JP7331470B2 - Manufacturing method of RTB system permanent magnet - Google Patents

Description

The present invention relates to a method for manufacturing an RTB system permanent magnet.

An RTB system permanent magnet containing a rare earth element R (such as neodymium), a transition metal element T (such as iron), and boron B has excellent magnetic properties. Remanent magnetic flux density Br (remanent magnetization) and coercive force HcJ are generally used as indexes representing the magnetic properties of RTB system permanent magnets.

RTB system permanent magnets are nucleation type permanent magnets. When a magnetic field opposite to the magnetization direction is applied to a nucleation type permanent magnet, nuclei of magnetization reversal are likely to occur in the vicinity of the grain boundaries of many crystal grains (main phase grains) forming the permanent magnet. This nucleus of magnetization reversal reduces the coercive force of the permanent magnet. Also, the coercive force of the RTB system permanent magnet decreases as the temperature rises. RTB permanent magnets used in motors, generators, etc. are required to have high coercive force even in high-temperature environments.

A heavy rare earth element such as dysprosium is added to the RTB permanent magnet in order to improve the coercive force of the RTB permanent magnet. The addition of the heavy rare earth element improves the anisotropic magnetic field and makes it difficult for magnetization reversal nuclei to occur, thereby increasing the coercive force. In recent years, the grain boundary diffusion method has been used to obtain high coercive force with a smaller amount of heavy rare earth elements. In the grain boundary diffusion method, the heavy rare earth element is diffused from the surface of the magnet along grain boundaries. As a result, the anisotropic magnetic field tends to increase locally in the vicinity of the grain boundaries, the nuclei of magnetization reversal are less likely to occur in the vicinity of the grain boundaries, and the coercive force increases.

For example, in the method for producing an RTB permanent magnet described in Patent Document 1 below, a sheet (molded body) containing a compound of a heavy rare earth element (fluoride and/or acid fluoride) and a resin component is used. . In the method for producing an RTB permanent magnet described in Patent Document 2 below, a sheet (molded body) containing an oxide of a heavy rare earth element and a resin component is used. The heavy rare earth element in the sheet diffuses into the sintered body by heating the magnet base at a temperature equal to or lower than the sintering temperature while the sheet is placed on the surface of the magnet base. A "diffusion agent" described below means a chemical substance containing at least a heavy rare earth element. The "diffusion material sheet" described below means a sheet containing a heavy rare earth element (diffusion material) and a resin component (binder).

International Publication No. 2016/093173 Pamphlet International Publication No. 2016/093174 Pamphlet

When the diffusion material sheet is arranged on the surface of the magnet base material, it is difficult for the diffusion material sheet to adhere uniformly to the surface of the magnet base material, and a gap is likely to be formed between the diffusion material sheet and the surface of the magnet base material. In addition, when the magnet base material on which the diffusion material sheets are stacked is handled, the position of the diffusion material sheet may shift from the predetermined position, or the diffusion material sheet may be peeled off from the surface of the magnet base material. Due to these problems, it is difficult for the heavy rare earth element in the diffusing material sheet to uniformly diffuse to the surface of the magnet base material. As a result, the composition and magnetic properties of the RTB system permanent magnet vary, and the coercive force of the RTB system permanent magnet is not sufficiently improved. The above problem is significant when the surface of the magnet base material is curved.

In the manufacturing methods described in Patent Documents 1 and 2, after the surface of the magnet base material is covered with the diffusing material sheet, a solvent (eg, ethanol) is sprayed from above the diffusing material sheet onto the diffusing material sheet. That is, the solvent is sprayed onto the surface of the diffusion material sheet that is not in contact with the surface of the magnet base material. As a result, part of the binder in the diffusing material sheet is dissolved, and the diffusing material sheet adheres to the surface of the magnet base material. Therefore, the diffusion material sheet and the magnet base material can be easily handled.

In order to uniformly adhere the diffusing material sheet to the surface of the magnet base material, it is necessary to dissolve the binder on the surface of the diffusing material sheet that is in contact with the surface of the magnet base material. However, in the manufacturing methods described in Patent Documents 1 and 2, the solvent is sprayed onto the surface of the diffusion material sheet from above the diffusion material sheet covering the magnet base material, so the solvent spreads from the front surface of the diffusion material sheet to the back surface thereof. Difficult to permeate evenly. In other words, it is difficult for the solvent to reach the interface between the diffusion material sheet and the magnet base material. The less the solvent sprayed onto the diffusion material sheet, the more difficult it is for the solvent to uniformly permeate from the surface to the back surface of the diffusion material sheet. As a result, it is difficult for the resin component to uniformly dissolve on the surface of the diffusion material sheet that is in contact with the magnet base material. Therefore, it is necessary to spray a large amount of solvent onto the diffusing material sheet in order to uniformly permeate the solvent from the front surface to the back surface of the diffusing material sheet. Thicker diffuser sheets require more solvent. However, the more the solvent sprayed onto the diffusion material sheet, the more the diffusion material sheet deforms excessively and the thickness of the diffusion material sheet becomes uneven. As a result, it is difficult for the heavy rare earth element to uniformly diffuse to the surface of the magnet base material. Also, the more the solvent sprayed onto the diffusion material sheet, the easier it is for part of the diffusion material contained in the diffusion material sheet to disperse in the solvent, and the diffusion material aggregates as the solvent evaporates (dries the diffusion material sheet). easy. As a result, it is difficult for the heavy rare earth element to uniformly diffuse to the surface of the magnet base material.

For the reasons described above, in the manufacturing methods described in Patent Documents 1 and 2, it is difficult for the diffusing material sheet to adhere uniformly to the surface of the magnet base material, and for the heavy rare earth element to diffuse uniformly to the surface of the magnet base material. In order to solve the problems of the manufacturing methods described in Patent Documents 1 and 2, it is necessary to control the amount of solvent sprayed onto the diffusion material sheet within a narrow tolerance. However, the allowable range for the amount of solvent will vary depending on the composition and thickness of the diffuser sheet. Also, the thicker the diffusion material sheet, the narrower the allowable range. Therefore, when the solvent is sprayed from above the diffusing material sheet covering the magnet base material, it is not easy to control the amount of the solvent within the allowable range. Therefore, after the solvent is sprayed onto the diffusing material sheet, variations in the state of the diffusing material sheet as described above are likely to occur, and finally, variations in the magnetic properties of the RTB permanent magnets become large. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing an RTB system permanent magnet capable of uniformly diffusing a heavy rare earth element into the interior of a magnet base material. do.

A method for producing an RTB permanent magnet according to one aspect of the present invention is a method for producing an RTB permanent magnet using a diffusing material sheet containing a heavy rare earth element and a binder, comprising: and a step of applying a solvent to the surface of at least one of the diffusion material sheet and the diffusion material sheet, and applying a diffusion material to at least a portion of the surface of the magnet base so that the diffusion material sheet is in contact with the magnet base on the surface to which the solvent is attached. a covering step of covering with a sheet; and a diffusion step of heating the diffusing material sheet and the magnet base material after the covering step to diffuse the heavy rare earth element into the magnet base material, wherein the magnet base material contains the rare earth element R , the transition metal element T, and boron, wherein at least a portion of the rare earth element R is neodymium and at least a portion of the transition metal element T is iron.

After the covering step, the method for producing an RTB permanent magnet may further include a conveying step of conveying the diffusion material sheet and the magnet base material into a heating furnace, and the diffusion step may be performed in the heating furnace. .

The method for manufacturing an RTB permanent magnet may further include a drying step for removing at least part of the solvent after the coating step, and a diffusion step may be performed after the drying step.

After the drying step, the method for producing an RTB permanent magnet may further include a conveying step of conveying the diffusion material sheet and the magnet base material into the heating furnace, and the diffusion step may be performed in the heating furnace. .

