JPH0413123B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a mold using a thin film filter, a method for molding articles using the same, and a pressure casting method. [Conventional technology] Conventionally, potter's wheel molding of inorganic materials such as ceramics,
BACKGROUND ART Plaster molds, synthetic resin molds, ceramic molds, and the like are known as molds used in cast molding, wet press molding, and the like. Such molds have a permeability function to remove the solvent contained in the molding base (sludge) of inorganic materials such as ceramics, and can dehydrate and release the molded product by suction or pressure. This method performs ion exchange with ions in the base material on the surface of the mold, aggregates the base particles, and dehydrates and releases the molded product. Recently, in order to prevent base particles from entering the mold and prevent clogging, as well as to improve dewatering efficiency, an outer layer with coarse pores and a molding surface layer with fine pores have been developed. A mold with a two-layer structure has been proposed (Special Publication No. 56-14451).
(see publication). [Problems to be Solved by the Invention] However, the gypsum mold has a drawback that its mechanical strength is low and its durability of use is very small. In addition, molds made of synthetic resin or ceramics become clogged after each molding, making it necessary to clean the molds.As the number of times they are used increases, the clogging lengthens the casting time and reduces moldability. to do,
Furthermore, since the desired pore diameter of the mold cannot be obtained, there are drawbacks such as the casting time varying depending on the mold and being difficult to control. On the other hand, even in the case of a mold having a two-layer structure, since the two layers are integrally constructed, the above-mentioned clogging cannot be eliminated, and the moldability decreases as the number of times of use increases. [Means for Solving the Problems] Therefore, the present invention provides a novel mold that solves the drawbacks of the conventional mold, and a method for molding an article and a pressure casting method using the same. The purpose is to According to the present invention, this purpose is to use a permeable mold having micropores on the solvent discharge side, and a mold in which the other parts are non-permeable, and the molding surface of the permeable mold is A mold comprising a thin film filter (first invention), a permeable mold having micropores on the solvent discharge side, the other part being a non-transparent mold, and a thin film on the molding surface side of the permeable mold. Introducing the slurry into a mold equipped with a filter,
A method for molding an article (second invention) in which a molded body is obtained by removing the solvent from the slurry through the permeable mold, and a permeable mold having micropores on the solvent discharge side is used, and the other parts are non-transparent. After injecting the slurry from the injection part into a mold made of a transmission mold, equipped with thin film filters on both sides of the molding mold, and equipped with a slurry injection part and a solvent discharge part in the slurry, Pressure casting method (third method) for obtaining a molded body by pressurizing the slurry and then removing the solvent from the discharge part of the mold through the permeable mold.
invention). The mold of the present invention is characterized in that a thin film filter is provided on the molding surface side of the mold having a permeable function. That is, the thin film filter is made separate from the transparent type, and used together.
For example, a means for bringing it into close contact with a transparent mold by vacuuming is used. Further, the adhesion can be achieved by a method of wetting with water, a method of heating, or the like. By adopting such a configuration, the filter can be replaced, and cleaning of the transparent mold itself becomes unnecessary, and as a result, moldability can be stably maintained. The material of the thin film filter is not particularly limited in type, but usually cellulose fibers, cellulose derivatives, synthetic fibers, synthetic resins,
Filter paper made of glass fiber, silica fiber, asbestos fiber, etc., filter cloth made of cotton, wool, synthetic fiber, etc.
Alternatively, a metal net or the like is preferably used. Moreover, it is preferable to use a screen type (membrane filter, metal sieve, wire mesh, etc.) whose pore diameter is accurately determined at the time of manufacture as the thin film filter. The screen type thin film filter used preferably has an average pore diameter of 0.1 to 25 μm, more preferably 0.3 to 15 μm. If the average pore diameter is smaller than 0.1 μm, it will be difficult to remove the solvent during molding, and molding defects will likely occur. On the other hand, the average pore size
If it exceeds 25 μm, fine particles in the slurry will pass through the filter, which may cause a change in composition. Furthermore, for thin film filters other than the above-mentioned screen type whose pore diameter cannot be measured, it is preferable to use a filter having a particle retention degree of 1 to 10 μm. If the particle retention degree is less than 1 μm, the casting time will be long, while if it exceeds 10 μm, there is a risk that fine particles will pass through. Here, the particle retention rate refers to the chemical precipitation method (JIS-
P3801) refers to the particle retention performance of filter paper. Further, the thickness of the thin film filter is preferably 1
mm or less, more preferably 0.5 mm or less. When the thickness is greater than 1 mm, it becomes difficult to provide a transparent mold with a curved surface. Furthermore, as is clear from the above, the thin film filter is preferably flexible. Further, it is preferable that the filter is prepared in advance in a shape suitable for the transparent mold. In addition, it is sufficient to provide a thin film filter in a transparent type, but it is preferable to have it in close contact with the filter.
