JPH07237959A - Method for manufacturing ceramic molded body - Google Patents

Abstract

(57) [Abstract] [Purpose] A ceramic compact having an arbitrary shape and an arbitrary shape and having a wall thickness that is twice or more different can be integrally molded by a sludge casting molding method. To obtain a ceramic molded body which has a very good yield and does not cause cracks or voids at the boundary between the uniform thickness layer and the thickened portion which is solidified later, and which has an extremely good yield. [Structure] Ceramic slurry containing a ceramic raw material powder, a solvent, and a dispersion medium soluble in the solvent is poured into a solvent-absorbing molding die to form a wall thickness of a predetermined thickness by a drainage casting method. After that, a molding die piece is placed on the surface of the surrounding inking layer to increase the wall thickness, and a weir is provided, and after injecting the ceramic slurry into the concave portion formed by the weir to solidify it, the mold is released to a predetermined size. A ceramic molded body having a predetermined shape in which the wall thickness at the position is increased is molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic compact by integrally molding ceramic compacts having different wall thicknesses by a slurry casting method.

[0002]

2. Description of the Related Art In recent years, along with the expansion of the field of use of ceramic products due to their characteristics, electronic parts utilizing conventional electrical characteristics have been used for rigid materials such as constituent members of various chemical industrial devices and mechanical parts of internal combustion engines. Moreover, ceramics have come to be widely used for decorative parts such as watches and accessories.

However, the requirement is different from the conventional ceramic products having a relatively simple shape, and the shapes of the various chemical industry constituent members, internal combustion engine mechanical parts, and decorative parts are complicated three-dimensional structures. In many cases, it is a large part with uneven thickness, and when it comes to a ceramic product with such a shape and form, its molding is technically extremely difficult, and it is necessary to obtain a high quality ceramic product that meets the requirements. It could not be manufactured easily.

Furthermore, even though it has excellent heat resistance and wear resistance as compared with metallic materials, has high strength, and has a small specific gravity, it is a brittle material because of its high hardness and cutting and grinding. However, it is difficult to mass-produce the ceramic product having the complicated three-dimensional structure as described above, and the extremely high product cost makes it more difficult to put various ceramic products into practical use.

Therefore, as a molding method for mass-producing various ceramic products having complicated shapes as described above, a solvent and a binder composed of an organic dispersion medium soluble in the solvent have been conventionally added and mixed to the ceramic raw material powder. The ceramic slurry prepared by pouring into a mold made of gypsum, etc., and obtaining a ceramic molded body by absorbing the solvent into the mold and injecting the ceramic raw material powder into the mold to obtain a ceramic molded body. Was being done.

In particular, when molding a large hollow ceramic product having a complicated shape, the surplus ceramic remaining after pouring the ceramic slurry into a molding die and inking it to a predetermined thickness A drainage mud casting method is used in which sludge is poured out of a molding die to obtain a ceramic molded body. With this drainage mud casting molding method, a hollow molded body having a uniform wall thickness can be molded relatively easily. However, it was not possible to integrally form a molded body having a partially different wall thickness.

As a result, large-sized, hollow ceramic products having a complicated shape whose wall thickness is largely different from each other are manufactured except that the molded body parts which are divided and molded for each wall thickness are joined and integrated. There was a problem that I could not.

In order to solve such a problem, as shown in FIG. 7, after the ceramic slurry 16 is injected into the molding die 17, the ceramic slurry 16 is vacuum sucked 19 through the molding die 18 to obtain the ceramic raw material powder. There are proposed methods such as a method of depositing a predetermined thickness to a predetermined position and a method of casting by using a split mold in which a large number of mold pieces made of mold materials having different solvent absorptivities are combined (Japanese Patent Publication No. 5-88163). Japanese Patent Laid-Open No. 1-141002).

