JP7285271B2 - Baking rack and baking jig - Google Patents

Description

This specification discloses a technology related to a baking rack and a baking jig. In particular, a technique relating to a firing rack for arranging a plate-shaped setter on which objects to be fired are loaded is disclosed.

2. Description of the Related Art In the process of firing an object to be fired, such as a ceramic product, a technique is known in which the object to be fired is placed on a setter and fired. International Publication No. WO2015/008503 (hereinafter referred to as Patent Document 1) discloses a technique of stacking a plurality of flat setters using a baking rack. In the baking rack of Patent Document 1, cross-shaped pillars (bridging parts) are provided in the openings surrounded by the frames so as to connect the frames, thereby preventing deformation of the flat setter during the baking process. are doing.

The baking rack of Patent Document 1 supports the center of the flat plate-shaped setter by the pillars, thereby preventing deformation of the flat plate-shaped setter. However, when using the baking rack of Patent Document 1, the part supported by the column (the part in contact with the column) and the part not supported by the column (the part not in contact with the column) , the temperature of the flat setter may be different. For example, in the temperature raising process, the temperature of the flat setter may be higher in the portion not in contact with the column than in the portion in contact with the column. On the other hand, in the temperature lowering step, the temperature of the flat setter may be lower in the portion not in contact with the pillar than in the portion in contact with the pillar. If temperature unevenness occurs in the plane of the flat setter, uneven firing may occur in the object to be fired. An object of the present specification is to provide a baking rack capable of reducing the in-plane temperature distribution of a flat setter to be loaded.

The baking rack disclosed in this specification is configured to arrange a flat setter on which the objects to be baked are placed. The baking rack is surrounded by a frame having a plate-shaped setter on its surface and an opening, a column extending between the frames so as to pass through the center of the frame, and the frame and the column. and a plurality of sub-columns extending from the center of the surrounding portion toward the frame or column.

This specification also discloses a firing jig comprising the firing rack described above and a flat setter disposed on the surface of the firing rack. In the firing jig, the firing rack and the flat setter may be made of the same material.

1 shows a plan view of the baking rack of the first embodiment. FIG. FIG. 2 shows a sectional view of a baking jig using the baking rack of the first embodiment. The perspective view of the state which laminated|stacked the jig|tool for baking is shown. The top view of the rack for baking of 2nd Example is shown. The top view of the rack for baking of 3rd Example is shown. The top view of the rack for baking of 4th Example is shown.

The features of the technology disclosed in this specification are summarized below. Note that each of the items described below has technical utility independently.

(Baking jig)
A firing jig disclosed in the present specification is used, for example, in a firing process of an object to be fired such as a ceramic product. The firing jig may include a flat setter for stacking the objects to be fired, and a firing rack configured to place the flat setter. That is, the firing jig may include a firing rack and a plate-shaped setter that is a component separate from the firing rack. The flat setter and firing rack may be made of materials such as alumina, mullite, zirconia, silicon nitride, and silicon carbide. The flat setter and the baking rack may be made of the same material or may be made of different materials. In order to improve the temperature followability during firing (temperature changes in the flat plate setter and firing rack due to changes in the temperature of the atmosphere inside the furnace), the flat plate setter and firing rack are made of the same material. preferably.

The material of the plate-shaped setter and/or the baking rack is particularly preferably silicon carbide. Silicon carbide is known to have high strength and excellent impact resistance. Therefore, if a flat setter and/or a baking rack are manufactured using a silicon carbide material, the thickness of the flat setter and/or the baking rack can be reduced. As a result, the weight of the firing jig can be reduced, and the heat capacity of the firing jig can be reduced. That is, by using silicon carbide as a material for the plate-like setter and/or the baking rack, it is possible to realize a baking jig with good temperature followability. In addition, silicon carbide has a higher thermal conductivity than the other materials described above, which also contributes to an improvement in temperature followability. The “silicon carbide” referred to in this specification means, excluding inevitable impurities, substantially simple SiC (recrystallized SiC), Si ₃ N ₄ —SiC (Si ₃ N ₄ : 20 to 30 wt %, SiC: 70 to 80 wt%) and Si-containing SiC (Si: 1 to 30 wt%, SiC: 70 to 99 wt%).

