JP2020167209A - Method for manufacturing r-t-b based permanent magnet - Google Patents

Abstract

To provide a method for manufacturing an R-T-B based permanent magnet, by which a heavy rare earth element can be uniformly diffused into a magnet base material.SOLUTION: A method for manufacturing an R-T-B based permanent magnet comprises: a covering step of covering at least part of a surface of a magnet base material 2 with a diffusion material sheet 4 containing heavy rare earth elements and a binder; a heating step of softening the binder by heating the diffusion material sheet 4 covering the at least part of the surface of the magnet base material 2; a cooling step of hardening the binder by cooling the diffusion material sheet 4 after the heating step; and a diffusion step of diffusing the heavy rare earth element into the magnet base material 2 by heating the diffusion material sheet 4 and the magnet base material 2 after the cooling step. The magnet base material 2 contains rare earth elements R, transition metal elements T and boron, at least part of the rare earth elements R is neodymium, and at least part of the transition metal elements T is iron.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing an RTB-based permanent magnet.

RTB-based permanent magnets containing a rare earth element R (neodymium or the like), a transition metal element T (iron or the like), and boron B have excellent magnetic properties. Generally, the residual magnetic flux density Br (residual magnetization) and the coercive force HcJ are used as indexes representing the magnetic characteristics of the RTB-based permanent magnets.

The RTB-based permanent magnet is a new creation type permanent magnet. By applying a magnetic field opposite to the magnetization direction to the new creation type permanent magnet, magnetization reversal nuclei are likely to occur near the grain boundaries of a large number of crystal particles (main phase particles) constituting the permanent magnet. The core of this magnetization reversal reduces the coercive force of the permanent magnet. The coercive force of the RTB permanent magnet decreases as the temperature rises. RTB permanent magnets used in motors, generators, etc. are required to have a high coercive force even in a high temperature environment.

Heavy rare earth elements such as dysprosium are added to the RTB permanent magnets in order to improve the coercive force of the RTB permanent magnets. The addition of heavy rare earth elements improves the anisotropic magnetic field and makes it difficult for magnetization reversal nuclei to occur, thus increasing the coercive force. In recent years, the grain boundary diffusion method has been used to obtain a high coercive force with a smaller amount of heavy rare earth elements. By diffusing heavy rare earth elements along the grain boundaries from the magnet surface, the anisotropic magnetic field tends to grow locally near the grain boundaries, making it difficult for magnetization reversal nuclei to occur near the grain boundaries, and the coercive force. Will increase.

For example, in the method for producing an RTB-based 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-based permanent magnet described in Patent Document 2 below, a sheet (molded product) containing an oxide of a heavy rare earth element and a resin component is used. By heating the magnet base material at a temperature equal to or lower than the sintering temperature while the sheet is arranged on the surface of the magnet base material, the heavy rare earth elements in the sheet are diffused into the sintered body.

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

When a sheet containing a heavy rare earth element is arranged on the surface of the magnet base material, the sheet does not sufficiently adhere to the surface of the magnet base material, and a gap is likely to be formed between the sheet and the surface of the magnet base material. Further, with the handling of the magnet base material on which the sheets are stacked, the position of the sheet deviates from a predetermined position, or the sheet peels off from the surface of the magnet base material. Due to these problems, it is difficult for the heavy rare earth elements in the sheet to diffuse uniformly to the surface of the magnet base material. As a result, the composition and magnetic characteristics of the RTB-based permanent magnets vary, and the coercive force of the RTB-based permanent magnets is not sufficiently improved. The above problem is remarkable when the surface of the magnet base material is a curved surface.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing an RTB-based permanent magnet capable of uniformly diffusing heavy rare earth elements into a magnet base material. To do.

The method for producing an RTB-based permanent magnet according to one aspect of the present invention includes a coating step of covering at least a part of the surface of the magnet base material with a diffuser sheet containing a heavy rare earth element and a binder, and a magnet base material. A heating step that softens the binder by heating a diffuser sheet that covers at least a part of the surface of the magnet, a cooling step that cures the binder by cooling the diffuser sheet after the heating step, and a cooling step. The magnet base material comprises a diffusion step of diffusing the heavy rare earth element into the magnet base material by heating the diffuser sheet and the magnet base material, and the magnet base material contains at least the rare earth element R, the transition metal element T, and boron. Some rare earth elements R are neodymium, and at least some transition metal elements T are iron.

The method for manufacturing the RTB-based permanent magnet may further include a transfer step of transporting the diffusing material sheet and the magnet base material into the heating furnace after the cooling step, and the diffusion step may be carried out in the heating furnace. ..

In the cooling step, the diffusing material sheet and the magnet base material may be conveyed into the heating furnace while the diffusing material sheet is being cooled, and the diffusing step may be carried out in the heating furnace.

In the heating step, the diffuser sheet and the magnet base material may be brought into close contact with each other by pressurizing at least one of the diffuser sheet and the magnet base material.

In the cooling step, the diffuser sheet and the magnet base material may be brought into close contact with each other by pressurizing at least one of the diffuser sheet and the magnet base material.

