JP3404345B2 - Method and apparatus for manufacturing ceramics - Google Patents

Description

Detailed Description of the Invention

[0001]

[Field of the Invention The present invention relates to a method and an apparatus for manufacturing a ceramic device.

[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 body. Is being 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 usual to gradually raise the temperature in the furnace so that thermal equilibrium can be maintained by heat conduction from the surface to the inside of the body to be fired. However, there is a problem in that the time required for firing becomes long.

Therefore, as a method for solving such a problem, a method of manufacturing a fired body has been proposed in which a body to be fired is fired using microwaves. (JP-A-60-2213
67, JP-A-3-257072, JP-A-3
-267304, JP-A-4-92870,
(Japanese Patent Laid-Open No. 9-183669)

[0004]

However, each of the fired bodies of the above publications is made of a fine ceramic material as a raw material, and is made of a ceramic material containing clay, feldspar, silica stone, or the like as a raw material. Is not disclosed.

It is considered that, in the case of a fired body made of a ceramic material, a large amount of liquid phase is generated around the firing temperature to rapidly increase microwave absorption, resulting in thermal runaway of the fired body. It is because it is being done. Therefore, it is difficult to apply firing by microwaves to the production of fired bodies made from ceramic materials, that is, ceramics, and many people think that the method of gradually heating the inside of the furnace to perform firing is the best. However, the current situation is that the application has not been sufficiently examined.

The present invention has been made by paying attention to the problems existing in the prior art as described above. And an object thereof is to provide a method and apparatus for manufacturing a ceramic device which can shorten the time required for sintering.

[0007]

In order to achieve the above object, the method of manufacturing a ceramic according to the invention of claim 1 is a method of molding a ceramic material into a molded body having a predetermined shape, and the molded body or molded body. In a method of manufacturing a ceramics by irradiating microwaves on a body to be fired consisting of unglazed or glazed ones, the position where the microwaves are incident on the inside of the chamber whose inner surface can reflect microwaves. A sphere
In addition to providing a reflector in the shape of a bulb, a firing chamber defined by a heat insulating partition wall that allows transmission of microwaves is provided, and the object to be fired made of a ceramic material disposed in the firing chamber is irradiated with microwaves. Use as a summary.

According to a second aspect of the present invention, there is provided a method for manufacturing a ceramic porcelain according to the first aspect, wherein the firing step
The gist is that a liquid phase of 10 to 85% is generated in the fired body .

An apparatus for manufacturing a ceramic according to the invention of claim 3
The inner surface and capable of reflecting chamber microwaves, the tea
The spherical shape for dispersing the microwaves
Irradiation of microwaves to a firing chamber that is provided by partitioning the inside of the chamber with a reflector and a heat insulating partition that allows microwaves to pass through, and an object to be fired made of a ceramic material disposed in the firing chamber. And a microwave generating means for performing the same.

[0010]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing the overall configuration of a ceramics manufacturing apparatus of an embodiment. This ceramics manufacturing apparatus includes a chamber 11 formed of a closed container. At least the inner surface of the chamber 11 is made of a material capable of reflecting microwaves. Examples of the material capable of reflecting the microwave include stainless steel.

A microwave oscillator 12 as a microwave generating means is connected to the chamber 11 via a waveguide 13, and the microwave output from the microwave oscillator 12 passes through the inside of the waveguide 13. Is made incident on the inside of 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 microwave wavelength is in the device and the body 16 to be burned as described later.
It is not preferable because it is significantly longer than the dimension. Conversely, 1
If the frequency exceeds 00 GHz, the microwave oscillator 12 becomes expensive, which is not preferable. Above all, 2.45 GHz is more preferable because an inexpensive microwave oscillator 12 can be used.

In the chamber 11, there is provided a firing chamber 15 defined by a heat insulating partition wall 14. The firing chamber 1
A body 16 to be fired can be arranged in the unit 5. The heat insulating partition 14 is formed of a material having heat insulating properties and permitting 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 a molded body formed of a ceramic material 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 thereof include those containing at least two kinds selected from clay, feldspar, porcelain stone, silica stone, kaolin and alumina, and preferably those containing at least three kinds of clay, feldspar and silica stone. Alternatively, porcelain stone may be used alone as a ceramic material. Furthermore, at least one of clay and kaolin is 40-60.
It is preferable to contain 25% by mass, 25-40% by mass of feldspar, and 20-35% by mass of silica stone.

