JPS6377704A - Manufacture of ceramic sintered body - Google Patents

Abstract

(57) [Abstract] 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 is a ceramic sintered body! Regarding the Flj manufacturing method.

The method of the present invention can be used in a method of manufacturing ceramic turbine wheels and the like.

[Prior Art] Conventionally, for example, an injection molding method has been adopted as one of the methods for manufacturing ceramic turbine wheels.

In this case, the hub part and blade part of the impeller are molded as a body object, so the structure of the slide core that forms the blade part of the mold is complicated, and due to the complicated shape and difference in wall thickness, there are many problems in mold production. It is costly and time consuming. There is also the problem that internal cracks and surface cracks occur during degreasing due to differences in shape and wall thickness.

In addition, as another conventional method for manufacturing ceramic turbine wheels, as described in Japanese Patent Application Laid-Open No. 56-46709, the thick portions of the ceramic turbine wheel, such as the disk or (shaft portion), are pressed in advance. After molding, a method is known in which the molded body is placed in a fixed position in a mold for molding, and then the thin-walled part of the turbine wheel is cleaned, degreased, and sintered. There are problems in that it takes a long time (usually one week) to degrease molded bodies molded by injection molding, and that degreasing must be carried out at a high temperature of about 400 to 500°C.

[Problems to be Solved by the Invention] The present invention overcomes the above-mentioned drawbacks, and is capable of suppressing the occurrence of cracks during demolding, allowing degreasing to be carried out at a relatively low temperature, and improving the bonding process. It is an object of the present invention to provide a method for manufacturing a ceramic sintered body such as a ceramic turbine wheel, which can greatly shorten the required time.

[Means for Solving the Problems] The method for producing a ceramic sintered body of the present invention involves molding and sintering Hiramix powder using a slip in which it is suspended in a dispersion medium together with a W glue. A method for producing a ceramic sintered body includes a molding step in which a thick portion of the ceramic sintered body is pre-molded to form a molded body, and a molded body is placed at a predetermined position in a slip casting mold. a placing step; a casting step of casting the slip into a cavity between the molded body and the inner wall of the slip casting mold, and simultaneously joining and integrating the slip with the molded body to form a cast molded body; It consists of a demolding process of releasing the mold from the slip casting mold, a drying process of drying the cast molded body after demolding, and a sintering process of sintering and densifying the brought-in molded body after drying. This is a feature that covers this.

The manufacturing method of the present invention involves slip casting a thick-walled hub or shaft part that has been pre-formed using a ceramic material such as silicon nitride (S+3N4), silicon carbide (S i C), or aluminum (Al2O2). The feature is that the slip is placed in a mold and integrated by casting into a cavity between the thick-walled molded body and the inner wall of the slip casting mold.

That is, the method for manufacturing a ceramic sintered body of the present invention includes a step of forming a thick inner part performed in advance, a placement step of disposing the molded product in a slip casting mold, a casting step of joining and integrating, It consists of a subsequent demolding process, a drying process, and firing one culm.

The thick portion can be formed in advance by selecting from the usual slip casting using a plaster mold or press forming using an isostatic mold. In this case, slip casting using a plaster mold is considered suitable. Isostatic pressing using a rubber mold is also suitable, but depending on the shape, machining may be required as post-processing. Press molding may result in non-uniform filling density, and as the thickness increases, it becomes bulkier.

The next step is to place the pre-formed thick-walled part into the groove C in the slip casting mold.
Arrangement as a culm It is one culm.

Next, a slip consisting of the composition described below was placed in the slip key 1F.
Casting mold casting [1 to pouring E case 4 Casting molding II culm is used to connect and integrate the molded body.

Demoulding after valley fill for a predetermined period of time (approximately 20 minutes) - Remove the mold. After demolding, the culm is dried and then sintered into a T-culm. The sintering can be performed, for example, at 1760° C. for 4 hours under nitrogen sintering, or at 2080° C. for 1 hour under a helium FF atmosphere.

