A plastic-steel composite pipe and its preparation method

Abstract

This invention discloses a plastic-steel composite pipe, comprising a steel pipe substrate, the outer surface of which is wrapped with vacuum-impregnated fiber cloth, and a composite plastic outer layer formed on the outer surface of the steel pipe substrate wrapped with vacuum-impregnated fiber cloth. The composite plastic outer layer includes a first plastic body, which is a pre-formed sleeve structure with several annular blind grooves formed on its inner side; a vulcanized silicone rubber is used as a filling structural layer between the first plastic body and the steel pipe substrate; a second plastic body is also formed on the inner surface of the steel pipe substrate and the outer surface of the first plastic body. This invention also discloses a method for preparing the above-mentioned plastic-steel composite pipe. The plastic-steel composite pipe prepared by this invention combines the characteristics of various pipes, possessing both the strength of steel pipes and the corrosion resistance, wear resistance, and low fluid resistance of plastic pipes, making it a safe, hygienic, high-strength, and well-bonded green pipe.

Description

Technical Field

[0001] This invention relates to composite pipe technology in the field of pipe fittings manufacturing, specifically to a plastic-steel composite pipe and its manufacturing method. Background Technology

[0002] Plastic-steel composite pipes, as a new type of pipe material, are among the best-performing pipes currently available. Using steel pipes as the base, a plastic outer layer is fused to the inner or both inner and outer surfaces of the steel pipe through molding processes such as spraying, rolling, dipping, and suction. This combination of advantages from both plastic and metal pipes results in high inherent strength and rigidity. The plastic outer layer further enhances the mechanical properties of the steel pipe and effectively protects the inner steel pipe from external corrosion. This overcomes the shortcomings of galvanized pipes, such as rusting, yellow water production, and dirt accumulation leading to small pipe diameters and blockages, as well as the weak strength of plastic pipes. Furthermore, it offers lower resistance to media flow. These properties contribute to the long service life and wide application range of plastic-steel composite pipes, making them suitable for transporting seawater, warm water, oil, and gas. They also significantly improve water quality and prevent secondary pollution, making them particularly advantageous for urban drinking water and industrial water supply pipelines.

[0003] Plastic-steel composite pipes come in a variety of types and models. Depending on the application, the thickness of the plastic anti-corrosion layer and the molding method also vary. However, under the current traditional molding methods, the resulting plastic-steel composite pipe structure has the following problems in practical applications:

[0004] I. Traditional spin coating methods often involve directly applying plastic powder to the surface of steel pipes. However, this method can lead to uneven distribution of the plastic powder and inconsistent coating thickness. Furthermore, the plastic powder requires a certain amount of time to solidify on the surface of the steel pipe substrate. During the solidification process, the coating material is prone to flow, resulting in unevenness defects on the pipe surface. As a result, the plastic layer of coated steel pipes is usually relatively thin during use. When forming large-sized medium and large-sized plastic-steel composite pipes with a thicker outer plastic layer, the plastic layer is easily damaged locally and fails, thus affecting its application range.

[0005] II. Plastic-steel composite pipes formed under non-spraying processes and similar fixed-jointing molding methods may have defects in bonding strength due to material differences between the outer plastic layer and the steel pipe substrate. During use, the interlayer structure is prone to delamination at the interface between the outer plastic layer and the steel pipe substrate due to external stress impacts, temperature changes, etc., which will destroy the overall consistency of the composite pipe and cause strength and structural defects in the composite steel pipe, directly affecting the performance and service life of the pipe. This defect will become more obvious when laid outdoors or pre-buried due to climate change, animal and plant activities, and soil environmental stress.

[0006] For the reasons mentioned above, it is necessary to improve the structure and molding process of existing plastic-steel composite pipes. Summary of the Invention

[0007] The technical problem solved by the present invention is to provide a plastic-steel composite pipe and its preparation method, so as to overcome the defects in the above-mentioned technical background.

[0008] The technical problem solved by this invention is achieved by the following technical solution:

[0009] A plastic-steel composite pipe includes a steel pipe substrate, the outer surface of which is wrapped with vacuum-impregnated fiber cloth, and a composite plastic outer layer is formed on the outer surface of the steel pipe substrate wrapped with vacuum-impregnated fiber cloth.

