JP2008243982A - Method of manufacturing metal magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a metal magnet wherein a metal magnet is manufactured by wet forming using an organic solvent and thereby a metal magnet having little degradation in magnetic characteristics can be obtained. <P>SOLUTION: The method of manufacturing a magnet in a preferred embodiment of the present invention includes: a mixing process wherein a material powder of the metal magnet and a lubricant comprising a chemical having a carboxyl group, hydroxyl group, or ester group are mixed and churned; a slurry manufacturing process wherein the material powder after mixed with the lubricant and an organic solvent are mixed to obtain a slurry; a forming process wherein the slurry is formed into an formed object; and a burning process of burning the formed object. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a metal magnet, and more particularly to a method for producing a metal magnet by wet forming.

  As a method of manufacturing a metal magnet, a method of undergoing a wet molding process in which a metal magnet powder as a raw material is mixed with a solvent such as oil or an organic solvent and then sintered is formed and then known. Yes. Since such a metal magnet contains a metal, it is easily oxidized by oxygen or moisture in the atmosphere. In particular, metal magnet powder, which is a raw material for use in wet forming, tends to be very easily oxidized because it is in powder form. When such oxidized metal magnet powder is used, a metal magnet whose magnetic properties are greatly deteriorated in many cases than obtained from its composition or the like is often obtained.

  Conventionally, in the above-described wet forming process, mineral oil or synthetic oil is often used as a solvent used for forming a slurry because it is a hydrophobic liquid and has a low oxygen solubility. (See Patent Document 1).

In addition, the use of an organic solvent is also being studied because of the advantage in production that the solvent can be easily removed before sintering and the cost can be reduced. In the method for producing a metal magnet using an organic solvent, the metal magnet powder obtained by pulverization is not directly exposed to the atmosphere or the like in the organic solvent in order to suppress oxidation of the metal magnet powder during wet forming. There is known a method of trapping (see Patent Document 2). This Patent Document 2 also describes that a lubricant is added to an organic solvent in order to improve the orientation of the collected metal magnet powder.
Japanese Patent Laid-Open No. 5-175088 JP-A-1-303710

  However, in the wet forming using the organic solvent as described above, it has still been difficult to sufficiently suppress the deterioration of the metal magnet.

  Therefore, the present invention has been made in view of such circumstances, and provides a method for producing a metal magnet that can obtain a metal magnet with little deterioration in magnetic properties in the production of a metal magnet by wet forming using an organic solvent. The purpose is to do.

  In order to achieve the above object, the present inventors have studied, and the organic solvent used for collecting the metal magnet powder in the conventional method often contains water unless special treatment is performed. It was confirmed that the water contained in the solvent may cause oxidation of the metal magnet powder. It is considered that the characteristic deterioration of the metal magnet is caused by such oxidation of the metal magnet powder.

  Based on such knowledge, the present inventors can obtain a metal magnet with little deterioration of magnetic properties if the metal magnet powder can be treated to suppress the influence of moisture in the organic solvent. As a result, the present invention has been completed.

  That is, the method for producing a metal magnet of the present invention comprises a mixing step of mixing and stirring a raw material powder of a metal magnet and a lubricant comprising a compound having a carboxyl group, a hydroxyl group or an ester group, and the raw material powder after the mixing step And a slurry production step of obtaining a slurry by mixing an organic solvent, a molding step of molding the obtained slurry to obtain a molded body, and a firing step of firing the molded body.

  In such a method for producing a metal magnet of the present invention, the raw material powder is mixed with a lubricant and stirred before the raw material powder of the metal magnet is mixed with an organic solvent. According to such a process, it is considered that the raw material powder and the lubricant are uniformly mixed, so that most of the constituent particles of the raw material powder are coated with the lubricant. Therefore, even if the raw material powder and the organic solvent are mixed after the mixing step, the raw material powder and the organic solvent are less likely to come into contact with each other due to the coating with the lubricant. As a result, even when moisture is contained in the organic solvent, the raw material powder is less likely to be oxidized, and a metal magnet with less characteristic deterioration can be obtained. It is considered that such an effect cannot be sufficiently obtained, for example, even if the lubricant is added simultaneously with the mixing of the raw material powder and the organic solvent, since the coating as described above cannot occur.

