JP5064930B2 - Permanent magnet and method for manufacturing permanent magnet - Google Patents

Description

  The present invention relates to a permanent magnet and a method for producing a permanent magnet, and in particular, a high magnetic specificity obtained by diffusing metal atoms of Dy and Tb in a grain boundary phase of an anisotropic ring magnet produced by hot plastic working. The present invention relates to a permanent magnet and a method for manufacturing the permanent magnet.

  In recent years, as an iron-boron-rare earth magnet, a permanent magnet having magnetic anisotropy is known by orienting crystal grains in a specific direction by performing plastic working hot ( Patent Document 1). This permanent magnet is obtained by first quenching the molten alloy to obtain amorphous or fine crystalline flakes and crushing them into a fine powder by a fine pulverization process. It is produced by hot plastic working, or by casting the molten alloy and hot plastic working the cast body.

  When a permanent magnet is manufactured as described above, a long-type anisotropic ring magnet can be produced, and magnetic identification in the circumferential direction can be made uniform (in this case, it can be magnetized with a single pole on the inner and outer peripheral surfaces). Moreover, even if ring magnets having different inner diameters are produced, it is difficult to make a difference in magnetic characteristics. Therefore, adoption in various products such as electronic devices, motors and generators for hybrid cars is also being studied.

However, when the iron-boron-rare earth magnet is produced by the hot plastic working method, if the rare earth metal content is less than 30% by weight, the residual magnetic flux density is improved among the magnetic properties, but the coercive force is reduced. There is a problem that it drops significantly. For this reason, attempts have been made to improve the magnetic flux density and coercive force by optimizing the component composition of iron-boron-rare earth magnet alloys (see Patent Document 1).
Japanese Patent Application Laid-Open No. 11-193449 (for example, see the description of claims and the description of the prior art)

  However, in the method of optimizing the composition of the iron-boron-rare earth magnet alloy, there is a limit to further improving the magnetic flux density and the coercive force. Is missing. On the other hand, if the coercive force is further increased, a product having a strong magnetic force can be obtained even if the thickness of the permanent magnet is reduced. Therefore, in order to reduce the size, weight and power consumption of this kind of permanent magnet product itself, it is desirable to develop a permanent magnet having a larger coercive force and higher magnetic characteristics than the above-mentioned conventional technology. It is.

  In view of the above, the first object of the present invention is to provide a permanent magnet having an extremely high coercive force and high magnetic properties. A second object of the present invention is to provide a method for producing a permanent magnet that can produce a permanent magnet having an extremely high coercive force and high magnetic properties at high productivity and at low cost.

  In order to solve the above-mentioned problem, the method of manufacturing a permanent magnet according to claim 1 is characterized in that an iron-boron-rare earth magnet is disposed in a processing chamber and heated, and Dy is disposed in the same or another processing chamber. The evaporation material containing at least one of Tb is heated to evaporate, and the evaporated metal atoms of Dy and Tb are attached by adjusting the supply amount to the magnet surface, and the attached metal atoms are attached to the magnet surface. A method of manufacturing a permanent magnet that diffuses into a grain boundary phase of a magnet before a thin film made of an evaporating material is formed, wherein the magnet is subjected to hot plastic working to provide magnetic anisotropy It is characterized by using.

  According to the present invention, evaporated metal atoms of Dy and Tb are supplied and attached to the magnet surface heated to a predetermined temperature. At that time, the magnet was heated to a temperature at which an optimum diffusion rate was obtained, and the supply amount of metal atoms to the magnet surface was adjusted, so that the metal atoms adhering to the surface were separated from the crystal grain boundaries of the magnet before forming the thin film. The phases are sequentially diffused (that is, the supply of metal atoms such as Dy and Tb to the magnet surface and the diffusion to the crystal grain boundary phase of the magnet are performed in a single process (vacuum vapor process)). For this reason, the surface state of the permanent magnet is substantially the same as the state before the above treatment, and the manufactured permanent magnet surface is prevented from being deteriorated (surface roughness is deteriorated). Dy and Tb are prevented from excessively diffusing in grain boundaries close to, and a separate post-process is not required, thereby achieving high productivity.