The method for producing an RTB permanent magnet includes, after the covering step, a heating step of heating a diffusing material sheet covering at least part of the surface of the magnet base material to soften the binder, and after the heating step, diffusion a cooling step of cooling the sheet of material to harden the binder, and after the cooling step a diffusion step may be performed.

The method for producing an RTB permanent magnet includes, after the drying step, a heating step of heating a diffusing material sheet covering at least a portion of the surface of the magnet base material to soften the binder, and after the heating step, diffusion a cooling step of cooling the sheet of material to harden the binder, and after the cooling step a diffusion step may be performed.

After the cooling step, the method for producing an RTB permanent magnet may further include a conveying step of conveying the diffusion material sheet and the magnet base material into the heating furnace, and the diffusion step may be performed in the heating furnace. .

In the heating step, at least one of the diffusing material sheet and the magnet base material may be pressed to bring the diffusing material sheet and the magnet base material into close contact with each other.

In the cooling step, at least one of the diffusion material sheet and the magnet base may be pressed to bring the diffusion material sheet and the magnet base into close contact with each other.

A laminate including a film and a diffusion material sheet overlapping the film may be used, and in the coating step, at least a portion of the surface of the magnet substrate is covered by the laminate so that the diffusion material sheet is in contact with the surface of the magnet substrate. may be covered.

A laminate including a film and a diffuser sheet overlying the film may be used, wherein the first surface of the diffuser sheet is the surface of the laminate that does not contact the film, and the second surface of the diffuser sheet is the surface of the laminate that does not contact the film. The film may be peeled off and removed from the diffusing material sheet before the coating step, and in the coating step, the surface of the magnet base material is brought into contact with the surface of the magnet base material so that the second surface is in contact with the surface of the magnet base material may be covered with a diffusion material sheet.

A laminate including a film and a diffuser sheet overlapping the film may be used, wherein the first surface of the diffuser sheet is the surface of the laminate that is not in contact with the film, and the second surface of the diffuser sheet is the laminate. It is the surface of the body that contacts the film, and the film may be peeled and removed from the diffusion material sheet before the coating process. may be covered with a diffusion material sheet.

According to the present invention, there is provided a method for manufacturing an RTB system permanent magnet that can uniformly diffuse the heavy rare earth element into the magnet base material.

(a) in FIG. 1, (b) in FIG. 1, and (c) in FIG. 1 show an overview of the coating process in the method for manufacturing an RTB permanent magnet according to the present embodiment. 2(a), 2(b), and 2(c) show an overview of the coating process in the method for manufacturing an RTB permanent magnet according to this embodiment.

Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, similar components are provided with similar reference numerals. The present invention is not limited to the following embodiments. All "permanent magnets" described below mean "RTB system permanent magnets".

[Preparation process of raw material alloy]
In the raw material alloy preparation process, an alloy material is produced from a metal raw material containing each element that constitutes a permanent magnet. The raw material alloy may be made by strip casting, book molding, or centrifugal casting. The metal raw material may be, for example, a simple substance of a rare earth element (simple metal), an alloy containing a rare earth element, pure iron, ferroboron, or an alloy containing these. These metal raw materials are weighed to match the composition of the desired magnet substrate. As raw material alloys, two or more alloys having different compositions may be produced.

The raw material alloy contains at least a rare earth element R, a transition metal element T, and boron (B).

At least part of R contained in the raw material alloy is neodymium (Nd). Permanent magnets contain, as other R, scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). OK. The raw material alloy may contain Pr. The raw material alloy may not contain Pr. The raw material alloy may contain one or both of Tb and Dy. The raw material alloy may not contain one or both of Tb and Dy.

At least part of the transition metal element T contained in the raw material alloy is iron (Fe). T may be Fe and cobalt (Co). All T may be Fe. All T may be Fe and Co. The raw material alloy may further contain transition metal elements other than Fe and Co. T described below means Fe only or Fe and Co.

The raw material alloy may further contain other elements in addition to R, T and B. For example, the raw material alloy contains other elements such as copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), manganese (Mn), carbon (C), nitrogen (N), oxygen (O), , calcium (Ca), nickel (Ni), silicon (Si), chlorine (Cl), sulfur (S) and fluorine (F).

[Pulverization process]
In the pulverization step, the alloy powder may be prepared by pulverizing the raw material alloy in a non-oxidizing atmosphere. The raw material alloy may be pulverized in two stages, a coarse pulverization process and a fine pulverization process. In the coarse pulverization step, for example, a pulverization method such as a stamp mill, jaw crusher, or Brown mill may be used. The coarse pulverization step may be performed in an inert gas atmosphere. After the hydrogen is occluded into the raw material alloy, the raw material alloy may be pulverized. In other words, hydrogen absorption pulverization may be performed as the coarse pulverization step. In the coarse pulverization step, the raw material alloy may be pulverized to a particle size of about several hundred μm. In the fine pulverization step following the coarse pulverization step, the raw material alloy that has undergone the coarse pulverization step may be further pulverized to an average particle size of several μm. A jet mill, for example, may be used in the pulverization step. The raw material alloy may be ground by a single grinding process only. For example, only the pulverization step may be performed. When multiple types of raw material alloys are used, each raw material alloy may be pulverized separately and then mixed. The alloy powder may contain at least one lubricant (grinding aid) selected from the group consisting of fatty acids, fatty acid esters, and metal salts of fatty acids (metal soaps). In other words, the raw material alloy may be ground together with the grinding aid.

[Molding process]
In the molding step, the alloy powder is molded in a magnetic field to obtain a compact containing the alloy powder oriented along the magnetic field. For example, the compact may be obtained by pressing the alloy powder in the mold while applying a magnetic field to the alloy powder in the mold. The pressure exerted by the mold on the alloy powder may be 20 MPa or more and 300 MPa or less. The strength of the magnetic field applied to the alloy powder may be 950 kA/m or more and 1600 kA/m or less.

[Sintering process]
In the sintering step, a sintered body may be obtained by sintering the above compact in a vacuum or an inert gas atmosphere. The sintering conditions may be appropriately set according to the desired composition of the permanent magnet, the pulverization method and grain size of the material alloy, and the like. The sintering temperature may be, for example, 1000° C. or higher and 1200° C. or lower. The sintering time may be from 1 hour to 20 hours.

[Aging treatment process]
In the aging treatment step, the sintered body may be heated at a temperature lower than the sintering temperature. In the aging treatment step, the sintered body may be heated in a vacuum or inert gas atmosphere. The diffusion step, which will be described later, may serve as the aging treatment step. In that case, an aging treatment process separate from the diffusion process may not be performed. The aging treatment step may consist of a first temporary treatment and a second treatment following the first temporary treatment. In the first temporary treatment, the sintered body may be heated at a temperature of 700°C or higher and 900°C or lower. The time for the first temporary treatment may be 1 hour or more and 10 hours or less. In the second aging treatment, the sintered body may be heated at a temperature of 500°C or higher and 700°C or lower. The time for the second aging treatment may be 1 hour or more and 10 hours or less.

A sintered body is obtained by the above steps. The sintered body is a magnet base material used in the diffusion process, which will be described later. A magnet substrate comprises a plurality of main phase particles sintered together. The main phase particles contain at least Nd, Fe and B. The main phase grains may contain crystals of R ₂ T ₁₄ B, at least a portion of R may be Nd, and at least a portion of T may be Fe. A part or the whole of the main phase grains may consist only of R ₂ T ₁₄ B crystals (single crystals or polycrystals). _R2T14B may be, _for example _{, Nd2Fe14B} . Part of Nd in Nd ₂ Fe ₁₄ B may be replaced with at least one of Pr, Tb and Dy. Part of Fe in Nd ₂ Fe ₁₄ B may be replaced with Co. The main phase grains may contain the above elements (elements that may be contained in the raw material alloy) in addition to R, T and B. The magnet substrate comprises grain boundaries formed between main phase grains. The magnet base material has a plurality of grain boundary triple points as grain boundaries. A grain boundary triple point is a grain boundary surrounded by at least three main phase grains. The magnet substrate also comprises a plurality of bi-grain boundaries as grain boundaries. A two-grain boundary is a grain boundary located between two adjacent main phase grains. The grain boundaries may contain at least Nd, and the content of Nd in the grain boundaries may be greater than the content of Nd in the main phase grains. That is, grain boundaries may contain Nd-rich phases. The grain boundary may contain at least one of Fe and B in addition to Nd.

