A manufacturing method for improving the rust resistance of a composite material mold

Abstract

The application discloses a manufacturing method for improving the rustproof performance of a composite material mold, the mold comprises a mold main body and a forming positioning assembly, and the manufacturing process comprises the following steps: S1, selecting a steel material with an atmospheric corrosion resistance performance coefficient greater than or equal to 5; S2, welding the selected steel material to obtain the mold, and performing heat treatment, aging, mechanical processing and polishing on the working surface of the mold main body; S3, performing rustproof treatment on the non-working surface of the mold main body; and performing rustproof treatment on the forming positioning assembly. The mold has excellent rustproof performance, and the risk of paint surface cracking and peeling does not occur, the mold has a long service life, the material cost is reduced by more than 70%, and the mold use and maintenance cost is reduced; the mold can ensure long-term stability of the composite material product profile precision and surface quality, is beneficial to batch production of the composite material part mold, and achieves the purposes of high quality and low cost.

Description

Technical Field

[0001] This invention relates to the field of composite material mold manufacturing technology, and in particular to a manufacturing method for improving the rust resistance of composite material molds. Background Technology

[0002] Modern aircraft manufacturing extensively utilizes advanced composite materials. Composite material parts are formed by hot pressing in an autoclave under a mold. The contour accuracy, high-temperature and high-pressure airtightness, and surface quality (roughness, waviness) of the mold used for forming have a significant impact on the accuracy and surface quality of composite material products. Therefore, the long-term stability of the accuracy, airtightness, and surface quality of composite material molds is a necessary condition to ensure the stability of the accuracy and surface quality of composite material products.

[0003] Currently, commonly used materials in mold manufacturing include low-expansion alloys, carbon fiber composites, aluminum alloys, and ordinary steel. Low-expansion alloys (such as 4J36) have a low coefficient of thermal expansion, high density, are not easily corroded by the atmosphere, have a long service life, and a short manufacturing cycle; however, their cost is more than 30 times that of ordinary steel. Carbon fiber composites have a low coefficient of thermal expansion, low density, and are not corroded by the atmosphere; however, their manufacturing cycle is long, their cost is more than 20 times that of ordinary steel, and their service life is relatively short. Both low-expansion alloys and carbon fiber composites are expensive and unsuitable for manufacturing composite material molds with low cost requirements. Aluminum alloys have a low density, are not easily corroded by the atmosphere, have a long service life, and a short manufacturing cycle; however, their coefficient of thermal expansion is very high, and their cost is 3-5 times that of ordinary steel, making them unsuitable for manufacturing molds for large, complex, and precision composite material products with curing temperatures exceeding 100℃. Ordinary steel has high density, low cost, short manufacturing cycle, and long service life; however, it has a large coefficient of thermal expansion and is prone to atmospheric corrosion. It is suitable for molds of general composite products with less stringent precision requirements and cost control requirements. Commonly used ordinary steel materials include domestic Q235A and 20 steel, and foreign ordinary steel materials such as AISI1015, ST37-2, ST52, and ASTM A572 GR50. Due to its lowest material cost, easiest procurement, and best welding, forming, and processing performance, it has long been the most commonly used material for molds of general composite products in the domestic and foreign aerospace fields. Rust prevention treatment for such ordinary steel composite molds is spraying high-temperature resistant paint or performing conventional oxidation treatment. After a period of use, steel molds will rust. Rust will directly affect the geometric accuracy and surface quality of composite parts, causing product quality problems, and in severe cases, leading to product scrapping and significant losses. Therefore, research on rust prevention technology for composite material molds, including the rust prevention performance of the matrix of various parts themselves, and the adaptive rust prevention treatment of various parts, is essential for improving the surface quality of composite material products, avoiding scrap, and reducing costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem in the prior art that low-cost ordinary steel composite material mold parts have poor rust resistance, which affects the surface quality of composite material products and even causes the composite material products to be scrapped. The invention provides a manufacturing method to improve the rust resistance of composite material molds, thereby improving the surface quality of composite material products and preventing the composite material products from being scrapped.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A manufacturing method for improving the rust resistance of composite material molds, the mold comprising a mold body and a forming and positioning assembly, the manufacturing process comprising the following steps:

[0007] Step S1: Select steel materials with an atmospheric corrosion resistance coefficient ≥ 5;

[0008] Step S2: The mold is obtained by welding the steel material selected in step S1, and then heat treatment and aging, machining, and polishing the working surface of the mold body.

