JP4716051B2 - Manufacturing method of sintered magnet - Google Patents

Description

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

  Conventionally, as a method for producing a sintered magnet, a raw material alloy of a magnet is roughly pulverized and finely pulverized to produce a fine powder having an average particle size of about several μm, and this fine powder is supplied into a mold cavity of a molding machine. A technique of press molding in a state in which the magnetic field is oriented is widely known.

  As a method for magnetic field orientation press molding of this magnetic powder, a dry molding method and a wet molding method are known. In wet molding, magnetic powder and a solvent such as oil are mixed to form a slurry, and then the magnetic powder is injected into a molding machine in a slurry state to be molded, and then the solvent is removed from the molded body. According to such wet molding, the magnetic field orientation at the time of molding is enhanced as compared with the case of dry molding, and a magnet having excellent magnetic properties can be obtained.

  On the other hand, magnetic powders of sintered metal magnets, especially magnetic powders containing rare earth metals, have high magnetic properties, and are used for applications that require high magnetic properties even in a small size. However, these magnetic powders have a feature that their pulverized surfaces are chemically very active, and are easily oxidized, for example, by oxygen in the atmosphere, thereby easily degrading magnetic properties. Therefore, also in the manufacture of such rare earth metal sintered magnets, the above manufacturing method by wet forming is effective.

  For example, in Patent Document 1, fine powder (magnetic powder) obtained by pulverizing a rare earth permanent magnet raw material is collected and stored in an oily solvent in an inert atmosphere, and the concentration of the slurry, which is a mixture of the fine powder and the oily solvent, is adjusted. A method for producing a rare earth permanent magnet is disclosed in which deterioration in magnetic properties due to oxygen in the atmosphere is suppressed by molding in a magnetic field.

  In the production of sintered magnets by wet molding, a magnetic field is applied during molding to orient the magnetic powder (magnetic field orientation), thereby enhancing the magnetic properties. In general, the higher the degree of orientation of the magnetic powder, the more excellent the magnetic properties (particularly the residual magnetic flux density (Br)) can be obtained. Therefore, in the production of this kind of sintered magnet, the degree of orientation of the magnetic powder is improved. Various methods have been studied.

  For example, in Patent Document 2, magnetic powder (fine powder) is recovered in a liquid composed of oil and a nonionic surfactant or an anionic surfactant to produce a slurry-like molding raw material. A method for producing a rare earth sintered magnet is disclosed in which the degree of orientation of magnetic powder is increased by molding a slurry-like forming raw material in a magnetic field.

  In Patent Document 3, magnetic powder is recovered in a liquid containing a lubricant composed of oil and a monohydric alcohol ester of a fatty acid, a monohydric alcohol ester of a polybasic acid, a fatty acid ester of a polyhydric alcohol, or a derivative thereof. Thus, a method for producing a rare earth sintered magnet is disclosed in which a slurry is produced and the degree of orientation is increased by molding the slurry in a magnetic field.

JP-A-9-289127 JP 2001-210508 A JP 2002-164238 A

  However, in recent years, there has been a tendency for higher performance of magnetic characteristics even though the composition is the same, and in particular, there is a demand for further increasing the residual magnetic flux density, that is, higher Br.

  The present invention has been made in view of such circumstances, and the purpose thereof is to produce a sintered magnet with a further increased residual magnetic flux density and further improved performance of magnetic properties, productivity and An object of the present invention is to provide a manufacturing method which is excellent in economic efficiency.

  In order to solve the above problems, the present inventors have conducted extensive research and found that the above problems can be solved by applying a specific treatment to the slurry used in wet press molding. It came to be completed.

  That is, the method for producing a sintered magnet according to the present invention includes a step of preparing (preparing) a slurry containing a magnetic powder having an average particle diameter of 1 to 10 μm and a solvent, a step of treating the slurry with a high-pressure homogenizer, It has the process of press-molding the slurry in the state which applied the magnetic field, and obtaining a molded object, and the process of deoiling and sintering the obtained molded object.

  When the present inventors implemented the manufacturing method comprised in this way, it turned out that the sintered magnet in which the residual magnetic flux density was raised further is obtained. The details of the mechanism of action that produces this effect are not yet clear, but are estimated as follows, for example.

