JP6922616B2 - Diffusion source - Google Patents

Description

The present disclosure relates to a diffusion source used in the production of RTB-based sintered magnets (R is a rare earth element, T is Fe or Fe and Co).

R _{-TB-based sintered magnets whose main phase is R 2} T ₁₄ B type compounds are known as the most high-performance magnets among permanent magnets, such as voice coil motors (VCMs) for hard disk drives and It is used in various motors such as motors for mounting on hybrid vehicles and home appliances.

_{Since the intrinsic coercive force H cJ} (hereinafter, simply referred to as "H _cJ ") of the RTB-based sintered magnet decreases at a high temperature, irreversible thermal demagnetization occurs. In order to avoid irreversible thermal demagnetization, it is required to maintain _{high HcJ} even at high temperatures when used for motors and the like.

It is known that _{H cJ of} R-TB-based sintered magnets is _{improved by substituting a part of R in the R 2} T ₁₄ B type compound phase with the heavy rare earth element RH (Dy, Tb). .. _{In order to obtain high H cJ} at high temperature, it is effective to add a large amount of heavy rare earth element RH to the RTB-based sintered magnet. However, the R-T-B based sintered magnet, replacing light rare-earth element RL as R a (Nd, Pr) in the heavy rare-earth element _RH, while _{the H cJ} is improved, the residual magnetic flux density _{B r} (hereinafter, simply " There is a problem that (denoted as "_{Br") is reduced.} Further, since the heavy rare earth element RH is a rare resource, it is required to reduce the amount used.

In recent years, so as not to reduce the B _r, to improve the H _cJ of the R-T-B based sintered magnets have been studied with less heavy rare-earth element RH. For example, fluorides or oxides of the heavy rare earth element RH and various metal M or M alloys can be present on the surface of the sintered magnet individually or mixed and heat-treated in that state to improve the coercive force. It has been proposed to diffuse the contributing heavy rare earth element RH into the magnet.

Patent Document ^1, the surface of the ^R 1 -T-B based sintered body as a main phase an _R 1 _{2 T 14} B type compound, a step of the presence of powder of an alloy containing ^{R 2} and M, heat treatment It discloses a method for manufacturing a rare-earth magnet and a step of diffusing from the alloy powder R ² element in the interior of the sintered body by. Here, R1 is one or more elements selected from rare earth elements including Sc and Y, and T is Fe and / or Co. Further, R ² is one or more kinds of elements selected from rare earth elements including Sc and Y, and M is a metal element such as B, C, Al, Si and Ti.

Japanese Unexamined Patent Publication No. 2011-14668

In the production method disclosed in Patent Document 1, a quenching alloy powder is used as the powder of the alloy containing ^{R 2 and M.} This quenching alloy powder contains microcrystalline or amorphous alloy having an average particle size of 3 μm or less.

The present disclosure realizes that at least one of Dy and Tb is diffused more uniformly in a method using a diffusion source containing at least one of Dy and Tb.

In an exemplary embodiment, the diffusion source according to the present disclosure is an alloy powder containing 40% by mass or more of a rare earth element R1 that always contains at least one of Dy and Tb, and the alloy powder is an average crystal. It is composed of particles of an intermetallic compound having a particle size of more than 3 μm, and the cross section of the particles is circular.

In certain embodiments, the oxygen content of the diffusion source is 0.5% by mass or more and 4.0% by mass or less.

In certain embodiments, the powder of the alloy is one or more selected from the group consisting of RHRLM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Tb and Dy. RL is at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu, and always contains at least one of Pr and Nd. One or more selected from Fe, Ga, Co, Ni, and Al, M1 = M2 may be used) powder.

In certain embodiments, the powder of the alloy is one or more selected from the group consisting of RHM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Tb and Dy. M1 and M2 are powders of one or more selected from Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2 may be used).

According to the embodiment of the present disclosure, since the structure of the diffusion source containing the heavy rare earth element RH is modified, the _HcJ of the RTB-based sintered magnet is improved while suppressing the variation in magnetic characteristics. Will be possible.

