Method for regenerating sintering setter and method for using sintering setter

Abstract

This method for regenerating a sintering setter includes: a removal step for removing a coating layer formed on the surface of a ceramic base material from a sintering setter to be regenerated, the sintering setter comprising the ceramic base material and the coating layer; and a coating step for forming a new coating layer on a post-removal surface of the base material from which the coating layer has been removed. In the removal step, the coating layer is removed under conditions that satisfy one or more of the following (1) to (3). (1) The surface roughness Ra of the post-removal surface is 0.005-0.1 mm. (2) The surface roughness Rz of the post-removal surface is 0.01-0.5 mm. (3) The thickness reduction amount, which is the value obtained by subtracting the thickness of the base material after the removal step from the thickness of the base material before the removal step, is 0.001-0.05 mm.

Description

Method for regenerating a firing setter and method for using a firing setter

[0001] The present invention relates to a method for regenerating a firing setter and a method for using a firing setter.

[0002] Conventionally, when manufacturing ceramic products such as ceramic capacitors, the object to be fired is set in a firing setter and fired. As a firing setter, a ceramic substrate having a coating layer formed on its surface has been proposed (see, for example, Patent Document 1). By providing the coating layer, it is possible to suppress a reaction between the firing setter and the object to be fired during firing.

[0003] JP 2023-160735 A

[0004] However, when a firing setter reaches the end of its life due to peeling of the coating layer or the like, it is simply discarded. Recently, from the viewpoint of resource conservation, it has been desired to recycle firing setters. However, no specific recycling method has been disclosed so far.

[0005] The present invention has been made to solve such problems, and a main object of the present invention is to provide a suitable method for regenerating a firing setter.

[0006] [1] The method for regenerating a firing setter of the present invention includes a removal step of removing the coating layer from a firing setter to be regenerated, the setter having a ceramic base and a coating layer formed on the surface of the base, and a coating step of forming a new coating layer on the surface of the base after the coating layer has been removed, wherein the removal step removes the coating layer under conditions that satisfy one or more of the following (1) to (3): (1) The surface roughness Ra of the surface after removal is 0.005 mm or more and 0.1 mm or less; (2) The surface roughness Rz of the surface after removal is 0.01 mm or more and 0.5 mm or less; and (3) The amount of thinning, which is the value obtained by subtracting the thickness of the base after the removal step from the thickness of the base before the removal step, is 0.001 mm or more and 0.05 mm or less.

[0007] In this method for regenerating a setter for firing, the coating layer is removed under conditions that satisfy one or more of the above (1) to (3). Under these conditions, the coating layer can be sufficiently removed without placing a large load on the substrate, resulting in a favorable post-removal surface. By forming a new coating layer on this post-removal surface, the setter for firing can be favorably regenerated.

[0008] [2] In the method for regenerating a setter for firing of the present invention (the method for regenerating a setter for firing described in [1] above), the ceramic substrate is preferably a silicon carbide material. Silicon carbide materials are less likely to deform or break during the removal process, allowing for high yield regeneration.

[0009] [3] In the method for regenerating a setter for firing of the present invention (the method for regenerating a setter for firing described in [1] or [2] above), the coating layer may be removed by blasting in the removal step. The blasting can relatively easily remove the coating layer under conditions that satisfy one or more of the above (1) to (3).

[0010] [4] In the method for regenerating a setter for firing of the present invention (the method for regenerating a setter for firing described in [3] above), it is preferable that the blasting treatment in the removal step be performed at a blasting pressure of 0.05 MPa or more and 0.8 MPa or less. A blasting pressure of 0.05 MPa or more allows for efficient removal of the coating layer, while a blasting pressure of 0.8 MPa or less makes it difficult for deformation or damage to occur in the substrate, allowing for high yields of regeneration.

[0011] [5] In the regeneration method for a setter for firing of the present invention (the regeneration method for a setter for firing described in any one of [1] to [4] above), the coating step may form the coating layer by any one of a spray coating method, a printing method, and a thermal spraying method. Of these, the spray coating method is more preferred.

[0012] [6] In the method for regenerating a setter for firing of the present invention (the method for regenerating a setter for firing described in any one of [1] to [5] above), the setter for firing to be regenerated may have a base material thickness of 3 mm or less.

