Nd amount is slightly different between the composition analysis result by EDS of the part b and the composition analysis result of the standard sample, the constituent elements are mainly R (Nd and Pr), Fe, and Ga, and the part shown in FIG. Since the result of the diffraction pattern characterizing the crystal structure of electron diffraction of b is the same as the crystal structure of the Nd ₆ Fe ₁₃ Ga compound, the site b was identified as the Nd ₆ Fe ₁₃ Ga compound.

Furthermore, from the results of composition analysis in Tables 13 to 15 and the results of diffraction patterns characterizing the crystal structure of electron beam diffraction at site c shown in FIG. 9, site c was identified as a TiB ₂ compound. That is, the composition analysis result by EDS of the part c is similar to the composition analysis result of the standard sample, the constituent elements are composed of Ti and B, and the electron diffraction diffraction crystal structure of the part c shown in FIG. Since the result of the attached diffraction pattern is the same as the crystal structure of the TiB ₂ compound, the site c was identified as the TiB ₂ compound.

As described above, by the addition of Ti hydride powder, in the sintering and / or heat treatment, R ₆ T ₁₃ M compound (typically Nd ₆ Fe ₁₃ Ga compound) and Ti boride (typically TiB) ₂ compounds) are produced. That is, the RTB-based sintered magnet obtained by the method for manufacturing an RTB-based sintered magnet of the present invention includes an R ₂ T ₁₄ B compound, an R ₆ T ₁₃ M compound, and a Ti boron. It is clear that it has an organization in which the chemical compound coexists.

Example 6
Sample No. 1 of Example 1 For any cross section of 1 to 7 R-T-B system sintered magnets (RH supply diffusion treatment, R-T-B system sintered magnets that have not been subjected to RH diffusion treatment), after mirror finishing, A part of the mirror surface was subjected to ion beam processing by a cross section polisher (SM-09010, manufactured by JEOL Ltd.). Next, the processed surface was observed by FE-SEM (field emission scanning electron microscope, JSM-7001F, manufactured by JEOL Ltd.) (acceleration voltage 5 kV, working distance 4 mm, TTL mode, magnification 2000 times). Then, the reflected electron image (BSE image) by FE-SEM is analyzed by image analysis software (Scandium, manufactured by OLYMPUS SOFT IMAGEING SOLUTIONS GMBH), and the R ₆ T ₁₃ M compound (typically Nd ₆ Fe ₁₃ Ga compound) is analyzed. The area ratio was determined. The BSE image by FE-SEM is displayed brighter as the average atomic number of the elements constituting the region is larger, and darker as the atomic number of the element is smaller. For example, the grain boundary phase (rare earth rich phase) is displayed brightly, and the main phase (R ₂ T ₁₄ B phase), oxide, etc. are displayed darkly. The R ₆ T ₁₃ M compound is displayed at about the mid-brightness. Analysis by image analysis software creates a graph with the brightness of the BSE image as the horizontal axis and the frequency (area) as the vertical axis by image processing, and R ₆ T ₁₃ M compound by EDS (energy dispersive X-ray spectroscopy). exploring, specific to brightness and response in the graph, to determine the area ratio of R 6 _T 13 _M compound. This analysis was performed for BSE images of five different fields of view on the cross section (the width of each field is 45 μm × 60 μm), and the average value was defined as the area ratio of the R ₆ T ₁₃ M compound. The results are shown in Table 16.

As described above, the R-T-B system sintered magnet (sample Nos. 2 to 6, examples of the present invention) obtained by mixing, forming, sintering and heat-treating TiH ₂ to the alloy powder, and R ₂ T ₁₄ B compound, It has a structure in which an R ₆ T ₁₃ M compound and a boride of Ti coexist, and as shown in Table 16, the R ₆ T ₁₃ M compound is present in an area ratio of 1% or more, and a particularly high H _cJ is obtained. When it has, R ₆ T ₁₃ M compound is present in an area ratio of 2% or more. On the other hand, a sample in which TiH ₂ powder is not mixed (sample No. 1, comparative example) and sample No. 1 which is a reproduction example of Patent Document 1. In No. 7 (Comparative Example), an R ₆ T ₁₃ M compound is present in an area ratio of 1% or more, but no boride of Ti is formed. The R-T-B based sintered magnet according to the present invention has a high _{H cJ} and high _H k _{/ H cJ} while suppressing a decrease in _{B r is} the R _{2 T 14} B _compound, and R _{6 T 13} M compound This is considered to be due to the structure in which Ti boride coexists and the abundance of the R ₆ T ₁₃ M compound.

