JPS61177205A - Slip casting molding method - 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 provides a slip casting molding method for molding turbine wheels for turbochargers, housings for turbine blades, gas turbine engine parts, etc. using ceramic raw materials. Regarding.

[Prior art]

Conventionally, to mold ceramic parts, ceramic powder was filled into a mold, molded, and then removed from the mold and heated and sintered.However, when the particles become smaller than 1 μm, it is difficult to fill them and the bulk density is 13r. /- level (filling of approximately 40 inches of theoretical density), it was not possible to obtain parts with high strength, and furthermore,
It was limited to simple shapes. In addition, the injection molding method requires a degreasing process of about one week, which is problematic in terms of productivity. Therefore, the slip casting method (pouring molding method) is considered to be an effective method for manufacturing ceramic parts with discrete shapes, but this method also has the following physical and mechanical property problems. be.

[Problem that the invention seeks to solve]

Slip casting is a process in which slip is prepared by adding enough water to ceramic raw materials such as silicon nitride, silicon carbide, sialon, etc. to enable casting, and the slip is poured into a water-absorbing slip casting mold and frozen. After drying, the cast body is removed from the mold and vacuum-dried while being thawed. However, since water is used as the slip forming liquid in the above method, the ceramic powder is oxidized by water vapor, which significantly reduces the high-temperature strength of the final product. There was a problem in that it caused cracks in the body.

The present invention has been made in view of the above problems, and aims to provide a slip casting molding method that adjusts slip without using water and prevents oxidation and cracking caused by water vapor.

[Specific means for solving the problem] The slip casting molding method of the present invention uses ceramic raw materials, sintering aids, and slip forming liquids that have a total weight ratio of 12 or less, a melting point of -20°C or higher, and a boiling point of -20°C or higher. The molded product is cast into a slip casting mold containing a solvent at 100° C. or lower, frozen, and vacuum dried to take out the molded product.

[Effect]

In the present invention, since an organic solvent is used as the slip forming liquid, the ceramic powder is not oxidized by water vapor as in the case of water, and coarse ice crystals are not formed when the cast body is frozen. There is no chemical change or physical impact on the molded product. However, a solvent with a melting point of -20°C or lower is difficult to freeze and is therefore unsuitable for the present invention, and if the boiling point is too high, it is difficult to evaporate even when dried in vacuum, so a solvent with a melting point of -20°C or higher and a boiling point of 100°C The following organic solvents are preferred, and three examples of such solvents include acetone cyanohydrin, benzene, ethyl sulfoxide, glyoxal, cyclohexane, and 1,4 dihydronaphthalene. Considering the latent heat of vaporization, etc., benzene, acetone cyanohydrin, and p-divinylbenzene are preferred, and among them, benzene is the most preferred because it is inexpensive and easy to handle. The melting points and boiling points of such organic solvents are shown in the table below.

In the present invention, the total weight ratio of the organic solvent used is 12
The reason why the amount is limited to less than % is because if it is used in excess, cracks will occur in the molded product due to shrinkage during drying.

Examples of sintering aids added to the ceramic powder include IJA, spinel, alumina, and magnesia, and boron, carbon, alumina, and the like for silicon carbide.

〔Example〕

Total weight ratio: 850% silicon powder [“Ultra Fine” manufactured by IBIDEN Co., Ltd., average particle size 0.4 μm]
], 0.9% by weight of carbon powder as a sintering agent, and 0.
．． 9 weight value boron powder, slip forming liquid 120
1.2% by weight of a surfactant (polyoxyethylene laurylamine) in a ball mill for 24 hours.
After processing for an hour, slips were prepared.

The above slip 150f was cast into a slip casting mold made of wax for radial turbine wheel molding by applying a pressure of 2 atmospheres while applying vibration, and then the above slip was cast into the slip casting mold. The slip was frozen by keeping it in a cold atmosphere at 0.degree. C. for 1 hour. Next, the frozen molded body was taken out from the slip casting mold, vacuum-dried for 20 hours in a frozen state, and then the temperature was gradually raised in the air, and finally the temperature was raised to 100° C. to melt and remove the wax.

The bulk specific gravity of the molded product thus obtained was 1.8 f/cd, and cracks were observed in only 2 out of 100 samples. Next, this molded body was heated and sintered at 2100°C in an argon gas atmosphere.
As a result of cutting out a small piece of mmX4+++mX40■ and measuring its three-point bending strength, it was 60 Kg f/1run2 at room temperature.
．． 72 Kp f /1ras2 in air at 1200℃
Met. On the other hand, the three-point bending strength of the sintered body obtained by the conventional method using water as the slip forming liquid is 35K at room temperature.
ft♂, 40 odor f/wa in air at 1200°C.

〔Effect of the invention〕

As described above, according to the present invention, fine powder of 1 μrn or less can be uniformly filled into a mold to obtain a molded product having a high bulk density and no cracking, and is not oxidized by water vapor as in the conventional method. Sintered parts with high high temperature strength can be obtained. Furthermore, the method of the present invention is a simple process and does not require particularly expensive equipment, so it is effective for mass production of ceramic parts with complex shapes.

Procedural amendment April 18, 1985 Patent Application No. 19556 2, Name of the invention Slip casting molding method 3, Relationship with the amended person's case Name of patent applicant (320) i Yota Jidosha Co., Ltd. 4, Agent address: 1-65, Kanda Surugadai, Chiyoda-ku, Tokyo, Daily publication of amendment orders ``Spontaneous'' 6, Subject of amendment 7, Contents of amendment (1) The scope of claims in the specification will be amended as shown in the attached sheet.

(2) r13g/cm'J on page 2, line 4 of the specification
Correct it to 1.3 g/cmFj.

(3) "12% or less" in the 6th line from the bottom of page 3 of the specification is corrected to "r40% or less".

(4) "12% or less" in the second line from the end of the table on page 5 of the specification is corrected to "40% or less."

(5) “850% by weight” in the second line from the bottom of page 5 of the specification
is corrected to ``r 89.0% by weight''.

(6) "r 12.0% by weight" on page 6, line 3 of the specification is corrected to "r 28.0% by weight."

(Attachment) [2. Scope of claims

Claims (1)

[Claims] (1) A slip containing an organic solvent having a melting point of -20°C or higher and a boiling point of 100°C or lower, with a total weight ratio of 12% or less as a ceramic raw material, a sintering aid, and a slip forming liquid, is cast into a slip casting mold, A slip casting molding method characterized by removing the molded product after freezing and vacuum drying.