JPH0917671A - Manufacturing method of rare earth sintered permanent magnet - Google Patents

Abstract

(57) [Summary] [Purpose] The reaction between the alloy powder and the binder is suppressed to reduce the residual oxygen content and residual carbon content of the sintered body, and
Improves fluidity, orientation and lubricity of powder during molding,
Provided is a method for manufacturing a rare earth-based sintered permanent magnet, which improves the dimensional accuracy of a molded body and improves productivity. [Structure] A rare earth-containing alloy powder such as R-Fe-B alloy powder or R-Co alloy powder is mixed with a very small amount of a binder composed of a water-soluble polymer and water and kneaded, and a slurry is granulated by a spray dryer device. Then, improve its fluidity, improve the magnetic field orientation of the powder by mixing a fatty acid ester or borate ester lubricant into the granulated powder, and after filling the granulated powder into the molding die. By applying a pulsed magnetic field and then molding, the granulated powder is crushed and the orientation is improved, and by molding, sintering, and heat treatment, the unit weight of the molded product, the density variation is small, and the thin shape and complex To obtain a rare earth-based sintered permanent magnet having a shape and excellent magnetic properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered permanent magnet using a granulated powder made of a rare earth (R) -containing alloy such as an R-Fe-B alloy or an R-Co alloy. By adding a binder consisting of a water-soluble polymer and water to the rare earth-containing alloy powder and forming a granulated powder with a spray dryer device, the fluidity and lubricity of the powder at the time of compression molding are improved, and the granulation is performed. By adding a fatty acid ester or borate ester compound to the powder, or by applying a pulsed magnetic field, the molding cycle can be improved, the dimensional accuracy of the molded body can be improved, and thin and complex shapes with excellent magnetic properties can be obtained. The present invention relates to a method for producing a rare earth-based sintered permanent magnet that can provide a sintered permanent magnet.

[0002]

2. Description of the Related Art Today, small motors and actuators used for home appliances, computer peripherals, automobiles, etc. are required to be small in size and light in weight and have high performance. Due to size reduction, weight reduction, and thinning, a product having a complicated shape is required, such as providing irregularities at predetermined positions on the surface of the magnet material or providing through holes. Ferrite magnets, R-Co based magnets, and R-Fe-B based magnets previously proposed by the applicant (Japanese Patent Publication No. 61-34242, etc.) can be cited as typical current sintered permanent magnet materials. . Among the above, in particular, rare earth magnets such as R—Co magnets and R—Fe—B magnets are remarkably superior in magnetic properties to other magnet materials, and are therefore widely used in various applications. .

The above-mentioned rare earth magnets such as R-Fe-B.
System sintered permanent magnet has the maximum energy product ((BH) ma
x) exceeds 40 MGOe and exceeds 50 MGOe at the maximum, and has extremely excellent magnetic properties, but in order to develop it, it is necessary to pulverize the alloy having the required composition into an average grain size of about 1 to 10 μm. . However, when the particle size of the alloy powder is reduced, the fluidity of the powder during molding deteriorates, which causes variations in the density of the compact and the life of the molding machine, and also causes variations in the dimensional accuracy after sintering. In particular, it has been difficult to obtain a product having a thin shape or a small shape.

Further, since the rare earth magnet contains as a main component a rare earth element or iron which is easily oxidized in the atmosphere, there is a problem that if the grain size of the alloy powder is reduced, the magnetic characteristics are deteriorated by the oxidation. The Fe-B sintered permanent magnet has a characteristic of exhibiting extremely excellent magnetic characteristics as compared with conventionally known rare earth cobalt magnets and the like, but has a new structure with rare earth or B which is a source of the magnetic characteristics. Since the specific compound and the compound phase are active, there is a problem that the magnetic properties are deteriorated by the oxidation when the particle size of the alloy powder is reduced.

[0005]

Therefore, in order to improve the moldability in particular, an alloy powder before molding is added with polyoxyethylene alkyl ether or the like (Japanese Patent Publication No. Hei 4-
80961), those to which paraffin or stearate is further added (Japanese Patent Publication No. 4-80962, Japanese Patent Publication No. 5-53842), and those to which oleic acid has been added (Japanese Patent Publication No. 62-36365). Was done. However, although the moldability can be improved to some extent, the effect of the improvement is limited, and it has been still difficult to form a thin or small shape required in recent years.

Further, as a method for manufacturing thin-walled shaped products and small-sized shaped products by further improving the moldability together with the addition of the above-mentioned binder and lubricant, saturated alloyed carboxylic acid and unsaturated fat are added to the alloy powder before molding. A method in which a lubricant composed of ethyl myristate or oleic acid is added to an aromatic carboxylic acid, and the mixture is kneaded and then granulated to form a molded product (JP-A-62-245).
No. 604), or a method in which a saturated aliphatic carboxylic acid, an unsaturated aliphatic carboxylic acid or the like is added to a paraffin mixture, kneaded, granulated and then molded (JP-A-63-237402).
Has also been proposed.

However, in the above method, it was difficult to realize sufficient fluidity of the powder because the binding force of the powder particles was not sufficient and the granulated powder was easily broken. In order to improve the moldability and the binding force of the powder particles, it is possible to increase the addition amount of various binders and lubricants, but if added in a large amount, the R component in the rare earth alloy powder and the binder The reaction increases the amount of residual oxygen and the amount of residual carbon in the sintered body after sintering, which causes deterioration of magnetic properties, so that the addition amount is also limited.

Although it is not intended for the rare earth-containing magnetic alloy powder, it is used as a binder for compression molding of the Co-based superalloy powder in an amount of 1.5 to 3.5 wt. % Methylcellulose and a composition in which glycerin and boric acid which are predetermined amounts of additives are further mixed (USP 4,118,480) are proposed, and as a binder for injection molding of alloy powder for tools,
It has a special composition and is 0.5-2.
A composition has been proposed in which water, a plasticizer such as glycerin, a lubricant such as a wax emulsion, and a release agent are added to 5 wt% of methyl cellulose (JP-A-62-37302).
However, all of them use a relatively large amount of binder such as 0.5 wt% or more as described above with respect to the target alloy powder in order to ensure a predetermined fluidity and compact strength. Moreover, since it is essential to add various binder additives, for example, plasticizers such as glycerin in the same amount as that of methyl cellulose, after injection molding or compression molding, after degreasing, even after sintering, a considerable amount of carbon and oxygen can be obtained. Remains, and particularly in the case of a rare earth-based sintered magnet, it causes deterioration of magnetism and cannot be easily applied.

