JP7000775B2 - Manufacturing method of RTB-based sintered magnet - Google Patents

Description

The present disclosure relates to a method for producing an RTB-based sintered magnet (R is a rare earth element, T is Fe or Fe and Co).

RTB _- based sintered magnets whose main phase is R2T _14B type compounds are known as the highest 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.

In the RTB-based sintered magnet, the intrinsic coercive force H _cJ (hereinafter, simply referred to as “H _cJ ”) decreases at a high temperature, so that irreversible thermal demagnetization occurs. In order to avoid irreversible thermal demagnetization, it is required to maintain high _HcJ even at high temperature when used for motors and the like.

It is known that the RTB-based sintered magnet improves _HcJ by substituting a part of R in the _R2 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, in the RTB-based sintered magnet, when the light rare earth element RL (Nd, Pr) is replaced with the heavy rare earth element RH as _R , H _cJ is improved, while the residual magnetic flux density Br (hereinafter, simply " There is a problem that (expressed as _Br ) decreases. Further, since the heavy rare earth element RH is a rare resource, it is required to reduce the amount used thereof.

Therefore, in recent years, it has been studied to improve the _HcJ of the _RTB -based sintered magnet by using a smaller amount of the heavy rare earth element RH so as not to lower Br. For example, fluorides or oxides of the heavy rare earth element RH and various metal Ms or M alloys can be present on the surface of a 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 describes a step of allowing an alloy powder containing ^R2 and M to exist on the surface of an ^R1 _- TB-based sintered body having an R12 T ₁₄ B ^- type compound as a main phase, and a heat treatment. Discloses a method for producing a rare earth magnet, which comprises a step of diffusing the ^R2 element from the alloy powder into the inside of the sintered body. Here, R ¹ 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 ^R2 and M. This quenching alloy powder contains a microcrystalline or amorphous alloy having an average particle size of the R2 ^- M intermetallic compound phase of 3 μm or less.

The present disclosure realizes reduction of magnetic property (H _cJ ) variation between individual magnets by more uniformly diffusing at least one of Dy and Tb in a method using a diffusion source containing at least one of Dy and Tb.

In the method for manufacturing an RTB-based sintered magnet according to the present disclosure, in an exemplary embodiment, an R1-TB-based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co) is prepared. The step of preparing an alloy containing 40% by mass or more of the rare earth element R2 that always contains at least one of Dy and Tb, and the step of preparing the alloy at a temperature 270 ° C. lower than the melting point of the alloy and below the melting point. The step of obtaining a diffusion source by performing heat treatment at a temperature and crushing the alloy after the heat treatment, and the R1-TB-based sintered magnet material and the diffusion source are arranged in a processing container, and the R1-T- The B-based sintered magnet material and the diffusion source are heated to a temperature equal to or lower than the sintering temperature of the R1-TB-based sintered magnet material, and at least one of Dy and Tb contained in the diffusion source is subjected to the R1-. The alloy includes a diffusion step of diffusing from the surface of the TB-based sintered magnet material to the inside, and the alloy is an alloy produced by a melt spinning method.

The method for producing an RTB-based sintered magnet according to the present disclosure is, in another exemplary embodiment, an R1-TB-based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co. ), A step of crushing an alloy containing 40% by mass or more of the rare earth element R2 containing at least one of Dy and Tb to prepare an alloy powder, and a step of preparing the alloy powder with the alloy powder. A step of performing heat treatment at a temperature 270 ° C. lower than the melting point of the powder and lower than the melting point to obtain a diffusion source from the powder of the alloy, and a processing container for the R1-TB-based sintered magnet material and the diffusion source. The R1-TB based sintered magnet material and the diffusion source are heated to a temperature equal to or lower than the sintering temperature of the R1-TB based sintered magnet material, and are included in the diffusion source. The alloy includes a diffusion step of diffusing at least one of Dy and Tb from the surface of the R1-TB-based sintered magnet material to the inside, and the alloy is an alloy produced by a melt spinning method.

In certain embodiments, 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 Tb and Dy. RL always contains 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, One or more selected from Ga, Co, Ni, and Al, M1 = M2 may be used).

In certain embodiments, 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 Tb and Dy. M1 and M2, which always include one, are 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 at least one of Dy and Tb is modified, _HcJ of the RTB-based sintered magnet can be obtained while suppressing the variation in the magnetic characteristics. It will be possible to improve.