FIG. 5 is a cross-sectional view schematically showing a part of the prepared RTB-based sintered magnet material in the embodiment of the present disclosure. FIG. 5 is a cross-sectional view schematically showing a part of an RTB-based sintered magnet material in contact with a diffusion source in the embodiment of the present disclosure.

As used herein, the rare earth element refers to at least one element selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoids. Here, lanthanoid is a general term for 15 elements from lanthanum to lutetium. R is a rare earth element, and R1 is a rare earth element that always contains at least one of Dy and Tb.

An exemplary embodiment of a diffusion source according to the present disclosure
(1) An alloy powder containing 40% by mass or more of the rare earth element R1 that always contains at least one of Dy and Tb.
(2) The powder of the alloy is composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm.
(3) The cross section of the particles is circular.

Since the diffusion source is composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm, it is possible to improve the _{HcJ of the RTB-based sintered magnet while suppressing variations in characteristics.} ..

In the present disclosure, the diffusion source is a powder produced by the atomization method. Therefore, the cross section of the powder particles constituting the diffusion source is circular.

Hereinafter, embodiments of the present disclosure will be described. In addition, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art. The inventors provide the accompanying drawings and the following description to allow those skilled in the art to fully understand the present disclosure. These are not intended to limit the subject matter described in the claims.

<Diffusion source>
[alloy]
The alloy is an alloy containing 40% by mass or more of the rare earth element R1 that always contains at least one of Dy and Tb. Typical examples of alloys are RHM1M2 alloy and RHRLM1M2 alloy. Examples of these RH alloys will be described below.

(RHM1M2 alloy)
Examples of alloys are, for example, one or more selected from the group consisting of, for example, RHM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy must be used. Including, M1 and M2 are one or more selected from Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2 may be used).

Typical examples of the RHM1M2 alloy are DyFe alloy, DyAl alloy, DyCu alloy, TbFe alloy, TbAl alloy, TbCu alloy, DyFeCu alloy, TbCuAl alloy and the like.

(RHRLM1M2 alloy)
Another example of the alloy is one or more selected from the group consisting of RHRLM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy is used. Always included, RL is at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, and always contains at least one of Pr and Nd, M1 and M2 are Cu, Fe, Ga, One or more selected from Co, Ni, and Al, M1 = M2 may be used). Typical examples of RHRLM1M2 alloys are TbNdCu alloys, DyNdCu alloys, TbNdFe alloys, DyNdFe alloys, TbNdCuAl alloys, DyNdCuAl alloys, TbNdCuCo alloys, DyNdCuCo alloys, TbNdCoGa alloys, DyNdCoGa alloys, DyNdCoGa alloys, TbCdPr be. The alloy is not limited to the above-mentioned RHM1M2 alloy and RHRLM1M2 alloy. An alloy that always contains at least one of Dy and Tb and that contains 40% by mass or more of the rare earth element R1 may contain other elements and impurities.

[Alloy powder]
In the present disclosure, the alloy powder is a powder produced by the atomizing method. The powder produced by the atomizing method is sometimes referred to as "atomized powder".

The atomizing method is one of the powder producing methods also called the molten metal spraying method, and includes known atomizing methods such as a gas atomizing method and a plasma atomizing method. For example, according to the gas atomization method, a metal or alloy is melted in a melting furnace to form a molten metal, and the molten metal is sprayed into an atmosphere of an inert gas such as nitrogen or argon to solidify. Since the sprayed molten metal scatters as fine droplets, it is cooled at a high speed and solidifies. Since each of the powder particles produced has a spherical shape, it is not necessary to perform mechanical pulverization thereafter. The size of the powder particles produced by the atomization method is distributed in the range of, for example, 10 μm to 200 μm (for example, confirmed by sieving). In addition, the cross section of the particles in the alloy powder (diffusion source) is circular because it is produced by the atomizing method. In the present disclosure, "the cross section of the particle is circular" means that the cross section of the particle in the alloy powder (diffusion source) is circular when observed. Further, the circular shape in the present disclosure means that the average roundness is in the range of 0.80 to 1.00. The roundness in the present disclosure is a value obtained by dividing (4π × area) of a target figure (powder particles of atomized powder) by (square of the perimeter). Perform these calculations 10 times (examine 10 powder particles) and obtain the average value to obtain the average value of roundness, and the average value of roundness is in the range of 0.80 to 1.00. Check if there is. The roundness in the present disclosure is 1.00 for a circle, and the value becomes smaller as the shape becomes elongated.

