JP6733398B2 - Method for manufacturing RTB-based sintered magnet - Google Patents

Description

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

The R-T-B system sintered magnet (R is at least one kind of rare earth element and always contains at least one of Nd and Pr, T is at least one kind of transition metal element and always contains Fe) is _It is composed of a main phase composed of a compound having a ₂ T ₁₄ B type crystal structure and a grain boundary phase located in the grain boundary portion of this main phase, and is known as the most high-performance permanent magnet. There is.

Therefore, it is used in various applications such as various motors such as voice coil motors (VCM) of hard disk drives, motors for electric vehicles (EV, HV, PHV), motors for industrial equipment, and home electric appliances.

However, the R-T-B system sintered magnet has a _problem that the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) decreases at high temperature and irreversible thermal demagnetization occurs. Therefore, when the _RTB -based sintered magnet is used for an application such as a motor for an electric vehicle that reaches a high temperature such as 100° C. to 160° C. during operation, H _cJ decreases during operation, The stable operation of the motor may not be obtained. Therefore, there is a small decrease in H _cJ at high temperatures, that is, improvement in the temperature coefficient of H _cJ of the R-T-B system sintered magnet ( _reduction of the absolute value of the temperature coefficient of H _cJ ) is required. ..

In Patent Document 1, a temperature of H _cJ is obtained by stacking R1 (at least one kind of rare earth element not containing Y and Ce)-T-B based crystal layer and (Y, Ce)-T-B based crystal layer. It is stated that the coefficient is improved.

JP, 2014-216462, A

However, in the method described in Patent Document 1, the R1-TB system crystal layer and the (Y, Ce)-TB system crystal layer have to be stacked by sputtering or the like, which is costly and mass-produced. Is difficult. Further, since it contains the (Y, Ce)-T-B based crystal layer, a decrease in the anisotropic magnetic field cannot be avoided, and high _HcJ cannot be obtained.

Embodiments of the present disclosure, the temperature coefficient of the H _cJ is improved, reduction of H _cJ at a high temperature is small, and provides a process for producing R-T-B based sintered magnet can obtain a high H _cJ ..

A non-limiting exemplary method of making an RTB based sintered magnet of the present disclosure is:
R: 29.5 mass% or more and 35.0 mass% or less (R is at least one kind of rare earth element and always contains at least one of Nd and Pr), B: 0.80 mass% or more and 0.90 mass% or less, Ga: 0.1% by mass or more and 0.8% by mass or less, M: 0% by mass or more and 2% by mass or less (M is at least one of Cu, Al, Nb, and Zr), balance T (T is at least a transition metal element) A rare earth element RH (RH is Dy), which is a kind of element and must contain Fe, and 10% or less of Fe can be replaced with Co) and an RTB-based sintered magnet material containing inevitable impurities; And at least one of Tb) and the RTB-based sintered magnet material are placed in a processing container and heated at a temperature of 760° C. or higher and 1000° C. or lower. And a temperature of 750° C. or higher and lower than 1000° C. and lower than the temperature of the first RH diffusion treatment with respect to the RTB-based sintered magnet material after the first RH diffusion treatment. A step of performing a second RH diffusion treatment of heating at a temperature, and 730° C. or more and 850° C. or less for the RTB-based sintered magnet after the second RH diffusion treatment, and the second The step of carrying out a high temperature heat treatment of heating to a temperature lower than the temperature of the RH diffusion treatment of No. 3 and cooling to 300° C. at a cooling rate of 5° C./min or more, and an RTB based sintered magnet after the high temperature heat treatment On the other hand, the step of performing a low temperature heat treatment of heating at a temperature of 440° C. or higher and 550° C. or lower.

In one embodiment, M of the RTB-based sintered magnet material always contains Cu, and Cu: 0.05% by mass or more and 0.30% by mass or less.

In one embodiment, the R-T-B based sintered magnet material is R: 30.0 mass% or more and 34.0 mass% or less.

In one embodiment, the RTB-based sintered magnet material is B: 0.82 mass% or more and 0.88 mass% or less.

In one embodiment, the R-T-B system sintered magnet material is Ga: 0.2 mass% or more and 0.8 mass% or less.

In one embodiment, the cooling rate in the step of performing the high temperature heat treatment is 15° C./minute or more.

According to embodiments of the present _disclosure, the temperature coefficient of the _{H cJ} is improved, less decrease in H _cJ is at high temperature, and provide a method for producing R-T-B based sintered magnet can obtain a high H _cJ can do.

