JPH0550963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for molding ceramic molded bodies, particularly cylindrical ceramic molded bodies.

Conventional technology In general, ceramics exhibit superior properties such as wear resistance, corrosion resistance, and high-temperature strength compared to metals and plastics. Alternatively, it is useful for liquid transportation of granular materials such as earth and sand and blast furnace granules, and further for transportation of corrosive fluids such as corrosive gases, waste liquid slurry, and sediment sludge.

BACKGROUND ART Conventionally, one of the methods for molding cylindrical ceramic molded bodies such as straight ceramic pipes and curved ceramic pipes is a mud casting method in which a slurry of ceramic powder is poured into a mold. Although there are several methods of mud-reduction casting, the mud-reduction method is generally applied when forming a cylindrical ceramic molded body. The mud removal method involves casting mud into a porous mold that has water absorption properties, such as a plaster mold.
This is a method of obtaining a cylindrical ceramic molded body having a thick wall by making it thick by absorbing water in a plaster mold over a certain period of time, and then discharging the excess plaster.

Problems to be Solved by the Invention By the way, in the above-mentioned mud removal method, especially when manufacturing large ceramic straight pipes or ceramic curved pipes, it is difficult to make the thickness and moisture of the mud deposited on the inner wall of the mold uniform. There was a problem that it could not be maintained and, for example, "cracking" occurred during drying. In addition, ceramic straight pipes and curved ceramic pipes are manufactured in some cases by cold isostatic compression molding and injection molding, but there are problems in handling the core, etc., and mold costs are high. There is a problem with this point. It is also manufactured by extrusion, but there are problems in that it is difficult to handle and cracks occur during drying. Furthermore, in the case of a curved pipe, there is a method in which the curved part is formed by extrusion, and the straight parts at both ends are formed by straightening after extrusion, but there are still technical problems.

As described above, methods such as mud casting, cold isostatic compression molding, injection molding, and extrusion have problems such as cracking during drying and core removal.
It takes a lot of effort to obtain predetermined dimensions and predetermined quality, leading to high product costs.

Therefore, an object of the present invention is to provide a method for molding a ceramic molded body that can solve the above problems.

Means for Solving the Problems In order to solve the above problems, the method for forming a ceramic molded body of the present invention is to form a large diameter pipe into which an elastic tube is fitted and a plurality of through holes are formed in the peripheral wall. A small-diameter pipe-shaped mold with an elastic tube fitted onto the outside and a plurality of through holes formed in the peripheral wall is inserted into the pipe-shaped mold, one end between both pipe-shaped molds is closed, and the next step is as follows. After putting ceramic powder or granules into the interior from the other end between both pipe-shaped molds, the other end is closed, and then, with the through hole of the large-diameter pipe-shaped mold closed, the small-diameter A liquid is injected between the through holes of the pipe-shaped mold and its elastic tube to pre-compress the ceramic powder or granules, and then a liquid is injected through the through-holes of both pipe-shaped molds to compress the ceramic powder or granules. This is a method in which granules are molded by cold isostatic compression molding.

Function According to the above molding method, after the ceramic powder or granules are pre-compressed, the whole is molded by cold isostatic compression molding through an elastic tube, so the ceramic powder or granules are compression molded more uniformly. There are no problems such as cracking. Furthermore, since it is compressed from the inner and outer surfaces of the cylindrical shape,
A gap is created between the two molds, and the ceramic molded product can be easily extracted from the mold, so that both long tubes and curved tubes can be manufactured easily. Furthermore, by adjusting the pressure during pre-compression, the inner diameter of the tube that is the molded product can be changed, and the outer diameter can also be changed.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

Reference numeral 1 denotes a large-diameter pipe-shaped mold (hereinafter referred to as large-diameter mold) in which a plurality of through holes 2 are formed in the peripheral wall, into which an elastic tube 3 made of elastic material such as rubber or plastic is fitted. . Reference numeral 4 denotes a small-diameter pipe-shaped mold (hereinafter referred to as a small-diameter mold) which is disposed within the large-diameter mold 1 and has a plurality of through holes 5 formed in the peripheral wall, and is made of the same material as the elastic tube 3. An elastic tube 6 is fitted onto the outside. 7 and 8 are in close contact with the upper and lower ends of the small-diameter mold 4 arranged at the same central position in the large-diameter mold 1, and are connected to the central space chamber 9 inside the small-diameter mold 4 and between the two molds 1 and 4. Annular space chamber 1
The upper and lower lids are for sealing the 0, and both lids 7 and 8 are tightened and fixed by tie bolts 11. In addition, an injection hole 12 for liquid injection is formed in the upper lid 7, and a large diameter mold 1 is formed in the upper lid 7.
A blind plug 13 is removably provided in the through hole 2 with a screw or the like.