A spherical reflector 17 for dispersing the microwaves in the chamber 11 is provided at the position where the microwaves are incident in the chamber 11. Further, the ceramic porcelain manufacturing apparatus includes a thermocouple 18 and an infrared thermometer (not shown) for measuring the surface temperature of the body 16 to be fired, which is arranged in the firing chamber 15. The heat insulating partition 14 and the chamber 11 have a peephole 1 for infrared temperature measurement.
9 and 20 are provided.

Next, a method of manufacturing a ceramic using this ceramic manufacturing apparatus will be described. When manufacturing ceramics, first form the ceramic material into a molded body of a specified shape,
A body to be fired 16 made of the molded body is arranged in the firing chamber 15. Subsequently, the object to be fired 16 disposed in the firing chamber 15
Then, the microwave output from the microwave oscillator 12 is irradiated. The microwave output from the microwave oscillator 12 enters the chamber 11 via the waveguide 13, is dispersed by the reflector 17, and then is transmitted to the chamber 11.
While being multiple-reflected on the inner surface of the material, the material is transmitted through the heat insulating partition 14 and absorbed by the body 16 to be fired. And, as a result, the object to be fired 1
When 6 heats up and reaches the firing temperature, the article to be fired 16 is fired and a ceramic is obtained.

In the process of firing the body to be fired 16,
It is preferable that 10 to 85% of the liquid phase is generated in the body 16 to be fired. If it is less than 10%, good ceramics may not be obtained. On the other hand, when 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 body 16 to be fired, which is made of a ceramic material, absorbs the microwave output from the microwave oscillator 12 and generates heat to be fired to form 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 risk of a temperature difference between the surface and the inside of the body to be fired 16 as in the case of a conventional electric furnace or gas furnace that heats the body to be fired 16 from the outside. Absent.

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

In particular, in the case of manufacturing a thick ceramic such as an insulator, the conventional method requires more time for heat conduction from the surface to the inside, so that the time required for firing becomes longer. However, in this embodiment, since the temperature difference between the surface and the inside of the body 16 to be fired is unlikely to occur, the time required for firing can be greatly shortened even when manufacturing a thick ceramic.

In addition, since the body to be fired 16 quickly reaches thermal equilibrium during the firing process, it is possible to prevent adverse effects such as thermal distortion due to the temperature gradient formed in the body to be fired 16 and to perform uniform firing. Is possible.

During the firing process, 10 to 10
A good ceramic can be obtained by generating 85% of liquid phase. Further, since the liquid phase has a higher microwave absorption efficiency than the solid phase, the microwave absorption efficiency of the entire body 16 to be baked can be increased. Therefore,
It is possible to quickly heat the object 16 to be fired.

Since the microwave 16 is applied to the object 16 to be fired while being reflected multiple times on the inner surface of the chamber 11, the object 16 to be fired can be uniformly irradiated with microwaves. The function of the heat insulating partition wall 14 having heat insulating properties can prevent the temperature of the body 16 to be baked from being influenced by the temperature in the chamber 11. Therefore, the temperature of the body 16 to be fired can be easily controlled by adjusting the microwave output from the microwave oscillator 12. Further, since the heat insulating partition 14 has the heat insulating property, the surface temperature inside the heat insulating partition 14 and the temperature in the baking chamber 15 can be gradually made substantially equal to the temperature of the body 16 to be baked during the baking process.
Therefore, it is possible to prevent the temperature of the body 16 to be baked from being lowered by radiation cooling.

[0024]

EXAMPLES Next, the above-mentioned 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 molded into a square plate shape, and the molded body was subjected to firing. Body 16 was formed. Then, the body to be fired 16 is fired by using the ceramics manufacturing apparatus of the embodiment shown in FIG.
I got ceramics. 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.
And the firing temperature (122
(0 ° C.) and baked at that temperature for 30 minutes. The chamber 11 is made of stainless steel, and the heat insulating partition 14 is made of alumina fiber and has a thickness of 4 mm.
What was formed in cm was used.

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

Example 3 In Example 1, the ceramic material was 44.0% by mass of clay, 36.0% by mass of feldspar, and silica stone 2.
Change to 0.0% by mass and change the firing temperature to 115
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, the ceramic material was clay 33.0% by mass, feldspar 27.0% by mass, silica stone 4
The same procedure as in Example 3 was repeated except that the content 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 body 16 to be fired as in Example 1 and Example 2 was heated to 1220 ° C. at a heating rate of about 2 ° C./min. 1220
Firing was performed by holding at 60 ° C. for 60 minutes. Table 1 shows the results of measuring the water absorption rate, bulk density, and bending strength of the obtained ceramics. The time-temperature curve of Comparative Example 1 is shown in FIG.