According to the atomizing method, the droplets of the molten alloy to be sprayed are small, and the surface area relative to the weight of each droplet is large, so that the cooling rate is high. Therefore, the powder particles formed are amorphous or microcrystalline.

When the molten alloy is rapidly cooled and solidified by the atomization method, it is difficult to strictly control the cooling rate. Therefore, the structure of the structure tends to vary from powder particle to powder particle. For example, the size of minute crystal grains generated in powder particles can vary greatly from particle to particle. Specifically, particles having an average crystal grain size of 1 μm are formed, or particles having an average crystal grain size of 3 μm are formed. If such a variation in the structure of the structure and the average crystal grain size occurs, the melting temperature of the phases constituting the particles and the rate of supplying Dy and Tb as a diffusion source will vary in the diffusion step described later. Such variations ultimately lead to variations in magnet characteristics.

In order to solve such a problem, in the embodiment of the present disclosure, the alloy powder (diffusion source) is composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm. As a result, the crystallinity of the powder particles constituting the alloy powder can be modified, and a diffusion source having excellent uniformity can be obtained. Then, by using the diffusion source, it is possible to suppress variations in magnetic characteristics in the diffusion step. Here, the intermetallic compound phase refers to the entire crystal grains of the intermetallic compound in the powder particles constituting the diffusion source. When there are a plurality of types of intermetallic compounds in the powder particles constituting the diffusion source, it means the entire crystal grains of the intermetallic compound having the highest content. Further, it is not always necessary that all of the alloy powders constituting the diffusion source are composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm. The effect of the present invention can be obtained if 80% by volume or more of the diffusion source (the entire alloy powder) is composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm.

In order to obtain such a configuration, for example, the heat treatment described below is performed.

[Heat treatment of alloy powder]
In one embodiment of the present disclosure, the alloy powder is heat-treated at a temperature 250 ° C. lower or lower than the melting point of the alloy powder.

The alloy powder constituting the diffusion source by this heat treatment is composed of particles having an average crystal grain size of more than 3 μm. For example, the heat treatment time can be 30 minutes or more and 10 hours or less.

If the heat treatment temperature for the alloy powder is less than 250 ° C. lower than the melting point of the alloy powder, the temperature is too low and the average crystal grain size of the intermetallic compound in the powder particles constituting the alloy powder becomes 3 μm or less. There is a possibility that the crystallinity will not be modified, and if the melting point is exceeded, the powders may be welded together and the diffusion treatment may not be efficient. Preferably, the average particle size of the powder particles constituting the diffusion source is 3.5 μm or more and 20 μm or less.

In this heat treatment, it is preferable that the oxygen content in the diffusion source after the heat treatment is 0.5% by mass or more and 4.0% by mass or less by adjusting the atmosphere in the furnace. By intentionally oxidizing the entire surface of the alloy particles constituting the atomized powder, it is possible to reduce the characteristic variation for each particle that may occur due to the difference in contact time and humidity between the powder particle and the atmosphere, and the diffusion step. The variation in magnetic characteristics in the above can be further reduced. It also reduces the possibility of ignition in contact with oxygen in the atmosphere. Therefore, quality control of the diffusion source becomes easy.

The diffusion source is in the powder state in the embodiment. The particle size of the diffusion source in powder form can be adjusted by sieving. Further, if the amount of powder excluded by sieving is within 10% by mass, the effect is small, so that the powder may be used without sieving.

Also, the diffusion source in powder form can be granulated with a binder, if desired.

Further, in order to obtain a diffusion source composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm, a method other than the above-mentioned heat treatment may be used. For example, particles of an intermetallic compound having an average crystal grain size of more than 3 μm may be obtained by adjusting the cooling conditions, holding temperature, and the like for the alloy powder obtained by the atomizing method.