  In the method for producing a metal magnet of the present invention, heating is preferably performed in the mixing step. By carrying out the mixing step while heating, the viscosity of the lubricant is lowered, thereby further promoting the mixing of the raw material powder and the lubricant. Further, even a lubricant that is in a solid state at normal temperature can be mixed well. As a result, it is considered that the raw material powder is easily coated with the lubricant, and a metal magnet with less deterioration in magnetic properties can be obtained.

  As the lubricant, a fatty acid having an aliphatic group having 6 to 18 carbon atoms and being liquid in the step of mixing the lubricant is preferable. Such fatty acids have low viscosity and are easily mixed with the raw material powder of the metal magnet, and are therefore easier to mix with the raw material powder. Such fatty acids are also considered to have an effect of reducing friction between particles in the raw material powder. As a result, in molding in a magnetic field, the orientation of each particle is favored and the degree of orientation of the entire metal magnet is increased. You can also.

  In the production method of the present invention, the metal magnet is preferably a rare earth magnet. Since rare earth magnets contain rare earth elements that are susceptible to corrosion, deterioration due to oxidation or the like is particularly likely to occur among metal magnets. Therefore, if the present invention is applied to the production of rare earth magnets, the effect of reducing the deterioration of magnetic properties can be obtained particularly remarkably.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the metal magnet from which the metal magnet with little deterioration of a magnetic characteristic is obtained in manufacture of the metal magnet by wet forming.

  Hereinafter, preferred embodiments of the present invention will be described. In the following description, a method of manufacturing a rare earth magnet particularly suitable for the present invention will be described. However, the method of manufacturing a magnet of the present invention is not limited to a rare earth magnet, and can be applied to other metal magnets without any particular limitation. it can.

  FIG. 1 is a flowchart showing a manufacturing process of a rare earth magnet according to a preferred embodiment.

  In manufacturing the rare earth magnet, first, an alloy is prepared so that a rare earth magnet having a desired composition can be obtained (step S11). In this process, for example, a simple substance, an alloy, a compound, or the like containing an element such as a metal corresponding to the composition of the 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, examples of the rare earth magnet include those containing mainly Nd and Pr as rare earth elements, and those having a combination of a rare earth element and a transition element other than the rare earth element are suitable. Specifically, R including at least one of Nd, Pr, Dy, and Tb 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 -Fe-B composition are preferred. Such a rare earth magnet has a composition that further includes other elements such as Co, Ni, Mn, Al, Cu, Nb, Zr, Ti, W, Mo, V, Ga, Zn, and Si as required. You may do it.

  Next, the obtained alloy is coarsely pulverized to obtain particles having a particle size of about several hundred μm (step S12). 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, by further finely pulverizing the powder obtained by the coarse pulverization (step S13), the raw material powder of a rare earth magnet having a particle diameter of preferably about 1 to 10 μm, more preferably about 3 to 5 μm (hereinafter simply referred to as “ The raw material powder ") is obtained. Fine pulverization is performed by further pulverizing the coarsely pulverized powder using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, and a wet attritor while appropriately adjusting conditions such as pulverization time. To do. This fine pulverization may be performed by adding a predetermined lubricant. By adding a lubricant, the pulverization property of the powder after coarse pulverization is improved, and a fine powder as a raw material powder is obtained, and the orientation of the raw material powder during molding tends to be improved. As the lubricant, those similar to those applied in the lubricant mixing step as described later can be applied.

  Next, a lubricant is added to the obtained raw material powder, and these are stirred and mixed (step S14; mixing step). Thereby, the constituent particles of the raw material powder are coated with the lubricant. As the lubricant, a known compound used as a lubricant and a compound having a carboxyl group, a hydroxyl group or an ester group is applied. The effect of the lubricant can be obtained regardless of whether it is liquid or solid in the mixing step (hereinafter referred to as “lubricant mixing step” for convenience of explanation), but the liquid is the raw material powder. Since it is easy to mix with, there is a tendency to obtain more excellent effects. When a solid lubricant is used, a solution dissolved in a predetermined dispersion medium may be used in order to improve dispersibility.