The present inventor performs a first RH diffusion treatment for diffusing a heavy rare earth element RH from an RH diffusion source into an RTB-based sintered magnet material for an RTB-based sintered magnet material having a specific composition. After carrying out, a second RH diffusion treatment of heating at a temperature lower than the temperature of the first RH diffusion treatment is carried out, and further 730° C. or higher and 850° C. or lower lower than the temperature of the second RH diffusion treatment. After performing the high temperature heat treatment of cooling to 300° C. at 5° C./minute or more, and the low temperature heat treatment of heating to a temperature of 440° C. or more and 550° C. or less, the RTB based firing is performed. It was _{found that} the temperature coefficient of H _cJ of the binder magnet is improved, the decrease of H _cJ at a high temperature such as 140° C. is small, and an _RTB -based sintered magnet that expresses high H _cJ can be obtained.

Hereinafter, details of each step in the manufacturing method of the RTB sintered magnet of the present disclosure will be described. In the present disclosure, the RTB-based sintered magnet before the second RH diffusion treatment and during the second RH diffusion treatment is referred to as “RTB-based sintered magnet material”, and the second The R-T-B system sintered magnet after the RH diffusion heat treatment is simply referred to as "R-T-B system sintered magnet".

[Step of preparing an RTB-based sintered magnet material]
A metal or alloy (melting raw material) of each element is prepared so that the RTB sintered magnet material has a specific composition described in detail below, and a flake-shaped raw material alloy is produced by a strip casting method or the like. .. Next, alloy powder is prepared from the flaky raw material alloy. Then, the alloy powder is molded to obtain a molded body. An RTB-based sintered magnet material is prepared by sintering the obtained compact.

The production of the alloy powder, the molding of the alloy powder, and the sintering of the molded body are performed as follows as an example.
The flaky raw material alloy obtained by the strip casting method or the like is pulverized with hydrogen to obtain coarsely pulverized powder of 1.0 mm or less, for example. Next, the coarsely pulverized powder is finely pulverized by a jet mill or the like in an inert gas, and has a particle diameter D ₅₀ (volume center value (volume-based median diameter) obtained by measurement by an airflow dispersion laser diffraction method) of 3 to, for example. Finely pulverized powder (alloy powder) of 5 μm is obtained. As the alloy powder, one kind of alloy powder (single alloy powder) may be used, or a so-called two-alloy method may be used in which alloy powder (mixed alloy powder) is obtained by mixing two or more kinds of alloy powder. The alloy powder may be prepared so as to have the composition of the embodiment of the present disclosure by using a known method. A known lubricant may be added as an auxiliary agent to the coarsely pulverized powder before the jet mill pulverization, the alloy powder during the jet mill pulverization and after the jet mill pulverization.

Next, the obtained alloy powder is molded in a magnetic field to obtain a molded body. Molding is performed by inserting dry alloy powder into the cavity of the mold and molding, and by injecting slurry containing alloy powder into the cavity of the mold and discharging the slurry dispersion medium. Any known molding method may be used, including a wet molding method for molding a powder.

An RTB-based sintered magnet material is obtained by sintering the compact. A known method can be used for sintering the molded body. In order to prevent oxidation due to the atmosphere during sintering, it is preferable to perform the sintering in a vacuum atmosphere or an inert gas atmosphere. It is preferable to use, for example, helium or argon as the inert gas.

Next, the composition of the RTB-based sintered magnet material will be described. The R-T-B system sintered magnet material is
R: 29.5 mass% or more and 35.0 mass% or less (R is at least one kind of rare earth element and always contains at least one of Nd and Pr),
B: 0.80 mass% or more and 0.90 mass% or less,
Ga: 0.1% by mass or more and 0.8% by mass or less,
M: 0% by mass or more and 2% by mass or less (M is at least one of Cu, Al, Nb, and Zr)
The balance T (T is at least one kind of transition metal element and always contains Fe, and 10% or less of Fe can be replaced with Co) and unavoidable impurities.
The amount of R, the amount of B, and the amount of Ga are set to the above-described specific ranges, respectively, a step of performing a first RH diffusion treatment described below, a step of performing a second RH diffusion treatment, a step of performing a high temperature heat treatment, and a low temperature. By performing the step of carrying out the heat treatment, the temperature coefficient of H _cJ is improved, the decrease of H _cJ at a high temperature is small, and an _RTB -based sintered magnet _exhibiting a high H _cJ can be obtained. ..

R is at least one kind of rare earth element and always contains at least one of Nd and Pr. Further, at least one kind of Dy, Tb, Gd and Ho may be contained in a small amount, and the content thereof is preferably 5% by mass or less based on the entire RTB sintered magnet. The content of R is 29.5% by mass or more and 35.0% by mass or less. When R is less than 29.5 mass%, there is a possibility that the densification during sintering becomes difficult, when it exceeds 35.0 wt%, it is impossible to main phase ratio to obtain a high B _r drops There is a fear. The content of R is preferably 30.0 mass% or more and 34.0 mass% or less. This is because a higher _Br can be obtained.

