Forming die and forming method of ceramic matrix composite slender thin-wall shaft part

Abstract

The invention relates to a fiber-containing ceramic product, in particular to a forming die and a forming method of a ceramic matrix composite slender thin-wall shaft part, which are used for solving the problems that an existing preparation method of a ceramic matrix composite slender thin-wall pipe fitting is only suitable for a thin-wall pipe with the diameter smaller than 20mm and cannot meet the requirements of parts with larger sizes; and as the fiber fabric cannot be sewed, the problems of layering and low yield in the forming process are aggravated. The forming mold of the ceramic matrix composite thin-walled shaft part comprises the core mold, the core mold is formed by splicing the multiple sub core molds, demolding operation is simple, the core mold is not affected by sewing fibers when retreating, and the situation that a prefabricated body is layered or cannot be demolded in the demolding process can be effectively avoided.

Description

Technical Field

[0001] The invention relates to a fiber-containing ceramic product, in particular to a molding die and a molding method for a slender thin-walled shaft part made of a ceramic-based composite material. Background Art

[0002] In the chemical vapor deposition molding process of ceramic-based composite materials, it is necessary to use a graphite core mold at high temperature (800-1900°C) for shaping. However, when preparing shaft parts with ultra-long-diameter ratios, due to the size limitations of the parts, the graphite core mold is difficult to remove, making conventional processes inapplicable. This limitation poses a challenge to the production of ultra-long-diameter ratio parts and restricts the application of ceramic-based composite materials in such parts.

[0003] Chinese patent CN115745640A discloses a ceramic-based composite material slender thin-walled tube forming process, which relates to the field of thin-walled tube forming technology, and includes the following steps: preparing fiber fabrics, placing the fiber fabrics into a forming tool for forming, placing the formed fiber fabrics into a shaping tool for shaping, and preparing the shaped fiber fabrics by a vertical hanging method. This process can prevent deformation of the fiber fabrics during the preparation process, achieve uniform wall thickness and straightness to meet the use requirements, and solve the problem of distortion and deformation during the forming process of the fiber fabrics of ceramic-based composite materials with ultra-long-diameter ratio thin-walled tubes.

[0004] Chinese patent CN114057502A discloses a method for preparing a ceramic-based composite material slender thin-walled pipe. First, C f / SiC or SiC f / SiC composite pipe fittings as the middle layer of the target pipe fittings; secondly, the middle layer of the processed ceramic matrix composite thin-walled pipe fittings is immersed in SiC whisker slurry for densification; secondly, SiC ceramic inner layer and SiC ceramic outer layer are prepared on the inner wall and outer wall of the middle layer of the densified ceramic matrix composite thin-walled pipe fittings; finally, the inner layer and outer layer of the prepared pipe fittings are polished. This method overcomes the problem that the existing methods cannot achieve ultra-long-diameter ratio and ultra-thin wall thickness C f / SiC or SiC f C / SiC ceramic matrix composite preform molding and preparation f / SiC or SiC f / SiC ceramic-based composite materials cannot meet the requirements for out-of-pile and in-pile assessments due to their large residual porosity.

[0005] Both of the above methods use a metal core or paper core for shaping, and then pull out the metal core or paper core before preparing the carbon interface layer to complete the preparation of the ultra-long thin-walled tube. However, these methods are only applicable to the preparation of pipe parts with a diameter of less than 20 mm, because if the diameter of the pipe part is more than 20 mm, the surface of the preform will collapse when the core mold is pulled out, and when a metal core or paper core is used, the fiber fabric cannot be sewn, resulting in defects such as delamination during the molding process and use, low yield and limited use. Summary of the invention

[0006] The purpose of the present invention is to solve the problems that the existing method for preparing slender thin-walled pipe fittings of ceramic-based composite materials is only suitable for thin-walled pipes with a diameter of less than 20 mm, cannot meet the needs of parts of larger sizes, and due to the inability to sew fiber fabrics, resulting in stratification and low yield during the molding process, and to provide a molding mold and a molding method for slender thin-walled shaft parts of ceramic-based composite materials.