[0013] [7] The method for using a firing setter of the present invention includes a regeneration step of carrying out the firing setter regeneration method of the present invention (the firing setter regeneration method described in any one of [1] to [6] above), and when the firing setter after the regeneration step reaches a predetermined state requiring regeneration, the firing setter in the state requiring regeneration is used as the firing setter to be regenerated and the regeneration step is carried out again, and this cycle is repeated one or more times.

[0014] In this method of using a firing setter, the regeneration process is performed multiple times, thereby reducing the amount of substrate waste. The state requiring regeneration may be determined empirically, and may be, for example, when the coating layer peels off or cracks, when the coating layer has changed color to a predetermined color, or when the surface of the coating layer has become rough.

[0015] [8] In the method for using a setter for firing of the present invention (the method for using a setter for firing described in [7] above), the predetermined state requiring regeneration may be a state in which peeling of the coating layer occurs.

[0016] [9] In the method for using the setter for firing of the present invention (the method for using the setter for firing described in [7] or [8] above), the regeneration step may be carried out 10 or more times.

[0017]

[10] In the method of using the firing setter of the present invention (the method of using the firing setter described in [9] above), the regeneration process may be carried out so as to satisfy one or more of the following: a 10-times weight loss, which is the value obtained by subtracting the thickness of the base material after the regeneration process has been carried out 10 times from the thickness of the base material before the regeneration process, is 1 mm or less; or a 10-times mass loss rate, which is the rate of reduction in the mass of the base material after the regeneration process has been carried out 10 times relative to the mass of the base material before the regeneration process, is 50% or less.

[0018] 1 is a perspective view schematically showing a firing setter 10. 2 is a cross-sectional view schematically showing a firing setter 10. 3 is an explanatory diagram schematically showing a method for regenerating a firing setter 10. 4 is a photograph of the appearance of a substrate of Experimental Example 1. 5 is a photograph of the appearance of a substrate of Experimental Example 2. 6 is a cross-sectional SEM image of Experimental Example 13 and Experimental Example 10.

[0019] [Firing setter] First, the firing setter to be recycled will be described. The firing setter comprises a substrate and a coating layer formed on the surface of the substrate. The firing setter can be suitably used, for example, in the manufacturing process (e.g., firing process or heat treatment process) of ceramic electronic components such as ceramic capacitors. The firing setter may be used to place an object to be fired on it, or may be used to position or fix the object to be fired. The firing setter may be in the shape of a plate, a box, or another shape.

[0020] The substrate is made of ceramic and may be plate-shaped, box-shaped, or other shapes depending on the shape of the firing setter. Examples of ceramics include silicon carbide materials, alumina materials, and mullite materials, with silicon carbide materials being preferred. Examples of silicon carbide materials include Si-SiC composite materials containing metal silicon (such as Si-bonded SiC and Si-impregnated SiC), recrystallized SiC, and atmospheric pressure sintered SiC, with Si-SiC composite materials being preferred. The thickness of the substrate may be, for example, 0.1 mm or more, 0.5 mm or more, or 0.7 mm or more. The thickness of the substrate may be, for example, 5 mm or less, 3 mm or less, or 2 mm or less.

[0021] The coating layer may be a single layer or a multi-layer structure of two or more layers. The coating layer may be made of ceramic. Examples of ceramic include zirconia, silicon carbide, alumina, mullite, silica, magnesia, and mixtures of two or more of these. The total thickness of the coating layer may be, for example, 5 μm or more, or 50 μm or more. The total thickness of the coating layer may be, for example, 2000 μm or less, or 500 μm or less.

[0022] The outermost layer of the coating layer may be made of, for example, zirconia or stabilized zirconia. Zirconia changes its crystalline phase from monoclinic to tetragonal to cubic as the temperature rises from room temperature. Stabilized zirconia is zirconia that has a stabilizer added to it, extending the stable range of cubic and tetragonal crystalline phases at high temperatures to the low-temperature side, so that it remains cubic or tetragonal even at room temperature. Examples of stabilizers include calcium-containing zirconia, such as CaO, and yttrium-containing zirconia, such as YO. Stabilized zirconia may be a single cubic phase, a single tetragonal phase, or a phase containing both cubic and tetragonal phases. Furthermore, stabilized zirconia may contain orthorhombic crystals. The thickness of the outermost layer of the coating layer may be, for example, 5 μm or more, or 50 μm or more. The thickness of the outermost layer of the coating layer may be, for example, 1000 μm or less, or 200 μm or less.

