JP2019062156A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

To provide a method which enables the enhancement of magnet characteristics of an R-T-B based sintered magnet.SOLUTION: A method for manufacturing an R-T-B based sintered magnet comprises: a step of preparing R1-T-B based sintered magnet materials (R1 is a rare earth element, and T is Fe or a combination of Fe and Co); a step of preparing an alloy including 40 mass% or more of a rare earth element R2 necessarily including at least one of Dy and Tb; a step of performing a thermal treatment on the alloy at a temperature in a range from a temperature lower than a melting point of the alloy by 230°C up to the melting point and pulverizing the resultant alloy after the thermal treatment, thereby obtaining a diffusion source; and a diffusion step of setting the R1-T-B based sintered magnet materials and the diffusion source in a process chamber, and heating the R1-T-B based sintered magnet materials and the diffusion source to a temperature equal to or lower than a sintering temperature of the R1-T-B based sintered magnet materials to diffuse at least one of Dy and Tb included in the diffusion source from the surface of the R1-T-B based sintered magnet materials to inside. In the method, the alloy is an alloy produced by a strip cast method.SELECTED DRAWING: None

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).

An RTB-based sintered magnet having an R ₂ T ₁₄ B-type compound as a main phase is known as the highest performance magnet among permanent magnets, and is used as a voice coil motor (VCM) of a hard disk drive or It is used for various motors such as motors for hybrid vehicles and household appliances.

In the _RTB -based sintered magnet, irreversible heat demagnetization occurs because the intrinsic coercivity H _cJ (hereinafter simply referred to as “H _cJ ”) decreases at high temperature. In order to avoid irreversible heat demagnetization, it is required to maintain high H _cJ even under high temperature when used for a motor or the like.

The RTB-based sintered magnet is known to improve H _cJ when a part of R in the R ₂ T ₁₄ B type compound phase is replaced with the heavy rare earth element RH (Dy, Tb) . In order to obtain high _HcJ 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 R-T-B based sintered magnet, when the light rare earth element RL (Nd, Pr) is replaced by the heavy rare earth element RH as R, H _cJ is improved while the residual magnetic flux density B _r (hereinafter simply referred to as “ There is a problem that B _r "is reduced. In addition, since the heavy rare earth element RH is a scarce resource, it is required to reduce its use amount.

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, fluoride or oxide of heavy rare earth element RH, or various metals M or M alloys may be individually or mixed to be present on the surface of a sintered magnet, and heat treated in this state to improve coercivity. 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, 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 elements selected from rare earth elements including Sc and Y, and M is a metal element such as B, C, Al, Si or Ti.

JP, 2011-14668, A

In the manufacturing method disclosed in Patent Document 1, a quenched alloy powder is used as a powder of an alloy containing R ² and M. The rapidly solidified alloy powder contains a microcrystalline or amorphous alloy having an average particle diameter of 3 μm or less of the R ² -M intermetallic compound phase.

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

  In an exemplary embodiment, a method of manufacturing an RTB-based sintered magnet according to the present disclosure is provided with an R1-TB-based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co). And preparing an alloy containing at least 40% by mass of a rare earth element R2 containing at least one of Dy and Tb, and a temperature not lower than the melting point of the alloy but not lower than 230 ° C. Heat treatment at a temperature to crush the alloy after heat treatment to obtain a diffusion source, the R1-T-B sintered magnet material and the diffusion source are disposed in a processing vessel, 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-T-B-based sintered magnet material, and at least one of Dy and Tb contained in the diffusion source is Inside from the surface of a T-B based sintered magnet material Anda diffusion step of diffusing the said alloy is an alloy made by the strip casting method.

