JP4863122B2 - Manufacturing method of sintered metal magnet - Google Patents

Description

  The present invention relates to a method for producing a sintered metal magnet, and more particularly to a technique for wet-forming a sintered magnet containing a rare earth metal.

  Conventionally, as a method for producing a sintered metal magnet, a raw alloy of a sintered metal magnet is roughly pulverized and finely pulverized to produce a fine powder having an average particle size of about several μm, and this fine powder is used as a mold cavity of a molding machine. A technique is widely known in which press molding is performed in a state of being supplied into a magnetic field and oriented in a magnetic field. Since the residual magnetic flux density of the sintered metal magnet thus obtained tends to be almost proportional to the degree of magnetic field orientation of the fine powder during press molding, a high performance sintered metal magnet having a higher residual magnetic flux density. In order to realize this, various attempts have been made to increase the degree of magnetic field orientation.

  As such an attempt, for example, a lubricant is added to a raw material alloy and finely pulverized, and the obtained lubricant-coated fine powder is supplied into a mold cavity of a molding machine, and dry press-molded in a state of being magnetically oriented. The dispersion of the lubricant is improved by rolling the lubricant-coated fine powder by the rotation of the rolling blade provided in the mold cavity or by adding the organic liquid and kneading the organic liquid. There has been proposed a method of dry press molding a fine powder obtained by volatilizing a liquid in a state where it is magnetically oriented.

  On the other hand, magnetic powders of sintered metal magnets, especially raw material powders containing rare earth metals, are pulverized surfaces that are chemically very active substances, and are easily oxidized by oxygen in the atmosphere, for example. The characteristic is that the characteristic is easily deteriorated.

  In order to solve this problem, Patent Document 1 describes the amount of dissolved oxygen such as mineral oil, synthetic oil or vegetable oil without performing fine pulverization step under low oxygen concentration and exposing the obtained fine powder to oxygen. A method is described in which a slurry is prepared by mixing with an oil-based solvent with a small amount of oil, this slurry is supplied into a mold cavity of a molding machine, and wet press-molded in a state of being magnetically oriented.

JP 9-289127 A

  Generally, the magnetic characteristics of a magnet are indicated by the maximum value of the maximum energy product (BH), which is the product of the residual magnetic flux density (Br) and the coercive force (Hc), and the larger this value, the stronger the magnet. Therefore, in order to obtain high magnetic characteristics, it is desirable to increase both the residual magnetic flux density and the coercive force. In particular, improving the residual magnetic flux density is important for achieving high magnetic characteristics of the magnet. Even for the rare earth magnets obtained by the manufacturing method, a higher residual magnetic flux density is required so as to obtain further high magnetic properties.

  However, when using dry press molding, to achieve a high residual magnetic flux density, it is necessary to introduce a strong external magnetic field source or to use a very highly classified fine powder as a raw material. For example, there is an inconvenience that the production cost is excessively increased with respect to the intended performance improvement, and the productivity and economic efficiency are deteriorated particularly in mass production. On the other hand, when wet press molding is used, the present situation is that a stable production method capable of realizing a high residual magnetic flux density and excellent in productivity and economy has not been established.

  Accordingly, the present invention has been made in view of such circumstances, and the object thereof is to enable highly magnetic field orientation of metal raw material powder (powder), thereby improving productivity and economy. It is providing the manufacturing method of a sintered magnet.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, the dispersion state of the magnetic powder in the slurry used in the wet press molding and the presence of the secondary particles are significantly different from the magnetic field orientation. It was found that there is a correlation, and the present invention has been completed.

That is, the method for producing a sintered metal magnet according to the present invention includes a stirring step of stirring a metal magnetic powder having an average particle diameter of 1 to 10 μm and containing a rare earth element , and a first stirrer. A step including a kneading step in which a kneaded product is added and kneaded to prepare a kneaded product, a slurrying step in which a second solvent is added to the kneaded product to prepare a slurry, and the slurry is applied with a magnetic field applied to the slurry. A molding process for obtaining a molded body by pressure molding, and a sintering process for sintering (firing) the molded body.

  When the present inventors carried out the manufacturing method configured as described above, the magnetic powder can be remarkably highly magnetically oriented without excessively degrading productivity and economy for the intended performance improvement. As a result, it has been found that the residual magnetic flux density is improved as compared with the conventional case. The details of the mechanism of action that produces this effect are not yet clear, but are estimated as follows, for example.