[0023] The coating layer may have an intermediate layer closer to the substrate than the outermost layer. The intermediate layer may be one layer or two or more layers. The intermediate layer may be made of a ceramic different from that of the outermost layer. Examples of ceramic include silicon carbide, alumina, mullite, silica, magnesia, and mixtures of two or more of these. The thickness of the intermediate layer of the coating layer may be, for example, 5 μm or more, or 50 μm or more. The thickness of the intermediate layer of the coating layer may be, for example, 1000 μm or less, or 300 μm or less.

[0024] A firing setter 10, which is an example of a firing setter, will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing the firing setter 10. FIG. 2 is a cross-sectional view schematically showing the firing setter 10. As shown in FIGS. 1 and 2, the firing setter 10 includes a ceramic substrate 12 and a coating layer 13 formed on the surface of the substrate 12. The coating layer 13 includes an intermediate layer 14 formed on the substrate 12 and an outermost layer 16 formed on the surface of the intermediate layer 14. As shown in FIG. 2, the surface 16a of the outermost layer 16 may be provided with irregularities. The substrate 12 is made of, for example, a Si-SiC composite material, the intermediate layer 14 is made of, for example, alumina, mullite, or a mixture thereof, and the outermost layer 16 is made of, for example, stabilized zirconia. The intermediate layer 14 may be omitted.

[0025] [Method for Regenerating Setters for Firing] Next, a method for regenerating setters for firing will be described. The method for regenerating setters for firing includes a removal step of removing a coating layer from the setter for firing to be regenerated, and a coating step of forming a new coating layer on the surface of the base material after the coating layer has been removed. The setter for firing to be regenerated may be any of the setters for firing described above, and may be one that has reached a predetermined state requiring regeneration. The state requiring regeneration may be determined empirically, for example, so that regeneration processing can be performed before problems occur in the firing of the object to be fired. The state requiring regeneration may be, for example, a state in which peeling or cracking of the coating layer has occurred. The presence or absence of peeling or cracking may be determined visually. The state requiring regeneration may be, for example, a state in which the color of the coating layer has changed to a predetermined color. The presence or absence of discoloration may be determined by, when an image of the coating layer is taken and its brightness is expressed in 256 gradations (gray scale) from 0 (black) to 255 (white), whether there are any areas where the brightness is 30 or more lower than the brightness before use, or whether the difference in brightness within the coating layer is 30 or more. The state requiring regeneration may be determined, for example, by a state in which the surface of the coating layer is roughened. The presence or absence of surface roughness may be determined by measuring the surface roughness Ra and determining whether the surface roughness Ra is 5 μm or more higher than the surface roughness Ra before use. The firing setter to be regenerated may be used or unused. Even if it is unused, it may become in a state requiring regeneration depending on how it is handled.

[0026] (Removal Step) In the removal step, (1) the coating layer may be removed under conditions such that the surface roughness (arithmetic mean roughness) Ra of the surface after removal is 0.005 mm or more and 0.1 mm or less. The surface roughness Ra of the surface after removal may be 0.01 mm or more or 0.015 mm or more, or 0.08 mm or less or 0.07 mm or less. In the removal step, (2) the coating layer may be removed under conditions such that the surface roughness (ten-point mean roughness) Rz of the surface after removal is 0.01 mm or more and 0.5 mm or less. The surface roughness Rz of the surface after removal may be 0.03 mm or more or 0.05 mm or more, or 0.4 mm or less or 0.3 mm or less. In the removal step, (3) the coating layer may be removed under conditions such that the amount of thinning, which is the value obtained by subtracting the thickness of the substrate after the removal step from the thickness of the substrate before the removal step, is 0.001 mm or more and 0.05 mm or less. The amount of thinning may be 0.0015 mm or more, 0.002 mm or more, 0.03 mm or less, 0.02 mm or less, or 0.015 mm or less. In the removal step, the coating layer may be removed under conditions that satisfy one or more of the above-mentioned (1) to (3). In addition, the coating layer may be removed under the condition (4) that the mass reduction rate, which indicates the rate of reduction in the mass of the substrate after the removal step relative to the mass of the substrate before the removal step, is 0.1% or more and 10% or less. The mass reduction rate may be 0.3% or more, 0.5% or more, or 5% or less, or 1% or less.