Further, for oxide powders such as ferrite, 0.6 to 1.0 wt% of polyvinyl alcohol as a binder is added to powder having an average particle size of 1 μm or less, and then granulated powder is manufactured by a spray dryer device. Then, a method of molding and sintering the granulated powder is known. However, each of them is 0.6 wt% with respect to the oxide powder.
% Using a large amount of binder, and since a considerable amount of carbon and oxygen remain in the sintered body after degreasing treatment, it has the property of being easily oxidized and carbonized,
The above-described method for oxides cannot be applied as it is to the rare earth-containing alloy powder targeted by the present invention, whose magnetic properties are extremely deteriorated by a little oxidation or carbonization.

Particularly, in the case of oxides, even if a relatively large amount of binder is used, it is possible to degrease and sinter in the air.
Although the binder burns during sintering, a certain amount of residual carbon can be suppressed.However, in the case of the rare earth-containing alloy powder, which is the object of the present invention, the magnetic properties are deteriorated due to oxidation, so that degreasing and sintering are performed in air. Therefore, the addition of a large amount of binder has a fatal adverse effect on the magnetic properties of the obtained sintered magnet. In this way, adding various binders and lubricants to the alloy powder before molding,
Although various attempts have been made to further improve the formability by granulating, a rare earth-based material having a thin shape or a small shape and excellent magnetic properties as required in recent years has been proposed by any method. It was difficult to manufacture a sintered magnet.

This invention suppresses the reaction between the alloy powder and the binder in the method for producing a rare earth-based sintered permanent magnet, reduces the residual oxygen content and the residual carbon content of the sintered body, and reduces the powder during molding. Sintering with a compact and complex shape and excellent magnetic properties by improving the powder feeding fluidity and powder orientation to improve the dimensional accuracy of the compact, productivity and magnetic properties. It is intended to provide a method for manufacturing a permanent magnet.

[0012]

Means for Solving the Problems The present inventors have proposed a method for suppressing the reaction between a rare earth-containing alloy powder and a binder used in spray dry granulation, and reducing the residual oxygen content and residual carbon content of a sintered body. As a result of various studies, it was possible to suppress the reaction between the rare earth-containing alloy powder and the binder in the process before sintering by using a binder composed of at least one kind of water-soluble polymer and water as the binder. It was found that the amount of residual oxygen and the amount of residual carbon of the subsequent sintered body can be significantly reduced.

More specifically, the rare earth-containing alloy powder and the above binder are added and kneaded to form a slurry, and the granulated powder obtained by using the slurry with a spray dryer has sufficient binding force and is pressed. It was found that the powder feed fluidity at the time of molding was good. However, when the granulated powder is molded as it is, there is a drawback that the magnetic properties are inferior because the powder (primary particles) constituting the granulated powder is not sufficiently blended due to the binding force.

Therefore, the present inventors mixed the granulated powder with a fatty acid ester or borate ester-based lubricant and press-molded the mixture so that the slip property between the primary particle powders after the granulated powder was destroyed. It was confirmed that the magnetic field orientation of the powder could be improved. Further, after filling the raw material granulated powder into a molding die, by applying a pulse magnetic field as a preliminary crushing magnetic field and then molding, the granulated powder is crushed and the orientation is improved, whereby The present inventors have completed the present invention by finding that a rare earth-based sintered permanent magnet having small weight and density variations and excellent magnetic characteristics in a small shape or a complicated shape can be efficiently obtained.

That is, according to the present invention, a binder composed of at least one water-soluble polymer and water is added to a rare earth-containing alloy powder and kneaded to form a slurry, and the slurry is granulated powder by a spray dryer device. And nothing,
Next, at least one or more fatty acid ester or borate ester compound is added to the granulated powder, followed by press molding, followed by sintering to obtain a sintered permanent magnet by a powder metallurgy method. It is a manufacturing method of a permanent magnet. In addition, in the above-mentioned configuration, the inventors have previously applied a pulse magnetic field of 10 kOe or more before press molding.
We also propose a method for manufacturing a rare-earth sintered permanent magnet that is applied more than once.

Rare Earth-Containing Alloy Powder In the present invention, the target rare earth-containing alloy powder is
Any composition containing the rare earth element R is applicable, but among them, R-Fe-B based alloy powder and R-Co.
Alloy powders or alloy powders thereof in which an element other than the rare earth element is replaced with another element, for example, R-Fe
It is most suitable to replace —B type Fe with a transition metal such as Co and replace B with a semi-metal such as C or Si. In particular, as the rare earth-containing alloy powder, a powder obtained by pulverizing a single alloy having a required composition, a powder prepared by mixing raw materials having different compositions to have a required composition, and added to improve coercive force or improve manufacturability. Well-known alloy powders such as those obtained by adding the elements at the time of blending the raw materials or before and after crushing can be used.

As the manufacturing method, known methods such as dissolution / pulverization method, ultra-quenching method, direct reduction diffusion method, hydrogen-containing disintegration method, atomizing method and the like can be appropriately selected, and the particle size thereof is also particularly limited. However, if the average particle size of the alloy powder is less than 1 μm, it is not preferable because it reacts easily with oxygen in the atmosphere or with a binder and a solvent to easily oxidize, which may deteriorate the magnetic properties after sintering, and exceeds 10 μm. The average particle size is not preferable because the particle size is too large and the sintered density is saturated at about 95%, and improvement in the density cannot be expected. Therefore, the average particle size of 1 to 10 μm is a preferable range. Particularly preferably, it is in the range of 1 to 6 μm.

Binder Component In the present invention, the binder to be added to the alloy powder is composed of at least one water-soluble polymer and water. As the water-soluble polymer, at least one selected from polyvinyl alcohol, polyacrylamide, water-soluble cellulose ether, polyethylene oxide, water-soluble polyvinyl acetal, polyacrylic acid, and polyacrylic acid derivative is selected.

The polymer selected from polyvinyl alcohol, polyacrylamide, water-soluble cellulose ether, polyethylene oxide, water-soluble polyvinyl acetal, polyacrylic acid and polyacrylic acid derivative is added in an amount of 100 parts by weight of alloy powder. Even if the amount is 0.5 parts by weight or less, the interparticle binding force of primary particles, which is sufficient to withstand the vibration in the feeder for supplying the powder to the mold at the time of molding, and the sufficient fluidity and molded body strength are obtained. be able to. Further, it is possible to form a uniform slurry by adding a small amount, and it is easy to adjust the viscosity of the slurry to a viscosity suitable for spray granulation, and it is possible to maintain a high binding force even after drying. Moreover, since the addition amount is small, the residual oxygen amount and residual carbon amount in the powder can be reduced.

