JPH0917673A - Manufacture of sintered rare earth magnet - Google Patents

Abstract

PURPOSE: To reduce the amounts of residual oxygen and carbon in a sintered product and to improve a dimensional accuracy and productivity of the product by adding a predetermined binder to magnetic powder and stirring them together into a slurry, forming the slurry into powder using a spray drier, and compressing and sintering it. CONSTITUTION: A binder consisting of an organic solvent and at least one type of polymer or an additional plasticizer is added to rare earth alloy powder and kneaded together into a slurry. The slurry is formed into powder by a spray drier, compressed into a compact and sintered to form a sintered permanent magnet. Thereby the fluidity of the powder can be remarkably improved, molding cycle can be improved, and a resultant magnet can have a small-sized shape with an excellent dimensional accuracy, a thin-wall structure and excellent magnetic characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an R-Fe-B system which is a spherical granulated powder having a high fluidity and which has excellent magnetic properties and is molded using the granulated powder. Alloy and R-
According to a method for producing a rare earth (R) -based permanent magnet such as a Co-based alloy, an organic solvent, a polymer soluble in the organic solvent, and a binder made of a plasticizer, if necessary, are added to the rare earth-containing alloy powder. Then, the mixture is stirred into a slurry and sprayed in the chamber of the spray dryer device to form droplets, which are instantly dried and solidified to form granulated powder, which allows the fluidity and lubrication of the powder during compression molding. Of a rare earth-based sintered magnet capable of improving the molding property, improving the molding cycle, improving the dimensional accuracy of the molded body, and providing a thin-walled or complex-shaped sintered permanent magnet having excellent magnetic properties. Regarding

[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 powder particles, it is possible to increase the addition amount of various binders and lubricants, but if added in large amounts, the R component in the rare earth alloy powder and the binder Due to the reaction, the amount of residual oxygen and the amount of residual carbon in the sintered body after sintering increase, leading to deterioration of magnetic properties, so the addition amount was 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 in particular in the case of rare earth magnets, 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 has been difficult to manufacture magnets.

According to the present invention, it is possible to easily produce the granulated powder required for producing a rare earth magnet having excellent magnetic properties, suppress the reaction between the rare earth-containing alloy powder and the binder, and burn after sintering. In addition to reducing the residual oxygen content and residual carbon content of the aggregate, it also improves the fluidity and lubricity of the powder during molding, improving the dimensional accuracy of the compact and improving productivity, and reducing the thin shape and complexity. An object of the present invention is to provide a method for producing a rare earth-based sintered permanent magnet such as an R—Fe—B system or an R—Co system that has a shape and excellent magnetic properties.

[0012]

Means for Solving the Problems As a result of various studies on a manufacturing method capable of easily manufacturing a granulated powder having good moldability, the inventors have paid attention to a rotary disk type spray dryer device, and have investigated a magnetic powder and a required amount. By adding a binder and kneading to form a slurry, and spraying and drying the slurry, the slurry can be made into a granulated powder having a required average particle diameter, and then the granulated powder is used. And molded,
Since the granulated powder itself has a sufficient binding force, the fluidity of the powder is remarkably improved, there is no variation in the density of compacts, the life of the molding machine is not reduced, and the dimensional accuracy after sintering is also excellent. It was found that a rare earth sintered permanent magnet having a thin shape or a complicated shape and excellent magnetic characteristics can be efficiently obtained.

In addition, as a result of various investigations by the present inventors, in the above-mentioned manufacturing method, as a result of various studies on binders that can suppress the reaction with the rare earth-containing alloy powder and reduce the residual oxygen content and residual carbon content of the sintered body, at least By using a binder composed of one or more solvent-based polymers and an organic solvent, it is possible to suppress the reaction between the rare earth alloy powder and the binder in the step before sintering, and then apply a normal powder metallurgy method. As a result, it was found that the amount of residual oxygen and the amount of residual carbon of the sintered body after sintering can be significantly reduced and a sintered magnet having an excellent residual magnetic flux density can be obtained.