[0027] Examples of methods for the removal step include blasting such as sandblasting, and grinding and polishing using a grinding stone or file, with blasting being preferred. In the removal step, blasting is preferably performed at a blasting pressure of 0.05 MPa or more and 0.8 MPa or less. A higher blasting pressure is preferred from the viewpoint of increasing the efficiency of the removal step, and for example, 0.1 MPa or more is more preferred. A lower blasting pressure is preferred from the viewpoint of increasing yield, and for example, 0.7 MPa or less is more preferred, and 0.6 MPa or less is even more preferred. The blasting material used in the blasting may be made of alumina. Furthermore, the blasting may be performed using a blasting material having an average particle size of 0.5 μm or more and 500 μm or less. The average particle size of the blasting material may be 1 μm or more, 10 μm or more, or 450 μm or less. The particle size of the blasting material may be F24 or less as specified in JIS R 6001:2017.

[0028] (Coating Process) In the coating process, a new coating layer is formed on the surface after removal. The new coating layer is the same as the coating layer described for the firing setter, and the configuration and conditions of the coating layer described for the firing setter can be applied. The new coating layer may be the same or different from the coating layer removed in the removal process in terms of the number of layers, layer thickness, etc., and the material of each layer may be the same or different. The new coating layer may be formed using a raw material containing ceramic, or may be formed using a raw material containing ceramic powder. Examples of ceramics include zirconia, silicon carbide, alumina, mullite, silica, magnesia, and mixtures of two or more of these.

[0029] Examples of methods for forming a coating layer include spray coating, printing, pouring, and thermal spraying. Of these, spray coating, printing, and pouring are preferred, with spray coating being more preferred. In the spray coating method, ceramic powder is dispersed in a solvent such as water or an organic solvent to prepare a slurry-like raw material, which is sprayed with a spray device to form a raw material layer, and dried or fired as needed to form a coating layer. In the printing method, a solvent such as water or an organic solvent is added to ceramic powder to prepare a slurry or paste-like raw material, which is then formed into a raw material layer using a printing method such as screen printing, and dried or fired as needed to form a coating layer. The pouring method is a method mainly used for coating setters with rims, such as saggers. In this method, ceramic powder is dispersed in a solvent such as water or an organic solvent to prepare a slurry-like raw material, which is poured onto a substrate to form a raw material layer, and dried or fired as needed to form a coating layer. The firing temperature may be, for example, 1000°C or higher and 1400°C or lower to fix the coating layer to the substrate surface, the firing atmosphere may be, for example, air or an inert atmosphere, and the firing time may be, for example, 1 hour or higher and 168 hours or lower. The average particle size of the ceramic powder may be, for example, 0.1 μm or higher, or 0.2 μm or higher. The average particle size of the ceramic powder may be, for example, 700 μm or lower, or 300 μm or lower. In this specification, the average particle size is defined as the volume-based median diameter D50 measured by laser diffraction.

[0030] The outermost layer of the new coating layer (also referred to as the new outermost layer) may be formed using, for example, a raw material containing stabilized zirconia. The stabilized zirconia may be stabilized with a calcium-containing stabilizer such as CaO, or with an yttrium-containing stabilizer such as YO. This stabilized zirconia may be in the form of a powder. The average particle size of the stabilized zirconia may be, for example, 0.1 μm or more, or 0.2 μm or more. The average particle size of the stabilized zirconia may be, for example, 700 μm or less, or 300 μm or less.