[0009]

However, in each of the above-mentioned sludge casting molding methods, a molded body having a predetermined shape can be molded, but the difference in wall thickness is only about 1.5 times the maximum. With a thickness of about 6 mm, such as a flange that becomes a fastening part when incorporating a gas turbine scroll, and parts that require twice or more the wall thickness from the viewpoint of strength integrally cause internal defects such as cracks and voids. There was a problem that it could not be molded so as not to exist.

For this reason, when it is attempted to obtain a molded body having a wall thickness that is twice or more different at a predetermined location, the molded body is molded into a wall thickness close to the wall thickness other than the portion where the wall thickness is thickest. It is necessary to grind and polish a large amount of the thinned part from the molded body, and in addition, the vacuum suction method requires an extremely complicated and large molding device, and the method using a split mold has a hollow shape. When a product is molded, there are various problems that the molded product may not be released from the split mold.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to integrally form ceramic molded bodies partially different in wall thickness by at least twice as much by a slurry casting method. The final shape and dimensions with extremely good yield can be obtained without causing cracks or voids inside the thickened portion of the molded body or cracks during the drying or firing process of the ceramic molded body after molding. To provide a method for manufacturing a ceramic molded body that is close to the above.

[0012]

According to the method for producing a ceramic molded body of the present invention, first, a ceramic raw material powder is prepared by mixing and stirring a so-called binder composed of a solvent and a dispersion medium soluble in the solvent. To do.

The obtained ceramic sludge was poured into a solvent-absorptive mold such as gypsum, and the ceramic raw material powder in the ceramic slurry was adhered to the wall surface of the mold until a predetermined wall thickness was obtained. After that, the waste sludge cast molding is performed to discharge the remaining excess unincorporated ceramic sludge from the molding die.

Then, a molding die piece having a predetermined shape is placed on the surface of the inking layer around which the wall thickness of the molded body is thickened so as to surround the thick portion, and a weir is provided to form the weir. The ceramic sludge is poured into the concave portion and allowed to stay therein, and the solvent-absorbing molding die is at least passed through the inking layer to absorb the solvent contained in the ceramic slurry and solidify, and then the molding die piece and the molding die are removed. , For molding a ceramic molded body of a predetermined shape thickened only at a predetermined position, in particular, the molding die piece is solvent-absorbing, and further, the molding die piece forming the weir and the inking layer It is more desirable to set the maximum depth of the concave portion consisting of (1) to 1.7 to 4.2 times the maximum thickness to be laminated on the inking layer.

In the method for manufacturing a ceramic molded body of the present invention, silicon nitride (Si ₃ N _{3) is} used as the ceramic raw powder.
₄ ), non-oxide ceramics such as silicon carbide (SiC), alumina (Al ₂ O ₃ ), zirconia (ZrO
₂ ) It can be applied to any of the oxide ceramics such as
A desired amount of various sintering aids can be added to the ceramic raw material powder, and the particle diameter of the ceramic raw material powder is preferably several microns to submicron.

In addition to water, the solvent may be a non-aqueous organic solvent such as a petroleum organic solvent, so long as it does not easily dissolve or decompose the solvent-absorbing mold. Any combination is possible.

Further, the mold piece that comes into contact with the inking layer may be solvent-absorptive or solvent-absorptive so long as its surface can be freely machined. For example, in addition to a gypsum mold, it may be porous or dense. A resin mold made of high-quality polyethylene or neoprene rubber, or a metal mold made of aluminum or bronze can also be used.

[0018]

According to the method for producing a ceramic molded body of the present invention, first, a thick wall layer having a uniform thickness is formed on the wall surface of the solvent-absorbing mold by the sludge casting molding method, and then the surface of the wall layer is formed. A dam is provided at a desired position with a mold piece, and ceramic sludge is newly injected to the inside of the weir up to the height of the mold, so that the previous inking layer forms a new mold, The solvent in the ceramic slurry newly injected into the solvent-absorbing mold through the layer will be absorbed, and voids or cracks will not occur at the boundary between the above-mentioned inking layer and the thickened part that was solidified later. After a while, the ceramic slurry solidifies and solidifies.