The content of B is 0.80 mass% or more and 0.90 mass% or less. When B is less than 0.80% by mass, R ₂ T ₁₇ phase is generated and high H _cJ cannot be obtained, and when it exceeds 0.90% by mass, a step of performing a first RH diffusion treatment described below, Even if all the steps of performing the second RH diffusion treatment, the high temperature heat treatment, and the low temperature heat treatment are performed, the temperature coefficient of H _cJ cannot be improved, and the high H _cJ at high temperature is not _increased . Can't get The content of B is preferably 0.82 mass% or more and 0.88 mass% or less. This is because the temperature coefficient can be further improved.

The content of Ga is 0.1% by mass or more and 0.8% by mass or less. By setting R and B within the above ranges and further setting the Ga content to 0.1% by mass or more and 0.8% by mass or less, R-T-Ga is formed in the grain boundary phase located in the grain boundary part of the main phase. Phase and R-Ga phase can be generated to obtain high _HcJ . Here, the RT-Ga phase includes R: 15% by mass or more and 65% by mass or less, T: 20% by mass or more and 80% by mass or less, Ga: 2% by mass or more and 20% by mass or less, For example, an R ₆ Fe ₁₃ Ga compound having a La ₆ Co ₁₁ Ga ₃ type crystal structure can be mentioned. The R-T-Ga phase may contain an element other than R, T, and Ga described above, and examples thereof include one or more elements selected from Al, Cu, and the like. The R-Ga phase includes R 70 mass% or more and 95 mass% or less, Ga 5 mass% or more and 30 mass% or less, and Fe 20 mass% or less (including 0), and examples thereof include R ₃ Ga compounds.

If the Ga content is less than 0.1% by mass, the amount of the R-T-Ga phase and the R-Ga phase produced may be too small to obtain high _HcJ , and the amount exceeds 0.8% by mass. and will be unnecessary Ga is present, the main phase ratio may be decreased is B _r drops. The content of Ga is preferably 0.2 mass% or more and 0.8 mass% or less. This is because higher H _cJ can be obtained at high temperature.

M is at least one of Cu, Al, Nb, and Zr, and the effect of the embodiment of the present disclosure can be obtained even if it is 0% by mass, but the total amount of Cu, Al, Nb, and Zr is 2% by mass or less. Can be included. H _cJ can be improved by containing Cu and Al. Further, by containing Nb and Zr, abnormal grain growth of crystal grains during sintering can be suppressed. Preferably, M always contains Cu, and contains Cu in an amount of 0.05% by mass or more and 0.30% by mass or less. This is because H _cJ can be further improved by containing Cu in an amount of 0.05% by mass or more and 0.30% by mass or less.

The balance T is at least one of transition metal elements and always contains Fe, and 10% or less of Fe can be replaced with Co. By containing Co, the corrosion resistance can be improved, but if the substitution amount of Co exceeds 10% of Fe, high _Br may not be obtained.
Further, the R-T-B system sintered magnet material contains Cr, Mn, Si, La, Ce, Sm, Ca as unavoidable impurities that are usually contained in didymium alloy (Nd-Pr), electrolytic iron, ferroboron, and the like. You may contain Mg etc. Further, O (oxygen), N (nitrogen), C (carbon) and the like may be contained as inevitable impurities in the manufacturing process. Further, in addition to the inevitable impurities, a small amount of Ti, V, Ni, Mo, Hf, Ta, W or the like may be contained.

[Step of performing first RH diffusion treatment]
An RH diffusion source containing a heavy rare earth element RH (at least one of Dy and Tb) and the above-mentioned R-T-B based sintered magnet material are arranged in a processing container, and the RH diffusion source and the R-T- The first RH diffusion step of diffusing the heavy rare earth element RH is performed on the RTB based sintered magnet material by heating the B based sintered magnet material at 760° C. or higher and 1000° C. or lower.
When the heating temperature is lower than 760°C, the amount of heavy rare earth element RH supplied to the RTB-based sintered magnet material may be too small to obtain a high _HcJ, and thus exceeds 1000°C. Then, _Br may be significantly reduced. The heating time is preferably 5 minutes or more and 500 minutes or less. The R-T-B based sintered magnet material may be subjected to mechanical processing such as grinding and then subjected to the RH diffusion step.
Step of performing a first RH diffusion process, the heavy rare-earth element RH is diffused from the R-T-B-based sintered magnet material surface of the crystal grains outside made of a compound having a R 2 _T 14 _B-type crystal structure A known method capable of concentrating the heavy rare earth element RH on the shell may be used. Examples of known methods include the methods described in References 1 to 3 described in detail below.

(1) Reference 1: The method described in WO2007/102391.
In the method described in Reference Document 1, an R-T-B based sintered magnet material and an RH diffusion source containing at least one of Dy and Tb are separately arranged via a net made of Nb, and R- While heating the TB-based sintered magnet material and the RH diffusion source to a predetermined temperature, at least one of Dy and Tb is supplied from the RH diffusion source to the surface of the RTB-based sintered magnet material. , Is a method of diffusing inside. The heating temperature of the RTB-based sintered magnet material and the heating temperature of the RH diffusion source are substantially the same.