A laminate containing a film and a diffuser sheet that overlaps the film may be used, and in the coating step, at least a part of the surface of the magnet substrate is a laminate so that the diffuser sheet is in contact with the surface of the magnet substrate. The heating step and the cooling step may be carried out in a state where the magnet base material may be covered and at least a part of the surface of the magnet base material is covered with the laminate.

After the cooling step, the film may be peeled and removed from the diffusing material sheet, and after the film is removed, the diffusing step may be carried out.

The diffusion step may be further carried out in a state where at least a part of the surface of the magnet base material is covered with the laminate.

A laminate containing a film and a diffuser sheet overlapping the film may be used, the first surface of the diffuser sheet may be a surface of the laminate that does not contact the film, and the second surface of the diffuser sheet may be. The surface of the laminate may be in contact with 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 magnet group so that the second surface is in contact with the surface of the magnet base material. At least a part of the surface of the material may be covered with a diffuser sheet.

A laminate containing a film and a diffuser sheet overlapping the film may be used, the first surface of the diffuser sheet may be a surface of the laminate that does not contact the film, and the second surface of the diffuser sheet may be. The surface of the laminate may be in contact with 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 magnet group so that the first surface is in contact with the surface of the magnet base material. At least a part of the surface of the material may be covered with a diffuser sheet.

According to the present invention, there is provided a method for producing an RTB-based permanent magnet capable of uniformly diffusing heavy rare earth elements into a magnet base material.

(A) in FIG. 1, (b) in FIG. 1, and (c) in FIG. 1 are a coating step, a heating step, and a cooling step in the method for manufacturing an RTB-based permanent magnet according to the present embodiment. The outline of is shown. (A) in FIG. 2, (b) in FIG. 2, and (c) in FIG. 2 are a coating step, a heating step, and a cooling step in the method for manufacturing an RTB-based permanent magnet according to the present embodiment. The outline of is shown.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, equivalent components are labeled with equivalent reference numerals. The present invention is not limited to the following embodiments. All of the "permanent magnets" described below mean "RTB-based permanent magnets".

[Preparation process of raw material alloy]
In the process of preparing the raw material alloy, an alloy material is produced from a metal raw material containing each element constituting a permanent magnet. The raw material alloy may be produced by a strip casting method, a book molding method, or a centrifugal casting method. The metal raw material may be, for example, a simple substance of a rare earth element (elemental substance of a metal), an alloy containing a rare earth element, pure iron, ferrobolon, or an alloy containing these. These metal raw materials are weighed to match the desired composition of the magnetic substrate. As the raw material alloy, 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 a part of R contained in the raw material alloy is neodymium (Nd). Other Rs of the permanent magnet are scandium (Sc), ittrium (Y), lantern (La), cerium (Ce), placeozim (Pr), promethium (Pm), samarium (Sm), europium (Eu), and gadolinium. Further comprises at least one selected from the group consisting of (Gd), terbium (Tb), displosium (Dy), holmium (Ho), erbium (Er), samarium (Tm), itterbium (Yb), and lutetium (Lu). It's fine. The raw material alloy may contain Pr. The raw material alloy does not have to 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 a part of the transition metal element T contained in the raw material alloy is iron (Fe). T may be Fe and cobalt (Co). All Ts may be Fe. All Ts may be Fe and Co. The raw material alloy may further contain other transition metal elements other than Fe and Co. The 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 has other elements such as copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), manganese (Mn), carbon (C), nitrogen (N), and oxygen (O). , Calcium (Ca), Nickel (Ni), Copper (Cu), Silicon (Si), Chlorine (Cl), Sulfur (S) and Fluorine (F) may contain at least one selected from the group.

[Crushing process]
In the pulverization step, an alloy powder may be prepared by pulverizing the above-mentioned raw material alloy in a non-oxidizing atmosphere. The raw material alloy may be pulverized in two steps, a coarse pulverization step and a fine pulverization step. In the coarse crushing step, for example, a crushing method such as a stamp mill, a jaw crusher, or a brown mill may be used. The coarse grinding step may be carried out in an inert gas atmosphere. After storing hydrogen in the raw material alloy, the raw material alloy may be crushed. That is, hydrogen storage pulverization may be performed as a coarse pulverization step. In the rough pulverization step, the raw material alloy may be pulverized until its particle size becomes 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 until its average particle size becomes several μm. In the pulverization step, for example, a jet mill may be used. The raw material alloy may be milled by only a one-step milling step. For example, only the pulverization step may be performed. When a plurality of types of raw material alloys are used, each raw material alloy may be mixed after being separately pulverized. 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 milled with the milling aid.

[Molding process]
In the molding step, by molding the above alloy powder in a magnetic field, a molded product containing the alloy powder oriented along the magnetic field may be obtained. For example, a molded product may be obtained by pressurizing the alloy powder with 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-mentioned molded product in a vacuum or an atmosphere of an inert gas. The sintering conditions may be appropriately set according to the composition of the target permanent magnet, the crushing method of the raw material alloy, the particle size, and the like. The sintering temperature may be, for example, 1000 ° C. or higher and 1200 ° C. or lower. The sintering time may be 1 hour or more and 20 hours or less.

