JP2858972B2 - Method for manufacturing ceramic molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing ceramic parts using a hydrostatic pressure molding method, and relates to a method for producing a near net shape and a high-density molded body when molding a part. WIP that can be heated up to the temperature range where the thermoplastic resin previously mixed with the powder is thermally softened when pressurized with water
The present invention relates to a method for producing a ceramic part capable of forming a near net shape when forming a part and forming a high-density molded body by using an apparatus.

[0002]

2. Description of the Related Art Among conventional ceramic parts, those parts which are difficult to impart a shape during press forming, are complicated and have a large wall thickness are manufactured by a slip casting method or an injection molding method. For reasons of complicated manufacturing processes, low yield, and the like, near net shaping is often used in many cases through a base material processing process.

[0003] The feature of the near net shaping that has been subjected to the base processing is that it has a high yield in a short-term manufacturing process.

[0004]

Problems to be solved by near net shaping include the following. The production method using the slip casting or injection molding method is excellent in giving complex shapes and mass productivity, but as the thickness of the part increases, the proportion of defective products generated during molding, degreasing, and sintering increases. Yield decreases.

[0005] In the base processing with the addition of a binder, there is a problem that the binder is not sufficiently plastically deformed at the time of press forming and a residual stress is applied, thereby causing cracks during processing and sintering.

[0006] In order to solve these problems, it is possible to relatively easily mold even a thick-walled one, and the temperature rises to a temperature range in which the thermoplastic resin previously mixed with the powder thermally softens when pressed with hydrostatic pressure. By using a WIP device having a heater for raising the temperature inside the pressure vessel or on the vessel wall or the outer wall of the vessel so that the temperature can be increased, near net shaping and high density of the molded body can be achieved when molding the parts. A method for manufacturing ceramic parts has been established according to the present invention.

Here, the above-mentioned hydrostatic pressurizable device capable of adjusting the temperature to a temperature range in which the thermoplastic resin is thermally softened at the time of hydrostatic pressurization can be adjusted to include a warm isostatic press. It is called WIP and is also described as WIP in the following description.

[0008]

Heretofore, a molding method using a hydrostatic press has been called a CIP (Cold Isostatic Press), and has been formed by compressing in water or a solution at room temperature.

A ceramic powder such as silicon nitride or silicon carbide is mixed with a thermoplastic resin such as polyethylene or polypropylene, and the mixture is subjected to primary molding, followed by rubber coating and secondary isostatic pressing, or In this case, the mixture was directly placed in a rubber mold or the like, and the molding was performed only by applying hydrostatic pressure.

According to the present invention, a thermoplastic resin such as polyethylene or polypropylene is thermally softened under hydrostatic pressure.
This is a method for producing a ceramic molded body, which comprises raising the temperature to a temperature range of from about 200 ° C. to about 200 ° C., maintaining the temperature, and simultaneously applying hydrostatic pressure to 100 to 7000 kgf / cm ² .

The heating and pressurizing are performed by a hydrostatic pressurizing device having a structure in which a heater for raising the temperature is provided in the pressure vessel, the vessel wall or the vessel outer wall.

It is preferable to use a hydrostatic pressurizing apparatus WIP capable of maintaining the temperature after the temperature is raised to a temperature range where the thermoplastic resin is thermally softened during the hydrostatic pressurization described above.

[0013] This makes it possible to use a WIP device capable of raising the temperature of a thermoplastic resin such as polyethylene or polypropylene which has been mixed with powder before molding into a temperature range in which the thermoplastic resin is thermally softened.・ Net shaping and high-density compacts are now possible.

[0014]

With the conventional method of compacting in water at room temperature or other medium at room temperature, it is difficult to obtain a high-density molded body.
Although the strength of the compact was low, it was difficult to perform the green body processing, and the density during sintering was difficult to exceed the theoretical density ratio by 99% at room temperature sintering.
In the present invention, before molding,

The thermoplastic resin such as polyethylene or polypropylene mixed with ceramic powders such as silicon nitride and silicon carbide is heated to a temperature range of 80 to 200 ° C. where the thermoplastic resin is thermally softened. , 100-7
By using a WIP device capable of isostatic pressing up to 000 kgf / cm ² , the thermoplastic resin is

[0016] It has thermal fluidity, suppresses bridging (void formation due to bridging), and promotes powder filling, so that high density of the compact can be achieved. As a result, the strength of the molded body increases,
It has become possible to perform the base processing required for forming a net and processing the molded body.

The following is a list of improvements from the conventional method.
The thermoplastic resin previously mixed with the powder becomes thermally flowable. The filling property of the powder is improved, and the density of the compact can be increased. The strength of the compact increases with the increase in density, and the base workability improves.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following embodiments. Silicon nitride powder (Ube Industries UBE-SN-E10; average particle size
0.3 μm) as 90% by weight, and various oxides (for example, yttrium oxide manufactured by Mitsubishi Kasei Kogyo Co., Ltd. and aluminum oxide manufactured by Sumitomo Chemical Co., Ltd.) were added and mixed in a total amount of 10% by weight.

The volume of these powders was adjusted to 75% by volume, and as a thermoplastic resin, PVA (polyvinyl alcohol) was adjusted to 25% by volume. These were combined and mixed by a ball mill for 24 hours.

The powder obtained here was formed into a sheet material by a forming method shown in the following table. The density of the compact at this time, the strength of the compact, and the density of the sintered compact after normal pressure sintering are shown.

[0021]

[Table 1] Density of compact, strength of compact and sintered compact density after normal pressure sintering * TD: Theoretical Density or theoretical density. In general,% TD indicates relative density.

From these results, it was confirmed that the molded article according to the present invention had a high density at the time of molding, and that the molded article had the necessary strength (20 MPa or more) at the time of complicated substrate processing.

In addition, since the thermoplastic resin is softened and the distance between the particles is approaching, the near-netting process for forming parts by punching, surfacing, and rubber pressing after various processes is performed. Shaping is now possible.

[0024]

As to the method for producing ceramic parts, there is a growing demand for complicated and large (thick) products.
Therefore, the fact that it is possible to achieve near net shaping and high density of a molded body when molding a part is excellent in that a high yield is obtained in a short-term manufacturing process.

According to the present invention, a molded article satisfying these requirements was obtained. These facts make it possible to improve the productivity of ceramic parts, and their industrial utility is very large.

Claims (1)

(57) [Claims] A ceramic powder is mixed with a thermoplastic resin, and the mixture is subjected to a primary molding, followed by a rubber coating and a secondary hydrostatic pressure molding, or by directly placing the mixture in a rubber mold or the like. A method for producing a ceramic molded body, wherein a temperature of a thermoplastic resin is raised to a temperature range in which a thermoplastic resin is thermally softened during hydrostatic pressure pressurization.