METHOD AND SYSTEM FOR MANUFACTURING LONG-SIZED SiC TUBE
The described method for manufacturing SiC tubes using slip casting and reaction bonding with clam shell molds and a mandrel addresses inefficiencies in conventional methods, achieving precise control and reduced costs by minimizing shrinkage and enabling complex shapes.
Patent Information
- Application Number
- JP2025076010
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-25
- Filing Date
- 2025-05-01
- Publication Date
- 2025-07-11
AI Technical Summary
Conventional methods for manufacturing long SiC tubes are costly, cumbersome, and inefficient, with issues such as shrinkage, non-uniform thickness, and difficulty in controlling wall thickness and shape complexity.
A method involving slip casting and reaction bonding processes using clam shell molds and a mandrel to form SiC tubes, utilizing an organic release layer to facilitate removal and achieve precise control of inner and outer diameters, reducing shrinkage and enabling complex shapes.
The method allows for the production of SiC tubes with improved tolerances and reduced costs by minimizing shrinkage and enabling variable inner diameters, thus overcoming the limitations of conventional methods.
Smart Images
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Abstract
Description
Technical Field
[0001]
[0001] This disclosure generally relates to methods and systems for manufacturing long SiC tubes.
Background Art
[0002]
[0002] Aspects of this disclosure relate to methods and systems for manufacturing long SiC tubes. Conventional solutions for manufacturing long SiC tubes may have various problems. In this regard, conventional systems and methods for manufacturing long SiC tubes may be costly, cumbersome, and / or inefficient.
[0003]
[0003] The limitations and drawbacks of conventional systems and methods will become apparent to those skilled in the art through a comparison of such approaches with some aspects of the methods and systems of this disclosure described in the remainder of this disclosure with reference to the drawings.
Summary of the Invention
Means for Solving the Problems
[0004]
[0005] Shown and / or described in connection with at least one of the drawings and more fully set forth in the claims are methods and systems for manufacturing long SiC tubes.
[0005]
[0006] These and other advantages, aspects, and novel features of this disclosure, as well as details of its illustrated embodiments, will be more fully understood from the following description and the drawings.
[0006]
[0007] The various features and advantages of this disclosure can be more readily understood by reference to the following detailed description, which is to be interpreted in conjunction with the accompanying drawings. In the drawings, the same reference numerals indicate the same structural elements.
Brief Description of the Drawings
[0007]
Figure 1
[0008] A diagram showing an exemplary slip casting process.
Figure 2
[0009] A diagram showing a reaction bonding process for obtaining a silicon carbide component.
Figure 3
[0010] A diagram showing an exemplary mold assembly including two clam shell molds and a mandrel.
Figure 4
[0011] A diagram showing an assembled mold attached to a movable jig and held in a vertical state.
Figure 5
[0012] A diagram showing an assembled mold attached to a movable jig and held in a horizontal state.
Figure 6
[0013] A diagram showing the removal of a mandrel from a mold in a horizontal state.
DETAILED DESCRIPTION OF THE INVENTION
[0008]
[0015] The following discussion provides various examples of methods and systems for manufacturing a long SiC tube. Such examples are non-limiting, and the appended claims should not be limited to the specific examples disclosed. In the following discussion, the terms "example" and "for example" are non-limiting.
[0009]
[0016] The drawings illustrate a general manner of construction, and well-known features and techniques may be omitted in order to avoid unnecessarily obscuring the present disclosure. In addition, the elements of the drawings are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be exaggerated relative to other elements in order to improve the understanding of the examples discussed in the present disclosure. The same reference numerals in different drawings indicate the same elements.
[0010]
[0017] The term "or" means any one or more of the items in a list joined by "or". As an example, "x or y" means any element of the three-element set {(x), (y), (x, y)}. As another example, "x, y, or z" means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}.
[0011]
[0018] The terms "comprises", "comprising", "includes", and / or "including" are "open ended" terms that specify the presence of the stated features but do not preclude the presence or addition of one or more other features.
[0012]
[0019] Terms such as "first", "second", etc. may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, for example, a first element discussed in the present disclosure may be referred to as a second element without departing from the teachings of the present disclosure.
