JP2010215992A - Method for producing compact for magnet and sintered magnet, and apparatus for producing compact for magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing a compact for a magnet, which can produce a compact having a sufficiently high orientation degree. <P>SOLUTION: The apparatus 100 for producing the compact for the magnet includes: a supply part 13 which supplies a slurry S containing a magnetic powder and a dispersion medium; a piping part 15 which has a flow path for transferring the slurry S supplied from the supply part 13; and a compacting part 12 which has a cavity C and a supply hole 121d for supplying the slurry S transferred by the piping part 15 into the cavity C. The flow path of the slurry S in a compacting part 12 side of the piping part 15 or in the supply hole 121d is narrower than the flow path in a supply part 13 side of the piping part 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnet molded body, a sintered magnet manufacturing method, and a magnet molded body manufacturing apparatus.

  A sintered magnet is usually manufactured by firing a molded body obtained by molding magnetic powder into a predetermined shape. For example, when a rare earth sintered magnet is manufactured, magnetic properties are improved by performing a so-called wet molding in which a compact is produced by wet molding using a slurry in which magnetic powder is dispersed.

  Sintered magnets are required to have further improved magnetic properties. In order to meet these requirements, sintered magnets are subjected to a process that fully exhibits the original magnetic properties of the raw magnetic powder. It is necessary to produce a magnetized magnet.

  However, in the case of rare earth sintered magnets, for example, since the magnetic properties of the raw magnetic powder are high, a phenomenon arises in which a bridge is formed and magnetic orientation is disturbed when forming a molded body by wet molding. Therefore, the current situation is that the magnetic properties of the magnetic powder are not fully utilized.

  In order to suppress the bridge formation between such magnetic powders, it has been proposed to use a specific solvent such as synthetic oil or vegetable oil for the preparation of the slurry (for example, Patent Document 1).

JP 7-57914 A

  However, even if a specific solvent is used as in Patent Document 1, the interaction between the magnetic powders is insufficiently reduced, and the degree of orientation when the sintered magnet is used cannot be sufficiently increased. It was still difficult to fully extract the original magnetic properties of the magnetic powder.

  This invention is made | formed in view of the said situation, For magnets which can manufacture the molded object which has a sufficiently high orientation degree, the manufacturing method of a sintered magnet, and the molded object which has a sufficiently high orientation degree It aims at providing the manufacturing apparatus of a molded object.

  In the present invention, in order to achieve the above object, a supply unit for supplying a slurry containing magnetic powder and a dispersion medium, a pipe unit having a flow path for transferring the slurry supplied from the supply unit, a cavity and a pipe unit are provided. And a molding part having a supply hole for supplying the slurry to be transferred into the cavity. A method for producing a magnet molding using a molding apparatus for a magnet molding, wherein the slurry is a pipe on the molding part side. The supply process for supplying the cavity to the cavity to which the magnetic field is applied through the flow path narrower than the flow path of the piping section on the supply section side, and the slurry supplied to the cavity. There is provided a method for producing a molded body for a magnet having a molding step of pressing in a magnetic field.

  According to the present invention, when the slurry passes through a flow path that is narrower than the flow path of the piping section on the supply section side in the piping section or supply hole on the molding section side, the shear stress generated in the slurry Thus, the aggregation of the magnetic powder is unraveled and the dispersibility of the magnetic powder in the slurry can be improved. Thereby, in the supplying step, it is possible to supply a slurry in which the aggregation of the magnetic powder is sufficiently reduced in the cavity, and the degree of orientation of the molded body obtained in the forming step can be sufficiently increased. Moreover, the sintered magnet which has a high magnetic characteristic can be obtained by using such a molded object and a sintered magnet.

  In the supply step of the method for producing a molded body for magnets in the present invention, it is preferable that the slurry pass through a slit provided in the supply hole or the piping part. Thereby, a larger shear stress is generated in the slurry, and the dispersibility of the magnetic powder in the slurry can be further improved. Therefore, the degree of orientation of the molded body obtained in the molding process can be further increased.

Moreover, in the above-mentioned supply process, it is preferable that the shear rate of the slurry in the pipe part on the supply part side or the flow path of the supply hole is 1 × 10 ⁴ (1 / min) or more. Thereby, it is possible to sufficiently suppress the aggregation of the magnetic powder, and the degree of orientation of the compact and the sintered magnet can be further increased.

  Moreover, in this invention, the manufacturing method of the sintered magnet which has the process of baking the molded object obtained by the manufacturing method of the above-mentioned molded object for magnets is provided. Since this sintered magnet manufacturing method uses a molded body with a high degree of orientation produced by the above-described manufacturing method, a sintered magnet having a sufficiently high degree of orientation and excellent magnetic properties can be produced.

  In the present invention, a supply unit that supplies a slurry containing magnetic powder and a dispersion medium, a piping unit that has a flow path for transferring the slurry supplied from the supply unit, and a cavity and a slurry transferred by the piping unit are cavities. A molded part for a magnet comprising a forming part having a supply hole to be supplied therein, wherein the flow path of the slurry in the forming part side of the piping part or the supply hole is on the supply part side of the piping part. An apparatus for manufacturing a molded article for a magnet that is narrower than a path is provided.

  When the apparatus for producing a molded body for magnets of the present invention is used, when the slurry passes through a flow path that is narrower than the flow path of the piping section on the supply section side in the piping section or supply hole on the forming section side. The aggregation of the magnetic powder can be unraveled by the shear stress generated in the slurry. For this reason, the dispersibility of the magnetic powder in the slurry can be improved. This makes it possible to supply a slurry in which the aggregation of the magnetic powder is sufficiently suppressed in the cavity, and the degree of orientation of the compact can be sufficiently increased. Moreover, the sintered magnet which has a high magnetic characteristic can be obtained by using such a molded object.