[0031] Prior to forming a new outermost layer, a new intermediate layer (or a raw material layer thereof) may be formed on the surface of the substrate, and a new outermost layer (or a raw material layer thereof) may then be formed on the surface of the new intermediate layer formed on the substrate. The new intermediate layer may be formed, for example, using a raw material different from that of the new outermost layer. The raw material for the intermediate layer may contain ceramic. Examples of ceramic that can be used include silicon carbide, alumina, mullite, silica, magnesia, and mixtures of two or more of these. The ceramic may be in the form of a powder. The average particle size of the ceramic powder may be, for example, 0.1 μm or more, or 0.2 μm or more. The average particle size of the ceramic powder may be, for example, 700 μm or less, or 300 μm or less. The method for forming the intermediate layer may be the same as or different from that for the outermost layer.

[0032] An example of a method for regenerating a setter for firing will be described with reference to the drawings. FIG. 3 is an explanatory diagram illustrating a method for regenerating a setter for firing 10. FIG. 3A is a schematic diagram of the setter for firing 10 to be regenerated. FIGS. 3B-C are schematic diagrams illustrating the removal process. FIGS. 3D-3E are schematic diagrams illustrating the coating process. FIG. 3F is a schematic diagram of a setter for firing 10b after regeneration. Here, we will explain the regeneration of a setter for firing 10 having a coating layer 13 consisting of an intermediate layer 14 and an outermost layer 16, as shown in FIG. 3A. In the removal process, as shown in FIG. 3B, a blasting device 20 is used to project blast material 22 onto the coating layer 13, thereby removing the coating layer 13. As a result, the coating layer 13 is removed from the surface of the substrate 12, exposing the surface 12b after removal, as shown in FIG. 3C. In this removal process, the coating layer is removed under conditions that satisfy one or more of the above-mentioned conditions (1) to (3). In the coating process, first, as shown in FIG. 3D , a new intermediate layer 14b is formed on the surface 12b of the removed substrate 12. The new intermediate layer 14b is made of ceramic, such as alumina, mullite, or a mixture thereof, and may be formed, for example, by spray coating. Next, a new outermost layer 16b is formed on the surface of the new intermediate layer 14b using a raw material 34 containing ceramic powder 32, such as stabilized zirconia. Specifically, as shown in FIG. 3D , the raw material 34 is sprayed onto the surface of the new intermediate layer 14b using a spray device 30 to form a raw material layer 36. The raw material layer 36 is then dried and fired as necessary to form the new outermost layer 16b. This results in a regenerated firing setter 10b, in which a new coating layer 13b is formed on the surface of the substrate 12, as shown in FIG. 3F . Although the raw material layer 36 is formed on the surface of the new intermediate layer 14b here, the raw material layer 36 may be formed on the surface of the raw material layer for the new intermediate layer 14b (e.g., a green body before firing) and the raw material layer for the intermediate layer 14b may be fired simultaneously. Also, the formation of the new intermediate layer 14b may be omitted.

[0033] In the regeneration method for a setter for firing described above, the coating layer is removed under conditions that satisfy one or more of the above conditions (1) to (3). Under these conditions, the coating layer can be sufficiently removed without placing a large load on the substrate, resulting in a favorable post-removal surface. Forming a new coating layer on the post-removal surface allows for favorable regeneration of the setter for firing. This regeneration method for a setter for firing is preferably carried out so that the incidence of coating peeling is 25% or less, more preferably 10% or less, and even more preferably 1% or less. The incidence of coating peeling is defined as the percentage of regenerated setters for firing in which peeling of the coating layer is confirmed by visual inspection. Furthermore, this regeneration method for a setter for firing is preferably carried out so that the particle breakage rate on the substrate surface (the surface on which the coating layer is formed) of the regenerated setter for firing is 30% or less, more preferably 15% or less, and even more preferably 10% or less. The particle breakage rate was calculated by taking an SEM image (composition image) of the cross section of the regenerated firing setter at 200x magnification, visually counting the number A of particles on the surface of the substrate that had a major axis of 20 μm or more, and then counting the number B of particles that were visually confirmed to be cracked, using the formula particle breakage rate [%] = B / A × 100.