[Aging process]
In the aging treatment step, the sintered body may be heated at a temperature lower than the sintering temperature. In the aging process, the sintered body may be heated in a vacuum or an atmosphere of an inert gas. The diffusion step described later may also serve as the aging treatment step. In that case, it is not necessary to carry out the aging treatment step different from the diffusion step. The aging treatment step may be composed of a first temporary aging treatment and a second treatment following the first temporary aging treatment. In the first temporary effect treatment, the sintered body may be heated at a temperature of 700 ° C. or higher and 900 ° C. or lower. The time of the first temporary effect 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 of 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 step described later. The magnetic substrate comprises a plurality of main phase particles sintered from each other. The main phase particles contain at least Nd, Fe and B. The main phase particles 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. Some or all of the main phase particles may consist only crystals of R 2 _T 14 _B (monocrystalline or polycrystalline). R ₂ T ₁₄ B may be, for example, Nd ₂ Fe ₁₄ B. A part of Nd in Nd ₂ Fe ₁₄ B may be replaced with at least one of Pr, Tb and Dy. A part of Fe in Nd ₂ Fe ₁₄ B may be replaced with Co. The main phase particles may contain the above elements (elements that can be contained in the raw material alloy) in addition to R, T and B. The magnetic substrate comprises grain boundaries formed between the main phase particles. 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 particles. The magnet base material also includes a plurality of two-particle grain boundaries as grain boundaries. A two-particle grain boundary is a grain boundary located between two adjacent main phase particles. The grain boundaries may contain at least Nd, and the content of Nd in the grain boundaries may be larger than the content of Nd in the main phase particles. That is, the grain boundaries may include the Nd-rich phase. The grain boundaries may include 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 value of the 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.

[Coating process, heating process, cooling process and diffusion process]
The method for manufacturing an RTB-based permanent magnet according to the present embodiment includes a coating step, a heating step, a cooling step, and a diffusion step in addition to the above steps. In the following, each step will be described with reference to the drawings. (A) in FIG. 1 and (a) in FIG. 2 show cross sections of the diffuser sheet 4 and the film 6 respectively, and these cross sections are perpendicular to the surfaces of the diffuser sheet 4 and the film 6 respectively. is there. (B) in FIG. 1 and (c) in FIG. 1 show cross sections of the diffuser sheet 4, the film 6 and the magnet base material 2, respectively, and these cross sections are the diffuser sheet 4, the film 6 and the magnet. The base material 2 is perpendicular to the surface of each. (B) in FIG. 2 and (c) in FIG. 2 show cross sections of the diffuser sheet 4 and the magnet base material 2, and these cross sections are the cross sections of the diffuser sheet 4 and the magnet base material 2, respectively. It is perpendicular to the surface.

In the coating step, at least a part of the surface of the magnet base material 2 is covered with the diffuser sheet 4. The diffusing material sheet 4 contains at least heavy rare earth elements and a binder. The heavy rare earth element may be, for example, at least one element of Tb and Dy. As described above, the magnet base material 2 contains a rare earth element R, a transition metal element T, and boron. At least some rare earth elements R are neodymium, and at least some transition metal elements T are iron.

Only a part of the surface of the magnet base material 2 may be covered with the diffuser sheet 4. The entire surface of the magnet base material 2 may be covered with the diffuser 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 diffuser sheet 4. When the magnet base material 2 has a plurality of surfaces, the plurality of surfaces of the magnet base material 2 may be covered with the diffuser sheet 4. For example, both the main surface of the magnet base material 2 and the back surface of the main surface may be covered with the diffuser 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 diffuser sheet 4.

In the heating step, the binder is softened by heating the diffuser sheet 4 that covers the surface of the magnet base material 2. Due to the softening of the binder, the diffuser sheet 4 is deformed along the concave and convex portions on the surface of the magnet base material 2, and the diffuser sheet 4 comes into close contact with the surface of the magnet base material 2. That is, the softening of the binder reduces the gap between the diffuser sheet 4 and the surface of the magnet base material 2. In the heating step, both the magnet base material 2 and the diffusing material sheet 4 may be heated. Only one of the magnet base material 2 and the diffuser sheet 4 may be heated. The heating method may be arbitrary. If the temperature of the diffusing material sheet 4 in the heating step is too high, the shape-retaining power of the diffusing material sheet 4 is insufficient, and the efficiency of the cooling step is lowered. Therefore, the temperature of the diffusing material sheet 4 should not be too high, and there is an optimum temperature of the diffusing material sheet 4. That is, the temperature of the diffusing material sheet 4 in the heating step may be adjusted according to the composition and softening temperature of the binder and the shape-retaining power of the diffusing material sheet 4. The temperature of the diffusing material sheet 4 in the heating step may be, for example, 60 ° C. or higher and 250 ° C. or lower.

In the heating step, the diffuser sheet 4 and the magnet base material 2 may be brought into close contact with each other by pressurizing at least one of the diffuser sheet 4 and the magnet base material 2. That is, at least one of the diffuser sheet 4 and the magnet base material 2 may be pressurized in parallel with the heating of the diffuser sheet 4. By pressurizing, 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 base material 2 may be pressurized. By sandwiching the diffuser sheet 4 and the magnet base material 2 with the pressurizing means, both the diffuser sheet 4 and the magnet base material 2 may be pressurized. After the diffuser sheet 4 is installed on a flat surface, the magnet base material 2 may be pressed against the diffuser sheet 4. The pressure applied to the diffusing material sheet 4 in the heating step may be, for example, 0.05 MPa or more and 10 MPa or less.

