JP4609644B2 - Manufacturing method of rare earth sintered magnet - Google Patents

Description

  The present invention relates to a method for producing a rare earth sintered magnet typified by an Nd—Fe—B system, and more particularly to a technique for obtaining a rare earth sintered magnet having excellent magnetic properties by increasing the dispersibility of a lubricant. .

  When manufacturing a rare earth sintered magnet, a lubricant is added to the raw material powder in order to improve magnetic orientation. For example, a technique for further improving the magnetic orientation by adding a lubricant before fine pulverization of the raw material is disclosed (Patent Document 1). In addition to the lubricant, an organic solvent is added to prevent oxidation and dry pulverization is performed (Patent Document 2). A lubricant in which a fatty acid ester is liquefied is pulverized with a raw material powder by a jet mill (patent) Reference 3), a technique of adding a fatty acid by finely pulverizing by adding air flow pulverization after adding and adding a hydrocarbon-based lubricant (Patent Document 4), and pulverizing while enjoying the improvement in orientation by the lubricant studied by the present applicant Various techniques such as a technique for preventing equipment wear (Patent Document 5) are disclosed.

Japanese Patent No. 2915560 Japanese Patent No. 2668219 JP-A-8-111308 Japanese Patent Laid-Open No. 7-240329 JP 2003-68551 A

By the way, the lubricant is not sufficiently dispersed only by adding the lubricant to the raw material powder. If the lubricant is not sufficiently dispersed, aggregated particles of the lubricant are generated, and pores may be formed in the magnet after sintering. In addition, when the raw material powder to which the lubricant is added is pulverized, variation in pulverization efficiency may occur, resulting in a decrease in magnetic orientation.
An object of this invention is to provide the manufacturing method of the rare earth sintered magnet which improves magnetic orientation by improving the dispersibility of a lubricant further, and has the outstanding magnetic characteristic.

In the method of manufacturing a rare earth sintered magnet of the present invention made in view of the above-described problems, the raw powder and lubricant of the rare earth sintered magnet are pulverized to obtain a pulverized powder, and then the pulverized powder and the organic liquid are added to the chamber. The organic liquid is added to the pulverized powder and rolled by relatively rotating the chamber and the rolling blade provided in the chamber. Then, a part or all of the organic liquid is removed from the pulverized powder after rolling , a magnetic field is applied to the pulverized powder from which the organic liquid has been removed, and pressure molding is performed to obtain a molded body. A rare earth sintered magnet is manufactured by sintering. As described above, when the raw material powder after pulverization and the lubricant are further mixed by rolling by adding an organic liquid, the dispersibility of the lubricant is enhanced. The above organic liquids are toluene, xylene, pinene, menthane, terpineol, ethanol, isobutyl alcohol, butyl cellosolve, cellosolve, carbitol, butyl carbitol, butyl carbitol acetate, cyclohexanol, dibutyl ether, ethyl acetate, n-butyl acetate. , Propionic anhydride, acetone (dimethyl ketone), methyl isobutyl ketone, and methyl ethyl ketone, and the amount of the organic liquid added is 30 to 150 vol% with respect to the pulverized powder.

The addition amount of the organic liquid is preferably a 40 to 90 vol% with respect to a ground powder. Or lubricant, may be either insoluble or soluble in an organic liquid. Prior to the step of applying a magnetic field to the end flour砕粉, pulverized powder after rolling can to remove some or all of the organic liquid from the grinding powder by exposure to a reduced pressure atmosphere.

In the method for producing a rare earth sintered magnet of the present invention, the raw powder and lubricant of the rare earth sintered magnet are pulverized to obtain a pulverized powder, and then an organic liquid is added to the pulverized powder in an amount of 30 to 150 vol% of the pulverized powder. Knead. Then, part or all of the organic liquid is removed from the pulverized powder after kneading , a magnetic field is applied to the pulverized powder from which the organic liquid has been removed, and pressure molding is performed to obtain a molded body. By sintering, a rare earth sintered magnet is manufactured. Thus, when the raw material powder and the lubricant are mixed by kneading in the presence of the organic liquid, the lubricant is sufficiently dispersed.

The kneading is performed by rolling the raw material powder, the lubricant, and the organic liquid by the main wing rotating in the chamber and the auxiliary wing rotating in a direction different from the main wing. In this case, the main wing can rotate around a substantially vertical axis in the chamber. Alternatively, the main wing can rotate about a substantially horizontal axis within the chamber.
The starting powder, for example, R ₂ T ₁₄ B phase (R is one or more elements selected from rare earth elements, T is one or selected from transition metal elements containing Fe, or Fe and Co The pulverized powder has, for example, an average particle diameter of 2.5 to 6 μm.