When granulating is carried out using a mixture of an organic solvent, a polymer soluble in the solvent, and a plasticizer as the binder, the addition amount of the alloy powder 1
Even if the amount is 0.5 parts by weight or less with respect to 00 parts by weight, the interparticle binding force of the primary particles is sufficient to withstand the vibration in the feeder for supplying the powder to the mold during molding, and the sufficient fluidity. Further, they found that the strength of the molded body can be obtained, and completed the present invention.

That is, according to the present invention, a binder composed of an organic solvent and at least one polymer or a plasticizer is added to a rare earth alloy powder and kneaded to form a slurry, and the slurry is sprayed with a spray dryer. A method for producing a rare earth-based sintered magnet, which is characterized in that a sintered permanent magnet is obtained by a powder metallurgy method of forming granulated powder and molding and sintering the granulated powder.

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 the required composition, or an alloy having a different composition,
Known powders such as powders that have been mixed and adjusted to the required composition, those that have added additional elements to improve coercive force and manufacturability
-Fe-B type alloy powder and R-Co type alloy powder 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.

In the present invention, the binder component added to make the alloy powder into a slurry has at least one organic solvent, at least one polymer soluble in the organic solvent, and optionally at least one polymer. A plasticizer is used.
The polymer used in the binder of the present invention is not particularly limited in its chemical structure, molecular weight, etc.,
The following characteristics are required. 1) Chemical stability Not only does it chemically react with the alloy powder to be used and does not easily react with the alloy powder during slurry kneading and in the state of granulated powder, it also adds an organic solvent and a plasticizer to be used. It is necessary that chemicals such as oxidation, decomposition and cross-linking do not occur in the agent to cause changes in physical and chemical properties.

2) Soluble in organic solvent It is necessary that the viscosity range is such that the organic solvent is easily dissolved in an organic solvent and that the slurry is stably supplied in the process of supplying the slurry to the spray dryer in the granulating step. . For example, at 20 ° C. and 1% by weight concentration,
The viscosity of the solution is preferably about 100 cps or less.
When a polymer having a viscosity exceeding this range is used, the slurry supply becomes unstable, and it is inefficient because the slurry concentration must be remarkably reduced for stable supply.

3) High interparticle binding force In order to easily granulate the alloy powder, it is necessary that the polymer itself has a high interparticle binding force with respect to the alloy powder. That is, it is necessary that the polymer itself has strong mechanical properties and, at the same time, has high adhesion to the alloy powder. Although it is difficult to directly measure this interparticle binding force quantitatively, as a guideline, a polymer simple substance is formed into a film by a method such as hot pressing or solvent casting, and the breaking strength of the polymer simple substance film is measured. It is possible to understand to some extent. The breaking strength measured in this way is as follows:
0.5 kgf / mm ² or more is preferable, and if it is less than such strength, the granulation property is insufficient and un-granulated raw material fine powder is mixed, or the polymer addition amount is increased in order to improve the granulation property. It is necessary to increase the amount, and as a result, a large amount of carbon remains in the resulting sintered body, resulting in deterioration of magnetic properties.

4) Softening temperature Although related to the above-mentioned interparticle bonding force, the obtained granulated powder is usually stored at room temperature and press-molded at room temperature, so that the required interparticle bonding force is maintained at room temperature. Therefore, the softening temperature needs to be room temperature or higher. In practice, in the case of adding a plasticizer in order to improve the magnetic field blending property as described below, the softening temperature of the film alone is 30%, considering that the softening temperature is slightly lowered due to the effect of the addition. C. or higher, more preferably 50.degree. C. or higher. Although there is no particular upper limit of the softening temperature, in the press molding step, for example, when molding is performed by applying ultrasonic waves, the granulated powder is softened by thermal energy by applying ultrasonic waves, and from the viewpoint of improving the magnetic field blending property. Two
It is preferably 00 ° C or lower.

