JP2003328005A - Segment die for centrifugal formation and method for centrifugal formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a method for high speed centrifugal separating formation wherein shape restriction is hardly caused, and time shortening of a process is enabled by taking measures capable of manufacturing a complicated shaped product by using a method for centrifugal formation. <P>SOLUTION: In the method for centrifugal formation for obtaining a solid formation body on a bottom portion of a die, by putting a prescribed amount of slurry formed by kneading a powder such as, of a metal, ceramic with a liquid into the die the bottom portion of which is sealed, and after the die is set on a centrifuge, by rotating the bottom portion of the die in the direction toward the outside of the rotational radius of the centrifuge, then, by eliminating the liquid separated on a top portion of the die, this segment die is used by being dipped into a die frame filled with a fluid. The segment die for the centrifugal formation is characterized in that an area ratio between the inner face and the outer face of the die is determined in accordance with densities of the slurry and the fluid so that the force caused by pressure from the fluid during the centrifugal formation and acting on the segment die in a closing direction can become more than the force acting on the segment die in an opening direction by an internal pressure of the slurry. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a centrifugal force to knead powders of metals, ceramics and the like into a liquid to form a solid form from a slurry (sometimes called a slurry or a suspension). To improve the centrifugal molding method for producing

[0002]

2. Description of the Related Art Conventionally, in the powder metallurgy industry or the ceramic industry for producing a sintered body of a predetermined shape from a powder of metal, ceramic or a mixture thereof, in order to finish various powders into a predetermined shaped body before firing. As a general method for producing a green body, 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 slurry, and the slurry is molded as described below. Various methods are known.

(1) The slurry is adhered to a strip-shaped base material with a certain thickness while scraping it with a doctor blade in the form of a rotating roll, and then the strip-shaped green sheet obtained by heating and drying is cut or punched to form a flat plate. Doctor blade method to obtain the formed form of. (2) A compression molding method in which a green compact is obtained by press-molding a molding powder obtained by spray-drying a slurry with a spray dryer in a shape of a certain shape. (3) A casting method in which the slurry is poured into a plaster mold and dried to finish it into a predetermined shape. (4) A pressure casting method in which the slurry is poured into a gypsum mold and pressure is applied to the slurry in the gypsum mold to increase the molding speed. However, these known methods have problems that the shape of the molded body is largely restricted, the quality of the molded body is inferior, or it is difficult to quickly separate the liquid component from the slurry.

Therefore, the present inventors have previously developed a method for producing a green body capable of solving such a problem (Japanese Unexamined Patent Publication No. Hei 5-
65504 publication). The method is that a predetermined amount of a fluid made by kneading powder into a liquid is filled in a mold with a closed bottom, and the mold is placed so that the bottom faces outward in the radial direction of rotation of the centrifugal molding machine. , The mold is rotated for a predetermined time by a centrifugal molding machine, and then the liquid separated on the upper part of the mold is removed to obtain a green compact.
CP method).

In this high-speed centrifugal separation molding method, the solid content in the fluid is settled in the mold by the centrifugal force, and the liquid component is separated above the forming mold, so that the solid-liquid separation is promptly performed, and In time, it is possible to obtain a green compact having an ideal particle packing rate that is almost equal to the closest packing rate of the powder, and it is possible to reduce the firing temperature and the heating rate by reducing the binder. Therefore, the manufacturing efficiency, dimensional accuracy, and yield of the sintered body can be improved.

[0006]

The HCP method is also called a dry isostatic pressing method (CIP method: isotropic pressing method. Example:
Compared with Japanese Patent Laid-Open No. 9-241704), in the CIP method, bulk reduction of about 20 to 30% occurs due to isotropic pressing, and internal stress remains in the depressurizing stage. Further, since the CIP method does not improve the uniformity of particle distribution in the molded body, there is no means for removing the abnormal particle size distribution inside the molded body.
On the other hand, the HCP method takes time because it requires a drying step, but since it is unidirectionally compressed in the direction of centrifugal force and does not undergo elastic deformation during depressurization, residual stress does not remain inside the formed body and coarse particles are removed. Therefore, there is an advantage that a higher quality green compact can be manufactured.

