JPH056484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for molding raw material powder in the manufacturing process of ceramic mechanical parts, such as ceramic parts constituting gas turbine engines and piston engines.

BACKGROUND TECHNOLOGY A slip casting method is known as a method for molding ceramic powder when producing complex-shaped ceramic mechanical parts, such as axial flow turbines used in gas turbine engines. This slurry casting method is a molding method in which ceramic raw material powder is dispersed in a solvent and poured into an absorptive mold such as plaster, and the solvent is absorbed in an amount suitable for shape retention to obtain a predetermined shape. It is possible to mold products with complex shapes by devising a mold structure, and if the slurry is properly prepared, a homogeneous molded product with a high bulk density can be obtained. Furthermore, the equipment and molds are inexpensive and easy to mold. It has the advantage of being able to be molded into

Problems to be Solved by the Invention However, the above-mentioned conventional powder molding method using slurry casting has the following problems.

That is, when performing the above-mentioned slurry casting, water or organic solvents such as ethanol or benzene are absorbed from the slurry cast into an absorbent mold, such as a plaster mold, and the remaining solid content is dried. At this time, tensile stress acts on the inside of the molded body due to shrinkage due to a decrease in liquid content. This has resulted in the disadvantage that cracks may occur in thin parts of the molded body or in parts with uneven density.
Such a problem is particularly noticeable when the raw material powder consists of fine particles because the rate of absorption during drying after casting is high, and cracks occur due to sink marks.

This invention has been made in view of the above-mentioned conventional circumstances, and is used when manufacturing parts with thin walled parts by slurry casting, or when using fine particles as a raw material powder for slurry casting. An object of the present invention is to provide a powder compacting method that can obtain a compact having a locally uniform density even if It is something.

Means for Solving the Problems In other words, the powder molding method of the present invention uses a mold with two facing cavities,
Using a mold in which one of the two opposing surfaces is made of a liquid-permeable material and the other surface is made of an elastic material, the cavity is filled with a uniform mixture of raw material powder and a liquid medium. After that, compressive stress is applied from the outside of the cavity to the inside of the cavity through the surface formed of the elastic material, while the outside of the surface formed of the liquid permeable material is brought into a reduced pressure state. It is something.

The powder compacting method of the present invention will be explained in more detail below with reference to FIG.

First, in this invention, two cavities are opposed to each other.
A mold consisting of two surfaces, one of which is made of a liquid-permeable material and the other of which is made of an elastic material, is used.
FIG. 1 shows an example of a mold used in the present invention. The mold 1 shown in FIG. 1 consists of a holding container 3 housed inside a sealed chamber 2 and a rubber container 4 housed inside the holding container 3. The inner portion of the holding container 3 is made of a sintered porous alloy layer 5 made of a liquid-permeable material, and the holding container 3 can be separated and removed. In addition, the rubber container 4
is housed in the holding container 3 such that the outer surface of the rubber container 4 has a predetermined distance from the inner surface of the holding container 3, that is, the surface of the sintered porous alloy layer 5. Thereby, a cavity 6 is formed between the surface of the sintered porous alloy layer 5 and the outer surface of the rubber container 4. That is, in the mold 1 shown in FIG. 1, the carrier 6 consists of two opposing surfaces, that is, the surface of the sintered porous alloy layer 5 and the outer surface of the rubber container 4, and one of the two opposing surfaces is The surface of a certain sintered porous alloy layer 5 is made of a sintered porous alloy which is a liquid-permeable material, and the outer surface of the rubber container 4 which is the outer surface is made of rubber which is an elastic material. Note that an air pipe 7 is installed at the opening of the rubber container 4.
can be connected.

In addition to the sintered porous alloy, gypsum, sponge, etc. can be used as the liquid permeable material. Furthermore, as the elastic material, in addition to rubber, plastics or the like having appropriate toughness and flexibility can be used as required.

Next, in the powder molding method of the present invention, the cavity of the mold is filled with a uniform mixture of the raw material powder and the medium. To explain using the mold 1 shown in FIG. A slurry consisting of a homogeneous mixture of raw powder and liquid medium is injected. The raw material powder that can be molded is not only ceramic powder, but also metal powder such as Fe powder. As a medium, water, ethanol,
Benzene etc. can be used.

Thereafter, in the present invention, compressive stress is applied from the outside of the cavity into which the slurry has been injected to the inside of the cavity through the surface formed of the elastic material. To explain the case where the mold 1 shown in FIG. 1 is used, after pouring slurry into the cavity 6 through the slurry inlet 8,
An air pipe 7 is connected to the upper opening of the rubber container 4, and a fluid such as air or water is sent into the rubber container 4 through the air pipe 7. As a result, the rubber container 4 is filled with mud in the cavity 6 filled with mud.
compressive stress is applied by

Further, in the method of the present invention, while compressive stress is applied to the slurry filled inside the cavity as described above, the outside of the mold on the side formed of a liquid permeable material is brought into a reduced pressure state. . That is, to explain the case in which the mold 1 shown in FIG. Exhaust air from the As a result, the inside of the sealed chamber 2 is brought into a reduced pressure state,
Further, the pressure inside the suction port 10 formed in advance on the side wall of the holding container 3 so as to reach the sintered porous alloy layer 5 from the outside is also reduced. As a result, the liquid content of the slurry filled in the cavity 6 is sucked through the sintered porous alloy layer 5 to the suction port 10 side, and the liquid content in the slurry permeates into the sintered porous alloy layer 5. , the slurry inside the cavity 6 is dried accordingly. As a result, the molded body, which is the solid content remaining in the cavity 6, is subjected to stress by the rubber container 4 during the drying process, so it becomes tightly compacted and even cracks due to shrinkage due to drying. etc. will not occur.