  It is preferable that the manufacturing apparatus of the molded object for magnets of this invention has a slit in a supply hole or a piping part. By passing the slurry through the slit, a larger shear stress is generated in the slurry, and the dispersibility of the magnetic powder in the slurry can be further improved. Therefore, the degree of orientation of the compact and the sintered magnet can be further increased.

  In the magnet molded body manufacturing apparatus according to the present invention, it is preferable that the flow path of the slurry in the pipe portion or the supply hole becomes narrower as it approaches the forming portion. When the slurry passes through such a flow path, a larger shear stress is generated in the slurry, and the dispersibility of the magnetic powder in the slurry can be further improved. Therefore, the degree of orientation of the molded body and the sintered body can be further increased.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the molded object for magnets which can manufacture the molded object which has a sufficiently high orientation degree, the manufacturing method of a sintered magnet, and the molded object which has a sufficiently high orientation degree is provided. be able to.

It is the schematic which shows 1st Embodiment of the manufacturing apparatus of the molded object for magnets which concerns on this invention. It is the schematic which shows 1st Embodiment of the manufacturing apparatus of the molded object for magnets which concerns on this invention. It is sectional drawing along the III-III line of the manufacturing apparatus 100 of the molded object for magnets which concerns on 1st Embodiment of this invention. It is a perspective view which shows an example of the rare earth sintered magnet manufactured with the manufacturing apparatus of the molded object for magnets which concerns on this invention. It is the schematic which shows 2nd Embodiment of the manufacturing apparatus of the molded object for magnets which concerns on this invention. It is a top view of the shaping | molding apparatus 14 of the manufacturing apparatus 200 of the molded object for magnets concerning 2nd Embodiment of this invention. It is a figure which shows the value of the orientation degree along the magnetic field orientation direction of the rare earth sintered magnet of an Example and a comparative example, and its dispersion | variation.

  Preferred embodiments of the present invention will be described below with reference to the drawings as appropriate. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG.1 and FIG.2 is schematic which shows one Embodiment of the manufacturing apparatus of the molded object for magnets which concerns on this invention. FIG. 1 shows a slurry supply process for supplying slurry into the molding apparatus, and FIG. 2 shows a molding process for pressure-molding the slurry supplied into the molding apparatus in a magnetic field.

  As shown in FIG. 1, the slurry supply device 13 that supplies the slurry S, the pipe portion 15 having a flow path for transferring the slurry from the slurry supply device 13, the cavity C, and the slurry S transferred by the pipe portion 15 are cavities A molding apparatus 12 having a supply hole for supplying to C and a magnetic field application apparatus (not shown) for applying a magnetic field to the slurry S in the cavity C are provided.

  The molding apparatus 12 includes a mortar mold (first mold) 121 having a through hole 121a at the center, a lower mold (second mold) 122 inserted into the through hole 121a of the mortar mold 121, and a through hole. An upper mold (third mold) 123 that forms a cavity C by closing 121a together with the lower mold 122 is provided.

  The die 121 has an inner wall surface 121b surrounding the through hole 121a and an outer wall surface 121c surrounding the inner wall surface 121b, and a slurry supply hole 121d for supplying the slurry S to the cavity C is formed in the inner wall surface 121b. Has been. The slurry supply hole 121d passes through the inner wall surface 121b and the outer wall surface 121c, and a slit 126 having a predetermined opening is provided therein.

  The cavity C includes a lower pressure surface 122 a on the upper mold 123 side of the lower mold 122, an upper pressure surface 123 a and an inner wall surface 123 e on the lower mold 122 side of the upper mold 123, and an inner wall surface 121 b of the mortar mold 121. .

  The slurry supply device 13 includes a metering pump 132 for supplying a predetermined amount of the slurry S into the cavity C of the molding device 12 through the pipe portion 15 and the slurry supply hole 121d. The slurry supply device 13 includes a slurry storage container 131 that supplies the slurry to the metering pump 132 on the upstream side of the valve 135.

  The slurry storage container 131 and the metering pump 132 are connected by a first slurry supply pipe 133, and a valve 135 is installed in the first slurry supply pipe 133. Further, a second slurry supply pipe 156 branches from a portion of the first slurry supply pipe 133 between the valve 135 and the metering pump 132, and is connected to the slurry supply hole 121d. A valve 157 is installed in the second slurry supply pipe 156.

  The metering pump 132 is connected to the first slurry supply pipe 133, and includes a chamber 21 whose volume can be changed, and a drive mechanism 22 for changing the volume of the chamber 21. The chamber 21 is formed by a cylindrical cylinder 23 and a piston 24 provided in the cylinder 23 so as to be capable of reciprocating along one direction. The cylinder 23 communicates with the first slurry supply pipe 133 via the communication portion 23a. In the present embodiment, a part of the first slurry supply pipe 133 connected to the communication portion 23 a is used as a part of the second slurry supply pipe 156 that supplies the slurry S to the molding apparatus 12.

  The drive mechanism 22 is composed of, for example, an expansion / contraction cylinder that is operated by pneumatic pressure or hydraulic pressure, and the piston 24 is connected to the tip of the operation rod 22 a of the drive mechanism 22. By actuating the drive mechanism 22 by air pressure or hydraulic pressure, the operation rod 22 a is advanced and retracted, and the piston 24 is moved in the cylinder 23. As the piston 24 moves, the volume of the chamber 21 changes accordingly. The drive mechanism 22 is not limited to the telescopic cylinder as long as the piston 24 can be moved within the cylinder 23, and other mechanisms can be appropriately employed.