  Suitable lubricants include aliphatic compounds having a carboxyl group, a hydroxyl group or an ester group. Specifically, an aliphatic carboxylic acid (fatty acid) in which a carboxyl group is bonded to the terminal of the aliphatic group, an aliphatic alcohol in which a hydroxyl group is bonded to the terminal of the aliphatic group, or an alkyl ester of the aforementioned fatty acid is preferable. . As the aliphatic group, a linear aliphatic group is preferable, and a linear saturated aliphatic group is more preferable. Moreover, as these aliphatic compounds, those having 6 to 18 carbon atoms, more preferably 8 to 12 carbon atoms, excluding carboxyl groups and ester groups are more preferable. An aliphatic compound satisfying such conditions has particularly good mixing properties with the raw material powder, and is advantageous for coating the raw material powder.

  Among these, as the lubricant, a fatty acid is preferable, a fatty acid having an aliphatic group having 6 to 18 carbon atoms is more preferable, and a saturated fatty acid having a saturated aliphatic group having 6 to 18 carbon atoms is particularly preferable. Fatty acids are excellent in lubricating the raw material powder and tend to be coated more satisfactorily. As such a fatty acid, for example, octanoic acid, decanoic acid, dodecanoic acid, octadecanoic acid and the like are preferable.

  The lubricant mixing step can be performed by, for example, mixing the raw material powder and the lubricant and then stirring them with a mixer or the like. At this time, if mixing and stirring are performed while heating, the viscosity of the lubricant is lowered and the raw material powder and the lubricant are mixed well, and coating of the raw material powder with the lubricant becomes more advantageous. Further, even when a solid lubricant is used at room temperature, it can be made liquid during the process by heating, so even a solid lubricant does not form a solution as described above. In some cases, good mixing can be performed.

  The addition amount of the lubricant varies depending on the raw material powder and the type of the lubricant, but is preferably 0.01 to 1.0% by mass with respect to the mass of the raw material powder, for example, 0.01 to 0.5 It is more preferable that it is mass%, and it is still more preferable that it is 0.01-0.2 mass%. If the addition amount of the lubricant is too small, it is considered that the coating of the raw material powder becomes insufficient. Therefore, when mixed with an organic solvent, the raw material powder tends to be deteriorated due to oxidation or the like. On the other hand, when there are too many lubricants, since the nonmagnetic component which remains in the sintered compact after sintering increases, there exists a possibility of leading to deterioration of a magnetic characteristic.

  As described above, the lubricant may be added in the fine pulverization step when preparing the raw material powder. In this case, the lubricant used in the fine grinding (herein referred to as “first lubricant”) and the lubricant used in the lubricant mixing step (herein referred to as “second lubricant”) are the same. Or different. Moreover, it is preferable that the addition amount of the lubricant in this case is such that the sum of the first and second lubricants is a suitable addition amount as described above. However, if the amount of the first lubricant added is too large, the pulverization property becomes too high, and there is a risk of causing wear of the pulverizer. From the viewpoint of preventing this, the amount of the first lubricant added is The amount of the second lubricant added is preferably about 50%.

  Following such a lubricant mixing step, an organic solvent is added to and mixed with the raw material powder mixed with the lubricant to produce a slurry containing the raw material powder (step S15; slurry production step). Here, in this embodiment, an organic solvent means a liquid composed of a single organic compound or a mixed liquid in which two or three kinds of such liquids are mixed, and is generally classified as oil. Liquids, vegetable oils, and the like that contain a large number of organic compounds such as mineral oil and synthetic oil are not included in the organic solvent.

  As the organic solvent used in the production of the slurry, a solvent having a property that hardly reacts with the raw material powder of the rare earth magnet is used. The organic solvent preferably has a boiling point that does not evaporate due to heat generated during mixing. However, when a large amount of the organic solvent remains in the sintered body after firing, the magnetic properties of the obtained magnet may be deteriorated, so that the boiling point is not too high. From such a viewpoint, the organic solvent preferably has a boiling point of about 50 to 250 ° C.