(Baking rack)
The baking rack may comprise a frame, pillars, enclosures, secondary pillars, and protrusions. The frame, pillars, sub pillars, and projections may be integrally molded, or part or all of them may be separate parts, and the baking rack is formed by assembling the parts. good too. Further, although the details will be described later, the surrounding portion is a region formed by the frame and the pillars.

The frame may go around the outer periphery of the baking rack and constitute the outer edge of the baking rack. The inside of the frame may be open. That is, the frame may be ring-shaped. The shape of the frame (outer edge shape of the baking rack) may be polygonal such as triangular or quadrangular, or circular. Although not particularly limited, the shape of the frame is preferably quadrangular, particularly preferably square or rectangular. When the shape of the frame is square or rectangular, the size of the frame (the outer edge of the baking rack) may be 100 to 500 mm. Moreover, the thickness of the frame may be 1 to 5 mm. The surface of the frame may constitute part of an arrangement surface (setter arrangement surface) for arranging the flat setter.

A plurality of protrusions may be provided on the surface of the frame. By providing a protrusion on the surface of the frame, when the flat plate-shaped setter is arranged on the baking rack, or when a baking jig in which the flat plate-shaped setter is arranged is used, the flat plate shape against the baking rack is reduced. The arrangement position of the setter can be regulated. For example, when the firing jig is used in a continuous firing furnace, it is possible to suppress displacement of the flat setter with respect to the firing rack due to vibrations received when the firing jig is conveyed. Further, the projecting portion functions as a spacer that provides a gap between the firing jigs (between the flat setter and the upper firing rack) when stacking the firing jigs. The thickness (protrusion height) of the projecting portion may be appropriately adjusted according to the size of the flat setter and the object to be fired. For example, the flat setter may have a thickness of 0.3 to 10 mm and the protrusion may have a thickness of 1 to 20 mm. Columns may be provided inside the frames to connect between the frames.

The pillars may extend linearly so as to pass through the centers of the frames and connect the frames to connect the frames. The "center of the frame" means the center point of the frame with respect to the outer edge or inner edge of the frame when the frame is viewed from above (observed from the side where the flat setter is arranged). If the width and thickness are constant in the circumferential direction, it corresponds to the "center of gravity of the frame". The thickness of the column may be the same as the thickness of the frame, for example, 1 to 10 mm, or 1 to 5 mm. Further, when the frame and the pillars are integrally molded, there is no clear boundary between the frame (the inner edge of the frame) and the pillars at the connecting portion. In such a case, it is possible to determine the "center of the frame" by connecting the inner edges of the frame that are not connected to the pillars to create a virtual inner edge that circles. As long as the column passes through the center of the frame, it may extend in one direction (there may be one column) or may extend in multiple directions (there may be multiple columns). (even if there is) good. In addition to the frame, the pillar may also be provided with a projecting portion. By providing the protruding portion on the column portion, when arranging a plurality of flat plate-shaped setters on the baking rack, the arrangement position of each flat plate-shaped setter can be regulated. The pillars divide the opening in the frame (the space surrounded by the inner edge of the frame) into a plurality of openings. That is, by providing the pillars in the frame, a plurality of surrounding parts surrounded by the frame and the pillars are formed.

The shape of the surrounding part depends on the shape of the frame and the pillars. For example, when the frame is quadrangular, if one pillar is formed so as to connect opposite sides of the frame (sides that do not share a vertex), the surrounding section will be quadrangular. Also, if one or two pillars are formed so as to connect opposite vertices (vertices that do not share a side) of the frame, the surrounding portion will be triangular. In addition, when the frame is rectangular or positive, if one or two pillars are formed perpendicular to the sides of the frame, each surrounding portion can be a rectangle of the same shape (same size). Become. Alternatively, when the frame is rectangular or positive, if one pillar is formed to connect opposite vertices of the frame, each surrounding portion will be a triangular shape of the same shape. Although not particularly limited, it is preferable that all of the plurality of surrounding portions formed in the frame have the same shape. In addition, when the shape of each surrounding part is the same shape, all the surrounding parts may be the same size, and may differ.

