TW201532083A - Rare earth permanent magnet and method of making rare earth permanent magnet - Google Patents

Abstract

This invention provides a rare earth permanent magnet and a method of making the rare earth permanent magnet capable of improving magnetic properties of permanent magnets by making the density of the magnet a high density. A magnet raw material is crushed into magnet power, which is then mixed with adhesives to generate a composite (12). The generated composite (12) is formed into sheets on a supporting base material (13) by hot melt molding and therefore raw sheets (14) are generated. Then the generated raw sheets (14) are heated to soften and a magnetic field is applied to the heated raw sheets (14) to conduct a magnetic field alignment. Furthermore, the raw sheets (14) with magnetic field alignment are calcined in a non-oxidizing environment and then sintered at a firing temperature. As a result, a permanent magnet (1) with a density larger than 95% is made.

Description

Method for manufacturing rare earth permanent magnet and rare earth permanent magnet

The invention relates to a method for manufacturing a rare earth permanent magnet and a rare earth permanent magnet.

In recent years, permanent magnet motors used in hybrid electric vehicles, hard disk drives, and the like have been required to be small, lightweight, high in output, and high in efficiency. Therefore, when the permanent magnet motor is reduced in size, weight, output, and efficiency, it is required to further improve the thickness and magnetic properties of the permanent magnet embedded in the motor.

Here, as a method of manufacturing a permanent magnet used in a permanent magnet motor, a powder sintering method has been conventionally used. Here, the powder sintering method firstly produces a magnet powder obtained by pulverizing a raw material by a jet mill (dry pulverization) or the like. Thereafter, the magnet powder is placed in a mold and press-formed into a desired shape. Then, the solid magnet powder formed into a desired shape is sintered at a specific temperature (for example, 1100 ° C when it is a Nd—Fe—B-based magnet), thereby producing a permanent magnet (for example, Japanese Patent Laid-Open No. 2) -266503). Further, in general, for permanent magnets, in order to improve magnetic characteristics, magnetic field alignment is performed by applying a magnetic field from the outside. Further, in the conventional method for producing a permanent magnet by a powder sintering method, a magnet powder is filled into a mold at the time of press molding, and a magnetic field is applied to perform magnetic field alignment, and then a pressure is applied to form a compacted body. Further, other methods for producing permanent magnets such as an extrusion molding method, an injection molding method, and a calender molding method apply pressure to an environment in which a magnetic field is applied to form a magnet. Thereby, it is possible to form a molded body in which the direction of the easy magnetization axis of each of the magnet particles constituting the permanent magnet coincides with the direction in which the magnetic field is applied.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 2-266503 (page 5)

Here, in order to improve the magnetic properties of the anisotropic magnet, it is important that the C-axis (easy magnetization axis) of more magnet particles among the magnet particles constituting the permanent magnet by the magnetic field alignment is uniform in the same direction (ie, the alignment is improved). degree). In the case where the magnet powder is molded by green sheet molding, since the binder is present on the surface of the particles, the frictional force at the time of alignment is improved, and the alignment property of the particles is lowered as compared with the powder molding, so that it is difficult to perform magnetic field alignment. problem.

Further, as a cause of deteriorating the magnetic properties of the permanent magnet, carbonaceous materials remain in the magnet. Therefore, a technique is proposed in which the formed body is subjected to calcination in a non-oxidizing atmosphere before sintering of the molded body which is a raw material of the magnet, whereby the carbonaceous material is thermally decomposed to remove the contained carbon.

However, the result of removing the carbon in the magnet by performing the above calcination treatment is to form a large amount of voids (i.e., a decrease in density) inside the magnet. Moreover, the magnet characteristics are greatly reduced due to the formed voids.

The present invention has been made in order to eliminate the above-mentioned problems, and an object of the invention is to provide a method for producing a rare earth permanent magnet and a rare earth permanent magnet which can improve the magnetic properties of a permanent magnet by making the density of the magnet high.

In order to achieve the above object, the rare earth permanent magnet of the present invention is characterized by being produced by the following steps and having a density of 95% or more: a step of pulverizing a magnet raw material into a magnet powder; and producing a powder having the above-mentioned pulverized magnet and bonding a step of mixing a mixture; a step of magnetic field alignment by applying a magnetic field to the mixture; The step of calcining the mixture in a non-oxidizing environment; and the step of sintering by maintaining the calcined mixture at a firing temperature.

Further, the rare earth permanent magnet of the present invention is characterized in that, in the step of calcining the mixture, the mixture is heated to a set temperature at a specific temperature increase rate in a non-oxidizing atmosphere, at the set temperature. The adhesive is scattered and removed for a certain period of time.

Further, the rare earth permanent magnet of the present invention is characterized in that the set temperature is a binder decomposition temperature.

Further, the rare earth permanent magnet of the present invention is characterized in that the temperature increase rate is 2 ° C / min or less.

Further, the rare earth permanent magnet of the present invention is characterized in that, in the step of performing the magnetic field alignment, the mixture is formed into a sheet shape, and then the mixture of the sheets is subjected to magnetic field alignment.

Further, the rare earth permanent magnet of the present invention is characterized in that, in the case where the mixture is formed into a sheet shape, the mixture is heated and melted to be formed into a sheet shape.

Further, the rare earth permanent magnet of the present invention is characterized in that in the step of performing the magnetic field alignment, the mixture formed into a sheet shape is heated, and a magnetic field is applied to the heated mixture to perform magnetic field alignment.

Further, the rare earth permanent magnet of the present invention is characterized in that the mixture is formed into a long sheet shape, and in the step of performing the magnetic field alignment, the in-plane direction and length of the mixture formed into a long sheet shape are formed. A magnetic field is applied in the direction, the in-plane direction, the width direction, or the vertical direction of the sheet surface to perform magnetic field alignment.

Further, the method for producing a rare earth permanent magnet of the present invention is characterized by comprising: a step of pulverizing a magnet raw material into a magnet powder; and a step of mixing a mixture of the pulverized magnet powder and a binder; and applying the mixture a magnetic field to perform a magnetic field alignment step; the above mixture of the magnetic field alignment is calcined in a non-oxidizing environment And a step of producing a rare earth permanent magnet having a density of 95% or more by sintering the calcined mixture at a firing temperature.

Further, in the method for producing a rare earth permanent magnet according to the present invention, in the step of calcining the mixture, the mixture is heated to a predetermined temperature at a specific temperature increase rate in a non-oxidizing atmosphere, and then The above-mentioned set temperature is maintained for a certain period of time, and the above-mentioned binder is scattered and removed.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is characterized in that the set temperature is a binder decomposition temperature.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is characterized in that the temperature increase rate is 2 ° C / min or less.

Further, in the method for producing a rare earth permanent magnet according to the present invention, in the step of performing the magnetic field alignment, after the mixture is formed into a sheet shape, the mixture of the sheets is subjected to magnetic field alignment.

Further, in the method for producing a rare earth permanent magnet according to the present invention, when the mixture is formed into a sheet shape, the mixture is heated and melted to be formed into a sheet shape.

Further, the method for producing a rare earth permanent magnet according to the present invention is characterized in that in the step of performing the magnetic field alignment, the mixture formed into a sheet shape is heated, and a magnetic field is applied to the heated mixture to thereby perform a magnetic field Orientation.

Further, the method for producing a rare earth permanent magnet according to the present invention is characterized in that the mixture is formed into a long sheet shape, and in the step of performing the magnetic field alignment, by in-plane forming the mixture into a long sheet shape A magnetic field is applied in the direction and the longitudinal direction, the in-plane direction, the width direction, or the vertical direction of the sheet surface to perform magnetic field alignment.

According to the rare earth permanent magnet of the present invention having the above configuration, when the mixture of the magnet powder and the binder is subjected to calcination treatment for decarburization, the rare earth is used. The density of the permanent magnet is set to 95% or more, and voids are not formed inside the magnet to prevent the magnetite characteristics from being greatly lowered by the voids.

