JP2008243951A - Manufacturing method of magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a magnet for reducing a variation in the weight of the magnet to be manufactured. <P>SOLUTION: The manufacturing method of a magnet includes: a storage process for storing a prescribed amount of slurry S containing magnetic powder and a solvent in a syringe 32; a slurry injection process for injecting the slurry S stored in the syringe 32 into a cavity C in a molding machine 20; a formation process for performing the wet formation of the slurry S injected into the cavity C in the slurry injection process; and a desolvation/baking process for baking a forming body 50 obtained by the formation process after desolvation, and forming a magnet containing magnetic powder. As a result, quantitativeness in the slurry S injected into the cavity C is improved, and a variation in the weight of the forming body 50 formed by the molding machine 20 is reduced, thus reducing a variation in the weight of the manufactured magnet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnet, and more particularly to a method for manufacturing a magnet used for wet forming.

Conventionally, when a sintered magnet is produced, a method by dry molding and a method by wet molding are known as methods for molding a magnetic powder as a raw material of a magnet. In this wet molding, a magnetic powder and a solvent such as oil are mixed to form a slurry, and then the magnetic powder is injected into a molding machine in a slurry state to be molded, and then the solvent is removed from the molded body. According to such wet molding, the magnetic field orientation at the time of molding is higher than in the case of dry molding, and a magnet having excellent magnetic properties can be obtained. In addition, the manufacturing method of the magnet using wet shaping | molding is disclosed by the following patent document 1, for example.
JP-A-9-289127

  However, the following problems exist in the conventional magnet manufacturing method described above. That is, in order to inject the slurry into the cavity of the molding machine used for wet molding, a metering pump is generally used to inject a predetermined amount of slurry, but the quantitative property of the pump is low. The reason is that the pump cannot be installed near the cavity of the molding machine. In that case, it is necessary to supply slurry from the pump to the cavity through a pipe having a certain length. This is probably because the ideal flow state of the slurry is hindered by the frictional resistance. As a result, the weight variation of the molded body is increased, and the weight variation of the magnet produced therewith is sometimes increased. Such weight variation is a variation in the size of the magnet, and it is necessary to mold the magnet in a larger size in consideration of the variation, which causes an increase in material costs and processing costs, and also causes variations in magnetic properties. Is also undesirable because it may cause

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a magnet in which the variation in the weight of the magnet to be manufactured is reduced.

  The magnet manufacturing method according to the present invention includes a storage step of storing a predetermined amount of slurry containing magnetic powder and a solvent in a syringe, and a slurry injection step of injecting the slurry stored in the syringe into a cavity of a molding machine. A molding process for wet-molding the slurry injected into the cavity in the slurry injection process, and a desolvation / firing process for forming a magnet containing magnetic powder by firing after removing the solvent from the molded body obtained by the molding process. including.

  In this magnet manufacturing apparatus, the slurry is once stored in a syringe during the storing step, and the slurry is injected from the syringe into the cavity of the molding machine. Thereby, since the quantitative property improvement of the slurry injected into the cavity is realized, the weight variation of the molded body formed in the molding machine is reduced, and the weight variation of the magnet produced therewith is reduced.

  Moreover, the aspect which performs an accommodation process may be sufficient when the slurry is shape | molded by a formation process. Thus, by performing the accommodation process and the molding process at the same time, the manufacturing time can be shortened as compared with an aspect in which the molding process is started after the accommodation process.

  In particular, when the molding machine has a plurality of cavities, the slurry is accommodated in each of the same number of syringes as the plurality of cavities as the accommodating process, and the slurry from one syringe to one cavity of the molding machine as the slurry injecting process. It is also possible to inject. When the molding machine has a plurality of cavities, if the slurry is supplied to each cavity with one pump, it is necessary to stop the molding machine during that period. It can be shortened.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the magnet in which reduction of the weight variation of the produced magnet was achieved is provided.

