JP2019011238A - Tool material for firing - Google Patents

Abstract

To provide a tool material for firing achieving weight saving and low heat capacity, and moderate surface roughness.SOLUTION: A tool material for firing 1 is a tool material for firing which mounts an article to be fired thereon and is accommodated in a firing furnace together with the article to be fired, the tool material for firing is composed of a silicon carbide body, and at least the thickness of a part 3 for mounting the article to be fired thereon is 0.2 mm or more and 1 mm or less and the porosity is 15% or more and 60% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a firing tool material, and relates to a firing tool material used for firing and heat treatment of ceramic electronic components and the like.

  For example, silicon carbide-based sintered bodies are used for firing tool materials used for firing and heat treatment of ceramic electronic parts such as setters, sheaths, and mortars. These firing tool materials are required to be thinner from the standpoint of improving the furnace packing efficiency and reducing the firing cost, and the silicon carbide high-temperature structural materials and thin plate-like silicon carbide sintered bodies disclosed in Patent Documents 1 and 2 are used. Proposed.

Specifically, in Patent Document 1, it is composed of a plate-like silicon carbide sintered body having a thickness of 0.5 to 3 mm and a relative density of 90% or more having an area of 100 cm ² or more, and is molded by a doctor blade method. Proposed silicon carbide-based high-temperature structural material that is formed by laminating and firing green sheets, and has an unprocessed surface roughness (Ra) of 1.0 μm or less and warpage (C) of 0.1% or less after firing. Has been.
Further, in Patent Document 1, green sheets formed by a doctor blade method from a slurry made of silicon carbide powder are laminated, and a predetermined portion of the surface of the laminated green sheets is roughened to a surface roughness (Ra) of 5 μm or more. A method of manufacturing a silicon carbide-based high-temperature structural material is proposed in which a coating layer containing zirconia is formed on the roughened surface portion by thermal spraying.

  Further, in Patent Document 2, a green sheet is prepared by a doctor blade method from a slurry in which a sintering aid, a dispersant, an organic binder, a plasticizer, and an organic solvent are mixed with silicon carbide fine powder having an average particle size of 1 μm or less, In the manufacturing process of degreasing and firing this, 10 to 20 parts by weight of an organic binder and 8 to 15 parts by weight of a plasticizer are added to 100 parts by weight of silicon carbide powder, and the relative density is 90% or more. A method for producing a thin plate-like silicon carbide sintered body has been proposed.

JP 2002-316874 A JP 10-297971 A

By the way, for firing ceramic electronic components, for example, a continuous furnace represented by roller hearth kiln is used, and the firing rate (temperature increase rate, temperature decrease rate) is increasing year by year.
However, when the heat capacity of a baking tool material such as a setter on which the object to be fired is loaded is large, it becomes difficult for the temperature of the baking tool material to follow the rise and fall of the furnace temperature, and the intended heat curve (firing) There was a technical problem that firing with speed characteristics was not possible.

  In order to quickly follow the temperature of the firing tool material to the furnace temperature and perform firing at the intended heat curve (firing rate characteristics), the silicon carbide firing described in Patent Documents 1 and 2 above is performed. It was necessary to achieve a thinner, lighter, and lower heat capacity than the bonded body.

Further, a hardly reactive zirconia layer for preventing adhesion of the firing tool material and the material to be fired is required on the surface of the firing tool material to be fired. Patent Document 1 discloses that the surface is roughened in order to improve adhesion, and a coating layer containing zirconia is formed on the roughened surface portion by thermal spraying.
In the formation of the coating layer containing zirconia shown in Patent Document 1, roughening is indispensable, and there is a problem that production costs increase.

The inventors of the present application have conducted intensive research under such circumstances, and have made the carbonization low density by making the thickness thinner than the conventional thickness, 0.2 mm to 1 mm, and the porosity of 15% to 60%. The inventors came up with a firing tool material using a silicon-based sintered body and completed the present invention.
Moreover, by setting the porosity to 15% to 60%, the surface roughness of the silicon carbide sintered body of the firing tool material can be set to an appropriate surface roughness, and this surface is coated by plasma spraying. As a result, it was found that a film having good adhesion could be obtained, and the present invention was completed.

  The present invention has been made under the above circumstances, and an object of the present invention is to provide a baking tool material that realizes light weight and low heat capacity, and realizes an appropriate surface roughness.

