Manufacturing method of high-performance carbon-carbon heater preform

Abstract

The invention discloses a manufacturing method of a high-performance carbon-carbon heater preform, which comprises the following steps: S1, groove preparation: selecting rectangular polyurethane foam, and processing a groove consistent with a target heater in appearance in the polyurethane foam; s2, carbon fiber laying and fixing: taking a continuous carbon fiber, laying the continuous carbon fiber from the starting point of the groove to the tail end along the groove line, covering a small amount of carbon fiber net tire at the tail end, and fixing the carbon fiber net tire through a needling process; laying the carbon fiber from the tail end to the starting point along the groove line, covering a small amount of carbon fiber net tire at the starting point, and fixing through a needling process; s3, forming a single layer; and S4, multi-layer stacking and demolding are carried out. The whole fiber is continuous, especially at the corner, the integrity and mechanical property of the fiber are kept, the current path is smooth, corner heating and fragmentation are not caused, the service life of the product is prolonged, no port is formed, and the oxidation resistance is better.

Description

Technical Field

[0001] This invention relates to the field of high-temperature material manufacturing technology, specifically a method for manufacturing a high-performance carbon heater preform. Background Technology

[0002] The bottom heater is a crucial thermal component of the single-crystal silicon pulling furnace. Used in conjunction with the main heater, it regulates the temperature by adjusting the power output, thus melting the silicon material within the crucible. Carbon-carbon composite materials possess excellent properties such as low density, high specific strength, wear resistance, high temperature resistance, and a low coefficient of thermal expansion, making them an ideal substitute for graphite products.

[0003] Currently available bottom heaters for crystal pulling hot zones are made by using a special "needle-punching" process to vertically "sew" short fibers together with barbed needles to form a thick carbon fiber felt prefabricated body. This prefabricated body is then cut to shape the heater, and finally manufactured into a finished heater through vapor deposition or liquid deposition.

[0004] The main drawbacks of existing processes are: ① On the cutting surface, a large number of carbon fibers that were originally wrapped or interwoven with the matrix carbon are cut off, and their ends are directly exposed on the surface. This area is prone to oxidation and its mechanical properties are significantly reduced. ② The defects at the corners are even more severe. At the cutting corners, not only is the current forced to concentrate, but the fiber network carrying the current is also "broken" at this point. The current must "jump" across these breaks, leading to increased local resistance and more severe heating. Furthermore, corners are stress concentration points, making the heater prone to breakage at the corners. Therefore, we propose a method for manufacturing a high-performance carbon-to-carbon heater preform. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing a high-performance carbon heater preform to solve the problems in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for manufacturing a high-performance carbon heater preform, comprising the following steps: S1. Groove preparation: Select a rectangular polyurethane foam and process a groove in the polyurethane foam that is consistent with the shape of the target heater. The outer surface dimension of the groove is greater than or equal to the outer surface dimension of the heater, the inner surface dimension is less than or equal to the inner surface dimension of the heater, and the depth is greater than or equal to the thickness dimension of the heater. S2. Carbon fiber laying and fixing: Take a continuous carbon fiber and lay it from the starting point of the groove along the groove line to the end. Cover the end with a small amount of carbon fiber mesh and fix it by needle punching. Then lay the carbon fiber back from the end to the starting point along the groove line, cover the starting point with a small amount of carbon fiber mesh and fix it by needle punching. S3. Single-layer molding: A complete carbon fiber mesh is laid on the surface of the groove filled with continuous carbon fiber. The carbon fiber mesh is tightly bonded to the continuous carbon fiber below by needle punching process to form a single-layer prefabricated structure. S4. Multi-layer stacking and demolding: Repeat steps S2-S3 until the stacked structure reaches the thickness requirement of the target heater preform. Then, remove the molded structure from the groove of the polyurethane foam to complete the demolding and obtain the high-performance carbon heater preform.

[0007] Preferably, in step S1, the compressive strength of the polyurethane foam is ≥0.3MPa and the resilience of the polyurethane foam is ≥80%.

[0008] Preferably, in step S2, the continuous carbon fiber is PAN-based carbon fiber with a single filament diameter of 5-10 μm and a tensile strength ≥3000 MPa.

[0009] Preferably, before laying the carbon fiber, the carbon fiber surface is bombarded with low-temperature plasma (such as argon or oxygen plasma), which can remove impurities such as wax and oil, and also activate the fiber surface. The treatment time is controlled at 3-10 minutes and the power is 50-100W.

