Guide cylinder for thermal field and manufacturing method thereof

Abstract

The invention belongs to the technical field of thermal field equipment, and discloses a guide cylinder for a thermal field and a manufacturing method of the guide cylinder. An integrated fiber prefabricated body is prepared on a mold, in the process, by controlling fiber layer laying, a barrel prefabricated part with the low fiber volume content, a ring prefabricated part with the high fiber volume content and a gradient transition area connecting the barrel prefabricated part and the ring prefabricated part are formed in the prefabricated body, and then a Z-direction reinforcing technology is adopted to enable the barrel prefabricated part, the ring prefabricated part and the gradient transition area to form a whole with continuous fibers; and carrying out densification treatment on the prefabricated body. By constructing an integrated structure with gradient performance, the guide cylinder body has excellent heat insulation performance, and the bottom ring piece has high mechanical strength. An anti-scouring functional layer with a reinforced bonding interface can be preferably arranged on the inner wall, and a bionic microscopic groove is machined, so that the structural reliability and the performance matching degree of the guide cylinder are cooperatively improved, and the service life of the guide cylinder is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of thermal field equipment technology, specifically relating to a thermal field guide tube and its manufacturing method. Background Technology

[0002] The flow guide tube is a key component in the thermal field system of monocrystalline silicon growth furnaces. Its main functions are to guide the flow of inert gas, stabilize the temperature gradient of the thermal field, and prevent silicon vapor from contaminating other components in the furnace. It has a significant impact on the growth quality and production efficiency of monocrystalline silicon.

[0003] Currently, carbon / carbon (C / C) composite materials are often used in thermal field guide tubes to replace traditional graphite materials in order to achieve a longer service life. However, existing manufacturing methods have the following main problems: First, the split design involves manufacturing the guide tube in parts such as the body and bottom ring separately, and then assembling them mechanically using bolts. The joints in this method become stress concentration points and heat leakage channels, easily loosening or breaking under long-term high-temperature and thermal cycling conditions, leading to guide tube failure and becoming a major bottleneck for structural reliability. Second, the overall uniform design, although avoiding weak joints through processes such as integral winding and needle punching, has significantly different performance requirements for different parts of the guide tube: the middle part of the body mainly serves as insulation and flow guide, requiring a dense structure and the lowest possible thermal conductivity; while the bottom ring, as a supporting structure, requires extremely high mechanical strength and thermal shock resistance. A uniform structural design cannot simultaneously meet these conflicting performance requirements, resulting in wasted material properties or insufficient local performance. Furthermore, the inner wall of the guide tube is constantly subjected to high-temperature, high-speed corrosive airflow, which easily damages ordinary carbon fiber, affecting its service life. Summary of the Invention

[0004] The present invention aims to at least partially solve the aforementioned technical problems. Therefore, the objective of the present invention is to provide a flow guide tube for a thermal field and a method for manufacturing the same.

[0005] The technical solution adopted in this invention is as follows:

[0006] To achieve the above objectives, the present invention provides a method for manufacturing a thermal field guide tube, comprising the following steps:

[0007] S1. A mold is provided, the mold comprising a cylindrical portion and an annular portion located at its bottom;

[0008] S2. Preparing an integral fiber preform on the mold, the preparation process including:

[0009] (a) A reinforcing fiber layer is laid on the surface of the cylindrical part and the ring part to form a precast cylindrical part and a precast ring part, wherein the fiber volume content of the precast ring part is controlled to be higher than that of the precast cylindrical part, and a gradient transition zone with gradually changing fiber volume content is formed between the precast cylindrical part and the precast ring part.

[0010] (b) The prefabricated cylindrical section, gradient transition zone and ring prefabricated section are processed by Z-direction reinforcement process to form a fiber-continuous integral structure.

[0011] S3. The integrated fiber preform is densified to obtain a flow guide tube.

[0012] Through the above method, this invention constructs a continuous, integrated fiber structure at the prefabrication stage, while introducing a functional gradient design. This results in the bottom ring of the final guide tube achieving high mechanical strength due to its high fiber volume content, fulfilling its support function; while the tube body achieves low thermal conductivity due to its lower fiber volume content, enhancing its insulation function. The gradient transition zone allows for a smooth transition between mechanical and thermal properties, avoiding stress concentration and significantly improving the structural stability of the guide tube under harsh thermal cycling conditions.