In the cooling step, the binder is cured by cooling the diffusing material sheet 4 that has undergone the heating step. By curing the binder, the diffuser sheet 4 is solidified in a state where the diffuser sheet 4 is in close contact with the surface of the magnet base material 2. That is, in the cooling step, the diffusing material sheet 4 is adhered to the surface of the magnet base material 2, and the diffusing material sheet 4 and the magnet base material 2 are integrated. As a result, the diffuser sheet 4 is fixed to the surface of the magnet base material 2, and peeling of the diffuser sheet 4 from the surface of the magnet base material 2 is suppressed after the cooling step. Further, after the cooling step, the displacement of the diffuser sheet 4 on the surface of the magnet base material 2 is suppressed. In the cooling step, the diffusing material sheet 4 may be cooled at room temperature.

In the cooling step, the diffuser sheet 4 and the magnet base material 2 may be brought into close contact with each other by pressurizing at least one of the diffuser sheet 4 and the magnet base material 2. That is, at least one of the diffuser sheet 4 and the magnet base material 2 may be pressurized in parallel with the cooling of the diffuser sheet 4. By pressurizing, 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 base material 2 may be pressurized. By sandwiching the diffuser sheet 4 and the magnet base material 2 with the pressurizing means, both the diffuser sheet 4 and the magnet base material 2 may be pressurized. After the diffuser sheet 4 is installed on a flat surface, the magnet base material 2 may be pressed against the diffuser sheet 4.

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

In the above coating step, one side of the magnet base material 2 is covered with the diffuser sheet 4, but two sides of the magnet base material 2 may be covered with the diffuser sheet 4. For example, the two opposing surfaces of the magnet base material 2 may be covered with the diffuser sheet 4. After the two different surfaces of the magnet base material 2 are covered with the diffuser sheet 4, the above-mentioned heating step and cooling step may be carried out. After the heating step and the cooling step are performed in a state where one surface of the magnet base material 2 is covered with the diffuser sheet 4, another surface of the magnet base material 2 may be further covered with the diffuser sheet 4. After another surface of the magnet base material 2 is covered with the diffuser sheet 4, the heating step and the cooling step may be performed again. When a plurality of surfaces of the magnet base material 2 are covered with the diffuser sheet 4, a coating step, a heating step, and a cooling step may be performed for each surface of the magnet base material 2. After the two or more surfaces of the magnet base material 2 are simultaneously covered with the diffuser sheet 4, the heating step and the cooling step may be performed.

In the diffusion step, the heavy rare earth element is diffused into the magnet base material 2 by heating the diffuser sheet 4 and the magnet base material 2 that have undergone the cooling step. By heating the diffusing material sheet 4 and the magnet base material 2, the heavy rare earth elements in the diffusing material are diffused from the surface of the magnet base material 2 to the inside of the magnet base material 2. Inside the magnet base material 2, heavy rare earth elements diffuse to the vicinity of the surface of the main phase particles via grain boundaries. Some light rare earth elements (Nd, etc.) are replaced with heavy rare earth elements in the vicinity of the surface of the main phase particles. When the heavy rare earth element is localized near the surface of the main phase particles and at the grain boundaries, the anisotropic magnetic field becomes locally large near the grain boundaries, and it becomes difficult for magnetization reversal nuclei to occur near the grain boundaries. .. As a result, the coercive force of the permanent magnet increases.

If the above heating step is not performed, it is difficult for the diffuser sheet 4 to adhere to the surface of the magnet base material 2. That is, a gap between the diffuser sheet 4 and the surface of the magnet base material 2 is likely to be formed. Therefore, when the diffusion step is carried out without going through the heating step, it is difficult for the heavy rare earth elements in the diffuser sheet 4 to uniformly diffuse to the surface of the magnet base material 2. That is, it is difficult for heavy rare earth elements to diffuse from the diffusing material sheet 4 to the magnet base material 2 on 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. As a result, the heavy rare earth elements are not sufficiently diffused into the magnet base material 2, the composition and magnetic properties of the RTB-based permanent magnets are varied, and the coercive force of the RTB-based permanent magnets is sufficient. Does not improve. On the other hand, since the heating step is carried out in this embodiment, the diffusing material sheet 4 is uniformly adhered to the surface of the magnet base material 2. Therefore, in the diffusion step, the heavy rare earth elements in the diffuser sheet 4 are likely to be uniformly diffused to the surface of the magnet base material 2. As a result, the heavy rare earth element is sufficiently diffused near the surface of the main phase particles of the magnet base material 2 and to the grain boundaries, and variations in the composition and magnetic characteristics of the RTB permanent magnet are suppressed, and the RT- The coercive force of the B-based permanent magnet is sufficiently increased.

