JPH05185414A - Cold isotropic pressure molding method of ceramics - Google Patents

Abstract

PURPOSE:To obtain a molded product reduced in residual strain and generating no crack at the time of baking in the production of a large-sized product as a result by the cold isotropic pressure molding of ceramics. CONSTITUTION:A cast molded product demolded after cast molding is dried and, after 1-7% of water is added to the dried cast molded product, latex is applied to the molded product. The latex coated cast molded product is subjected to cold isotropic pressure treatment (CIP treatment) and the latex is subsequently removed to obtain a molded product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold isostatic pressing method for ceramics which is formed by performing cold isostatic pressing (CIP) after casting.

[0002]

2. Description of the Related Art Heretofore, there has been known a cold isostatic pressing method for ceramics which is obtained by performing a cold isostatic pressing process (CIP process) after cast molding with a gypsum mold. That is, as shown in an example of the flowchart in FIG. 3, a ceramic slurry is cast into a molded body such as a gypsum mold, and then the mold is released and dried to obtain a cast molded body. A substance such as a latex that forms a rubber film was applied to the body, the cast molded product provided with the rubber film was subjected to CIP treatment, and finally the rubber film composed of the latex or the like was removed to obtain a molded product.

[0003]

However, in the above-mentioned conventional molding method, the cast molding has a residual strain due to a difference in density between the inside and the outside which occurs when it is cast into a plaster mold or the like. Since the molded body is directly subjected to CIP processing,
The residual strain still remains in the molded product after the CIP treatment. As a result, when the obtained molded body is fired, cracks are generated on the surface of the fired body, and there is a problem that it is not possible to obtain a ceramic fired body having good properties particularly in the production of large-sized products.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a cold isostatic pressing method for ceramics, which has a small residual strain and, as a result, can obtain a molded product which is free from cracking during firing even when manufacturing a large-sized product.

[0005]

According to the method for cold isostatic pressing of ceramics of the present invention, after the cast molding, the released cast molded article is dried, and the dried cast molded article is 1-7. % Of water is applied, latex is applied, and a casting is applied with cold, isotropic pressure treatment (CIP treatment) is performed, and then the latex is removed to obtain a molded article. Is to

[0006]

In the above-mentioned structure, the CIP treatment is not performed on the dry cast-molded product as it is, but the CIP treatment is performed after containing 1 to 7% of water.
The residual strain caused by the difference in density between the inside and outside during cast molding is CI
It can be relaxed during the P treatment, and a molded product with less residual strain can be obtained. As a result, by firing the obtained molded body, it is possible to obtain a fired body free from firing cracks even in the production of large-sized products.

In the present invention, the water content is 1 to 7
As will be apparent from the examples described below, when the water content is less than 1% or more than 7%, residual strain is not sufficiently removed and the obtained molded body is fired. This is because cracks due to firing breakage occur.
Further, it is preferable that the water content is 2 to 5% because cracks are not generated at all.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing the steps of an example of the cold isostatic pressing method for ceramics of the present invention. In this embodiment, first, a ceramic slurry prepared in advance is cast into a plaster mold or the like by various conventionally known methods to perform casting. Next, after a lapse of a predetermined time, after curing, the mold is released to obtain a cast molding, and the obtained cast molding is once dried. Next, the water content of the cast-molded body is adjusted to a range of 1 to 7% by means such as immersing the dried cast-molded body in water. Here, the drying step is not always essential, but it is preferable to previously dry a mold such as a gypsum mold because it becomes a standard for knowing the water absorption amount.

Thereafter, as in the conventional method, a substance such as a latex that forms a rubber film is applied to the cast molded product having the water content adjusted, and the cast molded product provided with the rubber film is subjected to CIP treatment, and finally. A rubber film made of latex or the like is removed to obtain a molded body. Here, conditions such as application of a substance such as a latex that will be a rubber film and CIP treatment are the same as those in the conventional method, and thus will not be described in detail here. Further, it is preferable that the latex coating is left for a fixed time of 48 hours or less so that the water content becomes uniform throughout the CIP treatment.

An actual example will be described below. EXAMPLE A slurry of partially stabilized zirconia was prepared as shown in FIG.
It is cast into a plaster mold for obtaining an impeller 5 including a cylindrical boss portion 1 having a shape shown in (a) and (b), a disc-shaped plate portion 2, a plurality of blade portions 3, and a plurality of protrusion portions 4. After the cast molding, the mold was released and dried to obtain a dried cast molded product having a water content of 0.5%. The water content of the obtained cast-molded body is adjusted by a method such as immersion in water to obtain a water content of 1.0% to 1%.
A cast molding containing 1.0% of the water content shown in Table 1 was prepared. After applying latex to the prepared cast molding,
CIP treatment was performed under a pressing force of 2500 kg / cm ² to obtain an impeller-shaped compact. After further drying the molded body after the CIP treatment, a plurality of strain gauges are installed at the same position of the molded body and the residual strain under each condition is measured by the strain gauge to obtain the maximum value of the compressive strain and the maximum value of the tensile strain. At the same time, the generation of cracks after firing the molded body under the same normal conditions was visually confirmed. The results are shown in Table 1.

[0011]

[Table 1]

From the results shown in Table 1, the water content before CIP was adjusted to 1.0 in consideration of at least the occurrence of cracks after firing.
% -7.0%, and must be 2.0
It can be seen that the range of up to 5.0% is preferable. This is because the inclusion of water within the range of the present invention improves the sliding between particles in the molded body, and a more uniform molded body can be obtained by CIP treatment.

[0013]

As is apparent from the above description, according to the present invention, molding with a small residual strain is performed by adding a predetermined amount of water to the cast-molded product before the CIP process and then performing the CIP process. A body can be obtained, and as a result, if the obtained molded body is fired, a fired body having no firing crack can be obtained even in the production of a large product.

[Brief description of drawings]

FIG. 1 is a flow chart showing steps of an example of a method for cold isostatic pressing of ceramics of the present invention.

FIG. 2 is a diagram showing a structure of a molded body in an example of the present invention.

FIG. 3 is a flow chart showing steps of an example of a conventional cold isostatic pressing method for ceramics.

Claims (1)

[Claims] 1. A cast-molded body which has been released from the mold after the cast-molding is dried, and the dried cast-molded body is impregnated with 1 to 7% of water and then coated with latex, and the cast is coated with latex. A method for cold isostatic pressing of ceramics, characterized in that a molded body is obtained by subjecting a molded body to cold isostatic pressing treatment (CIP treatment) and then removing latex.