JP2022152424A - R-t-b based permanent magnet and method of producing the same - Google Patents

Abstract

To provide an R-T-B based permanent magnet having both high residual magnetic flux density and high coercive force, and a method for producing the R-T-B based permanent magnet while suppressing the used amount of heavy rare earth elements.SOLUTION: A method for producing an R-T-B based permanent magnet includes the steps of: preparing a magnet base material 20 including an R-T-B based alloy; attaching a sheet 11a of a first diffusion material 11 including at least one RH to at least part of a first surface on the magnet base material 20; attaching a sheet 12a of a second diffusion material 12 including at least one kind of RL to at least part of a second surface on the magnet base material 20; and heating the magnet base material 20 to diffuse the RH and the RL to the inside of the magnet base material 20. In the magnet base material 20, the first surface (main surface 20a) and the second surface (lateral surface 20b) intersects to form a corner.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method of producing an RTB permanent magnet through a grain boundary diffusion process, and an RTB permanent magnet produced by the method.

A rare earth magnet having an RTB system composition (RTB system permanent magnet) has magnetic properties superior to those of other permanent magnets. Remanent magnetic flux density Br and coercive force HcJ are generally used as indicators of the magnetic properties of RTB system permanent magnets, and in recent years, various studies have been made with the aim of further improving these magnetic properties. there is

For example, Patent Literature 1 states that in an IPM rotating machine, it is effective to use permanent magnets having high HcJ at stator-side corners (magnet corners). In addition, in Patent Document 1, the HcJ at the corners of the magnet is improved by diffusing the heavy rare earth element from a plurality of surfaces constituting the corners of the magnet and concentrating the heavy rare earth element at the corners of the magnet.

However, in the manufacturing method of Patent Document 1, since the heavy rare earth element is applied to a plurality of surfaces forming the corners of the magnet, the consumption of the heavy rare earth element increases during the production process. In recent years, with the mass production and mass use of RTB permanent magnets, the scarcity of rare earth elements is increasing, and the reduction of the usage of heavy rare earth elements is particularly important. Therefore, it is desired to provide an RTB system permanent magnet having both high remanent magnetic flux density and high coercive force while suppressing the amount of heavy rare earth elements used in the manufacturing process.

JP 2015-223079 A

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an RTB permanent magnet having both a high residual magnetic flux density and a high coercive force, and an RTB permanent magnet comprising a heavy rare earth magnet. An object of the present invention is to provide a manufacturing method while suppressing the amount of elements used.

In order to achieve the above object, a method for producing an RTB permanent magnet according to the present invention comprises:
preparing a magnet base material containing an RTB alloy;
attaching a first diffusing material containing at least one heavy rare earth element to at least a portion of a first surface of the magnet substrate;
attaching a second diffusing material containing at least one light rare earth element to at least a portion of a second surface of the magnet base;
a step of heating the magnet base material to diffuse the heavy rare earth element and the light rare earth element into the magnet base material (diffusion step);
In the magnet base material, the first surface and the second surface intersect to form corners.

As a result of intensive studies, the present inventors have found that the light rare earth element (RL) is attached to the second surface adjacent to the first surface to which the heavy rare earth element (RH) is attached and grain boundary diffusion is performed. , it is possible to obtain an RTB system permanent magnet having both a high residual magnetic flux density Br and a high coercive force HcJ while suppressing the amount of heavy rare earth elements used. Moreover, in the manufacturing method described above, the amount of RH used in the manufacturing process can be reduced compared to the case where RH is diffused from both the first surface and the second surface.

Preferably, the attachment location of the first diffusion material and the attachment location of the second diffusion material are close to each other at the corner where the first surface and the second surface intersect.

Preferably, the second diffusing material includes an RL-M alloy containing the light rare earth element, and in the RL-M alloy, RL is the light rare earth element, and M is the eutectic temperature with RL. is an element with a temperature of 800° C. or lower.

Preferably, the second diffusing material contains at least one element selected from the group consisting of Nd and Pr as the light rare earth element, and the second diffusing material substantially contains a heavy rare earth element. not contained in

On the other hand, the first diffusing material preferably contains one or more elements selected from the group consisting of Tb and Dy as the heavy rare earth element.

Also, preferably, the first surface is a magnetic pole surface. When this requirement is satisfied, it is possible to further improve HcJ while ensuring a high Br at the ends (magnet corners) of the magnetic pole faces where the demagnetizing field tends to increase.

The RTB permanent magnet according to the present invention can be obtained, for example, by the manufacturing method described above,
RT wherein R is one or more light rare earth elements and one or more heavy rare earth elements consisting essentially of Nd, T is one or more iron group elements consisting essentially of Fe, and B is boron - a B-based permanent magnet,
The RTB permanent magnet has a corner where the first surface and the second surface intersect,
the content of the heavy rare earth element continuously decreases from the first surface of the RTB permanent magnet toward the inner center,
The content of the light rare earth element continuously decreases from the second surface of the RTB permanent magnet toward the inner center.

Since the RTB permanent magnet has the above characteristics, both Br and HcJ can be improved, and HcJ can be improved while maintaining a high Br, especially in the vicinity of the corners.

Further, the RTB permanent magnet of the present invention preferably contains an M element whose eutectic temperature with the light rare earth element is 800° C. or less,
It has a concentration distribution in which the content of the M element decreases from the second surface toward the inner central side.

The first surface is a magnetic pole surface, and the second surface is a surface that intersects the magnetic pole surface. When the RTB permanent magnet of the present invention satisfies these requirements, it is possible to further improve HcJ while ensuring a high Br at the ends (magnet corners) of the magnetic pole faces where the demagnetizing field tends to increase. .

Also, preferably, the content of the heavy rare earth element on the second surface is lower than the content of the heavy rare earth element on the first surface.

The RTB system permanent magnet of the present invention can be used as a component of motors, generators, compressors, actuators, magnetic sensors, speakers, etc., and is particularly suitable as a component of motors. In addition, the motor containing the RTB permanent magnet of the present invention can be mounted on various electronic devices and industrial devices, and is particularly suitable for use as a motor for automobiles (EV, HV, PHV, etc.). is.

FIG. 1 is a perspective view showing an example of a magnet base material. FIG. 2 is a schematic diagram schematically showing the flow of the diffusion process. FIG. 3A is a cross-sectional schematic diagram showing an enlarged cross section of the magnet base material. FIG. 3B is a schematic cross-sectional view showing an enlarged cross-section of the RTB system permanent magnet after the diffusion process. FIG. 4A is a perspective view showing an example of an RTB system permanent magnet and a sampling method. FIG. 4B is a perspective view showing an example of an RTB system permanent magnet and a sampling method. FIG. 5A is a cross-sectional view taken along line VA--VA shown in FIG. 4A. FIG. 5B is a cross-sectional view along line VB-VB shown in FIG. 4B. FIG. 6 is a schematic diagram showing a cross section of a core-shell particle. FIG. 7 is an SEM cross-sectional photograph of an RTB system permanent magnet according to Example (Sample 1). FIG. 8 is an SEM cross-sectional photograph of an RTB system permanent magnet according to Comparative Example 2. FIG. FIG. 9A is a schematic diagram showing a modification of the diffusion process. FIG. 9B is a schematic diagram showing a modification of the diffusion process. FIG. 10 is a schematic diagram of an IPM motor using RTB system permanent magnets of the present invention. FIG. 11 is a schematic diagram showing an automobile using the IPM motor shown in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In this embodiment, first, a method for manufacturing an RTB system permanent magnet will be described, and then the characteristics of the RTB system permanent magnet obtained by this manufacturing method will be described. The RTB-based permanent magnet of the present embodiment is produced by a step of preparing a magnet base material and a step of diffusing a heavy rare earth element (RH) and a light rare earth element (RL) into the magnet base material by a predetermined method. (Grain boundary diffusion step). Each step will be described below in order.

(Preparation step for magnet base material)
In this step, the magnet base material 20 shown in FIG. 1 is manufactured. First, the features of the magnet base material 20 will be described in detail. The magnet base material 20 is a sintered body of an RTB-based alloy, and is a material before performing the diffusion process described later. In FIG. 1, the magnet base 20 is a rectangular parallelepiped having two main surfaces 20a perpendicular to the Z-axis and four side surfaces 20b perpendicular to the X-axis or the Y-axis. However, the shape of the magnet base material 20 is not particularly limited, and may be, for example, a polygonal shape, a cylindrical shape, a hollow cylindrical shape, or an arc segment shape whose main surface is curved in an arc shape. In the present embodiment and drawings, the X-axis, Y-axis, and Z-axis are substantially perpendicular to each other, and the term "inside" means the side closer to the center of the magnet base material 20 or the permanent magnet 2. "Outer" means the side more distant from the center of the magnet substrate 20 or permanent magnet 2 .

In this embodiment, the two main surfaces 20a of the magnet base material 20 are used as magnetic pole surfaces. A magnetic pole surface is a surface through which magnetic flux mainly passes, and is a positive electrode (N pole) or a negative electrode (S pole) of a permanent magnet. When the RTB system permanent magnet to be manufactured is an anisotropic magnet, the magnetic pole faces can be determined by the direction of the magnetic field applied in the molding process, which will be described later. It should be noted that there is no particular limitation on which side of the magnet base material 20 is used as the magnetic pole surface, and any side surface 20b may be used as the magnetic pole surface.

In the RTB alloy forming the magnet base material 20, R is one or more rare earth elements essentially including Nd (neodymium), and T is one or more essentially Fe (iron). and B is boron. Here, the rare earth elements mean Sc, Y and lanthanoid elements belonging to Group 3 of the long period periodic table. They are called heavy rare earth elements (RH), and rare earth elements other than RH are called light rare earth elements (RL). Also, the iron group elements refer to Fe, Co, and Ni.

