A steel-plastic composite pipe sealing and steel skeleton reinforced pipe fitting processing method and system

Abstract

The present application relates to steel plastic composite pipe welding technical field, specifically disclose a kind of steel plastic composite pipe sealing and steel skeleton reinforced pipe fitting processing method and system, comprising: obtaining the steel plastic composite pipe to be processed, the steel plastic composite pipe to be processed includes to be welded end part;The to-be-welded end part is executed electrochemical etching treatment, obtains etched end part;The etched end part is executed heating treatment, obtains heated end part, and the heated end part is viscous flow state;Sealing treatment is executed based on viscous flow state of the heated end part, obtains sealed steel plastic composite pipe, and the sealed steel plastic composite pipe includes sealing site corresponding to the sealing treatment;Outer layer of the sealing site is executed reinforced coating treatment, obtains reinforced steel plastic composite pipe.By improving conventional welding process, the physical strength of pipe fitting after welding is improved, the sealing effect of steel strip in steel plastic composite pipe is ensured, and the subsequent use effect and service life are ensured.

Description

Technical Field

[0001] This invention relates to the field of steel-plastic composite pipe processing technology, specifically to a processing method and system for sealing steel-plastic composite pipes and steel skeleton reinforced pipe fittings. Background Technology

[0002] As a new type of composite pipe, steel-plastic composite pipe has been increasingly widely used in municipal water supply and drainage, gas transmission, and chemical media transmission in recent years. With the acceleration of urbanization and the increasing safety requirements of industrial pipeline systems, the market demand for steel-plastic composite pipe continues to grow, making it an important development direction in the field of pipeline technology.

[0003] Among them, the connection technology of steel-plastic composite pipes is a key factor affecting their overall performance and application reliability. Existing welding methods for pure plastic pipes mainly include hot-melt butt welding and electrofusion connection. However, the special structure of steel-plastic composite pipes lies in the fact that their pipe walls consist of an inner plastic layer, a steel strip skeleton layer, and an outer plastic layer from the inside out. The presence of the steel strip skeleton layer poses a serious challenge to traditional welding processes.

[0004] In practical applications, special treatments may be required for steel-plastic composite pipes at any time on-site, such as butt welding and bending. Existing technologies have significant shortcomings in handling welding problems of steel-plastic composite pipes:

[0005] On the one hand, if the traditional hot-melt butt welding method is used, the steel strip skeleton layer will axially prevent the plastic outer layer from melting and displacing in the butt direction, resulting in insufficient fusion depth at the weld and exposure of the steel strip skeleton layer. This makes it impossible to form an effective seal, and the airtightness and watertightness of the joint cannot meet the engineering requirements. On the other hand, if the steel strip in the welding area is removed in advance by mechanical cutting or milling to create welding space, the structural continuity of the steel skeleton will be destroyed, causing a significant decrease in the overall strength of the joint area. Existing experimental data shows that the joint strength after hollowing out welding is only 10% to 20% of the original pipe material. At the same time, the steel strip fracture is directly exposed to the external environment, posing a potential risk of pitting corrosion, crevice corrosion, and even stress corrosion cracking, seriously threatening the long-term operational safety of the pipeline system.

[0006] In addition, although chemical acid etching can remove the steel strip layer, it has process defects such as uncontrollable reaction rate, difficulty in precisely adjusting etching depth, and high waste liquid treatment cost, making it difficult to meet the standardization requirements of industrial production.

[0007] Therefore, the existing sealing and manufacturing processes for steel-plastic composite pipes have defects and cannot meet the actual needs of enterprises. Summary of the Invention

[0008] To overcome the aforementioned technical problems in the prior art, this invention provides a method and system for sealing steel-plastic composite pipes and processing steel-reinforced pipe fittings. By improving conventional welding processes, the physical strength of the welded pipe fittings is enhanced, while ensuring the sealing effect of the steel strip in the steel-plastic composite pipe, thus ensuring subsequent use and service life.