[0013]
[0020] Unless otherwise specified, the term "connected" is used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements. For example, if element A is connected to element B, element A may be in direct contact with element B or may be indirectly connected to element B by intervening element C. Similarly, the terms "over" or "on" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements.
[0014]
[0021] In the industry, ceramic tubes can be frequently used due to their wide range of applications. For example, ceramic tubes can be used in kiln equipment, precision structures, burners, high-temperature fluid or gas pipes (e.g., petrochemical industry), highly corrosive and / or high-wear slurry flows (e.g., for mining or oil sands), rollers, thermocouple protection, nuclear industry, and heat treatment.
[0015]
[0022] Ceramics can be any one of a variety of hard, brittle, heat-resistant, and corrosion-resistant materials produced by shaping inorganic materials and firing them at high temperatures. Such materials may include not only clay but also carbon and silicon. Well-known examples can be earthenware, porcelain, and bricks. In industry, ceramics are used because of their ability to withstand chemical erosion that occurs when other materials are exposed to acidic or caustic environments. Ceramics can also withstand high temperatures.
[0016]
[0023] The ceramic tube may be made of, for example, sintered SiC (silicon carbide), mullite, or Al2O3 (IPS ceramic). The manufacturing method can be a method of slip-casting a ceramic particle preform and then sintering it.
[0017]
[0024] Referring now to FIG. 1, FIG. 1 shows an exemplary slip-casting process. The slip-casting process 100 and exemplary steps in the slip-casting process from step 1 to step 4, which indicate the steps in time, are shown. Containers 110 and 160b, suspensions / slips 120, 120a, 120b, first mold parts 130, 130a, 130b, 130c, second mold parts 140, 140a, 140b, 140c, cakes 150a, 150b, 150c are shown. Reference numerals without appended letters may refer to step 1, and reference numerals with appended letters a - c may refer to steps 2 - 4 respectively. Elements with the same reference numeral may refer to the same element.
[0018]
[0025] In step 1, an aqueous suspension / slip 120 containing fine ceramic particles may be poured from a container 110 into a mold. The mold may preferably comprise a first mold part 130 and a second mold part 140 connected to each other. The mold parts 130, 140 may be made of a porous material, for example, plaster or polymer. The suspension 120 may be a liquid or semi-liquid (paste / gel-like) material containing fine ceramic particles homogeneously suspended in a liquid. Carbon or a suitable pH balance may help keep the particles homogeneously suspended in the suspension 120. The suspension 120 may sometimes be called a slip or a slurry.
[0019]
[0026] Since the mold is made of a porous material that acts hydrophilically, in step 2, some of the water in the suspension 120a can be absorbed from the suspension 120 into the first mold 130a and the second mold 140a. Absorption of moisture from the suspension 120a into the mold can cause the formation of a "densified cake" 150a on the mold walls. The formed cake 150a contains a layer of ceramic particles on the mold walls and has a relatively low water content.
[0020]
[0027] In step 3, the remaining excess suspension 120b may be poured out of the mold into some container 160b. As a result, the cake 150b may remain on the mold walls. In step 4, the first mold part 130c and the second mold part 140c may be separated, and the slip-cast part 150c may be removed from the mold. The slip-cast part 150c may sometimes be called a formed cake or a preform at this stage. Then, the slip-cast part 150c may be sintered, i.e., fired. A dense ceramic cast part may be obtained by the sintering process.
[0021]
[0028] In the slip casting process 100, it may be troubled by many problems inherent in the process. For example, the sintering process may shrink the slip cast part 150c by about 20%. Further, assuming a substantially uniform porous mold that results in similar water absorption throughout the mold surface, the slip casting process 100 may be suitable only for shapes having a constant wall thickness because the cake grows uniformly along the mold wall. In addition, since there is no mold element for controlling the thickness other than the absorption action, the thickness of the cake 150c may not be accurately controlled. The thickness of the cake 150c can typically be within an accuracy of 1 mm. Another problem is that the suspension 120 may preferably contain fine ceramic particles homogeneously suspended. In order to obtain a suspension 120 that remains homogeneous over a period of time, i.e., the fine ceramic particles do not settle to the bottom of the mold, it can be formulated only using a small amount of organic additives. This is also due to the requirement that the organic additives must not clog the molds 130, 140. Clogging of the molds 130, 140 may limit the absorption action of the molds that extract water and as a result form the cake 150a.