  Such a solvent is preferably an aprotic solvent such as a ketone solvent, an amide solvent, or a sulfur-containing solvent. Examples of the ketone solvent include diacetyl, 3-chloro-2-butanone, cyclohexanone, cyclopentanone, diisobutyl ketone (DIBK), 2-octanone, 3-octanone, 3-pentanone, and acetone. Examples of the amide solvent include N, N-dimethylformamide (DMF), and examples of the sulfur-containing solvent include dimethyl sulfoxide (DMSO). Among these, when DIBK, acetone, DMF or DMSO is used, a slurry can be formed satisfactorily and a magnet having an excellent degree of orientation and the like tends to be obtained.

  In the slurry production step, the raw material powder concentration in the resulting slurry is preferably 60 to 80% by mass, more preferably 65 to 75% by mass. The slurry having such a raw material powder concentration has fluidity suitable for transport to a molding machine.

  In this slurry production step, before obtaining a slurry having the above raw material powder concentration, after kneading at a higher concentration (kneading step), an organic solvent is added to the obtained kneaded product to obtain the above concentration. (Dilution step). By kneading at a high concentration, collisions between the raw material powders can be generated with high frequency. As a result, when the constituent particles of the raw material powder are aggregated to form secondary particles and the like, it is possible to obtain a slurry in which the primary particles are uniformly dispersed by crushing them. According to such a slurry, it becomes easy to produce the orientation at the time of the shaping | molding mentioned later, and the rare earth magnet which has a high altitude can be formed. The raw material powder concentration during the kneading is preferably 85 to 95% by mass, more preferably 88 to 94% by mass.

  The slurry thus obtained is preferably subjected to a step of dispersing the magnetic powder and the solvent again before forming (dispersing step). In the slurry, the magnetic powder and the solvent may be separated while being supplied to the molding machine, which may cause a supernatant of the solvent. If this slurry is used for molding as it is, the amount of raw material powder charged into the molding machine is not constant depending on the degree of separation, and as a result, the amount of magnetic powder in the molded body may vary. On the other hand, if the dispersion is performed before molding, the molding can be performed with little separation of the slurry, and variations in the molded body can be suppressed.

  The slurry can be dispersed by using a ball mill, ultrasonic diffusion, homogenizer, optimizer, or the like. For example, by incorporating an apparatus for performing these operations in the middle of a supply pipe that supplies the slurry to the molding machine, the dispersion can be favorably performed. From the viewpoint of obtaining a good effect by this dispersion, it is preferable to carry out the dispersion just before molding as much as possible.

  Thereafter, the dispersed slurry is put into a molding machine, and the molded product is obtained by molding the slurry while applying a magnetic field (step S16; molding process). By this molding step, a molded body having a predetermined degree of orientation is obtained. The molding can be performed, for example, by press molding. Specifically, after the slurry is filled in the mold cavity, the filled slurry is pressurized so as to be sandwiched between the upper punch and the lower punch, It is processed into a predetermined shape while extracting the solvent. At this time, the upper punch or the lower punch may be provided with a hole communicating with the outside in order to extract the solvent that has flowed out. However, it is preferable to place a cloth or paper filter on the punch surface, or to make the upper punch or the lower punch partly porous so that the magnetic powder does not flow out. The shape of the molded body obtained by molding is not particularly limited, and can be changed according to the desired shape of the rare earth magnet, such as a columnar shape, a flat plate shape, or a ring shape.

The pressing direction during molding may be the same as the magnetic field application direction, or may be perpendicular to the magnetic field application direction, but more excellent magnetic properties can be obtained by applying pressure perpendicular to the magnetic field application direction. There is a tendency. Moreover, the magnetic field intensity at the time of shaping | molding can be 15-20 kOe, and pressurization can be 0.3-3 ton / cm < ² >. Furthermore, the molding time is preferably several seconds to several tens of seconds. By forming in a magnetic field under such conditions, a rare earth magnet having good magnetic properties tends to be easily obtained.

  Next, the molded body is subjected to, for example, vacuum heating to remove the organic solvent remaining in the molded body (step S17; solvent removal step). Desolvation is performed under conditions that allow most of the organic solvent in the molded body to be removed. For example, the solvent is preferably heated at room temperature to 300 ° C. for 1 to 5 hours under a reduced pressure of about 1 to 50 Pa. In this solvent removal step, sintering of the molded body usually does not proceed, but partial sintering may proceed.

