JPH05139847A - Baking method for ceramic form - Google Patents

Abstract

PURPOSE:To provide the title method capable of effectively suppressing warpage development due to the shrinkage of a ceramic form, thus easy to improve the product's yield. CONSTITUTION:Forms 2 each prepared by stacking plural ceramic forms 1 along the thickness direction are put into a baking chamber 3 in parallel with one another followed by baking. In this case, the forms 2 are loaded with a cover 5 consisting of a ceramic material having the same composition as that of the ceramic forms 1 and pressing the forms 2 along their stacking direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing a ceramics compact, and more particularly to a method for firing thin ceramics compacts stacked in the thickness direction.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, in order to fire a ceramic molded body used for forming a positive temperature coefficient thermistor element or the like, a plurality of ceramic molded bodies 1 to be fired are formed in the thickness direction. The stacks 2 stacked along each other are accommodated in parallel in a box-shaped firing box 3 having only an upper surface opened, and the firing boxes 3 are preheated in a firing furnace (not shown). The method of sending to is generally adopted.

[0003]

By the way, according to the above-mentioned conventional method, the individual ceramic molded bodies 1 constituting the stacks 2 accommodated in parallel in the firing box 3 are formed.
The firing in No. 2 will progress from the outside to the inside in contact with the high-temperature furnace atmosphere. However, since these ceramic compacts 1 have the characteristic of shrinking as the firing proceeds, the ceramic compacts 1 forming the stack 2, in particular, the ceramic compacts 1 located above the stack 2. As a result of the large shrinkage, the warpage accompanying the shrinkage becomes large, and as a result, the product yield deteriorates.

The present invention was devised in view of such inconvenience, and it is possible to effectively suppress the occurrence of warpage due to the shrinkage of the ceramic molded body, and it is easy to improve the product yield. An object of the present invention is to provide a method for firing a ceramic molded body.

[0005]

In order to achieve such an object, the present invention stores a stack of a plurality of ceramic compacts stacked in the thickness direction in parallel in a firing box. In the method for firing a ceramic molded body, the stacked ceramics, which are stored in parallel, are made of a ceramic material having the same composition as the ceramic molded body, a so-called co-material material, and each stacked body is stacked in the stacking direction. It is characterized in that a dropping lid that is pressed along is placed and then fired.

[0006]

According to the above construction, the weight of the dropping lid is dispersedly added to the individual ceramic compacts constituting the stack, and each ceramic compact is pressed along the thickness direction. It will be fired in the state.

[0007]

Embodiments of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a cutaway perspective view for explaining the method of the present embodiment, and is a cutaway perspective view of a firing box in a state where a ceramic compact is housed. In FIG. 1, parts and portions which are the same as or correspond to those in FIG. 3 showing the conventional method are designated by the same reference numerals.

The method of this embodiment involves firing of a ceramic compact used for forming a positive temperature coefficient thermistor element or the like, and as shown in FIG. 1, the ceramic compact 1 to be fired, for example, barium titanate. The ceramic molded body 1 made of is formed into a stacked body 2 by stacking a plurality of required ceramics in the thickness direction. Then, each of the stacks 2 as described above is stored in parallel in a box-shaped firing box 3 whose upper surface is open, while being separated from each other by a predetermined distance. At this time, since the firing box 3 is generally made of alumina, a powder or rug made of zirconia may be spread over the bottom surface thereof in order to prevent the reaction with the ceramic molded body 1. A zirconia coating is applied in advance. By the way, the shape of the firing box 3 shown in FIG. 1 in plan view is rectangular, but the shape is not limited to this, and it goes without saying that it may be circular or the like.

Further, on each of the stacks 2 thus stored in parallel in the firing box 3, they are collectively covered, and the stacks 2 are pressed in the stacking direction. A lid 5 is placed. That is, the drop lid 5 is made by firing a ceramic material having the same composition as the ceramic molded body 1, for example, barium titanate, and is formed as a flat plate having a certain weight. The shape of the drop lid 5 in plan view is the same as the inner shape of the firing box 3, and the outer dimension thereof is smaller than the inner dimension of the firing box 3. By the way, at this time, the dropping lid 5 may be formed of alumina, mullite, or the like. However, in this case, a means for preventing the reaction between the dropping lid 5 and the ceramic molded body 1 is provided. Since it becomes necessary separately and the time and effort required for the firing work increase, it is preferable that the dropping lid 5 is made of a ceramic material having the same composition as the ceramic compact 1 to be fired. Further, depending on the composition of the molded body, it also has an effect of preventing volatilization of components during firing.

