JPH0565504A - Molding method - Google Patents

Abstract

PURPOSE:To rapidly produce a molding having a good particle packing rate from a slurry or suspension contg. powders of metals, ceramics, etc., by utilizing centrifugal force. CONSTITUTION:A prescribed volume of fluid, such as slurry 2 or suspension, prepd. by kneading the powders of metals, ceramics, etc., with liquid is put into a mold 1 and the mold is set to a centrifugal machine. The centrifugal machine is operated for a prescribed period of time by directing the bottom of the mold 1 toward the outside of a rotating radius to separate the liquid component of the slurry 2, etc., in the upper part of the mold 1, by which the solid green molding 6 is obtd. The green molding 6 is thereafter set in the mold having the liquid transparent bottom and the mold is operated by the centrifugal machine, by which the liquid in the green molding 6 is further discharged. The mold having the liquid transparent bottom may be used from the beginning as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved slip casting method for obtaining a solid green compact from a sludge containing metal, ceramic, etc. by utilizing centrifugal force.

[0002]

2. Description of the Related Art Conventionally, in powder metallurgy or the ceramic industry in which a sintered body of a predetermined shape is obtained from a powder of a metal, a ceramic or a mixture thereof, various powders are formed into a formed body of a predetermined shape before sintering. As a general molding method for finishing, for example, an organic binder, a plasticizer, a solvent, etc. are added to various powders crushed by a ball mill, and these are kneaded to prepare a sludge, which is then rotated. A strip-shaped grease obtained by applying it to a strip-shaped substrate with a uniform thickness while scraping it with a doctor blade and then heating and drying it.
The so-called doctor blade method in which a sheet is cut or punched out to obtain a flat green molded body, or the molding powder obtained by spray-drying the above sludge with a spray dryer is molded in a mold of a certain shape. A compression molding method and the like are known in which a green molded body is obtained by press molding with.

On the other hand, as a method with a simpler process,
There is a slip casting method in which fine powder is dispersed in an aqueous solution of ammonium alginate or the like to prepare a slurry, which is poured into a plaster mold and dried to finish it into a predetermined shape.

As a kind of such slip casting method, for example, as disclosed in Japanese Patent Laid-Open No. 1-179748, a slurry is cast into a water-absorbent mold such as gypsum and the mold is made to have its axial center. A molding method is known in the art, in which the mold is rotated about the center of rotation and the centrifugal force thereof causes the inner surface of the mold to be infiltrated with sludge to be molded.

[0005]

However, the above-mentioned conventional method has the following problems.

That is, the doctor blade method requires a drying furnace for drying the strip-shaped adhered material over a long distance after scratching with the doctor blade, which requires a large amount of equipment and heating. The amount of heat for is needed. In addition, it was necessary to degas the sludge in advance in vacuum in order to prevent the expansion of the gas mixed during the drying of the liquid, which required a great deal of time. Also, in the compression molding method, it is necessary to send high temperature hot air while scattering the sludge into particles in the spray drying process,
After all, a lot of equipment, time and heat were required.

On the other hand, the slip casting method, particularly the method disclosed in the above publication, does not require evaporation by heating to dry the liquid, so that it can be expected to save heat as compared with other methods. However, the conventional slip casting method takes a very long time to dry, and a water-absorbent mold such as gypsum has a problem of poor shape accuracy. The fact that it uses a water-absorbent mold has not changed. Further, since the centrifugal force acts more strongly on a substance having a large specific gravity, even if the mold containing sludge is rotated, water having a smaller specific gravity than a metal or ceramic having a large specific gravity,
The centrifugal force applied to organic solvents is small. Therefore, in the method of the above-mentioned publication, the action of removing the liquid to the outside by the centrifugal force is not so strong at about the gravity multiple, and even if the solid-liquid separation function is solely devoted to the water-absorbent mold, the rapid liquid separation is achieved. There was a problem that the effect could not be expected.

The present invention has been made in view of the above points, and an object thereof is to use a precise mold of metal, ceramic, plastic or the like, without being restricted by water absorption, and to rapidly remove a liquid component from sludge. By taking measures that can be separated into two, it is intended to accelerate the process such as shortening the drying time.

