JP2018078182A - Method for manufacturing rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth magnet capable of suppressing burr generation of a sintered compact.SOLUTION: A method for manufacturing a rare earth magnet comprises the steps of: obtaining a compact by pressing rare-earth alloy powders filled in a die by a punch; increasing the intensity of the compact by subjecting the compact to heat treatment; removing burrs from the compact after the heat treatment; and sintering the compact after removing the burrs.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a rare earth magnet.

  Rare earth magnets are components such as motors or actuators, such as hard disk drives, hybrid cars, electric cars, magnetic resonance imaging devices (MRI), smartphones, digital cameras, thin TVs, scanners, air conditioners, heat pumps, refrigerators, and vacuum cleaners. It is used in various fields such as washing and drying machines, elevators and wind power generators. Depending on these various applications, the dimensions and shape required for rare earth magnets vary. Therefore, in order to efficiently manufacture a wide variety of rare earth magnets, a molding method that can easily change the size and shape of the rare earth magnet is desired.

  In the production of a conventional rare earth magnet, a magnetic field is applied to the metal powder while pressing a metal powder (for example, an alloy powder) containing a rare earth element with a high pressure (for example, 50 MPa or more and 200 MPa or less). As a result, a compact is formed from the metal powder oriented along the magnetic field. Hereinafter, such a forming method is referred to as a “high-pressure magnetic field pressing method”. According to the high-pressure magnetic field pressing method, it is possible to obtain a molded body having a high residual magnetic flux density Br and excellent shape retention, since the metal powder is easily oriented. A sintered product is obtained by sintering the compact, and the sintered product is processed into a desired shape to complete a magnet product.

  However, in the high-pressure magnetic field pressing method, since it is necessary to apply a high pressure to the metal powder in a magnetic field, a large-scale and complicated molding apparatus is required, and the size and shape of a molding die are limited. Due to this limitation, the shape of a general molded body obtained by a high-pressure magnetic field pressing method is limited to a coarse block. Therefore, when manufacturing various types of magnet products by the conventional method, after obtaining the sintered body by sintering the block-shaped molded body, the sintered body is prepared according to the size and shape required for the magnet product. Need to be processed. In the processing of the sintered body, since the sintered body is cut or polished, scraps containing expensive rare earth elements are generated. As a result, the yield rate of the magnet product is reduced. In the high-pressure magnetic field pressing method, the mold or the molded body is easily damaged due to galling between the molds or between the mold and the molded body. For example, cracks may occur in a molded body obtained by a high-pressure magnetic field pressing method.

  For the above reasons, the manufacturing method using the conventional high-pressure magnetic field pressing method is not suitable for manufacturing a variety of products or a small amount of magnet products. As a forming method that replaces the high-pressure magnetic field pressing method, Patent Document 1 below discloses a method of forming alloy powder at a low pressure (0.98 MPa to 2.0 MPa). In this rare earth magnet manufacturing method, alloy powder is filled in a mold, and the alloy powder is pressurized at a low pressure to produce a molded body (filling process), and a magnetic field is applied to the molded body in the mold. The step of orienting the alloy powder in the compact (orientation step) and the step of sintering the compact taken out from the mold (sintering step) are provided. And in the manufacturing method of the following patent document 1, a filling process and an orientation process are performed in another place.

WO2016 / 047593

  When the alloy powder is molded at a low pressure as in the molding method described in Patent Document 1, durability against high pressure is not required for the mold, and a large-scale and complicated molding apparatus is not required. Therefore, when molding alloy powder at a low pressure, the material, size and shape of the mold are not limited, and various types of rare earth magnets can be manufactured relatively easily using molds having various sizes and shapes. it can. The high-pressure magnetic field press method takes a long time to form and orient the metal powder, but forming the alloy powder at a low pressure significantly reduces the time required for the forming and orientation and improves the productivity of rare earth magnets. To do.