The firing tool material according to the present invention made to achieve the above object is a firing tool material on which a material to be fired is placed and accommodated in a firing furnace together with the material to be fired. The tool material is made of a silicon carbide sintered body, and is characterized in that the thickness of at least the portion on which the object is placed is 0.2 mm or more and 1 mm or less and the porosity is 15% or more and 60% or less. .
As described above, the firing tool material having a thickness of at least 0.2 mm to 1 mm and a porosity of 15% to 60% at least on the part on which the object to be fired is placed should be reduced in weight and heat capacity. Thus, the temperature of the firing tool material can be made to quickly follow the furnace temperature, and firing can be performed with the intended heat curve (firing rate characteristics).

Here, it is desirable to have an SiO ₂ layer on at least the surface of the silicon carbide sintered body where the object to be fired is placed.
The silicon carbide sintered body (SiC) undergoes oxidation in a high temperature region (approximately 700 ° C. or higher) where oxygen is present. This oxidation changes the oxygen concentration in the firing furnace. In particular, there arises a problem that the oxygen concentration in the vicinity including the portion where the object to be fired is placed changes.
As described above, by forming the SiO ₂ layer on at least the surface of the silicon carbide sintered body where the object to be fired is placed, the oxidation of the silicon carbide sintered body (SiC) can be suppressed, The oxygen concentration can be controlled.

Moreover, it is desirable that the rate of increase in the oxidized weight is 5% or more and 10% or less with respect to the silicon carbide sintered body.
As described above, by forming the SiO ₂ layer on the surface of the silicon carbide sintered body within the range where the increase rate of the oxidized weight is 5% or more and 10% or less, sufficient strength as a firing tool material can be obtained. In addition, it is possible to obtain a firing tool material that does not peel even when a sprayed film is formed on the surface.

Moreover, when the oxidation weight increase rate is 5% or more and 10% or less with respect to the silicon carbide sintered body, a tool material for firing having a bending strength of 100 MPa or more and 200 MPa or less can be obtained.
When the bending strength is less than 100 MPa, the durability is inferior and breakage such as cracks may occur during traveling.

Moreover, it is desirable to further have at least one plasma sprayed film of mullite, alumina, or zirconia on the surface of the SiO ₂ layer.
As described above, since the porosity is 15% to 60%, the surface roughness of the surface can be set to an appropriate surface roughness, and when the surface is coated with plasma spraying, a plasma sprayed film having good adhesion is formed. can do.

  According to the present invention, it is possible to obtain a baking tool material that realizes a light weight and a low heat capacity, and also realizes an appropriate surface roughness.

FIG. 1 is a diagram showing an embodiment according to the present invention, in which (a) is a plan view and (b) is a side view. FIG. 2 is a diagram showing a surface state of the embodiment according to the present invention.

An embodiment of a baking tool material according to the present invention will be described. In this embodiment, a setter will be described as an example of a baking tool material.
As shown in FIG. 1, the setter 1 includes an upper surface 2 and a lower surface 3.
And to-be-fired materials, such as a ceramic electronic component, are mounted in the upper surface 2 of this setter 1, for example, a to-be-fired material is baked by the continuous furnace (baking furnace) represented by the roller hearth kiln.

This setter 1 is comprised with the silicon carbide sintered compact.
And the thickness t of the part which mounts a to-be-fired material in the upper surface 2 is 0.2 mm or more and 1 mm or less, and the porosity is 15% or more and 60% or less. The portion on which the object to be fired is placed means a part of the upper surface 2 including the region on which the object to be fired is placed, but is not limited to a part of the upper surface 2, and the thickness of the entire bottom plate portion. The thickness may be 0.2 mm to 1 mm, and the porosity may be 15% to 60%.

Here, the reason why the thickness t is set to 0.2 mm or more and 1 mm or less is to reduce the weight and the heat capacity of the setter 1 (baking tool material).
Thus, a reduction in the heat capacity of the setter 1 is desired because if the heat capacity of the setter 1 is large, the amount of heat required for heating the setter 1 is larger than the amount of heat required for heating the object to be fired, and the required baking is required. This is because the speed cannot be obtained (the speed cannot be increased).
The heat capacity of setter 1 (baking tool material) is calculated by the specific heat [J / (K · g)] of the setter (baking tool material) x setter (baking tool material) weight [g], reducing the heat capacity. To do this, the setter (baking tool material) weight must be reduced. On the other hand, if the thickness is less than 0.2 mm, handling is difficult and there is a risk of breakage.
Therefore, the thickness is preferably 0.2 mm or more and 1 mm or less.