Further, according to the rare earth permanent magnet of the present invention, the mixture is heated to a predetermined temperature in a non-oxidizing atmosphere at a specific temperature increase rate, and then held at a set temperature for a certain period of time to cause the binder to be scattered and removed. The carbon contained in the mixture is removed stepwise as the temperature changes during calcination.

Further, according to the rare earth permanent magnet of the present invention, the binder is scattered and removed by maintaining the mixture in a non-oxidizing environment at a binder decomposition temperature for a certain period of time, so that even in the case of adding a binder, It is also possible to reduce the amount of carbon contained in the magnet in advance. As a result, it is suppressed that αFe is precipitated in the main phase of the magnet after sintering, and the entire magnet can be densely sintered to prevent a decrease in coercive force.

Further, according to the rare earth permanent magnet of the present invention, the mixture is heated to a set temperature in a non-oxidizing atmosphere at a temperature increase rate of 2 ° C/min or less, and then maintained at a set temperature for a predetermined period of time to be calcined. Therefore, the carbon contained in the mixture can be removed stepwise with a slow temperature change. Therefore, a rare earth permanent magnet having a higher density can be formed without forming a large number of voids inside the magnet.

Further, according to the rare earth permanent magnet of the present invention, by forming a mixture of the magnet powder and the binder into a sheet-like green sheet, it is possible to more easily perform the formation of the final product shape or the control of the alignment direction. Moreover, productivity can also be improved.

Further, according to the rare earth permanent magnet of the present invention, the mixture is heated and melted to be formed into a sheet shape, so that the permanent magnet can be molded with high dimensional accuracy. Moreover, even when the permanent magnet is thinned, the material yield can be prevented from decreasing and the number of processing steps can be prevented from increasing. Moreover, there is no occurrence of liquid phase in the alignment of the magnetic field, that is, the thickness deviation of the sheet.

Further, according to the rare earth permanent magnet of the present invention, the formed mixture is heated, and a magnetic field is applied to the heated mixture to perform magnetic field alignment. Therefore, even after forming into a sheet shape, the mixture can be appropriately subjected to the mixture. Magnetic field alignment to increase permanent magnetism The magnetic properties of stone.

Further, according to the rare earth permanent magnet of the present invention, in the step of forming the mixture into a long sheet shape and performing magnetic field alignment, by in-plane direction and length direction, in-plane direction and width direction of the long sheet or Since the magnetic field is applied by applying a magnetic field in the vertical direction of the sheet surface, the magnetic field alignment can be appropriately performed, and the magnetic properties of the permanent magnet can be improved. Further, when the direction in which the magnetic field is applied is the in-plane direction of the long sheet, the longitudinal direction, or the in-plane direction and the width direction, the surface of the sheet is not fluffed when a magnetic field is applied. On the other hand, when the direction in which the magnetic field is applied is set to be perpendicular to the sheet surface, an anisotropic magnet having a film having a C-axis (easy magnetization axis) as a thickness direction can be obtained.

Further, according to the method for producing a rare earth permanent magnet of the present invention, when the mixture of the magnet powder and the binder is subjected to calcination treatment for decarburization, the density of the rare earth permanent magnet to be produced is set to 95. In the case of % or more, voids are not formed inside the magnet to prevent the magnetite characteristics from being greatly lowered by the voids.

Moreover, according to the method for producing a rare earth permanent magnet of the present invention, the mixture is heated to a predetermined temperature in a non-oxidizing atmosphere at a specific temperature increase rate, and then held at a set temperature for a certain period of time to cause the binder to scatter and remove. Therefore, the carbon contained in the mixture can be removed stepwise as the temperature changes during calcination.

Moreover, according to the method for producing a rare earth permanent magnet of the present invention, the binder is dispersed and removed by maintaining the mixture in a non-oxidizing environment at a binder decomposition temperature for a certain period of time, so that even if a binder is added In the case of the situation, the amount of carbon contained in the magnet may also be reduced in advance. As a result, it is suppressed that αFe is precipitated in the main phase of the magnet after sintering, and the entire magnet can be densely sintered to prevent a decrease in coercive force.

Further, according to the method for producing a rare earth permanent magnet of the present invention, the mixture is heated to a set temperature in a non-oxidizing atmosphere at a temperature increase rate of 2 ° C/min or less, and then held at a set temperature for a predetermined period of time to be forged. The calcination treatment can thus periodically remove the carbon contained in the mixture as the temperature changes slowly. Therefore, it may not be inside the magnet A large number of voids are formed to produce a rare earth permanent magnet having a higher density.

Further, according to the method for producing a rare earth permanent magnet of the present invention, by forming a mixture of a magnet powder and a binder into a sheet-like green sheet, it is possible to more easily perform the forming or aligning direction of the final product shape. Control, etc. Moreover, productivity can also be improved.

Further, according to the method for producing a rare earth permanent magnet of the present invention, since the mixture is heated and melted and formed into a sheet shape, the permanent magnet can be molded with high dimensional accuracy. Moreover, even when the permanent magnet is thinned, the material yield can be prevented from decreasing and the number of processing steps can be prevented from increasing. Moreover, there is no occurrence of liquid phase in the alignment of the magnetic field, that is, the thickness deviation of the sheet.

Further, according to the method for producing a rare earth permanent magnet of the present invention, the formed mixture is heated, and a magnetic field is applied to the heated mixture to perform magnetic field alignment. Therefore, even after forming into a sheet shape, it may be appropriately The magnetic field alignment of the mixture increases the magnetic properties of the permanent magnet.

Further, according to the method for producing a rare earth permanent magnet of the present invention, in the step of forming the mixture into a long sheet shape and performing magnetic field alignment, the in-plane direction and the length direction and the in-plane direction of the long sheet are Since the magnetic field is applied by applying a magnetic field in the width direction or the vertical direction of the sheet surface, the magnetic field alignment can be appropriately performed, and the magnetic characteristics of the permanent magnet can be improved. Further, when the direction in which the magnetic field is applied is the in-plane direction of the long sheet, the longitudinal direction, or the in-plane direction and the width direction, the surface of the sheet is not fluffed when a magnetic field is applied. On the other hand, when the direction in which the magnetic field is applied is set to be perpendicular to the sheet surface, an anisotropic magnet having a film having a C-axis (easy magnetization axis) as a thickness direction can be obtained.

1‧‧‧ permanent magnet

10‧‧‧ coarsely crushed magnet powder

11‧‧‧jet mill

12‧‧‧Complex

13‧‧‧Support substrate

14‧‧‧Life

15‧‧‧Mold

16‧‧‧ Block

17‧‧‧ Block

18‧‧‧ slit

19‧‧‧ cavity

20‧‧‧ supply port

21‧‧‧Spray outlet

22‧‧‧Application roller

25‧‧‧ Solenoid

26‧‧‧heating plate

27‧‧‧ arrow

30‧‧‧Magnetic field application device

31‧‧‧ coil department

32‧‧‧ coil part

33‧‧‧Magnetic pole pieces

34‧‧‧Magnetic pole pieces

35‧‧‧film

37‧‧‧ heating device

38‧‧‧Table components

39‧‧‧ hollow

40‧‧‧Formed body

41‧‧‧Sintering mould

42‧‧‧vacuum chamber

43‧‧‧Upper punch

44‧‧‧lower punch

45‧‧‧Upper punch electrode

46‧‧‧ Lower punch electrode

D‧‧‧ gap

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general view showing a permanent magnet of the present invention.

Fig. 2 is an explanatory view showing a manufacturing step of the permanent magnet of the present invention.

Fig. 3 is an explanatory view showing a step of forming a green sheet, particularly a green sheet, in the manufacturing process of the permanent magnet of the present invention.

Fig. 4 is an explanatory view showing a heating step and a magnetic field alignment step of a green sheet in the manufacturing process of the permanent magnet of the present invention.

Fig. 5 is a view showing an example in which a magnetic field is aligned in the vertical direction in the plane of the green sheet.

Fig. 6 is a view for explaining a heating device using a heat medium (polyoxygenated oil).

Fig. 7 is a view for explaining a heating state of a permanent magnet in the manufacturing process of the present invention, in particular, a calcination step.