The sub-pillars are provided inside the enclosure and extend from the center of the enclosure toward the frame or the pillars. A plurality of sub-columns may be provided in the surrounding portion, and all the sub-columns may be connected at the center of the surrounding portion. In addition, "the center of the surrounding part" means the center point when the surrounding part (baking rack) is viewed from above. It corresponds to the center of gravity of the surrounding part. In addition, when the sub-pillars are integrally molded with the frame and/or the pillars that constitute the surrounding portion, the inner surfaces (inner surfaces) of the portions to which the sub-pillars are not connected are connected to form a virtual surrounding that makes a circuit. By creating the section, the "center of the surrounding section" can be determined. The sub-columns may extend radially (linearly) from the center of the surrounding portion, or may extend curvedly (non-linearly). Moreover, when the sub-columns extend radially from the center of the surrounding portion, the angles formed by adjacent sub-columns may be equal. Furthermore, the direction in which the column (the member forming the surrounding portion) extends and the direction in which the sub-column extends may be the same or different. In addition, the surfaces of the frame, the pillars, and the sub-pillars may be included in the same plane. As a result, the entirety of the frame, the pillars, and the sub pillars can form the plane on which the flat setter is arranged. The thickness of the secondary column may be the same as the thickness of the column and frame, and may be, for example, 1 to 5 mm.

(First embodiment)
The baking rack 50 and the baking jig 60 will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 shows a baking rack 50, and FIG. 2 shows a baking jig 60 in which a plate-shaped setter 32 is arranged on the baking rack 50. As shown in FIG. 2 corresponds to a cross section taken along line II--II in FIG. The baking rack 50 and the setter 32 are made of SiC. The baking jig 60 is formed by arranging two setters 32 on one baking rack 50 . The firing jig 60 is used for loading ceramic products to be fired in a firing process for ceramic products and the like.

As shown in FIG. 1, the baking rack 50 includes a frame 2, a column 4 passing through the center 6 of the frame 2, and surrounding portions 10a and 10b surrounded by the frame 2 and the column 4. sub-columns 14a and 14b passing through the centers 12a and 12b of the frame body 2 and projections (ribs) 24 and 26 provided on a part of the frame 2 and the columns 4, respectively. The frame 2 is composed of two first frame portions 2a extending in the X direction and two second frame portions 2b extending in the Y direction perpendicular to the X direction. be. Therefore, an opening is formed inside the frame 2 . The column portion 4 extends in the Y direction (parallel to the second frame portion 2b) so as to connect the first frame portions 2a, 2a. As a result, the opening in the frame 2 is divided into two by the pillars 4 . Further, each of the two separated openings is divided into four by the sub-pillars 14a and 14b, so that a total of eight triangular openings 20a and 20b are formed in the frame 2. As shown in FIG. The width of the frame 2 (the length in the Y direction of the first frame portion 2a and the length in the X direction of the second frame portion 2b) is constant.

The baking rack 50 has two setter placement areas 30a and 30b. That is, two setters 32 can be arranged in one baking rack 50 . The setter arrangement areas 30a and 30b are composed of the frame 2, the pillars 4, and the sub-pillars 14a and 14b. Specifically, the setter arrangement area 30a is configured by a portion of the frame 2, a portion of the pillar 4, and the sub-pillar 14a. Also, the setter arrangement area 30b is configured by a portion of the frame 2, a portion of the column portion 4, and the sub-column portion 14b. Protrusions 24 and 26 are arranged so as to surround the setter arrangement regions 30a and 30b. The projecting portions 24 are provided at the four corners of the baking rack 50, and the projecting portions 26 are provided at both ends of the column portion 4 (center in the longitudinal direction (X direction) of the first frame portion 2a). The projecting portion 24 is arranged so as to surround both the setter arranging regions 30a and 30b, and the projecting portion 26 is provided so as to separate the setter arranging regions 30a and 30b. That is, the protrusions 24 and 26 form setter arrangement areas 30a and 30b.

In addition, the structure of the setter arrangement|positioning area|region 30a and the setter arrangement|positioning area|region 30b is substantially the same. Therefore, in the following description, when describing substantially the same structure, such as the component parts of the setter arrangement area 30a and the component parts of the setter arrangement area 30b, the alphabetical letters of the reference numbers may be omitted.

The surfaces of the frame 2, the pillars 4, and the sub-pillars 14 (arrangement surfaces on which the setter 32 is arranged) are included in the same plane (XY plane). That is, the surface of the setter arrangement area 30 is flat. Therefore, the setter 32 is supported by all of the frame 2 , the pillars 4 and the sub-pillars 14 . In addition, since the protrusions 24 and 26 are arranged so as to surround the setter arrangement area 30, the protrusions 24 and 26 should be positioned on the back surface of the setter 32 when the setter 32 is arranged on the baking rack 50. no.

