JP2000241082A - Tool material for firing ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a matter being fired against uneven firing, contamination, deformation and the like, by arranging, on the side face of the body of a sintering tool material having a required shape, with a heat insulating material having thermal conductivity lower than that of the body, thereby suppressing temperature difference occurring in the tool material and averaging the inner temperature distribution. SOLUTION: A sintering tool 1, e.g. a refractory pot or a shelf plate, being employed for firing a ceramic ware or ceramics for electronic part has the body 2 of a firing tool material in the shape of rectangular plate and a heat insulating material 3 having thermal conductivity lower than that of the compositional material of the body 2 is arranged on the four side faces of the body 2. Thermal conductivity of the heat insulating material 3 is preferably equal to or lower than 80% that of the body 2. Assuming the thermal conductivity of the body 2 is 100%, thermal conductivity of the heat insulating material 3 is preferably set at 0.2% or above, more specifically at 0.1% or above, and the arranging width L of the heat insulating material 3 is set at 0.1 mm or above. According to the arrangement, cracking or uneven firing can be prevented at quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to ceramics, tiles,
Alternatively, ceramic firing for use as a firing tool for thin plates, mortars, pods, shelves, setters, base plates, baking tables, etc. used when firing ceramics such as ferrite, ceramic capacitors and other electronic equipment materials Tool materials.

[0002]

2. Description of the Related Art In firing ceramics for ceramics and electronic parts, firing tools such as fireproof mortars and shelves are used.

[0003] As a tool material of this kind of firing tool, various materials are used depending on firing conditions and usage conditions, including a product to be fired, and generally, silicon carbide or silicon nitride is used. , Alumina-based, mullite-based, spinel-based, and zirconia-based materials are used.

[0004] These materials are selected in consideration of enhancing heat-resistant spalling properties and reducing reactivity with products. By the way, the material of the firing tool material that suppresses the reactivity with the product can be easily selected if the chemical composition of the product is determined, but the enhancement of the heat-resistant spalling property largely depends on the firing conditions and usage conditions. Therefore, it cannot be easily obtained only by selecting the material of the firing tool material.

From the above, various countermeasures have conventionally been taken. That is, a slit plate is provided on a refractory shelf board or an accessory tile grill (Japanese Patent Laid-Open No. 5-340678).
And Japanese Unexamined Patent Publication Nos. Hei 6-10798 and No. 6-10798), those having a recess or through hole in the required surface (Japanese Unexamined Patent Publication Nos. 9-89469 and 6-10798), and an empty space in the firing tool material. With holes (Japanese Patent Application Laid-Open No. 62-65988,
JP-A-8-38717 and JP-B-8-20186), and zirconia coated on a required surface (Japanese Patent Publication No.
JP-A-13710, JP-A-9-286678), and those in which dimensions such as the thickness of the firing tool material are specified (JP-B-7-76676, JP-A-6-11272) and the like. .

[0006]

However, even if the technology described in any of the above publications is intended to enhance the heat-resistant spalling property of the firing tool material, none of them can exhibit a sufficient effect. Not in.

[0007] That is, in the configuration in which the slit is provided in the firing tool member, unevenness is generated in the object to be fired placed above the slit portion.

When the object to be fired is placed so as to avoid the slit portion, the number of objects to be fired is reduced, and the production efficiency and the firing capacity are reduced.

The presence of the slit lowers the strength of the firing tool material, and may cause cracking when the object to be fired is placed.

Although the effect of the slit is easily obtained at the time of temperature rise, it is not effective at the time of cooling.

There is a problem that:

[0012] Next, in the configuration in which a dent or through hole is provided on a required surface of the firing tool material, the material to be fired has a very low strength because the raw material does not sinter until the temperature reaches a predetermined high temperature. In such a state, when the object to be fired is placed on the depression or the through hole at such a low strength, the object to be fired has irregularities, and in some cases, breaks.

[0013] As in the case of the slits, unevenness occurs in the through holes.

Although effective when the temperature is raised, it is not effective when cooled.

There is a problem that:

[0016] Next, in the case of having a hole in the firing tool material, the hole itself tends to be a source of cracks. Generally, spherical pores having a suitable size are considered to have a crack suppressing effect, but even if the pore forming material is spherical, the blended raw materials used are irregular in various forms. Because of the shape, many sharp micro-cracks are present around the hole after the hole-forming material is removed.
Stress tends to concentrate on such a small crack, and as a result, it tends to be a source of a large crack.

