JP4167292B1 - Magnet manufacturing method - Google Patents

Abstract

A magnet manufacturing method capable of sufficiently improving the magnetic properties of the obtained magnet is provided.
A kneading step of kneading a raw material powder of a magnet and a solvent to obtain a kneaded product, a diluting step of diluting the kneaded product to obtain a slurry, and forming at least a part of the slurry while applying an orientation magnetic field. The manufacturing method of the magnet including the process of depressurizing a slurry including the forming process which makes a formed object, and the baking process of baking a formed object.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a magnet.

Magnets are used in motors, motors such as generators, and magnetic products such as hard disk drives, and such magnets are required to have high magnetic properties. As a method for producing a magnet having such a high magnetic property, a method in which a raw material powder of a magnet is mixed with a solvent such as oil or an organic solvent and then a wet molding process is performed in which a slurry is formed and then sintered. It has been known. For example, in the magnet manufacturing method of Patent Document 1 below, the raw material powder of the magnet is collected in an oil-based solvent without being exposed to the atmosphere, mixed with stirring, the concentration of the resulting slurry is adjusted, and then the mold is molded into the mold of the molding machine. The molded body thus obtained is fired.
JP-A-9-289127

  However, the above-described conventional magnet manufacturing method described in Patent Document 1 cannot obtain a magnet having a sufficiently high residual magnetic flux density and density, and still has room for improvement in terms of improving the magnetic properties of the magnet. Was.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the magnet which can fully improve the magnetic characteristic of the magnet obtained.

  As a result of repeated investigations on the cause of the above problem, the present inventors have found that bubbles mixed in the slurry leave pores in the molded body, reduce the density of the obtained magnet, and apply an orientation magnetic field. It was thought that the magnetic field orientation of the raw material powder of the magnet might be disturbed to reduce the degree of orientation and the residual magnetic flux density. As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention includes a kneading step to obtain a kneaded product by kneading a raw material powder and a solvent of a rare earth magnet, and diluted to obtain a slurry by diluting the kneaded product, a step of depressurizing the slurry, the vacuum This is a method for producing a rare earth sintered magnet, comprising a forming step of forming a formed body by subjecting the slurry that has been subjected to pressure forming while applying an orientation magnetic field, and a firing step of firing the formed body.

  According to the production method of the present invention, the kneaded material of the magnet raw material powder and the solvent is diluted to form a slurry, and the slurry is decompressed to expel bubbles in the slurry. For this reason, the number of pores remaining in the molded body is reduced by the bubbles in the slurry, and the density of the obtained magnet can be improved. Further, since bubbles in the slurry are driven out, the magnetic field orientation of the magnet raw material powder is hardly disturbed during application of the orientation magnetic field. For this reason, the fall of an orientation degree is suppressed and a residual magnetic flux density can be improved.

The step of depressurizing the slurry and the molding step are performed in a cavity of the same mold, the slurry is accommodated in the cavity of the mold, the slurry in the cavity is depressurized, and the cavity it is preferred that the slurry of the inner and pressure molding while applying an orientation magnetic field comprises a molded body.

  In this case, a part of the slurry is accommodated in the mold cavity, and the slurry in the cavity is decompressed. For this reason, it is possible to easily perform sufficient deaeration in a short time as compared with the case where the whole slurry obtained by diluting the kneaded product or the slurry in the stock tank is decompressed. In addition, since the slurry can be decompressed and then transferred to the molding of the slurry as it is, re-mixing of air accompanying the transfer of the slurry after decompression can be avoided. Therefore, it is possible to obtain a magnet having a higher density and a magnet having a higher residual magnetic flux density.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the magnet which can fully improve the magnetic characteristic of the obtained magnet is provided.

  Hereinafter, an embodiment of a magnet manufacturing method according to the present invention will be described. In the following description, a method for producing a rare earth magnet particularly suitable for the present invention will be described as an example.

