JPH06257401A - Manufacture of ceramic disc wheel - Google Patents

Abstract

PURPOSE:To improve the balance of a disc wheel as a rotational body to increase the yield in manufacturing a ceramic disc wheel by applying a cross- linked coating film to an exposed surface, thereafter applying for integration and baking it. CONSTITUTION:A kneaded ceramic powder is injection-molded into a unit block 1, the shape of which is obtained by nearly equally dividing a disc wheel along its rotation axis. The unit block 1 is formed so as to be surrounded by two hub-lines L holding a blade 2 from both sides, the rotation axis C, and both end faces S. These unit blocks 1 are combined with each other before or after degreasing, and a crosslinked coating film is applied to the exposed surfaces of the unit blocks. Hydrostatic pressure is then applied to the unit blocks to integrate them into a body and the body is baked. The hydrostatic pressure is 4t/cm<2> on higher. Thus, since the ceramic disc wheel is completed by baking a homogeneous molded body, it is excellent in balance as a rotational body. Further, no cracks occur in the molded body during degreasing, and the manufacturing yield is thereby increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a ceramic impeller, which can be suitably used particularly for a ceramic turbine charger, a rotor and a ceramic gas turbine.

[0002]

2. Description of the Related Art In an engine with a turbocharger,
There is an acceleration response delay called a turbo lag, and as an improvement, a turbine body made of lightweight ceramic is used for parts of rotors, turbine blades, wheels, etc. that are rotated by a high temperature gas flow. Jar has been put to practical use. Ceramic products are 30% more than conventional Ni alloy products
The above is also light and the moment of inertia showing the force required for rotation is 4
It can be as low as 5%. Therefore, the turbo lug can be shortened by about 20% as compared with the metallic one. Further, it has been studied to manufacture gas turbine turbine wheels from ceramics having excellent heat resistance for the purpose of improving fuel consumption due to high temperature.

Conventionally, as a method of manufacturing such a ceramic impeller, an integral type injection molding method and a fitting type injection molding method are known. The integral injection molding method is one in which a kneaded material of ceramic powder and resin is injection-molded in one cycle so as to have the shape of the entire volume of an impeller as shown in FIG. 1, then degreased, and then the molded body is fired. Is the way to do it. This method has an advantage that the number of steps is small.

Further, in the fitting type injection molding method, an impeller having a shaft hole is injection molded and degreased in one cycle, and a shaft molded and degreased by another molding method is fitted into the shaft hole. In this state, hydrostatic pressure is applied to integrate them, followed by firing. Even if the total volume of the impeller is so large that the temperature distribution and pressure distribution during molding will spread too much and a uniform molded product cannot be obtained when the integrated injection molding method is applied, this method is relatively homogeneous. can do. Therefore, there is an advantage that a large molded body can be obtained.

[0005]

However, in both methods, since the filling volume of the molding material (kneaded material) at the time of injection molding is large, the temperature distribution and the pressure distribution inside the molding during the molding cycle are still large. However, it is difficult to obtain a homogeneous molded body. Therefore, the ceramic impeller completed by firing such a molded body has poor balance as a rotating body.

Further, since the filling volume is large, the volatile gas and the pyrolysis gas generated at the time of degreasing have a long distance to diffuse and move in the molded body. As a result, it takes a long time to complete degreasing, and cracks may occur in the molded body during degreasing. Further, the structure of the mold for injection molding is complicated and accurate dimensional accuracy is required, so that the cost is high. An object of the present invention is to solve such problems and to manufacture a homogeneous ceramic impeller with a small number of steps.

[0007]

[Means for Solving the Problems] The first means is to injection-mold a kneaded material of ceramic powder into unit blocks each having a shape in which an impeller is divided into approximately equal parts along its rotation center axis,
Before or after degreasing, these unit blocks are combined, the exposed surface is coated with a cross-linked film, hydrostatic pressure is applied to integrate the units, and then firing is performed.

A second means is to injection-mold the kneaded material of the ceramic powder into unit blocks each having a shape in which the outer peripheral portion of the impeller is divided into approximately equal parts along the rotation center axis thereof, and before or after degreasing. The combination of the unit block of 1) and the shaft part molded body of the impeller is applied to the exposed surface, a cross-linking film is applied, hydrostatic pressure is applied to integrate, and then firing is performed.

