JP2763812B2 - Method of firing ceramic products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a method for firing a ceramic product for firing a porous and hollow pipe-shaped ceramic product.

(Prior art) For example, a pipe-shaped product such as a porous ceramic filter used as a filter material or a porous ceramic product having a complicated shape is composed of an aggregate particle material and an inorganic binder material for binding these. It is manufactured by mixing, forming into a pipe shape or the like, drying, and then heating and firing to the melting temperature of the inorganic binder material. In this case, in order to minimize deformation of a pipe or a product having a complicated shape during firing, a firing method called “buried burning” is employed. This means that products such as pipes to be fired are housed side by side or vertically in a box-shaped kiln tool made of refractory material, and a pair of ceramic particles is scattered in the kiln tool to convert the product such as a pipe into ceramic particles. It is arranged in a firing furnace in a state of being buried. In this way, since ceramic pipes and products of complicated shapes are fired in a state of being wrapped in ceramic particles, the deformation of hollow products and products of complicated shapes that are easily thermally deformed due to their own weight during firing is relatively small. be able to.

(Problems to be Solved by the Invention) However, since the ceramic granules used for this burying and burning use a heavy coarse material having a specific gravity of 3 or more, such as alumina and mullite, the ceramic granules are included in the ceramic granules. It has been unavoidable that a relatively large load acts on a hollow product such as a buried ceramic pipe or a product having a complicated shape from a granular layer placed thereon. For this reason, there has been a problem that the ceramic pipe thermally softened by the high temperature is easily deformed by the load received from the granular material layer placed thereon.

Accordingly, an object of the present invention is to provide a method of firing a ceramic product which can prevent a porous and hollow pipe-shaped ceramic product from being deformed during firing.

[Constitution of the Invention] (Means for Solving the Problems) In a method for firing a ceramic product according to the present invention, an object to be fired is fired while being buried in countless hollow ceramic particles. Has a particle size of 4 to 8 times the average surface pore diameter of the article to be fired, and has a specific bulk density of 1.0.
It is characterized by being filled as follows.

(Action) Since the apparent bulk specific gravity of ceramic hollow granules is much smaller than that of conventional solid coarse-grained raw materials such as alumina and mullite, even if the same volume is used for filling and baking, the weight is still small. It becomes considerably smaller. For this reason, the load acting on the article to be fired is extremely small, and is hardly deformed. In this case, the load can be sufficiently reduced by filling the hollow particles so that the filling bulk specific gravity is 1.0 or less, and even if the article to be fired is a porous hollow pipe, its deformation is reduced. It can be effectively prevented. Then, the particle diameter of the hollow particles is set to 4 times the average surface pore diameter of the article to be fired.
By setting it to 不 具 合 8 times, it is possible to prevent problems such as hollow particles from entering the pores of the porous fired article and closing the pores, or roughening the surface of the fired article to make it uneven. it can. In addition, since the particles filled around the article to be fired are hollow and have low thermal conductivity,
The object to be fired can be uniformly heated over the entire area, and uniform firing can be performed. Furthermore, since it is a hollow particle and has a heat insulating effect due to the air layer, even if the cooling speed after firing is increased, it is possible to prevent the buried object to be fired from being rapidly cooled, and the spalling is performed. There is no risk of cracks and the like, and the firing schedule can be shortened.

(Example) FIG. 1 shows an example of a method for firing a ceramic pipe according to the present invention. Here, the ceramic pipe 1 as an article to be fired has a porous structure in which, for example, an alumina coarse-grained raw material is used as an aggregate and bonded with a glassy or crystalline inorganic binder, for example, a ceramic filter for food filtration or aluminum Used for filtration of molten metal. Its dimensions are, for example, an outer diameter of about 100 mm and an inner diameter of about 50 mm.

A plurality of ceramic pipes 1 are carried into a kiln while being housed in a refractory kiln tool 2 having a box shape, and each ceramic pipe 1 is buried in the kiln tool 2. Is filled with innumerable hollow ceramic particles 3 and firing is performed by so-called filling firing.

Each of the ceramic particles 3 has a hollow spherical shape as shown in FIG. 2 substantially in half, and in the case of this embodiment, is made of an alumina material. For example, a product sold under the trade name “alumina valve” can be easily obtained in various particle sizes. As the material of the hollow ceramic particles, alumina, silica, mullite, silicon carbide, etc. can be appropriately selected according to the firing temperature,
In order to avoid problems such as a reaction and coloring on the material to be fired, it is desirable to use hollow ceramic particles of the same material. At this time, the particle diameter of the hollow ceramic particles 3 is in the range of 4 to 8 of the average surface pore diameter of the article to be fired. If it is less than 4 times, there is a high possibility that the hollow ceramic particles will enter the pores from the surface of the fired article and close the pores, and if it is 8 times or more, the surface of the fired article will be roughened and uneven. It is. The specific gravity and the degree of filling of the ceramic granules 3 are selected so that the filling bulk specific gravity is 1.0 or less, more preferably 0.75 or less, in order to reduce the load acting on the ceramic pipe 1 from above. Is desirable.