As shown in FIG. 1, the column portion 4 passes through the center 6 of the frame 2 and extends in the Y direction between the first frame portions 2a. That is, the pillar 4 is parallel to the second frame 2b and orthogonal to the first frame 2a. The column portion 4 is integrally molded with the frame 2 (first frame portion 2a). The width (the length in the X direction) of the pillar 4 is constant in the Y direction (excluding the portion integrated with the frame 2). By providing the column portion 4 inside the frame 2, the surrounding portions 10 (10a, 10b) are formed on both sides of the column portion 4 (both sides in the X direction). The surrounding parts 10a and 10b are square and the size of both is equal.

Within the surrounding part 10, four sub-pillars 14 extend from the center 12 of the surrounding part 10 toward the frame 2 or the pillars 4 (toward the outside of the surrounding part 10). In addition, the surrounding portion 10 shown in FIG. It is a virtual range (virtual surrounding part) that extends and connects with the unconnected part). The sub-columns 14 radially extend from the center 12 toward the apex of the surrounding portion 10 . Therefore, the sub-columns 14 are non-parallel to the frame 2 and the columns 4 (extend in different directions). The angle formed by the adjacent sub-columns 14 is 90 degrees. Each sub-column 14, frame 2, and column 4 are integrally molded. Therefore, it can be considered that one sub-column 14 connecting the center 12 of the surrounding portion 10 and the four vertices is provided in the quadrangular (square) surrounding portion 10 .

Advantages of the baking rack 50 will be described. Since the baking rack 50 is formed by the frame 2 having an opening inside, the temperature difference between the setter central portion and the setter end portion (in-plane temperature distribution) can be reduced. In other words, the baking rack 50 can improve the temperature followability of the central portion of the setter. In addition, since the column 4 passes through the center 6 of the frame 2 and connects the frames 2, deformation of the frame 2 itself or the setter can be suppressed during firing. In addition, since the strength of the baking rack 50 is improved by providing the pillars 4, the thickness of the baking rack 50 (thickness of the setter arrangement surface) can be reduced, and a lightweight baking rack 50 can be realized. can be done. Incidentally, as the thickness of the setter arrangement surface becomes thinner, the heat capacity of the setter arrangement surface decreases, and the temperature followability of the setter improves.

The baking rack 50 can further reduce the in-plane temperature distribution of the setter during baking by providing the sub-pillars 14 in the surrounding part 10 surrounded by the frame 2 and the pillars 4 . As described above, by forming the baking rack 50 using the frame 2, it is possible to improve the temperature followability of the central portion of the setter. However, if the sub-column is not provided within the enclosing portion 10, between the portion corresponding to the center of the enclosing portion of the setter and the portion corresponding to the outside of the enclosing portion (the portion where the setter contacts the frame or the column) , temperature difference is more likely to occur. Specifically, the temperature of the setter is high in the portion corresponding to the center of the surrounding portion, and the temperature of the setter is low in the portion corresponding to the outside of the surrounding portion. When the sub-pillars 14 are provided in the surrounding part 10 like the baking rack 50, a thermal bridge is formed between the center 12 of the surrounding part 10 and the outside of the surrounding part 10, and the in-plane temperature distribution of the setter can be reduced. can.

As shown in FIG. 3, a plurality of firing jigs 60 (firing racks 50) may be stacked during firing. In this case, by providing the projecting portions 24 and 26 on the surface of the frame 2, when the baking racks 50 are stacked, there is a gap between the setter 32 and the baking rack 50 stacked on the upper stage of the setter 32. can be provided. A space (a space for arranging an object to be fired) can be secured on the surface of the setter 32 simply by stacking the firing racks 50 without using a spacer or the like separate from the firing rack 50 . Note that the baking rack 50 is provided on the rear surface of the frame 2 (the surface opposite to the surface on which the projections 24 and 26 are provided) on the tip portions of the projections 24 and 26 (ends in the projection direction (Z+ direction)). part). By accommodating the tips of the protrusions 24 and 26 in the recesses, it is possible to prevent the baking racks 50 from being displaced from each other.

