JP2019062153A - Method for manufacturing r-t-b-based sintered magnet - Google Patents

Abstract

To improve the magnet characteristics of an R-T-B-based sintered magnet.SOLUTION: A method for manufacturing an R-T-B-based sintered magnet includes the steps of: preparing an R-T-B-based sintered magnet material; preparing the Pr-Ga alloy produced by a strip casting method; obtaining a diffusion source from powders of the Pr-Ga alloy by subjecting the Pr-Ga alloy to heat treatment at a temperature equal to or higher than a temperature lower than a melting point of the Pr-Ga alloy by 230°C and a temperature equal to or lower than the melting point; and arranging the R-T-B-based sintered magnet material and the diffusion source in a processing container and diffusing Pr and Ga from the diffusion source into the R-T-B-based sintered magnet material by heating the R-T-B-based sintered magnet material and the diffusion source at a temperature higher than 600°C and equal to or lower than 950°C in a vacuum or in an inert gas atmosphere.SELECTED DRAWING: None

Description

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

  RTB sintered magnet (R is at least one of rare earth elements and must contain Nd. T is Fe or Fe and Co, B is boron) is the highest among permanent magnets. It is known as a high performance magnet, and is used in voice coil motors (VCMs) for hard disk drives, motors for electric vehicles (EV, HV, PHV etc.) motors, various motors such as motors for industrial equipment, and home appliances.

The RTB-based sintered magnet is composed of a main phase mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase located in a grain boundary portion of the main phase. The main phase R ₂ T ₁₄ B compound is a ferromagnetic material having high saturation magnetization and anisotropic magnetic field, and forms the basis of the characteristics of the RTB-based sintered magnet.

At high temperatures, the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) of the _RTB -based sintered magnet decreases, so that irreversible thermal demagnetization occurs. Therefore, in the _RTB -based sintered magnet used particularly for a motor for an electric vehicle, it is required to have a high _HcJ .

In the RTB-based sintered magnet, part of the light rare earth element RL (eg, Nd or Pr) contained in R in the R ₂ T ₁₄ B compound is a heavy rare earth element RH (eg, Dy or Tb) It is known that substitution improves H _cJ . H _cJ improves as the amount of substitution of RH increases.

However, replacing RL in the R ₂ T ₁₄ B compound with RH improves H _{cJ of the RTB} -based sintered magnet, while the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ” There is a decline). In addition, RH such as Dy has problems such as unstable supply and large price fluctuation due to the small amount of resources and limited production area. Therefore, in recent years, it is required to improve H _cJ without using RH as much as possible.

Patent Document 1 discloses an RTB-based rare earth sintered magnet having a high coercive force while suppressing the content of Dy. The composition of this sintered magnet is limited to a specific range in which the amount of B is relatively small compared to the R-T-B based alloy generally used, and is selected from Al, Ga, and Cu 1 It contains metal element M of a species or more. As a result, _R 2 _{T 17} phase is produced in the grain boundary, by the volume ratio of the _R 2 _{T 17} transition metal-rich phase formed in the grain boundary from phase _{(R 6 T 13} M) _{increases, H cJ} Improve.

International Publication No. 2013/008756

The R-T-B rare earth sintered magnets disclosed in Patent Document 1, although a high H _cJ is obtained while reducing the content of Dy, there is a problem that B _r is greatly reduced. Also, in recent years, _RTB -based sintered magnets having higher H _cJ have been required in applications such as motors for electric vehicles.

Various embodiments of the present invention, while reducing the content of RH, to provide a method of manufacturing a R-T-B based sintered magnet having a high B _r and high H _cJ.