  That is, the surface of magnetic powder, particularly powder containing rare earth elements, is chemically very active, and therefore, secondary particles in which a plurality of primary particles are reversibly aggregated in addition to finely divided primary particles. It is considered to be an aggregate containing particles. Conventionally, the magnetic powder was slurried in this state. However, the secondary particles have a lower mobility due to the magnetic field than the primary particles, and therefore are inferior in the magnetic field orientation, and may cause a deterioration in the degree of magnetic field orientation.

On the other hand, in the present invention, the metal magnetic powder having an average particle diameter of 1 to 10 μm and containing a rare earth element is stirred (that is, by stirring only the magnetic powder before adding a solvent or the like), During production, a strong shearing force is applied to the reversibly aggregated secondary particles, whereby the secondary particles, which are aggregates of the primary particles, are separated into primary particles before the aggregation (recovery). ) (Hereinafter, making the secondary particles into discrete primary particles, that is, dissociating the aggregates is referred to as “disintegration”.) As a result, the resulting agitated material is secondary particles with poor magnetic field orientation. The ratio of is sufficiently reduced. Furthermore, by applying a shearing force during stirring, the primary particles contained in the stirred product can be made smaller in size than before aggregation.

In addition, since the first solvent is added to the agitated material and kneaded to prepare a kneaded product, the active surface of the primary particles obtained by pulverizing the secondary particles is covered with the added first solvent. Is done. Thereby, re-formation of the secondary particles due to re-aggregation of the primary particles can be suppressed, and the dispersibility of the magnetic powder in the kneaded product can be improved. Moreover, even during this kneading, a shearing force due to collision between fine powders or flow stress is applied to the magnetic powder, and the secondary particles remaining in the kneaded product can be further crushed into primary particles. Furthermore, the size of the primary particles contained in the kneaded product can be made smaller than that before aggregation by applying a shearing force during kneading. Then, a slurry is prepared using the kneaded product, the slurry is wet press-molded in a molding process, and the resulting molded body is sintered in a sintering process. A sintered metal magnet oriented in a magnetic field is obtained. Moreover, in the stirring step, magnetic powder having an average particle size of 1 to 10 μm is used, so that the orientation during magnetic field orientation is significantly enhanced, and the sinterability and sintered body density in the sintering step are increased. Is more enhanced. However, the action is not limited to this.

  In the kneading step, it is preferable to prepare a kneaded product having a solid content concentration of 85 to 95% by mass (% by mass: the mass of the magnetic powder with respect to the mass of the total mass of the kneaded product). In this way, when the kneaded material is kneaded, a strong shearing force can be applied to the reversibly aggregated secondary particles, and the crushing effect on the primary particles can be further enhanced, and the ratio of the secondary particles Is further reduced.

  Furthermore, in the kneading step, it is more preferable to add the first solvent while continuing the stirring in the stirring step. In this way, the active surface of the primary particles obtained by crushing the secondary particles can be quickly coated, so that the re-formation of the secondary particles due to the reaggregation of the primary particles is further suppressed. The dispersibility of the magnetic powder in one solvent can be further improved. Further, the man-hour is shortened, and the production efficiency of the sintered metal magnet is increased.

  In the slurrying step, it is preferable to prepare a slurry having a solid concentration of 60 to 80% by mass. If comprised in this way, the fluidity | liquidity of a slurry will be improved and the supply property to the following process will be improved.

  In the stirring step, it is preferable to use magnetic powder containing 0.01 to 0.3% by mass of a grinding aid. By using the grinding aid at such a ratio, the agglomerated secondary particles are more easily crushed, so that the magnetic field orientation of the sintered metal magnet obtained by molding and sintering is further improved. .

  Furthermore, as the first solvent and / or the second solvent, a solvent used in a slurry in wet molding of a magnet can be applied without particular limitation. For example, oils such as mineral oil, synthetic oil, vegetable oil, acetone, alcohol Organic solvents and the like. Among these, it is preferable to use oil in order to prevent oxidation of the magnetic powder.

  Here, when a magnetic powder containing a rare earth element is used, the method for producing a sintered metal magnet according to the present invention is particularly effective. That is, the magnetic material containing rare earth elements has a fracture surface (the pulverized surface of the magnetic powder) that is chemically very active and highly reactive, so that the magnetic powder tends to agglomerate. It tends to work extremely effectively.