[0022]
[0029] Figure 2 shows an exemplary process for manufacturing reaction-bonded silicon carbide. Insertion view A corresponding to the first step and insertion view B corresponding to the second step are shown. Reaction-bonded silicon carbide (RB-SiC or SiSiC) parts can be manufactured as described below with reference to insertion view A and insertion view B. Referring to insertion view A, a preform 200 is shown that includes SiC particles 210 and carbon particles 220. The preform for reaction bonding 200 can typically be manufactured by casting a slurry / suspension that includes SiC particles 210, carbon particles 220, and an organic material (not shown) that can be converted to carbon by pyrolysis, such as phenols. As will be apparent to those skilled in the art, there are many other suitable compositions and variations of the slurry, and the present disclosure is not limited to the slurry composition disclosed above.
[0023]
[0030] Next, the preform cake 200 can be infiltrated with molten silicon. The molten silicon can act as both a reagent and a binder. Upon infiltration, the molten silicon reacts with the carbon 220 to form a reaction-formed SiC 240, as shown in the inset B, and joins the structure. As shown in the inset B, the final composite material may include the original SiC particles 210, the reaction-formed SiC 240, and the residual silicon 230. The composite material RB-SiC may have the advantage of not nominally shrinking during this process. A further advantage is the use of coarse SiC particles 210, because in this process it may be desirable for the particles to settle to the bottom of the mold. In contrast to slip casting, which requires a suspension containing uniformly suspended particles, in reaction bonding it is desirable for the particles and water to separate when the slurry enters the mold.
[0024]
[0031] As described above, sintering can nominally shrink slip-cast parts by 20%. Correspondingly, the slip-casting tube may nominally shrink by 20% during the sintering process, thereby becoming shorter. Without such shrinkage, longer tubes could be produced for a given furnace size. As described above, reaction bonding does not show nominal shrinkage, so reaction-bonded SiC tubes do not shrink like sintered tubes. Since reaction bonding does not significantly shrink the cast parts, defects caused by shrinkage such as cracks and internal stresses are less of a concern, enabling the manufacture of more complex shapes.
[0025]
[0032] Reaction bonding uses relatively coarse ceramic particles 210 that precipitate rapidly (by Stokes' law) in the slurry, so slip casting may not be a suitable technique for obtaining a reaction-bonded preform cake 200. As described above, rapidly precipitating particles, and thus an unstable suspension, are not suitable for slip casting. As a direct result of the unstable suspension, the thickness of the slip-cast part 150c may become non-uniform. Also, reaction bonding may require a high concentration of an organic material (e.g., phenols) in the slurry that can be used to produce carbon upon pyrolysis. This organic matter may clog the porous mold and may not be suitable for slip casting. Here, a suitable process for manufacturing an RB-SiC tube is described.
[0026]
[0033] Figures 3-6 show a preform manufacturing process suitable for an RB-SiC tube. Referring to Figure 3, a first clam shell mold 310, a second clam shell mold 320, and a mandrel 330 are shown. The mold can be formed by connecting the first clam shell mold 310 to the second clam shell mold 320. This mold can define the shape and outer diameter of the tube to be cast. The clam shell molds 310, 320 may be non-permeable, in contrast to the porous molds for slip casting. The mandrel 330, i.e., the core, can be surrounded by the connected clam shell molds 310 and 320 to form an assembled mold. The mandrel 330 can define the inner shape and diameter of the tube to be cast. In contrast, slip casting as shown in Figure 1 does not include a mandrel.
[0027]
[0034] The inner surfaces of the clam shell molds 310 and 320 and the mandrel 330 may all be covered with an organic release layer. The organic release layer may be operable to allow the casting preform to be removed from the mold and removed from the mandrel 330 from the casting preform. to be possible.
