JP3398738B2 - Method for granulating powder, granulating apparatus, method for producing compact, method for treating compact, and method for producing bonded magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for granulating various organic and inorganic powders of metals, ceramics, chemicals and the like. The purpose of granulation is roughly classified into (1) the purpose of increasing the commercial value and (2) the purpose of improving the process.
The so-called commercial value in (1) is subdivided into appearance, constant capacity, solubility, uniformity, powderiness (scatterability), preference for shape, storability and the like. The so-called process improvement in (2) further includes quantitative supply improvement, adhesion improvement, classification / segregation prevention, solubility improvement,
It is subdivided into powdering and drying. The present invention also relates to a method for producing a green compact used in powder metallurgy or resin bonding molding using a granulated powder, and a method for producing a final product and a bonded magnet by treating the green compact.

[0002]

BACKGROUND OF THE INVENTION Granulation refers to the operation of increasing the size of a powder by mechanically or chemically coalescing the powder for the purpose of improving the fluidity of the powder or preventing scattering and adhesion. In the powder industry, powder tends to become finer and finer, so that various problems such as deterioration of fluidity and easy scattering and adhesion occur. For example,
1-5 used in the production of ferrite magnets and rare earth magnets
Since the fine powder of μm has poor fluidity, the filling efficiency into the die is low, it takes a long time to fill, the productivity is low, and the filling amount tends to vary, resulting in large variations in product dimensions, high finishing processing costs, and raw materials. Yield loss comes. Therefore, the granulation technology which eliminates these points is becoming more important.
Also, in granulation other than magnet powder, it is beneficial to reduce the volume with high density, and to eliminate the binder is desirable in order to enhance the activity and effective utilization of the original substance. The following mainly describes magnets or magnetic materials, but the present invention can be applied to all materials that are granulated for the purpose described in the field of industrial application. A typical conventional granulation method is to use a drum, a spray dryer, an extruder, etc. as described below.

(1) Rolling granulation method In a rotary container such as a rotary drum or a rotary dish type,
This is a method in which a binder is sprinkled on the raw material powder while rolling the raw material powder, and the powder is agglomerated in a snowball manner to granulate.

(2) Crushing and granulating method This is a method of crushing and sizing briquettes and flakes compressed by a roll to obtain particles of a predetermined size. Although the yield is low and inefficient, it has not been industrially carried out, but in the case of a magnetic material, oriented granulated powder can also be obtained by crushing a compression-molded green compact in a magnetic field.

(3) Extrusion granulation method This is a method in which an organic binder is kneaded and the particles are extruded and granulated by a die and a screen.

(4) Spray Drying Granulation Method A powder obtained by suspending an organic solvent and mixing a binder is sprayed in a hot air stream in a drying tower, and the solvent is evaporated by hot air to obtain an aggregate of the powder. It is a method of granulating by drying.

(5) Others The method proposed in Japanese Patent Publication No. 4-42802 is as follows.
This is an improved version of the rolling granulation method (1), which is a method of granulating without a binder by utilizing the property that magnet powders having coercive force coagulate. It is devised so that it can be arranged well. The granulated powder granulated by the above method is used as a product as it is, or is further pressed, and optionally further sintered or resin-impregnated and used as a product.

[0008]

These conventional techniques have the following drawbacks. That is, in the tumbling granulation method (1) and the spray-drying granulation method (4), a large amount of binder is required to bind the powders together. In the extrusion method, the powder must be made into a paste in order to knead the powder, and thus a large amount of binder is also required. When the amount of the binder is too large, the properties of the powder are hindered, or when the granulation is performed after the granulation, the degreasing process takes time in the sintering process, which not only causes an increase in the manufacturing cost, but also the binder. Carbon in the product remains in the product and causes deterioration of the properties of the powder metallurgy product.

In the method of Japanese Patent Publication No. 4-42802, which is applied to the production of granulated powder such as ferrite magnets and rare earth magnets, the coercive force of the magnetic powder is used instead of the binder to bond the particles. Therefore, the granulated particles are soft, and if a large amount of the granulated powder is put into the feeder before filling the die, the granulated particles will be crushed by gravity. Further, since the powder is not oriented in the granulated particles, when oriented by orientation molding in a magnetic field, a sufficiently high orientation cannot be obtained due to aggregation of the powder. In particular, if the granulated particles are hardened by some method such as additional compression to prevent the granulated particles from being crushed, the powder may not be crushed by the magnetic field and the orientation may be extremely deteriorated. Thus, the hardness and the degree of orientation of the granulated particles cannot be simultaneously increased by this method.

Conventional granulation methods (1), (3) and (4)
Is a large amount of binder, for example, 1 to 5w with respect to the amount of powder.
Since t% is required, these binders are devised so as to be removed (evaporated) as much as possible during sintering in the powder metallurgy process. Since the furnace is contaminated by binder evaporation, the granulator is bulky and therefore expensive due to the need to install special chambers and traps to minimize contamination. Moreover, with active metals, no matter how devised to prevent contamination in the furnace, contamination by carbon in the binder cannot be avoided.

According to the crushing granulation method (2), granulation without a binder is possible and magnetically oriented granulated powder can be obtained. In the crushing and granulating method, the powder is compression-molded and then crushed, and an appropriate size (50 μm to 200 μm in powder metallurgy) is selected by sieving. It returns and repeats compression, crushing, and sieving. The proportion of particles of suitable size selected by the first compression, crushing, and sieving is 10 to 20% or less, and the remaining 80 to 90% must be returned and re-granulated. For this reason, the productivity is extremely low, and further, since the repeated treatment takes time, the fine metal powder is oxidized and the powder is deteriorated.

