JPS61256982A - Method of burning ceramic sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION - The above invention relates to a method for firing a ceramic sintered body (ceramic porcelain).

[1L of greasy translucent alumina tubes, furnace core tubes, and protective tubes are fired simultaneously over the entire length of the object to be fired using a large batch-type gas furnace and atmospheric furnace.

However, this type of object to be fired becomes very large and long when the shrinkage during firing is taken into account, and the furnace body becomes large in order to fire the entire object at once. Furthermore, since the firing is performed in a batch manner, it is necessary to repeat the heating and cooling steps, which causes problems in energy saving and equipment costs, and is therefore uneconomical.

When firing in a large batch type furnace at a temperature of 1400℃ or higher using reducing gas, etc., the lower part of the furnace and the furnace material are likely to deform, and the object to be fired (ceramic porcelain) may also be deformed. Easy to do.

1 Suction L1 Disturbance This invention was made to solve the above-mentioned problems, and it is possible to continuously fire the object to be fired without cooling the furnace, thereby reducing energy costs, and reducing the size of the furnace body. It is an object of the present invention to provide a method for firing a ceramic sintered body that is free from distortion due to deformation and shrinkage of furnace materials at high temperatures, uneven firing of objects to be fired, and deformation of objects to be fired.

Therefore, the gist of the present invention is a method for firing a ceramic sintered body, in which a ceramic sintered body is obtained by suspending an object to be fired in a heating furnace, moving it in the vertical direction, and firing it.

To do this: The object 7 to be fired is suspended in the heating furnace 1 and fired by moving the object 7 in the vertical direction.

- 1-1 The object to be fired can be continuously heat-treated at the same humidity without cooling the heating furnace 1.

! 111 FIG. 1 shows a firing apparatus for carrying out the method of the invention.

First, the structure of this firing apparatus will be explained.

A heating furnace 1 (Z one S 1nter furnace), an upper setting section 2, and a lower setting section 3 are arranged in series.

Heating furnace 1 is insulated! ! ! It has 4. This insulation layer 4
is constructed by connecting each of the segmented layers 5a to 5e in the axial direction. This heat insulating layer 4 may have a cylindrical shape, for example. A heating element 6 is set inside each of the divided layers 58 to 5e. This heating element 6 may be made of a heat generating material such as tungsten.

The partition layer 5b indicated by hatching in FIG. 1 functions as a high temperature region. That is, the heat generation temperature in the segmented layer 5b is
The heat generation temperature is set higher than that in the other partitioned layers 5a, 5c, 5d, and 5e. The maximum heat generation temperature of the partitioning layer 5b is set to at least 1400°C or more, for example 1900°C.

The heat insulating layer 4 is provided vertically within the heating furnace 1 . The atmosphere inside the furnace is made of reducing gas or inert gas. The atmosphere inside the furnace can be composed of hydrogen, for example.

The space of the upper setting part 2 has sufficient space for the integral object to be fired 7 to move in the vertical direction. Upper setting section 2
An upper opening 8 is provided on the side surface of the housing. This upper opening 8 can be opened and closed.

An upper shutter 9 is provided between the upper setting section 2 and the heating furnace 1. The upper shutter 9 is configured such that a pair of left and right shielding portions 9a can be closed or opened by an actuator 9b.

A moving wave [10] of the object to be fired 7 is provided above the upper setting part 2. The moving device 10 has a drive roller 11 and a contact roller 12.

The lower end of a high melting point metal live shell 13 is attached to the upper end of the object 7 to be fired. Therefore, the object to be fired 7 is moved by the moving device 10.
By activating the , it is possible to move vertically.

The lower end of the lower setting section 3 is closed. A lower opening 14 is provided on the side of the lower setting portion 3 as required. This lower opening 14 can be opened and closed.

Either the lower opening 14 or the upper opening 8 can be omitted depending on the application.

A lower shutter 15 is provided between the lower setting section 3 and the heating furnace 1. This lower shutter V shutter 15 has the same structure as the upper shutter 9.

The upper shutter 9 and the lower shutter 15 may be of the same type, or may be of different types.

Next, this invention will be explained in detail.

First, the processing procedure for the integrated object to be fired 7 will be explained.

High purity alumina powder (purity 99.9% > 100 parts, magnesium sulfate heptahydrate 0.5 parts, PVA as binder)
Mix 1 part (polyvinyl alcohol) and make a slip.

(Magnesium sulfate heptahydrate is a grain growth inhibitor.)
The raw material made into a slip is dried with a spray dryer and granulated.

This granulated powder is formed into a tube shape using an isostatic press at a pressure of, for example, 1 ton/Cl112, and then ground into a predetermined shape. The obtained processed body has, for example, an outer diameter x inner diameter x length of approximately 3011 + 1 x 27 mm x
It is 1300111111.

This is pre-fired at 1100°C to scatter the binder, and then fired in a hydrogen atmosphere using the above-mentioned firing apparatus.

The segmented layer 5b of the heating furnace 1 has an axial length of, for example, 30 mm.
It is set to 0111111. This axial length is
It is smaller than the axial length of the object 7 to be fired. The segmented layer 5b has a high temperature region in which the object to be fired 7 can be fired.

The object to be fired 7 is fired in the following manner.

The object to be fired 7 is held within the lower setting PiSa by the moving device 10.

The lower shutter 15 is closed. The high melting point metal live shellfish 13 is sandwiched between the lower shutter 15. In this case, the lower setting part 3 is the setting zone 16 of the object 7 to be fired. The lower setting section 3 is sealed and its atmosphere is replaced with air, N2, and N2 in this order.

Both the atmosphere in the lower setting part 3 and the atmosphere in the heating furnace 1 are composed of hydrogen.

the lower shutter 15 is heard, the moving device 10 is activated,
The object to be fired 7 is pulled upward from the setting zone 16. The object to be fired (a) is pulled upward within the heat insulating layer 4.

The object to be fired 7 passes through the section g5b of the heating zone 17, as shown in FIGS. 2 to 4.

As shown in FIG. 2, the upper end 7a of the object to be fired 7 passes through the partitioned layer 5b at a passing rate of, for example, 500 ml/hour. Next, as shown in FIG.
b is, for example, a passing speed of 100 m1Il/in the partitioning layer 5b.
pass in time. Further, the lower end 7c of the object to be fired 7 passes through the section 115b at a passing speed of 500III/hour.

In this way, the passing speed of the object 7 to be fired is changed, and the object 7 is sintered within the partitioned layer 5b.

Next, the upper shutter 9 is opened and the object to be fired 7 enters the upper setting section 2. The upper setting part 2 is a take-out part 18 for the object to be fired 7.
functions as

When the upper shutter 9 is closed, the atmosphere in the upper setting section 2 is H.
2, N Z , and air are substituted in this order. The object to be fired 7 is taken out from the upper setting section 2.

Note that the flow direction of N2 in the heating zone 17 is opposite to the direction in which the object to be fired 7 passes.

In this way, a monolithic ceramic sintered body, for example a translucent alumina tube, is obtained. The resulting tube has the particle size dependent properties shown in FIG.

In FIG. 5, the horizontal axis indicates the position from the top of the ceramic sintered body. Also, the vertical axis shows the average particle size, radial crushing strength, and expansion it! (Total) transmittance is high.

As already mentioned, the passing speed at the upper end 7a and lower end 7C of the object to be fired 7 is set to be faster than the passing speed at the intermediate section 7b.

From this, as shown in FIG. 5, the average particle diameter of the translucent alumina tube is 20 to 40 μm, and is set small at the upper and lower end portions, but large at the middle portion.

Properties that depend on this average particle size include extended fa (total) transmittance and radial crushing strength.

The diffuse (total) transmittance is small at the upper and lower ends of the translucent alumina tube, and is greater than 95% at the middle. Conversely, the radial crushing strength is large at the upper and lower end portions of the translucent alumina tube, and is small at the middle portion.

On the other hand, FIG. 6 shows the properties of a translucent alumina tube sintered by a conventional manufacturing method.

