JPH0552241B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a dispersion-strengthened composite ceramic molded article, and more specifically, to a dispersion-strengthened composite ceramic material that is employed as a means for improving the toughness of a ceramic material. The present invention relates to a method for forming a dispersion-strengthened composite ceramic molded body, in which reinforcing material in the form of short fibers or particles can be blended into desired areas of ceramic powder serving as a base material.

[Conventional technology]

Dispersion-reinforced composite materials are composite materials in which various properties of a base material are reinforced with short fiber or particulate reinforcing materials.High strength, high elasticity, and Because it can be imparted with unique properties such as low coefficient of thermal expansion and wear resistance, it is attracting attention as a material for various industrial parts in the future.

The reinforcing materials include boron, alumina,
Reinforcing materials such as silicon carbide are generally employed, and base materials such as plastic materials, metal materials, ceramic materials, etc. are commonly employed.

By the way, among the various dispersion-strengthened composite materials mentioned above, research and development is underway on dispersion-strengthened composite ceramic materials in order to improve the toughness of the ceramic material that is the base material, and methods for manufacturing the dispersion-strengthened ceramic materials have been progressing. A mechanical press molding method is one in which ceramic powder and reinforcing material are appropriately placed in a mold and then press molded.

A slip casting method in which reinforcing material is placed in the cavity of a mold that has at least a portion of a plaster mold, and then a slurry-like slip (sludge) mainly made of ceramic material is injected or sucked into the mold.

etc. have been adopted.

[Problem that the invention seeks to solve]

In view of the current state of the prior art as described above, the problem to be solved by the present invention is that in the conventional method for manufacturing dispersion-strengthened composite ceramic materials, the mechanical press molding method that can be manufactured by this method is Dispersion-strengthened composite ceramic molded bodies are not only limited in shape to simple shapes such as test pieces, but also require a long time for molding, which makes them uneconomical.

In the slip casting method, the slip of ceramic material is usually not as low viscous as molten metal, and in order to achieve low viscosity, the content of ceramic powder must be reduced, so Cracks tend to occur when drying ceramic molded bodies, and if the content of ceramic powder is increased to make it highly viscous, the reinforcing material may not be mixed well into the slip and may clump together, or the reinforcing material may fall out of place. It is difficult to move and dispense into the desired location, and there is no reliable positioning method for placement of the reinforcing material within the mold cavity.

etc.

In contrast, the present applicant has already applied for a patent regarding a ceramic material composited with long fibers. (Japanese Patent Application No. 60-148591; unknown) Therefore, an object of the present invention is to enable reinforcing materials in the form of short fibers or particles to be blended into desired areas, regardless of the shape of the molded product. be.

[Means for solving problems]

Therefore, in the present invention, a dispersion-reinforced composite ceramic molded body is produced by slip casting using a solvent that shrinks or eliminates the foamed resin, with the foamed resin molded body in which the reinforcing material is dispersed in advance mounted in a mold. It is characterized by obtaining.

Specifically, the method for molding a dispersion-strengthened composite ceramic molded article of the present invention involves filling a cavity of a mold having a predetermined shape with a resin material having foamability together with a reinforcing material in the form of short fibers or particles. After that, the first step is to foam and fill the cavity to disperse and fix the reinforcing material in predetermined positions, and then mold the foamed resin molded body with the reinforcing material dispersed and fixed in predetermined positions inside. a second step in which the core is installed in the cavity of a mold having the shape of a ceramic molded body, and a slurry in which a solvent capable of shrinking or disappearing the foamed resin, a surfactant, and ceramic powder are uniformly mixed; a third step of injecting a slip into the cavity of the mold to perform slip casting;
A method for molding a dispersion-strengthened composite ceramic molded body, comprising a fourth step of degreasing and drying the ceramic molded body that has been slip casted in the step, the method comprising: injecting the ceramic molded body into a cavity of a mold in the third step; The foamed resin is shrunk or disappeared with a solvent, and ceramic powder is filled in place of the foamed resin to form a ceramic molded body in which the reinforcing material is blended into the cavity in the mold.

Here, various types of slip (slurry) can be employed as shown in the following A to E, for example.

In addition, all the contents shown below are displayed by weight%.