[Diffusion aid]
The diffusion source produced by performing the above heat treatment on the alloy powder may further contain the alloy powder that functions as a diffusion aid. An example of such an alloy is the RLM1M2 alloy. RL is one or more selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu, and always contains at least one of Pr and Nd. M1 and M2 are Cu, Fe, Ga, Co, and Ni. , One or more selected from Al, and M1 = M2 may be used. Typical examples of the RLM1M2 alloy are NdCu alloy, NdFe alloy, NdCuAl alloy, NdCuCo alloy, NdCoGa alloy, NdPrCu alloy, NdPrFe alloy and the like. The powders of these alloys are used by mixing with the powders of the above alloys. A plurality of types of RLM1M2 alloy powders may be mixed with the RH alloy powder.

The method for producing the powder of the RLM1M2 alloy is not particularly limited. When manufactured by the quenching method or the casting method, it is preferable to set M1 ≠ M2 in order to improve the pulverizability, and to use, for example, an alloy of ternary system or more such as NdCuAl alloy, NdCuCo alloy, and NdCoGa alloy. The particle size of the RLM1M2 alloy powder is, for example, 200 μm or less, and the smaller one is about 10 μm.

When the diffusion source is mixed with the powder of the RLM1M2 alloy and used, it may be difficult to mix them uniformly with each other by mixing only these powders. The reason for this is that alloy powders are generally smaller in particle size than RLM1M2 alloy powders. Therefore, it is preferable to granulate the powder of the RLM1M2 alloy, the powder of the alloy, and the binder. By using such a granulated product, there is an advantage that the blending ratio of the RLM1M2 alloy powder and the alloy powder can be made uniform in the entire powder. Further, it can be uniformly present on the magnet surface.

As the binder, it is preferable that the powder particles constituting the diffusion source have smooth and fluidity without sticking or agglutinating when the dried or mixed solvent is removed. Examples of the binder include PVA (polyvinyl alcohol) and the like. As appropriate, an aqueous solvent such as water or an organic solvent such as NMP (n-methylpyrrolidone) may be used for mixing. The solvent evaporates and is removed in the process of granulation described later.

Any method of granulation with the binder may be used. For example, a rolling granulation method, a fluidized bed granulation method, a vibration granulation method, an impact method in a high-speed air flow (hybridization), a method of mixing powder and a binder, solidifying and then crushing, and the like can be mentioned.

In the embodiment of the present disclosure, it is not necessarily excluded that a powder other than the above powder (third powder) is present on the surface of the RTB-based sintered magnet material, but the third powder is in the diffusion source. Care must be taken not to prevent the diffusion of at least one of Dy and Tb into the inside of the RTB-based sintered magnet material. It is desirable that the mass ratio of the "alloy containing at least one of Dy and Tb" to the entire powder existing on the surface of the RTB-based sintered magnet material is 70% or more.

A method of using the diffusion source according to the embodiment of the present disclosure will be described. The usage method includes the following steps.
1. 1. Step of preparing RTB-based sintered magnet material 2. Step of preparing a diffusion source 3. Diffusion process

1. 1. Step of preparing R-TB-based sintered magnet material R-TB-based sintered magnet material (R is a rare earth element, T is a rare earth element, T is a target in which the heavy rare earth element RH, which is at least one of Dy and Tb, is diffused. Fe or Fe and Co) are prepared. As the RTB-based sintered magnet material, a known magnet base material can be used.

The RTB-based sintered magnet material has, for example, the following composition.
Rare earth element R: 12-17 atomic%
B (part of B (boron) may be replaced with C (carbon)): 5-8 atomic%
Selected from the group consisting of additive elements M (Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi. At least one): 0-5 atomic%
T (a transition metal element mainly containing Fe, which may contain Co) and unavoidable impurities: Remaining Here, the rare earth element R is at least one selected from the light rare earth elements RL (Nd, Pr). Although it is an element), it may contain a heavy rare earth element. When a heavy rare earth element is contained, it is preferable to contain at least one of Dy and Tb.

The RTB-based sintered magnet base material having the above composition can be produced by any production method. The RTB-based sintered magnet base material may be in a state of being sintered, or may be cut or polished. The shape and size of the RTB-based sintered magnet base material are arbitrary.