In the magnet industry, granulation has been extremely strongly required for both sintered magnets and bonded magnets. For example, Nd-Fe-B
With sintered magnets, the fine powder with a particle size of 3 μm was filled in the cavity as it was without granulation, so the fluidity of the powder was poor, so the filling amount in the cavity varied greatly each time, and the dimensional variation after molding and sintering Is very large. It is known that such problems can be solved by granulating, but Nd
Granules for the —Fe—B sintered magnet have been used as they are because there is no granulation method satisfying the requirement that the powders are oriented in the same direction and that no binder is used. Next, for anisotropic bonded magnets,
Granulation may be performed using a binder, but it is necessary that the direction of the powder is well oriented in the granulated body. Conventionally,
There is no way to efficiently make a granulated material in which the powder is well oriented,
The powder was used without being granulated.

[0013] Therefore, an object of the present invention is to provide a granulation method capable of granulating fine powder without crushing it without using a binder. Further, the present invention provides a magnet powder granulation method capable of granulating fine powder without a binder or with a binder, without crushing, and with good productivity to produce a granule having good orientation. Also aim. Furthermore, the present invention provides a method capable of significantly increasing the yield of a product with respect to a powder raw material by mixing the granulated powder produced by the above method with powder metallurgy or resin-impregnated resin powder and subjecting it to processing such as molding. The purpose is to provide. The present invention is also compact to implement this granulation method,
And it aims at providing the apparatus which can be automated if needed.

[0014]

Means and Actions for Solving the Problems A method of granulating powder according to the present invention is to fill powder into cavities provided on the surface of a rubber mold and to compress the rubber mold by substantially restraining the entire surface of the rubber mold. Then, the compression force is released, and the granulated powder is taken out from the rubber mold, which is a method for granulating powder having a size of 2 mm or less. In a preferred specific example thereof, the rubber in the die of the die press machine is used. When granulating powder filled in a large number of cavities provided on the surface of the mold, it is a granulating method characterized in that the rubber mold is compressed by a punch of a die press machine, and also granulation of the powder of the present invention The apparatus is characterized by comprising a die press machine having at least an upper punch, and a rubber mold having a large number of cavities arranged in the die and provided on the surface thereof. It is the location.

In the present invention, a large number of small cavities are provided on the surface of the rubber lump, and the cavities before unloading are removed even if the cavities before unloading are small by filling the cavities with powder and compressing the rubber lump and the powder at the same time with a punch. Since the compressed granulated particles are smaller than the loaded cavities, the granulated particles can be easily taken out from the cavity by gravity of the granulated particles, vacuum suction, magnetic attraction, or the like.

In the present invention, when the granulated particles are used for molding with a die, if the size of the granulated particles exceeds 2 mm, it becomes difficult to mold a small part or fill a die for making a ring-shaped part. Therefore, it is necessary to be 2 mm or less, and a dimension of about 0.2 mm is particularly preferable.

In granulation, it is important how much powder can be granulated per unit time.
The need to align each shape and size accurately is secondary. Therefore, the cavities should be formed as densely as possible. The cavity density is increased so that at least 50 or more, more preferably 100 or more, and most preferably 200 or more granules can be formed in one press. In granulation, the cavity depth is preferably 2 mm or less. In order to process a large amount of powder in a shallow small cavity, it is necessary to pack the spaces between the cavities as close as possible and process as much as possible in one press, and to speed up the press cycle. is necessary. In order to form such a large number of granules by one press, in the case of a well-type cavity, 3 or more, preferably 5 or more, more preferably 10 or more cavities per 1 cm ^{2 of the} surface of the rubber lump are used. At least 2, preferably 4 and more preferably 8 per cm in the case of a groove-shaped cavity.
It is desirable to form a grooved cavity in a book.

In the present invention, granulation can be carried out without a binder. However, in resin-bonded magnets, the binder does not affect the magnetic properties at all.
A binder may be used in order to improve the granulation moldability. In particular, at the time of granulation, the resin powder is mixed with the magnet powder in advance, and the granulated body is further compression molded and then cured by bonding. A magnet can be manufactured. In this case, as the binder, Sn, Pb, solder, soft metal powder such as In, camphor, PVA or other adhesive resin particles are coated with a layer or particles of a non-adhesive resin such as paraffin, or PVA or the like. It is preferable to use a microencapsulated resin surrounded by the adhesive resin particles, which exhibits adhesiveness when subjected to strong compression.

The present inventor first thought that granulated particles could be efficiently produced by providing a large number of minute cavity cavities on the surface of a rubber sheet, packing the powder therein, and continuously compressing them with a roll or a press. . Alternatively, it was thought that granulated particles could be efficiently formed by providing a minute cavity bity on the surface of the roll near the surface, packing the cavity with powder, and pressing it against another roll while rotating it. . As a result of various experiments embodying such an idea, the rubber deforms in the above method, but the force to reduce the volume of the cavity is not applied, so the powder in the cavity is not solidified and granulated particles cannot be formed. And found that in order to make granulated particles, the rubber must be constrained from substantially all directions so that the total volume of the cavity filled with rubber and powder is small during compression. .

The above-described compression method is provided with a large number of powder-filled cavities on the surface of a rubber plate, which is a material to be rolled,
A rolling method in which the surface of the depression is covered and a plate or the like is rolled between rolls, an extrusion method in which a rubber rod that is an extruded material is provided with a large number of powder-filled cavities,
The same effect can be obtained by a forging method in which a rubber lump having a large number of powder-filled cavities formed on its surface is freely forged by a hammer, or a method of CIPing a similar rubber lump, but the efficiency and the manufacturing efficiency are improved. It is most preferable to use a die press machine in terms of the uniformity of the granular powder.