  The manufacturing method of the R-T-B-based sintered magnet of the present disclosure includes: R: 27.5-35.0 mass% (R is at least one of rare earth elements and necessarily includes Nd); 80 to 0.99% by mass, Ga: 0 to 0.8% by mass, M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr), balance T (T is Fe or Fe and Co and Co) Step of preparing an RTB-based sintered magnet material containing a) and inevitable impurities, a step of preparing a Pr-Ga alloy, and a melting point of the Pr-Ga alloy in the Pr-Ga alloy. Heat treatment at a temperature not less than 230 ° C. and not more than the melting point, and a process of obtaining a diffusion source by crushing the Pr—Ga alloy after the heat treatment, the RTB sintered magnet material and the diffusion source The RTB sintered magnet material and the diffusion source are disposed in a processing vessel, and A diffusion process in which Pr and Ga contained in the diffusion source are diffused from the surface to the inside of the R-T-B-based sintered magnet material by heating at a temperature of 600 ° C. or more and 950 ° C. or less in an inert gas atmosphere. And the said Pr-Ga alloy is an alloy produced by the strip casting method.

  The manufacturing method of the RTB-based sintered magnet according to the present disclosure, in another exemplary embodiment, R: 27.5-35.0 mass% (R is at least one of rare earth elements, Nd is necessarily included, B: 0.80 to 0.99% by mass, Ga: 0 to 0.8% by mass, M: 0 to 2% by mass (M is at least one of Cu, Al, Nb, and Zr), Preparing an RTB-based sintered magnet material containing the remaining portion T (T is Fe or Fe and Co) and unavoidable impurities, and grinding the Pr-Ga alloy to obtain a Pr-Ga alloy powder Heat treatment is performed on the powder of the Pr-Ga alloy at a temperature not lower than the melting point of the Pr-Ga alloy and not lower than the melting point by 230 ° C., and a diffusion source is obtained from the powder of the Pr-Ga alloy And processing the RTB-based sintered magnet material and the diffusion source Are contained in the diffusion source by heating the R-T-B based sintered magnet material and the diffusion source at a temperature of more than 600.degree. C. and not more than 950.degree. C. in a vacuum or an inert gas atmosphere. And a diffusion step of diffusing Pr and Ga from the surface of the R-T-B-based sintered magnet material to the inside, and the Pr-Ga alloy is an alloy prepared by a strip casting method.

In one embodiment, the RTB-based sintered magnet material satisfies the following inequality (1).
[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T in mass%, [B] is the content of B in mass%)

  In one embodiment, the amount of Ga in the RTB-based sintered magnet material is 0 to 0.5% by mass.

  In one embodiment, the Nd content of the Pr—Ga alloy is equal to or less than the unavoidable impurity content.

According to an embodiment of the present disclosure, a diffusion source and a RTB-based sintered magnet material obtained by heat-treating a Pr—Ga alloy manufactured by a strip casting method are disposed in a processing container, and the diffusion process is performed. To diffuse Pr and Ga from particles having a homogenized structure of Pr—Ga alloy powder. Thus, it is possible to obtain a high _{B r} and _{H cJ.} Further, to suppress variations in the magnetic properties due to diffusion, it is possible to suppress the deterioration of the B _r and H _cJ due to variations in the magnetic properties.

In an embodiment of the present disclosure, it is a cross-sectional view schematically showing a part of a prepared RTB-based sintered magnet material. In embodiment of this indication, it is sectional drawing which shows typically a part of RTB type | system | group 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.

  Further, in the present invention, the RTB-based sintered magnet in the diffusion step and the diffusion step is referred to as "RTB-based sintered magnet material", and RTB-based sintering after the diffusion step The magnet is simply referred to as "R-T-B sintered magnet".

An exemplary embodiment of a method of manufacturing an RTB based sintered magnet according to the present disclosure is:
1. Preparing an RTB-based sintered magnet material (R is at least one of rare earth elements and necessarily includes Nd);
2. Preparing a Pr-Ga alloy;
3. Heat treating the Pr—Ga alloy at a temperature not lower than the melting point of the Pr—Ga alloy but not lower than the melting point by 230 ° C. and not higher than the melting point, and grinding the Pr—Ga alloy after the heat treatment to obtain a diffusion source;
4. The RTB-based sintered magnet material and the diffusion source are disposed in a processing vessel, and the RTB-based sintered magnet material and the diffusion source are heated to over 600 ° C. in a vacuum or inert gas atmosphere. It includes a diffusion step of diffusing Pr and Ga contained in the diffusion source from the surface of the RTB based sintered magnet material to the inside by heating at a temperature of 950 ° C. or lower.

