A light-weight corrosion-resistant coupling for large-diameter hose connections and a method of manufacturing the same

Abstract

The application discloses a kind of light-weight corrosion-resistant connector for large-diameter hose connection and its manufacturing method, including metal matrix and the inner cladding layer and outer cladding layer that integrally coat inside and outside surface thereof;Metal matrix is the thinning tubular structure of aluminum alloy material, and the outer periphery is provided with the clamping groove matched with the hoop;The inner cladding layer and outer cladding layer are made of high-performance polymer material, and are firmly combined with the metal matrix, so that the inner and outer surfaces are not exposed to metal, forming a composite structure integrating strength, corrosion resistance, wear resistance, buffering and sealing.The manufacturing method includes the steps of precision forming of metal matrix, surface sand blasting roughening and primer treatment, mold positioning and installation, polymer material pouring and coating forming and post-processing finishing.The application improves the wear resistance and impact resistance and dynamic sealing reliability through the synergistic design of structure thinning and functional coating, and the process is mature and cost controllable, especially suitable for high-pressure, strong corrosion, high mobility and large-diameter industrial fluid conveying scene.

Description

Technical Field

[0001] This invention belongs to the field of fluid transport and connection technology, and is mainly applied to large-diameter, high-pressure, highly corrosive and highly mobile fluid transport systems in industrial scenarios such as shale gas fracturing, mine drainage and environmental wastewater reuse. It involves the connection and sealing technology between hoses and pipelines, specifically a lightweight corrosion-resistant fastener for large-diameter water hose connections and its manufacturing method. Background Technology

[0002] In fields such as shale gas fracturing, mine drainage, and industrial wastewater reuse, large-diameter pipeline systems often transport highly corrosive fluids containing high concentrations of chloride ions and chemical additives. Furthermore, the frequent dragging, moving, and rewinding required for these operations place stringent demands on the crucial hose fittings: they must possess excellent chemical corrosion resistance, high sealing reliability, sufficient pressure resistance, and good resistance to external wear and impact. Currently, large-diameter hose fittings are mainly made of SS316L stainless steel or 6061-T6 aluminum alloy. While stainless steel fittings offer good corrosion resistance, their high density and weight, especially noticeable in large-diameter applications, make handling and installation extremely inconvenient. Aluminum alloy fittings, although lightweight, are prone to pitting and intergranular corrosion in highly corrosive media, resulting in poor durability. Neither type of fitting fully meets the comprehensive requirements of high-strength, high-mobility, and highly corrosive operating conditions.

[0003] Existing technologies lack a single material or mature technical solution that can simultaneously satisfy lightweight, high corrosion resistance, high strength, and good processability. Although fiber-reinforced resin matrix composites can theoretically achieve a combination of lightweight and corrosion resistance, the large, complex, and precision molds required for large-diameter joints are extremely expensive and have long manufacturing cycles. Furthermore, their structural strength, anti-delamination ability, and sealing surface stability under large dimensions face severe challenges, making it difficult to meet the cost and flexibility requirements of small-batch or customized production, which greatly limits their widespread application in practical engineering.

[0004] Furthermore, with the increase in pipeline diameter, joints face greater structural stress and sealing challenges under high-pressure fluid conditions. Traditional lightweight plastics are prone to deformation due to insufficient rigidity, affecting sealing; while composite materials, if their interfacial bonding strength and overall design are not sufficiently optimized, may experience interface debonding, cracking, and other failures under high-pressure pulses or external mechanical impacts. Therefore, the industry urgently needs a large-diameter hose connection technology that combines lightweight design, high corrosion resistance, strength, reliability, and good process economy to overcome current limitations in material and structural design and meet increasingly stringent industrial application requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a lightweight and corrosion-resistant coupling for large-diameter water hose connections and its manufacturing method, in order to solve the problem that existing large-diameter fluid transport couplings cannot simultaneously achieve lightweight, high strength, excellent corrosion resistance, high wear and impact resistance, and good economy.

[0006] The first objective of this invention is to provide a lightweight, corrosion-resistant coupling for connecting large-diameter water hoses, comprising: The metal substrate is a tubular structure made of aluminum alloy. The wall thickness is reduced by increasing the inner diameter and simultaneously decreasing the outer diameter. The outer periphery of the tube end of the metal substrate is provided with a groove structure for engaging with the clamp-type connector. The inner coating layer is made of polymer material. The inner coating layer is cast polyurethane with a Shore hardness of 80A-95A. It is tightly wrapped around the inner surface of the metal substrate. The outer coating is made of polymer material. The outer coating is cast polyurethane with a Shore hardness of 80A-95A. It is tightly wrapped around the outer surface of the metal substrate. The inner and outer surfaces of the metal substrate are not exposed. The inner and outer surfaces of the metal substrate are equipped with micromechanical anchoring structures. The inner and outer cladding layers are firmly bonded to the metal substrate through a casting and curing process, forming a composite structure that integrates the structural strength of the metal substrate with the corrosion resistance, wear resistance, buffering, and sealing functions of the polymer material. The end face sealing area of ​​the fastener is precision machined to a flatness of no more than 0.1 mm to ensure the sealing reliability with the mating parts.