When the method described in Reference 1 is used, the RH diffusion source is at least one selected from Dy metal, DyFe alloy, Tb metal, TbFe alloy, and the like. The shape of the RH diffusion source is, for example, a plate shape, a spherical shape, or the like, and the size is not particularly limited.
The temperature at which the RTB-based sintered magnet material and the RH diffusion source are heated is, for example, 760° C. or higher and 1000° C. or lower, and preferably 850° C. or higher and 1000° C. or lower. Further, the pressure of the atmospheric gas in the processing container is preferably 10 ⁻⁵ Pa or more and 500 Pa or less. In addition, the “atmosphere gas” in Reference Document 1 includes a vacuum or an inert gas. Further, the “inert gas” is, for example, a rare gas such as argon (Ar), but a gas that does not chemically react with the sintered body or the heavy rare earth element supply source (eg, nitrogen gas) is “inert gas”. Gas”.

(2) Reference 2: The method described in WO2012/008426.
In the method described in Reference Document 2, an RTB-based sintered magnet material and an RH diffusion source are inserted into a processing container so as to be relatively movable and close to or in contact with each other, and the RTB-based sintering magnet is burned. By heating the RTB-based sintered magnet material and the RH diffusion source while moving the binder magnet material and the RH diffusion source continuously or intermittently in the processing container, Dy and It is a method of diffusing at least one of Tb into the RTB-based sintered magnet material. The heating temperature of the RTB-based sintered magnet material and the heating temperature of the RH diffusion source are substantially the same.

When the method described in Reference 2 is used, the RH diffusion source is an alloy containing a heavy rare earth element RH (Dy, Tb, etc.) and 30% by mass or more and 80% by mass or less of Fe, and the form thereof is For example, a spherical shape, a linear shape, a plate shape, a block shape, a powder, or the like is arbitrary. When it has a ball shape, its diameter is preferably set to, for example, several hundred μm to several tens mm. In the case of powder, the particle size is preferably set within a range of 5 mm or less, for example. Further, in addition to the RH diffusion source and the R-T-B based sintered magnet material, it is preferable to load a stirring auxiliary member into the processing container. The agitation assisting member promotes contact between the RH diffusion source and the R-T-B based sintered magnet material, and the heavy rare earth element RH once attached to the agitation assisting member is indirectly transferred to the R-T-B based sintered magnet material. Play a role in supplying electricity. Further, the agitation assisting member also has a role of preventing chipping due to contact between the RTB based sintered magnet materials in the processing container. Examples of the agitation assisting member include a spherical shape and a cylindrical shape having a diameter of several hundred μm to several tens mm. The agitation assisting member is preferably formed of a material that does not easily react even if it comes into contact with the R-T-B based sintered magnet material and the RH diffusion source during the RH diffusion process. For example, zirconia, silicon nitride, silicon carbide. And so on.

The temperature for heating the RTB-based sintered magnet material and the RH diffusion source is preferably more than 850°C and 1000°C or less. Further, the pressure of the atmospheric gas in the processing container can be set to be equal to or lower than the atmospheric pressure, and can be set within the range of, for example, 0.001 Pa to the atmospheric pressure.

(3) Reference document 3: The method described in WO2006/043348.
In the method described in Reference Document 3, the RH diffusion source is heated at a temperature lower than the sintering temperature in a state where the RH diffusion source is present on the surface of the R-T-B system sintered magnet material, so that the RH diffusion source can generate Dy. And a method of diffusing at least one of Tb into the RTB-based sintered magnet material.

When the method described in Reference 3 is used, the RH diffusion source is preferably an R oxide, a fluoride, an oxyfluoride, or the like. The RH diffusion source is preferably in the form of particles, and its average particle size is preferably 100 μm or less.
Examples of the method of allowing the RH diffusion source to exist on the surface of the R-T-B system sintered magnet material include, for example, a method of directly spraying a particulate RH diffusion source onto the surface of the R-T-B system sintered magnet material, and RH. A method in which a solution in which a diffusion source is dissolved in a solvent is applied to the surface of an RTB-based sintered magnet material, and a slurry in which an RH diffusion source is dispersed in a dispersion medium is applied to the surface of an RTB-based sintered magnet material. And the like. Examples of the dispersion medium used for the slurry include alcohol, aldehyde, ethanol, ketone and the like.

The temperature at which the RTB-based sintered magnet material and the RH diffusion source are heated is equal to or lower than the sintering temperature, and specifically 900° C. is preferable. If the temperature is higher than the sintering temperature, the structure of the RTB-based sintered magnet material is deteriorated and high magnetic properties cannot be obtained, or the RTB-based sintered magnet material causes thermal deformation. There are cases. The pressure of the atmospheric gas in the processing container is preferably atmospheric pressure or lower.