Example 7
Sample No. 2 of Example 2 8 to 11 R-T-B system sintered magnets (RH supply diffusion treatment, R-T-B system sintered magnet not subjected to RH diffusion treatment) were subjected to R ₆ T in the same manner as in Example 6. The area ratio of ₁₃ M compound was determined. The results are shown in Table 17.

An R-T-B system sintered magnet (sample Nos. 8 to 11 and examples of the present invention) obtained by mixing, forming, sintering, and heat-treating TiH ₂ in an alloy powder, as described above, R ₂ T ₁₄ B compound, It has a structure in which an R ₆ T ₁₃ M compound and a boride of Ti coexist, and as shown in Table 17, the R ₆ T ₁₃ M compound is present in an area ratio of 1% or more.

Example 8
The raw materials of each element were weighed so as to have the alloy compositions shown in G and H of Table 18, and an alloy was produced by strip casting. Each obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. The composition of the mixed powder after mixing with the coarsely pulverized powder of the alloy G was the sample No. Mixing the mixed powder with TiH ₂ so as to have the composition shown in 48 to 52 were prepared (mixed powder of coarsely pulverized powder). Sample No. 47 is a coarsely pulverized powder of Alloy G, sample No. 53 is a coarsely pulverized powder of alloy H, and none of them is mixed with TiH ₂ . Sample No. 48-52 mixed powder and sample No. The coarsely pulverized powders 47 and 53 were each finely pulverized by a jet mill, and sample No. 4 having a particle size D50 (volume center value obtained by measurement by airflow dispersion type laser diffraction method, the same applies hereinafter) of 4.2 μm was obtained. 48-52 mixed powder (mixed powder of finely pulverized powder) and sample No. 47 and 53 finely pulverized powders were prepared.

Sample No. 48-52 mixed powder and sample No. The coarsely pulverized powders Nos. 47 and 53 were molded and sintered by the same method as in Example 1, and sample No. 48-52 mixed powder and sample No. RTB-based sintered magnet materials based on 47 and 53 coarsely pulverized powders were prepared. Sample No. In order to measure the magnetic properties of the 47 to 53 RTB-based sintered magnets, The same heat treatment and processing as in Example 1 were performed on 47 to 53 RTB-based sintered magnet materials. The obtained sample No. The magnetic properties of 47 to 53 RTB-based sintered magnets were measured with a BH tracer. Table 20 shows the measurement results. In addition, the area ratio of the R ₆ T ₁₃ M compound was determined by the same method as in Example 6. The results are shown in Table 20.

In this example, the composition of the alloy A of Example 1 was changed, and in particular, the Ga amount was increased from 0.4% by mass to 0.5% by mass. As shown in Table 20, RTB-based sintered magnets (sample Nos. 48 to 52, examples of the present invention) obtained by mixing, forming, sintering, and heat-treating TiH ₂ to alloy powders do not mix TiH ₂ powder. It turns out that it has high _HcJ compared with (sample No. 47, comparative example). On the other hand, Sample No. 53 R-T-B based sintered magnet is _{H cJ} and _{B r} is an invention example comparable although degraded greatly _H k _{/ H cJ.}

Also, R-T-B based sintered magnet according to the present embodiment, Ti amount is in the range of 0.22 to 0.27, has a 1500 kA / m or more high _{H cJ} while suppressing a decrease in _{B r} ing. For example, the sample No. of this example having the same Ti amount of 0.22. 50 and Sample No. 1 of Example 1. Comparing 3 _{and, B r} is hardly reduced to _{H cJ} is improved by about 50 kA / m.

Furthermore, the R—T—B system sintered magnet (sample Nos. 48 to 52, examples of the present invention) obtained by mixing, forming, sintering, and heat-treating TiH ₂ to the alloy powder is an R ₂ T ₁₄ B compound as described above. And an R ₆ T ₁₃ M compound and a boride of Ti coexist, and as shown in Table 32, the R ₆ T ₁₃ M compound is present in an area ratio of 2% or more.

Example 9
Raw materials of each element were weighed so as to have alloy compositions shown in I and J of Table 21, and an alloy was produced by a strip casting method. Each obtained alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. The composition of the mixed powder after mixing with the coarsely pulverized powder of Alloy I obtained was the sample No. TiH ₂ was mixed so as to have the composition shown in 55 to 59 to prepare a mixed powder (mixed powder of coarsely pulverized powder). Sample No. 54 is a coarsely pulverized powder of Alloy I, Sample No. 60 is a coarsely pulverized powder of Alloy J, and none of them is mixed with TiH ₂ . Sample No. 55-59 mixed powder and sample No. The coarsely pulverized powders Nos. 54 and 60 were each finely pulverized by a jet mill, and sample Nos. Having a particle diameter D50 (volume center value obtained by measurement by an air flow dispersion type laser diffraction method, the same shall apply hereinafter) of 4.2 μm. 55-59 mixed powder (mixed powder of finely pulverized powder) and sample no. 54 and 60 finely pulverized powders were prepared.

