JP2008251722A - Method and device for manufacturing magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for manufacturing magnets that facilitate a reduction in weight variation and dimensional variation among magnets to be obtained. <P>SOLUTION: The magnet manufacturing method as a suitable embodiment has a slurry manufacturing step for obtaining slurry including magnet material powder and a dispersion medium, a molding step for obtaining a molded body by molding the slurry, and a baking step for baking the molded body. In the slurry manufacturing step, an amount of slurry corresponding to an amount of slurry required for one-time molding executed in the molding step is manufactured. In the molding step, the whole amount of the slurry obtained in the slurry manufacturing step is molded at one time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a magnet, and more particularly to a method and an apparatus for manufacturing a magnet by wet molding.

As a method for producing a magnet, a method of undergoing a wet molding process in which a slurry obtained by mixing raw material powder of a magnet with a dispersion medium (solvent) such as oil or an organic solvent is molded and then sintered is known. ing. In such a magnet manufacturing method, a large amount of slurry is generally manufactured and stored, and a required amount of slurry is taken out from the slurry to be molded. For example, in Patent Document 1 below, slurry is stored in a slurry tank, the slurry is sent out from the slurry tank, and an amount necessary for molding is supplied into the mold cavity using a slurry feeder.
JP-A-8-120304

  However, in the case of the method in which the required amount is taken out after the slurry is manufactured and stored in a tank or the like as in the conventional case, there is a problem that the obtained magnet has a large variation in weight. Such weight variation leads to dimensional variation, and it is necessary to make adjustments by making a larger sample accordingly, which may increase material costs and processing costs, and may cause variations in magnetic properties. From the viewpoint of producing a magnet homogeneously, it is not preferable.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnet manufacturing method and a manufacturing apparatus that can easily reduce the weight variation between the obtained magnets.

  In order to achieve the above object, the present inventors conducted extensive research and found that the above-described magnet weight variation is caused by temporary storage after the slurry is manufactured. That is, the slurry is obtained by mixing and dispersing the magnet raw material powder and the dispersion medium, but since the raw material powder is usually heavier, the raw material powder is likely to settle during storage. In this case, since the concentration of the raw material powder varies depending on the part of the stored slurry, if the slurry is taken out and molded from here, the resulting magnet will have a weight variation. In order to prevent such sedimentation, a method of stirring the slurry during storage can be considered, but in a large amount of slurry, it is considered that some variation in the raw material powder concentration is unavoidable, and the weight of the magnet exceeds a certain level. It is still difficult to reduce the variation.

  Accordingly, the present inventors have found that, based on such knowledge, if the produced slurry is used for molding without being stored, the weight variation of the magnet can be reduced, and the present invention has been completed. .

  That is, the magnet manufacturing method of the present invention includes a slurry manufacturing process for obtaining a slurry containing a magnet raw material powder and a dispersion medium, a molding process for molding the slurry to obtain a molded article, and a firing process for firing the molded article. In the slurry manufacturing process, an amount of slurry corresponding to one molding performed in the molding process is manufactured, and in the molding process, the entire amount of the slurry obtained in the slurry manufacturing process is molded at a time. It is characterized by.

  In such a magnet manufacturing method of the present invention, a slurry for only one molding is prepared in the slurry manufacturing process, and the entire amount is used for one molding. Therefore, if a certain amount of slurry is used, the slurry A magnet having a constant weight can be obtained regardless of sedimentation during storage. Therefore, it is possible to reduce the weight variation between the obtained magnets as compared with the case where a large amount of slurry is produced and used for molding many times by a predetermined amount.

  Further, the viscosity of the slurry changes depending on the raw material powder concentration, and when this viscosity changes, the orientation during molding also changes. In the present invention, a slurry having a constant raw material powder concentration can be used for molding. Further, variation in the degree of orientation of the obtained magnet can be reduced. Further, in the present invention, the slurry used for the molding is produced for each molding, and therefore it is easy to change the raw material powder concentration in the slurry. Therefore, according to the present invention, it is possible to obtain an advantage that the set weight and size of the magnet can be easily changed.

  In the magnet manufacturing method of the present invention, it is preferable that in the molding process, molding is performed using a molding machine, and the entire amount of the slurry obtained in the slurry manufacturing process is supplied to the molding machine. In this way, the entire amount of the produced slurry can be reliably used for molding, and a magnet with a smaller weight variation can be produced.