Further, since the molding die piece contacting the inking layer can control the solidification direction of the ceramic slurry by controlling its volume and porosity, the wall thickness having an arbitrary shape at an arbitrary location. Parts can be integrally molded uniformly,
For example, it is possible to locally form a thick portion integrally inside the hollow molded body in the molding step.

[0020]

EXAMPLES The method for producing a ceramic molded body of the present invention will be described in detail below based on examples. (Example 1) A method for manufacturing a ceramic molded body according to the present invention,
It evaluated by the following experimental examples.

1 to 4 are explanatory views showing a method of manufacturing a ceramic molded body according to the present invention in the order of steps, and FIG. 5 illustrates a ceramic molded body molded in the steps shown in FIGS. FIG.

1 to 5, reference numeral 1 denotes a solvent absorbing mold 2 having a groove 3 into which a ceramic sludge 5 is injected, and an infiltration layer 6 is formed by a drainage casting method. The mold piece 7 is placed on the surface of the surrounding inking layer 6 for increasing the wall thickness to provide the weir 8, and the ceramic slurry 5 is injected into the recess 9 formed by the weir 8 and the inking layer 6 to be solidified. It is a ceramic molded body that is molded by doing so.

First, as a ceramic slurry for evaluation, silicon nitride (Si ₃ N ₄ ) raw material powder having an average particle size of 0.60 μm was added to alumina (Al ₂ O ₃ ) and yttria (Y ₂ O ₃ ) as sintering aids. ) Or lanthanum (La), cerium (C
e), neodymium (Nd), samarium (Sm) and other rare earth element oxides are added to 100 parts by weight, 25 parts by weight of an organic solvent such as methanol, and a dispersant such as sodium polyphosphate are added in an amount of 0. 8 parts by weight was added, and the mixture was placed in a stirring / mixing container together with a ball made of a silicon nitride sintered body, mixed and stirred for 12 hours in a rotary mill to form a slurry, and the obtained slurry was mixed with an E-type viscometer at 5 minutes per minute. Measure the viscosity under the condition of rotation,
A non-oxide ceramic slurry having a poise of 3.5-4.0 was prepared.

As oxide-based ceramics, alumina (Al ₂ O ₃ ) having an average particle size of 0.66 μm, magnesia (MgO), calcia (CaO), silica (Si).
O ₂ ), chromia (Cr ₂ O ₃ ) and other sintering aids are added to 100 parts by weight, and 25 parts by weight of water as a solvent and 0.8 parts by weight of a dispersant such as sodium polyphosphate are added. The mixture was placed in a stirring and mixing container together with alumina balls and mixed and stirred for 12 hours on a rotary mill, and the viscosity was measured using an E-type viscometer under the condition of 5 revolutions per minute, and 4.0 to 4.5 poise Was prepared.

The ceramic slurry for evaluation was defoamed in a vacuum vessel prior to casting.

On the other hand, as a solvent-absorptive mold for evaluation, a gypsum mold having a cavity of 100 mm in length, 100 mm in width, and 40 mm in depth, having a width of 50 mm on the bottom surface along one side of the cavity, A groove having different depths of 5 mm, 7.5 mm and 10 mm and having one groove formed to the full width was prepared.

In the first step, as shown in FIG. 1, the ceramic slurry 5 is poured into the cavity 4 of the solvent-absorbing mold 2 and allowed to stand for 50 to 60 minutes to have a substantially uniform thickness of 5 mm. After the wall surface of the mold 2 was inlaid, the remaining excess unincorporated ceramic slurry 5 was discharged to form the infiltration layer 6, as shown in FIG.

Next, as shown in FIG. 3, a mold piece 7 made of gypsum having various heights, the shapes of which are preliminarily arranged on the edges of the groove 3, is flush with the inking layer 6 of the groove 3. Thus, the weir 8 was provided.