[0009]

The shape obtained by injection molding is not the entire impeller but a unit block obtained by dividing the impeller. Therefore,
The filling volume of the molding material (kneaded material) at the time of injection molding is small.
Therefore, the temperature distribution and the pressure distribution inside the molded body during the molding cycle are reduced, and the residual strain is reduced.
Further, since the filling volume is small, the distance that the volatile gas and the pyrolysis gas generated at the time of degreasing diffuse and move in the molded body is short. Therefore, the diffusion movement proceeds smoothly.

Further, since the unit block has a shape in which the impeller or the outer peripheral portion of the impeller is divided into substantially equal parts along the rotation center axis thereof, when combined with the impeller shape, hydrostatic pressure is applied. Also, when firing, there is almost no variation in temperature and pressure between unit blocks. Table 1 shows each of these actions in comparison with the action by the conventional integral injection molding method and the action by the fitting type injection molding method.

[0011]

[Table 1] It is desirable that the shape of the unit block has two hub lines that sandwich one or more blades as ridge lines. That is,
In the case of the first means, as shown in FIG.
Is preferably a shape surrounded by two hub lines L sandwiching the blade 2, a rotation center axis C, and both end surfaces S. Further, in the case of the second means, as shown in FIG. 3, the unit block 1 preferably has a shape surrounded by two hub lines L sandwiching the blade, an abutting surface P for contacting the shaft molded body, and both end surfaces S. Because the blade is thin and curved, it is difficult to mold the unit block divided into the blade. Hydrostatic pressure is 4 ton / cm
^It is desirable that it is ² or more. This is because the unit blocks do not easily adhere to each other even if a hydrostatic pressure lower than 4 ton / cm ² is applied.

[0012]

Example Silicon nitride Si ₃ N ₄ powder 10 having an average particle size of 1 μm
0 parts by weight, 5 parts by weight of alumina Al ₂ O ₃ powder having an average particle size of 1 μm, 5 parts by weight of yttria Y ₂ O ₃ powder having an average particle size of 1 μm, 5 parts by weight of ethylene vinyl acetate copolymer resin, 15 parts by weight of microcrystal wax. And a raw material for injection molding composed of 4 parts by weight of dibutyl phthalate were mixed to prepare a silicon nitride kneaded product for firing.

Separately, a radial type turbine rotor having a maximum blade outer diameter of 119 mm, a shaft outer diameter of 22 mm, and 10 blades.
A mold having a basic unit shape obtained by dividing the above into 10 equal parts along the rotation center axis was manufactured. Further, a mold used in the conventional fitting type injection molding method and a mold used in the integral type injection molding method, which have the same outer diameter of the blade and the outer diameter of the shaft portion, were also prepared. The mold used in the fitting type injection molding method had a fitting diameter of 12 mm in the thin shaft portion and 22 mm in the thick shaft portion, and had a straight taper shape.

A turbine rotor was manufactured from a silicon nitride kneaded product for firing using various molds. The evaluation experiment in the intermediate step will be described. [Moldability evaluation experiment] The kneaded product was injection-molded under the conditions shown in Table 2 into a mold having a basic unit shape according to the example, and 300 unit blocks were molded. No defect was observed on the surface and inside of these unit blocks, and good moldability was recognized.

For comparison, the conventional fitting type injection molding method uses 30 blades having the same outer shape as the radial type turbine rotor and the radial type molding machine uses the integral type injection molding method. Thirty integral pieces having the same shape as the bin rotor were molded. The molded product obtained by the fitting type injection molding method (hereinafter referred to as “fitted molded product”) was good, but the molded product obtained by the integral injection molding method (hereinafter, “integrated molded product”) was 30 pieces. Three of them had cracks in the center of thickness.

[0016]

[Table 2] [Degreasing evaluation experiment] Next, a temperature rising rate of 2 ° C / H, 5 ° C / H
In a binder removal furnace adjusted to H, 10 ° C / H, 100 unit blocks each, 10 fitting type moldings 10 each, and integral injection moldings 9 each, the maximum The binder was removed at a temperature of 600 ° C.

As a result, no defect was found on the surface or inside of the unit block under any heating rate condition, and good degreasing property was recognized. However, with respect to the fitting type molded body and the integral type molded body, the rate of occurrence of defects on the surface and inside tends to increase as the heating rate increases.