In the embodiment of the present disclosure, it is sectional drawing which shows a part of the prepared R1-TB system sintered magnet material schematically. In the embodiment of the present disclosure, it is sectional drawing which shows typically a part of the R1-TB system sintered magnet material which is in contact with a diffusion source.

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. R1 and R are rare earth elements, and R2 is a rare earth element that always contains at least one of Dy and Tb.

An exemplary embodiment of the method for manufacturing an RTB-based sintered magnet according to the present disclosure is as follows.
1. 1. The process of preparing the R1-TB based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co), and
2. 2. A step of preparing an alloy containing 40% by mass or more of the rare earth element R2 that always contains at least one of Dy and Tb, and
3. 3. A step of heat-treating the alloy at a temperature equal to or higher than 270 ° C. lower than the melting point of the alloy and lower than the melting point, and crushing the heat-treated alloy to obtain a diffusion source.
4. The R1-TB based sintered magnet material and the diffusion source are arranged in a processing container, and the R1-TB based sintered magnet material and the diffusion source are used as the R1-TB based sintered magnet material. It includes a diffusion step of heating to a temperature equal to or lower than the sintering temperature of the above and diffusing at least one of Dy and Tb contained in the diffusion source from the surface of the R1-TB based sintered magnet material to the inside.

In the present invention, the alloy is an alloy produced by the melt spinning method.

Further, another exemplary embodiment of the RTB-based sintered magnet according to the present disclosure is.
1'. Step of preparing R1-TB based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co),
2'. A step of crushing an alloy containing 40% by mass or more of the rare earth element R2, which always contains at least one of Dy and Tb, to prepare an alloy powder.
3'. A step of heat-treating the alloy powder at a temperature equal to or higher than the melting point of 270 ° C. and lower than the melting point of the alloy powder to obtain a diffusion source from the alloy powder.
4'. The R1-TB based sintered magnet material and the diffusion source are arranged in a processing container, and the R1-TB based sintered magnet material and the diffusion source are used as the R1-TB based sintered magnet material. It includes a diffusion step of heating to a temperature equal to or lower than the sintering temperature of the above and diffusing at least one of Dy and Tb contained in the diffusion source from the surface of the R1-TB based sintered magnet material to the inside.

In the present disclosure, the alloy is an alloy produced by the melt spinning method.

The difference between the above 1 to 4 and the above 1'to 4'is that when the alloy is heat-treated and the heat-treated alloy is crushed to obtain a diffusion source (1 to 4 above), the alloy is crushed. This is only the difference from the case where the diffusion source is obtained by heat-treating the obtained alloy powder (1'to 4'above above). Therefore, the above 1 to 4 will be described, and the above description of 1'to 4'will be omitted.

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 for those skilled in the art to fully understand the present disclosure. These are not intended to limit the subject matter described in the claims.

1. 1. Step of preparing R1-TB based sintered magnet material R1-TB based sintered magnet material to which at least one of Dy and Tb is diffused (R1 is a rare earth element, T is Fe or Fe and Co) Prepare. As the R1-TB based sintered magnet material, a known magnet material can be used.

The R1-TB based sintered magnet material has, for example, the following composition.
Rare earth element R1: 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: balance Here, the rare earth element R1 is mainly Nd and Pr, but may contain at least one of Dy and Tb. good.

The R1-TB based sintered magnet material having the above composition can be produced by any known production method. The R1-TB based sintered magnet material may be in a state of being sintered, or may be cut or polished. The shape and size of the R1-TB based sintered magnet material are arbitrary.

2. 2. Process of preparing alloy [Alloy]
The alloy is an alloy containing 40% by mass or more of the rare earth element R2, which always contains at least one of Dy and Tb. An alloy containing 40% by mass or more of the rare earth element R2 that always contains at least one of Dy and Tb may be, for example, the rare earth element R2 may be composed of only at least one of Dy and Tb, or the rare earth element R2 may be composed of only one of Dy and Tb. It may be composed of at least one of Dy and Tb and at least one of Pr and Nd. In either case, the rare earth element R2 may occupy 40% by mass or more of the entire alloy. If the rare earth element R2 is less than 40% by mass of the whole, high _HcJ may not be obtained. Typical examples of alloys are RHM1M2 alloy and RHRLM1M2 alloy. Examples of these 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 an HRLM1M2 alloy (RH is one or more selected from the group consisting of Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy. 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, TbNdCoGa alloys, DyNdCoGa alloys, TbCdP 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 contains 40% by mass or more of the rare earth element R2 may contain other elements and impurities.