As a method of granulating a powder larger than the size specified in the present invention, a method of filling the powder with a die having a small cavity corresponding to the size of the granulated particle and compressing with a punch, or a pocket is called. A compression granulation method is a method in which a powder is supplied between two rolls having a large number of small dents, and the rolls are compressed while rotating to form briquettes having the size of the dents. This compression granulation method
In principle, granulation can be done without a binder, but cavities and pockets cannot be made very small. Furthermore, when a hard die or a hard roll is used, ejection of the granulated particles after compression requires protrusion by a punch or mechanical scraping from the roll surface. Utilizing means such as punches and scraping jigs to apply strong forces to the parts is virtually impossible in view of their life. It is possible to make granulated particles with a size of 2 mm or less by these methods, but the productivity becomes extremely poor. On the other hand, when the rubber mold is used as proposed by the present invention, the cavity is expanded to the original size by releasing the compressive force after compression, so that the granulated powder can be taken out very easily. Can be easily manufactured.

In a preferred embodiment of the present invention, the granulated powder is compressed so that its density is 20% or more of the theoretical density of each powder particle. Here, if the compression density is less than 20%, the hardness of the granulated powder will be insufficient, and the particles will collapse during handling or when a large amount is filled in a feeder, a die or the like, which is not preferable.

Further, when the powder is magnetic powder,
By applying a magnetic field to the powder before compression in the die press or at least part of the time during the compression, or by placing the magnetic field generator in a position separate from the die press or on the punch or die of the die press. The powder in the granulated particles is oriented in a certain direction by using the powder granulating device included in the vicinity. On the other hand, the granulated powder is not oriented, for example, Japanese Patent Publication No. 4-4280.
In order to improve the magnetic properties, the powder of No. 2 needs to be crushed during magnetic field orientation molding. If magnetic field orientation molding is performed without crushing the powder, the magnetic performance of the green compact or the sintered product will be poor because the orientation direction of each particle in the granulated powder is not constant. By performing this orientation method in the magnetic field under the condition of achieving the above-mentioned compressed density, orientation is performed while maintaining the shape of the granulated particles. For this reason, the granulated particles can be made sufficiently hard for convenient handling. The orientation in the magnetic field may be a static magnetic field or a pulsed magnetic field, and the magnetic field strength is 2 kOe or more, preferably 5 kOe or more, and more preferably 7 kOe or more.

As the magnetic material, all of the rare earth cobalt magnets, rare earth iron boron magnets, samarium iron nitrogen magnets or ferrite magnets TbFe ₂ giant magnetostrictive materials can be granulated. Since fine powders are used to obtain the desired results by granulating it. In particular, samarium-iron-nitrogen magnets are used for resin-bonded magnets, but when granulated by the method of the present invention, extremely fine powder particles of 2 to 3 μm are formed without the binder and individual particles are oriented in a specific direction. A 500 micron granulated powder is obtained.

Fine powders of materials other than permanent magnets also have problems in moldability, filling in the die cavity, etc. Therefore, granulation using a binder or lubrication by using a lubricant has been conventionally required. It has been done as a means of improvement,
In the present invention, since it is possible to mold without a binder, it is possible to mold fine powder while avoiding contamination by carbon.

The granulated powder according to the production method of the present invention has excellent fluidity, so that the density distribution in the die is uniform, and since the hardness is adjusted in advance, the density caused by compaction The non-uniformity is reduced and the variation of the filling amount in the die is reduced, so that the net size can be easily realized.

When an anisotropic magnetic material product is produced using the granulated powder, it is necessary to orient the granulated powder filled in the die in a magnetic field. In this case, the granulated particles themselves also require that individual powders be oriented,
A magnetic field is applied during the production of granulated particles. The magnetic field in the powder orientation may be a static magnetic field or a pulse magnetic field, and the magnetic field application timing can be freely selected before the powder is strongly compressed and the powder cannot rotate, and it is possible before the die press or even during the compression. The strength of the magnetic field is the same as in the normal magnetic field orientation method. Since magnet powder is generally extremely fine and easily aggregates, it is difficult to orient the aggregated powder, but the orientation is enhanced by applying a strong pulse at the time of granulation, and by the subsequent magnetic field orientation / die press method,
It is possible to obtain a product such as a sintered body, which has magnetic properties superior to those obtained by ordinary powder orientation / die pressing in a magnetic field.

Further, the above-mentioned excellent results are obtained by performing die press molding of the granulated powder with the rubber mold die press method and apparatus disclosed by the present applicant in European Patent Publication No. 0488334 (published on June 9, 1992). The characteristics can be further improved. That is, the feature of the rubber mold die pressing method, in which the granulated powder of the present invention, which has excellent fluidity and is easily filled uniformly in the die, is subjected to pseudo isotropic deformation by rubber mold die pressing becomes more remarkable. The essence of the method disclosed in the above publication is to prevent cracking, chipping, undesired deformation and the like of a green compact by pressing a rubber mold in which a powder is densely packed at a density higher than a natural packing density in a die, and to improve magnetic properties. It is to obtain an excellent product and / or to enhance the efficiency of die pressing. Since the smaller the packing density is, the smaller the granule can be obtained with the same cavity size, the packing density may be the natural packing density in the granulation of the present invention. In all other respects, all methods, devices disclosed in the above publications,
Processes, jigs, conditions, etc. can be adopted.

In order to carry out the granulation more efficiently, the punch for applying the compressive force is placed in close contact with the upper surface of the rubber mold and the inside thereof, and the punch acts in the direction opposite to the compressive force. An upper surface of the die supported by an elastic supporting means, and a granulating method of the powder applied to both, and a diameter of the punch is determined to be larger than a diameter of the rubber mold,
Further, there is provided a granulating device in which a die is supported by elastic supporting means acting in a direction opposite to the compressive force. Specifically, the steps of filling powder into the cavity of the rubber mold loaded in the die of the die press machine, compressing the rubber mold and powder by lowering the punch on the press machine, and taking out the green compact are performed. The above method and apparatus can be embodied in the case where the rotary table such as an index table that conveys the rubber mold is rotated and sequentially repeated in a circulating path. The rotary table may have a die cavity formed therein, or the die may be detachable. The lower punch may be fixed to the rotary table.