  In addition, Dy and Tb metal atoms are diffused in the grain boundary phase of the magnet and uniformly spread, so that the Dy and Tb rich phases (Dy and Tb are included in the range of 5 to 80% in the grain boundary phase. In addition, Dy and Tb diffuse only in the vicinity of the surface of the crystal grain, and Dy and Tb diffused in the grain boundary phase increase the crystal magnetic anisotropy on the surface of each crystal grain. The coercive force generation mechanism of the mold is strengthened, and as a result, the coercive force is remarkably improved, and a permanent magnet having high magnetic characteristics is obtained without decreasing the maximum energy product and the residual magnetic flux density.

  The hot plastic working is preferably hot extrusion molding, and the magnet is preferably produced in a ring shape by hot extrusion molding.

  In the above processing, if the magnet and the evaporating material are arranged apart from each other, it is possible to prevent the melted evaporating material from directly attaching to the magnet when evaporating the evaporating material.

  Also, if the specific surface area of the evaporating material disposed in the processing chamber is changed to increase or decrease the evaporation amount at a constant temperature, for example, separate components that increase or decrease the supply amount of Dy and Tb to the magnet surface are added to the processing chamber. It is possible to easily adjust the supply amount to the magnet surface without changing the configuration of the apparatus, such as by providing it on the surface.

  Prior to heating the processing chamber containing the magnet, the processing chamber is depressurized to a predetermined pressure in order to remove dirt, gas, and moisture adsorbed on the magnet surface before diffusing Dy and Tb into the grain boundary phase. It is preferable to hold it.

  In this case, in order to promote the removal of dirt, gas, and moisture adsorbed on the surface, it is preferable that the processing chamber is heated to a predetermined temperature after being reduced to a predetermined pressure.

  On the other hand, in order to remove the oxide film on the surface of the magnet before diffusing Dy and Tb into the grain boundary phase, it is preferable to clean the surface of the magnet with plasma prior to heating the processing chamber containing the magnet. .

  Furthermore, in order to solve the above-mentioned problem, the permanent magnet according to claim 8 has an iron-boron-rare earth magnet that has been subjected to hot plastic working to provide magnetic anisotropy, and this magnet is Heating and evaporating a vaporizing material containing at least one of Dy and Tb arranged in the same or another processing chamber while heating in the processing chamber, and evaporating the metal atoms of Dy and Tb on the magnet surface It is characterized in that the attached metal atom is diffused into the crystal grain boundary phase of the magnet before the thin film made of the evaporation material is formed on the magnet surface.

  As described above, the method for producing a permanent magnet according to the present invention has an effect that a permanent magnet having an extremely high coercive force and having high magnetic properties can be produced with high productivity and at low cost. Moreover, the permanent magnet of the present invention has an extremely high coercive force and high magnetic properties.

  Referring to FIGS. 1 to 3, the permanent magnet M of the present invention is an iron that has been magnetically anisotropic by orienting crystal grains in a specific direction by performing hot plastic working. A series of vaporized material V containing at least one of Dy and Tb is vaporized on the surface of the boron-rare earth magnet S to deposit metal atoms and diffused uniformly into the grain boundary phase of the magnet S. It is produced by performing the treatment (vacuum vapor treatment) simultaneously.

  As the iron-boron-rare earth magnet, for example, a Nd—Fe—B radial anisotropy ring magnet (hereinafter simply referred to as “ring magnet”) is used, and is manufactured as follows by a known method. ing. That is, Fe, B, and Nd are blended at a predetermined composition ratio to obtain an alloy raw material of an isotropic quenched Nd—Fe—B-based powder. In this case, it is preferable that the content of rare earth metal is less than 30% so that a high residual magnetic flux density is obtained. Moreover, you may add a small amount of Cu, Zr, Dy, Al, and Ga in the case of a mixing | blending. Next, the produced alloy raw material is preformed into a predetermined shape at room temperature by a known compression molding machine, and then hot pressed to obtain a high-density isotropic magnet. Subsequently, the hot anisotropic extrusion which is a hot plastic working is performed by a known extrusion molding machine, and the radially anisotropic ring magnet S is manufactured.