The polymer used in the present invention is not particularly limited in its chemical structure, molecular weight and the like as long as it satisfies the above-mentioned required characteristics. Acrylic resins such as polymethyl methacrylate, polybutyl methacrylate, cyclohexyl acrylate, polystyrene resins, polyvinyl acetate resins, polyvinyl acetal resins, polyvinyl butyral resins, cellulose ethers such as methyl cellulose and hydroxypropyl cellulose, polycarbonate resins, poly In addition to homopolymers such as arylate resins, copolymers such as ethylene vinyl acetate copolymers, ethylene-acrylate copolymers, styrene-methyl tacrylate copolymers can be mentioned.

The organic solvent used in the present invention can be appropriately selected for one or more polymers selected from the above. That is, it is not particularly limited as long as it has sufficient solubility in the polymer used and is chemically stable in the polymer and alloy powder. However, in order to industrially stably produce the granulated powder, it is preferable to select an organic solvent having a boiling point of about 30 ° C. to 150 ° C. under normal pressure. That is, the boiling point is 30 ° C
When the amount is less than the above, the volatilization of the organic solvent during the kneading of the slurry is remarkable, it is difficult to keep the slurry concentration constant, and the slurry tends to be non-uniform. On the contrary, 1
When an organic solvent having a boiling point of more than 50 ° C. is used, it is necessary to keep the granulated powder in a very high temperature atmosphere in the spray drying process, and it takes a long time to dry the granulated powder. The processing capacity of will be significantly reduced.

In the present invention, it is preferable to add a plasticizer to the binder. The plasticizer is added in order to permanently deform the powder morphology with a small force when press-molding the granulated powder. The polymers in the present invention have a high interparticle binding force for facilitating granulation, so that the shape retention is excellent,
It retains its shape-retaining property even under constant pressure during press molding, so that the green compact density decreases, and sometimes it is perfectly oriented due to its excellent interparticle bonding force against the applied magnetic field during magnetic field molding. Otherwise, the resulting residual magnetic flux density of the sintered body is reduced, which causes deterioration of magnetic characteristics.
Therefore, a plasticizer is added to lower the intermolecular interaction of polymer chains and lower the glass transition temperature.

The plasticizer to be used is a generally known plasticizer in consideration of the plasticizing effect on the polymer, compatibility with the polymer, chemical stability, physical properties (boiling point, vapor pressure, etc.), reactivity with alloy powder, and the like. Agents can be used, in the case of an organic solvent-based slurry as in the present invention, dibutyl phthalate,
Dioctyl phthalate, didecyl phthalate, phthalate ester plasticizers such as butylbenzyl phthalate, tricresyl phosphate, trioctyl phosphate, triphenyl phosphate, octyl didiphenyl phosphate, cresyl diphenyl phosphate and other phosphate ester plasticizers, Dioctyl adipate, adipate plasticizers such as diisodecyl adipate, dibutyl sebacate, sebacate ester plasticizers such as dioctyl sebacate, dioctyl azelate, azelaic ester plasticizers such as dihexyl azelate, triethyl citrate, Acetyl triethyl citrate, citric acid ester-based plasticizers such as tributyl citrate, methylphthalylethyl glycolate, ethylphthalylethyl glycolate, butylphthali Can be employed glycolic acid ester plasticizers butyl glycolate and the like, tributyl trimellitate, trimellitic acid ester plasticizers such as trioctyl trimellitate.

The addition amount of these plasticizers can be appropriately selected depending on the above-mentioned characteristics of the plasticizer, but is usually 2 to 100 parts by weight, preferably 5 to 70 parts by weight, relative to 100 parts by weight of the polymer added to the slurry. . If the added amount is less than 2 parts by weight, the plasticizing effect is not sufficient, the compoundability of the powder during the application of a magnetic field is not sufficiently improved, and the magnetic properties (residual magnetic flux density) of the obtained sintered body deteriorate. On the other hand, if it is added in excess of 100 parts by weight, the intergranular binding force of the obtained granulated powder is lowered and the granulating property is lowered, so that good fluidity cannot be obtained.