However, when the method developed by the inventors of the present invention is applied to the molding of a complicated shape using a split mold as a mold, when a high centrifugal force of about 5 kG (G is a gravitational acceleration) or more is applied. It was found that the slurry containing the powder easily leaked from the split surface of the split mold. Therefore, there is a difficulty in using the split mold particularly in a complicated shape, and the shape of the green body is considerably restricted.

If the shape is simple, for example, FIG.
As shown in (Japanese Unexamined Patent Publication No. 10-80909), a lower mold 16A having a hemispherical portion 20A and a slurry reservoir 18 having a funnel-shaped bottom and a slurry passage 22 at the center and a hemisphere. The upper die 16B having the shaped portion 20B is attached to the outer frame 1
It is possible to considerably prevent leakage from the split mold by fixing the split mold of the split mold in No. 0 with the fasteners 24, 26 and forming the molding space 19 with the split surface of the split mold in the direction orthogonal to the centrifugal force. However, this method has a problem in that the split-type bonding and disassembling have fairly complicated steps.

In order to solve this problem, the inventors of the present invention firstly, as shown in FIG. 4 (a), divide the divided surface into a frame 1 composed of a cylindrical member 1a and a disc-shaped bottom lid 1b. 2a (bottom portion) and a cylindrical split mold 2 having a split surface 2b are set and split mold 2
A method of manufacturing a green compact 7 by preventing leakage of slurry by backing up a split mold fixed by filling a low melting point alloy or wax 3 between the frame 1 and the frame 1 has been developed (Japanese Patent Laid-Open No. 6-58242). -293010 = Patent No. 3210700).

According to this method, since the wax hardly deforms even under a high centrifugal force, it is possible to prevent the slurry from leaking from the split mold for a complex-shaped product. However, a step of dissolving and removing from the split mold after centrifugation is required, and since the process time is required, further improvement in manufacturing efficiency is required.

The present invention has been made in view of the above points, and an object of the present invention is to limit the shape by providing a means capable of producing a complex shaped article by the centrifugal molding method while preventing the leakage of the slurry. It is to establish a high-speed centrifugal molding method that is difficult to receive and can shorten the process time.

[0012]

The present inventors have found that the shape of the split mold and the density of the outer fluid are related to the leakage of the slurry by elucidating the force acting on the split mold during centrifugal molding. , It was found that the above problems can be solved under specific conditions. That is, the present invention includes the following (1) to
It consists of (4).

(1) A predetermined amount of a slurry obtained by kneading a powder of metal, ceramic or the like with a liquid is placed in a mold whose bottom is closed, and the mold is set in a centrifuge, and then the centrifuge is used for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and then the liquid separated in the upper part of the mold is removed to obtain a solid green compact in the lower part of the mold. , A split mold used by being immersed in a mold filled with a fluid, the force acting in the closing direction of the split mold due to the pressure from the fluid during centrifugal molding causes the split mold to move due to the internal pressure of the slurry. To be more than the force that works in the opening direction,
A split mold for centrifugal molding, characterized in that the area ratio between the inner surface and the outer surface of the split mold is determined according to the densities of the slurry and the fluid.

(2) A predetermined amount of a slurry obtained by kneading a powder of metal, ceramic or the like with a liquid is placed in a mold having a closed bottom, and the mold is set in a centrifuge, followed by a centrifuge for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and then the liquid separated in the upper part of the mold is removed to obtain a solid green compact in the lower part of the mold. A split mold that is immersed in a mold filled with a fluid, and the value of ρ2 × S2 on the outer surface of the split mold is greater than or equal to the value of ρ1 × S1 on the inner surface of the split mold (where ρ1 is the density of the slurry. , Ρ2 is the density of the fluid, S1 is the representative area of the inner surface of the split mold, S
2 is the representative area of the split mold outer surface. ) Is a split mold for centrifugal molding. The representative area is defined as the projected area on a plane passing through the split surface of the mold.

