Production process of winding formed glass steel short pipe flange

Abstract

The application belongs to the technical field of pipeline connection, and particularly relates to a production process of a winding-formed glass fiber reinforced plastic (FRP) short pipe flange, which comprises the following steps: preparation of composite filler resin glue solution, pipeline winding forming, pipeline end surface treatment, preparation and assembly of a flange winding mold, flange winding forming, step-by-step curing and demolding, flange back gradient composite reinforcement, and finished product inspection and warehousing; the application adopts a composite filler modified resin system, combines a triple interface treatment process of physical polishing, chemical activation and homologous primer compounding, and realizes multi-dimensional collaborative innovation of material modification, interface strengthening, mold structure optimization, curing process regulation and gradient structure reinforcement, so that the mechanical bearing stability and long-term service reliability of the glass fiber reinforced plastic short pipe flange are significantly improved, and the glass fiber reinforced plastic short pipe flange is suitable for various outdoor complex pipeline working conditions.

Description

Technical Field

[0001] This invention belongs to the field of pipeline connection technology, specifically relating to a manufacturing process for fiberglass short pipe flanges formed by spiral winding. Background Technology

[0002] Fiberglass short pipe flanges, as core connecting accessories in petrochemical, municipal water supply and drainage, and environmental protection and corrosion-resistant pipeline systems, are gradually replacing traditional metal flanges due to their advantages such as lightweight, high strength, corrosion resistance, excellent insulation, and convenient molding. They are widely used in sealing connection scenarios for various medium and low pressure fluid transportation pipelines. Currently, the mainstream molding methods for fiberglass short pipe flanges in the industry are mainly divided into two categories: split bonding molding and integral spiral winding molding. The corresponding manufacturing processes have been publicly applied in existing technologies.

[0003] To improve the molding defects of FRP flanges, existing technologies generally employ conventional modification methods such as single mineral filler modification, conventional surface grinding, constant-temperature one-time curing, and simple homogeneous thickening reinforcement. For example, existing publicly available technologies often use conventional inorganic powders such as calcium carbonate, talc, and barium sulfate as resin filler modifiers, which only simply improve the matrix hardness and molding stability, resulting in defects such as limited filler function, easy generation of interlayer residual stress, and poor weather and aging resistance. Simultaneously, conventional processes only use simple physical grinding or simple coupling agent application for interface treatment, resulting in weak molecular bonding at the pipe-flange winding interface, failing to achieve a high-strength integrated bond. In summary, existing FRP pipe flange manufacturing processes generally suffer from the following technical shortcomings: high residual internal stress after molding, easy cracking during drilling, and insufficient weather and corrosion resistance; low bonding strength at the pipe-flange interface, and easy delamination and leakage. Therefore, there is an urgent need to develop a modified FRP short pipe flange production process that balances interface bonding strength, low-stress molding, weather resistance and crack resistance, and gradient reinforcement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a manufacturing process for fiberglass short pipe flanges using spiral winding. This invention employs a composite filler-modified resin system, combined with a triple interface treatment process involving physical polishing, chemical activation, and homogeneous primer coating. This is complemented by a complete process including precise assembly with a split mold featuring stress-buffered grooves, segmented gradient curing, and multi-dimensional gradient composite reinforcement on the back. Through multi-dimensional synergistic innovation in material modification, interface strengthening, mold structure optimization, curing process control, and gradient structural reinforcement, this invention effectively solves the technical shortcomings of traditional processes, such as stress concentration during molding, weak interface bonding, easy deformation and cracking of finished products, and insufficient aging resistance. It significantly improves the structural density, interface integrity, mechanical load-bearing stability, and long-term service reliability of fiberglass short pipe flanges. The product is suitable for various complex outdoor pipeline conditions, with strong process controllability and a high finished product qualification rate, possessing excellent industrial application prospects and technological advancement.

[0005] This invention provides a manufacturing process for fiberglass short pipe flanges formed by spiral winding, specifically including the following steps: Step 1, Preparation of composite filler resin solution: Prepare composite filler resin solution; Step 2, pipe winding and molding: The composite filler resin solution prepared in Step 1 is injected into the impregnation tank. Continuous glass fiber roving is used as the reinforcing material. After being fully impregnated with the composite filler resin solution in the impregnation tank, it is wound and molded on the pipe mandrel. The winding method is to alternate between circumferential winding and cross winding. After the pipe is wound, it is left to stand at room temperature for 30 to 60 minutes to obtain a pre-cured pipe semi-finished product. Step 3, Pipe End Surface Treatment: Grind the surface of the flange connection area at the pipe end to remove the resin-rich layer. Use an angle grinder with 60-120 grit sandpaper for grinding. Apply a chemical activation treatment solution to the ground surface. The activation treatment solution consists of: 5-10 parts methyl ethyl ketone peroxide, 20-30 parts acetone, 1-3 parts silane coupling agent KH-550, and 50-75 parts deionized water. After application, let it stand at room temperature for 10-15 minutes to allow the activation solution to fully react with the pipe surface. After activation treatment, wipe the surface 2-3 times with anhydrous ethanol to remove residual activation solution. After activation treatment, cleaning, and drying, apply a primer. The primer is a mixture of the following components: 100 parts epoxy resin and silane coupling agent KH-570. 3-5 parts, 1-3 parts of the composite filler from step one, and 10-20 parts of diluent (butyl glycidyl ether). After stirring the above components evenly, use a brush to evenly apply the mixture to the activated surface of the pipe end. The coating thickness should be controlled at 0.05-0.15 mm. After application, let it air dry at room temperature for 10-20 minutes until the surface of the primer is no longer sticky to the touch. This will give you a semi-finished pipe with activated ends and a primer coating. Step 4, Preparation and Assembly of Flange Winding Mold: Prepare an independent flange winding mold. Before use, clean the mold to remove surface dirt and apply 2-3 layers of release agent evenly. The flange winding mold is a split structure, including a flange baffle, flange core and connecting shaft. The mating surface between the mold and the pipe end is provided with an annular stress buffer groove. The groove depth is 10%-20% of the pipe wall thickness and the width is 30%-50% of the pipe wall thickness. After the flange is wound, the groove naturally forms an annular stress release structure at the root of the flange. Assemble the prepared flange winding mold to the end of the pipe semi-finished product that has been activated and coated with a base coating. The assembly method adopts a tapered fit. The inner taper of the mold is consistent with the outer taper of the pipe end to ensure the coaxiality of the mold and the pipe. After assembly, use a positioning clamp to fix the mold to obtain a pipe assembly with the flange winding mold. Step 5, Flange Winding: The composite filler resin solution prepared in Step 1 is used as the resin system for flange winding. After the continuous glass fiber roving is impregnated with the composite filler resin solution, the flange is wound on the flange winding mold of the pipe assembly equipped with the flange winding mold. The winding method is as follows: First, 2-3 layers of cross winding are made at the root of the flange, and then the main body of the flange is wound. The method of circumferential winding and radial alternating winding is adopted. During the winding process, every 2-3 layers are rolled with pressure rollers to remove air bubbles between layers, and a semi-finished product in which the pipe and flange are wound together is obtained. Step 6, Step-by-step curing and demolding: The semi-finished product with pipe and flange wrapped together is sent into the curing oven for distributed curing. First stage pre-curing: The semi-finished product with flange wrapped is sent into the curing oven and heated at 80~100℃ for 1.5~2 hours to make the resin reach the gel state but not completely cured. Second stage post-curing: After pre-curing, raise the temperature of the curing oven to 130~150℃ and keep it at that temperature for 2~3 hours to allow the resin to fully cure. Let it cool naturally to room temperature, demold, remove the positioning clamps, and remove the flange winding mold from the end of the pipe to obtain the demolded flange fitting. Step 7, Gradient Composite Reinforcement on Flange Back: The back of the demolded flange fitting is roughened by grinding. Then, a gradient reinforcement structure is made from the inside to the outside on the back of the flange. After the gradient reinforcement layer is laid, the product is placed in a curing oven and heated at 60~80℃ for 2~3 hours to complete the curing of the reinforcement layer. Drilling and finishing: The position of the bolt holes is determined according to the flange standard. The bolt holes are machined on the flange surface using a drilling machine. After drilling, the edges and walls of the bolt holes are ground and finished to obtain the flange fitting. Step 8, finishing: The sealing surface of the flange fitting is finished to produce a smooth and flat sealing surface. An annular sealing water line is machined on the sealing surface. After passing the inspection, the fiberglass flange short pipe is obtained.

