JP2009241400A - Calcined ceramic body and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calcined ceramic body having a hollow, bottomed and cylindrical shape into which an object with an outer dimension slightly smaller than the inner diameter of the cylindrical shape is easily insertable in the hollow part. <P>SOLUTION: The calcined ceramic body with an open cylindrical shape 4 is obtained using a dry CIP molding method, wherein the cylindrical shape is thicker in the periphery of the open end than in the depth side (inner side away from the open end) and has a flare inside the periphery of the open end. After the calcination, the body is cut at the AA chain line, with the second thick walled part 2 removed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ceramic fired body having an open cylindrical portion and a method for manufacturing the ceramic fired body.

  Cylindrical ceramic fired bodies are used in various applications including furnace tubes and heating component supports. Such a ceramic fired body is produced by molding a ceramic material by a forming means to obtain a cylindrical ceramic molded body and firing it.

  The present invention is based on the technology relating to such a cylindrical ceramic fired body. For example, Patent Literature 1 is cited as an example of prior literature based on the same technology.

JP-A-4-108670

  In a firing process for obtaining a cylindrical ceramic fired body, generally, a method is employed in which a ceramic shaped body having the same shape is obtained and fired while standing vertically with its open end down. However, in this method, the opening is narrowed due to deformation during firing of the ceramic molded body, which may cause a problem.

  2A and 2B are diagrams illustrating an example of a mullite tube (conventional ceramic fired body). FIG. 2B is a cross-sectional view showing a cylindrical portion including an open end of a mullite tube 20 that is a fired ceramic fired body 20b (sintered body), and FIG. 3 is a cross-sectional view illustrating a stage of a ceramic molded body 20a before firing the mullite tube 20. FIG. In order to ensure the strength required for the product, the mullite tube 20 adopts a mode in which the thickness (the thickness of the substantial portion) in the vicinity of the opening end is increased (preferably increased in two stages) while keeping the opening diameter the same. In some cases, FIGS. 2A and 2B show a mullite tube of that form.

  As shown in FIG. 2A, at the stage of the ceramic molded body 20a, the vicinity of the opening end corresponding to the first thick portion 21 and the second thick portion 22, and the first thick portion 21 and the second thick portion 21. The ceramic obtained by firing as shown in FIG. 2B even if the inner diameter D21 is the same on the back side corresponding to the thin portion 23 where the thickness of the substantial portion is relatively thin with respect to the thick portion 22. In the fired body 20b, a portion having an inner diameter D32 smaller than the inner diameter D31 on the back side is formed in the vicinity of the opening end. In the mullite tube 20 (ceramic fired body 20b), it is possible to remove the second thick portion 22 by cutting at the BB chain line portion (see FIG. 2B), but in order to ensure the strength required for the product. Since the provided first thick portion 21 cannot be removed, the portion that becomes the inner diameter D32 remains, and the problem that the inner diameter of the pressed portion near the opening end is smaller than the inner diameter of the inner thin portion is not solved. .

  If the ceramic fired body has an open hollow part and a thick wall, as well as a ceramic fired body with a hollow and bottomed cylindrical shape, such as a mullite tube, the above problems will be faced. It is thought that there is a risk. The present invention has been made in view of such circumstances, and the problem is that an object having an outer dimension slightly smaller than the inner diameter of the cylindrical portion can be easily inserted into the hollow portion of the cylindrical portion. Another object is to provide a ceramic fired body having an open cylindrical portion. As a result of repeated research, it has been found that the above problems can be solved by the following means.

  That is, first, according to the present invention, the cylindrical portion has an opening, and the cylindrical portion is thicker in the vicinity of the opening end than the back side (inside away from the opening end), and in the vicinity of the opening end. A ceramic fired body having an expanded inner surface side is provided.

  Next, according to the present invention, after obtaining a ceramic molded body having an opened cylindrical portion and expanding the inner surface side near the opening end of the cylindrical portion, the ceramic molded body is fired, Provided is a method for manufacturing a ceramic fired body in which a ceramic fired body is obtained in which the vicinity of the opening end of the cylindrical portion is thicker than the back side.

  In the method for producing a ceramic fired body according to the present invention, it is preferable to use a dry CIP (Cold Isostatic Pressing) forming method when expanding the vicinity of the opening end (of the ceramic formed body).