[0009]

In order to achieve the above object, the means of the invention of claim 1 is a fluid such as a slurry or a suspension obtained by kneading a powder of metal, ceramic or the like with a liquid. The present invention is directed to a molding method for obtaining a green molded body from.

Then, as a molding method, a predetermined amount of the fluid is put into a mold whose bottom is closed, and a mold containing the fluid is set in a centrifuge, and then the centrifuge is used for a predetermined period of time. The bottom of the mold was rotated radially outward of the centrifuge, after which the liquid separated at the top of the mold was removed to obtain a solid green form.

According to a second aspect of the present invention, in the invention of the first aspect, the obtained molded body is stored in a mold having a liquid-permeable bottom, and the mold containing the molded body is centrifuged. Then, the bottom of the mold is rotated by a centrifuge for a predetermined period of time toward the outer side in the radial direction of rotation of the centrifuge to drain the residual liquid in the formed body through the liquid permeable bottom. Then, the green form was demolded from the above mold.

The means of the invention of claim 3 is directed to a molding method for obtaining a green body from a fluid such as a slurry or a suspension obtained by kneading a powder of metal, ceramic or the like with a liquid. ..

As a molding method, a predetermined amount of the fluid is put into a mold having a liquid-permeable bottom, a mold containing the fluid is set in a centrifuge, and then the centrifuge is used for a predetermined time to perform the above-mentioned process. The bottom of the mold was rotated radially outward of the centrifuge, after which the liquid separated at the top of the mold was removed to obtain a solid green form.

According to a fourth aspect of the present invention, in addition to the second aspect of the invention, the mold in which the green body is housed is reset in the centrifuge, and then the mold is used for a predetermined time by the centrifuge. By rotating the bottom part of the centrifuge outward in the radial direction of the centrifuge to drain the residual liquid in the molded form through the liquid permeable bottom part, and then to demold the molded form from the mold. did.

According to a fifth aspect of the invention, in the invention of the first or third aspect, the average particle diameter of the powder is 0.1 to 0.1.
The centrifugal acceleration during operation of the centrifuge was 3000 G or more.

According to a sixth aspect of the invention, in the invention of the second or third aspect, the liquid permeable bottom portion is laid with a filter backed up by a member having a large number of through holes or a granular material. did.

[0017]

According to the above method, in the invention of claim 1, the solid component in the sludge and the suspension is settled in the mold by the centrifugal force, and the liquid component is separated above the forming form. Separation is rapid and green compacts with high particle packing are obtained in a short time.

In addition, unlike the conventional slip casting method, molding can be carried out without being affected by the concentration, viscosity and dispersion state of the sludge or suspension, and the binder can be reduced. As a result, the temperature rising rate at the time of firing is increased, and the degreasing and firing temperatures are low, so that the manufacturing efficiency, dimensional accuracy, and yield are improved. In addition, a wide range of applications from small precision products to large products are possible.

According to the second aspect of the present invention, the liquid component contained in the green body is further discharged through the liquid-permeable bottom portion by the liquid removal, and the liquid amount is further reduced as compared with the molding time. Degreasing and firing time is shortened further,
Due to the contraction effect due to the liquid removal, it is easy to remove the molded product from the mold, and there is no need for a mold removal gradient. In addition, this improves the shape accuracy of the product.

According to the third aspect of the present invention, by using the mold having the liquid permeable bottom portion from the first step, the liquid component is separated into the upper part in the mold, and at the same time, the liquid is discharged from the bottom part of the mold. The time of the molding process will be further shortened.

According to the invention of claim 4, in addition to the function of the invention of claim 3, the amount of liquid in the green compact is reduced by deliquoring, and the mold is easily contracted by contraction of the green compact. The function of the invention of Item 2 can also be obtained.

In the invention of claim 5, the average particle diameter is 0.1 to 0.1.
In the case of powder consisting of 1.0 μm fine particles, the gravity factor is 3
By setting the conditions (rotation radius and rotation speed) to be 000 G or more, such fine particles can be formed.

In the invention of claim 6, the liquid component is easily discharged from the large number of through holes of the member for backing up the filter or the particle gaps in the granular material, so that the molding time and the liquid removal time are remarkably shortened. Will be done.