2. Step of preparing the diffusion source The above-mentioned diffusion source is prepared. Since the diffusion source has already been explained, the description thereof will be omitted.

3. 3. Diffusion step In order to heat the RTB-based sintered magnet material and diffusion source to a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet material, first, the RTB-based sintered magnet material And the diffusion source is placed in the processing vessel. At this time, it is preferable that the RTB-based sintered magnet material and the diffusion source come into contact with each other in the processing container.

[Arrangement]
Any form may be used in which the RTB-based sintered magnet material and the diffusion source are brought into contact with each other. For example, a method of adhering a powdery diffusion source to an RTB-based sintered magnet material coated with an adhesive by using a fluid immersion method, or R in a processing container containing the powdery diffusion source. Examples include a method of dipping the −TB based sintered magnet material and a method of sprinkling a powdery diffusion source on the R—TB based sintered magnet material. Further, the processing container containing the diffusion source may be subjected to vibration, sway, or rotation, or the powder of the diffusion source may be made to flow in the processing container.

FIG. 1A is a cross-sectional view schematically showing a part of the RTB-based sintered magnet material 100 that can be used in the method for producing the RTB-based sintered magnet material according to the present disclosure. In the drawing, the upper surface 100a and the side surfaces 100b and 100c of the RTB-based sintered magnet material 100 are shown. The shape and size of the RTB-based sintered magnet material used in the manufacturing method of the present disclosure is not limited to the shape and size of the RTB-based sintered magnet material 100 shown. The upper surface 100a and the side surfaces 100b and 100c of the RTB-based sintered magnet material 100 shown are flat, but the surface of the RTB-based sintered magnet material 100 has irregularities or steps. It may be curved or curved.

FIG. 1B is a cross-sectional view schematically showing a part of the RTB-based sintered magnet material 100 in a state where the powder particles 30 constituting the diffusion source are located on the surface. The powder particles 30 constituting the diffusion source located on the surface of the RTB-based sintered magnet material 100 are formed on the surface of the RTB-based sintered magnet material 100 via an adhesive layer (not shown). May adhere to. Such an adhesive layer can be formed by being applied to the surface of the RTB-based sintered magnet material 100, for example. If the adhesive layer is used, the powder of the diffusion source can be applied to a plurality of regions (for example, the upper surface 100a and the side surface 100b) having different normal directions without changing the orientation of the RTB-based sintered magnet material 100. It can be easily adhered in one coating process.

Examples of the adhesive that can be used include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and PVP (polyvinylpyrrolidone). When the pressure-sensitive adhesive is a water-based pressure-sensitive adhesive, the RTB-based sintered magnet material may be preheated before coating. The purpose of preheating is to remove excess solvent to control the adhesive strength and to evenly adhere the adhesive. The heating temperature is preferably 60 to 100 ° C. This step may be omitted in the case of a highly volatile organic solvent-based pressure-sensitive adhesive.

Any method may be used to apply the adhesive to the surface of the RTB-based sintered magnet material. Specific examples of coating include a spray method, a dipping method, and coating with a dispenser.

In one preferred embodiment, the pressure-sensitive adhesive is applied to the entire surface (entire surface) of the RTB-based sintered magnet material. It may be attached to a part of the surface of the RTB-based sintered magnet material instead of the entire surface. In particular, when the thickness of the RTB-based sintered magnet material is thin (for example, about 2 mm), the diffusion source is on one surface having the largest area among the surfaces of the RTB-based sintered magnet material. At least one of Dy and Tb can be diffused over the entire magnet only by adhering the powder of the above, and HcJ may be improved.

As described above, the powder particles constituting the diffusion source in contact with the surface of the RTB-based sintered magnet material 100 have a structure having excellent uniformity. Further, as an embodiment, since the entire surface of the alloy particles is oxidized, the possibility that the powder particles come into contact with oxygen in the atmosphere and ignite is reduced, and the variation in characteristics due to the contact with the atmosphere is also reduced. doing. Therefore, when heating for diffusion described later is performed, at least one of Dy and Tb contained in the diffusion source can be efficiently diffused from the surface of the RTB-based sintered magnet material to the inside without waste. can.