(3) A predetermined amount of a slurry obtained by kneading a powder of metal, ceramic or the like with a liquid is placed in a mold having a closed bottom, and the mold is set in a centrifuge, followed by a centrifuge for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and then the liquid separated in the upper part of the mold is removed to obtain a solid green compact in the lower part of the mold. A split mold used by being immersed in a mold filled with a fluid, the split mold being a cylindrical split mold having a vertical split surface, the split mold being in a direction orthogonal to the centrifugal force direction When the outer radius of the cross section is r1, the inner radius of the split mold cross section is r2, the density of the fluid is ρ1, and the density of the slurry is ρ2, r2 ≦ r1 × (ρ1 / ρ2) Split mold for centrifugal molding.

(4) A predetermined amount of a slurry obtained by kneading a powder of metal, ceramic or the like with a liquid is placed in a mold having a closed bottom, and the mold is set in a centrifuge, followed by a centrifuge for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and then the liquid separated in the upper part of the mold is removed to obtain a solid green molded body. ) To (3), a step of filling the mold with the slurry, and a step of immersing the mold in a mold filled with a fluid.

[0017]

The split type includes various division methods such as 2 division and 4 division. Further, the division surface has a direction parallel to the centrifugal force (vertical division), a direction orthogonal to the centrifugal force (horizontal division), and the like. When such a split mold is immersed in the fluid in the mold and rotated by a centrifuge to apply a centrifugal force, static pressure due to the centrifugal force is generated in the slurry and the fluid, and the slurry is spread on each split surface of the split mold. Internal pressure from and external pressure from the fluid are applied.

(1) When the split mold of the present invention is used, the force in the compressing direction is greater than the force acting in the mold cross section in the direction of opening the split mold due to the relationship between the internal pressure, the external pressure and the external force applied to each split surface of the split mold. Are equal or large. Therefore, even if the mold is divided in any direction, the divided surface is not expanded, so that the leakage of the slurry from the divided surface can be prevented. Since the force for tightening the split mold in advance before putting it in the mold is not included in the calculation, if it is tightened with a constant force, leakage will be even more difficult.

(2) A typical example of the split mold of the present invention is a vertical split two-split cylindrical split mold. In this case, the projected area of the outside of the die on a plane passing through the split surface of the die (representative area is S1), the inner surface of the die on the same plane is S2, and the density of the fluid is ρ1. When the density of the slurry is ρ2, if S2 ≦ S1 × (ρ1 / ρ2), the force in the compressing direction becomes larger than the force acting in the mold opening direction in the mold cross section. Use the cross-sectional area of the molded product (projected area of the molded product on a plane that passes through the split surface) as the representative area of the split mold inner surface, and use the area of the split mold projected on the split surface as the representative area of the split mold outer surface. You can

Supposing that the length of the split mold is L, the radius of the outer side of the die is r1, and the radius of the inner side is r2, S1 = 2πL
Since xr1 and S2 = 2πL × r2,
The equation in (2) can be r2 ≦ r1 × (ρ1 / ρ2). When the outside and inside of the mold have a complicated shape, the average distances from the center of the mold to the outer wall and the inner wall of the mold may be r1 and r2, respectively. Alternatively,
The maximum distances from the center of the mold to the outer wall and the inner wall may be r1 and r2, respectively.

(3) The deformation of the mold can be prevented by the same operation as described in (1) above.

(4) When water is used as the fluid, since the density of the slurry is usually 3 kg / cm ³ or less, the area of the split mold mating surface is the cross sectional area of the compact (projection of the compact on the plane passing through the split surface). If it is twice or more of the area), the resultant force due to the centrifugal force will be the internal pressure or more.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below for the case of manufacturing a molded body of a ceramic bearing ball. (Preparation of Form) FIG. 1 shows an example of a split mold in which two ceramic bearing ball compacts are simultaneously prepared.
1A is a front view of the split mold 2A, FIG. 1B is a plan view of the split molds 2A and 2B, and FIG. 1C is A- of FIG.
It is a sectional view of A '. The split molds 2A and 2B are provided with a slurry injection port portion 31, a spherical bearing ball portion 32, and a slurry reservoir 33 for removing coarse particles. Also, split mold 2
A and 2B are connected by a bolt and a nut 34.