  By the way, even if the alloy powder is molded at a low pressure, burrs are often generated in the molded body. And since the burr | flash after sintering is hard and it is hard to remove, it is desired to remove a burr | flash from a molded object before sintering. However, in the case of a molded body obtained by low-pressure molding, if the burrs of the molded body before sintering are removed, non-burrs are also removed together, and the shape of the molded body may be impaired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a rare earth magnet that can remove burrs with high accuracy before sintering even if it is a molded body obtained by low pressure molding. .

The method for producing a first sintered magnet according to the present invention includes a step of pressing a rare earth alloy powder filled in a die with a punch to obtain a molded body,
Heat-treating the molded body;
Removing burrs from the molded body after the heat treatment;
And a step of sintering the molded body after removing the burrs.

  According to the present invention, since the burrs are removed after the heat treatment, the strength of the molded body is increased at the time of removing the burrs. Therefore, when the burrs are removed, it is possible to suppress removal of parts other than the burrs in the molded body together with the burrs. In addition, when removing burrs, handling such as holding / fixing of the molded body is facilitated. Furthermore, since the burrs are removed before sintering, the burrs are not too hard to be removed.

  In this case, the burr can be removed from the molded body by irradiating the burr with laser light. Burrs can be easily removed by the action of laser ablation or melting.

  The laser light can be near infrared light or green light.

  Such laser light is preferable because it is well absorbed by a metal material such as iron.

  Further, the burr can be removed from the molded body by bringing a brush into contact with the burr.

  Further, the burr can be removed from the molded body by bringing a magnet close to the burr.

  Furthermore, a nozzle that sucks gas or a nozzle that blows out gas can be brought close to the burr to remove the burr from the molded body.

  Furthermore, the method may further include a step of removing powder adhering to the molded body after the step of removing the burrs from the molded body and before the step of sintering the molded body. Thereby, a sintered compact with higher shape accuracy is obtained.

  Moreover, the pressure of a press can be 0.049-20 MPa.

  In the heat treatment, the molded body can be heated to 200 to 450 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rare earth magnet which can remove a burr | flash with high precision is provided even if it is a molded object by low pressure molding.

(A)-(c) of FIG. 1 is a schematic sectional drawing which shows in order the shaping | molding process which concerns on embodiment of this invention. 2A to 2D are schematic cross-sectional views showing a burr removal and powder removal process with a laser beam according to an embodiment of the present invention. (A)-(d) of FIG. 3 is a perspective view which shows the molded object which has a burr | flash. FIGS. 4A to 4C are schematic cross-sectional views showing a process of removing burrs according to another embodiment of the present invention.

  A preferred embodiment of a method for producing a rare earth magnet will be described with reference to the drawings.

(Preparation process of rare earth alloy powder)
First, a rare earth alloy powder is prepared. A rare earth alloy is an alloy containing a rare earth element.

  Examples of rare earth elements include one or more elements selected from the group consisting of scandium (Sc), yttrium (Y) and lanthanoids belonging to Group 3 of the long-period periodic table. Here, the lanthanoid is lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy). , Holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

Specific examples of the rare earth alloy are Sm—Co alloy, Nd—Fe—B alloy, and Sm—Fe—N alloy. Among these, an Sm—Co alloy represented by SmCo ₅ and Sm ₂ Co ₁₇ or an Nd—Fe—B alloy represented by Nd ₂ Fe ₁₄ B is preferable.

  When the rare earth alloy is an Nd—Fe—B alloy, the content of the rare earth element in the alloy is preferably 8 to 40% by mass, more preferably 15 to 35% by mass. Moreover, the content ratio of Fe in the Nd—Fe—B alloy is preferably 42 to 90% by mass, and more preferably 60 to 80% by mass. The content ratio of B in the Nd—Fe—B alloy is preferably 0.5 to 5% by mass. Further, a part of Fe may be substituted with cobalt (Co). A part of B may be substituted with one or more elements selected from the group consisting of carbon (C), phosphorus (P), sulfur (S), and copper (Cu).