According to the present invention, a slurry is prepared by adding the above-mentioned polymer, an organic solvent and, if necessary, a binder made of a plasticizer to alloy powder, and stirring and kneading the slurry. It can be appropriately selected from the viewpoints of dispersibility of the alloy powder, the amount of treatment in the spray granulation step, and the like. The alloy powder concentration in the slurry is preferably 40 to 80% by weight, and 40% by weight
If less than, solid-liquid separation occurs in the stirring and kneading step, the dispersibility of the slurry is reduced, not only becomes a non-uniform slurry, but also sedimentation occurs in the supply pipe during the supply from the stirring and kneading tank to the spray dryer device. If the obtained granulated powder is mixed with non-granulated fine powder or becomes a non-spherical granulated powder, and if it exceeds 80% by weight, the slurry viscosity increases remarkably and only uniform stirring and kneading cannot be performed. Therefore, 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, the above-mentioned polymers, an organic solvent, and a plasticizer to be added if necessary. The amount of the added polymers is the alloy. The amount is 0.05 to 0.7 parts by weight, preferably 0.05 to 0.5 parts by weight, based on 100 parts by weight of the powder. If the addition amount is less than 0.05 parts by weight, the bonding force between the particles of the alloy powder in the obtained granulated powder is weak, and the ungranulated raw material fine powder is mixed in the obtained granulated powder, The granulated powder is broken during powdering and the fluidity of the powder is significantly reduced. Also,
If it exceeds 0.7 parts by weight, the amount of residual oxygen and the amount of residual carbon in the obtained sintered body increase, the coercive force decreases, and the magnetic properties deteriorate. Further, if necessary, additives such as a deflocculant (dispersant), a lubricant, a defoaming 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.

Spray Dryer Device 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 dryer device, it is possible to use a known open type spray dryer device, but not only the organic solvent has an adverse effect on the environment, but the magnetic powder to be granulated is a rare earth-containing alloy powder. Since it is easily oxidized, it is preferable to have a closed structure in which the inside of the slurry storage section of the apparatus or the collection section of the granulated powder can be replaced with an inert gas and the oxygen concentration thereof can be constantly maintained at 3% or less.

Further, as a structure in the recovery part of the spray dryer device, an injection port for injecting a heated inert gas above the rotating disk in order to instantly dry the droplets sprayed by the rotating disk. 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 droplets cannot be dried sufficiently in a short time, so that the slurry supply amount 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 injection port and the discharge port of the inert gas is small, the processing efficiency tends to decrease, so that
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 on the obtained granulated powder with a sieve, it is possible to obtain a granulated powder having an extremely high fluidity. Further, the fluidity can be further enhanced by adding a small amount of a lubricant such as zinc stearate, magnesium stearate, calcium stearate, aluminum stearate, and borate esters to the granulated powder.

Manufacturing Method of Sintered Permanent Magnet The process of manufacturing a sintered permanent magnet using the granulated powder according to the present invention, that is, the conditions such as molding, sintering and heat treatment, and the method may be any known powder metallurgical means. Can be adopted. An example of preferable conditions is shown below. The molding can be carried out by any known molding method, but compression molding is most preferable, and the pressure is 0.3 to 2.0 ton.
/ Cm ² is preferred. A preferable range of the magnetic field strength when molding by applying a magnetic field is 10 to 20 kOe. Before sintering, a general method of heating in a vacuum or a temperature increase of 100 to 200 ° C./hour in flowing hydrogen for 3
The binder removal treatment is preferably performed by a method such as holding at 00 to 600 ° C. for about 1 to 2 hours. 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.
Further, 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, for example, 100 to 300 ° C./hour. A publicly known temperature raising method taken during sintering 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 6 hours, 45
An aging treatment step of holding at 0 to 800 ° C. for 1 to 8 hours is preferable.

Further, the rare earth-containing alloy powder is R-Fe-
In the case of B-based alloy powder, in order to suppress the reaction of the R component in the powder with the binder and the organic solvent, R-Fe having a required single composition generally used in the conventional powder metallurgy method.
In place of the B-based alloy raw material powder, a main phase-based alloy powder having an R ₂ Fe ₁₄ B phase as a main phase and an average particle size of 1 to 10 μm, and R ₃
The intermetallic compound phase of Co or Fe and R, including the Co phase, contains a part of R ₂ (FeCo) ₁₄ B phase, etc. and has a large amount of rare earth elements, so as to suppress the reaction with the organic binder as much as possible than the main phase alloy. The amount of residual oxygen after sintering can be reduced by using two kinds of raw material powders having a large average particle diameter and having an average particle diameter of 8 to 40 μm.