The total content of R contained in the magnet base material 20 can be 25% by mass to 35% by mass, preferably 27.5% by mass or more and 30.8% by mass or less. When the total content of R satisfies the above composition range, precipitation of α-Fe exhibiting soft magnetism is suppressed, and R ₂ T ₁₄ B crystals are more likely to be generated. Here, in the present embodiment, the "content rate of the predetermined element contained in the magnet base material 20" is the content rate per unit mass of the magnet base material 20, and the content of the predetermined element with respect to 100% by mass of the magnet base material. means ratio. That is, the above total R content is calculated as a ratio of the total mass of the rare earth elements to 100 mass % of the magnet base material. The content of a predetermined element in the permanent magnet 2, which will be described later, is also expressed in the same manner as above.

When a plurality of rare earth elements are included as R, the content of Nd included in the magnet base material 20 is not particularly limited, but is preferably 22% by mass or more. In this case, it is preferable that the magnet base material 20 contain Pr, Tb, and Dy as rare earth elements other than Nd. When a heavy rare earth element (RH) such as Tb or Dy is added as R other than Nd, the total content of RH contained in the magnet base material 20 is preferably 2.5% by mass or less.

The content of B contained in the magnet base material 20 can be 0.5% by mass to 1.5% by mass, preferably 0.92% by mass to 1.03% by mass.

On the other hand, the content of T contained in the magnet base material 20 is expressed as the balance, and may be appropriately determined according to the content of other elements. T may be Fe alone, or part of Fe may be substituted with Co. In this case, the Co content is not particularly limited, and can be, for example, 4% by mass or less, preferably 1% by mass or less.

In addition to R, T, and B described above, the magnet base material 20 preferably contains one or more m elements selected from the group consisting of Cu, Ga, Al, and Zr. As the m element, it is more preferable to contain Cu among the above.

The content of Cu contained in the magnet base material 20 is preferably 0.05% by mass or more and 0.50% by mass or less. In addition, when Ga, Al, and Zr are included as the m element, the content of these elements is not particularly limited. The Zr content is preferably 0.10 mass % or more and 0.30 mass % or less, and the Zr content is preferably 0.10 mass % or more and 0.30 mass % or less.

The magnet base material 20 may also contain carbon (C), nitrogen (N), and oxygen (O). The carbon content in the magnet base material 20 is preferably 1100 ppm by mass or less, more preferably 900 ppm by mass or less. The nitrogen content in the magnet base material 20 is preferably 1000 ppm by mass or less, more preferably 600 ppm by mass or less. The oxygen content in the magnet base material 20 is preferably 1200 ppm or less, more preferably 800 ppm or less.

Furthermore, the magnet base material 20 may contain unavoidable impurities such as Mn, Ca, Cl, S, and F in addition to the elements described above. It is about 1.0% by mass to 1.0% by mass.

The composition of the magnet base material 20 can be analyzed by a conventionally generally known method. For example, the contents of various elements such as R, T, and B can be measured by X-ray fluorescence spectroscopy (XRF) or inductively coupled plasma emission spectroscopy (ICP). Further, for example, the oxygen content can be measured by an inert gas fusion-nondispersive infrared absorption method, the carbon content can be measured by combustion in an oxygen stream-infrared absorption method, and the nitrogen content can be measured by an infrared absorption method. It can be measured by active gas fusion-thermal conductivity method.

As shown in FIG. 3A, the magnet base material 20 includes main phase grains 4 made of R ₂ T ₁₄ B crystals, grain boundaries 6 located between the main phase grains 4, and other magnetic properties. Secondary phases may be present to the extent that they are not harmful.

The average particle diameter of the main phase particles 4 is not particularly limited, and can be, for example, 1.0 μm to 10 μm, preferably 2.5 μm to 6.0 μm, in terms of circle equivalent diameter. Note that the average particle diameter of the main phase particles 4 is determined by observing the cross section of the magnet base material 20 as shown in FIG. It can be measured by measuring the equivalent circle diameter of the particles 4 .

In the R ₂ T ₁₄ B crystal forming the main phase particles 4, part of T, which is an iron group element, may be substituted with a transition metal element such as the m element.

The grain boundaries 6 include two grain boundaries 6a positioned between two adjacent main phase grains 4 and grain boundary multiple points 6b surrounded by three or more main phase grains 4. In addition, the grain boundaries 6 are composed of phases other than the main phase grains 4 (that is, phases other than the R ₂ T ₁₄ B crystal phase), and the types and proportions of the phases constituting the grain boundaries 6 are particularly limited. not. Other phases constituting the grain boundary 6 include, for example, a phase having a higher concentration of R than the main phase grains 4 (R-rich layer), a phase having a high concentration of transition metal elements such as T (iron group element) and Ga. , an oxide layer of a rare earth element, an R—O—C phase, and the like.

The magnet base material 20 having the characteristics described above is manufactured through a process of manufacturing a raw material alloy, a process of pulverizing the raw material alloy (pulverizing process), a process of molding the raw material alloy powder (forming process), and a process of sintering the compact. (Sintering step) and can be manufactured through.

First, raw metals corresponding to the composition of the RTB alloy described above are prepared, and the prepared raw metals are melted in a vacuum or an inert gas atmosphere such as Ar gas. After that, a raw material alloy is obtained by casting the melted raw material metal.

At this time, there is no particular limitation on the type of raw material metal, and for example, rare earth metals or rare earth alloys, pure iron, pure cobalt, ferroboron, and alloys and compounds thereof can be used. Also, the method of casting the raw material metal is not particularly limited, and examples thereof include an ingot casting method, a strip casting method, a book mold method, or a centrifugal casting method. Further, if the raw material alloy after casting has solidification segregation, it may be subjected to homogenization treatment (solution treatment) as necessary.

Next, the raw material alloy obtained in the above steps is pulverized. The atmosphere in each step from the pulverization step to the sintering step preferably has a low oxygen concentration from the viewpoint of obtaining high magnetic properties. The low oxygen concentration atmosphere is, for example, an atmosphere with an oxygen concentration of 200 ppm or less. By controlling the oxygen concentration in each step, the amount of oxygen contained in the magnet base material 20 and the finally obtained permanent magnet 2 can be controlled.

The pulverization process is carried out in two steps of coarse pulverization and fine pulverization. However, the raw material alloy may be pulverized in one stage of only the fine pulverization step.

In the coarse pulverization step, coarse pulverization is performed until the particle size reaches about several hundred μm to several mm to obtain a coarsely pulverized powder. The method of coarse pulverization is not particularly limited, and for example, a method of performing hydrogen absorption pulverization, a method of using a coarse pulverizer, or the like can be employed. When hydrogen absorption pulverization is performed, the amount of nitrogen contained in the magnet base material 20 and the finally obtained permanent magnet 2 can be controlled by controlling the nitrogen gas concentration in the atmosphere during dehydrogenation.

Next, the obtained coarsely pulverized powder is finely pulverized to an average particle size of about several μm to obtain a finely pulverized powder (raw material alloy powder). The average particle size of the finely pulverized powder is not particularly limited. By controlling the nitrogen gas concentration in the atmosphere in the pulverization step, the nitrogen content in the magnet base material 20 and the finally obtained permanent magnet 2 can be controlled.

The fine pulverization method is not particularly limited, and various fine pulverizers can be used. Further, it is preferable to add a pulverizing aid during the fine pulverization, and examples of the pulverizing aid include lauric acid amide and oleic acid amide. By using a grinding aid, a highly oriented finely ground powder can be obtained during molding. The amount of carbon contained in the magnet base material 20 and the finally obtained permanent magnet 2 can be controlled by changing the amount of the grinding aid added.

In the above steps (from the preparation step of the raw material alloy to the pulverization step), the raw material alloy powder was obtained by the one-alloy method, but the raw material alloy powder is produced by mixing two alloys, the first alloy and the second alloy. A two-alloy method may be employed.

Next, the obtained raw material alloy powder is formed into a predetermined shape. The molding method is not particularly limited, and may be dry molding or wet molding. In this embodiment, the raw material alloy powder is filled in a mold and pressed in a magnetic field (dry compaction).

The pressure during molding can be, for example, 20 MPa to 300 MPa, and the applied magnetic field can be 950 kA/m to 1600 kA/m. The magnetic field to be applied is not limited to a static magnetic field, and may be a pulsed magnetic field, or both a static magnetic field and a pulsed magnetic field may be used. When wet molding is employed, the raw material alloy powder is dispersed in a solvent such as oil to form a slurry, and the slurry is press-molded in the same manner as described above.

Next, the compact is sintered in vacuum or in an inert gas to obtain a sintered body. The sintering conditions may be appropriately determined according to various conditions such as the composition, pulverization method, and grain size of the raw material alloy powder. For example, the compact can be sintered by holding the compact at a temperature of 1000° C. to 1200° C. for 1 hour to 10 hours in vacuum or inert gas.

Moreover, after the sintering step, the sintered body may be decarbonized, if necessary. The decarbonization method is not particularly limited, and a known method may be adopted. For example, the carbon content in the sintered body can be reduced by attaching a predetermined metal S to the sintered body and heat-treating the sintered body. In the above, the predetermined metal S is a metal whose standard Gibbs energy of formation for forming metal carbide from the metal is lower than that of the rare earth element (especially Nd) in the sintered body. By attaching the metal S to the sintered body and heat-treating the sintered body, the carbon in the sintered body reacts with the metal S to form a carbide. The attached metal S hardly penetrates into the sintered body and stays on the surface of the sintered body. By performing the decarbonization treatment as described above, the amount of carbon contained in the magnet base material 20 and the finally obtained permanent magnet 2 can be reduced.

Further, the sintered body may be subjected to shape processing such as cutting and grinding, chamfering processing such as barrel polishing, and the like, if necessary. These processes are performed before the diffusion process described later.