Fig. 8 is an explanatory view showing a step of pressurizing and sintering of a green sheet in the manufacturing process of the permanent magnet of the present invention.

Fig. 9 is a view showing various measurement results of the respective magnets of the examples and the comparative examples.

Hereinafter, the method for producing the rare earth permanent magnet and the rare earth permanent magnet of the present invention will be described in detail with reference to the following embodiment.

[Composition of permanent magnets]

First, the configuration of the permanent magnet 1 of the present invention will be described. Figure 1 is a general view showing a permanent magnet 1 of the present invention. Further, the permanent magnet 1 shown in Fig. 1 has a fan shape, and the shape of the permanent magnet 1 changes depending on the punched shape.

The permanent magnet 1 of the present invention is an anisotropic magnet of the Nd-Fe-B system. Further, the content of each component is Nd: 27 to 40% by weight, B: 0.8 to 2% by weight, and Fe (electrolytic iron): 60 to 70% by weight. Further, in order to improve the magnetic properties, a small amount of Dy, Tb, Co, Cu, Al, Si, Ga, Nb, V, Pr, Mo, Zr, Ta, Ti, W, Ag, Bi, Zn, Mg, etc. may be contained. element. Fig. 1 is a view showing the entire permanent magnet 1 of the present embodiment.

Here, the permanent magnet 1 is a film-shaped permanent magnet having a thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm). The permanent magnet 1 is produced by sintering a molded body (green body) obtained by molding a mixture of a mixture of a magnet powder and a binder as described below. Further, the green body is mixed with a mixture of a magnet powder and a binder as described below (pulp) The material or composite) is formed into a specific shape (for example, a sheet shape, a block shape, a final product shape, etc.). Further, the mixture may be temporarily molded into a shape other than the shape of the final product, and then subjected to punching, cutting, deformation processing, or the like, thereby forming a shape of the final product. Further, in particular, when the mixture is formed into a sheet shape and then processed into a final product shape, productivity can be improved by production in a continuous step, and the precision of molding can be improved. When the mixture is formed into a sheet shape, a film member having a film thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm) is formed. Further, even in the case of forming a sheet shape, a large permanent magnet 1 can be produced by laminating a plurality of sheets.

Further, in the present invention, particularly in the case of producing the permanent magnet 1, the binder mixed in the magnet powder may be a resin, a long-chain hydrocarbon, a fatty acid ester or a mixture thereof.

Further, in the case where a resin is used as the binder, it is preferred to use a polymer having no oxygen atom and having depolymerization property in the structure. Further, as described below, the magnetic field alignment is performed in order to re-use the residue of the mixture produced by molding the mixture of the magnet powder and the binder into the final product shape, and in order to soften the formed mixture by heating it. And use a thermoplastic resin. Specifically, a polymer containing one or two or more polymers or copolymers selected from the monomers represented by the following formula (1) is suitable.

(wherein R ₁ and R ₂ represent a hydrogen atom, a lower alkyl group, a phenyl group or a vinyl group)

As the polymer satisfying the above conditions, for example, polyisobutylene (PIB) which is a polymer of isobutylene, polyisoprene which is a polymer of isoprene (isoprene rubber) Glue, IR), polybutadiene (butadiene rubber, BR) as a polymer of 1,3-butadiene, polystyrene as a polymer of styrene, as styrene and isoprene Styrene-isoprene block copolymer (SIS) of copolymer, butyl rubber (IIR) as copolymer of isobutylene and isoprene, styrene as copolymer of styrene and butadiene Butadiene block copolymer (SBS), 2-methyl-1-pentene polymer resin as a polymer of 2-methyl-1-pentene, polymer as 2-methyl-1-butene 2-methyl-1-butene polymer resin, α-methylstyrene polymer resin as a polymer of α-methylstyrene, and the like. Further, in order to impart flexibility to the α-methylstyrene polymer resin, it is preferred to add a low molecular weight polyisobutylene. Further, the resin used as the binder may be a polymer or a copolymer (for example, polybutyl methacrylate or polymethyl methacrylate) containing a small amount of a monomer containing an oxygen atom. Further, a monomer which does not belong to the above formula (1) may be partially copolymerized. Even in this case, the object of the invention can be achieved.

Further, as the resin used in the binder, in order to appropriately perform the magnetic field alignment, it is preferably a thermoplastic resin which is softened at 250 ° C or lower, more specifically, a glass transition point or a thermoplastic resin having a melting point of 250 ° C or lower.

On the other hand, in the case where a long-chain hydrocarbon is used as the binder, it is preferred to use a long-chain saturated hydrocarbon (long-chain alkane) which is solid at room temperature and liquid at room temperature or higher. Specifically, it is preferred to use a long-chain saturated hydrocarbon having a carbon number of 18 or more. Further, when the mixture of the magnet powder and the binder is subjected to magnetic field alignment as described below, the mixture is heated in a state where the mixture is heated at a temperature higher than the melting point of the long-chain hydrocarbon to soften the magnetic field.

Further, when a fatty acid ester is used as the binder, it is also preferred to use methyl stearate or methyl behenate which is solid at room temperature and liquid at room temperature or higher. Further, when the mixture of the magnet powder and the binder is subjected to magnetic field alignment as described below, the magnetic field alignment is performed in a state where the mixture is heated and softened at a temperature equal to or higher than the melting point of the fatty acid ester.

By using a binder satisfying the above conditions as a binder mixed in the magnet powder The agent can reduce the amount of carbon and oxygen contained in the magnet. Specifically, the amount of carbon remaining in the magnet after sintering is 2,000 ppm or less, more preferably 1,000 ppm or less. Moreover, the amount of oxygen remaining in the magnet after sintering is 5,000 ppm or less, more preferably 2,000 ppm or less.

Further, in order to increase the thickness precision of the molded body when molding the slurry or the composite which is heated and melted, the amount of the binder added is an amount which appropriately fills the space between the magnet particles. For example, the ratio of the binder to the total amount of the magnet powder and the binder is from 1 wt% to 40 wt%, more preferably from 2 wt% to 30 wt%, still more preferably from 3 wt% to 20 wt%.

[Method of manufacturing permanent magnet]

Next, a method of manufacturing the permanent magnet 1 of the present invention will be described with reference to Fig. 2 . Fig. 2 is an explanatory view showing a manufacturing procedure of the permanent magnet 1 of the embodiment.

First, an ingot containing a specific fraction of Nd-Fe-B (for example, Nd: 32.7 wt%, Fe (electrolytic iron): 65.96 wt%, B: 1.34 wt%) is produced. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a masher, a crusher or the like. Alternatively, the ingot is melted, and a sheet is produced by strip casting, and coarsely pulverized by a hydrogen crushing method. Thereby, the coarsely pulverized magnet powder 10 is obtained.

Then, the coarsely pulverized magnet powder 10 is finely pulverized by a wet method using a bead mill 11 or a dry method using a jet mill. For example, in the fine pulverization using the wet method using the bead mill 11, the coarsely pulverized magnet powder 10 is finely pulverized into a specific range of particle diameter (for example, 0.1 μm to 5.0 μm) in a solvent, and the magnet powder is dispersed. In the solvent. Thereafter, the magnet powder contained in the solvent after the wet pulverization is dried by vacuum drying or the like to extract the dried magnet powder. Further, the type of the solvent to be pulverized is not particularly limited, and examples thereof include alcohols such as isopropyl alcohol, ethanol, and methanol, esters such as ethyl acetate, and lower hydrocarbons such as pentane and hexane, and benzene, toluene, and An aromatic group such as toluene, a ketone, a mixture of the above, and the like. Further, it is preferred to use a solvent which does not contain an oxygen atom in the solvent.