  In the ceramic fired body and the method for producing the ceramic fired body according to the present invention, mullite and alumina are particularly preferable as the ceramic material constituting the ceramic fired body. In addition, as ceramic materials constituting the ceramic fired body, for example, oxide ceramics containing rare earth element oxides such as zirconia, titania, silica, magnesia, ferrite, cordierite, yttria, barium titanate, strontium titanate , Lead zirconate titanate, rare earth element manganite, rare earth element chromite, aluminum nitride, silicon nitride, sialon, silicon carbide, boron carbide, tungsten carbide, and the like.

  In this specification, that the vicinity of the opening end (in the opened cylindrical portion) is thicker than the back side means that the substantial part of the cylindrical portion is thicker in the vicinity of the opening end than the back side. Further, in this specification, the inner surface side in the vicinity of the opening end is expanded. The hollow portion (internal space portion) in the cylindrical portion (formed by the substantial portion) is larger than the opening end. It means that it is expanded in the vicinity (a portion including the opening (the portion where the hollow portion is connected to the external space) and close to the opening), and the substantial portion of the cylindrical portion is formed so as to be so. An inner surface refers to the surface of the substantial part with respect to the hollow part (space part) in a cylindrical shape part. In the present specification, the fact that the inner surface side in the vicinity of the opening end is expanded also simply means that the vicinity of the opening end is expanded. That is, in the ceramic fired body according to the present invention, the cylindrical portion has an opening end thicker and wider than the back side.

  The ceramic fired body according to the present invention has a cylindrical portion that is open (internally hollow), and the cylindrical portion is thicker and wider than the back end in the vicinity of the opening end. ), An object having an outer dimension slightly smaller than the inner diameter of the cylindrical portion can be easily inserted. If a part with an inner diameter smaller than the inner diameter on the back side is formed near the opening end, even if the smaller inner diameter is larger than the outer dimension of the object and the object can be accommodated in the hollow part of the cylindrical part, it is inserted. Comes with difficulties. Since ceramics is a brittle material, if the object to be inserted is a metal product, the metal product collides with the inner surface of the cylindrical part that is a part of the ceramic fired body, resulting in a chipping (debris) in the cylindrical part. May occur and the ceramic fired body may not be usable as a product. In particular, when an external force is applied to the corner of the opening end face, a defect is easily generated. In order to avoid this, careful insertion work must be performed with great care. According to the ceramic fired body according to the present invention, it is difficult for an object to collide with the end face of the cylindrical portion at the time of insertion, and a defect is not easily generated. In addition, the operation is much easier than before.

  The method for manufacturing a ceramic fired body according to the present invention includes a ceramic molded body having an open cylindrical shape (with a hollow interior) and having an enlarged vicinity of the open end of the cylindrical shaped portion, and then forming the ceramic molded body. Since the body is fired to obtain a ceramic fired body in which the vicinity of the opening end of the cylindrical part is thicker than the back side, the firing shrinkage rate due to firing of the thick part near the opening end is thicker because the vicinity of the opening end is thicker than the back side. However, it is possible to make the inner diameter after firing at least equal to or larger than the inner diameter on the back side of the cylindrical portion even if it is larger than other parts (thin wall portion on the back side of the cylindrical portion). . Therefore, in the obtained ceramic fired body, an object having an outer dimension slightly smaller than the inner diameter of the cylindrical portion can be easily inserted into the hollow portion of the cylindrical portion. Since the obtained ceramic fired body does not become unusable as a product, the yield is improved (occurrence of defective rate is suppressed).

  As described above, conventionally, a method has been adopted in which the ceramic molded body is fired upright with the opening end down, but in this case, in order to ensure the strength near the opening end, the cylindrical portion In order to obtain a ceramic fired body in which the vicinity of the opening end is thicker than the back side, the firing shrinkage ratio (or the amount of deformation due to shrinkage during firing) of the portion that is in direct contact with the stand is reduced and the inner diameter is On the other hand, the firing shrinkage rate of the thick-walled portion that is not in direct contact with the baking table or the like but is in the vicinity of the opening end is increased and the inner diameter is decreased. The firing shrinkage rate gradually decreases as the distance from the opening end increases and the inner side increases. For this reason, the inner diameter of the cylindrical portion of the obtained ceramic fired body is not uniform, and it is difficult to easily insert an object whose outer dimension is slightly smaller than the inner diameter of the cylindrical portion into the hollow portion of the cylindrical portion. . According to the method for manufacturing a ceramic fired body according to the present invention, it is possible to avoid such a problem.