[0010] The outer layer of the composite plastic material includes a first plastic body, which is a pre-formed sleeve structure. The sleeve thickness of the first plastic body is 1 / 3 to 1 / 2 of the thickness of the steel pipe base, and it is concentrically fitted onto the outer surface of the steel pipe base. Several annular blind grooves are formed at intervals along the length of the tube on the inner side of the first plastic body. Adjacent annular blind grooves have a communication portion reserved on the side that is in contact with the steel pipe base. Anchor columns arranged in an array are formed in the annular blind grooves.

[0011] A glue injection gap is reserved between the sleeve body of the first plastic material and the steel pipe base wrapped with vacuum impregnated fiber cloth, and the top surface of the anchor is tightly pressed against the surface of the vacuum impregnated fiber cloth of the steel pipe base.

[0012] The gap between the first plastic material body and the steel pipe matrix is ​​filled with vulcanized silicone rubber as a structural layer, and the filling structural layer is also mixed with modified reinforcing fibers with a mass ratio of 7-12%.

[0013] The plastic-steel composite pipe has a second plastic material formed on the inner pipe surface of the steel pipe substrate and the outer pipe surface of the first plastic material. The second plastic material is a film material with a thickness of 0.2 to 0.3 mm, which is formed on the above surface structure by spin coating or hot-dip plastic coating process.

[0014] As a further limitation, the steel pipe substrate is a galvanized welded steel pipe, a galvanized seamless steel pipe, or a spiral steel pipe that has undergone surface polishing.

[0015] As a further limitation, the first plastic body has a flared guide structure formed on its end face to facilitate the insertion of the steel pipe base. The flared guide structure is a spare structure that is cut off after the first plastic body is assembled into place on the steel pipe base.

[0016] As a further limitation, the sum of the lengths of the annular blind grooves formed on the first plastic body is 75% to 85% of the overall length of the pipe, and the length-to-diameter ratio of a single annular blind groove is 3:1 to 5:1; and the gap between the bottom of the annular blind groove and the surface of the steel pipe substrate wrapped with vacuum-impregnated fiber cloth is 1 / 5 to 1 / 3 of the pipe thickness of the first plastic body sleeve.

[0017] As a further definition, the connecting portion is an annular inner necking structure formed between adjacent annular blind grooves and abutting the steel pipe base, or multiple connecting channels formed on the sidewall between adjacent annular blind grooves, wherein the multiple connecting channels are evenly arranged on the corresponding annular surfaces; the projected size of the connecting portion on the radial section of the plastic-steel composite pipe is 20-30% of the projected size of the annular blind groove on the radial section of the plastic-steel composite pipe.

[0018] As a further limitation, the cross-section of the anchor post is cross-shaped or circular; the area of ​​the anchor post within the plane of the annular blind groove is 7-15%.

[0019] As a further limitation, the substrate of the vacuum impregnated fiber cloth is glass fiber cloth, aramid fiber cloth, or carbon fiber cloth modified with a silane coupling agent; the modified reinforcing fiber is a monofilament fiber modified with a silane coupling agent, and the monofilament fiber has a length of 4-7 mm, a fineness of 1-1.5D, and the fiber type is the same as that of the substrate of the vacuum impregnated fiber cloth.

[0020] As a further limitation, the filling structural layer is a one-piece molded structure formed by integral injection.

[0021] A method for preparing a plastic-steel composite pipe, specifically comprising the following steps:

[0022] S1 performs surface cleaning on the steel pipe substrate, and performs rust removal and dust removal treatment on the inner and outer surfaces of the steel pipe substrate respectively; after the rust removal and dust removal treatment is completed, a silane coupling agent is sprayed on the surface of the steel pipe substrate, and it is left to stand at room temperature. After the surface dries, it is placed in an oven and baked at a temperature of 40-60℃ for 30-50 minutes, and then cooled naturally.