The split molds 2A and 2B are made of a material such as aluminum which is easy to process. The mating surfaces of the split molds 2A and 2B are provided with a sufficiently narrow gap by rubbing, wire cutting, grooving or the like so that the smallest particles of the slurry cannot pass through. The formwork can be temporarily fixed by the bolts and nuts 34. Other than the bolts and nuts, any type that can be easily assembled and disassembled in the split mold may be used, and any method such as screwing, fitting, and contact with an elastic body may be applied.

The bearing ball portion 32 and the slurry reservoir 33 are connected by fine pores having a diameter that allows the powder having the maximum particle size allowed in the slurry to pass through. Further, the slurry injection port portion 31 and the bearing ball portion 32 are connected by pores having a diameter larger than that. The shape of the slurry injection port portion 31 is not directly related to the shape of the molded body and can be arbitrarily designed. Further, the shape of the slurry reservoir 33 can be any shape such as an ellipsoid.

In the following, in order to simplify the conditions, the case where the filling height of the slurry (the one-dot chain line in FIG. 1C) and the upper surface of the fluid filled in the mold are the same will be described. For any part of the mating surface of each split mold, the total value of the external pressure of the fluid working in the direction of closing the split mold and the external force working during centrifugal molding is determined accurately by stress analysis, etc. be able to.

In the example of FIG. 1, in order to simply obtain the force applied to the split mold, the "external pressure of the fluid working in the direction of closing the split mold that works during centrifugal molding" is orthogonal to the centrifugal force and Area of the surface in the direction of closing (H × L = S in FIG. 1: cross-sectional area of molded body)
Can be obtained by the product of the average fluid pressure and the "slurry internal pressure acting in the opening direction of the split mold" is determined by the product of the area of the slurry filling portion of the split mold (hatched portion in FIG. 1A) and the internal pressure. be able to.

Since the internal pressure and the external pressure are respectively proportional to the density and depth of the slurry and the fluid, it is necessary to consider the average value. In the case of FIG. 1, the area of the hatched portion of FIG.
Since it is sufficient if the slurry density ≦ S × fluid density, the dimensions of H and L are set so as to meet the conditions.

Water (density = 1.0) was used as the fluid, and the water content density of the slurry compact was 2.8 (high purity alumina; average particle size).
0.22 μm), H × L ≧ (2.8 / 1.0) S. As a result, no matter where the mold cross section that is orthogonal to the centrifugal force and that opens the split mold is taken, the force in the direction that compresses the split mold is equal or greater than the force that acts in the mold opening direction in the split mold cross section. Become. For this reason, even if the mold is divided, since the dividing surface is not expanded, it is possible to prevent the slurry from leaking from the dividing surface.

(Preparation) Next, a centrifugal molding method using a mold will be described with reference to FIG. As shown in FIG. 2 (a),
The mold 2 is set in a mold 1 having a gap that matches the shape of the mold 2 and can be easily taken in and out, and water, for example, is injected as a fluid 4 into the gap between the mold 1 and the mold 2. Since the mold 1 is subjected to static pressure from the inner and outer surfaces during centrifugal molding, a plastic, an alloy or the like may be used as long as the material has a small bulk modulus (κ ≦ 2.2: lead).

The fluid is not limited to water, but may be any non-compressible fluid having a density higher than the design density and easy to handle, and may be water added with a rust preventive agent and a lubricant. The mold 5 is filled with a predetermined amount of the slurry 5. The slurry 5 is obtained by adding a dispersant, a dispersion medium (water, an organic liquid, etc.) to a powder of metal, ceramic or a mixture thereof, which has been crushed in advance with a ball mill to a predetermined average particle size, and kneading the mixture.

