JPS60253505A - Manufacturing method of ceramic products - 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] [Field of Application of the Invention] The present invention relates to a method of manufacturing a ceramic product by casting a ceramic-containing slurry into a mold,
In particular, the present invention relates to a manufacturing method suitable for application to products such as automobile turbocharger casings and compressor rotors, which have complex shapes and have different wall thicknesses in their hollow parts.

[Background of the invention]

One method for manufacturing ceramic products is to cast a ceramic-containing slurry into a mold and solidify it.

In this type of generally known method, the entire mold is made of water-absorbing material. Therefore, the water in the slurry will be absorbed and removed from the entire area of the mold.

It is difficult to apply this method to manufacturing products that have complex shapes and parts with different wall thicknesses, such as automobile turbocharger casings.

When this method is applied, there will be areas within the mold where water in the slurry is absorbed quickly and areas where it is slow, resulting in large differences in the solidification rate of the slurry depending on the position within the mold. As a result,
Large variations in density occur in solidified ceramics.

When a solidified ceramic material having such large variations in density is removed from a mold, the surface of the solidified material may be damaged or cracked when the mold is released.

Further, when the ceramic solidified product taken out from the mold is dried and sintered, large dimensional changes occur due to shrinkage, often resulting in deformation or cracking of the solidified product.

As a method for making a hollow ceramic molded body, there is a method in which a ceramic-containing slurry is injected into a mold (a plaster mold), held for a predetermined period of time, and then the slurry is discharged. Although this method is extremely convenient and can produce uniform products, it has the problem that only uniform wall thicknesses can be obtained, and dimensional accuracy deteriorates when the wall thicknesses differ. Therefore, it is not suitable for manufacturing a molded body having a complicated hollow part such as a turbocharger casing. Therefore, in order to solve these problems, it is possible to use a core having the same shape as the hollow part. In this case, the core is limited to a shape that can be removed from the ceramic molded body. A method combining an organic material and a water-absorbing mold has been proposed as a method for obtaining a complex molded body. (Sho 56-286B?) This method heats the mold part (organic material) to a melting temperature in order to remove it, so it requires complicated steps such as maintaining a highly humid environment around the molded object and absorbing the molten material. There are problems such as the need to go through a processing process.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a ceramic product that is less prone to cracking and deformation when a solidified ceramic product is released from casting or sintered afterwards.

[Summary of the invention]

The present invention, casting a ceramic-containing slurry into a mold,
It causes directional coagulation.

In the present invention, the solidified product obtained by directional solidification of the ceramic-containing slurry is very dense and has little variation in density, and therefore does not crack during mold release.
Furthermore, this is based on the discovery that even when sintered, there is little deformation and cracks are less likely to occur.

In the present invention, after solidifying the ceramic-containing slurry in a mold, the soluble model is eluted, and then the molded body is dried and
It is characterized by firing to create the final ceramic product.

A ceramic-containing slurry is prepared by suspending the ceramic in a suitable medium. Any known ceramic material can be used. Ceramics suitable for applying the method of the present invention include silicon carbide,
Silicon nitride, Sialon, etc. Of course, alumina, zirconia, etc. can also be used.

The size of the ceramic particles in the ceramic-containing slurry may also be arbitrary.

Any medium can be used for suspending the ceramics as long as it has the property of uniformly dispersing the ceramics. The most preferred medium is water. When suspending ceramics in water to form a slurry, it is desirable to include a deflocculant.

In the case of a slurry containing silicon nitride and Sialon, a good deflocculant is, for example, a mixture of naphthalene sulfonic acid, sodium metaphosphate, and citric acid.

It is desirable that the amount of water be 20-40%.

As the water-absorbing mold, a plaster mold, a synthetic resin mold, or an unglazed mold can be used, and these can be used in an appropriate combination.

As the non-water-absorbing mold, a rubber mold, a metal mold, a synthetic resin mold, etc. can be used, and these can be used in an appropriate combination.

Polystyrene, wax, etc. can be used as the flat-soluble model, and any material that can be easily dissolved in organic matter can be used.

An organic solvent can be used as long as it dissolves the soluble model but does not dissolve the solidified material in the slurry.

In carrying out the method of the present invention, a mold is composed of a water-absorbing mold, a non-water-absorbing mold, and a soluble model.

[Embodiments of the invention]

Example 1 An example in which a cylindrical pipe was manufactured will be described.

The shape of the pipe is outer diameter 50mmφ and inner diameter 40+n+nφ.
The wall thickness is 5Wtrl and the length is 50+m+.

The mold was manufactured as follows. A plaster mold, which is a water-absorbing mold, was used for the bottom part. Plaster is commercially available calcined gypsum.
Gypsum was added to water at a ratio of 0.00 parts by weight to 80 parts by weight of water, and mixed for 2 minutes with a stirring mixer (rotation speed: 30 rpm) to prepare a slurry material. Next, mud was poured into the wooden model and molded. After the plaster had hardened, the model was removed and kept in a dryer at a temperature of 50°C for 24 hours to release moisture.