[0034] [Method of Using a Setter for Firing] Next, a method of using a setter for firing will be described. The method of using a setter for firing includes a regeneration step in which the above-mentioned method of regenerating a setter for firing is carried out. Then, when the setter for firing after the regeneration step reaches a predetermined state requiring regeneration, for example by being used to fire an object to be fired, the setter for firing in a state requiring regeneration is used as the setter for firing to be regenerated, and this cycle of carrying out the regeneration step again is carried out one or more times. In this method of using a setter for firing, the regeneration step (including the first regeneration step) is carried out two or more times. The number of times the regeneration step is carried out may be three or more, five or more, ten or more, etc. The regeneration step may be 100 times or less, 50 times or less, 20 times or less, etc.

[0035] In a method for using a setter for firing, the regeneration process may be performed so that the thickness reduction amount after 10 cycles, which is the value obtained by subtracting the thickness of the substrate after 10 cycles of the regeneration process from the thickness of the substrate before the regeneration process (e.g., a new substrate), is 1 mm or less. The thickness reduction amount after 10 cycles may be 0.1 mm or less, 0.05 mm or less, or 0.001 mm or more, or 0.01 mm or more.

[0036] In the method of using the firing setter, the regeneration step may be performed so that the 10-time mass reduction rate, which indicates the rate of reduction in the mass of the base material after 10 regeneration steps relative to the mass of the base material before the regeneration step (e.g., a new product), is 50% or less. The 10-time mass reduction rate may be 20% or less, 10% or less, or 0.1% or more, or 1% or more.

[0037] The method of using a setter for firing according to the embodiment described above includes a regeneration step of carrying out the above-mentioned regeneration method for a setter for firing, so that the setter for firing can be regenerated appropriately. Furthermore, in this method of using a setter for firing, the regeneration step is carried out multiple times, so that the amount of substrate waste can be reduced.

[0038] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0039] Below, examples in which the firing setter of the present invention was investigated will be described as examples. Experimental Example 1 corresponds to an example of the present invention, and Experimental Example 2 corresponds to a comparative example. Experimental Examples 5 to 13 correspond to examples of the present invention, and Experimental Examples 3 and 4 correspond to comparative examples.

[0040] [Experimental Example 1] 1. Preparation of a Setter for Firing First, a 2 mm-thick plate-shaped Si-impregnated SiC substrate was prepared. Water was added to mullite powder (average particle size 9.3 μm) to prepare a raw material for the intermediate layer. The raw material for the intermediate layer was then sprayed onto the surface of the substrate using a spray device to form a raw material layer for the intermediate layer with a thickness of 300 μm. Next, water was added to stabilized zirconia powder (average particle size 9.3 μm) to prepare a raw material for the outermost layer. The raw material for the outermost layer was then sprayed onto the surface of the raw material layer for the intermediate layer using a spray device to form a raw material layer for the outermost layer with a thickness of 150 μm. The setter was then fired in an air atmosphere at 1300°C for 3 hours to obtain a setter for sintering with a coating layer (intermediate layer and outermost layer) formed on the surface of the substrate.

[0041] 2. Firing of the object to be fired using a firing setter: The object to be fired (a general-purpose ceramic capacitor) was placed on the obtained firing setter and fired at 1200°C for 2 hours in an inert atmosphere. This operation was repeated until the firing setter reached the end of its life, and the firing setter was used as a refurbished object. The end of its life was defined as the time when peeling of the coating layer was confirmed visually.

[0042] 3. Reuse of the setter for firing Using a blasting device, alumina blasting material (particle size F24 or less (smaller than F24) as specified in JIS R 6001:2017) was projected onto the obtained setter for firing to be recycled at a blasting pressure (set pressure) of 0.4 MPa, removing the outermost layer and intermediate layer and exposing the surface of the base material (surface after removal) (removal process). The distance from the blasting device to the setter for firing to be recycled was 50 to 450 mm. Then, an intermediate layer and an outermost layer were formed on the surface after removal of the base material in the same manner as in the preparation of the setter for firing (coating process). In this way, a setter for firing after the recycling process was obtained (recycling process).

[0043] The setter for firing after the regeneration process was used to fire the object to be fired in the same manner as above, and this setter for firing was used as the setter for firing to be regenerated and the regeneration process was carried out again. This cycle was repeated nine times, for a total of 10 regeneration processes.