  Thereafter, the desolvated shaped body is fired to obtain a sintered body (step S18; firing step). Firing can be performed, for example, by heating the molded body at 1000 to 1200 ° C. for 1 to 10 hours in a vacuum or in the presence of an inert gas, and then rapidly cooling.

  After firing, the obtained sintered body is subjected to an aging treatment by heating the sintered body at a temperature lower than that during firing (step S19). The aging treatment is, for example, two-stage heating for 1 to 3 hours at 700 to 900 ° C., and further 1 to 3 hours at 500 to 700 ° C. Perform under conditions. Such an aging treatment can improve the magnetic properties of the sintered body.

  And the target rare earth magnet is obtained by performing the process which cut | disconnects to the desired size with respect to the sintered compact obtained in this way, or smoothes the surface. The obtained rare earth magnet may further be provided with a protective layer for preventing deterioration of the oxide layer, the resin layer, etc. on the surface.

  In the rare earth magnet manufacturing method of the above-described embodiment, the raw material powder of the magnet is mixed with a lubricant and then mixed with an organic solvent to prepare a slurry. Usually, when an organic solvent is used for the preparation of the slurry, the raw material powder is often oxidized and deteriorated by moisture or the like contained in the organic solvent. On the other hand, in this embodiment, since the constituent particles of the raw material powder are coated with the lubricant by mixing the raw material powder and the lubricant before the preparation of the slurry, It is considered that the constituent particles are less likely to come into contact with moisture contained in the organic solvent. Therefore, according to the manufacturing method of the present embodiment, even when an organic solvent is used for the preparation of the slurry, the raw material powder is hardly deteriorated, and as a result, a rare earth magnet having excellent magnetic properties is obtained. Be able to.

  As mentioned above, although the manufacturing method of the rare earth magnet was demonstrated as suitable embodiment of the manufacturing method of the magnet of this invention, this invention is not necessarily limited to embodiment mentioned above. For example, the metal magnet manufacturing method of the present invention is a manufacturing method including at least a lubricant mixing step, a slurry manufacturing step, a molding step, and a firing step, and as long as the effects of the present invention are sufficiently obtained, The process may be omitted.

  For example, in the case where the obtained slurry is immediately subjected to molding after the slurry is prepared, when the separation of the slurry before molding is small, the dispersion step before molding can be omitted. If sufficient magnetic properties are obtained only by firing after the firing step, the aging treatment after the firing step is not necessarily performed. Furthermore, in the magnet manufacturing method of the present invention, steps other than those described above may be further performed as necessary.

  Furthermore, as described above, the manufacturing method of the present invention is not limited to rare earth magnets and can be applied to the manufacture of other metal magnets. And even if it is a case where it applies to another magnet, it becomes possible to obtain a metal magnet with little deterioration of a magnetic characteristic, although an organic solvent is used for preparation of a slurry similarly to embodiment mentioned above.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Preparation of rare earth magnets]

Example 1
First, Nd: 24.5 wt%, Pr: 6.0 wt%, Dy: 1.8 wt%, Co: 0.5 wt%, Al: 0.2 wt%, Cu: 0.07 wt%, B: A raw material metal or a raw material alloy was blended so as to be 1.0 weight and the remaining Fe, and a raw material alloy thin plate was obtained through melting and casting by a strip casting method. The raw material alloy thin plate thus obtained was hydrogen crushed to obtain raw material alloy coarse powder. Next, 0.1% by weight of oleic acid amide as a lubricant is added to the raw material alloy coarse powder with respect to the coarse powder, and then finely pulverized in a high-pressure nitrogen atmosphere using an airflow pulverizer (jet mill). To obtain a raw material powder of the magnet.

  Next, after adding 0.05% by weight of octanoic acid, which is a lubricant, to the obtained raw material powder, stirring was performed (lubricant mixing step). Then, diisobutyl ketone (DIBK) which is an organic solvent was added to the raw material powder to which the lubricant was added and mixed to prepare a slurry (slurry manufacturing process).

  Then, the obtained slurry was molded in a magnetic field to obtain a molded body. Molding was performed by applying pressure between the upper punch and the lower punch in the cavity under the condition of 2.3 ton in a magnetic field of 14 kOe, and the solvent was sucked and removed from the upper punch during pressurization. At this time, the magnetic field direction was made to coincide with the pressing direction. The dimension of the molded body was 20 mm × 18 mm × 11 mm.

