JPS6149801A - Manufacture of ceramic product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention applies to ceramic products! lI manufacturing method, and in detail pressurized medium penetration prevention 1 used for coating ceramic molded bodies in isotropically pressurized T-culm! This is an improved method for removing two films.

[Conventional technology]

Ceramic products are generally made by preforming Relamix powder into a predetermined shape by injection molding, molding, or slip casting, and then molding it into a liquid or gas (
The material is manufactured by isotropically pressurizing it in a medium (hereinafter referred to as a pressurizing medium) to eliminate the internal density distribution, and then sintering it.

During the isotropic pressurization, the entire surface of the preform is coated with a pressurizing medium permeation prevention film such as silicone rubber to prevent the pressurizing medium from permeating into the preform. Moreover, the pressurized medium permeation prevention film is removed from the molded body after the pressurization and before sintering.

However, in the conventional method described in -1-, when removing the 1111 pressure medium permeation prevention crotch, the surface of the molded body may peel off together with the pressurized medium permeation prevention film, or if burning is used as a removal method. However, problems such as oxidation of the molded body and reduction in high-toned strength occur, which tends to impair the quality of the product.

[Problem that the invention seeks to solve]

The present invention has been devised in view of the drawbacks of the conventional methods mentioned above, and is a method for producing ceramic products. The object of the present invention is to provide a method for removing the molded article without impairing its quality.

[Means for solving problems]

In the present invention, the pressurized medium permeation prevention membrane is removed not by combustion but by thermal decomposition.

That is, the present invention provides a ceramic product in which a ceramic molded body is coated with a pressurized medium permeation prevention film, isotropically pressurized in a pressurized medium, the pressurized medium permeation preventive film is removed, and then sintered. ! In the manufacturing method II, the pressurized medium permeation prevention membrane is removed by heating and thermally decomposing the pressurized medium = 3 = permeation prevention membrane.

Here, the term "ceramic molded body" refers to a shaped object before sintering. This can be obtained by injection molding, molding or slip casting.

The pressurized medium permeation prevention membrane prevents the pressurized medium from permeating into the ceramic molded body. The pressurized medium permeation prevention membrane is:
It is formed of rubber or plastic over the entire surface of the ceramic molded body. The appropriate thickness is 0.2 to Q, about 3 mm, and it is preferable that there is no residue after thermal decomposition. The pressurized medium permeation prevention film is produced by uniformly applying the film-forming liquid containing the rubber or Plasdec to the entire surface of the ceramic molded body by dipping, spraying, coating, etc., and then drying it. or formed by reaction. When forming the pressurized medium permeation prevention +L film, it is recommended to interpose a powder intermediate layer between the pressurized medium permeation prevention film and the ceramic molded body to prevent the film-forming liquid from permeating into the ceramic molded body. . As the powder intermediate layer, organic powder, sublimable powder, highly refractory powder, carbon, etc. can be used.

The ceramic molded body on which the pressurized medium permeation prevention +L film is formed is evenly pressurized in a pressurized medium. Water as pressurizing medium;
Oil, air, etc. can be used.

After the above-mentioned isotropic pressurization, the pressure medium permeation prevention membrane is removed from the ceramic molded body by thermal decomposition. The thermal decomposition produces nitrogen (
Under an inert gas such as N2), in a vacuum, or several torr
! This is done by heating the pressurized medium permeation prevention membrane under reduced pressure of ￥ degrees. Here, the temperature increase rate should be as slow as possible, preferably 5° C./min or less, and even slower near the decomposition temperature of the pressurized medium permeation prevention 1F membrane. The rate of temperature increase and the temperature and time required for thermal decomposition vary depending on the material forming the pressurized medium permeation prevention 1F membrane. For example, when silicone rubber is used as a pressurized medium permeation prevention membrane, the decomposition temperature is about 650 to 700°C, and thermal decomposition is carried out by maintaining this temperature for about 1 hour. Also, the heating rate is 350
The rate should be 5°C/min or less up to around 700°C, and 2°C/min or less near 700°C.

After removing the pressurized medium permeation prevention film as described above, sintering is performed by a known method such as a normal sintering method or a reaction sintering method.
Obtain ceramic products.

(Function) In the method of the present invention, the pressurized medium permeable diaphragm is removed by thermal decomposition in a vacuum or in an inert gas. Therefore, there is no reduction in high-temperature strength due to oxidation of the ceramic product, and no peeling of the surface of the molded product occurs when the pressurized medium permeation prevention film is removed.