[0023] S2 wraps paper around the ends of the cooled steel pipe substrate; then, vacuum-impregnated fiber cloth is wrapped around the surface of the steel pipe substrate after the paper is wrapped around the ends. When wrapping the vacuum-impregnated fiber cloth, the paper wrapping at both ends of the steel pipe substrate is used as the boundary. After the vacuum-impregnated fiber cloth is wrapped, the paper wrapping at the ends is removed.

[0024] S3 selects a first plastic material body that matches the size of the steel pipe base body and fits it onto one end of the steel pipe base body. During fitting, the outer side of the first plastic material body is pressed onto the original pipe end paper wrapping position so that the vacuum impregnated fiber cloth area is embedded in the first plastic material body.

[0025] S4 uses vulcanized silicone rubber as raw material, and performs pressure injection from the reserved injection hole on the first plastic body to fill the gap between the first plastic body and the steel pipe substrate. Then, the overflowing rubber material is scraped off and heat vulcanization is performed.

[0026] S5 uses the pipe material processed in step S4 as raw material, and processes it using spin coating or hot-dip plastic coating to obtain the second plastic material body. After processing, the ends are polished, and the finished plastic-steel composite pipe material is obtained after passing the inspection.

[0027] The plastic-steel composite pipe of the present invention has the following advantages and beneficial effects:

[0028] The plastic-steel composite pipe of this invention possesses the advantages of traditional plastic-steel pipes. Compared with other metal pipes, plastic pipes, and composite pipes, it has low water absorption, high mechanical strength, and excellent structural stability. The pipe uses steel as its base material, providing superior physical strength, while the outer first and second plastic layers effectively protect the inner steel pipe from external corrosion. Furthermore, the plastic material ensures the pipe is not affected by other corrosive liquids or environmental conditions. This corrosion resistance significantly extends the service life of the composite pipe, reduces the frequency of steel pipe maintenance and replacement, and lowers operating costs. Simultaneously, the smooth inner surface of the pipe improves the pipeline's transport efficiency and performance, reduces transport resistance, and thus reduces energy consumption.

[0029] Compared to traditional plastic-steel composite pipes, the plastic-steel composite pipe of this invention combines the technical advantages of both coated and lined steel pipes through its first and second plastic body molding method. This ensures the bonding performance between the plastic and steel pipes and the stability of the pipe structure. Furthermore, the gap filling with vulcanized silicone rubber effectively prevents the decrease in impact resistance and interface delamination between the plastic and steel pipes caused by material differences, further improving the performance and service life of the plastic-steel composite pipe. It is particularly suitable for manufacturing medium to large-sized pipes and extending their service life.

[0030] The plastic-steel composite pipe of the present invention has strong adaptability to external environmental changes and stress impacts. It can adapt to working environments of -30℃ to 120℃ as well as underground, acid and alkali corrosion environments, and dusty environments. It can effectively broaden the application scenarios of plastic-steel composite pipes and effectively prevent damage to plant roots and soil environmental stress.

[0031] Compared to traditional plastic-steel composite pipes of the same size, the plastic-steel composite pipe of this invention has the advantages of being lightweight, easy to handle, install, and maintain. During construction, it can significantly shorten time, improve efficiency, and reduce labor costs. Attached Figure Description

[0032] Figure 1 This is a schematic axial cross-sectional view of the present invention.

[0033] Figure 2 for Figure 1 A detailed enlarged diagram of part A in the middle.

[0034] Figure 3 for Figure 1 A detailed enlarged diagram of part B.

[0035] Wherein: 1. Steel pipe base; 2. Composite plastic outer layer; 3. Second plastic body; 20. First plastic body; 21. Filling structural layer; 22. Annular blind groove; 23. Anchor post; 24. Vacuum impregnated fiber cloth; 25. Connecting part. Detailed Implementation

[0036] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0037] In the following embodiments, those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have a meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0038] See Figures 1-3 A preferred embodiment of a plastic-steel composite pipe is described. In this embodiment, the main body of the plastic-steel composite pipe is a steel pipe substrate 1. The steel pipe substrate 1 can be a galvanized welded steel pipe, a galvanized seamless steel pipe, or a spiral steel pipe with surface polishing in different embodiments. Different pipe thicknesses can be selected under different requirements, commonly including 0.5mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 4.0mm, 5.0mm, and 6.0mm. Considering the molding difficulty, structural stability after molding, and usage conditions, the steel pipe substrate 1 should preferably be a medium-to-large-sized steel pipe with a thickness of 3mm or more as the raw material. Simultaneously, the surface of the steel pipe substrate 1 is wrapped with vacuum-impregnated fiber cloth 24 during molding to serve as an interface stabilizing structure; and the vacuum-impregnated fiber cloth 24 also has an unwrapped section at both ends of the steel pipe substrate 1 as a buffer area.