By the above method, the magnet base material 20 shown in FIGS. 1 and 3A is obtained.

(Grain boundary diffusion process)
Next, the grain boundary diffusion process will be described. In the present embodiment, the grain boundary diffusion step includes a step of preparing two types of diffusing materials, a step of attaching a first diffusing material containing a heavy rare earth element (RH) to the first surface of the magnet base material, and a step of The method includes a step of attaching a second diffusion material containing (RL) to the second surface of the magnet base material, and a step of heating the magnet base material to diffuse RH and RL inside the magnet base material.

Preparation of Diffusion Material First, a first diffusion material 11 containing RH and a second diffusion material 12 containing RL are prepared.

The first diffusing material 11 contains at least one heavy rare earth element RH, and the added RH is preferably one or more elements selected from the group consisting of Tb and Dy. Also, the first diffusion material 11 can be a pure metal, an alloy, or a compound containing RH such as _TbH2 .

When the first diffusing material 11 is an alloy, if the total content of RH and metal elements other than RH contained in the first diffusing material (more specifically, RH + RL + M) is 100% by mass, the total 100% by mass It is preferable to adjust the amount of elements other than RH to be added so that the content of RH is 60% by mass or more. In this case, RL may be included as an element other than RH. The content of RL with respect to the above total of 100% by mass is preferably 22.5% by mass or less. Further, the first diffusion material 11 may contain a predetermined M element, and may be an RH-M alloy containing RH and M, or an RH-RL-M alloy. In this case, the content of the M element with respect to the above total of 100% by mass can be, for example, 5% by mass to 20% by mass. The element M will be described in detail when the second diffusion material 12 is described.

On the other hand, the second diffusion material 12 contains at least one kind of light rare earth element (RL), and the RL to be added is one or more elements selected from the group consisting of Nd and Pr. is preferred. The second diffusion material 12 can be a pure metal, an alloy, or a compound containing RL such as a hydride, and is particularly preferably an RL-M alloy containing RL and a predetermined M element.

Here, the M element is an element whose eutectic temperature between M and RL is 800° C. or less, and specifically, Al, Mg, Fe, Mn, Co, Ni, Cu, Zn, Ga, Ge, Ru , Rh, Pd, Ag, Sn, Sb, Pt, Au, Hg, Bi, Si, and Cl. Preferably, the M element is an element in which the eutectic temperature between M and RL is 700° C. or less. , Hg, Si, and Cl. More preferably, the M element is an element in which the eutectic temperature between M and RL is 600° C. or lower, specifically Mg, Co, Ni, Cu, and Cl. More preferably, the M element is Cu or Co.

Further, if the sum of RL and metal elements other than RL contained in the second diffusing material (more specifically, RH + RL + M) is 100% by mass, the total content of M elements with respect to the total 100% by mass is the selected M element Although it depends on the type, it is preferably 5 mass % to 20 mass %. In particular, when Cu is added as the M element, the content of Cu is preferably 10% by mass to 15% by mass with respect to the above total of 100% by mass. By including the M element in the second diffusion material 12 , the melting point of the second diffusion material 12 is lowered, and RL is easily diffused into the magnet base material 20 .

In addition, the second diffusing material 12 may contain a heavy rare earth element (RH). It is more preferable not to contain substantially. "Substantially free of RH" more specifically means that the content of RH is less than 0.5% by mass with respect to the above total of 100% by mass. In the grain boundary diffusion treatment of the present embodiment, since the second diffusing material 12 does not substantially contain RH, the magnetic properties in the vicinity of the corners of the magnet can be further improved, and RH during the manufacturing process can be improved. can be more suitably reduced.

As described above, the first diffusion material 11 mainly containing RH may also contain the M element. , and the addition amount of the M element can be the same as that of the second diffusion material 12 . However, the type of M element to be selected may be different or the same between the first diffusion material 11 and the second diffusion material 12 .

The first diffusing material 11 including the attaching step RH of the first diffusing material 11 is attached to at least part of the first surface of the magnet base material 20 . Here, the first surface to which the first diffusing material 11 is attached is preferably a magnetic pole surface, and may be only one of a pair of magnetic pole surfaces, or both magnetic pole surfaces may be used as the first surface. good. In this embodiment, as described at the beginning, the pair of main surfaces 20a perpendicular to the Z-axis are the magnetic pole surfaces, and the first diffusing material 11 is attached to both main surfaces 20a as shown in FIG. and

In the above description, "at least a portion of the first surface" means that the area of the first diffusion material 11 attached to one main surface 20a may be smaller than the area of the main surface 20a. The first diffusing material 11 may be adhered to the entire surface 20a (adhesion area of the first diffusing material 11≈the area of the main surface 20a). Although the adhesion area of the first diffusion material 11 is not particularly limited, the adhesion area of the first diffusion material 11 is at least a part of the intersection corner 20c between the main surface 20a and the side surface 20b. is preferably close to the attachment point of

Here, as shown in FIGS. 1 and 2, the crossing corners 20c between the main surface 20a and the side surface 20b are four crossing corners 20c substantially parallel to the X-axis and four crossing corners 20c substantially parallel to the Y-axis. There is a crossing corner 20c. Of the total eight crossing corners 20c, if the crossing corner 20c where the demagnetizing field is particularly large in the mode of use of a permanent magnet such as a motor is defined as a corner 20cD, the first diffusing material 11 adheres to at least the corner 20cD. It is preferable that the location and the attachment location of the second diffusing material 12 are close to each other. As shown in FIG. 2, in all cross corners 20c, the attachment points of the first diffusion material 11 and the attachment points of the second diffusion material 12 may be close to each other.

It should be noted that the adhering portion of the first diffusing material 11 and the adhering portion of the second diffusing material 12 are “adjacent” means that the adhering portion of the first diffusing material 11 and the adhering portion of the second diffusing material 12 are in direct contact. It means that they may be separated from each other by a predetermined distance. More specifically, the edge of the attachment point of the first diffusion material 11 may be separated from the intersection corner 20c by about 0 mm to 1 mm, and the edge of the attachment point of the second diffusion material 12 may be at the intersection corner 20c. may be 0 mm to 1 mm away from In the present embodiment, when the distance between the edge of the adhesion point and the crossing corner 20c satisfies the above numerical range, the adhesion point of the first diffusion material 11 and the adhesion point of the second diffusion material 12 are "near". judge that it is.

The method of adhering the first diffusing material 11 to the main surface 20a of the magnet base material 20 is not particularly limited. , sheet construction method, etc. can be used.

When the sheet construction method is employed, powdery first diffusion material 11 and a binder are mixed to produce a sheet 11a of the first diffusion material as shown in FIG. to adhere to. When the sheet 11a is adhered to the magnet base material 20, an organic solvent such as alcohol, aldehyde, or ketone may be applied to the surface of the sheet 11a or the surface of the magnet base material 20. FIG.

Moreover, when adopting the coating method, a slurry is prepared by dispersing the powdery first diffusion material 11 in an organic solvent such as alcohol, aldehyde, or ketone. Then, the slurry is applied to the main surface 20a of the magnet base material 20 using a spray, a brush, a jet dispenser, a nozzle, or the like. A binder may be added to the slurry so that the first diffusing material 11 can easily adhere to the surface of the magnet base material 20 . Alternatively, a paste having a higher viscosity than slurry may be prepared using the first diffusing material 11 and the paste may be applied to the main surface 20 a of the magnet base material 20 . In various printing methods, the above paste may be printed on the main surface 20a of the magnet base material 20 .

As described above, the first diffusing material 11 can be attached to the magnet base material 20 by a plurality of methods. It is preferable that it is controlled so that it is satisfied. That is, the total amount of RH to be attached is 0.1 to 2.0 parts by mass (more preferably 0.4 to 1.0 parts by mass) with respect to 100 parts by mass of the magnet base material. Moreover, it is preferable to control the adhesion amount of the first diffusion material 11 .

The second diffusing material 12 including the step RL of attaching the second diffusing material 12 is attached to at least part of the second surface of the magnet base material 20 . Here, the second surface to which the second diffusing material 12 is attached is a surface intersecting the first surface to which the first diffusing material 11 is attached, and preferably a surface intersecting the magnetic pole surface. In this embodiment, as shown in FIG. 2, the first diffusion material 11 is attached to the main surface 20a, which is the magnetic pole surface, so the second diffusion material 12 is attached to the side surface 20b intersecting the main surface 20a. . More specifically, the second diffusion material 12 may be attached to only one side surface 20b selected from the four side surfaces 20b, or may be attached to a plurality of side surfaces 20b. In this embodiment, as shown in FIG. 2, the second diffusion material 12 is attached to four side surfaces 20b.

In the above description, "at least part of the second surface" means that the area of the second diffusion material 12 attached to one side surface 20b may be smaller than the area of the main surface 20a. The second diffusing material 12 may be adhered to the entire surface (attachment area of the second diffusing material 12≈the area of the side surface 20b). The adhesion area of the second diffusion material 12 is not particularly limited. As described above, it is preferable that the attachment point of the second diffusion material 12 is adjacent to the attachment point of the first diffusion material 11 in at least a part of the intersection corner 20c, and is close to the attachment point of the first diffusion material 11. It is more preferable that there is a portion in direct contact.

Letting A _H be the adhesion area of the first diffusion material 11 on any one of the main surfaces 20a′ and A _L be the adhesion area of the second diffusion material 12 on the side surface 20b′ intersecting with the main surface 20a′, A It is preferred that _L /A _H is from 0.1 to 0.6.

The method of attaching the second diffusing material 12 is not particularly limited. A construction method or the like can be used. In FIG. 2, a sheet 12a of the second diffusion material 12 is used as an example, and the sheet 12a is obtained by mixing the powdery second diffusion material 12 and a binder to form a sheet. .