On the other hand, in the fine pulverization using a dry method using a jet mill, in (a) An environment containing an inert gas such as nitrogen, argon or helium in an oxygen content of substantially 0%, or (b) an inert gas containing nitrogen, argon or helium in an oxygen content of 0.0001 to 0.5%. The coarsely pulverized magnet powder is finely pulverized by a jet mill to form a fine powder having an average particle diameter of a specific range of particle diameters (for example, 0.7 μm to 5.0 μm). In addition, when the oxygen concentration is substantially 0%, it is not limited to the case where the oxygen concentration is completely 0%, and it means that oxygen may be contained in an amount which is extremely small in the surface of the fine powder.

Then, the magnet powder finely pulverized by the bead mill 11 or the like is formed into a desired shape. Further, the formation of the magnet powder is carried out by molding a mixture in which the magnet powder and the binder are mixed. In the following examples, the mixture is temporarily shaped into a shape other than the shape of the final product to perform magnetic field alignment, and then subjected to punching, cutting, deformation processing, or the like, thereby forming a final product shape. In particular, in the following examples, the mixture was formed into a sheet shape (hereinafter referred to as a green sheet) and then processed into a final product shape. Further, in the case of forming the mixture into a sheet shape in particular, for example, it is formed by hot-melt coating in which a composite in which a mixture of a magnet powder and a binder is heated and formed into a sheet shape is formed. Or, a slurry containing a magnet powder, a binder, and an organic solvent is applied to a substrate to form a sheet-like slurry coating or the like.

Hereinafter, the green sheet molding using hot melt coating will be specifically described.

First, a powdery mixture (composite) 12 containing a magnet powder and a binder is prepared by mixing a binder in a magnet powder finely pulverized by a bead mill 11 or the like. Here, as the binder, a resin, a long-chain hydrocarbon, a fatty acid ester, a mixture of these, or the like can be used as described above. For example, it is preferred to use a thermoplastic resin containing a polymer having no oxygen atom and having depolymerization in the case of using a resin, and, on the other hand, a solid at room temperature in the case of using a long-chain hydrocarbon. And a long-chain saturated hydrocarbon (long-chain alkane) which is liquid above room temperature. Further, in the case of using a fatty acid ester, methyl stearate or methyl behenate or the like is preferably used. Further, the amount of the binder added is such that the ratio of the binder in the composite 12 added as described above to the total amount of the magnet powder and the binder becomes 1 wt% to 40. The amount of wt%, more preferably 2% by weight to 30% by weight, still more preferably 3% by weight to 20% by weight.

Further, in order to increase the degree of alignment in the subsequent magnetic field alignment step, an additive for promoting alignment may be added to the composite 12. As the additive for promoting the alignment, for example, a hydrocarbon-based additive can be used, and it is particularly preferable to use an additive having a polarity (specifically, an acid dissociation constant pKa of less than 41). Further, the amount of the additive to be added depends on the particle diameter of the magnet powder, and the smaller the particle diameter of the magnet powder, the more the amount of addition is required. The specific addition amount is 0.1 parts to 10 parts, more preferably 1 part to 8 parts, per part of the magnet powder. Further, the additive added to the magnet powder adheres to the surface of the magnet particles, and has an effect of assisting the rotation of the magnet particles in the magnetic field alignment treatment described below. As a result, the alignment is easily performed when a magnetic field is applied, and the direction of the easy magnetization axis of the magnet particles can be made to coincide with the same direction (that is, the alignment degree is improved). In particular, when a binder is added to the magnet powder, a binder is present on the surface of the particles, so that the frictional force at the time of alignment is improved, and the alignment property of the particles is lowered, so that the effect of adding an additive becomes more remarkable.

Further, the addition of the binder is carried out in an environment containing an inert gas such as nitrogen, argon or helium. Further, the mixing of the magnet powder and the binder is carried out, for example, by introducing the magnet powder and the binder into a mixer and stirring them with a stirrer. Further, in order to promote kneading, heating and stirring may be performed. Further, the mixing of the magnet powder and the binder is preferably carried out in an atmosphere containing an inert gas such as nitrogen, argon or helium. Further, in particular, when the magnet powder is pulverized by the wet method, the magnet powder may not be extracted from the solvent used for pulverization, and a binder may be added to the solvent and kneaded, and then the solvent may be volatilized. The following composite 12 was obtained.

Then, a green sheet is produced by forming the composite 12 into a sheet shape. In particular, in the hot melt coating, the composite 12 is melted and heated by heating the composite 12, and then applied to a support substrate 13 such as a separator. Thereafter, it is solidified by heat dissipation to form a long sheet-like green sheet 14 on the support substrate 13. Further, the temperature at which the composite 12 is heated and melted varies depending on the type or amount of the binder to be used, and is set to 50 to 300. °C. Among them, it must be set to a temperature higher than the melting point of the binder used. Further, in the case of using a slurry coating, the magnet powder and the binder (which may further contain an additive for promoting alignment) are dispersed in a large amount of an organic solvent, and the slurry is applied onto a support substrate 13 such as a separator. . Thereafter, the organic solvent is volatilized by drying to form a long sheet-like green sheet 14 on the support substrate 13.

Here, the coating method of the molten composite 12 is preferably a method in which the layer thickness controllability such as a slit die method or a calender roll method is excellent. In particular, in order to achieve a high thickness precision, it is preferable to use a mold method or a notch wheel coating which is excellent in layer thickness control property (i.e., a layer which can apply a high-precision thickness layer on the surface of a substrate). the way. For example, in the slit die method, the composite 12 which is heated by the gear pump is extruded and inserted into a mold to perform coating. Further, in the calender roll method, a certain amount of the composite 12 is added to the gap between the two heated rolls, and the composite 12 which is thermally melted by the rolls is applied to the support substrate 13 while rotating the rolls. Further, as the support substrate 13, for example, a polyester film treated with polyfluorene oxide is used. Further, it is preferable to sufficiently perform the defoaming treatment so that air bubbles do not remain in the developed layer by using an antifoaming agent or heating vacuum defoaming. Further, it is also possible to adopt a configuration in which the melted composite 12 is formed into a sheet shape by extrusion molding or injection molding, and is extruded onto the support substrate 13 without being applied to the support substrate 13. The green sheet 14 is formed on the support substrate 13.

Hereinafter, the steps of forming the green sheet 14 by the slit mold method will be described in more detail with reference to Fig. 3 . Fig. 3 is a schematic view showing a step of forming a green sheet 14 by a slit mold method.

As shown in FIG. 3, the mold 15 used in the slit mold method is formed by overlapping the blocks 16 and 17, and the slit 18 and the cavity are formed by the gap between the blocks 16 and 17. (liquid storage unit) 19. The cavity 19 communicates with the supply port 20 provided in the block 17. Further, the supply port 20 is connected to a supply system of a coating liquid composed of a gear pump (not shown) or the like, and supplies the measured fluid-like composite 12 to the cavity 19 via the supply port 20 by a metering pump or the like. Enter On the other hand, the fluid-like composite 12 supplied to the cavity 19 is supplied with liquid to the slit 18, and is supplied at a constant amount per unit time and uniformly in the width direction, and is ejected from the slit 21 of the slit 18 in accordance with a predetermined coating width. ejection. On the other hand, the support base material 13 is continuously conveyed at a predetermined speed as the coating roller 22 rotates. As a result, the discharged fluid-like composite 12 is applied to the support substrate 13 with a specific thickness, and then heat-dissipated and solidified, whereby the long sheet-like green sheet 14 is formed on the support substrate 13.

Further, in the step of forming the green sheet 14 by the slit mold method, it is preferable to actually measure the thickness of the sheet of the green sheet 14 after the application, and the gap between the mold 15 and the support substrate 13 based on the measured value. D performs feedback control. Moreover, it is preferable that the fluctuation of the amount of the fluid-like composite 12 supplied to the mold 15 is as small as possible (for example, the variation is suppressed to ±0.1% or less), and the fluctuation of the coating speed is also reduced as much as possible ( For example, the suppression is ±0.1% or less). Thereby, the thickness precision of the green sheet 14 can be further improved. Further, the thickness accuracy of the formed green sheet 14 is set to within ±10%, more preferably within ±3%, and even more preferably within ±1% with respect to the design value (for example, 1 mm). Further, on the other hand, in the calender roll method, by controlling the calendering conditions based on the measured values in the same manner, the transfer film thickness of the composite 12 on the support substrate 13 can be controlled.