[0039]

The operation of the method for producing a sintered permanent magnet according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial explanatory view showing a disc portion of a rotary disc type spray dryer used in the present invention. The rotating disk 1 shown in FIG. 1 is such that a pair of disks 2 and 2 are provided with a plurality of non-magnetic material pins 3 of a required length vertically arranged at a predetermined interval on a circumferential portion and fixed by a nut 4 so as to face each other. This is a pin-type rotating disk having a structure in which a distance is maintained, a rotating shaft 5 is arranged at the center of the rotating disk 1, and a peripheral portion thereof serves as a slurry supply port.

A rotary disc 1 is horizontally arranged in a chamber (not shown) having a closed structure so as to be rotatable, and an inert gas nozzle is sprayed downward at a predetermined position above the rotary disc 1 so that it can be sprayed downward. Is the part for collecting granulated powder. The slurry obtained by adding and stirring a predetermined binder to the magnetic powder is supplied from the slurry stirrer to the spray dryer device, and the slurry is sprayed by the centrifugal force of the rotating disk 1. The sprayed droplets are instantly dried by the heated hot air of the inert gas to become granulated powder, and spontaneously drop to the lower part in the recovery section.

That is, R-Fe-B type alloy powder and R-
A rare earth-containing alloy powder such as a Co-based alloy powder is added with a binder comprising an organic solvent and a polymer soluble in the solvent, and a plasticizer to be added if necessary, and kneaded to form a slurry, By forming the slurry into a spherical granulated powder having high fluidity by the spray dryer device having the above-mentioned structure, the fluidity of the powder is remarkably improved in combination with the excellent fluidity of the binder itself, and the molding cycle is improved. In addition, a rare-earth sintered magnet with a thin shape and a complicated shape and excellent magnetic characteristics, which has excellent dimensional accuracy after sintering without variation in the density of the molded body and shortening the life of the molding machine, can get.

Since the granulated powder in the present invention is isotropic in itself, it naturally becomes an isotropic molded product when molded without applying a magnetic field, but a magnetic field is applied. However, when molded, 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, so that an anisotropic molded body is obtained.
It also has the advantage that both isotropic magnets and anisotropic magnets can be manufactured depending on the application. 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.

[0043]

【Example】

Example 1 Nd: 13.3 atomic%, Pr: 0.31 atomic%, Dy:
A raw material consisting of 0.28 atomic%, Co: 3.4 atomic%, B: 6.5 atomic%, balance: Fe and unavoidable impurities
High-frequency melting was performed in an r gas atmosphere to obtain a button-shaped ingot alloy. Next, the alloy was roughly pulverized, then pulverized with a jaw crusher or the like to have an average particle size of 15 μm, and further jet-milled to obtain a powder having an average particle size of 3 μm. Polymethylmethacrylate (breaking strength: 0.65 kgf / mm ² ) was used as a polymer, toluene was used as an organic solvent in the obtained powder, and the composition shown in Table 1 was added to 100 parts by weight of the alloy powder. A slurry is prepared by stirring and kneading at room temperature, and the slurry is granulated by a disk rotary spray dryer using nitrogen as an inert gas, setting the hot air inlet temperature to 100 ° C and the outlet temperature to 40 ° C. I went.

