JPH04310558A - Planetary slip casting of ceramics - Google Patents

Abstract

PURPOSE:To simultaneously mold a large number of products and structures of various shapes such as hollow-shaped ceramic products such as cylinder for ceramic engine, pipe and crucible, products in continuous form such as round bar, various products of complicated shape, uniform ceramics composed of two or more ceramics, multi-layer structure ceramics, fiber-reinforced ceramics and composite ceramics with a metal in high accuracy, inexpensively and in an integrated way. CONSTITUTION:Slip, soft slip or body-shaped raw material is casted into a stationary mold or a mold in a planetary motion or put in the mold and liquid in the raw material is partially absorbed in the mold while subjecting the mold to planetary motion to mold ceramics. A great number of the above-mentioned ceramic products and structures of various shapes can be simultaneously molded in an integrated way, molded articles have excellent accuracy, smooth and specular inner face and finishing processing is almost not required.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new method for molding ceramics, and is used in the production of ceramics, particularly in the field of molding.

0002

2. Description of the Related Art Generally, products are manufactured from ceramic powder raw materials through the following steps: raw material preparation, molding, drying, and sintering. Among them, the ceramic forming methods currently used industrially vary depending on the type of raw materials, the shape and dimensions of the product, etc., and include mold press molding, slurry casting, extrusion molding, and isostatic pressing. method, injection molding method, doctor blade method, etc. However, each of these methods has advantages and disadvantages, and it is possible to form hollow-shaped ceramic products such as pipes and crucibles, as well as relatively large and complex-shaped products, with high precision, uniformity, high density, in a short time, and at low cost. There's no way. Among them, the slurry casting method is effective for molding products with complex shapes, but it has problems with dimensional accuracy, molded body density, wall thickness, molding time, etc., and finishing processing is also required. Furthermore, as methods that fall under the category of slurry casting methods, there are vibratory casting methods, in which the mold is vibrated to effectively utilize the thixotropic properties of the slurry, and molding methods, which utilize the rotational movement of the mold, are methods. There are centrifugal casting methods that do this, but these methods are also insufficient in terms of accuracy and molding time. For this reason, after forming with mold press molding method or isostatic pressing method, machining such as cutting is performed to create a rough shape, and after firing, grinding and lapping are performed to create fine ceramic final products with hollow or complex shapes. It is common to manufacture
It requires multiple steps, takes a long time, and is extremely expensive to manufacture. For these reasons, it is desired to establish a method for forming fine ceramic products having a hollow shape or a relatively large complex shape as described above.

0003

[Problems to be Solved by the Invention] Conventional molding methods and techniques cannot produce ceramic engine cylinders that are cylindrical or
It is extremely difficult to form hollow fine ceramic products such as rectangular pipes, crucibles, and cups into one piece with high precision and low cost without finishing processing, grinding, or polishing. Furthermore, it is difficult to freely adjust the thickness of the molded product from ultra-thin to thick, and to create tapers on the inner and outer surfaces, and these are issues that must be solved as soon as possible. Furthermore, molding of other shaped products includes the molding of long products such as thick round bars, square bars, and perforated bars, as well as the molding of various relatively large and complex shaped products. In terms of raw materials and structure, we can mold homogeneous bodies using mixed raw materials of two or more types of ceramics with different densities, mold whiskers or fiber-reinforced ceramics, and mold composite ceramics in which metals and plastics are uniformly mixed. , forming multilayer ceramics such as two-layer and three-layer pipes is a challenge. Next, regarding the molding time, there is a need for a method of molding in a short time, or a method of molding many pieces at the same time to shorten the time required for molding each piece. Many such issues remain in the molding of ceramics. The present invention attempts to solve many of these problems at the same time.

0004

[Means for Solving the Problems] In order to solve the various problems mentioned above, it is necessary to convert the ceramic powder raw material into a slurry, such as the vibration casting method or centrifugal casting method, which falls under the slurry casting method. It is advantageous to mold the material by adjusting the shape to make effective use of its thixotropic properties. However, as mentioned above, these methods cannot sufficiently solve the problem. Therefore, instead of using only vibration or simple rotational motion of the mold as in those methods, we use planetary motion that allows the mold to revolve while rotating on its own axis, making use of the thixotropic properties of the slurry to form the mold. By doing so, many of the problems mentioned above can be solved at the same time. In other words, slurry or soft mud prepared by adding and kneading solvents, molding agents, molding aids, etc. to ceramic raw materials, or clay that contains a small amount of water and has a kneaded clay shape and exhibits fluidity by giving it planetary motion is used. Then, they are poured or charged into a forming mold that is stationary or in planetary motion, and while the forming mold is in planetary motion, a portion of the liquid of the prepared material in the form of slurry, soft mud, or clay is absorbed into the forming mold to form ceramics. What is necessary is to form a molded body. The mold for absorbing the solvent from the prepared material in the form of slurry, soft mud, or clay may be a plaster mold, or a porous mold such as a resin mold, a ceramic mold such as graphite, or a metal mold. . The number of molds attached to the molding machine is usually 2 to 8 or more, and the molds can be moved vertically, horizontally, or tilted in planetary motion. By molding ceramics using such means, it is possible to simultaneously mold a large number of hollow or complex shaped ceramic molded bodies homogeneously, with high density, and in a relatively short period of time. Furthermore, hollow-shaped products such as molded pipes and crucibles have smooth and mirror-like inner surfaces, and almost no finishing work is required. As described above, the present invention is a new method for molding ceramics using planetary motion as a means to solve the problems.