  That is, in the method for producing a sintered magnet according to the present invention, a slurry containing a magnetic powder having an average particle diameter of 1 to 10 μm and a solvent is processed by a high-pressure homogenizer, and therefore, high local impact such as pressurization, shearing, cavitation, etc. Due to the force, the magnetic powder is highly uniformly dispersed in the solvent. Moreover, according to such a wet dispersion process using a high-pressure homogenizer, not only the deterioration of the magnetic properties due to oxygen in the atmosphere is suppressed, but also the process can be performed in an extremely short time, so that a by-product is generated by a mechanochemical reaction. The amount of rare earth carbide produced is reduced.

  Therefore, when the slurry prepared as described above is wet press-molded and the resulting molded body is sintered, the magnetic field orientation is improved by the highly uniformly dispersed magnetic powder, oxygen in the atmosphere, rare earth carbide, etc. As a result, a sintered magnet with a further increased residual magnetic flux density can be obtained. However, the action is not limited to these.

  Here, in the step of treating the slurry with a high-pressure homogenizer, it is preferable to use a high-pressure homogenizer with a treatment pressure of 20 to 500 MPa. By using such a high-pressure homogenizer, the uniform dispersibility of the slurry is increased, and the processing time is further shortened.

  In the step of treating the slurry with a high-pressure homogenizer, it is preferable to treat the slurry with a high-pressure homogenizer after treating the slurry with a bead mill. When the slurry is previously processed in the bead mill in this way, the magnetic powder in the slurry is pulverized to a smaller particle size by the collision force of the beads and the shearing force between the beads, and agglomerates of magnetic powder that may exist in the slurry ( A strong shearing force is applied to the secondary particles in which a plurality of primary particles are reversibly aggregated, whereby the secondary particles are divided apart and changed (recovered) to primary particles before aggregation. As a result, a magnetic powder having an even smaller average particle size and an even particle size distribution (in other words, a particle size adjusted to a state close to monodispersion) is prepared. Then, when the slurry thus prepared is treated with a high-pressure homogenizer, a slurry in which magnetic powder is extremely highly uniformly dispersed in a solvent is obtained, and the residual magnetic flux density is reduced by molding in a magnetic field using this slurry. A particularly enhanced sintered magnet is obtained.

  In general, there is a trade-off relationship between the magnetic powder size reduction (micronization) and the magnetic powder dispersibility. Therefore, the improvement of the magnetic properties and the magnetic powder dispersibility due to the magnetic particle size reduction. Although it is difficult to achieve both improvement of magnetic properties by improvement, the manufacturing method of the present invention has been able to overcome this trade-off relationship by sequentially performing the specific processing by the bead mill and the high-pressure homogenizer. Compared to this, it has a particular advantage in that the magnetic properties can be further improved.

  Further, when the slurry is processed by a bead mill, it is preferable to use beads having a diameter of 0.01 to 2.0 mm as a medium. In this way, the contact point (action point) between the beads and the magnetic powder increases, so that the grinding and dispersion efficiency by the bead mill increases and the processing time can be further shortened.

  Moreover, it is suitable that the solid content density | concentration of a slurry is 60-80 mass%. If it does in this way, the fluidity | liquidity of a slurry will be improved and the supply property to the following process will be improved.

  It is preferable to use magnetic powder having an average particle diameter of 1 to 10 μm. By using a magnetic powder having an average particle size within this range, the orientation during magnetic field orientation is remarkably enhanced, and the sinterability and sintered body density in the sintering process are further enhanced.

  In addition, as a solvent to be blended in the slurry, a solvent used in the slurry in wet molding of a sintered magnet can be applied without particular limitation, for example, an oil such as mineral oil, synthetic oil, vegetable oil, an organic solvent such as acetone, alcohol, etc. Is mentioned. Among these, it is preferable to use oil in order to prevent oxidation of the magnetic powder.

  Here, when a magnetic powder containing a rare earth element is used, the method for producing a sintered magnet according to the present invention is particularly effective. In other words, a magnetic material containing rare earth elements has a fracture surface (pulverized surface of magnetic powder) that is chemically very active and highly reactive, so that a chemical reaction on the surface of the magnetic powder (reaction with oxygen in the atmosphere or Since the mechanochemical reaction) and the aggregation of magnetic powders are likely to occur, the action of the present invention tends to work very effectively.

  According to the method for producing a sintered magnet of the present invention, a sintered magnet having a remanently increased residual magnetic flux density can be obtained, and moreover, a sintered magnet can be produced in a short time. Economic efficiency can also be improved.

