JP2001199760A - Ceramic, method of producing the same and baking unit therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ceramics capable of being produced in such a state that the time required for being baked is decreased, to provide a method of producing the same, and to provide a baking unit therefor. SOLUTION: This baking unit for producing ceramics is equipped with a chamber 11 of which the inner surface is made of a material capable of reflecting the microwaves, wherein a baking section 15 which is partitioned with heat-insulating walls 14 allowing the microwaves to transmit is installed in the chamber 11. And the ceramic article is obtained by irradiating a material to be baked 16 arranged in the baking section 15 with the microwaves generated from a microwave oscillator 12 and baking. The material to be baked 16 comprises a molded material which is obtained by molding a ceramic material into a prescribed shape, or a product which is obtained by baking the molded material but not covering it with a glaze, or a product which is obtained by covering the molded or unglazed material with the glaze.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic, a method of manufacturing the same, and a manufacturing apparatus.

[0002]

2. Description of the Related Art Conventionally, when a fired body such as a ceramic is manufactured, the fired body is placed in a firing furnace such as an electric furnace or a gas furnace and the inside of the furnace is heated to fire the fired body. Has been done. In this case, since the object to be fired is heated from the outside, a temperature difference is likely to occur between the surface and the inside of the object to be fired, which may cause adverse effects such as thermal distortion. For this reason, it is common practice to gradually raise the temperature in the furnace so as to maintain thermal equilibrium by heat conduction from the surface of the object to be fired to the inside. However, there is a problem in that the time required for firing becomes long.

Therefore, as a method for solving such a problem, there has been proposed a method for manufacturing a fired body in which a fired body is fired using microwaves. (Japanese Patent Laid-Open No. 60-2213)
No. 67, Japanese Unexamined Patent Publication No. 3-257070, Japanese Unexamined Patent Publication No.
-267304, JP-A-4-92870,
JP-A-9-183669)

[0004]

However, the fired bodies disclosed in the above publications each use a fine ceramic material as a raw material, and a fired body obtained from a ceramic material containing clay, feldspar, silica stone and the like. Is not disclosed.

[0005] This is thought to be because, in the case of a fired body made of a ceramic material, a large amount of liquid phase is generated near the firing temperature, and the absorption of microwaves rapidly increases, resulting in thermal runaway of the fired body. It is because it is. Therefore, it is difficult to apply microwave firing to the manufacture of a fired body made of ceramic material, that is, ceramic, and it is generally believed that the method of firing the furnace by gradually heating the furnace is the best. At present, its application has not been sufficiently studied.

The present invention has been made by paying attention to the problems existing in the prior art as described above. It is an object of the present invention to provide a porcelain which can reduce the time required for firing, a method for manufacturing the same, and a manufacturing apparatus therefor.

[0007]

In order to achieve the above object, the ceramic according to the first aspect of the present invention comprises a ceramic material as a raw material, and a molded article or a green body molded into a predetermined shape. Alternatively, the gist is that the object to be fired, which is formed by glazing them, is fired by microwaves.

According to a second aspect of the present invention, there is provided a method for manufacturing a porcelain, wherein the porcelain material is formed into a molded body having a predetermined shape, and the molded body or the molded body is baked or glazed. The gist is that the body is irradiated with microwaves and fired.

A third aspect of the present invention is directed to the method of manufacturing a porcelain according to the second aspect, wherein a liquid phase of 10 to 85% is generated in the object to be fired in the course of firing. According to a fourth aspect of the present invention, there is provided the ceramic manufacturing method according to the second or third aspect, wherein a heat insulating partition which allows transmission of microwaves is provided inside a chamber whose inner surface is capable of reflecting microwaves. Set up a divided firing chamber,
The gist is to irradiate the object to be fired made of a ceramic material disposed in the firing chamber with microwaves.

According to a fifth aspect of the present invention, there is provided a porcelain manufacturing apparatus, wherein the inside of the chamber is partitioned by a chamber whose inner surface is capable of reflecting microwaves and a heat-insulating partition wall which allows transmission of microwaves. An apparatus for manufacturing ceramics, comprising: a chamber; and microwave generating means for irradiating a microwave to a body to be fired made of a ceramic material disposed in the firing chamber.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing the entire configuration of the ceramic manufacturing apparatus of the embodiment. This ceramic manufacturing apparatus includes a chamber 11 formed of a closed container. At least the inner surface of the chamber 11 is formed of a material capable of reflecting microwaves. As a material capable of reflecting the microwave, for example, stainless steel can be used.