Examples Examples of the powder compacting method of the present invention will be described below.

Example 1 Using the mold 1 shown in FIG. 1, the method of the present invention was carried out to mold powder.

The raw material powder used was silicon carbide having an average particle size of 0.4 μm mixed with 1 wt % of carbon black and 1 wt % of amorphous boron as sintering aids. The raw material powder was mixed in ethanol for 3 days in a ball mill to finally prepare slurry with an alcohol concentration of 60%. The slurry was filled into the cavity 6 of the mold 1 shown in FIG. Cavity 6
Silicone rubber having appropriate toughness and flexibility was used for the rubber container 4 forming the rubber container 4.

After filling the cavity 6 with mud, air was sent to the rubber container 4 through the air pipe 7, and a compressive stress of 15 atmospheres was applied to the mud inside the cavity 6. At the same time, the air was exhausted from the exhaust port 9 of the sealed chamber 2, and the pressure inside the sealed chamber 2 was reduced to about 5 torr.

After demolding the molded body obtained above, the presence or absence of defects was examined by visual inspection, ultrasonic flaw detection, and X-ray transmission inspection. As a result, no defects were discovered.
Further, the compact was sintered in the atmosphere at 2100° C. for 1 hour, but the sintered compact had shrunk into a similar shape and had no distortion.

Example 2 Using the mold 1 shown in FIG. 1, the method of the present invention was carried out to mold powder.

Al ₂ O ₃ with an average particle size of 0.02 μm was used as the raw material powder, and the raw material powder was dispersed in water at pH 3 to prepare a slurry containing 53 wt% water and 0.4% surfactant. Place the slurry in the cavity 6 of the mold 1.
After filling the tank, air was sent to the rubber container 4 through the air pipe 7, and a compressive stress of 4.5 atmospheres was applied to the mud in the cavity 6. At the same time, the air is exhausted from the exhaust port 9 of the sealed chamber 2, and the inside of the sealed chamber 2 is first
The pressure was reduced to about 500 torr, and then gradually reduced to about 5 torr.

When the molded product obtained above was inspected in the same manner as in Example 1, it was found to be free of defects such as cracks.

Example 3 Using the mold 1 shown in FIG. 1, the method of the present invention was carried out to mold iron powder.

The slurry is prepared by dispersing iron powder with an average particle size of 0.8 μm in benzene, the slurry is filled into the cavity 6 of the mold 1, water is sent into the rubber container 4 from the air pipe 7, and the cavity is filled. Like the mud inside 6
A compressive stress of 200 atm was applied. At the same time, the air is exhausted from the exhaust port 9 of the sealed chamber 2, and the inside of the sealed chamber 2 is
The pressure was reduced to about 5 torr.

When the molded product obtained above was examined for defects, no defects were found.

Comparative Example 1 Other than that, slurry casting was carried out in the same manner as in Example 1 without applying pressure from the rubber container 4. After exhausting air through the exhaust port 9 of the sealed chamber 2 and drying under reduced pressure, the molded product obtained cracked and collapsed and could not function as a molded product.

Comparative Example 2 Other than that, slurry casting was carried out in the same manner as in Example 2 without applying pressure from the rubber container 4. As a result, the solid content remaining in the cavity 6 was broken, and no molded product was obtained.

Comparative Example 3 Other than that, slurry casting was carried out in the same manner as in Example 3 without applying pressure from the rubber container 4. As a result, cracks were present in the molded product obtained.

Effects of the Invention As described above, according to the powder compacting method of the present invention, compressive stress is applied to the slurry in the cavity through the surface formed of an elastic material, while one surface forming the cavity is liquid permeable. By applying a reduced pressure to the outside of the surface formed from the material, it is possible to obtain a molded body with locally uniform density, and it is possible to obtain fine powder, specifically fine particles of 1 μm or less. Even when using a raw material powder made of No such defects will occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a mold used for carrying out the method of the present invention. 1... Molding mold, 2... Sealed chamber, 3... Holding container, 4... Rubber container, 5... Sintered porous alloy layer,
6... Cavity.

Claims (1)

[Claims] 1. Using a mold with a cavity consisting of two opposing surfaces, one of which is made of a liquid-permeable material and the other surface is made of an elastic material, After filling the cavity with a uniform mixture of the raw material powder and the liquid medium, compressive stress is applied to the slurry filled inside the cavity through the surface formed of the elastic material, and during that time, the liquid-permeable material is A powder compacting method characterized by bringing the outside of the formed surface into a reduced pressure state.