[0006] Furthermore, the composite filler resin solution comprises the following raw materials in parts by weight: the composite filler is composed of the following components in parts by weight: 3-8 parts of bio-based lignin micro powder, 2-5 parts of nano titanium dioxide, and 0.5-2 parts of graphene micro flakes.

[0007] The preparation steps of the composite filler resin solution are as follows: (1) Take bio-based lignin micro powder, nano titanium dioxide and graphene micro flakes and premix them. In a high-speed mixer, premix for 10 to 15 minutes at 500 to 1000 r / min to make the components initially uniformly distributed and form a composite filler. Add the composite filler to 100 parts of epoxy resin and then perform high-speed shear dispersion at 2000 to 3000 r / min for 20 to 30 minutes. Use shear force to break up the aggregates of graphene micro flakes and nano titanium dioxide, and at the same time promote the full adsorption of lignin on the graphene surface to obtain a mixture. (2) Place the mixture in an ultrasonic dispersion device for ultrasonic cavitation treatment. Ultrasonic treatment at 40kHz frequency for 15~20 minutes. After dispersion, add curing agent (methyltetrahydrophthalic anhydride, 80~90 parts) and accelerator (DMP-30, 1~2 parts), stir evenly, and obtain composite filler modified resin liquid.

[0008] Furthermore, the gradient reinforcement structure consists of an inner stress buffer layer, a middle shear transition layer, and an outer tensile reinforcement layer, arranged from the inside out. The preparation method is as follows: Stress buffer layer: Take chopped strand mat (CSSM) and cut it to the design size to match the reinforcement area on the back of the flange. Lay it over the central area and root transition area on the back of the flange. Apply the composite filler resin solution prepared in step one to the surface of the CSSM, ensuring the mat is fully impregnated with resin, controlling the resin content to 35-45 wt%. During the application process, repeatedly roll the mat with a pressure roller to remove air bubbles and ensure a tight bond between the CSSM and the back of the flange. Shear transition layer: When the resin on the surface of the stress buffer layer is not fully cured, take a piece of plain fiberglass cloth with a unit area mass of 200~400g / m², cut it into fan-shaped pieces, and lay it radially on the surface of the stress buffer layer with the center of the flange. During laying, control the fiber direction to be at an angle of ±45° to the radial direction of the flange, and the fiber direction between layers to be orthogonal. Use the composite filler resin solution prepared in step one to brush and impregnate, control the resin content, and roll with a pressure roller to remove air. Tensile reinforcement layer: After applying a coupling agent solution to the surface of the shear transition layer, continuous glass fiber roving is wound in a circumferential winding manner, with the fiber direction along the flange circumference, i.e., circumferentially wound at 90°. The composite filler resin solution prepared in step one is used for impregnation, with the resin content controlled.

[0009] Coupling agent solution is applied between the stress buffer layer and the shear transition layer, and between the shear transition layer and the tensile reinforcement layer, and then allowed to air dry for 3-5 minutes.

[0010] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention constructs a ternary synergistic composite filler system of bio-based lignin micropowder, nano titanium dioxide, and graphene microflakes. Relying on the non-covalent interaction between lignin and graphene and the amphiphilic compatibility of lignin, a stable and dense three-dimensional filler network structure is formed. This structure can effectively buffer the shrinkage stress of resin curing, shield against ultraviolet aging corrosion, and improve the cross-linking density of the resin. It improves the defects of fiberglass matrix, such as high brittleness, high residual stress, poor weather resistance, and high water absorption, from the material source, and significantly improves the structural stability and long-term aging and corrosion resistance of the flange matrix.

[0011] This invention employs a triple interface composite treatment process combining physical grinding, chemical activation, and homologous filler primer coating. Mechanical roughening constructs a physical interlocking structure, followed by chemical activation to introduce highly active reaction sites. Finally, a primer liquid containing homologous composite filler is applied, enabling the pipe substrate and subsequent flange winding layer to form a dual bonding mechanism of physical interlocking and chemical cross-linking, significantly improving the overall interface bonding and interlayer shear stability.

[0012] This invention employs a three-dimensional gradient composite reinforcement structure with differentiated fiber morphology, layup angle, and resin content from the inside out. The inner layer's disordered short fiber stress buffer structure is adapted to absorb impact stress, the middle layer's orthogonal cross-layup structure enhances interlayer shear resistance, and the outer layer's circumferentially continuous winding structure bears circumferential tensile loads. Combined with interlayer coupling reinforcement treatment, this achieves layered matching of stress on the flange back and progressive load bearing, significantly improving the flange's overall mechanical load-bearing capacity, fatigue resistance, and pressure sealing stability.