A microwave oscillator 12 as a microwave generating means is connected to the chamber 11 via a waveguide 13, and a microwave output from the microwave oscillator 12 passes through the waveguide 13. Thus, the light enters the chamber 11. The frequency of the microwave output from the microwave oscillator 12 is preferably 0.9 to 1
00 GHz. If this frequency is less than 0.9 GHz, the wavelength of the microwaves is
It is not preferable because the length is significantly longer than the size of Conversely, 1
If the frequency exceeds 00 GHz, the microwave oscillator 12 becomes expensive, which is not preferable. Among them, 2.45 GHz is more preferable because an inexpensive microwave oscillator 12 can be used.

In the chamber 11, a baking chamber 15 partitioned by a heat insulating partition 14 is provided.
An object to be fired 16 can be disposed in the inside of the element 5. The heat insulating partition 14 is formed of a material having heat insulating properties and allowing transmission of microwaves. Examples of the material having the heat insulating property and allowing the transmission of microwaves include alumina fiber and foamed alumina.

The body 16 to be fired is made of a ceramic material formed into a predetermined shape. Here, the ceramic material is not particularly limited as long as it has been conventionally used as a raw material for ceramics. Specific examples include those containing at least two types selected from clay, feldspar, porcelain stone, silica stone, kaolin, and alumina, and preferably those containing at least three types of clay, feldspar, and silica stone. Further, the pottery stone may be used alone as a pottery material. Further, at least one of clay and kaolin is used in an amount of 40 to 60.
It is preferable to contain 25 to 40% by mass of feldspar and 20 to 35% by mass of silica stone.

Further, a spherical reflector 17 for dispersing microwaves in the chamber 11 is provided at a position where the microwaves are incident in the chamber 11. Further, the ceramic manufacturing apparatus is provided with a thermocouple 18 for measuring the surface temperature of the object 16 disposed in the firing chamber 15 and an infrared thermometer (not shown). The heat insulating partition 14 and the chamber 11 are provided with a peephole 1 for infrared temperature measurement.
9 and 20 are provided.

Next, a description will be given of a method of manufacturing a ceramic using the ceramic manufacturing apparatus. In the case of manufacturing ceramics, first, the ceramic material is molded into a molded body of a predetermined shape,
The fired body 16 made of the molded body is disposed in the firing chamber 15. Subsequently, the firing target 16 disposed in the firing chamber 15
Is irradiated with a microwave output from the microwave oscillator 12. The microwave output from the microwave oscillator 12 enters the chamber 11 via the waveguide 13 and is dispersed by the reflector 17.
The light passes through the heat-insulating partition wall 14 while undergoing multiple reflections on the inner surface of the substrate, and is absorbed by the body 16 to be fired. Then, as a result, the fired body 1
6 generates heat, and when the temperature reaches the firing temperature, the fired body 16 is fired to obtain a ceramic.

In the process of firing the object 16,
It is preferable that a liquid phase of 10 to 85% is generated in the object 16 to be fired. If this is less than 10%, good porcelain may not be obtained. Conversely, if it exceeds 85%, deformation due to softening occurs, which is not preferable.

As described above, according to this embodiment, the following effects are exhibited. The fired body 16 made of a ceramic material absorbs the microwave output from the microwave oscillator 12 and generates heat to be fired to become a ceramic. At this time, the microwave is applied to the surface of the body 16 to be fired,
Since it is absorbed uniformly regardless of the inside, there is a possibility that a temperature difference may occur between the surface and the inside of the body 16 as in the case of a conventional electric furnace or gas furnace that heats the body 16 from the outside. Absent.

However, since there is a difference in the absorption of microwaves for each component constituting the ceramic material, a large number of temperature gradients are formed in the body 16 during the firing process. Therefore, also in this case, it is necessary to gradually heat as in the conventional case. However, this temperature gradient is such that thermal equilibrium is reached by microscopic heat conduction between the particles in the fired body 16, and the temperature gradient formed between the surface and the inside of the fired body 16 changes from the surface to the inside. It is clear that the thermal equilibrium can be reached very quickly compared to the case where the thermal equilibrium is reached by macroscopic heat conduction to the substrate. Therefore,
It is possible to increase the heating rate compared to the past,
The time required for firing can be greatly reduced. For this reason, the energy consumption at the time of baking can be suppressed compared with the case of the conventional electric furnace or gas furnace.