  In the slurry production process, it is preferable to mix the raw material powder of the magnet and the dispersion medium to disperse the raw material powder in the dispersion medium. In this way, a slurry in which the raw material powder is uniformly dispersed is obtained, which makes magnetic field orientation during molding advantageous, and makes it possible to manufacture a magnet with a high degree of orientation.

  Furthermore, in the present invention, it is more preferable that the molding process is performed using a molding machine having a cavity in which the slurry is molded, and the slurry manufacturing process is performed in this cavity. If it carries out like this, after manufacture of a slurry, it can shape | mold immediately with high dispersibility, and the magnet which has a further outstanding orientation degree will be obtained. Further, if the slurry is formed and then moved to the molding machine via a connecting pipe or the like, the raw material powder or the dispersion medium may adhere to the connecting pipe or the like. Although there is a possibility that variations may occur, such a problem does not occur when the slurry is produced in the cavity.

  The magnet manufacturing apparatus according to the present invention is suitable for the above-described magnet manufacturing method of the present invention, and includes a slurry manufacturing apparatus for manufacturing a slurry by mixing raw material powder of a magnet and a dispersion medium, and molding of the slurry. A raw material powder supply means for supplying raw material powder and a dispersion medium in an amount corresponding to the slurry for one molding by the molding machine to the slurry manufacturing device, respectively. Dispersion medium supply means is provided.

  According to such a manufacturing apparatus, a slurry corresponding to one molding can be easily obtained by the raw material powder supply means and the dispersion medium supply means. If the slurry thus obtained is molded by a single molding as in the production method of the present invention, it is possible to reduce variations in the weight and orientation degree of each magnet obtained.

  The production apparatus of the present invention is more preferably provided with a slurry supply means for supplying the entire amount of the slurry produced by the slurry production apparatus to the molding machine. By such slurry supply means, it becomes possible to reliably supply the entire amount of slurry corresponding to one molding to the molding machine, and it becomes possible to manufacture magnets with even smaller weight variations.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method and manufacturing apparatus of a magnet which are easy to make small the dispersion | variation in the weight between the magnets obtained.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the positional relationship such as up / down / left / right is based on the positional relationship of the drawings.

  First, a magnet manufacturing apparatus according to a preferred embodiment will be described. FIG. 1 is a diagram schematically showing a magnet manufacturing apparatus according to a preferred embodiment. As shown in FIG. 1, the magnet manufacturing apparatus 1 includes a slurry manufacturing apparatus 10 and a molding machine 50 disposed below the slurry manufacturing apparatus 10.

  The slurry manufacturing apparatus 10 has a powder supply means 20 for supplying magnet raw material powder (hereinafter simply referred to as “raw material powder”) and a dispersion medium supply means 30 for supplying a dispersion medium. Below the powder supply means 20 and the dispersion medium supply means 30, a mixing tank 40 for receiving and mixing the raw material powder and the dispersion medium respectively supplied from these is disposed.

  The powder supply means 20 includes a powder tank 22 that stores the raw material powder, a powder metering unit 24 that measures the raw material powder fed from the powder tank 22, and a powder supply pipe 26 that supplies the raw material powder to the mixing tank 40 from here. It consists of and. The dispersion medium supply means 30 includes a dispersion medium tank 32 that contains the dispersion medium, a dispersion medium metering unit 34 that measures the dispersion medium sent out from the dispersion medium tank 32, and a dispersion medium from the dispersion medium tank 34 to the mixing tank 40. A dispersion medium supply pipe 36 is provided.

  The mixing tank 40 is a cylindrical member that is open at the top and bottom. The lower opening of the mixing tank 40 is closed by the shutter 44 being disposed. The shutter 44 can be operated to open an opening at the bottom of the mixing tank 40 by moving to the side. On the side wall of the mixing tank 40, a vibrator 42 for mixing and stirring the raw material powder and the dispersion medium supplied therein is provided.

  The molding machine 50 includes a cylindrical mold 52 and a lower punch 54 that is inserted into the space in the mold 52 from below. In the molding machine 50, slurry is supplied to the space in the mold 52 and molded. That is, the space in the mold 52 functions as a cavity of the molding machine 50.

