JPH046521B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention involves injecting ceramic clay prepared by a vacuum clay mixing process into a clay holding part and holding it therein, and then soaking a part of the molding surface of an impermeable mold with water. This invention relates to a method and apparatus for molding ceramics by pressure injection into a mold made of a material with a contact angle of 80 degrees or more. [Prior Art] Injection molding, pressure casting, and wet pressure molding are conventionally known methods for producing ceramic molded bodies having relatively complex shapes. In the injection molding method, a ceramic molded body is obtained by mixing ceramic powder with an organic binder consisting of a resin such as polyethylene or polystyrene and wax, molding this mixed raw material with an injection molding machine, and degreasing the obtained molded body. It's a method. The pressure casting method involves mixing ceramic powder, water, and molding aids such as deflocculants to form a slurry, injecting this slurry into a casting mold, and pressurizing the slurry for casting. This is a method for obtaining ceramic molded bodies. In addition, the wet pressure molding method is a method of obtaining a ceramic molded body by mixing and kneading ceramic powder, water, and molding aids such as a binder to form a clay, and placing this clay in a mold and press-molding it. be. [Problems to be Solved by the Invention] However, the conventional injection molding method described above has a drawback in that the degreasing process of the injection molded article obtained by injection molding requires a long time. In addition, with the pressure casting method, shape retention after molding is poor, and it is difficult to release from the mold. Products with complex shapes are more likely to slip and leak than the surface of the mold, and the molding time is long. There are drawbacks such as the need for Furthermore, the wet pressure molding method has the problem that it is difficult to release from the mold and cracks are likely to occur. [Means for Solving the Problems] In view of the above-mentioned problems, the inventors of the present invention have made extensive studies and have arrived at the present invention. That is, according to the present invention, after the ceramic clay prepared by the vacuum clay kneading process is once injected into the clay holding part and held, the ceramic clay is made into a non-permeable type or a permeable type. A method for molding ceramics comprising a combination of non-permeable molds, characterized in that a part of the molding surface of the non-permeable molds is injected under pressure into a mold made of a material having a contact angle with water of 80 degrees or more. , and an injection/holding means for injecting and holding the ceramic clay prepared by the vacuum clay kneading process, and a mold for pressurizing and injecting the ceramic clay from the injection/holding means. , a non-permeable mold, or a combination of a permeable mold and a non-permeable mold, with a part of the molding surface of the non-permeable mold made of a material having a contact angle with water of 80 degrees or more. Provided is a ceramics molding device characterized by the following. In the present invention, a part of the molding surface of the non-permeable mold is made of a material having a contact angle with water of 80 degrees or more as a mold for pressure-injecting ceramic clay. In other words, in a mold consisting of a non-permeable mold or a combination of a permeable mold and a non-permeable mold, a part of the molding surface of the non-permeable mold is made of water, such as a fluororesin such as polytetrafluoroethylene. By forming the material with a contact angle of 80 degrees or more, preferably 85 degrees or more, more preferably 90 degrees or more,
This improves the releasability from the molded body. If the contact angle with water is smaller than 80 degrees, mold release properties will be poor. Especially when molding complex shapes such as ceramic turbine rotors, the contact angle with water is 90°.
It is preferable to use a material with a strength higher than 100% because there will be no damage due to mold release. Materials that form part of the non-permeable molding surface and have a contact angle with water of 80 degrees or more include polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polytrifluorochloroethylene,
Examples include fluororesins such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polypropylene, various waxes, and the like. In addition, as a means of constructing a part of the molding surface of the non-transparent mold using the above-mentioned material, the non-transparent mold itself may be created using this material, but from the viewpoint of economy, the molding surface of the non-transparent mold It is preferable to carry out this by coating. Furthermore, if a fluororesin or the like is used as the material, it can be easily directly coated on a metal non-transparent mold. Furthermore, as the transmission mold used in the present invention, conventionally known molds can be used. Permeable molds need to have good air permeability in order to improve air removal, while also ensuring the strength of the mold itself, and are usually used with an average pore diameter of 0.1 to 50 μm. .
In addition, molding surface layers with different average pore diameters of 0.1 to 50μ
It is also possible to use a mold with a two-layer structure consisting of a combination of a pore size of 50 m and a coarse pore size of about 50 to 500 μm in the lower layer. The material of the transparent type is not limited,
In addition to materials with good water absorption such as plaster, resins, ceramics, metals, composite materials thereof, etc. can also be used. Further, as the non-transparent mold used in the present invention, those conventionally and generally used can be used, and for example, in addition to a metal mold, a synthetic resin mold or a rubber mold can be used. The ceramic clay used in the present invention consists of ceramic powder containing a sintering aid, a forming aid, and water. Ceramic powders include conventionally known oxides such as alumina and zirconia, as well as nitrides such as silicon nitride, known as new ceramics, carbides such as silicon carbide, and composite materials thereof. be able to. The type of sintering aid is not particularly limited, and the commonly known sintering aids include Mg, Al, Y,
