JP2015225880A - Sintered magnet manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a sintered magnet with high density uniformity by using a press-less process (PLP) method in which a compression molding step is not implemented.SOLUTION: The manufacturing method includes: a mixing step 11 of mixing an alloy powder of a raw material of the sintered magnet and a dispersant of a liquid to create a slurry of the alloy powder, the quantity of the dispersant is a quantity to generate a supernatant of the dispersant in the case where the slurry is standing; a filling step 12 of filling a mold with the slurry; a dispersant removal step 13 of removing a part of or the entire dispersant from the slurry with which the mold is filled, to form a state where the mold is filled with the alloy powder while eliminating the supernatant of the dispersant; an orientation step 14 of applying a magnetic field to the alloy powder in the state where the mold is being filled with the alloy powder underwent the dispersant removal step 13; and a sintering step 15 of sintering the alloy powder in the state where the mold is being filled with the alloy powder underwent the orientation step 14.

Description

  The present invention relates to a method of manufacturing a sintered magnet.

  When manufacturing a sintered magnet, conventionally, a powder obtained by pulverizing a raw material alloy lump (hereinafter referred to as “alloy powder”) is filled in a mold (filling step), and a magnetic field is applied to the alloy powder in the mold. Thus, the particles of the alloy powder are orientated (orientation process), and pressure is applied to the oriented alloy powder to produce a compression molded body (compression molding process), and the compression molded body is taken out from the mold and heated. And then sintering (sintering process). Or the method of performing the said orientation process and compression molding process simultaneously by applying a pressure with a press machine, applying a magnetic field to alloy powder after a filling process is also taken. In any case, since compression molding is performed using a press, these methods are referred to as “press methods” in this specification.

  On the other hand, recently, the shape corresponding to the cavity of the mold can be obtained by filling the alloy powder into the mold and performing orientation and sintering while the alloy powder is still contained in the mold without performing compression molding. It has been found that a sintered magnet having the above can be manufactured (Patent Document 1). In the present specification, a method of manufacturing a sintered magnet without performing the compression molding step is referred to as a “PLP (Press-less Process) method”. In the PLP method, when the alloy powder is filled into the mold, the alloy powder is put into the mold with a pressure (generally 2 MPa or less) that is sufficiently lower than the pressure applied during compression molding (usually several tens of MPa). You may push in.

  The PLP method is particularly suitable for producing RFeB-based sintered magnets for the following reasons. RFeB sintered magnets are rare earth elements R (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or 1 or 2 Above), a sintered magnet containing Fe and B as main constituent elements and has many magnetic properties such as residual magnetic flux density higher than that of conventional permanent magnets, but has the disadvantage of low coercive force Have The coercive force indicates the ability to maintain the magnetization when an external magnetic field in a direction different from the magnetization is applied, and generally the coercive force decreases as the temperature increases. Therefore, in order to use RFeB-based sintered magnets in motors for automobiles, etc. that are used at relatively high temperatures of around 200 ° C. and whose magnetic field direction varies greatly, the coercive force must be sufficiently high. There is. In the NdFeB-based sintered magnet mainly containing Nd as the rare earth element R, the coercive force can be increased by containing Tb and / or Dy, but the residual magnetic flux density and the maximum energy product are reduced. The disadvantage is that Tb and Dy, which are more expensive and rarer than Nd, must be used. On the other hand, according to the PLP method, the coercive force can be increased and the residual magnetic flux density and the maximum energy product can be increased for the following reasons. Therefore, the amount of Tb and Dy used can be reduced or made zero.