In the case of this embodiment, the method of filling the ceramic granules 3 is as follows.
The ceramic granules 3 are laid in the kiln tool 2 with a thickness of about 5 mm to 20 mm, and a plurality of ceramic pipes 1 are arranged side by side on the ceramic granules 3. The ceramic granules 3 are sprayed so as to fill the space between the ceramic pipes 1, and finally, the ceramic granules 3 are sprayed over the entire surface of the ceramic pipe 1.
It was covered so as to have a thickness of 5 mm to 20 mm. As a result, each ceramic pipe 1 is buried in countless ceramic particles 3. In the present embodiment, since the fired ceramic pipe is used as a filter for filtration, when hollow ceramic particles are packed inside the hollow portion, hollow particles adhere to the inside of the pipe during firing, and an operation for removing this is necessary. Therefore, the hollow portion was not filled with ceramic particles. However, depending on the product, it may be more preferable to fill the hollow portion with ceramic particles in terms of dimensional accuracy.

In this state, if the kiln tool 2 is carried into the kiln and fired, the ceramic pipe 1 is heated together with the ceramic granules 3 and fired. According to this embodiment, the following effects can be obtained.

During firing, the ceramic pipe 1 becomes high temperature and softens. However, since the entire circumference is surrounded by the ceramic granules 3 so as to be clamped from the periphery, the fixed shape is maintained.
There is no risk of distortion due to its own weight.

Although the ceramic granules 3 are layered on the ceramic pipe 1, the ceramic granules 3 are lightweight and filled so that the filling bulk specific gravity is 1.0 or less. Even if the weight of the granular layer of the thermally softened ceramic pipe 1 acts as a load on the ceramic pipe 1, the ceramic pipe 1
Can be prevented as much as possible. Incidentally, the following table compares the amount of deformation of the ceramic pipe 1 according to the present embodiment method using the hollow ceramic granules 3 and that according to the conventional method using the conventional alumina coarse-grained raw material and the silicon carbide coarse-grained raw material. Show. Here, the product to be fired having an outer diameter of 100 mm was fired by the horizontal embedding method, and the vertical dimension of the outer diameter in the cross-sectional direction after firing was measured at three locations for one wire, and the average value of 10 wires was measured. Is determined, and the difference between the average value and the outer diameter of 100 mm before firing is defined as the amount of deformation.

As described above, according to the present embodiment, the deformation amount could be reduced from 1/5 of the related art to 1/7.

In this embodiment, the ceramic pipe 1 to be fired was used.
Uses an inorganic binder material consisting of borosilicate glass for 100 parts by weight of fused alumina of 28 mesh, which is an aggregate material.
10 parts by weight were added, kneaded with water and a binder, and the mixture was formed into a hollow pipe having an outer diameter of 100 mm, an inner diameter of 700 mm, and a length of 1 m. The hollow ceramic particles were made of alumina and had a particle size of 1 to 3 mm, and were buried and baked at 1400 ° C. in a state where the ceramic particles were layered on a ceramic pipe with a thickness of about 5 to 7 mm.

Since the ceramic granules 3 are hollow and the apparent specific heat is reduced, consumption of unnecessary heat energy that does not directly contribute to firing can be reduced.

Since the ceramic particles 3 are hollow and have low thermal conductivity, the ceramic pipe 1 is uniformly heated from the entire area, and uniform firing is possible.

When the kiln tool 2 is taken out of the kiln after the firing and cooled, the ceramic pipe 1 is gradually cooled because the three layers of ceramic particles made of countless hollow particles having a low thermal conductivity exhibit a heat insulating effect. And the occurrence of cracks and the like due to spalling can be prevented.

In the present embodiment, in particular, an alumina-based material having the same quality as that of the article to be fired is selected as the ceramic granules 3, so that the surface of the article to be fired is altered by the reaction with the article to be fired, or the ceramic particles 3 are fired. It can be prevented from sticking to the product.

Since the particle size of the ceramic particles 3 is 4 to 8 times the average surface pore diameter of the ceramic pipe 1, the ceramic particles 3 enter the pores of the porous ceramic pipe 1 to block the pores, It is possible to prevent a problem that the surface of the first member is roughened to make the surface uneven.

The present invention can be carried out with various changes within a range not departing from the gist, for example, the filling shape of the article to be fired can be not only horizontally but also vertically.

[Effects of the Invention] As described above, the present invention fires an article to be fired in a state of being buried in countless hollow particles made of ceramic,
The hollow particles at that time have an average surface pore diameter of 4 to
It has an eight-fold particle size and is characterized in that it is filled so that the filling bulk specific gravity is 1.0 or less. As a result, the load acting on the fired product can be reduced to prevent deformation of the fired product. ,
Further, even if the object to be fired can be uniformly fired, spalling of the object to be fired can be prevented even when the cooling rate of the furnace is increased to shorten the firing time.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a longitudinal sectional view showing a state of embedded burning, and FIG. 2 is a partial sectional view showing an example of ceramic particles. In the drawings, reference numeral 1 denotes a ceramic pipe (fired product), 2 denotes a kiln tool, and 3 denotes ceramic particles (hollow particles made of ceramic).

Continuation of front page (56) References JP-A-63-100074 (JP, A) JP-A-64-72969 (JP, A) JP-A-3-218983 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) C04B 35/64

Claims (1)

(57) [Claims] 1. A method for firing a porous and hollow pipe-shaped ceramic product, wherein the fired product is fired while being buried in countless hollow ceramic particles. At this time, the hollow granules have a particle diameter of 4 to 8 times the average surface pore diameter of the article to be fired, and have a specific bulk density of 1.
A method for firing a ceramic product, characterized in that the filling is performed so as to be 0 or less.