  According to the method for producing a rare earth sintered magnet of the present invention, by improving the dispersibility of the lubricant, it is possible to improve the orientation and to improve the magnetic properties of the finally obtained sintered magnet. Become.

Hereinafter, the present invention will be described in detail based on embodiments.
The raw material alloy used as the raw material of the sintered magnet can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting. In order to prevent segregation after dissolution, for example, it can be solidified by pouring into a water-cooled copper plate. An alloy obtained by the reduction diffusion method can also be used as a raw material alloy.
When obtaining an RTB-based sintered magnet, a so-called alloy using a R ₂ T ₁₄ B crystal grain (low R alloy) and an alloy containing more R than a low R alloy (high R alloy) is used. A mixing method can also be applied to the present invention.

The raw material alloy is first subjected to a grinding process. In the case of the mixing method, the low R alloy and the high R alloy are pulverized separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process.
In the coarse pulverization step, first, the raw material alloy is coarsely pulverized until the particle diameter becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by occluding hydrogen in the raw material alloy and then releasing it. The hydrogen releasing treatment is performed for the purpose of reducing hydrogen as an impurity as a rare earth sintered magnet. The temperature of heating and holding for releasing hydrogen is 200 ° C. or higher, desirably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the raw material alloy, etc., but is at least 30 minutes or longer, preferably 1 hour or longer. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. In the fine pulverization step, a lubricant is added to the coarsely pulverized powder for lubrication during molding, improvement of pulverization property and orientation, and the coarsely pulverized raw material powder is finely pulverized together with the lubricant. A pulverized powder is obtained. Lubricants include fatty acids or fatty acid derivatives and hydrocarbons such as zinc stearate and oleic acid zinc stearate, calcium stearate, aluminum stearate, stearic acid amide, oleic acid amide, ethylenebisisostearic acid amide, carbonized Examples thereof include paraffin and naphthalene which are hydrogen. The lubricant can be added at about 0.01 to 0.3 wt% of the coarsely pulverized powder during fine pulverization.

  A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2.5 to 6 μm, preferably 3 to 5 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing.

  In the case of the mixing method, the timing of mixing the two kinds of alloys is not limited. However, when the low R alloy and the high R alloy are separately pulverized in the pulverization step, the pulverized low R The alloy powder and the high R alloy powder are mixed in a nitrogen atmosphere. The mixing ratio of the low R alloy powder and the high R alloy powder may be about 80:20 to 97: 3 by weight. The mixing ratio when the low R alloy and the high R alloy are pulverized together is the same.

The raw powder and the lubricant are mixed by rolling the finely pulverized powder obtained above, that is, by giving the finely pulverized powder a movement that rolls each finely pulverized powder. Due to the rolling operation, a shear stress acts between the finely pulverized powders, and the lubricant existing between the finely pulverized powder surface and the finely pulverized powder can be sufficiently dispersed.
For rolling, a rolling mixing device 10 as shown in FIGS. 1 and 2 can be used.
As shown in FIGS. 1 and 2, the rolling mixing device 10 has a configuration in which a rolling blade (main wing) 12 and an auxiliary wing 13 are provided in a chamber 11.
The chamber 11 includes an openable / closable lid (not shown) and is hermetically sealed with the lid closed. Moreover, an organic liquid can be added to the chamber 11 by a fluid spray nozzle or a dropping nozzle (not shown).
The rolling blade 12 is provided with a plurality of blade members 12b on a rotary shaft 12a, and is driven to rotate about the axis of the rotary shaft 12a by a drive motor (not shown). Similarly, the auxiliary wing 13 is provided with a plurality of wing members 13b on the rotating shaft 13a, and a drive motor (not shown) or a drive motor for rotating the rolling wings 12 drives a gear, a timing belt, and the like. The drive force transmitted through the force transmission mechanism is rotationally driven around the axis of the rotary shaft 13a.