The green compact produced by the above method is processed by known methods and conditions. Treatments include sintering, resin impregnation,
All kinds of processing such as CIP processing and HIP processing are possible.

Next, desirable conditions for the granulation method using a rubber mold and a die press will be described. The type of rubber of the rubber mold is preferably urethane rubber, silicone rubber, natural rubber, fluororubber, isoprene rubber, nitrile rubber, chloroprene rubber and the like. Next, the hardness of rubber is 5
~ 90 is desirable, 10-70 is more desirable, 20
-60 is the most desirable.

The shape of the cavity formed on the surface of the rubber mold is classified into a well type or a groove type. The well type has a shape corresponding to one granulated particle and can be directly used as a granulated particle after compression. In the groove type, it is necessary to fold the compressed powder shortly after compression, and an extra step is required, but the powder filling is fast and efficient. The size of the cavity is 2.5 m to 0. 0 as one side of the cube or the width of the groove for granulation for press molding such as compacting powder for sintering and bonded magnet.
05 mm is desirable, and 2 mm to 0.1 mm is more desirable. Cavities of such dimensions result in granulated particle sizes corresponding to approximately 2 mm to 0.03 mm and 1.5 mm to 0.05 mm, respectively.
The shape of the well cavity is not limited to a cube,
It can be a cylinder, prism, cone, pyramid, sphere, hemisphere, or the like. In the groove type cavity, the shape of the groove cross section can be square, rectangular, semicircular, triangular and the like. Also, the groove is usually used that extends in one direction,
It may be a grid pattern.

The pressing pressure is in the range 10kg~3t / cm ² is preferable, a more preferable range is ^{50kg~2t / cm 2, 60kg~1.5t / cm} 2 is most desirable range.

The magnetic field for granulation in a magnetic field is preferably a pulsed magnetic field. The width of the pulse magnetic field is preferably 1 μs to 500 ms. It is desirable to apply a pulsed magnetic field outside the press because the cycle time will be faster, but if there is a problem that the powder jumps out of the cavity or the orientation is disturbed while moving between stages, magnetize inside the press. Apply voltage. At that time, it is desirable that the magnetic field application and the compression be performed at the same time or before the magnetic field is applied.

As described above, in the conventional granulating apparatus,
The operation is semi-continuous, and tens of thousands of products can be produced by one operation, whereas the die press machine adopted by the present invention has the number of products corresponding to the number of cavities at one time. Since one operation is completed by making, the process is batch type, and the number of products that can be made at one time is relatively small. Therefore, if such a die press machine is directly applied to the industrial production of granulated powder, it has a low efficiency. Therefore, in consideration of this point, the present invention provides a powder granulating apparatus including a powder filling into a rubber mold, compression of the rubber mold by a die press machine, and a circulation path for circulating the granulation powder from the rubber mold around the rubber mold. It is provided. According to this apparatus, a plurality of sets of rubber blocks having a die set and a large number of cavities are arranged along the circulation path, and at least three steps of powder filling, pressing, and taking out are sequentially performed to improve granulation efficiency. be able to. Hereinafter, the present invention will be described in more detail with reference to examples.

[0036]

EXAMPLE FIG. 1 shows the basic elements of a granulating apparatus.
a is an upper punch, 1b is a lower punch, 2 is a die, 10 is a rubber mold, and 10a is a cavity, respectively, and these are the most basic elements. Reference numeral 8 denotes a backup ring or a backup plate made of a hard material, which is provided so that the rubber does not get caught in the gap between the upper and lower punches and the die 2. When the rubber mold 10 is compressed by the upper and lower punches, the volume of the rubber mold 10 becomes smaller under the condition that the rubber mold 10 is constrained from all directions, so that granulation becomes possible. When the punch pressure is released, the rubber mold returns to its original dimensions and a gap is created around the powder so that the granulated powder can be removed from the cavity.

Further, according to the present invention, as shown in FIG. 2, powder is packed in a cavity 10a of a rubber mold having a plurality of cavities 10a on its upper surface, and the powder is set in a die 2.
The lower punch 1b is always inserted in the die 2, the upper punch 1a has a lower surface larger than the upper opening of the die 2,
When it is lowered, it is set so as to cover this opening without any clearance, and it is also possible to reduce the interval between the upper and lower punches to compress the rubber mold and the powder. 7 is a spring (rubber) for pushing up the die 2. In this method, the position of the cavity 10a is fixed with respect to the upper surface of the die, which facilitates filling and removing of powder. Further, since the upper punch 1a does not have to be inserted into the cavity of the die, the positional accuracy of the upper punch 1a and the die 2 is greatly eased, and the operation of packing the powder outside the press machine, setting it in the press machine and pressing it can be performed. It becomes very easy. As a result, the productivity is improved, and since the mechanical accuracy may be low, the price of the granulating device is reduced. Further, as shown in FIG. 12, it is also possible to use a rubber mold in which the upper edge of the rubber mold 10 is cut out to be fitted into the die 2.

FIG. 3 shows a rubber mold 10 having a groove-shaped cavity 10a.