As the metal and ceramic powder, austenitic stainless steel powder, cemented carbide, cermet,
Other powders for producing sintered metals, high-purity alumina powders, mixed powders obtained by adding magnesia, silica, titania, etc. to alumina (that is, powders for producing forsterite, mullite, cordierite, etc.) or beryllia, magnesia porcelain, etc. Examples include various ceramics, powders for producing magnetic parts such as ferrite, and the like.

(Molding) Form 1 prepared in this way
Is set in the centrifugal molding machine. FIG. 3 is a front view schematically showing the operation process of the centrifugal molding machine. As shown in FIG. 3A, the mold is set in the centrifugal molding machine. The centrifugal molding machine includes a rotary shaft 12 that rotates around a vertical axis by a motor 11 and a horizontal rod 13 fixed to the upper end of the rotary shaft 12,
Containers 15, 15 attached to both ends of the horizontal rod 13
Each of the molds 2 is set in the inside. At this time, the bottom cover side of the mold 1 is set so as to face outward in the radial direction of rotation of the centrifugal molding machine. Furthermore, each of the above containers 1
Numerals 5 and 15 are rotatably supported around the horizontal shafts 14 and 14 at both ends of the horizontal rod 13, and as shown in FIG. Container 1
The bottoms of the molds 5, 15, that is, the bottoms of the molds 2 are rotated outward in the radial direction of rotation of the centrifugal molding machine.

Then, by operating the centrifugal molding machine, the solid component having a high density in the slurry 5 is gradually settled to the bottom side of the mold 2 by the centrifugal force, and the liquid 6 is separated to the upper part thereof for a predetermined time. When the operation of the centrifugal molding machine is stopped after a lapse of time, as shown in FIG. 2B, most of the liquid 6 is separated into the upper part of the mold 2 and a solid green molded body 7 is obtained in the lower part of the mold.

At this time, the rotation speed of the centrifugal molding machine is determined by the particle size and density of the powder, the viscosity of the dispersion medium, the processing temperature and the like. For example, a slurry of powder having an average particle diameter of 0.2 to 0.4 μm requires a gravity multiple of about 10 to 20 kG, and if this gravity multiple is too small, the upper part of the green formed body after molding is completely filled. It is not possible, and the molding time becomes extremely long.
The particle filling rate of the green body 7 obtained at this time is 60.
It is about 65%.

(Removal of Mold) When the centrifugal force is removed, the mold is not in close contact with the fluid, so that a removing step such as backing up with a low melting point alloy is unnecessary, and the mold can be easily taken out and disassembled. The handling to the next process becomes quick. (Removal of liquid) Only the upper liquid 6 is removed from the inside of the mold 2 in the above state to form the green molded body 7 alone.

(Demolding) The mold 2 is taken out from the mold 1. Next, when the mold 2 is a split mold, the split mold is disassembled along the dividing surface to obtain a green body 7 as shown in FIG. 2 (c). (Drying) After that, the green compact 7 thus obtained is put into a drying furnace and dried by low-temperature heating. This drying time depends on the size of the green body, but is, for example, 40 ° C.
After 6 hours at 70 ° C. for 6 hours, it can be dried by further holding at 100 ° C. for 2 hours.

(Degreasing and firing) Finally, the green compact 7 after drying is fired in a furnace. At this time, in order to remove the binder, dispersant, etc. contained in the green body 7 in advance, for example, 120
Degreasing (calcination) is carried out by heating at a temperature rising rate of about ° C / hour, and at the same time, it is continuously heated at a temperature rising rate of about 120 ° C / hour to obtain a sintered body.

Therefore, in the above embodiment, in the centrifugal molding step, even if the mold 2 is a split mold, the slurry 5 in the mold does not leak from the dividing surface, and the slurry 5 is dispersed in the mold 5 by the centrifugal force. Since the solid component of 6 is settled and the liquid 6 is separated above the green body 7, the solid and liquid can be rapidly separated without substantially causing the loss of the solid component.
High yield of 80% or more and particle filling rate of 60 in a short time
% Or more of the green form 7 having the same shape as the prototype is obtained. At this time, since the mold 2 can be easily taken in and out of the mold 1, the process time can be significantly shortened.