In the polymer used in the present invention, polyvinyl alcohol is easily dissolved in water, has a strong adhesive force, is excellent in chemical stability, thermal decomposability and lubricity during compression molding, and is industrially used. Since it is available at a low price, it is suitable as the polymer used in the present invention. In order to make full use of these characteristics, as a measure of the degree of polymerization, 20
It is preferable to use a polymer having a 4% aqueous solution concentration of 3 to 70 cps at ℃. If the degree of polymerization is less than 3 cps, the breaking strength of the polymer itself will be low, the intergranular binding force of the obtained granulated powder will be reduced, and the granulated powder will not be completely granulated and will remain as fine powder of primary particles. Further, when the degree of polymerization exceeds 70 cps, the viscosity of the slurry is remarkably increased, and it becomes difficult to constantly supply the slurry to the spray dryer, resulting in a marked decrease in productivity. The saponification degree of the polymer used is preferably 70 to 99 mol%. If the saponification degree is less than 70 mol%, the properties inherent to polyvinyl alcohol cannot be sufficiently obtained due to the large number of residual acetyl groups, and conversely, it is difficult to industrially obtain a polymer having a saponification degree exceeding 99 mol%. is there.

In the polymer used in the present invention, polyacrylamide is easily dissolved in water, has a strong adhesive force, has a high breaking strength, is chemically stable, is thermally decomposable, and is a lubricant during compression molding. It is also suitable as the polymer used in the present invention because it has excellent properties and can be obtained industrially at low cost. In order to make full use of these characteristics, a polymer having an average molecular weight of several thousand to several million is preferable. At a degree of polymerization of about several thousand or less, the breaking strength of the polymer itself becomes low, the interparticle bonding force of the obtained granulated powder is reduced, and it is not completely granulated, and remains as fine powder of primary particles. Become. Also,
When the degree of polymerization is about 1 million or more, the slurry viscosity remarkably rises, making steady supply to the spray dryer difficult and the productivity remarkably lowered.

In the present invention, the cellulose ether is a compound in which the three hydroxyl groups (--OH) of the cellulose skeleton are partially etherified with an etherifying agent and an ether group (--OR) is introduced instead of the hydroxyl groups. This includes methyl cellulose (R: CH ₃ ), ethyl cellulose (R: C _2).
H ₅ ), benzyl cellulose (R: CH ₂ C ₆ H ₅ ), cyanethyl cellulose (R: CH ₂ CH ₂ CN), trityl cellulose (R: C (C ₆ H ₅ ) ₃ ), carboxymethyl cellulose (R: CH ₂ COOM, where M is a monovalent metal or ammonium group, hydroxypropyl cellulose (R: CH ₂ CH (OH) CH ₃ ), hydroxyethyl cellulose (R: CH ₂ CH ₂ OH), etc. Hydroxypropylmethylcellulose having a plurality of groups (R: CH ₂ CH ₂ OH, CH _3, CH ₃ ),
Hydroxyethyl methyl cellulose (R: CH ₂ CH ₂ O
H _, CH ₃ ) or the like can be used, and it is advisable to select the substituent and the degree of substitution according to the combination and the like.

These cellulose ethers are preferable because they are excellent in water solubility, have a thickening property, have surface activity, and have excellent chemical stability. The degree of polymerization of the polymer used varies depending on the type of etherification and the degree of substitution, but as a guide, the viscosity of a 2% aqueous solution at 20 ° C is 10 to 30000c.
About ps is preferable. If the degree of polymerization is less than 10 cps, the breaking strength of the polymer itself will be low, the intergranular bonding force of the obtained granulated powder will be reduced, and the granules will not be completely granulated and will remain as fine particles of the primary particles. In addition, when the polymerization degree exceeds 30,000 cps, the viscosity of the slurry significantly increases,
The constant supply to the spray dryer becomes difficult and the productivity is significantly reduced.

The above polymers can be used alone or in combination, and cellulose ether can be added in combination. A preferable combination is methylcellulose + hydroxypropylmethylcellulose.
Examples include methyl cellulose + hydroxyethyl methyl cellulose and the like.

In the polymer used in the present invention, polyethylene oxide is easily dissolved in water, does not gel even when heated, has good thermal decomposability, and has good dispersibility of powder during slurry preparation. Since it is excellent and has excellent lubricity during press molding, it is suitable as a polymer used in the present invention. In order to make full use of these characteristics, those having an average molecular weight of 20,000 to several million are preferable. Molecular weight 2
If it is less than 10,000, the polymer itself will change from a waxy solid to a liquid and the strength of the polymer itself will not be sufficient, and as a result, the binding force to the alloy particles after drying in the granulation process will be insufficient and the granulation will not be complete. , May remain as fine powder.
Further, when the molecular weight exceeds several million, the binding force is improved, but the viscosity of the aqueous solution is significantly increased, and the slurry viscosity becomes high even when added in a small amount during the preparation of the slurry, so that the supply stability to the rotating disk becomes poor. , The particle size distribution of the obtained granulated powder may be disturbed. Further, those having a higher molecular weight are not industrially and universally produced, and are economically disadvantageous.

In the polymer used in the present invention, the water-soluble polyvinyl acetal is a polymer obtained by the condensation reaction of polyvinyl alcohol and an aldehyde, and the characteristics of the polymer obtained by this reaction are the molecular weight of the starting polyvinyl alcohol, the saponification degree, and It greatly depends on the degree of acetalization. In the present invention, as long as it has a desired binding force and can obtain a proper slurry clay and slurry dispersibility, it is not limited to these values, but generally, the saponification degree is 70 to 99, and the polymerization is It is preferable to use a polymer in which polyvinyl alcohol of several hundred to several thousand is used and acetalized from several mol% to several tens mol%.

In the polymer used in the present invention, the polyacrylic acid and the polyacrylic acid derivative are water-soluble polyacrylic acid, polymethacrylic acid and their metal salts, ammonium salts and the like. Since polyacrylic acid and polymethacrylic acid are amorphous and are extremely hard polymers, they give sufficient bond strength to alloy particles, and as a result, granulation can be imparted with a small amount of addition. Is. Further, although those salts are inferior in strength to the above-mentioned two kinds of polymers, they have a peptizing action,
It is suitable for improving the uniformity of the slurry in the process of preparing the slurry.