Moreover, it is preferable that the adhesion amount of the second diffusing material 12 is controlled so as to satisfy a predetermined condition. That is, the total amount of RL to be attached is 0.1 to 1.5 parts by mass (more preferably 0.4 to 0.8 parts by mass) with respect to 100 parts by mass of the magnet base material. In addition, it is preferable to control the adhesion amount of the second diffusion material 12 .

The order in which the diffusion materials (11, 12) are attached is not particularly limited. For example, after attaching the second diffusion material 12 to the four side surfaces 20b, the first diffusion material 11 may be attached to the two main surfaces 20a. After the first diffusing material 11 is attached to the main surface 20a above the Z axis, the second diffusing material 12 is attached to the four side surfaces 20b. Finally, the first diffusing material 11 is attached to the main surface 20a below the Z axis. may be attached. The order of the adhesion steps may be appropriately determined in consideration of work efficiency.

Step of heating the magnet base material 20 (diffusion step)
Next, after each diffusion material (11, 12) is applied, the magnet base material 20 is heated under predetermined conditions to diffuse the RH and RL contained in each diffusion material inside the magnet base material 20. FIG.

The heat treatment conditions in this step are preferably a heat treatment atmosphere in a vacuum or an inert gas, a holding temperature of more than 700° C. and 1000° C. or less, and a temperature holding time of 1 hour or more and 24 hours or less. . Moreover, it is preferable to rapidly cool the magnet base material 20 after a predetermined holding time has passed. By performing the heat treatment under the above conditions, the RH contained in the first diffusion material 11 and the RL contained in the second diffusion material 12 (when the diffusion material contains the M element, RH, RL, and M element) , diffuses into the grain boundary 6 of the magnet base material 20 .

At this time, the RH that diffuses from the main surface 20a toward the inside of the magnet base material 20 reacts with part of the R ₂ T ₁₄ B crystals at the outer peripheral edges of the main phase particles 4 and is concentrated. That is, in the main phase particles 4 in the region where RH diffuses, a shell portion 42 with a high RH content is formed, and as shown in FIG. 3B, the main phase particles 4 become core-shell particles 4a.

On the other hand, the RL diffusing from the side surface 20b toward the inside of the magnet base material 20 reforms the grain boundaries 6 (especially the two grain boundaries 6a) without decomposing the R ₂ T ₁₄ B crystals of the main phase grains 4. It is thought that it shows the function of questioning. The modification of the grain boundary 6 is, for example, conceivable that the grain-boundary-diffused RL expands the grain boundary 6a of the two grains and promotes the diffusion of RH entering the inside of the magnet base material 20 from the main surface 20a. In addition, it is considered that the RL diffused into the grain boundary 6 acts to suppress the increase in the concentration of RH in the grain boundary 6 as a modification action of the grain boundary 6 . As a result, RH can be prevented from excessively reacting with the R ₂ T ₁₄ B crystal, and the thickness of the shell portion 42 can be prevented from becoming thicker than necessary.

It is believed that the modification of the grain boundary 6 as described above occurs particularly actively in the vicinity of the intersection corner 20c where the attachment point of the first diffusing material 11 and the attachment point of the second diffusing material 12 are in contact with each other. The magnetic properties (Br and HcJ) at the intersection corner 20c (the corner 2c of the permanent magnet) can be improved.

When the magnet base material 20 contains only Nd as R and the second diffusing material 12 contains RL other than Nd, such as Pr, R ₂ T constituting the main phase particles 4 In the ₁₄ B crystal, part of R(Nd) may be substituted with RL other than Nd.

After the diffusion step, an aging treatment may be performed. When the aging treatment is performed, it is carried out by holding the magnet base material 20 at a temperature of 450° C. to 700° C. for 0.2 to 3 hours in vacuum or in an inert gas after quenching in the diffusion process. It is preferable to cool rapidly after the retention time has elapsed.

Further, after the diffusion process, residues such as an oxide film may remain on the surface of the magnet base material 20 in some cases. Therefore, it is preferable to perform a processing step for removing the residue after the diffusion step. The method of removing the residue is not particularly limited. For example, chemical removal such as etching, physical cutting, shape processing such as grinding, or chamfering such as barrel polishing may be performed.

By the above manufacturing method, an RTB system permanent magnet 2 (FIG. 4A) having both a high residual magnetic flux density Br and a high coercive force HcJ is obtained, and the RTB system obtained by the above manufacturing method In the permanent magnet 2, a high Br and a high HcJ are obtained especially at the corner 2c of the permanent magnet 2 corresponding to the intersection corner 20c. Further, in the above manufacturing method, the magnetic properties (especially HcJ) can be improved without depositing RH on surfaces other than the pole faces, and the amount of RH used in the manufacturing process can be reduced. The features of the RTB system permanent magnet 2 obtained by the manufacturing method of the present embodiment will be described in detail below.

(RTB system permanent magnet 2)
In the RTB system permanent magnet 2 (hereinafter referred to as the permanent magnet 2) of this embodiment shown in FIG. The four side surfaces 2b intersecting the main surface 2a are surfaces to which the second diffusion material 12 is attached. In FIG. 4A, the permanent magnet 2 has a rectangular parallelepiped shape in accordance with the shape of the magnet base material 20 in FIG. However, the shape and dimensions of the permanent magnet 2 are not particularly limited, and may be, for example, a polygonal shape, a cylindrical shape, a hollow cylindrical shape, or an arc segment shape whose main surface is curved in an arc shape.

The permanent magnet 2 has a composition slightly different from the composition of the magnet base material 20 used at the time of manufacture due to grain boundary diffusion of RL, RH, etc. during the manufacturing process.

Specifically, in the permanent magnet 2, R includes at least one light rare earth element (RL) essentially including Nd and at least one heavy rare earth element (RH). RL other than Nd preferably contains Pr, and RH preferably contains Tb and/or Dy.

The total content of R with respect to 100% by mass of the permanent magnet can be 25% by mass to 35% by mass, preferably 28.4% by mass or more and 32.0% by mass or less. Further, the total content of RL is preferably 26.0% by mass or more and 31.5% by mass or less, and the total content of RH is preferably 0.3% by mass or more with respect to 100% by mass of the permanent magnet. It is preferably 3.0% by mass or less. In addition, the content of Nd with respect to 100% by mass of the permanent magnet is preferably 22.4% by mass or more and 31.5% by mass or less.

As described above, in the permanent magnet 2 , the R content increases more than the R content in the magnet base material 20 depending on the amount of RL and RH diffused by the diffusing materials (11, 12). On the other hand, the content of B in the permanent magnet 2 can be made approximately the same as the content of B in the magnet base material 20 . That is, the content of B with respect to 100% by mass of the permanent magnet can be 0.5% by mass to 1.5% by mass, preferably 0.92% by mass to 1.03% by mass. When the content of B satisfies the above composition range, the magnetic properties (Br, HcJ, squareness ratio Hk/HcJ, etc.) of the permanent magnet 2 tend to be further improved.

Further, the permanent magnet 2 preferably contains the element M added to the first diffusing material 11 and/or the second diffusing material 12 . The content C _M of the element M caused by the diffusing materials (11, 12) is preferably 0.5% by mass or less, and is preferably 0.05% by mass or more and 0.2% by mass with respect to 100% by mass of the permanent magnet. % or less. For example, when an element M _NO (Ag, Au, etc.) that is not substantially contained in the magnet base material 20 is selected as the M element added to the diffusing material, the above content C _M It becomes the content of _MNO . On the other hand, when the element MIN originally contained in the magnet base material 20 is selected as the M _element added to the diffusing material, the content of the element _MIN in the permanent magnet 2 is the same as the content in the magnet base material 20. , the range obtained by _adding the above content rate CM.

For example, when Fe, Co, or Ni is added as the M element to the first diffusing material 11 and/or the second diffusing material 12, the T content in the permanent magnet 2 is higher than that in the magnet base material 20 during the manufacturing process. _Slightly increased (the above content CM is added). Note that the content of T in the permanent magnet 2 is expressed as the remainder. The T of the permanent magnet 2 may be composed solely of Fe, or part of Fe may be replaced with Co. In this case, the Co content is not particularly limited, and can be, for example, 4% by mass or less, preferably 1% by mass or less. Containing Co improves the corrosion resistance of the permanent magnet 2 .

The permanent magnet 2 preferably contains one or more m elements selected from the group consisting of Cu, Ga, Al, and Zr, and more preferably contains Cu as the m element. preferable. This m element is added to the permanent magnet 2 due to the magnet base material 20 and/or the diffusion materials (11, 12). The total content of m elements with respect to 100% by mass of the permanent magnet is preferably 0.05% by mass or more and 1.5% by mass or less, more preferably 0.5% by mass or more and 1.0% by mass or less. .

More specifically, the content of Cu with respect to 100% by mass of the permanent magnet can be 0.05% by mass or more and 0.70% by mass or less, preferably 0.20% by mass or more and 0.70% by mass. . By containing Cu in the above ratio, the magnetic properties and corrosion resistance of the permanent magnet 2 are further improved. Moreover, when Ga, Al, and Zr are included as the m element, the content of these elements is not particularly limited. For example, the Ga content can be 0.08% by mass or more and 0.50% by mass or less, preferably 0.08% by mass or more and 0.3% by mass or less. Both the Al content and the Zr content can be 0.10% by mass or more and 0.50% by mass or less, and preferably 0.10% by mass or more and 0.30% by mass or less. By including Ga, Al, Zr, etc. in the above-mentioned predetermined amounts, it is possible to further improve magnetic properties (Br, HcJ, Hk/HcJ, etc.), reduce variations in properties, and improve manufacturing stability.

