JPH02279570A - Production of structural ceramics body - Google Patents

Abstract

PURPOSE:To produce a structural ceramics body which is excellent in dimensional precision and has a large size or a complex shape without causing a crack and a cutout in the molded body by previously and temporarily calcining the divided lightweight parts and thereafter joining and integrating the parts and recalcining these parts. CONSTITUTION:A temporarily calcined body is formed by utilizing casting slurry and molding two pieces of cylindrical molded bodies by a slurry cast molding method and calcining the molded bodies respectively at the prescribed temp. for a prescribed time. Slurry 3 is applied to the end faces of the temporarily calcined cylindrical bodies 1, 2. The end faces of two cylinders are allowed to abut and integrated. The integrated cylinders are air-dried and thereafter recalcined in the atmosphere of the prescribed temp. to obtain a sintered body wherein two cylinders have been joined. Thereby a structural ceramics body which is excellent in dimensional precision and has a large size or a complex shape is produced without causing a crack and a cutout.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic structure, particularly a large-sized or complicated-shaped ceramic structure.

[Conventional technology]

Conventionally, one of the methods for manufacturing ceramic structures having large or complicated shapes has been to mold the structure into multiple parts, and then to integrate the divided molded parts by joining them together. (JP-A-61-209964, JP-A-63-166767) In particular, in JP-A-63-166767, pre-segmented molding was performed using a slurry casting method (slip casting method). The raw molded bodies are mixed with a slurry having the same composition as the molded bodies (
A sintered body for a structure is obtained by bonding and integrating the materials by using a slip (slip) as an adhesive, drying, and then firing.

However, in this method, the raw molded body formed in one piece does not have sufficient strength, so cracks and chips may occur in the molded body due to handling operations when joining the raw divided molded bodies together. However, large-sized molded bodies also have the problem that the lower part of the molded body deforms due to its own weight during firing, and deformation due to shrinkage on the contact surface tends to occur.

[Problem to be solved by the invention]

The present invention has been made in view of the problems of the prior art described above, and it is possible to prevent cracks or chips from occurring in the molded body when joining the divided molded bodies, and to prevent the molded body from deforming during firing. Therefore, it is an object of the present invention to provide a method for manufacturing a ceramic structure with excellent dimensional accuracy.

[Means to solve the problem]

A method for manufacturing a ceramic structure according to the present invention.

The pre-fired bodies formed by the slurry casting method and fired are joined and integrated with a slurry having the same composition as the fired body, and then fired again. By adopting such a structure, the above-mentioned problems are solved. be.

In the present invention, the target ceramic structure is divided into elements having shapes that are easiest to mold, such as simple plate shapes, square shapes, and tube shapes, and a mold is used to mold each divided element. Prepare. As a mold, a plaster mold is generally used, but locally fired molds, metal molds, etc. can also be used. Each divided element is formed by pouring the 0-11-sized slurry into the mold. As a slurry casting method,
Various conventionally used forming methods can be employed, such as sludge casting, solid casting, vacuum casting, centrifugal casting, and pressure casting. Once the casting is complete, the molded body dries, contracts, and separates from the mold.

The segmented molded body cast in this manner is then dried and calcined. Although the pre-fired body has shrunk relative to the molded body, firing has not yet been completed, and there are voids in the fired body that allow the slurry used in the subsequent joining process to seep in. It is.

Generally, it is preferable that the calcined body has an apparent density of about 93% or less of the theoretical density, and has many voids in the calcined body.

The pre-fired divided calcined bodies are coated with a slip having the same composition as the calcined body at their joints, and after the calcined bodies are joined together to assemble the desired ceramic structure, the slip at the joints is applied. is dried, the assembled structure is heated to a sintering temperature, and fired again to complete sintering and obtain a finished product.

Ceramics to which the method of the present invention can be applied include magnesia, zirconia, alumina, cordierite, aluminum titanate, mullite, silicon nitride,
Examples include silicon carbide and sialon.