  The operation of the drive mechanism 22 is controlled by a controller (control unit) (not shown) of the slurry supply device 13. Specifically, this controller has a drive mechanism so that an amount of slurry S equal to or less than the volume of the cavity C when the lower mold 122 closes the slurry supply hole 121d is supplied into the cavity C through the slurry supply hole 121d. 22 is controlled. In the present embodiment, the drive mechanism 22 causes the volume of the cavity C at the time when the lower mold 122 closes the slurry supply hole 121d to cause the volume of the slurry S equal to or less than that volume to pass through the slurry supply hole 121d in the cavity C. The amount of movement of the operating rod 22a is controlled so as to be supplied.

  The metering pump is not limited to the plunger pump as in the present embodiment, and other pumps such as a gear pump, a screw pump, and a Mono pump can be used as appropriate.

  3 is a cross-sectional view taken along line III-III of the magnet molded body manufacturing apparatus 100 shown in FIG. As shown in FIG. 3, a slit 126 is provided in the slurry supply hole 121d. The slit 126 narrows the flow path of the slurry in the slurry supply hole 121d.

There is no restriction | limiting in particular in the size of the opening part 127 of the slit 126, It can adjust according to the solid content density | concentration of the slurry to be used, or the magnitude | size of magnetic powder. However, the shear generated in the slurry S is reduced by reducing the ratio of the cross-sectional area of the opening 127 of the slit 126 to the cross-sectional area (πD ² ) of the first slurry supply pipe 133 where the slit 126 is not provided. The speed is increased, and the dispersibility of the magnetic powder in the slurry S can be further improved.

  As shown in FIG. 1, the slit 126 can be securely fixed by arranging the lower mold 122 so that the upper end thereof is in contact with the lower portion where the opening 127 of the slit 126 is not provided. It becomes. Further, the upper end of the lower mold 122 may be disposed at a position where a part of the opening 127 of the slit 126 is blocked. Thereby, the cross-sectional area of the flow path in the slit 126 can be adjusted. A plurality of slits 126 may be provided.

  Next, the manufacturing method of the molded object using the manufacturing apparatus 100 of the molded object for magnets is demonstrated.

  The manufacturing method of the present embodiment includes a slurry preparation step of preparing a slurry by mixing a magnetic powder containing a rare earth element and a solvent, a dispersion step of dispersing the magnetic powder in the slurry in the solvent, and supplying the slurry to the slurry. A supply step of supplying from the device 13 and passing through the slurry supply hole 131d having the second slurry supply pipe 156 and the slit 126, and supplying the slurry into the cavity C to which a magnetic field is applied, and the slurry supplied into the cavity C are supplied. A molding step for producing a compact by applying pressure while applying a magnetic field, a desolvation step for removing the solvent contained in the compact from the compact, and firing to obtain a sintered magnet by firing the desolvated compact. Process. Details of each step will be described below.

  In the slurry preparation step, a slurry is prepared by mixing a magnetic powder containing a rare earth element such as Nd, Pr, Tb or Dy and an element different from the rare earth element such as Fe or B and a solvent. As the magnetic powder, a pulverized alloy containing an element capable of obtaining a rare earth sintered magnet having a desired composition can be used.

  For example, an alloy is prepared by, for example, dissolving a simple substance, an alloy, a compound, or the like containing an element such as a metal corresponding to the composition of a magnet in an inert gas atmosphere such as vacuum or argon, and using this, a casting method or a strip casting method. It is obtained by performing an alloy manufacturing process such as.

  The alloy thus obtained is coarsely pulverized into fine particles having a particle size of about several hundreds μm, and further pulverized to obtain an average particle size of about 1 to 10 μm (preferably 3 to 5 μm). A magnetic powder is obtained. The coarse pulverization of the alloy is performed by using a coarse pulverizer such as a jaw crusher, a brown mill, a stamp mill, or the like, or after the alloy has occluded hydrogen, it is self-destructive based on the difference in hydrogen occlusion between different phases. It can be performed by causing pulverization (hydrogen occlusion pulverization). The fine pulverization is performed by further pulverizing the coarsely pulverized powder using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, or a wet attritor while appropriately adjusting conditions such as pulverization time. Can do.

  Next, a magnetic powder and a solvent are mixed to prepare a slurry. As a solvent used for slurry preparation, an organic solvent such as alcohol can be used. The content of the magnetic powder in the slurry is preferably 60 to 80% by mass, and more preferably 70 to 78% by mass. By setting the content of the magnetic powder to 78% by mass or less, a rare earth sintered magnet having higher magnetic properties can be obtained.

  In the slurry preparation step, other additives can be added in addition to the solvent. Examples of the additive include dispersants such as cationic, anionic, betaine, and nonionic surfactants that can further improve the dispersion of the magnetic powder.

  In the dispersing step, in order to disperse the magnetic powder in the slurry more uniformly, for example, a slurry containing alcohol and magnetic powder is treated with a high-pressure homogenizer. The high-pressure homogenizer is a device that disperses magnetic powder in a slurry by pressurizing the slurry with an ultra-high pressure pump, and has a processing pressure of 20 to 500 MPa. By treating with a high-pressure homogenizer, a slurry in which magnetic powder is uniformly dispersed in a solvent can be obtained in a short time. High-pressure homogenizers include, for example, commercially available homogenizer H type (manufactured by Sanwa Kikai), homogenizer NS series (manufactured by Niro Soavi), pressure homogenizer EmulsiFlex C-5 (AVESTIN type), nano manufacturer (advanced nano Technology) or the like can be used.