[0044] 4. Measurement of the substrate The surface roughness Ra and Rz, thickness, and mass of a new substrate and the substrate after the removal process of the first, third, fifth, and tenth recycling processes were measured, and photographs of the appearance were taken. The surface roughness Ra and Rz of the substrate were measured using a Keyence VR-3000. The thickness of the substrate was measured using a micrometer.

[0045] [Experimental Example 2] An experiment was carried out in the same manner as in Experimental Example 1, except that an Al2O3 substrate was used instead of the plate-shaped Si-impregnated SiC substrate. However, in Experimental Example 2, the substrate was damaged early, so the regeneration process from the fourth time onwards was omitted.

[0046] [Results and Discussion] Table 1 summarizes the measurement results of the substrate for Experimental Examples 1 and 2. In Table 1, the amount of wall thickness reduction per treatment is the value obtained by dividing the amount of wall thickness reduction since the previous measurement by the number of (blast) treatments since the previous measurement. Furthermore, the mass reduction rate per treatment is the value obtained by dividing the amount of wall thickness reduction since the previous measurement by the mass of a new substrate, and then dividing that value by the number of (blast) treatments since the previous measurement. Furthermore, Figure 4 shows a photograph of the appearance of the substrate for Experimental Example 1, and Figure 5 shows a photograph of the appearance of the substrate for Experimental Example 2.

[0047] As shown in Table 1 and Figures 4 and 5, in Experimental Example 2, where (1) the surface roughness Ra of the surface after removal was not 0.005 mm or more and not 0.1 mm or less, (2) the surface roughness Rz of the surface after removal was not 0.01 mm or more and not 0.5 mm or less, and (3) the amount of metal loss per application was not 0.001 mm or more and not 0.05 mm or less, the substrate was damaged in the removal process, and the setter for firing could not be regenerated. On the other hand, in Experimental Example 1, where one or more of these conditions were met, the substrate was not damaged even after performing the regeneration process 10 times, and it was found that the setter for firing could be regenerated suitably. It was also found that when the amount of metal loss per application was 0.02 mm or less, the setter for firing could be regenerated more suitably. Since the substrate in Experimental Example 1 was Si-SiC and the substrate in Experimental Example 2 was Al2O3, it was inferred that the substrate should preferably be Si-SiC. However, it was inferred that, as in Experimental Example 1, even if the substrate is Al2O3 or the like, the regeneration of the firing setter can be suitably carried out by appropriately adjusting the conditions of the removal treatment so as to satisfy any one of (1) to (3).

[0048]

[0049] Experiments 3 to 13 were conducted in the same manner as in Experiment 1, except that the blast pressures shown in Table 2 were used and the regeneration process was performed once. Furthermore, the incidence of coating peeling, particle damage rate, and lifespan of the firing setter after one regeneration process were determined. The incidence of coating peeling was determined as the percentage of cases in which peeling of the coating layer was confirmed visually in four experiments. The particle damage rate was calculated as follows: First, the substrate coated in the regeneration process was embedded in resin, and cross-sectional composition images were acquired using an SEM at 200x magnification (N = 50 fields of view). In each field of view, the number of particles on the substrate surface with a major axis of 20 μm or more (A) was visually counted, and the number of particles with visible cracks (B) was counted. The particle damage rate [%] was calculated using the formula: B / A × 100. For reference, an example of a cross-sectional SEM image of Experiment 13 is shown in Figure 6A, and an example of a cross-sectional SEM image of Experiment 10 is shown in Figure 6B. When the particle damage rate was high as in Figure 6A, the cracks were relatively large, whereas when the particle damage rate was low as in Figure 6B, the cracks were relatively small. Also, in Figure 6A, the coating layer peeled off from the substrate.

[0050] Table 2 summarizes the experimental results of Experimental Examples 3 to 13. Specifically, the substrate surface roughness Ra, substrate surface roughness Rz, and thickness reduction amount for the substrate after the removal step in the first recycling step are summarized. Also summarized are whether recoating can be applied, the rate of coating peeling, the rate of particle damage, and the lifespan.