  Above the molding machine 50, a piston 62 and an upper punch 60 are arranged in order from the bottom at a position facing the molding machine 50 across the mixing tank 40. The diameter of the piston 62 is substantially equal to the inner diameter of the mixing tank 40. The piston 62 is driven downward to function to extrude the slurry inside the mixing tank 40 through the inside of the mixing tank 40 and supply it to the mold 52.

  Next, a magnet manufacturing method using the magnet manufacturing apparatus 1 having such a configuration will be described. In the following description, a method for manufacturing a rare earth magnet particularly suitable for the present invention will be described.

  FIG. 2 is a flowchart showing a manufacturing process of a rare earth magnet according to a preferred embodiment.

  In manufacturing the rare earth magnet, first, an alloy is prepared so that a rare earth magnet having a desired composition can be obtained (step S11). In this process, for example, a simple substance, an alloy, a compound, or the like containing an element such as a metal corresponding to the composition of the rare earth magnet is dissolved in an inert gas atmosphere such as vacuum or argon, and then used for casting or stripping. An alloy having a desired composition is manufactured by performing an alloy manufacturing process such as a casting method.

  Here, examples of rare earth magnets include those containing mainly Nd and Sm as rare earth elements, and those having a composition in which a rare earth element and a transition element other than the rare earth element are combined are suitable. Specifically, R—Fe containing at least one of Nd, Pr and Dy as a rare earth element (represented by “R”), 1 to 12 atomic% of B as an essential element, and the balance being Fe. Those having a -B composition are preferred. Such a rare earth magnet has a composition further containing other elements such as Co, Ni, Mn, Al, Nb, Zr, Ti, W, Mo, V, Ga, Zn, and Si as required. May be.

  Next, the obtained alloy is coarsely pulverized to obtain particles having a particle size of about several hundred μm (step S12). 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. It can be performed by causing pulverization (hydrogen occlusion pulverization).

  Subsequently, the powder obtained by coarse pulverization is further finely pulverized (step S13), preferably 1 to 10 μm, more preferably rare earth magnet raw material powder having a particle size of about 1 to 5 μm (hereinafter simply referred to as “ The raw material powder ") is obtained. 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, and a wet attritor while appropriately adjusting conditions such as pulverization time. To do.

  After producing the raw material powder in this way, a molded body is produced by the magnet manufacturing apparatus 1 using this. That is, first, the raw material powder stored in the powder tank 22 is sent out from the powder tank 22 using a pump, a feeder, or the like. The raw material powder sent out from the powder tank 22 is weighed in the powder metering unit 24 (step S14). Here, the raw material powder is measured so that only the amount contained in the slurry for one molding in the molding process described later is sent out.

  In parallel with the measurement of the raw material powder, the dispersion medium is sent out from the dispersion medium tank 32, and the dispersion medium measurement unit 34 measures the amount to be contained in the slurry used for one molding (step S15). Here, as the dispersion medium, a solvent or the like used for the slurry in the wet molding of the magnet can be applied without particular limitation. Examples thereof include oils such as mineral oil, synthetic oil and vegetable oil, and organic solvents such as acetone and alcohol. Of these, oil is preferable in order to prevent oxidation of the raw material powder.

  The raw material powder and the dispersion medium measured by the powder measurement unit 24 and the dispersion medium measurement unit 34 are supplied into the mixing tank 40 through the powder supply pipe 26 and the dispersion medium supply pipe 36, respectively. At this stage, the shutter 44 is positioned so as to close the lower opening of the mixing tank 40, whereby the raw material powder and the dispersion medium are held in the mixing tank 40.

  When the raw material powder and the dispersion medium are supplied to the mixing tank 40, the vibrator 42 provided on the side wall is driven. Thereby, a vibration is applied to the mixture of the raw material powder and the dispersion medium in the mixing tank 40, and the raw material powder and the dispersion medium are mixed and stirred by this vibration to obtain a slurry in which the raw material powder is dispersed in the dispersion medium. (Step S16; slurry production process). In the slurry manufacturing process, as described above, since the raw material powder and the dispersion medium are supplied to the mixing tank 40 in an amount to be contained in the slurry for one molding, an amount of slurry corresponding to one molding is obtained. .

