JPH063066A - Ceramic shelf plate for calcination - Google Patents

Abstract

PURPOSE:To uniformly calcine an article by constructing a title shelf plate with a plate-shaped structure which is formed by coupling columnar or rectangular ceramic units each having an opening through a surface thereof, and specifying an area ratio of holes formed vertically through each unit and through side surfaces of each unit and further specifying hole diameters. CONSTITUTION:A ceramic shelf plate useable for supporting an article to be calcined and so on upon manufacturing various ceramic products comprises a plate-shaped structure formed by coupling columnar or rectangular ceramic units each having an opening through a surface thereof. Each unit includes a pillar structure on the surface thereof as indicated by (c), (d) for reinforcing the strength thereof. An area ratio of holes formed through vertical surfaces of each unit is set to range from 39% to 80%, and an area ratio of side surfaces is set to range from 5% to 50%. When intervals between adjacent parallel lines of respective sets putting the hole 1 therebetween and crossing each other are assumed to be s, L, a hole diameter is assumed to be (s+L)/2 and is set to be 0.5-4mm, and further density of the plate-shaped structure is set to be 7000g/m<2> or smaller with the thickness of the same being set to be 8mm or smaller. The shelf plate has smaller heat strength, so that the article is uniformly calcined.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a ceramic shelf for firing. More specifically, various ceramic products such as ceramic electronic components, ceramic sliding materials, general porcelain, and bite manufactured by powder metallurgy for supporting objects to be fired, baking jigs such as floor boards The present invention relates to a ceramic shelf board useful for applications.

[0002]

2. Description of the Related Art Ceramic shelves for firing must have a high degree of heat resistance to withstand repeated high temperature heating and cooling and mechanical strength according to the application. On the other hand, in order to reduce energy costs and productivity by reducing the heat energy consumed by them when using the furnace and shortening the time required for heating and cooling, lightweight products with as little heat capacity as possible Was desired. Also,
Currently, in addition to simple energy saving and productivity improvement, it is required to save or reduce the overall energy consumption by excluding or reducing the extra post-treatment by uniformly baking the material to be fired. There is. As an example of extra post-treatment, treatment to correct the difference in electrical characteristics due to uneven heating on the contact surface with the firing jig and on the surface exposed to the surrounding gas, or in the material to be fired In the binder decomposition and removal process, the re-baking process is performed to correct that the upper surface of the object to be baked shrinks due to the difference in the decomposition rate due to uneven heating on the upper and lower surfaces and the object to be baked has a trapezoidal shape or warps. is there.

As a conventional ceramic shelf board for firing, there is known a refractory material obtained by firing a compression-molded powder by a press or the like. In such a firing jig, in order to uniformly fire the object to be fired, a triangular pyramid-shaped protrusion is formed on the surface, or through holes are formed in the upper and lower surfaces of the refractory material to make the object to be fired. Investigations have been made to make the ambient gas and temperature distribution uniform. However, even if protrusions are formed on the refractory surface, the difference between the speed at which the refractory is heated and the speed at which the surrounding gas is heated is large. A large temperature difference occurs,
The organic substances such as the binder are not decomposed uniformly, and the uneven heating including sintering adversely affects the object to be fired. Further, when the through hole is provided, not only the same problem as described above occurs in the refractory but also the free movement of the surrounding gas is hindered. For example, in firing silicon nitride or the like, nitrogen is used as a surrounding gas, but from the replacement surface of the surrounding gas,
The through-holes are blocked by the object to be fired and the replacement of the surrounding gas becomes insufficient, causing unevenness in the firing of the object to be fired.

Recently, the use of porous ceramic bodies has also been proposed. As a porous ceramic body, a honeycomb and a ceramic foam using urethane foam are widely known. A method for manufacturing a honeycomb structure by extruding an extrudable ceramic raw material from an orifice is disclosed in JP-A-48-55960. Is disclosed in. Further, JP-A-62-56771 discloses a ceramic porous body obtained by forming a sheet obtained by a papermaking method from an aluminosilicate fiber which is an inorganic fiber and a ceramic raw material powder into a honeycomb filter and firing it. There is. According to this method, a ceramic porous body having a large number of through holes can be obtained, but a problem arises because the free movement of the surrounding gas is obstructed in the same manner as the above through holes.