[0007] The second objective of this invention is to provide a manufacturing method for producing the lightweight, corrosion-resistant fastener described above, comprising the following steps: S1 Precision Forming of Metal Matrix: Using aluminum alloy blanks, a metal matrix with a reduced wall thickness structure, as well as slots and sealing steps, is directly machined through mechanical processing. S2 Surface Pretreatment: The processed metal substrate is degreased and cleaned to remove surface oil, and then its inner and outer surfaces are roughened by sandblasting to form a micro-rough surface. S3 Primer Treatment: A special primer for polymer materials is uniformly coated on the inner and outer surfaces of the pretreated metal substrate and then dried and cured. S4 Mold Preparation and Installation: A set of combined molds for forming inner and outer coating layers is provided. The mold includes an inner mold core for forming the inner coating layer and an outer mold cavity for forming the outer coating layer. The metal substrate that has been primed is coaxially positioned between the inner mold core and the outer mold cavity. S5 polymer material coating molding: The uniformly mixed polymer material casting material is injected into the mold cavity that has been preheated to the set temperature, and then heated and cured to form a tightly bonded inner coating layer and an outer coating layer on the inner and outer surfaces of the metal matrix. S6 Post-processing and Finishing: Cool the molded product, demold it, and remove excess fly and overflow.

[0008] The present invention has the following beneficial effects: (1) The present invention scientifically reduces the wall thickness of the metal substrate by increasing the inner diameter and decreasing the outer diameter. Combined with the application of aluminum alloy substrate material, the weight of the fastener body is reduced while ensuring the pressure bearing and structural strength. This reduces the weight of large-diameter products, reduces the labor intensity of on-site handling, installation and frequent disassembly of heavy water hose systems, and improves work efficiency and flexibility.

[0009] (2) The composite structure of the present invention constructs a comprehensive functional barrier from the inside out: the inner coating completely isolates the highly mineralized and chemically corrosive fluid from the metal matrix, eliminating pitting corrosion and intergranular corrosion. The outer coating, with its excellent wear resistance and impact resistance, effectively resists friction and collision in the field environment, protecting the buckle body and the connected hose; at the same time, the elastic polymer material is not only resistant to damage itself, but its adaptive deformation when the hose is fitted and the clamp is tightened can also effectively fill the micro gaps, forming a more reliable dynamic sealing interface, improving the sealing stability, durability and safety of the entire connection system.

[0010] (3) This invention adopts a process route of precision metal processing and polymer coating molding, which has strong versatility of process equipment and is particularly suitable for medium-batch and customized production, significantly reducing the industrialization threshold and cost. At the same time, it surpasses other key performance aspects such as corrosion resistance and lightweighting. It has broad market application prospects and significant competitive advantages in demanding industrial fields such as shale gas fracturing, mine drainage, and environmental wastewater reuse, which have high requirements for large diameter, corrosion resistance, and mobility. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a cross-sectional view of the lightweight and corrosion-resistant fastener and clamp-type connector for connecting large-diameter water hoses according to an embodiment of the present invention. Figure 2This is a cross-sectional view of a lightweight, corrosion-resistant fastener for connecting large-diameter water hoses according to an embodiment of the present invention. Figure 3 This is a structural diagram of the lightweight, corrosion-resistant fastener and clamp-type connector for connecting large-diameter water hoses according to an embodiment of the present invention. Figure 4 This is a structural diagram of a lightweight, corrosion-resistant fastener for connecting large-diameter water hoses according to an embodiment of the present invention. Figure 5 This is a flowchart illustrating the manufacturing method of a lightweight, corrosion-resistant fastener for connecting large-diameter water hoses, according to an embodiment of the present invention.

[0013] Explanation of reference numerals in the attached drawings: 1-Connector; 2-Annular groove; 3-Metal substrate; 4-Inner covering layer; 5-Outer covering layer; 6-Slot structure; 7-Clamp one; 8-Clamp two; 9-Bolt connection hole; 10-Sealing gasket; 11-Water hose. Detailed Implementation

[0014] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0015] To fully understand this invention, detailed steps and structures will be presented in the following description to illustrate the technical solution of this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0016] Example 1 like Figures 1 to 4 In one embodiment of the lightweight corrosion-resistant fastener for large-diameter water hose connections of the present invention, the lightweight corrosion-resistant fastener for large-diameter water hose connections mainly includes a metal substrate 3, an inner covering layer 4, and an outer covering layer 5.