  According to the method for producing a sintered metal magnet of the present invention, the proportion of secondary particles that cause deterioration in magnetic field orientation in magnetic powder can be significantly reduced, and the dispersibility of magnetic powder can be improved. Therefore, it is possible to highly magnetically orient the magnetic powder, thereby improving the productivity and economics of a sintered metal magnet with a further increased residual magnetic flux density (Br).

  Embodiments of the present invention will be described below. In addition, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. The following embodiments are examples for explaining the present invention, and the present invention is not limited only to the embodiments.

(First embodiment)
FIG. 1 is a flowchart (process diagram) showing a procedure for producing a rare earth metal sintered magnet using a preferred embodiment of a method for producing a rare earth metal sintered magnet according to the present invention. The production method of the present embodiment includes a raw material alloy preparation step S11, a pulverization step S12, a stirring (pulverization) step S13, a kneading step S14, a slurrying step S15, a wet forming step S16, a solvent removing step S17, and a sintering step S18. And the aging treatment process S19 is included, and the mixing process S1 is comprised from the stirring process S13 and the kneading | mixing process S14. Hereinafter, each step will be described in detail.

<Raw material alloy preparation step S11>
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.

<Crushing step S12>
Next, the obtained alloy is coarsely pulverized to obtain particles (coarse powder) 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 fine powder (hereinafter also simply referred to as “magnetic powder”) having a particle size of 10 μm or less, preferably 1 to 10 μm. . For fine pulverization, the coarsely pulverized coarse powder is further pulverized 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. To implement. Here, in order to improve grindability, dispersibility during dispersion, orientation during molding, and lubricity, a grinding aid such as a lubricant or a dispersant may be added and stirred (grinding aid addition step A12). ). Although it does not specifically limit as a grinding aid used here, For example, a fatty acid or a derivative of a fatty acid, a hydrocarbon etc. can be mentioned. The addition amount of the grinding aid is not particularly limited, and is preferably about 0.01 to 0.03% by mass of the coarse powder.

<Stirring Step S13 and Kneading Step S14: Mixing Step S1>
Next, the fine powder as the magnetic powder obtained in the pulverization step S12 is supplied to the stirring (pulverization) step S13 and the kneading step 14. The stirring (pulverizing) step S13 is a step of stirring the magnetic powder obtained in the pulverizing step S12 using, for example, a so-called kneader having kneading blades as kneading means, and the stirred product is prepared by stirring the magnetic powder. The By this stirring, the secondary particles are crushed into primary particles. In the kneading step 14, a solvent is added to knead the agitated material, so that the surface of the magnetic powder is covered with the first solvent, and a sufficient amount of the first solvent is supplied to the magnetic powder. This includes a state in which a mixture of solvents is kneaded. The stirring (pulverization) step S13 and the kneading step 14 may be performed continuously, or the stirring of the stirring (pulverization) step S13 may be temporarily stopped and the kneading step 14 may be performed after a predetermined time has elapsed. From the viewpoint of preventing re-aggregation of the primary particles crushed in the agitation (disintegration) step S13, the first solvent is added while continuing the agitation in the agitation (disintegration) step S13, and the agitation (disintegration) ) It is preferable to perform the step S13 and the kneading step S14 continuously. These stirring (pulverization) step S13 and kneading step S14 can be carried out easily and continuously by using a so-called kneader having kneading blades or the like as the kneading means. In this case, in the stirring (pulverization) step S13, the magnetic powder is put into a container (chamber) of a kneader, and the magnetic powder is stirred with a kneading blade provided in the container to produce a stirred product. At this time, the secondary particles are crushed into primary particles by stirring. Further, the first solvent is supplied into the container of the kneader while continuing the stirring, and the kneaded product and the solvent are kneaded by the kneading blade, and the kneading step S14 is performed to prepare the kneaded product. Prior to the agitation (pulverization) step S13 and the kneading step S14, in order to prevent the magnetic powder from being oxidized by the air present in the container or in the voids of the magnetic powder, the inside of the container is vacuum degassed and the oxygen concentration is increased. Replacement with an inert gas atmosphere such as nitrogen of 500 ppm or less is preferable.