  Since there is no need to use a press in the PLP method, the equipment can be made smaller than in the press method, and the entire equipment can be easily placed in an oxygen-free atmosphere. Therefore, since the particles of the alloy powder are less likely to be oxidized during the production of the sintered magnet than in the pressing method, the average particle size can be reduced (the total surface area of the particles in the entire alloy powder is increased). When the average particle size of the alloy powder is thus reduced, the average particle size of the microcrystals in the sintered magnet to be manufactured is also reduced. As a result, when an external magnetic field in a direction different from the magnetization is applied, it is difficult to form a magnetic domain whose magnetization is reversed, so that the coercive force is improved. Further, by not applying pressure to the alloy powder during and after the orientation process, it is possible to prevent the disorder of orientation, so that the residual magnetic flux density and the maximum energy product can be increased.

  When the frictional force between the particles is large during the alignment step, the alloy powder particles are prevented from being aligned, which causes a decrease in residual magnetic flux density and maximum energy product. Therefore, in order to reduce the frictional force between the particles, a small amount of solid or liquid lubricant is added to the alloy powder (0.1 to 1% by mass with respect to the alloy powder in the case of the RFeB system) before the filling step. It is desirable (patent document 1).

International Publication WO2006 / 004014 JP 2006-303433 A

  In the filling process, it is difficult to uniformly supply the alloy powder to the mold, and the alloy powder may be biased in the mold. Such unevenness of the alloy powder can be reduced to some extent by adding a lubricant to the alloy powder as described above or pushing the alloy powder into the mold. Further, in the case of the press method, since the compression molding is performed, the unevenness of the alloy powder is considerably eliminated. However, since the PLP method does not perform compression molding, the orientation process and the sintering process are performed while the bias of the alloy powder remains. If it does so, the density of the sintered magnet obtained will become non-uniform | heterogenous and the part with low magnetic characteristics will arise.

  The problem to be solved by the present invention is to provide a method of manufacturing a sintered magnet having high density uniformity using the PLP method.

The sintered magnet manufacturing method according to the present invention made to solve the above problems is as follows.
a) A step of preparing a slurry of the alloy powder by mixing a raw alloy powder of a sintered magnet and a liquid dispersion medium, the amount of the dispersion medium being equal to the dispersion medium when the slurry is allowed to stand. A mixing step, which is the amount of supernatant produced;
b) a filling step of filling the mold with the slurry;
c) Dispersion medium removing step of forming a state in which there is no supernatant of the dispersion medium and the alloy powder is filled in the mold by removing a part or all of the dispersion medium from the slurry filled in the mold When,
d) an alignment step of applying a magnetic field to the alloy powder while the mold is filled with the alloy powder that has undergone the dispersion medium removal step;
e) a sintering step of sintering the alloy powder that has undergone the orientation step while being filled in the mold.

  In the present invention, the mold is filled with a slurry in which the alloy powder is mixed with a liquid dispersion medium. Here, since the amount of the dispersion medium is such an amount that a supernatant of the dispersion medium is generated when the slurry is allowed to stand, rearrangement of the particles of the alloy powder occurs when the alloy powder precipitates in the dispersion medium. It is easy to deposit the alloy powder in a uniform and dense state. In this state, after removing the dispersion medium in the dispersion medium removal step, the density of the sintered magnet obtained through the orientation step and the sintering step is uniform and becomes high.

  Further, at least up to the filling step, the particles of the alloy powder are prevented from being oxidized by being protected by the dispersion medium, so that these steps can be performed in the air.

  The amount of the dispersion medium mixed with the alloy powder in the mixing step is preferably 50% by mass or more in the slurry, that is, the same mass or more as the alloy powder. As a result, the slurry has sufficient fluidity, and the slurry can be uniformly filled in the mold without unevenness in the filling step.

  In terms of making the density of the sintered magnet uniform and thereby making the magnetic properties uniform, the dispersion medium may be completely removed in the dispersion medium removal step. However, if the dispersion medium is completely removed, the frictional force between the particles is increased in the alignment step, and the alignment of the particles is deteriorated, so that the residual magnetic flux density and the maximum energy product are reduced. On the other hand, if only a minimum amount of the dispersion medium is removed to eliminate the supernatant, and a large amount of the dispersion medium remains in the alloy powder, the magnetic field is removed after applying the magnetic field in the orientation process and aligning it. In addition, the particles of the alloy powder move due to the interaction of magnetization of each particle, and the orientation state is relaxed. As a result, the residual magnetic flux density and the maximum energy product are reduced. For this reason, it is desirable to appropriately set the amount of the dispersion medium to be removed in the dispersion medium removal step so that an amount of the dispersion medium within a predetermined range remains in the alloy powder after the dispersion medium removal step.