[0013] In a preferred embodiment, step S2(a) further includes: before laying the reinforcing fiber layer, first laying a functional fiber layer on the inner surface of the mold. Preferably, the functional fiber is selected from silicon carbide fiber or carbon fiber with a silicon carbide coating on the surface, so as to give the inner wall of the guide tube excellent resistance to high-temperature airflow erosion and oxidation.

[0014] Furthermore, at the interface between the functional fiber layer and the reinforcing fiber layer, the bonding between the two is strengthened by staggered blending or dense Z-axis reinforcement. This creates a physically interlocking structure, greatly enhancing the interfacial bonding force between the functional layer and the matrix, and effectively preventing interlayer delamination failure under the combined effects of thermal stress and airflow erosion.

[0015] In a preferred embodiment, the fiber volume content of the precast ring part is 40%-60%, and the fiber volume content of the precast cylinder part is 20%-35%, thereby ensuring the thermal insulation performance of the cylinder and the support strength of the ring part.

[0016] To further optimize the on-demand distribution of performance, in step S2(a), the reinforcing fibers of the precast cylindrical part are mainly pitch-based carbon fibers, which have low thermal conductivity; the reinforcing fibers of the precast ring part are mainly polyacrylonitrile (PAN)-based carbon fibers, which have excellent mechanical properties.

[0017] In a preferred embodiment, the Z-axis reinforcement process is a three-dimensional needle punching or stitching process; and it is carried out using a regional density control method, with the needle punching or stitching density in the gradient transition zone and at the connection with the ring prefabricated part being higher than the needle punching or stitching density in other areas. This refined process of strengthening connections in key stress areas further ensures the reliability of the overall structure.

[0018] In a preferred embodiment, the densification treatment employs a chemical vapor infiltration (CVI) process or a precursor impregnation pyrolysis (PIP) process.

[0019] In a preferred embodiment, the method further includes step S4: refining the inner wall of the densified guide tube to form a microgroove array for optimizing the airflow boundary layer. Preferably, the microgroove array is a rib array with a sharkskin-like structure. This biomimetic structure can stabilize the airflow in the near-wall region, forming a protective gas boundary layer and reducing thermal shock and erosion wear caused by turbulence.

[0020] The present invention also provides a thermal field guide tube manufactured by any of the above methods. It includes a cylinder, a bottom ring, and a gradient transition region connecting the two. The cylinder, the gradient transition region, and the bottom ring are formed into an integral structure by a continuous internal reinforcing fiber layer, and the density is distributed in a gradient increasing distribution from the cylinder through the gradient transition region to the bottom ring.

[0021] Preferably, the inner surface of the guide tube is configured as a functional fiber reinforcement layer. The functional fiber reinforcement layer and the guide tube body form a reinforced bonding interface with a physically interlocking structure. The inner wall surface of the functional fiber reinforcement layer is provided with an array of microgrooves for optimizing the airflow boundary layer.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention achieves integrated fiber connection between the cylinder and the bottom ring during the prefabrication stage and designs a gradient transition zone, eliminating physical connection interfaces and stress abrupt change points, thereby improving the overall structural strength and thermal fatigue resistance of the guide tube.

[0024] This invention adopts the functional gradient design concept and combines the selection of heterogeneous fibers to give the guide tube body excellent thermal insulation performance and the bottom excellent mechanical support performance, realizing the on-demand distribution and maximum utilization of material properties in a single component.

[0025] This invention significantly enhances the draft tube's resistance to harsh working conditions by introducing a layer of anti-erosion and anti-oxidation functional fibers with a reinforced interface into the inner wall, and supplementing it with biomimetic micro-grooves that optimize airflow. This effectively extends its service life and reduces replacement frequency and production costs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the flow guide tube for the thermal field in an embodiment of the present invention.

[0027] Figure 2 This is a flowchart of the method for manufacturing the guide tube in an embodiment of the present invention.

[0028] In the figure: 11-cylinder; 12-bottom ring; 13-gradient transition zone. Detailed Implementation

[0029] The present invention will be further explained below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0030] Example 1

[0031] This embodiment provides a method for manufacturing a flow guide tube for a thermal field, such as... Figure 2 As shown, the specific steps include:

[0032] Step S1: Mold Preparation

[0033] A detachable graphite mold is provided. The overall shape of the mold is consistent with the target guide tube, including a cylindrical body and an annular flange-shaped ring located at the lower end of the body. The mold surface is polished and uniformly coated with boron nitride (BN) release agent.