Sintering aids such as oxides, nitrides, and carbides of Ce, Zr, Sr, B, Ta, etc. can be used, and are appropriately selected depending on the ceramic powder used. The mixing ratio of ceramic clay is 100 parts by weight of ceramic powder, 10 to 45 parts by weight of water, and 0.1 to 30 parts by weight of molding aid.
parts by weight, preferably 100 parts by weight of ceramic powder,
15 to 35 parts by weight of water and 0.6 to 15 parts by weight of molding aid.
Further, a more preferable mixing ratio of water is 10 to 25 parts by weight. If the proportion of water is less than 10 parts by weight, the kneading properties will be poor and a homogeneous clay for molding will not be obtained; if it exceeds 45 parts by weight, the density of the resulting molded product will be low and the firing shrinkage will be large. It becomes difficult to obtain products with high dimensional accuracy. On the other hand, if the amount of molding aids such as binders and dispersants is less than 0.1 parts by weight, there is no effect, and if it exceeds 30 parts by weight, it will take time to remove the molding aids and the product will be prone to cracking, which is undesirable. When preparing ceramic clay using the vacuum clay kneading process, a vacuum clay kneading machine that combines a commonly used pack mill and an auger machine can be used to produce homogeneous and defect-free clay. To achieve this, it is necessary to consider the structure of the auger screw, pillar ring, die, etc., extrusion speed, temperature adjustment of the clay, etc. The degree of vacuum in the vacuum clay kneading step may be in a reduced pressure state, but it is usually preferably 60 cmHg or more. By being in a reduced pressure state, the diffusion of water becomes significant, the formation of a water film on the clay becomes faster, and a homogeneous clay is obtained.
Furthermore, for products requiring high strength such as ceramic turbine wheels, the degree of vacuum is preferably 70 cmHg or higher, since air bubbles in the clay may cause breakage. Next, in the present invention, the ceramic clay adjusted to a predetermined value by the vacuum clay kneading process is once injected into the clay holding part and held therein. By separating the vacuum clay kneading process and the molding process, molding conditions such as increasing the pressure and pressure injection speed can be easily set according to the molded product, and it is also possible to create a homogeneous mold with no difference in temperature distribution. Soil can be prepared and a molded body without molding defects can be obtained. In addition, by using a material with a contact angle of 80 degrees or more with water for the clay contacting part of the clay holding part, the friction between the clay holding part and the clay is reduced, reducing pressure loss and frictional heat. This is preferable. Specifically, a plunger type extruder is preferably used as the clay holding part (ie, injection/holding means), but other ordinary cylinders and the like can also be used. The size of the injection port of the clay holding part into the mold needs to be set depending on the shape and volume of the molded object.In order to reduce the friction between the clay holding part and the clay, the size of the injection port The larger the size, the better. On the other hand, the pressure applied to the ceramic clay mold is preferably 5 kg/cm ² or more, more preferably 10 kg/cm ² or more. If the pressure is less than 5 Kg/cm ² , the clay may not be filled or the density of the molded product will be low, making it easy to deform. It is also possible to use a high pressure of over 700 kg/cm ² as the pressurizing pressure, but due to the high pressure, the mold becomes larger and heavier, and the molding machine becomes larger, so operation Sexuality becomes worse. For this reason, it is preferable to conduct the heating at 700 kg/cm ² or less. The pressurized injection speed when injecting ceramic clay into a mold is the ratio of the pressurized injection speed (cm ³ /sec) to the molded object surface area (cm ² ) (pressure injection speed /
The surface area of the molded product is desirably 0.7 or more and 10 or less. If the above ratio is less than 0.7, defects such as cracks and wrinkles are likely to occur on the surface of the molded product. On the other hand, even if the ratio exceeds 10, molding is possible, but the molding equipment becomes larger, resulting in poor operability, and unnecessarily high costs are required, which is not economical. [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 to these Examples. Example 1 SiC powder containing sintering aid (average particle size 0.7 μm) 100
To the weight part, 25 parts by weight of water, 5 parts by weight of a binder as a molding aid, and 1 part by weight of a dispersant were mixed, and the mixture was kneaded using a pressure kneader. Thereafter, vacuum clay kneading was performed at the degree of vacuum shown in Table 1, and clay of 60 mm (φ) x 100 mm (length) was extruded. Next, after injecting the clay 9 into the clay holding part 5 of the molding device for a turbine rotor (blade diameter 85 mmφ, blade height 30 mm) shown in FIG. 1 through the clay holding part injection port 11, the pressurizing piston 8 is lower it,
After the clay holding part inlet 11 was sealed, the clay holding part 5 was vacuum degassed from the discharge port 7. Then Table-1
Pressurized injection was carried out from the injection port 6 [12 mm (φ)] using the pressure shown in FIG. For comparison, molding of clay only kneaded with a pressure kneader without vacuum kneading, and the surfaces of the molded bodies of non-permeable molds 1 and 3 and non-permeable slide core 2 shown in FIG. Molding without Teflon coating (polytetrafluoroethylene, contact angle (θ) 108 degrees) was also conducted at the same time to obtain molded products as shown in Table 1. Next, the molded body was dried at 100° C. for 5 hours using a constant temperature and humidity chamber at a rate of 5° C./hr while the humidity was gradually lowered from 98%. As is clear from Table 1, it can be seen that by using the molding method and molding apparatus of the present invention, a molded product with good mold releasability and no cracks in appearance or cracks after drying can be obtained. .