In this state, the same ceramic sludge 5 that was used to form the thickening layer 6 having a substantially uniform thickness of 5 mm was formed by the weir 8 and the thickening layer 6 as shown in FIG. The ceramic slurry 5 was poured into the recess 9 up to the height of the mold piece 7.

After that, it was confirmed that the ceramic sludge 5 in the recess 9 was completely solidified, the mold piece 7 and the solvent-absorbing mold 2 were sequentially removed from the inking layer 6, dried and shown in FIG. A ceramic molded body 1 for evaluation as described above was obtained.

The uniform thickness layer of the ceramic molded body thus obtained and the minimum wall thickness of the thickly molded portion are measured respectively, and the recess formed by the mold piece and the wall layer forming the weir is measured. The maximum depth D and the maximum wall thickness d to be laminated on the inking layer are calculated, and the ratio of D / d and the wall thickness ratio of the thickly formed part to the wall thickness of the uniform inking layer are obtained. It was

On the other hand, the presence or absence of external defects such as cracks on the surface of the molded body is checked by visual inspection, and the presence or absence of internal defects at the boundary between the uniform inking layer and the subsequently solidified thick part is determined by X-ray radiography. Was inspected.

For confirmation, after degreasing the obtained ceramic molded body, the non-oxide type ceramics were placed in a nitrogen atmosphere and the oxide type ceramics were placed in an atmosphere of 175 respectively.
After firing at a temperature of 0 ° C. and 1600 ° C., the obtained sintered body was subjected to nondestructive inspection by a fluorescent penetrant flaw detection method, an ultrasonic flaw detection method, etc., but no external or internal defects were found.

[0034]

[Table 1]

(Embodiment 2) Next, the case where the method for manufacturing a ceramic molded body of the present invention is applied to the molding of a scroll for a gas turbine engine having flange portions having different wall thicknesses will be described in detail as an example.

FIG. 6 is a perspective view of an essential portion showing a state in which a molding die piece 12 is placed around the flange portion 11 in order to thickly form and integrate the flange portion 11 of the gas turbine engine scroll 10. .

First, 92% by weight of raw material powder of silicon nitride (Si ₃ N ₄ ) having an average particle diameter of 0.60 μm was added with ₃ % by weight of alumina (Al ₂ O ₃ ) as a sintering aid and yttria (Y ₂ O ₃ ).
5% by weight of ₃ ) is added to 100 parts by weight, 25 parts by weight of an organic solvent such as methanol and 0.8 parts by weight of a dispersant such as sodium polyphosphate are added to make a ball made of a silicon nitride sintered body. Stored in a stirring and mixing container together with a rotary mill for 12
The mixture was stirred and mixed for a long time to form a slurry, and the viscosity was measured using an E-type viscometer at a condition of 5 revolutions per minute to prepare a ceramic slurry showing 3.9 poise.

After defoaming the obtained ceramic slurry in a vacuum vessel, the ceramic slurry was molded to a maximum outer diameter of 26.
It is poured into a scroll molding die for gas turbine engines of 0 mm with a maximum width of 177 mm, and after inking to a thickness of 6 mm, excess ceramic sludge that has not yet been inlaid is discharged to form a uniform inking layer 13. did.

Subsequently, the position of the molding die 14 is changed, and the molding die 14 is fixed so that the flange portion 11 faces downward,
A weir 15 was formed by placing a gypsum molding die piece 12 having a maximum height of 10 mm around the inking layer 13 of the flange portion 11 inside the hollow scroll 10.

After that, the uniform layer 1 is formed on the inside of the weir 15.
The same ceramic slurry as used to form No. 3 is injected to the height of the molding die piece 12 and retained therein, and a uniform inking layer 13 is formed.
And after leaving still until the thickened flange portion 11 is completely solidified, the internal molding die piece 12 is removed, and then the gypsum gas turbine engine scroll molding die 14 outside the molded body is demolded and dried. did.