  In the present invention, the Pr-Ga 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 RTB-based sintered magnet material (R is at least one of rare earth elements and necessarily includes Nd);
2 '. Grinding the Pr-Ga alloy to prepare a powder of the Pr-Ga alloy;
3 '. Heat treating the powder of the Pr-Ga alloy at a temperature not lower than the melting point of the powder of the Pr-Ga alloy and not lower than the melting point to obtain a diffusion source from the powder of the Pr-Ga alloy;
4 '. The RTB-based sintered magnet material and the diffusion source are disposed in a processing vessel, and the RTB-based sintered magnet material and the diffusion source are heated to over 600 ° C. in a vacuum or inert gas atmosphere. It includes a diffusion step of diffusing Pr and Ga contained in the diffusion source from the surface of the RTB based sintered magnet material to the inside by heating at a temperature of 950 ° C. or lower.

  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 the diffusion source is obtained by heat treating the Pr—Ga alloy and crushing the Pr—Ga alloy after the heat treatment (the above 1 to 4) And the case where the diffusion source is obtained by heat treating the powder of the Pr—Ga alloy obtained by pulverizing the Pr—Ga alloy (the above 1 ′ to 4 ′). 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 for preparing RTB-based sintered magnet material Pr and RTB -based sintered magnet material to which Ga is diffused (R is at least one of rare earth elements and necessarily contains Nd) Prepare.

The RTB-based sintered magnet material is
R: 27.5 to 35.0% by mass (R is at least one of rare earth elements and necessarily includes Nd),
B: 0.80 to 0.99 mass%,
Ga: 0 to 0.8% by mass,
M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr),
Remainder T (T is Fe or Fe and Co) and unavoidable impurities,
Contains

(R)
The content of R is 27.5 to 35.0% by mass. If R is less than 27.5% by mass, the liquid phase is not sufficiently formed in the sintering process, and it becomes difficult to fully densify the sintered body. On the other hand, although the effect of the present invention can be obtained even if R exceeds 35.0% by mass, the alloy powder becomes very active during the manufacturing process of the sintered body, and significant oxidation or ignition of the alloy powder occurs. 35 mass% or less is preferable since it may occur. R is more preferably 28% by mass to 33% by mass or less, and further preferably 29% by mass to 33% by mass or less. As for content of RH, 5 mass% or less of the whole RTB type sintered magnet raw material is preferable. Because the present invention can obtain a high B _r and high H _cJ without using RH, it can reduce the amount of RH even be asked a higher H _cJ.

(B)
Content of B is 0.80-0.99 mass%. The content of B with respect to 0.80 to 0.99 wt% content are R-T-B based sintered magnet material was, by diffusing the Pr-Ga alloy to be described later, a high _{B r} and high _{H cJ} You can get There is a possibility that the content of B is lowered and _{B r} is less than 0.80 wt%, there is a possibility _{that H cJ} is reduced when it exceeds 0.99 wt%. Also, part of B can be replaced by C.

(Ga)
The content of Ga in the RTB-based sintered magnet material before diffusing Ga from the powder of the Pr—Ga alloy is 0 to 0.8 mass%. The present invention introduces Ga by diffusing a powder of a Pr-Ga alloy into an RTB-based sintered magnet material, so the amount of Ga in the RTB-based sintered magnet material is relatively small. (Or contains no Ga). If the content of Ga exceeds 0.8% by mass, the magnetization of the main phase may be reduced by the inclusion of Ga in the main phase, and a high B _r may not be obtained. Preferably, the content of Ga is 0.5% by mass or less. Higher _Br can be obtained.

(M)
The content of M is 0 to 2% by mass. M is at least one of Cu, Al, Nb, and Zr, and even if it is 0% by mass, the effect of the present invention can be exhibited, but containing 2% by mass or less in total of Cu, Al, Nb, and Zr Can. H _cJ can be improved by containing Cu and Al. Cu and Al may be positively added, or may be those which are inevitably introduced in the process of producing the used raw materials and the alloy powder. Further, by containing Nb and Zr, abnormal grain growth of crystal grains can be suppressed at the time of sintering. Preferably, M always contains Cu and contains 0.05 to 0.30% by mass of Cu. By containing 0.05 to _0.30 mass% of Cu, it is because _HcJ can be improved more.