[Table] *1 There are slight unfilled areas at two blade tips Example 2 Si ₃ N ₄ powder containing sintering aid (average particle size 1 μm)
, a molding aid, and water were mixed as shown in Table 2,
Knead using a pressure kneader, then use a vacuum kneader (vacuum degree 75cmHg) to 60mm (φ) x 70mm (length)
We extruded clay having the shape of . Next, the four blade shapes shown in Figure 2 [blade diameter 90 mm (φ), blade height 40 mm]
Materials with different contact angles were fixed to the surface of the wing part 10 of the mold, and the injection port was placed at a pressure of 500 kg/cm ² using the clay 9 prepared as described above under the molding conditions shown in Table 2. 6. Inject under pressure from [24mm (φ)], 10
The mold was released after a few seconds to obtain a molded product as shown in Table 2. As is clear from Table 2, it was found that a good molded product could be obtained by using a material with a contact angle (θ) of 80 degrees or more on the surface of the mold. In addition, when molding a turbine rotor etc. with a more complex shape,
It is clear that it is necessary to use a material with a contact angle (θ) of 90 degrees or more that does not cause even the slightest chipping, since it becomes more difficult to release from the mold. Next, the molded body was dried at 100° C. for 5 hours using a constant temperature and humidity chamber at a rate of 5° C./Hr while gradually lowering the humidity from 98%. Next, it was degreased at 500℃ for 10 hours using a hot air circulation electric furnace, then packed in ice packs and rubber press molded at a pressure of 3 tons/cm ² , and then heated at 1730℃ in an N ₂ atmosphere. Sintering was performed for 1 hour to obtain a sintered body.