[0024]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

(Preparation) First, a predetermined amount of sludge 2 of metal, ceramic or a mixture thereof is put into a mold 1 composed of a cylindrical tubular member 1a and a disc-shaped bottom member 1b (FIG. 1).
(A)). The slurry 2 is obtained by adding a dispersant, a solvent (water, an organic solvent, etc.) to a powder of metal, ceramic or the like, which has been previously crushed to a predetermined average particle size by a ball mill, and kneading. Here, in the above-mentioned slurry 2, the powder particles are dispersed to almost the primary particles.

(Molding) Next, as shown in FIG. 2A, the mold 1 is set in the centrifuge 3. The centrifuge 3 is
A rotating shaft 12 which rotates around a vertical axis by a motor 11 and a horizontal rod 13 fixed to the upper end of the rotating shaft 12 are provided, and containers 15 and 1 attached to both ends of the horizontal rod 13 are provided.
One of the molds 1 is set in each of the five. Here, the molds 1 and 1 are the containers 15 and 15
The bottom members 1b, 1b are set inward, and the respective containers 15, 15 are rotatably supported by the both ends of the horizontal rod 13 about the horizontal shafts 14, 14.
(B), during operation of the centrifuge 3, the centrifugal force causes the bottom of the containers 15, 15 or the bottom members 1b, 1b of the respective molds 1, 1 to move outward in the radial direction of the centrifuge 3. It is rotated toward. Then, by operating the centrifuge 3, the solid component 4 having a high density in the sludge 2 is gradually settled to the bottom member 1b side of the mold 1 by the centrifugal force, and the liquid component 5 is separated to the upper part ( When the operation of the centrifuge 3 is stopped after a lapse of a predetermined time, most of the liquid component 5 is separated into the upper part of the mold 1 and a solid green form 6 is obtained below it, as shown in FIG. 1 (b). (See FIG. 1 (c)). At this time, the rotation speed of the centrifuge 3 is determined by the particle size and density of the powder, the viscosity of the solvent, the processing temperature, and the like. For example, an average particle size of 0.2 to
The powder of 0.4 μm requires a gravity multiple of about 10000 G. If this gravity multiple is too small, the upper part of the molded body 6 after molding cannot be completely filled and the molding time becomes extremely long. The particle filling rate of the green compact 6 obtained at this time is about 60 to 65%.

(Removal of liquid) Next, only the liquid component 5 on the upper side is discarded from the mold 1 in the above-described state to form the green body 6 alone (see (d) of FIG. 1).

(Draining) Next, the bottom member 1b of the mold 1 is replaced with a disk 1c having a large number of through holes 7, 7, ... (A diameter of about 0.5 to 1.0 mm). At that time, a filter paper 8 is laid under the green body 6 (see (e) in FIG. 1). And
The liquid-permeable mold 1 is set in the centrifuge 3 again, and the centrifuge 3 is operated for a fixed time. At this time,
The liquid component remaining in the green body 6 is passed through the filter paper 8 to
It is discharged from the through holes 7, 7, ... Of the bottom member 1c (for example, about 2 to 3% of the volume of the green body 6). Note that the above-mentioned liquid removal step can be omitted.

Finally, the bottom member 1c of the mold 1 is removed from the tubular member 1a, and then the green body 6 is attached to the tubular member 1a.
From below (see FIG. 1 (f)). At this time,
By performing the above-mentioned liquid removal, the green compact 6 contracts (for example, about 0.7 to 1.0% in diameter), and is easily released from the tubular member 1a of the mold 1.

(Drying) After that, the green compact 6 obtained above is put into a drying oven and dried by low temperature heating. This drying time depends on the size of the green body, but is, for example, 40
After holding at 70 ° C for 6 hours and at 70 ° C for another 100 hours,
It can be dried by a treatment such that it is kept at ℃ for 2 hours.

(Degreasing and Sintering) Finally, the green compact 6 after drying is sintered in a furnace. At this time, in order to remove the binder, dispersant, etc. contained in the green body 6 in advance, for example, 120 ° C.
/ H is degreased (calcined) by heating at a heating rate of about / H, and continuously heated as it is at a heating rate of about 200 ° C / H for sintering to obtain a final product.

In the above embodiment, the fluid to be molded is a slurry in which powder is kneaded with a dispersant and a binder, but the present invention is not limited to this embodiment.
It is also possible to set the powder from a suspension prepared by simply dispersing the powder in a solvent in a centrifuge and mold it by centrifugal force.