Such a rolling mixing device 10 includes a vertical type as shown in FIG. 1 and a horizontal type as shown in FIG. 2 depending on the installation form of the rolling blades 12.
In the vertical rolling mixing device 10 </ b> V shown in FIG. 1, the rotating blade 12 is provided such that the rotating shaft 12 a has an axis in the substantially vertical direction in the chamber 11. The auxiliary blade 13 is provided above the rolling blade 12, and the rotation shaft 13 a is provided so as to have an axis in the horizontal direction in the chamber 11.
In the horizontal type rolling mixing device 10 </ b> H shown in FIG. 2, the rolling blade 12 is provided such that the rotary shaft 12 a has an axis in the horizontal direction in the chamber 11. The blade member 12b of the rolling blade 12 extends along the peripheral wall 11a continuous in the circumferential direction of the chamber 11, and the auxiliary blade 13 is provided so as to be located inward of the blade member 12b. .

In such a rolling mixing device 10V, 10H, a predetermined amount of the finely pulverized powder obtained in the process as described above is charged into the chamber 11, and the rolling blade 12 and the auxiliary blade 13 are driven to rotate. Mix by rolling.
Note that after the finely pulverized powder is introduced into the chamber 11, the inside of the chamber 11 is preferably replaced with an inert gas such as nitrogen in order to prevent oxidation of the finely pulverized powder. At this time, it is more preferable to rotate the rolling blades 12 for a certain period of time to loosen the finely pulverized powder and to replace the inside of the chamber 11 with an inert gas while expelling air present in the voids of the finely pulverized powder.

An organic liquid is added when rolling the finely pulverized powder . By adding an organic liquid, the dispersibility of the lubricant can be further enhanced.
The timing of adding the organic liquid may be the same as that of the finely pulverized powder, but it is preferable that the organic liquid is charged after the rolling blades 12 are rotated for a certain time after the finely pulverized powder is charged as described above.
Further, even after a predetermined amount of the organic liquid has been introduced, it is preferable to rotate the rolling blade 12 for a certain period of time so that the organic liquid is adapted to the finely pulverized powder to promote mixing by rolling.

At this time, the organic liquid to be used includes hydrocarbon compounds, alcohol compounds, ether compounds (including glycol ether compounds), ester compounds (including glycol ester compounds), ketone compounds, fatty acid compounds, terpene compounds. It can be selected from one or more compounds. Specific examples of such organic liquids include hydrocarbon compounds such as toluene, xylene, pinene, menthane, alcohol compounds such as terpineol, ethanol, isobutyl alcohol, and ether compounds such as butyl cellosolve, cellosolve, Carbitol, butyl carbitol, butyl carbitol acetate, cyclohexanol, dibutyl ether, ester compounds include ethyl acetate, n-butyl acetate, propionic anhydride, ketone compounds include acetone (dimethyl ketone), methyl isobutyl There are ketone, methyl ethyl ketone and the like.
Of course, the organic liquid is not limited to the organic liquids listed here, and other organic liquids such as ethylene glycol, diethylene glycol, and glycerin can also be used. Further, the organic liquid may be one in which the lubricant can be dissolved or insoluble in the lubricant. Therefore, the combination of the lubricant and the organic solvent can be selected as appropriate according to the budget, ease of use, and the like.
The organic liquid includes a substance generally called an organic solvent, but is called an organic liquid because it does not function as a solvent in the present invention.

  The amount of organic liquid added to the finely pulverized powder is not particularly limited, but it is recommended that the amount of organic liquid added to the finely pulverized powder be 30 to 150 vol%. When an organic liquid of this level is added, it is kneaded when rolling, so that the dispersibility of the lubricant is increased and the finely pulverized powder is further mixed. Here, kneading is the minimum necessary coating operation of liquid or paste around the granular material, and can be realized using, for example, the above-described rolling mixing devices 10V and 10H. In addition, although it can also mix with an organic liquid with a Nauta mixer etc., there exists a possibility that an organic liquid may isolate | separate and cannot fully knead | mix. When the amount of the organic liquid added is too small, the dispersibility of the lubricant is lowered. On the other hand, when the amount of the organic liquid added is too large, it may be difficult to remove the organic liquid within a predetermined time when the organic liquid is removed from the pulverized powder after kneading, and the friction between the finely pulverized powders may be reduced. This may reduce the dispersibility. A more desirable addition amount of the organic liquid to the finely pulverized powder is 30 to 120 vol%, and a more desirable addition amount of the organic liquid is 40 to 90 vol%.