  Embodiments of the present invention will be described below. In addition, the following embodiment is an illustration for demonstrating this invention, and this invention is not limited only to the embodiment.

(First embodiment)
FIG. 1 is a flowchart (process diagram) showing the procedure of a preferred embodiment of a method for producing a sintered magnet according to the present invention. The method for producing a sintered magnet of the present embodiment includes a raw material alloy preparation step S11, a pulverization step S12, a slurrying step S13, a high-pressure homogenizer treatment step S14, a wet forming step S15, a solvent removal step S16, a sintering step S17, and an aging process. The process step S18 is included. Hereinafter, each step will be described in detail.

<Raw material alloy preparation step S11>
In the manufacture of a sintered magnet, first, a raw material alloy is prepared so that a sintered magnet having a desired composition can be obtained. Specifically, in this step, 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 desired sintered magnet was dissolved in an inert gas atmosphere such as vacuum or argon or nitrogen. Thereafter, a raw material alloy is manufactured by performing an alloy manufacturing process such as a casting method or a strip cast method using the same.

  Here, as the sintered magnet, a magnet having a composition combining a rare earth element and a transition element other than the rare earth element (hereinafter, also referred to as “rare earth metal sintered magnet”) is preferable. Specifically, the rare earth element (represented by “R”) contains at least one of Nd, Pr and Dy in an amount of 26 to 33% by mass, B contains 0.5 to 1.5% by mass as an essential element, And what has the composition of the R-Fe-B type | system | group whose remainder is Fe is preferable. Such a rare earth metal sintered magnet has a composition further containing other elements such as Co, Ni, Mn, Al, Nb, Zr, Ti, W, Mo, V, Ga, Zn, and Si as required. You may have. The rare earth metal sintered magnet may have a Sm-Co composition containing Sm and Co.

<Crushing step S12>
Next, the obtained raw material alloy is coarsely pulverized to obtain particles (coarse powder) having a particle size of about several hundred μm. Coarse pulverization of the raw material alloy is, for example, self-destructive based on the difference in the hydrogen storage amount between different phases after using a coarse pulverizer such as a jaw crusher, brown mill, stamp mill, etc. It can be performed by causing pulverization (hydrogen occlusion pulverization).

  Subsequently, the coarse powder obtained by coarse pulverization is further finely pulverized to obtain fine powder (hereinafter simply referred to as “magnetic”) having an average particle diameter (number average particle diameter) of 10 μm or less, preferably 1 to 10 μm. Also called “powder”.). Fine pulverization, for example, further pulverizing the coarsely pulverized coarse powder using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, or a wet attritor while appropriately adjusting conditions such as pulverization time. It can be done by doing. A dry jet mill is preferable. Here, in order to improve grindability, dispersibility during dispersion, orientation during molding, and lubricity, a grinding aid such as a lubricant or a dispersant may be added and stirred. Specific examples of these grinding aids include, for example, fatty acids or fatty acid derivatives and hydrocarbons. The amount of the grinding aid added is not particularly limited, but is usually about 0.01 to 0.2% by mass with respect to the total mass of the coarse powder. The average particle size was evaluated by the number average when the particle size distribution was measured, and the particle size D50 (value when the cumulative frequency reached 50%) was used.

<Slurry process S13>
Next, the obtained fine powder as the magnetic powder is subjected to the slurrying step S13. In the slurrying step S13, a magnetic powder having an average particle diameter of 1 to 10 μm and a solvent are mixed to produce a slurry. The slurrying step S13 is preferably performed under a low oxygen concentration of 100 ppm or less, such as in an inert gas atmosphere such as argon or nitrogen, in order to prevent the magnetic powder from being oxidized.

  As described above, the solvent used in the slurry in the wet molding of the magnet can be applied without particular limitation as the solvent used here. Further, a lubricant or a dispersant may be added and stirred in order to improve crushability, dispersibility during dispersion, orientation during molding, and lubricity. Specific examples of lubricants or dispersants include, for example, fatty acids or fatty acid derivatives (eg stearic acid, oleic acid, behenic acid, lauric acid, zinc stearate, calcium stearate, aluminum stearate, stearamide, oleamide) , Behenic acid amide, caprylic acid amide, cabric acid amide, lauric acid amide, ethylenebisisostearic acid amide), hydrocarbon paraffin, naphthalene, camphor and the like.