The average particle size of the main phase particles is not particularly limited, but may be, for example, 1.0 μm or more and 10.0 μm or less. The total volume ratio of the main phase particles in the magnet base material is not particularly limited, but may be, for example, 75% by volume or more and less than 100% by volume.

The magnet base material used in the diffusion step may be processed in advance into a predetermined size and shape. In addition, pretreatment such as acid cleaning may be performed for the purpose of cleaning the surface of the magnet base material.

[Adhesion step, coating step, heating step, cooling step and diffusion step]
(Adhesion process, coating process, and diffusion process)
In the method for manufacturing a permanent magnet according to this embodiment, a diffusion material sheet containing at least a heavy rare earth element (diffusion material) and a binder is used. The heavy rare earth element may be, for example, at least one of Tb and Dy. As described above, the magnet base material 2 contains the rare earth element R, the transition metal element T, and boron. At least a portion of the rare earth element R is neodymium and at least a portion of the transition metal element T is iron. (a) in FIG. 1 shows a cross section of a laminate 8 including a film 6 and a diffusion material sheet 4 overlapping the film 6 . (a) in FIG. 2 shows a cross section of each of the diffusion material sheet 4 and the film 6 . These cross-sections are perpendicular to the surfaces of the diffuser sheet 4 and film 6, respectively. (b) in FIG. 1 and (c) in FIG. 1 show cross sections of the diffusing material sheet 4, the film 6, and the magnet base material 2, respectively. These cross-sections are perpendicular to the surfaces of the diffuser sheet 4, film 6 and magnet substrate 2, respectively. (b) in FIG. 2 and (c) in FIG. 2 show cross sections of the diffusion material sheet 4 and the magnet base material 2, respectively. These cross sections are perpendicular to the surface of each of the diffusion material sheet 4 and the magnet base material 2 .

The method for manufacturing a permanent magnet according to the present embodiment includes at least an adhering step, a covering step and a diffusing step in addition to the above steps. A coating step is performed after the deposition step, and a diffusion step is performed after the coating step.

In the attaching step, the solvent is attached to the surface of at least one of the magnet base material 2 and the diffusion material sheet 4 . For example, in the case of (a) in FIG. 1, (b) in FIG. 1, and (c) in FIG. The solvent may adhere to the surface of the magnet base material 2 facing the first surface 4 a of the diffusion material sheet 4 . The solvent may adhere to both the first surface 4 a of the diffusion material sheet 4 and the surface of the magnet base material 2 .

In the covering step, at least part of the surface of the magnet base material 2 is covered with the diffusion material sheet 4 so that the diffusion material sheet 4 contacts the magnet base material 2 on the surface to which the solvent is attached. The diffusion material sheet 4 is arranged on the surface of the magnet base material 2 by the covering step.

In the diffusion step, the magnet base material 2 covered with the diffusion material sheet 4 is heated. By heating the diffusion material sheet 4 and the magnet base material 2 in the diffusion step, the heavy rare earth element in the diffusion material sheet 4 diffuses from the surface of the magnet base material 2 into the magnet base material 2 . Inside the magnet base material 2, the heavy rare earth element diffuses through grain boundaries to the vicinity of the surface of the main phase grains. Some of the light rare earth elements (such as Nd) are replaced with heavy rare earth elements in the vicinity of the surface of the main phase grains. The localization of the heavy rare earth element near the surface of the main phase grains and at the grain boundaries locally increases the anisotropic magnetic field near the grain boundaries, making it difficult for nuclei of magnetization reversal to occur near the grain boundaries. . As a result, the coercivity of the permanent magnet increases.

The permanent magnet manufacturing method may further include a drying step for removing the solvent after the coating step. After the drying step, a diffusion step may be performed. At least part of the solvent is removed from the diffusion material sheet 4 and the magnet base material 2 in the drying step. The drying step may remove all solvent. By drying the diffusion material sheet 4 and the magnet base material 2 in the drying process, the diffusion material sheet 4 is fixed to the surface of the magnet base material 2 . In addition, drying the diffusion material sheet 4 increases the shape retention force and mechanical strength of the diffusion material sheet 4 . Therefore, by performing the drying process, it is easy to suppress misalignment of the diffusion material sheet 4 , peeling of the diffusion material sheet 4 from the magnet base material 2 , and breakage of the diffusion material sheet 4 . The drying process method is not particularly limited. For example, the diffusion material sheet 4 and the magnet base material 2 may be dried with hot air. The hot air tends to soften the binder in the diffusing material sheet 4 , so that the diffusing material sheet 4 more easily adheres to the surface of the magnet base material 2 . The diffusion material sheet 4 and the magnet base material 2 may be dried in an ambient temperature atmosphere. In the coating process performed before the drying process, the diffusion material sheet 4 may be attached to the surface of the magnet base material 2 while lightly pressing the diffusion material sheet 4 against the surface of the magnet base material 2 . By such a sticking method, air bubbles are easily expelled from between the diffusing material sheet 4 and the magnet base material 2 , and the diffusing material sheet 4 is easily adhered to the surface of the magnet base material 2 . In order to suppress misalignment, breakage, and excessive deformation of the diffusing material sheet 4, it is better not to press the undried diffusing material sheet 4 after the covering step. For the same reason, it is better not to move the diffusion material sheet 4 and the magnet base material 2 until the diffusion material sheet 4 is dried. By removing the solvent in the drying process after the coating process, the binder dissolved in the solvent in the adhering process is reprecipitated during the drying process, and the diffusing material sheet 4 and the magnet base material 2 are separated through the reprecipitated binder. are adhered, and the diffusion material sheet 4 is firmly fixed to the surface of the magnet base material 2 . As a result, displacement of the diffusing material sheet 4 due to handling after the drying process is further suppressed, and peeling of the diffusing material sheet 4 from the surface of the magnet base material 2 is further suppressed. Even in the diffusion process that is performed after the drying process, the diffusion material sheet 4 is uniformly and strongly adhered to the surface of the magnet base material 2 . Therefore, the heavy rare earth element in the diffusing material sheet 4 can be more uniformly diffused to the surface of the magnet base material 2 . As a result, the composition and magnetic properties of the permanent magnet are less likely to vary.

In the adhesion step, the solvent may adhere only to the surface of the magnet base material 2 . The solvent may adhere only to the surface of the diffusion material sheet 4 . The solvent may adhere to both the surface of the magnet base material 2 and the surface of the diffusion material sheet 4 . In the attaching step, it is preferable to attach the solvent to the entire surface of the magnet base material 2 that is in contact with the diffusing material sheet 4 . As a result, the diffusing material sheet 4 tends to adhere uniformly to the surface of the magnet base material 2 in the covering step. For the same reason, it is preferable to apply the solvent to the entire surface of the diffusion material sheet 4 that is in contact with the magnet base material 2 in the adhesion step. A surface of the surface of the magnet base material 2 that is in contact with the diffusing material sheet 4 is referred to as a "contact surface". The surface of the diffusion material sheet 4 that is in contact with the magnet base material 2 is also referred to as the "contact surface". A surface of the magnet base material 2 other than the contact surface is referred to as a “non-contact surface”. A surface of the magnet base material 2 other than the contact surface is also referred to as a “non-contact surface”.