[0039] A composite plastic outer layer 2 is formed on the outer surface of the steel pipe substrate 1, and a second plastic body 3 is formed on the entire outer surface of the composite plastic outer layer 2 and the inner surface of the steel pipe substrate 1. The second plastic body 3 is a plastic film material with a thickness of 0.2 to 0.3 mm, and there are two molding methods in different embodiments:

[0040] One method involves using a spin coating process in conjunction with a pipe spin coating equipment to form the coating onto the aforementioned surface structure.

[0041] The second method involves molding the material onto the aforementioned surface structure using a hot-dip plastic coating process and equipment.

[0042] In this embodiment, the main body of the outer layer 2 of the composite plastic material includes a first plastic material body 20, which is a pre-formed sleeve structure. During molding, it is fixed to the outer tube surface of the steel pipe base 1 in a set manner by a jig. The sleeve thickness of the first plastic material body 20 is 1 / 3 to 1 / 2 of the tube thickness of the steel pipe base 1.

[0043] The inner side of the first plastic body 20 is formed with a plurality of annular blind grooves 22 at intervals along the length of the pipe. These annular blind grooves 22 are of the same size, shape and structure and are evenly spaced along the length of the inner side of the first plastic body 20. In different embodiments, the length-to-diameter ratio of a single annular blind groove 22 is 3:1 to 5:1, and a gap of 1 / 5 to 1 / 3 of the thickness of the sleeve corresponding to the first plastic body 20 is reserved between the bottom of a single annular blind groove and the surface of the vacuum-impregnated fiber cloth 24 wrapped on the steel pipe substrate 1. The sum of the lengths of the annular blind grooves 22 per unit length of the first plastic body 20 is 75% to 85% of the overall length of the pipe.

[0044] The first plastic body 20 has a connecting portion 25 formed on the inner side of the sleeve corresponding to the position between the annular blind grooves 22. The connecting portion 25 is used to form a connecting space between the annular blind grooves 22. The connecting portion 25 has two structural forms in different embodiments:

[0045] One such Figure 1 The variable diameter structure shown is an annular structure with an inner necking formed on the side of the steel pipe base 1 between adjacent annular blind grooves 22.

[0046] Another method involves forming multiple channel connection structures on the connecting side wall of adjacent annular blind grooves 22. These multiple channels are evenly arranged on the corresponding annular surface of the annular blind groove 22, i.e., arranged in annular radial pattern.

[0047] The common feature of the two different structural forms of the connecting part 25 is that the projected size of the corresponding connecting part 25 on the radial section of the plastic-steel composite pipe is 20 to 30% of the projected size of the annular blind groove 22 on the radial section of the plastic-steel composite pipe, so as to ensure the structural stability, strength and impact resistance of the sidewalls between the annular blind grooves 22 that act as partitions and supports.

[0048] In addition, in the embodiments of the present invention, the bottom of the corresponding annular blind groove 22 is also formed with anchor posts 23 arranged in an array. The cross-section of these anchor posts 23 is cross-shaped or circular. The area of ​​the anchor posts 23 in the plane of the annular blind groove is 7 to 15%. The top surface of the anchor posts 23 is tightly pressed against the surface of the vacuum impregnated fiber cloth 24 of the steel pipe substrate 1.

[0049] The gap between the steel pipe substrate 1 and the first plastic material body 20, and the gap between the corresponding anchors 23 in the annular blind groove 22, are the injection gaps, and vulcanized silicone rubber is filled in the injection gaps as a filling structural layer 25. As a preferred molding method, the vulcanized silicone rubber in the filling structural layer 25 is an integrally injected molding structure.