In the present invention, a slurry is prepared by adding the above polymer and water as a solvent to the alloy powder, and stirring and kneading the mixture. The slurry concentration is the slurry viscosity, the dispersibility of the alloy powder, and the spray granulation process. The amount of the alloy powder in the slurry is preferably 40 to 80% by weight, although it can be appropriately selected from the viewpoint of the amount of treatment and the like. If it is less than 40% by weight, solid-liquid separation occurs in the stirring and kneading step, and the dispersibility of the slurry decreases,
Not only does it become a non-uniform slurry, but sedimentation occurs in the supply pipe during the supply from the agitating and kneading tank to the spray dryer device, and the resulting granulated powder is mixed with non-granulated fine powder, or has a spherical shape. It is not granulated powder. Also,
On the other hand, when it exceeds 80% by weight, the viscosity of the slurry is remarkably increased and uniform stirring and kneading cannot be performed, and the slurry cannot be supplied from the stirring and kneading tank to the spray dryer device.

In the present invention, the slurry supplied to the spray dryer comprises at least alloy powder, polymers containing the above polymer, and water as a solvent. The amount of the polymers added at this time is 100 weight% of the alloy powder. It is 0.05 to 0.7 parts by weight, preferably 0.05 to 0.5 parts by weight, based on parts. If the addition amount is less than 0.05 parts by weight, the bonding force between the particles in the granulated powder is weak, and ungranulated fine powder is mixed in the powder, or the granulated powder is broken during powder feeding before molding and the powder The fluidity of is significantly reduced. Also,
This is because if the amount exceeds 0.7 parts by weight, the amount of residual oxygen and the amount of residual carbon in the sintered body increase, the coercive force decreases, and the magnetic properties deteriorate.

Water which is a solvent used in the present invention is R-F.
In order to suppress the reaction of the e-B alloy powder with the R component as much as possible, it is desirable to use deionized oxygen-treated pure water or water bubbled with an inert gas such as nitrogen.

In the present invention, the addition of the binder to the alloy powder and the stirring of the slurry are preferably carried out in the temperature range of 0 ° C. to 30 ° C., and the oxidation reaction between the alloy powder and water can be further suppressed. . On the contrary, stirring in the temperature range of more than 30 ° C. accelerates the oxidation reaction between the alloy powder and water, resulting in an increase in the amount of residual oxygen in the resulting sintered body, resulting in poor magnetic properties. Therefore, it is necessary to maintain the stirring in the temperature range of 0 ° C. to 30 ° C. For that purpose, it is possible to use water that has been cooled to the temperature in advance, or to employ means such as keeping the stirring tank cold with cooling water. it can.

When a plasticizer is added to the slurry, the powder form can be permanently deformed with a little force when press-molding the granulated powder. The polymers according to the present invention have a high interparticle bonding force for facilitating granulation, and thus have excellent shape-retaining properties, but retain their shape-retaining properties even under constant pressure during press molding. For this reason, the green compact density decreases, and sometimes the magnetic field applied during molding in a magnetic field does not completely align due to its excellent interparticle bonding force, and the residual magnetic flux density of the resulting sintered body decreases. However, this may cause deterioration of magnetic characteristics. Therefore, decrease the intermolecular interaction of the polymer chain,
It is preferable to add a plasticizer in order to lower the glass transition temperature.

As the plasticizer, in consideration of its plasticizing effect, compatibility with a polymer, chemical stability, physical properties (boiling point, vapor pressure, etc.), reactivity with an alloy powder, and the like, generally known plasticizers are used. Agents can be used, and in the case of an aqueous slurry using a water-soluble polymer as in the present invention, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, propylene glycol, glycerin, butanediol. , Diethylene glycol, triethylene glycol and the like can be used.

The amount of the plasticizer added to the water-soluble slurry can be appropriately selected depending on the above-mentioned characteristics of the plasticizer, but is usually 2 to 100 relative to 100 parts by weight of the polymer added to the slurry.
Parts by weight, preferably 5 to 70 parts by weight. Addition amount is 2
When the amount is less than the weight part, the plasticizing effect is not sufficient, the orientation in a magnetic field is not improved, and the magnetic properties (residual magnetic flux density) of the obtained sintered body are deteriorated. On the other hand, if it is added in an amount of more than 100 parts by weight, not only the interparticle bonding force is lowered, the granulation property is lowered and the fluidity is lowered, and since these water-soluble plasticizers generally have high hygroscopicity, There is a problem that the drying property in the process is deteriorated, the residual water content in the powder is increased to cause oxidation, and the powder absorbs moisture during storage. If necessary,
Additives such as a deflocculant (dispersant), a lubricant, an antifoaming agent, and a surface treatment agent can be added within a range in which the residual carbon concentration of the sintered body does not significantly increase.

For example, as the binder, glycerin, wax emulsion, stearic acid, phthalic acid ester,
Dispersion of the slurry is achieved by adding at least one of a dispersant such as petriol and glycol and a lubricant, or by further adding an antifoaming agent such as n-octyl alcohol, a polyalkylene derivative and a polyether derivative. It is possible to obtain a spherical granulated powder having improved properties and homogeneity and a good powdered state in a spray dryer, less bubbles, and excellent in slipperiness and fluidity. In addition,
When added, if the content is less than 0.03 wt%, it has no effect on improving the releasability after molding the granulated powder.
%, The residual carbon content and oxygen content in the sintered body increase, the coercive force decreases, and the magnetic properties deteriorate.
A content of wt% to 0.3 wt% is preferable.

Granulation Method In the present invention, the slurry obtained by adding the above-mentioned binder to the alloy powder and kneading the mixture into granulated powder by a spray dryer device. First, a method for producing granulated powder using a spray drier will be described. A slurry is supplied from a slurry stirrer to a spray drier, for example, sprayed by centrifugal force of a rotating disk, or atomized by a pressure nozzle tip. The sprayed droplets are instantaneously dried by hot air of the heated inert gas to become granulated powder, and fall naturally to the lower part in the collection unit.

In the present invention, the rotary disk type as a spray dryer device is a vane type, a Kessner type,
Although there are various types such as a pin type, in principle, each type is configured by two upper and lower disks, and the disks are configured to rotate. As the configuration of the entire spray drier, a known open type spray drier may be used. It is preferable that the inside of the powder recovery section be replaced with an inert gas or the like, and the hermetic structure be such that the oxygen concentration can always be maintained at 3% or less.