  Hereinafter, preferred embodiments of 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. However, the method for producing a magnet of the present invention is not limited to a rare earth magnet, and other metal magnets, ferrite magnets, etc. Any sintered magnet obtained by sintering can be applied without particular limitation.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a magnet manufacturing apparatus 1 according to a first embodiment of the present invention. As shown in FIG. 1, a storage tank 10 in which the slurry S is stored, a molding machine 20 to which the slurry S stored in the storage tank 10 is supplied, and a supply pump 30 that supplies the slurry S to the molding machine 20 are provided. I have.

  The storage tank 10 contains magnetic powder and a solvent, and is for temporarily storing the slurry S to be supplied to the molding machine 20. A rotating blade 14 for slurry agitation is disposed in the container 12 of the storage tank 10 to prevent the slurry S from being separated into a magnetic powder and a solvent.

  A conveyance pipe 40 for conveying the slurry is attached to the lower part of the container 12, and the slurry S stored in the storage tank 10 is carried out of the container 12 through the conveyance pipe 40. The transport pipe 40 is provided with a transport pump 42, and the slurry S in the transport pipe 40 is transported by the transport pump 42.

  The transfer pipe 40 is provided with a branching portion 40a in the middle thereof, and branches into two routes at the branching portion 40a. One of the two routes is a route for returning the slurry S into the container 12 (circulation route), and the other is a route for conveying the slurry S toward the molding machine 20 (conveyance route). By providing the above circulation route and keeping the slurry S in a fluid state, it is possible to suppress the situation where the slurry S is separated into the magnetic powder and the solvent. In addition, the well-known valve control mechanism is employ | adopted for the branch part 40a, and it can switch the slurry S to a circulation route and a conveyance route at a predetermined timing. Moreover, in this branch part 40a, it is also possible to deliver the slurry S to both routes as needed (for example, when delivering the slurry S to the transport route, part of it is also delivered to the circulation route). It is.

  Next, the molding machine 20 of the manufacturing apparatus 1 will be described with reference to FIG.

  The molding machine 20 is a device that wet-forms the slurry S supplied from the storage tank 10. The molding machine 20 includes a lower die 22, a guide portion 24 in which a guide hole 24 a for guiding the lower die 22 in the vertical direction is formed, and an upper die 26 disposed on the upper end side of the guide portion 24. Yes. A cavity C of the molding machine 20 is defined by the inner peripheral surface of the guide hole 24 a of the guide portion 24 and the upper surface of the lower mold 22. A magnetic field application coil 27 is provided around the cavity C, so that a magnetic field can be applied during molding.

  More specifically, the guide part 24 of the molding machine 20 has a rectangular parallelepiped shape as shown in FIG. 3, and one guide hole 24a is provided in parallel. These guide holes 24a are holes having a rectangular cross section, and penetrate from the upper surface 24b on the upper mold 26 side to the lower surface 24c on the lower mold 22 side.

  Then, the molding machine 20 compresses and molds the slurry S injected into the cavity C to produce a molded body to be a magnet. The upper mold 26 is provided with a solvent discharge path 26a for discharging the solvent that is discharged from the slurry S during molding to the outside of the cavity. The solvent discharge path 26 a is connected to a vacuum pump 29, and the discharge of the solvent is promoted by the suction of the vacuum pump 29. A filter 28 is interposed between the upper mold 26 and the guide portion 24 to prevent the magnetic powder from flowing out from the solvent discharge path 26a. The filter 28 may be a filter (filter paper) made of cloth, paper, or the like.

  When the slurry S is formed in the molding machine 20, the slurry S in the cavity C is gradually compressed as the lower mold 22 rises. At this time, only the solvent in the slurry passes through the filter 28 and is discharged out of the cavity from the solvent discharge path 26 a provided in the upper mold 26. The molded body obtained by compressing the slurry S in this manner is taken out of the cavity C of the molding machine 20 with the upper mold 26 removed, for example.

  Next, the supply pump 30 of the magnet manufacturing apparatus 1 shown in FIG. 1 will be described with reference to FIG. The supply pump 30 includes a cylinder body 30a and a piston 30b. Then, the slurry S sent from the storage tank 10 via the transport pipe 40 is accommodated in the cylinder body 30a, and the piston 30b is driven by a drive control circuit (not shown) to be provided in the cylinder body 30a. A predetermined amount of slurry S is discharged from the discharge port 30c.