[0010] Preferably, in step S2, the areal density of the carbon fiber mesh used for temporary fixation is 50-100 g / m², and the needle-punching density of the needle-punching process is 20-50 needles / cm².

[0011] Preferably, in step S3, the areal density of the complete carbon fiber mesh is 100-200 g / m², the needle-punching depth is 15-20 mm, and the needle-punching density is 30-40 needles / cm².

[0012] Preferably, in S4, each time S2 is repeated, adjacent two layers of continuous carbon fibers are laid out alternately. During the multi-layer stacking process, a small amount of carbon fiber impregnating agent needs to be applied between each layer, with an application amount of 5-10 g / m².

[0013] Preferably, in step S4, the demolding process employs mechanical pushing, and the demolding force is controlled within the range of 50-100N.

[0014] Compared with the prior art, the beneficial effects of the present invention are: By eliminating the cutting process and reducing material waste, polyurethane foam grooves precisely matched to the heater's shape are created through CNC engraving (the outer / inner surfaces and depth are all precisely correlated with the product dimensions), achieving "near-size molding." Unlike traditional processes that require pre-molding and then cutting, this eliminates carbon fiber loss during cutting, increasing material utilization to over 95% and directly reducing raw material costs. The simplified process also reduces production energy consumption and labor costs. Steps such as continuous carbon fiber laying, segmented needle punching, and multi-layer stacking can be automated using CNC equipment (CNC fiber laying machine, CNC needle punching machine), reducing manual intervention (such as trimming and grinding after traditional cutting). Furthermore, the elimination of secondary processing steps after cutting shortens the production cycle by 30%-40%, indirectly reducing equipment energy consumption and labor management costs.

[0015] Employing a "continuous back-and-forth laying and segmented fixing" process, the carbon fiber is laid without any breaks (especially at the corners of the heater), avoiding the problem of exposed fiber ends caused by traditional cutting. The continuous fibers form a "break-free conductive network," allowing current to be smoothly conducted along the fibers without having to "jump" over the break point as with traditional cutting. Local resistance is reduced by 50%-70%, completely solving the problem of "heat concentration" at corners. During heater operation, the temperature difference between the corner and the main body is controlled within ±5℃, preventing breakage due to local overheating and extending product lifespan by 2-3 times.

[0016] With no cutting surfaces throughout the process and carbon fiber ends not directly in contact with air, combined with pretreatment (400-500℃ inert gas dewaxing) and shaping treatment (130-160℃ stress relief), the preform's oxidation resistance is improved by over 60%. In an 800℃ high-temperature air environment, the weight loss rate is reduced from 8%-12% in traditional processes to below 3%. Applying an epoxy resin-based sizing agent during multi-layer stacking increases interlayer bonding strength by over 35%, preventing interlayer delamination during high-temperature use. Simultaneously, the carbon fiber volume fraction is precisely controlled between 30%-45%, balancing structural density and high-temperature breathability, meeting the temperature resistance requirements of high-temperature scenarios such as crystal pulling hot zones.

[0017] The grooves are customizable to fit various heater sizes; the grooves (length, width, and depth can be adjusted as needed) can be flexibly processed according to the three-dimensional model of different heaters using a CNC engraving machine, without the need to replace the entire set of molds. It is compatible with bottom heaters of different specifications in the crystal pulling hot zone, has strong versatility, and reduces the mold development cost for multi-specification products. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0020] Please see Figure 1 In this embodiment of the invention, a method for manufacturing a high-performance carbon heater preform includes the following steps: S1. Groove preparation: Select a rectangular polyurethane foam and process a groove in the polyurethane foam that is consistent with the shape of the target heater. The outer surface dimension of the groove is greater than or equal to the outer surface dimension of the heater, the inner surface dimension is less than or equal to the inner surface dimension of the heater, and the depth is greater than or equal to the thickness dimension of the heater. S2. Carbon fiber laying and fixing: Take a continuous carbon fiber and lay it from the starting point of the groove along the groove line to the end. Cover the end with a small amount of carbon fiber mesh and fix it by needle punching. Then lay the carbon fiber back from the end to the starting point along the groove line, cover the starting point with a small amount of carbon fiber mesh and fix it by needle punching. S3. Single-layer molding: A complete carbon fiber mesh is laid on the surface of the groove filled with continuous carbon fiber. The carbon fiber mesh is tightly bonded to the continuous carbon fiber below by needle punching process to form a single-layer prefabricated structure. S4. Multi-layer stacking and demolding: Repeat steps S2-S3 until the stacked structure reaches the thickness requirement of the target heater preform. Then, remove the molded structure from the groove of the polyurethane foam to complete the demolding and obtain the high-performance carbon heater preform.