The amount of at least one of Dy and Tb contained in the diffusion source located on the magnet surface is in the range of, for example, 0.5 to 3.0% by mass ratio with respect to the RTB-based sintered magnet material. Can be set to. It may be set to be in the range of 0.7 to 2.0% in order to obtain a higher H _cJ.

The amount of at least one of Dy and Tb contained in the diffusion source depends not only on the concentration of Dy and Tb of the powder particles but also on the particle size of the powder particles constituting the diffusion source. Therefore, it is possible to adjust the amount of Dy and Tb diffused by adjusting the particle size of the powder particles constituting the diffusion source while keeping the concentrations of Dy and Tb constant.

[Heat treatment]
The temperature of the heat treatment for diffusion is not more than the sintering temperature of the RTB-based sintered magnet material (specifically, for example, 1000 ° C. or less). When the diffusion source contains a powder such as an RLM1M2 alloy, the temperature is higher than the melting point of the alloy, for example, 500 ° C. or higher. The heat treatment time is, for example, 10 minutes to 72 hours. Further, after the heat treatment, further heat treatment at 400 to 700 ° C. for 10 minutes to 72 hours may be performed if necessary.

By such heat treatment, at least one of Dy and Tb contained in the diffusion source can be diffused from the surface of the RTB-based sintered magnet material to the inside.

(Experimental Example 1)
First, by a known method, composition ratio Nd = 23.4, Pr = 6.2, B = 1.0, Al = 0.4, Cu = 0.1, Co = 1.5, balance Fe (mass%). RTB-based sintered magnet material was produced. The dimensions of the RTB-based sintered magnet material were 5.0 mm in thickness × 7.5 mm in width × 35 mm in length.

Next, an alloy powder having the composition shown in Table 1 was prepared by an atomizing method. The particle size of the obtained alloy powder was 106 μm or less (confirmed by sieving). Next, the powder of the alloy is heat-treated under the conditions (temperature and time) shown in Table 1 (however, No. 1 is not heat-treated), so that the powder of the alloy is diffused from the diffusion source (No. 1 to 20). ) Was obtained. Further, by adjusting the atmosphere in the furnace during the heat treatment, the oxygen contents of the diffusion sources (Nos. 1 to 20) were prepared so as to be approximately the amounts shown in Table 1. The oxygen content of the diffusion source is shown in Table 1. The composition of the alloy powder in Table 1 was measured using radio frequency inductively coupled plasma emission spectroscopy (ICP-OES). The oxygen content of the diffusion source was measured using a gas analyzer by the gas melting-infrared absorption method.

In addition, the average crystal grain size of the intermetallic compound phase in the obtained diffusion source was measured by the following method. First, the cross section of the powder particles constituting the diffusion source is observed with a scanning electron microscope (SEM) and distinguished from the contrast, and the composition of each phase is analyzed using energy dispersive X-ray spectroscopy (EDX) to obtain an intermetallic compound phase. Identified. Next, using image analysis software (Scandium), the intermetallic compound phase having the highest area ratio was designated as the intermetallic compound phase having the highest content, and the crystal grain size of the intermetallic compound phase was determined. Specifically, the number of crystal grains and the total area of crystal grains in the intermetallic compound phase are obtained using image analysis software (Scandium), and the average area is calculated by dividing the total area of the obtained crystal grains by the number of crystal grains. I asked. Then, the crystal grain size D was obtained from the average area obtained by Equation 1.

Here, D is the crystal grain size and S is the average area.

These operations were performed 5 times (5 powder particles were examined), and the average value was obtained to determine the average crystal grain size of the intermetallic compound phase at the diffusion source. The results are shown in the average crystal grain size in Table 1. In addition, No. In No. 1, since the diffusion source was not heat-treated, the crystal grain size of the intermetallic compound phase was too small (fine crystal grains of 1 μm or less) and could not be measured.