(Remaining part T)
The balance is T (T is Fe or Fe and Co) and impurities. In one embodiment, T satisfies inequality (1). It is preferable that 90% or more of T in mass ratio is Fe. A part of Fe can be replaced by Co. However, the substitution amount of Co is greater than 10% of the total T by mass ratio is not preferable because the B _r drops. Furthermore, the RTB-based sintered magnet material of the present invention is an unavoidable impurity usually contained in alloys such as didymium alloy (Nd-Pr), electrolytic iron, ferroboron, etc. and in the manufacturing process, and a small amount of other than the above. Elements (elements other than R, B, Ga, M, and T described above) may be contained. For example, Ti, V, Cr, Mn, Ni, Si, La, Ce, Sm, Ca, Mg, O (oxygen), N (carbon), C (nitrogen), Mo, Hf, Ta, W, etc. You may

Preferably, the RTB based sintered magnet material of the present disclosure satisfies inequality (1).
[T] /55.85> 14 [B] /10.8 (Inequality (1))

By satisfying this inequality (1), the content of B is smaller than that of a general R-T-B-based sintered magnet. A general R-T-B-based sintered magnet does not form an Fe phase or R ₂ T ₁₇ phase other than the R ₂ T ₁₄ B phase which is the main phase [T] /55.85 (atomic weight of Fe) Is less than 14 [B] /10.8 (atomic weight of B) ([T] is the content of T in mass%, and [B] is the content of B in mass% Is). In a preferred embodiment of the present disclosure, the RTB-based sintered magnet material is different from a general RTB-based sintered magnet in that [T] /55.85 (atomic weight of Fe) is 14 [14]. B) is defined by inequality (1) so as to be greater than 10.8 (atomic weight of B). In addition, since T is Fe as a main component in the RTB-based sintered magnet material of the present invention, the atomic weight of Fe is used.

2. Process of preparing Pr-Ga alloy
[Pr-Ga alloy]
Pr of Pr-Ga alloy is 65 to 97 mass% of the whole of Pr-Ga alloy. Up to 30% by mass of this Pr can be replaced by Nd, and up to 20% by mass of Pr can be replaced by Dy and / or Tb. Ga is 3% by mass to 35% by mass of the whole of the Pr—Ga alloy, and 50% by mass or less of Ga can be replaced with Cu. The Pr-Ga alloy may contain unavoidable impurities. In the present invention, “30% or less of Pr can be substituted with Nd” means that the content (mass%) of Pr in the Pr—Ga alloy is 100%, and 30% of them can be substituted with Nd. Means For example, if Pr in a Pr—Ga alloy is 70% by mass (Ga is 30% by mass), Nd can be substituted up to 21% by mass. That is, 49% by mass of Pr and 21% by mass of Nd are obtained. The same applies to Dy, Tb, and Cu.

By performing a diffusion process to be described later with respect to the R-T-B-based sintered magnet material of the composition range of the present invention, a powder of a Pr-Ga alloy containing Pr and Ga in the above range allows Ga to pass through grain boundaries. It can be diffused deep inside the magnet. Pr is, Nd, may be replaced with Dy and / or Tb, for each of the substitution amount is too small, Pr exceeds the above range, it is impossible to obtain a high B _r and high H _cJ. Preferably, the Nd content of the Pr-Ga alloy is equal to or less than the unavoidable impurity content (approximately 1 mass% or less). Although 50% or less of Ga can be substituted by Cu, if the substitution amount of Cu exceeds 50%, there is a possibility that _HcJ may decrease.

  In the present disclosure, the Pr—Ga alloy is produced by a strip casting method.

  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 melt of a Pr-Ga alloy is quenched and solidified by a strip casting method, it is difficult to precisely control the cooling rate. For this reason, in the powder particles constituting the powder of the Pr—Ga alloy after grinding the Pr—Ga alloy, the structure of the structure is likely to vary among the powder particles. For example, the size of the fine grains formed in the Pr-Ga 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 Pr and Ga are supplied as diffusion sources in the diffusion step described later. Such variations eventually lead to variations in magnet characteristics. As a result, there is a case where the R-T-B based sintered magnet having no high _{B r} and high _{H cJ} obtained.