[0017] The metal substrate 3 is a tubular structure made of aluminum alloy. Compared with traditional all-metal fasteners of the same specifications, the wall thickness of the metal substrate 3 of this invention is significantly reduced. This thinning is achieved through a specific structural optimization method, namely, increasing the inner diameter while simultaneously reducing the outer diameter. For example, for an aluminum alloy blank of the original specifications, its inner diameter can be increased by 3mm while its outer diameter is reduced by 3mm, thereby reducing the overall wall thickness by 6mm. This method of increasing the inner diameter and decreasing the outer diameter can minimize weight while meeting the requirements of pressure resistance and structural strength. The outer periphery of the metal substrate 3 is provided with an annular groove 2, and the outer periphery of the pipe tail of the metal substrate 3 is machined with a slot structure 6 for engaging with the clamp-type connector to achieve a tight connection of the hose 11.

[0018] Both the inner coating layer 4 and the outer coating layer 5 are composed of high-performance polymer materials. The inner coating layer 4 is completely and tightly covered on the inner surface of the metal substrate 3, and the outer coating layer 5 is completely and tightly covered on the outer surface of the metal substrate 3. Neither the inner nor outer surface of the metal substrate 3 is exposed. The inner coating layer 4 and the outer coating layer 5 are firmly bonded to the metal substrate 3 as a single integral structure through a molding process.

[0019] The wall thickness of the metal substrate 3 is reduced through optimized design. Its inner diameter is increased by 3mm and its outer diameter is reduced by 3mm compared with the traditional metal fastener of the same specification, thereby reducing the overall wall thickness by 6mm. This allows the weight of the large-diameter fastener to be significantly reduced. At the same time, the subsequent coating with polymer materials compensates for some of the performance that may be lost due to the thinning of the metal substrate and gives it additional functionality.

[0020] The slot structure 6 is located on the outer periphery of the pipe tail of the metal substrate 3 and is used to mate with the clamp-type connector. The contour of the slot structure 6 is precisely designed to ensure a stable and reliable connection with the standard clamp. The inner cladding layer 4 and the outer cladding layer 5 are also tightly bonded to the metal substrate 3 in the area of ​​the slot structure 6, ensuring that the corrosion resistance and cushioning protection performance of this critical connection area are not weakened.

[0021] The inner coating layer 4 is composed of a polymer material and is tightly wrapped around the inner surface of the metal substrate 3. The thickness of the inner coating layer 4 can be adjusted according to the corrosiveness, flow rate, and wear resistance requirements of the medium. Its smooth inner surface helps to reduce fluid resistance. The inner coating layer 4 completely isolates the conveying medium from direct contact with the metal substrate 3, and is the core solution to the problem of metal corrosion.

[0022] The outer coating layer 5 is composed of a polymer material and is tightly wrapped around the outer surface of the metal substrate 3. The thickness of the outer coating layer 5 can be designed according to the requirements of external environment such as wear, impact strength, and insulation. Its outer surface can be designed with different textures or hardness as needed to provide better grip or wear resistance. The outer coating layer 5 protects the metal substrate 3 from external mechanical damage and environmental corrosion.

[0023] The inner coating layer 4 and the outer coating layer 5 are firmly bonded to the metal substrate 3 through a molding process, forming a composite structure that integrates the structural strength of the metal substrate with the corrosion resistance, wear resistance, buffering and sealing functions of the polymer material. It works as a whole component, synergistically leveraging the respective advantages of the metal and the polymer material.

[0024] The buckle 1 of the present invention, as a whole, consists of a metal base 3, an inner covering layer 4, and an outer covering layer 5, which together form a complete connecting component. It can be directly used for connecting large-diameter water hoses. With the help of standard clamps 7, clamps 8, and bolts, it can be quickly installed and reliably sealed through bolt connection holes 9 and sealing gaskets 10.

[0025] In one specific embodiment, the surface where the metal substrate 3 is bonded to the inner coating layer 4 and the outer coating layer 5 has a microscopic anchoring structure formed by sandblasting roughening treatment. Specifically, 80-120 mesh alumina or glass beads can be used for sandblasting. Under a pressure of 0.4-0.6 MPa, the sandblasting distance is maintained at 100-200 mm. The surface roughness Ra after treatment reaches 3.2-12.5 μm, forming uniformly distributed microscopic pits and protrusions. This increases the surface area of ​​the metal and provides countless tiny mechanical anchoring points for the inflow and curing of polymer materials, thereby physically enhancing the bonding force between the polymer layer and the metal substrate and preventing delamination under high pressure, temperature changes, or long-term use conditions.

[0026] In one specific embodiment, to further optimize connection reliability, the slot structure 6 is designed as an asymmetric wedge-shaped groove with self-reinforcing function. The asymmetric wedge-shaped groove has a smaller inclination angle (8-12 degrees) on the sidewall near the pipe tail and the insertion end of the hose 11, forming a relatively gentle slope. The sidewall near the pipe opening, i.e., the fluid outlet end, has a larger inclination angle (20-30 degrees). The outer covering layer 5 is locally thickened in the area corresponding to the wedge-shaped groove, with a thickness increase of 2-3 mm compared to conventional covering layers, forming an elastic, adaptive wedge-shaped locking ring. When the hose 11 is fitted and pressed by clamps 7 and 8, especially when the internal system pressure increases, the axial pressure applied by the hose 11 and clamps 7 and 8 to the wedge-shaped locking ring is converted into a larger radial clamping force, allowing the locking ring to wedge more tightly into the slot structure 6. This achieves a self-locking and anti-dislodgement function with automatic enhancement of locking force when pressure increases, improving connection safety and reliability under high-pressure conditions.