Also, by providing the projections 24 and 26 , the setter 32 can be positioned on the surface of the baking rack 50 . That is, movement of the setter 32 with respect to the baking rack 50, such as dropping of the setter 32 from the baking rack 50, can be suppressed. Even if a projecting portion is provided on the rear surface of the frame 2, a gap can be provided between the firing jigs. However, in this case, the setter 32 cannot be positioned on the surface of the baking rack, and the setter 32 may be displaced from the baking rack due to vibration or the like. Therefore, the baking rack provided with the projecting portion on the rear surface of the frame 2 is not suitable for use in, for example, a continuous baking furnace in which the baking rack is likely to be vibrated. The baking rack 50 can be used in various types of baking furnaces because the setter 32 is positioned by the protrusions 24 and 26 provided on the surface of the frame 2 . In addition, when using a setter larger in size than the setter 32 (eg, twice the size of the setter 32), the projecting portion 26 may be omitted. Even in this case, if the projecting portions 24 are provided at the four corners of the frame 2, a space can be secured on the surface of the setter, and the setter can be positioned on the surface of the baking rack.

The baking racks 150, 250 and 350 will be described below. Baking racks 150 , 250 and 350 are modifications of baking rack 50 . Therefore, with regard to the baking racks 150, 250 and 350, the parts that are substantially the same as the baking rack 50 are given the same reference numbers as those given to the baking rack 50 or the reference numbers having the same last two digits. may be omitted. The baking racks 150, 250 and 350 also form a baking jig by arranging a setter on their surfaces.

(Second embodiment)
In the baking rack 150 shown in FIG. 4 , the direction in which the secondary columns 16 and 18 extend is different from that of the secondary column 14 of the baking rack 50 . Specifically, the sub-columns 16 (16a, 16b) extend parallel to the second frame 2b (in the Y direction) and connect the first frames 2a, 2a. Further, the sub-columns 18 (18a, 18b) extend parallel to the first frame 2a (in the X direction) and connect the second frame 2b and the column 4. As shown in FIG. The interiors of the surrounding portions 10a and 10b are each divided into four by the sub-pillar portions 16 and 18, and are divided into a total of eight square openings 120a and 120b. Even in this form, thermal bridges (secondary columns 16, 18) are formed from the center of the surrounding part 10 to the ends of the surrounding part 10, and the in-plane temperature distribution of the setter can be reduced. In addition, in the baking rack 150, the sub-pillars 14a (see FIG. 1) may be provided instead of the sub-pillars 16a and 18a in the surrounding part 10a without changing the structure inside the surrounding part 10b.

(Third embodiment)
In the baking rack 250 shown in FIG. 5, the outer shape of the frame 2 is ring-shaped in a substantially normal direction. The baking rack 250 includes a first column 4a connecting the first frames 2a, 2a and a second column 4b connecting the second frames 2b, 2b. The first columnar portion 4a extends in the Y direction (parallel to the second frame portion 2b), and the second columnar portion 4b extends in the X direction (parallel to the first frame portion 2a). Four surrounding parts 10 (10a, 10b, 10c, 10d) are formed in the frame 2 by the pillars 4a, 4b. Inside each surrounding portion 10, there are four sub-pillars 14 (14a, 14b, 14c, 14d) extending from the center 12 (12a, 12b, 12c, 12d) of each surrounding portion 10 toward the top of each surrounding portion 10. is provided. As a result, the baking rack 250 has a total of 16 triangular openings 20 (20a, 20b, 20c, 20d) formed in the frame 2. As shown in FIG. The structure of each surrounding portion 10 (the form of the frame body 2, the column portion 4, and the sub-column portion 14 that constitute the surrounding portion 10) is the same.

In the baking rack 250, the protrusions 24 are provided at the four corners of the baking rack 250, and the protrusions 26 are provided at both ends of the pillar 4b and the center of the pillar 4b (the center 6 of the baking rack 250). , which is also the center of the column portion 4a). As a result, the baking rack 250 is formed with four setter arrangement areas 30 (30a, 30b, 30c, 30d). That is, four setters can be arranged in one baking rack 250 . Each setter placement area 30 includes one surrounding portion 10 . As described above, the structure of each surrounding portion 10 (10a, 10b, 10c, 10d) is the same. Therefore, the structure of each setter arrangement area 30 (30a, 30b, 30c, 30d) is also the same. Incidentally, in the baking rack 250, sub-pillars 16 and 18 (see FIG. 4) may be provided instead of the sub-pillars 14 for any or all of the surrounding parts 10a, 10b, 10c, and 10d. Alternatively, the projecting portion 26 may be removed and one or two setters may be arranged in one baking rack 250 (one or two setter arrangement areas may be arranged).