As shown in FIG. 2, the vacuum vapor processing apparatus 1 that performs the above processing on the ring magnet S has a predetermined pressure (for example, 1 ×) via a vacuum exhausting means 11 such as a turbo molecular pump, a cryopump, or a diffusion pump. The vacuum chamber 12 can be held at a reduced pressure up to 10 ⁻⁵ Pa). In the vacuum chamber 12, a box body 2 is installed that is composed of a rectangular parallelepiped box portion 21 whose upper surface is opened, and a detachable lid portion 22 on the upper surface of the opened box portion 21.

A flange 22a bent downward is formed on the outer peripheral edge portion of the lid portion 22 over the entire circumference. When the lid portion 22 is mounted on the upper surface of the box portion 21, the flange 22a is fitted to the outer wall of the box portion 21. Thus (in this case, a vacuum seal such as a metal seal is not provided), and the processing chamber 20 isolated from the vacuum chamber 11 is defined. Then, when the vacuum chamber 12 is depressurized to a predetermined pressure (for example, 1 × 10 ⁻⁵ Pa) through the evacuation unit 11, the processing chamber 20 has a pressure (for example, 5 × 10 ⁻⁴ ) that is approximately half orders of magnitude higher than the vacuum chamber 12. The pressure is reduced to Pa).

  The volume of the processing chamber 20 is set so that the metal atoms in the vapor atmosphere are supplied to the ring magnet S from a plurality of directions directly or repeatedly in consideration of the mean free path of the evaporation material V. Moreover, the wall thickness of the box part 21 and the cover part 22 is comprised so that it may set so that it may not thermally deform when heated by the heating means mentioned later, and it does not react with the evaporation material V.

That is, when the evaporation material V is Dy, Tb, if Al ₂ O ₃ often used in a general vacuum apparatus is used, Dy, Tb and Al ₂ O ₃ in the vapor atmosphere react to generate a reaction on the surface. As well as forming an object, there is a risk that Al atoms may enter the vapor atmosphere of Dy or Tb. For this reason, the box 2 is made of, for example, Mo, W, V, Ta, or an alloy thereof (including rare earth-added Mo alloy, Ti-added Mo alloy, etc.), CaO, Y ₂ O ₃ , or rare earth oxide. They are manufactured or formed by depositing these materials as a lining film on the surface of another heat insulating material. In addition, a placement portion 21a is formed at a predetermined height position from the bottom surface in the processing chamber 20 by arranging, for example, a plurality of Mo wires (for example, φ0.1 to 10 mm) in a grid pattern. A plurality of ring magnets S can be placed side by side on the placement portion 21a. On the other hand, the evaporation material V is an alloy containing at least one of Dy and Tb or Dy and Tb that greatly improves the magnetocrystalline anisotropy of the main phase (Nd ₂ Fe ₁₄ B). Or it arrange | positions suitably on an upper surface etc.

  The vacuum chamber 12 is provided with heating means 3. The heating means 3 is made of a material that does not react with the evaporation material V of Dy and Tb, similar to the box 2, and is, for example, made of Mo that is provided so as to surround the box 2 and has a reflective surface on the inside. It is comprised from a heat insulating material and the electric heater which is arrange | positioned inside and has a filament made from Mo. Then, the inside of the processing chamber 20 can be heated substantially uniformly by heating the box 2 with the heating means 3 under reduced pressure and indirectly heating the inside of the processing chamber 20 via the box 2.