  The reason why the porosity is 15% or more and 60% or less is to reduce the weight, lower heat capacity, and mass productivity of the setter 1 (baking tool material). Moreover, it is for the improvement of the adhesiveness of the zirconia layer formed in the setter 1 (tool material for baking). When a zirconia layer is provided on the surface of the setter 1 (baking tool material), it is preferably formed on the upper and lower surfaces of the setter.

Since the setter 1 is used in a large amount, it is preferable to produce it by press molding with high mass productivity and sheet molding such as a doctor blade. However, it is difficult to produce a setter having a porosity of 60% or more by these production methods. In addition, the method of firing the slurry and casting can increase the porosity, but the manufacturing cost becomes high. In addition, when the thickness is 0.2 mm or more and 1 mm or less, when the porosity exceeds 60%, the mechanical strength is weakened, the yield decreases during production, and cracks occur frequently during use. There are disadvantages.
Therefore, the porosity is preferably 60% or less.

On the other hand, if the porosity is less than 15%, the weight of the setter (baking tool material) is large and the heat capacity is large. For this reason, the ratio of the amount of heat required for heating the setter is increased, and the required firing rate cannot be obtained (the speed cannot be increased).
Moreover, when the porosity is less than 15%, the surface roughness is small, and the zirconia layer formed on the setter may be peeled off.
Therefore, the porosity is preferably 15% or less.

The state of the pores V of the setter 1 is shown in FIG. FIG. 2 shows a structure in which the surface of the setter 1 (silicon carbide sintered body) (the state in which the SiO ₂ layer is formed (the state in which the plasma sprayed film is not formed)) is enlarged 1000 times using an electron microscope. FIG.
The setter 1 is formed of pores V and particles P. The particles P preferably have an average particle diameter of 5 to 25 μm and are connected to each other. The air holes V are continuous air holes and have air permeability.

Further, the surface of the silicon carbide sintered body of the portion for mounting at least the baked product, SiO ₂ layer is formed.
As shown in the following chemical formula, this SiO ₂ layer is formed by heating at 800 ° C. to 1600 ° C. in a mixed gas atmosphere containing air, oxygen, and oxygen to oxidize the SiC surface to form the SiO ₂ layer. (Oxidation treatment).
SiC + 3 / 2O ₂ → SiO ₂ + CO

Thus, by forming the SiO ₂ layer on the surface of the setter 1 (silicon carbide sintered body), the oxidation of the silicon carbide sintered body (SiC) can be suppressed, and the oxygen concentration change in the firing furnace can be suppressed. .
The portion on which the object to be fired is placed means a part of the upper surface 2 including the region on which the object to be fired is placed, but is not limited to a part of the upper surface 2 and is formed on the entire upper surface. You may do it. In particular, it is more preferable to form a SiO ₂ layer on the entire setter 1.

At least one or more of mullite, alumina, zirconia or a plasma sprayed film is formed by a plasma spraying method or the like on the SiO ₂ layer on the surface of the silicon carbide sintered body at least on the part on which the object to be fired is placed. Is preferred.
It is necessary to provide a layer of zirconia, alumina or the like on the surface of a firing tool material for ceramic electronic parts (for example, dielectric BaTiO ₂ or the like) that cannot be fired by being directly loaded on SiC (SiO ₂ ).

The plasma sprayed film may be one of mullite, alumina, or zirconia, or may be a plurality of sprayed films selected from mullite, alumina, and zirconia.
In particular, since the zirconia film has a larger thermal expansion than SiC, when a mullite film having an intermediate thermal expansion and an alumina film are formed in order between the two layers, each sprayed film is difficult to peel off and has excellent peeling resistance. Have sex.

The thickness of the plasma sprayed film is preferably as thin as possible because the influence of thermal expansion is smaller as the thickness is thinner, and is preferably about 20 μm to 160 μm.
The plasma sprayed film can be formed by a known method such as plasma spraying, slurry coating and baking, cold spraying, aerosol deposition, or the like.

  Next, a method for manufacturing the setter will be described.

  First, for the molding of the setter, sheet molding by a doctor blade method or sheet molding by a press molding method is preferable. Then, the green sheet obtained by the doctor blade method and the compact obtained by the press method are degreased (400 ° C. to 800 ° C.) and fired (2100 ° C. or higher) in a non-oxidizing atmosphere to obtain a sintered body.

  To give a specific example, a green sheet is produced by a doctor blade method from a slurry in which a silicon carbide raw material and an organic solvent, a dispersant, a binder and a plasticizer are mixed.