A: Ultra fine grade SiC; 76% polycarboxylic acid peptizer; 1.5%, polyacrylic binder; 1.0%, benzene; 21.5%, B: Si ₃ N ₄ powder; 80.5%, polycarboxylic acid type Peptizer; 0.6%, toluene; 18.9%, C: Si ₃ N ₄ powder; 79.0%, water glass peptizer;
0.4%, distilled water; 20.6%, D: borosilicate glass powder; 73.5%, (average particle size 1.5μ)
Polyoxyalkyl phosphate peptizer; 0.8,
Polyacrylic binder; 1.2%, trichlorethylene; 24.5%, E: Carbonyl Ni powder; 78.6%, (average particle size 3.8μ)
Polycarboxylic acid peptizer: 0.5%, benzene: 20.9%, etc.

Among the five types of slip compositions mentioned above, A, B, and D
The solvent liquid used in E and E is an organic solvent such as benzene, toluene, and trichloroethylene. These organic solvents can cause expanded polystyrene to shrink or disappear significantly. Therefore, these organic solvents cause the foamed polystyrene containing the reinforcing material inside to extremely shrink or disappear, and are replaced by the ceramic molded body containing the reinforcing material inside.

In addition, since slip C uses distilled water as the solvent, the expanded polystyrene cannot be removed as it is.

Therefore, when using slip C, it is necessary to mix an organic solvent such as benzene into the slip containing distilled water as a solvent. Then, when this slip is injected into the mold cavity, the organic solvent such as benzene mixed in the slip shrinks or disappears the expanded polystyrene, and the slip follows the mold cavity. Fill up.

[Effect]

According to the configuration of the present invention described above, since the reinforcing material is dispersed and fixed in the foamed resin in advance, the reinforcing material can be blended into a desired region. Then, the reinforcing material is combined into a foamed resin with the reinforcing material dispersed and fixed, using a slip that causes the foamed resin to shrink or disappear extremely, and the foamed resin and the slip are replaced at the same time as slip casting. .

〔Example〕

(First Embodiment) This embodiment is an example of application to a ceramic valve in which the valve seat portion is partially reinforced.

1 to 6 are diagrams showing a method of molding a ceramic valve according to a first embodiment of the present invention.

Hereinafter, a first embodiment of the present invention will be described based on the accompanying drawings.

In the first step, SiC whisker (β-SiC with a diameter of less than 1 μm manufactured by Tokai Carbon Co., Ltd.)
Whiskers) 25g were dispersed in 1000g of n-hexane medium and thoroughly loosened through a 150 mesh sieve in the medium to form a paste. Next, spread the paste on a flat surface to a thickness of about 1 mm and heat it to about 60°C.
It was dried for 2 hours. After drying, 100 g of foamed polystyrene resin raw material particles (about 1 mm in diameter) were placed on top of it, and it was applied to a vibrator to give vibrations at about 250 KHz.
SiC whisker powder was sufficiently attached to the raw material particles. The thus obtained foamed polystyrene raw resin to which the SiC whisker powder was attached was filled into the cavity 14 by pneumatic transport through the resin injection hole 12 of the core molding die 10 shown in FIG. Thereafter, water vapor is supplied in a conventional manner from a steam outlet (not shown) provided in the mold 10 to foam the foam at a foaming rate of 30 times, resulting in a cavity-shaped SiC whisker powder, the appearance of which is shown in Figure 3. A foamed polystyrene core 16 containing the following was formed. This core 16 has a shape corresponding to the surface portion of the valve seat, and has a surface thickness of approximately 3 mm.

Next, in the second step, the expanded polystyrene core 16 containing the SiC whisker powder produced in the first step is installed in the cavity 20 of the plaster mold 18 shown in FIG. , upper mold 2
6 in order to complete the installation.

In the third step, first, a slip is prepared. Slip is made of silicon nitride powder, which is the matrix component.
80.5Wt%, slip medium toluene 18.9Wt%
and 0.6 Wt% of a polycarboxylic acid peptizer were mixed in a Pall mill. This slip 28,
As shown in FIG. 4, slip casting was performed by injecting through the upper opening 30 of the plaster mold 18 to which the core 16 was attached. Injected slip 28
flows to the lower valve seat portion 32, and the core 1
Contact 6. The toluene medium in the slip 28 comes into contact with the foamed polystyrene resin core 16 and causes the foamed polystyrene resin to disappear. Then, by filling the cavity with silicon nitride powder in place of the foamed polystyrene resin, a ceramic valve molded body 34 containing SiC whisker powder is formed, the appearance of which is shown in FIG. 5.