If the cooling step is not performed after the heating step, the diffuser sheet 4 is not fixed to the surface of the magnet base material 2. As a result, as the diffuser sheet 4 and the magnet base material 2 are handled after the heating step, the position of the diffuser sheet 4 shifts from a predetermined position, or the diffuser sheet 4 peels off from the surface of the magnet base material 2. Or Due to these problems, it is difficult for the heavy rare earth elements in the diffusing material sheet 4 to uniformly diffuse to the surface of the magnet base material 2 in the diffusing step. As a result, the composition and magnetic characteristics of the RTB-based permanent magnets vary, and the coercive force of the RTB-based permanent magnets is not sufficiently improved. On the other hand, since the cooling step is carried out in this embodiment, the diffuser sheet 4 is fixed to the surface of the magnet base material 2 in a state where the diffuser sheet 4 is in close contact with the surface of the magnet base material 2. Therefore, the displacement and peeling of the diffuser sheet 4 after the cooling step are suppressed. That is, even in the diffusion step, the diffusion material sheet 4 is uniformly adhered to the surface of the magnet base material 2 at a predetermined position. As a result, the heavy rare earth elements in the diffuser sheet 4 are easily diffused uniformly to the surface of the magnet base material 2, the variation in the composition and magnetic characteristics of the RTB permanent magnet is suppressed, and the RTB The coercive force of the system permanent magnet is sufficiently increased.

As described above, when the heating step is not carried out, the diffusing material sheet 4 is not integrated with the magnet base material 2 without any gaps, so that the effect of the cooling step is not exhibited. By eliminating the gap between the diffusing material sheet 4 and the magnet base material 2 by the heating step and then performing the cooling step, the diffusing material sheet 4 can be fixed to the surface of the magnet base material 2 without any gap. That is, the diffusing material sheet 4 can be fixed to the surface of the magnet base material 2 without a gap only by the interaction between the heating step and the cooling step.

In the diffusion step, the diffuser sheet 4 and the magnet base material 2 may be heated in the heating furnace. In order to suppress the oxidation of the magnet base material 2 in the diffusion step, after the magnet base material 2 to which the diffusing material sheet 4 is adhered is installed in the heating furnace, the atmosphere in the heating furnace is vacuum or argon (Ar) or the like. Becomes an inert gas. The air pressure in the heating furnace changes due to the introduction of exhaust gas and / or inert gas accompanying the control of the atmosphere in the heating furnace. An air flow is generated in the heating furnace as the air pressure changes. If the above heating step and cooling step are not performed, the diffuser sheet 4 is likely to be peeled off from the surface of the magnet base material 2 due to the influence of the air flow generated in the heating furnace. However, in the present embodiment, since the heating step and the cooling step are carried out before the diffusion step, the diffuser sheet 4 is uniformly adhered to the surface of the magnet base material 2. As a result, the peeling of the diffusing material sheet 4 due to the generation of the air flow is suppressed, and the heavy rare earth elements in the diffusing material sheet 4 are easily diffused uniformly to 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 heating the diffusing material sheet 4 and the magnet base material 2 at the above temperature may be 1 hour or more and 50 hours or less. Before heating the diffusing material sheet and the magnet base material at the above temperature, the binder in the diffusing material sheet 4 may be burnt down by heating the diffusing material sheet 4 at a temperature lower than the above temperature. That is, the binder removal treatment may be performed as a preliminary step of the diffusion step.

The method for manufacturing a permanent magnet may further include a transfer step of transporting the magnet base material 2 to which the diffuser sheet 4 is adhered into the heating furnace after the cooling step. In the process of transportation, the magnet base material 2 to which the diffusing material sheet 4 is adhered may be temporarily stored in the warehouse. When the diffusing material sheet 4 comes into contact with another object in the transporting process, a force may act on the diffusing material sheet 4. Further, there is a possibility that a force acts on the diffusing material sheet 4 due to vibration and / or acceleration during transportation. If the cooling step is not carried out, the force acts on the diffusing material sheet 4 in the middle of the conveying process, so that the position of the diffusing material sheet 4 deviates from a predetermined position, or the diffusing material sheet 4 is the magnet base material 2. It peels off from the surface of the magnet. However, since the heating step and the cooling step are carried out before the transfer step, the misalignment and peeling of the diffuser sheet 4 in the transfer step are suppressed. For the same reason, in the cooling step, the diffuser sheet 4 and the magnet base material 2 may be conveyed into the heating furnace while the diffuser sheet 4 is being cooled. That is, the transfer process may also serve as the cooling process.

The diffuser sheet 4 may be produced by the following method. The diffusing materials described below are chemical substances containing at least heavy rare earth elements. The diffusing material may be particles or powder. The particle size of the diffusing material may be adjusted by the same means as in the coarse pulverization step and the fine pulverization step described above. The median diameter D50 of the diffusing material may be, for example, 3 μm or more and 15 μm or less.

A lacquer is prepared by stirring and mixing the binder and the organic solvent in a predetermined ratio. 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 organic solvent is not limited as long as it is a liquid in which the binder dissolves. The organic solvent may be, for example, a kind of compound consisting of ethanol, butanol, octanol, methyl ethyl ketone, xylene, butyl carbitol, turpineol, and dihydro turpineol. Multiple types of organic solvents may be used. After adding the diffusing material to the lacquer, they are mixed. If necessary, a plasticizer may be further added to the lacquer. Subsequently, a dispersion treatment of the mixture of the diffusing material and the lacquer is performed. The means for the dispersion treatment may be a rotation / revolution mixer, a triple roll, a high-pressure homogenizer, or an ultrasonic homogenizer. Distributed processing may be performed using a plurality of means.