Next, the inventors of the present invention used the drop lid 5
In order to compare the advantages and disadvantages of the method of the present example using the method of Example 1 and the conventional method not using the drop lid 5, a large number of ceramic molded bodies 1 made of barium titanate having a diameter of 16.8 mm and a thickness of 0.6 mm were prepared. Since the firing experiment was carried out by preparing it, the firing experiment will be described.

First, in this firing experiment, the inner dimensions are 88 mm length × 88 mm width × 24 mm height (thickness 6 m
m) of the firing box 3 is used, and the stack 2 formed by stacking 20 pieces of the ceramic molded bodies 1 having the above-mentioned size is accommodated in the firing box 3 in 5 columns and 5 rows. .. The drop lid 5 was made of barium titanate and was formed into a flat plate having a length of 84.5 mm × a width of 84.5 mm × a thickness of 1 mm. In this firing experiment, the firing box 3 (the method of this embodiment) containing the ceramic molded body 1 pressed by the dropping lid 5 and the firing case containing only the ceramic molded body 1 without the dropping lid 5 were used. After both Box 3 (conventional example method) was baked at a temperature of 1350 ° C. for 1 hour,
When the warpage caused by taking out the ceramic molded body 1 located at the uppermost part of the stack 2 where the adverse effect due to firing would appear most was measured, the results shown in Table 1 were obtained. Here, as shown in FIG. 2, x and y in Table 1 are the average values of the respective dimensions of the fired ceramics molded body 1, and xy is the average value of the degree of warpage, σ indicates the standard deviation of xy.

[0013]

[Table 1]

Further, according to Table 1 showing the firing experiment results, the ceramics fired by the method of this embodiment using the dropping lid 5 rather than the warpage of the ceramic molded body 1 fired without using the dropping lid 5. It is clear that the warp appearing in the molded body 1 is greatly reduced. Furthermore, in the method of this embodiment, since the stacks 2 stored in parallel in the firing box 3 are pressed by the dropping lids 5, external force such as vibration during transportation is applied to the firing box 3. Even if the ceramic molded body 1
It has also been confirmed that there is an advantage that the ceramic molded body 1 can be prevented from being cracked or chipped without causing mutual displacement.

[0015]

As described above, according to the present invention,
On the stack, which is stored in parallel in the firing box, is made of a ceramic material of the same composition as the ceramic compact,
Moreover, since the drop lid that presses each stack along the stacking direction is placed, the weight of the drop lid is dispersed and added to each ceramic molded body that constitutes the stack. Thus, each ceramic compact is fired while being pressed along the thickness direction. As a result, it is possible to effectively suppress the occurrence of warpage due to the shrinkage of the ceramic molded body, and it is possible to easily improve the product yield.

[Brief description of drawings]

FIG. 1 is a cutaway perspective view of a sagger for firing according to the method of this embodiment in a state where a ceramic compact is housed.

FIG. 2 is a side view showing a warped state of a fired ceramics compact.

FIG. 3 is a cutaway perspective view of a firing box in a state in which a ceramic compact is housed according to the conventional method.

[Explanation of symbols]

 1 Ceramic Formed Body 2 Stacked Body 3 Baking Box 5 Drop Lid

Claims (1)

[Claims] 1. A method for firing a ceramic molded body, in which a stack (2) obtained by stacking a plurality of ceramic molded bodies (1) along the thickness direction is accommodated in parallel in a firing box (3) and then fired. On the stacked bodies (2) stored in parallel, a drop made of a ceramic material having the same composition as the ceramic molded body (1) and pressing each stacked body (2) along its stacking direction. A method for firing a ceramic molded body, which comprises firing with a lid (5) placed thereon.