Therefore, in the above embodiment, in the first molding step (solid-liquid separation step), the slurry 1 is moved in the mold 1 by centrifugal force.
Since the solid content 4 therein settles and the liquid component 5 is separated above the green compact 6, solid-liquid separation is performed quickly, and the green compact 6 having a particle packing ratio of 60% or more can be obtained in a short time. As a result, the drying time can be greatly shortened (about 1/2 to 1/5 of the ordinary slip casting method), and the temperature rising rate during firing can be increased (3 to 3 of the ordinary slip casting method). It is possible to improve manufacturing efficiency.

In addition, unlike the conventional slip casting method, molding can be performed without being affected by the concentration, viscosity, and dispersion state of the slurry 1 (or suspension), and the slurry and turbidity before molding can be obtained. There is no need to vacuum degas the liquid.
In addition, the binder is 1 / of the conventional slip casting method.
3 to 1/5 is sufficient, and as a result, the degreasing and firing temperatures can be lowered, so that dimensional accuracy and yield are improved, and
It can also be applied to thick, large-sized products. For example, wall thickness 0.1mm
A wide range of applications are possible from the following small precision products to large products with a wall thickness of 100 mm or more.

In particular, the deliquoring step in the above embodiment is not always necessary, but the amount of liquid contained in the green body due to deliquoring is 2 to more than that obtained by the normal slip casting method.
3 (volume%) can be reduced, the subsequent drying time, degreasing, and firing time can be further shortened, and the contraction effect due to liquid removal can be obtained, so that the molded product 6 is easily demolded from the mold 1,
There is an advantage that it is not necessary to provide the draft to the tubular member 1a.

Further, in the above embodiment, the bottom member 1b of the mold 1 is hermetically sealed in the first molding step, but it is also possible to make the liquid permeable bottom member 1c from the first step.
In that case, since the liquid component 5 is separated into the upper part within the mold 1, the liquid is discharged through the bottom member 1c, which further shortens the time of the molding step.

In the case of powder consisting of fine particles having an average particle diameter of 0.1 to 1.0 μm, the conditions (rotation radius and rotation speed) are set so that the gravity factor is 3000 G or more.
It becomes possible to form such fine particles.

Further, in the case where a filter such as the bottom member 1c having a large number of through holes or the filter paper 8 backed up by the granular material is provided as the constitution of the liquid permeable bottom portion as in the above embodiment, the conventional slip casting method is used. Compared with exchanging the plaster mold as described above, the filter paper can be exchanged easily and at low cost, and the liquid can be easily discharged from the through hole, so that the molding time and the liquid removal time can be significantly shortened. It will be.

(Specific Example) Next, a specific example of the present invention will be described. The slurry shown in Table 1 below was prepared.

[0040]

[Table 1]

At this time, the viscosity of the slurry is 80 to 10
It was 000 Pa · s.

Then, the above sludge is set in a centrifuge,
By operating for 40 minutes, a green molded body having a diameter of 12 mm and a height of 50 mm was obtained. At this time, the weight of the green form is 14 to 1
It is 5 g. Further, this green body was set in a liquid-permeable mold in a centrifuge and dehydrated for 40 minutes to obtain a green body having a water content of 12.5 (wt%). At this time, the density of the green compact was 2.4 to 2.6 (g / cm ³ ), and the particle packing rate was 60 to 65 (%).

Next, the green compact is changed to 9 by changing the firing temperature.
The densities and relative densities when fired for 0 minutes are shown in Table 2 below.

[0044]

[Table 2]

That is, as shown in Table 2 above, high-purity alumina can be fired at a very low firing temperature and a short firing time, and the effect of the present invention is clearly shown. There is.

The present invention can be applied to the molding of most fine powders containing various ceramics and various metals in addition to the high-purity alumina as in the above specific examples.

[0047]

As described above, according to the invention of claim 1, as a molding method for molding a green body from a slurry or suspension prepared by kneading a powder of metal, ceramic or the like into a liquid, Put the sludge in the mold, and rotate the mold by centrifugal force for a predetermined time to settle the sludge in the mold and the solid content in the suspension, so that the liquid component is separated to the upper side of the forming mold. By promoting the separation of solid and liquid, a green molded body having a high particle packing rate can be obtained in a short time, and the reduction of the binder can reduce the firing temperature and the heating rate. In addition, manufacturing efficiency, dimensional accuracy, and yield can be improved.