  After the slurry is prepared in the mixing tank 40, the shutter 44 located at the lower part of the mixing tank 40 is slid sideways, thereby opening the lower opening of the mixing tank 40. At the same time, the piston 62 is driven downward to enter the space in the mixing tank 40 from the upper opening. At this time, the powder supply pipe 26, the dispersion medium supply pipe 36, and the like are retracted so as not to disturb the movement of the piston 62.

  By such an operation of the piston 62, the slurry in the mixing tank 40 is pushed out from the lower opening, and the entire amount is supplied into the mold 52 in the molding machine 50. Note that the total amount here is an amount that can normally move the slurry from the mixing tank 40 to the mold 52, and in reality, a small amount of the raw material powder and the dispersion medium remain on the inner wall of the mixing tank 40. May be.

  When the slurry is supplied into the mold 52, the mixing tank 40 and the piston 62 inserted therein are retracted, and then the upper punch 60 is lowered and brought into contact with the upper part of the mold 52. Close the top opening of 52. At the same time, the lower punch 54 is moved upward. By such an operation, the slurry in the mold 52 is pressed and molded between the upper mold frame constituted by the lowered upper punch 60 and the lower punch 54 (step S17; molding process). Molding is performed in a magnetic field, whereby a magnetic field is applied to the slurry during molding. Thereby, the molded object which has a predetermined degree of orientation comes to be obtained. The magnetic field during molding can be applied, for example, by placing the mold 52 in the magnetic field. In addition, the shape of the molded object obtained by shaping | molding is not restrict | limited in particular, It can change according to the shapes of desired rare earth magnets, such as columnar shape, flat plate shape, and ring shape.

  Since the slurry is pressurized during molding, the dispersion medium in the slurry flows out. Therefore, it is preferable to perform the molding while extracting the dispersion medium that has flowed out of the slurry. Therefore, for example, the upper punch 60 or the lower punch 54, which is the upper mold, may be provided with a hole communicating with the outside in order to extract the dispersion medium. However, it is necessary to prevent outflow of the raw material powder in the slurry. For this purpose, a filter made of cloth, paper, or the like is disposed on the pressing surface, or a part of the upper punch 60 or the lower punch 54 is disposed. The material is preferably porous.

The pressing direction during molding may be the same as the magnetic field application direction, or may be perpendicular to the magnetic field application direction. However, if pressurization is performed perpendicular to the magnetic field application direction, better magnetic properties can be obtained. It tends to be. Moreover, the magnetic field intensity at the time of shaping | molding can be 12-20 kOe (960-1600 kA / m), and a pressurization can be 0.3-3 ton / cm < ² > (30-300 MPa). Furthermore, the molding time is preferably several seconds to several tens of seconds. By forming in a magnetic field under such conditions, a rare earth magnet having good magnetic properties tends to be easily obtained.

  Thus, after forming a molded object by the magnet manufacturing apparatus 1, the dispersion medium which removes the dispersion medium, lubricant, etc. which remain | survived in the molded object by performing vacuum heating with respect to the obtained molded object, for example. A process is performed (step S18; dedispersion medium process). It is preferable that the dedispersion medium is heated to 50 to 200 ° C. for 1 to 5 hours under a condition where most of the organic solvent and the like in the molded body can be removed, for example, under a pressure reduced to about 10 to 3000 Pa.

  Thereafter, the molded body from which the dispersion medium has been removed is fired to obtain a sintered body (step S19; firing process). Firing can be performed, for example, by heating the molded body at 1000 to 1200 ° C. for 1 to 10 hours in a vacuum or in the presence of an inert gas, and then rapidly cooling.

  After firing, the sintered body is subjected to an aging treatment by heating the sintered body at a temperature lower than that during firing (step S20). The aging treatment is, for example, two-stage heating for 1 to 3 hours at 700 to 900 ° C., and further 1 to 3 hours at 500 to 700 ° C. Perform under conditions. Such an aging treatment can improve the magnetic properties of the sintered body.

  And the target rare earth magnet is obtained by performing the process which cut | disconnects to the desired size with respect to the sintered compact obtained in this way, or smoothes the surface. The obtained rare earth magnet may further be provided with a protective layer for preventing deterioration of the oxide layer, the resin layer, etc. on the surface.