The diffusing material may be, for example, a simple substance of a heavy rare earth element, an alloy containing a heavy rare earth element, or a compound containing a 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 simple substance of the heavy rare earth element may be one or both of the simple substance of Tb and the simple substance of Dy. The alloy containing a heavy rare earth element may be at least one selected from the group consisting of an alloy composed of Tb and Fe, an alloy composed of Dy and Fe, and an alloy composed of Tb, Dy and Fe. The hydrides of heavy rare earth elements include, for example, hydrides of alloys consisting of TbH ₂ , TbH ₃ , Tb and Fe, hydrides of alloys consisting of DyH ₂ , DyH ₃ , Dy and Fe, and Tb, Dy and Fe. It may be at least one selected from the group consisting of hydrides of alloys consisting of. The diffusing material may further contain at least one element selected from the group consisting of Nd, Pr and Cu. For example, the diffuser contains a simple substance of Nd, a simple substance of Pr, an alloy containing Nd and Pr, a hydride of an alloy containing NdH ₂ , NdH ₃ , PrH ₂ , PrH ₃ , Nd and Pr, a simple substance of Cu, and Cu. alloy, CuH, may further comprise at least one selected from the group consisting of Cu ₂ O and CuO.

By the above method, a paste containing a diffusing material, a binder and an organic solvent is prepared. 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 design 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 adhesion of the diffusing material sheet 4. Coarse grains and agglomerates may be removed from the paste by filtering 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 content of the binder in the paste may be, for example, 1% by mass or more and 15% by mass or less. The content of the organic solvent in the paste may be, for example, 10% by mass or more and 59% by mass or less.

By applying the paste to the surface of the film 6, a coating film is formed on the surface of the film 6. The thickness of the coating film is preferably constant. The film 6 may consist of, for example, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), or graphite. The surface of the film 6 to which the paste is applied may be previously covered 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, a doctor blade, a bar coater, an inkjet coater, a roll coater or a die coater.

By drying the coating film and removing the organic solvent from the coating film, the diffuser sheet 4 shown in FIG. 1A can be obtained. That is, the laminated body 8 including the film 6 and the diffuser sheet 4 overlapping the film 6 is obtained. The first surface 4a of the diffuser sheet 4 is a surface of the laminated body 8 that does not come into contact with the film 6. The second surface 4b of the diffusing material sheet 4 is the surface of the laminated body 8 in contact with the film 6. The method for drying the coating film may be, for example, infrared heating, hot air drying, or vacuum drying. The drying conditions may be set according to the vapor pressure of the organic solvent contained in the coating film. The organic solvent may remain in the diffusing material sheet 4. The thickness of the diffuser 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 diffuser sheet 4. The thickness of the magnet base material 2 may be, for example, 0.5 mm or more and 25 mm or less.

The laminate 8 may be used in the coating step. As shown in FIG. 1B, in the coating step, at least a part of the surface of the magnet base material 2 is covered with the laminate 8 so that the diffuser 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 heating step and the cooling step may be carried out in a state where the surface of the magnet base material 2 is covered with the laminate 8. That is, the diffusing material sheet 4 may be transferred from the film 6 to the surface of the magnet base material 2 by the heating step and the cooling step using the laminated body 8. When the laminate 8 is used in the coating step, the diffusing material sheet 4 may be pressurized via the film 6 in at least one of the heating step and the cooling step. 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 laminate 8. When the magnet base material 2 has a plurality of surfaces, the plurality of surfaces of the magnet base material 2 may be covered with the laminate 8. For example, both the main surface of the magnet base material 2 and the back surface of the main surface may be covered with the laminate 8. 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 laminate 8.

As shown in (c) in FIG. 1, the film 6 may be peeled off and removed from the diffuser sheet 4 after the cooling step. After the cooling step, the diffuser sheet 4 is adhered to the surface of the magnet base material 2, and the diffuser sheet 4 and the magnet base material 2 are integrated. Therefore, by peeling the film 6 from the diffuser sheet 4 after the cooling step, a part of the diffuser sheet 4 is unlikely to remain on the surface of the peeled film 6. That is, the breakage of the diffuser sheet 4 due to the peeling of the film 6 is suppressed. Further, by peeling the film 6 from the diffuser sheet 4 after the cooling step, it is possible to prevent the diffuser sheet 4 from peeling from the surface of the magnet base material 2 together with the film 6.

In the above coating step, one surface of the magnet base material 2 is covered with the laminate 8, but two surfaces of the magnet base material 2 may be covered with the laminate 8. For example, the 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 heating step and the cooling step described above may be carried out. After the heating step and the cooling step are performed in a state where one surface of the magnet base material 2 is covered with the laminate 8, another surface of the magnet base material 2 may be further covered with the laminate 8. After the other surface of the magnet base material 2 is covered with the laminate 8, the heating step and the cooling step may be performed again. When a plurality of surfaces of the magnet base material 2 are covered with the laminate 8, a coating step, a heating step, and a cooling step may be performed for each surface of the magnet base material 2. After the two or more surfaces of the magnet base material 2 are simultaneously covered with the laminate 8, the heating step and the cooling step may be carried out.