[0034] Step S2: Preparation of the integrated fiber preform

[0035] (a) Laying the functional layer and constructing a reinforced interface: First, a layer of surface-treated silicon carbide (SiC) fiber cloth is laid on the inner surface of the mold (i.e., the inner wall of the future guide tube) to form a functional fiber layer. Next, the first layer of PAN-based carbon fiber non-woven fabric and PAN-based carbon fiber mesh are laid layer by layer from the inside out, and a high-density, shallow-depth needle punching process (80 needles per square centimeter, 2mm depth) is used to make some SiC fibers and carbon fibers form a strong physical entanglement at the interface, forming a reinforced bonding interface.

[0036] (b) Laying the main reinforcing fiber layer and establishing a performance gradient:

[0037] Above the reinforced bonding interface of the cylindrical section, pitch-based carbon fiber nonwoven fabric and pitch-based carbon fiber mesh are laid layer by layer to form a low-density prefabricated cylindrical section. The spacing between the layers and the tension of each layer are controlled by an automatic fiber placement table to maintain the fiber volume content in this area at approximately 30%.

[0038] Above the reinforced bonding interface of the ring component, PAN-based carbon fiber nonwoven fabric is laid out using a tighter layup method and additional radial fiber bundles to form a high-density ring component prefabrication section. The fiber volume content in this area is controlled to reach approximately 55%.

[0039] At the junction of the low-density bobbin prefabrication section and the high-density ring prefabrication section, the fiber volume content is smoothly increased from 30% to 55% within a height range of about 30-50mm by controlling the tension of the automatic fiber placement table through a program, forming a gradient transition zone 13.

[0040] (c) Overall Z-axis enhancement enables integrated connectivity:

[0041] After all fiber layers are laid, a three-dimensional needle punching table is used for overall Z-axis reinforcement treatment (Z-axis reinforced fibers). The needle punching process parameters are controlled by a program to implement variable-density needle punching in different areas.

[0042] In the gradient transition zone 13, the needle density is the highest, reaching 60-70 needles per square centimeter, and the needle depth penetrates the entire connection area, playing the role of reinforcing ribs.

[0043] In other areas of the low-density cylindrical prefabrication section and the high-density ring prefabrication section, the needle-punching density is 20-30 needles per square centimeter, which serves as the main body connection.

[0044] In this way, the Z-direction fibers firmly stitch all the layers, functional layers, cylinder, transition zone and ring parts together to form a continuous fiber network and a monolithic prefabricated body without physical interfaces.

[0045] Step S3: Densification treatment

[0046] The prepared integral fiber preform is removed from the mold and placed in a chemical vapor infiltration (CVI) reactor. Methane (CH4) is introduced as the carbon source gas under a temperature of 950℃-1100℃ and a negative pressure. The carbon atoms generated by the cracking of methane are deposited in the interstices of the fiber skeleton of the preform. This process is repeated multiple times until the overall density of the preform reaches above 1.80 g / cm³ and the porosity is below 8%.

[0047] Step S4: Post-processing and finishing

[0048] The densified C / C composite material guide tube blank is placed in an ultra-high temperature graphitization furnace and heated to 2200℃ for graphitization under inert gas protection. After graphitization, according to the design drawings, the end face and dimensions of the guide tube are precision machined using a five-axis CNC machine tool and diamond tools. Specifically, femtosecond laser ablation is used to machine a micro-groove array with a depth of 0.15mm and a spacing of 0.3mm, resembling sharkskin ribs, on the inner wall of the guide tube. The final product guide tube is obtained, as shown below. Figure 1 As shown, the finished guide tube includes a tube body 11, a bottom ring 12, and a gradient transition zone 13 connecting the two.

[0049] To verify the beneficial effects of the present invention, the flow guide tube (sample A) prepared in Example 1 was subjected to performance tests with two comparative samples.

[0050] Comparative Sample B: Manufactured using the split-type method described in the background art. The cylinder and ring are separately fabricated as C / C composite parts, and then connected by graphite bolts.

[0051] Comparison Sample C: Manufactured using a conventional integral uniform needle punching method. The entire guide tube has a uniform structure, with a fiber volume content of approximately 40%, and no special functional layer on the inner wall.