Since the solvent directly adheres to the contact surface in the adhesion step, the binder in the diffusion material sheet 4 dissolves along the contact surface. In other words, the contact surface of the diffusion material sheet 4 is softened. As a result, the diffusing material sheet 4 is deformed along the concave and convex portions on the surface of the magnet base material 2 , and the gap between the diffusing material sheet 4 and the surface of the magnet base material 2 is reduced. In other words, the diffusing material sheet 4 uniformly adheres to the surface of the magnet base material 2 in the covering step. As a result, displacement of the diffusing material sheet 4 due to handling after the covering step is suppressed, and peeling of the diffusing material sheet 4 from the surface of the magnet base material 2 is also suppressed. The diffusion material sheet 4 is uniformly adhered to the surface of the magnet base material 2 also in the diffusion process performed after the covering process. Therefore, the heavy rare earth element in the diffusing material sheet 4 tends to diffuse uniformly to the surface of the magnet base material 2 . As a result, the composition and magnetic properties of the permanent magnet are less likely to vary, and the coercive force of the permanent magnet is sufficiently improved.

The surface of the magnet base material 2 covered with the diffusing material sheet 4 may be curved. Since the adhering step is performed before the covering step, the diffusion material sheet 4 tends to be uniformly adhered to the curved surface, the positional deviation of the diffusion material sheet 4 on the curved surface is easily suppressed, and the peeling of the diffusion material sheet 4 from the curved surface is suppressed. easy to be If the adhering step is not performed before the covering step, it is difficult for the diffusion material sheet 4 to adhere uniformly to the curved surface, the position of the diffusion material sheet 4 tends to shift on the curved surface, and the diffusion material sheet 4 tends to separate from the curved surface.

In the methods described in Patent Documents 1 and 2, the solvent is sprayed onto the back side of the contact surface of the diffusion material sheet 4 . That is, the solvent is sprayed onto the non-contact surface of the diffusion material sheet 4 . Since it is difficult for the solvent to uniformly permeate from the non-contact surface to the contact surface, it is difficult for the binder to dissolve uniformly on the contact surface. Therefore, it is difficult for the diffusion material sheet 4 to adhere uniformly to the surface of the magnet base material 2 . That is, a gap is likely to be formed between the diffusing material sheet 4 and the surface of the magnet base material 2 . In the portion of the surface of the diffusing material sheet 4 that is not in contact with the surface of the magnet base material 2 , the heavy rare earth element is difficult to diffuse from the diffusing material sheet 4 to the magnet base material 2 . Therefore, in the methods described in Patent Documents 1 and 2, it is difficult for the heavy rare earth element in the diffusing material sheet 4 to uniformly diffuse to the surface of the magnet base material 2 . As a result, the heavy rare earth element does not sufficiently diffuse into the magnet base material 2, the composition and magnetic properties of the permanent magnet vary, and the coercive force of the RTB system permanent magnet does not sufficiently improve.

In contrast to the methods described in Patent Documents 1 and 2 above, in the deposition step of the present embodiment, the solvent directly adheres to the contact surface. Therefore, in the covering step, the binder in the diffusion material sheet 4 is uniformly dissolved along the contact surface. As a result, the diffusion material sheet 4 uniformly adheres to the surface of the magnet base material 2 . Moreover, in the adhesion step of the present embodiment, the solvent does not need to permeate from the non-contact surface to the contact surface, so the amount of solvent is reduced compared to the methods described in Patent Documents 1 and 2 above. As a result, excessive deformation of the diffusion material sheet 4 is suppressed, and the thickness of the diffusion material sheet 4 is easily maintained uniform. Further, in the adhesion step of the present embodiment, since the amount of solvent is reduced, part of the diffusing material contained in the diffusing material sheet 4 is difficult to disperse in the solvent. As a result, aggregation of the diffusion material due to evaporation of the solvent (drying of the diffusion material sheet 4) is suppressed. For these reasons, the heavy rare earth element can be uniformly diffused to the surface of the magnet substrate in the diffusion step. Further, in the adhesion step of the present embodiment, it is not necessary to allow the solvent to permeate from the non-contact surface to the contact surface, so there is no need to manage the amount of solvent within a narrow allowable range. In this respect, variations in the magnetic properties of the permanent magnets are suppressed.

In this embodiment, since the solvent directly adheres to the contact surface, the binder in the diffusion material sheet 4 is easily and uniformly dissolved along the contact surface. Therefore, even if the content of the binder in the diffusing material sheet 4 is less than that of the conventional diffusing material sheet, the diffusing material sheet 4 can uniformly adhere to the surface of the magnet base material 2 . Therefore, it is possible to shorten the time required for the binder removal process before the diffusion process. In this respect, the productivity of permanent magnets is improved.

When the solvent adheres to the contact surface of the magnet base material 2 in the adhesion process, the solvent tends to uniformly adhere to the contact surface of the magnet base material 2, making it easy to manage the adhesion state of the solvent.

When the solvent adheres to the contact surface of the magnet base material 2 in the adhering step, the surface of the magnet base material 2 can be covered with the diffusion material sheet 4 through the solvent in the coating step. Due to the presence of the solvent, an adhesive force due to the interfacial tension of the solvent acts between the magnet base material 2 and the diffusing material sheet 4, but the diffusing material sheet 4 is not fixed. Therefore, after covering the surface of the magnet base material 2 with the diffusion material sheet 4 , the diffusion material sheet 4 can be moved on the surface of the magnet base material 2 . That is, after provisionally arranging the diffusion material sheet 4 on the surface of the magnet base material 2 , the position of the diffusion material sheet 4 can be finely adjusted. By evaporating the solvent after the position of the diffusion material sheet 4 is adjusted, the diffusion material sheet 4 is fixed to the surface of the magnet base material 2 . The easier the solvent evaporates, the faster the diffusion material sheet 4 is fixed to the surface of the magnet base material 2 . Therefore, in order to secure time for adjusting the position of the diffusion material sheet 4, it is preferable that the boiling point of the solvent is high. For example, the boiling point of the solvent may be above 100°C.

Even if the solvent adheres to the contact surface of the diffusion material sheet 4 in the adhesion step, the position of the diffusion material sheet 4 can be adjusted after the diffusion material sheet 4 is arranged on the surface of the magnet base material 2 . However, if the solvent adheres to the contact surface of the diffusing material sheet 4, depending on the composition or amount of the solvent, the shape-retaining force of the diffusing material sheet 4 may decrease, and the diffusing material sheet 4 may be damaged during handling. have a nature. In order to prevent the diffusion material sheet 4 from being damaged, a laminate 8 including the film 6 and the diffusion material sheet 4 overlapping the film 6 may be used. Damage to the diffusing material sheet 4 is suppressed by the film 6 . In other words, the film 6 protects the diffusion material sheet 4 . The film 6 may be peeled off from the diffuser sheet 4 after the coating or drying process. If necessary, the diffuser sheet 4 may be transferred from the film 6 to another film (second film). For example, after the diffuser sheet 4 is transferred from the film 6 to another film (second film), the adhering, covering and drying steps may be performed. After the coating step or drying step, the second film may be peeled off from the diffuser sheet 4 .

When the solvent adheres to the contact surface of the diffusion material sheet 4 in the adhesion step, the flexibility of the diffusion material sheet 4 is improved as the binder in the diffusion material sheet 4 swells. As a result, the diffusion material sheet 4 easily deforms along the surface of the magnet base material 2 having a curved surface with a small curvature in the covering step, and the diffusion material sheet 4 easily adheres to the surface of the magnet base material 2 .

The method of attaching the solvent to the contact surface in the attaching step is not limited. For example, a solvent may be applied to the contact surfaces. A solvent may be sprayed onto the contact surfaces. The solvent is not limited as long as it is a liquid that dissolves the binder. For example, the solvent can be an organic solvent. The solvent may be, for example, a class of compounds consisting of ethanol, butanol, octanol, methyl ethyl ketone, xylene, butyl carbitol, terpineol, and dihydroterpineol. Multiple types of solvents may be used.