  In the manufacturing method of the rare earth magnet of the embodiment described above, only the slurry for one molding is manufactured at the time of manufacturing the slurry, and the entire amount thereof is used for molding.For example, the slurry is manufactured and stored in large quantities, The raw material powder concentration of the slurry used for molding can be made constant as compared with the case where the required amount is taken out and molding is performed. Therefore, according to such a method, it is possible to reduce the weight variation of the obtained magnet, and as a result, it is possible to greatly reduce the size variation and magnetic property variation of the sintered body. In addition, since the slurry is produced for each molding, there is an advantage that it is possible to easily and inexpensively produce a small variety of products with different compositions and shapes.

  As mentioned above, although the manufacturing method of the rare earth magnet was demonstrated as suitable embodiment of the manufacturing method of the magnet of this invention, this invention is not necessarily limited to embodiment mentioned above. For example, in the embodiment described above, the slurry is manufactured in the mixing tank 40, but such a mixing tank 40 may be omitted. That is, for example, a vibrator 42 similar to the mixing tank 40 is provided in the mold 52, the raw material powder and the dispersion medium are directly supplied into the mold 52, the slurry is produced in the mold 52, and then the molding is performed as it is. You may make it perform. By so doing, it is possible to eliminate the loss inevitably caused when the slurry is supplied from the mixing tank 40 to the mold 52.

  In addition, the mixing of the raw material powder and the dispersion medium is not limited to the method using the vibrator 42. For example, a stirring blade may be disposed in the mixing tank 40 and rotated. Instead of 40, other methods that can uniformly mix two or more components may be applied. Examples of such a method include a method using a ball mill, a homogenizer, an optimizer and the like.

  Furthermore, in the above embodiment, the method of forming one molded body by one molding has been described as an example, but the entire amount of the slurry manufactured in the slurry manufacturing process is molded by one molding. As long as it is not limited to such an example. For example, a molding machine having a plurality of cavities may be used, slurry may be supplied to each of the plurality of cavities, and all of these may be molded at once. Furthermore, the present invention includes a case where a number of slurry production apparatuses corresponding to a plurality of cavities of a molding machine are provided, slurry is supplied to each cavity from the individual slurry production apparatuses, and these are molded at a time.

  Furthermore, the present invention is not limited to the rare earth magnets described above, and can be applied to any sintered magnet obtained by sintering magnetic powder, such as other metal magnets and ferrite magnets.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Preparation of magnet raw material powder]

  First, raw material powders of rare earth (Nd—Fe—B-based) magnets and ferrite magnets used in the following Examples and Comparative Examples were prepared according to the following production methods.

(Nd-Fe-B raw material powder)
First, a raw material alloy having a composition of 26.5 wt% Nd-5.9 wt% Dy-0.25 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-Fe by strip casting. Was made. Next, after hydrogen was occluded in the raw material alloy at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere.

  Then, 0.05 to 0.1% of a lubricant that improves the pulverization property and the orientation during molding was mixed with the alloy subjected to the hydrogen pulverization treatment. This lubricant was mixed for about 5 to 30 minutes using, for example, a Nauta mixer. Thereafter, a raw material powder having an average particle diameter of 5.0 μm was obtained using a jet mill.

(Ferrite raw material powder)
As starting materials, iron oxide (Fe ₂ O ₃ ), strontium carbonate (SrCO ₃ ), and lanthanum hydroxide (La (OH) ₃ ) were prepared. These starting materials were weighed so that the main composition after firing was Sr _0.8 La _0.2 Co _0.15 Fe _11.85 O ₁₉ . This mixed raw material was mixed and pulverized with a wet attritor for 2 hours to obtain a slurry-like raw material composition. After drying the slurry, calcination was performed in the atmosphere at 1100 to 1150 ° C. for 2.5 hours. The obtained calcined powder was coarsely pulverized with a small rod vibration mill for 10 minutes.

