JPH0570209A - Method for sintering ceramic - Google Patents

Abstract

PURPOSE:To attain accurate sintering without warpage or deformation when molded bodies formed by press-molding are sintered to obtain ceramic. CONSTITUTION:Molded bodies formed by press-molding are separately heat- treated at 150-300 deg.C to remove the containing water and are piled and sintered. Ceramic free from warpage and deformation can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic firing method for uniformly firing a pressure-formed compact without deformation.

[0002]

2. Description of the Related Art So-called fine ceramic materials having various electromagnetic functions, high strength and abrasion resistance have no moldability by themselves, and therefore, after being molded by adding various organic compounds as binders. , It becomes a ceramic by firing.

Various molding methods have been used, but the equipment and operation are simple, the molding speed is fast, the switching is easy, and it is suitable for the production of a wide variety of small quantities. For the reason that the firing is relatively easy and the like, pressure molding (also referred to as press molding) in which a granulated powder is pressed to obtain a molded body is often used.

The pressure-molded compacts, for example, in the shape of a disc or a square plate, are referred to as spread powder between the compacts in order to prevent fusion during firing and facilitate separation of the ceramics. The powder is interposed and stacked, placed in a bowl and baked.

[0005]

However, in the above-mentioned conventional method, there is a problem that warpage or deformation occurs during firing, especially for discs or square plates having a small thickness with respect to the area. There was also a phenomenon that the whole body was warped in the same direction, and there was a problem that it was necessary to re-load it and heat it at a temperature lower than the firing temperature while applying a load to correct warpage and deformation. ..

An object of the present invention is to solve the above-mentioned conventional problems and to provide a ceramic firing method for obtaining a ceramic with high dimensional accuracy without warpage or deformation.

[0007]

In order to achieve this object, a method of firing a ceramic according to the present invention is one in which a molded body formed by pressure molding is heat-treated alone at 150 ° C. to 300 ° C. without stacking, and This is a method in which after removing the water content, a plurality of layers are stacked and fired.

[0008]

According to this method, the moisture in the molded body is prevented from rapidly evaporating and scattering after the temperature has risen to prevent warping or deformation of the molded body.

[0009]

EXAMPLE The present inventor has conducted various studies as to at what stage during press firing a warped or deformed molded body causes warping and deformation, and as a result, the occurrence of warping and deformation has a close relationship with the movement of water. The inventors have found out that they have the present invention and have completed the present invention.

That is, when the molded articles containing water are stacked and fired, the moisture in the molded articles moves slowly, so that the scattering of water from the central portion of the stacked molded articles or the bottom surface portion in contact with the bowl is hindered. However, it is considered that warp or deformation is induced in the molded body because the material tends to evaporate and scatter rapidly after reaching a high temperature.

Therefore, in the present invention, before stacking in a casket, the molded bodies are arranged one by one and placed in a drier to remove the water content in the molded bodies, and then intervene with a spreading powder for peeling. By doing so, they are stacked and fired to prevent warpage and deformation of the element body during firing.

An embodiment of the present invention will be described below with reference to the drawings. A binder made of polyvinyl alcohol was added to porcelain powder containing barium titanate as a main component and pressure-molded at a pressure of 1000 kg per square centimeter to obtain a disk-shaped molded body having a diameter of 48 mm and a thickness of 1.5 mm. ..

The molded bodies were placed one by one on a stainless steel net and put in a dryer at 200 ° C. to remove the water content for 1 hour. Thereafter, as shown in FIG. 1, while interposing the molded body 1 with the spread powder 2 made of porcelain powder of the same material,
It was stacked in 10 steps, placed in the bowl 3 and fired at 1350 ° C. for 2 hours to obtain a ceramic.

Further, as a comparative example, a porcelain powder having the same components as in this example was used to form a disk shape in the same manner as in this example, and the formed body was made of the same material without removing the water content. The ceramic powder was obtained by stacking the porcelain powder in 10 steps while placing a bed of porcelain powder in between and placing it in a bowl and firing at 1350 ° C. for 2 hours.

The test results of warpage and deformation of ten ceramic samples of this example and the comparative example are shown in comparison with (Table 1).

[0016]

[Table 1]

As is clear from (Table 1), no warpage or deformation is observed in the ceramics produced by the ceramic firing method of the present invention, and excellent effects can be obtained.

The heat treatment temperature for removing the water content may be any temperature as long as the water content can be sufficiently removed, but is preferably in the range of 150 ° C to 300 ° C.

This is not preferable when the temperature is too low, because the water content remains and it takes time to remove it.
On the other hand, when the temperature is too high, the binder is decomposed, so that the strength of the molded product is remarkably reduced, and it becomes difficult to stack and place the molded product in the casket.

In this embodiment, the molded body was put in a dryer to remove the water content, but the method of removing the water content is not limited to this, and for example, heating by microwaves or the like can be performed. Other methods may be used.

The binder used is not limited to polyvinyl alcohol, but may be a cellulose derivative, starch, wheat flour, an acrylic compound or the like.

[0022]

As is apparent from the above description of the embodiments of the present invention, according to the present invention, a pressure-molded compact is heat-treated alone at 150 ° C. to 300 ° C. to remove the water content of the compact, By stacking and firing a plurality of ceramics, it is possible to obtain a ceramic having good dimensional accuracy without deformation or warpage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which formed bodies of a ceramic firing method according to an embodiment of the present invention are stacked and placed in a sagger.

[Explanation of symbols]

 1 molded product 2 spread powder 3 bowl

Claims (1)

[Claims] 1. A compact formed by pressurizing ceramic powder is independently heat-treated at 150 ° C. to 300 ° C. to remove water content of the compact, and then a plurality of the compacts are stacked and fired. Ceramic firing method.