In particular, when manufacturing thick ceramics such as insulators, the conventional method requires more time for heat conduction from the surface to the inside, so that the time required for firing is further increased. However, in this embodiment, a temperature difference is hardly generated between the surface and the inside of the body 16 to be fired, so that the time required for firing can be greatly reduced even in the case of manufacturing a thick porcelain.

Further, since the body 16 to be fired quickly reaches thermal equilibrium during the firing process, it is possible to prevent adverse effects such as thermal distortion caused by a temperature gradient formed in the body 16 to be fired, and to achieve uniform firing. Is possible.

In the course of firing, 10 to 10
By producing 85% of the liquid phase, good ceramics can be obtained. Furthermore, since the liquid phase has a higher microwave absorption efficiency than the solid phase, the microwave absorption efficiency of the entire fired body 16 can be increased. Therefore,
The object to be fired 16 can be quickly heated.

Since the microwave is applied to the object 16 while being reflected multiple times on the inner surface of the chamber 11, the object 16 can be uniformly irradiated with the microwave. The function of the heat insulating partition 14 having heat insulating properties can prevent the temperature of the fired body 16 from being affected by the temperature in the chamber 11. Therefore, by adjusting the microwave output from the microwave oscillator 12, the temperature of the body 16 to be fired can be easily controlled. Further, since the heat insulating partition 14 has heat insulating properties, the surface temperature inside the heat insulating partition 14 and the temperature inside the firing chamber 15 can be gradually made substantially equal to the temperature of the object 16 during firing.
For this reason, it can suppress that the temperature of the to-be-fired body 16 falls by radiation cooling.

[0024]

Next, the embodiment will be described more specifically with reference to examples and comparative examples. (Examples 1 and 2) A ceramic material composed of 38.4% by mass of clay (kaolin), 31.5% by mass of feldspar, and 30.1% by mass of alumina was formed into a square plate shape, and fired from the formed body. Body 16 was formed. Then, the object 16 to be fired is fired using the ceramic manufacturing apparatus of the embodiment shown in FIG.
Obtained porcelain. However, in Example 1 and Example 2, alumina having different particle sizes was used. At this time, the frequency of the microwave output from the microwave oscillator 12 is 84 GHz.
At a heating rate of about 20 ° C./min.
(0 ° C.) and kept at that temperature for 30 minutes to perform firing. The chamber 11 is made of stainless steel, and the heat insulating partition 14 is made of alumina fiber having a thickness of 4 mm.
cm was used.

The results of measuring the water absorption, the bulk density, and the bending strength of the obtained porcelain are shown in Table 1.
Table 2 shows the results of the line diffraction. FIG. 2 shows a time-temperature curve representing the relationship between “time” and “temperature of the body 16 to be fired” during firing in Example 1.

Example 3 In Example 1, 44.0% by mass of clay, 36.0% by mass of feldspar, and 2% by mass of porcelain were used.
0.0 mass%, and the firing temperature was 115
The firing and measurement were performed in the same manner as in Example 1 except that the temperature was changed to 0 ° C. The results are shown in Tables 1 and 2.

Example 4 In Example 3, 33.0% by mass of clay, 27.0% by mass of feldspar and 4% of silica stone were used.
The same operation as in Example 3 was performed except that the composition was changed to 0.0% by mass. The results are shown in Tables 1 and 2.

(Comparative Example 1 and Comparative Example 2) Using a conventional electric furnace, the same object 16 to be fired as in Examples 1 and 2 was heated to 1220 ° C. at a rate of about 2 ° C./min. , 1220
Calcination was performed by holding at 60 ° C. for 60 minutes. Table 1 shows the results of measuring the water absorption, the bulk density, and the bending strength of the obtained porcelain. FIG. 2 shows a time-temperature curve of Comparative Example 1.

(Comparative Example 3) In Comparative Example 1, the object to be fired 16 was changed to use the same one as in Example 3,
The same operation as in Comparative Example 1 was performed except that the firing temperature was changed to 1150 ° C. Table 1 shows the results.

Comparative Example 4 Comparative Example 3 was carried out in the same manner as in Comparative Example 3 except that the object 16 to be fired was changed to the same one as in Example 4. Table 1 shows the results.

[0031]

[Table 1]

[0032]

[Table 2] From the results in Table 1, it was shown that the water absorption, the bulk density, and the bending strength of Examples 1 to 4 were equal to or better than those of Comparative Examples 1 to 4, respectively. From this,
It was shown that by using microwaves for firing, the rate of temperature rise can be increased about 10 times compared to the case of a conventional electric furnace, and the time for maintaining the firing temperature can be reduced to half.