Further, unlike the ordinary slip casting method, the slurry 5 can be molded without being strongly influenced by the concentration, viscosity and dispersion state of the slurry 5, and the slurry 5 before molding needs to be degassed in vacuum. There is no. The binder may be about ⅓ of the usual slip casting method, and as a result, the degreasing and firing temperatures can be lowered, so that the dimensional stability and yield of the sintered body will be good. Further, for example, it is possible to mold a small precision product having a wall thickness of 0.2 mm or less, and further, it can be widely applied to large products.

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 a suspension obtained by simply dispersing powder in a dispersion medium in a centrifugal molding machine and obtain a green compact by centrifugal force.

Further, in the example of the split mold for bearing balls shown in FIG. 1, since the slurry reservoir 33 is provided at the bottom of the split mold, even if there are coarse particles exceeding the specified particle size distribution, The coarse particles are separated into the slurry reservoir 33,
No coarse particles remain inside the green body. Even if air bubbles remain in the slurry, they are removed from the green body by a strong centrifugal force. Therefore, there is no abnormal portion that becomes a crack source, and the quality of the sintered body is improved.

Further, at this time, since the powder agglomerates formed in the slurry reservoir 33 and the slurry injection port portion 31 can be removed before sintering and mixed again with the slurry, it can be used as a slurry vs. formed form. Raw material yield is almost 100
% Can be increased. Furthermore, since the particle size distribution of the green compact in the mold becomes coarser toward the bottom, if the particle distribution of the powder agglomerate (or the removed part) of the slurry reservoir 33 and the slurry inlet 31 is measured, The maximum and minimum values of the particle size distribution in the body can be guaranteed, and the quality can be easily guaranteed.

[0044]

EXAMPLES Example 1 Next, examples of the present invention will be described. A cylindrical split mold was prepared as a mold in order to obtain a simple cylinder as a green body. The split mold was made of aluminum, and the split mold surface was made into a mating surface by wire cutting. It was fixed to the outer two places with snap rings. A slurry having a composition composed of austenitic stainless steel powder (average particle size 4 μm) shown in Table 1 below was prepared.

[0045]

[Table 1]

The calculated density of the above slurry is 2.532.
Density ρ2 = 2,532kg / m ³ of slurry, the density of water .rho.1 = 1,00
0 kg / m ^3, when the outer radius r1 = 9 mm split mold, split type inner radius r2 ≦ r1 × (ρ1 / ρ2 ) = 3.55mm force from the outside if the less becomes more force due to internal pressure, 3.55 mm When it exceeds, the internal pressure becomes stronger than the external pressure.

Therefore, a split mold having an inner diameter of 6 mm was prepared for a split mold having an outer diameter of 18 mm and a length of 90 mm. The maximum rotational speed of the centrifugal molding machine was 9,000 rpm, and the centrifugal molding was performed for 10 minutes. There was no leakage of the slurry, and a green formed product having a predetermined shape was obtained in the radially outer portion of the split mold during centrifugal rotation.

Comparative Example 1 Centrifugal molding was carried out under the same conditions as in Example 1 except that a split mold having an inner diameter of 8 mm was used. All of the slurry leaked and the green body could not be molded.

[0049]

According to the method of the present invention, as a method for producing a green formed body from a slurry obtained by kneading a powder of metal, ceramic or the like into a liquid, a fluid is put between an outer frame and a split mold, By rotating the outer frame for a predetermined time by centrifugal force, even if it is a split mold, the fluid does not leak from the split surface of the mold, and the solid component of the fluid in the split mold is settled at the bottom of the mold,
Since the liquid component is separated on top of the solid component,
By preventing the loss of the solid component and promoting the separation of the solid and the liquid, it is possible to obtain a green shaped product having a high particle packing rate and having the same shape as the prototype in a short time.