The shape of the molded product can be made into more regular dimensions. By further adhering, the solvent in the molded article can be removed uniformly, and a more homogeneous molded article can be obtained. Next, as a permeable type to which the above-mentioned thin film filter is brought into close contact, a conventionally known type can be used.
In order to improve solvent removal and drying efficiency, the permeable type must have good air permeability and ensure the strength of the mold itself, and is usually used with a coarse pore size of 50 to 500 μm. Ru. The material of the permeable mold is not limited, but if the material is not to be suctioned from the discharge part during normal pressure casting, it is necessary to use a material with a large number of pores and strong water absorption, such as plaster. . By using a permeable mold having such micropores, it is possible to remove the solvent uniformly, and it is possible to obtain a molded article with few drying cracks and no density unevenness. Further, when pressure casting is performed, resins, ceramics, metals, composite materials thereof, etc. may be used. Further, by using a transparent mold on the solvent discharge side of the mold and using a non-transmissive mold on the other parts, it is possible to impart high shape accuracy to the molded article. For example, it is possible to accurately mold articles such as ceramic turbine rotors that have complex shapes and require high shape accuracy. When performing cast molding, slurry (base material containing a solvent) is introduced into the container of the mold, and then passed through a thin film filter and a permeable mold.
By removing the solvent directly from the discharge part or removing the solvent by suction, a molded article is obtained. As the slurry component (or base component), inorganic materials such as ceramics, water or organic solvents as solvents, and molding aids (binder, lubricant, deflocculant, antifoaming agent, etc.) are generally used. , ceramic turbine rotors and other articles are formed. On the other hand, the mold used in the pressure casting method, which performs casting by applying pressure, differs from the above-mentioned normal pressure casting mold in that it has a slurry injection part to pressurize the slurry. The other structures are the same. Naturally, it is also possible to carry out atmospheric pressure casting using a pressure casting mold having a slurry injection part. Next, the molding conditions for molding using the above-described mold will be explained. First, the solvent contained in the slurry is usually in the range of 15 to 70% by weight, preferably 25 to 60% by weight, and the viscosity of the slurry is usually 0.01 to ¹⁰⁵ poise, preferably 0.1 to ¹⁰³ poise. use something. On the other hand, the pressurizing pressure of the slurry in the injection part is preferably 5 kg/cm ² or more, more preferably 10 kg/cm 2 or more.
Use Kg/cm2 or ^more . If the pressure is less than 5 Kg/cm ² , the solvent removal performance from the discharge section will be poor and the casting time will be longer. In addition, it is possible to use a high pressure of 500 kg/cm ² or more as the pressurizing pressure, but the high pressure makes the mold larger and heavier, resulting in poor operability. It is preferable to use ² or less. Next, the mold of the present invention will be explained using the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a mold according to the present invention, and 2 is a container portion whose sides are surrounded by a non-transparent mold 1, and the lower side of the container portion 2 is coated with a thin film. A transparent mold 4 tightly covered with a filter 3 is disposed, and a discharge section 5 is provided further below the transparent mold 4. The thin film filter 3, the transparent mold 4, and the discharge part 5 are all integrally surrounded by a non-transmissive mold 6 on the side. Here, the container part 2 has an appropriate shape according to the intended molded article. Further, the non-transparent mold 1 and the non-transparent mold 6 are formed as separate bodies from the viewpoint of ease of manufacture and workability. FIG. 2 is a sectional view showing another embodiment of the mold according to the present invention. The difference from the mold shown in FIG. 1 is that a non-transparent mold 1 and a non-transparent mold It further has an injection part 8 whose side is surrounded by a non-transparent mold 7 which is separate from 6, and which is mainly used as a mold for pressure casting. [Examples] Hereinafter, the present invention will be explained in more detail based on Examples, but it will be clear that the present invention is not limited thereto. Example 1 SiC powder containing sintering aid (average particle size 1 μm) 100
45 parts by weight of water, 0.8 parts by weight of ammonium polyacrylate (deflocculant), and 0.25 parts by weight of octyl alcohol (antifoaming agent) were mixed with the parts by weight to obtain a slurry. This slurry had a pH of 11.50 and a viscosity of 12 poise. Next, in order to remove air bubbles in the slurry, the slurry was held at a vacuum level of 70 cmHg for 5 minutes while stirring to perform vacuum degassing. This slurry is poured into the container part 2 from the injection part 8 of the pressure casting mold for the turbine rotor shown in FIG.