The permanent magnet 2 may also contain carbon (C), nitrogen (N), and oxygen (O). The carbon content in the permanent magnet 2 is preferably 1100 mass ppm or less, more preferably 900 mass ppm or less. The nitrogen content in the permanent magnet 2 is preferably 1000 mass ppm or less, more preferably 600 mass ppm or less. The coercive force HcJ tends to improve as the carbon content rate and the nitrogen content rate decrease. The oxygen content in the permanent magnet 2 is preferably 1200 ppm or less, more preferably 800 ppm or less. Corrosion resistance tends to improve as the oxygen content decreases.

Furthermore, the permanent magnet 2 may contain unavoidable impurities such as Mn, Ca, Cl, S, and F in addition to the elements described above. % to 1.0% by mass.

The composition of the permanent magnet 2 is determined by XRF, ICP, inert gas fusion - non-dispersive infrared absorption method, combustion in oxygen current - infrared absorption method, inert gas fusion - in the same manner as the composition analysis of the magnet base material 20. It can be measured by a thermal conductivity method or the like. In the composition analysis, for example, the permanent magnet 2 may be pulverized to an average particle size of about 1 mm using a stamp mill or the like, and a plurality of particles randomly extracted from the pulverized particles may be used as samples.

Inside the permanent magnet 2 in this embodiment, a concentration distribution of a predetermined element occurs. Specifically, the permanent magnet 2 has a concentration distribution in which the RH content continuously decreases (gradually decreases) from the main surface 2a (magnetic pole surface) toward the inner center side. Such a concentration distribution of RH is caused by grain boundary diffusion of the RH of the first diffusing material 11 into the magnet base material 20 from the main surface 20a. Here, the “inner center side” means the side closer to the magnet center than the surface of the permanent magnet 2 .

Further, the permanent magnet 2 has a concentration distribution in which the content of RL continuously decreases (gradually decreases) from the side surface 2b toward the inner center. Such a concentration distribution of RL is caused by grain boundary diffusion of the RL of the second diffusing material 12 into the inside of the magnet base material 20 from the side surface 20b.

Furthermore, in the permanent magnet 2, the content of the M element (preferably one or more selected from Cu, Al, Fe, and Co) continuously decreases (gradually decreases) from the side surface 2b toward the inner center side. It is preferred to have a concentration distribution. Such a concentration distribution of the M element can be produced by grain boundary diffusion of the M element contained in the second diffusing material 12 into the magnet base material 20 from the side surface 20b. In the second diffusing material 12, when an iron group element (Fe, Co, or Ni) is added as the M element, the concentration distribution of the M element described above becomes the T concentration distribution. Therefore, when an iron group element is selected as the M element of the second diffusing material 12, it is preferable that the content of T continuously decreases (gradually decreases) from the side surface 2b toward the inner center.

The concentration distribution of each element (RL, RH, M element) described above can be confirmed using, for example, a plurality of samples α shown in FIG. 4A and a plurality of samples β shown in FIG. 5A.

Specifically, as shown in FIG. 4A, a prismatic sample α1 having a width of about 1 mm in the X-axis direction, a width of 1 mm in the Y-axis direction, and a width of T0 in the Z-axis direction is placed at substantially the center of the side surface 2b in the X-axis direction. break the ice. The width T0 of the sample α1 in the Z-axis direction is approximately the same as the width of the permanent magnet 2 in the Z-axis direction, and corresponds to the distance between the magnetic pole faces in this embodiment. A plurality of samples α (α1, _α2 . The dimensions of the sample α are not necessarily limited to the above dimensions, but the width in the Y-axis direction is preferably 1 mm or less, or 1/20 times or less the width of the permanent magnet 2 in the Y-axis direction. is preferred.

Then, each of the collected samples α is subjected to component analysis using ICP. In the permanent magnet 2 of the present embodiment, as a result of the above analysis, it can be confirmed that the RL content tends to continuously decrease as the sampling location of the sample α moves from the side surface 2b toward the center of the permanent magnet 2. . Also, when the M element is added to the second diffusing material 12, it can be confirmed that the content of the M element continuously decreases.

In particular, when the difference in the content of the predetermined element (α1−α _center ) is measured between the sample α1 including the side surface 2b and the sample α _center including the magnet center, the difference in the content of RL is 0.1 mass. % to 0.5% by mass, and the difference in the content of the M element is preferably about 0.1% to 0.3% by mass. Note that when a plurality of types of R are added to the second diffusion material 12, the above-described RL content is the total RL content. The same applies to the content of the M element.

On the other hand, the concentration distribution of RH may be confirmed using a plurality of samples β as shown in FIG. 5A. Specifically, as shown in FIG. 5A, a prism-shaped sample β1 having a width of about 5 mm in the X-axis direction×a width of about 1 mm in the Y-axis direction×a width of Tβ in the Z-axis direction is placed substantially in the center of the main surface 2a in the X-axis direction. cut out. The prismatic samples as described above are continuously cut out along the Z-axis direction until the center of the permanent magnet 2 is included to obtain a plurality of samples β (β1, β2 . . . βn, β _center ). Although the dimensions of the sample β are not necessarily limited to the above dimensions, the width Tβ in the Z-axis direction is preferably 1 mm or less, or 1/10 times the width T0 of the permanent magnet 2 in the Z-axis direction. The following are preferable.

Then, each of the collected samples β is subjected to component analysis using ICP. In the permanent magnet 2 of the present embodiment, as a result of the above analysis, it is confirmed that the RH content tends to continuously decrease as the sampling location of the sample β moves from the main surface 2b toward the center of the permanent magnet 2. can. In particular, when the difference in the content of the predetermined element (β1−β _center ) is measured between the sample β1 including the main surface 2a and the sample β _center including the magnet center, the difference in RH content is 0.1. It is preferably about 0.5% by mass to 0.5% by mass.

In addition to the above measuring methods, the concentration distribution of each element (RL, RH, M element) can be measured by line analysis or mapping analysis by EDX or EPMA, or by laser ablation-ICP mass spectrometry when observing the cross section of the permanent magnet 2. It can also be confirmed by performing (LA-ICP-MS).

In the permanent magnet 2 of the present embodiment, when the RH content is compared between the main surface 2a and the side surface 2b, the RH content of the side surface 2b is lower than that of the main surface 2a. preferable. The RH content in main surface 2a or side surface 2b may be measured using, for example, sample γ1 and sample γ2 shown in FIG. 4B.

Specifically, at the center of the main surface 2a, a sample γ1 (dimensions: about 5 mm width in the X-axis direction × about 1 mm width in the Y-axis direction × 1 mm width in the Z-axis direction) including the main surface 2a is taken, and the sample is By performing component analysis by ICP using γ1, the content of RH in the main surface 2a can be measured. Further, at the center of the side surface 2b, a sample γ2 including the side surface 2b (dimensions: about 5 mm width in the X-axis direction × 1 mm width in the Y-axis direction × about 1 mm width in the Z-axis direction) was taken, and the sample γ2 was used. By performing component analysis by ICP, the content of RH in the side surface 2b can be measured.

In the above measurements, the dimensions of the samples γ1 and γ2 are not necessarily limited to the above dimensions, but the width of the sample γ1 in the Z-axis direction is preferably 1 mm or less, and the width of the sample γ2 in the Y-axis direction is preferably 1 mm or less. is preferably 1 mm or less. Also, the RH content in the main surface 2a or the side surface 2b can be analyzed by using, for example, LA-ICP-MS or 3DAP, in addition to the above measuring method.

FIG. 3B is an enlarged schematic diagram of a cross section near the corners of the permanent magnet 2 . In the present embodiment, the term "near the corner" means a range within a radius of 1 mm around the corner 2c (magnet corner). As described above, in the permanent magnet 2, the main phase particles 4 are core-shell particles 4a in the RH diffused region. This core-shell particle 4 a has a core portion 41 made of R ₂ T ₁₄ B crystals and a shell portion 42 covering the core portion 41 and having a higher RH content than the core portion 41 . The average particle diameter of the core-shell particles 4a is not particularly limited.

Note that the shell portion 42 does not need to cover the entire circumference of the core portion 41 , and may cover at least a portion of the core portion 41 . Although the coverage of core portion 41 by shell portion 42 is not particularly limited, for example, 50% or more of the outer peripheral edge of core portion 41 is preferably covered by shell portion 42 . Moreover, in the cross section as shown in FIG. 3B, not all main phase particles 4 need to be core-shell particles 4a, and main phase particles 4 having no core-shell structure may be present.

As described above, the formation of the shell portion 42 in which the RH is concentrated around the outer periphery of the main phase grain 4 suppresses the generation of nuclei of magnetization reversal near the grain boundary, thereby improving the coercive force HcJ. can.

In the permanent magnet 2 of the present embodiment, as described above, the direction of the RH concentration distribution and the direction of the RL concentration distribution intersect. More specifically, the direction of the RH concentration distribution is the direction in which the RH concentration continuously decreases, which is the direction along the Z-axis in this embodiment. The direction of the RL concentration distribution is the direction in which the RL concentration continuously decreases. In this embodiment, since the second diffusing material 12 is grain boundary diffused from the four side surfaces 20b, both the direction along the X axis and the direction along the Y axis are directions of the concentration distribution of RL. In the permanent magnet 2, since the direction of the concentration distribution of RH and the direction of the concentration distribution of RL intersect, it is possible to achieve both high Br and high HcJ. HcJ can be further improved over the inner center of the magnet while maintaining Br. For example, when measuring the magnetic properties of sample α1 shown in FIG. 4A, Br of 1450 mT or more and HcJ of 1800 kA/m or more can be obtained.