[0007] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions:

[0008] A forming die for a ceramic-based composite material slender thin-walled shaft part, which is special in that it comprises a tubular core mold, which is composed of a plurality of sub-core molds of equal length, a plurality of sewing grooves uniformly distributed around the circumference and penetrating the core mold are arranged axially on the core mold, and a positioning ring is arranged at both ends and the middle of the inner cavity of the core mold;

[0009] Each of the sewing grooves is at least mm away from both ends of the core mold, and each sewing groove is provided with a plurality of reinforcing plates with a thickness equal to the width of the sewing groove along the length direction, and the distance between each reinforcing plate and the central axis of the core mold is less than the distance between the outer surface of the core mold and the central axis of the core mold.

[0010] Furthermore, the core mold is composed of four sub-core molds of equal length, and the four sub-core molds include a first core mold and a third core mold with the same structure and symmetrically arranged along the axis, and a second core mold and a fourth core mold with the same structure and symmetrically arranged along the axis;

[0011] The inner wall surfaces of the first core mold and the third core mold are parallel to each other.

[0012] Furthermore, the width of each sewing groove is 2-4 mm, the axial length of the sewing groove is L+20-30 mm, the axial length of the core mold is L+40-60 mm, and L is the length of the ceramic-based composite material shaft part.

[0013] Furthermore, the interval between adjacent reinforcing sheets in each sewing groove is 100 to 150 mm.

[0014] At the same time, the present invention also provides a method for forming a ceramic-based composite material slender thin-walled shaft-like part, which is special in that a forming mold of the ceramic-based composite material slender thin-walled shaft-like part is used, and the method comprises the following steps:

[0015] Step 1, winding multiple layers of fiber cloth on the surface of the core mold, and providing an adhesive between the surface of the core mold and the fiber cloth, to obtain a preform located on the surface of the core mold;

[0016] Step 2, using carbon fiber to pass through each sewing groove to sew the preform obtained in step 1;

[0017] Step 3, two hanging holes evenly distributed around the circumference are provided between the two ends of the core mold and the multiple sewing grooves, and on the preform at the corresponding positions;

[0018] Step 4, placing one end of the core mold on the bottom plane of the equipment, and hanging the other end through two hanging holes, so that the preform obtained in step 3 and the core mold are placed vertically in the chemical vapor deposition equipment to prepare the carbon interface layer;

[0019] Step 5, placing one end of the core mold on the bottom plane of the equipment, and hanging the other end through two hanging holes, so that the preform obtained in the step and the core mold are placed vertically in the chemical vapor deposition equipment to deposit the silicon carbide substrate;

[0020] Step 6: When the density of the preform reaches the first preset density of 1.2 to 1.4 g / cm 3 When the preform is cut, one end of the core mold is cut off along the end surface of the sewing groove at the same end, and the remaining core mold is taken out from the other end of the preform;

[0021] Step 7, depositing a silicon carbide substrate in the manner of step 5;

[0022] Step 8: Wait until the density of the preform reaches the second preset density of 1.5-1.6 g / cm 3 When removing the sewing fibers in the cavity of the preform;

[0023] Step 9, conducting flow-guiding deposition on the inner and outer surfaces of the preform;

[0024] Step 10: When the density of the preform reaches the preset required density, the inner and outer surfaces and length of the preform are processed to obtain a ceramic matrix composite shaft part.

[0025] Furthermore, the step 9 is specifically as follows: connecting one end of the graphite paper tube to the air inlet, inserting the other end into the preform body cavity, introducing gas into the preform body mold surface, and performing deposition on the inner surface.

[0026] Furthermore, in step 4 and step 5, the other end is suspended through two suspension holes by passing a fixing rod through the two suspension holes at the other end, and sleeves the other end through a graphite tube, so that the inner wall of the graphite tube is fixed to both ends of the fixing rod.

[0027] Furthermore, in step 2, the distance between two adjacent needles during the sewing process is 5-10 mm, and the carbon fiber is 1k or 3k.

[0028] Furthermore, in step 3, the diameter of each of the hanging holes is 10 to 15 mm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention provides a molding die for a ceramic-based composite material slender thin-walled shaft-type part, comprising a core mold, wherein the core mold is assembled from a plurality of sub-core molds, and a sewing groove on the core mold is a through groove along the axial length, so that the core mold is not affected by the sewing fibers when withdrawing, and the demolding operation is relatively simple, which can effectively prevent the preform from being delaminated or unable to be demolded during the demolding process.