Further, the thickness of the green sheet 14 is preferably set to be in the range of 0.05 mm to 20 mm. When the thickness is less than 0.05 mm, it is necessary to laminate a plurality of layers, so that productivity is lowered.

Then, the magnetic field alignment of the green sheet 14 formed on the support substrate 13 by the above-described hot melt coating is performed. Specifically, first, the green sheet 14 is softened by heating the green sheet 14 continuously conveyed together with the support base material 13. Specifically, the viscosity is softened until the green sheet 14 has a viscosity of 1 to 1500 Pa. s, more preferably 1~500Pa. s so far. Thereby, the magnetic field alignment can be appropriately performed.

Further, the temperature and time when the green sheet 14 is heated vary depending on the type or amount of the binder to be used, and is, for example, 100 to 250 ° C for 0.1 to 60 minutes. Among them, in order to make The green sheet 14 is softened and must be set to a temperature above the glass transition point or melting point of the binder used. Further, as a heating method for heating the green sheet 14, there is, for example, a heating method using a hot plate or a heating method using a heat medium (polyoxygenated oil) as a heat source. Then, a magnetic field is applied to the in-plane direction and the longitudinal direction of the green sheet 14 which is softened by heating, thereby performing magnetic field alignment. The intensity of the applied magnetic field is set to 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe]. As a result, the C-axis (easy magnetization axis) of the magnet crystal contained in the green sheet 14 is aligned in one direction. Further, as a direction in which the magnetic field is applied, a magnetic field may be applied to the in-plane direction and the width direction of the green sheet 14. Further, it is also possible to adopt a configuration in which a plurality of green sheets 14 are simultaneously aligned with a magnetic field.

Further, when a magnetic field is applied to the green sheet 14, a step of applying a magnetic field simultaneously with the heating step may be employed, and a step of applying a magnetic field may be performed after the heating step and before the green sheet is solidified. Further, it is also possible to adopt a configuration in which the green sheet 14 coated by the hot melt coating is subjected to magnetic field alignment before solidification. In this case, no heating step is required.

Next, the heating step and the magnetic field alignment step of the green sheet 14 will be described in more detail using FIG. Fig. 4 is a schematic view showing a heating step and a magnetic field alignment step of the green sheet 14. Further, in the example shown in Fig. 4, an example in which the magnetic field alignment step is performed simultaneously with the heating step will be described.

As shown in Fig. 4, the heating and the magnetic field alignment of the green sheet 14 coated by the slit die method are performed on the long sheet-like green sheet 14 in a state of being continuously conveyed by a roller. That is, the apparatus for performing heating and magnetic field alignment is disposed on the downstream side of the coating device (such as a mold), and is carried out by a step that is continuous with the coating step.

Specifically, on the downstream side of the mold 15 or the application roller 22, the solenoid 25 is placed so that the conveyed support substrate 13 and the green sheet 14 pass through the solenoid 25. Further, the heating plate 26 is disposed in the solenoid 25 in the upper and lower sides of the green sheet 14 in pairs. Then, the green sheet 14 is heated by the heating plate 26 disposed in pairs up and down, and an electric current is supplied to the solenoid 25, thereby in the in-plane direction of the long sheet-like green sheet 14 (ie, with the green sheet) 14 sheets are parallel to the direction) And a magnetic field is generated in the longitudinal direction. Thereby, the continuous conveyance of the green sheet 14 is softened by heating, and a magnetic field is applied to the in-plane direction of the softened green sheet 14 and the longitudinal direction (the direction of the arrow 27 in Fig. 4), whereby the green sheet 14 can be appropriately aligned uniformly. The magnetic field. In particular, by setting the direction in which the magnetic field is applied to the in-plane direction, the surface of the green sheet 14 can be prevented from fluffing.

Further, the heat dissipation and solidification of the green sheet 14 after the magnetic field alignment is preferably carried out in a conveyed state. Thereby, the manufacturing steps can be further streamlined.

In the case where the magnetic field is aligned in the in-plane direction and the width direction of the green sheet 14, a pair of magnetic field coils are disposed on the right and left sides of the transported green sheet 14 instead of the arrangement of the solenoids 25. Further, by applying an electric current to each of the field coils, a magnetic field can be generated in the in-plane direction and the width direction of the long sheet-like green sheet 14.

Further, the magnetic field alignment may be set to be perpendicular to the surface of the green sheet 14. In the case where the magnetic field is aligned in the direction perpendicular to the surface of the green sheet 14, it is performed by, for example, a magnetic field applying device using a magnetic pole piece or the like. Specifically, as shown in FIG. 5 , the magnetic field applying device 30 using a magnetic pole piece or the like includes two annular coil portions 31 and 32 that are arranged in parallel so that the central axis is the same axis, and are disposed in the coil portions 31 and 32, respectively. The two substantially cylindrical pole pieces 33 and 34 of the annular hole are arranged at a predetermined interval with respect to the conveyed green sheet 14. Then, by applying a current to the coil portions 31 and 32, a magnetic field is generated in a direction perpendicular to the surface of the green sheet 14, and the magnetic field alignment of the green sheet 14 is performed. Further, when the direction of the magnetic field alignment is set to be perpendicular to the surface of the green sheet 14, it is preferable that the green sheet 14 is also on the opposite side of the laminated support substrate 13 as shown in FIG. The laminated film 35. Thereby, the raising of the surface of the green sheet 14 can be prevented.

Further, instead of the heating method using the heating plate 26, a heating method using a heat medium (polyoxygenated oil) as a heat source may be used. Here, Fig. 6 is a view showing an example of a heating device 37 using a heat medium.

As shown in Fig. 6, the heating device 37 has a configuration in which a substantially U-shaped cavity 39 is formed inside the flat member 38 which is a heating element, and is heated to a specific temperature in the cavity 39. A polyoxyxene cycle as a heat medium (for example, 100 to 300 ° C). Further, in the solenoid 25, a heating device 37 is disposed in the upper and lower rows of the green sheet 14 in place of the heating plate 26 shown in Fig. 4 . Thereby, the continuously conveyed green sheet 14 is softened by the flat member 38 which generates heat by the heat medium. Further, the flat member 38 may be in contact with the green sheet 14, or may be disposed at a predetermined interval. Further, by applying a magnetic field to the in-plane direction and the longitudinal direction (the direction of the arrow 27 in FIG. 4) of the green sheet 14 by the solenoid 25 disposed around the softened green sheet 14, the green sheet 14 can be appropriately aligned. A uniform magnetic field. Further, in the heating device 37 using the heat medium shown in Fig. 6, the heating wire is not provided inside the heating plate 26 as usual, and therefore, even in the case of being placed in a magnetic field, there is no Lorentz force ( Lorentz force) The heating of the green sheet 14 can be appropriately performed by vibrating or cutting the heating wire. Further, when the current is controlled, there is a problem that the heating wire is vibrated due to the ON or OFF of the power source, which causes fatigue fracture. However, by using the heating device 37 using the heat medium as the heat source, the problem can be eliminated. .

Here, in the case where the green sheet 14 is formed by a liquid material having a high fluidity such as a slurry by a conventional slit die method or a doctor blade method without using hot melt molding, if a magnetic field is generated When the green sheet 14 is moved in the gradient, the magnet powder contained in the green sheet 14 is pulled to the side where the magnetic field is strong, and the liquid phase of the slurry forming the green sheet 14, that is, the thickness deviation of the green sheet 14 is generated. On the other hand, when the composite 12 is formed into the green sheet 14 by hot melt forming as in the present invention, the viscosity at room temperature reaches tens of thousands to hundreds of thousands of Pa. s, the concentration of magnetic powder when the magnetic field gradient passes does not occur. Further, by carrying out the transportation and heating in a uniform magnetic field, the viscosity of the adhesive can be lowered, and the same C-axis alignment can be performed only with the torque in the uniform magnetic field.