JP-A-48-81907 and JP-A-52-77114 disclose that a ceramic slurry is adhered to the surface of an organic foam having an internal communication space, and the foam is dried and fired. Is disclosed. These allow free movement of the surrounding gas in the lateral direction as compared with the through holes. However, there is no through hole in the upper and lower surface directions, and the hole diameter is generally as small as 0.5 mm or less, and the thickness is large from the viewpoint of strength, and as a result, the air ventilation resistance is very large.

[0006]

The ceramic shelves for firing are required to have an optimum structure in consideration of heat transfer phenomenon and ventilation phenomenon near the shelves as well as light weight and high strength. From the viewpoint of the present inventors, as a result of diligent study to solve the above-mentioned drawbacks of the conventional ceramic shelf boards for firing,
The present invention has led to the invention of a baking shelf that is light in weight and can be baked uniformly.

[0007]

According to the present invention, there is provided a plate-shaped body formed by connecting cylindrical or prismatic ceramic units each having an opening on a surface thereof and connecting the openings to each other. The area ratio of the surface holes is 30% to 80%, the area ratio of the side holes is 5% to 50%, and the hole diameter is 0.5 m.
The ceramic shelf plate for firing has a structure of m to ⁴ mm, the weight of the plate-shaped body is 7,000 g / m ² or less, and the thickness is 8 mm or less.

In order to uniformly burn the object to be fired, it is necessary that the gas (air flow) around the object to be fired moves freely. To do so, on the lower surface of the object to be fired,
Not only is it in contact with the surrounding gas through the single pore,
On the side surface of the hole, the gas around the firing is free to move by communicating with other pores, so that the gas around the firing is made uniform as a whole. However, it is not only necessary that the holes communicate with the side surfaces. Unless it is below a certain ventilation resistance, the air flow cannot move freely and the gas around the firing cannot be made uniform. That is, if the holes are small, the ventilation resistance is large and the air flow cannot move freely. However, if the pores are large, the portion of the columnar structure must be enlarged in order to have strength, and in that case, firing unevenness is generated as in the case of forming through holes in the compression molded article of the prior art. As a result of diligent investigations to solve this problem, the present inventors have found a baking shelf that satisfies the above requirements.

The shelf board of the present invention is, for example, as shown in FIGS. 1a to 1d, a plate-like body formed by connecting ceramic units each having a cylindrical or prismatic shape having an opening in its surface. The shape of the unit may be any shape such as a cylinder, a triangular prism, a quadrangular prism, a pentagonal prism, and a hexagonal prism. In order to increase the strength, a columnar structure may be added to the surface as shown in c and d of FIG.

In the present invention, the area ratio of the holes in the vertical surface of each unit must be 30% or more and 80% or less, preferably 40% or more and 70% or less. Three
If it is less than 0%, the ventilation resistance becomes large, and the airflow in the upper and lower directions of the shelf plate cannot move freely enough to prevent uniform firing.
If it exceeds 80%, the strength becomes weak. Side area ratio is 5
% Or more and 50% or less is necessary, and preferably 10% to 40%. If it is less than 5%, the movement of the air current in the lateral direction cannot be sufficiently increased because the ventilation resistance becomes large, and uniform firing cannot be achieved. However, the strength of the column portion in the lateral direction is important for providing strength while being thin and lightweight. From this viewpoint, if it exceeds 50%, the strength becomes weak.

The pore size is determined according to the following definition. As shown in FIG. 3, of the set of two parallel lines sandwiching the hole 1, the interval of the parallel lines of the set having the minimum interval is s, and the interval of the parallel lines sandwiching the hole 1 orthogonal to the parallel line is s. L and the hole diameter is (s
+ L) / 2 is defined. Pore diameter is 0.5mm or more, 4mm
It is necessary to be the following. More preferably 0.8 mm
It is 3 mm or less. If it is less than 0.5 mm, the ventilation resistance becomes large and it becomes difficult to make the gas around the firing uniform. On the other hand, if it exceeds 4 mm, the diameter of the skeleton-shaped column becomes large when molded in consideration of strength, resulting in firing unevenness.

The weight of the shelves is 7,000 g in order to be lightweight.
/ M ² or less is required. More preferably 4000 g /
m ² . The lower limit is not particularly limited, but 1000 g / m ² or more is preferable in terms of strength retention. The thickness is required to be 8 mm or less, preferably 5 mm or less. The lower limit of the thickness is preferably 1 mm or more for maintaining strength.

