JPH04257401A - Slip casting method and mold - Google Patents

Abstract

PURPOSE:To provide slip casting method and mold, in which water absorption properties are improved and casting rate can be made larger. CONSTITUTION:For the casting method concerned, a casting mold 1 is employed which is made of water permeable porous material and in the interior of which cavity parts (piping parts) 3 and 4 are provided. Slip 6 is poured in said cavity mold 1. Said cavity parts (the piping parts) 3 and 4 are evacuated, resulting in improving the water absorption speed of said casting mold 1 and consequently increasing the casting rate of the solids in said slip to the mold. In addition, the surfaces of the casting mold 1 excluding its cavity surface 13 are covered by airtight layer 5.

Description

Detailed Description of the Invention [0001] The present invention relates to a slip casting molding method and a mold used therein, and particularly to a molding method that can improve water absorption and increase ink deposition speed. and regarding molds. 2. Description of the Related Art Slip casting is a typical method for producing ceramic molded bodies. This slip casting molding method uses a mold made of water-absorbing material such as gypsum, and solidifies the slip by absorbing moisture from the slip (suspension of ceramic raw powder) injected into the cavity of the mold. This is a method for producing a ceramic molded body. This method is generally suitable for producing relatively thin-walled molded bodies or molded bodies with complex shapes. [0003] This slip casting molding method is
Manufacture of (green) molded bodies for ceramic products that require high shape and dimensional accuracy, such as automobile turbine rotors, because it is relatively simple and can easily produce homogeneous molded bodies without distortion. Applications are being attempted. [0004] By the way, this slip casting molding method generally involves filling a cavity of a mold with slip under atmospheric pressure, and dewatering the slip by natural water absorption by the mold. However, when producing a relatively thick molded body, it takes a long time to dehydrate the slip inside the cavity. [0005] Therefore, a so-called pressure casting method has been used in which pressure is applied to the slip in the cavity to forcibly dehydrate the slip, but this method does not damage the relatively fragile mold made of plaster or the like. Problems such as mold cracking occur. Therefore, an object of the present invention is to provide a method of increasing the water absorption rate of a mold and increasing the ink deposition rate without pressure casting, and a mold capable of realizing the same. It is to be. Means for Solving the Problems In view of the above object, as a result of intensive research, the present inventor provided a cavity inside a mold made of a porous material having moisture permeability, and If the pressure inside the cavity is reduced after the slip is injected into the cavity, water will infiltrate from the slip into the mold faster, increasing the deposition speed and making it possible to produce even relatively thick molded products in a short time. They discovered that it is possible to do this, and came up with the present invention. That is, the slip casting molding method of the present invention uses a mold made of a moisture-permeable porous material and has a cavity inside, injects slip into the mold, and reduces the pressure inside the cavity. This improves the water absorption rate of the mold, thereby increasing the rate at which the solid content in the slip is attached to the mold. Further, the slip casting mold of the present invention made of a moisture permeable porous material has a cavity inside, the cavity communicates with an external reduced pressure source, and the cavity surface in contact with the slip. The mold walls, except for the mold walls, are characterized by being covered with an airtight material. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic sectional view showing a slip casting mold according to an embodiment of the present invention. The mold 1 of this embodiment has two partial molds 11.
, 12, and these partial molds 11 and 12 are combined to form a cavity 13 corresponding to the outer shape of the intended molded body. A tube portion is formed inside each partial mold. In the partial mold 11 serving as the side mold of the cavity, the tube portion 3 runs spirally inside the mold so as to surround the cavity 13, as can be seen from FIGS. 1 and 2. In addition, in the partial mold 12 serving as the bottom mold, B- in FIG.
As shown in FIG. 3, which is a cross-sectional view of B, the tube portion 4 is formed to meander within the mold 12. In this way, in each partial mold, the tube portion is formed so as to spread as evenly over the entire mold as possible. The tube parts 3 and 4 are tubes (sizing tubes) whose walls are made of porous material.
can be formed by embedding it at the time of forming the partial mold. One end of each tube 3, 4 is closed in the mold, and the other end has an opening 30, 40, respectively, in which an external suction pump (not shown) is inserted.
It is connected to suction means such as The partial molds 11 and 12 are both made of water-permeable porous material. Specifically, plaster,