[0027] In one specific embodiment, to improve the load-bearing capacity of stress concentration areas, the metal substrate 3 has a locally thickened reinforcing rib structure in the stress-bearing area corresponding to the clamp bolt hole 9. The thickness of the reinforcing rib is 40-60% greater than the conventional wall thickness of the substrate. The outer covering layer 5 completely covers this reinforcing structure during the molding process, ensuring a smooth transition between its outer contour and the overall snap fastener. This design specifically strengthens the localized high-stress area generated by bolt tightening, effectively preventing plastic deformation or fatigue cracking in this area under repeated disassembly or high pressure. Simultaneously, the complete coverage of the outer covering layer 5 avoids metal exposure, maintaining the overall corrosion resistance and aesthetic consistency of the snap fastener 1.

[0028] In one specific embodiment, the metal substrate 3 is designed with a biomimetic structure, and its wall thickness is non-uniformly distributed. Mimicking the load-bearing principle of bamboo or bones, areas with high stress, such as the base of the slot structure 6, around the bolt holes 9, and at the end flanges, are locally thickened, increasing the thickness to 1.5-2 times the conventional wall thickness. Conversely, areas with low stress, such as the middle of the tube, are appropriately thinned, reducing the thickness to 0.6-0.8 times the conventional wall thickness. This design concept of distributing materials as needed can, while meeting or even improving overall stiffness and strength, eliminate redundant materials to the maximum extent, achieving further weight reduction. It also makes the stress distribution more uniform, avoiding localized stress concentration, thereby improving the product's fatigue life.

[0029] In one specific embodiment, to improve the environmental adaptability and sealing reliability of the fastener 1, an insulating sealing ring is integrally formed from a polymer material of the inner covering layer 4 or the outer covering layer 5 during the molding process on the connecting end face of the fastener 1. Firstly, it provides electrical insulation. When the aluminum alloy fastener 1 of this invention is connected to flanges or joints made of other metal materials such as stainless steel or carbon steel, the polymer sealing ring can physically isolate the direct contact between the two metals, thereby effectively blocking the path of galvanic corrosion, also known as galvanic corrosion, and preventing the aluminum alloy from being accelerated to corrode as the anode. Secondly, it provides auxiliary sealing. The elastomeric sealing ring is compressed when the bolts are tightened, which can compensate for minor unevenness in the end face machining or assembly, providing an additional reliable static seal, thereby improving the sealing level of the entire connection interface.

[0030] In one specific embodiment, to achieve a more uniform distribution of clamping force and protect the metal substrate 3, an adaptive clamping fit structure may be included. This structure includes an elastic buffer pad that conforms to the outside of the slot structure 6. The buffer pad is made of silicone rubber or polyurethane rubber with a Shore hardness of 50-60A, and adjustable limiting blocks symmetrically arranged at both ends of the buffer pad. During installation, by finely adjusting the position of the limiting blocks, the clamping force of the clamp can be guided to act more evenly on the entire circumference of the slot structure 6. Through the compliant deformation of the elastic buffer pad and the adjustable limiting, manufacturing tolerances or installation deviations of the clamp can be compensated, resulting in a uniform distribution of clamping force. This avoids deformation or damage to the metal substrate 3 caused by excessive local stress during traditional rigid pressing, while also protecting the outer covering layer 5 and extending the service life of the fastener 1.

[0031] In one specific embodiment, the inner surface of the inner coating layer 4 is not a traditional smooth cylindrical surface. Instead, during the casting process, a microgroove array mimicking the sharkskin scale structure is integrally replicated using a pre-set sharkskin scale-like negative mold on the inner mold core surface. The microgrooves are arranged in an orderly manner along the fluid transport direction within the water strip 11, and the cross-sectional profile of each microgroove is asymmetrical sawtooth or arc-shaped corrugated. During high-pressure fluid transport, the biomimetic microgroove array guides the orderly flow of fluid within the turbulent boundary layer, reducing the intensity of turbulent bursts, thereby reducing the friction coefficient and transport energy consumption. Simultaneously, when solid particles such as sand and rock fragments entrained in the fluid impact the surface of the inner coating layer 4, the elastomeric material of the microgrooves absorbs and dissipates the impact energy through its own elastic deformation, preventing the particles from directly cutting and ploughing the inner coating layer 4, significantly improving the erosion resistance life of the inner coating layer 4. In addition, the axial continuity of the microgroove array facilitates the smooth discharge of fluid-carried particles along the bottom of the grooves, reducing particle retention and accumulation on the inner surface and further ensuring fluid transport efficiency.