  Examples of the dispersion medium include hydrocarbon organic solvents (n-hexane, n-heptane, cyclohexane, cyclohexanone, etc.), liquid paraffin, naphthenic organic solvents (naphthenesol, etc.), silicone organic solvents (silicone oil, etc.), etc. 1 type (s) or 2 or more types can be used. Of these, it is desirable to use a low-boiling point dispersion medium having a boiling point of 60 ° C. or more and less than 120 ° C. because the dispersion medium can be easily removed. Alternatively, it is also desirable to use a combination (mixed) of a high boiling point dispersion medium having a boiling point of 120 ° C. or higher such as silicone oil and the low boiling point dispersion medium described above. In this case, after removing the dispersion medium to some extent by evaporating the low boiling point dispersion medium in the dispersion medium removal process, the orientation process is performed with the high boiling point dispersion medium remaining. Since the high-boiling point dispersion medium serves as a protective film and can prevent oxidation of the particles, the alignment step after the low-boiling point dispersion medium is evaporated can also be performed in the air. Use of a high boiling point dispersion medium having a boiling point of less than 200 ° C. is desirable in terms of easy removal of the dispersion medium after the alignment step.

  Components other than the components of the dispersion medium may be added to the dispersion medium. For example, lubricant (methyl butyrate, methyl hexanoate, methyl n-octanoate, methyl decanoate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate) is dispersed. It can be added to the medium.

The dispersion medium can be removed from the slurry by, for example, the following method.
In the first method, the slurry filled in the mold is allowed to stand, and after the alloy powder is precipitated, the supernatant dispersion medium is removed by suction or the like.
The second method is to evaporate the dispersion medium. According to this method, more dispersion medium can be removed than the amount of supernatant. Here, if a dispersion medium having volatility at room temperature is used, the dispersion medium can be removed simply by allowing the slurry to stand still. Alternatively, a dispersion medium having a boiling point lower than the sintering temperature of the alloy powder (900 ° C. to 1100 ° C. for RFeB-based sintered magnets) is used, and the slurry is heated to a temperature higher than the boiling point and lower than the sintering temperature. May be actively evaporated by heating. The dispersion medium remaining in the alloy powder after the dispersion medium removing step can be evaporated by heating in the sintering step.

In the present invention, a sleeve member is placed on the periphery of the upper opening of the mold having a cavity space having a volume corresponding to the volume of the alloy powder after removal of the dispersion medium,
In the filling step, the slurry is filled into a cavity space of a mold on which the sleeve member is placed and an internal space of the sleeve member,
The dispersion medium may be removed from the slurry by removing the sleeve member from the mold after removing the dispersion medium from the slurry in the dispersion medium removing step, or by removing the sleeve member from the mold. In this case, the dispersion medium may be removed by suction, evaporation, or the like. However, after the slurry is allowed to settle and the alloy powder has settled, the sleeve member is simply removed from the mold, so that the inner space of the sleeve member can be removed. The dispersion medium in the supernatant that has stayed can be removed (that is, the dispersion medium is removed from the slurry by removing the sleeve member from the mold).