Next, in the configuration in which the required surface of the firing tool material is coated with zirconia, when a material different from the firing tool material as the base material is used for the coating material, The shape retention is reduced, and the raw material grains of the coating material fall off during repeated use, and eventually, the function as the coating material is not achieved.

There is a problem.

Finally, when the dimensions and thickness of the firing tool material are specified, the firing tool material has a shape having irregularities in the thickness direction (Japanese Patent Publication 7-7-7).
In the case of producing a molded article having irregularities in advance in the production of the article (No. 6676), unevenness in the sealing tends to occur during molding, which causes cracks during use and produces a uniform molded article without irregularities. After that, when forming the irregularities by processing, the processing cost increases, and it becomes impossible to provide a firing tool material at low cost.

Although effective at the time of temperature rise, it has no effect at the time of cooling.

There are the following problems.

[0022] As described above, a sufficient effect cannot be obtained by any of the conventional techniques, and especially, a large temperature firing tool capable of mounting a large amount of objects to be fired at a time by increasing productivity by rapid temperature rise and temperature decrease. Further heat-resistant spalling properties are needed for low-cost operation due to the improvement of the production amount due to the use of materials and the maintenance of durability that can withstand repeated use. In this regard, the conventional measures for improving the heat-resistant spalling property mainly focus on measures for preventing thermal shock at the time of temperature rise.
They are almost ineffective at the time of cooling,
Therefore, slow cooling was required, resulting in low productivity.

Accordingly, the present invention is applicable not only at the time of temperature rise but also at the time of rapid temperature fall, thereby improving the productivity, and does not cause unevenness, dirt, deformation or the like of the product to be fired, thereby improving the yield. It is another object of the present invention to obtain a large-sized firing tool material that maintains the strength and improve the production amount.

In order to solve the above-mentioned problems, first, the cause of the cracks in the currently used firing tool material was examined by thermal stress calculation using the finite element method.

As a result, it was found that a large temperature gradient and a complicated temperature distribution generated inside the firing tool material caused large thermal stress. That is, since heating or cooling at the time of raising and lowering the temperature is performed from the outer surface of the firing tool material, the rate of temperature rise and fall at the corners of the firing tool material is the fastest and the speed at the center is the slowest. At this time, a large temperature difference and a complicated temperature distribution occur in the firing tool material. In particular, when the temperature is rapidly raised and lowered, a still larger temperature difference is generated, and the temperature distribution tends to be complicated, so that a large thermal stress is easily generated.

As an example, FIG. 3 shows the result of the thermal stress value generated during rapid temperature rise and fall. In the figure, the arrow indicates the direction of the stress, and cracks occur in a direction perpendicular to the direction of the stress.

As shown in the figure, a large stress (2.07 MPa) is generated at the center of each side of the flat surface of the firing tool material a, and the firing tool material a has a tensile strength of 1.6 to 1. .9MP
Since it is a, it was found that the above thermal stress value far exceeded the tensile strength of the firing tool material a.

Therefore, the slit b, one of the prior arts,
FIG. 4 shows the results of an examination of the case where b... were applied to the center of each side of the firing tool material a. According to this study,
Although no large stress is generated at the opening ends c of the slits b, b..., The opening ends c of the slits b, b. A large stress is generated in the central portion between them. The value is about 5% reduction when no slit is provided.
It was found that the tensile strength was higher than the tensile strength. That is, it is proof that the slits b, b... Do not give a sufficient effect. Therefore, although the slits b, b... Have an effect at the time of temperature rise, they have no effect at the time of temperature decrease as described above.

[0029]

Means for Solving the Problems As a means for solving the above-mentioned problems of the prior art and for solving the above-mentioned problems, the present invention provides a heating tool body having a required shape on a side face of the body. In other words, a heat insulating material having a thermal conductivity lower than the conductivity is provided.

The heat insulating material preferably has a thermal conductivity of 80% or less of the thermal conductivity of the firing tool body. Further, the arrangement width of the heat insulating material is preferably 0.1 mm or more.