[0028]
[0035] According to various embodiments of the present patent, acrylics for a release layer may be sprayed inside the clam shell molds 320 and 330. The acrylic release layer can be attached / burned off at about 160°C. The acrylic release layer may be operable to be burned off when the preform cake hardens so that the casting preform tube can be easily removed from the mold. As is known to those skilled in the art, many other polycarbonates may be suitable for the release layer instead of acrylics.
[0029]
[0036] The mandrel 330 may be covered with a sheet wax layer for the release layer. The sheet wax release layer on the mandrel 330 can melt / burn off at about 80°C. The sheet wax release layer may be operable to burn off before removing the mandrel 330 from the mold.
[0030]
[0037] The mandrel 330 covered with sheet wax may be inserted into the connected molds 310, 320, and both molds may be covered with a sprayed acrylic layer. This assembled mold may form a mold cavity between the mandrel and the mold.
[0031]
[0038] Referring to FIG. 4, an assembled mold 410, a filling opening 420, and a jig 430 are shown. The assembled mold 410 may include clam shell molds 310, 320, and a mandrel 330 as described with reference to FIG. 3. The filling opening 420 may be operable to receive a reaction bonding slurry into the assembled mold 410. The jig 430 may be operable to hold the assembled mold 410 in a desired position. The jig 430 may include wheels, for example, so that it can be moved from the mold assembly to the furnace and further to the mold disassembly. The jig 430 may further include a shaft mounting clamp 440 operable to fix the assembled mold 410 to the jig 430. The shaft mounting clamp 440 may enable the assembled mold 410 to be rotated to the horizontal state shown in FIG. 5. Elements having the same reference numerals shown in FIG. 5 may be identical to those shown in FIG. 4.
[0032]
[0039] Correspondingly, after the assembled mold 410 is attached to the jig 430 and rotated to the desired vertical state shown in FIG. 4, the RB-SiC slurry may be poured into the mold cavity through the filling opening 420. The slurry may then settle to form a hard preform cake.
[0033]
[0040] Since the sheet wax layer may be thicker than the acrylic spray release layer, it may be advantageous to use the sheet wax layer for the release layer on the mandrel 330. Even if the reaction bonding silicon carbide manufacturing process nominally does not shrink the preform 200, the preform 200 may clamp around the mandrel 330 when the slurry settles to form a hard preform cake. Correspondingly, it may be advantageous to use a slightly thicker release layer around the mandrel 330 to more easily remove the mandrel 330 and ensure that the preform 200 does not break / crack during the precipitation process. Applying the sheet wax layer may be more costly and time-consuming than applying the acrylic spray release layer, so generally it may be preferable to use acrylics for the clam shell molds 310, 320.
[0034]
[0041] Next, the rig 430 with the assembly mold 410 may be moved into a heating chamber / furnace (not shown). Inside the furnace, the mold assembly 410 is heated to about 85° C. to melt the sheet wax release layer on the mandrel 330. Next, the rig 430 is removed from the furnace, and the assembly mold 410 may be rotated to the horizontal state shown in FIG. 5. Since the sheet wax layer on the mandrel 330 may have melted, as shown in FIG. 6, the man drel 330 may be removed from the assembly mold 410. According to various embodiments of the present patent, the mandrel 330 may be removed before further heating or after further heating, as described in the next paragraph. Removing the mandrel 330 before further heating may be advantageous with respect to drying time.
[0035]
[0042] Next, the mold assembly 410 may be removed from the rig 430 and placed in a furnace. Inside the furnace, the mold assembly 410 may typically be heated to over 500° C. in nitrogen gas (N2). This heating in an inert gas allows the acrylic release layer on the inner surface of the mold assembly 410 to decompose, and for example, the organic slurry containing phenols to pyrolyze into carbon. Thus, this heating process may result in a casting preform 200 as shown in FIG. 2. As is known to those skilled in the art, any other inert gas or gas mixture may be used, and the present patent disclosure is not limited to the use of nitrogen gas.
[0036]
[0043] Next, the mold 410 may be removed from the furnace, where the assembly mold 410 may be disassembled. Since the acrylic release layer may have decomposed during heating, the preform 200 can be easily removed from the mold by disassembling the clam shell molds 310, 320. As will be apparent to those skilled in the art, the assembly mold 410 may similarly be disassembled in a vertical state.