The silicon carbide raw material is not particularly limited, and commercially available products can be used.
As the solvent, for example, propanol, benzene, toluene, hexane, water and the like can be used.

  As the binder, PVB (polyvinyl butyral), methyl cellulose, PVA (polyvinyl alcohol), acrylic, or the like can be used. As the plasticizer, DBP (dibutyl phthalate), DEHP (bis (2-ethylhexyl) phthalate), BBP (butyl benzyl phthalate), or the like can be used.

After the firing, a SiO ₂ layer is formed.
The SiO ₂ layer is formed by heating at 800 ° C. to 1600 ° C. in a mixed gas atmosphere containing air, oxygen, and oxygen to oxidize the SiC surface.

Furthermore, after firing the SiO ₂ layer, when firing electronic components such as ceramic capacitors, thermistors, ferrite cores, LTCC, zirconia that has the least reaction with the electronic components is selected so that the setter does not react with these electronic components. Covering the contact points with the electronic component is performed. The film thickness of the zirconia film is about 10 μm to 200 μm.

Moreover, since the zirconia film has a larger thermal expansion than SiC, it is preferable to sequentially form a mullite film having an intermediate thermal expansion and an alumina film between the two layers, and has excellent peeling resistance.
The film thickness of the mullite film at this time is about 10 μm to 200 μm. The film thickness of the alumina film is about 10 μm to 200 μm.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limitedly interpreted by the following Example. In the following examples and comparative examples, a thin flat setter was used.

(Experiment 1)
As shown in Examples 1 to 6 and Comparative Examples 1 and 2 below, the porosity of the porous silicon carbide sintered body was changed, and the state of peeling of the film was verified.
Example 1
A silicon carbide raw material having an average particle diameter of 4.5 μm was mixed with ethanol as a solvent, polyvinyl butyral (PVB) as a binder, and dibutyl phthalate (DBP) as a plasticizer by a ball mill to prepare a slurry.
Using this slurry, a green sheet was prepared by adjusting the slurry thickness so that the sheet thickness was 0.5 mm by a doctor blade method.
The green sheet was sintered (recrystallized) at 2300 ° C. in an argon atmosphere to obtain a porous thin plate-like silicon carbide sintered body having a length of 150 mm, a width of 150 mm, and a thickness of 0.5 mm.

This silicon carbide sintered body was heated in the atmosphere at 1400 ° C. to form a SiO ₂ layer on the SiC surface.
This silicon carbide sintered body had a weight of 23 g and an apparent porosity of 39%. This apparent porosity was measured based on JIS R 2205.
Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Example 2)
A green sheet having a thickness of 0.25 mm was produced in the same manner as in Example 1, and the same firing, oxidation treatment and thermal spraying as in Example 1 were performed to produce a setter. The silicon carbide sintered body before spraying had a weight of 11 g and an apparent porosity of 39%.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Example 3)
Methyl cellulose and water were added as an organic binder to a silicon carbide raw material having an average particle size of 5.3 μm to produce granulated powder for press molding. The granulated powder was molded by a uniaxial press at a molding pressure of 100 MPa to obtain a SiC molded body having a length of 150 mm, a width of 150 mm, and a thickness of 0.8 mm. Thereafter, firing, oxidation treatment, and thermal spraying were performed in the same manner as in Example 1 to produce a setter.
The weight of the silicon carbide sintered body before spraying was 43 g, and the apparent porosity was 21%.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Example 4)
Using a silicon carbide raw material having an average particle size of 2.0 μm, a silicon carbide sintered body having different apparent porosity and thickness was obtained. Specifically, a green sheet having a thickness of 0.4 mm was produced in the same manner as in Example 1 except that a silicon carbide raw material having an average particle diameter of 2.0 μm was used, and the same firing and oxidation as in Example 1 were performed. Treatment and thermal spraying were performed to prepare a setter. The silicon carbide sintered body before spraying had a weight of 11 g and an apparent porosity of 60%.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Example 5)
Using a silicon carbide raw material having an average particle size of 5.0 μm, a silicon carbide sintered body having different apparent porosity and thickness was obtained. Specifically, a green sheet having a thickness of 0.2 mm was produced in the same manner as in Example 1 except that a silicon carbide raw material having an average particle diameter of 5.0 μm was used. Treatment and thermal spraying were performed to prepare a setter. The silicon carbide sintered body before spraying had a weight of 12 g and an apparent porosity of 15%.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Example 6)
Using a silicon carbide raw material having an average particle size of 4.0 μm, a silicon carbide sintered body having different apparent porosity and thickness was obtained. Specifically, a green sheet having a thickness of 1 mm was produced in the same manner as in Example 3 except that a silicon carbide raw material having an average particle size of 4.0 μm was used, and the same firing and oxidation treatment as in Example 3 were performed. Thermal spraying was performed to prepare a setter. The weight of the silicon carbide sintered body before spraying was 38 g, and the apparent porosity was 45%.
As a result, as shown in Table 1, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film.