[0050] The plastic-steel composite pipe in this embodiment is prepared by the following method:

[0051] In order to better mold the plastic material onto the wall of the steel pipe substrate 1, the steel pipe substrate 1 needs to be cleaned first. That is, the steel pipe of the steel pipe substrate 1, which is used as raw material, needs to be cleaned first. After cleaning, the surface of the steel pipe is preheated using heat treatment equipment to remove moisture. Then, the surface dust is blown away by a dust collector. Then, the outer and inner surfaces of the steel pipe are derusted using a shot blasting machine and an internal derusting head. After derusting, the steel pipe substrate 1 is dusted using a roller brush dust collector. After dust removal, the steel pipe substrate 1 that can be processed is obtained.

[0052] The obtained steel pipe substrate 1 is treated with a silane coupling agent by spraying it onto its surface. After spraying, it is left to stand at room temperature until the surface is dry, and then placed in an oven and baked at 50°C for 40 minutes before naturally cooling. Paper is then wrapped around both ends of the cooled steel pipe substrate 1. Vacuum-impregnated fiber cloth 24 is then wrapped around the surface of the steel pipe substrate 1 after the paper wrapping. The wrapping is done with the paper wrapping at both ends of the steel pipe substrate 1 as the boundary. After wrapping, the paper wrapping is removed, and the surface of the steel pipe substrate 1 is rolled to ensure the adhesion between the vacuum-impregnated fiber cloth 24 and the steel pipe substrate 1. The vacuum-impregnated fiber cloth 24 should be made of fiber cloth with good physical and chemical properties (such as glass fiber cloth, aramid fiber cloth, or carbon fiber cloth), and the corresponding substrate should be pretreated with a silane coupling agent before impregnation. The corresponding pre-impregnated adhesive is epoxy resin.

[0053] Then, the outer layer 2 of the composite plastic material is formed. When forming the outer layer 2 of the composite plastic material, a first plastic material body 20 that matches the size of the steel pipe base 1 is selected. After alignment, it is pressed onto the outer pipe surface of the steel pipe base 1 using a jig. The two ends of the first plastic material body 20 are pressed onto the original pipe end wrapping paper position. At the same time, the top surface of the anchor column 23 in the annular blind groove 22 is pressed against and pressed onto the surface of the vacuum impregnated fiber cloth 24, so that the vacuum impregnated fiber cloth 24 is completely embedded in the first plastic material body 20.

[0054] In order to facilitate the insertion of the first plastic body 20, in different embodiments, a horn-shaped guide structure for facilitating the insertion of the steel pipe base 1 can also be formed on the end face of the first plastic body 20. This horn-shaped guide structure is a single-end or double-end excess structure, which can be sawn off after the first plastic body 20 is assembled on the steel pipe base.

[0055] Considering that the poor bonding between plastic and metal is mainly due to the significant difference in their properties, the plastic will shrink considerably after molding and cooling, resulting in a significant difference in the coefficient of thermal expansion between the plastic and the metal. Therefore, in this embodiment, the steel pipe base 1 after the first plastic body 20 is assembled can be concentrically held by the anchor 23 and pressure injection can be performed. Two-component vulcanized silicone rubber (RTV-2 rubber) is used for pressure injection. This type of vulcanized silicone rubber has a wide range of component ratios, and one variety can produce vulcanized products with various specifications and properties. It can be selected according to actual needs to achieve the performance objectives of insulation, encapsulation, caulking, sealing, moisture protection, and shock resistance. At the same time, two-component vulcanized silicone rubber can also be deeply vulcanized to buffer external stress and fill the structural deformation caused by temperature changes through deformation filling, thereby further improving the impact resistance of the pipe body and forming a heat-resistant and cold-resistant buffer zone. In addition, in order to optimize the above-mentioned effects of the filling structure layer 21, improve the adhesion performance between the filling structure layer 21 and the vacuum impregnated fiber cloth 24, improve the anchoring and molding effect of the anchor post 23, and improve the overall physical structural strength and impact resistance of the filling structure layer 21, modified reinforcing fibers with a mass ratio of 7-12% are added to the two-component vulcanized silicone rubber for physical modification. These modified reinforcing fibers are monofilament fibers modified by silane coupling agents. The monofilament length of these monofilament fibers is 4-7 mm, the fineness is 1-1.5D, and the fiber type is the same as the base material of the vacuum impregnated fiber cloth.