  The treatment pressure by the high-pressure homogenizer is preferably 20 to 300 MPa, and more preferably 30 to 200 MPa. Further, the treatment time by the high-pressure homogenizer can be appropriately adjusted according to the viscosity of the slurry, the amount of the slurry, the treatment pressure, etc., but from the viewpoint of reducing the mechanochemical reaction and improving the productivity and economy, it is preferable that the treatment time is 0. It is preferably 1 to 30 minutes, and more preferably 0.1 to 10 minutes.

  In the dispersion step, the slurry may be processed with a bead mill before the above-described processing with the high-pressure homogenizer. The bead mill is a device that stirs 0.01 to 2.0 mm beads in a vessel at a high speed of several hundred rpm or more using a disk or a pin rotor. By performing the treatment with the bead mill, the average particle size of the magnetic powder in the slurry is further reduced and the particle size distribution is adjusted to a state close to monodispersion. Thereby, the dispersibility of the magnetic powder in the slurry can be further improved.

  As the bead mill, for example, an SC mill, an MSC mill (manufactured by Mitsui Mining), a star mill LMZ, a star mill ZRS, a star mill nanogetter, a star mill LME, a star mill AMC (manufactured by Ashizawa Finetech) and the like can be used.

  As described above, the slurry subjected to the dispersion treatment is introduced into the slurry storage container 131 of FIG. 1 and the supply process is started.

  In the supply process, first, in FIG. 1, with the valve 157 closed and the valve 135 opened, the slurry S is supplied from the slurry storage container 131 to the metering pump 132 via the first slurry supply pipe 133. At this time, in the metering pump 132, the piston 24 is retracted by the drive mechanism 22, and the volume of the chamber 21 is increased. Thus, the slurry S is introduced into the chamber 21.

  Next, the valve 135 is closed and the valve 157 is opened, and the lower mold 122 is disposed at a position where a part of the slurry supply hole 121d is opened (that is, a position where the slurry supply hole 121d is not completely closed). Keep it. In this state, the operating rod 22a is actuated by the drive mechanism 22, the slurry S is discharged from the chamber 21 by the piston 24, and the cavity C of the molding apparatus 12 passes through the communication portion 23a, the second slurry supply pipe 156, and the slurry supply hole 121d. Slurry S is supplied inside. When the slurry S is supplied into the cavity C, a magnetic field is applied to the cavity C by a magnetic field application device.

  When the slurry passes through the slurry supply hole 121d, shear stress is generated in the slurry at the slit 126. Thereby, since the magnetic aggregation of the magnetic powder contained in the slurry can be solved, the dispersibility of the magnetic powder of the slurry S supplied into the cavity C can be improved.

The shear rate γ (1 / min) of the slurry S when the slurry S passes through the slit 126 can be calculated by the following mathematical formula (1).
γ = 3 × Q / (W × d ² ) (1)
In Equation (1), Q is the flow rate of the slurry passing through the slit 126 (ml / min), W is the width of the slit 126 (cm, see FIG. 3), and d is the height of the slit (cm, see FIG. 3). Indicates.

The shear rate γ of the slurry S calculated by the above formula (1) is preferably 1 × 10 ⁴ (1 / min) or more, more preferably 5 from the viewpoint of producing a molded body having an excellent degree of orientation. × 10 ⁴ (1 / min) or more, more preferably 4 × 10 ⁵ (1 / min) or more. Further, from the viewpoint of shortening the time of the slurry supply step, the shear rate γ of the slurry S calculated by the above equation (1) is preferably 1 × 10 ¹⁰ (1 / min) or less, more preferably 1 ×. 10 ⁷ (1 / min) or less.

  When supplying the slurry S into the cavity C, the drive mechanism 22 supplies the slurry S in an amount equal to or less than the volume based on the volume of the cavity C when the lower mold 122 closes the slurry supply hole 121d. The movement amount of the operating rod 22a is controlled so as to be supplied into the cavity C to which the magnetic field is applied through the hole 121d. Therefore, the slurry S is supplied so as to have an amount equal to or less than the volume of the cavity C when the lower mold 122 closes the slurry supply hole 121d.

  Thereafter, the lower mold 122 is moved toward the upper mold 123, and the slurry supply hole 121d is closed by the lower mold 122 (FIG. 2). At this time, the slurry S is supplied so as to have an amount equal to or less than the volume of the cavity C when the lower mold 122 closes the slurry supply hole 121d. For this reason, if the lower mold | type 122 is further moved toward the upper mold | type 123 after that, it will become possible to pressure-mold the slurry S. FIG. At the time of pressure molding, a magnetic field is applied to the slurry S by a magnetic field applying device (not shown).

  The lower mold 122, the upper mold 123, or the mortar mold 121 is formed with a flow path for discharging the solvent contained in the slurry S (not shown). The flow path may be covered with a cloth or paper filter. Further, instead of forming the flow path, in order to exclude the solvent from the cavity C, a part of the lower mold 122, the upper mold 123, or the mortar mold 121 may be formed of a porous filter material.

  In the supplying step and the forming step, the magnitude of the magnetic field to be applied is not particularly limited, and can be, for example, 12 to 20 kOe (960 to 1600 kA / m). The magnetic field to be applied is not limited to a static magnetic field, and may be a pulsed magnetic field, or a static magnetic field and a pulsed magnetic field may be used in combination.

  The pressurizing pressure at the time of molding is not particularly limited, and can be, for example, 30 to 100 MPa. When the pressurizing pressure is less than 30 MPa, the strength of the molded product tends to decrease, and when it exceeds 100 MPa, the degree of orientation tends to decrease.