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

3. Process of obtaining diffusion source
[Heat treatment of Pr-Ga alloy]
In an embodiment of the present disclosure, a heat treatment is performed on the Pr—Ga alloy at a temperature not lower than 230 ° C. and not higher than the melting point of the Pr—Ga alloy.

  Thereby, the crystallinity of the powder particle which comprises the powder of Pr-Ga alloy is reformed. And the diffusion source excellent in uniformity can be obtained by grinding the Pr-Ga alloy (Pr-Ga alloy after heat treatment), and the dispersion of the magnetic characteristics in the diffusion process is suppressed by using the diffusion source. can do. The grinding of the Pr—Ga alloy may be carried out by a known grinding method such as pin mill grinding, and the size of the powder particles after grinding may be 300 μm or less (preferably 200 μm or less). Also, for example, the heat treatment time may be 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 Pr-Ga alloy is less than 230 ° C. lower than the melting point of the powder of the Pr-Ga alloy, the temperature may be too low and the crystallinity of the powder particles constituting the powder of the alloy may not improve If the temperature exceeds the melting point, the powders may be welded together and the diffusion process may not be performed efficiently.

  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 Pr-Ga alloy, it is possible to reduce the variation in characteristics among particles which may be caused by the contact time between the powder particles and the atmosphere or the difference in humidity, and the magnetic characteristics in the diffusion process. 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.

4. Diffusion Step The RTB-based sintered magnet material and the diffusion source are disposed in a processing vessel, and the RTB-based sintered magnet material and the diffusion source are placed in a vacuum or inert gas atmosphere 600. By heating at a temperature higher than 0 ° C. and not higher than 950 ° C., Pr and Ga contained in the diffusion source are diffused from the surface of the R-T-B based sintered magnet material to the inside. As a result, a liquid phase containing Pr and Ga is generated from the diffusion source, and the liquid phase is diffused and introduced from the surface of the sintered material through grain boundaries in the RTB-based sintered magnet material. . As a result, Ga together with Pr can be diffused deep through the grain boundaries of the RTB-based sintered magnet material. If the temperature of the heat treatment is 600 ° C. or less, the amount of liquid phase containing Pr and Ga may be too small to obtain high H _cJ, and if it exceeds 950 ° C., the H _cJ may decrease. is there. In addition, preferably, the RTB-based sintered magnet in which the diffusion step (more than 600 ° C. and not more than 950 ° C.) is performed is cooled to 300 ° C. at a cooling rate of 5 ° C./min or more from the temperature performed in the diffusion step. It is preferable to Higher H _cJ can be obtained. More preferably, the cooling rate to 300 ° C. is 15 ° C./min or more.

  In the diffusion step, first, the RTB-based sintered magnet material and the diffusion source are disposed in the processing container. At this time, it is preferable that the RTB-based sintered magnet material and the diffusion source be in contact in the processing container. For example, the surface of the RTB-based sintered magnet material can be covered with a diffusion source (powder layer) to perform the diffusion process. For example, after a slurry in which a diffusion source is dispersed in a dispersion medium is applied to the surface of an RTB-based sintered magnet material, the dispersion medium is evaporated to diffuse the diffusion source and the RTB-based sintered magnet material You may make contact. In addition, alcohol (ethanol etc.), an aldehyde, and a ketone can be illustrated as a dispersion medium. Furthermore, for example, a method of adhering a powdery diffusion source to an RTB-based sintered magnet material to which an adhesive has been applied by using a fluid immersion method, to an RTB-based sintered magnet material There is a method of sprinkling a powdery diffusion source, 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 RTB-based sintered magnet material 100 that can be used in the method of producing an RTB-based sintered magnet according to the present disclosure. The upper surface 100a and the side surfaces 100b and 100c of the RTB-based sintered magnet material 100 are shown in the drawing. The shape and size of the RTB-based sintered magnet material used in the manufacturing method of the present disclosure are not limited to the shape and size of the illustrated RTB-based sintered magnet material 100. The upper surface 100a and the side surfaces 100b and 100c of the R-T-B-based sintered magnet material 100 illustrated are flat, but the surface of the R-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 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 positioned on the surface of the R-T-B-based sintered magnet material 100 are the surface of the R-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 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 attached in one application step.