With the above configuration, it was found that the temperature difference generated inside the firing tool material was small and the temperature distribution showed a monotonous change from the flat plate surface in the thickness direction. Therefore, the generated stress was very small, and it was found that crack generation could be sufficiently suppressed. Incidentally, the thermal stress generated at the time of rapid temperature decrease was 60% lower than that shown in FIG. 3, and was less than half the tensile strength of the firing tool material.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of a firing tool 1 according to the present invention, in which a heat insulating material having a lower thermal conductivity than the constituent material of the main body 2 is provided on the four circumferential side surfaces of a firing tool body 2 having a square plate shape. The conductive material 3 is provided. Note that the firing tool material body 2
May be the same as a conventional firing tool material.

The thermal conductivity of the heat insulating material 3 is preferably not more than 80% of the thermal conductivity of the firing tool body 2. If it exceeds 80%, the inflow of heat from the side surface of the firing tool main body 2 cannot be ignored, so that the temperature gradient in the firing tool material is increased and a complicated temperature distribution is generated. As a result, the firing tool main body 2 There is a possibility that a thermal stress exceeding the tensile strength of No. 2 is generated, and a sufficient effect cannot be obtained.

In general, the heat insulating material has a low strength because the porosity is increased and the thermal conductivity is reduced if the raw material of the aggregate is the same. Therefore, considering the material properties that can secure the necessary strength at the time of transportation, preferably, the thermal conductivity of the heat insulating material 3 is 0.1% when the thermal conductivity of the firing tool body 2 is 100%.
It is desirable that the content be 2% or more, more preferably 0.1% or more.

On the other hand, the arrangement width L of the heat insulating material 3 is 0.1 m.
More than m is effective. If it is less than 0.1 mm, the inflow of heat from the side cannot be ignored, the temperature gradient in the firing tool becomes large, and a complicated temperature distribution occurs,
As a result, thermal stress exceeding the tensile strength of the firing tool main body 2 is generated, and a sufficient effect cannot be obtained.

The arrangement width L of the heat insulating material 3 is 0.1 mm.
The upper limit is not limited as long as it is above, but the strength of the heat insulating material 3 is low as described above, so that the material is easily peeled and hardly conveyed, or the heat insulating material 3 which can be secured with respect to the volume of the firing furnace used. Preferably, the arrangement width L is 20 mm or less, more preferably 5 m
m or less, and can be excellent in durability.

The material of the heat-insulating material 3 may be the same as the material constituting the firing tool main body 2 as long as it satisfies the above-mentioned heat conduction characteristics and the arrangement width L.
Alternatively, another material may be used. Further, a combination of the two may be used. In the case of using the same material as the firing tool main body 2, the microstructure of the material may be controlled in order to change the heat conduction characteristics. For example, it is realized by setting the porosity higher than the configuration of the firing tool main body 2. Can be achieved.

Other constituent materials of the heat insulating material 3 include, for example, alumina, zirconia, magnesia,
It is possible to use ceramic fiber blanket such as spinel, rock wool, diatomaceous earth, kibushi clay, frog eye clay, kaolin, pyroxene, kyanite, bauxite, etc. it can.

The means for disposing the heat-insulating material 3 includes means for previously disposing the heat-insulating material 3 at a predetermined width around the firing tool main body 2 when forming the firing tool main body 2, and integrally forming the same. Or, mortar,
Means to be disposed via an adhesive such as an organic binder, an inorganic binder, pitch, tar, or the like, or a means for mechanically pressing without using an adhesive, and further, only a heat-insulating material previously formed in a predetermined width and shape. Is preliminarily heated and expanded, and a firing tool material body 2 at room temperature is fitted and adhered thereto, and then the heat insulating material is cooled to room temperature to press-fit.

In addition, means for coating the side surface of the sintering tool main body 2 by pouring or spraying a slurry, and then heating for removing or baking volatile components, and spraying the heat insulating material 3 with the sintering tool material by thermal spraying There are means for fixing to the side surface of the main body 2 and the like. Further, a means having a so-called blur structure in which mutual materials are mixed and joined at a boundary surface between the firing tool main body 2 and the heat insulating material 3 can be used.

In the above-mentioned means, when an adhesive is interposed, the volatile components generated from the adhesive after bonding can be used by heating and removing them in advance.