Further, as a constitution in the recovery part of the spray dryer device, an injection port for injecting a heated inert gas above the rotary disc in order to instantly dry the droplets sprayed by the rotary disc. In addition, a discharge port for discharging the injected gas to the outside of the recovery unit is provided in the lower part of the recovery unit, but at that time, it is not possible to heat it to the required temperature outside the device or with a heater attached to the device in advance. It is preferable to maintain the injection port at a temperature corresponding to the temperature of the inert gas, for example, 60 to 150 ° C. so as not to lower the temperature of the active gas.

That is, when the temperature of the inert gas decreases, the sprayed liquid droplets cannot be dried sufficiently in a short time, so that the supply amount of the slurry must be reduced and the efficiency decreases. Also, when making a granulated powder with a relatively large particle size, the rotation speed of the rotating disk is lowered, but if the temperature of the inert gas is lowered at that time, the sprayed droplets are sufficiently dried. Since it is not possible, as a result, by reducing the supply amount of the slurry, the efficiency becomes extremely low when a granulated powder having a large particle size is obtained. Therefore, in order to feed the preheated inert gas into the recovery unit while maintaining the temperature as it is, it is preferable to maintain the temperature of the injection port at 60 to 150 ° C, and most preferably about 100 ° C. .

Further, when the temperature difference between the inert gas injection port and the exhaust port is small, the processing efficiency tends to decrease.
The temperature of the outlet is desirably set at 50 ° C. or lower, preferably 40 ° C. or lower, and particularly preferably at room temperature. As the inert gas, nitrogen gas or argon gas is preferable, and the heating temperature is preferably 60 to 150 ° C.

The particle size of the obtained granulated powder can be controlled by the concentration of the slurry supplied to the spray dryer device, the amount of the slurry supplied, or the rotation speed of the rotating disk. Particle size is 10
If it is less than μm, the fluidity of the granulated powder is hardly improved, and if the average particle size exceeds 400 μm, the particle size is too large, the packing density in the mold during molding is reduced, and the density of the compact is reduced. This is not preferable because the density of the sintered body after sintering is lowered. Therefore, the average particle size of the granulated powder is preferably 10 to 400 μm. More preferably, it is 40 to 200 μm. Further, by performing undercutting and overcutting with a sieve, it is possible to obtain a granulated powder having an extremely high fluidity.
Naturally, the granulated powder is isotropic.

Then, a fatty acid ester or borate ester compound is added to this granulated powder as a lubricant.
This is because the individual powders constituting the granulated powder are easily oriented by the magnetic field during press molding. Since the binder adheres to the surface of each powder and has an inter-particle bonding force, and the sliding effect of the binder is not sufficient, and the blending property by the magnetic field is inferior to the granulated powder, this granulated powder is used. Although the magnetic properties of the permanent magnet, particularly Br (residual magnetic flux density), are lowered, the addition of the above-mentioned lubricant improves the slip between particles and improves Br.

The reason why the fatty acid ester or borate ester is used is that addition of a small amount has a large sliding effect and a small amount of carbon remains in the sintered body, which does not adversely affect magnetic properties. In the present invention, the fatty acid ester compound is preferably a fatty acid ester having a C _{12 to} C ₃₀ saturated (unsaturated) aliphatic group, and examples thereof include methyl laurate, ethyl laurate, methyl palmitate, methyl stearate, Examples thereof include monocarboxylic acid esters such as methyl oleate and polyvalent carboxylic acid esters such as ethylene glycol distearate. Fatty acid esters of C ₁₂ or less have low lubricity, while fatty acid esters of C ₃₀ or more are industrially difficult to obtain.

In the present invention, the boric acid ester compound means boric acid (orthoboric acid H ₅ BO ₃ and metaboric acid H ₅
(Including BO ₂ ) or boric anhydride (B ₂ O ₃ ) is meant a boric acid triester type compound obtained by reacting with one or more monohydric or polyhydric alcohols for esterification. .

Examples of monohydric or polyhydric alcohols that can be used for the esterification of boric acid or boric anhydride include the following compounds (1) to (4). (1) General formula: monohydric alcohol represented by R ₁ —OH, (2) diol represented by the following general formula, (3)
Glycerin or substituted glycerin and their mono- or cis-esters, (4) Polyhydric alcohols other than the above (2) and (3), and their ester or alkylene oxide adducts.

[0046]

Embedded image

In the above general formula, R ₁ has 3 to 2 carbon atoms.
The two aliphatic, aromatic or heterocyclic saturated or unsaturated organic groups, R _2, R ₃ , R ₄ and R ₅ may be the same or different and each is H or aliphatic having 1 to 15 carbon atoms. Or an aromatic saturated or unsaturated monovalent organic group, R ₆ is a single bond, —O—, —S—, —SO ₂ —, —CO—, or an aliphatic or aromatic group having 1 to 20 carbon atoms. It means a saturated or unsaturated organic divalent group.

Examples of the monohydric alcohol (1) include n-butanol, iso-butanol, n-pentanol, n-hexanol, n-hebutanol, n-octanol, 2-ethylhexanol, nonanol, decanol, undecanol, dodecanol. , Tridecanol, tetradecanol, ventadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol and the like, and preferably has 3 to 18 carbon atoms.
Is alcohol. In addition, aliphatic unsaturated alcohols such as allyl alcohol, crotyl alcohol, and probargyl alcohol, alicyclic alcohols such as cyclopentanol and cyclohexanol, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, and furfuryl alcohol. Heterocyclic alcohols can also be used.

A boric acid ester with a monohydric alcohol (methanol or ethanol) having 2 or less carbon atoms has a low boiling point and may volatilize after being mixed with the R—Fe—B alloy powder, which is not preferable. Further, boric acid ester with a monohydric alcohol having 22 or more carbon atoms has a high melting point,
In addition to being slightly inferior in homogeneity, it may remain as residual carbon after sintering.

Examples of the diol (dihydric alcohol) of (2) include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol and 2-methyl-2. , 4-
Bentandiol, Neobenthyl glycol, 1,6-
Hexanediol, 1,7-heptanediol, 1,8
-Octanediol, 1,9-nonanediol, 1,1
Α, ω-glycols such as 0-decanediol; pinacol, hexane-1,2-diol, octane-1,
Symmetrical α such as 2-diol, butanoyl-α-glycol
-Glycols. Total carbon number is 10 or less,
A diol having a relatively low melting point is preferable because it is easy to synthesize and is advantageous in cost.