Example 1 The present invention will now be explained with reference to examples. 1 (First Embodiment) This embodiment will be explained as an example of the case where a ceramic turbine wheel is manufactured.

The hub part or the shaft 71 to 71 parts, which are the thick parts of the ceramic turbine wheel, are preformed by either Rislip 1 casting, hydrostatic molding using a rubber mold, or press molding using a mold. The molding mouth [firstly, the culm is formed 1. As a ceramic material (silicon carbide (SiC) represented by silicon nitride (Si3N4))
Although it is also possible to use alumina (Δ1703) or the like, it is preferable to use a material suitable for high-temperature production.

The composition of the slip is as follows: (1) β-8iC average particle size 0.25 μm, 98°02
wt%, J] Crystalline boron average particle size 0.15 μm, 0.28 wt%
, Carbon black average particle size 0.02μm 11.70wt
%, 69.0 wt % of the mixture of Meju, a sodium alkyl phosphate salt peptizer consisting of 1.6 W4 [%, polycarbonate oxygen peptizer i, Q wt % and benzene 28.4 wt %, Or (2) α-8i3N4 average particle size 0.9 μm, 97°Qw
t%, Y2O3 average particle size 0.8 um, 1. swt%, MaO average particle size 0.01 μm, 0.4 wt%, Δ1203 average particle size 0.02 μm1 1.1 wt%, 75.0 wt% of the above mixture, 0.4 wt% of water glass as a deflocculant, and pure Water (consisting of ion exchange after distillation >24.6 wt%) A slip having the composition shown in (1) or (2) below was used.

The above pre-formed hub or shaft part molded body A is
It was placed in the cavity 5 of the slip casting mold shown in the figure as shown by diagonal lines in FIG. In Figure 1,
7 is a turbo wheel, 8 is a hub portion, 9 is a wing portion, and 10 is a rotating shaft portion. Figure 2 shows the configuration of a slip casting mold for a turbo wheel, where 1 is a non-water-absorbing plastic mold, 2 to 4 are plaster molds, 5 is a cavity, and 6 is a slip casting mold [1]. In addition, the above 2! XJ f'
Movable mold for forming Js 9 (can move forward and backward during demolding) C
be.

After wetting the surface exposed to the cavity 5 of the molded body arranged in this manner with a liquid consisting of two components, pure water and water glass, the slip having the composition ratio of (2) above is wetted, and then the slip having the composition of (2) is It was poured through the casting port 6 shown in Figure 2 and allowed to ink for 20 minutes. After inking, remove the plus book mold 1 (Fig. 2), move the movable mold 2 that forms the wing shape backwards, and remove the mold 1.
Dry as usual. After drying, the integrated molded body (outermost diameter 102 mm) was heated at 9.5 kQ/cm20) under nitrogen pressure.
The product was sintered at 760°C for 4 hours. No cracks were found during external and internal inspection (ultrasonic flaw detection, transmitted X-ray).

(Second Example) The pre-formed hub portion or the molded body 8 of the shaft 71 to the third
As shown by diagonal lines in the figure, it was placed in the cavity 5 of the slip quellesting mold shown in FIG.

- Among the slips having the composition (1) above, a weight ratio of 1.5 polycarboxylic acid deflocculant, 1.0 polyacrylic binder, and 21.5 benzene was placed in the cavity 5. The surface of the arranged molded body was sprayed and wetted, and the slip having the composition of <1) was brought in as shown in Figure 2 in Example 1 and Ib.
From slip casting y! Pour it inside and apply it (
After 35 minutes), the mold was removed and dried.

After drying, the entire integrated molded body is immersed in a toluene solution of polyacrylic resin (A degree 23%), the excess liquid is poured off, and after drying, a flexible polyester with a thickness of about 0°2 nm is coated on the surface of the molded body. An acrylic resin film was formed and sealed. Then,
Hydrostatic pressurization of 3 ton/cm 2 was applied in water to obtain a high-density and thin molded body. This molded body was heated to 1400℃ for 10 tons.
The product was evacuated to a vacuum level of orr or less, and then sintered at 2080° C. for 1 hour in an atmosphere of 1 atm of helium to obtain a product. No cracks were observed during external and internal inspection.