[Brief description of drawings]

FIG. 1 shows an example in which a split mold for centrifugal molding according to the present invention is applied to centrifugal molding of a ceramic bearing ball. (A) is a front view of the split mold as a whole, (b) is Similarly, a plan view and (c) are sectional views taken along the line AA ′ of (a).

FIG. 2 is a conceptual diagram showing a process of separating a slurry solid and a liquid in a split mold by centrifugal molding to form a green compact in the method of the present invention.

FIG. 3 is a front view schematically showing an operating process of the centrifugal molding machine.

4 (a) is a sectional view showing the structure of a split mold using a low melting point alloy, wax, etc. in the conventional method, FIG.
(B) is a sectional view showing the structure of a split mold divided in a plane orthogonal to the centrifugal force direction in the conventional method.

[Explanation of symbols]

1 formwork Type 2 2A, 2B split type 3 Low melting point alloy, wax, etc. 4 fluid 5 slurry 6 liquid 7 Solid form 11 motors 12 rotation axes 13 horizontal poles 14 horizontal axis 15 containers 31 Slurry injection port 32 spherical bearing ball part 33 Slurry reservoir 34 bolts and nuts

Claims (4)

[Claims] 1. A predetermined amount of a slurry obtained by kneading a powder of metal, ceramics or the like into a liquid is placed in a mold whose bottom is closed, the mold is set in a centrifuge, and then the centrifuge is used for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and thereafter, the liquid separated in the upper part of the mold is removed to obtain a solid green molded product in the lower part of the mold. A split mold used by being immersed in a mold filled with a fluid, and a force exerted in the direction of closing the split mold by the pressure from the fluid during centrifugal molding opens the split mold by the internal pressure of the slurry. A split mold for centrifugal molding, characterized in that the area ratio between the inner surface and the outer surface of the split mold is determined according to the densities of the slurry and the fluid so as to be equal to or greater than the force acting in the direction. 2. A predetermined amount of a slurry obtained by kneading a powder of metal, ceramics or the like into a liquid is placed in a mold having a closed bottom, the mold is set in a centrifuge, and then the centrifuge is used for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and thereafter, the liquid separated in the upper part of the mold is removed to obtain a solid green molded product in the lower part of the mold. A split mold used by being immersed in a mold filled with a fluid, in which the value of ρ2 × S2 on the outer surface of the split mold is greater than or equal to the value of ρ1 × S1 on the inner surface of the split mold (where ρ1 is the density of the slurry. , Ρ2 is the density of the fluid, S1 is the representative area of the inner surface of the split mold, S
2 is the representative area of the split mold outer surface. ) Is a split mold for centrifugal molding. 3. A predetermined amount of a slurry obtained by kneading a powder of metal, ceramics or the like into a liquid is placed in a mold whose bottom is closed, the mold is set in a centrifuge, and then the centrifuge is used for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and thereafter, the liquid separated in the upper part of the mold is removed to obtain a solid green molded product in the lower part of the mold. A split mold used by being immersed in a mold filled with a fluid, wherein the split mold is a cylindrical split mold having a vertical split surface, and a split mold cross section in a direction orthogonal to the centrifugal force direction. Where r1 is the outer radius, r2 is the inner radius of the split mold section, ρ1 is the density of the fluid, and ρ2 is the density of the slurry, r2 ≦ r1 × (ρ1 / ρ2) The split mold for centrifugal molding according to claim 1. 4. A predetermined amount of a slurry obtained by kneading a powder of metal, ceramics or the like into a liquid is placed in a mold whose bottom is closed, the mold is set in a centrifuge, and then the centrifuge is used for a predetermined time. In the centrifugal molding method, the bottom of the mold is rotated outward in the radial direction of rotation of the centrifuge, and then the liquid separated on the top of the mold is removed to obtain a solid green molded body.
A centrifugal molding method comprising: a step of filling the split mold of any one of claims 1 to 3 with a slurry; and a step of immersing the mold in a mold filled with a fluid.