  The kneading machine includes at least a container into which magnetic powder is charged and a kneading blade (stirring blade) as a kneading means in the container, and the magnetic powder charged in and deposited in the container can be stirred with the kneading blade and kneaded. In the step S14, so-called kneaders, mixers or agitators can be used without distinction as long as they can knead the magnetic powder and the solvent. Examples of this type of typical kneader include, but are not limited to, a planetary mixer and a Henschel mixer.

  Here, FIG. 2 is a schematic configuration diagram showing an example of a system for manufacturing a sintered metal magnet according to the present invention. The manufacturing apparatus 1 includes a kneader 20 and a molding machine 30. The kneading machine 20 is connected to the molding machine 30 through the pressure feed pump P1 and the feed pipe 20a, and the slurry is fed into a mold cavity (not shown) of the molding machine 30 by the opening / closing operation of the valve 20b and the pressure feed operation of the pressure feed pump P1. Liquid feeding is possible.

  The kneading machine 20 includes a container 22 into which magnetic powder is charged, and kneading blades 23 and 24 as kneading means for stirring and kneading the inside of the container 22. The container 22 includes a lid 22a that can be opened and closed, and is configured so that the inside of the container 22 is hermetically sealed with the lid 22a and the valve 20b closed. The container 22 is connected to a vacuum pump and a nitrogen gas cylinder (not shown) so that the inside of the container 22 can be vacuum degassed and replaced with a nitrogen atmosphere having an oxygen concentration of, for example, 500 ppm or less.

  In the kneading blades 23 and 24, blade members 23b and 24b are integrally provided at lower ends of the rotation shafts 23a and 24a, and gears, timing belts, and the like are driven at upper ends of the rotation shafts 23a and 24a. A drive motor (not shown) is connected via a transmission mechanism (both not shown). The kneading blades 23 and 24 are configured to perform a planetary motion by driving the drive motor. That is, the kneading blades 23 and 24 revolve around the revolution axis Z (illustrated Z) along the peripheral wall in the container 22 and rotate around the rotation axes 23a and 24a.

  A fine powder tank 25 serving as a storage tank for storing fine powder is detachably connected to the container 22 via a pipe 25a. The fine powder tank 25 is connected to a vacuum pump and a nitrogen gas cylinder (not shown), and the fine powder tank 25 is evacuated and replaced with, for example, a nitrogen atmosphere of 500 ppm or less. The fine powder tank 25 communicates with the container 22 via a valve (not shown), and fine powder is introduced into the container 22 by opening and closing the valve.

  In addition, a solvent tank 26 as a solvent supply unit for storing the first solvent is detachably connected to the container 22 via a pipe 26a. The solvent tank 26 is connected to a vacuum pump and a nitrogen gas cylinder (not shown), and the inside of the solvent tank 26 is evacuated and replaced with a nitrogen atmosphere of, for example, 500 ppm or less. The solvent tank 26 communicates with the container 22 via a valve (not shown), and the first solvent is supplied into the container 22 by opening and closing the valve.

  Further, a control device 50 as a control unit is connected to the kneading blades 23 and 24, the fine powder tank 25, and the solvent tank 26, and each operation is controlled. Specifically, the control device 50 stirs the kneading blades 23 and 24 of the kneader 20, inputs fine powder from the fine powder tank 25 into the container 22, and supplies the solvent from the solvent tank 26 into the container 22. Integrated control such as supply. That is, the control device 50 operates the kneading blades 23 and 24 to stir the fine powder before supplying the first solvent from the solvent tank 26 into the container 22 so as to produce an agitated material, and After the first solvent is supplied to the agitated material, operation control is performed such that the kneading blades 23 and 24 are operated again to knead the fine powder and the first solvent to produce a kneaded material. . The operation control by the control device described below may be performed manually by an operator or may be performed automatically by a continuous sequence programmed in advance.

  More specifically, first, a fine powder tank 25 containing fine powder in a nitrogen purged state and a solvent tank 26 storing a first solvent in a nitrogen purged state are attached to the container 22. Then, in accordance with a control command (control signal or the like) from the control device 50, the inside of the container 22 is evacuated and nitrogen gas is introduced, and the inside of the container 22 is purged with nitrogen to 500 ppm or less.