[Step of performing second RH diffusion treatment]
Second heating to the RTB based sintered magnet material after the first RH diffusion treatment at a temperature of 750° C. or higher and lower than 1000° C. and a temperature lower than the temperature of the first RH diffusion treatment. RH diffusion processing is performed. By performing the second RH diffusion treatment, the heavy rare earth element RH is suppressed from diffusing the heavy rare earth element RH from the RH diffusion source as compared with the first RH diffusion treatment, and the heavy rare earth element RH is added to the RTB-based sintered magnet. It is possible to diffuse into the inside of the material (diffuse not only in the vicinity of the surface of the magnet material but also toward the center), and a high H _cJ can be obtained. The temperature of the second RH diffusion treatment is set lower than the heating temperature of the RTB-based sintered magnet material in the first RH diffusion treatment. For example, when the RTB-based sintered magnet material is heated at 900° C. in the first RH diffusion treatment, the second RH-diffusion treatment is performed when the RTB-based sintered magnet material is less than 900° C. To heat. Preferably, the temperature is set to be 10° C. or more lower than the temperature of the first RH diffusion treatment and heating is performed. By performing the second RH diffusion process, the heavy rare earth element RH supplied near the surface of the R-T-B system sintered magnet material during the first RH diffusion process is transferred to the R-T-B system through grain boundaries. The sintered magnet material can be diffused deeply (central portion). When the temperature of heating the RTB-based sintered magnet material in the second RH diffusion treatment exceeds the temperature of the first RH diffusion treatment, the main phase near the surface of the RTB-based sintered magnet material heavy rare-earth element RH to the center of the crystal grains are diffused B _r may be lowered. Further, if the temperature of the second RH diffusion treatment is less than 750° C., the heavy rare earth element RH cannot be diffused deep into the RTB-based sintered magnet material, and high H _cJ can be obtained. If the temperature is 1000° C. or higher, the temperature exceeds the temperature of the first RH diffusion treatment, and as described above, _Br may decrease. The pressure of the second RH diffusion treatment may be set to 200 Pa or more and 2 kPa or less. As a result, the supply of the heavy rare earth element RH from the RH diffusion source is almost eliminated and only diffusion into the RTB-based sintered magnet material proceeds. The heating time is preferably 5 minutes or more and 300 minutes or less.

[Process for carrying out high temperature heat treatment]
With respect to the RTB-based sintered magnet after the second RH diffusion treatment, the temperature is 730° C. or higher and 850° C. or lower and lower than the temperature of the second RH supply diffusion treatment (second RH). After heating at a temperature lower than the heating temperature of the RTB-based sintered magnet material in the diffusion treatment), a high temperature heat treatment is performed to cool to 300°C at a cooling rate of 5°C/min or more. By performing the first RH diffusion treatment and the second RH diffusion treatment, and further performing both the high temperature heat treatment and the low temperature heat treatment described later, it is possible to improve the temperature coefficient and obtain high H _cJ at high temperature. it can.

The heating time is preferably 5 minutes or more and 500 minutes or less. Further, in the step of performing the high temperature heat treatment of the embodiment of the present disclosure, after heating to a temperature of 730° C. or more and 850° C. or less, it is cooled to 300° C. at a cooling rate of 5° C./min or more. If the cooling rate is less than 5° C./minute, the temperature coefficient is not improved, and high H _cJ cannot be obtained at high temperature. Furthermore, unless cooled to 300° C., which is a temperature sufficiently lower than the temperature of the low temperature heat treatment described later, the temperature coefficient is not improved and high H _cJ cannot be obtained at high temperature. The cooling rate may be 5° C./minute or more, and the cooling rate may vary. For example, immediately after the start of cooling, the cooling rate may be changed to 35° C./minute or 30° C./minute as the temperature approaches 300° C. at a cooling rate of about 40° C./minute. Further, preferably, the cooling rate in the step of carrying out the high temperature heat treatment is 15° C./min or more and cooling to 300° C. This is because the temperature coefficient can be further improved.

[Step of carrying out low temperature heat treatment]
After the high temperature heat treatment, the RTB-based sintered magnet is subjected to a low temperature heat treatment of heating it to a temperature of 440° C. or higher and 550° C. or lower. If the temperature of the low temperature heat treatment step is lower than 440° C., the RT-Ga phase may not be generated and high H _cJ may not be obtained, and if it exceeds 550° C., high H _cJ may be obtained at high temperature. I may not be able to. The temperature of the step of carrying out the low temperature heat treatment is preferably 480° C. or higher and 550° C. or lower. The heating time is preferably 5 minutes or more and 500 minutes or less. Further, the cooling rate after heating at 440° C. or higher and 550° C. or lower is not particularly limited.