[0031] (2) The present invention provides a method for forming slender thin-walled shaft parts made of ceramic-based composite materials, which solves the problem in the prior art that shaft parts with ultra-long-diameter ratios cannot be sewn. The parts sewn through fibers have better interlayer bonding, thus avoiding stratification during subsequent use.

[0032] (3) In the present invention, the inner cavity of the part with a large aspect ratio is subjected to flow-guiding deposition, which can effectively solve the problem of uneven density deposition on the inner surface of the part due to its small diameter and long length.

[0033] (4) The present invention uses a graphite barrel and a fixed rod for support, so that the preform remains stable during the deposition process and avoids the axial deformation problem caused by uneven force. Compared with the traditional vertical suspension method, the support scheme of this method significantly improves the structural stability of the preform and helps to maintain the dimensional accuracy of the parts under high-temperature deposition conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of an embodiment of a molding die for a ceramic-based composite material slender thin-walled shaft-type part of the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of the first core mold in an embodiment of the present invention;

[0036] Figure 3 It is a schematic structural diagram of the preform and the core mold obtained in step 3 of an embodiment of a method for forming an elongated thin-walled shaft-like part of a ceramic-based composite material according to the present invention;

[0037] The reference numerals are as follows: 001 - preform;

[0038] 100-core mold, 110-first core mold, 120-second core mold, 130-third core mold, 140-fourth core mold; 200-sewing groove; 300-positioning ring; 400-reinforcement sheet; 500-hanging hole. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0040] Reference Figure 1 A forming mold for slender thin-walled shaft parts of ceramic-based composite materials includes a tubular core mold 100, which is composed of four sub-core molds of equal length. The four sub-core molds include a first core mold 110 and a third core mold 130 with the same structure and symmetrically arranged along the axis, and a second core mold 120 and a fourth core mold 140 with the same structure and symmetrically arranged along the axis.

[0041] The inner wall surfaces of the first core mold 110 and the third core mold 130 are parallel to each other.

[0042] The core mold 100 is provided with a plurality of sewing grooves 200 which are evenly distributed around the circumference and penetrate the core mold 100 in the axial direction, and a positioning ring 300 is provided at both ends and the middle of the inner cavity of the core mold 100. The function of the positioning ring 300 is to ensure that the position of the core mold 100 remains unchanged during the molding process to avoid shape deviation of the workpiece due to position displacement; at the same time, the distribution of the positioning ring 300 can evenly disperse the pressure and reduce the risk of deformation.

[0043] L (less than or equal to 2m) is the length of the ceramic-based composite shaft part, the axial length of the core mold 100 is L+50mm, the axial length of the sewing groove 200 is L+25mm, each sewing groove 200 is 12.5mm away from both ends of the core mold 100, and the width of each sewing groove 200 is 3mm.

[0044] like Figure 2 As shown, a plurality of reinforcing sheets 400 having a thickness equal to the width of the sewing groove 200 are arranged in the length direction of each sewing groove 200, and the distance between each reinforcing sheet 400 and the central axis of the core mold 100 is less than the distance between the outer surface of the core mold 100 and the central axis of the core mold 100 (not protruding from the sewing groove 200), and the interval between adjacent reinforcing sheets 400 in each sewing groove 200 is 125 mm. The addition of the reinforcing sheets 400 improves the overall strength of the core mold 100, especially helps to maintain the shape of the mold during high temperature treatment. This step ensures the stability of the fiber cloth winding during the molding process and reduces the possibility of deformation.

[0045] In other embodiments, the axial length of the core mold 100 is L+40-60 mm, the axial length of the sewing groove 200 is L+20-30 mm, each sewing groove 200 is at least 10 mm away from both ends of the core mold 100, the width of each sewing groove 200 is 2-4 mm, and the interval between adjacent reinforcement plates 400 in each sewing groove 200 is 100-150 mm.

