JPH01304902A - Method and apparatus for forming ceramic - Google Patents

Abstract

PURPOSE:To shorten a formation time by a method wherein ceramic body, which is once poured and held in a body holding part, is finally poured in a forming mold, which is non-permeable and a part of the forming surface of which consists of material having the contact angle of 80 deg. or more to water. CONSTITUTION:Ceramic body containing sintering aid and the like is prepared by kneading and pugging. Body 9 is poured from a body holding part pouring port 11 to the body holding part 5 of a forming device of turbine rotor. After that, the body holding part pouring port 11 is tightly closed by lowering a pressurizing piston 8 so as to deaerate the body holding part 5 by vacuum through an exhaust port 7. Next, the pouring of the body through a pouring port 6 under pressure is done by applying pressurizing force to the body in order to produce a formed body. As the forming mold for pouring the ceramic body under pressure, the mold is made non-permeable and a part of its forming surface consists of Teflon, the contact angle of which to water is 80 deg. or more, resulting in improving the shape retention and releasability of an item having complicated shape.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method of injecting ceramic clay prepared by a vacuum clay kneading process into a clay holding part and holding it therein, and then pouring it into a molding surface of a non-permeable mold. The present invention relates to a method and apparatus for molding ceramics by injecting a portion of the ceramic under pressure into a mold made of a material having a contact angle with water of 80 degrees or more.

[Prior Art] Injection molding, pressure casting, and wet pressure molding are conventionally known methods for manufacturing 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 resin such as polyethylene or polystyrene and wax, molding this mixed raw material with an injection molding machine, and degreasing the resulting molded body. It's a method.

The pressure casting method involves mixing ceramic powder, water, and forming aids such as deflocculants to create a slurry, injecting this slurry into a casting mold, and pressurizing the slurry to perform casting. This is a method for obtaining a ceramic molded body.

In addition, the wet pressure molding method is a method in which a ceramic molded body is obtained by mixing and kneading ceramic powder, water, and molding aids such as a binder to form a clay, and placing the 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, and products with complex shapes are more likely to slip and leak than the mating surface, resulting in a long molding time. There are drawbacks such as the need for

Furthermore, the wet pressure molding method has problems in 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 conducted intensive 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, 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 forming apparatus is provided, characterized in that it consists of:

In the present invention, as a mold for pressure-injecting ceramic clay, 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. That is, in a mold consisting of a non-transparent mold or a combination of a transparent mold and a non-transparent mold, a part of the molding surface of the non-transparent mold is, for example,
By forming it from a material such as a fluororesin such as polytetrafluoroethylene, which has a contact angle with water of 80 degrees or more, preferably 85 degrees or more, and more preferably 90 degrees or more, it has good mold releasability from the molded product. It will become.

If the contact angle with water is less than 80 degrees, the mold releasability will be poor. Particularly when molding a complex-shaped object such as a ceramic turbine rotor, it is preferable to use a material having a contact angle with water of 90 degrees or more, since there will be no damage due to mold release.

Materials that form part of the molding surface of non-permeable molds and have a contact angle with water of 80 degrees or more include polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polytrifluorochloroethylene, and tetrafluoroethylene. Orethylene-
Examples include fluororesins such as barfluoroalkyl vinyl ether copolymers, 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, it is possible to create the non-transparent mold itself using this material, or 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 transparent type used in the present invention, conventionally known types can be used. The permeable mold needs to have good air permeability in order to improve air removal, while also ensuring the strength of the mold itself, and usually has an average pore diameter of 0.1 to 50 J.
Lm is used. In addition, the molding surface layer with a different average pore diameter has a pore diameter of 0°1 to 50 JLm, and the lower surface layer has a pore diameter of 5.
A two-layer mold having a combination of coarse pore diameters of about 0 to 500 gm can also be used. The material for the transparent type is not limited, and 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.

As ceramic powder, in addition to conventionally known oxides such as alumina and zirconia, nitrides such as silicon nitride, carbides such as silicon carbide, which are known as new ceramics, and composite materials of these are used. be able to.

The type of sintering aid is not particularly limited, and generally known Mg, An, Y, Ce, Zr,
Sintering aids such as oxides such as Sr, B, and Ta, nitrides, and carbides can be used, and are appropriately selected depending on the ceramic powder used.