  Rare earth alloys are made of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), bismuth (Bi) from the viewpoint of improving coercive force, improving productivity and reducing costs. Niobium (Nb), Tantalum (Ta), Molybdenum (Mo), Tungsten (W), Antimony (Sb), Germanium (Ge), Tin (Sn), Zirconium (Zr), Nickel (Ni), Silicon (Si) , Gallium (Ga), copper (Cu) and / or hafnium (Hf) may be included.

  The rare earth alloy may contain oxygen (O), nitrogen (N), carbon (C), and / or calcium (Ca) as inevitable impurities.

  The rare earth alloy powder can be prepared by the following procedure. First, an alloy containing a rare earth metal constituent element in a desired ratio is cast by a slip casting method or the like to obtain rare earth alloy flakes. Next, the obtained flakes are coarsely pulverized using a pulverizer such as a stamp mill to obtain coarse powder having a particle size of about 10 to 100 μm. At this time, hydrogen may be occluded in the flakes before coarse pulverization, and hydrogen may be released from the coarse powder by heat treatment after coarse pulverization. Subsequently, a lubricant is added as necessary, and further pulverized to a particle size of about 0.5 to 10 μm using a jet mill or the like to obtain a rare earth alloy powder.

  Examples of lubricants include hydrocarbons such as paraffin wax; fatty acids such as stearic acid and stearyl alcohol; oleic acid amide, stearic acid amide, palmitic acid amide, pentadecylic acid amide, myristic acid amide, lauric acid amide, capric acid amide, Aliphatic amides such as pelargonic acid amide, caprylic acid amide, enanthic acid amide, caproic acid amide, valeric acid amide and butyric acid amide; organic substances such as metal soap such as metal stearate (zinc stearate, calcium stearate) . The lubricant can be a powder or a liquid. The density | concentration of the organic substance used as the lubrication agent in rare earth alloy powder can be 0.01-1.0 mass%.

(Forming process of rare earth alloy powder)
Next, the molding process will be described with reference to FIGS. First, as shown to (a) of FIG. 1, the die | dye 10 which has the cylindrical part 10a and the baseplate part 10b, and the punch 15 are prepared. A cylindrical portion 10 a is placed on the upper surface of the bottom plate portion 10 b, and a cavity V is formed in the die 10. Subsequently, the rare earth alloy powder 5 ′ is filled in the cavity V of the die 10. Note that a magnetic field may be applied to the rare earth alloy powder 5 ′ in the die 10 after filling the powder and before forming.

  Subsequently, as shown in FIG. 1B, the punch 15 is inserted into the cavity V, and the rare earth alloy powder 5 ′ is pressed with a predetermined pressure by the punch 15 to obtain the compact 5.

The press pressure can be a low pressure, that is, 0.049 to 20 MPa (0.5 to 200 kgf / cm ² ). The press pressure is, for example, the pressure exerted by the punch tip surface on the alloy powder. Low pressure molding is preferable because the consumption of the die and punch is small. Therefore, it is possible to use a die or punch made of resin or the like, and it is possible to reduce the cost.

  A magnetic field may be applied and demagnetized to the molded body 5 in the die 10 after being formed by the punch and before being taken out from the die 10. The application of a magnetic field may be performed during molding. The intensity of the magnetic field can be, for example, 796 to 5173 kA / m (10 to 65 kOe).

  Thereafter, as shown in FIG. 1C, the molded body 5 is taken out from the cavity of the die 10. For example, as shown in FIG. 1C, the molded body 5 can be taken out from the bottom of the tenth, but the taking-out method is not limited.

The density of the molded body before the heat treatment step is, for example, 3.0 to 4.4 g / cm ³ , preferably 3.2 to 4.2 g / cm ³ , more preferably 3.4 to 4.0 g / cm ³ . It may be adjusted.

(Heat treatment process of molded body)
Subsequently, since the molded body 5 molded at a low pressure has low strength and is difficult to handle, the molded body 5 is heat treated to increase the strength of the molded body 5.
The temperature of the molded body in the heat treatment step can be adjusted to 200 to 450 ° C. In a heat treatment process, you may adjust the temperature of a molded object to 200-400 degreeC or 200-350 degreeC.