In addition, when the green sheet 14 is formed by a liquid material having a high fluidity such as a slurry containing an organic solvent, a conventional slit type die method or a doctor blade method is used without using a hot melt molding. When a sheet having a thickness of more than 1 mm is produced, foaming due to vaporization of an organic solvent contained in a slurry or the like during drying becomes a problem. Furthermore, if it is to suppress foaming Increasing the drying time causes precipitation of the magnet powder, which in turn causes a deviation in the density distribution of the magnet powder from the direction of gravity, which causes the warpage after firing. Therefore, in the molding of the slurry, in order to substantially regulate the upper limit of the thickness, it is necessary to form the green sheet to a thickness of 1 mm or less, and then laminate the green sheet. However, in this case, the binders are insufficiently fused to each other, and interlayer peeling occurs in the subsequent debonding step (calcining treatment), which becomes a decrease in the alignment of the C-axis (easy magnetization axis), that is, residual magnetic flux. The reason for the decrease in density (Br). On the other hand, when the composite 12 is formed into the green sheet 14 by hot melt forming as in the present invention, since the organic solvent is not contained, even when a sheet having a thickness of more than 1 mm is produced, it can be eliminated. The fear of foaming as described above. Further, since the binder is in a state of being sufficiently fused, there is no possibility that interlayer peeling occurs in the debonding step.

Further, when a magnetic field is applied to the plurality of green sheets 14 at the same time, for example, continuous deposition is carried out in a state in which a plurality of sheets (for example, 6 sheets) of the green sheets 14 are laminated so that the green sheets 14 of the layers are placed on the solenoid 25 It is formed by means of internal passage. Thereby, productivity can be improved.

Thereafter, the green sheet 14 subjected to the magnetic field alignment is punched into a desired product shape (for example, a fan shape as shown in Fig. 1), and the formed body 40 is molded.

Then, by forming the formed body 40 at atmospheric pressure, or by pressure to a pressure higher than atmospheric pressure or a pressure lower than atmospheric pressure (for example, 1.0 Pa or 1.0 MPa) (especially in the present invention, a hydrogen atmosphere) Or in a mixed gas atmosphere of hydrogen and an inert gas, at a temperature at which the binder decomposes (in the case of adding an additive for promoting the alignment, a temperature which satisfies the conditions above the thermal decomposition temperature of the additive) for several hours to several tens The calcination treatment is carried out for an hour (for example, 5 hours). In the case of performing in a hydrogen atmosphere, for example, the supply amount of hydrogen in calcination is set to 5 L/min. By performing the calcination treatment, an organic compound such as a binder can be decomposed into monomers by a depolymerization reaction or the like and scattered and removed. That is, so-called decarburization which reduces the amount of carbon in the molded body 40 is performed. In addition, the calcination treatment is carried out under the conditions that the amount of carbon in the molded body 40 is 2,000 ppm or less, more preferably 1,000 ppm or less. Thereby, the entire permanent magnet 1 can be densely sintered by the subsequent sintering treatment without causing residual magnetic flux. Density or coercive force is reduced. In the case where the pressurization condition at the time of the calcination treatment is carried out at a pressure higher than atmospheric pressure, it is preferably 15 MPa or less. Further, when the pressurization condition is set to a pressure higher than atmospheric pressure, more specifically 0.2 MPa, the effect of reducing the amount of carbon can be expected in particular.

Further, the binder decomposition temperature is determined based on the analysis results of the binder decomposition product and the decomposition residue. Specifically, a temperature range is selected in which the decomposition product of the binder is collected, no decomposition products other than the monomer are produced, and no side reaction due to the residual binder component is detected in the residue analysis. product. The decomposition temperature of the binder varies depending on the type of the binder, and is set to 200 ° C to 900 ° C, more preferably 400 ° C to 600 ° C (for example, 450 ° C).

Further, it is preferable that the calcination treatment slows down the temperature increase rate as compared with the case of sintering a normal magnet. Specifically, the temperature increase rate is set to 2 ° C / min or less (for example, 1.5 ° C / min). Therefore, in the case of performing the calcination treatment, as shown in FIG. 7, the temperature is raised at a specific temperature increase rate of 2 ° C/min or less, and after reaching a preset set temperature (adhesive decomposition temperature), the temperature is maintained at the set temperature. The calcination treatment is carried out for several hours to several tens of hours. The calcining treatment as described above removes the carbon in the formed body 40 stepwise rather than sharply by slowing down the rate of temperature rise, so that the density of the permanent magnet after sintering can be increased (i.e., reduced in the permanent magnet) Void). In addition, when the temperature increase rate is 2° C./min or less, the density of the permanent magnet after sintering can be made 95% or more, and high magnet characteristics can be expected.

Further, the molded body 40 obtained by calcining by calcination may be further subjected to a dehydrogenation treatment while maintaining the vacuum atmosphere. In the dehydrogenation treatment, NdH ₃ (large activity) in the molded body 40 produced by the calcination treatment is changed stepwise from NdH ₃ (large activity) to NdH ₂ (small activity). The activity of the molded body 40 activated by the calcination treatment is lowered. Thereby, even when the molded body 40 calcined by the calcination treatment is moved to the atmosphere, Nd can be prevented from being combined with oxygen, and the residual magnetic flux density or coercive force is not lowered. Further, an effect of restoring the structure of the magnet crystal from NdH ₂ or the like to the Nd ₂ Fe ₁₄ B structure can be expected.

Then, a sintering treatment for sintering the formed body 40 which has been calcined by calcination is performed. In addition, as the sintering method of the molded body 40, in addition to the usual vacuum sintering, pressure sintering or the like for sintering the molded body 40 in a pressurized state may be used. For example, when sintering is performed by vacuum sintering, the temperature is raised to a firing temperature of about 800 ° C to 1080 ° C at a specific temperature increase rate for about 0.1 to 2 hours. In this period, vacuum firing is performed, and as the degree of vacuum, it is preferably 5 Pa or less, preferably 10 ^-2 Pa or less. Thereafter, the mixture was cooled, and heat treatment was again performed at 300 ° C to 1000 ° C for 2 hours. Then, sintering is performed, and as a result, permanent magnet 1 is produced.

On the other hand, as the pressure sintering, there are, for example, hot press sintering, hot press pressure (HIP) sintering, ultrahigh pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering. In order to suppress the grain growth of the magnet particles during sintering and to suppress the warpage caused by the magnet after sintering, it is preferably used for uniaxial pressure sintering in a uniaxial direction and by electric conduction sintering. Sintered SPS is sintered. Further, in the case of sintering by SPS sintering, it is preferred to set the pressurization value to, for example, 0.01 MPa to 100 MPa, and to increase the temperature to 10 ° C/min to 940 ° C in a vacuum atmosphere of several Pa or less, and thereafter to maintain 5 minute. Thereafter, the mixture was cooled, and heat treatment was again performed at 300 ° C to 1000 ° C for 2 hours. Then, sintering is performed, and as a result, permanent magnet 1 is produced.

Hereinafter, the pressure sintering step of the molded body 40 by SPS sintering will be described in more detail with reference to Fig. 8 . Fig. 8 is a schematic view showing a pressure sintering step of the formed body 40 by SPS sintering.

When SPS sintering is performed as shown in FIG. 8, first, the molded body 40 is provided in the graphite sintered mold 41. Further, the calcination treatment may be performed in a state where the molded body 40 is placed on the sintering mold 41. Then, the formed body 40 provided in the sintering mold 41 is held in the vacuum chamber 42, and the upper punch 43 and the lower punch 44, which are also made of graphite, are provided. Then, using a punch electrode 45 connected to the upper portion of the upper punch 43 and a punch electrode 46 connected to the lower portion of the lower punch 44, a low-voltage and high-current DC pulse voltage/electricity is applied. flow. At the same time, a load is applied to the upper punch 43 and the lower punch 44 from the vertical direction by a pressurizing mechanism (not shown). As a result, the molded body 40 provided in the sintering mold 41 is pressed while being pressed. Further, in order to improve productivity, it is preferred to simultaneously perform SPS sintering on a plurality of (for example, ten) shaped bodies. Further, when a plurality of molded bodies 40 are simultaneously subjected to SPS sintering, a plurality of molded bodies 40 may be disposed in one space, or each molded body 40 may be disposed in a different space. Further, when each molded body 40 is disposed in a different space, the molded body 40 is pressurized in each space, and the upper punch 43 or the lower punch 44 is integrated into each space. (That is, the upper punch 43 and the lower punch 44 which are integrally driven are configured to simultaneously press a plurality of molded bodies in each space).