The blending ratio of ceramic clay is 100% ceramic powder.
parts by weight, 10 to 45 parts by weight of water, 0.1 to 30 parts by weight of molding aid, preferably 100 parts by weight of ceramic powder, 15 parts by weight of water.
~35 parts by weight, and 0.6 to 15 parts by weight of the molding aid. Further, a more preferable blending ratio of water is 10 to 25 parts by weight. When the proportion of water is less than 10 parts by weight, crosstalk is poor and a homogeneous molding clay cannot be obtained, and when it exceeds 45 parts by weight, the density of the obtained molded product becomes low and the firing shrinkage becomes large. It becomes difficult to obtain products with high dimensional accuracy.

On the other hand, molding aids such as binder and dispersant are 0. If it is less than 1 part by weight, the effect will not be achieved, and if it exceeds 30 parts by weight, it will take a long time to remove the molding aid and the product will be prone to cracking, which is not preferable.

When preparing ceramic clay by the vacuum clay kneading process, a commonly used device that combines a back mill and an auger machine can be used as the vacuum clay kneading machine.
In order to obtain homogeneous and defect-free clay, it is necessary to consider the structure of the auger screw, post ring, die, etc., extrusion speed, temperature adjustment of the clay, etc.

The degree of vacuum in the vacuum clay kneading step may be reduced as long as it is under reduced pressure, but it is usually preferably 60 cmHg or more. By being in a reduced pressure state, the diffusion of water becomes remarkable, and the formation of a water film on the clay becomes faster, resulting in a homogeneous clay. In addition, for products that require high strength, such as ceramic turbine wheels, the degree of vacuum is 70 cm because air bubbles in the clay can cause destruction.
It is preferable that it is Hg or higher.

Next, in the present invention, the ceramic clay prepared in a predetermined manner 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 to suit the molded product.
Furthermore, it is possible to prepare a homogeneous clay with no difference in temperature distribution, and it is possible to obtain a molded article without molding defects. 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. It is preferable to make it.

Specifically, a plunger type extruder is preferably used as the clay holding part (ie, injection/holding means), but other ordinary cylinders and the like may 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 value, the better.

On the other hand, the pressure applied to the mold of the ceramic clay is preferably 5 kg/cm2 or more, more preferably 10 kg/cm2 or more. Pressure: 5 kg/c
If it is smaller than m2, the clay may not be filled or the density of the molded body may be low, causing deformation.

In addition, it is possible to use a high pressure of over 700 kg/c*2 as the pressurizing pressure, but due to the high pressure, the mold becomes larger and heavier, and the molding machine becomes larger, etc. The operability deteriorates. For this reason 700
It is preferable that the weight is less than 2 kg/c.

The pressure injection speed when injecting the ceramic clay into the mold is the ratio of the pressure injection speed (cm'/5ec) to the surface area of the molded body (c+++2) (pressure injection speed/surface area of the molded body) or 0.7. It is desirable that the value is from 10 to 10.

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, if the above ratio exceeds 10, the molding can still be carried out in circular motions, but the molding apparatus becomes larger, resulting in poor operability and unnecessarily high costs, which is not economical.

[Examples] The present invention will be explained in more detail based on Examples below.
It will be clear that the invention is not limited to these examples.

(Example 1) SiC powder containing sintering aid (average particle size 0.7.pm) 1
00 parts by weight, 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 in a pressure kneader. Thereafter, vacuum clay kneading was carried out at the degree of vacuum shown in Table 1, and clay of 60 mm (φ) x 100 mm (length) was extruded. Next, the turbine rotor (blade diameter 85
After injecting the clay 9 into the clay holding part 5 of the molding device for molding apparatus (mmφ, blade height 30cm) from the clay holding part injection port 11, the pressurizing piston 8 is lowered, and the clay holding part injection port 11 is injected. After sealing,
The clay holding part 5 was vacuum degassed from the discharge lower.

Thereafter, by applying the pressure shown in Table 1, the injection port 6 (12 mm
(φ)], and the mold was released after 20 seconds to obtain a molded product as shown in Table 1.