[0046] A method for forming a ceramic-based composite material slender thin-walled shaft part comprises the following steps:

[0047] Step 1: multiple layers of fiber cloth are wound around the surface of the core mold 100, and an adhesive is provided between the surface of the core mold 100 and the fiber cloth after treatment;

[0048] Specifically, a fiber cloth having the same length as the core mold 100 is spread out on a table, an adhesive is applied on the surface of the fiber cloth, and then the core mold 100 is placed on one end of the fiber cloth, and the core mold 100 is rolled to tightly wrap the fiber cloth around the core mold 100; the adhesive may be water-soluble glue, hot melt adhesive, or low melting point polymer adhesive, which should meet the requirements of uniform bonding, no residue or volatilization at high temperature, and compatibility with the deposition process, so as to ensure that the fiber cloth is tightly wound and not loose, and at the same time ensure the smooth progress of subsequent processes;

[0049] Step 2, using carbon fiber to pass through each sewing groove 200, sewing the preform 001 obtained in step 1, and the distance between two adjacent needles during the sewing process is 7 mm;

[0050] In other embodiments, the distance between two adjacent needles is 5 to 10 mm, and the sewing process increases the connection strength of the fiber fabric, effectively preventing delamination during high temperature treatment and subsequent use. The sewing groove 200 not only provides sewing guidance, but also enhances the stability of the overall structure;

[0051] Step 3: Two hanging holes 500 evenly distributed around the circumference are set between the two ends of the core mold 100 and the ends of the multiple sewing grooves 200, and on the preform 001 at the corresponding positions, with a hole diameter of 12 mm. Figure 3 As shown;

[0052] In other embodiments, the diameter of the hanging hole 500 is 10-15 mm. The design of the hanging hole 500 allows the preform 001 to be hung in the device during the subsequent deposition process to maintain a vertical state, thereby avoiding structural deformation caused by gravity; in addition, these holes are also convenient for further reinforcement and operation;

[0053] Step 4, place one end of the core mold 100 on the bottom plane of the equipment, pass the fixing rod through the two hanging holes 500 at the other end, and cover the other end with a graphite tube, so that the inner wall of the graphite tube and the two ends of the fixing rod are fixed, and the preform 001 and the core mold 100 obtained in step 3 are placed vertically in the chemical vapor deposition equipment to prepare the carbon interface layer;

[0054] The fixing rod is made of graphite rod or C / SiC pin;

[0055] Step 5, place one end of the core mold 100 on the bottom plane of the equipment, pass the fixing rod through the two hanging holes 500 at the other end, and cover the other end with a graphite tube, so that the inner wall of the graphite tube is fixed to the two ends of the fixing rod, and place the preform 001 and the core mold 100 obtained in step 3 vertically in the chemical vapor deposition equipment to deposit the silicon carbide substrate;

[0056] Step 6: When the density of the preform 001 reaches the first preset density of 1.2-1.4 g / cm 3 When the core mold 100 is cut off at one end along the end surface of the sewing groove 200 at the same end, the remaining core mold 100 is taken out from the other end of the preform 001;

[0057] Step 7, depositing a silicon carbide substrate in the manner of step 5;

[0058] Step 8: When the density of the preform 001 reaches the second preset density of 1.5-1.6 g / cm 3 When the preform 001 is used, the sewing fibers in the inner cavity of the preform 001 are removed; removing the sewing fibers avoids the delamination and structural failure of the material during use, and further improves the stability and reliability of the parts;

[0059] Step 9, conducting flow-guiding deposition on the inner and outer surfaces of the preform 001;

[0060] Specifically, one end of the graphite paper tube is connected to the air inlet, and the other end is inserted into the inner cavity of the preform 001 by a distance of about 5 to 15 cm, and the gas is introduced into the inner mold surface of the preform 001 to perform deposition on the inner mold surface;

[0061] Step 10: When the density of preform 001 reaches the preset required density of 1.8 g / cm 3 When the preform 001 is machined, the inner and outer surfaces and the length are processed to obtain a ceramic matrix composite shaft part.

Claims

1. A molding die for a ceramic-based composite material slender thin-walled shaft part, characterized in that: The invention comprises a tubular core mold (100), wherein the core mold (100) is composed of a plurality of sub-core molds of equal length, a plurality of sewing grooves (200) uniformly distributed around the circumference and penetrating the core mold (100) are arranged on the core mold (100) along the axial direction, and a positioning ring (300) is arranged at both ends and the middle of the inner cavity of the core mold (100); Each of the sewing grooves (200) is at least 10 mm away from both ends of the core mold (100), and a plurality of reinforcing sheets (400) having a thickness equal to the width of the sewing groove (200) are arranged in each sewing groove (200) along the length direction, and the distance between each reinforcing sheet (400) and the central axis of the core mold (100) is less than the distance between the outer surface of the core mold (100) and the central axis of the core mold (100).