In the present disclosure, the alloy is made by the melt spinning method.

In the melt spinning method, the molten alloy is sprayed onto the surface of a metal cooling roll that rotates at high speed to bring the molten alloy into contact with the surface of the cooling roll and quench and solidify it. In order to bring an appropriate amount of the molten alloy into contact with the surface of the cooling roll, the molten alloy is sprayed through an orifice (hole) having an inner diameter narrowed to, for example, about 1 mm. The alloy formed is amorphous or microcrystalline. Further, the alloy to be formed exhibits a ribbon-shaped thin band or a scaly thin band, and the thickness thereof is on the order of 10 μm (less than 100 μm). However, in the present disclosure, as will be described later, by heat-treating the alloy, the amorphous material is crystallized and the microcrystals are coarsened, and finally, the alloy has a structure suitable as a diffusion source. To.

When the molten alloy is rapidly cooled and solidified by the melt spinning method, it is difficult to strictly control the cooling rate. Therefore, the structure of the structure tends to vary depending on the powder particles after crushing. Specifically, amorphous particles are formed, and fine crystal particles having an average crystal grain size of 1 μm or less are formed. When 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 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 heat treatment described below is performed.

3. 3. Step to obtain diffusion source [heat treatment of alloy]
In the embodiment of the present disclosure, the alloy is heat-treated at a temperature equal to or higher than 270 ° C. lower than the melting point of the alloy and lower than the melting point.

This modifies the crystallinity of the particles that make up the alloy. Then, a diffusion source having excellent uniformity can be obtained by crushing the alloy (alloy after heat treatment), and variation in magnetic characteristics in the diffusion step can be suppressed by using the diffusion source. The alloy may be pulverized by a known pulverization method such as pin mill pulverization, and the size of the powder particles after pulverization may be 300 μm or less (preferably 200 μm or less). The heat treatment time may be, for example, 30 minutes or more and 10 hours or less. In such a diffusion source, the average crystal grain size of the intermetallic compound phase is more than 3 μm. Preferably, the average crystal grain size of the intermetallic compound phase in the diffusion source is 3.5 μm or more and 20 μm or less. Here, the intermetallic compound phase refers to the entire crystal grain 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.

If the heat treatment temperature for the alloy powder is less than 270 ° C. lower than the melting point of the alloy powder, the temperature is too low and the crystallinity of the powder particles constituting the alloy powder may not be improved, which exceeds the melting point. There is a possibility that the powders will be welded together and the diffusion treatment cannot be performed efficiently.

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, it is possible to reduce the variation in characteristics of each particle that may occur due to the difference in contact time and humidity between the powder particles and the atmosphere, and the variation in magnetic characteristics in the diffusion process can be reduced. It 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 embodiment, in the form of a powder. The particle size of the diffusion source in powder form can be adjusted by sieving. Further, if the powder excluded by sieving is within 10% by mass, the influence 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.

[Diffusion aid]
The diffusion source produced by subjecting the alloy to the above heat treatment and further pulverizing the alloy may further contain powder of the alloy 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 powder may be mixed with the 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 adopt, for example, a ternary or higher alloy such as an NdCuAl alloy, an NdCuCo alloy, or an 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.

As described above, the diffusion source in the embodiment of the present disclosure contains the powder of the heat-treated alloy as an essential component, and may contain the powder formed from other materials.

When the diffusion source is mixed with the powder of the RLM1M2 alloy, it may be difficult to mix them uniformly with the powder alone. The reason for this is that the alloy powder generally has a relatively smaller particle size than the RLM1M2 alloy powder. 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. In addition, it can be uniformly present on the magnet surface.

The binder is preferably one in which the powder particles constituting the diffusion source have smooth and fluidity without sticking or agglomerating 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. Examples thereof include 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, and crushing after solidification.

In the embodiment of the present disclosure, it is not always excluded that a powder other than the above powder (third powder) is present on the surface of the R1-TB based sintered magnet material, but the third powder is in the diffusion source. Care must be taken not to prevent at least one of Dy and Tb from diffusing into the inside of the R1-TB 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 R1-TB based sintered magnet material is 70% or more.