Next, manufacture of the ring-shaped permanent magnet M using the said vacuum vapor processing apparatus 1 is demonstrated. First, the ring magnet S produced by the above method is placed on the placement portion 21 a of the box portion 21, and Dy that is the evaporation material V is placed on the bottom surface of the box portion 21 (thereby, a ring is formed in the processing chamber 20. The magnet S and the evaporation material V are arranged apart from each other). And after attaching the cover part 22 to the upper surface which the box part 21 opened, the box 2 is installed in the predetermined position enclosed by the heating means 3 in the vacuum chamber 12 (refer FIG. 2). Then, the vacuum chamber 12 is evacuated and depressurized until it reaches a predetermined pressure (for example, 1 × 10 ⁻⁴ Pa) through the vacuum evacuation unit 11 (the processing chamber 20 is evacuated to a pressure approximately half digit higher). ) When the vacuum chamber 12 reaches a predetermined pressure, the heating means 3 is operated to heat the processing chamber 20.

  When the temperature in the processing chamber 20 reaches a predetermined temperature under reduced pressure, Dy installed on the bottom surface of the processing chamber 20 is heated to substantially the same temperature as the processing chamber 20 and starts to evaporate. An atmosphere is formed. When Dy starts to evaporate, the ring magnets S and Dy are arranged apart from each other, so that the melted Dy does not directly adhere to the ring magnet S in which the surface Nd-rich phase is melted. Then, Dy atoms in the Dy vapor atmosphere are directly or repeatedly collided and supplied from a plurality of directions toward the surface of the ring magnet S heated to substantially the same temperature as Dy, and the attached Dy is attached to the ring. The permanent magnet M is obtained by diffusing into the crystal grain boundary phase of the magnet S.

  By the way, when the Dy atoms in the Dy vapor atmosphere are supplied to the surface of the ring magnet S so that the Dy layer (thin film) L1 is formed on the surface of the ring magnet S, they are deposited and deposited on the surface of the ring magnet S. When Dy is recrystallized, the surface of the permanent magnet M is remarkably deteriorated (surface roughness is deteriorated), and the Dy deposited and deposited on the surface of the ring magnet S heated to substantially the same temperature during processing is dissolved. As a result, it excessively diffuses in the grain boundary in the region R1 close to the surface of the ring magnet S, and the magnetic characteristics cannot be effectively improved or recovered.

  That is, once a Dy thin film is formed on the surface of the ring magnet S, the average composition of the ring magnet surface S adjacent to the thin film becomes a Dy rich composition. (Ie, the main phase dissolves and the amount of liquid phase increases). As a result, the vicinity of the surface of the ring magnet S melts and collapses, and the unevenness increases. In addition, Dy excessively penetrates into the crystal grains together with a large amount of liquid phase, and the maximum energy product and the residual magnetic flux density showing the magnetic characteristics are further lowered.

In the present embodiment, bulky (substantially spherical) Dy having a small surface area (specific surface area) per unit volume at a ratio of 1 to 10% by weight of the ring magnet S is disposed on the bottom surface of the processing chamber 20, and is kept at a constant temperature. The amount of evaporation underneath was reduced. In addition, when the evaporation material V is Dy, the heating means 3 is controlled so that the temperature in the processing chamber 20 is set to a range of 800 ° C. to 1050 ° C., preferably 900 ° C. to 1000 ° C. (for example, When the processing chamber temperature is 900 ° C. to 1000 ° C., the saturated vapor pressure of Dy is about 1 × 10 ⁻² to 1 × 10 ⁻¹ Pa).

  If the temperature in the processing chamber 20 (and hence the heating temperature of the ring magnet S) is lower than 800 ° C., the diffusion rate of Dy atoms adhering to the surface of the ring magnet S to the crystal grain boundary layer becomes slow, and the surface of the ring magnet S Before the thin film is formed, it cannot be diffused into the crystal grain boundary phase of the ring magnet S and distributed uniformly. On the other hand, at a temperature exceeding 1050 ° C., the vapor pressure of Dy increases, and Dy atoms in the vapor atmosphere are excessively supplied to the surface of the ring magnet S. Further, there is a possibility that Dy diffuses into the crystal grains, and when Dy diffuses into the crystal grains, the magnetization in the crystal grains is greatly reduced, so that the maximum energy product and the residual magnetic flux density are further lowered.