For comparison, molding of clay only kneaded in a pressure kneader without vacuum kneading and molding of the molded body of the non-permeable mold 1.3 and the non-permeable slide core 2 shown in Fig. 1 were carried out. teeth,
Teflon (polytetrafluoroethylene, contact angle (θ)
Molding without coating (108 degrees) was also performed at the same time to obtain molded products as shown in Table 1.

Next, the molded body was heated at 5° C./hr using a constant temperature and humidity chamber and dried at 100° C. for 5 hours while the humidity was gradually lowered from 98%.

As is clear from Table 1, 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. .

(Example 2) Si, N, powder (average particle size lJLm) containing a sintering aid, a forming aid, and water were mixed as shown in Table 2, and kneaded using a pressure kneader. After that, vacuum clay kneading machine (vacuum level 75)
cmHg) 60■(φ) x 70mm (length)
We extruded clay having the shape of . Next, 4 shown in Figure 2
Materials with different contact angles were adhered to the surface of the blade part 10 of a mold having a blade shape (blade diameter 90 mm (φ), blade height 40 cm) and prepared as described above under the molding conditions shown in Table 1-2. Pressure injection was carried out from the injection port 6 (24+l (φ)) at a pressure of 500 kg/C112 using the molded molding material ±9, and the mold was released after 10 seconds to obtain a molded product as shown in Table 2. .

As is clear from Table 2, the contact angle (θ) on the mold surface
It has been found that a good molded body can be obtained by using a material having a temperature of 80 degrees or higher. Furthermore, when molding turbine rotors with more complex shapes, it becomes more difficult to release the mold, so it is clear that it is necessary to use materials with a contact angle (θ) of 90 degrees or more that will not cause even the slightest chipping. It is.

Next, the molded body was heated to 100°C for 5 hours using a constant temperature and humidity chamber at a rate of 5°C/Hr, and then dried while gradually lowering the humidity from 98%. Next, using a hot air circulation electric furnace,
Degreased for 10 hours in SO'C, packed in a container to remove water, and rubber press molded at a pressure of 3 tons/cm2.
Thereafter, sintering was performed at 1730° C. for 1 hour in a N2 atmosphere to obtain a sintered body.

(Hereafter, blank space) (Example 3) Si3N powder containing sintering aid (average particle size 0.8 gm)
100 parts by weight were mixed with 24 parts by weight of water, 3 parts by weight of a binder as molding aids, and 0.5 parts by weight of a dispersant, and kneaded in a pressure kneader. After that, vacuum clay kneading (vacuum degree 76c)
mllg) to extrude a clay having a length of 60 mm (φ)×: lOO× (length). Next, we tested the test piece type (60 mm x 60 mm) shown in Figure 3, the piston cavity type (outside diameter 10 ha (φ) x height 25 am) shown in Figure 4, and the turbine rotor type (blade diameter 75 mm (φ), blade height). 3
5 mm) 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 the clay holding part injection port 1 is injected.
After sealing 1, the clay holding part 5 was vacuum degassed from the discharge lower. 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 body 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 cracks in appearance can be obtained.

It is also seen that a molded product with a better appearance can be obtained by simply installing a transparent mold in areas of the mold where air escape is difficult, or by performing vacuum degassing from the transparent mold.

Furthermore, it can be seen that when the pressure injection speed/molded article surface area is 0.7 or more, a molded article with no cracks or wrinkles in appearance can be obtained.

(Hereinafter, blank space) [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 cracks or deformation can be obtained.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing a ceramic molding apparatus according to an embodiment of the present invention. l... non-transparent type, 2... non-transparent slide core,
3... Non-permeable type, 4... Transparent type, 5... Clay holding part, 6... Inlet, 7... Outlet, 8... Pressurizing piston, 9... ... Clay, 10 ... Wings, 11.
... Clay holding part injection 0.12 ... outlet.

Claims (2)

[Claims] (1) 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 divided into non-permeable type, permeable type and non-permeable type. A method for molding ceramics, comprising: injecting a part of the molding surface of the non-permeable mold under pressure into a mold made of a material having a contact angle with water of 80 degrees or more. (2) 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, 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 device characterized by: