JPH05270927A - Method for burning ceramic compact - Google Patents

Abstract

PURPOSE:To simplify the separation of a setter after burning a ceramic compact formed into a bottomed cylindrical shape, prevent a material to be burned from being damaged and improve the yield. CONSTITUTION:A ceramic compact 1 formed into a bottomed cylindrical shape with an opened lateral end (1a) downward is placed on a setter 2 and burned. The setter 2 is provided with a through hole 3 for allowing a gas to flow into an inner space (1b) of the material 1 to be burned. Since the pressure of the inner space (1b) of the material 1 to be burned is not lowered from that of the outside with the through hole 3 even if the burnt material 1 is taken out in a state of the setter 2 sticking thereto after the burning, the separation of the setter is simplified so much.

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 ceramic molded body, more specifically, a ceramic molded body of a beta-alumina solid electrolyte (beta-alumina tube) used for sodium-sulfur batteries, thermoelectric conversion and the like. The present invention relates to a method of firing a ceramic molded body having a bottomed tubular shape with one end opened.

[0002]

2. Description of the Related Art It is known that, during the manufacturing process of a beta-alumina-based solid electrolyte, it is difficult and particularly difficult to fire a ceramic molded body, which is known to have a low yield. In this process, 1
Since the temperature is 500 ° C. or higher, the shaped body of beta-alumina pipe (hereinafter, also simply referred to as a shaped body) is easily deformed or damaged, and thus the product to be fired is likely to have dimensional defects or chipping. In the firing process, it is important to suppress the volatilization of the alkali component to improve the density, and at the same time, to make the large shrinkage unobstructed and uniform to improve the dimensional accuracy.

Under these circumstances, conventionally, as shown in FIG.
A flat base K made of refractory is placed in a firing furnace, a lid 54 of a container 55 to be covered later is placed on the base K, and the molded body 51 is erected vertically with its end on the opening side facing downward, and Although the container 55 is covered with the cover 55, the open end of the molded body 51 and the lid 54 are covered in order to prevent deformation and maintain accuracy during firing.
Between the solid body and the molded body 51,
A disk-shaped setter 52 is interposed. By doing so, it is effective in preventing accuracy defects such as deformation (poor circularity) of the object to be fired (molded body 51) due to difference in contraction and distortion in the radial direction of the pipe (molded body). On the other hand, in the firing process, the end face on the opening side of the object to be fired 51 and the upper surface of the setter 52 are tightly (solid) adhered to each other due to seizure or the like. It is necessary to lightly tap the outer periphery of the setter 52 to separate (remove) it.

[0004]

However, in the above-mentioned conventional technique, not only the opening-side end surface of the object to be fired 51 and the upper surface of the setter 52 are stuck to each other due to burning, but also the setter 52. Is a solid plate-like material, and because it closes the inner space 51b of the object to be fired 51, after cooling, the volume of gas in the inner space 51b decreases, so that space is at a lower pressure than the outside. Will be. For this reason, the setter 52 is strongly adsorbed or fixed to the object to be fired 51. Therefore, it becomes difficult to separate the setter 52 from the object to be fired 51, or if the setter 52 is forcibly removed, the setter 52 sticks to the setter 52. A part, that is, the opening end of the article to be fired (solid electrolyte) 51 may be chipped or cracked, which has been a factor of lowering the yield.

The present invention simplifies the separation of the setter after firing the ceramic molded body formed in the shape of a cylinder with a bottom, and prevents damage to the fired product during the separation, thus improving the yield. An object of the present invention is to provide a method for firing a molded body that can be achieved.

[0006]

In order to achieve the above-mentioned object, the present invention places a ceramic molded body formed in a cylindrical shape having a bottom so that the end portion on the opening side is in contact with the setter. Then, in the method of firing under that state, the setter, at least after firing, is configured to include a gas flow means for flowing gas from the outer side of the object to be fired to the inner space thereof. ..

[0007]

With the above structure, a molded product (baked product) which is baked and taken out with the setter stuck after cooling.
The gas flows from the outside to the inside space through the gas flow means of the setter. Therefore, in the firing process, even if the opening-side end surface of the object to be fired and the upper surface of the setter are in close contact with each other, a pressure difference between the inside and the outside does not occur. As a result, separation of the setter after firing is simplified, and the occurrence of damage to the fired object during separation is reduced accordingly,
Yield improves.

