A method for controlling the surface state of a low-density weak-rigidity heat-resistant material

Abstract

The application discloses a low-density weak-rigidity heat-proof material surface state control method, which comprises the following steps: installing a workpiece made of low-density weak-rigidity heat-proof material on a machining platform; after clamping is completed, determining rough machining removal and fine machining removal according to the allowance setting and size requirement of the workpiece, and selecting machining tools and machining parameters in the rough machining stage and the fine machining stage; in the rough machining stage, rough machining is performed on a process area according to the selected machining tools and machining parameters, and the excess of the machining tools and the material surface is cleaned up in the machining process; after the rough machining is completed, a tool head cover is installed on a machining tool head; in the fine machining stage, fine machining is performed on the process area according to the selected machining tools and machining parameters, and the excess of the machining tools and the material surface is cleaned up in the machining process. The application solves the problem of surface state control of the low-density weak-rigidity heat-proof material surface directly implementing a heat control functional coating.

Description

Technical Field

[0001] This invention relates to a method for controlling the surface condition of a low-density, weakly rigid heat-resistant material, belonging to the field of heat-resistant material molding. Background Technology

[0002] Advanced thermal protection technologies are constantly facing new demands and more stringent requirements alongside the rapid development of space exploration technology. Ablation-type lightweight and efficient thermal protection materials are a key technology for the thermal protection of reentry vehicles, ensuring the safe and reliable completion of reentry missions. Lightweighting of thermal protection structures is of great significance to the development of thermal protection technology; that is, pursuing weight reduction of thermal protection materials while meeting thermal protection requirements. Therefore, low-density thermal protection materials have a wide range of applications. Currently, ablation-type low-density, weakly rigid thermal protection materials are generally fiber-reinforced thermal protection materials.

[0003] However, driven by the demand for weight reduction, low-density, weakly rigid heat-resistant materials face new challenges in engineering implementation. For example... Figure 1 This is a schematic diagram of the existing processing principle. Traditionally, in the application of thermal protection structures, the outermost layer of thermal protection material needs to be coated with a functional coating, such as a thermal control coating, to meet the comprehensive functional requirements of the space application environment. The implementation of this thermal control coating requires a smooth surface on the thermal protection material substrate to ensure the bonding of the thermal control coating interface and to prevent wrinkles, cracks, or even peeling of the coating substrate during application, which could affect the overall performance of the thermal protection structure. Currently, engineering practices use a surface penetration method to harden the thermal protection material, followed by surface polishing to meet the surface requirements for coating implementation. This often results in an increase in the overall weight of the thermal protection structure, large dispersion in the hardened weight, and a complex and poorly controllable process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: the present invention provides a method for controlling the surface state of low-density, weakly rigid heat-resistant materials, which solves the problem of controlling the surface state of low-density, weakly rigid heat-resistant materials with functional coatings such as thermal control directly applied.

[0005] The technical solution adopted in this invention is: a method for controlling the surface condition of a low-density, weakly rigid heat-resistant material, comprising:

[0006] Step 1: Mount the workpiece made of low-density, weak-rigidity heat-resistant material on the processing platform. During clamping, clamp the process area of ​​the workpiece to prevent the clamping tool from contacting the product area and ensure that there are no clamping marks on the material surface of the workpiece. The process area is the part of the workpiece other than the product area, which is reserved according to the process requirements during the material process design.

[0007] Step 2: After clamping, determine the roughing removal amount and finishing removal amount according to the workpiece's allowance setting and size requirements, and select the machining tools and machining parameters for the roughing and finishing stages;

[0008] Step 3: In the roughing stage, the process area is roughed according to the selected machining tools and machining parameters. During the machining process, the excess material on the tool and material surface is removed and cleaned.

[0009] Step 4: After rough machining is completed, install the head cover on the machining head;

[0010] Step 5: In the finishing stage, the process area is finished according to the selected machining tools and machining parameters. During the machining process, excess materials on the tool and material surface are removed and cleaned.

[0011] Furthermore, rough machining is used to remove the dimensional area that is ≥1mm away from the product area, and fine machining is used to process the remaining dimensions.