(Comparative Example 1)
Add boron and carbon as sintering aids to silicon carbide raw material of average particle size submicron order, ethanol as organic solvent, maleic polyanion as dispersant, polyvinyl butyral (PVB) as binder, dibutyl phthalate as plasticizer ( DBP) was mixed with a ball mill to prepare a slurry.
Using this slurry, a green sheet having a sheet thickness of 1 mm was prepared by a doctor blade method.
Four layers of this green sheet were stacked and pressure-bonded, and the resulting sheet was heated at 2150 ° C. in an argon atmosphere to obtain a porous thin plate-like silicon carbide sintered body. The weight of the thin plate-like silicon carbide sintered body was 70 g, and the porosity was 0%. Plasma spraying was performed on this silicon carbide sintered body, but peeling occurred and a sprayed layer could not be formed. The results are shown in Table 1.

(Comparative Example 2)
Boron and carbon were added as a sintering aid to silicon carbide raw material with an average particle size of submicron order, and methyl cellulose and water were added as organic binders to produce granulated powder for press molding.
The granulated powder was molded by a uniaxial press at a molding pressure of 100 MPa to obtain a SiC molded body having a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.
This molded body was fired in the same manner as in Comparative Example 1 to obtain a porous thin plate-like silicon carbide sintered body. This silicon carbide sintered body had a weight of 140 g and a porosity of 0%. Plasma spraying was performed on this silicon carbide sintered body, but peeling of the coating occurred and a sprayed layer could not be formed. The results are shown in Table 1.

  As can be seen from Examples 1 to 6, the setter weight (before thermal spraying) thinly molded with a porous silicon carbide sintered body (porosity 15% to 60%) was 11 g to 43 g, which is the denseness of Comparative Examples 1 and 2. Compared to 70 g to 140 g of the sintered silicon carbide (porosity 0%), the weight is reduced to half or less, and the heat capacity proportional to the weight is also reduced.

Moreover, in the said Examples 1-6, even if it let the continuous furnace (roller hearth kiln) pass at high speed, there were no malfunctions, such as a crack, and peeling of the film did not arise.
On the other hand, in the dense silicon carbide sintered bodies of Comparative Examples 1 and 2, since the surface was smooth, film formation by plasma spraying was peeled off, which was not preferable. In order to prevent this peeling, it is necessary to roughen the surface.
That is, in the firing tool material according to the present invention, the sprayed film bites into the pores on the surface, the anchor effect works, and good adhesion is obtained.

(Experiment 2)
As shown in Examples 7 to 9 and Comparative Examples 3 and 4 below, the rate of increase in the oxidized weight of the porous silicon carbide sintered body was changed, and the state of peeling of the film and the state of the tool material for firing were verified.
(Example 7)
As in Example 1, a silicon carbide raw material having an average particle size of 4.5 μm was mixed with ethanol as a solvent, polyvinyl butyral (PVB) as a binder, and dibutyl phthalate (DBP) as a plasticizer in a ball mill to prepare a slurry. .
Using this slurry, a green sheet was prepared by adjusting the slurry thickness so that the sheet thickness was 0.25 mm by the doctor blade method.
The green sheet was sintered (recrystallized) at 2300 ° C. in an argon atmosphere to obtain a porous thin plate-like silicon carbide sintered body having a length of 150 mm, a width of 150 mm, and a thickness of 0.25 mm.

This silicon carbide sintered body was heated in air at 1350 ° C. to form a SiO ₂ layer on the SiC surface. The weight of the silicon carbide sintered body before spraying was 10.9 g, and the apparent porosity was 39%.
At this time, the rate of increase in oxidized weight was 5.8%. The rate of increase in oxidation weight was determined by (W1−W0) / W0 × 100 (%), where W0 represents the weight before the oxidation treatment and W1 represents the weight after the oxidation treatment.
The bending strength was 103 MPa.
The bending strength was obtained by a three-point bending test with a span of 30 mm using 75 mm × 30 mm × T (thickness) mm as a sample.

  Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.
As a result, as shown in Table 2, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film. Further, it was found that the setter was satisfactory without cracking or breakage.

(Example 8)
The temperature for forming the SiO ₂ layer on the SiC surface of the silicon carbide sintered body was 1450 ° C., and the other conditions were the same as those in Example 7.

The silicon carbide sintered body before spraying had a weight of 11.1 g and an apparent porosity of 38%.
At this time, the rate of increase in oxidized weight was 7.9%. The bending strength was 140 MPa.
Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.
As a result, as shown in Table 2, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film. Further, it was found that the setter was satisfactory without cracking or breakage.

Example 9
The temperature for forming the SiO ₂ layer on the SiC surface of the silicon carbide sintered body was 1550 ° C., and the other conditions were the same as those in Example 7.

The weight of the silicon carbide sintered body before spraying was 11.3 g, and the apparent porosity was 36%.
At this time, the rate of increase in oxidized weight was 9.4%. The bending strength was 189 MPa.
Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.
As a result, as shown in Table 2, the furnace was passed five times, but the setter film was not peeled off, and it was confirmed that the film was a good film. Further, it was found that the setter was satisfactory without cracking or breakage.

(Example 10)
The temperature for forming the SiO ₂ layer on the SiC surface of the silicon carbide sintered body was 1200 ° C., and other conditions were the same as those in Example 7.

The weight of the silicon carbide sintered body before spraying was 10.7 g, and the apparent porosity was 43%.
At this time, the rate of increase in oxidized weight was 4.1%. The bending strength was 70 MPa.
Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.
As a result, as shown in Table 2, the furnace was passed through 5 times, but the setter film was not peeled off and was a good coating, but during the fourth roller hearth travel (while passing through the furnace) Cracking occurred.

(Example 11)
The temperature at which the SiO ₂ layer was formed on the SiC surface of the silicon carbide sintered body was 1650 ° C., and other conditions were the same as in Example 7.

The weight of the silicon carbide sintered body before spraying was 11.4 g, and the apparent porosity was 34%.
At this time, the rate of increase in oxidized weight was 10.8%. The bending strength was 220 MPa.
Further, a mullite sprayed layer having a thickness of 30 μm was formed on the surface by plasma spraying, and a zirconia sprayed layer was further formed on the surface by 30 μm.

  The obtained thin plate-like setter was subjected to a furnace test (maximum heating rate (° C./H)=100,000) using a roller hearth kiln.

As can be seen from Examples 7 to 11, when the rate of increase in oxidized weight is less than 5%, sufficient strength as a firing tool material cannot be obtained, and breakage such as cracking may occur. On the other hand, when the rate of increase in the oxidized weight exceeds 10%, the temperature becomes high during the oxidation treatment, so that there is a risk of deformation or peeling of the sprayed film. Moreover, because of the oxidation treatment at a high temperature, the energy cost and the furnace material cost increase, which is not realistic. Therefore, by forming the SiO ₂ layer on the surface of the silicon carbide sintered body within the range where the increase in the oxidized weight is 5% or more and 10% or less, sufficient strength as a firing tool material can be obtained. Moreover, when the rate of increase in the oxidized weight is 5% or more and 10% or less with respect to the silicon carbide sintered body, it is possible to obtain a firing tool material having a bending strength of 100 MPa or more and 200 MPa or less, and breakage such as cracks. Can be suitably used as a baking tool material.

1 Setter 2 Upper surface 3 Lower surface t Thickness

Claims (5)

A firing tool material placed on a firing object and housed in a firing furnace together with the firing object,
The firing tool material comprises a silicon carbide sintered body,
And the tool material for baking characterized by having a thickness of at least 0.2 mm or more and 1 mm or less and a porosity of 15% or more and 60% or less. The firing tool material according to claim 1, further comprising an SiO ₂ layer on the surface of at least a portion of the silicon carbide sintered body on which the object to be fired is placed.   The firing tool material according to claim 2, wherein the rate of increase in oxidized weight is 5% or more and 10% or less with respect to the silicon carbide sintered body.   The baking tool material according to any one of claims 1 to 3, wherein the bending strength is 100 MPa or more and 200 MPa or less. The firing tool material according to any one of claims 1 to 4, further comprising at least one plasma sprayed film of mullite, alumina, or zirconia on the surface of the SiO ₂ layer.