[0013] The fiberglass short pipe flange prepared by this invention has high interfacial bonding strength, low residual stress, high dimensional accuracy, excellent weather resistance and corrosion resistance, and excellent mechanical load-bearing stability. The reliability and service life of the product are significantly improved, and it is suitable for various medium and high pressure, corrosive, and complex outdoor pipeline conditions, and has extremely high industrialization and promotion value. Attached Figure Description

[0014] Figure 1 This is a flow chart of the production process of the fiberglass short pipe flange formed by winding according to the present invention; Figure 2 The figure shows the aging resistance results of the fiberglass short pipe flange prepared according to the present invention. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0017] Unless otherwise specified, all methods described in the following examples are conventional. Unless otherwise specified, all materials used in the following examples are new materials purchased from the market. Specifically, the epoxy resin is type E-44; the graphene microsheets are 1-10 µm in size and 1-5 nm in thickness; and the glass fiber chopped strand mat has a unit area mass of 300-450 g / m². 2 Resin content 35~45wt%; glass fiber plain weave fabric, unit area mass 200~400g / m² 2 Fiber angle ±45°, resin content 25~35wt%; glass fiber untwisted roving, fiber angle circumferential 90°, resin content 20~25wt%.

[0018] according to Figure 1 The production process flow diagram of the fiberglass short pipe flange formed by winding of this invention is illustrated in the following embodiment: Example 1: This example provides a manufacturing process for a spiral wound fiberglass short pipe flange, specifically including the following steps: Step 1, Preparation of composite filler resin solution: Prepare composite filler resin solution; Step 2, pipe winding and molding: The composite filler resin solution prepared in Step 1 is injected into the impregnation tank. Continuous glass fiber roving is used as the reinforcing material. After being fully impregnated with the composite filler resin solution in the impregnation tank, it is wound and molded on the pipe mandrel. The winding method is to alternate between circumferential winding (90°) and cross winding (±45°). The number of winding layers is determined according to the pipe design pressure. After the pipe is wound, it is left to stand at room temperature for 30 minutes to allow the resin to reach the gel state but not to be completely cured, thus obtaining a pre-cured pipe semi-finished product. Step 3, Pipe End Surface Treatment: Grind the surface of the flange connection area at the pipe end to remove the resin-rich layer and expose the glass fiber. The surface roughness Ra after grinding is 12.5 μm. Apply a chemical activation treatment solution to the ground surface. The activation treatment solution consists of 5 parts methyl ethyl ketone peroxide, 20 parts acetone, 1 part silane coupling agent KH-550, and 74 parts deionized water. After application, let it stand at room temperature for 10 minutes to allow the activation solution to fully react with the pipe surface. After activation treatment, wipe the surface twice with anhydrous ethanol to remove residual activation solution. After activation treatment, cleaning, and drying, apply a primer. The primer is a mixture of the following components: 100 parts epoxy resin and silane coupling agent KH-570. 3 parts, 1 part of the composite filler from step one, and 10 parts of butyl glycidyl ether are mixed evenly and then evenly brushed onto the activated surface of the pipe end with a brush. The coating thickness is controlled at 0.05 mm. After brushing, the pipe is dried at room temperature for 10 minutes until the surface of the primer is no longer sticky. This yields a semi-finished pipe with activated ends and a primer coating. Step 4, Preparation and Assembly of Flange Winding Mold: Prepare an independent flange winding mold. The mold material is steel or fiberglass. The mold surface matches the required flange shape. Before use, clean the mold to remove surface dirt and evenly apply two layers of release agent. The flange winding mold is a split structure, including a flange baffle, a flange core, and a connecting shaft. The mating surface between the mold and the pipe end is provided with an annular stress buffer groove. The groove depth is 10% of the pipe wall thickness, and the width is 30% of the pipe wall thickness. After the flange is wound, this groove naturally forms an annular stress release structure at the flange root. Assemble the prepared flange winding mold to the end of the pipe semi-finished product that has been activated and coated with a base layer. The assembly method adopts a tapered fit. The inner taper of the mold is consistent with the outer taper of the pipe end to ensure the coaxiality of the mold and the pipe. After assembly, use a positioning clamp to fix the mold to obtain a pipe assembly with the flange winding mold. Step 5, Flange Winding: Using the composite filler resin solution prepared in Step 1 as the resin system for flange winding, continuous glass fiber roving is impregnated with the composite filler resin solution. Then, the flange is wound on the flange winding mold of the pipe assembly equipped with the flange winding mold. The winding method is as follows: First, two layers are wound at ±45° cross-winding at the root of the flange (where the flange and the pipe meet) to ensure continuous fiber transition at the root. Then, the main body of the flange is wound, using a combination of circumferential winding (90°) and radial alternating winding until the designed thickness is reached. During the winding process, a pressure roller is used to roll every two layers to remove air bubbles between layers, resulting in a semi-finished product in which the pipe and flange are wound together. Step 6, Step-by-step curing and demolding: The semi-finished product with pipe and flange wound together is sent into the curing oven for distributed curing. First stage pre-curing: The semi-finished product with flange wound is sent into the curing oven and heated at 80°C for 2 hours to make the resin reach the gel state but not completely cured. During the pre-curing process, the composite filler in the resin system fills the micro-voids with the resin flow, and at the same time releases the internal stress generated during the winding process. The second stage is post-curing: After pre-curing, the temperature of the curing oven is raised to 130℃ and kept at that temperature for 2 hours to allow the resin to fully cure. In the post-curing stage, the nano titanium dioxide and graphene micro-flakes in the composite filler further participate in the curing and cross-linking of the resin, increasing the cross-linking density. After natural cooling to room temperature, demolding is performed, the positioning clamps are removed, and the flange winding mold is removed from the end of the pipe. During the demolding process, care is taken to protect the flange root to avoid collision damage, and the demolded flange fitting is obtained. Step 7, Gradient Composite Reinforcement on the Flange Back: The back of the demolded flange fitting is roughened by grinding using an angle grinder with a 40-grit abrasive wheel to achieve a surface roughness Ra of 12.5μm. Then, a gradient reinforcement structure is fabricated from the inside out on the flange back. After the gradient reinforcement layer is laid, the product is placed in a curing oven and heated at 60℃ for 2 hours to complete the curing of the reinforcement layer. Then, drilling and finishing are performed. The bolt hole positions are determined according to the flange standard, and bolt holes are machined on the flange surface using a drilling machine. After drilling, the hole walls are ground and finished to remove burrs and exposed fibers, resulting in a flange fitting with completed drilling and finishing. Step 8, finishing: The sealing surface of the flange fitting is finished to produce a smooth and flat sealing surface. Then, an annular sealing water line is machined. After passing the inspection, the fiberglass flange short pipe is obtained.