Next, a specific example of the granulating apparatus utilizing the circulating path will be described with reference to FIG. FIG. 4 is a perspective view for explaining the outline of the dusting work in each part of the circulation path. In the figure, reference numeral 20 is an index table used for indexing or the like, which is modified to fix the rubber mold 10 and rotate integrally. In this embodiment, four rubber molds 10 are evenly distributed around the rotation axis. A large number of circles shown in the rubber mold 10 are cavities for granulating powder. The powder supplied by the raw material feeder (not shown) is uniformly filled in the cavity of the rubber mold 10 by the brush rotating in the container 21. The filling with a brush is not always necessary, but it is effective for filling when the particle size or true specific gravity of the powder is small.

FIG. 5 is a diagram showing a vibrating mechanism that can be effectively used for filling when the particle size or true specific gravity of the powder is small. In the figure, 22 is a raw material powder supply feeder,
23 is a raw material powder hopper, 24 is a rotating brush, 25
Is a backup plate for the rubber mold 10, and 37 is a support for the backup plate. Reference numeral 26 is a sub-plate that is a part of the index table 20, and 27 is a spring support portion that is fixed to the sub-plate 26 and is engaged with a die support 29 that supports the rubber mold 10 by a spring 28. Therefore, the die 2 is sandwiched between the sub-table 26 and the die support 29, and rotates as the index table rotates. Further, the spring 28 expands and contracts according to the vibration of the vibrator described below, and increases the packing density of the powder in the rubber mold 10. Reference numeral 30 denotes an oscillating table having an inverted U-shaped cross section, which is arranged with a slight gap from the lower surface of the die supporting table 29. Reference numeral 31 denotes an eccentric rotation shaft or the like, which applies vibration to the vibration table 30. Shaking table 30
Is supported on the base 33 by the spring 32,
It vibrates as the eccentric rotation shaft 31 rotates.

FIG. 6 is an enlarged view of the filling machine. The raw material powder supply feeder 22 has a shaft 34 rotatably mounted therein.
It is equipped with a spiral screw 35 fixed around it, and the powder is fed into the container 21 through its front outlet. The rotary shaft 32 penetrating through the hole provided in the upper portion of the container 21 is rotated by a motor 33, and a T-shaped brush support is fixed to the tip of the rotary shaft 32, so that a large number of brushes 24 are rotated by the motor 33. The powder is sent by the raw material supply feeder 22 while being rotated to drop into the cavity one after another.

Referring again to FIG. 4, reference numeral 40 is a die press machine, a part of which is shown. Therefore, FIG. 4 shows a state in which the index table 20 is located on the press stage which is one of the indexing positions. The powder filling is performed while moving from one indexing position to another indexing position in FIG. 4, but of course it may be performed at any indexing position. Further, although one filling machine is shown in FIG. 4, when filling takes time, a plurality of filling machines may be used to fill the plurality of rubber molds with powder at the same time.

FIG. 7 shows the detailed structure of the die press section used in FIG. In this structure, the support base 40 is provided below the die support base 29. When the upper punch 1a hits the die 2, the die 2 is lowered against the die pushing-up rubber 7 made of urethane rubber or the like and the spring 28, and the die support base 29 strikes the support base 40. Thereafter, the die 2 is further lowered, and the powder is compressed by pseudo hydrostatic pressure. The sub-table 26 hardly receives the force of the punch 1a in the series of processes. When the force of the upper punch 1a is removed after the compression, the granulated powder compressed isotropically enters the cavity of the rubber mold. The rubber mold 10 after pressing returns to the position before pressing by the elastic force of itself and the force of the die 2 for pushing up the die pushing spring 7.

After the die press, while the index table is rotating to the next indexing position or after that, the granulated powder is taken out from the rubber mold 10 (see FIG. 4).
Taken out at. It can be taken out by a suction device such as a vacuum cleaner, or by a magnetic field adsorption device when the powder is a ferromagnetic material, or by using them together as a vibrator. FIG. 8 shows an example of a suction type granulated powder extractor. In this suction type granulated powder extractor, there is a suction device (not shown) at the tip of the suction port 51, and when the suction device sucks air through the suction port 51, air is taken into the container through the air intake port 50. . At this time, the granulated powder below the air intake port 50 is also sucked at the same time. A sieve or the like is provided in the middle of the suction port 51 or at the inlet of the suction device to collect the granulated powder.

FIG. 4 shows an example of four indexing positions (number), that is, four stages. However, the indexing position may be one or more, and it depends on the kind of powder in consideration of economical efficiency, machine durability, and cycle time. Design the indexing position (number) in consideration of the difficulty of granulation. Generally, the index position (number) is 2 to 8, and particularly preferably 3 to 6.

FIG. 9 shows an apparatus for orienting and granulating a permanent magnet in a magnetic field. This apparatus is provided with an orientation magnetic field coil 45, and a filling section 21 and a take-out section 60.
The device has the same configuration as that of the device shown in FIG. 4 except that a large amount of non-magnetic material is used. FIG. 10 shows details of the device structure of the orientation section in the magnetic field. In this device structure, most of the members are shown in FIG.
The magnetic field coils 45 and 46 are provided above and below the rubber mold 10. The magnetic field coils 45, 46 may be stationary, but may be movable to the positions shown. One of the orientation magnetic field coils 45 and 46 may be omitted. The current supplied to the orientation magnetic field coils 45 and 46 may be a direct current, but a pulse current generated by a capacitor bank or the like is preferable because a high magnetic field can be effectively generated with less power consumption.