Sample No. 55-59 mixed powder and sample No. The coarsely pulverized powders Nos. 54 and 60 were molded and sintered by the same method as in Example 1, and sample No. 55-59 mixed powder and sample No. RTB-based sintered magnet materials based on 54, 60 coarsely pulverized powders were prepared. Sample No. In order to measure the magnetic properties of the 54 to 60 RTB-based sintered magnets, The same heat treatment and processing as in Example 1 were performed on 54 to 60 RTB-based sintered magnet materials. The obtained sample No. The magnetic properties of 54 to 60 RTB-based sintered magnets were measured with a BH tracer. The measurement results are shown in Table 23. In addition, the area ratio of the R ₆ T ₁₃ M compound was determined by the same method as in Example 6. The results are shown in Table 23.

In this example, the Al content of the alloy G of Example 8 was increased from 0.1% by mass to 0.3% by mass. As shown in Table 23, RTB-based sintered magnets (sample Nos. 55-59, examples of the present invention) obtained by mixing, forming, sintering, and heat-treating TiH ₂ to alloy powders do not mix TiH ₂ powder. It turns out that it has high _HcJ compared with (sample No. 54, comparative example). On the other hand, Sample No. 60 R-T-B based sintered magnet is _{H cJ} and _{B r} are the same level as the present invention example is reduced greatly _H k _{/ H cJ.}

In addition, the RTB-based sintered magnet according to this example has a Ti content of about 1500 kA / m when the amount of Ti is 0.19% by mass, and 1500 kA / m or more when the amount of Ti is 0.22 to 0.27% by mass. Of high _HcJ . Furthermore, the RTB-based sintered magnet according to the present example has a structure in which the R ₂ T ₁₄ B compound, the R ₆ T ₁₃ M compound, and the boride of Ti coexist as described above. As shown in Table 23, the sample No. ₆ in which the R ₆ T ₁₃ M compound has an H _cJ of 1.9% or more and particularly higher H _cJ by area ratio. In 56 to 59, the R ₆ T ₁₃ M compound is present in an area ratio of 2% or more.

  The RTB-based sintered magnet obtained by the present invention is suitably used for various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles, motors for hybrid vehicles, and home appliances. be able to.

Claims (3)

An R ₂ T ₁₄ B compound (R is at least one rare earth element and always contains Nd, T is at least one transition metal element and always contains Fe),
R ₆ T ₁₃ M compound (R is at least one rare earth element and always contains Nd, T is at least one transition metal element and always contains Fe, M is at least one of Ga, Al, Cu and Si) Is a type and must contain Ga)
Ti boride,
Have a coexisting organization,
An R-T-B system sintered magnet manufacturing method in which the area ratio of the R6T13M compound in an arbitrary cross section is 2% or more,
R: 27 to 35% by mass (R is at least one of rare earth elements and must contain Nd),
B: 0.9 to 1.0% by mass,
Ga: 0.15-0.6 mass%,
Preparing an alloy powder containing the balance T (T is at least one of transition metal elements and necessarily contains Fe) and inevitable impurities;
Preparing a powder of Ti hydride;
Mixing the alloy powder and Ti hydride powder so that Ti contained in 100% by mass of the mixed powder after mixing is 0.3% by mass or less to prepare a mixed powder;
Forming a mixed powder to prepare a molded body; and
A step of sintering the compact and preparing an R-T-B system sintered magnet material;
A step of heat-treating the RTB-based sintered magnet material;
The manufacturing method of the RTB type | system | group sintered magnet characterized by including. In place of the step of heat-treating the RTB-based sintered magnet material,
Providing an RH diffusion source comprising a metal, alloy or compound containing Dy and / or Tb;
Supplying RH diffusion source Dy and / or Tb to the RTB-based sintered magnet material, and performing an RH supply diffusion treatment;
A step of heat-treating the RTB-based sintered magnet material after the RH supply diffusion treatment step;
The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 characterized by the above-mentioned.   B: It is 0.91-1.0 mass%, The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 or 2 characterized by the above-mentioned.

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