[0008]

【Example】

-Example 1- Next, Example 1 which materialized this invention is demonstrated in detail with reference to FIG. In the figure, reference numeral 1 denotes a molded body (material to be fired) fired in a firing furnace, and in this example, a beta-alumina bottomed tube. However, the outer diameter is about 43 m
m, and the length is 36 mm. On the other hand, the setter 2 used in this example is a disk-shaped member having a uniform thickness, is formed in an annular shape with a through hole 3 as a gas flow means in the center, and is a molded body of the material 1 to be fired and a common substrate. It consists of By the way, the diameter is about 48m, which is slightly larger than the outer diameter of the molded body.
m (40 mm), the thickness is about 6 mm (5 mm),
The through hole 3 has a diameter of about 15 mm. The values in parentheses are the dimensions after sintering.

Next, the setter 2 is placed on a base K indicated by a chain double-dashed line in the drawing, and is placed concentrically on a disk-shaped lid 4. .. Then, the molded body 1 is erected vertically with the opening side end (face) portion 1a abutting thereon. However, the molded body 1 is made concentric with the setter 2, and the peripheral edge of the through hole 3 is positioned at the inner circumference of the opening. Then, a predetermined container (crucible) 5 is covered. In this set state, the through hole 3 provided in the setter 2 is blocked by the upper surface of the lid body 4, and thus the inner space 1b of the molded body 1 is maintained in a substantially sealed state.

After that, firing is carried out at a predetermined temperature (holding at 1600 ° C. for 30 minutes) according to a conventional method. Then, after a predetermined time has elapsed and after cooling, the container 5 is removed and the molded body (work object) 1 is taken out. Then, the setter 2 is seized on the opening-side end surface portion 1a of the object to be fired 1 by seizing.
Even if they are in close contact with each other, the pressure in the inner space 1b does not decrease because of the through hole 3, so that the setter 2 can be easily separated.

In order to concretely confirm the effect of this example, a comparative test was conducted as follows in the case where the conditions were changed only in that the setter had no through holes (prior art). However, the number of samples was 50 for each of the objects to be fired by the method of this example and the prior art. The material to be fired (solid electrolyte) 1 has an outer diameter of 36 mm, a thickness of 3 mm, and a length of 300 mm.
The density was 3.23 and the radial crushing strength was 230 MPa. The test was performed by the device D shown in FIG. 2 so that the to-be-baked material 1 with the setter 2 attached thereto was allowed to fall naturally from a height of h (3 cm) with the setter 2 facing upward, as shown in FIG. By contacting the lower surface of the protruding setter 2 with the stopper S, it is separated (removed),
At that time, a test was carried out to determine that the product to be burned 1 that was damaged was a defective product. In addition, F is a buffer material.

As a result, the conventional sample produced 7 defects in the same sample (14% defective rate).
In the firing method of this example, there were no defects.
However, the quality was judged to be defective when damage such as cracks or cracks extending 1 cm or more in the axial direction from the open end of the material to be fired 1 was judged as defective. As can be seen from this test result, in the case of this example, even if the opening-side end surface 1a of the object to be fired 1 and the upper surface of the setter 2 are in close contact with each other due to seizure during the firing process, the pressure difference between the inside and outside It is proved that since the setter can be easily separated after firing, the occurrence of damage to the article to be fired 1 at the time of separation is reliably reduced, and the yield is improved. By the way, when the roundness (minimum value with respect to the maximum value) of the outer diameters of the end portions on the opening side of all the samples was measured, and when it exceeded 1.01, it was determined that the accuracy was poor. The basic function of maintaining the original dimensional accuracy was not impaired.

In this embodiment, the through hole is provided at the center of the setter 2, but a plurality of through holes may be provided. However, in order to prevent the occurrence of dimensional defects such as poor circularity of the object to be fired due to contraction or deformation of the setter during firing, one should be provided as much as possible, and when multiple holes are opened, they should be concentric and equiangularly spaced. It is preferable to provide it. The diameter of the holes is set to an appropriate size depending on the molded product.

Second Embodiment Next, a second embodiment will be described. However, in this embodiment, only the point that the gas flow means in the setter is changed to the configuration shown in FIG. Will be explained. That is, in the setter 12 used in this example, the substrate is a disk body having a uniform thickness as in the previous example, but the groove 13 is provided on one (upper) surface as a gas flow means in a + shape in a plan view. It is a thing. In this example, the groove 13 has a width of 5 mm and a depth of 2 mm. Although not shown in the figure, the molded body is placed and set and fired in exactly the same manner as in the case of the previous example. In the space, since the grooves 13 and 13 serve as ventilation paths to allow gas to flow from the outside, the inside space and the outside of the molded body communicate with each other not only after firing but also before and during firing. Since the seizure between the end surface on the opening side of the object to be fired and the upper surface of the setter occurs before reaching the predetermined baking temperature, in the case of baking using a conventional setter, the internal space of the object to be baked at the predetermined temperature The gas expands to high pressure. Therefore, if the object to be fired is thin, it may not be able to withstand the pressure and may crack, but this does not occur in the technique of this example, so it is particularly suitable when firing a thin object. .. The same comparative test as in the previous example was carried out for this example as well, but the result was exactly the same as in the case of the previous example and there were no defects.