In order to diffuse Dy into the grain boundary phase before the Dy thin film is formed on the surface of the ring magnet S, the processing chamber 20 has a total surface area of the ring magnet S installed on the mounting portion 21a of the processing chamber 20. The ratio of the total surface area of bulk Dy installed on the bottom is set to be in the range of 1 × 10 ⁻⁴ to 2 × 10 ³ . If the ratio is outside the range of 1 × 10 ^{−4 to} 2 × 10 ³ , a thin film of Dy or Tb may be formed on the surface of the ring magnet S, and a permanent magnet with high magnetic properties cannot be obtained. In this case, the ratio is preferably in the range of 1 × 10 ⁻³ to 1 × 10 ³ , and the ratio is more preferably in the range of 1 × 10 ⁻² to 1 × 10 ² .

  Thus, the vapor pressure is lowered and the amount of Dy evaporated is reduced, so that the amount of Dy atoms supplied to the ring magnet S is suppressed, and the diffusion rate is increased by heating the ring magnet S in a predetermined temperature range. Coupled with the fact that the Dy atoms adhering to the surface of the ring magnet S are efficiently diffused into the grain boundary phase before being deposited on the surface of the ring magnet S and forming a Dy layer (thin film). Can be distributed evenly (see FIG. 3). As a result, it is possible to prevent the surface of the permanent magnet M from being deteriorated, to suppress excessive diffusion of Dy into the grain boundary in the region close to the surface of the ring magnet S, and to form a Dy rich phase (Dy) in the grain boundary phase. In addition, Dy diffuses only in the vicinity of the surface of the crystal grains, so that the magnetization and coercive force are effectively improved, and no finishing process is required. A permanent magnet M excellent in productivity can be obtained.

  Finally, after performing the above process for a predetermined time (for example, 1 to 72 hours), the operation of the heating unit 3 is stopped, and Ar gas of 10 kPa is introduced into the processing chamber 20 through a gas introduction unit (not shown). Then, the evaporation of the evaporation material V is stopped, and the temperature in the processing chamber 20 is once lowered to, for example, 500 ° C. Subsequently, the heating means 3 is operated again, the temperature in the processing chamber 20 is set in a range of 450 ° C. to 650 ° C., and heat treatment for removing the distortion of the permanent magnet is performed in order to further improve or recover the coercive force. Finally, it is rapidly cooled to about room temperature and the box 2 is taken out.

  In the present embodiment, the example in which Dy is used as the evaporation material V has been described as an example. However, the vapor pressure is low in the heating temperature range (range of 900 ° C. to 1000 ° C.) of the ring magnet S that can increase the diffusion rate. Tb can be used, or an alloy of Dy and Tb may be used. Further, in order to reduce the amount of evaporation at a constant temperature, the bulk evaporating material V having a small specific surface area is used. However, the present invention is not limited to this. And the specific surface area may be reduced by storing the granular or bulk evaporation material V in the saucer. Further, after the evaporation material V is accommodated in the saucer, a plurality of openings are provided. A lid (not shown) may be attached.

  In the present embodiment, the ring magnet S and the evaporation material V are arranged in the processing chamber 20. However, for example, a vacuum is used so that the ring magnet S and the evaporation material V can be heated at different temperatures. In the chamber 12, an evaporation chamber (another processing chamber: not shown) is provided separately from the processing chamber 20, and other heating means for heating the evaporation chamber is provided, and the evaporation material V is evaporated in the evaporation chamber. The metal atoms in the vapor atmosphere may be supplied to the ring magnet S in the processing chamber 20 via a communication path that connects the processing chamber 20 and the evaporation chamber.

In this case, when the evaporation material V is Dy, the saturation vapor pressure of Dy is about 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ Pa when the evaporation chamber is 700 ° C. to 1050 ° C. (when 700 ° C. to 1050 ° C. ) May be heated within the range. At a temperature lower than 700 ° C., the vapor pressure at which Dy can be supplied to the surface of the ring magnet S is not reached so that Dy diffuses in the grain boundary phase and spreads uniformly. On the other hand, when the evaporation material V is Tb, the evaporation chamber may be heated in the range of 900 ° C to 1150 ° C. At a temperature lower than 900 ° C., the vapor pressure that can supply Tb atoms to the surface of the ring magnet S is not reached. On the other hand, at a temperature exceeding 1150 ° C., Tb diffuses into the crystal grains, thereby reducing the maximum energy product and the residual magnetic flux density.