(First embodiment)
First, prior to the description of the method for manufacturing a rare earth magnet, a device for manufacturing a rare earth magnet will be described. FIG. 1 is a flowchart schematically showing an example of a magnet manufacturing apparatus for performing the magnet manufacturing method according to the present embodiment. As shown in FIG. 1, a magnet manufacturing apparatus 100 includes a slurry manufacturing apparatus 1 that manufactures a slurry containing raw material powder that is a raw material of a rare earth magnet and a solvent that disperses the raw material powder. The slurry manufacturing apparatus 1 includes a container 2, a stirring member 3 disposed in the container 2, and a stirring drive unit 4 that rotationally drives the stirring member 3. Here, a vacuum pump 17 is connected to the container 2 via an exhaust pipe 16. Further, the container 2 is sealed by a stirring drive unit 4.

  A container 2 of the slurry production apparatus 1 is connected to a stock tank 6 via a slurry transfer pipe 5. A liquid feed pump 7 is installed in the slurry transfer pipe 5. An agitating member 8 is disposed inside the stock tank 6, and the slurry in the stock tank 6 can be agitated and mixed by its rotational drive. A vacuum pump 10 is connected to the stock tank 6 through an exhaust pipe 9.

  The stock tank 6 is connected to a molding machine 12 via a slurry transfer pipe 11. In the slurry transfer pipe 11, a circulation pump 13 and a molding machine filling pump 14 are installed sequentially from the stock tank 6. A return pipe 15 for returning the slurry to the stock tank 6 extends from between the circulation pump 13 and the molding machine filling pump 14 to the slurry transfer pipe 11.

  Next, a method for manufacturing a rare earth magnet using the magnet manufacturing apparatus 100 will be described.

  In the production of a rare earth magnet, first, an alloy is prepared so that a rare earth magnet having a desired composition can be obtained. 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, as the rare earth magnet, a magnet having a composition in which a rare earth element and a transition element other than the rare earth element are combined is 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. The rare earth magnet may have an Sm—Co composition containing Sm and Co.

  Next, the obtained alloy is coarsely pulverized to obtain particles having a particle size of about several hundred μm. 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).

  Subsequently, the powder obtained by coarse pulverization is further finely pulverized to obtain a rare earth magnet raw material powder (hereinafter simply referred to as “raw material powder”) having a particle size of 10 μm or less, preferably 1 to 10 μm. 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, the raw material powder and the solvent in which the raw material powder is dispersed are kneaded in the slurry production apparatus 1 to obtain a kneaded product (kneading step).

  In the slurry manufacturing apparatus 1, the raw material powder is put into the container 2. On the other hand, the container 2 is charged with a solvent and, if necessary, an additive. And the stirring drive part 4 is driven, the stirring member 3 is rotationally driven, and raw material powder and a solvent are stirred and mixed.

  At this time, the ratio of the input amount of the raw material powder and the input amount of the solvent is adjusted so that the solid content concentration is preferably 85 to 95% by weight, more preferably 88 to 94% by weight. When the solid content concentration is 85 to 95%, as compared with the case where the solid content concentration is out of the range, an appropriate load is applied to the kneaded product, and the raw material powder is sufficiently wetted by the solvent. The raw material powder can be dispersed more effectively. The kneading time is preferably 10 minutes or longer. In this case, as compared with the case of less than 10 minutes, kneading is sufficiently performed, and the ratio of the remaining secondary particles (aggregated particles) can be sufficiently reduced.

  In addition, as a solvent, organic solvents, such as acetone and hexane, mineral oil, synthetic oil, vegetable oil, etc. are used, for example. Among these, oily solvents such as mineral oil, synthetic oil, vegetable oil and the like are preferable from the viewpoint of preventing oxidation of the raw material powder. Moreover, since it is hard to volatilize by the pressure reduction of the slurry mentioned later, it is preferable to use the solvent whose boiling point is 200 degreeC or more.

  After kneading the raw material powder and the solvent as described above to obtain a kneaded product, a solvent is added to the kneaded product in the container 2, and the kneaded product is diluted to, for example, 60 to 80% by weight to obtain a slurry ( Dilution step). The solvent to be added to the kneaded product can be appropriately selected from the above-mentioned solvents and is usually the same solvent as the solvent used for kneading with the raw material powder.