  In another exemplary embodiment, the method for producing an RTB-based sintered magnet according to the present disclosure is, in another exemplary embodiment, an R1-T-B-based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co and Co). B) preparing an alloy powder by pulverizing an alloy containing at least 40 mass% of the entire rare earth element R2 including at least one of Dy and Tb, and preparing the powder of the alloy Heat treatment is performed at a temperature lower than the melting point of the powder by 230 ° C. and lower than the melting point to obtain a diffusion source from the powder of the alloy, the R1-T-B sintered magnet material and the diffusion source are treated And the heat source is contained in the diffusion source by heating the R1-T-B sintered magnet material and the diffusion source to a temperature equal to or lower than the sintering temperature of the R1-T-B sintered magnet material. At least one of Dy and Tb is the R1-T-B. And a diffusion step of diffusing from the surface to the inside of the sintered magnet material, wherein the alloy is an alloy made by the strip casting method.

  In one embodiment, the alloy is a RHRLM1M2 alloy (RH is at least one selected from the group consisting of Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and at least Tb and Dy). RL is at least one member selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu, and includes at least one of Pr and Nd. M1 and M2 are Cu, Fe, and the like. One or more selected from Ga, Co, Ni, and Al, and M1 may be M2).

  In one embodiment, the alloy is one or more selected from the group consisting of RHM1M2 alloys (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 may be M2).

According to the embodiment of the present disclosure, since the structure of the diffusion source including at least one of Dy and Tb is modified, the H _cJ of the _RTB -based sintered magnet can be suppressed while suppressing the dispersion of the magnetic characteristics. It is possible to improve.

In the embodiment of the present disclosure, it is a cross-sectional view schematically showing a part of the prepared R1-T-B-based sintered magnet material. In embodiment of this indication, it is sectional drawing which shows typically a part of R1-TB based sintered magnet raw material in the state 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 lanthanides. Here, lanthanoid is a generic term of 15 elements from lanthanum to lutetium. R1 and R are rare earth elements, and R2 is a rare earth element containing at least one of Dy and Tb.

An exemplary embodiment of a method of manufacturing an RTB based sintered magnet according to the present disclosure is:
1. Preparing a R1-T-B based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co);
2. Preparing an alloy containing at least 40% by weight or more of a rare earth element R2 which always contains at least one of Dy and Tb;
3. Heat treating the alloy at a temperature not less than 230 ° C. and not more than the melting point of the alloy and crushing the alloy after the heat treatment to obtain a diffusion source;
4. The R1-T-B based sintered magnet material and the diffusion source are disposed in a processing vessel, and the R1-T-B-based sintered magnet material and the diffusion source are referred to as the R1-T-B based sintered magnet material And the diffusion step of diffusing at least one of Dy and Tb contained in the diffusion source from the surface of the R1-T-B based sintered magnet material to the inside by heating to a temperature not higher than the sintering temperature of

  In the present invention, the alloy is an alloy produced by a strip casting method.

Also, another exemplary embodiment of the RTB-based sintered magnet according to the present disclosure is:
1 '. Preparing an R1-T-B based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co);
2 '. Crushing an alloy containing at least 40% by mass of a rare earth element R2 necessarily containing at least one of Dy and Tb to prepare a powder of the alloy;
3 '. Heat treating the powder of the alloy at a temperature not lower than the melting point of the alloy powder but not lower than the melting point by 230 ° C. to obtain a diffusion source from the powder of the alloy;
4 '. The R1-T-B based sintered magnet material and the diffusion source are disposed in a processing vessel, and the R1-T-B-based sintered magnet material and the diffusion source are referred to as the R1-T-B based sintered magnet material And the diffusion step of diffusing at least one of Dy and Tb contained in the diffusion source from the surface of the R1-T-B based sintered magnet material to the inside by heating to a temperature not higher than the sintering temperature of

  In the present disclosure, the alloy is an alloy produced by a strip casting method.

  The difference between the above 1 to 4 and the above 1 'to 4' is that when heat treatment is performed on the alloy and the diffusion source is obtained by crushing the alloy after the heat treatment (the above 1 to 4), the alloy is crushed This is only the difference from the cases (1 'to 4' above) where the diffusion source is obtained by heat treating the powder of the alloy obtained above. Therefore, the said 1-4 are demonstrated and description of said 1'-4 'is abbreviate | omitted.

