JPH0714606B2 - Method for preparing ceramic clay - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preparing a ceramic body that does not contain defects such as gaps.

[Prior Art] Conventionally, in extrusion molding of ceramics using a poorly plastic non-clay material such as Si ₃ N ₄ , SiC, Al ₂ O ₃ and ZrO ₂ , defects such as minute gaps and voids are included. It is difficult to obtain an extruded kneaded clay, and when extrusion molding is performed using a kneaded clay containing such defects, defects caused by the defects in the above kneaded clay remain in the compact and the sintered body. However, it was a cause of defects.

Therefore, conventionally, in order to remove such defects, a method of applying hydrostatic pressure after coating a hydrostatic protective film on an extrusion-molded body has been generally used.

[Problems to be Solved by the Invention] However, in the method of applying hydrostatic pressure to a molded product, it is difficult to form a hydrostatic pressure protective film on a molded product having a complicated shape, and the molded product is damaged. I was afraid.

[Means for Solving the Problems] Accordingly, the present invention is intended to solve the above-mentioned conventional problems, and according to the present invention, the ceramic kneaded clay previously vacuum-kneaded is at least 300 kg / cm. Provided is a method for preparing a ceramic kneaded clay which is pressurized with ^two or more hydrostatic pressures.

That is, the present invention is characterized in that the hydrostatic pressure is applied to the ceramic kneaded clay that has been subjected to vacuum kneading in advance before molding, not to the molded body.

The hydrostatic pressure condition is required to be at least 300 kg / cm ² , and preferably 500 kg / cm ² or more. If the hydrostatic pressure is lower than 300 kg / cm ² , it is difficult to remove the defects in the kneaded clay.

The ceramic kneaded material used in the present invention is of course applicable even if it is made of a clay-containing raw material, but is particularly useful for a clay-free non-clay raw material having poor plasticity. This is because it is difficult to obtain a uniform kneaded material containing no internal defects even by the usual vacuum kneading with the ceramic kneaded material made of such a non-clay-based raw material having poor plasticity.

The type of the non-clay-based raw material is not particularly limited, and powders such as Si ₃ N ₄ , SiC, Al ₂ O ₃ , and ZrO ₂ are used, and are used for manufacturing ceramic products according to their material characteristics. . For example, ceramic honeycomb structure, especially when used in pressure wave type supercharger, etc., Si ₃ N ₄ , SiC, etc., lightweight,
A raw material having excellent properties such as heat resistance, low thermal expansion and high strength will be used.

Further, it is preferable to subject the ceramic kneaded clay to vacuum kneading in advance, from the viewpoint of improving the defect removal effect when hydrostatic pressure is applied. This is because if vacuum kneading is not performed, the air at the time of kneading remains and the defect does not disappear even if hydrostatic pressure is applied.

The water content of the ceramic kneaded material is generally 15 to 20%, and it is preferable to add a binder such as methylcellulose as necessary to impart plasticity to the kneaded material.

Since the ceramic kneaded clay prepared as described above does not include defects such as gaps in the kneaded clay as described above, a molded body after extrusion molding using the kneaded clay and a sintered body after firing ( Ceramics products) have very few defects.

Similarly, when the kneaded material is used for forming a round iron, the defects in the molded body and the sintered body after firing are extremely reduced.

Further, naturally, even when the main body is used as a raw material and ground into an arbitrary shape, defects are extremely reduced in the obtained molded body and the sintered body after firing.

Next, a process for producing a ceramic product using the ceramic kneaded clay prepared by the method of the present invention will be described.

First, the ceramic kneaded material previously subjected to vacuum kneading as described above is pressurized with a hydrostatic pressure of at least 300 kg / cm ² to prepare the ceramic kneaded material of the present invention, and the kneaded material is then formed into, for example, a honeycomb structure. By extrusion molding into a molded body such as a body, then drying, firing, and if necessary, grinding,
Ceramic products such as honeycomb structures are manufactured.

In the drying step, the molded body is heated and dried with hot air or the like, and then calcined in the air at a temperature of about 500 ° C. to decompose and remove the organic binder, and then, for example, silicon nitride (Si
₃ O ₄ ) in a nitrogen atmosphere at 1700 to 1800 ° C for 1 to 4 hours, and in the case of silicon carbide (SiC) in an Ar gas atmosphere.
Bake at 950-2200 ° C for 1-2 hours. Then, after firing, the obtained sintered body is subjected to grinding if necessary, whereby a ceramic product can be obtained.

[Examples] Hereinafter, the present invention will be described in more detail based on examples, but it will be apparent that the present invention is not limited to these examples.

(Examples 1 to 5, Comparative Examples 1 and 2) 500 kg of a raw material composed of 100 parts of silicon nitride powder having an average particle size of 10 microns, 8 parts of magnesium oxide as a sintering aid, and 5 parts of cerium oxide, and 6 parts of methylcellulose powder as a binder. Part and 22 parts of water are added externally, and after sufficiently kneading with a kneader to make a mud state, auger screw diameter 100 mm
(Φ) vacuum kneading machine vacuum kneading machine, diameter 130mm
(Φ), a solid columnar kneaded clay having a length of 500 mm was produced.

Each of the 6 columnar kneaded clay thus produced was vacuum-deaerated in a vinyl bag while being hermetically packaged.
100kg / cm ² , 300kg / cm ² , 500kg / cm ² , 1000kg / cm
^The pressure was applied by a hydrostatic pressure of ² , 2500 kg / cm ² , 7,000 kg / cm ² .