  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 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 RTB-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, the adhesive is applied to the entire surface (entire surface) of the RTB-based sintered magnet material. You may make it adhere to not the whole surface of RTB system sintered magnet raw material but one part. In particular, when the thickness of the R-T-B-based sintered magnet material is thin (for example, about 2 mm), one of the surfaces of the R-T-B-based sintered magnet material with the largest area is the diffusion source In some cases, Pr and Ga can be diffused throughout the magnet simply by depositing the powder of H. It is possible to improve H _cJ .

  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 with excellent uniformity. For this reason, when heating for diffusion to be described later is performed, Pr and Ga contained in the diffusion source can be efficiently diffused from the surface of the RTB-based sintered magnet material to the inside without waste.

  The coating amount of the diffusion source on the magnet surface is, for example, 0.1 to 1.0% by mass (preferably 0%) of the amount of Ga of the diffusion source with respect to 100% by mass of the RTB based sintered magnet. .1 to 0.5 mass%) can be set.

  The amounts of Pr and Ga contained in the diffusion source depend not only on the concentrations of Pr and Ga in 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 Pr and Ga diffused also by adjusting the particle size of the powder particles constituting the diffusion source while keeping the concentrations of Pr and Ga constant. After the diffusion step, heat treatment may be further performed at 400 to 800 ° C. for 10 minutes to 72 hours, if necessary.

  Moreover, although 1 '-4' description is abbreviate | omitted as mentioned above, 1 '-4' grind | pulverizes Pr-Ga alloy produced by the strip casting method by well-known methods, such as a pin mill grinding | pulverization, Preparing an alloy powder, and heat treating the powder of the Pr-Ga alloy at a temperature not lower than the melting point of the Pr-Ga alloy by 230 ° C. or more and a temperature not higher than the melting point It may be produced.

Experimental Example 1
[Preparation of RTB based sintered magnet material]
The R-T-B based sintered magnet material is approximately No. 1 in Table 1. Raw materials of the respective elements were weighed so as to have the compositions shown in A-1 and A-2, and an alloy was produced by a strip casting method. The obtained alloys were roughly pulverized by a hydrogen pulverizing method to obtain roughly pulverized powder. Next, 0.04 mass% of zinc stearate as a lubricant is added to the obtained coarsely pulverized powder with respect to 100% by mass of roughly pulverized powder and mixed, and then using an air flow crusher (jet mill apparatus) was dry milled in a nitrogen stream, the crushed particle diameter D ₅₀ was obtained finely pulverized powder of 4μm (the material alloy powder). Zinc stearate as a lubricant was added to the finely pulverized powder in an amount of 0.05% by mass with respect to 100% by mass of the finely pulverized powder, and the mixture was mixed in a magnetic field to obtain a compact. As a forming apparatus, a so-called perpendicular magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing direction are orthogonal to each other was used. The resulting molded body is sintered in vacuum at 1060 ° C. or more and 1090 ° C. or less (select the temperature at which densification by sintering sufficiently occurs for each sample) for 4 hours, and an RTB-based sintered magnet material is obtained Obtained. The density of the obtained RTB-based sintered magnet material was 7.5 Mg / m ³ or more. Table 1 shows the results of the components of the obtained RTB-based sintered magnet material. Each component in Table 1 was measured using high frequency inductively coupled plasma emission spectrometry (ICP-OES). The same applies to Tables 2 and 4 below. Further, when the inequality (1) of the present invention is satisfied, “o” is described, and when not satisfied, “x” is described. In addition, even if each composition of Table 1 is totaled, it does not become 100 mass%. This is because components other than the components listed in Table 1 (for example, O (oxygen), N (nitrogen), etc.) are present.