  Below the discharge port 30c of the supply pump 30, one syringe 32 is disposed at a position for receiving the slurry S discharged from the discharge port 30c.

  The syringe 32 extends along the vertical direction, and the upper end of the syringe 32 is an opening, while the lower end of the syringe 32 is blocked by a thin tube 32a (for example, a diameter of 0.1 to 3.0 mm). ing. Therefore, the slurry S discharged from the supply pump 30 is accommodated in the syringe from the upper end opening of the syringe 32. The tube 32a can be provided with an opening / closing means such as a mechanical pinch or a check valve as necessary. The tube 32a may be made of rubber or metal (such as a needle).

  After the slurry S is accommodated in the syringe 32, the syringe 32 is conveyed to above the guide portion 24 of the molding machine 20 as shown in FIG. At this time, the syringe 32 is disposed at the position of the guide hole 24 a of the guide portion 24. All of the syringes located above the guide portion 24 are covered with a gas supply panel 34, and high pressure nitrogen gas (or other compression is supplied from the gas supply port 34 a provided at the syringe corresponding position of the panel 34. Gas, compressed air) is supplied to the syringe 32. Thereby, a gas pressure is applied to the syringe 32, and as a result, the slurry S in the syringe 32 flows out from the tube 32a at the lower end and is injected into the cavity C in the guide hole 24a.

  In addition, for example, due to the solvent having a specific gravity of about 0.8 to 0.9 and the magnetic powder having a specific gravity of more than 7, in the slurry S, the solvent is easily separated as a supernatant, Magnetic powder tends to settle. Therefore, a slight solvent supernatant is generated in the slurry S accommodated in the syringe 32. Therefore, when nitrogen gas is supplied from the upper end opening of the syringe 32 and flows out from the tube 32a at the lower end of the syringe, the supernatant rinses away the magnetic powder remaining in the syringe 32. Therefore, since all the magnetic powder of the slurry S accommodated in the syringe 32 flows out, high quantitativeness is realized.

  Next, a procedure of a manufacturing method for manufacturing a magnet using the manufacturing apparatus 1 described above will be described with reference to FIG. Here, FIG. 6 is a flowchart showing the procedure of the magnet manufacturing method according to the first embodiment of the present invention.

  In manufacturing the magnet, first, an alloy is prepared so that a 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 magnet is dissolved in an inert gas atmosphere such as vacuum or argon, and then used for casting or strip casting. An alloy having a desired composition is produced by performing an alloy manufacturing process such as a method.

  Here, examples of the magnet include those containing mainly Nd and Sm as rare earth elements, and those having a combination of a rare earth element and a transition element other than the rare earth element 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 form fine particles having a particle size of about several hundreds μm (step S12), and further finely pulverized (step S13), 1 to 10 μm (preferably 3 to 5 μm). ) A magnetic powder having a particle size of about a degree 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, the magnetic powder and the solvent are mixed using a known slurry production apparatus to produce a slurry S (step S14; slurry production step). As a solvent, the solvent used for the slurry S in the wet molding of a 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. The solvent is preferably oil in order to prevent the magnetic powder from being oxidized.

  In addition, in a slurry preparation process, the other additive from which a desired characteristic is acquired can also be further added besides a solvent. Examples of the additive include dispersants such as cationic, anionic, betaine, and nonionic surfactants that can promote dispersion of the magnetic powder.

  Thereafter, the slurry S prepared in the slurry preparation step is temporarily stored in the storage tank 10, and then the slurry S is sent from the storage tank 10 to the supply pump 30, and a predetermined amount of the slurry S is stored in the syringe 32 by the supply pump 30. (Step 15; accommodation process).

  And the slurry S is inject | poured into the cavity C of the molding machine 20 from the syringe 32 which accommodated the slurry S (step S16; slurry injection process).

  In this slurry injection step, as shown in FIG. 7A, the lower mold 22 of the molding machine 20 is lowered to the lower molding start position. Then, as shown in FIG. 7B, nitrogen gas is sprayed onto the syringe 32 in which the slurry S is accommodated, and the slurry S is injected into the cavity C from the tube 32 a at the lower end of the syringe 32.