[0051] As shown in Table 2, in Experiments 3 and 4, where the blast pressure was 0.02 MPa or less, the coating layer of the firing setter to be regenerated could not be removed, and recoating was not possible. In Experiments 5 to 13, where the blast pressure was 0.05 MPa or more and 1 MPa or less, recoating was possible. However, in Experiments 12 to 13, where the blast pressure was 0.9 MPa or more, coating peeling occurred, and the recoating yield was lower than in Experiments 5 to 11. From the above, it was found that a blast pressure of 0.05 MPa or more and 0.8 MPa or less is preferable. Of these, in Experiments 6 to 11, where the blast pressure was 0.1 MPa or more, the coating layer was peeled off in a short time of 10 minutes or less, and recoating could be performed efficiently. From these results, it was found that a blast pressure of 0.1 MPa or more and 0.8 MPa or less is more preferable. It was also found that the life of the setter after recoating could be extended when the particle damage rate of the substrate was 5% or more and 12% or less.

[0052]

[0053] This application claims priority from Japanese Patent Application No. 2024-129890, filed on August 6, 2024, the entire contents of which are incorporated herein by reference.

[0054] The present invention can be used in a firing tool used in a manufacturing process of ceramic parts, such as a firing process or a heat treatment process.

[0055] 10 Firing setter, 10b Firing setter after regeneration, 12 Base material, 12b Surface after removal, 13 Coating layer, 13b New coating layer, 14 Intermediate layer, 14b New intermediate layer, 16 Outermost layer, 16a Surface, 16b New outermost layer, 20 Blast device, 22 Blast material, 30 Spray device, 32 Ceramic powder, 34 Raw material, 36 Raw material layer.

Claims

1. A method for regenerating a firing setter, comprising: a removal step of removing the coating layer from a firing setter to be regenerated, the firing setter having a ceramic base and a coating layer formed on the surface of the base; and a coating step of forming a new coating layer on the surface of the base from which the coating layer has been removed, wherein the removal step removes the coating layer under one or more of the following conditions (1) to (3): (1) The surface roughness Ra of the surface after removal is 0.005 mm or more and 0.1 mm or less. (2) The surface roughness Rz of the surface after removal is 0.01 mm or more and 0.5 mm or less. (3) The amount of thinning, which is the value obtained by subtracting the thickness of the base after the removal step from the thickness of the base before the removal step, is 0.001 mm or more and 0.05 mm or less.

2. The method for regenerating a firing setter according to claim 1, wherein the ceramic substrate is a silicon carbide material.

3. A method for regenerating a firing setter according to claim 1 or 2, wherein the coating layer is removed by blasting in the removal step.

4. A method for regenerating a firing setter according to claim 3, wherein the blasting process is carried out at a blasting pressure of 0.05 MPa or more and 0.8 MPa or less in the removing step.

5. A method for regenerating a firing setter according to claim 1 or 2, wherein in the coating step, the coating layer is formed by any one of a spray coating method, a printing method, and a thermal spraying method.

6. A method for regenerating a firing setter according to claim 1 or 2, wherein the firing setter to be regenerated has a base material thickness of 3 mm or less.

7. A method for using a firing setter, comprising a regeneration step of carrying out the regeneration method for a firing setter according to claim 1 or 2, wherein when the firing setter after the regeneration step reaches a predetermined state requiring regeneration, the firing setter in the state requiring regeneration is used as the firing setter to be regenerated and the regeneration step is carried out again, this cycle being carried out one or more times.

8. The method for using a baking setter according to claim 7, wherein the predetermined state requiring regeneration is a state in which the coating layer has peeled off.

9. The method for using a firing setter according to claim 7, wherein the regeneration step is carried out 10 or more times.

10. A method for using a firing setter as described in claim 7, wherein the regeneration process is carried out so as to satisfy one or more of the following: a 10-times weight loss, which is the value obtained by subtracting the thickness of the base material after performing the regeneration process 10 times from the thickness of the base material before performing the regeneration process, is 1 mm or less; or a 10-times mass loss rate, which is the rate of loss in the mass of the base material after performing the regeneration process 10 times relative to the mass of the base material before performing the regeneration process, is 50% or less.

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