  Hereinafter, embodiments of the present disclosure will be described. In addition, detailed description more than necessary may be omitted. For example, detailed description of already well-known matters and redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. The inventors provide the attached drawings and the following description so that those skilled in the art can fully understand the present disclosure. They are not intended to limit the subject matter recited in the claims.

1. Process of preparing an R1-T-B-based sintered magnet material R1-T-B-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. A well-known magnet material can be used as a R1-T-B type | system | group sintered magnet material.

The R1-T-B based sintered magnet material has, for example, the following composition.
Rare earth element R: 1:12 to 17 atomic%
B (part of B (boron) may be substituted by C (carbon)): 5 to 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 at%
T (a transition metal element mainly composed of Fe and may contain Co) and unavoidable impurities: Remaining part Here, the rare earth element R1 is mainly Nd, Pr, but also contains at least one of Dy and Tb Good.

  The R1-T-B-based sintered magnet material of the above composition can be manufactured by any known manufacturing method. The R1-T-B-based sintered magnet material may be in a sintered state, or may be subjected to cutting or polishing. The shape and size of the R1-T-B based sintered magnet material are arbitrary.

2. Process of preparing alloy [alloy]
The alloy is an alloy containing 40 mass% or more of the entire rare earth element R2 including at least one of Dy and Tb. With an alloy containing at least 40 mass% of the entire rare earth element R2 including at least one of Dy and Tb, for example, the rare earth element R2 may be composed of at least one of Dy and Tb, or the rare earth element R2 is It may be composed of at least one of Dy and Tb and at least one of Pr and Nd. In any 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 H _cJ may not be obtained. Typical examples of alloys are RHM1M2 alloy and RHRLM1M2 alloy. Hereinafter, examples of these alloys will be described.

(RHM1M2 alloy)
Examples of the alloy are, for example, RHM 1 M 2 alloy (RH is at least one selected from the group consisting of Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy And M1 and M2 are one or more selected from Cu, Fe, Ga, Co, Ni, and Al, and M1 may be M2).

  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 a RHRLM1M2 alloy (RH is at least one selected from the group consisting of Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and at least one of Tb and Dy Inclusively, RL is one or more selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu, and invariably contains at least one of Pr and Nd, M1, M2 is Cu, Fe, Ga, One or more selected from Co, Ni, and Al, M1 may be M2). Typical examples of the RHRLM1M2 alloy are TbNdCu alloy, DyNdCu alloy, TbNdFe alloy, DyNdFe alloy, TbNdCuAl alloy, DyNdCuAl alloy, TbNdCuCo alloy, DyNdCuCo alloy, TbNdCoGa alloy, DyNdCoGa alloy, TbNdPrCu alloy, DyNdPhFe alloy is there. The alloy is not limited to the above-described RHM1M2 alloy and RHRLM1M2 alloy. As long as it is 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, it may contain other elements and impurities.

  In the present disclosure, the alloy is made by strip casting.

  The strip casting method is a method of continuously casting a thin plate-like alloy by pouring a molten metal on a rotating roll and quenching and solidifying the thin plate. The alloy to be formed has a thin plate shape, and its thickness is on the order of 100 μm (for example, about 100 μm to about 500 μm). In the present disclosure, as described later, by performing heat treatment on the alloy, crystals are coarsened, and finally, it has a texture suitable as a diffusion source.

  When the molten alloy is rapidly solidified by strip casting, it is difficult to precisely control the cooling rate. For this reason, the structure of the structure is likely to vary among powder particles after the alloy is crushed. For example, the size of the fine grains produced in the alloy can vary widely from grain to grain. 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. Such variations in the structure of the structure and the average grain size cause variations in the melting temperature of the phase constituting the particles and in the rate at which Dy and Tb are supplied as a diffusion source in the diffusion step described later. Such variations eventually lead to variations in magnet characteristics.

  In order to solve such a subject, in the embodiment of the present disclosure, heat treatment described below is performed.

3. Process to obtain diffusion source [heat treatment of alloy]
In an embodiment of the present disclosure, heat treatment is performed on the alloy at a temperature not less than 230 ° C. lower than the melting point of the alloy and not more than the melting point.