According to the second aspect of the invention, the green body obtained in the first aspect of the invention is rotated again by the centrifuge in the mold having the liquid permeable bottom portion, so that the green body remains in the green body. By removing the liquid, it is possible to further reduce the amount of liquid contained in the green body, shorten the subsequent drying time, degreasing, and firing time. It is possible to easily release the molded product from the mold, and thus it is possible to improve the shape accuracy of the product.

According to the third aspect of the invention, when the slurry or the like is put in the mold and the mold is rotated by the centrifugal force for a predetermined time, the mold having the liquid permeable bottom is used from the first step. Therefore, the liquid component can be separated into the upper part in the mold, and the liquid can be discharged from the mold itself, thereby further shortening the time of the molding step.

According to the invention of claim 4, since the molded body obtained in the invention of claim 3 is rotated again in the mold having the liquid permeable bottom portion by the centrifuge, the molded body is removed by deliquoring. The amount of the liquid in the inside is reduced, the mold release is facilitated by the contraction of the green body, and the effect of the invention of claim 2 can be obtained together.

According to the invention of claim 5, the average particle diameter is 0.
In the case of powder composed of fine particles of 1 to 1.0 μm, since the centrifuge is operated under the condition that the gravity multiple is 3000 G or more, such fine particles can be molded.

According to the invention of claim 6, in the invention of claim 2 or 3, the liquid permeable bottom portion has a structure in which the filter backed up by a member having a large number of through holes or a granular material is the bottom portion of the mold. Since it is laid in the above, the liquid component can be easily discharged, and therefore, the molding time and the liquid removal time can be remarkably shortened.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing each step of a molding method according to an embodiment.

FIG. 2 is a front view schematically showing an operating process of a centrifuge.

[Explanation of symbols]

 1 type 1a tubular member 1b, 1c bottom member 2 sludge 3 centrifuge 6 generation form 7 through hole 8 filter paper (filter)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shunzo Tajima 1-7-7 Yokogawa-cho, Nishi-ku, Hiroshima-shi, Hiroshima Barmy Yokogawa-404

Claims (6)

[Claims] 1. A molding method for obtaining a green body from a fluid such as a slurry or a suspension obtained by kneading a powder of a metal, a ceramic or the like with a liquid, the method comprising the steps of: Put a predetermined amount of fluid, set the mold containing the fluid in the centrifuge, and then rotate the bottom of the mold by the centrifuge for a predetermined time toward the outside in the radial direction of rotation of the centrifuge. After that, the liquid separated in the upper part of the mold is removed to obtain a solid green molded body. 2. The molding method according to claim 1, wherein the obtained green molded body is housed in a mold having a liquid permeable bottom, and the mold containing the green molded body is set in a centrifuge,
The bottom of the mold is rotated by the centrifuge for a predetermined time toward the radial outside of the centrifuge, and the residual liquid in the green body is deliquored through the liquid permeable bottom. A molding method characterized by demolding a green body. 3. A molding method for obtaining a green body from a fluid such as a slurry or a suspension obtained by kneading a powder of a metal, a ceramic or the like with a liquid, the method comprising a mold having a liquid-permeable bottom. Put a predetermined amount of the fluid, set the mold containing the fluid in the centrifuge, and then rotate the bottom of the mold by the centrifuge for a predetermined time toward the radial outside of the centrifuge, After that, the liquid separated on the upper part of the mold is removed to obtain a solid green molded body. 4. The molding method according to claim 3, wherein the mold containing the green body is reset in the centrifuge, and then the bottom of the mold is placed outside the radial direction of rotation of the centrifuge by the centrifuge for a predetermined time. A molding method, which comprises rotating the molded body by rotating it toward one side to drain the residual liquid in the molded body through the liquid permeable bottom portion, and then demolding the molded body from the mold. 5. The molding method according to claim 1 or 3, wherein the average particle size of the powder is 0.1 to 1.0 μm, and the centrifugal acceleration during operation of the centrifuge is 3000 G or more. Molding method. 6. The molding method according to claim 2 or 3, wherein the liquid permeable bottom portion comprises a member having a large number of through holes or a filter backed up by a granular material.