[0012] Furthermore, in the roughing stage: the machining head is a metal grinding head, the machining speed is 2000-5500 r / min, the machining depth is 0.5-1.5 mm, and the machining step is 0.5-1.2 mm.

[0013] Furthermore, in the finishing stage: the machining head is a diamond grinding head, and the ball head type and size radius of the machining head are matched and selected according to the flat and curved surface characteristics of the workpiece. The machining speed is 5500~9000r / min, the machining depth is 0.1~0.5mm, and the machining step is 0.1~0.5mm.

[0014] Furthermore, the cutter head cover is fixed to the cutter head by a snap-fit ​​connection. The cutter head cover is a metal hollow structure with a number of evenly distributed round holes or striped hollow structures on its surface. The diameter of a single round hole is 0.1 to 0.5 mm, or the width of a single stripe is 0.1 to 0.5 mm and the length is 3 to 15 mm. A spring plate is provided at the snap-fit ​​connection position between the cutter head cover and the cutter head, so that the cutter head cover is pressed close to the cutter head during processing and returns to its original position after being released.

[0015] The advantages of this invention compared to the prior art are:

[0016] This invention provides a novel method for controlling the surface condition of low-density, weakly rigid heat-resistant materials used as functional coating substrates. It differs significantly from the traditional method of impregnating the material surface with resin, hardening it, and then polishing it. This method solves the problems of increased overall heat-resistant structure weight, large weight dispersion, complex process, and poor controllability caused by traditional post-processing techniques involving resin impregnation, hardening, and polishing. Furthermore, it effectively avoids the risks associated with foreign matter and new coating interface bonding issues arising from resin surface hardening. Therefore, addressing the urgent needs for weight reduction and multifunctionality in heat-resistant structures, this technology of directly applying coatings to the surface of low-density, weakly rigid heat-resistant materials is of great significance for the technological application and engineering practice of heat-resistant technology. It saves on the weight of resin used for surface hardening, reducing the overall weight of the heat-resistant structure while eliminating the cumbersome surface hardening process, improving the controllability of the overall weight of the heat-resistant structure, and optimizing the heat-resistant structure process technology. This invention effectively reduces technical costs and risks, provides stable process control, and is highly feasible. It can be applied to the surface condition control of low-density, weakly rigid heat-resistant materials with different application requirements. This technology has a wide range of applications, strong applicability, and significant engineering application value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the existing processing principle;

[0018] Figure 2 This is a schematic diagram illustrating the processing principle of the present invention. Detailed Implementation

[0019] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0020] This invention addresses the technical challenges and requirements of low-density, weakly rigid heat-resistant materials. These challenges include the presence of powder and numerous protruding fiber tufts (>0.3mm~0.8mm) on the surface after processing, resulting in poor surface smoothness and affecting the interfacial bonding and surface continuity of the thermal control coating (thickness <0.2mm). Furthermore, the direct application of functional coatings to the surface fails to meet the engineering requirements for heat-resistant structural applications. This invention provides an explanation of surface condition control technology for low-density, weakly rigid heat-resistant materials. The low-density, weakly rigid heat-resistant material is a porous aerogel composite material impregnated with phenolic resin and fiber preforms. Its low-density, porous fiber structure results in the presence of a large amount of powder and numerous 100-micron-sized fiber fracture tufts on its surface. After existing machining, a large amount of these tufts remain and are randomly distributed. After large-scale removal by machine, the short, protruding fiber tufts remaining on the surface exhibit weak fiber rigidity. During contact with rigid machining tools, the tool's travel direction "wobbles," making effective cutting impossible. The technical challenge of this invention is to solve the problem of the "wobbling" of the short, protruding fiber tufts during machining, achieve effective "rigid-to-rigid" cutting, and ensure that the surface condition meets the requirements for subsequent thermal control and other functional coatings.

[0021] The technical solution of this invention, represented by low-density, weakly rigid heat-resistant materials, proposes a method for removing fiber tufts protruding at the hundred-micron level (>0.3mm~0.8mm) to achieve surface condition control. The principle is to fix and reinforce or harden the weakly rigid, short fiber tufts that "wobble" in contact with a rigid cutting tool to increase fiber stiffness, thereby forming an effective cut between the fiber tuft protrusions and the cutting tool. This reduces the surface fiber tuft protrusions to <0.2mm, achieving surface condition control of the low-density, weakly rigid heat-resistant material and meeting the requirements of subsequent coatings for the substrate surface condition.