  This modifies the crystallinity of the particles that make up the alloy. And the diffusion source excellent in uniformity can be obtained by grinding the alloy (alloy after heat treatment), and the dispersion of the magnetic characteristics in the diffusion process can be suppressed by using the diffusion source. The alloy may be ground by a known grinding method such as pin milling, and the size of the powder particles after grinding 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 grains of the intermetallic compound in the powder particle constituting the diffusion source. When there are a plurality of types of intermetallic compounds in the powder particle constituting the diffusion source, the whole grains of the intermetallic compound having the highest content are said.

  If the heat treatment temperature for the powder of the alloy is less than 230 ° C. lower than the melting point of the powder of the alloy, the temperature is too low and the crystallinity of the powder particles constituting the powder of the alloy may not be improved. And powder may be deposited and the diffusion process may not be efficient.

  In the heat treatment, it is preferable to adjust the oxygen content in the diffusion source after the heat treatment to 0.5 mass% or more and 4.0 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 between particles which may occur due to the contact time between the powder particles and the atmosphere or the difference in humidity, and the variation in magnetic characteristics in the diffusion process. It can be further reduced. In addition, the possibility of ignition on contact with oxygen in the atmosphere is reduced. This facilitates quality control of the diffusion source.

  The diffusion source, in embodiments, is in the form of a powder. The particle size of the diffusion source in powder form can be adjusted by sieving. Moreover, since the influence is small if the powder excluded by sieving is 10 mass% or less, it may be used without sieving.

  Also, the diffusion source in the form of powder may be granulated with a binder, if necessary.

[Diffusion aid]
The diffusion source produced by subjecting the alloy to the above-described heat treatment and then grinding the alloy may further include a powder of the alloy that functions as a diffusion aid. An example of such an alloy is RLM1 M2 alloy. RL is one or more selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu, and includes at least one of Pr and Nd, and M1 and M2 are Cu, Fe, Ga, Co, Ni And one or more selected from Al, and M1 may be M2. Typical examples of RLM1M2 alloys 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 in combination with the powders of the above-mentioned alloys. Plural kinds of RLM1M2 alloy powder may be mixed in the powder of the alloy.

  The method of producing the powder of RLM1M2 alloy is not particularly limited. In the case of producing by a quenching method or a casting method, in order to improve the grindability, it is preferable to adopt M1 ≠ M2, and, for example, a ternary or higher alloy such as NdCuAl alloy, NdCuCo alloy, NdCoGa alloy or the like. The particle size of the RLM 1 M 2 alloy powder is, for example, 200 μm or less, and the smaller one is about 10 μm.

  Thus, the diffusion source in the embodiment of the present disclosure includes powder of heat-treated alloy as an essential component, and may include powder formed of other materials.

  When a diffusion source is used by mixing with a powder of RLM 1 M 2 alloy, it may be difficult to mix uniformly with each other only by mixing these powders. The reason for this is that the powder of the alloy is generally smaller in particle size than the powder of the RLM1 M2 alloy. For this reason, it is preferable to granulate the powder of RLM1M2 alloy, the powder of the alloy, and the binder. The use of such a granulated product has the advantage that the compounding ratio of the RLM1M2 alloy powder to the alloy powder can be made uniform throughout the powder. Moreover, it becomes possible to make it exist uniformly on the magnet surface.

  As the binder, preferred is one capable of causing the powder particles constituting the diffusion source to be free flowing and free from sticking or aggregation when the dried or mixed solvent is removed. As an example of a binder, PVA (polyvinyl alcohol) etc. are mention | raise | lifted. As appropriate, mixing may be performed using an aqueous solvent such as water or an organic solvent such as NMP (n-methylpyrrolidone). The solvent is evaporated and removed in the process of granulation described later.

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

  In the embodiment of the present disclosure, although the powder other than the above powder (third powder) is not necessarily excluded from being present on the surface of the R1-T-B-based sintered magnet material, the third powder is in the diffusion source. It is necessary to be careful not to inhibit the diffusion of at least one of Dy and Tb into the inside of the R1-T-B based sintered magnet material. The mass ratio of “an alloy containing at least one of Dy and Tb” in the whole powder present on the surface of the R1-T-B-based sintered magnet material is desirably 70% or more.