The organic liquid can be partially or completely removed from the pulverized powder kneaded as described above.
The specific means for removing the organic liquid is not particularly limited, but it is simple and effective to volatilize the granules by exposing them to a reduced-pressure atmosphere. The reduced-pressure atmosphere may be room temperature, but may be a heated reduced-pressure atmosphere or a heated atmosphere that is not reduced in pressure. What is necessary is just to adjust the pressure of a pressure-reduced atmosphere with the organic liquid to be used. If the heating temperature at this time is too low, the volatilization of the organic liquid does not proceed sufficiently. On the other hand, if the heating temperature is too high, the primary alloy particles constituting the granules may be oxidized and the magnetic properties may be deteriorated. Therefore, in the present invention, the heating temperature is desirably 40 to 80 ° C.

Subsequently, the pulverized powder is subjected to molding in a magnetic field to obtain a molded body.
The molding pressure in the magnetic field molding may be in the range of 0.3 to 3 ton / cm ² (30 to 300 MPa). The molding pressure may be constant from the beginning to the end of molding, may be gradually increased or gradually decreased, or may vary irregularly. The lower the molding pressure is, the better the orientation is. However, if the molding pressure is too low, the strength of the molded body is insufficient and handling problems occur. Therefore, the molding pressure is selected from the above range in consideration of this point. The final relative density of the molded body obtained by molding in a magnetic field is usually 50 to 60%.
The applied magnetic field may be about 12 to 20 kOe (960 to 1600 kA / m). By applying a magnetic field of this degree, the pulverized powder collapses and is decomposed into primary alloy particles. The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can also be used in combination.

Next, the molded body is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, the difference of an average particle diameter, and a particle size distribution, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. This process is an important process for controlling the coercive force. In the case where the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment in the vicinity of 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by the heat treatment at around 600 ° C., the aging treatment at around 600 ° C. is preferably performed when the aging treatment is performed in one stage.

Next, a rare earth sintered magnet to which the present invention is applied will be described.
The present invention is particularly preferably applied to an RTB-based sintered magnet. This RTB-based sintered magnet contains 25 to 37 wt% of a rare earth element (R). Here, R in the present invention has a concept including Y, and therefore 1 of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is selected from species or two or more species. If the amount of R is less than 25 wt%, the R ₂ T ₁₄ B phase, which is the main phase of the R-T-B system sintered magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated and retained. The magnetic force is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%, and a more desirable amount of R is 29 to 33 wt%.

Further, the RTB-based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The RTB-based sintered magnet to which the present invention is applied has a Co content of 2.0 wt% or less (not including 0), preferably 0.1 to 1.0 wt%, more preferably 0.3 to 0. .7 wt% can be contained. Co forms the same phase as Fe, but is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.

Moreover, the RTB-based sintered magnet to which the present invention is applied can contain one or two of Al and Cu in a range of 0.02 to 0.5 wt%. By including one or two of Al and Cu in this range, it is possible to increase the coercive force, increase the corrosion resistance, and improve the temperature characteristics of the obtained RTB-based sintered magnet. In the case of adding Al, the desirable amount of Al is 0.03 to 0.3 wt%, and the more desirable amount of Al is 0.05 to 0.25 wt%. Further, in the case of adding Cu, the desirable amount of Cu is 0.15 wt% or less (not including 0), and the more desirable amount of Cu is 0.03 to 0.12 wt%.
The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is preferably 5000 ppm or less, more preferably 3000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.

Although it is desirable to apply the present invention to an RTB-based sintered magnet, the present invention can also be applied to other rare earth sintered magnets. For example, the present invention can be applied to an R—Co based sintered magnet.
The R—Co based sintered magnet contains R, one or more elements selected from Fe, Ni, Mn, and Cr, and Co. In this case, it preferably further contains Cu or one or more elements selected from Nb, Zr, Ta, Hf, Ti and V, and particularly preferably from Cu and Nb, Zr, Ta, Hf, Ti and V. Containing one or more selected elements. Among these, in particular, an intermetallic compound of Sm and Co, preferably an Sm ₂ Co ₁₇ intermetallic compound, is the main phase, and a subphase mainly composed of SmCo ₅ exists at the grain boundary. The specific composition may be appropriately selected according to the production method, required magnetic characteristics, and the like. For example, R: 20 to 30 wt%, particularly about 22 to 28 wt%, Fe, Ni, Mn, and Cr Above: about 1 to 35 wt%, one or more of Nb, Zr, Ta, Hf, Ti and V: 0 to 6 wt%, especially about 0.5 to 4 wt%, Cu: 0 to 10 wt%, especially 1 to 10 wt% To the extent, Co: the balance composition is desirable.
The R-T-B sintered magnet and the R-Co sintered magnet have been described above, but the present invention does not prevent application to other rare earth sintered magnets.