The reason why HcJ is particularly improved near the corners is considered to be related to the thickness of the shell portion 42 . In the permanent magnet 2 of the present embodiment, the shell thickness of the core-shell particles 4a can be made thinner near the corners compared to conventional permanent magnets in which RH is diffused from both the main surface 2a and the side surfaces 2b. Actually, FIG. 7 is a cross-sectional photograph of the permanent magnet 2 of this embodiment, and FIG. 8 is a cross-sectional photograph of a conventional permanent magnet in which RH is diffused from both the main surface 20a and the side surface 20b. 7 and 8 are cross sections near the corners perpendicular to the principal surface 2a, and are cross sections obtained by observing a range from the principal surface 2a to a predetermined depth. 7 and 8, the brightest contrast is the grain boundary phase, the darkest contrast is the core portion 41 (main phase grain 4), and the gray contrast surrounding the core portion 41 is It is the shell part 42 .

In the conventional permanent magnet shown in FIG. 8, it can be clearly recognized that a gray shell portion exists around the core portion, and a thick shell portion of submicron order to micron order is formed near the corners. can be confirmed. On the other hand, in the cross section of the permanent magnet 2 of this embodiment shown in FIG. 7, it can be seen that the thickness of the shell portion 42 near the corners is clearly thinner than that of the conventional permanent magnet shown in FIG.

More specifically, in the permanent magnet 2 of the present embodiment, the average maximum thickness t1 of the shell portion 42 at predetermined locations near the corners is preferably 0.5 μm or less, more preferably 0.2 μm or less. is preferred, and 0.1 μm or less is more preferred. By reducing the thickness of the shell portion 42 in the vicinity of the corner portions in this way, it is considered that the RH concentration in the shell portion 42 becomes higher than that of the conventional permanent magnet (FIG. 8) due to the reduced thickness. As a result, in the permanent magnet 2 of this embodiment, it is considered that HcJ can be improved more efficiently without lowering Br.

In the above, the predetermined location near the corner means a section A (for example, the XY plane indicated by the dashed line in FIG. 5B) at a depth of 100 μm from the main surface 2a in the vicinity of the corner as shown in FIG. 5B. Then, the maximum thickness t1 of the shell portion 42 is calculated by analyzing the core-shell particles 4 included in the cross section A by the following method.

First, in the vicinity of the corner, at a position 100 μm deep from the main surface 2a, the section A is exposed, and an observation sample for STEM is taken from the section. As a method for sampling, a microsampling method using FIB processing or the like may be adopted. Then, the main phase particles 4 contained in the sampled observation sample (observation cross section) are analyzed by STEM-EDS. In this embodiment, the core portion 41 and the shell portion 42 are distinguished based on the concentration difference Dc of the heavy rare earth element and the concentration E of the heavy rare earth element.

Specifically, when performing the cross-sectional analysis, a virtual rectangle VR (see FIG. 6) that contains the main phase particles 4 to be measured and has the smallest area with respect to the main phase particles 4 is prepared. Let the intersection be the particle center 41c. Then, after obtaining the concentration distribution of RH and the concentration distribution of RL in the main phase particles 4 by _EDS , the difference ( _{Ch n} −Ch _center ) is the RH concentration difference Dc (unit: wt %). Further, the molar ratio of RH to RL at a predetermined location is defined as _MH/L ⁿ , the molar ratio of RH to RL at the particle center 41c is defined as _MH/L ^center , and the ratio of _MH/L ⁿ to _MH/L ^center is the RH concentration E (unit: none).

In the present embodiment, the shell portion 42 has the concentration difference Dc of 0.7 wt % or more and the concentration E of 1.25 or more. That is, in the cross-sectional analysis, the region that satisfies the two requirements is identified as the shell portion 42 , and the region other than the shell portion 42 of the main phase particle 4 is identified as the core portion 41 . However, the RH concentration detected at the particle center 41c may be less than 0.2 wt%. In this case, considering the measurement noise, it is assumed that RH is not substantially detected at the particle center 41c (that is, Ch _center ≈ 0), and the RH concentration is 0.7 wt% or more (that is, the concentration difference Dc is 0.7 wt% % or more) can be identified as the shell portion 42 . Note that when the cross-sectional sample is observed with an HAADF image or the like, it is also possible to easily distinguish between the core portion 41 and the shell portion 42 due to the difference in contrast.

After defining the boundary between the core portion 41 and the shell portion 42, as shown in FIG. 6, the thickness of the thickest portion of the shell portion 42 within the unit particle is measured. The measurement is performed for at least 20 core-shell particles 4a, and the average value is taken as the maximum thickness t1 described above. The shell thickness can also be analyzed using a three-dimensional atom probe (3DAP).

As described above, in the permanent magnet 2 of the present embodiment, the direction of the concentration distribution of RH and the direction of the concentration distribution of RL intersect each other, thereby suppressing an increase in the thickness of the shell portion 42 in the vicinity of the corner portion 2c. can. As a result, it is possible to further improve HcJ while maintaining a high Br in the vicinity of the corner 2c.

(Application field of RTB system permanent magnet 2)
The RTB system permanent magnet 2 of this embodiment can be used as a component of motors, generators, compressors, actuators, magnetic sensors, speakers, etc., and is particularly suitable as a component of motors.

As a motor using the permanent magnet 2, for example, there is an IPM motor 50 as shown in FIG. The IPM motor 50 has a rotor 51 and a stator core 52 , and the permanent magnets 2 of this embodiment are embedded in the rotor 51 . The permanent magnets 2 in the rotor 51 face the coils 54 present in the stator through the gaps 53 .

In the IPM motor 50 as shown in FIG. 8, generally, the influence of the demagnetizing field increases at the corner 2cD of the permanent magnet 2 that is close to the coil 54. As shown in FIG. As a result, heat generation or loss increases at the corner 2cD. In the permanent magnet 2 of the present embodiment, RH is diffused from the main surface 20a and RL is diffused from the side surface 20b at the time of manufacture, thereby improving HcJ at the corner 2c shown in FIG. 8 while maintaining a high Br. be able to. Therefore, when the permanent magnet 2 is mounted on the IPM motor 50, the vicinity of the corner portion 2c with improved magnetic properties is placed in the corner portion 2cD, which is particularly susceptible to the demagnetizing field, to reduce the size of the IPM motor 50. It is possible to achieve high performance, high performance, and high efficiency.

It should be noted that the permanent magnet 2 of this embodiment is not limited to the IPM motor shown in FIG. 8, and can be applied to other various motors such as an SPM motor.

In addition, the motor including the permanent magnet 2 of the present embodiment can be mounted on various electronic equipment, industrial equipment, etc., and in particular, as an automobile motor 50 (EV, HV, PHV, etc.) as shown in FIG. Use is preferred. Although FIG. 9 shows a general EV vehicle 101 and HV 102 in a simple schematic diagram, the application of the motor including the permanent magnet 2 is not limited to the mode shown in FIG. In FIG. 9, reference numeral 60 is an inverter, reference numeral 70 is a battery, reference numeral 80 is an engine, and reference numeral 90 is a generator.

(Summary of embodiment)
In the manufacturing method of the RTB permanent magnet 2 according to the present embodiment, the first diffusion material 11 containing the heavy rare earth element (RH) is diffused from the main surface 20a (first surface), and the light rare earth element (RL ) is diffused from the side surface 20b. The permanent magnet 2 of the present embodiment manufactured by such a method has a concentration distribution in which the RH content decreases from the main surface 2a toward the inner center side, and the RL concentration decreases from the side surface 20b toward the inner center side. has a concentration distribution in which the content of As a result, in the permanent magnet 2 of this embodiment, both Br and HcJ can be improved. That is, in the method of manufacturing the permanent magnet 2 of the present embodiment, the magnetic properties (especially HcJ) can be improved without attaching RH to surfaces other than the magnetic pole surfaces, and the amount of RH used in the manufacturing process can be reduced. can be reduced.

In addition, in the manufacturing method of the present embodiment and the permanent magnet 2 obtained by the method, it is possible to suppress an increase in the thickness of the shell portion 42 particularly in the vicinity of the corners. As a result, in the vicinity of the corners of the permanent magnet 2, HcJ can be further improved compared to the inside of the magnet while maintaining a high Br. Although the reason why the effect is obtained is not necessarily clear, for example, the reasons shown below are conceivable.

First, it is considered that suppression of decomposition of R ₂ T ₁₄ B crystals (main phase) by RH is related. In the grain boundary diffusion treatment, when RH permeates along the grain boundary and comes into contact with the R ₂ T ₁₄ B crystal in a heated state, the outer edge of the R ₂ T ₁₄ B crystal (particularly the Nd ₂ Fe ₁₄ B crystal) becomes RH. It is thought to react and decompose into crystal phases and liquid phases different from the main phase (for example, RFe ₂ phase, RFe ₄ B ₄ phase, etc.). It is believed that the different crystal phases and liquid phases generated by this decomposition are recrystallized to form a shell portion in which RH is concentrated.

Conventionally, when RH is diffused at grain boundaries on a plurality of surfaces such as a magnetic pole surface and a side surface that intersects with the magnetic pole surface, high-concentration RH near the surface and near the corners of the magnet It is thought that the above-described decomposition reaction of the R ₂ T ₁₄ B crystals will actively occur due to contact with the ₂ T ₁₄ B crystals. As a result, in the conventional grain boundary diffusion treatment, a thick shell is formed near the surface and near the corners of the magnet. Although the shell portion in which RH is concentrated has the effect of improving HcJ, the thickness of the shell necessary for improving HcJ is only a few nanometers, and a shell with an excessive thickness warps and causes a decrease in Br. it is conceivable that. In addition, in the conventional step-by-step process, a large amount of the deposited RH is consumed near the surface and near the corners of the magnet, making it difficult for the RH to sufficiently diffuse into the interior of the magnet, which is thought to weaken the effect of improving HcJ. .