  Next, according to a control command from the control device 50, a valve (not shown) of the fine powder tank 25 is opened while operating the kneading blades 23 and 24, and a predetermined amount of fine powder is put into the container 22. By this operation, the fine powder deposited in the container 22 is agitated by the planetary motion of the kneading blades 23 and 24, and a fine powder agitation is produced. The stirring operation may be performed simultaneously with the addition of the fine powder or after a predetermined time has elapsed since the addition. At this time, the stirring time by the kneading blades 23 and 24 is not particularly limited, and may be set as appropriate according to the rotational speed, rotational torque of the kneading blades 23 and 24, the weight and shape of the kneading blades 23 and 24, and the productivity. And considering the cost, it is preferably about 2 to 60 minutes, more preferably 3 to 30 minutes. Through these series of operations, a shearing force is applied to the fine powder due to a collision between the fine powder and the kneading blades 23, 24, a collision between the fine powder and the inner wall of the container 22, a collision between the fine powders, and the like. Aggregated secondary particles are crushed into primary particles.

  Then, in accordance with a control command from the control device 50, while continuing to operate the kneading blades 23 and 24, a valve (not shown) of the solvent tank 26 is opened to supply a predetermined amount of the first solvent into the container 22 (solvent addition step). A14). Thus, in the present embodiment, the stirring step S13 and the kneading step S14 are performed in this order in the kneader 20.

  The first solvent may be supplied in a state where the operation of the kneading blades 23 and 24 is temporarily stopped. However, re-aggregation of primary particles generated by pulverization is suppressed and dispersibility in the first solvent is suppressed. From the viewpoint of improving the ratio, it is preferable to supply the first solvent while the kneading blades 23 and 24 are driven, that is, while stirring the fine powder. The method for supplying the first solvent may supply the amount necessary for kneading at one time or may be supplied in a plurality of times. Furthermore, a predetermined amount of the first solvent may be supplied. , May be added gradually, intermittently or intermittently. If the wettability between the magnetic powder and the solvent is not good, the powder may be debris (lumps) and re-aggregation of the part may occur. It is preferable to supply in divided portions.

  As described above, the solvent used in the slurry in the wet molding of the magnet can be used as the first solvent used here without any particular limitation. Further, in order to improve crushability, dispersibility during dispersion, and orientation and lubricity during molding, a lubricant or a dispersant may be added and stirred. Although it does not specifically limit as what is used here, For example, fatty acid or a derivative of fatty acid (for example, stearic acid, oleic acid, behenic acid, lauric acid, zinc stearate, calcium stearate, aluminum stearate, stearin Acid amide, oleic acid amide, behenic acid amide, caprylic acid amide, cabric acid amide, lauric acid amide, ethylenebisisostearic acid amide), hydrocarbon paraffin, naphthalene, camphor and the like.

  The amount of the first solvent added is not particularly limited, but is preferably adjusted so that the solid content concentration of the obtained kneaded product is 85 to 95% by mass, and more preferably the obtained kneaded product. The solid content concentration is adjusted to 88 to 94% by mass. When the solid content concentration of the kneaded product exceeds 95% by mass, coating of the fine powder with the first solvent at the time of kneading tends to be insufficient, and uniform dispersion of primary particles tends to be difficult. On the other hand, if the solid content concentration of the kneaded product is less than 85% by mass, the load at the time of kneading decreases, and the shear force of the aggregated secondary particles due to friction between the fine powders or kneading operation tends to be disadvantageously weakened. is there.

  Further, in accordance with a control command from the control device 50, the kneading step S14 is carried out, and the agitated material and the first solvent accumulated in the container 22 are sufficiently kneaded by the kneading blades 23 and 24 to produce a kneaded material. To do. The kneading time at this time may be appropriately set according to the viscosity of the kneaded material, the rotational speed of the kneading blades 23 and 24, the rotational torque, and the like, and is preferably about 5 minutes to 2 hours in consideration of productivity and cost. Is about 10 minutes to 1 hour. Through these series of operations, the active surface of the primary particles generated by pulverization is coated with the first solvent, and a kneaded product in which the primary particles are more uniformly dispersed is obtained.