  After the magnet molded body is obtained as described above, the upper mold 123 is separated from the mortar mold 121, the lower mold 122 is moved further upward, and the molded body is taken out. In this way, for example, a molded body having a relative density of 50 to 60% can be produced.

  In the solvent removal step, the molded body obtained in the molding step is heated under reduced pressure to remove the solvent and additives remaining in the molded body. The reduced pressure heating is preferably performed, for example, at a temperature of 100 to 160 ° C. for 1 to 5 hours under a reduced pressure of 10 to 3000 Pa. In the solvent removal step, sintering of the molded body usually does not proceed, but partial sintering may proceed.

  In the solvent removal step, it is preferable to reduce the contents of the solvent and the additive in the molded body as much as possible. By performing such a desolvation step, it becomes possible to sufficiently reduce the amount of carbon component produced during the firing step described later, and a rare earth sintered magnet having excellent magnetic properties can be obtained.

  In the firing step, the compact is fired to produce a rare earth sintered magnet that is a sintered body. Such a sintered body can be obtained, for example, by baking the molded body at a temperature of 1000 to 1200 ° C. for 1 to 10 hours in a vacuum or in the presence of an inert gas and then rapidly cooling it.

  If the firing temperature is less than 1000 ° C., the residual magnetic flux density of the rare earth sintered magnet tends to decrease, and if it exceeds 1200 ° C., abnormal grain growth occurs and the coercive force tends to decrease.

  In addition, after producing a sintered compact, it is preferable to give an aging treatment to a sintered compact by heating this sintered compact at the temperature lower than the time of baking. The aging treatment may be performed, for example, by two-stage heating in which heating is performed at 700 to 900 ° C. for 1 to 3 hours and 500 to 700 ° C. for 1 to 3 hours, or one-stage heating in which heating is performed near 600 ° C. for 1 to 3 hours. it can. Such an aging treatment can improve the magnetic properties of the rare earth sintered magnet.

  In this way, a rare earth sintered magnet 10 as shown in FIG. 4 can be obtained. If necessary, the rare earth sintered magnet 10 may be obtained by cutting the sintered body obtained in the firing step into a desired size or smoothing the surface. Further, the obtained rare earth sintered magnet 10 may be provided with a protective layer on its surface for preventing deterioration of rust and the like.

  As described above, in the present embodiment, a large shear rate is generated in the slurry S when the slurry S passes through the slit 126 serving as the throttle portion of the flow path. For this reason, in the slurry S, the dispersibility of the magnetic powder for a rare earth sintered magnet that is easily magnetically aggregated can be sufficiently improved. And since a magnetic field is applied and shaping | molding in a magnetic field immediately after unwinding magnetic aggregation, the molded object for magnets with a high degree of orientation can be obtained.

  When a magnetic molded body is produced by raising and pressing the lower mold 122 in the z direction while applying the magnetic field H in the y direction in FIG. 4, the inner wall surface 121b of the mortar mold 121 and the inner wall surface of the upper mold 123 are usually obtained. There was a tendency for the degree of orientation to decrease at the end portions (portions on the surfaces 10a and 10b side in the rare earth sintered magnet 10) due to friction with 123e. However, in this embodiment, since the magnetic powder in the slurry is uniformly dispersed, a magnet molded body having a sufficiently high degree of orientation can be obtained even at the end portion. For this reason, it is possible to produce a rare earth sintered magnet that is excellent in magnetic characteristics and in which variations in magnetic characteristics due to positions along the magnetic field application direction are sufficiently suppressed.

(Second Embodiment)
FIG. 5 is a schematic view showing another embodiment of a magnet molded body manufacturing apparatus according to the present invention. FIG. 5 shows a supply process for supplying the slurry into the molding apparatus as in FIG.

  As shown in FIG. 5, the magnet molded body manufacturing apparatus 200 includes a slurry supply apparatus 13 that supplies the slurry S, a pipe portion 15 that has a flow path for transferring the slurry from the slurry supply apparatus 13, a cavity C, and a pipe. A molding device 14 having a supply hole for supplying the slurry S transferred by the unit 15 to the cavity C and a magnetic field applying device (not shown) for applying a magnetic field to the slurry S in the cavity C are provided.

  That is, the magnet molded body manufacturing apparatus 200 includes the molding apparatus 14 having the slurry supply hole 141d whose cross-sectional area is gradually narrowed toward the cavity C, and thus the magnet of the first embodiment. This is different from the molding device manufacturing apparatus 100. The overlapping description is abbreviate | omitted and the shaping | molding apparatus 14 is demonstrated below.

  The molding apparatus 14 includes a mortar mold (first mold) 141 having a through hole 141a at the center, a lower mold (second mold) 142 inserted into the through hole 141a of the mortar mold 141, and a through hole. An upper die (third die) 143 that forms a cavity C by closing 141a together with the lower die 142 is provided.

  The die 141 has an inner wall surface 141b surrounding the through hole 141a and an outer wall surface 141c surrounding the inner wall surface 141b. A slurry supply hole 141d for supplying the slurry S is formed in the inner wall surface 141b. . The slurry supply hole 141d passes through the inner wall surface 141b and the outer wall surface 141c.

  The inner diameter of the slurry supply hole 141d gradually decreases from the outer wall surface 141c toward the inner wall surface 141b. That is, the flow path of the slurry S becomes narrower as it approaches the cavity C.

  The cavity C includes a lower pressure surface 142 a on the upper mold 143 side of the lower mold 142, an upper pressure surface 143 a and an inner wall surface 143 e on the lower mold 142 side of the upper mold 143, and an inner wall surface 141 b of the mortar mold 141. .