Referring again to FIG. 9, the rubber mold 10 having the cavity filled with the permanent magnet powder at the illustrated position is temporarily stopped at the indexing position of the orientation portion. Simultaneously with or immediately after the stop, the lid having the magnetic field generating coil at its tip is lowered to cover the rubber mold 10. Then a magnetic field is generated. The index table rotates after orientation in the orientation section and temporarily stops at the next indexing position (press section). At the same time as or immediately after the stop, the punch descends and
It is the same as FIG. 4 in that the pseudo hydrostatic pressing is performed as in the case of the general material shown in FIG. However, in many cases, a current (any of direct current, alternating current, pulse, and attenuated alternating current) for generating a magnetic field in the direction opposite to the orientation is generated in the magnetic field coil 46 before or after the press is finished and before the punch is raised. The demagnetizing magnetic field attached to the punch 1a or the press plunger 40 (not shown) is passed through the generating coil, or the magnetic field generated by a permanent magnet (not shown) is used to demagnetize to remove the residual magnetization of the granulated powder. It is preferable.

FIG. 11 shows an apparatus for orienting and granulating a permanent magnet in a magnetic field, which is different from FIG. 9 only in that orientation and pressing are performed at the same place. In the operation of this apparatus, after the permanent magnet powder is filled in the rubber mold in the filling section, the index table 20 stops at the orientation position, the punch 1a descends at the same time as or immediately after the stop, and the surface of the die and the rubber mold 10 is stopped. Stop. At this time, the punch acts as a lid. Alternatively, the punch may descend in advance to the surface of the lower die and the rubber mold and stand by before the index table stops at the orientation position after filling. After applying the magnetic field, the punch is further lowered to compress and granulate the powder. The operation of the other devices is the same as that described with reference to FIG. However, since the orientation, pressing, and demagnetization are performed on the same stage in this device, the number of indexes can be one.

The present invention will be described below with reference to experimental examples.

Example 1 The die press used in the experiment had the structure shown in FIG. 1, and the die 2 was made of stainless steel and had an outer diameter of 70 mm and an inner diameter of 50 m.
The punch 2 is also made of stainless steel and has a clearance that allows the die to enter with negligible friction, and the upper punch lower surface and the lower punch upper surface have a clearance of 3 m.
A m-square backup ring (polyurethane rubber) is attached. The rubber mold 10 is made of urethane rubber having a hardness of 40 and has a diameter of 49.9 mm and a height of 25 mm.
Then, well-type cavities having a depth of 1 mm and a diameter of 1 mm were formed on the upper surface at intervals of 3 mm. The rubber having such a cavity was produced by first forming a metal master mold and pouring the rubber raw material into the master mold. Set the rubber mold on the die,
The lower punch was pushed up so that the upper surface of the rubber mold was aligned with the upper surface of the die, and in this state, the following powders were packed in the cavity without a binder.

Fe: grain size 10 μm Fe-Si: grain size 12 μm Fe-Co: grain size 13 μm Al: grain size 3 μm Ni: grain size 3 μm Al ₂ O ₃ : grain size 1 μm (MnO) ₃₁ (ZnO) ₁₁ (Fe) ₂ O ₃ ) ₅₈ : 0.6μ
m

Powder filling was performed by covering the upper surface of rubber with powder, rubbing it with a brush and dropping it into the cavity. After removing the powder adhering to the flat surface other than the cavity on the upper surface of the rubber, use a hydraulic press to apply the total pressure to the upper and lower punches.
25t~5t (1cm ² per 63.7~255kg)
Was applied. When the rubber mold was taken out after unloading and the rubber mold was turned upside down, cylindrical granulated particles having a diameter of 0.4 to 0.6 mm and a height of 0.3 to 0.5 mm were formed for each powder.

All the powders before granulation have extremely poor fluidity. For example, a glass tube having an inner diameter of 10 mm and a length of 200 mm is packed with 10 g of powder at one end and the other end is tilted slightly downward. Although it was vibrated lightly, the powder repeated sudden movements and moved downward. However, in the powder granulated by the above process, the fluidity was remarkably improved, and when the same test as above was conducted, the granulated particles smoothly moved in the tube. From this, it was confirmed that all particles were granulated as particles having excellent fluidity without using the binder.

Example 2 A granulation test was performed on the same powder as in Example 1 with the configuration of FIG. However, as shown in Fig. 3, urethane rubber with a hardness of 40 is used on the rubber surface, and it is 49.9 mm square and 25 mm high.
Then, a rectangular and groove-shaped cavity having a depth of 1.5 mm, a width of 1.5 mm and a length of 40 mm was formed. However, a wedge-shaped protrusion having a height of 0.3 mm was provided at every 1.3 mm on the bottom of the groove-shaped cavity. The groove-shaped cavity filled the powder faster than the well-type cavity. After filling, excess powder on the upper surface of the rubber was removed, and a total pressure of 2.5 t to 7 t was applied by the upper punch. After unloading, the rod-shaped green compact was taken out from the rubber mold with a vacuum suction device and transferred to a container. When stirred a little in the container, the rod-shaped green compact broke from the wedge-shaped constriction to form granulated powder. The average size of the granulated powder is 1.1 × 1.0 × 1.
It was 1 mm. It was demonstrated by the same test as in Example 1 that the fluidity was significantly improved by granulation.

Example 3 With the structure shown in FIG. 2, three sets of a die, a rubber with a cavity, a lower punch and a rubber for pushing up the die were prepared. However, the opening on the die was made small as shown in FIG. 5 so that the rubber with a cavity would not jump out from the die, and the rubber was made smaller at the upper surface portion accordingly. 500m diameter for the above 3 sets
An automatic granulator with three indexing positions was manufactured, which were arranged at equal intervals along the circumference of the upper surface of the index table of m, and each stopped at the same position of any one of pressing, filling and unloading. The cavity was the same as in Example 2 and the powder was the same as in Example 1. Automatic granulation was performed under these conditions. In stage 1, after the powder was charged by a shaker and vibration, the upper surface of the rubber was automatically cleaned with a brush and the powder was further pressed. After that, the rubber mold filled with powder is carried to the next stage 2 by the index table with the die and the lower punch attached, and the total pressure of 0.5t to 5t is brought by the air cylinder by the upper punch attached to this stage. Was applied to the set. After unloading, this set was again transported to the next stage by the index table. At this stage, the rod-shaped molded body was taken out by vacuum suction and carried to the outside of the index table. The set was then returned to the original filling stage for repeated filling, compression and unloading steps. One cycle could be shortened to 3 seconds. Granules were easily obtained from the obtained rod-shaped compact by agitating it a little as in Example 2. It was possible to granulate very efficiently without using any binder.

