JPH0248404B2 - SERAMITSUKUSUNOKAATSUIKOMISEIKEIHOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a pressure casting method used for molding ceramics. More specifically, it is characterized in that the ceramic slurry is pressurized and dehydrated via a hydrophobic pressurized medium such as oil. (Prior Art) Conventionally, in addition to press molding methods, injection molding methods, cast molding methods, etc., pressure casting methods have been attracting attention in recent years as methods for molding ceramics.
In this pressure casting method, as shown in FIGS. 5 and 6, one injection port 12 of a casting mold 17 having a desired shape is
By injecting the ceramic slurry 15 from the inlet, pressurizing it with gas such as air 18 from the injection port 12, and dehydrating it through the mold 13 having a permeable function (permeable mold) from the other side of the casting mold 17, A high-density ceramic molded body is obtained. (Problems to be Solved by the Invention) However, according to the conventional pressure casting method described above, the cast slurry is directly pressurized via gas such as air or gas, so in particular When used above cm ² , it is subject to usage regulations under the High Pressure Gas Control Law, and there is a high risk of an accident such as an explosion, so it has the disadvantage that it cannot be used easily. In addition, in order to facilitate the release of the mold without a permeable function (non-permeable mold) or the permeable mold and the molded product after dehydration, the area where the non-permeable mold or permeable mold contacts the ceramic slurry is added. A mold release agent is applied in advance to the mold release agent, but it is permeated through the permeable mold by pressure or pressure suction during pressure casting, and the mold release agent from the non-permeable mold or permeable mold and the molded product is not able to be released. There were some drawbacks that made it difficult. Further, depending on the shape and size of the molded product, there is also the drawback that it becomes more difficult to release the molded product. Furthermore, when pressurizing with air or the like from the injection port and dehydrating through a mold with a permeable function from the other side of the casting mold, near the completion of molding, a part of the interface between the non-permeable mold and the molded object, or a part of the interface between the non-permeable mold and the molded object, Air, etc. pass through a part of the interface of the molded body, and the drying progresses only in the part through which the air passes, resulting in a drawback that drying cracks are likely to occur. An object of the present invention is to provide a pressure casting method for ceramics that eliminates the above-mentioned problems, allows easy release from the mold after completion of molding, and does not cause cracks on the surface of the molded product. . (Means for solving the problems) The pressure casting method for ceramics of the present invention includes:
A high-density ceramic molded body is produced by injecting ceramic slurry from one injection port of the casting mold, pressurizing it from the injection port, and dewatering it from the other casting mold through a mold with a permeable function. A molding method to obtain a molding method, wherein after injecting a predetermined ceramic slurry into a casting mold, the injection port is filled with a hydrophobic pressurizing medium, thereby pressurizing and dewatering the ceramic slurry through the hydrophobic pressurizing medium. It is characterized by performing the following. (Function) Hereinafter, the present invention will be explained in detail using the drawings. FIG. 1 is a sectional view for explaining the concept of the pressure casting method of the present invention. In Figure 1, 1
2 is an injection port for injecting ceramic slurry, 3 is a permeable mold that is permeable, 4 is a hydrophobic pressurizing medium, and 5 is a molding port. The ceramic slurry 6 is a suction port for sucking moisture through the permeable mold 3. Suitable hydrophobic pressure media include animal and vegetable oils such as olive oil and rapeseed oil, which are liquid and fluid and do not mix with water, and lubricating oils for machine tools such as Daphne Super Multi 32 (trade name). used. Transparent types include ceramic/metal composites, synthetic resin/inorganic compound composites, gypsum, porous metal sintered bodies, etc., and non-permeable types include metals, hard acrylic, ceramics, etc. Non-permeable materials that can withstand pressure can be suitably used. In the present invention, the pressing force is preferably 10 Kg/cm ² or more. The reason for this is that the desired high-density ceramics can be industrially obtained in a short time. In addition, pressurization with liquid and pressurization with gas are possible ways to obtain a pressure of 10 kg/cm ² or more, but pressurization with gas is subject to restrictions on use under the High Pressure Gas Control Law, so pressurization with liquid will be selected as the preferred method. Alternatively, the hydrophobic pressurizing medium may be directly pressurized using a hydraulic pump or the like. In the above-described configuration, the actual pressure casting operation is performed as follows. First, a predetermined ceramic slurry 5 to be molded is injected into a casting mold through the injection port 2. Next, fill the injection port 2 with a hydrophobic pressurized medium 4 such as olive oil,
Pressurization is applied from above the injection port 2 using a hydraulic device or the like, and water in the ceramic slurry 5 is removed through the permeable mold 3 using a vacuum device such as a vacuum pump or a pressure reducing device such as a water jet pump through the suction port 6. Aspirate permeation. In this case, suction by vacuum or reduced pressure from the suction port 6 is not essential, and suction may be omitted, but it is preferable to perform suction in order to improve the shape retention of the molded article. Furthermore, although the pressing force from the injection port 2 may be constant, it is preferable to change the pressing force during pressurization depending on the shape of the molded body, the position of the transparent mold, etc., in order to prevent the occurrence of cracks in the molded body. According to this method, when the molding is completed, the hydrophobic pressurized medium 4 enters the interface between the non-permeable mold 1 and the molded body and acts as a mold release agent, so that the mold can be easily released. The mold can be easily released from the transparent mold 3 by pressing the molded product with air or the like through the suction port 6 during mold release, since the contact area between the molded product and the transparent mold has a simple shape. can. The pressure from the suction port 6 at this time may be as low as 2 to 3 kg/cm ² . In addition, if the ceramic slurry is directly pressurized with air or the like, if the hydrophobic pressurizing medium 4 such as olive oil is poured after the completion of molding, air or the like will enter the interface between the molded body and the impermeable mold 1 and the molded body It is preferable to pour in the hydrophobic pressurizing medium 4, such as olive oil, by the time the molding is completed, since this may dry partially and cause cracks. Furthermore, the amount of the hydrophobic pressurized medium 4 to be poured depends on the shape and size of the molded body, the pressurizing force, etc.