It is formed from a water-absorbing material such as porous resin, porous glass, and porous metal. Among such water-absorbing porous materials, gypsum is the most practical. The surface of the mold 1 other than the wall surface of the cavity 13 that comes into contact with the slip is covered with an airtight layer 5. A resin film can be used as this airtight layer. Further, a rubber or resin paint or the like may be applied to the surface of the mold. The slip 6 is injected into the cavity of the mold 1 described above, and the insides of the tubes 3 and 4 are suctioned. Then, the entire interior of the porous mold 1 is brought into a reduced pressure state, and the rate of water absorption from the cavity surface 13 into the mold increases. When the water absorbency of the mold is improved in this way, the speed at which the slip solids adhere to the cavity surface becomes faster. [0016] This deposition speed varies depending on the shape and material of the mold, the state of formation of the pipe, etc., but according to the research of the present inventor, when plaster is used as the mold, 20T
If the pressure is reduced to about .000.degree. The method and mold of the present invention can be applied to a wide variety of slips, including powders of oxides, nitrides, borides, metals, etc. [0018] In the above description, an example has been given of a mold in which a pipe is formed as a hollow part within the mold, but the present invention is not limited to this, and the strength of the mold is ensured, and the mold itself is As long as manufacturing is easy, the shape of the cavity in the mold may be changed as appropriate. Note that when the mold of the present invention is used, after the solidified molded body is taken out from the mold 1, the tube portion 3 is removed.
, 4, by blowing air or the like in reverse, the mold can be dried in a short time, reducing the loss time until the next slip casting molding. The present invention will be explained in more detail with the following specific examples. Examples 1 to 3 A mold having the shape shown in FIG. 1 was produced. Here, partial type 11
and 12 are made of plaster, and the inner pipe parts 3 and 4 are made of plaster.
were each formed by embedding a nylon sizing tube during molding of the partial mold. Then, wide cellophane tape was attached to the surface of the mold other than the cavity surface. [0021] 85% by weight of Al2O3 powder and ZrO
2 Ceramic powder consisting of 15% by weight of powder, a deflocculant, a binder (polyvinyl alcohol), and an antifoaming agent,
Weigh out ion-exchanged water so that it has the composition shown in Table 1,
This was mixed in a ball mill for 24 hours to prepare a slip. The viscosity of each slip is also shown in Table 1. Note that the numbers in Table 1 indicate parts by weight in columns other than viscosity. This slip was injected into the cavity of the mold, the open end of the sizing tube was connected to a suction pump, and the pressure inside the sizing tube was reduced to 20 Torr. The deposition rate of the ceramic component while this pressure reduction was continued was determined by (deposition thickness)2/(deposition time). The results are shown in Table 2. Incidentally, the unit of the inking speed in Table 2 is 10-4 cm2/sec. After about 4 hours had elapsed from the start of the above-described pressure reduction, the slurry was removed, dried, and demolded to obtain a vessel-shaped molded product. Then, the density of the obtained molded body was measured. The results are also shown in Table 2. Comparative Examples 1 to 3 As a comparison, a mold having the same shape as the mold used in Example 1 but without a tube inside its body was made from plaster. [0025] The slips used in Examples 1 to 3 were respectively injected into the above-mentioned comparative molds, and molded bodies were produced by natural water absorption under atmospheric pressure. During this casting, the deposition rate of the ceramic component was measured in the same manner as in Example 1. The results are shown in Table 1. Examples 4 and 5 90% by weight of Si3 N4 powder as ceramic powder
Using a mixture consisting of , 5% by weight of Y2O3 powder, and 5% by weight of Al2O3 powder, this and the deflocculant, binder, and antifoaming agent used in Example 1 were mixed at the compounding ratios shown in Table 1. Mixing was carried out in the same manner as in Example 1 to obtain a slip. [0027] This slip was poured into the mold used in Example 1, and a molded article was produced in the same manner as in Example 1. During this casting, the deposition rate of the ceramic component was measured in the same manner as in Example 1. The results are shown in Table 2. Also,
The density of the obtained molded body was measured. The results are also shown in Table 2. Comparative Examples 4 and 5 For comparison, molded articles were prepared in the same manner as in Comparative Example 1 using the slips of Examples 4 and 5 and the mold used in Comparative Example 1. During this casting, the deposition rate of the ceramic component was measured in the same manner as in Example 1. Table 2 shows the results.
Shown below. In addition, the density of the obtained molded body was measured. The results are also shown in Table 2. [0029]
Table 1 Ceramic