Examples of the glycerins of (3) include glycerin itself, glycerin and C8-18.
And monoesters or diesters with fatty acids of. Representative examples of these esters are lauric acid mono and diglycerides, oleic acid mono and diglycerides and the like. In addition, substituted glycerin (eg, butane-1,
2,3-triol, 2-methylpropane-1,2,3
-Triol, pentane-2,3,4-triol, 2
-Methylbutane-1,2,3-triol, hexane-
2,3,4-triol, etc.) as well as their monoesters or diesters with fatty acids having 8 to 18 carbon atoms can be used.

Examples of the polyhydric alcohol of (4) include trimethylolpropane, bentaerythritol, arabite, sorbit, sorbitan, mannitol and mannitan. Further, ester products such as monoesters, diesters or triesters of these polyhydric alcohols and fatty acids having 8 to 18 carbon atoms (however, at least one OH group remains), and alkylene oxides in these polyhydric alcohols. An ether type adduct obtained by adding 1 to 20 mol, preferably 4 to 18 mol of (ethylene oxide, propylene oxide, etc.) can also be used.

The esterification reaction of boric acid or boric anhydride with the above alcohols proceeds easily by simply heating the reaction components together. Although the reaction temperature varies depending on the type of alcohol, it is usually about 100 to 180 ° C. The reaction components are preferably reacted in a substantially stoichiometric ratio. The properties of the borate ester obtained are usually liquid or solid.

In the present invention, if the amount of the fatty acid ester or borate ester added is less than 0.01 wt%, the granulated powder will be insufficiently coated, and the effect of improving the mixability during molding in a magnetic field will be sufficiently obtained. If it exceeds 2.0 wt%, carbon remains in the sintered body after sintering and the magnetic properties deteriorate, so 0.01 to 2.0 wt% is a preferable addition amount, and more preferably 0 The range is from 0.1 to 1.0 wt%.

Steps after press molding Next, the granulated powder mixed with a lubricant is press-molded. At this time, it is desirable to apply a magnetic field in advance before press-molding. When an anisotropic magnet is manufactured by press-forming alloy powder, primary particles are blended, and therefore the process is usually performed in a static magnetic field having a magnetic field strength of 8 to 15 kOe during press forming. However, at the time of molding the granulated powder, due to the binding force between the individual particles due to the binder, the static magnetic field of the above-mentioned strength level does not cause sufficient orientation, so after applying a pulse magnetic field at least once before press molding, Press molding is preferable. At this time, the magnetic field is applied also during press molding, but the magnetic field applied during press molding may be a static magnetic field or a continuation of the pulse magnetic field. Magnetic field strength when applied is 10k
Oe or more is desirable, and when the pulsed magnetic field is continuously applied during press molding, the number of pulses is preferably 3 or more including the pulse before press molding in order to obtain high orientation. The molding pressure is about 0.3 to ² ton / cm ² .

It is necessary to lubricate the surface of the mold at the time of molding with a fatty acid ester or the like to prevent baking.
For example, it is desirable to use a non-magnetic superhard material, and Si
If a ceramic material such as C or Si ₃ N ₄ is used, the orientation will be further improved. In addition, before sintering, a general method of heating in a vacuum, a method of raising the temperature at 100 to 200 ° C./hour in flowing hydrogen, and holding at 300 to 600 ° C. for about 1 to 2 hours, etc. It is preferable to perform a binder removal treatment. By performing the binder removal treatment, almost all carbon in the binder is decarburized, which leads to improvement in magnetic properties.

Since the alloy powder containing the R element easily absorbs hydrogen, it is preferable to carry out the dehydrogenation treatment step after the binder removal treatment in flowing hydrogen. In the dehydrogenation treatment, the stored hydrogen is almost completely removed by raising the temperature in a vacuum at a rate of 50 to 200 ° C./hour and maintaining the temperature at 500 to 800 ° C. for about 1 to 2 hours. You.
After the dehydrogenation treatment, it is preferable to subsequently perform heating and heating to perform sintering, and the temperature rising rate after the temperature exceeds 500 ° C. may be arbitrarily selected, and for example, 100 to 300 ° C./hour or the like. A publicly known temperature rising method taken at the time of binding can be adopted.

Sintering of the molded product after the binder removal treatment and heat treatment conditions after the sintering are appropriately selected according to the selected alloy powder composition. For example, in the case of R-Fe-B magnets, Sintering and heat treatment conditions after sintering are 10
Sintering process of holding at 0 to 1200 ° C. for 1 to 2 hours, 45
An aging treatment step of holding at 0 to 800 ° C. for 1 to 8 hours is preferable.

[0059]

According to the present invention, in the production of a rare earth sintered permanent magnet, the powder feeding fluidity and the powder orientation of the powder at the time of molding are improved to improve the dimensional accuracy of the molded product, the productivity and the magnetic properties. Conventionally, rare earth-containing alloy powder is 1 to 1 for improvement.
In view of the fact that the fine powder having a particle size of about 0 μm has poor fluidity and stable press molding cannot be performed, the fluidity is improved by granulating the alloy powder with a specific binder, and further the binder particles are used. In contrast to the fact that the orientation is not sufficiently improved by the binding force, it is improved by mixing a granulated powder with a lubricant containing at least one of a fatty acid ester or a borate compound, or by pulse magnetic field molding. The fluidity and orientation of the powder are significantly improved, the molding cycle is improved, and the variation in the density of molded products and the life of the molding machine are not reduced, and the dimensional accuracy after sintering is also excellent. A rare earth-based sintered permanent magnet having a complicated shape and excellent magnetic properties can be obtained.

In the granulated powder according to the present invention, the primary particles of the original fine powder are anisotropic, but the granulated powder itself is isotropic. Therefore, when the granulated powder is molded without applying a magnetic field, As a matter of course, it becomes an isotropic molded body, but when molded while applying a magnetic field, the granulated powder is broken into the original primary particles by the action of the compressive stress and the magnetic field, and the primary particles are oriented by the magnetic field. , An anisotropic molded product can be obtained.
Since the ease of movement of the secondary particles determines the Br value, the internal lubricant and pulsed magnetic field of the present invention promote the improvement of the blendability of the primary particles. Further, since the granulated powder according to the present invention is coated with the binder, it is difficult to oxidize in the air, and thus there is an advantage that workability in the molding process is improved.