[0032] In one specific embodiment, a ring of anti-rotation grooves is machined on the outer periphery of the metal substrate 3 in the region near the insertion direction of the hose 11 at the front end of the slot structure 6. The anti-rotation grooves are located axially between the annular groove 2 and the slot structure 6. The anti-rotation grooves consist of multiple axially distributed grooves along the circumference, each with a rectangular or trapezoidal cross-section and a depth controlled to 1 / 3 to 1 / 2 of the local wall thickness of the metal substrate 3. Unlike the annular groove 2, which serves as an axial anti-pull-out function, the axial extension geometry of the anti-rotation grooves specifically provides anti-torsion functionality. During the casting process, uniformly mixed polyurethane casting material flows into each axial groove of the anti-rotation grooves, and after curing, forms polymer anti-rotation bonds embedded in each axial groove. The outer surface contour of the outer coating layer 5 in the anti-rotation groove region remains a smooth cylindrical surface or slightly convex. When the hose 11 is dragged and twisted during actual operation, clamps 7 and 8 are tightly pressed against the slot structure 6 and the outer coating layer 5 in the anti-rotation groove region due to the bolt preload. The polymer anti-rotation key, formed by filling the outer coating layer 5 with the material, forms a toothed engagement with the inner walls of clamp 7 and clamp 8, which can effectively resist circumferential shear force and prevent relative rotation between the hose 11 and the fastener 1. This distributes the torsional torque evenly to the entire circumference of the metal substrate 3 through multiple anti-rotation keys, avoiding the problems of clamp loosening and hose entanglement caused by lack of circumferential restraint, and ensuring the stability and safety of the connection system under complex working conditions such as dragging and turning.

[0033] Example 2 like Figure 5This embodiment illustrates a manufacturing method for producing the lightweight, corrosion-resistant fastener described in Example 1. The core of this method lies in combining precision machining with reaction injection molding or casting molding processes to ensure high-precision forming of the metal substrate 3 and achieve a high-strength, defect-free composite of the polymer material and the metal substrate 3. The method includes the following steps, which are described in detail with specific parameter examples.

[0034] S1 Precision Forming of Metal Matrix: A metal substrate 3 with a reduced wall thickness structure, a slot 6, and a sealing step is directly machined from a metal billet. Specifically, SS316L or 6061-T6 aluminum alloy forged bars can be used as the billet to ensure material density and strength. The entire process is performed using a high-precision five-axis CNC machine tool. The inner diameter is increased by 3mm, while the outer diameter is decreased by 3mm. The precise slot structure 6, sealing end face, and necessary steps are milled simultaneously.

[0035] S2 Surface Pretreatment: The processed metal substrate 3 is degreased and cleaned to remove surface oil, and then its inner and outer surfaces are roughened by sandblasting to form a micro-rough surface. This step is crucial to ensuring the adhesion of the subsequent coating layer. First, the processed metal substrate 3 is thoroughly degreased and cleaned, for example, by ultrasonic cleaning with an alkaline or neutral cleaning agent to completely remove contaminants such as oil and cutting fluid. Then, its inner and outer surfaces are roughened by sandblasting. Alumina or diamond abrasive with a particle size of approximately 150μm (80-120 mesh) is used for sandblasting at appropriate pressure and distance to form uniform, clean micro-anchoring points with appropriate roughness, creating conditions for the wetting and mechanical interlocking of the polymer material.

[0036] S3 Primer Treatment: A layer of a specialized primer for polymer materials is uniformly coated onto the pretreated metal substrate 3 surface and then dried and cured. Using a polymer primer containing special functional groups, such as Chemlock 205, air spraying or dip coating is employed, controlling the dry film thickness between 10 and 20 μm. After spraying, the primer is flash-dried at room temperature for 5 to 10 minutes to allow the solvent to evaporate, then placed in an oven at 80 to 100°C for 15 to 30 minutes to fully cure the primer. The primer forms a chemically active transition layer on the metal surface, forming strong chemical bonds with both the metal surface and the polymer material. This is crucial for ensuring adhesion, especially long-term resistance to hydrolysis and heat aging.

[0037] S4 Mold Preparation and Installation: A combined mold for forming the inner and outer coating layers 5 is provided. This mold includes an inner core for forming the inner coating layer 4 and an outer cavity for forming the outer coating layer 5. The pre-coated metal substrate 3 is coaxially positioned between the inner core and the outer cavity. The mold cavity is precisely designed to form the required coating layer thickness and external contour, such as adapting to the shape of the wedge-shaped locking ring. The pre-coated metal substrate 3, preheated to, for example, 70 to 80°C to facilitate the flow and adhesion of the polymer material, is coaxially and precisely positioned at the center of the annular cavity between the inner core and the outer cavity. The mold itself also needs to be preheated to a similar temperature. The mold is equipped with overflow channels and vents to ensure the cavity is completely filled and gas is expelled, avoiding defects such as air bubbles or insufficient material.