  Thereafter, the molded body was heated in vacuum at 150 ° C. for 1 hour to remove the solvent and the like contained in the molded body (desolvent), and further baked in vacuum at 1070 ° C. for 5 hours. Thereafter, the obtained sintered body was subjected to an aging treatment at 800 ° C. for 1 hour and then at 540 ° C. for 1 hour to obtain a rare earth magnet.

  In Example 1, an organic solvent in which water was added to DIBK that had been dehydrated in advance was used when the slurry was prepared. And the rare earth magnet was similarly manufactured on the several conditions using the organic solvent from which a moisture content differs, and the several rare earth magnet corresponding to each condition was obtained.

(Comparative Example 1)
Rare earth magnets were produced under a plurality of conditions using organic solvents having different moisture contents in the same manner as in Example 1 except that the lubricant was not added or mixed in the lubricant mixing step.
[Characteristic evaluation]

(Measurement of oxygen content)
Gas analysis of each rare earth magnet obtained in Example 1 and Comparative Example 1 was performed by a non-dispersive infrared absorption method, and the amount of oxygen contained in each rare earth magnet was measured. The obtained results are shown in FIG.

  FIG. 2 is a graph showing the oxygen content of each of the rare earth magnets of Example 1 and Comparative Example 1, and obtained with the rare earth magnet manufactured under the conditions with respect to the water content (solvent water content) of the organic solvent at the time of slurry production. It is the graph which plotted the value of the obtained oxygen amount. The larger the value of the oxygen amount, the more the raw material powder is oxidized, indicating that the deterioration is large. In FIG. 2, L11 is a curve corresponding to the rare earth magnet obtained in Example 1 and L12 is obtained in Comparative Example 1, respectively.

  From FIG. 2, it was confirmed that in Example 1 in which mixing with octanoic acid as a lubricant was performed before slurry production, the increase in oxygen content was small even when the water content in the organic solvent increased. On the other hand, in Comparative Example 1 in which no octanoic acid was mixed, the amount of oxygen increased significantly with an increase in the water content of the organic solvent. In Comparative Example 1, when the water content was higher than 5% by weight, the amount of oxygen in the raw material powder was too large, and the liquid phase component was insufficient, making it difficult to perform firing.

(Measurement of coercive force)
Moreover, the magnetic characteristics of each rare earth magnet were evaluated using a BH tracer, and their coercive force was measured. The obtained results are shown in FIG. FIG. 3 is a graph showing the coercive force of each rare earth magnet obtained in Example 1 and Comparative Example 1, and obtained with the rare earth magnet manufactured under the conditions with respect to the water content of the organic solvent at the time of slurry production. The value of coercive force (HcJ) is plotted. In FIG. 3, L11 corresponds to the rare earth magnet obtained in Example 1 and L12 corresponds to Comparative Example 1, respectively.

As shown in FIG. 3, in Example 1 in which octanoic acid as a lubricant was added, the water content of the organic solvent was increased to 0, 1 and 3% by weight as compared with Comparative Example 1 in which octanoic acid was not added. It was also confirmed that the decrease in coercive force was extremely small.
[Preparation of rare earth magnets]

(Example 2)
A plurality of organic solvents having different moisture contents were used in the same manner as in Example 1 except that the lubricant used in the lubricant mixing step was ethyl octoate and the solvent used in the slurry production step was isopropyl alcohol. A rare earth magnet was manufactured under the conditions.

(Comparative Example 2)
Rare earth magnets were produced under a plurality of conditions using organic solvents having different moisture contents in the same manner as in Example 2 except that the lubricant was not added or mixed in the lubricant mixing step.
[Characteristic evaluation]

  In the same manner as described above, the amount of oxygen and the coercive force of each rare earth magnet obtained in Example 2 and Comparative Example 2 were measured. FIG. 4 shows the measurement result of the oxygen amount, and FIG. 5 shows the measurement result of the coercive force. 4 and 5, L21 is a curve corresponding to the rare earth magnet obtained in Example 2 and L22 is obtained in Comparative Example 2, respectively.