[Examples]

Hereinafter, an embodiment of the present invention will be described in comparison with a comparative example.

(Example 1)

Example 1 was a Nd-Fe-B based magnet, and the alloy composition was set to Nd/Fe/B = 32.7 / 65.96 / 1.34 in wt%. Further, a composite is produced by adding a binder to the magnet powder. As the binder, polyisobutylene (PIB) is used. Further, an additive for promoting the alignment is also added to the composite. Further, the amounts of the binder and the additive added to the magnet powder were respectively set to 4 parts. Further, the heat-melted composite was applied to a substrate by a slit die method to form a green sheet having a thickness of 8 mm. Further, the formed green sheets were heated by a hot plate heated to 200 ° C for 5 minutes, and magnetic field alignment was performed by applying a magnetic field of 12 T to the green sheets in the in-plane direction and the longitudinal direction. Then, after the magnetic field is aligned, the green sheets which have been punched into a desired shape are subjected to calcination in a hydrogen atmosphere, and thereafter, sintered by vacuum sintering. The conditions of the calcination treatment were such that the temperature increase rate was 1.5 ° C/min and the temperature was maintained at 450 ° C for 5 hours at 450 ° C. In addition, the other steps are the same as the above [manufacturing method of permanent magnet].

(Comparative Example 1)

The conditions of the calcination treatment were set to a temperature increase rate of 15 ° C / min and maintained at 450 ° C for 5 hours. Other conditions are the same as in the first embodiment.

(Comparative Example 2)

The additive for promoting the alignment is not added to the magnet powder, and the composite is produced by adding only the binder. As the binder, polyisobutylene (PIB) was used, and the amount of the binder added to the magnet powder was set to 8 parts. Other conditions were the same as in Comparative Example 1.

(Comparative Example vs. Comparative Example)

The density [%] and the degree of alignment [%] of each of the sintered magnets of Example 1 and Comparative Examples 1 and 2 were measured. Further, the residual magnetic flux density [kG] and the coercive force [kOe] were measured for each of the magnets of Example 1 and Comparative Examples 1 and 2. In addition, the measurement of the degree of alignment is performed by using a DC self-recording magnetic fluxmeter ("TRF-5BH-25auto" manufactured by Dongying Industrial Co., Ltd., the maximum applied magnetic field of 25 kOe) for Br (residual magnetic flux density) and Jmax ( The maximum magnetization was measured and calculated by calculating Br/Jmax. A list of measurement results is shown in FIG.

When the permanent magnet of Example 1 was compared with the density of the permanent magnet of Comparative Example 1, the density of the permanent magnet of Example 1 was higher than that of the permanent magnet of Comparative Example 1, and the density was 99%. On the other hand, the permanent magnet of Comparative Example 1 had a density of 90%, and it was predicted that a large number of voids were formed in the magnet. Further, in the permanent magnet of Comparative Example 1, since the temperature increase rate of the calcination treatment was set to 15 ° C/min, the temperature increase rate was fast, so that the carbon in the molded body was rapidly removed during the calcination treatment. A void is created in the permanent magnet. On the other hand, in the permanent magnet of the first embodiment, since the temperature increase rate is low, the carbon in the molded body is removed stepwise, and the void in the permanent magnet can be reduced as compared with the comparative example 1. Further, as shown in Fig. 9, the density of the permanent magnet has a large influence on the characteristics of the magnet, and the permanent magnet of the first embodiment having a high density shows a high value in terms of residual magnetic flux density or coercive force. In addition, when the density is 95% or more, sufficient magnetic properties can be exhibited, and when the temperature increase rate of the calcination treatment is 2° C./min or less, a permanent magnet having a density of 95% or more can be obtained.

Further, when the permanent magnet of the first embodiment or the comparative example 1 and the permanent magnet of the comparative example 2 are compared, it is understood that the permanent magnet of the first embodiment or the comparative example 1 has a higher degree of alignment than the permanent magnet of the comparative example 2. That is, more magnet particles are aligned in one direction (in-plane direction and length direction of the green sheet in the direction in which the magnetic field is applied). The reason for predicting the result is that the permanent magnet of the first embodiment or the comparative example 1 functions to assist the rotation of the magnet particles by attaching the additive of the assisted alignment added to the magnet powder to the surface of the magnet particles. Make the alignment of the magnet easy. On the other hand, in the permanent magnet of Comparative Example 2 in which the additive for promoting the alignment was not added, since the effect of the additive for the above-mentioned assisted alignment could not be obtained, the magnet particles which could not be completely aligned could be increased even if a magnetic field was applied. Here, basically, the higher the degree of alignment of the anisotropic magnet, the higher the magnet characteristics. Therefore, as shown in FIG. 9, the permanent magnet of Example 1 or Comparative Example 1 also shows a higher value in terms of residual magnetic flux density or coercive force.

As described above, in the method of manufacturing the permanent magnet 1 and the permanent magnet 1 of the present embodiment, the magnet raw material is pulverized into a magnet powder, and the pulverized magnet powder is mixed with a binder to produce the composite 12. Then, the resulting composite 12 is formed into a sheet shape on the support substrate 13 by hot melt forming to produce a green sheet 14. Thereafter, the formed green sheet 14 is heated to be softened, and a magnetic field is applied to the heated green sheet 14, thereby performing magnetic field alignment, and further, by sintering the green sheet 14 after the magnetic field is aligned, permanent production is performed. Magnet 1. As a result, the shrinkage due to sintering becomes uniform without deformation such as warpage or dent after sintering, and the pressure is not uniform at the time of pressurization, so that the correction processing after the previous sintering is not required, and the manufacturing can be simplified. step. Thereby, the permanent magnet can be formed with higher dimensional accuracy. Moreover, even when the permanent magnet is thinned, the material yield can be prevented from decreasing and the number of processing steps can be prevented from increasing. Further, since the formed green sheet 14 is heated and a magnetic field is applied to the heated green sheet 14 to perform magnetic field alignment, even after the formation, the green sheet 14 can be appropriately aligned with the magnetic field to improve the permanent magnet. Magnetic properties. Further, there is no occurrence of liquid phase in the alignment of the magnetic field, that is, the thickness deviation of the green sheet 14. Further, by The transfer and heating in a uniform magnetic field can lower the viscosity of the adhesive, and the same C-axis alignment can be performed only with the torque in a uniform magnetic field. Further, even when the green sheet 14 having a thickness of more than 1 mm is produced, it does not foam and the binder is sufficiently fused, so that no delamination occurs in the debonding step (calcining treatment). .

In the case where the green sheet is subjected to calcination treatment for decarburization, by setting the density of the rare earth permanent magnet to 95% or more, voids are not formed inside the magnet, and the magnet characteristics are largely prevented from being lowered by the voids.

Further, by heating the green sheet 14 to a set temperature at a specific temperature increase rate in a non-oxidizing atmosphere, the binder is held at a set temperature for a predetermined period of time, and the binder is scattered and removed, so that it can be used as it is calcined. The temperature changes, and the carbon contained in the green sheet 14 is removed stepwise.

Further, by holding the green sheet 14 in a non-oxidizing atmosphere for a certain period of time at the decomposition temperature of the binder, the binder is scattered and removed, so that even in the case of adding a binder, the magnet can be reduced in advance. The amount of carbon contained. As a result, it is suppressed that αFe is precipitated in the main phase of the magnet after sintering, and the entire magnet can be densely sintered to prevent a decrease in coercive force.