In the covering step, the contact surface of the diffusion material sheet 4 impregnated with the solvent may cover the surface of the magnet base material 2 . In the covering step, the surface of the magnet base material 2 may be covered with the diffusion material sheet 4 so that the solvent is arranged between the magnet base material 2 and the diffusion material sheet. That is, a film or layer formed from a solvent may be present between the magnet substrate 2 and the diffuser sheet.

In the covering step, only part of the surface of the magnet base material 2 may be covered with the diffusing material sheet 4 . In the covering step, the entire surface of the magnet base material 2 may be covered with the diffusing material sheet 4 . When the magnet base material 2 has a plurality of surfaces, only one surface of the magnet base material 2 may be covered with the diffusing material sheet 4 in the covering step. When the magnet base material 2 has multiple surfaces, the multiple surfaces of the magnet base material 2 may be covered with the diffusion material sheet 4 in the covering step. For example, both the main surface and the back surface of the main surface of the magnet base material 2 may be covered with the diffusion material sheet 4 . When the magnet base material 2 has a plurality of surfaces, all the surfaces of the magnet base material 2 may be covered with the diffusing material sheet 4 in the covering step.

In the diffusion step, the diffusion material sheet 4 and the magnet base material 2 may be heated in a heating furnace. In order to suppress the oxidation of the magnet base material 2 in the diffusion process, after the magnet base material 2 with the diffusion material sheet 4 in close contact with the magnet base material 2 is placed in the heating furnace, the atmosphere in the heating furnace is vacuum or argon (Ar) or the like. become an inert gas. Exhaust gas and/or introduction of inert gas accompanying control of the atmosphere in the heating furnace changes the atmospheric pressure in the heating furnace. An air current is generated in the heating furnace as the atmospheric pressure changes. If the adhesion step described above were not performed, the diffusion material sheet 4 would easily peel off from the surface of the magnet base material 2 due to the influence of the airflow generated in the heating furnace. However, in the present embodiment, since the adhering step is performed before the covering step, the diffusing material sheet 4 is evenly adhered to the surface of the magnet base material 2 . As a result, the diffusion material sheet 4 is suppressed from being peeled off due to the generation of the airflow, and the heavy rare earth element in the diffusion material sheet 4 is easily diffused uniformly onto the surface of the magnet base material 2 .

The temperature of the atmosphere in the heating furnace in the diffusion step may be, for example, 800° C. or higher and 950° C. or lower. The time for which the diffusion material sheet 4 and the magnet base material 2 are heated at the above temperature may be 1 hour or more and 50 hours or less. Before heating the diffusion material sheet 4 and the magnet base material 2 at the above temperature, the binder in the diffusion material sheet 4 may be burned off by heating the diffusion material sheet 4 at a temperature lower than the above temperature. That is, the binder removal process may be performed as a pre-stage of the diffusion process.

The permanent magnet manufacturing method may further include a transporting step of transporting the diffusion material sheet and the magnet base material into the heating furnace after the coating step, and the diffusion step may be performed in the heating furnace. During the transportation process, the magnet base material 2 with the diffusion material sheet 4 in close contact with it may be temporarily stored in a warehouse. A force may be applied to the diffusion material sheet 4 due to the diffusion material sheet 4 coming into contact with other objects during the transportation process. In addition, force may act on the diffusion material sheet 4 due to vibration and/or acceleration during transportation. If the adhesion step were not performed, force would act on the diffusing material sheet 4 during the conveying step, causing the diffusing material sheet 4 to deviate from the predetermined position, or cause the diffusing material sheet 4 to fall on the surface of the magnet base material 2 . peel off from However, by performing the adhering step before the covering step, misalignment and peeling of the diffusing material sheet 4 during the conveying step are suppressed.

After the drying step, a conveying step may be performed. By performing the drying process before the conveying process, the diffusion material sheet 4 is more likely to be prevented from being displaced and peeled off during the conveying process. In the drying step, the diffusion material sheet 4 and the magnet base material 2 may be conveyed into the heating furnace while drying the diffusion material sheet 4 . In other words, the transporting process may serve as the drying process.

(Heating process and cooling process)
The permanent magnet manufacturing method may further include a heating step and a cooling step in addition to the adhering step, the coating step and the diffusion step. However, the heating step and the cooling step are not essential steps. That is, even if the heating process and the cooling process are not performed, the effect of the present invention can be obtained. When the permanent magnet manufacturing method further comprises a heating step and a cooling step, the heating step is performed after the coating step or the drying step, the cooling step is performed after the heating step, and the diffusion step is performed after the cooling step. When the heating step is performed, the drying step may not be performed. That is, the heating process may serve as the drying process. Both drying and heating steps may be performed.

In the heating step, the binder is softened by heating the diffusion material sheet 4 covering the surface of the magnet base material 2 . Due to the softening of the binder, the diffusion material sheet 4 deforms along the recesses and protrusions on the surface of the magnet base material 2 , and the diffusion material sheet 4 uniformly adheres to the surface of the magnet base material 2 . That is, the softening of the binder further reduces the gap between the diffusion material sheet 4 and the surface of the magnet base material 2 . Therefore, in the diffusing step, the heavy rare earth element in the diffusing material sheet 4 tends to diffuse uniformly to the surface of the magnet base material 2 . As a result, the heavy rare earth element is easily diffused to the vicinity of the surface and the grain boundary of the main phase grains of the magnet base material 2, the variation of the composition and magnetic properties of the permanent magnet is easily suppressed, and the coercive force of the permanent magnet is further increased. do.

In the heating step, both the magnet base material 2 and the diffusion material sheet 4 may be heated. Only one of the magnet base material 2 and the diffusion material sheet 4 may be heated. Any heating method may be used. If the temperature of the diffusing material sheet 4 in the heating process is too high, the shape retention force of the diffusing material sheet 4 decreases, and the efficiency of the cooling process decreases. Therefore, the temperature of the diffusion material sheet 4 should not be too high, and there is an optimum temperature for the diffusion material sheet 4 in the heating process. That is, the temperature of the diffusion material sheet 4 in the heating process may be adjusted according to the composition and softening temperature of the binder and the shape retention force of the diffusion material sheet 4 . The temperature of the diffusion material sheet 4 in the heating step may be, for example, 60° C. or higher and 250° C. or lower.

In the heating step, at least one of the diffusion material sheet 4 and the magnet base material 2 may be pressed to bring the diffusion material sheet 4 and the magnet base material 2 into close contact with each other. That is, at least one of the diffusion material sheet 4 and the magnet base material 2 may be pressurized in parallel with the heating of the diffusion material sheet 4 . Due to the pressurization, the diffusing material sheet 4 further adheres to the surface of the magnet base material 2 . Only the diffuser sheet 4 may be pressurized. Only the magnet substrate 2 may be pressurized. Both the diffusion material sheet 4 and the magnet base material 2 may be pressurized by sandwiching the diffusion material sheet 4 and the magnet base material 2 with the pressurizing means. The pressure applied to the diffusion material sheet 4 in the heating step may be, for example, 0.05 MPa or more and 10 MPa or less.

In the cooling process, the binder is hardened by cooling the diffusion material sheet 4 that has undergone the heating process. By hardening the binder, the diffusion material sheet 4 hardens in a state of being in close contact with the surface of the magnet base material 2 . That is, the diffusion material sheet 4 is adhered to the surface of the magnet base material 2 by the cooling process, and the diffusion material sheet 4 and the magnet base material 2 are integrated. That is, the diffusion material sheet 4 is fixed to the surface of the magnet base material 2 more firmly. As a result, displacement of the diffusing material sheet 4 on the surface of the magnet base material 2 is suppressed after the cooling step. Moreover, peeling of the diffusing material sheet 4 from the surface of the magnet base material 2 is suppressed after the cooling step. Therefore, in the diffusing step, the heavy rare earth element in the diffusing material sheet 4 tends to diffuse uniformly to the surface of the magnet base material 2 . As a result, the heavy rare earth element is easily diffused to the vicinity of the surface and the grain boundary of the main phase grains of the magnet base material 2, the variation of the composition and magnetic properties of the permanent magnet is easily suppressed, and the coercive force of the permanent magnet is further increased. do. In the cooling step, the diffusion material sheet 4 may be cooled at room temperature.