  Although the compounding quantity of a solvent is not specifically limited, Preferably, it adjusts so that solid content concentration of the obtained slurry may be 60-80 mass%. When the solid content concentration of the slurry exceeds 80% by mass, the supply capability of the slurry decreases. On the other hand, when the solid content concentration of the slurry is less than 60% by mass, the dispersion state of the magnetic powder in the slurry is likely to be non-uniform, such as the magnetic powder is settled, and a slurry with a constant concentration can be stably and continuously supplied. It tends to be difficult.

  The solvent supply method may be a method in which a necessary amount is supplied at a time or may be supplied in a plurality of times, and a predetermined amount of solvent is continuously, intermittently or intermittently supplied. In particular, it may be gradually added. If the wettability between the magnetic powder and the solvent is not good, the magnetic powder may be lumped (agglomerated) and the magnetic powder may agglomerate. Therefore, gradually supply the solvent or divide it into multiple times. It is preferable to supply. A lubricant or a dispersant may be added as necessary when the slurry is prepared.

<High pressure homogenizer treatment step S14>
Subsequently, the obtained slurry is treated with a high-pressure homogenizer. Here, the high-pressure homogenizer is a device that mixes, emulsifies or disperses solids and liquids or a mixed fluid of liquids and liquids by pressurizing them with an ultrahigh pressure pump, and has a processing pressure of about 20 to 500 MPa. Say. In this embodiment, the magnetic powder is very highly uniformly dispersed in the solvent in a short time by treating the slurry containing the fine powder having an average particle diameter of 1 to 10 μm and the solvent with such a high-pressure homogenizer. A slurry is made. Such high-pressure homogenizers include, for example, homogenizer H type (manufactured by Sanwa Kikai), homogenizer NS series (manufactured by Niro Soabi), pressure-type homogenizer EmulsiFlex C-5 (manufactured by AVESTIN), nano maker (advanced nano technology) Etc.) are commercially available.

  The processing pressure by the high-pressure homogenizer is preferably 25 to 300 MPa, more preferably 30 to 200 MPa. By increasing the treatment pressure, local high impact forces such as pressurization, shearing and cavitation tend to act more effectively.

  The treatment time by the high-pressure homogenizer may be appropriately set according to the viscosity, treatment flow rate, treatment pressure, etc. of the slurry, and is not particularly limited, but is a viewpoint that reduces mechanochemical reaction and improves productivity and economy. Therefore, it is preferably about 0.1 to 30 minutes, more preferably about 0.1 to 10 minutes. In addition, from the viewpoint of suppressing chemical and physical changes such as mechanochemical reaction, the treatment with the high-pressure homogenizer is preferably performed at a low temperature of about 10 to 100 ° C.

<Bead mill processing step S14a>
Prior to the above-described high-pressure homogenizer treatment step S14, a slurry containing a magnetic powder having an average particle diameter of 1 to 10 μm and a solvent is preferably treated in advance by a bead mill (bead mill treatment step S14a). A bead mill stirs beads (media) of about 0.01 to 2.0 mm in a vessel at a high speed of several hundred rpm or more using a disk or a pin rotor, and the like. It is an apparatus for pulverizing or dispersing an object (object to be crushed or object to be dispersed). By previously treating the slurry with a bead mill in this way, the magnetic powder in the slurry is sized so that the average particle size is further reduced and the particle size distribution is close to monodisperse (the particle size distribution is sharp). Is done. The object of the present invention can be achieved by performing the above-described high-pressure homogenizer treatment without performing the bead mill treatment. However, when the above-described high-pressure homogenizer is performed after the bead mill treatment, the treatment pressure is greatly reduced. Therefore, productivity and economy are further improved. Examples of such bead mills include SC mill, MSC mill (Mitsui Mine), Star Mill LMZ, Star Mill ZRS, Star Mill Nano Getter, Star Mill LME, Star Mill AMC (manufactured by Ashizawa Finetech), Nano Glen Mill, Pure Glen Mill, Pico Glen Mill (manufactured by Asada Tekko), Ultra Visco Mill UVM, Ultra-X Visco Mill UVX, New Visco Mill NVM (manufactured by Imex), Super Apex Mill (manufactured by Kotobuki Industries), Dino Mill (manufactured by Shinmaru Enterprises), Spike Mill (Inoue Seisakusho) Etc.) are commercially available.