The slurry was poured into the slurry through the slurry reservoir 9, and then pressurized from the injection part 8 and dehydrated by suction from the discharge part 5 to complete the molding. In this example, the permeable type 4 has an average pore diameter of 120 μm, and the thin film filter 3 has an average pore diameter of 120 μm.
A screen type filter with a pore diameter of 3 μm and a thickness of 0.1 mm was used.
Continuous pressure casting was performed at 100Kg/ ^cm2 . The thin film filter was replaced with a new one for each molding. The results are shown in Table 1 (a). For comparison, a ceramic type with a two-layer structure was used as a permeable type, and the first layer had an average pore diameter.
The second layer had an average pore diameter of 250 μm, and the first layer was on the molding surface side. Also, the pressing force is
Continuous pressure casting was carried out at 100Kg/cm ² .
The results are shown in Table 1(b). As is clear from Tables 1 (a) and (b), when the mold of the present invention is used, the change in casting time is extremely small even when the number of castings increases, and continuous casting is possible. This was possible, and the molded product itself was in good condition with no cracks, insufficient filling, or deformation. The shape of the container part of the pressure casting mold shown in Fig. 3 is matched to the shape of the turbine rotor, which is the molded object, with a blade diameter of 80 mm (φ) and a blade height of 35 mm.
It was warm in mm.

【table】

[Table] Example 2 Si ₃ N ₄ powder containing sintering aid (average particle size 0.7 μm)
100 parts by weight, 50 parts by weight of water, 1 part by weight of polyacrylic acid (deflocculant), octyl alcohol (defoaming agent)
0.5 parts by weight were mixed using a pot mill to obtain a slurry. Next, in order to remove air bubbles in the slurry, the slurry was stirred and kept in an atmosphere with a degree of vacuum of 75 cmHg for 5 minutes to perform vacuum deaeration. 230 c.c. of this slurry is poured into the container part 2 from the injection part 8 of the mold for pressurized casting shown in FIG. The molding process was completed. The molding was carried out using the thin film filter and under the pressure conditions shown in Table 2. The results are shown in Table 2. In addition, the shape and dimensions for pressure casting molding in Figure 2 are as follows:
It is as follows. Container part 2: Diameter 55mm (φ) Height 100mm Thin film filter 3: Permeable type shown in Table 2 4: Diameter 60mm (φ) Thickness 15mm Average pore diameter 50μm Non-permeable type: Cylindrical shape with outer diameter 100mm (1, 6, 7) The molded product obtained by molding to a total height of 150 mm or more had no defects such as cracks and was in good condition. Next, after drying the obtained molded body, using an electric furnace,
Degreased at 400℃ for 3 hours, then under _N2 atmosphere,
It was baked at 1700°C for 3 hours. A test piece was cut out from this sintered body and tested for four-point bending strength (JIS R1601).
Table 2 shows the results of measuring the density. From Table 2, the pressurizing pressure is 2Kg/cm ² , 5Kg/cm 2
It can be seen that the casting time is shorter when the diameter is cm ² or more. Furthermore, filters with predetermined pore diameters, such as membrane filters, are shorter in casting time and have better sintered properties than filter paper or filter cloth. Furthermore, it is clear that the density of the sintered body is more stable when the average pore diameter of the membrane filter is 25 μm or less.