As is clear from this, conventionally it is not possible to arbitrarily set the diffused (total) transmittance and radial crushing strength by changing the average particle diameter.

Incidentally, the object to be fired 7 is passed through the lower setting part 3 and the heating furnace 1 and taken out from the upper setting part 2.

However, the object to be fired 7 may be fired as follows.

For example, the object to be fired 7 is introduced from the upper opening 8 of the upper setting part 2, passes through the heating zone 17, and then
It can also be taken out from the lower opening 14.

In this case, the upper setting section 2 functions as a setting zone. The lower setting section 3 functions as a take-out section.

Alternatively, the object to be fired 7 may be introduced from the lower setting part 3, passed through the heating zone 17, raised to the upper setting part 2, and lowered again to the lower setting part 3 and taken out from the lower opening 14. good. In this case, the lower setting section 3 functions as a setting and removal section. Furthermore, put the object to be fired 7 from the upper setting part 2 and lower it to the lower setting part 3 again.
You can return it and take it out.

FIG. 7 shows another embodiment of the firing device.

Above and below the heating furnace 41, there are an upper setting section 42 and a lower setting section 43.
is the provision. The heating furnace 41 has a heat insulating layer (firebrick) 3
0.31.32. The heat insulating layer 30 is provided with a tungsten heater 30a. The heat insulating layer 31 includes
An auxiliary heater 31a is provided. The heat insulating layer 32 is provided with an auxiliary heater 32a. Further, an upper shutter 49 is provided between the heating furnace 41 and the upper setting section 42.

A lower shutter 4 is provided between the heating furnace 41 and the lower setting part 43.
5 is a provision.

Above the upper setting section 42 is a moving device.

The object to be fired 37 is made as follows.

High purity alumina powder with an average particle size of 0.5 μm or less (sIl!
99.9% > 100 copies, l
0.5 part of magnesium sulfate hydrate as a lubricant and 1 part of PVA (polyvinyl alcohol) as a binder are mixed, dried with a spray dryer, and granulated.

Next, this granulated powder is pressed to 1 ton/cm using a rubber press.
Pressurize with a pressure of 2, for example, diameter 4011I11 x length 2
000IIIm ~ Diameter 70ml x Length 2500I!
Form the Il pipe.

After machining this with a lathe, it is pre-fired at 1100°C.

The object to be fired 37 made in this manner is placed in advance from the upper setting part 42 and placed into the lower setting part 43 (see FIG. 8). In the figure, 56 is a setting zone for the object to be fired 37.

The object to be fired 37 is suspended by a high melting point metal live shell 33.

As shown in FIG. 8, the lower shutter 45 is closed to seal the lower setting section 43. Then, the atmosphere inside the lower setting section 43 is
Air, N2, and H2 are replaced in this order to make the setting zone 56 and heating zone 57 have the same atmosphere.

Thereafter, the lower shutter 45 is opened and the object to be fired 37 is pulled up at a moving speed (passing speed) of, for example, 200 mm/hour. The inside of the heat insulation 1i130 of the heating zone 57 is maintained in advance at a temperature of 1400°C or higher, for example, 1800°C to 1850°C.

As shown in FIG. 9, the object to be fired 37 passes through the heating zone 57 at a constant moving speed. Thereby, the object to be fired 37 is fired continuously and uniformly along its longitudinal direction.

Next, as shown in FIG. 10, the upper shutter 49 is opened and the object to be fired 37 is lifted into the take-out section 58 (upper setting section 42).

Then, the upper shutter 49 is closed again, and the upper setting section 42 is closed again.
is in a sealed state. The atmosphere of the upper setting section 42 is 8.
2, N2, and air are substituted in this order.

Thereafter, the ceramic sintered body 37) is removed from the take-out section 5.
It is taken out from 8.

Note that the object to be fired 37 can be moved not only in an upward direction (it may also be moved downward).

The characteristics of ceramic sintered bodies, such as translucent alumina, are
It is shown in Table-1.

Table 1 shows examples (No. 1 to 1) made according to the present invention.
8) and examples made by the conventional method (Nos. 9 to 11) are shown. In Table 1, the bending in the examples made according to the present invention is smaller than that in the conventional example.