[0038] S5 Polymer Coating Molding: A uniformly mixed polymer casting material is injected into a preheated mold cavity at a set temperature and then heat-cured to form a tightly bonded inner coating layer 4 and outer coating layer 5 on both the inner and outer surfaces of the metal substrate 3. This is the core step in functional layer forming. Taking a two-component cast polyurethane as an example, a polyether-type or polyester-type prepolymer, such as Adiprene R990, is mixed with a corresponding curing agent, such as Vibracure A245, at a precise stoichiometric ratio. The mixture is then thoroughly stirred and vacuum degassed to remove air bubbles. The degassed mixture is then poured into a preheated mold cavity and heat-cured at 110°C. The curing process can be divided into two stages: initial curing and post-curing. Initial curing is performed in the mold at 110°C for approximately one hour to give the material sufficient strength for demolding. After demolding, the product still needs to undergo post-curing in an oven at 110°C for up to 16 hours. Post-curing enables more complete cross-linking of the polymer material, resulting in stable physical and mechanical properties such as hardness, tensile strength, abrasion resistance, and hydrolysis resistance. Through this step, the polymer material is simultaneously formed on both the inner and outer surfaces of the metal matrix 3, and through mechanical anchoring and chemical bonding with the pretreated metal surface, forms a firmly bonded inner coating layer 4 and an outer coating layer 5 free of interfacial defects. By adjusting the type and ratio of the prepolymer and curing agent, coating layers with different hardnesses, such as Shore A85A, 90A, and 95A, and properties can be obtained to meet various application requirements.

[0039] S6 Post-processing and Finishing: After molding, the product is cooled, demolded, and excess flash and overflow are removed. The post-vulcanized product is cooled to room temperature. Then, machining methods such as CNC precision milling are used to remove flash and overflow generated during casting. Crucially, the flange end faces require high-precision milling to ensure flatness and surface finish, which is key to reliable end-face sealing. Finally, cleaning, inspection, and packaging are performed.

[0040] Combining precision metal machining with polymer reaction molding technology results in a mature and reliable process that eliminates the need to develop extremely expensive and complex molds for large-diameter composite material joints, such as fiber winding or resin transfer molding molds. This approach is particularly suitable for medium-volume and customized production, achieving high-performance composite structures while offering good cost control and industrialization prospects.

[0041] Example 3 This embodiment details a specific manufacturing process for a buckle 1, aiming to demonstrate how the present invention can be achieved through specific process parameters.

[0042] Metal substrate forming: 6061-T6 aluminum alloy forging bar with a diameter of 408mm and a wall thickness of 25mm was selected as the raw material. The blank was milled into a tubular metal substrate 3 with an inner diameter of 386mm and an outer diameter of 403mm using a five-axis CNC machine tool. This is equivalent to increasing the inner diameter by 3mm and decreasing the outer diameter by 3mm.

[0043] Surface treatment: The processed metal substrate 3 is subjected to ultrasonic degreasing and cleaning to remove surface oil. Subsequently, the inner and outer surfaces of the metal substrate 3 are roughened by sandblasting with 100-mesh alumina abrasive, with an alumina particle size of approximately 10 μm.

[0044] Primer application: A uniform layer of Chemlock 205 primer is sprayed onto the sandblasted metal substrate 3 surface. This primer is a gray, opaque adhesive formed by dissolving organic polymers and dispersing fillers in a solvent system such as methyl isobutyl ketone, specifically designed for bonding rubber / plastic to metal. The sprayed film thickness is controlled to approximately 15 μm.

[0045] Mold and Overmolding: Preheat the metal substrate 3, coated with primer, and the overmolding mold to 70-80℃. Mix the polycarbonate prepolymer ADIPRENE R990 and its curing agent Vibracure A245 at a mass ratio of 100:10.39 until homogeneous, and perform vacuum degassing. Inject the degassed mixture into the preheated mold cavity. After curing at 110℃ for 1 hour, perform initial curing and demolding. The demolded product continues to undergo post-curing at 110℃ for 16 hours. The hardness of the polyurethane overmolding layer after curing is Shore A 95A.

[0046] Post-processing: After the post-vulcanization is completed and cooled to room temperature, the product is precision milled by CNC to remove the overflow edges generated during molding, and the flange sealing surface is precision machined to ensure that its flatness is less than or equal to 0.15mm.

[0047] Example 4 This embodiment provides another specific manufacturing process for the buckle 1. The main difference from embodiment 3 is that a different formulation of polymer material is used to obtain a coating layer with different hardness and performance.

[0048] Metal substrate forming: A 6061-T6 aluminum alloy forged bar with a diameter of 408mm and a wall thickness of 25mm was selected. The metal substrate 3 with an inner diameter of 386mm and an outer diameter of 403mm was machined as a whole using a five-axis CNC machine tool.

[0049] Surface treatment: The metal substrate 3 is ultrasonically degreased and cleaned, and then roughened by sandblasting with 100-mesh alumina abrasive.