  Then, as a molding step (step S17), the slurry S supplied to the cavity C of the molding machine 20 is molded while applying a magnetic field by the magnetic field application coil 27 (see FIG. 7C), and the molded body 50 is formed. Obtained (see FIG. 7D). In addition, when performing this shaping | molding process continuously, efficiency improvement of an operation | work is achieved by accommodating the slurry S in the syringe 32 during a shaping | molding process.

  Next, the molded body 50 obtained by the molding process is desolvated to remove the solvent and additives remaining in the molded body 50 by, for example, vacuum heating (step S18). Solvent removal is performed under conditions such that most of the solvent in the molded body 50 can be removed, and for example, heating at 100 to 160 ° C. for 1 to 5 hours is preferable under reduced pressure to about 10 to 3000 Pa. In this solvent removal step, sintering of the molded body 50 does not normally proceed, but part of the sintering may proceed.

  Thereafter, the desolvated molded body 50 is fired to obtain a sintered body (step S19; firing process). Sintering 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. The solvent removal / firing process in the present invention corresponds to the solvent removal process in step 18 and the baking process in step 19.

  After sintering, the sintered body is subjected to an aging treatment by heating the obtained 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.

  As described above, in the magnet manufacturing method described above, the slurry is temporarily stored in the syringe 32 from the supply pump 30 in the storing step, and the slurry S is injected from the syringe 32 into the cavity C of the molding machine 20. .

  That is, when the slurry S is directly supplied from the discharge port 30c of the supply pump 30 to the cavity C of the molding machine 20, the situation that the quantitative property of the slurry S is reduced due to the frictional resistance in the piping of the discharge port 30c is effective. Has been eliminated. Then, by filling the syringe 32 with the necessary amount of the slurry S, the quantitativeness of the slurry S supplied into the cavity C is improved. In particular, since the supernatant of the solvent in the syringe 32 causes all of the magnetic powder of the slurry S accommodated in the syringe 32 to flow out when nitrogen gas is supplied, higher quantitativeness is realized. Therefore, the quantitative improvement of the slurry S injected into the cavity C of the molding machine 20 is significantly realized, the weight variation of the molded body 50 is reduced, and the weight variation of the magnet produced is reduced accordingly. ing.

  In addition, when the storing step (step S15) is performed when the slurry S is being formed in the forming step (step S17), the forming step may be performed while the slurry S is being stored in the syringe 32. Therefore, compared with the aspect which starts a shaping | molding process after an accommodation process, work efficiency improvement and shortening of the manufacturing time of a magnet can be aimed at.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment described above in that a magnet is manufactured using a molding machine 20 having a plurality of cavities C.

  In the second embodiment, the guide portion 24 of the molding machine 20 is provided with four guide holes 24a in parallel as shown in FIG. These guide holes 24a are holes having a rectangular cross section of the same size, and all of the guide holes 24a penetrate from the upper surface 24b on the upper mold 26 side to the lower surface 24c on the lower mold 22 side. The four guide holes 24a are arranged at equal intervals in the short direction of the cross section.

  Further, in the second embodiment, as shown in FIG. 9, below the discharge port 30c of the supply pump 30, the same number of four syringes 32 as the cavity C receive the slurry S discharged from the discharge port 30c. Is arranged. The four syringes 32 all extend along the vertical direction and are arranged in a line. The supply pump 30 is movable so that the slurry S can be supplied to each of the four syringes 32 by a driving means (not shown).

  As shown in FIG. 10, the four syringes 32 are accommodated in the interior of each of the four syringes 32 after the slurry S is accommodated therein, and the guide unit 24 of the molding machine 20 is arranged as shown in FIG. It is carried to above. At this time, one syringe 32 is disposed at the position of one guide hole 24 a of the guide portion 24. And all the one syringe 32 located above the guide part 24 is covered with the panel 34 for gas supply, and high pressure nitrogen gas is supplied from the four gas supply ports 34a provided in the syringe corresponding position of the panel 34. It is supplied to each syringe 32. Thereby, a gas pressure is applied to each syringe 32, and as a result, the slurry S in the syringe 32 flows out of the tube 32a at the lower end and is injected into the cavity C in each guide hole 24a.