Comparative Example 3 In Comparative Example 1, the same material as in Example 3 was used as the body 16 to be fired,
The same procedure as in Comparative Example 1 was performed except that the firing temperature was changed to 1150 ° C. The results are shown in Table 1.

Comparative Example 4 Comparative Example 3 was carried out in the same manner as Comparative Example 3 except that the same material as in Example 4 was used as the material 16 to be fired. The results are shown in Table 1.

[0031]

[Table 1]

[0032]

[Table 2] From the results in Table 1, it was shown that the water absorption rates, bulk densities, and bending strengths of Examples 1 to 4 were equivalent to or superior to those of Comparative Examples 1 to 4, respectively. From this,
It was shown that by using the microwave for the firing, the temperature rising rate can be increased about 10 times as compared with the case of the conventional electric furnace, and the time for holding the firing temperature can be shortened to half.

The above embodiment may be modified as follows. In the embodiment, a molded body formed by molding a ceramic material into a predetermined shape is used as the body to be fired 16. However, if desired, the molded body is unglazed, or the molded body is glazed or unglazed. You may use as the to-be-baked body 16 what consists of what was glazed to the formed body. Even with such a configuration, it is possible to perform firing in the same manner as in the case of the embodiment.

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

As ceramic materials, Mino ware, Arita ware,
You may use raw materials, such as Seto ware. The technical idea understood from the above embodiment will be described below. -The method of manufacturing a ceramic according to claim 1 or 2 , wherein the frequency of the microwave is set to 0.9 to 100 GHz. With this configuration, the body to be fired can be fired reliably and inexpensively.

[0036]

[0037]

Since the present invention is constructed as described above, it has the following effects. According to the method for manufacturing a ceramic according to the invention of claim 1, the heat insulation effect of the heat insulation partition wall is improved.
The temperature difference inside the object to be fired during firing is further reduced.
Therefore, it is possible to perform firing in a short time.

According to the method of manufacturing a ceramic ware of the second aspect, in addition to the effect of the invention of the first aspect, a good ceramic can be obtained. Furthermore, it is possible to quickly heat the body to be fired during firing .

According to the apparatus for manufacturing a ceramic ware of the third aspect , the time required for firing the ceramic ware can be shortened.

[0040]

[Brief description of drawings]

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

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

[Explanation of reference numerals] 11 ... Chamber, 12 ... Microwave oscillator as microwave generation means, 14 ... Adiabatic partition wall, 15 ... Firing chamber, 16
... Subject to be fired.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seizo Obata 3-11 Hoshigadai, Tajimi City, Gifu Prefecture Gifu Prefecture Ceramics Research Institute (72) Tadashi Shimada 3-chome Hoshigadai Tajimi City, Gifu Prefecture No. 11 Gifu Prefectural Ceramics Research Institute (72) Inventor Motoyasu Sato 322-6 Shimoishi-cho, Toki City, Gifu Prefectural Institute of Fusion Science (56) Reference JP-A-7-318262 (JP, A) Japanese Patent Publication Sho 60-1747 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 33/32, 35/64 H05B 6/64-6/80

Claims (3)

(57) [Claims] 1. A ceramic body, which is formed by molding a ceramic material into a molded body having a predetermined shape, and the molded body or the molded body which is unglazed or which is glazed is irradiated with microwaves and burned. In the manufacturing method, the microphone is placed inside the chamber whose inside surface can reflect microwaves.
If a spherical reflector is installed at the position where the B wave is incident,
In addition, a firing chamber defined by a heat insulating partition wall that allows transmission of microwaves is provided, and a firing target made of a ceramic material disposed in the firing chamber is irradiated with microwaves. Manufacturing method. 2. The material to be fired has a content of 10 to 85% in the firing process.
2. The method for manufacturing a ceramics according to claim 1, wherein the liquid phase is generated. 3. A chamber whose inner surface is capable of reflecting microwaves, and which disperses the microwaves that have entered the chamber.
A spherical reflector for refining, a firing chamber provided by partitioning the inside of the chamber with a heat insulating partition wall that allows transmission of microwaves, and an object to be fired made of a ceramic material disposed in the firing chamber. An apparatus for manufacturing ceramics, comprising: a microwave generation unit that irradiates microwaves.