The obtained molded body 34 is degreased, dried, and fired in a fourth step to obtain a ceramic bulk. Degreasing is carried out at approximately 450℃ for 1 hour.
Remaining organic components are removed. After that, about 1750
Firing takes place at 0C for 2 hours. As shown in FIG. 6, which corresponds to the cross-sectional view taken along the - arrow in FIG.
It is a dispersion-strengthened composite material of SiC whiskers and silicon nitride with a thickness of t mm.

Ceramic valve 36 manufactured in this way
In all cases, good products with no cracks were obtained.

(Second Embodiment) This embodiment is an example of application to a ceramic turbo rotor on the exhaust side in which the blade tip of the exhaust gas inlet portion is partially reinforced.

7 to 10 are diagrams showing a method of molding a ceramic rotor according to a second embodiment of the present invention. A second embodiment of the present invention will be described below based on the accompanying drawings.

In the first step, first, the foamed polystyrene raw material resin with SiC whisker powder attached thereto, prepared in the same manner as in the first example, is air-transported from the resin injection hole 112 of the core molding die 110 shown in FIG. The cavity 114 was filled with the following steps. after that,
Steam was supplied in a conventional manner from a steam outlet (not shown) provided in the mold 10, and the foam was foamed at a foaming rate of 30 times. A foamed polystyrene core 116 was formed. This core 116 has a shape that corresponds to a portion of the blade of the ceramic rotor near the exhaust gas inlet.

Next, in the second step, the expanded polystyrene core 116 containing the SiC whisker powder created in the first step is installed in the cavity 120 of the mold 118 shown in FIG.
24, the upper die 126 and the presser die 128 are placed in this order to complete the installation. The upper mold 126 is a split mold that is movable along the blades of the turbo rotor.

In the third step, a slip prepared in the same manner as in the first example is prepared. This slip 130,
As shown in the figure, slip casting was performed by injecting through the upper opening 132 of the mold 118 to which the core 116 was attached. Injected slip 1
30 flows downward and contacts the core 116. The toluene medium in the slip 130 comes into contact with the foamed polystyrene resin core 116, and silicon nitride powder is filled into the cavity instead of the foamed polystyrene resin.

Note that when pouring the slip 130, the lower mold 12
A vibrator 134 provided below the mold 118 was activated to vibrate the mold 118, so that the slip 130 was sufficiently spread over the narrow cavity portion corresponding to the blade portion.

The obtained ceramic rotor molded body is then degreased, dried, and fired in a fourth step to obtain a ceramic rotor. Degreasing is carried out at approximately 450° C. for 1 hour to remove remaining organic components. Afterwards, it is fired at approximately 1750°C for 4 hours. Turbo rotors have thinner parts with more complex shapes than valves, so
More heating time is required. The obtained ceramic turbo rotor 136 has blades 138 near the exhaust inlet, as shown in FIG.
It is a dispersion-strengthened composite material of SiC whiskers and silicon nitride. All of the ceramic rotor rotors 136 manufactured in this manner were in good condition with no cracks.

(Third Example) This example is an example of application to a ceramic valve in which the blending ratio of reinforcing materials is varied and the valve seat portion is partially reinforced.

The content of the reinforcing material in the dispersion-strengthened composite portion of the ceramic valve in the first embodiment is varied stepwise.

The manufacturing method differs from the first embodiment only in the first step.

In this embodiment, the reinforcing material is dispersed and fixed in three layers so that the content of the reinforcing material increases toward the surface of the valve seat portion of the valve.

In the first step, first, 25 g of SiC whiskers (beta-SiC whisker powder of 1 μm or less, manufactured by Tokai Carbon Co., Ltd.) are dispersed in 1000 g of n-hexane medium, and thoroughly passed through a 150 mesh sieve in the medium. It was loosened and made into a paste. Next, spread the paste on a flat surface to a thickness of about 1 mm and heat it to about 60°C.
It was dried for 2 hours. After drying, raw material particles (about 1 mm in diameter) of expanded polystyrene resin were placed on top of it, and it was applied to a vibrator to give vibrations at about 250 KHz, so that SiC whisker powder was sufficiently attached to the raw material particles. At this time, the amount of expanded polystyrene resin to be placed was divided into three types, and 45 g, 100 g, and 200 g were placed respectively, and SiC whisker powder was attached. The foamed polystyrene raw material resin with the SiC whisker powder attached thus obtained is pneumatically transported through the resin injection hole 12 of the core molding die 10 shown in FIG. , was filled into the cavity 14. after that,
Foaming was performed in the same manner as in the first example at a foaming rate of 30 times,
An expanded polystyrene core containing cavity-shaped SiC whisker powder was formed. As shown in a partially cutaway external view of FIG. 11, this core 21
0 is made of foamed polystyrene from the surface portion 212 that corresponds to the valve seat to the intermediate portion 214 and inner layer portion 216.
The content of SiC whiskers is decreasing. Then, in the second step, the
A polystyrene foam core 210 containing SiC whisker powder is installed in the cavity 20 of the plaster mold 18 shown in FIG.
Place them in order to complete the installation.