Next, it was confirmed whether the powder particles constituting the diffusion source were circular. Observe the cross section of the powder particles constituting the diffusion source with a scanning electron microscope (SEM), and use image analysis software (Scandium) to measure (4π x area) of (powder particles) with (square of the surrounding length). The divided value was calculated. These calculations were performed 10 times (10 powder particles were examined), and the average value was obtained to obtain the average value of roundness. No. 1-No. It was confirmed that the average value of roundness at 20 was in the range of 0.99 to 1.00, and the cross section of the particles was circular (within the range of 0.80 to 1.00 μm).

Next, an adhesive was applied to the RTB-based sintered magnet material. As a coating method, the RTB-based sintered magnet material was heated to 60 ° C. on a hot plate, and then an adhesive was applied to the entire surface of the RTB-based sintered magnet material by a spray method. PVP (polyvinylpyrrolidone) was used as the pressure-sensitive adhesive.

Next, the No. 1 in Table 1 was applied to the RTB-based sintered magnet material coated with the adhesive. 1 to 20 diffusion sources were attached. 50 RTB-based sintered magnet materials to which the diffusion source was attached were prepared for each type of diffusion source (No. 1 to 20). The method of attachment is to spread the diffusion source (alloy powder) in the container, cool the RTB-based sintered magnet material coated with the adhesive to room temperature, and then set the diffusion source in the container to the RTB-based. It was attached to the entire surface of the sintered magnet material so as to be sprinkled.

Next, the RTB-based sintered magnet material and the diffusion source are placed in the processing container and heated at 900 ° C. (below the sintering temperature) for 8 hours to obtain Dy and Tb contained in the diffusion source. A diffusion step was performed in which at least one of the above was diffused from the surface of the RTB-based sintered magnet material to the inside. A cubic body having a thickness of 4.5 mm, a width of 7.0 mm, and a length of 7.0 mm is cut out from the central portion of the RTB-based sintered magnet after diffusion, and is used for each type of diffusion source (every No. 1 to 20). The coercive force was measured by 10 BH tracers, and the value obtained by subtracting the minimum value of the coercive force from the maximum value of the obtained coercive force was obtained as the magnetic characteristic variation ( _{ΔH cJ} ). _{The values of ΔH cJ} are shown in Table 1.

As shown in Table 1, No. 1 in which the alloy powder was not heat-treated. No. 1 (Comparative Example) and No. 1 in which the heat treatment temperature is outside the scope of the present disclosure. In each of the examples of the present invention (No. 2 to 5, No. 7 to 20) as compared with 6 (Comparative Example), ΔH _cJ is less than half, and the variation in magnetic characteristics in the diffusion step is suppressed. Further, the oxygen content of the diffusion source is 0.5% by mass or more and 4.0% by mass or less. _{In Nos.} 7 to 10, ΔH cJ is 18 kA / m or less, and the variation in magnetic characteristics in the diffusion step is further suppressed.

_{The diffusion source according to the embodiment of the present disclosure can improve the HcJ} of the RTB-based sintered magnet by using a smaller amount of the heavy rare earth element RH, and thus manufactures a rare earth sintered magnet that requires a high coercive force. Can be used for.

30 Powder particles constituting the diffusion source 100 RTB-based sintered magnet material 100a Top surface of RTB-based sintered magnet material 100b Side surface of RTB-based sintered magnet material 100c RT- Side surface of B-based sintered magnet material

Claims (4)

An alloy powder containing 40% by mass or more of the rare earth element R1 which is at least one of Dy and Tb.
The alloy powder is composed of particles of an intermetallic compound having an average crystal grain size of more than 3 μm.
A diffusion source in which the cross section of the particles is circular. The diffusion source according to claim 1, wherein the oxygen content is 0.5% by mass or more and 4.0% by mass or less. The powder of the alloy is one or more selected from the group consisting of RHRLM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy must be used. Including, RL is one or more selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, and always contains at least one of Pr and Nd, M1 and M2 are Cu, Fe, Ga, Co. , Ni, Al, one or more selected from, M1 = M2), the diffusion source according to claim 1 or 2. The powder of the alloy is one or more selected from the group consisting of RHM1M2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy must be used. The diffusion source according to claim 1 or 2, wherein M1 and M2 are powders of one or more selected from Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2).

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