The shape of the firing tool 1 may be any shape such as an elliptical plate, a circular plate, a polygonal plate, a mortar, a base plate, etc., in addition to the square plate shape shown in FIG. In any case, the heat-insulating material 3 is provided on the side surface of the firing tool material main body 2. (Example)

[0044]

[Table 1] Table 1 shows specific embodiments of the present invention.

In Table 1, the numbers in parentheses indicate the shape of the firing tool body 2, and are as follows: (1).
(2) ... oval plate, (3) ... disk, (4) ... polygonal plate,
(5) ... bowl shape, (6) ... base plate. The index “1” indicates the ratio of the thermal conductivity value of the heat insulating material 3 when the thermal conductivity value of the firing tool body 2 used is “1”. In the index “2”, the maximum thermal stress value generated in the firing tool body 2 when the thermal stress calculation by the finite element method is performed is divided by the tensile strength of the firing tool body 2 using the maximum thermal stress value. When the value is “1”, it means that the maximum thermal stress value is equal to the tensile strength. When the value exceeds “1”, a crack is generated. When the value is less than “1”, a crack is generated. Means no occurrence. The index “3” indicates an index when the number of times of use when used in an actual machine is based on the number of times of use of the comparative product “1”.

In Table 1, the numbers in the circles indicate the manner of disposing the heat insulating material 3. The heat insulating material 3 is formed with a predetermined width in advance around the firing tool main body 2 when the firing tool main body 2 is formed. By disposing them and molding them together. Is a mortar having a predetermined thickness on the side surface of the formed firing tool material body 2;
A method in which a heat insulating material is provided via an adhesive such as an organic binder, an inorganic binder, pitch, and tar, and a volatile component generated from the adhesive after bonding is removed by heating in advance. Is based on a method in which a heat insulating material is mechanically pressed without using an adhesive. Is to heat-expand only a heat-insulating material formed in a predetermined width and in a predetermined shape in advance, fit the firing tool main body 2 at room temperature into the inside thereof, and bring the heat-insulating material down to room temperature. Tool body 2 for firing
By crimping to the side of Is a tool material body 2 for firing a heat insulating material by pouring or spraying a slurry.
By coating on the side surface and then heating to remove or bake volatile components. Means that a heat insulating material is disposed on the side surface of the firing tool body 2 by thermal spraying.

As can be seen from Table 1 above, no matter what the shape of the firing tool material body 2 according to the present invention is (1) to (6), the shape as shown in FIG. Thermal stress does not concentrate on a specific location, and comparative products 1 to 6
And the number of times of use was prolonged by 2 to 6 times.

[0047]

As described above, according to the present invention, a heat-insulating material having a thermal conductivity lower than that of the main body of the firing tool is provided on the side surface of the main body of the firing tool. The temperature difference generated inside the tool material can be reduced, and the internal temperature distribution is averaged, so that even if the temperature is raised and lowered quickly, the generated stress value is extremely small, and the occurrence of cracks and cracks is suppressed. In addition, the durability of the firing tool material can be significantly improved.

In particular, since the object to be fired is not adversely affected by unevenness in burning, dirt, deformation due to voids in the crack surface generated in the firing tool material, and drop damage during transportation, the product yield is improved. It can be performed regardless of the size and shape of the firing tool material, so that it is possible to increase the production amount of the product and to control the production amount optimally.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing a maximum thermal stress value generated when the temperature of the firing tool material shown in FIG. 1 is rapidly lowered, a generation position thereof, and a direction thereof.

FIG. 3 is an explanatory diagram showing a maximum thermal stress value generated when a conventional flat plate-shaped firing tool material is rapidly cooled down, and a generation position and a direction thereof.

FIG. 4 is an explanatory diagram showing a maximum thermal stress value, a generation position thereof, and a direction thereof when a slit orthogonal to the side is provided at the center of each side of the firing tool material of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Firing tool material 2 Firing tool material body 3 Insulating material

Claims (3)

[Claims] 1. A tool for firing ceramics, wherein a heat-insulating material having a thermal conductivity lower than the thermal conductivity of the body is disposed on a side surface of a firing tool body having a required shape. 2. The ceramic firing tool according to claim 1, wherein the thermal conductivity of the heat insulating material is 80% or less of the thermal conductivity of the firing tool main body. 3. The ceramic firing tool according to claim 1, wherein the width of the heat insulating material is 0.1 mm or more.