  6 is a top view of the molding apparatus 14 of the magnet molded body manufacturing apparatus 200 shown in FIG. As shown in FIG. 6, a second slurry supply pipe 156 having a constant inner diameter is connected to the slurry supply hole 141 d of the molding apparatus 14. The slurry supply hole 141d is gradually narrowed toward the cavity C. As described above, in the magnet molded body manufacturing apparatus 200, the slurry supply hole 141 d is a throttle part of the flow path of the slurry S.

Slurry supply holes inside diameter _{D 1} of 141d in the inner wall surface 141b of the cavity C, for example, is preferably 1 / 10-1 / 3 of the inner diameter D of the slurry supply holes 141d in the outer wall surface 141c. This makes it possible to generate a sufficiently high shear rate in the slurry S when the slurry S passes through the slurry supply hole 141d while maintaining the time required for the supply process, and the magnetic powder in the slurry S can be generated. Dispersibility can be made sufficiently good.

  Next, the manufacturing method of the molded object using the manufacturing apparatus 200 of the molded object for magnets is demonstrated.

  The method for producing a molded body of the present embodiment includes a slurry preparation step in which a magnetic powder containing a rare earth element and a solvent are mixed to prepare a slurry, a dispersion step in which the magnetic powder in the slurry is dispersed in the solvent, The supply step of supplying from the slurry supply device 13 and passing through the second slurry supply pipe 156 and the slurry supply hole 141d and supplying the slurry into the cavity C to which the magnetic field is applied, and the slurry supplied into the cavity C to the magnetic field Forming step by applying pressure while producing a molded body, a solvent removing step for removing the solvent contained in the molded body from the molded body, and a firing step for firing the desolvated molded body to obtain a sintered magnet And have.

  Among the above steps, the slurry preparation step, the dispersion step, the molding step, the solvent removal step, and the firing step are the same as those in the first embodiment. Therefore, the redundant description is omitted here, and the supply step and the accompanying part are omitted. This will be described in detail below.

  In the supply step, first, in FIG. 5, with the valve 157 closed and the valve 135 opened, the slurry S is supplied from the slurry storage container 131 to the metering pump 132 via the first slurry supply pipe 133. At this time, in the metering pump 132, the piston 24 is retracted by the drive mechanism 22, and the volume of the chamber 21 is increased. Thus, the slurry S is introduced into the chamber 21.

  Next, the valve 135 is closed and the valve 157 is opened, and the lower mold 142 is disposed at a position where the slurry supply hole 141d is opened (that is, a position where the slurry supply hole 141d is not blocked). In this state, the operating rod 22a is actuated by the drive mechanism 22, the slurry S is discharged from the chamber 21 by the piston 24, and the cavity C of the molding apparatus 14 passes through the communication portion 23a, the second slurry supply pipe 156, and the slurry supply hole 141d. Slurry S is supplied inside. When the slurry S is supplied into the cavity C, a magnetic field is applied to the cavity C by a magnetic field application device.

  When the slurry passes through the slurry supply hole 141d, the flow path in the slurry supply hole 141d becomes narrower as it approaches the cavity C, so that a large shear rate is generated in the slurry S. Thereby, since the magnetic aggregation of the magnetic powder contained in the slurry S can be solved, the dispersibility of the magnetic powder of the slurry S supplied into the cavity C can be improved.

The shear rate γ (1 / min) of the slurry S when the slurry S passes through the slurry supply hole 141d having a circular tube shape can be calculated by the following mathematical formula (2).
γ = 16 × Q / (π × D ₁ ³ ) (2)
Wherein (2), Q represents the flow rate of the slurry through the slurry supply hole 141d of the (ml / min), _{D 1} is the inside diameter of slurry supply holes 141d at a point the flow path of the slurry S is narrowest ( cm, see FIG. 6).

The shear rate γ of the slurry S calculated by the above formula (2) is preferably 1 × 10 ⁵ (1 / min) or more, more preferably 1 from the viewpoint of producing a molded body having an excellent degree of orientation. × 10 ⁶ (1 / min) or more, more preferably 4 × 10 ⁶ (1 / min) or more. Further, from the viewpoint of shortening the time of the slurry supply step, the shear rate γ of the slurry S calculated by the above equation (1) is preferably 1 × 10 ¹⁰ (1 / min) or less, more preferably 1 ×. 10 ⁸ (1 / min) or less.

  When supplying the slurry S into the cavity C, the driving mechanism 22 supplies the slurry S in an amount equal to or less than the volume of the cavity C based on the volume of the cavity C when the lower mold 142 closes the slurry supply hole 141d. The movement amount of the operating rod 22a is controlled so as to be supplied into the cavity C to which the magnetic field is applied through the hole 141d. Therefore, the slurry S is supplied so as to have an amount equal to or less than the volume of the cavity C when the lower mold 142 closes the slurry supply hole 141d.

  Thereafter, the lower die 142 is moved toward the upper die 143, and the slurry supply hole 141d is closed by the lower die 142. At this time, the slurry S is supplied so as to have an amount equal to or less than the volume of the cavity C when the lower mold 142 closes the slurry supply hole 141d. Therefore, when the lower die 142 is further moved toward the upper die 143, the slurry S can be pressure-molded. At the time of pressure molding, a magnetic field is applied to the slurry S by a magnetic field applying device (not shown).

  The lower mold 142, the upper mold 143, or the mortar mold 141 is formed with a flow path for discharging the solvent contained in the slurry S (not shown). The flow path may be covered with a cloth or paper filter. Further, instead of forming the flow path, in order to exclude the solvent from the cavity C, a part of the lower mold 142, the upper mold 143, or the mortar mold 141 may be formed of a porous filter material.