  And also in this 2nd Embodiment, a magnet is produced according to the procedure of the manufacturing method of the magnet which concerns on 1st Embodiment shown in FIG.

  That is, also in the second embodiment described above, as in the first embodiment, the slurry is temporarily stored in the syringe 32 from the supply pump 30 during the storing step, and the slurry S is injected from the syringe 32 into the cavity C of the molding machine 20. Is done. Therefore, as in the first embodiment, the quantitativeness of the slurry S is improved, the weight variation of the molded body 50 is reduced, and the weight variation of the magnet produced therewith is reduced.

  In addition, in the second embodiment, since the same number of syringes 32 as the four cavities C are used, the time for supplying the slurry S to the cavities C can be shortened. That is, when the slurry S is injected into the four cavities with a pump having a smaller number of cavities, the molding machine 20 needs to be stopped until the slurry supply is completed. Thus, since the slurry supply can be completed at one time, it is not necessary to stop the molding machine 20 for a long time.

  The present invention is not limited to the above embodiment, and various modifications are possible. For example, the magnet manufacturing method according to the present invention is a manufacturing method including at least a slurry injection process, a molding process, and a desolvation / firing process, and as long as the effects of the present invention are sufficiently obtained, It may be omitted.

  Furthermore, as described above, the present invention is not limited to rare earth magnets but can be applied to the manufacture of magnets other than rare earth magnets, such as other metal magnets and ferrite magnets. And even if it is a case where it applies to another magnet, it is possible to produce the magnet by which the weight variation was suppressed similarly to embodiment mentioned above.

  In addition, you may increase / decrease the number of cavities and the number of syringes as needed. Moreover, when supplying a slurry to several syringes, you may supply using several pumps.

It is the schematic block diagram which showed the manufacturing apparatus of the magnet which concerns on embodiment of this invention. It is the schematic block diagram which showed the molding machine in the manufacturing apparatus of the magnet shown in FIG. It is the schematic perspective view which showed the guide part of the molding machine shown in FIG. It is the figure which showed the supply pump and syringe in the manufacturing apparatus of the magnet shown in FIG. It is the figure which showed the positional relationship of the guide part at the time of inject | pouring a slurry, and a syringe. It is the flowchart which showed the procedure of the manufacturing method of the magnet which concerns on 1st Embodiment of this invention. It is the figure which showed the state of the molding machine in a slurry injection | pouring process and a formation process. It is the schematic perspective view which showed the guide part of the molding machine which concerns on 2nd Embodiment of this invention. It is the figure which showed the supply pump and syringe in the manufacturing apparatus of the magnet which concerns on 2nd Embodiment of this invention. In the magnet manufacturing apparatus which concerns on 2nd Embodiment of this invention, it is the figure which showed the positional relationship of the guide part at the time of inject | pouring a slurry, and a syringe.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnet manufacturing apparatus, 10 ... Storage tank, 20 ... Molding machine, 22 ... Lower mold, 24 ... Guide part, 26 ... Upper mold, 30 ... Supply pump, 32 ... Syringe, 50 ... Molded body, C ... Cavity, S: Slurry.

Claims (3)

An accommodating step of accommodating a predetermined amount of slurry containing magnetic powder and a solvent in a syringe;
A slurry injection step of injecting the slurry contained in the syringe into a cavity of a molding machine;
A molding step of wet-molding the slurry injected into the cavity in the slurry injection step;
A method for producing a magnet, comprising: a desolvation / firing step of forming a magnet including magnetic powder after removing the solvent from the molded body obtained by the molding step.   The method for manufacturing a magnet according to claim 1, wherein the accommodating step is performed when the slurry is being formed in the forming step. When the molding machine has a plurality of the cavities,
As the accommodating step, the slurry is accommodated in each of the syringes in the same number as the plurality of cavities,
The magnet manufacturing apparatus according to claim 1 or 2, wherein, as the slurry injection step, the slurry is injected from one syringe into one cavity of the molding machine.

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