[0019] The composite filler resin solution comprises the following raw materials in parts by weight: the composite filler is composed of the following components in parts by weight: 3 parts bio-based lignin micro powder, 2 parts nano titanium dioxide, and 0.5 parts graphene micro flakes. The preparation steps of the composite filler resin solution are as follows: (1) Take bio-based lignin micro powder, nano titanium dioxide and graphene micro flakes premixed and premixed in a high-speed mixer at 500 r / min for 15 minutes to make the components initially uniformly distributed to form a composite filler. Add the composite filler to 100 parts of epoxy resin and then perform high-speed shear dispersion at 2000 r / min for 20 minutes. Use shear force to break up the aggregates of graphene micro flakes and nano titanium dioxide, and at the same time promote the full adsorption of lignin on the graphene surface to obtain a mixture. (2) The mixture was placed in an ultrasonic dispersion device for ultrasonic cavitation treatment. The ultrasonic treatment was carried out at a frequency of 40kHz for 15 minutes. After dispersion, 80 parts of curing agent methyltetrahydrophthalic anhydride and 1 part of accelerator DMP-30 were added and stirred evenly to obtain composite filler modified resin liquid.

[0020] The gradient reinforcement structure consists of, from the inside out, an inner stress buffer layer, a middle shear transition layer, and an outer tensile reinforcement layer. The fabrication method is as follows: Stress buffer layer: Take glass fiber chopped strand mat and cut it to a size that matches the reinforcement area on the back of the flange. Lay it on the central area and root transition area of ​​the back of the flange. Apply the composite filler resin solution prepared in step one to the surface of the chopped strand mat, so that the mat is fully impregnated with resin. Control the resin content to 35wt%. During the application process, use a pressure roller to repeatedly roll the mat to remove air bubbles between layers and ensure that the chopped strand mat is tightly bonded to the back of the flange. Shear transition layer: When the resin on the surface of the stress buffer layer is not fully cured, take glass fiber plain weave cloth, cut it into fan-shaped pieces, and lay it radially on the surface of the stress buffer layer with the center of the flange. When laying, control the fiber direction to be at an angle of ±45° with the radial direction of the flange, and the fiber direction between layers is orthogonal. Use the composite filler resin solution prepared in step one to brush and impregnate, control the resin content to be 25wt%, and use a pressure roller to roll and degas. Tensile reinforcement layer: After applying a coupling agent solution to the surface of the shear transition layer, continuous glass fiber roving is wound in a circumferential winding manner, with the fiber direction along the flange circumference, i.e., circumferentially wound at 90°. The composite filler resin solution prepared in step one is used for impregnation, controlling the resin content to be 20 wt%. Coupling agent solutions were applied between the stress buffer layer and the shear transition layer, and between the shear transition layer and the tensile reinforcement layer. The coupling agent solutions were prepared by mixing silane coupling agent KH-550 and anhydrous ethanol at a volume ratio of 1:19. After application, the solutions were allowed to air dry for 3 minutes.

[0021] Example 2: This example provides a manufacturing process for a spiral wound fiberglass short pipe flange, specifically including the following steps: Step 1, Preparation of composite filler resin solution: Prepare composite filler resin solution; Step 2, Pipe winding and molding: The composite filler resin solution prepared in Step 1 is injected into the impregnation tank. Continuous glass fiber roving is used as the reinforcing material. After being fully impregnated with the composite filler resin solution in the impregnation tank, it is wound and molded on the pipe mandrel. The winding method is to alternate between circumferential winding (90°) and cross winding (±55°). The number of winding layers is determined according to the pipe design pressure. After the pipe is wound, it is left to stand at room temperature for 45 minutes to allow the resin to reach the gel state but not to be completely cured, thus obtaining a pre-cured pipe semi-finished product. Step 3, Pipe End Surface Treatment: Grind the surface of the flange connection area at the pipe end to remove the resin-rich layer and expose the glass fiber. The surface roughness Ra after grinding is 13.5 μm. Apply a chemical activation treatment solution to the ground surface. The activation treatment solution consists of: 8 parts methyl ethyl ketone peroxide, 25 parts acetone, 2 parts silane coupling agent KH-550, and 65 parts deionized water. After application, let it stand at room temperature for 12 minutes to allow the activation solution to fully react with the pipe surface. After activation treatment, wipe the surface three times with anhydrous ethanol to remove residual activation solution. After activation treatment, cleaning, and drying, apply a primer. The primer is a mixture of the following components: 100 parts epoxy resin and silane coupling agent KH-570. 4 parts, 2 parts of the composite filler from step one, and 15 parts of butyl glycidyl ether are mixed evenly and then evenly brushed onto the activated surface of the pipe end with a brush. The coating thickness is controlled at 0.1 mm. After brushing, the pipe is dried at room temperature for 15 minutes until the surface of the primer is no longer sticky. This yields a semi-finished pipe with activated end and primer coating. Step 4, Preparation and Assembly of Flange Winding Mold: Prepare an independent flange winding mold. The mold material is steel or fiberglass. The mold surface matches the required flange shape. Before use, clean the mold to remove surface dirt and evenly apply 3 layers of release agent. The flange winding mold is a split structure, including a flange baffle, a flange core, and a connecting shaft. The mating surface between the mold and the pipe end is provided with an annular stress buffer groove. The groove depth is 15% of the pipe wall thickness and the width is 40% of the pipe wall thickness. After the flange is wound, the groove naturally forms an annular stress release structure at the root of the flange. Assemble the prepared flange winding mold to the end of the pipe semi-finished product that has been activated and coated with a base layer. The assembly method adopts a tapered fit. The inner taper of the mold is consistent with the outer taper of the pipe end to ensure the coaxiality of the mold and the pipe. After assembly, use a positioning clamp to fix the mold to obtain a pipe assembly with the flange winding mold. Step 5, Flange Winding: Using the composite filler resin solution prepared in Step 1 as the resin system for flange winding, continuous glass fiber roving is impregnated with the composite filler resin solution. Then, the flange is wound on the flange winding mold of the pipe assembly equipped with the flange winding mold. The winding method is as follows: First, three layers are wound at ±45° cross-winding at the root of the flange (where the flange and the pipe meet) to ensure continuous fiber transition at the root. Then, the main body of the flange is wound, using a combination of circumferential winding (90°) and radial alternating winding until the designed thickness is reached. During the winding process, a pressure roller is used to roll every three layers to remove air bubbles between layers, resulting in a semi-finished product in which the pipe and flange are wound together. Step 6, Step-by-step curing and demolding: The semi-finished product with pipe and flange wound together is sent into the curing oven for distributed curing. First stage pre-curing: The semi-finished product with flange wound is sent into the curing oven and heated at 90°C for 2 hours to make the resin reach the gel state but not completely cured. During the pre-curing process, the composite filler in the resin system fills the micro-voids with the resin flow, and at the same time releases the internal stress generated during the winding process. The second stage is post-curing: After pre-curing, the temperature of the curing oven is raised to 140℃ and kept at that temperature for 2.5 hours to allow the resin to fully cure. In the post-curing stage, the nano titanium dioxide and graphene micro-flakes in the composite filler further participate in the curing and cross-linking of the resin. After natural cooling to room temperature, the mold is removed, the positioning clamps are removed, and the flange winding mold is removed from the end of the pipe. During the demolding process, care is taken to protect the root of the flange to avoid collision damage, and the demolded flange fitting is obtained. Step 7, Gradient Composite Reinforcement on the Back of the Flange: The back of the flange fitting after demolding is roughened by grinding with an angle grinder and a 60-mesh grinding wheel to achieve a surface roughness Ra of 13.5μm. Then, a gradient reinforcement structure is made from the inside to the outside on the back of the flange. After the gradient reinforcement layer is laid, the product is placed in a curing oven and heated at 70℃ for 2.5 hours to complete the curing of the reinforcement layer. Then, the flange fitting is drilled and trimmed to obtain the flange fitting with completed drilling and trimming. Step 8, finishing: The sealing surface of the flange fitting is finished to produce a smooth and flat sealing surface. Then, an annular sealing water line is machined. After passing the inspection, the fiberglass flange short pipe is obtained.