In the cooling step, at least one of the diffusion material sheet 4 and the magnet base material 2 may be pressed to bring the diffusion material sheet 4 and the magnet base material 2 into close contact with each other. That is, at least one of the diffusion material sheet 4 and the magnet base material 2 may be pressurized in parallel with the cooling of the diffusion material sheet 4 . Due to the pressurization, the diffusing material sheet 4 further adheres to the surface of the magnet base material 2 . Only the diffuser sheet 4 may be pressurized. Only the magnet substrate 2 may be pressurized. Both the diffusion material sheet 4 and the magnet base material 2 may be pressurized by sandwiching the diffusion material sheet 4 and the magnet base material 2 with the pressurizing means. The pressure applied to the diffusion material sheet 4 in the cooling step may be, for example, 0.05 MPa or more and 10 MPa or less.

The pressurization may be performed only in one of the heating process and the cooling process. The pressurization may be performed in both the heating step and the cooling step.

As described above, the gap between the diffusion material sheet 4 and the magnet base material 2 is further reduced by the heating process, and the diffusion material sheet 4 is easily fixed to the surface of the magnet base material 2 by the cooling process after the heating process. That is, due to the interaction between the heating process and the cooling process, the diffusing material sheet 4 can be fixed to the surface of the magnet base material 2 without gaps.

After the cooling step, the transfer step described above may be performed. By performing the cooling process before the conveying process, the diffusion material sheet 4 is likely to be prevented from being displaced and peeled off during the conveying process. In the cooling step, the diffusion material sheet 4 and the magnet base material 2 may be conveyed into the heating furnace while cooling the diffusion material sheet 4 . In other words, the transporting process may serve as the cooling process.

(Method for producing diffusion material sheet 4)
The diffusion material sheet 4 may be produced by the following method. As described above, the diffusing agent is a chemical containing at least a heavy rare earth element. The diffusing material may be particles or powder. The particle size of the diffusing agent may be adjusted by means similar to the coarse and fine grinding steps described above. The median diameter D50 of the diffusing material may be, for example, 0.5 μm or more and 15 μm or less.

A lacquer is prepared by stirring and mixing a binder and a solvent in a predetermined ratio to dissolve the binder. The binder may be a thermoplastic resin. The binder may be, for example, at least one compound selected from the group consisting of ethyl cellulose resin, polyvinyl butyral resin, polyvinyl acetal resin and acrylic resin. Multiple types of binders may be used. The solvent is not limited as long as it is a liquid that dissolves the binder. The solvent may be an organic solvent. The solvent may be, for example, a class of compounds consisting of ethanol, butanol, octanol, methyl ethyl ketone, xylene, butyl carbitol, terpineol, and dihydroterpineol. Multiple types of solvents may be used. After adding the diffuser to the lacquer, they are mixed. If desired, a plasticizer may additionally be added to the lacquer. A dispersion treatment of a mixture of diffuser and lacquer follows. The dispersing means may be a rotation/revolution mixer, three rolls, a high-pressure homogenizer, or an ultrasonic homogenizer. Distributed processing may be performed using a number of means.

The diffusing material may be, for example, a single heavy rare earth element, an alloy containing the heavy rare earth element, or a compound containing the heavy rare earth element. The compound containing a heavy rare earth element may be, for example, at least one selected from the group consisting of hydrides, fluorides and oxides. The elemental heavy rare earth element may be one or both of elemental Tb and elemental Dy. The alloy containing the heavy rare earth element may be at least one selected from the group consisting of an alloy consisting of Tb and Fe, an alloy consisting of Dy and Fe, and an alloy consisting of Tb, Dy and Fe. The hydrides of heavy rare earth elements are, for example, hydrides of alloys consisting of _TbH2 , _TbH3 , Tb and Fe, hydrides of alloys consisting of _DyH2 , _DyH3 , Dy and Fe, and Tb, Dy and Fe. may be at least one selected from the group consisting of hydrides of alloys consisting of The diffusion material may further contain at least one element selected from the group consisting of Nd, Pr and Cu. For example, the diffusion material includes elemental Nd, elemental Pr, alloys containing Nd and Pr, hydrides of _NdH2 , _NdH3 , _PrH2 , _PrH3 , alloys containing Nd and Pr, elemental Cu, and Cu. It may further contain at least one selected from the group consisting of alloys, CuH, _Cu2O and CuO.

A paste containing a diffusion material, a binder and a solvent is prepared by the above method. The content of the diffusing material in the paste may be appropriately adjusted in consideration of the thickness of the magnet base material 2, the designed composition of the permanent magnet, and the coatability of the paste. The content of the binder in the paste may be appropriately adjusted in consideration of the coatability of the paste and the flexibility and adhesiveness of the diffusion material sheet 4 . Filtration of the paste may remove coarse particles and agglomerates from the paste. The content of the diffusing material in the paste may be, for example, 40% by mass or more and 85% by mass or less. The binder content in the paste may be, for example, 1% by mass or more and 15% by mass or less. The content of the solvent in the paste may be, for example, 10% by mass or more and 59% by mass or less.

A coating film is formed on the surface of the film 6 by applying the paste to the surface of the film 6 . It is preferable that the thickness of the coating film is constant. Film 6 may consist, for example, of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) or graphite. The surface of the film 6 to which the paste is applied may be pre-coated with a release agent. The method of applying the paste may be a method of controlling the thickness of the coating film to an arbitrary value and controlling the thickness of the coating film to be constant. The method of applying the paste may be, for example, an applicator, doctor blade, bar coater, inkjet coater, roll coater or die coater.

By drying the coating film to remove the solvent from the coating film, the diffusion material sheet 4 shown in FIG. 1(a) is obtained. That is, the laminate 8 including the film 6 and the diffusion material sheet 4 overlapping the film 6 is obtained. The first surface 4 a of the diffusion material sheet 4 is the surface of the laminate 8 that does not come into contact with the film 6 . The second surface 4 b of the diffusion material sheet 4 is the surface of the laminate 8 that contacts the film 6 . The method for drying the coating film may be, for example, infrared heating, hot air drying, or reduced pressure drying. Drying conditions may be set according to the vapor pressure of the solvent contained in the coating film. A solvent may remain in the diffusion material sheet 4 . The thickness of the diffusion material sheet 4 may be, for example, 5 μm or more and 200 μm or less. The thickness of the magnet base material 2 is much larger than the thickness of the diffusion material sheet 4 . The thickness of the magnet base material 2 may be, for example, 0.5 mm or more and 25 mm or less.

It is possible to cover the entire surface of the magnet base material 2 with the above paste. For example, by immersing the entire magnet base material 2 in the above paste, the entire surface of the magnet base material 2 can be covered with a coating film. However, since the coating film formed by immersion is affected by gravity and the like, it is difficult to make the thickness of the coating film uniform. Moreover, when the magnet base material 2 is immersed in the paste, it is difficult to cover only a portion of the surface of the magnet base material 2 with the coating film. The diffusion material sheet 4 is useful for solving these problems. For example, after processing the diffusing material sheet 4 so that the shape of the diffusing material sheet 4 matches the shape of any part of the surface of the magnet base material 2 , any part of the surface of the magnet base material 2 is changed to the diffusing material sheet 4 . By covering with the diffusing material sheet 4 having a uniform thickness, only a necessary portion of the magnet base material 2 can be covered.