(Function) A pre-fired body formed and fired using the slurry casting method has sufficiently high strength compared to a raw molded body, so it has a much higher strength than when joining raw molded bodies together. In addition, the bonded and assembled structure does not deform due to its own weight or due to shrinkage on the contact surface when re-firing, as in the case of an assembled structure of green compacts. Moreover, the slurry applied to the joint surface seeps into the minute spaces of the re-calcined body at the joint surface, and after firing, the image-bounded body is firmly joined by the throwing effect.

(Example) Next, examples of the present invention will be described.

Example 1: A casting slurry having the following composition is prepared.

Using this casting slurry, two cylindrical compacts were formed by a slurry casting method, and each was fired at 1550°C for 5 hours to obtain a pre-fired body. As shown in the first factor, the slip 3 was applied to the end face of this cylindrical pre-fired body 1.2 of aluminum titanate, and the end faces of the two cylinders were brought together and integrated.

After drying this naturally for about 1 day, it was placed in the atmosphere at 1500℃ for 2
Firing is performed again for a certain period of time to obtain a fired crystal of aluminum titanate to which the z-bond cylinder is joined.

We cut out 15 test pieces from the parts including the joints of this product, and measured the bending strength of the test pieces.
It was MPa.

Example 2: A casting slurry having the following composition is prepared.

Using this slurry, two cylindrical molded bodies were molded in the same manner as in Example 1 by the slurry casting method. Each of these cylindrical silicon nitride molded bodies was heated to 1200°C in a furnace in a nitrogen atmosphere.
Temporarily bake for 3 hours. The above-mentioned slurry is applied to the end face of the resulting cylindrical fired body of silicon nitride, and the end faces of the two cylinders are brought together and integrated.

After naturally drying this for about one day, it is fired for 5 hours in a nitrogen atmosphere at 1750°C to obtain a fired crystal of silicon nitride in which two cylinders are joined. As a result of measuring the bending strength of this product in the same manner as in Example 1, the average strength was 520.
It was MPa.

Comparative Example 1: A cylinder with the same material and shape as in Example 1 was integrally molded and fired to create a cylindrical fired crystal of aluminum titanate, and 15 test pieces were cut out from this product to measure the bending strength. As a result, the average pressure was 29 MPa.

As is clear from the comparison between Comparative Example 1 and Example 1,
It can be seen that the product of Example 1, which has a joint part, has the same bending strength as the product of Comparative Example 1, which does not have a joint part.

Comparative Example 2: A cylinder made of the same material and shape as in Example 2 was integrally molded and fired to create a cylindrical silicon nitride product. 15 test pieces were cut out from this product and the bending strength was measured. , average 5
It was 10 MPa.

As is clear from the comparison between Comparative Example 2 and Example 2,
It can be seen that the product of Example 2, which has a joint part, has the same bending strength as the product of Comparative Example 2, which does not have a joint part.

(Effects of the Invention) According to the present invention, the divided lightweight parts are pre-fired in advance, then joined and integrated, and fired again, so there is almost no deformation during the second firing. Unlike the conventional technology in which raw molded bodies are joined and fired, there is no problem of cracks or chips occurring in the molded bodies during joining or deformation of the assembly during firing, and the process achieves excellent one-dimensional accuracy. Ceramic structures with large or complex shapes can be manufactured. In addition, the slurry applied to the joints of the pre-fired bodies seeps into the fine spaces of the image boundary bodies at the joint surface, and after firing, the image boundary bodies are joined by the throwing effect, resulting in extremely strong adhesion. Ru.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cylindrical calcined body joined by slurry according to the present invention. 1 , 2 , , , Cylindrical pre-fired body 3 , , ,
,, Sludge Figure 1 3 Child compensation patent applicant Toyota Motor Corporation representative Patent attorney Yumi Kaede (and 2 others)

Claims (1)

[Claims] 1. A method for manufacturing a ceramic structure, characterized in that pre-fired bodies formed by a slurry casting method and fired are joined and integrated with a slurry having the same composition as the fired body, and then fired again.