JPH04259507A - Manufacture of ceramic sintered body possessing hollow part - Google Patents

Abstract

PURPOSE:To obtain easily a ceramic sintered body possessing a hollow part or a through hole, by a method wherein ceramic raw material powder and a binder consisting mainly of an organic polymeric compound are mixed up with each other and the same is extrusion molded so that at least one line comprised of carbon fiber is coated with the same. CONSTITUTION:Ceramic raw material is passed through a breaker plate 13 while kneading the same in a gap between a cylinder 12 held at 130 deg.C by a heater and a screw 11 and extruded within a head 18. The title method is set up so that 48 pieces of lines comprised of carbon fibers having the diameter of 0.7mum phi are sent into the head 18 through a holder 15 at the same speed as a flow speed of raw materials at a mouth piece part 17. The extrusion molded body is cut into lengths of 20mm under a state containing the line and inserted into a degreasing furnace. Degreasing is performed by such a method that a temperature rise is performed from a room temperature at a rate of 6 deg.C/hour within an open air atmosphere and held for 3 hours at 400 deg.C. Furthermore, the degreased body is sintered for 3 hours at 1200 deg.C within the open air atmosphere, the lines are removed by firing and a sintered body is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing ceramics, and more particularly to a method of obtaining a product having a shape that is difficult to mold using conventional manufacturing methods, or to reducing manufacturing costs by improving the process of conventional manufacturing methods.

0002

2. Description of the Related Art Ceramic products are generally manufactured by a method of filling a mold with raw material powder and compression-molding the resulting green compact, which is then sintered. The shape of the powder compact obtained by this method is limited to relatively simple shapes such as cylinders and cylinders, and the density in the compression direction is limited to the ratio of the length in the compression direction to the area of the surface perpendicular to the compression direction. There were limitations due to the difficulty in obtaining a uniform green compact and the increased frictional resistance when ejecting from the mold. The above-mentioned problems are particularly noticeable in shapes having hollow portions or through holes.

[0003] As a solution to this problem, a molded body obtained by adding a binder mainly composed of 10 to 20% by weight of an organic polymer compound to ceramic raw powder to impart fluidity and extrusion molding. A method of obtaining sintered products by degreasing and sintering is attracting attention. Extrusion molding is an established technology for ordinary plastic products, and products with various cross-sectional shapes, such as rain gutters made of hard vinyl chloride, are available on the market.

0004

[Problem to be Solved by the Invention] However, when obtaining ceramic products using the manufacturing method described above, the degree of freedom in cross-sectional shape is usually lower than that achieved by conventional compression molding due to the following reasons 1) and 2). The product had no choice but to be somewhere between the plastic extrusion molded product and the product. In addition, this tendency was particularly noticeable in those with through holes. 1) Because the raw material used for extrusion molding contains a large amount of powder with a relatively high specific gravity, it has a higher density than ordinary plastic, and is likely to deform due to its own weight immediately after the raw material is extruded from the die. 2) Conventional sizing techniques cannot be applied to it because it is more fragile than ordinary plastic. Therefore, the technical problem of the present invention is to easily produce a ceramic sintered body having a large length to cross-sectional area ratio and having a hollow portion or through hole with an increased degree of freedom in cross-sectional shape. The purpose is to provide a method for manufacturing.

[0005]

[Means for solving the problem] Generally, when extruding a shape that has a hollow section or a through hole in its cross section, it is difficult to maintain the shape of the hollow section or through hole after the raw material is extruded from the die. Therefore, various sizing methods have been devised and put into practical use. However, in powder compacts such as those described above, organic substances that are completely destroyed by combustion are removed during the sintering process and do not remain in the product, so in the positions that should become hollow parts or through holes,
There is no problem even if a core material made of such a material is inserted, and deformation can be easily prevented by this core material.

[0006] The present inventors have focused on the advantages of this manufacturing method, and also considered that the core material has a certain degree of heat resistance, since if it is thermoplastic, it will be thermally deformed during the degreasing process. There are many advantages to having such a core material, and we have discovered a filament made of carbon fiber as one of the core materials suitable for this purpose, and have come up with the present invention.

That is, according to the present invention, at least one filament made of carbon fiber is coated with a mixture obtained by mixing and kneading a ceramic raw material powder and a binder mainly composed of an organic polymer compound. An extrusion molding process in which a molded body with a composite structure is obtained by extrusion molding and cutting to a required length, and a degreased body is obtained by subjecting the molded body to heating or extraction treatment to remove the binder. A method for manufacturing a ceramic sintered body having a hollow portion is obtained, which comprises a degreasing step and a firing step of removing the filaments and sintering the degreased body. Therefore, the most distinctive feature of the present invention is the manufacturing process of the molded body, and regarding the equipment, the extruder is equipped with a crosshead to feed the core material into the flow path of the raw material. Regarding the core material, carbon fiber was used.

