JPS61252102A - Method of molding ceramic - 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 Field of Application) The present invention relates to a method for molding ceramic materials, and in particular, in a molding method using a slurry casting method, it is possible to eliminate air bubbles remaining in the slurry to form a sintered body. The invention relates to a method for reducing bore defects in.

(Prior Art) In recent years, ceramic products made of high-purity oxides, carbides, nitrides, silicides, and composite compounds thereof have been widely used as various industrial materials. By the way, hot press method, injection molding method, extrusion molding method, slurry casting method, and many other methods are known as molding methods for obtaining these ceramic products. In particular, slurry casting method is complicated. This method is widely used when obtaining a ceramic molded body having a specific shape.

However, in the slurry casting method, if air bubbles in the slurry remain in the compact, bore defects will occur after sintering, reducing the strength of the ceramic, so degassing from the slurry is a problem.

Vacuum defoaming is a commonly used degassing method for slurry, but in this method, air bubbles are drawn into the slurry when it is taken out of a vacuum container or poured into a casting mold. It may remain. There is also a pressure casting method in which the vacuum container is pressurized in the opposite direction and the material is directly fed to the casting mold, but this method requires the strength of the casting mold to be pressurized at a pressure of 2 to 10 ka/cm2. Therefore, it was unsuitable when using a mold made of soft Si rubber or the like that is easily deformed or a mold with low molding strength.

(Problem to be Solved by the Invention) In the slurry casting method, slurry is normally poured into a plaster mold or a water-absorbing mold in the presence of air, but the air involved at this time can cause problems due to the viscosity of the slurry. Often not completely removed. For this reason, if a non-water-absorbing material is used for the mold, air bubbles attached to the sides of the mold cannot easily escape to the outside of the slurry, and if the shape of the mold is such that air pockets are likely to occur, air may remain. Often.

Therefore, when such a molded body is sintered, bores remain in the sintered body, which becomes a starting point for fracture of the ceramic and causes a decrease in strength. In particular, bore defects on the surface of the sintered body cause a significant decrease in strength.

Therefore, an object of the present invention is to provide a novel ceramic molding method in which no air bubbles remain in the slurry, which causes the above-mentioned decrease in strength.

(Means for Solving the Problems) In order to prevent the above-mentioned bore from remaining, the present invention reduces the pressure of the atmosphere during casting to a level close to vacuum, thereby minimizing the amount of air involved during casting. It is characterized by performing cast molding in a state.

In the present invention, the atmospheric pressure during casting is -
If the vacuum pressure is less than 600 smH (2), sufficient deaeration will not be achieved, while if the vacuum pressure is -720 ml Ha or higher, the water, which is the solvent for the slurry, will start to boil, which is undesirable. Therefore, the vacuum pressure of the atmosphere during casting is -6001□ll-
It is preferably within the range of 1 to 720 miHg.

Furthermore, in the present invention, since casting is performed under reduced pressure, a mold with good deformability, such as a Si rubber mold, can be used as the mold.

(Example) Hereinafter, the present invention will be explained in more detail according to Examples.

In weight%, Si3Na raw material (average particle size 0.5 μα conversion rate 9
0% or more) 90% and Y203 raw material (average particle size 10μ)
7% and 3% 21R solid solution (average particle size 3μ), mixed with 4 to 5% by weight of Aα2o3 (average particle size 0.3μ), was mixed with alcohol as a solvent in a ball mill. The mixture was vacuum dried for 72 hours and then heat treated at 500°C. Then,
23 Illσ of distilled water was added to this mixed powder raw material 1009, and 1 mQ of a 10% solution of ammonium polycarboxylate was added as a peptizing agent to 100 g of the raw material.
A slurry was prepared by dispersing in a ball mill for 24 hours, and this slurry was placed in a vacuum tank for defoaming of a vacuum casting device. On the other hand, in a chamber for a casting chamber communicating with the vacuum tank, a casting mold was placed, which was placed on a plaster mold formed in a lower frame, fixed around the periphery with an outer frame, and provided with an upper frame. As this casting mold, we used a casting mold for a turbocharger rotor in which the material of the blade part is made of Si rubber, and such a casting mold has a weight of approximately 0.2 kg/cm2.
It cannot be used for pressure casting because it deforms with just a moderate amount of pressure applied. The lower frame, outer frame, and upper frame were all made of A1. Next, the pressure inside the tank and the chamber was reduced to -7601111H (l) using a vacuum pump. At this time, air bubbles were removed from the slurry in the tank charged into the vacuum tank. , open the leak valve, -700i
After leaking to mHiJ, the bottom cock of the vacuum tank was opened and the slurry was poured into the casting mold inside the chamber. As a result, the defoamed slurry is cast without coming into contact with the outside air, thereby preventing air from being entrained during casting. Thereafter, the inside of the chamber was returned to atmospheric pressure, the casting mold was taken out, and after the slurry had solidified, the mold was broken down. After drying, it was held at 1800° C. for 5 hours in a N2 atmosphere to obtain a sintered body.

FIG. 1 shows JISJ point bending transverse rupture strength Weibull plots of the sintered body obtained by the above-mentioned present invention and the sintered body obtained by slurry casting in normal air according to the conventional method. . As is clear from the figure, the strength of the sintered body according to the present invention is significantly improved, and the average strength is 45.
1kg/mm2 increases to 55.1kQ/mm2, and the Weibull series number also increases from 4.35 to 17.6.
It improved to 1.

That is, according to the present invention, there is an effect of significantly reducing the bores remaining in the sintered body and improving its strength.

In addition, since the casting is carried out under reduced pressure, Si, which is easily deformed, is
It can also be used with molds made of rubber or the like, and has the advantage of being low in cost and being able to be molded with high precision.

[Brief explanation of the drawing]

FIG. 1 shows a sintered body cast in vacuum according to the present invention,
It is a transverse rupture force Weibull plot diagram of a sintered compact cast in normal atmosphere. Figure 7 Gokei (K//~2)

Claims (3)

[Claims] (1) A slurry made of a ceramic material containing a binder is placed in a container, the pressure inside the container is reduced to remove air bubbles from the slurry, and then the slurry is poured into a slurry caster provided in a chamber having approximately the same pressure as the inside of the container. A ceramic molding method characterized by pouring into a pouring mold and molding. (2) The reduced pressure atmosphere is from -600mmHg to -73mmHg.
2. The method of forming a ceramic according to claim 1, wherein the temperature is within a range of 0 mmHg. (3) The ceramic molding method according to claim 1 or 2, wherein the mold is made of easily deformable Si rubber or the like.