[0022] The composite filler resin solution comprises the following raw materials in parts by weight: the composite filler is composed of the following components in parts by weight: 5 parts of bio-based lignin micro powder, 3 parts of nano titanium dioxide, and 1.2 parts of graphene micro flakes. The preparation steps of the composite filler resin solution are as follows: (1) Take bio-based lignin micro powder, nano titanium dioxide and graphene micro flakes premixed and premixed in a high-speed mixer at 800 r / min for 15 minutes to make the components initially uniformly distributed to form a composite filler. Add the composite filler to 100 parts of epoxy resin and then perform high-speed shear dispersion at 2500 r / min for 25 minutes. Use shear force to break up the agglomerates of graphene micro flakes and nano titanium dioxide, and at the same time promote the full adsorption of lignin on the graphene surface to obtain a mixture. (2) The mixture was placed in an ultrasonic dispersion device for ultrasonic cavitation treatment. The ultrasonic treatment was carried out at a frequency of 40 kHz for 20 minutes. After dispersion, 85 parts of curing agent methyltetrahydrophthalic anhydride and 1.5 parts of accelerator DMP-30 were added and stirred evenly to obtain composite filler modified resin liquid.

[0023] The gradient reinforcement structure consists of, from the inside out, an inner stress buffer layer, a middle shear transition layer, and an outer tensile reinforcement layer. The fabrication method is as follows: Stress buffer layer: Take glass fiber chopped strand mat and cut it to a size that matches the reinforcement area on the back of the flange. Lay it on the central area and root transition area of ​​the back of the flange. Apply the composite filler resin solution prepared in step one to the surface of the chopped strand mat, so that the mat is fully impregnated with resin. Control the resin content to 40wt%. During the application process, use a pressure roller to repeatedly roll the mat to remove air bubbles between layers and ensure that the chopped strand mat is tightly bonded to the back of the flange. Shear transition layer: When the resin on the surface of the stress buffer layer is not fully cured, take glass fiber plain weave cloth, cut it into fan-shaped pieces, and lay it radially on the surface of the stress buffer layer with the center of the flange. When laying, control the fiber direction to be at an angle of ±45° with the radial direction of the flange, and the fiber direction between layers is orthogonal. Use the composite filler resin solution prepared in step one to brush and impregnate, control the resin content to be 30wt%, and use a pressure roller to roll and degas. Tensile reinforcement layer: After applying a coupling agent solution to the surface of the shear transition layer, continuous glass fiber roving is wound in a circumferential winding manner, with the fiber direction along the flange circumference, i.e., circumferentially wound at 90°. The composite filler resin solution prepared in step one is used for impregnation, controlling the resin content to be 25 wt%. Coupling agent solutions were applied between the stress buffer layer and the shear transition layer, and between the shear transition layer and the tensile reinforcement layer. The coupling agent solutions were prepared by mixing silane coupling agent KH-550 and anhydrous ethanol at a volume ratio of 1:19. After application, the solutions were allowed to air dry for 5 minutes.