According to the manufacturing method of the present invention, a ceramic sintered body having a hollow portion or a through hole, which is difficult to manufacture by compression molding and extrusion molding methods, can be easily obtained.

[0009]

EXAMPLES Next, the present invention will be explained in more detail by way of examples with reference to the drawings. FIG. 1 is a sectional view showing an example of the configuration of an apparatus for manufacturing an extrusion molded ceramic sintered body of the present invention.

In FIG. 1, the extrusion molding manufacturing apparatus includes a cylinder 12 housing a screw 1 and having a heater 11a around it, a head 18 connected to the cylinder 12 via a breaker plate 13,
It has a core material delivery port holder 15 protruding into a cavity within the head 18, and a base 17 provided at a position on the distal end side of this holder 15. Core material outlet holder 15
The core material 16 is fed out through the hole 17a of the base 17 of the holder 15. Further, the cap 17 and the head 18 are fixed together with bolts 19a and 19b. The kneaded ceramic raw material is sent to the right by the screw 11, passes through the breaker plate, passes through the guide portion 18b, and is fed into the head cavity 18a, where it is formed by the tapered surface 17b of the base 17 together with the core material 16. The tip hole 17 of the cap 17 is compressed in the space
The extruded molded body is sent out from a.

A specific example of production using the extrusion molding apparatus shown in FIG. 1 is shown below. For 100 parts by weight of calcined powder of Ni-Zn ferrite with an average particle size of about 1 μm, 3.5 parts by weight of polybutyl acrylate with a number average molecular weight of about 140,000, and a few parts by weight with a vinyl acetate content of 14%. Average molecular weight: approx. 18
0,000 ethylene-vinyl acetate copolymer; 3.5 parts by weight; melting point; paraffin wax; 60°C; 2 parts by weight were each weighed, the total amount was 109 parts by weight, and the mixture was put into a pressure kneader and heated to 30°C at 130°C. Separate kneading was performed to obtain a raw material mixture. This mixture was made into pellets with a diameter of about 4 mm and a length of about 5 mm using an extruder (not shown) equipped with a rotary knife in the die. As shown in Figure 1, this pellet is equipped with a heater (not shown) around the pellet, and this heater
While kneading in the gap between the cylinder 12 and the screw 11 maintained at 0° C., the mixture was passed through the breaker plate 13 and extruded into the head 18. Forty-eight filaments made of carbon fibers each having a diameter of 0.7 mm were fed into the head 18 via the holder 15 at the same speed as the flow rate of the raw material in the mouthpiece 17. As a result, an extrusion molded article having the cross-sectional shape shown in FIG. 2 was obtained. This extrusion molded product, including the filaments, was cut into a length of 20 mm and inserted into a degreasing furnace. Degreasing was carried out in an air atmosphere by increasing the temperature at room temperature at a rate of 6° C./hour and holding it at 400° C. for 3 hours. Furthermore, this degreased body was heated at 1,200°C for 3 hours in an air atmosphere.
Sintering was carried out for a period of time, and the filaments were removed by incineration to obtain a sintered body having the dimensions shown in Table 1. In addition, for comparison, except for using the carbon fiber filament as a fixed center core in the previous example,
A sintered body was obtained by a series of steps from extrusion molding to sintering under the same conditions as in the example, and the dimensions are also shown in Table 1. In the table, ■ to ■ correspond to parts ■ to ■ shown in FIG.

0012

[Table 1]

From Table 1, it can be seen that the sintered bodies according to the examples of the present invention have less deformation in each part than those of the comparative examples.

[0014]

[Effects of the Invention] As described above, according to the present invention, sintered products with shapes that cannot be obtained by conventional powder compacting methods can be obtained.
This will greatly contribute to expanding the uses of sintered products. Further, even if the ferrite product having the shape shown in the embodiment is manufactured on the assumption that it will be subjected to post-processing, it is difficult to manufacture from the viewpoint of manufacturing cost, and it is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a head of an extrusion molding machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing an extrusion molded article produced by the apparatus shown in FIG. 1.

[Explanation of symbols]

11 Screw 12 Cylinder (with heater) 13 Breaker plate 14 Hatched areas indicate raw materials for molding 15 Core material delivery port holder 16 Core material 17 Base 18 Head

Claims (1)

[Claims] [Claim 1] A mixture obtained by mixing and kneading a ceramic raw material powder and a binder whose main component is an organic polymer compound is extruded so as to cover at least one filament made of carbon fiber. , an extrusion molding process to obtain a molded body with a composite structure by cutting it to the required length;
A degreasing process in which the molded body is heated or extracted to remove the binder to obtain a degreased body, and a firing process in which the filaments are removed and sintered by firing the degreased body. A method for producing a ceramic sintered body having a characteristic hollow part.