Example 3 Next, Example 3 will be described. In this example, the gas flow means in the setter is different only in that the setter is formed of a porous body. is there.
That is, in this example, as shown in FIG. 4, the setter 22 has a disk shape, but after firing, at least the object to be fired is placed on the inside and the outside of the object to be fired under the condition that the object is placed. Is formed into a porous body in which innumerable small pores are formed. Here, the small pores are formed by mixing powder, which is the material of the molded body, with a pore-forming material such as a binder that is burned out in the firing process, but set to a suitable gas permeability (passability). Has been done. After firing, the cross section of the hole is such that the gas can pass through as much as possible, but specifically, the average diameter is preferably about 5 microns or more.

In the same way as in each of the above-mentioned embodiments, the molded body is set on the setter 22 of this embodiment and set and fired. In this embodiment, the setter is used in the firing process. The gas flow means is configured by burning out the pore-forming material mixed with the molded body of (1) to form innumerable small holes, and the gas flows into and out of the object to be burned after firing. Therefore, also in this example, a pressure difference does not occur between the inside and the outside after firing. In this example, a comparative test was performed in exactly the same manner as in each of the above-mentioned examples. As a result, two defects were generated, but the number of defects generated by the conventional technique was 7, and the yield was still good. Has been proven.

Although the setters used in the present invention are all made of beta-alumina co-base material, ceramic moldings made of appropriate materials such as alumina, magnesia and spinel can be used. ..
However, it is preferable to use the setter having the same shrinkage ratio as that of the material to be fired, in order to prevent the deformation during the firing process and improve the accuracy. Further, in the above-mentioned embodiments, all the setters are simultaneously fired as a molded body in the firing process, but a sintered body can be used although the accuracy is reduced.

The gas flow means of the setter in the method of the present invention is not limited to the above. At least after firing, that is, after cooling, the gas is circulated (penetrated or passed) from the outside of the object to be burned so that the volume of the gas in the inner space of the object is not reduced and the space is at a lower pressure than the outside. ), And the specific configuration of the gas vent hole (through hole) or the vent passage may be an appropriate configuration.

[0020]

According to the present invention, as described above, even if the molded body is fired and taken out in a state in which the setter is stuck after cooling, it passes through the setter from the outside of the object to be fired and the inner space thereof. Since the gas can flow through, even if the end surface on the opening side of the object to be fired and the upper surface of the setter are in close contact with each other in the firing process, the pressure inside and outside the same is maintained. Therefore, the setter can be easily separated after firing, and the amount of damage to the article to be fired at the time of separation can be reduced accordingly, so that the yield is improved and the productivity is expected to be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main part in a fired state for explaining an example of a firing method according to the present invention.

FIG. 2 is an explanatory diagram showing a test method for comparing the effect of the firing method according to the present invention with the case of the conventional technique.

3A is a front view of a setter used in Example 2 of the firing method according to the present invention, and FIG. 3B is a plan view of the setter.

FIG. 4 is a front view of a setter used in Example 3 of the firing method according to the present invention.

FIG. 5 is a schematic sectional view showing a firing state for explaining a conventional firing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bottomed cylindrical ceramic molded body (baking object) 1a Opening side end part 1b Inner space 2,12,22 Setter 3 Through hole (gas distribution means) 13 Ventilation path (gas distribution means)

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

EXAMPLES Example 1 Next, Example 1 embodying the present invention will be described in detail with reference to FIG. In the figure, reference numeral 1 denotes a molded body (material to be fired) fired in a firing furnace, and in this example, a beta-alumina bottomed tube. However, the outer diameter is about 43 m
m and the length is 360 mm. On the other hand, the setter 2 used in this example is a disk-shaped member having a uniform thickness, is formed in an annular shape with a through hole 3 as a gas flow means in the center, and is a molded body of the material 1 to be fired and a common substrate. It consists of By the way, the diameter is about 48m, which is slightly larger than the outer diameter of the molded body.
m (40 mm), the thickness is about 6 mm (5 mm),
The through hole 3 has a diameter of about 15 mm. The values in parentheses are the dimensions after sintering.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Iijima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (1)

[Claims] 1. A ceramic molded body having a bottomed tubular shape is placed with its end on the opening side abutting against a setter,
In the method of firing under that condition, the setter is configured to have a gas flow means for flowing gas from the outer side to the inner space of the object to be fired at least after firing. , A method for firing a ceramic molded body.