[0024] Example 3: This example provides a manufacturing process for a spiral wound fiberglass short pipe flange, specifically including the following steps: Step 1, Preparation of composite filler resin solution: Prepare composite filler resin solution; Step 2, pipe winding and molding: The composite filler resin solution prepared in Step 1 is injected into the impregnation tank. Continuous glass fiber roving is used as the reinforcing material. After being fully impregnated with the composite filler resin solution in the impregnation tank, it is wound and molded on the pipe mandrel. The winding method is to alternate between circumferential winding (90°) and cross winding (±60°). The number of winding layers is determined according to the pipe design pressure. After the pipe is wound, it is left to stand at room temperature for 60 minutes to allow the resin to reach the gel state but not to be completely cured, thus obtaining a pre-cured pipe semi-finished product. Step 3, Pipe End Surface Treatment: Grind the surface of the flange connection area at the pipe end to remove the resin-rich layer and expose the glass fiber. The surface roughness Ra after grinding is 14μm. Apply a chemical activation treatment solution to the ground surface. The activation treatment solution consists of: 10 parts methyl ethyl ketone peroxide, 30 parts acetone, 3 parts silane coupling agent KH-550, and 74 parts deionized water. After application, let it stand at room temperature for 15 minutes to allow the activation solution to fully react with the pipe surface. After activation treatment, wipe the surface three times with anhydrous ethanol to remove residual activation solution. After activation treatment, cleaning, and drying, apply a primer. The primer is a mixture of the following components: 100 parts epoxy resin and silane coupling agent KH-570. 5 parts, 3 parts of the composite filler from step one, and 20 parts of butyl glycidyl ether are mixed evenly and then evenly brushed onto the activated surface of the pipe end with a brush. The coating thickness is controlled at 0.15 mm. After brushing, the pipe is dried at room temperature for 20 minutes until the surface of the primer is no longer sticky. This yields a semi-finished pipe with activated ends and a primer coating. Step 4, Preparation and Assembly of Flange Winding Mold: Prepare an independent flange winding mold. The mold material is steel or fiberglass. The mold surface matches the required flange shape. Before use, clean the mold to remove surface dirt and evenly apply 3 layers of release agent. The flange winding mold is a split structure, including a flange baffle, a flange core, and a connecting shaft. The mating surface between the mold and the pipe end is provided with an annular stress buffer groove. The groove depth is 20% of the pipe wall thickness, and the width is 50% of the pipe wall thickness. After the flange is wound, the groove naturally forms an annular stress release structure at the root of the flange. Assemble the prepared flange winding mold to the end of the pipe semi-finished product that has been activated and coated with a base layer. The assembly method adopts a tapered fit. The inner taper of the mold is consistent with the outer taper of the pipe end to ensure the coaxiality of the mold and the pipe. After assembly, use a positioning clamp to fix the mold to obtain a pipe assembly with the flange winding mold. Step 5, Flange Winding: Using the composite filler resin solution prepared in Step 1 as the resin system for flange winding, continuous glass fiber roving is impregnated with the composite filler resin solution. Then, the flange is wound on the flange winding mold of the pipe assembly equipped with the flange winding mold. The winding method is as follows: First, three layers are wound at ±45° cross-winding at the root of the flange (where the flange and the pipe meet) to ensure continuous fiber transition at the root. Then, the main body of the flange is wound, using a combination of circumferential winding (90°) and radial alternating winding until the designed thickness is reached. During the winding process, a pressure roller is used to roll every three layers to remove air bubbles between layers, resulting in a semi-finished product in which the pipe and flange are wound together. Step 6, Step-by-step curing and demolding: The semi-finished product with pipe and flange wound together is sent into the curing oven for distributed curing. First stage pre-curing: The semi-finished product with flange wound is sent into the curing oven and heated at 100°C for 2 hours to make the resin reach the gel state but not completely cured. During the pre-curing process, the composite filler in the resin system fills the micro-voids with the resin flow, and at the same time releases the internal stress generated during the winding process. The second stage is post-curing: After pre-curing, the temperature of the curing oven is raised to 150℃ and kept at that temperature for 3 hours to allow the resin to fully cure. In the post-curing stage, the nano titanium dioxide and graphene micro-flakes in the composite filler further participate in the curing and cross-linking of the resin, increasing the cross-linking density. After natural cooling to room temperature, demolding is performed, the positioning clamps are removed, and the flange winding mold is removed from the end of the pipe. During the demolding process, care is taken to protect the root of the flange to avoid collision damage, and the demolded flange fitting is obtained. Step 7, Gradient Composite Reinforcement on Flange Back: The back of the demolded flange fitting is roughened by grinding using an angle grinder with an 80-grit abrasive wheel to achieve a surface roughness Ra of 14 μm. Then, a gradient reinforcement structure is fabricated from the inside out on the flange back. After the gradient reinforcement layer is laid, the product is placed in a curing oven and heated at 80°C for 3 hours to complete the curing of the reinforcement layer. Then, drilling and finishing are performed. The bolt hole positions are determined according to the flange standard, and bolt holes are machined on the flange surface using a drilling machine. After drilling, the hole walls are ground and finished to remove burrs and exposed fibers, resulting in a flange fitting with completed drilling and finishing. Step 8, finishing: The sealing surface of the flange fitting is finished to produce a smooth and flat sealing surface. Then, an annular sealing water line is machined. After passing the inspection, the fiberglass flange short pipe is obtained.

[0025] The composite filler resin solution comprises the following raw materials in parts by weight: the composite filler is composed of the following components in parts by weight: 8 parts of bio-based lignin micro powder, 5 parts of nano titanium dioxide, and 2 parts of graphene micro flakes. The preparation steps of the composite filler resin solution are as follows: (1) Take bio-based lignin micro powder, nano titanium dioxide and graphene micro flakes premixed and premixed in a high-speed mixer at 1000 r / min for 15 minutes to make each component initially uniformly distributed to form a composite filler. Add the composite filler to 100 parts of epoxy resin and then perform high-speed shear dispersion at 3000 r / min for 30 minutes. Use shear force to break up the aggregates of graphene micro flakes and nano titanium dioxide, and at the same time promote the full adsorption of lignin on the graphene surface to obtain a mixture. (2) The mixture was placed in an ultrasonic dispersion device for ultrasonic cavitation treatment. The ultrasonic treatment was carried out at a frequency of 40kHz for 20 minutes. After dispersion, 90 parts of curing agent methyltetrahydrophthalic anhydride and 2 parts of accelerator DMP-30 were added and stirred evenly to obtain composite filler modified resin liquid.

[0026] The gradient reinforcement structure consists of, from the inside out, an inner stress buffer layer, a middle shear transition layer, and an outer tensile reinforcement layer. The fabrication method is as follows: Stress buffer layer: Take glass fiber chopped strand mat and cut it to a size that matches the reinforcement area on the back of the flange. Lay it on the central area and root transition area of ​​the back of the flange. Apply the composite filler resin solution prepared in step one to the surface of the chopped strand mat, so that the mat is fully impregnated with resin. Control the resin content to 45wt%. During the application process, use a pressure roller to repeatedly roll the mat to remove air bubbles between layers and ensure that the chopped strand mat is tightly bonded to the back of the flange. Shear transition layer: When the resin on the surface of the stress buffer layer is not fully cured, take glass fiber plain weave cloth, cut it into fan-shaped pieces, and lay it radially on the surface of the stress buffer layer with the center of the flange. When laying, control the fiber direction to be at an angle of ±45° with the radial direction of the flange, and the fiber direction between layers is orthogonal. Use the composite filler resin solution prepared in step one to brush and impregnate, control the resin content to be 35wt%, and use a pressure roller to roll and degas. Tensile reinforcement layer: After applying a coupling agent solution to the surface of the shear transition layer, continuous glass fiber roving is wound in a circumferential winding manner, with the fiber direction along the flange circumference, i.e., circumferentially wound at 90°. The composite filler resin solution prepared in step one is used for impregnation, controlling the resin content to be 25 wt%. Coupling agent solutions were applied between the stress buffer layer and the shear transition layer, and between the shear transition layer and the tensile reinforcement layer. The coupling agent solutions were prepared by mixing silane coupling agent KH-550 and anhydrous ethanol at a volume ratio of 1:19. After application, the solutions were allowed to air dry for 5 minutes.