Next, a method of forming a ceramic straight pipe will be explained.

First, as shown in FIG. 1, the large-diameter mold 1 is placed on the upper surface of the lower lid 8, and the small-diameter mold 4 is placed in the center of the large-diameter mold 1. Next, ceramic powder or granules A such as alumina, zirconium, silicon nitride, or silicon carbide are filled into the annular space chamber 10 between the two molds 1 and 4. After filling, the top cover 7 is attached under atmospheric pressure or reduced pressure, and the tie bolts 1 are attached.
1, the annular space chamber 10 is sealed. Next, the through hole 2 of the large diameter mold 1 is inserted into the blind plug 13.
After closing, liquid is injected under pressure into the central space chamber 9 through the injection hole 12 of the upper lid 7. Then, the liquid enters between the through hole 5 of the small diameter mold 4 and the elastic tube 6, and as shown in ^FIG. preforming is carried out (at a certain pressure). In addition, in this state, the small diameter mold 4
A predetermined gap is created between the elastic tube 6 and the elastic tube 6.
Thereafter, molding is performed by cold isostatic compression molding. That is, a liquid is supplied under pressure from the through holes 2 and 5 of each of the molds 1 and 4, and the ceramic powder or granules A are uniformly pressed from the inner and outer surfaces to compression mold.
After molding, the upper and lower lids 7 and 8 may be removed and the tubular ceramic molded body may be extracted. This extraction can be easily performed since there are gaps between the inner and outer surfaces of the molded body and the molds 1 and 4. By changing the pressure of the pressurizing liquid during pre-compression, the inner diameter of the compact can be adjusted, and together with the pressure during cold isostatic compression, the outer diameter of the compact can be adjusted. In other words, the thickness can also be adjusted.

By the way, in the above embodiment, the manufacturing of straight pipes has been described, but of course it can also be applied to manufacturing curved pipes. In addition, during molding, after filling the annular space chamber with ceramic powder or granules, the through hole of the large diameter mold was closed with a blind plug. It's okay.

Effects of the Invention According to the method for molding a ceramic molded body of the present invention, the ceramic powder or granules are pre-compressed and then molded as a whole by cold isostatic compression molding through an elastic tube. The granules can be compression molded more uniformly, and problems such as cracking do not occur. In addition, since compression is performed from the inner and outer surfaces of the cylindrical shape, a gap is created between the molds and the ceramic molded product can be easily pulled out of the mold.
Even curved pipes can be easily manufactured, leading to cost reductions. Furthermore, by adjusting the pressure during pre-compression, the inner diameter of the tube, which is the molded product, can be changed, and the outer diameter can also be changed.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views for explaining a molding method according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Large diameter pipe-shaped mold, 2...Through hole, 3...Elastic tube, 4...Small diameter pipe-shaped die, 5...Through hole, 6...Elastic tube, 7...Upper cover, 8...Lower cover, 1
0... Annular space chamber, 12... Injection hole, 13... Blind stopper.

Claims (1)

[Claims] 1. A large diameter pipe-shaped mold in which an elastic tube is fitted inside and a plurality of through holes are formed in the peripheral wall, and a small diameter pipe mold in which an elastic tube is fitted externally and a plurality of through holes are formed in the peripheral wall. Insert a pipe-shaped mold, then close one end between both pipe-shaped molds, then put ceramic powder or granules inside from the other end between both pipe-shaped molds, and then close the other end. Then, with the through hole of the large diameter pipe mold closed, liquid is injected between the through hole of the small diameter pipe mold and the elastic tube to form ceramic powder or granules. 1. A method for molding a ceramic molded body, which comprises pre-compressing, then injecting a liquid through the through holes of both pipe-shaped molds, and molding ceramic powder or granules by cold isostatic compression molding.