  In the mixing step, the slurry is preferably prepared by pulverizing an alloy lump having the same composition as the alloy powder in the dispersion medium. Here, the alloy lump means one larger than the particles of the alloy powder, and typically has a diameter in the range of about several hundred μm to several tens of mm. By preparing the slurry by this method, there is no need to perform a separate step of preparing the alloy powder, and even when handled in the air, the alloy lump and the alloy powder are prevented from coming into contact with oxygen in the air. Can do. The pulverization of the alloy lump in such a dispersion medium can be performed using a wet attritor, a ball mill, or the like. At that time, it is desirable to use a dispersion medium in which a low-boiling point dispersion medium and a high-melting point dispersion medium are mixed because the dispersion medium can be easily removed after pulverization while suppressing the amount of the dispersion medium that evaporates during pulverization.

Among RFeB-based sintered magnets, R ^L FeB-based sintered magnets containing light rare earth elements R ^L that are either one or both of Nd and Pr as rare earth elements R include R ^L By attaching a powder containing heavy rare earth element ^RH , which is one or more of Tb, Dy and Ho, to the surface of the sintered body of the FeB magnet, heating is performed. ^RH is supplied only to the vicinity of the grain boundary among the particles in the aggregate (see, for example, Patent Document 2). This method is called the grain boundary diffusion method, and compared to the case of making RFeB-based sintered magnets using alloy powder containing ^RH , the coercive force is increased to the same extent and the amount of ^RH used is suppressed. It is something that can be done. In this grain boundary diffusion method, the powder for grain boundary diffusion treatment to be adhered to the surface of the sintered body of the R ^L FeB magnet is obtained by pulverizing an alloy lump as a raw material of the powder in a dispersion medium, and then the dispersion medium. It is desirable to produce by removing a part or all of. Thus, even when the alloy lump is pulverized in the air, the alloy lump and the alloy powder containing ^RH can be prevented from coming into contact with oxygen in the air. In addition, if a part of the dispersion medium is removed after pulverization, that is, if a part of the dispersion medium is left in the powder, the alloy powder containing ^RH can be prevented from coming into contact with oxygen even after pulverization. Can do.

  According to the present invention, a sintered magnet with high density uniformity can be manufactured using the PLP method.

The figure which shows the process of one Example of the sintered magnet manufacturing method which concerns on this invention. Schematic diagram showing the state in which the mold is filled with the slurry in the filling step (a), Schematic diagram showing the state in which the alloy powder is precipitated after the filling step and the supernatant of the dispersion medium is generated (b), the supernatant in the dispersion medium removal step Schematic (c) showing suction removal, schematic diagram (d) showing a state in which a lid is inserted in the mold and the orientation process, showing that the dispersion medium remaining in the alloy powder is evaporated after the orientation process Schematic (e) and schematic (f) showing the sintering process. Schematic which shows the modification of a present Example.

The Example of the sintered magnet manufacturing method which concerns on this invention is described using FIGS. 1-3. In the following, a case where an RFeB-based sintered magnet is manufactured will be described as an example, but the same applies to the case where an RCo (RCo ₅ , R ₂ Co ₇ ) -based sintered magnet and other sintered magnets are manufactured.

  In FIG. 1, the process of the sintered magnet manufacturing method of a present Example is shown with a schematic diagram. In this example, the RFeB-based alloy flakes produced by the strip casting method (referred to as “alloy lump” in the present specification because they are sufficiently larger than the produced alloy powder grains) are used as a raw material in the mixing step 11. The RFeB-based sintered magnet is manufactured through the five steps of filling step 12, dispersion medium removing step 13, orientation step 14, and sintering step 15. In this embodiment, a drying step 145 for removing the dispersion medium remaining in the alloy powder is performed between the orientation step 14 and the sintering step 15, but this step is not an essential requirement in the present invention.

  In the mixing step 11, the operation of mixing the pulverized alloy powder and the dispersion medium is performed in the following two steps while the alloy lump produced by the strip casting method is pulverized by the wet method described below. In addition, it is not essential to perform the operation of mixing the alloy powder and the dispersion medium in two steps as described above, and the operation may be performed in one step or three or more steps.