  In the heat treatment step, when the temperature of the molded body 5 is 200 ° C. or higher, the molded body 5 starts to harden, and the shape retention of the molded body 5, in other words, the mechanical strength of the molded body 5 is improved. Since the shape retaining property of the molded body 5 is improved, the molded body 5 is hardly damaged when the molded body 5 is conveyed or when the molded body% is handled in a subsequent process. For example, when the molded body 5 is gripped by a transport chuck or the like and arranged on the baking tray, the molded body 5 is unlikely to collapse. As a result, defects in the finally obtained rare earth magnet are suppressed.

  If the temperature of the molded body 5 exceeds 450 ° C. in the heat treatment step, cracks are easily formed in the molded body 5 in the firing step performed after the heat treatment step. The reason for the formation of cracks is not clear. For example, there is a possibility that cracks may be formed in the molded body 5 because hydrogen remaining in the molded body 5 blows out as a gas to the outside of the molded body 5 due to a rapid temperature rise of the molded body 5 in the heat treatment step. However, the crack of the molded object 5 in a baking process is suppressed by adjusting the temperature of the molded object 5 to 450 degrees C or less in a heat treatment process. As a result, cracks in the finally obtained rare earth magnet are easily suppressed. Moreover, since the temperature of the molded body 5 is adjusted to 450 ° C. or lower in the heat treatment step, the time required for heating or cooling the molded body 5 is suppressed, and the productivity of the rare earth magnet is improved. Further, since the temperature of the molded body 5 in the heat treatment step is 450 ° C. or lower and lower than a general firing temperature, even if the molded body 5 is heated together with a part of the die 10 (for example, the bottom plate portion 10b), the die 10 Or chemical reaction between the molded body 5 and the die 10 hardly occurs. Therefore, even a die composed of a composition (for example, resin) that does not necessarily have high heat resistance can be used.

  The mechanism by which the shape retention of the molded body 5 is improved by adjusting the temperature of the molded body 5 to 200 ° C. or higher and 450 ° C. or lower is not clear. For example, there is a possibility that an organic substance (for example, a lubricant) added to the alloy powder becomes carbon in the heat treatment step, and the alloy powders are bound via carbon. As a result, the shape retention of the molded body 5 may be improved. If the temperature of the molded body 5 exceeds 450 ° C. in the heat treatment step, metal carbide constituting the alloy powder may be generated or the alloy powder may be directly sintered. On the other hand, when the temperature of the molded body 5 is adjusted to 200 ° C. or higher and 450 ° C. or lower, metal carbide is not necessarily generated, and alloy particles are not necessarily sintered directly.

  The time for maintaining the temperature of the molded body 5 at 200 ° C. or higher and 450 ° C. or lower in the heat treatment step is not particularly limited, and may be appropriately adjusted according to the size and shape of the molded body 5.

  In the heat treatment step, the molded body 5 may be heated by irradiating the molded body 5 with infrared rays. By directly heating the molded body 5 by irradiation with infrared rays (that is, radiant heat), the time required for raising the temperature of the molded body 5 is shortened compared to heating by conduction or convection, and production efficiency and energy efficiency are increased. However, in the heat treatment step, the molded body 5 may be heated by heat conduction or convection in the heating furnace. The infrared wavelength may be, for example, 0.75 μm to 1000 μm, preferably 0.75 μm to 30 μm. The infrared rays may be at least one selected from the group consisting of near infrared rays, short wavelength infrared rays, medium wavelength infrared rays, long wavelength infrared rays (thermal infrared rays), and far infrared rays. Of the above infrared rays, near infrared rays are relatively easily absorbed by metals. Therefore, when near-infrared rays are irradiated to the molded body, the temperature of the metal (alloy powder) is easily raised in a short time. On the other hand, far infrared rays among the above infrared rays are relatively easily absorbed by organic substances and easily reflected by metal (alloy powder). Therefore, when irradiating a far infrared ray to a molded object, the organic substance (for example, lubricant) mentioned above is easy to be selectively heated, and a molded object is easy to harden by the above-mentioned mechanism resulting from an organic substance. In the case of irradiating the molded body with infrared rays, for example, an infrared heater (such as a ceramic heater) or an infrared lamp may be used.