[0009] Step S3: Perform rust prevention treatment on the non-working surfaces of the mold body according to the following steps:

[0010] Step S311: Clean the non-working surfaces of the mold body; the surface cleaning process includes sandblasting to remove rust, grinding the surface welding slag and unremoved oxides, and then removing oil and dust.

[0011] Step S312: Spray a heat-resistant primer onto the non-working surface of the mold body and cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes.

[0012] Step S313: Spray a heat-resistant topcoat onto the non-working surface of the mold body and cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes.

[0013] The forming and positioning components shall be rust-proofed according to the following steps:

[0014] Step S321: Perform surface cleaning treatment on the forming and positioning components; the surface cleaning treatment includes pickling, degreasing, rust removal, and washing;

[0015] Step S322: Chemically plate an anti-corrosion alloy on the surface of the forming and positioning component, and then heat the forming and positioning component to 220±20℃ and hold for 120±20 minutes.

[0016] This invention provides a manufacturing process for rust-resistant steel molds. Steel with an atmospheric corrosion resistance coefficient ≥5 is selected for mold manufacturing. The steel is cut and welded according to the mold structure, followed by heat treatment aging and machining. The working surfaces of the mold body are polished to meet the geometric accuracy and roughness requirements of the mating surfaces. The mold, made of steel with an atmospheric corrosion resistance coefficient ≥5, has excellent rust resistance. Then, the mold body and forming / positioning components are subjected to rust-proofing treatment. The rust-proofing of the non-working surfaces of the mold body involves spraying a high-temperature resistant primer and topcoat. Both the primer and topcoat are cured by heat. This results in better adhesion between the primer and the metal substrate steel, and better adhesion between the topcoat and primer, reducing the risk of paint cracking and peeling caused by thermal expansion and contraction during the mold's "cold-hot-cold" cycle, thus effectively improving rust resistance. The rust-proofing of the forming / positioning components uses a chemically plated anti-corrosion alloy. The mold has excellent wear resistance and a highly dense surface layer, resulting in superior rust prevention.

[0017] Furthermore, the specific process for selecting steel materials is as follows:

[0018] Step S11: Conduct chemical composition testing on the spare steel material;

[0019] Step S12: Calculate the atmospheric corrosion resistance coefficient based on the chemical composition using the Larrabee-Coburn method;

[0020] Step S13: Select steel with an atmospheric corrosion resistance coefficient ≥ 5 as the mold material.

[0021] Furthermore, when selecting steel materials, an atmospheric corrosion resistance coefficient ≥ 6.5 is required. The atmospheric corrosion resistance coefficient reflects the corrosion resistance of the steel material. The higher the atmospheric corrosion resistance coefficient, the better the rust prevention performance of the mold prepared. In practical engineering, steel materials with an atmospheric corrosion resistance coefficient that meets the requirements can be selected according to the application needs.

[0022] Furthermore, the selected steel material is Q235NH or Q295GNH.

[0023] Furthermore, the mold body includes a frame, forming template, and gantry. The mold body is the main structure of the entire mold and has a relatively large size. The forming and positioning components include reinforcing rib forming blocks, small inserts, drill templates, and vacuum joints. The forming and positioning components are used for the forming and positioning of composite materials and have a relatively small size.

[0024] Furthermore, the corrosion-resistant alloy is a nickel-phosphorus alloy.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The rust-proof steel material mold of this invention selects steel material with an atmospheric corrosion resistance coefficient ≥5. The steel material is cut and welded according to the mold structure, followed by heat treatment aging and machining. The working surface of the mold body is polished to meet the geometric accuracy and roughness requirements of the mating surface. The mold uses steel material with an atmospheric corrosion resistance coefficient ≥5, and the working surface of the mold still has good rust resistance. Then, the mold body and the forming and positioning components are respectively subjected to rust prevention treatment. The rust prevention treatment of the mold body is to spray a primer and topcoat with high temperature resistance. After spraying the primer and topcoat, they are cured by heating. The primer has better adhesion to the metal substrate steel material, and the topcoat has better adhesion to the primer. This can reduce the risk of paint cracking and peeling caused by thermal expansion and contraction during the "cold-hot-cold" cycle of the mold, thereby effectively improving the rust prevention ability. The rust prevention treatment of the forming and positioning components is to use chemical anti-corrosion alloy plating, which greatly improves the wear resistance and corrosion resistance of the mold, and the surface layer is extremely dense, resulting in excellent rust prevention effect.