A raw material alloy having a composition of 26.5 wt% Nd-5.9 wt% Dy-0.25 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-Fe is produced by strip casting. did.
Next, after hydrogen was occluded in the raw material alloy at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere.
0.1 wt% of the lubricant shown in Table 1, which contributes to the improvement of pulverization and the orientation during molding, was mixed with the alloy subjected to the hydrogen pulverization treatment. The mixing and fine pulverization of the lubricant may be performed for about 5 to 30 minutes using, for example, a Nauter mixer. Thereafter, a finely pulverized powder having an average particle size of 5.0 μm was obtained using a jet mill.

The above finely pulverized powder was put into a chamber of a tumbling mixer, and the inside of the chamber was filled with nitrogen to prevent oxidation. At this time, the rolling mixer used was a horizontal type as shown in FIG. 2 (chamber volume is 1.5 liters: high-speed flow type Spartan Luzer (manufactured by Dalton)).
Thereafter, the rolling blades of the rolling mixing device were rotated at a predetermined speed to roll the finely pulverized powder. Furthermore, the auxiliary wing was rotated. At this time, the organic liquid shown in Table 1 was added in the amounts shown in Table 1, respectively.
Even after all the organic liquids were added, the rolling blades and the auxiliary blades were rotated and kneaded for a certain period of time (conditioning time t2) in order to make the organic liquid and finely pulverized powder blend together. Thereafter, the rolling blades and auxiliary blades were stopped, and the pulverized powder after kneading was taken out of the chamber.

  Subsequently, the organic liquid contained in the pulverized powder taken out was evaporated. In order to prevent oxidation of the finely pulverized powder, a vacuum chamber was used for evaporation, and evaporation was performed in a reduced pressure atmosphere.

The obtained pulverized powder was then molded in a magnetic field. Specifically, molding was performed at a pressure of 1.4 t / cm ² (140 MPa) in a magnetic field of 15 kOe (1200 kA / m) to obtain a molded body.
The obtained molded body was heated to 1080 ° C. in vacuum and Ar atmosphere and held for 4 hours for sintering. Next, the obtained sintered body was subjected to a two-stage aging treatment of 800 ° C. × 1 hour and 560 ° C. × 1 hour (both in an Ar atmosphere) to obtain a sintered magnet.

  Further, as a comparative example, instead of rolling using a rolling mixing device, mixing was performed using a ball mill, or pulverized powder was obtained by mixing in a fluidized bed type using an Agromaster (manufactured by Hosokawa Micron). Except for this, a sintered magnet of a comparative example was obtained in the same manner as in the example.

  Table 1 shows the results of measuring the magnetic properties of the obtained sintered magnets of Examples and Comparative Examples. The Br (%) in Table 1 means a sintered magnet obtained by applying a magnetic field in the same manner as in Example except that the organic liquid is not added and kneaded, that is, the finely pulverized powder is not rolled or mixed. It is a relative value when Br of the sample is used as a reference (100%).

As shown in the examples of Table 1, in all of Examples 1 to 8 (Note: Example 1 in which no organic liquid is added is a reference example) , Br is improved over the sintered magnet sample. Br was superior to 2. It is considered that the shear stress acts between the finely pulverized powders due to the rolling operation, and the lubricant existing between the finely pulverized powder surface and the finely pulverized powder is more sufficiently dispersed. As shown in Example 1 (Reference Example) , Br was improved only by rolling the finely pulverized powder without adding the organic liquid. However, as shown in Examples 2 to 8, the organic liquid was added. The kneading improved the Br. This is thought to be due to the presence of liquid, the finely pulverized powders approach each other due to the adhesion of the liquid, and the lubricant is easily loosened. In particular, as shown in Example 3, when 83 vol% of the organic liquid was added, moderate kneading occurred when rolling, and the sintered magnet had the highest Br. When the amount of the organic liquid added is small, the effect of dispersing the lubricant is small. On the other hand, as shown in Example 4, when the amount of the organic liquid added was as large as 166 vol%, the Br of the sintered magnet was lowered. This is presumably because friction between the powders during rolling is also contributing to the redispersion of the lubricant, but if there is too much organic liquid, the friction is reduced and this effect is reduced.

  When Example 5 and Example 6 were compared, the toluene of Example 6 having higher solubility of the lubricant zinc stearate showed a slightly higher Br than the ethanol of Example 5. On the other hand, in Example 7 and Example 8, the toluene of Example 8 having no solubility of the lubricant stearamide was improved over Br of ethanol of Example 7. This shows that the solubility of the lubricant in the organic liquid is not a necessary condition.