Next, silicon oxide (SiO ₂ ) was added to the obtained coarsely pulverized powder so as to be 0.6 wt% with respect to the main component, and calcium carbonate (CaCO ₃ ) was added so as to be 1.4 wt%. Further, 0.5 wt% sorbitol was added, and pulverization was performed by a wet ball mill until the specific surface area (BET value 8.5 m ² / g) was reached. The solid content concentration of the finely pulverized slurry thus obtained was adjusted to 70 to 75%.
[Manufacture of magnets]

  Using the above raw material powder, magnets were produced according to the methods of the following Examples and Comparative Examples.

(Example: Nd-Fe-B magnet)
First, 20 g of Nd—Fe—B-based raw material powder was weighed and put into a mixing tank from a supply pipe. This mixing tank is installed on the upper part of the mold. In addition, mineral oil was added as a dispersion medium from a supply pipe to a mixing tank using a tube pump so that the Nd—Fe—B-based raw material powder was 75 wt%. After feeding the Nd—Fe—B-based raw material powder and the dispersion medium, the two supply pipes were retracted from the mixing tank. Next, the piston was lowered into the mixing tank, and the Nd—Fe—B raw material powder and the dispersion medium were sealed in the mixing tank. Then, ultrasonic vibration was applied to both by an ultrasonic transducer installed on the inner wall of the mixing tank for 30 seconds, and this was used as a slurry.

  Thereafter, the shutter at the bottom of the mixing tank was opened, and the piston was further lowered, thereby pushing out all the slurry in the mixing tank into the mold. Note that the inside of the mold is a space formed by the mold and a lower punch inserted into the mold from below. After retracting the piston and mixing tank from the upper part of the mold, the upper punch was lowered and brought into contact with the upper part of the mold to seal the slurry in the mold. In addition, as the upper punch, a plurality of through-holes were used, and the through-holes were connected to a vacuum pump through a tube.

A 1.5 T magnetic field was applied in the mold in the horizontal direction by a magnetic field application device installed on both sides of the mold. Then, while raising the lower punch, the vacuum pump was started so that the liquid in the slurry could be sucked out from the through hole. A pressure of 1 ton / cm ² (100 MPa) was applied by a lower punch, this was held for 5 seconds, and a magnetic field was applied in the opposite direction for 1 second. Thereafter, the upper punch was raised, and then the mold was lowered, and the molded body obtained by pressurization in a magnetic field was taken out from the mold. Molding was performed so that the shape of the molded body was 18 mm long × 20 mm wide × 13 mm high.

  Then, a dedispersion medium was applied to the obtained molded body. The conditions for the dedispersion medium were 150 ° C. and 5 hours in vacuum. Next, this compact was heated to 1080 ° C. in a vacuum and in an Ar atmosphere, and sintered for 4 hours. The obtained sintered body was subjected to a two-stage aging treatment of 800 ° C. × 1 hour and 560 ° C. × 1 hour (both in an Ar atmosphere). This obtained the Nd-Fe-B magnet.

(Example: ferrite magnet)
Using a ferrite raw material powder, a compact was produced in the same manner as in the case of the NdFeB magnet. Molding was performed so that the shape of the molded body was 18 mm long × 20 mm wide × 19 mm high. The obtained molded body was sufficiently dried at room temperature in the air, and then baked by being held at 1180 to 1220 ° C. in the air for 1 hour. Thereby, a ferrite magnet was obtained.

(Comparative example: Nd-Fe-B magnet)
A predetermined amount of Nd—Fe—B raw material powder was weighed and put into a slurry tank. Further, a predetermined amount of mineral oil as a dispersion medium was put into a slurry tank by a pump. At this time, the slurry concentration was set to 75 wt%. The slurry in the slurry tank was stirred for 10 hours with a stirring blade.

  Of the slurry thus prepared, a constant volume of slurry was introduced into the mold through the supply pipe so that the slurry amount was about 27 g per molding. A feed pump was used for charging. Next, after the supply pipe was retracted from the upper part of the mold, the upper punch was lowered and the slurry was sealed in the mold by bringing it into contact with the upper part of the mold. In addition, as the upper punch, a plurality of through-holes were used, and the through-holes were connected to a vacuum pump through a tube.