Note that the conventional method uses a batch furnace.

Further, the embodiment according to the present invention and the embodiment according to the conventional method have the same composition.

Table 2 shows the characteristics of another example made by the method of the present invention.

In this case, 100 parts of high-purity spinel powder (purity 99.9%) with an average particle size of 0.5 μm or less and 5 parts of methylcellulose as a binder are mixed, and the mixture is dried with a spray dryer and granulated.

The granulated powder is then pre-calcined in the same manner as described above, and is then fired in the apparatus shown in FIG. 7 at a moving speed of 100 cm/hour. Insulation I of heating zone 57 at this time! The temperature within t30 is 1450 to 1600°C. The properties of the translucent spinel thus obtained are shown below.
It is shown in 2.

As is clear from Table 2, Examples (Nos. 1 to 6) made by the method of the present invention and conventional examples (Nos. 7 to 9)
), the bending of the embodiment according to the present invention is smaller.

Table 3 shows the characteristics of the lζ furnace core tube made as follows.

Alumina (purity 99°9%) with an average particle size of 3 to 4 μI 10
0 parts, and 0.0 parts of magnesium sulfate salt water as a grain growth inhibitor.
Add 5 parts of PVA to this as a binder and add 1 Pi of PVA as a binder.
I mix and dry this with a spray dryer and granulate it.

The granulated powder was molded and processed in the same manner as described above.
Calcinate at 00°C. The object to be fired is heated at 50°C in a hydrogen atmosphere.
Firing was performed at a travel speed of 0 mm/hour. Heat insulation layer 3
The temperature within 0 is set at 1750-1800°C.

As is clear from Table 3, the examples (Nos. 1 to 6) produced by the method of the present invention are different from the conventional examples (Nos. 7 to 9).
) The curve is smaller than that of

By the way, this invention is not limited to the content described above. For example, it can be used for continuous firing of short objects to be fired. It can also be used for translucent ceramics (alumina) and opaque structural ceramics. It can also be used to fire other materials such as mullite and magnesia. Further, the length of the temperature range a of the uniform temperature may be 1/2 or less of the length of the object to be fired. Note that a reducing gas or an inert gas can be used as the atmosphere.

11. ■ Energy costs can be reduced because the heating furnace can be used continuously without cooling.

■ The furnace body is small, reducing equipment costs and equipment space.

■ There is no distortion due to deformation or shrinkage of the furnace material at high temperatures. Furthermore, there is no deformation of the ceramic sintered body.

(2) Since the objects to be fired are fired while passing through the same temperature zone, uniform and dense sintered bodies of translucent ceramics and ceramics for opaque structures can be obtained without uneven firing due to temperature differences.

■ Eliminates the need for heating-cooling cycles, extending the life of furnaces and heaters.

■ Because the amount of furnace bricks used is small, there is less impurity contamination from the bricks.

■ High-quality ceramic sintered bodies (ceramic porcelain) can be obtained at low cost.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the firing apparatus used in the method of the present invention, Figures 2 to 4 are diagrams for explaining the firing process of the object to be fired, and Figure 5 is a diagram showing the firing apparatus used in the method of the present invention. A diagram showing an example of the characteristics of a translucent alumina tube, FIG. 6 is a diagram showing an example of the characteristics of an alumina tube made by a conventional method, and FIG. 7 is another firing apparatus used in the method of the present invention. 8 to 10 are diagrams for explaining the firing process of the object to be fired. 1.41... Heating Furnace 7.37 Items to be fired Figure 1 Figure 2 Figure 3 Figure 4 Figure 7 7C Figure 5? Position from top edge (mm) Figure 6 Position from top edge (mm)

Claims (2)

[Claims] (1) A method for firing a ceramic sintered body in which a ceramic sintered body is obtained by suspending an object to be fired in a heating furnace, moving it in the vertical direction, and firing it. (2) The method for firing a ceramic sintered body according to claim 1, wherein the high temperature range of the heating furnace is 1400°C or higher.