  In the first mixing step 111, the alloy lump is pulverized using a wet attritor. A wet attritor generally introduces a material to be crushed into a pulverization tank together with a liquid, and coarsely pulverizes the material to be pulverized by rotating blades in the pulverization tank. In the present embodiment, a sufficiently large amount of dispersion medium of the same mass or more as the alloy powder is used so that the dispersion medium supernatant is generated in the dispersion medium removal step 13.

  In the second mixing step 112, the alloy coarse powder obtained by pulverizing the alloy lump in the first mixing step 111 is further pulverized using a bead mill and mixed with a dispersion medium. The bead mill generally pulverizes an object to be processed by adding and mixing beads, which are harder pulverization media (media), to the object to be processed. In the present embodiment, beads are added while being mixed with a coarse alloy powder and a dispersion medium that have been pulverized to some extent by a wet attritor, and the coarse alloy powder is pulverized so that the diameter is smaller than that of the beads. After the grinding by the bead mill, the beads are filtered from the mixture to obtain a slurry that is a mixture of the remaining alloy powder and dispersion medium.

  In the filling step 12, as shown in FIG. 2A, the slurry S is filled into the mold 21 having the cavity space 211 corresponding to the shape of the magnet of the final product. In the present embodiment, a mold 21 having a cavity space 211 having the same dome-shaped longitudinal section in one axial direction is used. The shape of the cavity space 211 is not limited to this, and may be another shape such as a rectangular parallelepiped. In the present embodiment, the mold 21 is made of dense carbon such as a carbonaceous extruded material, a graphite extruded material, a graphite mold pressing material, an isotropic graphite material, or a carbon fiber reinforced carbon composite material. A mold using dense carbon has features that there are fewer voids in the wall than those using alumina or the like, and the alloy powder hardly diffuses into the mold wall during sintering.

  After standing for a while (1 hour in this example) after the filling step 12, the alloy powder in the slurry S is densely precipitated by its own weight, and a supernatant L of the dispersion medium is generated (FIG. 2 (b)). In the dispersion medium removing step 13, the supernatant L is removed by suction ((c)). As a result, the dispersion medium mixed alloy powder PL in which the dispersion medium is mixed at a smaller content than the slurry S remains in the mold 21. In addition, the dispersion medium removing step 13 was conducted as a preliminary experiment, and the amount of the removed supernatant was measured or the mass of the dispersion medium mixed alloy powder PL remaining in the mold 21 was measured, and then the dispersion medium was completely evaporated. Further, by measuring the mass, the amount of the dispersion medium to be mixed with the alloy powder (alloy lump) in the mixing step 11 can be estimated. When further removing the dispersion medium from the dispersion medium mixed alloy powder PL remaining in the mold 21 after removing the supernatant, for example, vacuum (reduced pressure) drying at room temperature or heating to a temperature higher than the boiling point of the dispersion medium. Perform operations such as Although all of the dispersion medium may be removed by this operation, it is desirable that a part of the dispersion medium remains in order to increase the degree of orientation and prevent ignition in the atmosphere in the next alignment step 14.

  The volume of the dispersion medium mixed alloy powder PL is smaller than the volume of the space in the mold 21. A lid 22 which is a dense carbon plate material is placed on the upper surface of the dispersion medium mixed alloy powder PL (see FIG. 2D). As a result, the evaporation of the dispersion medium in the vicinity of the upper surface of the dispersion medium-mixed alloy powder PL is delayed, and the occurrence of surface defects such as cracks can be suppressed. Note that the use of the lid 22 is not essential in the present invention.

  In the orientation step 14, the alloy powder is oriented by applying a magnetic field to the dispersion medium mixed alloy powder PL while the mold 21 is filled with the dispersion medium mixed alloy powder PL ((e)). At this time, in this embodiment, the remaining dispersion medium has a role of a lubricant, and the frictional force between the particles of the alloy powder is suppressed, so that the orientation becomes easy.