[0061]

【Example】

Example 1 As R, Nd 30.5 at%, Pr 0.31 at%,
A raw material composed of Dy 1.5 at%, Co 2.5 at%, B 1.0 at%, the balance Fe and unavoidable impurities is Ar.
High frequency melting was performed in a gas atmosphere to obtain a button-shaped ingot alloy. Next, after roughly pulverizing the alloy, it was pulverized with a jaw crusher or the like to an average particle size of about 15 μm, and further, a powder having an average particle size of 3 μm was obtained by a jet mill. Binders (A, B) of the types and addition amounts shown in Table 1 in the powder,
Water, a lubricant, etc. are added and kneaded at room temperature to form a slurry, and the slurry is heated by a disc rotary spray dryer using nitrogen as an inert gas and a hot air inlet temperature of 1
Granulation was carried out at 00 ° C. and the outlet temperature set to 40 ° C.

The obtained granulated powder was subjected to undercutting of fine particles with a sieve of # 350 and overcutting of coarse particles with a sieve of # 70 to obtain granulated powder No. 1 having an average grain size shown in Table 1. I got 1 and 2. At this time, the yield of # 350 to # 70 was 90%. Lubrication obtained by subjecting the granulated powder to a condensation reaction of oleic acid monoglyceride, n-butanol and boric acid in equimolar proportions, typically a boric acid ester compound represented by the following structure, which is twice diluted with n-dodecane: The agent was sprayed at a ratio of 0.2 wt% to 100 parts of the granulated powder, and dry mixed at room temperature with a universal mixing stirrer to uniformly disperse the lubricant in the granulated powder. At this time, stirring was performed at a low speed for a short time so that the granulated powder was not crushed. The obtained lubricant-mixed granulated powder was No. 3, 4, 5, 6
And

[0063]

Embedded image

Next, these granulated powders are molded under a molding pressure of 1.3 t.
Magnetic field press molding was performed at on / cm ² . No. 1,
Nos. 2, 3 and 4 are static magnetic field moldings with a magnetic field strength of 10 kOe, No.
For 5 and 6, pulsed magnetic field shaping with a magnetic field strength of 40 kOe (pulse number: 1 time before shaping, 2 times during shaping, 3 times in total)
Was done. Methyl myristate was used for mold lubrication, the molding pressure was 1.3 ton / cm ² , and the shape of the molded body was a ring shape of φ25 mm × φ18 mm × thickness 10.0 mm. The above-mentioned molded body is subjected to a binder removal treatment by heating it from room temperature to 300 ° C at a temperature rising rate of 100 ° C / h in a hydrogen atmosphere, and subsequently, sintering is carried out by raising the temperature to 1100 ° C in vacuum and holding it for 4 hours. , After further sintering,
Introduce Ar gas and cool to 800 ° C at a rate of 7 ° C / min, then cool at a rate of 100 ° C / h to 550 ° C.
Then, a time treatment of holding for 2 hours was performed to obtain an anisotropic sintered body.

Flowability of granulated powder at the time of molding, size of molded body,
Density and residual oxygen content of the obtained sintered magnet, residual carbon content,
The magnetic properties are shown in Table 2. The flowability was measured by the time required for 100 g of the raw material powder to fall naturally through a funnel having an inner diameter of 8 mm and to pass through. In all cases, no cracks, cracks or deformations were observed in the obtained sintered bodies. As is clear from Table 2, the internal lubrication of the granulated powder improves the mixability, increases the Br and (BH) max, and improves the magnetic properties. Furthermore, it can be seen that the magnetic characteristics are greatly improved by applying the pulsed magnetic field.

Further, using the same 3 μm powder as in the conventional example, the static magnetic field strength was 10 kOe and the molding pressure was 1.3 ton / cm by the same magnetic field press machine without granulation.
Φ2 mm x φ18 mm x thickness 10.0 mm under ² conditions
Ring was molded. Mold lubrication is the same fatty acid ester as in the present invention. Then, the molded body is vacuumed at 1100.
Sintering for 4 hours at ℃, and after completion of sintering,
After introducing r gas and cooling at a rate of 7 ° C / min to 800 ° C, and then at a rate of 100 ° C / h, 550 ° C
After aging treatment of holding for 2 hours at No. 7 sintered magnet was obtained.

Powder No. at the time of molding The flowability of No. 7 and each characteristic of the molded product are shown in Table 2 as a conventional example. Non-granulated powder N
o. The flowability of No. 7 is poor, and the dimensional variation of the press-formed product is large. On the other hand, the granulated powder No. of the comparative example. Nos. 1 and 2 have good flowability and small dimensional variation, but the orientation is a little low, and B
r and (BH) max are small. However, the present invention example No. According to Nos. 3, 4, 5 and 6, it is clear that the flowability is improved, the orientation is improved, and the magnetic characteristics are excellent.

[0068]

[Table 1]

[0069]

[Table 2]

Example 2 Sm 11.9 at%, Cu 8.8 at%, Fe 1
A raw material composed of 2.6 at%, Zr1.2 at%, the balance Co and unavoidable impurities was subjected to high frequency melting in an Ar gas atmosphere to obtain a button-shaped ingot alloy. Next, after roughly crushing the alloy, an average particle size of about 1 is obtained with a jaw crusher or the like.
Grind to 5 μm, and then use a jet mill to obtain an average particle size of 3
A μm powder was obtained. Binder, water, lubricant, etc. of the types and addition amounts shown in A of Table 1 are added to the powder and kneaded at room temperature to form a slurry, and the slurry is mixed with nitrogen in an inert gas by a disk rotary spray dryer device. Using
Granulation was performed by setting the hot air inlet temperature to 100 ° C and the outlet temperature to 40 ° C.

The obtained granulated powder was undercut with a sieve of # 350 to overcut fine particles, and the coarse particles were overcut with a sieve of # 70 to obtain granulated powder 8 having an average grain size shown in Table 3. At this time, the yield of # 350 to # 70 is 86.
%Met. For the granulated powder, a lubricant obtained by diluting the boric acid ester used in Example 1 with n-dodecane to 2 times was granulated powder 100.
0.2 wt% to the parts was added by spraying, and the mixture was dry-mixed at room temperature by a universal mixing stirrer to uniformly disperse the lubricant in the granulated powder. At this time, stirring was performed at a low speed for a short time so that the granulated powder was not crushed. The obtained lubricant mixed granulated powder is set to 9,10.