Since the amount varies depending on the pressurization time, it is necessary to determine the appropriate amount for each. In other words, an amount of at least enough to cover the entire surface of the molded body is required. FIG. 2 is a cross-sectional view of the case where the transparent mold is arranged so as to be in contact with the molded body in a large proportion. In FIG. 2, the same members as those in the embodiment shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. First, a predetermined amount of ceramic slurry 5 to be formed is injected into the casting mold through the injection port 2. At this time, the amount of ceramic slurry 5 to be injected must be determined depending on the desired shape and thickness of the molded body. Next, the injection port 2 is filled with a hydrophobic pressurizing medium 4 such as olive oil, and pressurized from above the injection port 2 by a hydraulic device or the like, and the ceramic slurry 5 is poured into the ceramic slurry 5 through the suction port 6 by a vacuum device such as a vacuum pump. The moisture is permeated and sucked through the permeable mold 3. As the ink buildup progresses to the permeable type, the liquid level above the slurry decreases, and eventually the hydrophobic pressurized medium 4 changes to the permeable type 3.
The liquid reaches the point where it is permeated and sucked through a part of the permeable mold 3. In this case, the hydrophobic pressurized medium 4 can be passed through a part of the permeable mold 3 without suction.
is transmitted. At this time, by stopping the suction from the suction port 6 and reducing or stopping the pressurizing force, the hydrophobic pressurized medium 4 is applied to the interface between the molded body and the transparent mold 3 and near the molded body side of the transparent mold. penetrates and acts as a mold release agent, making it easy to release the mold. In this case, in order to facilitate the infiltration of the hydrophobic pressure medium 4, suction from the suction port 6 may be stopped as well as pressure may be applied from the suction port 6; Therefore, it is necessary to confirm that the amount of water in the permeable mold 3 does not damage the molded product or affect mold release, and to apply pressure at a pressure that does not prevent the hydrophobic pressurizing medium 4 from penetrating. In addition, the pressurizing force when the pressurizing force from the injection port 2 is reduced is:
Since the pressure varies depending on the shape of the molded body, the size of the pores in the permeable mold 3, etc., it is necessary to set a suitable pressure for each. Furthermore, when the pressure from the injection port 2 is stopped, the pressure may be applied again, and the pressure applied at this time also varies depending on the shape of the molded product, the size of the pores of the permeable mold 3, etc. need to be set. The mold can be released more easily if the ceramic slurry 5 and hydrophobic pressure medium 4 remaining in the casting mold are discharged from the injection port 2, and then the molded body is released while being pressurized with air or the like from the suction port 6. can. An actual example will be described below with reference to FIGS. 3 and 4. In FIGS. 3 and 4, the same members as those in the embodiment shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. Example 1 58 parts by weight of water was added to 100 parts by weight of Si ₃ N ₄ powder containing a sintering aid.
parts by weight, 1 part by weight of triethylamine (peptizer),
A slurry was obtained by mixing 1.4 parts by weight of a binder. Next, in order to remove the air in the slurry, the slurry was kept in an atmosphere with a vacuum degree of 73 cmHg for 5 minutes while stirring to perform vacuum degassing. 100 c.c. of this slurry was poured into the turbine rotor type shown in Fig. 3 from the injection port 2, and then Daphne Super Mulch 32 was poured from the injection port 2 as a hydrophobic pressurizing medium, and pressure was applied from the injection port 2 using a hydraulic device. Pressure was applied at 70 kg/cm ² and suction dehydration was performed through the suction port 6 to complete molding in 8 minutes. At this time, the releasability between the molded body and the non-transparent mold 1 and the transparent mold 3 was good. Further, Table 1 shows the molding results obtained by changing the molding conditions using the same slurry.