  Thereafter, in this embodiment, in the drying step 145, the dispersion medium-mixed alloy powder PL is heated and dried (atmosphere heating drying or reduced pressure heating drying) in the range of 50 to 200 ° C. to remove a part of the dispersion medium (same as above). (f)). At that time, the vaporized dispersion medium G is discharged to the outside through the gap between the mold 21A and the lid 22A. Then, the alloy powder P is sintered by heating the dispersion medium-mixed alloy powder PL from which a part of the dispersion medium has been removed to 900 to 1100 ° C. while being accommodated in the mold 21 in the sintering step 15. At the same time, the remaining dispersion medium is removed ((f)). Thereby, an RFeB-based sintered magnet is obtained. The drying step 145 is not essential, but if the temperature is rapidly increased to the sintering temperature in the sintering step 15, the dispersion medium may bump out. Therefore, the drying step 145 is removed at a temperature lower than the sintering temperature. It is desirable to perform heat drying for the dispersion medium.

  In the above examples, the alloy powder was prepared (alloy lump crushing) and the dispersion medium was mixed at the same time, but the alloy lump was pulverized by a dry method (for example, the alloy lump was made to absorb hydrogen and then mechanically Then, the alloy powder may be further finely pulverized using a jet mill, and then the alloy powder and the dispersion medium may be mixed.

  Samples were prepared by the method of this example under the following conditions 1 to 8. All of these samples were obtained using the slurry prepared in the same mixing step 11. The difference between conditions 1 to 8 is in the amount of the dispersion medium remaining in the alloy powder after the dispersion medium removing step 13. The difference in the amount is that, in the dispersion medium removing step 13, only the supernatant is removed under the condition 1, and under the conditions 2 to 8, vacuum drying is performed for different times for each sample so that the dispersion medium does not completely evaporate after the removal of the supernatant. By doing. The composition of the alloy used to make the slurry was Nd: 25.8 mass%, Pr: 4.7 mass%, Dy: 0.3 mass%, B: 0.98 mass%, Cu: 0.1 mass%, Al: 0.2 mass%, and the balance Fe is there. The dispersion medium is n-hexane. The alloy lump pulverization performed in the mixing step 11 was finally performed so that the average particle size measured by the dynamic light scattering method (laser method) was 5 μm or less. The alignment step 14 was performed using a 4T pulse magnetic field, and the sintering step 15 was performed by maintaining at 1000 ° C. for 4 hours in a nitrogen gas atmosphere.

Table 1 shows the results of measuring the production conditions and the degree of orientation of the obtained RFeB-based sintered magnets for the samples obtained under each condition. Here, the amount of the dispersion medium remaining in the alloy powder after the dispersion medium removal step 13 which is a manufacturing condition was measured in a state where the lid 22 was placed on the upper surface of the dispersion medium mixed alloy powder PL after the dispersion medium removal step 13. It calculated | required by subtracting the mass of the obtained RFeB type | system | group sintered magnet, the mold 21, and the lid | cover 22 from the total mass (The mold 21, the lid | cover 22, alloy powder, and the residual dispersion medium). Since the mold 21 and the lid 22 are made of dense carbon having almost no voids, it is assumed that the dispersion medium hardly penetrates into the mold 21 and the lid 22 after the dispersion medium removing step 13 and exists in the alloy powder. . Under each condition, 18 samples were prepared, and the degree of orientation was measured for 5 samples randomly extracted from them. In Table 1, the degree of orientation indicates an average value and a minimum value in five samples, and indicates a difference between the maximum value and the minimum value, and a standard deviation σ.

  As a result of this experiment, the average value is 95% or more when the amount of the dispersion medium (residual dispersion medium after the removal process) remaining in the alloy powder after the dispersion medium removal process 13 is 0.05 to 10% with respect to the total mass. In particular, the average degree of orientation reached 96% or more within the range of 0.1 to 0.5%. Further, the amount of the residual dispersion medium after the removal step is preferably 0.1 to 5% by mass because the difference between the maximum value and the minimum value of the orientation degree and the standard deviation is 0.5 or less. Since the standard deviation becomes the smallest when the value is within the range, it is more preferable. This means that a plurality of sintered magnets can be obtained with the highest homogeneity when the amount of the residual dispersion medium after the removal step is within the above range. Under any of the conditions, the produced 18 samples had no defects such as defects.