  When the molded body 5 taken out from the cavity of the die 10 is heated in the heat treatment step, deterioration (for example, deformation, hardening or wear) of the die 10 due to heating is easily suppressed, and seizure between the molded body 5 and the die 10 is also suppressed. It is easy to be done. Further, when the molded body 5 taken out from the cavity of the die 10 is heated, the molded body 5 is easily heated because there is no heat insulation by the die. As a result, the shape retention of the molded body 5 is improved. When the molded body 5 taken out from the cavity V is heated, the possibility that the die 10 chemically reacts with the molded body 5 is low. For this reason, the die 10 is not necessarily required to have heat resistance, and the material of the die 10 is not easily limited. Therefore, as a material for the die 10, it is easy to process into a desired size and shape, and it is easy to select an inexpensive material. If the molded body 5 held in the cavity is heated together with the die 10 in the heat treatment step, stress is applied to the molded body 5 due to the difference in thermal expansion coefficient between the molded body 5 and the die 10. It is easy to act, and the molded body 5 is deformed or damaged. Further, since the volume and heat capacity of the entire heating target are large, the number of the molded bodies 5 is limited, the time required for the heat treatment process is lengthened, energy is wasted, and the productivity of the rare earth magnet is reduced.

  In the heat treatment step, for example, the molded body 5 placed on the bottom plate portion 10b may be heated. In the heat treatment step, the molded body 5 placed on the heat treatment step tray may be heated. In the heat treatment step, the molded body 5 may be heated in an inert gas or vacuum to suppress oxidation of the molded body 5. The inert gas may be a noble gas such as argon.

  In the heat treatment step, after the temperature of the molded body 5 is adjusted to 200 ° C. or higher and 450 ° C. or lower, the molded body 5 may be cooled to 100 ° C. or lower. When the surface of the chuck used for transporting the molded body 5 after the heat treatment step is made of a resin, the cooling of the molded body 5 suppresses the chemical reaction between the surface of the chuck and the molded body 5, and the deterioration of the chuck. Contamination of the surface of the molded body 5 is suppressed. The cooling method may be natural cooling, for example.

When the strength of the molded body 5 is increased through the heat treatment step, the molded body 5 molded at a low pressure can be easily grasped by a robot hand or the like, and the handling property in the subsequent process is improved.
The density of the green body before sintering is also adjusted to 3.0 to 4.4 g / cm ³ , preferably 3.2 to 4.2 g / cm ³ , more preferably 3.4 to 4.0 g / cm ^3. It's okay.

(Deburring process of molded body)
Subsequently, burrs are removed from the molded body 5 after the heat treatment. In the above molding, burrs are often generated in the molded body 5 by the rare earth alloy powder entering the gap between the die and the punch.
Specifically, when the punch is pushed in, the gas in the die escapes from the gap between the die and the punch, and at this time, burrs are often formed by entraining the rare earth alloy powder.

For example, as shown in FIG. 2A, in the case of the columnar shaped body 5, a burr 5BR extending in the axial direction of the press is formed at the edge of the end surface (for example, the upper surface) to which the punch 15 is applied. Sometimes.
The burr 5BR is a protrusion extending from the end of the molded body 5. For example, when the contour of the upper surface 5U of the molded body 5 has three straight lines and one curve as shown in FIG. 3A, the burr 5BR may extend upward from each straight line and curve. Further, when the contour of the upper surface of the molded body 5 has four straight lines as shown in FIG. 3B, the burr 5BR may extend upward from each straight line. The height of each burr 5BR is not always constant, and is often non-uniform as shown in FIGS. 3 (a) and 3 (b). Moreover, the burr | flash 5BR may be bent along the upper surface 5U of the molded object 5, as shown to (c) and (d) of FIG. The burr 5BR may be bent along the side surface.