Further, in order to remove dirt, gas and moisture adsorbed on the surface of the ring magnet S before diffusing Dy and Tb into the grain boundary phase, the vacuum chamber 12 is set to a predetermined pressure (for example, 1) through the vacuum exhaust means 11. The pressure may be reduced to × 10 ⁻⁵ Pa), and the processing chamber 20 may be held for a predetermined time after being reduced to a pressure (for example, 5 × 10 ⁻⁴ Pa) approximately half an order higher than the vacuum chamber 12. At that time, the heating means 3 may be operated to heat the inside of the processing chamber 20 to, for example, 100 ° C. and hold it for a predetermined time.

  On the other hand, a plasma generating device (not shown) having a known structure for generating Ar or He plasma is provided in the vacuum chamber 12, and a pretreatment for cleaning the surface of the ring magnet S by plasma is performed prior to the processing in the vacuum chamber 12. It may be performed. When the ring magnet S and the evaporation material V are arranged in the same processing chamber 20, a known transfer robot is installed in the vacuum chamber 12, and the lid portion 22 is installed in the vacuum chamber 12 after cleaning is completed. That's fine.

  Further, in the present embodiment, the description has been given of the case in which the lid portion 22 is mounted on the upper surface of the box portion 21 to constitute the box body 2. However, the vacuum chamber 12 is isolated from the vacuum chamber 12 and the vacuum chamber 12 is decompressed. For example, after the ring magnet S is stored in the box portion 21, the upper surface opening may be covered with a thin film made of, for example, Mo, as long as the processing chamber 20 is decompressed. Good. On the other hand, for example, the processing chamber 20 may be sealed in the vacuum chamber 12 and may be configured to be maintained at a predetermined pressure independently of the vacuum chamber 12.

  In Example 1, as a ring magnet, a quenched powder having a composition of 28Nd-0.5Ce-6Co-0.6Ga-0.9B was hot pressed and then hot extruded at 800 ° C. to give an outer diameter of 20 mm and an inner diameter of 20 mm. What was processed into 6 mm and length 10 mm was used. The ring magnet surface was pretreated by chemical etching using nitric acid.

Next, the permanent magnet M was obtained by the said vacuum vapor processing using the said vacuum vapor processing apparatus 1. FIG. In this case, 60 magnets S are arranged at equal intervals on the placement portion 21a in the Mo box 2. Further, bulk Dy (about φ1 mm) or Tb (about φ1 mm) having a purity of 99.9% was used as the evaporation material, and the total amount of g was arranged on the bottom surface of the processing chamber 20. Next, the vacuum evacuation unit is operated to temporarily depressurize the vacuum chamber to 1 × 10 ⁻⁴ Pa (the pressure in the processing chamber is 5 × 10 ⁻³ Pa), and the heating temperature of the processing chamber 20 by the heating unit 3 is evaporated. It was set to 875 ° C. when the material was Dy and 975 ° C. when the evaporation material was Tb. And after the temperature of the process chamber 20 reached each temperature according to evaporation material, the said vacuum vapor process was performed in this state for 4 hours or 10 hours.
(Comparative Example 1)

  In Comparative Example 1, an Nd—Fe—B based sintered magnet was used. In this case, the sintered magnet has a composition of 28Nd-0.5Ce-6Co-0.6Ga-0.9B-bal. Using a thing of Fe, it processed into a rectangular parallelepiped shape of 40 × 10 × 2 mm. In this case, Fe, Nd, B, Co, Cel, and Ga are blended in the above composition ratio to produce an alloy of about 0.5 mm by the strip cast method, and once coarsely pulverized by a known hydrogen pulverization process, An alloy raw material powder was obtained by pulverization by a jet mill pulverization process. Next, this alloy raw material powder is filled into a cavity of a known uniaxial pressurizing compression molding machine, molded into a predetermined shape in a magnetic field, and then the compact is stored in a known sintering furnace and sintered. Then, annealing for strain removal was performed to obtain the sintered magnet. Next, the sintered magnet surface was subjected to chemical etching using nitric acid and pretreated, and then subjected to vacuum vapor treatment using the vacuum vapor treatment apparatus 1 under the same conditions as in Example 1.