  Next, the modification of the sintered magnet manufacturing method of a present Example is demonstrated using FIG. In this modification, the following mold 21A and sleeve member 23 are used. The mold 21A has a volume corresponding to the volume of the alloy powder (dispersion medium mixed alloy powder PL) remaining in the cavity space 211A after the dispersion medium removing step 13. The sleeve member 23 is placed on the peripheral edge 213 of the opening 212 at the top of the mold 21A, and has an internal space 231 penetrating vertically. The mold 21A and the sleeve member 23 are both made of dense carbon.

  In the sintered magnet manufacturing method of the present modification, first, the slurry S is prepared by the same method as in the above-described embodiment. Next, the sleeve member 23 is placed on the peripheral edge 213 of the mold 21A (FIG. 3A), and the slurry S is filled into the cavity space 211A of the mold 21A and the internal space 231 of the sleeve member 23 (FIG. 3B). When allowed to stand in that state, the slurry S is separated into the dispersion medium mixed alloy powder PL and the supernatant L ((c)). Here, since the capacity of the mold 21A is set as described above, the dispersion medium-mixed alloy powder PL just fills the cavity space 211A of the mold 21A. Next, the sleeve member 23 is removed from the mold 21A ((d)). Thereby, the supernatant L flows out from the internal space 231 of the sleeve member 23, and only the dispersion medium mixed alloy powder PL without a supernatant is filled in the cavity space 211A of the mold 21A. Thereafter, a lid 22A made of dense carbon is attached to the opening 212 of the mold 21A. Thereafter, the orientation step (same (e)) and the sintering step (same (f)) are carried out in the same manner as in the above example. In this modification, since the drying process is not performed between the orientation process and the sintering process, the vaporized dispersion medium G is discharged to the outside through the gap between the mold 21A and the lid 22A during the sintering process. . Moreover, in this modification, you may implement a drying process between an orientation process and a sintering process.

Next, an example of the grain boundary diffusion method will be described. In the grain boundary diffusion method, generally, any of Tb, Dy, and Ho is formed on the surface of an R ^L FeB-based sintered magnet containing R ^L (Nd and / or Pr) as the rare earth element R as in the above-described embodiment. An ^RH- containing alloy powder containing one or more heavy rare earth elements ^RH is deposited and then heated. Here, it is desirable to produce the ^RH- containing alloy powder by a wet method.

For example, introduced into a wet attritor the alloy ingot containing heavy rare-earth element R ^H such TbNiAl alloy or DyNiAl alloy with hexane, mixed with hexanes with a roughly pulverized alloy ingot. Subsequently, the coarsely pulverized alloy coarse powder and hexane mixture are introduced into a bead mill together with a pulverizing medium, and further pulverized and mixed. Next, the beads are filtered from the mixture, and silicone oil having a boiling point higher than that of hexane is added to the remaining mixture, and then hexane is removed under vacuum (reduced pressure). Since the silicone oil / ^RH containing alloy powder thus obtained does not ignite even in the air, the mixing operation can be easily performed not only in the inert gas but also in the air. Further, by adding silicone grease to the silicone oil / ^RH containing alloy powder (for example, by adding 8% of the ^RH containing alloy powder in a mass ratio so that each of the silicone grease and the silicone oil is 1), knead well. A mixed paste of ^RH- containing alloy powder, silicone grease, and silicone oil can be obtained without ignition in the atmosphere. After this mixed paste is applied to the surface of the R ^L FeB-based sintered magnet, it is heated at 700 to 1000 ° C. (preferably 850 to 950 ° C.).