4. In order to heat at least one of the diffusion step R1-T-B based sintered magnet material and diffusion source of Dy and Tb to a temperature not higher than the sintering temperature of the R1-T-B based sintered magnet material, first, R1-T The B-based sintered magnet material and the diffusion source are disposed in the processing vessel. At this time, it is preferable that the R1-T-B-based sintered magnet material and the diffusion source be in contact in the processing container.

[Placement]
The form in which the R1-T-B based sintered magnet material and the diffusion source are in contact with each other may be any form. For example, a method of adhering a powdery diffusion source to an R1-T-B-based sintered magnet material coated with an adhesive by using a fluid immersion method, R1 in a processing container containing a powdery diffusion source A method of dipping a T-B based sintered magnet material, a method of sprinkling a powdery diffusion source on an R1-T-B based sintered magnet material, and the like. Alternatively, the processing container containing the diffusion source may be vibrated, shaken, rotated, or the powder of the diffusion source may be flowed in the processing container.

  FIG. 1A is a cross-sectional view schematically showing a part of an R1-T-B-based sintered magnet material 100 that can be used in the method of manufacturing an RTB-based sintered magnet according to the present disclosure. The upper surface 100a and the side surfaces 100b and 100c of the R1-T-B-based sintered magnet material 100 are shown in the drawing. The shape and size of the R1-T-B-based sintered magnet material used in the manufacturing method of the present disclosure are not limited to the shape and size of the illustrated R1-T-B-based sintered magnet material 100. The upper surface 100a and the side surfaces 100b and 100c of the R1-T-B-based sintered magnet material 100 illustrated are flat, but the surface of the R1-T-B-based sintered magnet material 100 has irregularities or steps. It may be curved or may be curved.

  FIG. 1B is a cross-sectional view schematically showing a part of the R1-T-B-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-T-B-based sintered magnet material 100 are the surface of the R1-T-B-based sintered magnet material 100 via an adhesive layer (not shown). It may adhere to Such an adhesive layer may be applied to the surface of the R1-T-B-based sintered magnet material 100, for example. If an adhesive layer is used, the powder of the diffusion source is not removed from 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 R1-T-B based sintered magnet material 100. It can be easily attached in one application process.

  Examples of usable pressure-sensitive adhesives include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PVP (polyvinyl pyrrolidone) and the like. When the pressure-sensitive adhesive is a water-based pressure-sensitive adhesive, the R1-T-B-based sintered magnet material may be preliminarily heated before coating. The purpose of the preheating is to remove excess solvent and control the adhesion, and to adhere the adhesive uniformly. The heating temperature is preferably 60 to 100 ° C. In the case of a highly volatile organic solvent-based adhesive, this step may be omitted.

  Any method may be used to apply the adhesive to the surface of the R1-T-B-based sintered magnet material. Specific examples of the application include a spray method, an immersion method, application by a dispenser, and the like.

In a preferred embodiment, an adhesive is applied to the entire surface (entire surface) of the R1-T-B-based sintered magnet material. You may make it adhere not to the whole surface of R1-T-B type | system | group sintered magnet raw material but to a part. In particular, when the thickness of the R1-T-B-based sintered magnet material is thin (for example, about 2 mm), the diffusion source is one of the surfaces of the R1-T-B-based sintered magnet material having the largest area. In some cases, it is possible to diffuse at least one of Dy and Tb throughout the magnet simply by depositing the powder of H. It is possible to improve _HcJ .

  As described above, the powder particles constituting the diffusion source in contact with the surface of the R1-T-B-based sintered magnet material 100 have a structure with excellent uniformity. Further, since the entire surface of the alloy particle is oxidized as an embodiment, the powder particle is less likely to be ignited in contact with oxygen in the atmosphere, and the variation in characteristics due to the contact with the atmosphere is also reduced. doing. Therefore, when heating for diffusion to be described later is performed, it is possible to efficiently diffuse at least one of Dy and Tb contained in the diffusion source from the surface of the R1-T-B based sintered magnet material into the inside without waste. it can.