  The beads as media used in the bead mill preferably have a bead diameter of 0.01 to 2.0 mm, more preferably 0.3 to 1.5 mm, and still more preferably 0.3 to 0.8 mm. If the bead diameter exceeds 2.0 mm, the effect of improving the intended magnetic properties tends to be poor. On the other hand, if the bead diameter is smaller than 0.01 mm, the bead and the object (the object to be crushed or the object to be dispersed) ) Tends to be difficult to separate. The material of the bead is not particularly limited, but zirconia, alumina, or silicon nitride is preferable, and zirconia is more preferable from the viewpoint of suppressing contamination due to wear of the bead itself.

  The treatment time of the slurry by the bead mill may be appropriately set according to the viscosity of the slurry, the rotation speed or the rotation torque of the bead mill, and is not particularly limited, but the mechanochemical reaction is reduced, and the productivity and economy are reduced. From the viewpoint of improving, it is preferably about 5 minutes to 6 hours, more preferably about 10 minutes to 3 hours.

  The magnetic powder contained in the slurry obtained after the bead mill treatment is preferably reduced in average particle size to 5 μm or less from the viewpoint of improving magnetic properties, but the amount of impurities is significantly increased below 0.5 μm. Since the characteristics, particularly the coercive force is lowered, the thickness is more preferably 1 to 4 μm, still more preferably 1 to 3.5 μm.

<Wet molding process S15>
Subsequently, the slurry processed with the high-pressure homogenizer is pressure-molded in a state where a magnetic field is applied to obtain a molded body. More specifically, after the slurry is fed into the mold cavity of the molding machine by pressure feeding, etc., a predetermined magnetic field is applied to the mold cavity to pressurize the magnetic powder in a magnetically oriented state, and in the slurry The solution is pressure molded while filtering the solvent.

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

  Although the magnitude | size of the magnetic field to apply is not specifically limited, Usually, it is about 12-20 kOe (960-1600 kA / m). Further, the magnetic field to be applied is not limited to a static magnetic field, but can be a pulsed magnetic field, and a static magnetic field and a pulsed magnetic field can be used in combination.

Further, the molding pressure is not particularly limited, but is usually about 0.3 to ³ ton / cm ³ (30 to 300 MPa). The pressurization may be performed constantly from the start to the end of molding, may be gradually increased or decreased, or may be changed irregularly (randomly). The lower the molding pressure, the better the degree of orientation, but if the molding pressure is too low, the resulting molded product will have insufficient strength and the handling property will tend to decrease. The pressure can be appropriately selected. The final relative density of the molded body obtained by molding in a magnetic field is not particularly limited, but is usually about 50 to 60%. Moreover, it is preferable to store the obtained molded object in the container substituted by inert gas atmosphere, such as argon and nitrogen, and oxygen concentration being 100 ppm or less.

<Solvent removal step S16>
Next, the solvent contained in the molded body obtained as described above is removed. Here, it is desirable that the solvent, grinding aid, lubricant, dispersant and the like contained in the molded body are almost completely removed from the viewpoint of preventing the magnetic properties from being deteriorated by the remaining carbon component. More specifically, the compact is preferably maintained at 100 to 200 ° C, more preferably 100 to 180 ° C for 30 minutes or more in a vacuum having a degree of vacuum of 1 Torr or less. At this time, it can also carry out in inert gas or reducing gas atmosphere, such as argon and nitrogen, evacuating with a vacuum pump.

<Sintering step S17>
Further, the compact from which the solvent has been removed is sintered in a vacuum or an inert gas atmosphere using a sintering machine. The sintering conditions may be appropriately adjusted in consideration of various conditions such as the raw material alloy pulverization method, the composition of the magnetic powder, the difference in the average particle size and the particle size distribution of the magnetic powder, and is usually 1 at 950 to 1150 ° C. About 10 hours. If the sintering temperature exceeds 1150 ° C., crystal grains may grow abnormally and the coercive force may decrease, and if it is less than 950 ° C., the residual magnetic flux density of the sintered body tends to decrease to an inconvenient level.