[0056] As an example, in this embodiment, during pressure injection, the gap between the sleeve of the first plastic body 20 and the steel pipe substrate wrapped with vacuum-impregnated fiber cloth is 0.4 mm (the injection gap and the corresponding injection hole are reserved), while the gap between the bottom surface of the annular blind groove 22 and the vacuum-impregnated fiber cloth 24 wrapped on the surface of the steel pipe substrate 1 is 0.3-0.5 mm. The corresponding two-component vulcanized silicone rubber is prepared with α,ω-dihydroxypolydimethylsiloxane as the base rubber, silica as the reinforcing filler, dimethyl silicone oil as the plasticizer, and crosslinking agent, tackifier and catalyst added. After injection molding, the overflow rubber is scraped off and subjected to heat vulcanization treatment. After the treatment is completed, it is allowed to stand for 20 minutes.

[0057] The processed pipe is used as raw material and hot-dip plastic coating process is used to obtain the second plastic body 3. After processing, the end is polished and sent for inspection. The quality inspection items such as electric spark leak detection, anti-delamination thickness detection, end inspection, peel strength, etc. are carried out in sequence. After passing the inspection, the finished plastic-steel composite pipe is obtained.

[0058] Under the technical conditions of this embodiment, the corresponding first plastic body can be one of heat-resistant polyethylene, cross-linked polyethylene, polyurethane, alicyclic epoxy fiberglass, and polyimide fiberglass, while the second plastic body can be one of polyethylene, epoxy resin, and polyurethane. The molded plastic-steel composite pipe possesses excellent corrosion resistance, structural strength, good electrical insulation, and a series of other superior properties. Due to the structural combination of the first plastic body 20 and the filling structural layer 21, the outer layer 2 of the composite plastic material in the pipe body can withstand greater external forces in various applications without deformation. Furthermore, the first plastic body 20 and the steel pipe substrate 1 are less prone to interlayer delamination failure due to temperature changes and external impacts, exhibiting better stability in chemically corrosive environments. This allows the pipe body to maintain stable performance under various harsh working environments, and its service life is effectively extended.

[0059] In summary, the plastic-steel composite pipe of this embodiment has excellent properties such as high temperature and high pressure resistance, oil resistance, corrosion resistance, temperature change resistance, and good structural stability, which makes it suitable for use in urban water supply network systems, building water supply and drainage, gas and floor radiant heating systems, industrial fluid transportation, as well as agricultural irrigation pipelines, postal and telecommunications lines, and power cable protection conduits, thus having a wide range of applications.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A plastic-steel composite pipe, characterized in that, It includes a steel pipe substrate, the outer surface of which is wrapped with vacuum-impregnated fiber cloth, and a composite plastic outer layer is formed on the outer surface of the steel pipe substrate wrapped with vacuum-impregnated fiber cloth. The outer layer of the composite plastic material includes a first plastic body, which is a pre-formed sleeve structure. The sleeve thickness of the first plastic body is 1 / 3 to 1 / 2 of the thickness of the steel pipe base, and it is concentrically fitted onto the outer surface of the steel pipe base. Several annular blind grooves are formed at intervals along the length of the tube on the inner side of the first plastic body. Adjacent annular blind grooves have a communication portion reserved on the side that is in contact with the steel pipe base. Anchor columns arranged in an array are formed in the annular blind grooves. A glue injection gap is reserved between the sleeve body of the first plastic material and the steel pipe base wrapped with vacuum impregnated fiber cloth, and the top surface of the anchor is tightly pressed against the surface of the vacuum impregnated fiber cloth of the steel pipe base. The gap between the first plastic material body and the steel pipe matrix is ​​filled with vulcanized silicone rubber as a structural layer, and the filling structural layer is also mixed with modified reinforcing fibers with a mass ratio of 7-12%. The plastic-steel composite pipe has a second plastic material formed on the inner pipe surface of the steel pipe substrate and the outer pipe surface of the first plastic material. The second plastic material is a film material with a thickness of 0.2 to 0.3 mm, which is formed on the above surface structure by spin coating or hot-dip plastic coating process.