The ceramic shelf board of the present invention uses a three-dimensional knitted fabric comprising two front and back knitted fabrics obtained by weaving and weaving a fibrous material and a connecting portion for connecting the front and back to each other. It is produced by impregnating with and baking the coated product. Examples of the organic fibers used for manufacturing the ceramic shelf for firing of the present invention include cellulosic fibers, polyamide fibers, polyester fibers, polyacrylic fibers, polyolefin fibers, polyurethane fibers and the like. Moreover, you may compound the said fiber.

The form of the fibers may be long fibers,
It may be a short fiber. The form of the yarn may be any of monofilament, multifilament, spun yarn, or a composite of these. A three-dimensional woven or knitted fabric using this yarn is composed of two front and back woven and knitted fabrics formed of warp yarns and weft yarns and a connecting portion for connecting the front and back faces to each other. The opening position and the opening diameter of the front and back can be set by the gauge and knitting density of the knitting machine used. The opening diameter and the opening are holes (voids) formed by the structure of the woven or knitted material.

As the thread of the connecting portion, a thread having a rigidity sufficient to hold at least two front and back woven and knitted fabrics in three dimensions is used. In the case of retaining a three-dimensional structure, usually, a monofilament is preferable from the viewpoint of rigidity, and a multifilament or spun yarn is preferable from the side of the holding surface at the connecting portion of the ceramic slurry in the ceramic coating step described later. As a result of studying the rigid surface and the holding surface at the connecting portion of the ceramic slurry, by using the monofilament and multifilament yarns of the connecting yarn at the same time, it is not necessary to maintain the three-dimensional structure by post-processing such as resin processing. It was found to be a three-dimensional woven or knitted fabric for a base cloth. In other words, by designing the structure by dividing the part that holds the ceramic slip of the ceramic forming the skeleton that opens between the adjacent cells and the part that requires rigidity to three-dimensionally hold the structure of the connecting yarn, A three-dimensional woven or knitted fabric does not need to maintain a three-dimensional structure by post-processing such as resin processing. It is also possible to form one or more woven or knitted fabrics between the connecting portions included between the two woven and knitted fabrics on the front and back sides, which allows more control of the fluid.

The woven or knitted fabric may be used as it is in the next step of applying the ceramic slurry, or the step of removing the oil agent, the sizing agent and the like before the knitting and weaving step, the stability against water and other solvents and heat. In order to improve the temperature, heat treatment may be performed. The ceramic raw material may be selected according to the purpose of use. Oxide ceramics such as cordierite, alumina and stabilized zirconia, nitrides such as silicon nitride and aluminum nitride, and carbides such as silicon carbide are generally used.
The present invention is not limited to these, including powder such as metal.
Further, the particle size of the ceramic raw material powder is preferably changed according to the diameter of the single fiber to be used, and the particle size distribution such as the closest packing is more preferable. The maximum particle diameter is less than or equal to the fiber diameter, and preferably less than or equal to 1/2 with respect to the fiber diameter. In preparing the ceramic slurry, the composition and viscosity are set so as to obtain uniform impregnation and adhesion to the special woven or knitted fabric. The adhesion rate depends on the density of the powder used,
When the true density of alumina is 3.9 g / cc, it is 200% by weight or more and 1000% by weight or less, preferably 400% by weight or more and 800% by weight or less with respect to the fiber weight. The adhesion rate changes depending on the bulk density of the powder. For example, if a powder having a true density of 7.8 g / cc is used, the weight becomes 400% by weight or more and 2000% by weight or less with respect to the fiber weight, and the volume is the same. To be

If the amount is 200% by weight or less, the fibers and the surface of the fiber assembly are not coated, resulting in poor strength or the shape collapses during firing. Above 1000% by weight,
Ceramics fill the openings, especially the openings between adjacent cells. Generally, a ceramic raw material powder is dispersed in a dispersion medium such as water together with a deflocculant and a binder (eg, methyl cellulose, ethyl cellulose, polybutyl cellulose, polyvinyl alcohol, wax, etc.) to form a slurry.