[0021] In step S1, the compressive strength of the polyurethane foam is ≥0.3MPa, and the resilience of the polyurethane foam is ≥80%, ensuring no significant deformation during the groove processing. The length of the polyurethane foam is 5-10mm larger than the maximum external length of the target heater, the width is 5-10mm larger than the maximum external width of the target heater, and the thickness is 8-15mm larger than the designed thickness of the target heater. Using a CNC engraving machine, a groove consistent with the heater's shape is processed on the polyurethane foam substrate based on the three-dimensional model of the target heater. The outer surface dimension of the groove is 0.5-2mm larger than the heater's outer surface dimension, the inner surface dimension is 0.5-2mm smaller than the heater's inner surface dimension, the depth is 1-3mm larger than the heater's thickness, and the surface roughness of the inner wall of the groove is ≤Ra6.3μm.

[0022] The continuous carbon fiber is PAN-based carbon fiber with a single filament diameter of 5-10 μm and a tensile strength ≥3000 MPa. The areal density of the carbon fiber mesh used for temporary fixation is 50-100 g / m², the needle-punching density of the needle-punching process is 20-50 needles / cm², and the fiber-laying accuracy of the CNC fiber-laying machine is ±0.1 mm, with a fiber-laying path deviation ≤0.2 mm, ensuring the accuracy of carbon fiber placement.

[0023] Before laying the carbon fiber, the carbon fiber surface is bombarded with low-temperature plasma (such as argon or oxygen plasma) to remove impurities such as wax and oil, and to activate the fiber surface. The treatment time is controlled at 3-10 minutes, and the power is 50-100W. The pretreated continuous carbon fiber is laid along the groove line using a CNC fiber placement machine, with the fiber placement tension controlled at 15-20N, from the beginning to the end of the groove. During the laying process, the adhesion between the carbon fiber and the inner wall of the groove is ≥95%. At the end of the laying area, a short-cut carbon fiber mesh with a surface density of 50-100g / m² (short-cut fiber length of 3-10mm) is placed and needled and fixed using a single-head needle punching machine to ensure that the bonding strength between the carbon fiber and the mesh is ≥5N / 25mm. The carbon fiber is then laid in the reverse direction along the groove line, from the end back to the beginning, with the same fiber placement parameters as above. The needle fixing operation is repeated in the laying area at the beginning. The back-and-forth laying process is repeated, and there are no obvious defects such as bubbles or wrinkles.

[0024] In step S3, the areal density of the complete carbon fiber mesh is 100-200 g / m², the needle-punching depth is 15-20 mm, the needle-punching density is 30-40 needles / cm², and the flatness of the needle plate of the CNC needle-punching machine is ≤0.1 mm / m to ensure uniform needle-punching depth and avoid local over-punching or under-punching. A continuous carbon fiber mesh with an areal density of 100-200 g / m² is laid on the surface of the groove filled with carbon fiber, and the alignment deviation between the mesh and the groove is ≤1 mm. The entire structure is needle-punched using a CNC needle-punching machine, with a needle-punching density of 30-40 needles / cm² and a needle-punching depth of 15-20 mm. During the needle-punching process, negative pressure is used for uniform adsorption (negative pressure value is -0.02 to -0.05 MPa) to prevent material displacement. After needle-punching, the thickness uniformity of the single-layer preform (thickness deviation ≤±0.3 mm) and the areal density deviation (deviation ≤±5%) are checked. Defective products need to be re-laid and needle-punched.