The step of performing the first RH diffusion treatment step, the step of performing the second RH diffusion treatment step, the step of performing the high temperature heat treatment, and the step of performing the low temperature heat treatment described above may be performed separately or continuously. You may go. For example, after performing the step of performing the first RH diffusion treatment and the step of performing the second RH diffusion treatment, the step of subsequently performing the high temperature heat treatment may be performed. After the step of performing the high-temperature heat treatment, the RTB-based sintered magnet cooled to 300° C. is heated to 440° C. or higher and 550° C. or lower to continue the low-temperature heat treatment after the step of performing the high-temperature heat treatment. The effect of the embodiment of the present disclosure can be obtained even if the step of carrying out is performed.

The obtained R-T-B based sintered magnet may be subjected to mechanical processing such as grinding in order to adjust the size of the magnet. In that case, the step of performing the high temperature heat treatment and the step of performing the low temperature heat treatment may be performed before or after machining. Further, the obtained RTB-based sintered magnet may be surface-treated. The surface treatment may be a known surface treatment, and for example, surface treatment such as Al vapor deposition, electric Ni plating or resin coating can be performed.

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

<Experimental Example 1>
R-T-B system using didymium alloy, Nd metal, Pr metal, ferroboron alloy, electrolytic Co, Al metal, Cu metal, Ga metal, ferrozirconium alloy and electrolytic iron (all metals are 99% or more in purity) Each metal and alloy are blended so that the sintered magnet material has the composition shown in Table 1, and the raw materials are melted and cast by the strip casting method, and a flake-shaped raw material alloy having a thickness of 0.2 to 0.4 mm. Got The obtained flaky raw material alloy was pulverized with hydrogen and then subjected to dehydrogenation treatment by heating and cooling in vacuum to 550° C. to obtain coarsely pulverized powder. Next, after adding 0.04% by mass of zinc stearate as a lubricant to 100% by mass of the roughly crushed powder and mixing the obtained roughly crushed powder with a jet mill device, a dry method was performed in a nitrogen stream. Pulverization gave a finely pulverized powder (alloy powder) having a particle size D ₅₀ of 4 μm. The particle size D ₅₀ is a volume-based median diameter obtained by a laser diffraction method using an air flow dispersion method.

Zinc stearate as a lubricant was added to the alloy powder in an amount of 0.05% by mass with respect to 100% by mass of the alloy powder, and the mixture was molded in a magnetic field to obtain a molded body. As the forming device, a so-called orthogonal magnetic field forming device (transverse magnetic field forming device) in which a magnetic field applying direction and a pressurizing direction are orthogonal to each other was used. The obtained molded body was held in vacuum at 1070°C to 1090°C for 4 hours depending on the composition and sintered to obtain an RTB-based sintered magnet material. The density of the RTB-based sintered magnet material was 7.5 Mg/m ³ or more. Table 1 shows the analysis results of the components of the obtained RTB-based sintered magnet material. In addition, each component in Table 1 was measured using the high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition, O (oxygen amount) is a gas melting-infrared absorption method, N (nitrogen amount) is a gas melting-heat conduction method, and C (carbon amount) is a combustion-infrared absorption method. Was measured. As shown in Table 1, the sample No. Each of 1-3, 4-6, and 7-9 has substantially the same composition except that the amount of B is different.

Next, a step of performing the first RH diffusion treatment was performed on the obtained RTB-based sintered magnet material. A plurality of DyFe alloys containing 60% by mass of Dy were prepared as RH diffusion sources. The DyFe alloy had a thickness of 1.5 mm to 2.5 mm. Further, a plurality of zirconia spheres having a diameter of 5 mm were prepared as stirring aid members.

The obtained RTB-based sintered magnet material, the RH diffusion source, and the stirring auxiliary member were charged into the processing container, the processing chamber was evacuated, and then Ar gas was introduced. Then, the processing chamber was heated and rotated to perform the first RH diffusion process. The treatment chamber was rotated at a peripheral velocity of 0.03 m/sec, the RH diffusion source and the RTB-based sintered magnet material were heated to 900° C. and held for 4 hours, and then cooled to room temperature. By the first RH diffusion treatment, 0.4% by mass of Dy was introduced into the RTB-based sintered magnet material. A second RH diffusion treatment was carried out on the RTB-based sintered magnet material after the first RH diffusion treatment in the same manner as the first RH diffusion treatment except that the temperature was 870°C.