4. Diffusion step of at least one of Dy and Tb In order to heat the R1-TB based sintered magnet material and diffusion source to a temperature equal to or lower than the sintering temperature of the R1-TB based sintered magnet material, first, R1-T -Place the B-based sintered magnet material and diffusion source in the processing container. At this time, it is preferable that the R1-TB 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 R1-TB-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 R1-TB-based sintered magnet material coated with an adhesive by using a fluid immersion method, R1 in a processing container containing the powdery diffusion source. -A method of dipping the TB-based sintered magnet material, a method of sprinkling a powdery diffusion source on the R1-TB-based sintered magnet material, and the like. Further, the processing container containing the diffusion source may be subjected to vibration, vibration, 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 an R1-TB-based sintered magnet material 100 that can be used in the method for manufacturing an R-TB-based sintered magnet according to the present disclosure. The drawings show the upper surface 100a and the side surfaces 100b and 100c of the R1-TB based sintered magnet material 100. The shape and size of the R1-TB based sintered magnet material used in the manufacturing method of the present disclosure is not limited to the shape and size of the illustrated R1-TB based sintered magnet material 100. The upper surface 100a and the side surfaces 100b and 100c of the illustrated R1-TB-based sintered magnet material 100 are flat, but the surface of the R1-TB-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 R1-TB 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 R1-TB based sintered magnet material 100 are present on the surface of the R1-TB 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 R1-TB 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 direction of the R1-TB based sintered magnet material 100. It can be easily attached in one coating process.

Examples of the pressure-sensitive adhesive that can be used include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PVP (polyvinylpyrrolidone) and the like. When the pressure-sensitive adhesive is a water-based pressure-sensitive adhesive, the R1-TB-based sintered magnet material may be preheated before application. The purpose of preheating is to remove excess solvent to control the adhesive strength and to uniformly adhere the adhesive. The heating temperature is preferably 60 to 100 ° C. In the case of a highly volatile organic solvent-based pressure-sensitive adhesive, this step may be omitted.

Any method may be used to apply the adhesive to the surface of the R1-TB-based sintered magnet material. Specific examples of the coating include a spray method, a dipping method, and a dispenser coating.

In one preferred embodiment, the pressure-sensitive adhesive is applied to the entire surface (entire surface) of the R1-TB based sintered magnet material. It may be attached to a part of the surface of the R1-TB-based sintered magnet material instead of the entire surface. In particular, when the thickness of the R1-TB 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 R1-TB 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 R1-TB 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 ignite in contact with oxygen in the atmosphere is reduced, and the variation in characteristics due to contact with the atmosphere is also reduced. is 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 R1-TB 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 R1-TB 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 R1-TB 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, a heat treatment may be further performed at 400 to 700 ° C. for 10 minutes to 72 hours, 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 R1-TB based sintered magnet material to the inside.

Further, as described above, the description of 1'to 4'is omitted, but for 1'to 4', the alloy produced by the melt spinning method is crushed by a known method such as pin mill crushing to prepare an alloy powder. The alloy powder may be produced by the same method as 1 to 4, except that the alloy powder is heat-treated at a temperature 270 ° C. lower than the melting point of the alloy powder and lower than the melting point.

(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%). R1-TB based sintered magnet material was produced. The dimensions of the R1-TB based sintered magnet material were 5.0 mm in thickness × 7.5 mm in width × 35 mm in length.

Next, an alloy was prepared and prepared by the melt spinning method so as to have the composition shown in Table 1. Specifically, in a chamber having an argon atmosphere of 80 kPa, the raw material was melted at high frequency in a quartz nozzle having an orifice diameter of 0.8 mm, and then back pressure of 100 kPa was applied to inject the molten metal onto the Cu roll. .. The Cu roll peripheral speed was set in the range of 10 to 40 m / s depending on the composition. Next, the alloy is heat-treated under the conditions (temperature and time) shown in Table 1 (however, No. 1 is not heat-treated), and the heat-treated alloy is pulverized with a pin mill to make a diffusion source (No. 1 to 13). Got The particle size of the diffusion source (alloy powder) was 200 μm or less (confirmed by sieving) when sieved. The composition of the alloy powder in Table 1 was measured using radio frequency inductively coupled plasma atomic emission spectroscopy (ICP-OES).