Example 4 The following powder was tested for magnetic field oriented granulation: Nd ₁₅ Fe ₇₇ B ₈ 3.4 μm SmCo ₅ 3.5 μm Sm ₂ Fe ₁₇ N ₃ 2.8 μm SrO.6Fe ₂ O ₃ 0. 8 μm Here, Nd ₁₅ Fe ₇₇ B ₈ and SmCo ₅ were obtained by crushing an ingot obtained by high frequency melting with a jet mill using a jaw crusher and N ₂ gas. Sm ₂ Fe ₁₇
N ₃ was made by first using an ingot of Sm ₂ Fe ₁₇ by high frequency melting, and using a jaw crusher and a disc mill, 50 μm
Made of powder. 450 this powder in N ₂ at 25 atm
Nitriding was performed by heating at 0 ° C. for 20 hours. Then, it was pulverized with a jet mill to a predetermined particle size. As the ferrite powder, a commercially available ferrite powder for dry pressing was used.

The above-mentioned powder was used in the following magnetic field granulation test with the same constitution as in Example 2 and using the same rubber mold. After the powder was packed in the cavity of the die / rubber mold set, the powder on the upper surface of the mold was removed with a brush, and the powder was oriented by a pulse magnetizing coil outside the press machine. When the magnetic field was applied, the upper surface of the rubber mold was lightly held by the rubber plate so that the powder would not jump out of the cavity. The maximum strength of the pulsed magnetic field was 20 kOe and the width was 5 ms. After that, a total pressure of 3 t was applied with a pressing machine. After packing the powder in the cavity, the powder on the upper surface of the mold was removed with a brush, and the die / rubber mold set was set in the press. The upper punch was slowly lowered to contact the upper surface of the rubber mold, and in this state, the Pal magnetic field generating coil set in the press was excited to orient the powder in the cavity. The maximum strength of the pulsed magnetic field was 20 kOe and the width was 5 ms. Then, the upper punch was lowered, and a total pressure of 3 t was applied to the die rubber mold set.

After the above, in the compressed state, a depressing alternating magnetic field was applied to the powder by the pulse coil to demagnetize.
Then, after unloading, the elongated shaped powder was easily taken out from the mold, and granulated particles were obtained by simply agitating it in a container.

The granulated particles were molded by a die press machine in a magnetic field. 10 mm with non-magnetic carbide die and punch
Corner green compacts were molded. The magnetic field was a direct current magnetic field of 12 kOe, and was perpendicular to the pressing direction (transverse magnetic field press).

For Sm ₂ Fe ₁₇ N ₃ , the green compact was impregnated with epoxy resin. Sm thus obtained
₂ Fe ₁₇ N ₃ bond magnet and Nd-Fe-B, Sm-Co
Table 1 shows the magnetic properties of the sintered ferrite magnet.

[0061]

The granulated particles produced as described above have remarkably improved fluidity in all the powders as compared with those not granulated. In addition, since the granulated particles were solidly granulated, the particles did not collapse during handling, the handling was easy, and the generation of fine powder was negligible and negligible. Further, since the magnetic characteristics of the magnets in Table 1 are almost the same as those of the comparative example without granulation (rather good), it was found that the powder in the granulated particles was extremely well oriented.

Example 5 Furthermore, the dispersion of the powder filling amount in the cavity was examined before and after granulation. That is, a cavity with a diameter of 3 mm and a depth of 15 mm is 100 × 150 × 30 mm of aluminum plate 100 ×
It was placed on a surface of 150 mm, the powder was put in a container (cup) of 100 cm ³ , the opening was turned down on an aluminum plate, and it was slid onto the cavity, and the cup was attached to the aluminum plate at the top of the cavity. As it was, it was shaken three times with an amplitude of 10 mm. After that, the cup was shifted from the cavity portion and the weight of the powder filled in the cavity was measured. The fine powders of all powders had a variation of ± 10 to 30%, but when the granulated powder granulated according to the present invention was used, the variation was reduced to ± 3% or less.

[0064]

The method according to claims 1 and 2 and the apparatus according to claim 5 compress the rubber mold when granulating the powder filled in the cavities provided in large numbers on the surface of the rubber mold in the die. Since this is a common feature, hard granulated particles can be formed without a binder. Therefore, the present invention is effective for granulating a product in which the incorporation of an organic binder or water is harmful. It has been extremely difficult to produce particles having a size of 2 mm or less, especially 1 mm or less by the conventional compression granulation method using a press or roll, but the method of the present invention can easily produce granules of 1 mm or less. it can. As a result of the markedly improved flowability of the powder, it has become possible to industrially transport and fill the powder. Conventionally, fine powder could not be supplied at a constant rate even when trying to send powder with a screw feeder or a vibration feeder, but the use of the granulation method according to the present invention makes it possible to provide a constant rate supply with any of the above feeders. It was The ability to supply a fixed amount in this way has made it possible to industrially use various powder machines with high productivity. In addition, since a higher density (higher density of powder other than the binder relative to the granulated powder) can be obtained compared to the conventional granulated powder using the binder, the volume can be reduced and the reaction does not occur because the binder does not exist on the surface. The properties and catalytic activity are high, and the reaction rate and efficiency are high when the powder is used in the chemical reaction step.