On the other hand, in the grain boundary diffusion treatment in this embodiment, RH is diffused from the main surface 20a (magnetic pole surface) and RL is diffused from the side surface 20b intersecting with the main surface 20a. Between RL and R ₂ T ₁₄ B crystals (specifically, between Nd ₂ Fe ₁₄ B crystals and Nd or Pr), no metallic compound phase other than R ₂ T ₁₄ B is generated, so RL is a magnet. It is thought that even if it diffuses into the grain boundary 6 inside, the decomposition reaction of the main phase that occurs between RH and the R ₂ T ₁₄ B crystal does not occur. Therefore, it is considered that RL is enriched at the grain boundary 6 and the ratio of RH to all rare earth elements at the grain boundary 6 can be relatively reduced. It is considered that such modification of the grain boundaries 6 by RL is particularly likely to occur in the vicinity of the corners of the magnet.

That is, in the grain boundary diffusion treatment according to the present embodiment, RH comes into contact with the R ₂ T ₁₄ B crystal in a lower concentration state near the corner than in the conventional grain boundary diffusion treatment, and the decomposition reaction of the main phase occurs. is thought to be suppressed. As a result, in the present embodiment, the thickness of the shell portion 42 can be reduced in the vicinity of the corner portion, and it is thought that the RH concentration in the shell portion 42 can be increased by the amount of the reduced thickness. can be improved. In addition, in the present embodiment, the suppression of the decomposition reaction of the main phase suppresses the consumption of RH in the vicinity of the corners of the magnet, making it easier for RH to diffuse into the magnet. As a result, the effect of improving HcJ by diffusion of RH is enhanced, and it is considered that both high HcJ and high Br can be achieved.

In addition, the reason why RH is likely to diffuse into the interior is considered to be that the two-particle grain boundary 6a is extended by the diffusion of RL. It is believed that the expansion of the grain boundaries 6 by the RL makes it easier for the RH that enters from the main surface 2a to diffuse into the interior of the magnet, resulting in a higher HcJ than the conventional method.

In addition, when the magnet base material 20 used in manufacturing has a predetermined composition, the effect of improving Br and HcJ described above becomes more remarkable. That is, in the magnet base material 20 (RTB alloy), the total R content is 27.5% by mass or more and 30.8% by mass or less, and the Cu content is 0.05% by mass. % or more and 0.5 mass % or less, and the B content is 0.92 mass % or more and 1.03 mass % or less. In this composition, the total content of R is lower than the composition range of general RTB alloys. Thus, by using the magnet base material 20 with a low R content, the effect of improving Br and HcJ by the two-stage grain boundary diffusion treatment is further enhanced.

(Modification)
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

For example, the first diffusing material 11 and the second diffusing material 12 do not necessarily need to be adhered to a plurality of surfaces, and may be adhered to at least one surface corresponding to the intersecting corner 20c (in this case, the first diffusing material The material 11 may be attached to one first surface, and the second diffusion material 12 may be attached to one second surface intersecting the first surface). Also, in the magnet base material 20, when a specific corner portion 20c whose HcJ is desired to be improved is determined, the second diffusing material 12 may be attached to the side surface 20b including the corner portion 20c. For example, in FIG. 9A, the second diffusing material 12 is attached only to the side surface 20b1 substantially perpendicular to the Y-axis in order to improve the magnetic properties at the corner 20c1 substantially parallel to the X-axis.

Also, FIG. 9B shows an example in which the diffusing materials (11, 12) are attached only to a part of the predetermined surface. Specifically, in FIG. 9B, the first diffusing material 11 is attached only to a portion of the main surface 20a adjacent to the corner 20c1, aiming at improving the magnetic properties at the corner 20c1 substantially parallel to the X-axis. . Also, the second diffusing material 12 is attached only to a portion of the side surface 20b adjacent to the corner 20c1. In this way, by limiting the attachment locations of the diffusing materials (11, 12) to specific locations aiming at improving HcJ, it is possible to more effectively reduce the usage of rare earth elements such as RH.

EXAMPLES The present invention will be described in more detail below using examples and comparative examples. However, the present invention is not limited to the following examples.

Experiment 1
In Experiment 1, an RTB system permanent magnet according to Sample 1 was produced by the procedure shown below, and the magnetic properties of the sample were evaluated.

(sample)
First, Nd, electrolytic iron, and low-carbon ferroboron alloy were prepared as raw materials. Also, Al, Cu, Co, and Zr were prepared in the form of pure metals or alloys with Fe. Then, the raw materials were weighed so that the magnet base material 20 had the composition shown in Table 1, and a raw material alloy was produced by a strip casting method. The thickness of the raw material alloy obtained here was 0.2 mm to 0.6 mm.

Next, hydrogen gas was allowed to flow through the raw material alloy at room temperature for 1 hour to cause hydrogen to be occluded. After that, the atmosphere was changed from hydrogen gas to Ar gas, dehydrogenation treatment was performed at 450° C. for 1 hour, and the raw material alloy was hydrogen pulverized. The pulverized raw material alloy was cooled and then classified using a sieve to obtain a powder having a particle size of 400 μm or less (coarsely pulverized material). A low-oxygen atmosphere with an oxygen concentration of 200 ppm or less was always maintained from this hydrogen absorption pulverization to the sintering step described later.

Next, oleic acid amide was added as a grinding aid to the coarsely ground material and mixed. Then, this coarsely pulverized material was finely pulverized in a nitrogen stream using a collision plate type jet mill to obtain a fine powder (raw material alloy powder) having an average particle size of about 3.9 μm to 4.2 μm. In the pulverization step, the amount of oleic acid amide added was adjusted so that the carbon content in the magnet base material 20 was within the desired range. The above average particle size is the average particle size D50 measured with a laser diffraction type particle size distribution meter.

Next, the raw material alloy powder was compacted in a magnetic field to produce a compact. At this time, the applied magnetic field was a static magnetic field of 1200 kA/m, the pressing force during molding was set to 120 MPa, and the magnetic field application direction and the pressurizing direction were perpendicular to each other. When the density of the molded body obtained in this molding step was measured, the density of the molded body was within the range of 4.10 Mg/m ³ or more and 4.25 Mg/m ³ or less.

Next, the molded body was sintered to obtain a sintered body made of an RTB alloy. As for the sintering conditions, the processing atmosphere was a vacuum, and the compact was held at a temperature of 1070° C. for 4 hours. The sintered density obtained in this sintering process ranged from 7.45 Mg/m ³ to 7.55 Mg/m ³ or less. After that, the sintered body was vertically processed into a size of 15 mm×15 mm×5 mm (5 mm in thickness in the direction of easy magnetization) to obtain a magnet base material 20 .

Here, the average composition of the magnet base material 20 was measured. In sample 1, a sintered body for analysis is extracted from a plurality of sintered bodies produced, and the sintered body for analysis is pulverized to a size of about 1 mm in average particle size with a stamp mill, and the pulverized product is randomly A sample for compositional analysis was obtained by extraction. The contents of various metal elements were measured using XRF and ICP. In addition, the oxygen content is measured by an inert gas fusion-nondispersive infrared absorption method, the carbon content is measured by combustion in an oxygen stream-infrared absorption method, and the nitrogen content is measured by an inert gas It was measured by the melt-thermal conductivity method. Table 1 shows the measurement results of the average composition. The reason why the content of Fe is the balance is that the content of elements not listed in Table 1 is included in the content of Fe, and the total of R, T, B and m is 100% by mass. Meaning.

Subsequently, grain boundary diffusion treatment was applied to the magnet base material 20 according to the flow shown below. First, a diffusion material 1-A containing Tb(RH) and a diffusion material 2-A containing Nd(RL) having the compositions shown in Table 2 were produced. The diffusing material 1-A was a Tb metal powder, and the diffusing material was an alloy powder having the composition shown in Table 2.

Next, as a pretreatment for grain boundary diffusion, the magnet base material 20 was subjected to an etching treatment. Specifically, a mixed solution of 100% by mass of ethanol and 3% by mass of nitric acid was prepared, and the magnet base material 20 was immersed in the mixed solution for 3 minutes to be etched, and then immersed in ethanol for 1 minute to be washed. The above etching was performed twice.

Next, 75 parts by mass of diffusion material 1-A containing Tb, 23 parts by mass of alcohol, and 2 parts by mass of acrylic resin were kneaded to obtain a first paste. The alcohol used at this time was the solvent, and the acrylic resin was the binder. Then, the first paste was evenly applied to both of the pair of magnetic pole faces of the magnet base material 20 . At this time, the amount of the first paste applied was adjusted so that the total amount of Tb contained in the diffusion material 1-A was 0.5 parts by mass with respect to 100 parts by mass of the magnet base material. Further, a diffusion material 2-A containing Nb: 75 parts by mass, alcohol: 23 parts by mass, and acrylic resin: 2 parts by mass were kneaded to obtain a second paste. Then, the second paste was uniformly applied to each of the four side surfaces intersecting the magnetic pole surface. At this time, the application amount of the second paste containing the diffusion material 2-A is such that the total amount of Nd contained in the diffusion material 2-A is 0.5 parts by mass with respect to 100 parts by mass of the magnet base material. It was adjusted.

After applying the diffusion material 1-A and the diffusion material 2-A in the manner described above, the magnet base material 20 was held at 900° C. for 10 hours in an Ar atmosphere at atmospheric pressure, and then rapidly cooled. After the heat treatment, the surface of the magnet base material 20 was polished using No. 1200 polishing paper until the residue present on the surface was removed.

An RTB system permanent magnet 2 according to sample 1 was obtained through the above steps. The average composition of the RTB permanent magnet 2 was measured in the same manner as the average composition of the magnet base material 20 described above.

In addition, magnet samples for analysis were randomly extracted from the plurality of RTB permanent magnets 2 produced in the sample 1, and samples α, shown in FIGS. Sample β, samples γ1 and γ2 were cut out. Then, the components of each sample obtained here were analyzed by ICP. As a result, in the RTB system permanent magnet 2 of Sample 1, it was confirmed that the Tb content tended to decrease continuously from the magnetic pole surface (main surface 2a) toward the inner center side. It was confirmed that both the Nd content and the Cu content tended to decrease continuously from the side surface 2b toward the inner center. Further, when the compositions of sample γ1 and sample γ2 as shown in FIG. 4B were compared, the content of Tb in sample γ2 including side surface 2b was lower than the content of Tb in sample γ1 including main surface 2a. was confirmed.