The amount of at least one of Dy and Tb contained in the diffusion source located on the magnet surface is, for example, in the range of 0.5 to 3.0% by mass ratio with respect to the R1-T-B based sintered magnet material It can be set to be It may be set to be in the range of 0.7 to 2.0% in order to obtain 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 also 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 equal to or less than the sintering temperature of the R1-T-B based sintered magnet material (specifically, for example, 1000 ° C. or less). When the diffusion source contains a powder such as RLM 1 M 2 alloy, the temperature is higher than the melting point of the alloy, for example, 500 ° C. or more. The heat treatment time is, for example, 10 minutes to 72 hours. Moreover, you may heat-process for 10 minutes-72 hours at 400-700 degreeC further as needed after the said heat processing.

  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-T-B-based sintered magnet material to the inside.

  Moreover, although 1 '-4' description is abbreviate | omitted as mentioned above, 1 '-4' grind | pulverizes the alloy produced by the strip casting method by well-known methods, such as a pin mill grinding, and prepares the powder of an alloy The powder may be prepared in the same manner as 1 to 4 except that the heat treatment is performed on the powder of the alloy at a temperature which is lower by 230 ° C. than the melting point of the powder of the alloy and not higher than the melting point.

(Experimental example 1)
First, by a known method, the composition ratio Nd = 23.4, Pr = 6.2, B = 1.0, Al = 0.4, Cu = 0.1, Co = 1.5, balance Fe (mass%) An R1-T-B based sintered magnet material was produced. The dimensions of the R1-T-B based sintered magnet material were 5.0 mm in thickness × 7.5 mm in width × 35 mm in length.

  Next, an alloy was prepared by a strip casting method so as to have a composition approximately as shown in Table 1. Next, heat treatment is performed on the above-mentioned alloy under the conditions (temperature and time) shown in Table 1 (however, No. 1 is not heat treatment), and the diffusion source (No. 1 to 12) is obtained by pin milling the alloy after heat treatment. Obtained. The particle size of the diffusion source (alloy powder) was 200 μm or less (confirmed by sieving). The composition of the powders of the alloys in Table 1 was measured using high frequency inductively coupled plasma emission spectroscopy (ICP-OES).

  Further, the average 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 particle constituting the diffusion source is observed with a scanning electron microscope (SEM), the phase is separated from the contrast, the composition of each phase is analyzed using energy dispersive X-ray spectroscopy (EDX), and the intermetallic compound phase is Identified. Next, using an image analysis software (Scandium), the intermetallic compound phase with the highest area ratio was regarded as the intermetallic compound phase with 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 determined using image analysis software (Scandium), and the total area of crystal grains thus determined is divided by the number of crystal grains to obtain an average area. I asked. The crystal grain size D was determined from the average area obtained by Equation 1.

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

  These operations were performed five times (five powder particles were examined), and the average value was determined to determine the average grain size of the intermetallic compound phase in the diffusion source. The results are shown in Table 1 average grain size. No. Since No. 1 did not heat-process to a diffusion source, the crystal grain diameter of the intermetallic compound phase was too small, and (microcrystal grain of 1 micrometer or less) was not able to be measured.

  Next, an adhesive was applied to the R1-T-B based sintered magnet material. The coating method was such that the R1-T-B 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-T-B based sintered magnet material by a spray method. As an adhesive, PVP (polyvinyl pyrrolidone) was used.

  Next, with respect to the R1-T-B-based sintered magnet material coated with a pressure-sensitive adhesive, No. 1 in Table 1 is used. 1 to 12 diffusion sources were attached. Fifty R 1 -T-B-based sintered magnet materials having diffusion sources attached thereto were prepared for each type of diffusion sources (for each of Nos. 1 to 12). In the adhesion method, the diffusion source (alloy powder) is spread in a container, the R1-T-B based sintered magnet material coated with the adhesive is cooled to room temperature, and then the diffusion source is R1-T-B based in the container It was made to adhere to the entire surface of the sintered magnet material.