[0027] The difference between Comparative Example 1 and Example 2 is that the composite filler was omitted; otherwise, they are exactly the same as Example 2.

[0028] The difference between Comparative Example 2 and Example 2 is that step eight is omitted; the rest is exactly the same as Example 2.

[0029] The difference between Comparative Example 3 and Example 3 is that the step-by-step curing is eliminated and a one-time high-temperature curing is used. The rest is exactly the same as Example 2.

[0030] Experimental Example: Using the spiral-wound fiberglass short pipe flanges prepared in Examples 1-3 and Comparative Examples 1-3 of this invention as test samples, the following experimental examples were conducted: 1. Mechanical properties: Tensile strength: Refer to GB / T 1447-2005 "Test Method for Tensile Properties of Fiber Reinforced Plastics". Cut straight strip specimens along the fiber direction from the flange body, with a specimen width of 25 mm and a gauge length of 50 mm. The specimen surface should be smooth, free of burrs, notches, or other defects. Five valid specimens are used per test group. A universal testing machine is used, with a load accuracy of ±1%, and the centerline deviation between the fixture and the specimen should not exceed 0.5 mm. Measure the specimen width b and thickness h with vernier calipers, accurate to 0.01 mm; clamp the specimen symmetrically at both ends in the testing machine fixtures, ensuring the specimen centerline is aligned with the centerlines of the upper and lower fixtures; set the loading speed to 5 mm / min, and apply a uniform and continuous load until the specimen breaks; record the maximum breaking load P, and observe and record the specimen failure mode.

[0031] Bending strength: Refer to GB / T 1449-2005 "Test Method for Bending Properties of Fiber Reinforced Plastics". Rectangular specimens were cut from the gradient reinforcement area on the back of the flange (including the complete structure of the inner, middle, and outer layers). The specimen length L = 20h (h is the specimen thickness) and the specimen width b = 15mm. Five specimens were used per group. A universal testing machine equipped with a three-point bending test fixture was used. The loading head radius R = 5mm and the support radius r = 20mm. The specimen width b and thickness h were measured to an accuracy of 0.01mm; the support span l = 16h was adjusted to an accuracy within ±0.5mm; the specimen was placed on two supports, ensuring the specimen centerline was aligned with the loading head centerline; the loading speed was set to 10mm / min (routine test), and uniform loading was applied until specimen failure; the maximum bending load P and the specimen failure mode were recorded.

[0032] Interlaminar shear strength: Refer to ASTM D2344 / ISO 14130 "Determination of interlaminar shear strength of fiber-reinforced plastic composites (short beam method)". Short beam specimens are cut from the gradient reinforcement area on the back of the flange (mainly for the bonding area between the shear transition layer and adjacent layers). The specimen length is l = 6 h, and the width is b = 2 h, where h is the specimen thickness. The two end faces of the specimen should be parallel and smooth. A universal testing machine equipped with a three-point bending short beam shear fixture is used, with a loading head radius R = 3 mm and a support radius r = 1.5 mm. The specimen width b and thickness h are measured to an accuracy of 0.01 mm; the span L = 5 h is adjusted to ensure an accuracy of ±0.1 mm; the specimen is placed on the fixture support so that the specimen centerline is directly below the loading head; the loading speed is set to 1 mm / min, and uniform loading is applied until interlaminar shear failure occurs; the maximum shear load Pmax and the specimen failure mode (delamination, fracture, or crushing) are recorded. The tensile strength, flexural strength, and interlaminar shear strength results are recorded in Table 1.

[0033] 2. Heat aging resistance: With reference to GB / T 2573-2008 Test Method for Aging Properties of Glass Fiber Reinforced Plastics, tensile specimens are cut from the flange body along the fiber direction, and the specimen size and preparation method are the same as those of the aforementioned tensile strength specimens. There are 5 valid specimens in each group. A constant temperature and humidity test chamber is used, with temperature control accuracy of ±2°C and humidity control accuracy of ±3%RH. The initial tensile strength of the specimens is measured as the reference value before aging; the specimens are placed in the constant temperature and humidity test chamber, with the set temperature of 70°C and relative humidity of 95%RH, for continuous exposure of 1000h; during the aging process, the specimens are taken out every 200h to observe and record appearance changes (surface color, cracks, blistering, pulverization, delamination, etc.). After reaching the specified aging time, the specimens are taken out and conditioned at room temperature for 24h; the tensile strength of the aged specimens is measured according to the aforementioned tensile strength test method. The test results are shown in Figure 2 as follows.

[0034] 3. Hydrostatic pressure sealing test: With reference to HG / T 21633 and GB / T 9119, the hydrostatic test is carried out at 1.5 times the design pressure. The finished flange and the matching blind flange are assembled into a closed pipe section, a sealing gasket is installed at the flange connection, and the bolts are tightened according to the standard torque. An electric pressure test pump is used, the pressure gauge has an accuracy of class 1.5, and the measuring range is 2.0 times the test pressure. Water is injected into the closed pipe section, and the exhaust valve is opened at the same time to drain all air. The exhaust valve is closed after water continuously flows out without bubbles; the pressure test pump is started to slowly increase the pressure, and the pressure rising rate is controlled at about 0.3MPa / min; when the pressure rises to 1.5 times the design pressure, the pressurization is stopped and the pressure is maintained for 30min; the pressure gauge reading is observed during the pressure holding period, and it is qualified if the pressure drop does not exceed 0.05MPa; the flange sealing surface, the connection between the flange and the pipe, and the area around the bolt holes are inspected, and it is qualified if there is no leakage; after the pressure holding is completed, the pressure is slowly reduced to zero, and the test results are recorded. The results are recorded in Table 1.