The scroll molded body for a gas turbine engine thus obtained has a uniform wall thickness of about 6 mm, while the flange has a sufficient wall thickness of 15 mm, and the X-ray of the molded body is secured. In the transmission imaging method as well, the result of non-destructive inspection of the internal and external defects of the sintered body, which was degreased and fired at a temperature of 1750 ° C. for 2 hours by X-ray transmission imaging and ultrasonic flaw detection, showed no defects. I was not able to admit.

[0042]

As described above in detail, in the method for producing a ceramic molded body of the present invention, a ceramic slurry containing a ceramic raw material powder, a solvent, and a dispersion medium soluble in the solvent is used as a solvent-absorbing mold. After forming a thickening layer of a predetermined thickness by pouring into the sludge and molding method, a molding die piece is placed on the surface of the surrounding thickening layer to increase the thickness and a weir is provided. After injecting ceramic slurry into the formed recess and solidifying it, it is removed from the mold to form a ceramic molded body of a predetermined shape with a thick wall at a predetermined position. Ceramic molded bodies having thick portions having different thicknesses can be integrally formed by the slurry casting method, and cracks or voids can be formed at the boundary between the uniform inking layer and the thickened portion that is solidified later. To the final shape and dimensions with extremely good yield. It can be obtained similar to the ceramic molded body.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a step of first injecting a ceramic slurry into a solvent-absorbing mold in the method for manufacturing a ceramic molded body of the present invention.

FIG. 2 shows a method for manufacturing a ceramic molded body according to the present invention,
It is explanatory drawing which shows the mud discharge process after forming the inking layer.

FIG. 3 is a method for manufacturing a ceramic molded body according to the present invention,
It is explanatory drawing which shows the process of mounting a shaping | molding die piece and providing a weir on the surface of an inking layer.

FIG. 4 is a method for manufacturing a ceramic molded body according to the present invention,
It is explanatory drawing which shows the process of injecting a ceramic sludge inside a weir and shaping a thick part.

FIG. 5 is a perspective view showing a cross section of a ceramic molded body molded by the method for manufacturing a ceramic molded body according to the present invention.

FIG. 6 shows a method for manufacturing a ceramic molded body according to the present invention,
FIG. 3 is an explanatory view showing a main part of a state in which a weir is provided by applying a molding die piece around a flange portion for thickly molding and integrating the flange portion, which is applied to molding of a scroll for a gas turbine engine.

FIG. 7 is an explanatory view showing a method for manufacturing a conventional ceramic molded body.

[Explanation of symbols]

 1 Ceramic Molded Body 2, 14 Solvent Absorbing Mold 3 Groove 4 Void 5 Ceramic Sludge 6, 13 Inking Layer 7, 12 Mold Piece 8, 15 Weir 9 Recess 10 Gas Turbine Engine Scroll 11 Flange Part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kozo Hamayama 1-4 Yamashita-cho, Kokubun-shi, Kagoshima Kyocera Stock Company Research Institute

Claims (3)

[Claims] 1. A ceramic raw material powder, a solvent, and a ceramic slurry containing a solvent and a dispersion medium soluble in the solvent are poured into a solvent-absorbing mold to allow the ceramic raw material powder to have a predetermined wall thickness. The remaining excess ceramic sludge is discharged from the molding die, and then the wall thickness of the molded body is increased. The molding die piece is placed on the surface of the surrounding inking layer to provide a weir, and the recess formed in the weir. After injecting the ceramic slurry, the solvent contained in the ceramic slurry is absorbed into a solvent-absorbing mold through at least the inking layer and solidified, and then demolded to increase the wall thickness at a predetermined position. A method for producing a ceramic molded body, which comprises molding the ceramic molded body. 2. The method for producing a ceramic molded body according to claim 1, wherein the mold piece is solvent-absorbing. 3. The maximum depth of a recess formed by the mold piece of the weir and the inking layer is 1.7, which is the maximum thickness to be laminated on the inking layer.
It sets to 4.2 times, The manufacturing method of the ceramic molded body of Claim 1 characterized by the above-mentioned.