After removing the film 6, a diffusion step may be performed. Since the film 6 is removed before the diffusion step, carbides of the film 6 are not formed on the surface of the magnet base material 2 in the diffusion step. As a result, the carbon derived from the film 6 does not penetrate into the magnet base material 2 in the diffusion step, and the deterioration of the magnetic properties of the permanent magnet due to the excessive carbon content is suppressed. However, the diffusion step may be carried out in a state where at least a part of the surface of the magnet base material 2 is covered with the laminate 8. That is, the diffusion step may be carried out without removing the film 6. For example, when the film 6 is made of graphite, the graphite is easily burned out by heating in the diffusion step, so that the diffusion step may be carried out without removing the film 6.

When the laminate 8 is used in 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 base material 2 before the coating step. After the coating step (before the heating step), the dimensions and shape of the laminate 8 may be adjusted so as to match the dimensions 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 laminated body 8, the laminated body 8 may be divided. The dimensions and shape of the laminated body 8 may be adjusted by cutting the laminated body 8.

As shown in (a) in FIG. 2, the film 6 may be peeled and removed from the diffusing material sheet 4 before the coating step. As shown in (b) in FIG. 2, in the coating step, at least a part of the surface of the magnet base material 2 is diffused so that the second surface 4b of the diffuser sheet 4 is in contact with the surface of the magnet base material 2. It may be covered with a material sheet 4. In the process of forming the coating film from the paste, the diffusing 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 tends to be unevenly distributed on the second surface 4b side that was in contact with the film 6. Further, the second surface 4b in contact with the film 6 is flatter than the first surface 4a. Therefore, since the second surface 4b of the diffusing material sheet 4 overlaps the surface of the magnet base material 2, the diffusing material in the diffusing material sheet 4 is easily uniformly arranged along the surface of the magnet base material 2, and the diffusing material sheet is easily arranged. 4 easily adheres 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 FIG. 2C, in the coating step, at least a part of the surface of the magnet base material 2 is covered with the diffuser sheet 4 so that the first surface 4a is in contact with the surface of the magnet base material 2. You may be broken.

When the film 6 is peeled off and removed from the diffuser sheet 4 before the coating step, the size and shape of the laminate 8 are adjusted to match the size and shape of the surface of the magnet base material 2, and then the film 6 May be peeled off and removed from the diffuser sheet 4. The diffuser sheet 4 may be peeled from the film 6 after the dimensions and shape of the diffuser sheet 4 are adjusted to match the dimensions and shape of the surface of the magnet base material 2. After the film 6 is peeled off and removed from the diffuser sheet 4, the dimensions and shape of the diffuser sheet 4 may be adjusted to match the dimensions and shape of the surface of the magnet base material 2. After the coating step (before the heating step), the dimensions and shape of the diffuser sheet 4 may be adjusted to match the dimensions 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 diffuser sheet 4, the diffuser sheet 4 may be divided. The dimensions and shape of the diffuser sheet 4 may be adjusted by cutting the diffuser sheet 4.

For handling the laminated body 8 or the diffusing material sheet 4, means for sucking and desorbing the laminated body 8 or the diffusing material sheet 4 by suction or magnetic force may be used. If necessary, the diffuser sheet 4 may be transferred from the film 6 to another film.

It is possible to cover the entire surface of the magnet base material 2 with a coating film containing a diffusing material. 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, the thickness of the coating film is difficult to be uniform because the coating film formed by immersion is affected by gravity or the like. Further, when the magnet base material 2 is immersed in the paste, it is difficult to cover only a part of the surface of the magnet base material 2 with the coating film. In order to solve these problems, the diffuser sheet 4 is useful. For example, after processing the diffuser sheet 4 so that the shape of the diffuser sheet 4 matches the shape of an arbitrary portion of the surface of the magnet base material 2, the diffuser sheet 4 is formed on an arbitrary portion of the surface of the magnet base material 2. By covering with, only the necessary portion of the magnet base material 2 can be covered with the diffuser sheet 4 having a uniform thickness.

The surface of the magnet base material 2 covered with the diffuser sheet 4 may be a curved surface. In the conventional method for manufacturing a permanent magnet, it is difficult for the diffuser sheet 4 to adhere uniformly to the curved surface, the position of the diffuser sheet 4 tends to shift on the curved surface, and the diffuser sheet 4 easily peels off from the curved surface. On the other hand, in the present embodiment, since the heating step and the cooling step are carried out, the diffusing material sheet 4 easily adheres uniformly to the curved surface, the misalignment of the diffusing material sheet 4 on the curved surface is easily suppressed, and the diffusing material sheet from the curved surface is easily suppressed. The peeling of 4 is easily suppressed.

[Heat treatment process]
The magnet base material 2 that has undergone the diffusion step may be used as a finished product of a permanent magnet. A heat treatment step may be performed after the diffusion step. 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 (particularly the coercive force) of the permanent magnet.

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

By the above method, the permanent magnet is completed.