[0005]

[Action] Fine ceramics have many excellent functions that metals and plastics do not have, such as heat resistance, corrosion resistance, hardness, piezoelectricity, and semiconductivity, so they are currently being further developed for use as both functional and structural materials. is being promoted. but,
In order to create components that fully demonstrate these functions, the most important issue is establishing a manufacturing process, especially a molding process. Unless this molding process is fully established, there will be a limit to the widespread use of ceramics. By using the method of the present invention, various molding problems that could not be solved by conventional methods can be solved, so I believe that it can contribute to the spread and development of fine ceramics that have many functions.

[0006]

[Example 1] As ceramic raw materials, fine alumina powder (purity 99.8%, average particle size 0.79 μm), zirconia powder (contains 5.26% yttria, average particle size 1.1
8 μm), and silicon nitride powder (gelatinization rate 97.0%,
Each slurry (slip) for casting molding was prepared by adding and kneading appropriate amounts of water, a binder, a dispersing peptizer, a plasticizer, and an antifoaming agent to these powder raw materials (average particle size: 0.60 μm). Next, these various slurries are cast into a plaster mold that is stationary or in planetary motion at low speed.
The rotation speed of the mold is 225 rpm, and the revolution speed is 100 rpm.
Four pieces were molded at the same time using planetary motion for about 1 hour at m. The dimensions of the molded product are cylindrical pipes and cylinders with an outer diameter of 20 to 50 mm and a length of 90 mm, and their wall thickness is 1 to 6 m.
It was m. The molded product thus obtained had a smooth inner surface and was precisely molded to have a mirror surface. Outer diameter φ30mm
The compact density and relative density of a pipe with a wall thickness of 4 mm are shown below. The density of those compacts is 10 by conventional mold press molding method.
The densities of the specimens molded into a cylindrical shape of φ20 x 20 mm using a molding pressure of 0 MPa (2.52, 2.50,
1.95 g/cm3).

[0007]

[Example 2] Alumina slurry is poured into a plaster mold, and while the mold is tilted and planetary motion is performed at a revolution speed of 60 to 120 rpm, the outer diameter is φ40, the height is 90, and the thickness is 2 to 4 m.
A flat-bottomed crucible with a diameter of 80 mm and an uneven cup with a height of 80 mm were molded. The density of these molded bodies is approximately 2.6 g/c
in m3

The values were similar to those in Example 1. Although the thickness of the molded product was slightly uneven at the bottom, the inner surface was smooth and mirror-like, and no finishing work was required.

[0008]

[Example 3] Cylindrical pipes and rectangular pipes were manufactured using ceramic mixed raw materials with different specific gravities of 98% alumina and 2% chromia, and mixed ceramic and metal raw materials consisting of 99% alumina and 1% aluminum foil powder.

[Example 1
] was molded under the same conditions. Microscopic observation of the cross section of the compact revealed that chromia and aluminum foil powder were uniformly dispersed in alumina. In this way, it was also possible to mold a mixture of two or more raw materials with different specific gravities.

[0009]

[Example 4] Using alumina slurry

After molding to a thickness of 2 mm under the same conditions as in Example 1, chromia was molded to a thickness of 2 mm on the inner surface of the molded body to produce a cylindrical multilayer pipe/cylinder of alumina and chromia. Similarly, a three-layer multilayer pipe consisting of alumina, chromia, and alumina each having a thickness of approximately 1 mm, and a fiber-reinforced multilayer pipe consisting of alumina, graphite fiber, and alumina were formed. These molded bodies had good smooth inner surfaces, the thickness of each layer was constant, and the bonding between the layer interfaces was also good.

0010

[Effects of the Invention] The effects of the molding method according to the present invention are as follows. (1) Since planetary motion is used, it is possible to cast into multiple molds, and multiple molded bodies can be molded at the same time. (2) By tilting the mold vertically, horizontally, or tilted, various hollow-shaped products and complex-shaped products can be molded. (3) It is possible to mold everything from ultra-thin to thick-walled products. In addition, the inner surface of the molded body is smooth and mirror-like, and almost no finishing work is required. (4) Two or more types of ceramic raw materials with different specific gravity or mixed raw materials of ceramics and metal can be molded. (5) Multilayer ceramics and fiber-reinforced ceramics can be molded.

Claims (1)

[Claims] 1. Ceramics characterized by pouring or charging raw material prepared into slurry, soft mud, or plastic clay into a mold, and molding the ceramic using the planetary motion of the mold. molding method.