  FIG. 5 is a table showing the average value of the magnetic characteristics when the permanent magnet M is obtained under the above conditions using Dy as the evaporation material V, together with the average value of the magnetic characteristics before the vacuum vapor treatment. According to this, it can be seen that when the vacuum steam treatment is performed, the coercive force can be improved to a value exceeding about 20 k0e without lowering the maximum energy product and the residual magnetic flux density, and a permanent magnet having high magnetic properties can be obtained.

  FIG. 4 is a table showing the average value of the magnetic characteristics when the permanent magnet M is obtained under the above conditions using Dy as the evaporation material V, together with the average value of the magnetic characteristics before the vacuum vapor treatment. According to this, it can be seen that when the vacuum steam treatment is performed, the coercive force can be improved to about 20 k0e without lowering the maximum energy product and the residual magnetic flux density, and a permanent magnet having high magnetic properties can be obtained.

  In the case of sintered magnets, the coercive force can be improved by increasing the vacuum vapor treatment time. However, ring magnets that have been subjected to hot plastic working have strain due to plastic deformation caused by pressure. Thus, Dy is easily diffused into the grain boundary phase, so that the coercive force can be improved in a short time, and high productivity can be achieved.

  FIG. 5 is a table showing the average value of the magnetic characteristics when the permanent magnet M is obtained under the above conditions using Tb as the evaporation material V, together with the average value of the magnetic characteristics before the vacuum vapor treatment. According to this, it can be seen that when the vacuum steam treatment is performed, the coercive force can be improved to about 22 k0e without lowering the maximum energy product and the residual magnetic flux density, and a permanent magnet having high magnetic properties can be obtained.

The figure explaining the manufacturing process of an anisotropic ring magnet. The figure which shows schematically the vacuum processing apparatus which implements the process of this invention. The figure which illustrates typically the vacuum steam process to the permanent magnet surface. The table | surface which shows the magnetic characteristic of the permanent magnet produced in Example 1 by making evaporation material into Dy. The table | surface which shows the magnetic characteristic of the permanent magnet produced in Example 1 by making evaporation material Tb.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum vapor processing apparatus 12 Vacuum chamber 20 Processing chamber 21 Box 22 Lid 3 Heating means S Ring magnet M Permanent magnet V Evaporating material

Claims (4)

An iron-boron-rare earth magnet is placed in a processing chamber and heated to a temperature in the range of 800 ° C. to 1050 ° C. , and an evaporating material containing at least one of Dy and Tb is placed in the same or another processing chamber. It is evaporated by heating to a temperature in the range of 700 ° C. to 1150 ° C. , and the evaporated metal atoms of Dy and Tb are attached by adjusting the supply amount to the magnet surface, and the attached metal atoms are attached to the magnet surface. A method of manufacturing a permanent magnet that diffuses into a grain boundary phase of a magnet so that a thin film made of an evaporation material is not formed, the magnet being subjected to hot plastic working and magnetically anisotropic A method for producing a permanent magnet, characterized by being used.   2. The method of manufacturing a permanent magnet according to claim 1, wherein the hot plastic working is hot extrusion molding, and the magnet is manufactured in a ring shape by hot extrusion molding.   The method of manufacturing a permanent magnet according to claim 1, wherein the magnet and the evaporation material are arranged apart from each other.   4. The supply amount is adjusted by changing the specific surface area of the evaporating material disposed in the processing chamber to increase or decrease the evaporation amount at a constant temperature. Of manufacturing permanent magnets.