As a means to apply hydrostatic pressure, at a hydrostatic pressure of 2500 kg / cm ² or less, put the kneaded clay sealed in a plastic bag in a steel pressure container, fill it with water as a pressure medium, and then add it to the intensifier. In this method, the pressure medium that has been pressurized by pressurizing is press-fitted to increase the pressure to a predetermined pressure. With a hydrostatic pressure of 7000 kg / cm ² , a steel pressure vessel was similarly filled with an antifreeze solution containing ethylene glycol as a pressure medium, and the lid of the pressure vessel was directly pressed into the kneaded clay that was hermetically wrapped in a vinyl bag. Was applied. Of course, the same effect can be obtained by using not only liquid but also gas as the pressure medium. Needless to say, it is necessary to select a hermetically sealed packaging material that is impermeable to the pressure medium gas or liquid.

Furthermore, as the pressure medium temperature, it is important to select a temperature at which the kneaded clay does not deteriorate. For example, when methylcellulose is used, the pressure medium must be controlled at a temperature below 40 ° C which is the gelation temperature.

In addition, for comparison, a columnar kneaded clay to which no hydrostatic pressure was applied was also prepared at the same time.

From each of the columnar kneaded clay, a plate having a thickness of 10 mm was cut out perpendicularly to the extrusion direction and the extrusion direction and observed by X-ray. As shown in FIG. 6 (Comparative Example 1), the kneaded clay was subjected to no hydrostatic pressure. As can be seen, it was found that many spiral layered defects were included.

In addition, as the hydrostatic pressure was increased, the defects in the kneaded clay decreased, and FIGS. 1 to 5 (Examples 1 to 5) and 7
As shown in the figure (Comparative Example 2), at least 300 kg / cm ²
It was found that the above defects completely removed the defects in the kneaded clay.

(Examples 6 to 10, Comparative Examples 3 to 5) Using the kneaded clay obtained in Examples 1 to 5 and Comparative Examples 1 and 2, 60 mm (width) x 60 mm (length) x 10 mm (height) Extruded into square plate, dried and then calcined in air at 500 ° C to decompose and remove the organic binder, fired at 1750 ° C for 1 hour in N ₂ atmosphere, and processed into 3mm x 4mm x 40mm test piece The strength was measured.

Incidentally, after molding and drying, a rubber coating was applied and hydrostatic pressure of 2500 kg / cm ² was applied to remove defects in the molded body. N
O.8)].

The results are shown in Table 1.

As is clear from Table 1, according to the present invention in which extrusion molding is performed by using a kneaded clay to which hydrostatic pressure is applied, the average strength of test pieces is improved, and at the same time, variations in strength are reduced. Further, since the Weibull coefficient, which is a reliability parameter, is also improved, it is clear that the effect of the present invention is remarkable.

(Examples 11 to 15 and Comparative Examples 6 to 7) The kneaded clay obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was used to extrude a rod of 25 mm (φ) × 100 mm (length). ,
After drying, the organic binder was decomposed and removed by calcining at 500 ° C. in the air, and calcined at 1750 ° C. for 1 hour under N ₂ atmosphere. When the hydrostatic pressure for pressing the kneaded material was 100 kg / cm ² or less, such large-diameter solid compacts had many cracks during drying due to defects existing in the compacts. Further, as shown in Table 2, the 4-point bending strength of the cut-out test piece of 3 mm × 4 mm × 40 mm also shows the same tendency as in Examples 6 to 10 and Comparative Examples 3 to 4, and the hydrostatic pressure for pressing the kneaded clay was At least 300 kg / cm ²
Above, the value was almost constant.

(Examples 16 to 20 and Comparative Examples 8 to 9) The kneaded clay obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was cut into a length of 250 mm to obtain a cylindrical kneaded clay having a diameter of 130 mm and a length of 250 mm. This kneaded material was crushed into a circular trowel by pressing at a pressure of ² kg / cm ² to form a suspended insulator having a diameter of 250 mm. After drying, the organic binder was decomposed and removed by calcining at 500 ° C. in the air, and calcined at 1790 ° C. for 1 hour under N ₂ atmosphere. Hydrostatic pressure
In the molded body using the kneaded material of 100 kg / cm ² or less, cracks frequently occurred during drying due to defects inside the molded body caused by defects in the kneaded material as shown in FIGS. 6 and 7. .

Further, as shown in Table 3, Examples 6 to 10 and Comparative Examples 3 to
The same tendency as in No. 4 was exhibited, and the hydrostatic pressure for pressurizing the kneaded material was at least 300 kg / cm ² or more, and showed a substantially constant value.

[Effects of the Invention] As described above, according to the method for preparing a ceramic kneaded clay of the present invention, it is possible to obtain a ceramic kneaded clay that does not include defects such as layered minute gaps and voids in the kneaded clay. As a result, as a result, layered defects, streak-shaped defects, and continuous defects of small holes are similarly removed in the molded body and the sintered body produced using the ceramic kneaded clay, so that the average strength is An improved and reliable product can be obtained.

[Brief description of drawings]

1 to 5 are X-ray photographs of the kneaded clay obtained by the method for preparing a ceramic kneaded clay according to the present invention, and FIGS. 6 to 7 are the kneaded clay obtained by a method other than the present invention. It is an X-ray photograph of the soil. In these drawings, the left photograph shows a cross section perpendicular to the extrusion direction, and the right photograph shows a central cross section cut parallel to the extrusion direction.

Claims (3)

[Claims] 1. A ceramic kneaded material which has been subjected to vacuum kneading in advance,
A method for preparing a ceramic kneaded clay, which comprises applying a hydrostatic pressure of at least 300 kg / cm ² or more. 2. The method for preparing a ceramic kneaded clay according to claim 1, wherein the hydrostatic pressure is 500 kg / cm ² or more. 3. The method for preparing a ceramic kneaded clay according to claim 1, wherein the kneaded clay does not contain clay.