  After obtaining the slurry in this manner, the vacuum pump 17 is operated, and the inside of the container 2 is exhausted through the exhaust pipe 16 to decompress the inside of the container 2 (decompression step). Thereby, since pressure reduction of a slurry is performed, the air in a slurry can be driven out.

  Here, the inside of the container 2 is preferably decompressed to 66.66 kPa (500 Torr) or less. In this case, compared with the case where the inside of the container 2 is depressurized to a pressure exceeding 66.66 kPa, the magnetic properties of the obtained magnet can be improved more sufficiently.

  The inside of the container 2 is more preferably decompressed to 26.66 kPa (200 Torr) or less. In this case, the air in the slurry can be effectively expelled. For this reason, compared with the case where the inside of the container 2 is depressurized to a pressure outside the above range, the magnetic properties of the obtained rare earth magnet can be further improved. However, for defoaming in the slurry, even if a high vacuum such as less than 1.33 Pa (0.01 Torr) is used, there is no significant difference in the effect, and there is a concern about the volatilization of the solvent. . The time for depressurization is, for example, 5 seconds to 30 minutes, depending on the amount of slurry to be treated and the degree of vacuum.

  Next, the liquid feed pump 7 is operated to transfer the slurry in the container 2 to the stock tank 6 through the slurry transfer pipe 5. In the stock tank 6, the stirring member 8 is rotated to stir the slurry. The slurry in the stock tank 6 is discharged from the stock tank 6 by operating the circulation pump 13, and then returned to the stock tank 6 through the slurry transfer pipe 11 and the return pipe 15 and circulated. Thus, the dispersibility of the raw material powder in the slurry can be improved.

  At this time, it is preferable to depressurize the inside of the stock tank 6 by operating the vacuum pump 10 and exhausting the inside of the stock tank 6 through the exhaust pipe 9. Thereby, even if air is remixed in the slurry during the transfer from the slurry manufacturing apparatus 1 to the stock tank 6, the air can be driven out again, and the state in which the air is extremely low in the slurry can be maintained. it can. At this time, the pressure inside the stock tank 6 may be reduced in the same manner as the pressure inside the container 2 described above. However, regarding the time for depressurization, it is preferable to keep the slurry in a depressurized state at all times because the slurry is always circulated.

  The slurry in the stock tank 6 is closed by closing a valve (not shown) installed in the return pipe 15, opening a valve (not shown) installed in the slurry transfer pipe 11, and operating the circulation pump 13. Part of the slurry in the stock tank 6 is injected into the molding machine filling pump 14. A predetermined amount of slurry is supplied to the molding machine 12 by operating the molding machine circulation pump 14 at a predetermined timing.

  In the molding machine 12, the slurry is subjected to pressure molding while applying an orientation magnetic field in a certain direction to obtain a molded body (molding step). For example, the molding is performed by filling the slurry in the cavity of the mold. Here, the mold includes, for example, a cylindrical die having a through hole, an upper punch disposed on the upper end side of the through hole to close the through hole, and a lower punch inserted from the lower end side of the through hole. Things are used. The cavity of the mold is constituted by a space surrounded by an inner wall surface that forms a through hole of the die, and a lower punch and an upper punch. The pressure molding is performed by sandwiching the slurry between the upper punch and the lower punch.

  For the slurry, the solvent in the slurry is removed. In this case, if the solvent discharge hole for discharging the solvent is provided on the contact surface of the upper punch and the lower punch of the mold that contacts the slurry, the solvent can be removed simultaneously with the molding. Here, it is preferable that the contact surfaces of the upper punch and the lower punch are covered with a filter made of cloth, paper, or the like because the raw material powder can be prevented from flowing out during pressure molding. Instead of covering the contact surfaces of the upper punch and the lower punch with a filter, a part of the upper punch and the lower punch may be made of a porous filter material.

  Next, a desolvation step for removing the solvent and additives remaining in the molded body is performed on the molded body obtained as described above by, for example, vacuum heating. The solvent removal step is performed under such a condition that most of the solvent in the molded body can be removed. For example, it is preferably heated at 100 to 160 ° C. for 1 to 5 hours under a reduced pressure of about 10 to 3000 Pa. In this solvent removal step, sintering of the molded body usually does not proceed, but partial sintering may proceed. Thereafter, the desolvated compact is heated to the sintering temperature and held at that temperature for a certain period of time. That is, the molded body is fired. Thus, the molded body is used as a sintered body (firing step). 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 obtained sintered body is subjected to an aging treatment by heating the sintered body at a temperature lower than that during firing. The aging treatment is, for example, two-stage heating in which heating is performed at 700 to 900 ° C. for 1 to 3 hours, further heating at 500 to 700 ° C. for 1 to 3 hours, or one-stage heating in which heating is performed at around 450 to 600 ° C. for 1 to 3 hours. It carries out on the appropriate conditions. Such an aging treatment can improve the holding force (Hc) and the like.

  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 as mentioned above, 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.

  When the rare earth magnet is manufactured as described above, the kneaded product of the raw material powder and the solvent is diluted to form a slurry, and then the slurry is decompressed to expel bubbles in the slurry. For this reason, the number of pores remaining in the molded body is reduced by the bubbles in the slurry, and the density of the obtained magnet can be improved. Further, since bubbles in the slurry are driven out, the magnetic field orientation of the magnet raw material powder is hardly disturbed during application of the orientation magnetic field. For this reason, the fall of an orientation degree is suppressed and a residual magnetic flux density can be improved.

(Second Embodiment)
Next, 2nd Embodiment of the manufacturing method of the magnet which concerns on this invention is described using FIG.2 and FIG.3. 2 and 3, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals. FIG. 2 is a flowchart schematically showing an example of a magnet manufacturing apparatus for performing the magnet manufacturing method according to the present embodiment.

  The magnet manufacturing method according to the present embodiment is different in that a magnet manufacturing apparatus 200 shown in FIG. 2 is used instead of the magnet manufacturing apparatus 100 of FIG. 1 as a magnet manufacturing apparatus.

  As shown in FIG. 2, the magnet manufacturing apparatus 200 of the present embodiment omits the stock tank 6, the vacuum pump 10, the exhaust pipe 9, the circulation pump 13, and the return pipe 15 in FIG. The pipe 11 is connected to the slurry transfer pipe 18 and is different from the magnet manufacturing apparatus 100 in that a molding machine 22 is used instead of the molding machine 12.

  Here, the molding machine 22 will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing the molding machine 22, wherein (a) to (c) respectively show a step of filling the mold with slurry, a step of decompressing the slurry in the cavity, and a slurry in the cavity. The process of pressure forming is shown. As shown in FIG. 3A, the molding machine 22 includes a cylindrical die 23 having a through hole 23a, and a lower punch that is slidably inserted into the through hole 23a from the lower end side of the die 23. 24 and an upper punch 25 that closes the through hole 23 a from the upper end side of the die 23. The upper punch 25 has a flat plate shape, for example, and has a contact surface 25a that closes the through hole 23a of the die 23 and contacts the slurry. A plurality of intake holes 25b are formed in the contact surface 25a, and the intake holes 25b communicate with the air collecting chamber 25c inside the upper punch 25. The upper punch 25 is connected to an exhaust pipe 26 communicating with the air collecting chamber 25c, and the exhaust pipe 26 is connected to a vacuum pump 27. Further, the upper punch 25 is movable in the extending direction of the die 23 (the direction of arrow A in FIG. 3A). Accordingly, when the lower punch 24 is inserted into the through hole 23a of the die 23 and the upper punch 25 is brought into contact with the die 23 and closes the through hole 23a, the inner wall surface 23b forming the through hole 23a, A cavity 28 is formed by the punch 24 and the upper punch 25. When the vacuum pump 27 is operated, the air inside the cavity 28 is collected in the air collecting chamber 25c through the intake hole 25b and discharged through the exhaust pipe 26.

  Next, a method for manufacturing a rare earth magnet using the magnet manufacturing apparatus 200 will be described.

  First, the raw material powder and the solvent are kneaded in the slurry production apparatus 1 in the same manner as in the first embodiment to obtain a kneaded product (kneading step).

  After kneading the raw material powder and the solvent as described above to obtain a kneaded product, the solvent is added to the kneaded product in the container 2 in the same manner as in the first embodiment, and the kneaded product is diluted to obtain a slurry. obtain.

  After the slurry is thus obtained, the liquid feed pump 7 is operated, and a part of the slurry in the container 2 is transferred to the molding machine 22 through the slurry transfer pipe 18.

  In the molding machine 22, the lower punch 24 is inserted in advance into the through hole 23a of the die 23 from the lower end side of the die 23 (see FIG. 3A). In this state, the slurry is put into the through hole 23 a of the die 23.

  After the completion of the addition of the slurry, the upper punch 2 is moved and brought into contact with the upper end of the die 23 to close the through hole 23a of the die 23. Thus, the cavity 28 is formed by the lower punch 24, the upper punch 25, and the inner wall surface 23b of the through hole 23a of the die 23 (see FIG. 3B). Next, the vacuum pump 27 is operated. Then, the air in the cavity 28 is exhausted through the filter 29, the intake hole 25 b, the air collection chamber 25 c, and the exhaust pipe 26. Thus, the pressure inside the cavity 28 is reduced. Thereby, pressure reduction of a slurry is performed and the air in the slurry 30 can be driven out. In addition, what is necessary is just to perform the pressure of the pressure reduction inside the cavity 28 similarly to the case where the pressure inside the container 2 performed in 1st Embodiment is pressure-reduced. However, the decompression time is preferably a time that does not affect the molding cycle. The time that does not affect the molding cycle is, for example, 5 to 20 seconds.

  Next, as shown in FIG. 3 (b), the lower punch 24 is slid toward the upper punch 25 along the direction of arrow B in FIG. 3 (b), and as shown in FIG. 25 and the lower punch 24 sandwich and pressurize the slurry 30 to form a molded body (molding step). At this time, an orientation magnetic field is applied to the slurry 30 in a certain direction by a magnetic field generator (not shown). The decompression of the cavity 28 is finished before molding and may not be performed during molding, but is preferably performed not only before molding but also during molding. When the cavity 28 is depressurized, that is, the slurry 30 is depressurized not only before molding but also during molding, the slurry 30 is removed during the molding, and the solvent is sufficiently removed from the slurry 30. Can do. At this time, it is preferable that the contact surface 25a of the upper punch 25 is covered with a filter 29 made of cloth, paper, or the like because the raw material powder can be prevented from flowing out during pressure molding.

  The molded body obtained as described above is fired and subjected to an aging treatment to finally obtain a target rare earth magnet. The firing and aging treatment may be performed in the same manner as in the first embodiment.

  When the rare earth magnet is manufactured as described above, the bubbles in the slurry 30 are expelled by reducing the pressure of the slurry 30 after the formation of the slurry 30, so that the degree of orientation of the obtained rare earth magnet is similar to that of the first embodiment. The decrease is suppressed and the residual magnetic flux density can be improved.

  In particular, in this embodiment, a part of the slurry in the container 2 of the slurry production apparatus 1 is filled in the cavity 28 of the molding machine 22 and the slurry 30 in the cavity 28 is decompressed. For this reason, it becomes possible to perform sufficient deaeration easily in a short time compared with the case where pressure reduction is applied to all of the slurry in the stock tank 6. Further, since the slurry 30 can be depressurized and then transferred to the forming of the slurry 30 as it is, re-mixing of air accompanying the transfer of the slurry 30 after depressurization can be avoided. Therefore, it is possible to obtain a rare-earth magnet having a higher density and a higher-density rare-earth magnet.

  The present invention is not limited to the above embodiment. For example, in the magnet manufacturing apparatus 100 of the first embodiment, the slurry is depressurized in either the slurry manufacturing apparatus 1 or the stock tank 6, but it is sufficient that the slurry is depressurized in any one of them. However, it is preferable to depressurize the slurry in the stock tank 6 because the distance between the stock tank 6 and the molding machine 12 is closer and less re-mixing of the air after depressurization is required.