(Usage of laminate 8)
As described above, laminate 8 may be used in the deposition and coating steps. As shown in FIG. 1B, in the covering step, at least part of the surface of the magnet base material 2 is covered with the laminate 8 so that the diffusion material sheet 4 is in contact with the surface of the magnet base material 2. you can The entire surface of the magnet base material 2 may be covered with the laminate 8 . The drying step may be performed in a state where the surface of the magnet base material 2 is covered with the laminate 8 . The heating step and the cooling step may be performed while the surface of the magnet base material 2 is covered with the laminate 8 . When the laminate 8 is used in the adhesion step and the covering step, the diffusion material sheet 4 may be pressurized through the film 6 in at least one of the heating step and the cooling step. If the magnet base material 2 has multiple surfaces, only one surface of the magnet base material 2 may be covered with the laminate 8 . When the magnet base material 2 has multiple surfaces, the multiple surfaces of the magnet base material 2 may be covered with the laminate 8 . For example, both the main surface and the back surface of the main surface of the magnet base material 2 may be covered with the laminate 8 . If the magnet base material 2 has multiple surfaces, all the surfaces of the magnet base material 2 may be covered with the laminate 8 .

In the case of (a) in FIG. 1, (b) in FIG. 1, and (c) in FIG. 1, one surface of the magnet base material 2 is covered with the laminate 8 in the covering step. However, two surfaces of the magnet base material 2 may be covered with the laminate 8 . For example, two opposing surfaces of the magnet base material 2 may be covered with the laminate 8 . After the two different surfaces of the magnet base material 2 are covered with the laminate 8, the drying process described above may be performed, and after the drying process, the heating process and the cooling process described above may be performed. After the two different surfaces of the magnet base material 2 are covered with the laminate 8, a heating step and a cooling step may be performed. When multiple surfaces of the magnet base material 2 are covered with the laminate 8 , the covering step and the series of steps described above may be performed for each surface of the magnet base material 2 . For example, another surface of the magnet base material 2 may be covered with the laminate 8 after the drying process is performed in a state where one surface of the magnet base material 2 is covered with the laminate 8 . After another surface of the magnet base material 2 is covered with the laminate 8, the drying step may be performed again, and after the drying step, the heating and cooling steps may be performed again. After the heating step and the cooling step are performed with one surface of the magnet base material 2 covered with the laminate 8 , another surface of the magnet base material 2 may be covered with the laminate 8 . After another side of the magnet substrate 2 is covered with the laminate 8, the heating and cooling steps may be performed again. After two or more surfaces of the magnet substrate 2 are simultaneously covered with the laminate 8 in the covering step, the above series of steps may be performed.

As shown in FIG. 1(c), the film 6 may be peeled off and removed from the diffuser sheet 4 after the coating, drying or cooling process. After the coating process, drying process, or cooling process, the diffusion material sheet 4 is in close contact with the surface of the magnet base material 2 . Therefore, even if the film 6 is peeled off from the diffusion material sheet 4 after the coating process, the drying process, or the cooling process, part of the diffusion material sheet 4 is less likely to remain on the surface of the peeled film 6 . That is, damage to the diffusing material sheet 4 due to peeling of the film 6 is suppressed. By peeling the film 6 from the diffusion material sheet 4 after the covering process, the drying process, or the cooling process, it is possible to prevent the diffusion material sheet 4 from peeling off from the surface of the magnet base material 2 together with the film 6 .

After removal of film 6, a diffusion step may be performed. By removing the film 6 before the diffusion process, the carbide of the film 6 is not formed on the surface of the magnet base material 2 in the diffusion process. As a result, the carbon derived from the film 6 does not enter the magnet base material 2 in the diffusion step, and the deterioration of the magnetic properties of the permanent magnet due to excessive carbon content is suppressed. However, the diffusion step may be performed in a state in which at least part of the surface of the magnet base material 2 is covered with the laminate 8 . In other words, the diffusion step may be performed without removing the film 6 . For example, if the film 6 is made of graphite, the diffusion process may be performed without removing the film 6 because graphite is easily burned off by heating in the diffusion process.

When the laminate 8 is used in the coating process, the dimensions and shape of the laminate 8 may be adjusted to match the dimensions and shape of the surface of the magnet base material 2 before the coating process. After the coating step, the dimensions and shape of the laminate 8 may be adjusted to match the dimensions and shape of the surface of the magnet substrate 2 . After the surfaces of the plurality of magnet base materials 2 are covered with one laminate 8, the laminate 8 may be divided. The dimensions and shape of the laminate 8 may be adjusted by cutting the laminate 8 .

As shown in FIG. 2(a), the film 6 may be peeled off and removed from the diffuser sheet 4 before the adhering step or the covering step. As shown in FIG. 2B, in the covering step, at least part of the surface of the magnet base material 2 is diffused so that the second surface 4b of the diffusion material sheet 4 is in contact with the surface of the magnet base material 2. It may be covered with a sheet of material 4 . In this case, the solvent may adhere to the second surface 4b of the diffusion material sheet 4 in the adhesion step. In the process of forming a coating film from the paste, the diffusion material tends to settle on the surface of the film 6 due to its own weight. As a result, the diffusing material in the diffusing material sheet 4 is likely to be unevenly distributed on the second surface 4 b side in contact with the film 6 . Also, the second surface 4b that was in contact with the film 6 is flatter than the first surface 4a. Therefore, since the second surface 4b of the diffusion material sheet 4 directly overlaps the surface of the magnet base material 2, the diffusion material in the diffusion material sheet 4 is easily arranged uniformly along the surface of the magnet base material 2. The sheet 4 tends to adhere uniformly to the surface of the magnet base material 2 . As a result, the diffusing material tends to diffuse uniformly to the surface of the magnet base material 2 in the diffusing step. As shown in (c) of FIG. 2, in the covering step, at least part of the surface of the magnet base material 2 is diffused so that the first surface 4a of the diffusion material sheet 4 is in contact with the surface of the magnet base material 2. It may be covered with a material sheet 4 . In this case, the solvent may adhere to the first surface 4a of the diffusion material sheet 4 in the adhesion step.

In the case of (a) in FIG. 2, (b) in FIG. 2, and (c) in FIG. However, two surfaces of the magnet base material 2 may be covered with the diffusion material sheet 4 . For example, two opposing surfaces of the magnet base material 2 may be covered with the diffusion material sheet 4 . After the two different surfaces of the magnet base material 2 are covered with the diffusing material sheet 4, the drying process, which will be described later, may be performed, and after the drying process, the heating process and the cooling process described above may be performed. After the two different surfaces of the magnet base material 2 are covered with the diffusion material sheet 4, the heating process and the cooling process may be performed. When a plurality of surfaces of the magnet base material 2 are covered with the diffusing material sheet 4 , the covering step and the series of steps described above may be performed for each surface of the magnet base material 2 . For example, another surface of the magnet base material 2 may be covered with the diffusion material sheet 4 after the drying process is performed with one surface of the magnet base material 2 covered with the diffusion material sheet 4 . After another surface of the magnet base material 2 is covered with the diffusion material sheet 4, the drying process may be performed again, and after the drying process, the heating process and the cooling process may be performed again. After the heating step and the cooling step are performed with one surface of the magnet base material 2 covered with the diffusion material sheet 4 , another surface of the magnet base material 2 may be covered with the diffusion material sheet 4 . After another surface of the magnet base material 2 is covered with the diffuser sheet 4, the heating and cooling steps may be performed again. After two or more surfaces of the magnet base material 2 are simultaneously covered with the diffuser sheet 4 in the covering step, the above series of steps may be performed.