[Step of obtaining diffusion source]
No. shown in Table 2. The Pr-1 Ga alloy of a-1 was prepared by strip casting. Next, heat treatment is performed on the Pr-Ga alloy at 500 ° C. (a temperature lower by 80 ° C. than 580 ° C., which is the melting point of Pr-Ga alloy of No. a-1) for 2 hours. A diffusion source was obtained by pin milling the Ga alloy. The particle size of the diffusion source (alloy powder) was 200 μm or less (confirmed by sieving).

[Diffusion process]
Table 1 No. The RTB based sintered magnet materials of A-1 and A-2 were cut and ground to form cubes of 7.4 mm × 7.4 mm × 7.4 mm. Next, No. In the RTB-based sintered magnet material of A-1, 3 parts by mass of the diffusion source per 100 parts by mass of the RTB-based sintered magnet material in a plane (two planes) perpendicular to the orientation direction (1.5 parts by mass per side) was dispersed. Thereafter, a diffusion step of heating at 900 for 4 hours in a reduced pressure argon controlled at 50 Pa was performed. Furthermore, the RTB-based sintered magnet after the diffusion step and the No. 1 sintered magnet. A-2 (R-T-B sintered magnet material not subjected to the diffusion step) was subjected to a second heat treatment at 500 ° C. for 3 hours in reduced pressure argon controlled at 50 Pa. B-based sintered magnets (No. 1 and 2) were produced. The No. of the obtained RTB-based sintered magnet. The entire surface of each sample is cut by 0.2 mm using a surface grinder to remove the concentrated part of the Pr—Ga alloy relative to No. 1, and a cube of 7.0 mm × 7.0 mm × 7.0 mm I got a sample of No. 3 of RTB-based sintered magnets. The same cutting process was applied to 2 to obtain a cube-shaped sample of 7.0 mm × 7.0 mm × 7.0 mm. The obtained No. The composition of the R-T-B-based sintered magnet (a sample in which Pr or Ga is diffused using a diffusion source) is measured using high-frequency inductively coupled plasma emission spectrometry (ICP-OES). , No. The composition was the same as that of No. 2 (No. 2 has the same composition as No. A-2 because no diffusion source was used).

[sample test]
The obtained sample was measured for B _r and H _cJ by B-H tracer. The measurement results are shown in Table 3.

As described above, No. 1 and 2 despite the almost same composition, high B _r and high H _cJ towards as shown in Table 3 embodiment of the present invention (No.1) is obtained.

Experimental Example 2
Similarly to Experimental Example 1, Nd: 24.0%, Pr: 7.0%, B: 0.86%, Cu: 0.1%, Al: 0.1%, Ga: 0: 2 in mass ratio. An RTB-based sintered magnet material having a composition of 2%, Co: 0.8%, Fe: 67.0% was produced (the inequality (1) is satisfied). The dimensions of the RTB-based sintered magnet material were: thickness 5.0 mm × width 7.5 mm × length 35 mm.

  Next, a Pr—Ga alloy having a composition shown in Table 4 was prepared and prepared by strip casting in the same manner as in Example 1. Next, the Pr-Ga alloy is heat-treated under the conditions (temperature and time) shown in Table 4 (with the exception that No. 3 is not heat-treated), and the heat-treated Pr-Ga alloy is pin milled. The diffusion source (No. 3-15) was obtained. The particle size of the diffusion source (alloy powder) was 200 μm or less (confirmed by sieving). 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 4 average grain size. No. Since No. 3 did not heat-process to a diffusion source, the crystal grain size of the intermetallic compound phase was too small, and it was not able to measure (micro crystal grain of 1 micrometer or less).

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

  Next, with respect to the R-T-B-based sintered magnet material coated with the pressure-sensitive adhesive, the No. 1 in Table 4 was used. Three to fifteen diffusion sources were deposited. 50 pieces of RTB-based sintered magnet materials to which diffusion sources were attached were prepared for each type of diffusion sources (every No. 3 to 15). In the adhesion method, the diffusion source (alloy powder) is spread in a container, and the RTB-based sintered magnet material coated with the adhesive is cooled to room temperature, and then the diffusion source is RTB-based in the container. It was made to adhere to the entire surface of the sintered magnet material.