[Table] The obtained molded body was placed in a constant temperature and humidity chamber (40℃80% → 60℃
50%) and a constant temperature dryer (100°C) for 4 days, calcined in the air at 500°C for 3 hours to remove the forming aid, and then sintered at 1750°C in an N ₂ atmosphere for 1 hour. As shown in Table 2, this sintered body had no local differences in room temperature bending strength or density, was free from external damage, and was in good condition, satisfying the desired shape. Note that the room temperature bending strength was determined using a three-point bending test method in accordance with JIS-1601.

[Table] Example 2 45 parts by weight of water and 1 part by weight of polycarboxylic acid (peptizer) were mixed with 100 parts by weight of SiC powder containing a sintering aid to obtain a slurry. Next, the slurry was vacuum degassed as in Example 1. 210 c.c. of this slurry is poured into the turbine rotor type shown in Figure 3, pressurized with a pressure of 20 kg/cm ² from the injection port 2 using a piston-type pressurizing device, and suction dewatered from the suction port 6 for 30 minutes. I went. After that, remove the excess slurry from the inlet 2 and add 120 c.c. of olive oil as a hydrophobic pressurized medium to the inlet 2.
After pouring, the mixture was further pressurized with a pressure of 8 kg/cm ² from the injection port 2 using an air compressor, and suction dehydration was performed from the suction port 6 for 5 minutes to complete the molding. At this time, the molding was completed to the extent that the poured olive oil remained on the upper part of the molded product. The obtained compact had good mold releasability, and when it was dried in the same manner as in Example 1 and sintered at 2100° C. for 1 hour in an Ar atmosphere, a sintered compact with a density of about 3.1 was obtained. This sintered body had no local density differences or external damage, and was in good condition, satisfying the desired shape. Example 3 A slurry was prepared in the same manner as in Example 1, and 520 c.c. of the slurry was poured into the split mold shown in FIG. 2, and pressurized with a pressure of 30 kg/cm ² from the injection port 2 using a hydraulic device, and suction dehydration was performed from the suction port 6 for 1 minute. Thereafter, suction dehydration was stopped and pressurization was stopped for 1 minute, and then the pressure was increased to 3 kg/cm ² for 3 minutes to complete molding. Next, the slurry remaining in the casting mold and the Daphne spar hydraulic fluid 32
was discharged and released from the mold. The mold release was performed while pressurizing the mold with air from the suction port 6 at a pressure of 2 kg/cm ² . The obtained molded product had good mold releasability and was in good condition with no external damage. Thereafter, the molded body was dried, calcined, and sintered in the same manner as in Example 1, and as a result, a sintered body with a wall thickness of approximately 10 mm was obtained. This sintered body had no local density difference or wall thickness difference, and was satisfactory in that it had no external damage and satisfied the desired shape. (Effects of the Invention) As is clear from the above detailed explanation, according to the pressure casting method for ceramics of the present invention, the injection port is filled with a hydrophobic pressurizing medium and the hydrophobic pressurizing medium is By performing pressurization and dehydration through the wafer, molding can be performed safely and easily under high pressure. In addition, even after molding is completed, the hydrophobic pressurized medium enters the interface between the non-permeable mold and the permeable mold and the molded object and acts as a mold release agent, making mold release easier and the surface smoother. It is also possible to prevent cracks from occurring without drying.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views for explaining the concept of the pressure casting method of the present invention, and Figures 3 and 4 show an embodiment of an apparatus for carrying out the pressure casting method of the present invention. 5 and 6 are cross-sectional views for explaining the concept of the conventional pressure casting method. 1... Non-permeable type, 2... Inlet, 3... Permeable type, 4... Hydrophobic pressurized medium, 5... Slime, 6...
...Suction port, 7...Cast mold.

Claims (1)

[Scope of Claims] 1. By injecting ceramic slurry from one injection port of a casting mold, pressurizing it from the injection port, and dehydrating it from the other casting mold through a mold with a permeable function, A molding method for obtaining a high-density ceramic molded body, which comprises: after pouring a specified ceramic slurry into a casting mold;
A method for pressure casting and molding of ceramics, characterized in that the injection port is filled with a hydrophobic pressurizing medium to pressurize and dehydrate the ceramic slurry through the hydrophobic pressurizing medium. 2. The pressure casting method for ceramics according to claim 1, wherein the casting mold is a solid casting mold.