2. The plastic-steel composite pipe according to claim 1, characterized in that, The steel pipe substrate is a galvanized welded steel pipe, a galvanized seamless steel pipe, or a spiral steel pipe that has undergone surface polishing.

3. The plastic-steel composite pipe according to claim 1, characterized in that, The first plastic body has a flared guide structure formed on its end face to facilitate the insertion of the steel pipe base. The flared guide structure is a spare structure that is cut off after the first plastic body is assembled into place on the steel pipe base.

4. The plastic-steel composite pipe according to claim 1, characterized in that, The sum of the lengths of the annular blind grooves formed on the first plastic body is 75% to 85% of the overall length of the pipe, and the length-to-diameter ratio of a single annular blind groove is 3:1 to 5:1; and the gap between the bottom of the annular blind groove and the surface of the steel pipe substrate wrapped with vacuum-impregnated fiber cloth is 1 / 5 to 1 / 3 of the thickness of the pipe body of the first plastic body sleeve.

5. The plastic-steel composite pipe according to claim 1, characterized in that, The connecting part is an annular inner necking structure formed between adjacent annular blind grooves and abutting the steel pipe base, or multiple connecting channels formed on the sidewall between adjacent annular blind grooves. The multiple connecting channels are evenly arranged on the corresponding annular surfaces. The projection size of the connecting part on the radial section of the plastic-steel composite pipe is 20-30% of the projection size of the annular blind groove on the radial section of the plastic-steel composite pipe.

6. The plastic-steel composite pipe according to claim 1, characterized in that, The cross-section of the anchor is cross-shaped or circular; the area of ​​the anchor within the plane of the annular blind groove accounts for 7-15%.

7. The plastic-steel composite pipe according to claim 1, characterized in that, The substrate of the vacuum impregnated fiber cloth is glass fiber cloth, aramid fiber cloth, or carbon fiber cloth modified with a silane coupling agent; the modified reinforcing fiber is a monofilament fiber modified with a silane coupling agent, and the monofilament fiber has a length of 4-7 mm, a fineness of 1-1.5 D, and the fiber type is the same as that of the substrate of the vacuum impregnated fiber cloth.

8. The plastic-steel composite pipe according to claim 1, characterized in that, The filling structural layer is a one-piece molded structure formed by integral injection.

9. A method for preparing a plastic-steel composite pipe, used to prepare the plastic-steel composite pipe according to claim 1, specifically comprising the following steps: S1 performs surface cleaning on the steel pipe substrate, and performs rust removal and dust removal treatment on the inner and outer surfaces of the steel pipe substrate respectively; after the rust removal and dust removal treatment is completed, a silane coupling agent is sprayed on the surface of the steel pipe substrate, and it is left to stand at room temperature. After the surface dries, it is placed in an oven and baked at a temperature of 40-60℃ for 30-50 minutes, and then cooled naturally. S2 wraps paper around the ends of the cooled steel pipe substrate; then, vacuum-impregnated fiber cloth is wrapped around the surface of the steel pipe substrate after the paper is wrapped around the ends. When wrapping the vacuum-impregnated fiber cloth, the paper wrapping at both ends of the steel pipe substrate is used as the boundary. After the vacuum-impregnated fiber cloth is wrapped, the paper wrapping at the ends is removed. S3 selects a first plastic material body that matches the size of the steel pipe base body and fits it onto one end of the steel pipe base body. During fitting, the outer side of the first plastic material body is pressed onto the original pipe end paper wrapping position so that the vacuum impregnated fiber cloth area is embedded in the first plastic material body. S4 uses vulcanized silicone rubber as raw material, and performs pressure injection from the reserved injection hole on the first plastic body to fill the gap between the first plastic body and the steel pipe substrate. Then, the overflowing rubber material is scraped off and heat vulcanization is performed. S5 uses the pipe material processed in step S4 as raw material, and processes it using spin coating or hot-dip plastic coating to obtain the second plastic material body. After processing, the ends are polished, and the finished plastic-steel composite pipe material is obtained after passing the inspection.

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