DESCRIPTION OF SYMBOLS 11 ... Mixing process 111 ... 1st mixing process 112 ... 2nd mixing process 12 ... Filling process 13 ... Dispersing medium removal process 14 ... Orientation process 145 ... Drying process 15 ... Sintering process 21, 21A ... Mold 211, 211A ... Mold Cavity space 212... Mold opening 213... Opening peripheral edge 22, 22 A. Mold lid 23... Sleeve member 231.

Claims (10)

a) A step of preparing a slurry of the alloy powder by mixing a raw alloy powder of a sintered magnet and a liquid dispersion medium, the amount of the dispersion medium being equal to the dispersion medium when the slurry is allowed to stand. A mixing step, which is the amount of supernatant produced;
b) a filling step of filling the mold with the slurry;
c) Dispersion medium removing step of forming a state in which there is no supernatant of the dispersion medium and the alloy powder is filled in the mold by removing a part or all of the dispersion medium from the slurry filled in the mold When,
d) an alignment step of applying a magnetic field to the alloy powder while the mold is filled with the alloy powder that has undergone the dispersion medium removal step;
e) A sintered magnet manufacturing method including a sintering step of sintering the alloy powder that has undergone the orientation step while being filled in the mold.   The sintered magnet manufacturing method according to claim 1, wherein in the dispersion medium removing step, the slurry filled in the mold is allowed to stand, and after the alloy powder is precipitated, the dispersion medium in the supernatant is removed.   The sintered magnet manufacturing method according to claim 1, wherein, in the dispersion medium removing step, the dispersion medium is evaporated from the slurry filled in the mold. A sleeve member is placed on the periphery of the upper opening of the mold having a cavity space having a volume corresponding to the volume of the alloy powder after the dispersion medium is removed,
In the filling step, the slurry is filled into a cavity space of a mold on which the sleeve member is placed and an internal space of the sleeve member,
The dispersion medium is removed from the slurry by removing the sleeve member from the mold after removing the dispersion medium from the slurry in the dispersion medium removing step, or removing the sleeve member from the mold. The sintered magnet manufacturing method of any one of Claims 1.   The sintered magnet manufacturing method according to any one of claims 1 to 4, wherein the dispersion medium has a boiling point of 60 ° C or higher and lower than 120 ° C.   5. The mixture according to claim 1, wherein a low boiling point dispersion medium having a boiling point of 60 ° C. or more and less than 120 ° C. and a high boiling point dispersion medium having a boiling point of 120 ° C. or more are used as the dispersion medium. The sintered magnet manufacturing method.   As the dispersion medium, one or more selected from hydrocarbon solvents, liquid paraffin, naphthenic organic solvents, and silicone organic solvents are used. In the dispersion medium removing step, the dispersion medium is converted into the alloy powder. The method for producing a sintered magnet according to any one of claims 1 to 6, wherein the dispersion medium is removed so that 0.1 to 10% by mass remains.   Lubricant that is one or more of methyl butyrate, methyl hexanoate, methyl n-octanoate, methyl decanoate, methyl laurate, methyl myristate, methyl palmitate, and methyl stearate in the dispersion medium The method for producing a sintered magnet according to any one of claims 1 to 7, wherein an agent is added.   The sintered magnet manufacturing method according to any one of claims 1 to 8, wherein, in the mixing step, the slurry is prepared by pulverizing an alloy lump having the same composition as the alloy powder in the dispersion medium. The base material of the R ^L FeB system sintered magnet containing the light rare earth element ^RL which is any one or both of Nd and Pr as the rare earth element R, the iron element, and the boron element, respectively. Produced by the sintered magnet manufacturing method described in
By crushing an alloy lump containing heavy rare earth element ^RH that is one or more of Tb, Dy and Ho in a dispersion medium, and then removing a part or all of the dispersion medium A sintered magnet manufacturing method in which the produced powder for grain boundary diffusion treatment is attached to the surface of the base material, and the base material is heated to a predetermined temperature equal to or lower than a sintering temperature.

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