Next, these granulated powders were subjected to magnetic field press molding. No. 8 is a magnetic field strength of 10 kOe and a molding pressure of 1.
No. 3 ton / cm ² static magnetic field molding. For 9 and 10, static magnetic field shaping with magnetic field strength of 10 kOe and magnetic field strength of 1
Pulsed magnetic field shaping of 0 kOe (Number of pulses: Before shaping 1
Times, twice during molding, a total of 3 times). Mold lubrication uses fatty acid ester, molding pressure is both 1.3 ton / c
m ² and the shape of the molded body is φ25 mm × φ18 mm
× It was a ring shape with a thickness of 10.0 mm.

The above molded body was heated in a hydrogen atmosphere from room temperature to 3
A binder removal treatment is performed by heating up to 00 ° C. at a temperature rising rate of 100 ° C./h, followed by sintering by raising the temperature to 1200 ° C. in a vacuum and holding for 1 hour.
The solution heat treatment is performed at 60 ° C., Ar gas is introduced, and then 80
Multi-step aging treatment was performed from 0 ° C to 400 ° C. Table 3 shows the flowability of the granulated powder at the time of molding, the size and density of the molded body, the residual oxygen content, residual carbon content, and magnetic characteristics of the obtained sintered magnet. The flowability was measured by the time required for 100 g of the raw material powder to fall naturally through a funnel having an inner diameter of 8 mm and to pass through.
In all cases, cracks, cracks or deformations were not observed in the obtained sintered bodies. As is clear from Table 3, the internal lubrication of the granulated powder improves the mixability, and Br,
(BH) max is increased and the magnetic characteristics are improved. Further, it can be seen that the magnetic characteristics are greatly improved by applying the pulsed magnetic field.

Further, as the conventional example, the same 3 μm powder was used, without granulation, using the same magnetic field press machine as it was, at a magnetic field strength of 10 kOe and a pressure of 1 ton / cm ² .
After being molded into a shape of mm × 15 mm × thickness of 10 mm, sintering was carried out at 1200 ° C. for 1 hour in vacuum, and after completion of sintering, multi-step aging treatment was performed under the same conditions as in Example 2. Table 3 shows the flowability of the granulated powder at the time of molding, the size and density of the molded body, the amount of residual oxygen, the amount of residual carbon, and the magnetic properties of the obtained sintered magnet (No. 11) together with the examples. Powder No. at the time of molding The flowability of No. 11 and the characteristics of the molded product are shown in Table 3 as a conventional example. Powder No. which is not granulated The flowability of No. 11 is poor, and the dimensional variation of the press-formed product is large. on the other hand,
Granulated powder No. of the comparative example. No. 8 has good flowability and small dimensional variation, but its orientation is a little low, and Br, (BH) max
Is getting smaller. However, according to the present invention No. 9.10
According to the document, it is clear that the flowability is improved and the orientation is improved, and the magnetic properties are excellent.

[0075]

[Table 3]

Example 3 Granulation was carried out in the same manner as in Example 1 except that the binder compositions shown in Table 1 were replaced with the binders C to G having 5 kinds of compositions shown in Table 4. Granulate powder No. 12-16 were obtained. Table 1 shows the average particle size and the yield of the granulated powder obtained at this time. Here, polyethylene oxide having an average molecular weight of 500000 is used as polyvinyl acetal, and average molecular weight is 30,000 and an acetal group is 10 mo.
1%, acetyl groups 5 mol% and hydroxyl groups 85 mol% were used as polyacrylic acid having an average molecular weight of 10,000 and ammonium polyacrylate having an average molecular weight of 20,000. Then, the borate ester used in Example 1 was mixed in the same manner, and the lubricant-mixed granulated powder No. 17-26 were prepared. And these N
o. Magnetic field press molding was performed using 12 to 26 granulated powder. Here, No. 12 to 16, 17, 19, 21, 2
For Nos. 3 and 25, molding was performed while applying a static magnetic field of 10 kOe, and No. For 18, 20, 22, 24, and 26, a pulsed magnetic field of 40 kOe was applied before press molding, and then molding was performed while applying a static magnetic field of 10 kOe.

The obtained molded body was sintered in the same manner as in Example 1,
Aging treatment was performed to obtain a sintered magnet. The test results are shown in Tables 5 and 6. Moreover, the obtained sintered body was not cracked, cracked or deformed in any case. As is clear from Table 5, no matter which binder was used for granulation, the compounding property was improved by internally lubricating the granulated powder in the same manner as in Examples 1 and 2, and Br and (BH) max were increased. The magnetic properties are improved. Furthermore, by applying a pulsed magnetic field in advance before press molding, the magnetic characteristics are greatly improved.

[0078]

[Table 4]

[0079]

[Table 5]

[0080]

[Table 6]

[0081]

The method for producing a rare earth-based sintered permanent magnet according to the present invention comprises a rare earth-containing alloy powder such as an R—Fe—B alloy powder or an R—Co alloy powder, and at least one water-soluble polymer. A binder composed of water and water is added and kneaded to form a slurry, and the slurry is formed into a highly fluid spherical granulated powder by a spray dryer device. The granulated powder and a fatty acid ester or borate ester lubricant are used. By mixing and press-molding, it is possible to improve the slidability between the primary particle powders after the granulated powder is broken, and improve the magnetic field orientation of the powders. Furthermore, granulation is used instead of the static magnetic field during molding. After filling powder into a molding die, applying a pulse magnetic field or a pulse magnetic field and a static magnetic field as a preliminary crushing magnetic field and then molding to crush the granulated powder and improve the orientation. Moldings unit weight, small density variations, and rare earth metal-based sintered permanent magnet having excellent magnetic properties at small shape or a complicated shape can be efficiently obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihisa Kishimoto, 4-53, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (72) Osamu Yamashita, Egawa 2-chome, Shimamoto-cho, Mishima-gun, Osaka Prefecture 15ー 17 Sumitomo Special Metals Co., Ltd. Yamazaki Works

Claims (2)

[Claims] 1. A rare earth-containing alloy powder is added with a binder consisting of at least one water-soluble polymer and water and kneaded to form a slurry, and the slurry is formed into a granulated powder by a spray dryer device, and then the granulated powder is prepared. A rare earth-based sintered permanent magnet characterized in that a sintered permanent magnet is obtained by a powder metallurgy method in which at least one of fatty acid ester or borate ester-based compound is added to granulated powder, followed by press molding and subsequent sintering. Manufacturing method. 2. The method for manufacturing a rare earth-based sintered permanent magnet according to claim 1, wherein a pulse magnetic field of 10 kOe or more is applied once or more in advance before press molding.