<Slurry process S15>
Here, before being subjected to the subsequent wet molding step S16, a predetermined amount of the second solvent is added to the kneaded material having a solid content concentration of 85 to 95% by mass (solvent addition). Step A16) A slurrying step S15 for preparing a slurry having a solid content concentration of 60 to 80% by mass by kneading is performed. When the solid content concentration of the slurry exceeds 80% by mass, the supply property of the slurry is lowered, and the orientation of the magnetic powder during wet press molding by magnetic field orientation, which will be described later, easily deteriorates to an inconvenient level. There exists a tendency for the residual magnetic flux density of the metal sintered magnet obtained to fall. On the other hand, when the solid content concentration of the slurry is less than 60% by mass, the dispersion state of the magnetic powder in the slurry is likely to be non-uniform, such as the magnetic powder being precipitated with a solvent, and it is difficult to supply a slurry with a constant concentration. Tend to be.

  In this embodiment, the same solvent as the first solvent described above is used as the second solvent. Therefore, in this slurrying step S15, in accordance with a control command from the control device 50, while continuously operating the kneading blades 23 and 24, a valve (not shown) of the solvent tank 26 for storing the second solvent is opened, and the container 22 is placed inside. A predetermined amount of the second (first) solvent is supplied. Then, by continuing the operation of the kneading blades 23 and 24, the kneaded product and the second solvent are sufficiently kneaded to obtain a slurry in which the solid content concentration is diluted to 60 to 80% by mass.

  Note that a different solvent from the first solvent may be used as the second solvent. In this case, after the aforementioned solvent addition step A14, the first solvent in the solvent tank 26 is replaced with the second solvent, or the solvent tank 26 itself is replaced with the solvent tank 26 storing the second solvent. And what is necessary is just to perform the said solvent addition process A16. The 2nd solvent used in this case is not specifically limited, It can select suitably from what was illustrated by the 1st solvent mentioned above.

  Moreover, in this embodiment, although the procedure which produces the slurry in the kneader 20 which produced the kneaded material was illustrated, it is slurrying process S15 using another mixer for slurry preparation separately from the kneader 20. May be performed. Furthermore, you may perform a dispersion | distribution process using dispersers, such as a homogenizer, as needed. In this case, a disperser may be connected between the kneader 20 and the molding machine 30, and the kneaded material (slurry) may be sequentially sent to the disperser and the molding machine 30 to form a continuous process.

<Wet molding process S16>
Next, the slurry produced as described above is subjected to pressure molding in a state where a magnetic field is applied to obtain a molded body. More specifically, first, the slurry produced in the kneader 20 is pumped to the molding machine 30 through the feed pipe 20a by opening the valve 20b and driving the pumping pump P1, and the molding machine 30 is illustrated. Do not supply to mold cavity. Then, a predetermined magnetic field is applied to the mold cavity to pressurize the magnetic powder in a magnetically oriented state, and pressure molding is performed while filtering the solvent in the slurry.

  Filtration of the solvent in the slurry during pressure molding can be performed according to a so-called wet molding conventional method. For example, a flow path for discharging the solvent is formed in a part of the mold cavity, and the flow path is made of cloth. Alternatively, it may be covered with a paper filter, or a part of the mold cavity may be formed with a porous filter material.

  Moreover, as a magnitude | size of the magnetic field to apply, about 12-20 kOe (960-1600 kA / m) is mentioned, for example, Furthermore, the magnetic field to apply is not limited to a static magnetic field, It can also be made into a pulse-shaped magnetic field. It is also possible to use a static magnetic field and a pulsed magnetic field in combination.

Furthermore, examples of the molding pressure include 0.3 to ³ ton / cm ³ (30 to 300 MPa). The molding pressure may be constant from the start to the end of molding, may be gradually increased or decreased, or may be irregular. It may change to (random). The lower the molding pressure, the better the degree of orientation, but if the molding pressure is too low, the resulting molded product will have insufficient strength and the handling property will tend to decrease. The pressure can be appropriately selected. In addition, the final relative density of the molded body obtained by molding in a magnetic field is usually 50 to 60%. Moreover, it is preferable to store the obtained molded object in the container substituted by inert gas atmosphere, such as Ar and nitrogen, and oxygen concentration being 1000 ppm or less.