Next, high temperature heat treatment was performed on the RTB-based sintered magnet after the second RH diffusion treatment. In the high temperature heat treatment, the RTB sintered magnet was heated to 800° C. and held for 2 hours, and then the RTB sintered magnet was cooled to room temperature. Cooling was performed by introducing an argon gas into the furnace, and the average cooling rate was 15° C./min. From less than 300° C. to room temperature, cooling was performed at an average cooling rate of 2° C./min. The variation in cooling rate (difference between the maximum value and the minimum value of the cooling rate) at each average cooling rate (15°C/min and 2°C/min) was within 2°C/min. Next, the RTB-based sintered magnet after the high temperature heat treatment was subjected to the low temperature heat treatment. In the low temperature heat treatment, the RTB-based sintered magnet after the high temperature heat treatment was heated to 500° C. and held for 2 hours, and then cooled to room temperature at a cooling rate of 20° C./min. The heating temperature of the RH diffusion source and the RTB-based sintered magnet material in the first and second RH diffusion treatments, and the heating temperature and cooling rate of the high temperature heat treatment and the low temperature heat treatment are A thermocouple was attached to the -TB sintered magnet for measurement.

Table 2 shows the results of measuring the magnetic properties of the obtained RTB-based sintered magnet. Table _"H cJ 23 ° C." in 2 is the value of _{H cJ} at room temperature (23 ° C.), _"B r 140 ° C." is the value of _{B r} at 140 ° C., _"H cJ 140 ° C." is 140 ° C. _Is the value of H _cJ . These _{B r,} the value of _{H cJ} is by machining the R-T-B based sintered magnet after the low temperature heat treatment step, processing the sample to 7 mm × 7 mm × 7 mm, was measured by BH tracer. Further, “ _{ΔH cJ} ” is a value obtained by subtracting the value of H _cJ of “H _cJ 140° C.” from the value of H _cJ of “H _cJ 23° C.”, and the smaller this value, the lower the H _cJ at high temperature. Is low. Furthermore, the temperature coefficient (β:23 to 140° C.) was determined as follows.
Temperature coefficient=( _{HcJ of} 140° C.− _{HcJ of} 23° C.)/ _{HcJ of} 23° _C./(140° C.−23° C.)×100%
The smaller the absolute value of the temperature coefficient, the better the temperature coefficient.

As shown in Table 2, the samples (No. 1, 2, ₄ , 5, ₇ , ₈ , _{10 to} 17) produced by the composition range and the production method of the present invention have an improved temperature coefficient of _HcJ and a high temperature. It is possible to obtain a high H _cJ with a small decrease in H _cJ . For example, sample No. Sample Nos. 1 to 3 of the present invention have almost the same composition except for the amount of B. Sample Nos. 1 and 2 of the comparative example are A high H _cJ is obtained at 140° C. as compared with 3 (B amount outside the range of the present invention). Further, _{ΔH cJ} and temperature coefficient are the same as those of the sample No. of the present invention. Sample Nos. 1 and 2 are comparative sample Nos. The value is smaller than 3 (the temperature coefficient is an absolute value). Sample No. The same applies to 4 to 6 and 7 to 9. In addition, the sample No. No. 10 to 17 have no comparative examples having almost the same composition, but all have an absolute value of the temperature coefficient of 0.54%/° C. or less (0.54%/° C. to 0.52%/° C.). Comparative sample No. The absolute value of the temperature coefficient is smaller than that of 3, 6, 9 (0.57%/°C to 0.56%/°C).
Further, as shown in Table 2, the range of B is preferably 0.82 to 0.88 mass% (the present invention other than sample Nos. 2, 10 and 11), and the absolute value of the temperature coefficient (0.53% /°C to 0.49%/°C) is small. In addition, sample No. having almost the same composition except for Ga. 12, 15 to 17, the Ga range is preferably 0.2 to 0.8 mass% (Sample Nos. 12, 15, and 17), and higher H _cJ is obtained at high temperature (140° C.). ing.

<Experimental example 2>
Sample No. of Experimental Example 1 using didymium alloy, Nd metal, Pr metal, ferroboron alloy, electrolytic Co, Al metal, Cu metal, Ga metal, ferrozirconium alloy and electrolytic iron (all metals have a purity of 99% or more). ． 5 was mixed so as to have the same composition as in Example 5, and an RTB-based sintered magnet material was obtained in the same manner as in Experimental Example 1. The density of the RTB-based sintered magnet material was 7.5 Mg/m ³ or more. The components and gas analysis results of the obtained RTB-based sintered magnet material are shown in Sample No. 1 of Experimental Example 1. It was equivalent to 5. Further, the obtained RTB-based sintered magnet material was subjected to the steps of performing the first RH diffusion treatment and the second RH diffusion treatment in the same manner as in Experimental Example 1.