Next, the R-T-B-based sintered magnet material and the diffusion source are placed in a processing vessel and heated at 900 ° C. for 8 hours to remove Pr and Ga contained in the diffusion source as the R-T- A diffusion step of diffusing from the surface of the B-based sintered magnet material to the inside was performed. From the central part of the R-T-B based sintered magnet after diffusion, a cube of 4.5 mm in thickness × 7.0 mm in width × 7.0 mm in length is cut out, and for each type of diffusion source (for each of Nos. 3 to 15) 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 4.

As shown in Table 4, the powder of the Pr—Ga alloy powder not subjected to heat treatment No. 3 (comparative example) and the heat processing temperature are out of the range of this indication. As compared with No. 9 (comparative example), in each of the inventive examples (No. 4 to 8, No. 10 to 15), ΔH _cJ is about half, and the variation of the magnetic characteristics in the diffusion process is suppressed.

  According to the present invention, an RTB-based sintered magnet having a high residual magnetic flux density and a high coercive force can be manufactured. The sintered magnet of the present invention is suitable for various motors such as a motor for hybrid vehicle mounting exposed to high temperature, home appliances, and the like.

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

Claims (5)

R: 27.5 to 35.0% by mass (R is at least one of rare earth elements and necessarily includes Nd),
B: 0.80 to 0.99 mass%,
Ga: 0 to 0.8% by mass,
M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr),
Remainder T (T is Fe or Fe and Co) and unavoidable impurities,
Preparing an R-T-B-based sintered magnet material containing
Preparing a Pr-Ga alloy;
Heat treating the Pr—Ga alloy at a temperature not lower than the melting point of the Pr—Ga alloy but not lower than the melting point by 230 ° C. and not higher than the melting point, and grinding the Pr—Ga alloy after the heat treatment to obtain a diffusion source;
The RTB-based sintered magnet material and the diffusion source are disposed in a processing vessel, and the RTB-based sintered magnet material and the diffusion source are heated to over 600 ° C. in a vacuum or inert gas atmosphere. A diffusion step of diffusing Pr and Ga contained in the diffusion source from the surface to the inside of the RTB-based sintered magnet material by heating at a temperature of 950 ° C. or lower;
Including
The method for producing an RTB-based sintered magnet, wherein the Pr-Ga alloy is an alloy produced by a strip casting method. R: 27.5 to 35.0% by mass (R is at least one of rare earth elements and necessarily includes Nd),
B: 0.80 to 0.99 mass%,
Ga: 0 to 0.8% by mass,
M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr),
Remainder T (T is Fe or Fe and Co) and unavoidable impurities,
Preparing an R-T-B-based sintered magnet material containing
Grinding the Pr-Ga alloy to prepare a powder of the Pr-Ga alloy;
Heat treating the powder of the Pr-Ga alloy at a temperature not lower than the melting point of the powder of the Pr-Ga alloy and not lower than the melting point to obtain a diffusion source from the powder of the Pr-Ga alloy;
The RTB-based sintered magnet material and the diffusion source are disposed in a processing vessel, and the RTB-based sintered magnet material and the diffusion source are heated to over 600 ° C. in a vacuum or inert gas atmosphere. A diffusion step of diffusing Pr and Ga contained in the diffusion source from the surface to the inside of the RTB-based sintered magnet material by heating at a temperature of 950 ° C. or lower;
Including
The method for producing an RTB-based sintered magnet, wherein the Pr-Ga alloy is an alloy produced by a strip casting method. The method of manufacturing an RTB-based sintered magnet according to claim 1, wherein the RTB-based sintered magnet material satisfies the following inequality (1).
[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T in mass%, [B] is the content of B in mass%)   The method for producing an R-T-B-based sintered magnet according to any one of claims 1 to 3, wherein the Ga content of the RTB-based sintered magnet material is 0 to 0.5 mass%.   The manufacturing method of the RTB-based sintered magnet according to any one of claims 1 to 4, wherein the Nd content of the Pr-Ga alloy is equal to or less than the unavoidable impurity content.

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