  Thereafter, the rare earth sintered magnet 10 as shown in FIG. 4 can be obtained by performing the molding process, the solvent removal process and the firing process in the same manner as in the first embodiment.

  As described above, in the present embodiment, a large shear rate is generated in the slurry S when the slurry S passes through the slurry supply hole 141d serving as the throttle portion of the flow path. For this reason, in the slurry S, the dispersibility of the magnetic powder for a rare earth sintered magnet that is easily magnetically aggregated can be sufficiently improved. And since a magnetic field is applied and shaping | molding in a magnetic field immediately after unwinding magnetic aggregation, the molded object for magnets with a high degree of orientation can be obtained.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the method for producing a rare earth sintered magnet has been described. However, the magnet molded body and the method for producing a sintered magnet according to the present invention can be used for magnets other than rare earth sintered magnets such as ferrite sintered magnets. The present invention can also be applied to the production of compacts and sintered magnets.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, this invention is not limited to a following example at all.

[Preparation of rare earth sintered magnet]
(Example 1-1)
Nd: 30% by mass, Dy: 1.8% by mass, Al: 0.2% by mass, Co: 0.5% by mass, B: 1.0% by mass, and blending raw materials so that the balance is Fe The raw material alloy sheet was cast by the strip casting method.

  Raw material alloy thin powder was prepared by hydrogen pulverization of the raw material alloy sheet. After adding a grinding aid to this raw material alloy coarse powder, it was finely pulverized in a high-pressure nitrogen gas atmosphere using an airflow pulverizer (jet mill). The magnetic powder thus obtained and an organic solvent were blended, and a slurry was prepared using a mixer.

A molded body was produced from the prepared slurry using the magnet molded body manufacturing apparatus 200 shown in FIGS. Specifically, the slurry S was press-fitted into the mold cavity C using the metering pump 132 while applying an orientation magnetic field of 10 kOe. The pipe internal pressure in the second slurry supply pipe 156 when the slurry S was press-fitted and filled was 14 MPa. The inner diameter D of the slurry supply hole 141d is 5 mm, the inner diameter _{D 1} was 1 mm.

  Further, the stroke speed (filling speed) of the metering pump 132, the slurry flow rate in the slurry supply hole 141d, and the shear rate of the slurry in the slurry supply hole 141d determined by the above mathematical formula (2) were as shown in Table 1.

  After the slurry S was filled in the mold cavity, the orientation magnetic field was increased to 20 kOe while the magnetic field was applied, and molding was performed in the magnetic field to obtain a molded body. Molding in the magnetic field was performed while pressurizing at a pressure of 65 MPa in a direction perpendicular to the magnetic field direction and sucking the solvent in the slurry S from the upper mold 143. Thus, a rectangular parallelepiped shaped body (size: 20 mm × 18 mm × 11 mm) was obtained.

  The produced molded body was heated in a vacuum of 100 Pa at a temperature of 150 ° C. for 100 minutes to remove the organic solvent contained in the molded body (desolvation). Next, the sintered compact was produced by baking a molded object on the conditions of 1100 degreeC and 5 hours in the vacuum of 0.067 Pa. The obtained sintered body was subjected to aging treatment at 500 ° C. for 1 hour to obtain a rare earth sintered magnet as shown in FIG. This was used as the rare earth sintered magnet of Example 1-1.

(Examples 1-2 and 1-3)
Except having changed the filling rate and the slurry flow rate as shown in Table 1, the rare earth sintered magnets of Example 1-2 and Example 1-3 were produced in the same manner as Example 1-1.

(Example 2-1)
5mm inner diameter D of the slurry supply holes 141d, except that the inner diameter _{D 1} was 3 mm, to prepare a rare earth sintered magnet in the same manner as in Example 1-1. This was used as the rare earth sintered magnet of Example 2-1.

(Examples 2-2 and 2-3)
Rare-earth sintered magnets of Example 2-2 and Example 2-3 were produced in the same manner as in Example 2-1, except that the filling rate and the slurry flow rate were changed as shown in Table 1.

(Comparative Example 1-1)
5mm inner diameter D of the slurry supply holes 141d, except that the inner diameter _{D 1} was 5mm, to prepare a rare earth sintered magnet in the same manner as in Example 1-1. This was used as the rare earth sintered magnet of Comparative Example 1-1.

(Comparative Examples 1-2 and 1-3)
Rare earth sintered magnets of Comparative Example 1-2 and Comparative Example 1-3 were produced in the same manner as Comparative Example 1-1 except that the filling rate and the slurry flow rate were changed as shown in Table 1.

(Comparative Example 2)
A rare earth sintered magnet was produced in the same manner as Comparative Example 1-1 except that the filling of the slurry S into the mold cavity was performed without applying pressure. This was used as the rare earth sintered magnet of Comparative Example 2.

(Example 3-1)
Instead of the magnet molded body manufacturing apparatus 200 shown in FIGS. 5 and 6, a molded body was manufactured using the magnet molded body manufacturing apparatus 100 shown in FIGS. 1 to 3. Specifically, the slurry S was press-fitted into the mold cavity C using the metering pump 132 while applying an orientation magnetic field of 10 kOe to the slurry S prepared in the same manner as in Example 1-1. The inner diameter D of the slurry supply hole 121d was 5 mm, the width W of the opening 127 of the slit 126 provided in the slurry supply hole 121d was 17 mm, and the height d was 5 mm. During the press-fitting and filling of the slurry S, a part of the opening 127 of the slit 126 was closed with the upper end of the lower mold 122, and the height d of the opening was set to 1 mm. The pipe internal pressure in the second slurry supply pipe 156 when the slurry S was press-fitted was 4 MPa.