The inner diameter of the soluble model was molded from polystyrene foam. Commercially available polystyrene beads were fabricated by two-stage foam molding. That is, the raw material beads were pre-foamed by heating them in hot water at 93 to 95° C. for 2 minutes. After draining the water, it was lightly filled into an aluminum mold and sealed. Next, the mold is held in hot water at 95° C. for 30 minutes and then cooled with cold water to obtain the desired foam.

The mold for the outer diameter part was a rubber mold divided in half.

The plaster mold, rubber mold, and foamed polystyrene model were assembled into one piece.

The ceramic-containing slurry was prepared using the following formulation.

Refractory particles: Siyalon powder 100 parts by weight Water °40 300 gr of the above material was placed in a polyethylene container together with a plastic ball and mixed by rotation for 75 hours. Next, in order to remove the air in the slurry, vacuum treatment is performed at a vacuum level of 73.
．． It was left for 5 minutes in an atmosphere of 5 cmHg or higher. The slurry thus obtained was poured into the integrated mold through the opening (upper surface) and filled.

The slurry gradually absorbs water from the plaster mold and solidifies. Thereafter, one plaster mold was removed and the entire mold was immersed in a methyl acetate solution, and the foamed polystyrene model immediately began to melt, and the melting was completed in one minute.

The mold is then removed from the solution and the rubber mold is released to obtain a green body.

Next, the following drying process was performed to remove moisture from the green body. The mixture was heated and maintained in a dryer at 60°C±2°C for 24 hours, and further heated to 105°C for 2 hours. Next, sintering was performed. The sintering process was as follows.

The compact was placed in a graphite container, the graphite container was placed in a sintering furnace, the atmosphere was made into a vacuum of 4 x 10-', nitrogen gas was introduced, and the pressure was maintained at 1 kg/rl and heating was performed. . Temperature transfer is 5℃/win up to 500℃, from 500℃
The mixture was heated and held at 1600°C for 2 hours at a rate of 10°C/win to 1600°C, then raised to 1750°C at a temperature increase rate of 10°C/win, heated and held at that temperature for 5 hours, and then cooled in a furnace. As a result, a sintered pipe with no deformation and high surface and dimensional accuracy was obtained.

The relative velocity was 99.5%.

Example 2 An example in which a casing for an automobile supercharger was manufactured will be described.

FIG. 1 is a sectional view showing the structure of the mold.

The ceramic-containing slurry was prepared using the following formulation.

Refractory particles: Silicon nitride 100 parts by weight Water 40 300 gr of the above material was placed in a polyethylene container together with a plastic ball, and mixed by rotation for 75 hours to obtain a desired slurry. Next, in order to remove the air in the slurry, a vacuum treatment was performed by leaving it for 5 minutes in an atmosphere with a degree of vacuum of 73.5 cmHH.

The slurry thus obtained is poured into a water-absorbing mold 4 made of gypsum and filled through the sprue 1, where the water in the slurry is removed and solidified directionally. When the sprue part solidifies, the entire mold is turned over, the gypsum water-absorbing mold is removed, and methyl acetate solution is injected into the expanded polystyrene model 3 from part 5, and the model immediately begins to melt and finally melts. It becomes liquid. At this time, by further tilting the mold and draining the liquid, the desired cavity can be obtained.

Next, the non-water-absorbing model is removed to obtain a molded body. By cutting out the sprue part, a desired molded casing (green body) is obtained.

Next, in order to remove moisture from the green body, it was heated and dried at 50°C for 24 hours and at 110°C for 5 hours.

Next, sintering was performed. The sintering process was as follows.

The molded body was placed in a graphite container, and the surrounding area was filled with silicon nitride powder. This graphite container is placed in a sintering furnace,
After the atmosphere was reduced to a vacuum of 8 x 10-', nitrogen gas was introduced and heating was performed while maintaining the pressure at 0.2 kg/d. After being maintained at a maximum temperature of 1750° C. for 1.5 hours at a heating rate of 10° C./sin, it was cooled in a furnace. As a result, the sintered body was not deformed and a casing with high surface and dimensional accuracy was obtained.

The relative density was 90%.

〔Effect of the invention〕

As described above, according to the present invention, the density of the green body can be increased, and a product with a smooth surface that can be easily released from the mold can be obtained. This is especially effective when producing molded bodies with complex hollow parts.

Furthermore, a product with stable dimensions and less deformation during drying and sintering can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a mold in an embodiment of the present invention. 2... Non-water-absorbing template, 3... Soluble model, 4...
Absorbent mold. Agent Patent Attorney Akio Takahashi Page 1 Continued 0 Inventor Kei Kuniya - Hitachi City Saiwaimachi 3-chome Office

Claims (1)

[Claims] (1) A ceramic-containing slurry is cast into a female mold composed of a water-absorbing mold, a non-water-absorbing mold, and a soluble model, and after directional solidification, the soluble model is eluted with an organic solvent, and then, A method for manufacturing ceramic products, which is characterized by drying and firing a molded body. 2. The water-absorbing mold is made of plaster or an unglazed mold, the non-water-absorbing mold is made of rubber, synthetic resin, or metal, and the soluble model is polystyrene.
The method for producing a ceramic product according to claim 1, wherein the ceramic product is wax.