As a method for impregnating the ceramic slurry, the woven or knitted material is dipped in the ceramic slurry and then squeezed with a mangle, or the excess slurry is removed by centrifugal separation, blowing compressed air or the like, or a kiss roll or a gravure. Any method such as using a roll may be used, or a combination thereof may be used. The point is that the ceramic raw material is impregnated between the single fibers of the fiber assembly that constitutes the woven or knitted fabric, and the voids of the fiber assembly are filled with the ceramic raw material and are uniformly mixed with the ceramic raw material on the surface of the fiber assembly. Any method may be used as long as it can create a state in which the surface of the fiber assembly is covered with the ceramic raw material.

This is a significant difference from the case of using a conventional organic foam. When an organic foam is used, the side of the organic material that forms the skeleton is inevitably large, and when applying the ceramic raw material to the skeleton surface, the strength is maintained due to the presence of the hollow part after the organic matter is decomposed and removed after firing. In order to achieve this, it is necessary to secure a certain ceramic coating thickness. For this reason, the porosity of the ceramic porous body (excluding the hollow portion in the skeleton) is reduced.
Another problem is that the communication space of the ceramic porous body is blocked because the ceramic is not applied uniformly.

The ceramic-impregnated knitted fabric is then dried. The drying condition may be a temperature below the temperature at which the organic fibers are not decomposed and a temperature at which the shape of the woven or knitted fabric of the knitted fabric does not collapse. The firing can be performed by a known method. However, regarding the decomposition and removal of the organic matter, it is necessary to set the temperature rising rate such that the shape of the porous ceramic structure does not collapse due to decomposition gas and melting.

[0021]

The present invention will be specifically described with reference to examples. Bending Strength Measurement Method A sample 1 having a length of 170 mm, a width of 50 mm and a thickness t is shown in FIG.
On the fulcrum base 2 set at a distance of 150 mm as shown in FIG. 1, the sample end and the tip of the fulcrum base are placed with a distance of 10 mm.

When the load fulcrum base 3 having a pressing tip at a distance of 50 mm is placed in the center of the sample and the strength at the time of breaking the sample when a load is applied is F, the bending strength is 3F / t
Required by ² .

[0023]

Example 1 A three-dimensional knitted fabric was produced using a double Raschel machine equipped with 6 guides. The knitting machine used is 18 gauge (has 18 needles per inch), the yarns are arranged in a 1-in / 2-out yarn array, and the guide bar L
1, L2, L5, L6 form a net on the front and back, L3,
A connecting portion for connecting the front and back sides was formed by L4, and holes were formed between the net-like objects on the front and back sides to communicate between adjacent cells.
A 1000d / 192f polyester yarn was used for L1 and L6, a 150d / 48F polyester ester yarn was used for L2, L3, and L5, and a 180d / 1F nylon monofilament yarn was used for L4. The obtained knitted fabric had a thickness of 4.5 mm. For the stability of the knitted fabric in the intermediate step, refining and dry heat setting were performed to obtain a knitted fabric having a thickness of 3.5 mm. This knitted fabric was made of an alumina raw material powder having an average particle size of 0.5 μ (Showa Denko AL
-160SG-3) 100 parts, deflocculant (Cerkyo Diesel Serna D-305) 1 part, binder (Chukyo Yushi Co. Serna WE-518) 5 parts, distilled water 30 parts using a ball mill. I created a rally. The knitted fabric is dipped in the created ceramic slurry, squeezed with a mangle, dried, and then dipped in the ceramic slurry again, excess ceramic slurry is removed using compressed air, and the dried product is then electrically converted. The organic fibers were decomposed and removed in a furnace, the alumina sintering temperature was raised to 1600 ° C., and held for 1 hour for sintering.

The obtained ceramic shelf board maintains the appearance of a skeleton structure, forms a mesh on the front and back sides, forms a connecting portion for connecting the front and back, and adjoins the knitted materials on the front and back sides. The holes communicating between the holes were formed. The average area ratio of the holes in the upper and lower surfaces of the unit was 64%, the side surface direction was 15%, and the average hole diameter was 2.0 mm. The basis weight of the plate is 3300g.
/ M ² , and the thickness was 3.3 mm, and a lightweight and thin structure was obtained. The bending strength was 105 kg / cm ² .

[0025]

Example 2 A ceramic shelf board for firing was molded in the same manner as in Example 1. A knitting structure was formed in accordance with each specification in order to change the average area ratio in the upper and lower surface directions of the unit from 20% to 90%. Unit average pore size 2.0m
m, 15% in the lateral direction, and the thickness of the plate-shaped body was 3.3 mm. The results are shown in Table 1.