<Solvent removal step S17>
Next, the solvent contained in the obtained molded body is removed. Here, it is desirable that the solvent, grinding aid, lubricant, dispersant, and the like contained in the molded body are almost completely removed from the viewpoint of preventing the deterioration of the magnetic properties due to the remaining carbon. More specifically, in a vacuum with a degree of vacuum of 1 Torr or less, the molded body is preferably maintained at 100 to 250 ° C., more preferably 120 to 200 ° C. for 30 minutes or more. At this time, it can also carry out in inert gas, such as Ar and nitrogen, or reducing gas atmosphere, evacuating with a vacuum pump.

<Sintering step S18>
Further, the compact from which the solvent has been removed is sintered in a vacuum or an inert gas atmosphere using a sintering machine (not shown). The sintering conditions are appropriately adjusted in consideration of various conditions such as the composition of the magnetic powder, the raw material alloy pulverization method, the difference in the average particle size and the particle size distribution of the magnetic powder, and, for example, at 1000 to 1200 ° C. for 1 to 10 hours. A degree of sintering. If the sintering temperature exceeds 1200 ° C, the crystal grains may grow abnormally and the holding power may decrease. If the sintering temperature is less than 1000 ° C, the residual magnetic flux density of the sintered body tends to decrease to an inconvenient level.

<Aging treatment step S19>
Then, an aging treatment is applied to the obtained sintered body. This aging treatment step S19 is an important step for controlling the coercive force (HcJ), and heat-treats the sintered body in a vacuum or an inert gas atmosphere according to a conventional method. The aging treatment step S19 is preferably a two-stage aging treatment. When performing in two stages, holding for a predetermined time in the vicinity of 800 ° C. and 600 ° C. is effective. For example, in the first stage aging treatment step, it is preferable to provide a first quenching step in which the sintered body is held at 700 to 900 ° C. for 1 to 3 hours and then rapidly cooled to a range of room temperature to 200 ° C. Moreover, it is preferable to provide the 2nd quenching process which hold | maintains a sintered compact at 500-700 degreeC for 1 to 3 hours, and then rapidly cools to room temperature in the 2nd stage aging treatment process. Since the coercive force greatly increases by heat treatment near 600 ° C., it is preferable to perform aging treatment near 600 ° C. when the aging treatment is performed in one stage. Further, when an R-T-B sintered magnet is produced by a mixing method using a low R alloy and a high R alloy, the coercive force increases when heat treatment is performed at around 800 ° C. after sintering. So it is especially effective.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

Example 1
Nd: 30%, Dy: 1.8%, Al: 0.2%, Co: 0.5%, B: 1.0% Coarsely pulverized ingot consisting of Fe, coarse powder having an average particle size of 100 μm Got the body. Next, the coarse powder was finely pulverized using a jet mill in a nitrogen atmosphere to obtain a fine powder having an average particle size of 4 μm as a magnetic powder. The resulting fine powder was collected in a nitrogen purged container.

  After the container containing the fine powder and the solvent tank storing the synthetic oil are attached to the kneading machine (Planetary Disper: manufactured by Asada Seiko Co., Ltd.), the container (chamber) of the kneading machine is vacuum degassed. Nitrogen gas was supplied and purged with nitrogen so that the oxygen concentration in the container was 100 ppm or less.

  Subsequently, the piping valve connecting the recovery tank and the kneader was opened, and the fine powder was put into the container of the kneader, and the stirring blade of the kneader was driven to start stirring the fine powder. After 3 minutes, a synthetic oil having a fractional distillation point of 200 to 250 ° C. (Idemitsu Kosan Co., Ltd .: Idemitsu Supersol FP-30) was removed from the solvent tank while the stirring blade was operated and the fine powder was stirred. And a dispersant (sorbitan monooleate) were fed into the container so that the solid content concentration of these mixtures was 92% by mass. Thereafter, the stirring blade was continuously operated and kneaded for 1 hour to prepare a kneaded product having a solid content of 92% by mass.

  After 1 hour, the synthetic oil having an amount of solid content of 70% by mass was further supplied into the container while the stirring blade was continuously driven to prepare a slurry in which the solid content concentration was diluted to 70% by mass. .

  The obtained slurry having a solid content concentration of 70% by mass is fed using a pump, filled in a mold cavity of a wet press molding machine, and wet press molded at a pressure of 2.0 ton while being magnetically oriented at 15 kOe. A molded product was produced.