[0022] A method for controlling the surface condition of a low-density, weakly rigid heat-resistant material includes the following steps:

[0023] Step 1: The low-density, weakly rigid heat-resistant material is a low-density fiber preform reinforced with a functional resin-based heat-resistant material. The preform is made of short-cut fibers needle-punched, with a density of 0.15–0.50 g / cm³. 3 It exhibits a three-dimensional disordered porous structure. Reinforcing resins generally refer to functional resins with ablation properties, and their density ranges from 0.05 to 0.35 g / cm³. 3 The reinforced resin microstructure exhibits a nano-three-dimensional network structure, and the configuration of low-density, weakly rigid heat-resistant materials is generally planar, curved, or rotating. When mounting the low-density, weakly rigid heat-resistant material workpiece on the processing platform, clamping should be performed on the process area of ​​the heat-resistant structure workpiece, ensuring no contact with the product area and no clamping marks on the material surface. The process area is reserved during the material process design based on the processing platform, clamping, and processing characteristics.

[0024] Step 2: After the weak rigid heat-resistant material is clamped, determine the roughing and finishing removal amounts according to the product allowance and size requirements, and select the machining tools and machining parameters for the roughing and finishing stages: Roughing stage: machining speed is 2000~5500r / min, machining depth is 0.5~1.5mm, and machining step is 0.5~1.2mm;

[0025] In this invention, surface condition control adopts a combination of roughing and finishing. Taking into account factors such as processing efficiency, processing cost, and wear and tear of machine tools and cutting tools, the surface condition control technology of this invention adopts the principle of roughing to remove a large amount of size, and finishing to remove the remaining size. Here, a large amount of size refers to the size area ≥ 1 mm away from the product area, and the remaining size refers to the size area < 1 mm away from the product area.

[0026] The processing parameters used vary at different processing stages. In the roughing stage: ordinary metal grinding head is used, the processing speed is 2000-5500 r / min, the processing depth is 0.5-1.5 mm, and the processing step is 0.5-1.2 mm. The processing parameters are adjusted and selected according to the different process allowances of the product.

[0027] In the finishing stage: a special diamond grinding head is used for machining. The ball head type and radius of the machining head are matched and selected according to the flat and curved surface characteristics of the product. The machining speed is 5500~9000r / min, the machining depth is 0.1~0.5mm, the machining step is 0.1~0.5mm, and the machining parameters are adjusted and selected according to the product's process allowance and dimensional accuracy requirements.

[0028] Step 3: In the roughing stage, process according to the selected machining tools and parameters. During the machining process, remove and clean the waste chips and dust particles generated on the tool and material surface in a timely manner to avoid the adhesion of particles or short fibers to the tool, which will cause long-term tool wear and reduced cutting efficiency. After a large amount of dimensional removal is completed, the roughing is finished.

[0029] Step 4: After rough machining, finish machining is performed. Before finishing, a special tool head cover is installed on the machining tool. This tool head cover is a high-strength, thin-walled, hollow metal structure. The head cover and the tool head are connected and fixed by a snap-fit. The surface of the tool head cover in contact with the low-density, weak-rigidity heat-resistant material is generally flat, but can also be curved. The surface of the head cover has a uniformly distributed, fine porous or striped hollow structure. The porous hollow structure is generally circular, but can also be a striped structure. The diameter of the holes or the crack width is designed so that the fiber tufts on the material surface can pass through or form an effective grip. The diameter of a single circular hole is 0.1–0.5 mm, or a single… Each stripe has a width of 0.1–0.5 mm and a length of 3–15 mm (depending on the size of the cutting head). The stripes are evenly distributed along the diameter or generatrix direction. The gaps between multiple holes or stripes are designed to ensure the connection rigidity between the holes or stripes, guaranteeing the maximum perforation structure, typically 0.2 mm. A mechanism with a high-toughness spring is installed at the connection point between the cutting head cover and the cutting head mounting clip. During processing, the fiber protrusions on the surface of the heat-resistant material are inserted into the perforated structure on the surface of the cutting head cover. The head cover provides a holding and fixing constraint to the weakly rigid fiber protrusions. A schematic diagram of the head cover principle is shown below. Figure 2 As shown, this design effectively avoids the "wobbling" problem during direct cutting when fiber tufts contact the high-speed tool, thus achieving effective cutting. Simultaneously, the spring plate of the head cover has extremely high rebound sensitivity, ensuring effective cutting while preventing rigid scratch damage to the surface of weak materials during prolonged processing. After selection, it is installed on the machining head, and machining is performed according to the selected machining tool and parameters. The machining speed is 5500–9000 r / min, the depth of cut is 0.1–0.5 mm, and the machining step distance is 0.1–0.5 mm.