[0027] 2. The rust-resistant steel material mold of this invention has excellent rust-resistant performance. Under the "cold-hot-cold" conditions during composite material part preparation, there is no risk of paint cracking or peeling. The mold has a long service life, and the maintenance cost is reduced. This invention uses low-cost steel plate material to manufacture the mold, which has good rust resistance. Compared with low-expansion alloy materials and carbon fiber composite materials with good rust resistance, the material cost of this invention is reduced by more than 70%. Compared with traditional rust-resistant technology for Q235A material, the rust resistance of the mold prepared by this invention can be improved by 5-10 times, ensuring the long-term stability of the surface accuracy and quality of composite material products. This is beneficial for mass production of molds for composite material parts, achieving high quality and low cost, and ensuring stable precision and quality of mass-produced composite material parts. Attached image description:

[0028] Figure 1 A flowchart illustrating a manufacturing method for improving the rust resistance of composite material molds;

[0029] Figure 2 The images show the on-site results of atmospheric corrosion resistance tests on steel materials: (a) Q235NH; (b) Q235A. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0031] Example 1

[0032] The molds used in the production of composite material parts are made of low-cost steel. The working surfaces of the molds have very high requirements for geometric accuracy, surface roughness, and high temperature, high pressure and airtightness. The surface of the molds is treated with high-temperature resistant paint. In actual production, it has been found that after a period of use, in the closed environment of the autoclave heated by high-speed airflow, the high-temperature resistant paint will loosen and delaminate due to the inconsistency of the coefficient of thermal expansion and contraction with the steel material. Rust will occur where the delaminated paint falls off. Loose, delaminated, paint skin, paint chips, rust skin, and rust chips of different sizes will fall off, which will not only contaminate the instruments and meters of the autoclave, but may also puncture the vacuum seal bag, causing the composite material parts to be scrapped due to the bag breaking. The corrosion of the working surface of the mold directly affects the geometric accuracy and surface quality of the composite material parts.

[0033] A method for improving the rust resistance of composite material molds, wherein the mold includes a mold body and forming and positioning components, such as... Figure 1 As shown, the manufacturing process includes the following steps:

[0034] Step S1: Select steel materials with an atmospheric corrosion resistance coefficient ≥ 5;

[0035] The specific process for selecting steel materials is as follows:

[0036] Step S11: Conduct chemical composition testing on the spare steel material;

[0037] Step S12: Calculate the atmospheric corrosion resistance coefficient based on the chemical composition using the Larrabee-Coburn method;

[0038] Step S13: Select steel with an atmospheric corrosion resistance coefficient ≥ 5 as the mold material.

[0039] The steel material standards selected are GB / T 4171-2008 "Weathering Structural Steel" and GB / T 699-2015 "High-Quality Carbon Structural Steel". The atmospheric corrosion resistance coefficients of common steel materials were calculated using the Larrabee-Coburn method. The calculation results are shown in Table 1 below.

[0040] Table 1 Performance parameters of common steel materials

[0041]

[0042] Commonly used steel materials exhibit significant variations in their chemical composition, resulting in substantial fluctuations in their actual atmospheric corrosion resistance. As shown in Table 1, some materials have very low maximum values ​​for their atmospheric corrosion resistance index (I). max <2, such as domestic Q235A and foreign ST52, theoretically have very poor atmospheric corrosion resistance. Some materials have a relatively high minimum value of atmospheric corrosion resistance index I (I min>5), such as domestically produced Q235NH and Q295GNH, theoretically have good atmospheric corrosion resistance, and the higher the I value, the better the atmospheric corrosion resistance. Some materials have very low minimum atmospheric corrosion resistance index I and very high maximum values, such as domestically produced 20 steel, whose atmospheric corrosion resistance varies greatly, ranging from poor (I=0.25) to good (I=6.4). In this embodiment, Q235NH is selected as the steel material for manufacturing the mold.