  Moreover, although the pressure reduction of the slurry is performed by the magnet manufacturing apparatus 200 of the said 2nd Embodiment, the slurry manufacturing apparatus 1, or the molding machine 22, the pressure reduction of the slurry should just be performed in any one. However, in that case, it is preferable to depressurize the slurry with the molding machine 22 because it is possible to effectively depressurize the slurry.

  Moreover, in the said 1st and 2nd embodiment, although demonstrated about the manufacturing method of the rare earth magnet as an example, the manufacturing method of the magnet which concerns on this invention is not limited to the manufacturing method of a rare earth magnet, Wet forming It is applicable also to the manufacturing method of the magnet which applies. Examples of the magnet manufactured by applying such wet forming include a sintered magnet obtained by sintering magnetic powder such as a ferrite magnet.

  Moreover, in the said embodiment, although organic solvents, such as acetone and hexane, and oil-based solvents, such as mineral oil, synthetic oil, and vegetable oil, are used as a solvent to disperse | distribute raw material powder, a solvent is not limited to these. . For example, when the magnet manufactured by the manufacturing method of the present invention is a ferrite magnet that is an oxide, an aqueous solvent such as water can be used as the solvent used in the present invention. Even in this case, if the air adhering to the surface of the raw material powder is separated, it is possible to go around the raw material powder.

  Further, in the first embodiment, the molded product may be desolvated after the kneaded product is molded. However, the desorbing treatment can be performed simultaneously with the firing.

  In the first and second embodiments, the slurry is supplied to the stock tank or the molding machine. However, before supplying the slurry to the stock tank or the molding machine, if necessary, the slurry is dispersed by a homogenizer, an ultrasonic dispersing machine, or the like. Processing may be performed. In this case, primary particles of secondary particles can be sufficiently prevented, and the degree of orientation of the obtained rare earth magnet, and thus the residual magnetic flux density, can be further improved.

  Hereinafter, although the content of the present invention will be described more specifically with reference to examples and comparative examples, the present invention is not limited to the following examples.

(Example 1)
Nd: 24 atomic%, Dy: 6.8 atomic%, Al: 0.2 atomic%, Co: 0.5 atomic%, Zr: 0.2 atomic%, B: 1.0 atomic%, and the balance The ingot in which Fe is Fe was coarsely pulverized. Then, the pulverized product was finely pulverized in a nitrogen atmosphere until the average particle diameter became 4 μm using a jet mill to obtain a fine powder as a rare earth magnet raw material powder.

  Next, the fine powder, the dispersant, and the synthetic oil having a distillation point of 200 to 250 ° C. obtained as described above were charged into a container so that the solid concentration was 92% by mass, and planetary desper (Asada And kneading for 1 hour. Next, the synthetic oil was added to the kneaded product and mixed to prepare a slurry having a solid content concentration of 70% by mass. The slurry was depressurized by depressurizing the inside of the container to 6.67 kPa (50 Torr) using a vacuum pump, and vacuum defoaming was performed for 10 minutes. At this time, the pressure inside the container was measured using a Pirani gauge. The obtained slurry was molded using a wet press while applying an orientation magnetic field of 15 kOe in a certain direction to obtain a molded body.

  After removing the synthetic oil from the obtained molded body at 150 ° C. in a vacuum, the molded body was fired at 1100 ° C. for 5 hours in a vacuum to obtain a sintered body. Subsequently, the sintered body was subjected to an aging treatment at 500 ° C. for 1 hour. Thus, a rare earth magnet was obtained.

(Example 2)
A rare earth magnet was produced in the same manner as in Example 1 except that the vacuum degassing time was 30 minutes and the slurry was depressurized.

(Example 3)
A rare earth magnet was produced in the same manner as in Example 1 except that the pressure in the container was 26.66 kPa (200 Torr) and the slurry was depressurized.

Example 4
At the time of kneading, a rare earth magnet was produced in the same manner as in Example 1 except that the inside of the container was reduced to 6.67 kPa (50 Torr) using a vacuum pump.