Using a compression magnetic field molding machine, the above granulated powder was subjected to a magnetic field strength of 15 kOe and a pressure of 1 ton / cm ² and a pressure of 10 mm ×.
After forming into a shape of 15 mm × 10 mm, the binder was removed by heating from room temperature to 300 ° C. at a heating rate of 100 ° C./hour in a hydrogen atmosphere. Sequentially, the temperature is raised to 1100 ° C. in vacuum and the sintering is performed for 1 hour, and after the sintering is completed, Ar gas is introduced and the sintering is performed at a rate of 7 ° C./min.
Aging was performed by cooling to 00 ° C., then cooling at a rate of 100 ° C./hour, and holding at 550 ° C. for 2 hours to obtain an anisotropic sintered body. Fluidity of granulated powder during molding,
Table 1 shows the residual oxygen content, the residual carbon content, and the magnetic properties of the obtained sintered magnet. The fluidity was measured by the time required for 50 g of the powder to spontaneously drop and pass through a funnel tube having an inner diameter of 5 mm. In addition, cracks, cracks, and deformation were not observed in the obtained sintered body at all.

Example 2 Instead of polymethylmethacrylate as the polymer, polyvinyl butyral (breaking strength: 1.0 kgf / m
m ² ) was used, and granulated powder was prepared in the same manner as in Example 1 except that dioxane was used instead of toluene as the organic solvent, and a sintered body was obtained using this granulated powder. The test results similar to those in Example 1 are shown in Table 1.

Example 3 An ethylene-methyl methacrylate copolymer (breaking strength: 0.55 kgf / mm ² ) was used as the polymer, and a mixed solvent of dichloroethane and xylene (1/1) was used as the organic solvent.
1: weight ratio), and except that the composition shown in Table 1 was added to 100 parts by weight of the alloy powder, a granulated powder was prepared in the same manner as in Example 1, and a sintered body was prepared using this granulated powder. Obtained. Example 1
The test results similar to the above are shown in Table 1.

Example 4 Polycarbonate as a polymer (breaking strength: 3.5 k
gf / mm ² ), dichloroethane as the organic solvent, dibutyl phthalate as the plasticizer, and the composition shown in Table 1 with respect to 100 parts by weight of the alloy powder. Was produced, and a sintered body was obtained using this granulated powder. The test results similar to those of Example 1 are shown in Table 1.
Shown in

Example 5 Polyvinyl butyral (breaking strength: 4.
0 kgf / mm ² ), using dioxane as the organic solvent and dioctyl adipate as the plasticizer,
Granulated powder was produced in the same manner as in Example 1 except that 100 parts by weight of the alloy powder was mixed with the composition shown in Table 1, and a sintered body was obtained using this granulated powder. The test results similar to those in Example 1 are shown in Table 1.

Example 6 Polyarylate as a polymer (breaking strength: 4.5 kg
f / mm ² ), using benzene as an organic solvent,
Using butylphthalyl butyl glycol as a plasticizer,
Granulated powder was produced in the same manner as in Example 1 except that 100 parts by weight of the alloy powder was mixed with the composition shown in Table 1, and a sintered body was obtained using this granulated powder. The test results similar to those in Example 1 are shown in Table 1.

Comparative Example 1 The powder having an average particle size of 3 μm obtained in Example 1 was used, as it was in the same manner as in Example 1, without granulation, by press molding, sintering,
Aging treatment was performed to obtain a sintered body. Table 1 shows the test results.

[0051]

[Table 1]

Examples 7 to 12 Sm 11.9 at%, Cu 8.8 at%, Fe 12.6
A raw material comprising at%, Zr1.2 at%, 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 coarsely pulverizing the alloy, the average particle size is about 15 μm with a jaw crusher or the like.
m, and average particle size 3 μm by jet mill
Was obtained. The amount of the polymer shown in Table 2 added to the powder,
An organic solvent and a plasticizer are added, and the mixture is kneaded at room temperature and stirred to form a slurry, and the slurry is heated by a disk rotary spray dryer using nitrogen as an inert gas, a hot air inlet temperature of 100 ° C., and an outlet temperature of 100 ° C. Granulation was performed by setting the temperature to 40 ° C.