When the film 6 was peeled off and removed from the diffuser sheet 4 before the attachment process or before the coating process, the dimensions and shape of the laminate 8 were adjusted to match the dimensions and shape of the surface of the magnet base material 2. Afterwards, the film 6 may be peeled and removed from the diffuser sheet 4 . After the size and shape of the diffusion material sheet 4 are adjusted to match the size and shape of the surface of the magnet base material 2 , the diffusion material sheet 4 may be peeled off from the film 6 . After the film 6 is peeled and removed from the diffuser sheet 4 , the size and shape of the diffuser sheet 4 may be adjusted to match the size and shape of the surface of the magnet substrate 2 . After the coating process, the size and shape of the diffuser sheet 4 may be adjusted to match the size and shape of the surface of the magnet base material 2 . After the surfaces of the plurality of magnet base materials 2 are covered with one diffusing material sheet 4, the diffusing material sheet 4 may be divided. The size and shape of the diffusion material sheet 4 may be adjusted by cutting the diffusion material sheet 4 .

For handling the laminate 8 or the diffusion material sheet 4, means for adsorbing and detaching the laminate 8 or the diffusion material sheet 4 by suction or magnetic force may be used.

[Heat treatment process]
The magnet base material 2 that has undergone the diffusion process may be used as a finished permanent magnet. After the diffusion step, a heat treatment step may be performed. In the heat treatment step, the magnet base material 2 may be heated at 450° C. or higher and 600° C. or lower. In the heat treatment step, the magnet base material 2 may be heated at the above temperature for 1 hour or more and 10 hours or less. The heat treatment process tends to improve the magnetic properties (especially coercive force) of the permanent magnet.

After the diffusion step or the heat treatment step, the dimensions and shape of the magnet base material 2 may be adjusted by processing methods such as cutting and polishing.

A permanent magnet is completed by the above method.

The composition of each of the magnet base material and the permanent magnet can be determined, for example, by energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF) analysis, high frequency inductively coupled plasma (ICP) emission spectroscopy, inert gas fusion- It may be identified by analytical methods such as a non-dispersive infrared absorption method, a combustion in an oxygen stream--infrared absorption method, and an inert gas fusion--thermal conductivity method.

The size and shape of the permanent magnet vary depending on the application of the permanent magnet and are not particularly limited. The shape of the permanent magnet can be, for example, cuboid, cube, rectangle (plate), polygonal prism, arc segment, fan, annular sector, sphere, disk, cylinder, ring, or capsule. The cross-sectional shape of the permanent magnet may be, for example, polygonal, circular arc (circular chord), arcuate, arched, or circular. The size and shape of the magnet substrate 2 may also vary as with the permanent magnets.

Permanent magnets are used in hybrid vehicles, electric vehicles, hard disk drives, magnetic resonance imaging (MRI), smartphones, digital cameras, flat-screen TVs, scanners, air conditioners, heat pumps, refrigerators, vacuum cleaners, washing machines, elevators, wind power generators, etc. may be used in various fields of Permanent magnets may be used as materials that constitute motors, generators or actuators.

The invention is not limited to the embodiments described above. For example, the magnet substrate used in the diffusion process may be a hot worked magnet rather than a sintered body. A hot-worked magnet may be produced by the following manufacturing method.

The raw material of the hot-worked magnet may be the same alloy as the raw material alloy used to produce the sintered body. By melting this alloy and then quenching it, a ribbon made of the alloy is obtained. By pulverizing the ribbon, flaky alloy powder is obtained. A compact is obtained by cold pressing (forming at room temperature) the alloy powder. After preheating the molded body, the molded body is hot pressed to obtain an isotropic magnet. An anisotropic magnet is obtained by hot plastic working of an isotropic magnet. A magnet substrate made of a hot-worked magnet is obtained by aging the anisotropic magnet. A magnet base material composed of a hot-worked magnet contains a large number of main phase particles bonded together, similar to the sintered body described above.

According to the method for manufacturing an RTB permanent magnet according to the present invention, an RTB permanent magnet that can be applied to motors or generators mounted on hybrid vehicles or electric vehicles can be obtained.

Reference numerals 2... Magnet base material 4... Diffusion material sheet 4a... First surface of diffusion material sheet 4b... Second surface of diffusion material sheet 6... Film 8... Laminate.

Claims (12)

A method for producing an RTB system permanent magnet using a diffusion material sheet containing a heavy rare earth element and a binder, comprising:
an attaching step of attaching a solvent to the surface of at least one of the magnet base material and the diffusing material sheet;
a covering step of covering at least part of the surface of the magnet base material with the diffusion material sheet so that the diffusion material sheet is in contact with the magnet base material on the surface to which the solvent is attached;
a diffusion step of heating the diffusing material sheet and the magnet base material after the coating step to diffuse the heavy rare earth element into the magnet base material;
with
The magnet base material contains a rare earth element R, a transition metal element T, and boron,
at least a portion of the rare earth element R is neodymium,
At least part of the transition metal element T is iron,
A method for producing an RTB permanent magnet. After the covering step, the method further comprises a conveying step of conveying the diffusion material sheet and the magnet base into a heating furnace,
The diffusion step is performed in the heating furnace,
The method for producing an RTB permanent magnet according to claim 1. After the coating step, further comprising a drying step of removing at least part of the solvent,
After the drying step, the diffusion step is performed,
3. The method for producing an RTB system permanent magnet according to claim 1 or 2. After the drying step, the method further comprises a conveying step of conveying the diffusion material sheet and the magnet base into a heating furnace,
The diffusion step is performed in the heating furnace,
4. The method for producing an RTB system permanent magnet according to claim 3. a heating step of softening the binder by heating the diffusing material sheet covering at least part of the surface of the magnet base material after the covering step;
a cooling step of hardening the binder by cooling the diffusion material sheet after the heating step;
further comprising
After the cooling step, the diffusion step is performed,
3. The method for producing an RTB system permanent magnet according to claim 1 or 2. After the drying step, a heating step of softening the binder by heating the diffusion material sheet covering at least part of the surface of the magnet base material;
a cooling step of hardening the binder by cooling the diffusion material sheet after the heating step;
further comprising
After the cooling step, the diffusion step is performed,
5. The method for producing an RTB system permanent magnet according to claim 3 or 4. After the cooling step, the method further comprises a conveying step of conveying the diffusion material sheet and the magnet base material into a heating furnace,
The diffusion step is performed in the heating furnace,
7. The method for producing an RTB system permanent magnet according to claim 5 or 6. In the heating step, at least one of the diffusion material sheet and the magnet base is pressed to bring the diffusion material sheet and the magnet base into close contact with each other.
A method for manufacturing an RTB permanent magnet according to any one of claims 5 to 7. In the cooling step, at least one of the diffusion material sheet and the magnet base is pressed to bring the diffusion material sheet and the magnet base into close contact with each other.
A method for manufacturing an RTB permanent magnet according to any one of claims 5 to 8. A laminate including a film and the diffusion material sheet overlapping the film is used,
In the covering step, at least part of the surface of the magnet base is covered with the laminate so that the diffusion material sheet is in contact with the surface of the magnet base.
A method for manufacturing an RTB permanent magnet according to any one of claims 1 to 9. A laminate including a film and the diffusion material sheet overlapping the film is used,
the first surface of the diffusion material sheet is a surface of the laminate that does not contact the film;
the second surface of the diffusion material sheet is the surface in contact with the film in the laminate,
the film is peeled off and removed from the diffusion material sheet before the coating step;
In the covering step, at least part of the surface of the magnet base material is covered with the diffusion material sheet so that the second surface is in contact with the surface of the magnet base material.
A method for manufacturing an RTB permanent magnet according to any one of claims 1 to 9. A laminate including a film and the diffusion material sheet overlapping the film is used,
the first surface of the diffusion material sheet is a surface of the laminate that does not contact the film;
the second surface of the diffusion material sheet is the surface in contact with the film in the laminate,
the film is peeled off and removed from the diffusion material sheet before the coating step;
In the covering step, at least part of the surface of the magnet base material is covered with the diffusion material sheet so that the first surface is in contact with the surface of the magnet base material.
A method for manufacturing an RTB permanent magnet according to any one of claims 1 to 9.

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