<Aging treatment step S18>
Then, an aging treatment is applied to the obtained sintered body. This aging treatment step S18 is an important step for controlling the coercive force (HcJ), and the sintered body may be heat-treated in a vacuum or an inert gas atmosphere according to a conventional method, but a two-stage aging treatment is performed. It is preferable. When the aging treatment is performed in two stages, holding for a predetermined time at around 800 ° C. and around 600 ° C. is effective. For example, in the first stage aging treatment step, it is preferable to provide a first quenching step in which the sintered body is held at 700 to 900 ° C. for 1 to 3 hours and then rapidly cooled to a range of room temperature to 200 ° C. Moreover, it is preferable to provide the 2nd quenching process which hold | maintains a sintered compact at 500-700 degreeC for 1 to 3 hours, and then rapidly cools to room temperature in the 2nd stage aging treatment process. Since the coercive force is greatly increased by the heat treatment near 600 ° C., it is preferable to perform the aging treatment near 600 ° C. when the aging treatment is performed in one stage. Further, when an R-T-B sintered magnet is produced by a mixing method using a low R alloy and a high R alloy, the coercive force increases when heat treatment is performed at around 800 ° C. after sintering. So it is especially effective.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these, In the range which does not deviate from the summary, it can change suitably and can implement.

  In addition, the particle size measurement of the magnetic powder in an Example and a comparative example was performed using Mastersizer2000 by Malvern. The obtained measurement results were evaluated by the number average, and the average particle diameter was D50 (value when the cumulative frequency reached 50%).

Example 1
First, a raw material metal or a raw material alloy is blended and melted and cast by a strip casting method. Nd: 24.0% by mass, Dy: 7.0% by mass, Co: 0.5% by mass, Al: 0.2 A raw material alloy sheet consisting of mass%, Cu: 0.07 mass%, B: 1.0 mass%, Zr: 0.18 mass%, and the balance Fe was prepared. The obtained raw material alloy sheet was pulverized with hydrogen. Next, after adding lauric acid amide as a grinding aid to this raw material alloy coarse powder (0.15% by mass with respect to the total amount), it is finely pulverized in a high-pressure nitrogen atmosphere using an airflow pulverizer (jet mill). To obtain fine powder as magnetic powder. The obtained magnetic powder had an average particle diameter D50 (number average particle diameter) of 4.08 μm.

  Subsequently, the magnetic powder obtained as described above was synthesized from polyoxyethylene-2-lauryl ether as a dispersant and synthetic oil having a fractional distillation point of 200 to 250 ° C. as a solvent (trade name: IP Solvent 2028, Idemitsu). And a slurry having a solid content concentration of 70% by mass was prepared. Here, the blending amount of polyoxyethylene-2-lauryl ether (trade name: Emulgen 102 kG, manufactured by Kao Corporation) is 0.05 mass% with respect to the total amount of the slurry, and the blending amount of the synthetic oil is It was 30 mass% with respect to the total amount.

  Next, 5 liters of the slurry thus prepared having a solid content concentration of 70% by mass is supplied into a vessel of an SC mill (model name: SC-100, manufactured by Mitsui Mine), and 0.5 mm zirconia beads (trade name) : YTZ ball (manufactured by Nikkato Co., Ltd.) 800 g was used, and the treatment was performed at 1600 rpm for 60 minutes. The average particle diameter D50 of the magnetic powder obtained by drying the slurry after the bead mill treatment was 3.01 μm.

  Next, the slurry after the bead mill treatment was treated for 0.5 minutes under the condition of 150 MPa using a high-pressure homogenizer (model name: manufactured by Nano Maker, Advanced Nano Technology).

  Thereafter, the slurry after the high-pressure homogenizer treatment is fed using a pump, filled in the mold cavity of a wet press molding machine, and a static magnetic field of 14 kOe (1120 kA / m) is applied in the same direction as the press direction. Then, wet pressing was performed at a pressure of 2.3 ton (230 MPa) while orienting the magnetic field to form a molded body having a size of 20 mm × 18 mm × 12 mm. This wet press molding was performed by applying pressure between the upper punch and the lower punch in the mold cavity, and the solvent was sucked and removed from the upper punch during the pressurization.

  Thereafter, the obtained molded body was held at 150 ° C. under a pressure of 1 to 20 Pa for 2 hours to remove the synthetic oil and the dispersant contained in the molded body. Next, the temperature is raised at 8 ° C./min and the molded body is fired by holding at 1030 ° C. for 4 hours, and then the obtained sintered body is held at 800 ° C. and 570 ° C. for 1 hour, respectively. The sintered body of Example 1 (rare earth metal sintered magnet) was obtained.

  Table 1 shows the magnetic characteristics of the obtained sintered magnet of Example 1. The magnetic properties were measured using a BH tracer (manufactured by Toei Kogyo Co., Ltd.) using a sample obtained by grinding the obtained sintered magnet to a size of 11 mm × 11 mm × 11 mm with a vertical processing machine. It was.