Using a compression magnetic field press, the granulated powder was 10 mm × with a magnetic field strength of 15 kOe and a pressure of 1 ton / cm ^2.
After being formed into a shape of 15 mm × 10 mm in thickness, debinding treatment is performed in a hydrogen atmosphere from room temperature to 300 ° C. at a heating rate of 100 ° C./hour, followed by heating to 1200 ° C. in vacuum for 1 hour Perform sintering to hold,
After completion of sintering, a solution treatment is performed at 1160 ° C.
A multi-stage aging treatment was performed from 800 ° C. to 400 ° C. by introducing Ar gas. Table 2 shows the fluidity of the granulated powder at the time of molding, the residual oxygen content, the residual carbon content, and the magnetic properties of the obtained sintered magnet. In addition, the fluidity of a funnel tube with an inner diameter of 5 mm is 50
It was measured by the time required for the raw material powder of g to fall naturally and pass. Moreover, cracks, cracks, deformation, etc. were not observed at all in the obtained sintered body.

Comparative Example 2 Using the same 3 μm powder as in Example 7, without granulation,
As it is, the same magnetic field pressing machine as in the example was used, with a magnetic field strength of 15 kOe and a pressure of 1 ton / cm 2, 10 mm × 15 m.
After molding into a shape of m × thickness 10 mm, 120 in vacuum
Sintering was carried out at 0 ° C. for 1 hour, and after completion of sintering, solution treatment was performed at 1160 ° C., Ar gas was introduced, and multi-step aging treatment was performed from 800 ° C. to 400 ° C.
Table 2 shows the fluidity and density of the granulated powder at the time of molding, the residual oxygen content, the residual carbon content, and the magnetic characteristics of the obtained sintered magnet together with the examples.

As is apparent from Tables 1 and 2, according to the present invention, R-Fe is used by using an organic solvent and a binder comprising a polymer soluble in the organic solvent and a plasticizer added as necessary. A rare earth alloy powder such as —B alloy powder or R—Co alloy powder is slurried and granulated with a spray dryer to obtain a granulated powder having excellent fluidity. By performing press molding, debinding, sintering, and aging treatment, it has excellent fluidity and excellent continuous press moldability, as well as improved dimensional accuracy and a non-aqueous slurry. Can be significantly suppressed, and a sintered magnet having excellent magnetic properties after sintering can be obtained.

[0056]

[Table 2]

[0057]

The method for producing a rare earth-based sintered permanent magnet according to the present invention uses a rare earth-containing alloy powder such as an R—Fe—B alloy powder or an R—Co alloy powder, an organic solvent, and the organic solvent. A soluble polymer and, if necessary, a binder made of a plasticizer are added and kneaded to form a slurry, and the slurry is formed into a highly fluid spherical granulated powder by a spray dryer device. Since it is used for compression molding, debinding, sintering, and aging treatment, the oxidation reaction of the alloy powder is greatly suppressed because water is not used,
The magnetic properties of the obtained sintered body are greatly improved,
Combined with the excellent fluidity of the granulated powder binder itself,
The fluidity of the powder has been remarkably improved, the molding cycle has been improved, and the compact shape and thin wall shape have excellent dimensional accuracy without reducing the density variation of the molded body or shortening the life of the molding machine. A rare earth-based sintered magnet having magnetic characteristics can be efficiently obtained.

[Brief description of the drawings]

FIG. 1 is a partial explanatory view showing a rotary disk portion of a rotary disk type spray dryer device used in the present invention.

[Explanation of symbols]

 1 rotating disk 2 disk 3 non-magnetic material pin 4 nut 5 rotating shaft

Claims (2)

[Claims] 1. A rare earth alloy powder, a binder comprising an organic solvent and at least one or more polymers are added and kneaded to form a slurry, and the slurry is formed into granulated powder by a spray dryer device, and the granulated powder is formed. Molding with powder,
A method for producing a rare earth-based sintered magnet, characterized in that a sintered permanent magnet is obtained by a powder metallurgy method of sintering. 2. A rare earth alloy powder is added with an organic solvent and a binder comprising at least one polymer and a plasticizer and kneaded to form a slurry, and the slurry is formed into granulated powder by a spray dryer device. A method for producing a rare earth-based sintered magnet, characterized in that a sintered permanent magnet is obtained by a powder metallurgy method of molding and sintering the granulated powder.