[0025] In step S4, during each repetition of S2, adjacent layers of continuous carbon fibers are laid out alternately. During the multi-layer stacking process, a small amount of carbon fiber impregnating agent (epoxy resin-based) needs to be applied between each layer, with an application amount of 5-10 g / m², to enhance the interlayer bonding strength. The demolding process uses mechanical pushing, with the demolding force controlled within the range of 50-100 N to avoid damaging the preform structure. When stacking multiple layers, adjacent carbon fiber layers are laid alternately each time, and the surface of the groove must be cleaned before each layer is laid (cleaning method: blow off surface dust with compressed air at a pressure of 0.3-0.5MPa); when the number of stacked layers reaches the design requirements (calculated based on the heater thickness, with each layer thickness controlled at 0.5-2mm), and the overall preform thickness deviation is ≤±0.5mm, stacking is stopped; a mechanical jacking demolding method is adopted (pressure relief is required during jacking), the jacking points of the jacking device are evenly distributed (at least one jacking point is set for every 100cm²), the jacking force is controlled at 50-100N, and the preform is slowly removed from the polyurethane foam, with the demolding speed controlled at 15-20mm / min; after demolding, the preform is inspected for appearance (no cracks, missing corners, and smooth edges) and dimensions (critical dimension deviation ≤±0.3mm), and after passing the inspection, a high-performance carbon heater preform is obtained.

[0026] After demolding, the preform is also shaped: the qualified preform is placed in an oven at 130-160℃ for 2-4 hours to eliminate internal stress. After shaping, the dimensional stability of the preform is ≥98% (the dimensional change rate is ≤0.2% after being placed at 25℃ and 50% humidity for 72 hours).

[0027] The working principle of this invention is as follows: A groove matching the shape of the heater is cut out of a rectangular polyurethane foam. The outer surface dimension is greater than or equal to the outer dimension of the heater, the inner surface dimension is less than or equal to the inner dimension of the heater, and the depth is greater than or equal to the thickness of the heater. A fiber is laid from the starting point of the groove to the end, where it is secured with a small amount of carbon fiber mesh. This process is repeated until the entire groove is covered with carbon fiber. A layer of mesh is then laid and needled to form the final product thickness. Finally, the product is demolded to form the final preform.

[0028] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a high-performance carbon heater preform, characterized in that, Includes the following steps: S1. Groove preparation: Select a rectangular polyurethane foam and process a groove in the polyurethane foam that is consistent with the shape of the target heater. The outer surface dimension of the groove is greater than or equal to the outer surface dimension of the heater, the inner surface dimension is less than or equal to the inner surface dimension of the heater, and the depth is greater than or equal to the thickness dimension of the heater. S2. Carbon fiber laying and fixing: Take a continuous carbon fiber and lay it from the starting point of the groove along the groove line to the end. Cover the end with a small amount of carbon fiber mesh and fix it by needle punching. Then lay the carbon fiber back from the end to the starting point along the groove line, cover the starting point with a small amount of carbon fiber mesh and fix it by needle punching. S3. Single-layer molding: A complete carbon fiber mesh is laid on the surface of the groove filled with continuous carbon fiber. The carbon fiber mesh is tightly bonded to the continuous carbon fiber below by needle punching process to form a single-layer prefabricated structure. S4. Multi-layer stacking and demolding: Repeat steps S2-S3 until the stacked structure reaches the thickness requirement of the target heater preform. Then, remove the molded structure from the groove of the polyurethane foam to complete the demolding and obtain the high-performance carbon heater preform.

2. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In step S1, the compressive strength of the polyurethane foam is ≥0.3MPa, and the resilience of the polyurethane foam is ≥80%.

3. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In S2, the continuous carbon fiber is PAN-based carbon fiber with a single filament diameter of 5-10 μm and a tensile strength ≥3000 MPa.

4. The method for manufacturing a high-performance carbon heater preform according to claim 3, characterized in that, Before laying the carbon fiber, the surface of the carbon fiber is bombarded with low-temperature plasma to remove wax, oil and other impurities and activate the fiber surface. The treatment time is controlled at 3-10 minutes and the power is 50-100W.

5. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In step S2, the areal density of the carbon fiber mesh used for temporary fixation is 50-100 g / m², and the needle-punching density of the needle-punching process is 20-50 needles / cm².

6. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In S3, the areal density of the complete carbon fiber mesh is 100-200 g / m², the needle-punching depth is 15-20 mm, and the needle-punching density is 30-40 needles / cm².

7. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In S4, each time S2 is repeated, adjacent layers of continuous carbon fibers are laid out alternately. During the multi-layer stacking process, a small amount of carbon fiber impregnating agent needs to be applied between each layer, with an application amount of 5-10 g / m².

8. The method for manufacturing a high-performance carbon heater preform according to claim 1, characterized in that, In S4, the demolding process adopts a mechanical pushing method, and the demolding force is controlled within the range of 50-100N.

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