[0030] Step 5: During finishing, promptly remove and clean any excess material such as chips and dust particles from the tool and material surfaces to prevent particles or short fibers from adhering to the tool, causing prolonged tool wear and reduced cutting efficiency. Also, promptly clean and blow away excess dust and chips from the tool head cover to complete the finishing process.

[0031] The surface condition of low-density, weakly rigid heat-resistant materials treated with existing methods and the method of this invention were randomly tested, and the results are shown in Table 1. The results show that the surface condition treated with this invention is significantly improved, decreasing from 0.252 mm to 0.124 mm, which meets the substrate requirements for subsequent functional coatings.

[0032] Table 1 Surface state processed by the method of the present invention

[0033]

[0034] The parts of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for controlling the surface condition of a low-density, weakly rigid heat-resistant material, characterized in that, include: The workpiece made of low-density, weak-rigidity heat-resistant material is clamped on the processing platform; After clamping, determine the roughing removal amount and finishing removal amount according to the workpiece's allowance setting and size requirements, and select the machining tools and machining parameters for the roughing and finishing stages. In the roughing stage, the process area is roughed according to the selected machining tools and machining parameters. During the machining process, the excess material on the tool and material surface is removed and cleaned. After rough machining is completed, a cutter head cover is installed on the machining cutter head; the cutter head cover is connected and fixed to the cutter head by a snap fastener, and the cutter head cover is a metal hollow structure with a number of evenly distributed round holes or striped hollow structures on the surface of the cutter head cover. During the finishing stage, the process area is finished according to the selected machining tools and machining parameters. During the machining process, excess material on the tool and material surface is removed and cleaned.

2. The method for controlling the surface condition of a low-density, weakly rigid heat-resistant material according to claim 1, characterized in that, When a workpiece made of low-density, weak-rigidity heat-resistant material is clamped on a processing platform, the process area of ​​the workpiece is clamped to prevent the clamping tool from contacting the product area and to ensure that there are no clamping marks on the material surface of the workpiece. The process area is the part of the workpiece outside the product area that is reserved according to the process requirements during the material process design.

3. The method for controlling the surface condition of a low-density, weakly rigid heat-resistant material according to claim 1, characterized in that, Rough machining is used to remove areas ≥1mm away from the product area, and fine machining is used to process the remaining dimensions.

4. The method for controlling the surface condition of a low-density, weakly rigid heat-resistant material according to claim 1, characterized in that, In the roughing stage: the machining head is a metal grinding head, the machining speed is 2000~5500 r / min, the machining depth is 0.5~1.5mm, and the machining step is 0.5~1.2mm.

5. The method for controlling the surface condition of a low-density, weakly rigid heat-resistant material according to claim 1, characterized in that, In the finishing stage: the machining head is a diamond grinding head. The ball head type and size radius of the machining head are matched and selected according to the flat and curved surface characteristics of the workpiece. The machining speed is 5500~9000 r / min, the machining depth is 0.1~0.5mm, and the machining step is 0.1~0.5mm.

6. The method for controlling the surface condition of a low-density, weakly rigid heat-resistant material according to claim 1, characterized in that, The diameter of a single circular hole on the surface of the cutter head cover is 0.1~0.5mm, or the width of a single stripe is 0.1~0.5mm and the length is 3~15mm; a spring plate is provided at the snap-fit ​​connection between the cutter head cover and the cutter head, so that the cutter head cover is pressed close to the cutter head during processing and returns to its original position after being released.

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