(Example 5)
The slurry obtained with the planetary spars of Example 1 was transferred to a stock tank, held at a pressure of 6.67 kPa (50 Torr), depressurized, vacuum degassed for 10 minutes, and then molded in the same manner as in Example 1. Thus, a rare earth magnet was produced.

(Example 6)
A rare earth magnet was produced in the same manner as in Example 5 except that the pressure in the stock tank was maintained at 26.66 kPa (200 Torr).

(Example 7)
A rare earth magnet was produced in the same manner as in Example 5 except that the pressure in the stock tank was maintained at 66.66 kPa (500 Torr).

(Example 8)
The slurry obtained from the planetary spars of Example 1 was transferred to a stock tank, and a predetermined amount of slurry in the stock tack was filled into the mold cavity, and the inside of the cavity was maintained at a pressure of 6.67 kPa (50 Torr). Then, after depressurization and vacuum defoaming for 10 seconds, a rare earth magnet was produced in the same manner as in Example 1 except that the wet magnetic press was used to mold while applying an orientation magnetic field of 15 kOe in a certain direction.

Example 9
A rare earth magnet was manufactured in the same manner as in Example 8 except that the pressure inside the cavity was reduced to 26.66 kPa (200 Torr).

(Example 10)
A rare earth magnet was produced in the same manner as in Example 1 except that the pressure in the container was 0.133 kPa (1 Torr) and the slurry was depressurized.

(Comparative Example 1)
A rare earth magnet was produced in the same manner as in Example 1 except that the vacuum defoaming was not performed on the slurry obtained by the planetary desper.

Magnetic properties of the rare earth magnets obtained in Examples 1 to 10 and Comparative Example 1 were confirmed. Specifically, the density and residual magnetic flux density (Br) of the rare earth magnet were measured by Archimedes method using a BH tracer. The degree of orientation was determined from the following formula.
Br = Ms × main phase volume ratio × relative density × orientation degree (where Ms represents the saturation magnetization of the main phase in the obtained rare earth magnet)
The results are shown in Table 1 below.

  From the results shown in Table 1, the degree of orientation, Br, and density of the rare earth magnets of Examples 1 to 10 were higher than those of the rare earth magnet according to Comparative Example 1.

  From the above, it was confirmed that the magnetic characteristics of the obtained magnet can be sufficiently improved by the magnet manufacturing method according to the present invention.

It is a flowchart which shows roughly an example of the magnet manufacturing apparatus which enforces the manufacturing method of the magnet which concerns on this invention. It is a flowchart which shows schematically the other example of the magnet manufacturing apparatus which enforces the manufacturing method of the magnet which concerns on this invention. FIG. 3 is a cross-sectional view schematically showing the molding machine of FIG. 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Slurry manufacturing apparatus, 2 ... Container, 3 ... Stirring member, 4 ... Stirring drive part, 5 ... Slurry transfer pipe, 6 ... Stock tank, 7 ... Liquid feed pump, 8 ... Stirring member, 9 ... Exhaust pipe, 10 ... Vacuum pump, 11 ... slurry transfer pipe, 12 ... molding machine, 13 ... circulation pump, 14 ... molding machine filling pump, 15 ... return pipe, 16 ... exhaust pipe, 17 ... vacuum pump, 18 ... slurry transfer pipe, 22 ... molding Machine, 100, 200 ... Magnet manufacturing apparatus.

Claims (2)

A kneading step of kneading a rare earth magnet raw material powder and a solvent to obtain a kneaded product;
A dilution step of diluting the kneaded material to obtain a slurry;
Depressurizing the slurry;
The slurry that has undergone the depressurizing step is subjected to pressure forming while applying an orientation magnetic field to form a molded body, and
A firing step of firing the molded body,
Manufacturing method of rare earth sintered magnet. The step of decompressing the slurry and the molding step are performed in the same mold cavity,
Accommodating the slurry into the die cavity,
Depressurizing the slurry in the cavity,
Including subjecting the slurry in the cavity to pressure molding while applying an orientation magnetic field to form a molded body,
The method for producing a rare earth sintered magnet according to claim 1.

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