Further, the green sheet 14 is heated to a set temperature at a temperature increase rate of 2 ° C/min or less in a non-oxidizing atmosphere, and then held at a set temperature for a predetermined period of time to perform a calcination treatment, so that it can be accompanied by a slow temperature. The carbon contained in the green sheet 14 is removed stepwise. Therefore, a rare earth permanent magnet having a higher density can be formed without forming a large number of voids inside the magnet.

Further, by forming a mixture of the magnet powder and the binder into a sheet-like green sheet, it is possible to more easily perform the formation of the final product shape or the control of the alignment direction. Moreover, productivity can also be improved.

Further, the green sheet 14 is in the form of a long sheet, and in the step of performing the magnetic field alignment, by the in-plane direction of the green sheet 14 and the longitudinal direction, the in-plane direction, the width direction, or the vertical direction of the sheet surface. Since the magnetic field is aligned by applying a magnetic field, the magnetic field alignment can be appropriately performed, and the magnetic properties of the permanent magnet can be improved. Further, when the direction in which the magnetic field is applied is the in-plane direction of the green sheet 14, the longitudinal direction, or the in-plane direction and the width direction, the surface of the green sheet 14 is not fluffed when a magnetic field is applied. On the other hand, when the direction in which the magnetic field is applied is set to be perpendicular to the sheet surface of the green sheet 14, an anisotropic magnet having a film having a C-axis (easy magnetization axis) as a thickness direction can be obtained.

It is a matter of course that the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

For example, the pulverization conditions, the kneading conditions, the molding conditions, the magnetic field alignment step, the calcination conditions, the sintering conditions, and the like of the magnet powder are not limited to the conditions described in the above examples. For example, in the above embodiment, the magnet raw material is pulverized by wet pulverization using a bead mill, or may be pulverized by dry pulverization using a jet mill. Moreover, if the environment in the case of calcination is a non-oxidizing environment, it may be carried out in an environment other than a hydrogen atmosphere (for example, a nitrogen atmosphere, a helium atmosphere, or the like, an argon atmosphere, or the like).

Further, in the above-described embodiment, the mixture of the magnet powder and the binder is temporarily formed into a sheet shape and then subjected to magnetic field alignment, and may be formed into a shape other than the shape of the sheet, and then magnetic field alignment may be performed. Composition. For example, it may be formed into a block shape. Further, the molded body having a block shape aligned by the magnetic field is further processed into a final product shape.

Further, in the above examples, a resin, a long-chain hydrocarbon or a fatty acid ester is used as the binder, and other materials may be used.

Further, in the above embodiment, after the magnet powder is molded, calcination is carried out in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen gas and an inert gas, and the magnet powder before molding may be calcined to be calcined. The magnet powder of the body is formed into a molded body, and then sintered to produce a permanent magnet. According to this configuration, since the powdery magnet particles are calcined, they can be expanded as compared with the case where the magnet particles after molding are calcined. The surface area of the magnet of the calcined object. That is, the amount of carbon in the calcined body can be more surely reduced. However, in order to thermally decompose the binder by the calcination treatment, it is preferred to carry out the calcination treatment after the molding.

Further, in the above embodiment, the heating step and the magnetic field alignment step of the green sheet 14 are simultaneously performed, and the magnetic field alignment step may be performed after the heating step and before the green sheet 14 is solidified. Further, when the green sheet 14 to be applied is solidified (that is, the green sheet 14 is softened even if the heating step is not performed), the heating step may be omitted.

Further, in the above embodiment, the coating step, the heating step, and the magnetic field aligning step by the slit mold method may be carried out by one successive series of steps, or may be configured not by continuous steps. Further, it may be divided into a first step before the coating step and a second step after the heating step, and each step is carried out. In this case, the green sheet 14 to be coated may be cut to a specific length, and the magnetic field may be aligned by heating and magnetic field application of the green sheet 14 in a stationary state.

Further, in the present invention, an Nd-Fe-B-based magnet is exemplified, and other magnets (for example, lanthanum-cobalt magnet, alnico magnet, ferrite magnet, or the like) may be used. Further, in the alloy composition of the magnet, in the present invention, the Nd component is made more than the metered composition, and may be a metering composition.

1‧‧‧ permanent magnet

10‧‧‧ coarsely crushed magnet powder

11‧‧‧jet mill

12‧‧‧Complex

13‧‧‧Support substrate

14‧‧‧Life

15‧‧‧Mold

25‧‧‧ Solenoid

40‧‧‧Formed body

Claims (16)

A rare earth permanent magnet, which is produced by the following steps and having a density of 95% or more: a step of pulverizing a magnet raw material into a magnet powder; and a step of mixing a mixture of the above-mentioned pulverized magnet powder and a binder; a step of performing magnetic field alignment by applying a magnetic field to the mixture; a step of calcining the mixture subjected to magnetic field alignment in a non-oxidizing atmosphere; and performing the calcination temperature by maintaining the calcined mixture The step of sintering. The rare earth permanent magnet of claim 1, wherein in the step of calcining the mixture, the mixture is maintained at the set temperature by heating the mixture to a set temperature at a specific temperature increase rate in a non-oxidizing atmosphere. For a certain period of time, the above adhesive is scattered and removed. The rare earth permanent magnet of claim 2, wherein the set temperature is a binder decomposition temperature. The rare earth permanent magnet of claim 2, wherein the temperature increase rate is 2 ° C / min or less. The rare earth permanent magnet according to any one of claims 1 to 4, wherein in the step of performing the magnetic field alignment, the mixture is formed into a sheet shape, and then the mixture of the sheets is subjected to magnetic field alignment. The rare earth permanent magnet of claim 5, wherein when the mixture is formed into a sheet shape, the mixture is heated and melted to form a sheet. The rare earth permanent magnet of claim 6, wherein the step of magnetic field alignment is performed as described above In the above, the above mixture formed into a sheet shape is heated, and a magnetic field is applied to the heated mixture to thereby perform magnetic field alignment. The rare earth permanent magnet of claim 5, wherein the mixture is formed into a long sheet shape, and in the step of performing the magnetic field alignment, by in-plane direction and length direction of the mixture formed into a long sheet shape, A magnetic field is applied in the in-plane direction and in the width direction or in the vertical direction of the sheet surface to perform magnetic field alignment. A method for producing a rare earth permanent magnet, comprising: a step of pulverizing a magnet raw material into a magnet powder; and a step of mixing a mixture of the pulverized magnet powder and a binder; and applying a magnetic field to the mixture a step of aligning a magnetic field; a step of calcining the mixture subjected to magnetic field alignment in a non-oxidizing atmosphere; and sintering by maintaining the calcined mixture at a firing temperature to produce a density of 95% or more The step of rare earth permanent magnets. The method for producing a rare earth permanent magnet according to claim 9, wherein in the step of calcining the mixture, the mixture is heated to a predetermined temperature in a non-oxidizing environment at a specific temperature increase rate, and then set in the above setting. The adhesive is dispersed and removed while maintaining a certain temperature for a certain period of time. The method for producing a rare earth permanent magnet according to claim 10, wherein the set temperature is a binder decomposition temperature. The method for producing a rare earth permanent magnet according to claim 10, wherein the temperature increase rate is 2 ° C / min or less. The method for producing a rare earth permanent magnet according to any one of claims 9 to 12, wherein in the step of performing the magnetic field alignment, the mixture is formed into a sheet shape, and then The above mixture of flakes is subjected to magnetic field alignment. The method for producing a rare earth permanent magnet according to claim 13, wherein when the mixture is formed into a sheet shape, the mixture is heated and melted to form a sheet. The method for producing a rare earth permanent magnet according to claim 14, wherein in the step of performing the magnetic field alignment, the mixture formed into a sheet shape is heated, and a magnetic field is applied to the heated mixture to perform magnetic field alignment. The method for producing a rare earth permanent magnet according to claim 13, wherein the mixture is formed into a long sheet shape, and in the step of performing the magnetic field alignment, by in-plane direction of the mixture formed into a long sheet shape and A magnetic field is applied in the longitudinal direction, the in-plane direction, the width direction, or the vertical direction of the sheet surface to perform magnetic field alignment.