[0043] To test the atmospheric corrosion resistance of Q235NH, Q235NH and Q235A material specimens were hot-pressed together with the composite material specimens in an autoclave. The hot-pressing conditions were 180-200℃ / 24-72h, cyclically repeated. After about 3 months, no rust powder was found on the surface of the Q235NH steel. Figure 2 (a)), while Q235A suffered severe corrosion ( Figure 2 (b) indicates that the rust prevention performance of Q235NH is significantly higher than that of Q235A.

[0044] In some embodiments, when selecting steel materials, an atmospheric corrosion resistance coefficient ≥ 6.5 is required. The atmospheric corrosion resistance coefficient reflects the corrosion resistance of the steel material. The higher the atmospheric corrosion resistance coefficient, the better the rust prevention performance of the mold prepared. In practical engineering, steel materials with an atmospheric corrosion resistance coefficient that meets the requirements can be selected according to the application needs.

[0045] Step S2: The mold is obtained by welding the steel material selected in step S1, and then heat treatment and aging, machining, and polishing the working surface of the mold body.

[0046] According to different functions, the mold is divided into a mold body and forming and positioning components. The mold body includes a frame, forming template, gantry, etc., and is the main structure of the entire mold. The mold body is relatively large. The forming and positioning components include reinforcing rib forming blocks, small inserts, drill templates, and vacuum joints, etc. The forming and positioning components are used for forming and positioning composite materials and are relatively small. The mold body and forming and positioning components are manufactured using different steel materials according to different requirements, but all must meet an atmospheric corrosion resistance coefficient ≥5. Using the steel material selected in step S1, each part is cut using CNC machining allowance according to the mold's numerical model, and then assembled and welded to obtain mold bodies and forming and positioning components with different structures. Then, the mold body and forming and positioning components undergo heat treatment aging. The heat treatment aging conditions are heating to 600 degrees Celsius, holding for 2 hours, and cooling at a set rate. Machining is used to process the shapes that need to be set in the mold, such as curved surface machining. Polishing is used to treat the working surface of the mold body, which refers to the contact surface between the mold and the composite material part. Polishing ensures that the working surface of the mold meets the geometric accuracy and roughness requirements of the contact surface.

[0047] Step S3: Perform rust prevention treatment on the non-working surfaces of the mold body according to the following steps:

[0048] Step S311: Clean the non-working surfaces of the mold body; the surface cleaning process includes sandblasting to remove rust, grinding the surface welding slag and unremoved oxides, and then removing oil and dust.

[0049] Step S312: Spray a primer with a temperature resistance of ≥300℃ onto the non-working surface of the mold body, and then cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes.

[0050] Step S313: Spray a topcoat with a temperature resistance of ≥300℃ onto the non-working surface of the mold body, and then cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes.

[0051] The forming and positioning components shall be rust-proofed according to the following steps:

[0052] Step S321: Perform surface cleaning treatment on the forming and positioning components; the surface cleaning treatment includes pickling, degreasing, rust removal, and washing;

[0053] Step S322: Chemically plate an anti-corrosion alloy onto the surface of the forming and positioning component, then heat the forming and positioning component to 220±20℃ and hold for 120±20 minutes. During the coating process, the anti-corrosion alloy is a nickel-phosphorus alloy, and the coating thickness is 0.008-0.01mm. After the coating is completed, heat harden and stabilize the coating. The surface hardness of the finished forming and positioning component is ≥HV700.

[0054] The mold body and the forming positioning component are located in different positions of the mold and play different roles in the process of forming composite materials. Therefore, the requirements for rust prevention are also different. The forming positioning component has higher requirements for wear resistance and rust prevention during use. Since the liquid tank of the chemical coating equipment has size limitations, the forming positioning component is small in size and can meet the requirements. Therefore, the surface of the forming positioning component is treated with chemical nickel-phosphorus alloy plating. All surfaces and inner holes can be coated. The mold body is treated with high temperature resistant paint for rust prevention.