[0035] Table 1: Performance test result table of the glass fiber reinforced plastic short pipe flange prepared by the present invention

[0036] It can be seen from Table 1 that the tensile strength, flexural strength and interlaminar shear strength of Examples 1-3 are all higher than those of Comparative Examples 1-3, indicating that there is a significant synergistic effect among the full-process composite filler doping modification, the back gradient composite reinforcement structure and the step curing process provided by the present invention. The hydrostatic pressure sealing test results show that Example 2 maintains the pressure for 30 minutes under 1.5 times the design pressure, the pressure drop is only 0.01MPa, and there is no leakage in all parts of the flange. In Comparative Example 1, since the composite filler is omitted, leakage occurs at the root of the flange, indicating that the addition of the composite filler improves the interface bonding between the resin and the fiber, and effectively eliminates the micro leakage channel at the root of the flange.

[0037] Figure 2As can be seen, the tensile strength retention rate of Examples 1-3 is above 90%, while the comparative sample without the addition of the ternary composite filler of the present invention has significantly weaker matrix anti-aging ability and significantly lower tensile strength retention rate, which fully confirms the anti-aging synergistic effect of the composite filler system.

[0038] In summary, this invention integrates a ternary composite filler modification system, multiple composite interface treatments, a split mold assembly with stress-relieving structure, step-by-step gradient curing, and a multi-dimensional gradient back reinforcement process. This invention overcomes the technical limitations and performance bottlenecks of traditional processes. Through multi-dimensional synergistic optimization of materials, interfaces, molds, curing, and structure, it effectively improves the density and stability of the flange substrate, strengthens the integrated bonding effect between the pipe body and the flange, significantly releases residual molding stress, inhibits crack initiation and propagation, and significantly improves the product's aging resistance and sealing pressure resistance. The overall process has strong adaptability, and the comprehensive performance and service stability of the finished product are significantly better than existing conventional products. It is suitable for various complex pipeline connection conditions and possesses outstanding technical advancement and industrial practical value. The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A manufacturing process for fiberglass short pipe flanges formed by spiral winding, characterized in that, Specifically, the following steps are included: Step 1, Preparation of composite filler resin solution: Prepare composite filler resin solution; Step 2, pipe winding and molding: Continuous glass fiber roving is impregnated into composite filler resin solution, wound and molded on pipe mandrel, and left to stand to obtain pre-cured pipe semi-finished product; Step 3, Pipe end surface treatment: The end flange connection area of ​​the pre-cured pipe semi-finished product is treated to obtain a pipe semi-finished product with activated ends and coated with a primer. Step 4, preparation and assembly of flange winding mold: Assemble the flange mold to the end of the activated and coated pipe semi-finished product. After assembly, fix the mold to obtain a pipe assembly with flange winding mold. Step 5, flange winding molding: After impregnating continuous glass fiber roving with composite filler resin solution, the flange is wound on the flange winding mold of the pipe assembly obtained in Step 4, to obtain a semi-finished product in which the pipe and flange are wound together. Step 6, Step-by-step curing and demolding: The semi-finished product, in which the pipe and flange are integrally wound, is cured in steps, cooled, and demolded to obtain the demolded flange fitting; Step 7, Gradient Composite Reinforcement on Flange Back: The demolded flange fitting is roughened by grinding, and then a gradient reinforcement structure is made on the back of the flange, cured, and drilled and trimmed to obtain the flange fitting. Step 8, finishing: The flange sealing surface of the flange fitting is finished and the sealing water line is machined to obtain the FRP flange short pipe.

2. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 1, characterized in that, In step one, the composite filler resin solution comprises the following raw materials in parts by weight: 3-8 parts of bio-based lignin micro powder, 2-5 parts of nano titanium dioxide, and 0.5-2 parts of graphene micro flakes.

3. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 2, characterized in that, The preparation steps of the composite filler resin solution are as follows: (1) Take bio-based lignin micro powder, nano titanium dioxide and graphene micro flakes premixed to form a composite filler, add the composite filler to epoxy resin, and then perform high-speed shear dispersion to obtain a mixture; (2) The mixture is subjected to ultrasonic cavitation treatment, and a curing agent and an accelerator are added and stirred evenly to obtain a composite filler modified resin solution.

4. The manufacturing process for a spiral-wound fiberglass short pipe flange according to claim 3, characterized in that, In step three, the surface treatment includes: physical polishing, chemical activation treatment, and primer coating treatment.

5. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 4, characterized in that, The chemical activation solution used in the chemical activation treatment consists of: 5-10 parts methyl ethyl ketone peroxide, 20-30 parts acetone, 1-3 parts silane coupling agent KH-550, and 57-74 parts deionized water. The primer used in the primer composite treatment is composed of the following components: 100 parts epoxy resin, 3-5 parts silane coupling agent KH-570, 1-3 parts composite filler, and 10-20 parts diluent.

6. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 1, characterized in that, In step five, the flange winding method is as follows: first, cross winding is performed at the flange root, and then the flange body is wound, using alternating circumferential winding and cross winding. During the winding process, pressure rollers are used to roll every 2 to 3 layers.

7. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 1, characterized in that, In step six, the step-by-step curing process is as follows: First stage pre-curing: The semi-finished product with completed flange winding is sent into the curing oven and heated at 80~100℃ for 1.5~2 hours; Second stage post-curing: After pre-curing, raise the temperature of the curing oven to 130~150℃ and keep it at that temperature for 2~3 hours to allow the resin to fully cure.

8. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 1, characterized in that, In step seven, the gradient reinforcement structure consists of an inner stress buffer layer, a middle shear transition layer, and an outer tensile reinforcement layer.

9. The manufacturing process for a spiral wound fiberglass short pipe flange according to claim 8, characterized in that, The method for preparing the gradient reinforcement structure is as follows: Stress buffer layer: Take glass fiber chopped strand mat, cut it, and lay it on the back and root of the flange. Apply the composite filler resin solution prepared in step one to the surface of the chopped strand mat. Shear transition layer: When the resin on the surface of the stress buffer layer is not fully cured, take glass fiber plain cloth, cut it, and lay it on the surface of the stress buffer layer in a radial pattern with the center of the flange. Apply and impregnate it with the composite filler resin solution prepared in step one, and roll it with a pressure roller to remove air. Tensile reinforcement layer: After applying a coupling agent solution to the surface of the shear transition layer, continuous glass fiber roving is wound in a circumferential winding manner, with the fiber direction along the circumference of the flange, and impregnated with the composite filler resin solution prepared in step one.

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