  In many cases, the roundness of the ceramic fired body is reduced by firing, and it is difficult to expand the inner diameter by means such as machining with respect to the ceramic fired body whose inner diameter is not uniform. In the method for manufacturing a ceramic fired body according to the present invention, a shape with an inner diameter expanding toward the end face can be obtained without performing a process of expanding the inner diameter after firing, which is also advantageous in this respect.

  In a preferred embodiment of the method for producing a ceramic fired body according to the present invention, when the vicinity of the opening end (of the ceramic formed body) is expanded, a dry CIP forming method is used. In the dry CIP molding method, the surface of the ceramic molded body forming the hollow portion can be molded by transferring the shape of the molding mandrel to the ceramic molded body. Therefore, as long as the molding mandrel is manufactured in a desired shape, the vicinity of the opening end can be expanded with high accuracy. Before firing the ceramic molded body, as a method of expanding the inner diameter in the vicinity of the opening end, there is a method of polishing by machining other than the dry CIP molding method, but a grinding wheel having a diameter smaller than the inner diameter of the ceramic molded body is used. Since it is necessary to insert and polish, processing time becomes long and productivity becomes low. In addition, it is difficult to machine with good coaxiality.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate, but the present invention should not be construed as being limited thereto. Various changes, modifications, improvements, and substitutions can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention. For example, the drawings show preferred embodiments of the present invention, but the present invention is not limited by the modes shown in the drawings or the information shown in the drawings. In practicing or verifying the present invention, the same means as described in this specification or equivalent means can be applied, but preferred means are those described below.

  1A and 1B are views for explaining an embodiment of a method for producing a ceramic fired body according to the present invention, and FIG. 1B shows an embodiment of the ceramic fired body according to the present invention. FIG. 1A and 1B are views corresponding to FIGS. 2A and 2B, and are cross-sectional views showing a cylindrical portion including an open end of a mullite 5 having a bottomed cylindrical shape. FIG. 1A shows the stage of the ceramic molded body 5a before firing, and FIG. 1B shows the stage of the ceramic fired body 5b (sintered body) after firing. In FIGS. 1A and 1B, as in FIGS. 2A and 2B, a state in which firing is performed vertically with the open end down is shown.

  As shown in FIG. 1B, the mullite tube 5 (ceramic fired body 5 b) after firing has an open cylindrical part 4, and the cylindrical part 4 includes the first thick part 1 and the second thick part 1. The vicinity of the opening end constituted by the thick part 2 is thicker than the back side constituted by the thin part 3. The mullite tube 5 is expanded in the vicinity of the opening end formed by the first thick portion 1 and the second thick portion 2. The second thick part 2 occupies about 10 to 30 mm from the end face of the opening (in the axial direction of the cylindrical part 4 (up and down in FIG. 1B)), and preferably occupies a range of about 20 mm. The 1st thick part 1 occupies about 10-30 mm following the 2nd thick part 2, Preferably it occupies the range of about 20 mm.

  When the mullite tube 5 is normally used as a product for a furnace tube, a heating component support or the like, the mullite tube 5 is cut off at the AA chain line portion and the second thick portion 2 is removed (see FIG. 1B). The first thick part 1 is left to ensure the required strength. Even in the mullite tube 5 after the second thick part 2 is removed, the opened cylindrical part 4 has an inner diameter in the vicinity of the opening end constituted by the first thick part 1, but the thin part 3. It can be made larger than the back side.

A method of manufacturing such a mullite tube 5 is as follows. First, for example, α-Al ₂ O ₃ powder raw material, SiO ₂ is prepared at a ratio that mullite can be produced, and uniformly mixed to obtain a slurry. Next, the slurry is dried to obtain a granulated product, and then the tube is formed in a desired size and thickness (bottomed cylindrical shape) using a dry CIP molding apparatus and a molding mandrel. A ceramic molded body 5a is obtained.

  At this time, the first thick portion 1 and the second thick portion 2 are provided in the vicinity of the opening end of the cylindrical portion 4, and the thickness is increased in two stages. The first thick portion 1 is provided to give the strength required as a ceramic product so that the obtained mullite tube can be used as a product in a furnace tube, a heating component support, or the like. The thick portion 2 is provided in order to reduce shrinkage deformation during subsequent firing.