Furthermore, after cutting out the sample α1 shown in FIG. 4A, the sample α1 was magnetized by applying a pulse magnetic field of 4000 kA/m. Then, using a BH tracer, the residual magnetic flux density Br (mT) and coercive force HcJ (kA/m) of each sample (sample α1) were measured. The magnetic properties of the sample α1 are the magnetic properties in the vicinity of the corners of the permanent magnet 2, and Table 3 shows the measurement results. In this example, Br of 1450 mT or more was judged to be particularly good, and HcJ of 1800 or more was judged to be particularly good.

(Comparative example 1)
In Comparative Example 1, the diffusion material 1-A was applied to each of the pair of magnetic pole faces of the magnet base material. After that, the magnet base material coated with the diffusing material 1-A alone without being coated with the diffusing material on all sides intersecting the magnetic pole faces was heat-treated under the same conditions as the sample 1. Experimental conditions other than the above in Comparative Example 1 were the same as those of Sample 1, and the same evaluation as that of Sample 1 was performed. Table 3 shows the evaluation results of Comparative Example 1. In Comparative Example 1, the concentration distributions of Tb and Nd were measured in the same manner as in Sample 1. In Comparative Example 1, although a concentration distribution related to the content of RH (Tb) was observed, RL (Nd ) and other elements could not be observed.

(Comparative example 2)
In Comparative Example 2, the diffusion material 1-A was applied to each of the pair of magnetic pole faces and four side surfaces intersecting the magnetic pole faces of the magnet base material. Specifically, the amount of diffusion material paste applied to each magnetic pole face was controlled so that the mass of Tb diffused from a pair of magnetic pole faces was 0.5 parts by mass with respect to 100 parts by mass of the magnet base material. Similarly, the amount of diffusion material paste applied to each side surface was controlled so that the mass of Tb diffused from the four side surfaces was 0.5 parts by mass with respect to 100 parts by mass of the magnet base material. That is, in Comparative Example 2, the total amount of Tb diffused from all surfaces was set to 1.0 parts by mass with respect to 100 parts by mass of the magnet base material. After that, the magnet base material coated with only the diffusing material 1-A was heat-treated under the same conditions as the sample 1. Experimental conditions other than the above in Comparative Example 2 were the same as those of Sample 1, and the same evaluation as that of Sample 1 was performed. Table 3 shows the evaluation results of Comparative Example 2. In Comparative Example 2, the concentration distributions of Tb and Nd were measured in the same manner as in Sample 1. In Comparative Example 1, although a concentration distribution related to the content of RH (Tb) was observed, RL (Nd ) and other elements could not be observed.

As shown in Table 3, in Comparative Examples 1 and 2, the target values of Br and HcJ could not both be satisfied. Specifically, in Comparative Example 1 in which the grain boundary diffusion treatment was performed only on the magnetic pole face, the magnetic properties could not be sufficiently improved in the vicinity of the corners which are susceptible to the demagnetizing field. In addition, in Comparative Example 2 in which RH was diffused from the magnetic pole surface and side surfaces, HcJ tended to increase because RH (Tb) was diffused more than in Sample 1 and Comparative Example 1. In return, Br has decreased.

On the other hand, in Sample 1 in which RH and RL were diffused from different planes, the amount of RH used in the manufacturing process was reduced more than in Comparative Example 2, and a high Br of 1450 mT or more and a high HcJ of 1800 kA/m or more were obtained. was gotten. From this result, it was found that the permanent magnet 2 having both high Br and high HcJ near the corners can be obtained by diffusing RH and RL from different predetermined surfaces.

Further, as described above, in the permanent magnet 2 of the sample 1, it can be confirmed that the direction of the concentration distribution of RH and the direction of the concentration distribution of the RL intersect. It was found that the thickness of the shell portion 42 in the vicinity of the portion was thinner than that of Comparative Example 1. 7 is an SEM photograph of the permanent magnet 2 actually obtained in Sample 1, and FIG. 8 is an SEM photograph of the permanent magnet obtained in Comparative Example 1. As shown in FIG.

In the SEM photograph of Comparative Example 1 in FIG. 8, it can be confirmed that a thicker shell is formed than in the SEM photograph of FIG. 7, and it can be seen that the shell is particularly thick on the surface side. On the other hand, in the SEM photograph of Sample 1 shown in FIG. 7, it can be confirmed that the thickness of the shell portion 42 is clearly thinner than that of Comparative Example 1. ) to a depth of 100 μm, the maximum thickness t1 of the shell portion 42 was less than 0.5 μm. From this result, when the direction of the concentration distribution of RH and the direction of the concentration distribution of RL intersect, the thickness of the shell portion 42 in the vicinity of the corner becomes thin, and both high Br and high HcJ can be realized. I found out.

(Experiment 2)
In Experiment 2, a plurality of types of diffusing materials shown in Table 4 were produced, and the grain boundary diffusion treatment was performed using combinations of the diffusing materials shown in Table 5. In all samples 1 to 11 of experiment 2, the composition of the magnet base material 20 was the same as that of sample 1 in experiment 1, and RT was performed under the same conditions as in experiment 1 except that the composition of the diffusing material was changed. A permanent magnet 2 of -B system was produced. Table 5 shows the evaluation results of samples 1 to 11 in Experiment 2.

As shown in Table 5, Samples 1 to 11 (except Sample 10) of Experiment 2 were all 1450 mT≦Br and 1800 kA/m≦HcJ. Incidentally, comparing Sample 10 with other Samples 1 to 9 and 11, it was found that Tb is more effective than Dy as RH to be diffused. Sample 10, in which Dy was diffused instead of Tb as RH, had a lower HcJ than the other samples (1 to 9, 11) in which Tb was diffused. It was confirmed that the HcJ was improved compared to the case where the was diffused.

From the above results, it was found that when the diffusion materials (11, 12) are within the composition range shown in Table 4, both Br and HcJ can be improved. Although not shown in Tables 4 and 5, in all samples 1 to 11 of Experiment 2, the RH content continuously decreases from the magnetic pole surface (main surface 2a) toward the inner center side. A tendency was confirmed, and a tendency that the content of RL continuously decreased from the side surface 2b toward the inner center side was confirmed. Furthermore, in samples 1 to 7 and 11 in which the second diffusing material 12 contains the M element, it was confirmed that the content of the M element continuously decreased from the side surface 2b toward the inner center.

2 ... RTB system permanent magnet 2a ... main surface (magnetic pole surface)
2b... side surface 2c (2c1, 2c2, 2cD)... corner portion 4... main phase particle 4a... core-shell particle 41... core portion 42... shell portion 6... grain boundary 6a... two-particle grain boundary 6b... grain boundary multiple point 20... magnet Base material 20a Main surface 20b Side surface 20c Intersecting corner 50 IPM motor 51 Rotor 52 Stator core 53 Gap 54 Coil 101 EV vehicle 102 HV vehicle 60 Inverter 70 Battery 80 Engine 90 Generator

Claims (12)

preparing a magnet base material containing an RTB alloy;
attaching a first diffusing material containing at least one heavy rare earth element to at least a portion of a first surface of the magnet substrate;
attaching a second diffusing material containing at least one light rare earth element to at least a portion of a second surface of the magnet base;
heating the magnet base material to diffuse the heavy rare earth element and the light rare earth element into the magnet base material;
A method for producing an RTB permanent magnet, wherein the first surface and the second surface of the magnet base material intersect to form a corner. 2. The R- according to claim 1, wherein the attachment location of the first diffusion material and the attachment location of the second diffusion material are close to each other at the corner where the first surface and the second surface intersect. A method for producing a TB permanent magnet. The second diffusing material includes an RL-M alloy containing the light rare earth element,
In the RL-M alloy,
RL is the light rare earth element,
3. The method for producing an RTB permanent magnet according to claim 1, wherein M is an element whose eutectic temperature with RL is 800° C. or lower. The second diffusing material contains at least one element selected from the group consisting of Nd and Pr as the light rare earth element, and the second diffusing material does not substantially contain a heavy rare earth element. 4. A method for producing an RTB permanent magnet according to any one of Items 1 to 3. The RTB permanent magnet according to any one of claims 1 to 4, wherein the first diffusing material contains, as the heavy rare earth element, at least one element selected from the group consisting of Tb and Dy. Production method. 6. The method for manufacturing an RTB permanent magnet according to claim 1, wherein said first surface is a magnetic pole surface. RT wherein R is one or more light rare earth elements and one or more heavy rare earth elements consisting essentially of Nd, T is one or more iron group elements consisting essentially of Fe, and B is boron - a B-based permanent magnet,
The RTB permanent magnet has a corner where the first surface and the second surface intersect,
the content of the heavy rare earth element continuously decreases from the first surface of the RTB permanent magnet toward the inner center,
The RTB system permanent magnet, wherein the content of the light rare earth element continuously decreases from the second surface of the RTB system permanent magnet toward the inner center side. contains an M element whose eutectic temperature with the light rare earth element is 800 ° C. or less,
8. The RTB permanent magnet according to claim 7, wherein the content of the M element continuously decreases from the second surface toward the inner center. 9. The RTB system permanent magnet according to claim 7, wherein said first surface is a magnetic pole surface. 10. The RTB permanent magnet according to claim 7, wherein the content of said heavy rare earth element on said second surface is lower than the content of said heavy rare earth element on said first surface. A motor having the RTB system permanent magnet according to any one of claims 7 to 10. A motor vehicle comprising a motor according to claim 11.

Images