(Fourth embodiment)
In the baking rack 350 shown in FIG. 6, the outer shape of the frame 2 is ring-shaped in a substantially positive direction, and the opposing apexes of the frame 2 (the intersections of the first frame portion 2a and the second frame portion 2b) are connected to each other. It is provided with a first columnar portion 304a and a second columnar portion 304b connecting vertexes different from the vertexes connected by the first columnar portion 304a. That is, in the baking rack 350, the pillars 304a and 304b extend in a direction different from that of the frame 2 (the first frame 2a and the second frame 2b). In the baking rack 350, four triangular surrounding parts 310 (310a, 310b, 310c, 310d) are formed in the frame 2 by the pillars 304a, 304b. Within each surrounding portion 310, there are three sub-columns (one sub-column 15 and two A single sub-column 17) is extended. The sub-column 15 extends from the center 312 toward the intersection of the columns 304a and 304b (toward the center 6 of the baking rack 350). The sub-column 17 extends from the center 312 toward the intersection of the column 304 and the frame 2 . Three triangular openings 21 , 22 , 23 are formed in each enclosing part 310 , and a total of 12 openings 21 , 22 , 23 are formed in the frame 2 . The structure of each surrounding portion 310 (the form of the frame 2, the column portion 304, and the sub-column portions 15 and 17) is the same.

In the baking rack 350, the projections 24 and 26 are provided at substantially the same positions as the baking rack 250 (see FIG. 5 for comparison). Specifically, the protrusions 24 are provided at the four corners of the baking rack 350, and the protrusions 26 are positioned between the intersection of the pillars 304a and 304b (the position including the center 6 of the baking rack 350) and the second frame 2b. is provided at the midpoint of the longitudinal direction (Y direction). As a result, the baking rack 350 is formed with four setter arrangement areas 30 (30a, 30b, 30c, 30d) at the same positions as the baking rack 250 (FIG. 5). Therefore, in the baking rack 350 , each setter arrangement area 30 is composed of a part of two surrounding parts 310 . However, since the structure of each surrounding part 310 is the same, the structure of each setter arrangement area 30 is also the same as a result. In the baking rack 350, the protruding portion 26 may be removed, and one or two setters may be arranged in one baking rack 350 (one or two setter arrangement areas may be arranged). .

In any of the baking racks 50, 150, 250, and 350 described above, a column (column 4, 304) passing through the center 6 of the frame 2 and extending between the frames 2 is provided in the frame 2 having an opening. is provided, and in the surrounding part (surrounding part 10, 310) surrounded by the frame 2 and the column part (pillar part 4, 304), the center of the surrounding part (center 12, 312) to the end part of the surrounding part ( It has a common feature of having a plurality of sub-columns (sub-columns 14, 15, 16, 17, 18) extending toward the frame 2 and the columns). As a result, during firing, the temperature difference (difference in temperature followability) between the center of the surrounding portion and the end portion of the surrounding portion is reduced, and the in-plane temperature distribution of the setter can be reduced.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. In addition, the technical elements described in this specification or in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

2: Frame 4: Column 6: Center of frame 10: Surrounding part 14: Secondary column 32: Flat setter 50: Firing rack 60: Firing jig

Claims (4)

A firing jig comprising a flat setter on which an object to be fired is placed and a firing rack on which the flat setter is arranged,
The baking rack is
a frame on which the flat setter is arranged and which has an opening;
a pillar portion passing through the center of the frame and extending between the frames;
a plurality of surrounding parts surrounded by the frame and the pillars;
a plurality of sub-columns extending from the center of the surrounding portion toward the frame or the column;
with
The flat setter is supported by all of the frame, the column and the sub-column,
Both the firing rack and the flat setter are made of the same material selected from alumina, mullite, zirconia, silicon nitride and silicon carbide,
The surface of the frame is provided with a plurality of projecting portions arranged to surround each of the surrounding portions so as to regulate the position of the flat setter,
A jig for baking, wherein the back surface of the frame body is provided with a recess for accommodating each of the tip portions of the plurality of protrusions. 2. A firing jig according to claim 1, wherein each of said surrounding portions has the same polygonal shape. 3. The firing jig according to claim 1, wherein the extending direction of the column and the extending direction of the sub-column are different. 4. The firing jig according to any one of claims 1 to 3, wherein the firing rack and flat setter are made of silicon carbide.

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