  And it is important to make the shape of the cylindrical portion 4 not the shape of a straight tube, but a shape expanded on the opening end side. That is, the inner diameter D2 near the opening end constituted by the first first thick portion 1 and the second thick portion 2 of the cylindrical portion 4 is made larger than the inner diameter D1 on the back side. In the ceramic molded body 5a shown in FIG. 1A, the inner diameter D2 on the opening end side (including the second thick part 2) from the approximate center of the first thick part 1 is made larger than the inner diameter D1 on the back side. Yes (expands). The inner diameter difference d (see FIG. 1A, = D2-D1) is preferably 0.5 to 2.5 mm, more preferably 1.0 to 2.0 mm, and 1.5 mm. Is particularly preferred. The inner diameter difference d is preferably 1 to 4% of the inner diameter D1 on the back side, more preferably 2 to 3%, and particularly preferably 2.5%. preferable.

  Next, the ceramic molded body 5a is fired at 1500 ° C. for 60 minutes to obtain a ceramic fired body 5b (see FIG. 1B). Then, using a grinding device using a diamond blade, the mullite tube 5 that can be used as a product for a furnace tube, a heating component support, or the like is obtained by cutting away at the AA chain line portion and removing the second thick portion 2. can get.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

  Example 1 First, a ceramic molded body 5a shown in FIG. 1A was obtained using a dry CIP molding apparatus and a molding mandrel.

  FIG. 1C is a cross-sectional view showing a molding mandrel used for molding. In the molding mandrel 35 shown in FIG. 1C, the length L1 (height) was set to 570 mm. Then, from the top (uppermost in FIG. 1C) to the position of 46 mm with reference to the bottom (lowermost in FIG. 1C) (L2 = 46 mm), the diameter d41 is φ64.45 mm, and the diameter gradually increases toward the bottom. At a position 23 mm from the bottom (L3 = 23 mm), the diameter d42 was set to φ65.20 mm which was 0.75 mm larger than that, and the diameter from the position to the bottom was kept at φ65.20 mm.

  Since the amount of elastic recovery during CIP molding is added, the inner diameter of the ceramic molded body 5a is slightly larger than the diameter (outer diameter) of the molding mandrel 35. Specifically, the inner diameter of the ceramic molded body 5a is about 0.4 to 0.5% larger than the diameter of the molding mandrel 35. In this example, the diameter is increased by 0.45% (about 0.3 mm), and the inner diameter D1 of the ceramic molded body 5a is φ64.75 mm, which is 0.3 mm larger than the diameter d41 (= φ64.45 mm) of the molding mandrel. The inner diameter D2 of the ceramic molded body 5a is φ65.50 mm, which is 0.3 mm larger than the diameter d42 (= φ65.20 mm) of the molding mandrel.

  The thickness of the thin portion 3 of the ceramic molded body 5a is 2.05 mm (= (outer diameter φ68.85 mm−inner diameter D1φ64.75 mm) / 2). The thickness of the first thick portion 1 is 3. 65 mm (= (outer diameter φ72.8 mm−inner diameter D2φ65.50 mm) / 2), and the thickness of the second thick part 2 is 6.75 mm (= (outer diameter φ79.0 mm−inner diameter D2φ65.50 mm). / 2). The length of the 1st thick part 1 was 12 mm, and the length of the 2nd thick part 2 was 18 mm.

  Next, the ceramic molded body 5a having the above dimensions was fired to obtain a mullite tube (ceramic fired body 5b shown in FIG. 1B). The inner diameter of the thin part 3 of the obtained mullite tube (ceramic fired body 5b) was 56.00 mm, and the inner diameter of the first thick part 1 was 56.30 mm. The inner diameter D12 of the first thick part 1 could be made larger than the inner diameter D11 of the thin part 3.

  (Comparative Example 1) According to Example 1, using a dry CIP molding device and a molding mandrel, a ceramic molded body 20a shown in FIG. 2A was obtained.

  FIG. 2C is a cross-sectional view showing a molding mandrel used for molding. In the molding mandrel 45 shown in FIG. 2C, the length (height) was 570 mm, and the diameter d51 was φ64.45 mm.