(Third Example) Pre-formed hub part or molded body A or 8 of the shaft part 71 to 8
was placed in the cavity 5 shown in FIG. Similar to the first and second embodiments, the step of wetting the cavity side surface of the molded body with liquid is no longer necessary.

In this example, it is important to attach the culm for a short time (about 5 to 10 minutes) so that the wing does not deform. In a state in which the attached body is prone to cracking, and the attached body is insufficiently dried (sufficient shrinkage does not occur), the slip-cast molded body is immersed in a toluene solution of polyacrylic resin, and After drying and covering the surface with a water-impermeable membrane in the same manner as in the second example, hydrostatic pressure (1,5 to 3 tons) was applied.
/cm2).

In addition, when solidifying the plaster mold for slip casting, it is better to have a mirror finish on the surface of the movable mold for forming the first straight part of the airfoil shape, and it is also 100 kg.
It is better to apply a pressure of about /cm2. By doing this, the mold releasability of the attached body is improved to a large IJ, and it is possible to prevent the occurrence of cracks between the wings of the attached body during demolding (when the movable mold is retreated). More preferably, the surface of the movable mold is coated with a soap release agent such as polytetrafluoro-1-ethylene.

After the hydrostatic pressurization, the product was baked by the method of either the first or second embodiment.

[Effects of the Invention] According to the method for manufacturing a ceramic sintered body of the present invention, a product, such as a ceramic turbine wheel, which has a thick inner part and a thin part and is solidified by integral injection molding, can be produced by using a slip casting method. It can be manufactured in a much shorter time than conventional methods, and the occurrence of cracks in the product can be reliably suppressed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the slip casting method of a molded body molded by the method of the present invention and the arrangement state in a cavity. FIG. 2 is a sectional view showing the configuration of a slip casting mold for a Hiramic turbine wheel. FIG. 3, like FIG. 1, is an explanatory view showing slip casting of a molded body molded by the method of the present invention and its arrangement in a cavity. 1...Plastic mold 2.3.4...Gypsum mold 5...Mold cavity 6...Slip casting ports A, B...Molded body 7...Ceramic turbine wheel = 13-8 ...Ceramic turbine wheel hub part 9...
Blade portion 10 of ceramic turbine wheel...Rotating shaft portion of ceramic turbine wheel Patent applicant Toyota Motor Corporation agent Patent attorney Hirodo Okawa Patent attorney Akio Maruyama-14=

Claims (5)

[Claims] (1) In a method for producing a ceramic sintered body formed by molding and sintering using a slip in which ceramic powder is suspended in a dispersion medium together with a deflocculant, the thick portion of the ceramic sintered body is formed. a molding step of pre-molding a portion to be molded to form a molded body; a placement step of installing the molded body at a predetermined position in a slip casting mold; and a step of placing the slip in a cavity between the molded body and the inner wall of the slip casting mold. A casting process for obtaining a casting body by joining and integrating the casting body at the same time as casting, a demolding process for releasing the casting body from the slip casting mold, and after demolding, the casting process. A method for manufacturing a ceramic sintered body, comprising: a drying step of drying the body; and a sintering step of sintering and densifying the cast body after drying. (2) The method for producing a ceramic sintered body according to claim 1, wherein the forming step of preforming the thick portion of the ceramic sintered body is performed by a slip casting method. (3) The method for manufacturing a ceramic sintered body according to claim 1, wherein the forming step of preforming the thick portion of the ceramic sintered body is performed by isostatic pressing. (4) The method for manufacturing a ceramic sintered body according to claim 1, wherein the forming step of preforming the thick portion of the ceramic sintered body is press molding. (5) After the drying process, the integrated molded body is immersed in a toluene solution of polyacrylic resin (concentration 23%), and then dried to form a polyacrylic resin film on the surface of the molded body, and further subjected to hydrostatic pressure. The method for manufacturing a ceramic sintered body according to claim 1, wherein a firing step is performed after the above-mentioned steps are performed.