The above embodiment can be modified as follows. In the embodiment, a molded body obtained by molding a ceramic material into a predetermined shape is used as the body 16 to be fired, but if desired, the molded body is unglazed, or the molded body is glazed or unglazed. The object to be baked 16 may be made of an article obtained by applying a glaze to the formed article. Even in the case of such a configuration, it is possible to perform firing similarly to the case of the embodiment.

A heater may be provided inside the firing chamber 15. With this configuration, the surface temperature inside the heat insulating partition 14 and the temperature inside the firing chamber 15 can be made substantially equal to the temperature of the object 16 to be fired. Therefore, it is possible to further suppress a decrease in the temperature of the fired body 16 due to the radiation cooling.

As ceramic materials, Mino ware, Arita ware,
Raw materials such as Seto ware may be used. The technical idea grasped from the above embodiment will be described below. The method according to any one of claims 2 to 5, wherein the microwave has a frequency of 0.9 to 100 GHz. With this configuration, the object to be fired can be fired reliably and inexpensively.

The ceramic material comprises 40 to 60% by mass of at least one of clay and kaolin, and 25 to 4% of feldspar.
The porcelain according to claim 1, which contains 0% by mass and 20 to 35% by mass of silica stone. With such a configuration, the time required for firing can be reduced for a ceramic containing at least one of clay and kaolin, feldspar and silica stone in a well-balanced manner.

[0037]

The present invention is configured as described above, and has the following effects. According to the porcelain of the first aspect, the time required for firing can be reduced.

According to the method for manufacturing ceramics according to the second aspect of the present invention, the time required for firing the ceramics can be reduced. According to the method for manufacturing ceramics according to the third aspect, in addition to the effects of the invention according to the second aspect, good ceramics can be obtained. Further, it is possible to quickly heat the object to be fired during firing.

According to the method of manufacturing the porcelain according to the fourth aspect of the present invention, in addition to the effect of the second or third aspect of the present invention, the temperature difference generated in the fired body during firing due to the heat insulating effect of the heat insulating partition. Can be further reduced, so that firing in a shorter time is possible.

According to the apparatus for manufacturing ceramics according to the fifth aspect of the present invention, the time required for firing the ceramics can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an overall configuration of a ceramic manufacturing apparatus according to an embodiment.

FIG. 2 is a graph showing time-temperature curves of Example 1 and Comparative Example 1.

[Explanation of symbols]

11: chamber, 12: microwave oscillator as microwave generating means, 14: heat insulating partition, 15: firing chamber, 16
... the object to be fired.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatoshi Mizuno 3-11 Hoshigadai, Tajimi-shi, Gifu Inside the Gifu Prefectural Ceramics Research Institute (72) In-flight Naruzo Obata 3-11 Hoshigadai, Tajimi-shi, Gifu Address: Gifu Prefectural Ceramics Research Institute (72) Inventor Tadashi Shimada 3-11 Hoshigadai, Tajimi-shi, Gifu Prefecture Gifu Prefectural Ceramics Research Institute (72) Inventor Motoyasu Sato 322-6 Shimoishi-cho, Toki City, Gifu Prefecture Ministry of Education, Culture and Science Institute

Claims (5)

[Claims] 1. A ceramic material is used as a raw material, and a molded body formed into a predetermined shape, a molded body obtained by sintering the molded body, or a body to be baked formed by glazing the molded body is microwave-fired. Pottery. 2. A method in which a ceramic material is formed into a molded body having a predetermined shape, and the molded body or a green body obtained by sintering the molded body or a body to be glazed is irradiated with microwaves and fired. Characteristic method of manufacturing ceramics. 3. In the course of firing, 10 to 85%
3. The method according to claim 2, wherein a liquid phase is generated. 4. A firing chamber defined by a heat-insulating partition wall permitting microwave transmission inside a chamber whose inner surface is capable of reflecting microwaves, and a firing target made of a ceramic material disposed in the firing chamber. The method for producing ceramics according to claim 2, wherein the body is irradiated with microwaves. 5. A chamber whose inner surface is capable of reflecting microwaves, a firing chamber provided by partitioning the interior of the chamber by a heat-insulating partition that allows microwave transmission, and a ceramic provided in the firing chamber. An apparatus for manufacturing ceramics, comprising: a microwave generating means for irradiating a microwave to a material to be fired made of a material.