  Since the amount of elastic recovery during CIP molding is added, the inner diameter of the ceramic molded body 20a is slightly larger than the diameter (outer diameter) of the molding mandrel 45. Specifically, the inner diameter of the ceramic molded body 20a is about 0.4 to 0.5% larger than the diameter of the molding mandrel 45. In this example, the diameter is increased by 0.45% (about 0.3 mm), and the inner diameter D21 of the ceramic molded body 20a is uniformly 0.3 mm larger than the diameter d51 (= φ64.45 mm) of the molding mandrel. It became 75 mm.

  The thickness of the thin portion 23 of the ceramic molded body 20a is 2.05 mm (= (outer diameter φ68.85−inner diameter D21φ64.75) / 2), and the thickness of the first thick portion 21 is 4. 025 mm (= (outer diameter φ72.8 mm−inner diameter D21 φ64.75 mm) / 2), and the thickness of the second thick portion 22 is 7.125 mm (= (outer diameter φ79.0 mm−inner diameter D21 φ64.75 mm). / 2).

  Next, the ceramic molded body 20a having the above dimensions was fired to obtain a mullite tube (ceramic fired body 20b shown in FIG. 2B). An inner diameter D31 of the thin portion 23 of the obtained mullite tube (ceramic fired body 20b) was 56.00 mm, and an inner diameter D32 of the first thick portion 21 was 55.75 mm. The inner diameter D32 of the first thick part 21 is 0.25 mm smaller (narrower) than the inner diameter D31 of the thin part 23.

  (Consideration) In Comparative Example 1, when the ceramic molded body 20a is fired, the second thick part 22 is thicker (larger) than the thin part 23, so that the shrinkage rate due to firing is increased. Although the inner diameter D33 of the thick wall portion 22 seems to be smaller than the inner diameter D31 of the thin wall portion 23, this is not the case. This is considered to be because the shrinkage is hindered by the frictional resistance with the baking table. Actually, the inner diameter D33 of the second thick portion 22 is larger than the inner diameter D31 of the thin portion 23 (FIG. 2B). See). That is, in appearance, the opening of the mullite tube (ceramic fired body 20b) appears to expand.

  However, the effect of inhibiting the shrinkage due to the frictional resistance is reduced as the distance from the baking table is reduced, and therefore, the first thick part 21 has no effect, and the shrinkage rate due to the thick (large) thickness is reduced. The larger effect will contribute. Therefore, it is considered that the inner diameter D32 of the first thick part 21 is smaller than the inner diameter D31 of the thin part 23 (see FIG. 2B).

  On the other hand, in Example 1, since the vicinity of the opening end is expanded from the back side at the stage of the ceramic molded body 5a, the inner diameter of the first thick portion 1 in the mullite tube (ceramic fired body 5b). It is considered that D12 did not become smaller than the inner diameter D11 of the thin portion 3.

  The ceramic fired body according to the present invention can be used as a product, for example, in a furnace tube or a heating component support. The method for producing a ceramic fired body according to the present invention can be suitably used as a means for producing these ceramic fired bodies according to the present invention.

It is a figure for demonstrating one Embodiment of the manufacturing method of the ceramic sintered body which concerns on this invention, and is sectional drawing showing the stage of the ceramic molded object before baking. 1 is a cross-sectional view illustrating an embodiment of a ceramic fired body according to the present invention. It is sectional drawing showing the mandrel for shaping | molding used in the Example (Example 1). It is a figure for demonstrating an example of the manufacturing method of the conventional ceramic sintered compact, and is sectional drawing showing the stage of the ceramic molded object before baking. It is sectional drawing showing an example of the conventional ceramic sintered compact. It is sectional drawing showing the mandrel for shaping | molding used in the Example (comparative example 1).

Explanation of symbols

1, 2: 1st thick part, 2, 22: 2nd thick part, 3, 23; Thin part, 4: Cylindrical part, 5, 10, 20: Mullite tube.

Claims (3)

  A ceramic fired body having an opened cylindrical portion, the cylindrical portion being thicker in the vicinity of the opening end than the back side, and the inner surface side in the vicinity of the opening end being expanded.   After obtaining a ceramic molded body having an open cylindrical shape portion and expanding the inner surface near the open end of the cylindrical shape portion, the ceramic molded body is fired so that the vicinity of the open end of the cylindrical shape portion is at the back. A method for producing a ceramic fired body that provides a thicker ceramic fired body.   The method for producing a ceramic fired body according to claim 2, wherein a dry CIP forming method is used for expanding the vicinity of the opening end.

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