  In this step, such burrs 5BR are removed from the molded body 5. Specifically, as shown in FIG. 2 (b), the laser beam LB from the laser light source LS is irradiated onto the burr 5BR (for example, the root) of the molded body 5, and then from the molded body 5 by the action of ablation or melting. The burr 5BR is cut, whereby the burr 5BR can be removed from the molded body 5.

The laser beam LB is preferably near-infrared (750 to 2500 nm) or green light (495 to 570 nm) from the viewpoint of high absorptance to metal. Specifically, it is preferable to use an Nd: YAG laser (fundamental wavelength 1064 nm, second harmonic 532 nm (green laser)) or an Nd: YVO ₄ laser (1064 nm). Further, Yb: fiber laser (1090 nm), semiconductor laser (375 to 2000 nm), or the like may be used. On the other hand, a 10.2 μm CO ₂ laser has a low absorptivity with respect to metal and is not so suitable.

As shown in FIG. 2B, the laser beam LB may be irradiated in parallel to the upper surface 5U (along the upper surface), but at an angle of, for example, 30 to 60 ° with respect to the upper surface 5U. Irradiation may be performed only on the corners of the molded body 5.
Thereby, the molded object 5 from which the burr | flash was removed is obtained like (c) of FIG.

(Fine powder removal process of molded body)
Due to the above deburring, fine powder may adhere to the surface of the molded body 5. Therefore, the fine powder P generated by deburring is removed from the molded body 5 as necessary. For example, as shown in FIG. 2 (d), the fine powder can be removed by the suction device VA. The suction device VA includes a suction pump 56, a nozzle 52, and a line 54 that connects the suction pump 56 and the nozzle 52. By bringing the nozzle 52 for sucking the gas closer to the surface of the molded body 5, the fine powder P adhering to the surface of the molded body 5 can be sucked and removed together with the surrounding gas. The suction pump 56 of the suction device VA may be blown out of the nozzle 52 instead of the blower. In this case, the fine powder P adhering to the molded body 5 can be blown off and removed by bringing the nozzle 52 for ejecting gas closer to the surface of the molded body 5.

(Sintering process of molded body)
Next, the molded body 5 from which burrs have been removed is sintered to obtain a sintered body. A conventionally known method can be applied to the sintering. The sintering temperature and sintering time can be appropriately set according to the rare earth alloy. The sintering temperature can be, for example, 900 ° C. or higher and 1200 ° C. or lower. The sintering time can be, for example, 0.1 hours or more and 100 hours or less. The sintering process may be repeated. In the sintering step, the compact may be heated in an inert gas or vacuum. The inert gas may be a noble gas such as argon. If necessary, the sintered body after sintering can be subjected to post-processing steps such as cutting and grinding, a surface treatment step, and a magnetization step.

(Function)
According to the method of manufacturing a rare earth magnet according to the present embodiment, since the burrs are removed after the heat treatment, the strength of the molded body is high at the time of removing the burrs. Therefore, even when the low pressure molding is performed, it is possible to suppress the removal of the portions other than the burrs in the molded body together with the burrs when the burrs are removed. In addition, handling such as holding / fixing of the molded body during deburring is facilitated. Furthermore, since the burrs are removed before sintering, the burrs are not too hard to be removed. As a result, a sintered body with high shape accuracy can be easily obtained.

  Furthermore, since laser light is used, deburring can be performed quickly. In particular, a near-infrared laser and a green laser beam are preferable because of their high absorbability with respect to metals such as iron.

  Furthermore, since fine powder is removed by gas suction or gas blowing, the shape accuracy of the sintered body can be further improved.

  The present invention is not limited to the above embodiment, and various modifications can be made.