  Further, the filling speed of the metering pump 132, the flow rate of the slurry in the slurry supply hole 121d, and the shear rate of the slurry in the slurry supply hole 121d determined by the above mathematical formula (1) were as shown in Table 1.

  A rare earth sintered magnet was produced in the same manner as in Example 1-1 using the molded body produced as described above. This was used as the rare earth sintered magnet of Example 3-1.

(Examples 3-2 and 3-3)
Rare-earth sintered magnets of Example 3-2 and Example 3-3 were produced in the same manner as in Example 3-1, except that the filling rate and the slurry flow rate were changed as shown in Table 1.

[Evaluation of orientation degree 1]
The rare earth sintered magnets of Examples and Comparative Examples produced as described above were cut into a predetermined size. The surface parallel to the magnetic field orientation direction of each cut rare earth sintered magnet was mirror-polished using abrasive paper, and then etched for 3 minutes using a 3% by mass ethanol ethanol solution to prepare a sample. The prepared sample was subjected to X-ray diffraction measurement, and the degree of orientation was calculated from the obtained measurement value by the Lotgering method. The degree of orientation was measured for each rare earth sintered magnet of Examples 1-1 to 1-3, and the average value was obtained. The results are shown in Table 1. The degree of orientation was also measured for other examples and comparative examples, and the average value was obtained. X-ray diffraction was measured by a θ-2θ method using a Cu tube with an output of 1.8 kW. 2θ was 20 to 60 °.

  As shown in Table 1, in Examples 1-1 to 1-3 and 2-1 to 2-3, where the flow path in the slurry supply hole becomes narrower as it approaches the cavity, the flow path in the slurry supply hole is constant. The degree of orientation was higher than that of certain Comparative Examples 1-1 to 1-3. Moreover, the rare earth sintered magnets of Examples 3-1 to 3-3 in which the slurry was provided in the slurry supply holes and the slurry was supplied to the cavities had the highest degree of orientation.

[Evaluation of orientation degree 2]
The rare earth sintered magnets of Examples 1-1 and 3-1 and Comparative Example 2-1 were shaved along the magnetic field orientation direction, and the degree of orientation was measured in the same manner as in Evaluation 1 of the degree of orientation. By this measurement, how much the degree of orientation changed along the y direction in FIG. 4 in each rare earth sintered magnet was evaluated. The results are shown in FIG.

  FIG. 7 is a diagram showing the degree of orientation value and its variation along the magnetic field orientation direction of the rare earth sintered magnets of Examples and Comparative Examples. As shown in FIG. 7, Example 3-1 in which the slurry was provided in the slurry supply hole with the slit and the slurry was supplied to the cavity had little and high variation in the degree of orientation from the end portion to the center portion of the rare earth sintered magnet. It was confirmed to have an orientation degree.

  DESCRIPTION OF SYMBOLS 10 ... Rare earth sintered magnet, 10a, 10b ... Surface, 12, 14 ... Molding device, 13 ... Slurry supply device, 21 ... Chamber, 22 ... Drive mechanism, 22a ... Operation rod, 23 ... Cylinder, 23a ... Communication part, 24 ... Piston, 24 ... Cylinder, 100, 200 ... Molded product manufacturing apparatus, 121,141 ... Mould, 121a, 141a ... Through hole, 121b, 141b ... Inner wall surface, 121c, 141c ... Outer wall surface, 121d, 141d ... slurry supply holes, 122, 142 ... lower mold, 122a, 142a ... lower pressure surface, 123, 143 ... upper mold, 123a, 143a ... upper pressure surface, 123e, 143e ... inner wall surface, 126 ... slit, 127 ... opening 131 ... Slurry storage container, 131d ... Slurry supply hole, 132 ... Metering pump, 133 ... Slurry supply pipe, 135, 157 ... Lube.

Claims (7)

A supply unit for supplying a slurry containing magnetic powder and a dispersion medium;
A piping unit having a flow path for transferring the slurry supplied from the supply unit;
A molded part for a magnet using a molding device for a molded article for a magnet, comprising a cavity and a supply part for supplying the slurry transferred by the pipe part into the cavity,
The slurry passes through a flow path narrower than the flow path of the pipe part on the supply part side in the pipe part or the supply hole on the molding part side, and enters the cavity to which a magnetic field is applied. A supply process to be supplied; and
A molding process for pressurizing the slurry supplied to the cavity and molding the slurry in a magnetic field.   The method for producing a molded body for a magnet according to claim 1, wherein in the supplying step, the slurry passes through a slit provided in the supply hole or the pipe portion. 3. The magnet according to claim 1, wherein in the supplying step, the shear rate of the slurry in the flow path of the pipe section or the supply hole on the supply section side is 1 × 10 ⁴ (1 / min) or more. Manufacturing method of a molded object.   The manufacturing method of the sintered magnet which has the process of baking the molded object obtained by the manufacturing method of the molded object for magnets as described in any one of Claims 1-3. A supply unit for supplying a slurry containing magnetic powder and a dispersion medium;
A piping unit having a flow path for transferring the slurry supplied from the supply unit;
A molding part for a magnet, comprising a cavity and a molding part having a supply hole for supplying the slurry transferred by the pipe part into the cavity,
The apparatus for producing a molded body for magnet, wherein a flow path of the slurry in the forming section side of the piping section or the supply hole is narrower than a flow path of the piping section on the supply section side.   The manufacturing apparatus of the molded object for magnets of Claim 5 by which the said supply hole or the said piping part is provided with the slit. The apparatus for producing a molded body for a magnet according to claim 5 or 6, wherein a flow path of the slurry in the piping section or the supply hole becomes narrower as the molding section is approached.

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