(Examples 2-3)
The same treatment as in Example 1 was conducted except that the blending amount of polyoxyethylene-2-lauryl ether as a dispersant was changed to 0.2% by mass and 0.5% by mass, respectively. The sintered magnet (rare earth metal sintered magnet) was obtained. Table 1 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry after the bead mill treatment.

(Comparative Examples 1-3)
Except not performing the high-pressure homogenizer process of a slurry, it processed similarly to Examples 1-3, and obtained the sintered magnet (rare earth metal sintered magnet) of Comparative Examples 1-3. Table 1 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry after the bead mill treatment.

(Examples 4 to 7)
The dispersant was treated in the same manner as in Example 1 except that monosorbitole oleate (trade name: Span 80, manufactured by Kanto Chemical Co., Ltd.) was used and the blending amount was changed to the amount shown in Table 2. 4-7 sintered magnets (rare earth metal sintered magnets) were obtained. Table 2 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry after the bead mill treatment.

(Examples 8 to 11)
The sintered magnets (rare earth metal sintered magnets) of Examples 8 to 11 were obtained in the same manner as in Example 1 except that the dispersant was changed to the amount shown in Table 3. Table 3 shows the average particle diameter D50 and magnetic characteristics of the magnetic powder obtained by drying the slurry after the bead mill treatment.

(Examples 12 to 15)
The dispersing agent was replaced with triphenyl phosphite (trade name: triphenyl phosphite, manufactured by Tokyo Chemical Industry Co., Ltd.), and the same treatment as in Example 1 was carried out except that the blending amount was as shown in Table 4. Thus, sintered magnets (rare earth metal sintered magnets) of Examples 12 to 15 were obtained. Table 4 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry after the bead mill treatment.

(Examples 16 to 19)
Except not carrying out the bead mill process of a slurry, it processed similarly to Examples 4-7, and obtained the sintered magnet (rare earth metal sintered magnet) of Examples 16-19. Table 5 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry.

(Comparative Examples 4-7)
Except not performing the bead mill process and high-pressure homogenizer process of a slurry, it processed similarly to Examples 4-7, and obtained the sintered magnet (rare earth metal sintered magnet) of Comparative Examples 4-7. Table 6 shows the average particle diameter D50 and magnetic properties of the magnetic powder obtained by drying the slurry.

  From the results shown in Tables 1 to 6, the sintered magnets of Examples 1 to 19 have a significantly increased residual magnetic flux density Br compared to the sintered magnets of Comparative Examples 1 to 7, and from this, It was confirmed that a sintered magnet having excellent magnetic properties can be obtained by subjecting the slurry to a high-pressure homogenizer treatment before magnetic field application molding.

  Further, from the results shown in Tables 2, 5 and 6, it was confirmed that a sintered magnet having better magnetic properties can be obtained by subjecting the slurry to bead mill treatment and then high-pressure homogenizer treatment.

  As described above, according to the method for producing a sintered magnet according to the present invention, a sintered magnet with improved magnetic properties can be easily produced, thereby improving productivity and economy, For example, the present invention can be used widely and effectively in permanent magnet applications such as in-vehicle motors and hard disks that require particularly light weight, small size, and high output, and devices, devices, systems, and the like equipped with them.

It is a flowchart which shows the procedure of one Embodiment of the manufacturing method of the sintered magnet by this invention.

Claims (4)

Producing a slurry containing a magnetic powder having an average particle size of 1 to 10 μm and a solvent;
Treating the slurry with a high pressure homogenizer;
A step of pressure-molding the slurry in a state where a magnetic field is applied to the slurry to obtain a molded body;
Deoiling and sintering the molded body;
The manufacturing method of the sintered magnet which has this. In the step of treating the slurry with the high-pressure homogenizer, a high-pressure homogenizer having a treatment pressure of 20 to 500 MPa is used.
The manufacturing method of the sintered magnet of Claim 1. In the step of treating the slurry with the high-pressure homogenizer, after treating the slurry with a bead mill, the slurry is treated with a high-pressure homogenizer.
The manufacturing method of the sintered magnet of Claim 1 or Claim 2. When the slurry is processed by the bead mill, beads having a diameter of 0.01 to 2.0 mm are used.
The manufacturing method of the sintered magnet of Claim 3

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