The subsequent steps are similar to those in the first embodiment, and upon completion of the fourth and final step, a ceramic valve 218 as shown in cross section in FIG. 12 is obtained. This ceramic valve 218 has a main body portion 220 made of silicon nitride, and a valve seat portion 222.
disperses SiC whiskers as a reinforcing material. The content rate of SiC whiskers is different in the surface portion 224, the intermediate layer 226, and the inner layer portion 228,
Each formed a layer with a thickness of 2 mm, 25 Wt%,
Contains 10Wt% and 4Wt%.

In this example, since the content of the reinforcing material in the surface portion 224 of the valve seat portion 222 was made highest, it was possible to cause compressive stress to remain in the surface portion 224. Therefore, the toughness of the valve seat portion 222 has increased.

In addition, in the valve seat portion 222, the surface portion 22
Since the content of the reinforcing material was changed stepwise from No. 4 to the inner layer portion 226, the strength of the product as a whole was increased.

Here, the foaming rate of expanded polystyrene is
A ratio of 15 to 60 times is desirable; if the ratio exceeds 60 times, the expanded polystyrene will be easily deformed, and if the ratio is less than 15 times, the residue of the expanded polystyrene will tend to remain in the ceramic molded body in the subsequent fourth step, resulting in cavities in the ceramic powder molded product. This is not preferable because it tends to cause

〔Effect of the invention〕

As is clear from the above, according to the method for forming a dispersion-strengthened composite ceramic molded article according to the present invention,
It is possible to mold a dispersion-reinforced composite ceramic molded article in which short fiber or particulate reinforcing material is blended into desired areas.

[Brief explanation of drawings]

FIG. 1 shows the method of molding a ceramic valve according to the first embodiment of the present invention, and FIG. Figure 3 is an external view of the core, Figure 4 is a cross-sectional view of the mold showing the state in which the slip is poured, and Figure 5 is a cross-sectional view of the mold for molding the core. FIG. 6 is a cross-sectional view of the ceramic valve corresponding to the view taken along the - arrow in FIG. 1 is a cross-sectional view of a mold for molding expanded polystyrene cores containing reinforcing material;
Figure 8 is an external view of the molded core, Figure 9 is a cross-sectional view of the mold with the core attached and slip poured in, and Figure 10 is a post-molding process such as degreasing. Cross-sectional view of the ceramic rotor, 1st
Figure 1 shows a method for molding a ceramic valve according to a third embodiment of the present invention, and shows cross-sectional views of expanded polystyrene cores molded to contain different reinforcing material contents; The figure is a cross-sectional view of the completed ceramic valve. 10... Mold (for foamed resin molding), 16... Foamed resin molded body, 18... Molding die, 20... Cavity, 28... Slip.

Claims (1)

[Claims] 1 In the cavity of a mold having a predetermined shape,
A first step of filling a foamable resin material together with a reinforcing material in the form of short fibers or particles, and then foaming it to fill the cavity to disperse and fix the reinforcing material in a predetermined position; A second step in which the foamed resin molded product with the material dispersed and fixed in a predetermined position is installed in the cavity of a mold having the shape of the ceramic molded product to be molded in the form of a core, and the foamed resin is shrunk or A third step of performing slip casting by injecting a slip in the form of a slurry in which a solvent, a surfactant, and ceramic powder that can be eliminated is uniformly mixed into the cavity of the mold; The ceramic molded body
A method for molding a dispersion-strengthened composite ceramic molded article, which comprises a fourth step of degreasing and drying, and in the third step, the foamed resin is shrunk or disappeared by a solvent injected into the cavity of the mold, and the foamed resin is 1. A method for molding a dispersion-strengthened composite ceramic molded body, which comprises filling ceramic powder instead of resin to form a ceramic molded body in which the reinforcing material is blended into a cavity in a mold.