Next, the R1-T-B-based sintered magnet material and the diffusion source are disposed in a processing vessel, and heated at 900 ° C. (sintering temperature or less) for 8 hours, Dy and Tb contained in the diffusion source A diffusion step of diffusing at least one of them from the surface of the R1-T-B based sintered magnet material to the inside is performed. A cube of 4.5 mm in thickness × 7.0 mm in width × 7.0 mm in length is cut out from the central portion of the R-T-B-based sintered magnet after diffusion, and each type of diffusion source (for each of Nos. 1 to 12) The coercivity was measured by B-H tracer every 10 pieces, and the value obtained by subtracting the minimum value of the coercivity from the maximum value of the obtained coercivity was determined as the magnetic characteristic variation ( _{ΔH cJ} ). The values of _{ΔH cJ} are shown in Table 1.

As shown in Table 1, the alloy powder was not heat treated. No. 1 (comparative example) and the heat processing temperature are out of the range of this indication. As compared with No. 6 (comparative example), in all of the inventive examples (No. 2 to 5 and No. 7 to 12), ΔH _cJ is half or less, and the variation of the magnetic characteristics in the diffusion process is suppressed.

The embodiment of the present disclosure can improve the _HcJ of the RTB-based sintered magnet with less Dy and Tb, and therefore can be used to manufacture a rare earth sintered magnet that requires high coercivity. The present disclosure can also be applied to the diffusion of other metal elements other than the heavy rare earth element RH into the rare earth sintered magnet from the surface.

30 Powder particle 100 constituting a diffusion source R1-T-B-based sintered magnet material 100a R1-T-B-based sintered magnet material top surface 100b R1-T-B-based sintered magnet material side surface 100c R1-T- Side of B-based sintered magnet material

Claims (4)

Preparing a R1-T-B based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co);
Preparing an alloy containing at least 40% by weight or more of the rare earth element R2 invariably containing at least one of Dy and Tb;
Heat treating the alloy at a temperature not less than 230 ° C. and not more than the melting point of the alloy and crushing the alloy after the heat treatment to obtain a diffusion source;
The R1-T-B based sintered magnet material and the diffusion source are disposed in a processing vessel, and the R1-T-B-based sintered magnet material and the diffusion source are referred to as the R1-T-B based sintered magnet material A diffusion step of heating at a temperature equal to or lower than the sintering temperature of D. to diffuse at least one of Dy and Tb contained in the diffusion source from the surface of the R1-T-B based sintered magnet material to the inside;
Including
The method for producing an RTB-based sintered magnet, wherein the alloy is an alloy produced by a strip casting method. Preparing a R1-T-B based sintered magnet material (R1 is a rare earth element, T is Fe or Fe and Co);
Pulverizing an alloy containing at least 40% by mass of a rare earth element R2 necessarily containing at least one of Dy and Tb to prepare a powder of the alloy;
Heat treating the powder of the alloy at a temperature not lower than the melting point of the alloy powder but not lower than the melting point by 230 ° C. to obtain a diffusion source from the powder of the alloy;
The R1-T-B based sintered magnet material and the diffusion source are disposed in a processing vessel, and the R1-T-B-based sintered magnet material and the diffusion source are referred to as the R1-T-B based sintered magnet material A diffusion step of heating at a temperature equal to or lower than the sintering temperature of D. to diffuse at least one of Dy and Tb contained in the diffusion source from the surface of the R1-T-B based sintered magnet material to the inside;
Including
The method for producing an RTB-based sintered magnet, wherein the alloy is an alloy produced by a strip casting method.   The alloy is a RHRLM1M2 alloy (RH is at least one selected from the group consisting of Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and 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 includes at least one of Pr and Nd, and M1 and M2 are Cu, Fe, Ga, Co, Ni The method for producing an RTB-based sintered magnet according to claim 1 or 2, wherein M1 is at least one selected from Al, and M1 may be M2.   The alloy is one or more selected from the group consisting of RHM 1 M 2 alloy (RH is Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and always contains at least one of Tb and Dy. The R-T-B-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 may be M2). Method.

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