[0050] Primer treatment: Chemlock 205 primer is uniformly sprayed onto the surface of the metal substrate 3, and the film thickness is controlled to be about 15μm.

[0051] Mold and Coating: Preheat the metal substrate 3 and the mold to 70-80℃. Mix the three components of polycarbonate prepolymer ADIPRENE R990, Vibracure R613, and Vibracure A245 at a mass ratio of 100:25.42:8.52 until homogeneous, and then perform vacuum degassing. Inject the mixture into the mold, demold after initial curing at 110℃ for 1 hour, and then post-cured at 110℃ for 16 hours. The resulting polyurethane coating has a Shore A hardness of 85A and exhibits better elasticity.

[0052] Post-processing: After the product cools, the overflow is removed by CNC precision milling and the flange sealing surface is precision machined to ensure that the flatness is less than or equal to 0.15mm.

[0053] Example 5 This embodiment demonstrates the manufacturing process of a fastener 1 applicable to another common specification, illustrating the applicability of the invention.

[0054] Metal substrate forming: A 6061-T6 aluminum alloy forged bar with a diameter of 325mm and a wall thickness of 25mm was selected. The metal substrate 3 with an inner diameter of 300mm and an outer diameter of 321mm was milled out using a five-axis CNC machine tool, realizing the thinning design of increasing the inner diameter by 3mm and decreasing the outer diameter by 3mm.

[0055] Surface treatment: The metal substrate 3 is ultrasonically degreased and cleaned, and then roughened by sandblasting with 100-mesh alumina abrasive.

[0056] Primer treatment: Chemlock 205 primer is uniformly sprayed onto the surface of the metal substrate 3, and the film thickness is controlled to be about 15μm.

[0057] Mold and Coating: Preheat the metal substrate 3 and the mold to 70-80℃. Mix the polycarbonate prepolymers ADIPRENE R990, Vibracure R613, and Vibracure A245 at a mass ratio of 100:14.12:9.35 until homogeneous, and then perform vacuum degassing. Inject the mixture into the mold, allow it to initially cure at 110℃ for 1 hour, then demold, followed by post-curing at 110℃ for 16 hours. The hardness of the polyurethane coating formed after curing is Shore A 90A.

[0058] Post-processing: After the product cools, the overflow is removed by CNC precision milling and the flange sealing surface is precision machined to ensure that the flatness is less than or equal to 0.15mm.

[0059] Performance testing To verify the superior performance of the buckle 1 of the present invention, a series of tests were conducted on the buckle 1 samples prepared according to the methods of Examples 3, 4 and 5.

[0060] 1. Pulse fatigue test The samples were subjected to 5,000 pulse fatigue tests, with pressure cycling between 0.1 MPa and 2 MPa.

[0061] Table 1. Results of Pulse Fatigue Test 2. Pressure test The sample was subjected to a hydrostatic burst test at 6 MPa.

[0062] Table 2 Pressure Test Results

[0063] Test results show that all sample joints corresponding to Examples 3, 4 and 5 remained intact without cracking or permanent deformation, proving that the composite structure of the snap fastener 1 has extremely high pressure resistance and structural integrity.

[0064] 3. Residual chlorine resistance test To evaluate the corrosion and aging resistance of the coating material, standard samples of the composite adhesive layers corresponding to each embodiment were prepared and immersed in an aqueous solution at 80°C with a residual chlorine concentration of 100 ppm for 120 days. After immersion, the tensile strength of the samples before and after immersion was tested according to the method of national standard GB / T528, and the tensile strength retention rate was calculated.

[0065] Table 3 Results of Residual Chlorine Resistance Test

[0066] Test results show that the tensile strength retention rate of the sample corresponding to Example 3 is 86.8%, that of the sample corresponding to Example 4 is 81.6%, and that of the sample corresponding to Example 5 is 85.7%. All results exceed 80%, proving that the polymer coating material used has excellent durability and mechanical property stability in a strong oxidizing and corrosive environment, and can effectively protect the metal matrix 3 for a long time.

[0067] The test results above comprehensively show that the lightweight and corrosion-resistant fastener 1 provided by the present invention exhibits excellent and balanced performance in terms of lightweight, high pressure resistance, fatigue resistance and strong corrosion resistance, and fully meets the requirements for use in harsh industrial environments.