[Evaluation experiment for hydrostatic pressure] Next, the unit blocks after degreasing were combined to form a radial type turbine rotor, and the exposed surface was subjected to latex rubber coating treatment, and then 4 ton / cm ² Hydrostatic pressure treatment was performed at a pressure of 1 to integrate them to prepare 30 unfired ceramic impellers. Temperature rising rate in degreasing process is 10 ℃ /
With the exception of only one defective adhesion between the unit blocks in the degreased body of H, no defect was observed on the surface or inside of these impellers, and good results were obtained.

On the other hand, by combining the fitting type molded body with the corresponding shaft portion molded body into the shape of a radial type turbine rotor, hydrostatic pressure treatment is similarly performed to integrate the molded body into 29 unfired ceramic impellers. It was created. As a result, a slightly greater number of poor adhesions between the fitting type molded body and the shaft portion molded body were observed as compared with the unfired ceramic impeller obtained from the unit block. In addition, when the monolithic molded body was subjected to hydrostatic pressure treatment under the same conditions to prepare 23 unfired ceramic impellers,
Products with a heating rate of 5 ° C / H and 10 ° C / H after degreasing
The product surface was cracked.

[Firing Evaluation Experiment] Finally, 29 unfired ceramic impellers obtained from the unit block were fired in a nitrogen atmosphere at a temperature of 1750 ° C. for 2 hours. As a result, no defect was observed on the surface and inside of the fired body, and good results were obtained.

On the other hand, when 27 unfired ceramic impellers obtained from the fitting type molded body and 19 unfired ceramic impellers obtained from the integral type molded body were fired under the same conditions,
The former had two impellers and the latter had three impellers. [Comprehensive Evaluation] Table 3 shows the results of the above-mentioned various experiments and the yields from raw materials to finished products.

[0022]

[Table 3] As can be seen from Table 3, the yield of the ceramic impeller obtained according to the manufacturing method of the present invention from the raw material to the finished product was 10 when the temperature rising rate during degreasing was 5 ° C./H or less.
0% and 90% at 10 ° C./H.

On the other hand, the yield of the ceramic impeller obtained according to the fitting type injection molding method is 90% when the heating rate during degreasing is 5 ° C./H or less, and 10% when the heating rate is 10 ° C./H. Was 70%. Further, the yield of the ceramic impeller obtained by the integral injection molding method was 50% when the temperature rising rate during degreasing was 5 ° C./H or less, and 40% when it was 10 ° C./H.

[0024]

As described above, since the ceramic impeller manufactured by the manufacturing method of the present invention is completed by firing a homogeneous molded body, it has an excellent balance as a rotating body. In addition, degreasing is completed in a short time, and cracks do not occur in the molded body during degreasing, which improves the yield. Further, since the mold only needs to have a shape corresponding to the unit block, the manufacturing cost of the mold is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a ceramic impeller.

FIG. 2 is a perspective view showing an example of the shape of a unit block.

FIG. 3 is a perspective view showing another example of the shape of the unit block.

[Explanation of symbols] 1 unit block 2 blades L Habrine

Claims (4)

[Claims] 1. A kneaded material of ceramic powder is injection-molded into unit blocks each having a shape in which an impeller is divided into substantially equal parts along its rotation center axis, and these unit blocks are combined before or after degreasing and exposed. A method for producing a ceramic impeller, comprising applying a cross-linking film to the surface of the ceramic impeller, applying hydrostatic pressure to integrate the surfaces, and then firing. 2. A kneaded material of ceramic powder is injection-molded into unit blocks each having a shape in which an outer peripheral portion of an impeller is approximately equally divided along a rotation center axis thereof, and the unit blocks are formed before or after degreasing. A method for manufacturing a ceramic impeller, which comprises combining with a shaft part molded body of an impeller, applying a cross-linking film on the exposed surface, applying hydrostatic pressure to integrate, and then firing. 3. The method for manufacturing a ceramic impeller according to claim 1, wherein the shape of the unit block is such that two hub lines that sandwich one or more blades are ridge lines. 4. The method for producing a ceramic impeller according to claim 1, wherein the hydrostatic pressure is 4 ton / cm ² or more.