〔Example〕

The present invention will be explained in detail below based on specific examples.

Figure 1 is a schematic cross-sectional view showing how a silicone rubber film is formed on the entire surface of a ceramic molded body to prevent the penetration of pressurized media. FIG. 2 is a schematic cross-sectional view showing how it is made into powder.

First, silicon nitride (Si 3N4) 92wt%, ittria (YzO3) 4vt%, spinel (M!]Δ1204)
A ceramic molded body 1 was prepared by preforming a Relamix mixed powder containing 4 wt % into the shape of a turbocharger rotor.

Next, carbon powder was applied to the surface of the obtained ceramic molded body 1 by spraying to form a carbon powder layer 2.

Next, this was immersed in a silicone rubber solution as a film-forming liquid, pulled up, and dried to form a silicone rubber film 3 as a pressurized medium penetration prevention film.

Next, the ceramic molded body 1 with the silicone rubber film 3 formed thereon was placed in water, and a hydrostatic pressure of 1.4 ton/(ill+" was applied thereto), then pulled up and placed under reduced pressure (several torr).
First heated to 350 °C at a temperature increase rate of 5 °C/min, then further heated to 700 °C at a temperature increase rate of 2 °C/min, and then kept at 700 °C for 1 hour and cooled in a furnace. The silicone rubber film 3 was thermally decomposed. As a result of the thermal decomposition, the silicone rubber film 3 became an amorphous powder 30 as shown in FIG.

After the silicone rubber film 3 was thermally decomposed and removed in this way, it was fired at 1760° C. for 4 hours to obtain a ceramic rotor for a turbocharger, which is a ceramic product.

As another example, instead of thermally decomposing the silicone rubber film 3 in a vacuum (several torr or less), thermally decomposing the silicone rubber film 3 in a nitrogen (N2) gas atmosphere was also performed.

Next, for comparison, a ceramic turbocharger rotor was manufactured using a conventional method.

Here, the conventional method means that in the method of the above-described embodiment, the silicone rubber membrane 3 is removed by thermal decomposition in a nitrogen (N2) gas atmosphere or in a vacuum, and the silicone rubber membrane 3 is removed in air. This is a method that involves combustion. That is,
In the conventional method carried out for comparison, the silicone rubber membrane 3 was heated in air for 1 to 100° C., kept at 500° C. for 2 hours, and then burned and removed.

In ceramic turbocharger rotors manufactured by such conventional methods, surface peeling defects occurred in more than 80% of the final products, whereas in products manufactured by the method of the embodiments of the present invention described above, such surface peeling defects occurred in more than 80% of the final products. This defect did not occur.

〔Effect of the invention〕

In summary, the present invention is a manufacturing method for ceramic products.
Pressurized medium penetration prevention used in isostatic pressurization process 1
The film is removed not by combustion but by thermal decomposition in an inert gas atmosphere, in vacuum, or under reduced pressure.

As mentioned in the examples, it is clear that in the method of the present invention, the film on the pressurized medium penetration barrier 1 is removed by thermal decomposition, so almost no oxidation occurs in the ceramic product, and therefore, the ceramic product is not exposed to high temperatures. There is no decrease in strength. Moreover, defects such as peeling of the surface of the molded article do not occur when the pressurized medium permeation prevention film is removed.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing how a silicone rubber film is formed on the surface of a ceramic molded body to prevent penetration of a pressurized medium. FIG. −〇 − 1...Ceramic molded body 2...Carbon powder layer 3...Silicon rubber film 30...Amorphous powder

Claims (5)

[Claims] (1) A method for manufacturing a ceramic product, in which a ceramic molded body is coated with a pressurized medium permeation prevention film, isotropically pressurized in a pressurized medium, the pressurized medium permeation preventive film is removed, and then the ceramic product is sintered. A method for producing a ceramic product, wherein the removal of the pressurized medium permeation prevention film is carried out by heating and thermally decomposing the pressurized medium permeation prevention film. (2) The manufacturing method according to claim 1, wherein a carbon intermediate layer is formed between the ceramic molded body and the pressurized medium permeation prevention film. (3) The manufacturing method according to claim 1, wherein the heating is performed in an inert gas. (4) The manufacturing method according to claim 1, wherein the heating is performed under reduced pressure. (5) The manufacturing method according to claim 3 or 4, wherein the pressurized medium permeation prevention membrane is made of silicone rubber, and the heating is performed at about 650 to 700°C.