Viscosity Example No.
Powder Binder Deflocculant
Antifoaming agent Water (dPaS) Example 1 75 0.15 0
．． 4 0.05 25
21.5 Example 2 65 0.
15 0.4 0.05
35 9.5 Example 3
60 0.15 0.6
0.05 40 17.5
Comparative example 1 75 0.15
0.4 0.05 25
21.5 Comparative Example 2 65
0.15 0.4 0.
05 35 9.5 Comparative example 3 60 0.15 0
．． 6 0.05 40
17.5 Example 4 35 1.
5 2.5 0.5
65 6.3 Example 5
30 1.5 1.0
0.5 70 16
Comparative example 4 35 1.5
2.5 0.5 65
6.3 Comparative Example 5 30
1.5 1.0 0.
5 70 16 0030
Table 2
Example No. Thickening speed (1)
Density (2)
Example 1 15.0
4.1 Example 2
17.6 4.1
Example 3 1
5.0 4.1
Comparative example 1 0.9
4.1 Comparative example 2 1.4 4
．． 1 Comparative example 3
1.2 4.1
Example 4
1.1 3.20
Example 5 1.0
3.20
Comparative example 4 0.3
3.20 Comparative example 5 0.3 3.2
0 Notes to Table 2 (1): Unit is 10-4cm2
/second. Note to Table 2 (2): Unit is g/cm3. [0031] As can be seen from the above, in this example, the deposition rate for the slip of alumina ceramic material was more than 10 times that of the conventional method (method using natural water absorption under atmospheric pressure). Meat speed was obtained. In addition, a deposition rate more than three times faster than that of silicon nitride-based ceramic material was obtained. Effects of the Invention As detailed above, in the slip casting molding method of the present invention, the water absorption of the mold can be improved without pressure casting, and the deposition rate of the ceramic component can be increased. Can be done. Moreover, it is possible to avoid mold cracking, etc., which is a problem with the pressure casting method.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a slip casting mold according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG. 1;

FIG. 3 is a sectional view taken along line BB in FIG. 1;

[Explanation of symbols]

1 Slip casting mold 3, 4 Pipe section 5 Airtight material 6 Slip 11, 12 Partial mold 13 Cavity 30, 40 opening

Claims (5)

[Claims] 1. Using a mold made of a moisture-permeable porous material and having a cavity inside, slip is injected into the mold and the inside of the cavity is depressurized to increase the water absorption rate of the mold. A slip casting molding method characterized by increasing the rate at which the solid content in the slip is deposited on the mold. 2. The slip casting method according to claim 1, wherein the hollow portion is a pipe portion. 3. A slip casting mold made of a moisture-permeable porous material, having a cavity inside, the cavity communicating with an external reduced pressure source, and having a cavity surface in contact with the slip. A slip casting mold characterized in that the wall surface of the mold except for is covered with an airtight material. 4. The slip casting mold according to claim 3, wherein the cavity is a pipe. 5. The slip casting mold according to claim 4, wherein the tube portion is formed by embedding a tube having a porous wall in the mold.