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 phased from the contrast, and the composition of each phase is analyzed using energy dispersion 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 the formula 1.

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

These operations were performed 5 times (five 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, an adhesive was applied to the R1-TB based sintered magnet material. As a coating method, the R1-TB based sintered magnet material was heated to 60 ° C. on a hot plate, and then the adhesive was applied to the entire surface of the R1-TB 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 R1-TB based sintered magnet material coated with the adhesive. 1 to 13 diffusion sources were attached. Fifty R1-TB-based sintered magnet materials to which a diffusion source was attached were prepared for each type of diffusion source (every No. 1 to 13). The method of adhesion is as follows: spread the diffusion source (alloy powder) in a container, cool the R1-TB-based sintered magnet material coated with the adhesive to room temperature, and then use the diffusion source in the container as the R1-TB-based. It was attached to the entire surface of the sintered magnet material so as to be sprinkled.

Next, the R1-TB 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 inward from the surface of the R1-TB-based sintered magnet material. A cube with 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 part of the RTB-based sintered magnet after diffusion, and each type of diffusion source (No. 1 to 13). 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 the heat treatment temperature are outside the scope of the present disclosure. Compared with No. 6 (Comparative Example), in each of the examples of the present invention (No. 2 to 5, No. 7 to 13), _{ΔH cJ} is about half, and the variation in magnetic characteristics in the diffusion step is suppressed.

The embodiment of the present disclosure can be used for manufacturing a rare earth sintered magnet that requires a high coercive force because the _HcJ of the RTB-based sintered magnet can be improved by using less Dy and Tb. The present disclosure can also be applied to diffuse a metal element other than the heavy rare earth element RH from the surface of the rare earth sintered magnet.

30 Powder particles constituting the diffusion source 100 R1-TB-based sintered magnet material 100a Top surface of R1-TB-based sintered magnet material 100b Side surface of R1-TB-based sintered magnet material 100c R1-T- Side of B-based sintered magnet material

Claims (4)

The process of preparing the R1-TB based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co), and
A step of preparing an alloy containing 40% by mass or more of the rare earth element R2 that always contains at least one of Dy and Tb, and
A step of heat-treating the alloy at a temperature equal to or higher than 270 ° C. lower than the melting point of the alloy and lower than the melting point, and crushing the heat-treated alloy to obtain a diffusion source.
The R1-TB based sintered magnet material and the diffusion source are arranged in a processing container, and the R1-TB based sintered magnet material and the diffusion source are used as the R1-TB based sintered magnet material. A diffusion step in which at least one of Dy and Tb contained in the diffusion source is diffused from the surface of the R1-TB-based sintered magnet material to the inside by heating to a temperature equal to or lower than the sintering temperature of the above.
Including
The alloy is an alloy produced by a melt spinning method, which is a method for manufacturing an RTB-based sintered magnet. The process of preparing the R1-TB based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co), and
A step of crushing an alloy containing 40% by mass or more of a rare earth element R2 that always contains at least one of Dy and Tb to prepare an alloy powder, and a step of preparing an alloy powder.
A step of heat-treating the alloy powder at a temperature equal to or higher than the melting point of 270 ° C. and lower than the melting point of the alloy powder to obtain a diffusion source from the alloy powder.
A step of arranging the diffusion source in the processing container after performing the heat treatment for obtaining the diffusion source, and a step of arranging the diffusion source in the processing container.
With the R1-TB based sintered magnet material and the diffusion source arranged in the processing container, the R1-TB based sintered magnet material and the diffusion source are placed in the R1-TB system. A diffusion step in which at least one of Dy and Tb contained in the diffusion source is diffused from the surface of the R1-TB-based sintered magnet material to the inside by heating to a temperature equal to or lower than the sintering temperature of the sintered magnet material. ,
Including
The alloy is an alloy produced by a melt spinning method, which is a method for manufacturing an RTB-based sintered magnet. 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 always contains at least one of Tb and Dy. 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, may be M1 = M2). The method for producing an RTB-based sintered magnet according to claim 1 or 2. 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 always contains at least one of Tb and Dy. The production of the RTB-based sintered magnet according to claim 1 or 2, wherein M1 and M2 are one or more selected from Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2 may be used). Method.

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