[0068] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, nor is it limited to lightweight corrosion-resistant couplings for large-diameter hose connections and their manufacturing methods. Equipment and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. A lightweight, corrosion-resistant coupling for connecting large-diameter water hoses, characterized in that, include: The metal substrate is a tubular structure made of aluminum alloy. The wall thickness is reduced by increasing the inner diameter and simultaneously decreasing the outer diameter. The outer periphery of the tube end of the metal substrate is provided with a groove structure for engaging with the clamp-type connector. The inner coating layer is made of polymer material. The inner coating layer is cast polyurethane with a Shore hardness of 80A-95A. It is tightly wrapped around the inner surface of the metal substrate. The outer coating is made of polymer material. The outer coating is cast polyurethane with a Shore hardness of 80A-95A. It is tightly wrapped around the outer surface of the metal substrate. The inner and outer surfaces of the metal substrate are not exposed. The inner and outer surfaces of the metal substrate are equipped with micromechanical anchoring structures. The inner and outer cladding layers are firmly bonded to the metal substrate through a casting and curing process, forming a composite structure that integrates the structural strength of the metal substrate with the corrosion resistance, wear resistance, buffering, and sealing functions of the polymer material. The end face sealing area of ​​the fastener is precision machined to a flatness of no more than 0.1 mm to ensure the sealing reliability with the mating parts.

2. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The micro-anchoring structure formed on the surface where the metal substrate is combined with the inner and outer cladding layers is roughened by sandblasting to enhance the bonding force between them.

3. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The metal matrix has a biomimetic structure with a non-uniform distribution of tube wall thickness to optimize stress distribution and further achieve lightweighting; specifically, the biomimetic structure is a multi-level variable thickness structure that imitates bamboo or bone and / or an internal microporous network structure.

4. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The slot structure is an asymmetric wedge-shaped groove with self-reinforcing function. The inclination angle of the side wall near the pipe tail is smaller than that near the pipe opening. The outer coating layer is locally thickened in the area corresponding to the wedge-shaped groove to form an adaptive wedge-shaped locking ring. When the internal pressure of the water hose increases, the locking ring is further compressed to achieve self-locking and anti-detachment.

5. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The connecting end face of the buckle is provided with an integrally formed polymer material insulating sealing ring. The insulating sealing ring is formed by the extension of the inner or outer covering layer of polymer material covering the end face. It is used to block the galvanic corrosion path and provide auxiliary sealing when connected with mating parts of different materials.

6. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The metal substrate has a locally thickened reinforcing rib structure or a pre-embedded metal insert in the stress area corresponding to the clamp bolt hole. The outer covering layer completely covers the reinforcing rib structure or metal insert, so that its outer contour smoothly transitions with the overall outer contour of the fastener.

7. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: It also includes an adaptive clamping structure, which includes an elastic buffer pad and an adjustable limiting block. The elastic buffer pad is attached to the outside of the slot, and the adjustable limiting block is symmetrically arranged at both ends of the elastic buffer pad. By finely adjusting the position of the limiting block, the clamp and the slot are evenly attached, dispersing the compression stress and preventing the metal substrate from deforming due to excessive local stress.

8. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The inner surface of the inner coating layer has an array of microgrooves that mimic the structure of shark skin scales. The microgrooves are arranged in an orderly manner along the fluid transport direction to form an orderly low-speed flow field in the fluid boundary layer, thereby reducing the turbulence intensity and friction resistance during high-pressure transport. At the same time, the elastic deformation of the microgrooves absorbs the impact energy of solid particles in the fluid, thus having both drag reduction and erosion resistance functions.

9. The lightweight corrosion-resistant coupling for connecting large-diameter water hoses according to claim 1, characterized in that: The outer circumference of the metal substrate's pipe tail is also provided with a ring of anti-rotation grooves at the front end of the slot structure. The anti-rotation grooves are composed of multiple axial grooves or axial protrusions evenly distributed along the circumference. The anti-rotation grooves are used to provide circumferential positioning to resist torsional torque. The outer coating layer completely fills or wraps the anti-rotation grooves during molding, forming an integrated polymer anti-rotation key. When the hose is subjected to circumferential torsional torque, the polymer anti-rotation key transmits the torsional force to the entire circumferential surface of the metal substrate by interlocking with the inner wall of the clamp, preventing relative torsional displacement between the hose and the fastener and preventing the clamp from loosening.

10. A method for manufacturing a lightweight corrosion-resistant fastener as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1 Precision Forming of Metal Matrix: Using aluminum alloy blanks, a metal matrix with a reduced wall thickness structure, as well as slots and sealing steps, is directly machined through mechanical processing. S2 Surface Pretreatment: The processed metal substrate is degreased and cleaned to remove surface oil, and then its inner and outer surfaces are roughened by sandblasting to form a micro-rough surface. S3 Primer Treatment: A special primer for polymer materials is uniformly coated on the inner and outer surfaces of the pretreated metal substrate and then dried and cured. S4 Mold Preparation and Installation: A set of combined molds for forming inner and outer coating layers is provided. The mold includes an inner mold core for forming the inner coating layer and an outer mold cavity for forming the outer coating layer. The metal substrate that has been primed is coaxially positioned between the inner mold core and the outer mold cavity. S5 polymer material coating molding: The uniformly mixed polymer material casting material is injected into the mold cavity that has been preheated to the set temperature, and then heated and cured to form a tightly bonded inner coating layer and an outer coating layer on the inner and outer surfaces of the metal matrix. S6 Post-processing and Finishing: Cool the molded product, demold it, and remove excess fly and overflow.

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