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

The dimensions and shape of the permanent magnets vary depending on the use of the permanent magnets and are not particularly limited. The shape of the permanent magnet may be, for example, a rectangular parallelepiped, a cube, a rectangle (plate), a polygonal column, an arc segment, a fan, an annular sector, a sphere, a disk, a cylinder, a ring, or a capsule. The cross-sectional shape of the permanent magnet may be, for example, a polygon, an arc (bowstring), a bow, an arch, or a circle. The size and shape of the magnet base material 2 may be as diverse as the permanent magnet.

Permanent magnets include 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, washer-dryers, elevators, wind power generators, etc. It may be used in various fields of. Permanent magnets may be used as materials to make up motors, generators or actuators.

The present invention is not limited to the above embodiments. For example, the magnet base material used in the diffusion step may be a hot-worked magnet instead of a sintered body. The hot-worked magnet may be manufactured by the following manufacturing method.

The raw material of the hot-worked magnet may be an alloy similar to the raw material alloy used for producing the sintered body. By melting this alloy and further quenching it, a thin band made of the alloy is obtained. Flake-shaped alloy powder is obtained by crushing the strip. A molded product is obtained by cold pressing (molding at room temperature) of the alloy powder. After preheating the molded product, an isotropic magnet is obtained by hot pressing the molded product. Anisotropic magnets are obtained by hot plastic working of isotropic magnets. The aging treatment of the anisotropic magnet gives a magnet substrate made of a hot-worked magnet. A magnet base material made of a hot-worked magnet contains a large number of main phase particles bonded to each other, similar to the above-mentioned sintered body.

According to the method for manufacturing an RTB permanent magnet according to the present invention, an RTB permanent magnet applied to a motor or a generator mounted on a hybrid vehicle or an electric vehicle can be obtained.

2 ... Magnet base material, 4 ... Diffusing material sheet, 4a ... First surface of diffusing material sheet, 4b ... Second surface of diffusing material sheet, 6 ... Film, 8 ... Laminated body.

Claims (10)

A coating process in which at least a part of the surface of the magnet base material is covered with a diffuser sheet containing a heavy rare earth element and a binder,
A heating step of softening the binder by heating the diffuser sheet that covers at least a part of the surface of the magnet base material.
After the heating step, a cooling step of curing the binder by cooling the diffuser sheet, and
After the cooling step, the diffusing material sheet and the magnet base material are heated 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 part of the rare earth element R is neodymium.
At least some of the transition metal elements T are iron.
A method for manufacturing an RTB-based permanent magnet. After the cooling step, a transport step of transporting the diffuser sheet and the magnet base material into the heating furnace is further provided.
The diffusion step is carried out in the heating furnace.
The method for manufacturing an RTB-based permanent magnet according to claim 1. In the cooling step, the diffuser sheet and the magnet base material are conveyed into the heating furnace while the diffuser sheet is cooled.
The diffusion step is carried out in the heating furnace.
The method for manufacturing an RTB-based permanent magnet according to claim 1. In the heating step, the diffuser sheet and the magnet base material are brought into close contact with each other by pressurizing at least one of the diffuser sheet and the magnet base material.
The method for manufacturing an RTB-based permanent magnet according to any one of claims 1 to 3. In the cooling step, the diffuser sheet and the magnet base material are brought into close contact with each other by pressurizing at least one of the diffuser sheet and the magnet base material.
The method for manufacturing an RTB-based permanent magnet according to any one of claims 1 to 4. A laminate containing the film and the diffuser sheet that overlaps the film is used.
In the coating step, at least a part of the surface of the magnet base material is covered with the laminate so that the diffuser sheet is in contact with the surface of the magnet base material.
The heating step and the cooling step are carried out in a state where at least a part of the surface of the magnet base material is covered with the laminate.
The method for manufacturing an RTB-based permanent magnet according to any one of claims 1 to 5. After the cooling step, the film is peeled and removed from the diffuser sheet.
After removing the film, the diffusion step is carried out.
The method for manufacturing an RTB-based permanent magnet according to claim 6. The diffusion step is further carried out in a state where at least a part of the surface of the magnet base material is covered with the laminate.
The method for manufacturing an RTB-based permanent magnet according to claim 6. A laminate containing the film and the diffuser sheet that overlaps the film is used.
The first surface of the diffuser sheet is a surface of the laminated body that does not come into contact with the film.
The second surface of the diffuser sheet is a surface of the laminate that is in contact with the film.
Prior to the coating step, the film was stripped and removed from the diffuser sheet.
In the coating step, at least a part of the surface of the magnet base material is covered with the diffuser sheet so that the second surface is in contact with the surface of the magnet base material.
The method for manufacturing an RTB-based permanent magnet according to any one of claims 1 to 5. A laminate containing the film and the diffuser sheet that overlaps the film is used.
The first surface of the diffuser sheet is a surface of the laminated body that does not come into contact with the film.
The second surface of the diffuser sheet is a surface of the laminate that is in contact with the film.
Prior to the coating step, the film was stripped and removed from the diffuser sheet.
In the coating step, at least a part of the surface of the magnet base material is covered with the diffuser sheet so that the first surface is in contact with the surface of the magnet base material.
The method for manufacturing an RTB-based permanent magnet according to any one of claims 1 to 5.

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