[0037]
[0044] As described above with respect to FIG. 2, the cast preform 200 including carbon particles 220 and SiC particles 210 may then be infiltrated with molten silicon to obtain a finished reaction-bonded silicon carbide ceramic tube.
[0038]
[0045] Exemplary processes using a mandrel-forming process can allow for better tolerances of about ±0.25 mm, compared to slip casting and sintering that result in tolerances of about ±1 mm. As described above, this is mainly because shrinkage can be avoided. Further, by using the mandrel 330, precise control of the inner diameter becomes possible, and it may be possible to produce cast parts with a variable inner diameter. This is in contrast to slip casting which can only produce a constant wall thickness.
[0039]
[0046] Since the reaction-bonded silicon carbide process can operate at a lower temperature, the described process may also be more cost-effective than slip casting and sintering processes. For example, while a sintering process may require a maximum temperature of about 2000°C, the reaction-bonded silicon carbide process may require a maximum temperature of about 1400°C to melt silicon for the infiltration process. Since the reaction-bonded silicon carbide process uses a lower temperature, the costs of raw materials, machinery, and energy used in the process may be lower than the costs required for slip casting and sintering processes.
[0040]
[0047] Although this disclosure includes references to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of this disclosure. In addition, modifications may be made to the disclosed embodiments without departing from the scope of this disclosure. Accordingly, this disclosure is not intended to be limited to the disclosed embodiments, but is intended to cover all embodiments falling within the scope of the appended claims.
Description of the Reference Numerals
[0041] 200 preform 210 SiC particles 220 Carbon, carbon particles 230 Si, residual silicon 240 Reaction-formed SiC 310 First clam shell mold, clam shell mold 320 Second clam shell mold, clam shell mold 330 Mandrel 410 Assembled mold, mold assembly, mold 420 Filling opening 430 Rig 440 Shaft mounting clamp
Claims
1. A method for casting a preform part for reaction bonding, comprising: coating the inner surface of a mold with a first release layer; coating the surface of a mandrel with a second release layer; inserting the coated mandrel into the coated mold to form an assembled mold, wherein the assembled mold comprises a mold cavity; pouring a slurry into the mold cavity; forming a preform cake by precipitating the slurry in the mold cavity; thermally removing the second release layer; removing the mandrel from the assembled mold; thermally decomposing the organic content of the preform cake into a carbonaceous content; and thermally removing the first release layer .
2. The method according to claim 1, wherein a space between the coated mandrel and the coated mold within the assembled mold forms the mold cavity.
3. The method according to claim 1, comprising thermally removing the second release layer by heating the second release layer above 80°C to melt or burn it off.
4. The method according to claim 1, comprising heating the preform cake and the first release layer above 500°C to achieve the thermal decomposition and thermally removing the first release layer.
5. The method according to claim 1, wherein the step of coating the inner surface of the mold comprises coating the inner surfaces of a plurality of mold parts that form the mold.
6. The method according to claim 1, comprising forming the mold from a plurality of clam shell molds.
7. The method according to claim 5, wherein the plurality of mold parts are clam shell molds.
8. The method according to claim 1, wherein the first release layer is an acrylic layer.
9. The method according to claim 8, comprising spraying the acrylic layer.
10. The method according to claim 1, wherein the second release layer is a sheet wax layer.
11. The method according to claim 1, wherein the first release layer and / or the second release layer is an organic release layer.
12. The method according to claim 1, wherein the slurry is a liquid containing silicon carbide particles and an organic content.
13. The method according to claim 12, wherein the organic-containing substance includes an organic binder. **Claim 14** The method according to claim 1, wherein the preform part is a tube. **Claim 15** The method according to claim 1, comprising the step of infiltrating the preform part with molten silicon to form a reaction-bonded silicon carbide part. **Claim 16** The method according to claim 15, wherein the preform part is a tube. **Claim 17** The method according to claim 1, comprising the step of selecting the separation between the mandrel and the mold in the assembled mold such that the separation is different at different positions of the assembled mold, resulting in preform cakes of different thicknesses.