[0055] In existing technologies, the rust prevention treatment of the mold body involves spraying high-temperature resistant paint, which has the problems of easy paint peeling and easy mold corrosion. The rust prevention treatment of the mold body of the present invention involves heating and curing both the primer and topcoat after spraying. The primer has better adhesion to the metal substrate steel material, and the topcoat has better adhesion to the primer. This can reduce the risk of paint cracking and peeling caused by thermal expansion and contraction during the "cold-hot-cold" cycle of the mold, thereby effectively improving the rust prevention ability. The rust prevention performance of the mold body manufactured by the existing technology and the mold body treated with the rust prevention of the present invention were tested. The test results showed that the rust prevention performance of the steel plate made of Q235NH material, when heated and cured with the high-temperature resistant paint of the present invention, was improved by more than 5 times.

[0056] In existing technologies, the rust prevention treatment for forming and positioning component molds involves oxidation (bluing). However, the surface layer of rust-preventive material (mainly Fe3O4) lacks density and has very low hardness. Especially during the "cold-hot-cold" cycle of composite material molds, the bonding force between the surface rust-preventive material and the substrate weakens due to thermal expansion and contraction, making delamination highly likely. The loose layer absorbs moisture from the air, further accelerating substrate corrosion, leading to increasingly poor surface rust prevention and more severe mold corrosion. The forming and positioning component of this invention uses chemical nickel-phosphorus alloy plating and heat hardening, with a plating thickness of 0.008-0.01 mm, achieving a plating hardness ≥ HV700. The mold after forming exhibits excellent wear resistance and extremely high surface density, resulting in superior rust prevention. Rust prevention performance tests were conducted between forming and positioning component molds manufactured using existing technology and those treated with the rust prevention of this invention. The chemical nickel-phosphorus alloy plating and heat hardening method of this invention improved rust prevention performance by 10 times.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A manufacturing method for improving the rust resistance of composite material molds, characterized in that, The mold includes a mold body and forming and positioning components. The manufacturing process includes the following steps: Step S1, Select steel material with an atmospheric corrosion resistance coefficient ≥5; Step S2: The mold is obtained by welding the steel material selected in step S1, and then heat treatment and aging, machining, and polishing the working surface of the mold body. Step S3: Perform rust prevention treatment on the mold body according to the following steps: Step S311: Clean the non-working surfaces of the mold body; the surface cleaning treatment includes sandblasting to remove rust from the non-working surfaces, grinding the surface welding slag and unremoved oxides, and then removing oil and dust. Step S312: Spray a heat-resistant primer onto the non-working surface of the mold body and cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes. Step S313: Spray a heat-resistant topcoat onto the non-working surface of the mold body and cure it. The curing conditions are: heat up to 80±10℃ and keep it at that temperature for 50±20 minutes. The forming and positioning components shall be rust-proofed according to the following steps: Step S321: Perform surface cleaning treatment on the forming and positioning components; the surface cleaning treatment includes pickling, degreasing, rust removal, and washing; Step S322: Chemically plate an anti-corrosion alloy onto the surface of the forming and positioning component, and then heat the forming and positioning component to 220± Keep warm at 20℃ for 120±20 minutes.

2. The manufacturing method for improving the rust resistance of composite material molds according to claim 1, characterized in that, The specific process for selecting steel materials is as follows: Step S11, chemical composition testing of the prepared steel materials; Step S12: Calculate the atmospheric corrosion resistance coefficient based on the chemical composition using the Larrabee-Coburn method; Step S13: Select steel with an atmospheric corrosion resistance coefficient ≥ 5 as the mold material.

3. The manufacturing method for improving the rust resistance of composite material molds according to claim 2, characterized in that, When selecting steel materials, the atmospheric corrosion resistance coefficient is required to be ≥6.

5.

4. The manufacturing method for improving the rust resistance of composite material molds according to claim 1, characterized in that, The main body of the mold includes a frame, a forming template, and a gantry frame. The forming and positioning components include a reinforcing rib forming block, a small insert, a drilling template, and a vacuum connector.

5. The manufacturing method for improving the rust resistance of composite material molds according to claim 1, characterized in that, The corrosion-resistant alloy is a nickel-phosphorus alloy.

6. The manufacturing method for improving the rust resistance of composite material molds according to any one of claims 1 or 2, characterized in that, The selected steel material is Q235NH or Q295GNH.

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