2. The forming die of a ceramic matrix composite material slender thin-walled shaft part according to claim 1, characterized in that: The core mold (100) is composed of four sub-core molds of equal length, the four sub-core molds comprising a first core mold (110) and a third core mold (130) having the same structure and symmetrically arranged along the axis, and a second core mold (120) and a fourth core mold (140) having the same structure and symmetrically arranged along the axis; The inner wall surfaces of the first core mold (110) and the third core mold (130) are parallel to each other.

3. A molding die for a ceramic matrix composite thin-walled shaft part according to claim 1 or 2, characterized in that: The width of each sewing groove (200) is 2 to 4 mm, the axial length of the sewing groove (200) is L+20 to 30 mm, the axial length of the core mold is L+40 to 60 mm, and L is the length of the ceramic-based composite material shaft part.

4. The forming die of a ceramic matrix composite material slender thin-walled shaft part according to claim 3, characterized in that: The interval between adjacent reinforcing sheets (400) in each sewing groove (200) is 100 to 150 mm.

5. A method for forming a ceramic-based composite material slender thin-walled shaft part, characterized in that: The molding die for the ceramic matrix composite slender thin-walled shaft parts according to claim 1 comprises the following steps: Step 1: multiple layers of fiber cloth are wound on the surface of the core mold (100), and an adhesive is provided between the surface of the core mold (100) and the fiber cloth, so as to obtain a preform (001) located on the surface of the core mold (100); Step 2, using carbon fibers to pass through each sewing groove (200) to sew the preform (001) obtained in step 1; Step 3, two hanging holes (500) evenly distributed around the circumference are provided between the two ends of the core mold (100) and the plurality of sewing grooves (200), and on the preform (001) at corresponding positions; Step 4: Place one end of the core mold (100) on the bottom plane of the equipment, and suspend the other end through two suspension holes (500), so that the preform (001) and the core mold (100) obtained in step 3 are vertically placed in the chemical vapor deposition equipment to prepare the carbon interface layer; Step 5, placing one end of the core mold (100) on the bottom plane of the equipment, and hanging the other end through two hanging holes (500), so that the preform (001) and the core mold (100) obtained in step 3 are vertically placed in the chemical vapor deposition equipment to deposit the silicon carbide substrate; Step 6: When the density of the preform (001) reaches the first preset density of 1.2-1.4 g / cm 3 When the core mold (100) is cut off at one end along the end surface of the sewing groove (200) at the same end, the remaining core mold (100) is taken out from the other end of the preform (001); Step 7, depositing a silicon carbide substrate in the manner of step 5; Step 8: When the density of the preform (001) reaches a second preset density of 1.5 to 1.6 g / cm 3 When removing the sewing fibers in the inner cavity of the preform (001); Step 9, conducting flow-guiding deposition on the inner and outer surfaces of the preform (001); Step 10: When the density of the preform (001) reaches the preset required density, the inner and outer surfaces and the length of the preform (001) are processed to obtain a ceramic-based composite material shaft part.

6. The method for forming a ceramic matrix composite thin-walled shaft part according to claim 5, characterized in that: The step 9 specifically comprises: connecting one end of the graphite paper tube to the air inlet, inserting the other end into the inner cavity of the preform (001), introducing gas into the inner mold surface of the preform (001), and performing deposition on the inner mold surface.

7. The method for forming a ceramic matrix composite thin-walled shaft part according to claim 5, characterized in that: In step 4 and step 5, the other end is suspended through the two suspension holes (500) by passing the fixing rod through the two suspension holes (500) of the other end, and sleeve the other end through the graphite tube, so that the inner wall of the graphite tube is fixed to the two ends of the fixing rod.

8. The method for forming a ceramic matrix composite thin-walled shaft part according to claim 5, characterized in that: In step 2, the distance between two adjacent needles during the sewing process is 5-10 mm, and the carbon fiber is 1k or 3k.

9. The method for forming a ceramic matrix composite thin-walled shaft part according to claim 5, characterized in that: In step 3, the diameter of each of the hanging holes (500) is 10 to 15 mm.

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