As shown in FIG. 4, in Example 2 in which ethyl octoate was added as a lubricant, the increase in the amount of oxygen was small even when the water content of the organic solvent was increased, compared with Comparative Example 2 in which ethyl octoate was not added. It was confirmed. From FIG. 5, it was confirmed that the decrease in coercive force accompanying the increase in the water content of the organic solvent in Example 2 was significantly smaller than that in Comparative Example 2.
[Rare earth magnet manufacturing method]

(Example 3)
A plurality of organic solvents having different moisture contents were used in the same manner as in Example 1 except that the lubricant used in the lubricant mixing step was octanol and the solvent used in the slurry production step was methyl ethyl ketone (MEK). A rare earth magnet was manufactured under the conditions.

(Comparative Example 3)
Rare earth magnets were produced under a plurality of conditions using organic solvents having different moisture contents in the same manner as in Example 3 except that the addition and mixing of the lubricant were not performed in the lubricant mixing step.
[Characteristic evaluation]

  In the same manner as described above, the amount of oxygen and the coercive force of each rare earth magnet obtained in Example 3 and Comparative Example 3 were measured. The measurement result of the oxygen amount is shown in FIG. 6, and the measurement result of the coercive force is shown in FIG. 6 and 7, L31 is a curve corresponding to the rare earth magnet obtained in Example 3 and L32 is obtained in Comparative Example 3, respectively.

FIG. 6 confirms that in Example 3 in which octanol was added as a lubricant, the increase in the amount of oxygen was small even when the water content of the organic solvent was increased, compared to Comparative Example 3 in which octanol was not added. It was. From FIG. 7, it was confirmed that the decrease in coercive force accompanying the increase in the water content of the organic solvent in Example 3 was significantly smaller than that in Comparative Example 3.
[Rare earth magnet manufacturing method]

(Examples 4 to 9)
The lubricant used in the lubricant mixing step was valeric acid (aliphatic group carbon number = 5; Example 4), octanoic acid (same as 8; Example 5), decanoic acid (same as 10; Example 6), dodecane. Except that it was replaced with acid (same 12; Example 7), octadecanoic acid (same 18; Example 8), and arachidic acid (same 20; Example 9), respectively, and the water content of the organic solvent was 3% by weight. In the same manner as in Example 1, the rare earth magnets of Examples 4 to 9 were manufactured.
[Characteristic evaluation]

The rare earth magnets of Examples 4 to 9 were subjected to gas analysis in the same manner as described above, and their oxygen content was measured. The obtained results are shown in Table 1.

  From Table 1, as the lubricant in the lubricant mixing step, in the case of fatty acids, the amount of oxygen compared to the case where the number of carbons of the aliphatic group is larger than 5 and smaller than 20 is out of this range. It was found that a rare earth magnet with a small amount can be obtained.

It is a flowchart which shows the manufacturing process of the rare earth magnet which concerns on suitable embodiment. 4 is a graph showing the oxygen amount of each rare earth magnet of Example 1 and Comparative Example 1. 5 is a graph showing coercivity of each rare earth magnet of Example 1 and Comparative Example 1. It is a graph which shows the oxygen content of each rare earth magnet of Example 2 and Comparative Example 2. It is a graph which shows the coercive force of each rare earth magnet of Example 2 and Comparative Example 2. 6 is a graph showing the oxygen amount of each rare earth magnet of Example 3 and Comparative Example 3. 4 is a graph showing coercivity of each rare earth magnet of Example 3 and Comparative Example 3.

Claims (4)

A mixing step of mixing and stirring the raw material powder of the metal magnet and a lubricant composed of a compound having a carboxyl group, a hydroxyl group or an ester group;
A slurry production step of obtaining a slurry by mixing the raw material powder after the mixing step and an organic solvent;
A molding step of molding the slurry to obtain a molded body;
A firing step of firing the molded body,
A method for producing a metal magnet.   The method of manufacturing a metal magnet according to claim 1, wherein heating is performed in the mixing step.   The said lubricant is a fatty acid which has a C6-C18 aliphatic group, and is a liquid state in the said mixing process, The metal magnet manufacture of Claim 1 or 2 characterized by the above-mentioned. Method.   The said metal magnet is a rare earth magnet, The manufacturing method of the metal magnet as described in any one of Claims 1-3 characterized by the above-mentioned.

Images