【table】

[Table] *1 There were slight chips in two places on the tip of the wing.
*2 There was a slight chip on one part of the wing tip.
Example 3 Si ₃ N ₄ powder containing sintering aid (average particle size 0.8 μm)
100 parts by weight were mixed with 24 parts by weight of water, 3 parts by weight of a binder as a molding aid, and 0.5 parts by weight of a dispersant, and kneaded using a pressure kneader. After that, vacuum soil kneading (degree of vacuum 76cmHg) was performed, and the size was 60mm (φ) x 300mm (length).
The clay was extruded. Next, the test piece type (60 mm x 60 mm) shown in Fig. 3, the piston cavity type (outside diameter 100 mm (φ) x height 25 mm) shown in Fig. 4, and the turbine rotor type (blade diameter 75 mm (φ)), Wing height 35mm)
are respectively set in the molding device, and after injecting the prepared clay into the clay holding part 5 from the clay holding part injection port 11, the pressurizing piston 8 is lowered, and after sealing the clay holding part injection port 11. Then, the clay holding part 5 was vacuum degassed through the discharge port 7. Thereafter, pressurized injection was performed from the injection port 6 under the molding conditions shown in Table 3, the mold was released after 15 seconds, and molded under the molding conditions shown in Table 3 to obtain the molded product shown in Table 3. Ta. The molded surfaces of the non-transparent molds 1 and 3 and the non-transparent slide core 2 are coated with Teflon (polytetrafluoroethylene, contact angle (θ) 90 degrees). As is clear from Table 3, by using the molding method and molding apparatus of the present invention, molded products with good mold releasability and no appearance cracks can be obtained. It is also seen that a molded article with a better appearance can be obtained by only installing a transparent mold in areas of the mold where air escape is difficult, or by performing vacuum degassing from the transparent mold. Furthermore, the pressure injection speed/molded object surface area
It can be seen that a molded article with no cracks or wrinkles in appearance can be obtained at a value of 0.7 or higher.

[Table] [Effects of the Invention] As explained above, according to the ceramic molding method and molding apparatus of the present invention, the molding time is short, no leakage occurs during molding, the mold releasability is good, and the appearance is improved. , a good molded product without deformation can be obtained.

[Brief explanation of drawings]

1 to 4 are cross-sectional views showing ceramic molding apparatuses that are embodiments of the present invention. 1... Non-transparent type, 2... Non-transparent slide core, 3... Non-transparent type, 4... Transparent type, 5...
Clay holding part, 6... Inlet, 7... Outlet, 8...
...pressurizing piston, 9... clay, 10... wing section,
11... Clay holding part inlet, 12... Outlet.

Claims (1)

[Claims] 1. Once the ceramic clay prepared by the vacuum clay kneading process is injected into the clay holding part and held,
The ceramic clay is made of a non-permeable type or a combination of a permeable type and a non-permeable type, and a part of the molding surface of the non-permeable mold is made of a material having a contact angle with water of 80 degrees or more. A ceramic molding method characterized by pressurized injection into a mold. 2. Injection/holding means for injecting/holding the ceramic clay prepared by the vacuum clay kneading process;
A mold for pressurizing and injecting the ceramic clay from the injection/holding means, which is composed of a non-permeable mold or a combination of a permeable mold and a non-permeable mold, and the molding die of the non-permeable mold. A ceramic molding device comprising a mold whose surface is partially made of a material having a contact angle with water of 80 degrees or more.