The method of claim 3 and the apparatus of claims 7 and 9 can enhance the efficiency of granulation, and also enable continuous automatic granulation.

The method according to claim 4 and the apparatus according to claims 6 and 8 are extremely useful for the magnet industry because the magnetic powder can be oriented and granulated in that state without using a binder.

According to the method of the tenth aspect, it is possible to manufacture a net-shaped green compact by increasing the yield of the green compact with respect to the raw material powder before granulation and reducing the variation in the powder filling amount.

According to the eleventh aspect, a green compact having excellent magnetic performance can be manufactured. According to the twelfth aspect of the present invention, since the method for treating a green compact is characterized by sintering a molded body, the step of debinding is unnecessary, or the debinding time can be greatly shortened.

According to the thirteenth to seventeenth aspects, since the bonded magnet can be manufactured by using the granulated powder, the yield is increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a granulating apparatus.

FIG. 2 is a sectional view showing another embodiment of the granulating apparatus.

FIG. 3 is a perspective view of a rubber mold having a groove.

FIG. 4 is a perspective view showing an embodiment of a granulating apparatus using a circulation path.

FIG. 5 is a partial front view of FIG.

FIG. 6 is an enlarged view of the filling machine.

FIG. 7 is a cross-sectional view showing another embodiment of the granulating apparatus using the circulation path.

FIG. 8 is a cross-sectional view of a suction granulated powder takeout portion.

FIG. 9 is a perspective view showing an embodiment of a granulating apparatus that granulates permanent magnet powder using a circulating path.

FIG. 10 is a partial front view of FIG.

FIG. 11 is a perspective view showing an embodiment of a granulating apparatus that granulates permanent magnet powder using a circulating path.

FIG. 12 is a sectional view showing another embodiment of the granulating apparatus.

[Explanation of symbols]

1 punch Two dies 7 Rubber for pushing up 8 backup ring 10 rubber mold 10a cavity 20 index table 30 shaking table 45 magnetic field coil 46 magnetic field coil

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Itaya 1 Ellie Part 2 401, No. 22, Matsumuro Ouegami-cho, Nishikyo-ku, Kyoto, Kyoto (56) Reference JP-A-3-88758 JP, A) JP 4-363010 (JP, A) JP 6-188136 (JP, A) JP 5-271705 (JP, A) JP 5-101957 (JP, A) JP Flat 5-43904 (JP, A) JP-A-2-207997 (JP, A) Actual Development Flat 2-138095 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 2 / 00-2/30 B22F 1/00-8/00

Claims (17)

(57) [Claims] 1. A powder mold is filled with cavities provided on the surface of a rubber mold, the rubber mold is constrained and compressed on the entire surface , and then the compression force is released to take out the granulated powder from the rubber mold. By so doing, a granulated powder having a size of 2 mm or less is produced. 2. The method for granulating powder according to claim 1, wherein the compressing force is applied by a punch of a die press machine. 3. The punch for applying the compressive force is supported by an elastic supporting means which is disposed in close contact with the upper surface of the rubber mold and inside the die and which acts in a direction opposite to the compressive force. The method for granulating powder according to claim 2, wherein the method is applied to both the upper surface of the die and the upper surface of the die. 4. The method for granulating powder according to claim 2, wherein a magnetic field is applied to the powder before or during at least a part of the compression in the die press. 5. A powder press having a size of 2 mm or less, comprising at least a die press having an upper punch, and a rubber mold having a large number of cavities arranged in the die and having a large number of cavities on its surface. Grain equipment. 6. The granulating apparatus according to claim 5, further comprising a magnetic field generator at a position separated from the die press machine or in the vicinity of the die of the die press machine. 7. The method of filling powder into the rubber mold, compressing the rubber mold with a die press machine, and taking out the granulated powder from the rubber mold are performed along a circulation path for circulating the rubber mold. Item 5. The granulating apparatus according to item 5. 8. The granulating apparatus according to claim 7, further comprising a magnetic field generator for applying a magnetic field before or during compression of the rubber mold in the circulating path. 9. The punch is set to have a diameter larger than that of the rubber mold, and the die is supported by elastic supporting means acting in a direction opposite to the compression force. The granulating apparatus according to any one of 1 to 6 above. 10. Production of a powder compact, characterized in that the granulated powder produced by the method according to any one of claims 1 to 4 is filled in a mold or a rubber mold and compressed by a punch. Method. 11. An orientation characterized in that the granulated powder produced by the method according to claim 4 is filled in a mold or a rubber mold, and the granulated powder is oriented by applying a magnetic field and compressed by a punch. Method for manufacturing molded body. 12. A method for treating a green compact, which comprises sintering a compact formed by the method according to claim 10. 13. A method for treating a powder compact, which comprises impregnating a resin into a molded article molded by the method according to claim 10. 14. filled with magnet powder and a binder on a number provided cavities on the surface of the rubber mold, the rubber
A bond characterized in that a binder-bonded granulated powder having a size of 2 mm or less is obtained by restraining the mold on the entire surface and compressing it, then releasing the compressive force, and taking out the granulated powder from the rubber mold. Magnet manufacturing method. 15. The method for producing a bonded magnet according to claim 14, wherein the compressive force is applied by a punch of a die press machine. 16. The punch for applying the compressive force is supported by an elastic supporting means which is arranged in close contact with the upper surface of the rubber mold and inside the die and which acts in a direction opposite to the compressive force. 15. The method of manufacturing a bonded magnet according to claim 14, wherein the method is applied to both the upper surface of the die and the upper surface of the die. 17. The method for producing a bonded magnet according to claim 15, wherein a magnetic field is applied to the powder before or during at least a part of the compression in the die press.