The obtained molded body was held in vacuum at 150 ° C. to remove the solvent (synthetic oil), then subjected to sintering treatment in vacuum at 1100 ° C. for 5 hours, and further subjected to aging treatment at 500 ° C. and 1 hour. The rare earth metal sintered magnet of Example 1 was obtained. Table 1 shows the main production conditions and the degree of orientation as magnetic characteristics of the obtained rare earth metal sintered magnet. Regarding the degree of orientation, the following formula (1);
Br = Ms × main phase volume ratio × relative density × degree of orientation (1),
It was obtained from the relationship represented by Here, in Formula (1), Ms shows the saturation magnetization of the main phase in the obtained rare earth magnet.

(Examples 2 to 5 and Comparative Example 1)
Examples 2 to 5 and Comparative Example were the same as Example 1 except that the presence or absence of stirring (crushing) by stirring blades and the stirring time and the solid content concentration of kneading were changed as shown in Table 1. 1 sintered rare earth metal magnet was obtained. The magnetic properties of the obtained rare earth metal sintered magnets are also shown in Table 1.

  From the results shown in Table 1, the rare earth metal sintered magnets of Examples 1 to 5 according to the present invention have a significantly higher degree of orientation than the rare earth metal sintered magnet of Comparative Example 1, and from this, In the sintered metal magnet according to the present invention, it was confirmed that the magnetic field orientation is highly enhanced and the residual magnetic flux density can be improved by performing the stirring (crushing) treatment of the magnetic powder before preparing the slurry. It was.

  In addition, as above-mentioned, this invention is not limited to the said embodiment and Example, In the range which does not deviate from the summary, it can add suitably.

  As described above, according to the method for producing a sintered metal magnet according to the present invention, it is possible to extremely finely orient a fine powder in a magnetic field without excessively degrading productivity and economy, and a residual magnetic flux density. Can be manufactured easily, and these can also improve productivity and economy, for example, particularly light weight, downsizing, and high output of in-vehicle motors and hard disks, etc. Can be used widely and effectively in applications for permanent magnets, devices, apparatuses, systems, and the like including them.

It is a flowchart (process drawing) which shows the manufacture procedure of suitable one Embodiment of the manufacturing method of the rare earth metal sintered magnet by this invention. It is a schematic block diagram which shows an example of the system for manufacturing the metal sintered magnet by this invention.

Explanation of symbols

  S1 ... Mixing step, S11 ... Raw material alloy preparation step, S12 ... Crushing step, S13 ... Stirring (disintegration) step, S14 ... Kneading step, S15 ... Slurry step, S16 ... Wet forming step, S17 ... Solvent removal step, S18 ... Sintering step, S19 ... Aging treatment step, A12 ... Grinding auxiliary agent addition step, A14, A16 ... Solvent addition step, P1 ... Pressure feed pump, 1 ... Production equipment, 20 ... Kneader, 20a ... Pipe, 20b ... Valve, 22 ... container, 23, 24 ... kneading blade, 25 ... fine powder tank, 26 ... solvent tank, 30 ... molding machine, 50 ... control device.

Claims (6)

An agitation step in which a metal magnetic powder having an average particle diameter of 1 to 10 μm and containing a rare earth element is agitated to produce an agitated material, and a kneaded material is produced by adding a first solvent to the agitated material and kneading. A step including a kneading step;
A slurrying step of adding a second solvent to the kneaded product to prepare a slurry;
A molding step of obtaining a molded body by pressure molding the slurry in a state where a magnetic field is applied to the slurry;
A sintering step of sintering the molded body;
The manufacturing method of the metal sintered magnet which has this. In the kneading step, the kneaded product is prepared with a solid content concentration of 85 to 95% by mass.
The manufacturing method of the metal sintered magnet of Claim 1. In the kneading step, the first solvent is added while continuing the stirring in the stirring step.
The manufacturing method of the metal sintered magnet of Claim 1 or 2. In the slurrying step, the slurry has a solid content concentration of 60 to 80% by mass.
The manufacturing method of the sintered metal magnet of any one of Claim 1 to 3.   The stirring step and the kneading step are performed in a nitrogen purged state.
The manufacturing method of the metal sintered magnet of any one of Claim 1 to 4. In the stirring step, as the magnetic powder, a powder containing 0.01 to 0.3% by mass of a grinding aid is used.
The manufacturing method of the sintered metal magnet of any one of Claim 1 to 5.

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