A 1.5 T magnetic field was applied in the mold in the horizontal direction by a magnetic field application device installed on both sides of the mold. Then, while raising the lower punch, the vacuum pump was started so that the liquid in the slurry could be sucked out from the through hole. A pressure of 1 ton / cm ² (100 MPa) was applied by a lower punch, this was held for 5 seconds, and a magnetic field was applied in the opposite direction for 1 second. Thereafter, the upper punch was raised, and then the mold was lowered, and the molded body obtained by pressurization in a magnetic field was taken out from the mold. Molding was performed so that the shape of the molded body was 18 mm long × 20 mm wide × 13 mm high. The obtained molded body was dedispersed and fired in the same manner as in the example to obtain an Nd—Fe—B magnet.

(Comparative example: Ferrite magnet)
A comparative ferrite magnet was produced in the same manner as in the case of the Nd—Fe—B magnet except that the ferrite raw material powder was used. In addition, shaping | molding performed so that the shape of a molded object might become 18 mm long x 20 mm wide x 19 mm in height.
[Characteristic evaluation]

  About the manufacturing method of the NdFeB magnet and the ferrite magnet in an Example and a comparative example, it evaluated by the following method, respectively. In addition, about each Example and the comparative example, multiple types of slurry was prepared, the magnet was manufactured, respectively, and all were evaluated similarly. The results obtained are summarized in Table 1.

(Measurement method of weight variation and dimensional variation)
For each example and comparative example, 50 molded bodies were prepared for each slurry. And the average value and standard deviation of 50 molded objects corresponding to each Example or Comparative Example were obtained. Then, the standard deviation was divided by the average value, and this was multiplied by 100 to calculate the weight variation (%). In addition, the dimensional variation was calculated in the same manner as described above for the height value obtained for each molded body.

  From Table 1, in the example where the entire amount of slurry used for one molding was used for molding, compared with the comparative example in which only a necessary amount was taken out after storing the slurry in the slurry tank, It was confirmed that the dimensional variation was reduced. Further, it has been found that such an effect is remarkable in a rare earth (Nd—Fe—B) magnet.

It is a figure which shows schematically the manufacturing apparatus of the magnet of suitable embodiment. It is a flowchart which shows the manufacturing process of the rare earth magnet which concerns on suitable embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnet manufacturing apparatus, 10 ... Slurry manufacturing apparatus, 20 ... Powder supply means, 22 ... Powder tank, 24 ... Powder measuring part, 26 ... Powder supply pipe, 30 ... Dispersion medium supply means, 32 ... Dispersion medium tank, 34 ... Dispersion medium metering device 36 ... Dispersion medium supply pipe 40 ... Mixing tank 42 ... Vibrator 44 ... Shutter 50 ... Molding machine 52 ... Die 54 ... Lower punch 60 ... Upper punch 62 ... Piston

Claims (6)

A slurry manufacturing process for obtaining a slurry containing a raw material powder of a magnet and a dispersion medium;
A molding step of molding the slurry to obtain a molded body;
A firing step of firing the molded body,
In the slurry manufacturing process, an amount of slurry corresponding to one molding performed in the molding process is manufactured,
The said manufacturing process WHEREIN: The whole quantity of the slurry obtained at the said slurry manufacturing process is shape | molded at once, The manufacturing method of the magnet characterized by the above-mentioned.   2. The magnet manufacturing method according to claim 1, wherein in the molding step, molding is performed using a molding machine, and the entire amount of the slurry obtained in the slurry manufacturing step is supplied to the molding machine.   The magnet manufacturing method according to claim 1 or 2, wherein, in the slurry manufacturing step, the raw material powder of the magnet and the dispersion medium are mixed and the raw material powder is dispersed in the dispersion medium. The molding step is performed using a molding machine having a cavity in which slurry is molded, and
The said slurry manufacturing process is performed in the said cavity, The manufacturing method of the magnet as described in any one of Claims 1-3 characterized by the above-mentioned. A slurry production apparatus for producing a slurry by mixing a raw material powder of a magnet and a dispersion medium;
A molding machine for molding the slurry,
The slurry production apparatus is provided with raw material powder supply means and dispersion medium supply means for supplying the raw material powder and the dispersion medium in an amount corresponding to the slurry for one molding by the molding machine to the slurry production apparatus, respectively. Being
A magnet manufacturing apparatus characterized by the above.   The magnet manufacturing apparatus according to claim 5, further comprising a slurry supply unit that supplies the entire amount of the slurry manufactured by the slurry manufacturing apparatus to the molding machine.

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