The step of performing the high temperature heat treatment under the conditions shown in Table 3 is performed on the RTB-based sintered magnet after the step of performing the first RH diffusion treatment and the step of performing the second RH diffusion treatment, Further, the RTB-based sintered magnet after the high temperature heat treatment was subjected to the step of performing the low temperature heat treatment under the conditions shown in Table 3. The temperature (° C.) of the high temperature heat treatment and the low temperature heat treatment in Table 3 is the heating temperature of the RTB based sintered magnet, and the holding time (Hr) is the holding time of the heating temperature. The cooling rate (° C./minute) indicates the average cooling rate from the temperature at which the RTB-based sintered magnet was held to 300° C. after the holding time had elapsed. Further, in both the high temperature heat treatment and the low temperature heat treatment, cooling was performed at an average cooling rate of 7° C./minute from below 300° C. to room temperature. The cooling rate variation (difference between the maximum value and the minimum value of the cooling rate) at the average cooling rate (from the held temperature to 300°C and from less than 300°C to room temperature) was within 2°C/minute. Further, the heating temperature and cooling rate of the high temperature heat treatment and the low temperature heat treatment were measured by attaching a thermocouple to the RTB sintered magnet. By machining the R-T-B based sintered magnet of the low-temperature heat treatment Engineering, in the same manner as in Experimental Example 1, _"H cJ 23 ° C.", _"B r 140 ° C." measure _"H cJ 140 ° C." Then, in the same manner as in Experimental Example 1, “ _{ΔH cJ} ”and the temperature coefficient were obtained. The measurement results are shown in Table 4.

As shown in Table 4, after heating the RTB based sintered magnet material to a temperature of 730° C. or more and 850° C. or less, high temperature heat treatment of cooling it to 300° C. at 5° C./min or more is performed, and after the high temperature heat treatment, All of the examples (the present invention in Table 4) in which the RTB-based sintered magnet was subjected to the low-temperature heat treatment of heating it to a temperature of 440° C. or higher and 550° C. or lower were higher at 140° C. than the comparative examples. H _cJ is obtained, and the absolute value of the temperature coefficient is small. On the other hand, the sample No. 1 whose temperature of the high temperature heat treatment is out of the range of the present invention. 31 or the sample No. 31 having a cooling rate outside the scope of the present invention in the step of performing the high temperature heat treatment. 26 or the sample No. 6 having a low temperature heat treatment temperature outside the range of the present invention. _No. 30 has a large absolute value of the temperature coefficient of H _cJ as compared with the present invention, and it is not possible to obtain high H _cJ at higher temperatures. Further, as shown in Table 4, the cooling rate in the step of performing the high temperature heat treatment is preferably 15° C./min or more (the present invention other than sample No. 23), and the absolute value of the temperature coefficient (0.53%/° C.). .About.0.52%/° C.) is small.

Claims (6)

R: 29.5 mass% or more and 35.0 mass% or less (R is at least one kind of rare earth element and always contains at least one of Nd and Pr),
B: 0.80 mass% or more and 0.90 mass% or less,
Ga: 0.1% by mass or more and 0.8% by mass or less,
M: 0% by mass or more and 2% by mass or less (M is at least one of Cu, Al, Nb, and Zr)
A step of preparing an RTB-based sintered magnet material containing the balance T (T is at least one of transition metal elements and always contains Fe, and 10% or less of Fe can be replaced with Co) and unavoidable impurities. When,
An RH diffusion source containing a heavy rare earth element RH (RH is at least one of Dy and Tb) and the R-T-B based sintered magnet material are arranged in a processing container, and the RH diffusion source and the R- A step of performing a first RH diffusion treatment of heating the TB-based sintered magnet material at a temperature of 760° C. or higher and 1000° C. or lower;
Second heating to the RTB based sintered magnet material after the first RH diffusion treatment at a temperature of 750° C. or higher and lower than 1000° C. and a temperature lower than the temperature of the first RH diffusion treatment. Performing a RH diffusion process of
After heating the RTB based sintered magnet after the second RH diffusion treatment at 730° C. or higher and 850° C. or lower and at a temperature lower than the temperature of the second RH diffusion treatment, 5° C. A step of performing a high temperature heat treatment of cooling to 300° C. at a cooling rate of not less than 1 minute/minute
A step of performing a low temperature heat treatment of heating the RTB-based sintered magnet after the high temperature heat treatment at a temperature of 440° C. or higher and 550° C. or lower;
The manufacturing method of the RTB type|system|group sintered magnet containing. The R-T-B system sintered magnet according to claim 1, wherein M of the R-T-B system sintered magnet material always contains Cu and Cu: 0.05 mass% or more and 0.30 mass% or less. Manufacturing method. The method for producing an R-T-B system sintered magnet according to claim 1 or 2, wherein the R-T-B system sintered magnet material is R: 30.0 mass% or more and 34.0 mass% or less. The said RTB type|system|group sintered magnet raw material is B: 0.82 mass% or more and 0.88 mass% or less, The RTB type|system|group sintered magnet of any one of Claims 1-3. Production method. The R-T-B system sintered magnet material according to claim 1, wherein the R-T-B system sintered magnet material is Ga: 0.2% by mass or more and 0.8% by mass or less. Production method. The method for manufacturing an RTB-based sintered magnet according to claim 1, wherein a cooling rate in the step of performing the high-temperature heat treatment is 15° C./min or more.