  In addition, as can be seen from a comparison between Example 3 and Comparative Examples 1 and 2 in which the lubricant, the type of organic liquid, and the amount of organic liquid added are the same, in Example 3, Br is clarified by the rolling of the pulverized powder. It has improved. On the other hand, in the mixing by the ball mill of Comparative Example 1, it seems that a part of the finely pulverized powder is flattened and the magnetic field orientation is deteriorated, so that Br is lowered. Thus, it is difficult to obtain excellent Br when the lubricant is dispersed by the collision force through the media. In addition, it was considered that Br did not improve much in the mixing using the fluidized bed of Comparative Example 2 because the lubricant was not sufficiently dispersed.

  In addition to this, as long as it does not deviate from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows the structure of a vertical-type rolling mixing apparatus, (a) is a front sectional view, (b) is a top view, (c) is a right view of (b). It is a figure which shows the structure of a horizontal type rolling mixing apparatus, (a) is a front sectional view, (b) is a right view of (a).

Explanation of symbols

  10, 10H, 10V ... rolling mixing device, 11 ... chamber, 12 ... rolling blade (main wing), 13 ... auxiliary blade

Claims (10)

A step of pulverizing the raw powder and lubricant of the rare earth sintered magnet to obtain a pulverized powder;
Adding the pulverized powder and the organic liquid into the chamber, rotating the chamber and a rolling blade provided in the chamber relatively, and adding the organic liquid to the pulverized powder and rolling the pulverized powder and the organic liquid; ,
Removing a part or all of the organic liquid from the pulverized powder after rolling;
Applying a magnetic field to the pulverized powder from which the organic liquid has been removed, and obtaining a molded body by pressure molding; and
Sintering the molded body;
With
The organic liquid is toluene, xylene, pinene, menthane, terpineol, ethanol, isobutyl alcohol, butyl cellosolve, cellosolve, carbitol, butyl carbitol, butyl carbitol acetate, cyclohexanol, dibutyl ether, ethyl acetate, n-butyl acetate, It consists of one or more of propionic anhydride, acetone (dimethyl ketone), methyl isobutyl ketone, methyl ethyl ketone,
The method for producing a rare earth sintered magnet, wherein the addition amount of the organic liquid is 30 to 150 vol% with respect to the pulverized powder.   2. The method for producing a rare earth sintered magnet according to claim 1, wherein the organic liquid is removed by exposing the pulverized powder after rolling to a reduced pressure atmosphere.   The method for producing a rare earth sintered magnet according to claim 1 or 2, wherein the addition amount of the organic liquid is 40 to 90 vol% with respect to the pulverized powder.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 3, wherein the lubricant is insoluble or soluble in the organic liquid.   The method for producing a rare earth sintered magnet according to any one of claims 1 to 4, wherein all of the organic liquid is removed from the pulverized powder after rolling. A step of pulverizing the raw powder and lubricant of the rare earth sintered magnet to obtain a pulverized powder;
Adding an organic liquid to the pulverized powder and kneading; and
Removing part or all of the organic liquid from the pulverized powder after kneading;
Applying a magnetic field to the pulverized powder from which the organic liquid has been removed, and obtaining a molded body by pressure molding; and
Sintering the molded body;
With
The kneading is performed by rolling the pulverized powder, the lubricant, and the organic liquid with a main wing that rotates in a chamber and an auxiliary wing that rotates in a direction different from the main wing.
The method for producing a rare earth sintered magnet, wherein the addition amount of the organic liquid is 30 to 150 vol% with respect to the pulverized powder.   The method for producing a rare earth sintered magnet according to claim 6, wherein all of the organic liquid is removed from the pulverized powder after kneading.   The method for producing a rare earth sintered magnet according to claim 6 or 7, wherein the main wing rotates about an axis in a substantially vertical direction in the chamber.   The method of manufacturing a rare earth sintered magnet according to claim 6 or 7, wherein the main wing rotates around an axis in a substantially horizontal direction in the chamber. The raw material powder is R ₂ T ₁₄ B phase (R is one or more elements selected from rare earth elements, T is one or two elements selected from transition metal elements including Fe, Fe and Co) Having a composition containing the above elements)
The method for producing a rare earth sintered magnet according to any one of claims 6 to 9, wherein the pulverized powder has an average particle diameter of 2.5 to 6 µm.

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