[0052] The test results are shown in the table below:

[0053] Test Project Sample A Sample B Sample C Shear strength of the connection zone (MPa) >45 (Material strength) 18.5 (Bolt connection strength) 42 (Material Strength) Thermal cycling fatigue life (cycles, 20-1600℃) >500 (Not expired) 120 (Loose bolts at the connection) 350 (Micro-cracks appear in the cylinder) Functional layer / matrix interface bonding strength (MPa) 25.8 (Enhanced Interface) - 9.5 (Conventional laminated interface) Thermal conductivity of the middle part of the cylinder (W / m·K, 1200℃) 12 28 28 Weight loss rate of inner wall due to high-temperature erosion (mg / cm²·h) 0.3 2.5 2.5 Simulated operating condition life test (hours) >3500 Approximately 800 (connection failure) Approximately 1200 (thinning due to internal wall scouring)

[0054] As can be seen from Table 1:

[0055] Sample A, being an integral fiber connection with a gradient transition zone and reinforced Z-axis connection, has a connection strength equal to the material's own strength, and its thermal fatigue life far exceeds that of samples B and C, fundamentally eliminating the risk of connection failure and stress concentration cracking.

[0056] Because the middle part of the cylinder of sample A uses low-density pitch-based carbon fiber, its high-temperature thermal conductivity (12 W / m·K) is significantly lower than that of samples B and C (28 W / m·K), which can more effectively reduce heat loss and improve the energy efficiency of the thermal field. At the same time, its bottom ring still maintains high mechanical strength (not listed in the table, but its strength is comparable to that of sample C).

[0057] Sample A exhibited the longest simulated operating life. The synergistic effect of its SiC functional fiber layer, reinforced interface, and biomimetic microgroove array gave it extremely strong resistance to high-temperature airflow erosion, with a weight loss rate only 1 / 8 that of the control sample. This is the key to its significantly extended lifespan (>3500 hours vs 800 / 1200 hours).

[0058] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for manufacturing a flow guide tube for a thermal field, characterized in that, Includes the following steps: S1. A mold for providing a guide tube, the mold comprising a cylindrical portion and an annular portion located at its bottom; S2. Preparing an integral fiber preform on the mold, the preparation process including: A reinforcing fiber layer is laid on the surface of the cylindrical part and the ring part to form a precast cylindrical part and a precast ring part. The fiber volume content of the precast ring part is controlled to be higher than that of the precast cylindrical part, and a gradient transition zone with gradually changing fiber volume content is formed between the precast cylindrical part and the precast ring part. The prefabricated cylindrical section, gradient transition zone and ring prefabricated section are processed by Z-direction reinforcement process to form a fiber-continuous integral structure. S3. The integrated fiber preform is densified to obtain a flow guide tube.

2. The manufacturing method according to claim 1, characterized in that, Step S2 further includes: before laying the reinforcing fiber layer, first laying a functional fiber layer on the inner surface of the mold.

3. The manufacturing method according to claim 2, characterized in that, The functional fibers are selected from silicon carbide fibers or carbon fibers with a silicon carbide coating on the surface; and at the interface between the functional fiber layer and the reinforcing fiber layer, the combination of the two is strengthened by interlacing or dense Z-direction reinforcement.

4. The manufacturing method according to claim 1, characterized in that, The fiber volume content of the precast ring part is 40%-60%, and the fiber volume content of the precast cylinder part is 20%-35%.

5. The manufacturing method according to claim 1, characterized in that, In step S2, the reinforcing fibers of the precast cylindrical part include pitch-based carbon fiber, and the reinforcing fibers of the precast ring part include polyacrylonitrile-based carbon fiber.

6. The manufacturing method according to claim 1, characterized in that, The Z-axis reinforcement process is a three-dimensional needle punching or stitching process; it is carried out by controlling the density in different regions, with the needle punching or stitching density in the gradient transition zone and at the connection with the ring prefabrication part being higher than the needle punching or stitching density in other regions.

7. The manufacturing method according to any one of claims 1-6, characterized in that, It also includes step S4: finely machining the inner wall of the densified guide tube to form a micro-groove array for optimizing the airflow boundary layer.

8. A flow guide tube for a thermal field, characterized in that, It is manufactured by the manufacturing method of any one of claims 1-7. The guide tube includes a cylinder, a bottom ring and a gradient transition zone connecting the two. The cylinder, the gradient transition zone and the bottom ring are formed into an integral structure through an internal continuous reinforcing fiber layer, and the density is distributed in a gradient increasing distribution from the cylinder through the gradient transition zone to the bottom ring.

9. The thermal field guide tube according to claim 8, characterized in that, The inner surface of the guide tube is provided with a functional fiber reinforcement layer, and the functional fiber reinforcement layer and the guide tube body are a reinforced bonding interface with a physical interlocking structure.

10. The flow guide tube for a thermal field according to claim 9, characterized in that, The inner wall surface of the functional fiber reinforcement layer is provided with a micro-groove array for optimizing the airflow boundary layer.

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