[0026]

[Table 1]

[0027]

Example 3 A ceramic shelf plate for firing was molded in the same manner as in Example 1. The average area ratio of the side of the unit is 1
% To 60%, the knitting structure was formed according to each specification. The average area ratio in the direction of upper and lower surfaces is 64
%, The average pore diameter was 2.0 mm, and the plate-shaped body had a thickness of 3.3 mm. The results are shown in Table 2.

[0028]

[Table 2]

[0029]

[Comparative Example 1] A commercially available ceramic shelf board for firing was used in which crystalline alumina short fibers were molded and fired. Since the structure does not have holes that allow the movement of surrounding gas, the area ratio in the top surface direction and side surface direction is 0%, and the average hole diameter is 0.1 mm.
The following was a very small one. The basis weight of the plate is 10
The thickness was 000 g / m ² and the thickness was 10 mm.

[0030]

[Comparative Example 2] In Comparative Example 1, nine through holes having a diameter of 5 mm were opened per square inch so that the gas could be freely moved in the vertical direction. Area ratio 27% in upper and lower surface direction, 0% in side surface direction, hole diameter 5 mm, basis weight 7300 g / m ² , thickness 1
It was 0 mm.

[0031]

COMPARATIVE EXAMPLE 3 A commercially available product, a porous ceramic having a foam structure having an internal communication space, was used. The material is alumina, which is obtained by immersing a ceramics slurry in polyurethane foam and drying and firing it. It had many small holes due to the foam structure and had a diameter of 0.2 mm. The area ratio in the upper and lower direction is 50%, the side direction is 50%,
The basis weight was 13000 g / m ² and the thickness was 15 mm.

As the material to be fired, a ceramic slurry used in Example 1 was molded into a 5 cm square and a thickness of 2 cm using a gypsum mold. This fired product was placed on three kinds of the product of the present invention and the comparative example, carbon paper cut into the same size was placed in such a manner that the fired product was vertically sandwiched, and each of them was placed in 5 stages at an interval of 3 cm from the furnace bottom. It was racked and heated at 100 ° C./Hr, and the decomposition behavior of the carbon paper above and below the object to be fired was examined.

As a result, when the shelf board of Example 1 is used,
The carbon paper above and below the object to be fired was decomposed and removed at 400 ° C. When the shelf of Comparative Example was used, the carbon paper on the upper surface of the object to be fired was decomposed and removed, but the lower surface was not decomposed and removed over the entire surface of Comparative Example 1, and the end surface of the paper was slightly oxidized and decomposed. It was Even at 1200 ° C, about 25% of the surface area remained. It is considered that this is because the heat insulating property was high and the adhesiveness with the surface of the lightweight quality shelf plate was high, so that oxygen was not sufficiently supplied and decomposed and removed. In the through-hole type of Comparative Example 2, the through-hole portion was almost decomposed and removed, but the portion other than the hole was not decomposed and removed. Almost all of it was decomposed and removed at 1000 ° C. Comparative Example 3 is not easily decomposed and removed at 900 ° C.
It was decomposed and removed on almost the entire surface. As can be seen from the above results, by using the firing jig of the present invention, the surrounding gas (temperature, gas (air in this case)) can sufficiently reach the object to be fired. It can be seen that the fired product can be fired uniformly.

[0034]

EFFECTS OF THE INVENTION Since the ceramic shelf board for firing of the present invention is constructed as described above, it is very useful as a shelf board for firing, which is light in weight and capable of uniformly firing an object to be fired.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a ceramic unit constituting a shelf board of the present invention.

FIG. 2 is a diagram showing a ceramic unit obtained in the first embodiment.

FIG. 3 is a diagram showing a method for measuring a pore diameter.

FIG. 4A is a side view of an apparatus for measuring the bending strength of a shelf board according to the present invention, and FIG. 4B is a plan view thereof.

[Explanation of symbols]

 1 sample 2 fulcrum stand 3 load fulcrum stand

Claims (1)

[Claims] 1. A plate-shaped body formed by connecting columnar or prismatic ceramic units each having an opening in a surface and having the openings communicating with each other, wherein the area ratio of the holes in the vertical direction of each unit is 30% to 80%, area ratio of side holes 5% to
50%, a hole diameter of 0.5 to 4 mm, a plate-shaped body weight of 7,000 g / m ² or less, and a thickness of 8 mm or less.