  For example, as shown in FIG. 4 (a), the bristles 42 of the brush BRS are brought into contact with the burr 5BR by stroking the surface of the molded body 5 with the brush BRS, and the burr 5BR is folded to remove the burr 5BR from the molded body 5. It can also be removed. Specifically, the surface having the burr 5BR (for example, the upper surface) is swept with the brush BRS from the center to the edge, or swept from the edge toward the center, or at the edge of the surface with the burr 5BR. It can be swept with a brush BRS along the circumference. The brush BRS has hairs 42 and a holding part 40 that holds the hairs 42. Specific examples of the brush BRS are a linear brush in which the bristles 42 are linearly provided on the holding portion 40 and a roll brush in which bristles are provided radially on the outer peripheral surface of the cylindrical holding portion. Examples of the hair 42 are horse hair and nylon hair, and the diameter of the hair is, for example, 0.01 to 0.05 mm.

  Further, as shown in FIG. 4B, the burr 5BR can be removed from the molded body 5 by bringing the strong magnet Mg close to the burr 5BR and sucking the burr 5BR to the magnet Mg. Suitable magnets are permanent magnets and electromagnets (coils). A direct current or an alternating current can be applied to the electromagnet to form a direct magnetic field or an alternating magnetic field. The strength of the magnetic field (magnetic flux density) can be 500 to 1000 G.

  Further, as shown in FIG. 4C, the burr 5BR is sucked into the nozzle 52 by using the above-described suction device VA to bring the tip of the nozzle 52 connected to the suction pump 56 close to the burr 5BR. The burr 5BR can be removed from the molded body 5. When sucking burrs with the nozzle 52, unnecessary raw material powder adhering to the surface of the molded body, such as powder generated when the burrs 5BR are removed, can also be sucked. Further, the burrs can be blown off with the gas emitted from the nozzle 52 by replacing the suction pump 56 with a blower.

  Moreover, in the said embodiment, although press pressure is made into the range of said low pressure, even if it shape | molds with a higher press pressure, implementation is possible.

  Further, the shapes and structures of the die 10 and the punch 15 and the shape of the cavity V are not limited to the above-described embodiment, and various shapes can be taken according to the shape of the target magnet. For example, in the above-described embodiment, the die can be divided into two upper and lower dies, but may be divided into three or more or may not be divided.

  The size and shape of the rare earth magnet vary depending on the use of the rare earth magnet and are not particularly limited. The shape of the rare earth magnet may be, for example, a rectangular parallelepiped shape, a cubic shape, a polygonal column shape, a segment shape, a fan shape, a rectangular shape, a plate shape, a spherical shape, a disc shape, a columnar shape, a ring shape, or a capsule shape. The cross-sectional shape of the rare earth magnet may be, for example, a polygonal shape, a chordal shape, an arc shape, or a circular shape.

  DESCRIPTION OF SYMBOLS 10 ... Die, 15 ... Punch, 5 '... Rare earth alloy powder, 5 ... Molded body, 5BR ... Burr, LB ... Laser beam, BRS ... Brush, Mg ... Magnet, 52 ... Nozzle, P ... Fine powder.

Claims (9)

A step of pressing a rare earth alloy powder filled in a die with a punch to obtain a molded body; and
Heat-treating the molded body;
Removing burrs from the molded body after the heat treatment;
And a step of sintering the compact after removing the burr.   The method according to claim 1, wherein the burr is removed from the compact by irradiating the burr with a laser beam.   The method according to claim 2, wherein the laser light is near infrared light or green light.   The method according to claim 1, wherein the burr is removed from the formed body by bringing a brush into contact with the burr.   The method according to claim 1, wherein the burr is removed from the molded body by bringing a magnet close to the burr.   The method according to claim 1, wherein a nozzle for sucking gas or a nozzle for blowing gas is brought close to the burr to remove the burr from the molded body.   The method of any one of Claims 1-6 further equipped with the process of removing the powder adhering to the said molded object after the process of removing the said burr | flash from the said molded object and before the process of sintering the said molded object. The method described in 1.   The method according to claim 1, wherein the pressure of the press is 0.049 to 20 MPa.   The method according to any one of claims 1 to 8, wherein in the heat treatment, the molded body is heated to 200 to 450 ° C.

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