[Table] Example 3 100 parts by weight of Si powder (average particle size 5 μm) containing a sintering aid, 35 parts by weight of water, 0.5 parts by weight of polyacrylic acid,
0.5 parts by weight of octyl alcohol was mixed to obtain a slurry. Next, vacuum deaeration was performed to remove air bubbles in the slurry. This slurry is transferred to the container part 2 of the mold shown in Figure 1.
Pour 140 c.c. and perform casting under normal pressure.
Suction dehydration was performed from the discharge section 5, and molding was completed in 120 minutes. The thin film filter 3 was made of Ni and had a pore diameter of 25 μm. The shape and dimensions of the mold shown in FIG. 1 were as follows. Container part 2: Diameter 50mm (φ) Height 80mm Transparent type 4: Diameter 60mm (φ) Thickness 10mm Average pore diameter 500μm Non-permeable type: Cylindrical shape with outer diameter 100mm (1, 6) Overall height: 150mm Obtained The molded body was dried using a constant temperature and humidity chamber, and then nitrided at 1400° C. for 20 hours in an N ₂ atmosphere to obtain a sintered body. This sintered body was in good condition with no defects such as cracks or deformation. [Effects of the Invention] As explained above, according to the present invention, since the mold has a transparent mold in which a thin film filter separate from the transparent mold is adhered, the thin film filter must be removed each time it is used. By replacing the transparent mold, clogging of the transparent mold does not occur, cleaning of the mold itself becomes unnecessary, and a stable molded product can be obtained even after long-term use. As a result, manufacturing costs can be reduced. Furthermore, since any thin film filter can be used, it can be easily adapted to the mold that matches the desired molded object, and can also be adjusted to suit the particle size, pH, viscosity of the slurry, material of the raw powder, etc. Since it is possible to select the material, pore diameter (pore diameter), shape, etc. of the thin film filter, even if the material of the molded body is different, by changing only the thin film filter (other types). It has the advantage that the parts can be molded as they are. Furthermore, in the present invention, since a transparent mold with micropores is used, it is possible to remove the solvent uniformly, and it is possible to obtain a molded product with few drying cracks and no density unevenness. Since it was used on the solvent discharge side of the mold and the other parts were non-transmissive, it was possible to mold a molded article with high shape accuracy.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the mold according to the present invention, FIG. 2 is a sectional view showing another embodiment of the mold according to the present invention, and FIG. 3 is a sectional view showing another embodiment of the mold according to the present invention. FIG. 7 is a cross-sectional view showing another example. DESCRIPTION OF SYMBOLS 1... Non-transmissive type, 2... Container part, 3... Thin film filter, 4... Transparent type, 5... Discharge part, 6
...Non-transmissive type, 7... Non-transmissive type, 8... Injection part,
9... Slurry reservoir part, 10... Non-transparent type.

Claims (1)

[Scope of Claims] 1. A mold using a permeable mold having micropores on the solvent discharge side, and a non-permeable mold in other parts, and a thin film filter is provided on the molding surface side of the permeable mold. A mold that is characterized by: 2. The mold according to claim 1, further comprising an injection part for injecting slurry and pressurizing the slurry, and a discharge part for discharging a solvent in the slurry. 3. The mold according to claim 1, wherein the thin film filter has a thickness of 1 mm or less. 4. The mold according to claim 1, wherein the thin film filter is of a screen type. 5. The mold according to claim 4, wherein the thin film filter has an average pore diameter of 0.1 to 25 μm. 6. The mold according to claim 1, wherein the thin film filter has flexibility. 7. Using a permeable mold with micropores on the solvent discharge side, the other parts are non-permeable, and introducing slurry into a mold equipped with a thin film filter on the molding surface side of the permeable mold, A method for molding an article, characterized in that a molded article is obtained by removing the solvent from the slurry through the permeable mold. 8 A permeable mold having micropores on the solvent discharge side is used, the other parts are non-permeable, and a thin film filter is provided on the molding surface side of the permeable mold, and the slurry injection part and the solvent in the slurry are A molded body is obtained by injecting slurry from the injection part into a mold equipped with a discharge part, pressurizing the slurry, and then removing the solvent from the discharge part of the mold through the permeable mold. A pressure casting method characterized by: 9. The pressure casting method according to claim 8, wherein the article is a ceramic turbine rotor. 10. The pressure casting method according to claim 8, wherein the pressurizing pressure is 5 kg/cm ² or more.