[0009] To achieve the above objectives, embodiments of the present invention provide a method for sealing steel-plastic composite pipes and processing steel-reinforced pipe fittings. The method includes: obtaining a steel-plastic composite pipe to be processed, the steel-plastic composite pipe to be processed including an end to be welded; performing an electrochemical etching process on the end to be welded to obtain an etched end; performing a heat treatment on the etched end to obtain a heated end, the heated end being in a viscous flow state; performing a sealing process on the heated end based on the viscous flow state to obtain a sealed steel-plastic composite pipe, the sealed steel-plastic composite pipe including a sealing portion corresponding to the sealing process; and performing a reinforcement coating process on the outer layer of the sealing portion to obtain a reinforced steel-plastic composite pipe.

[0010] Preferably, the step of performing electrochemical etching on the end to be welded to obtain the etched end includes: determining the exposed area of ​​the steel strip at the end to be welded; applying a protective agent to the exposed area of ​​the steel strip to obtain the coated end; determining the range of the steel strip to be etched and the desired corrosion efficiency, and determining etching electrical parameters based on the range of the steel strip to be etched and the desired corrosion efficiency, the etching electrical parameters including etching charge and etching current magnitude; immersing the coated end as the anode and the stainless steel auxiliary electrode as the cathode in an electrolyte; and performing electrochemical etching on the exposed area of ​​the steel strip based on the etching charge and etching current magnitude to obtain the etched end.

[0011] Preferably, the method further includes: determining an etching efficiency based on the etching current magnitude; determining whether the etching efficiency is less than a preset efficiency value; if so, performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the etching current magnitude; otherwise, determining a hydrogen evolution rate based on the etching current magnitude; determining the disturbance effect of the electrochemical etching process on the plastic layer of the exposed area of ​​the steel strip based on the hydrogen evolution rate; if the disturbance effect is less than a preset disturbance value, performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the etching current magnitude; if the disturbance effect is greater than or equal to the preset disturbance value, determining a maximum etching current based on the preset disturbance value, and performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the maximum etching current.

[0012] Preferably, the sealing process performed on the heated end portion based on the viscous flow state to obtain a sealed steel-plastic composite pipe includes: obtaining the diameter of the steel-plastic composite pipe to be processed, and determining the pressing pressure based on the diameter; performing a pressing sealing process on the heated end portion based on the pressing pressure to obtain a sealed end portion; performing a pressure holding and cooling process on the sealed end portion to obtain a cooled end portion; performing a sealing effect test on the cooled end portion based on an electric spark detection device to obtain a sealing test result; and determining that a sealed steel-plastic composite pipe has been obtained if the sealing test result is qualified.

[0013] Preferably, the step of performing a reinforcing coating treatment on the outer layer of the sealed portion to obtain a reinforced steel-plastic composite pipe includes: roughening the outer surface of the sealed portion by grinding to obtain a roughened portion; determining the fusion layer coating thickness and the target injection molding thickness of the roughened portion; uniformly coating the fusion layer on the outer surface of the roughened portion based on the coating thickness to obtain a coated portion; and performing a high-pressure reinforcing injection molding operation on the coated portion based on the target injection molding thickness to obtain a reinforced steel-plastic composite pipe.

[0014] Preferably, determining the fusion layer coating thickness and target injection molding thickness of the polished portion includes: obtaining the physical strength index of the steel-plastic composite pipe to be processed; determining the minimum injection molding thickness of the polished portion based on the physical strength index; obtaining the weight index of the steel-plastic composite pipe to be processed; determining the maximum injection molding thickness of the polished portion based on the weight index; determining the target injection molding thickness based on the minimum and maximum injection molding thickness; and determining the fusion layer coating thickness based on the target injection molding thickness.

[0015] Preferably, determining the coating thickness of the fusion layer based on the target injection molding thickness includes: determining the tensile parameters of the fusion layer; determining the tensile requirement value based on the target injection molding thickness and a preset rated vibration index; and determining the coating thickness of the fusion layer based on the tensile parameters and the tensile requirement value.

[0016] Preferably, the injection molding material used in the high-pressure enhanced injection molding operation is the same as the body material of the steel-plastic composite pipe to be processed.

[0017] On the other hand, the present invention also provides a processing system for sealing steel-plastic composite pipes and steel-reinforced pipe fittings. The system includes: a composite pipe acquisition module for acquiring a steel-plastic composite pipe to be processed, the steel-plastic composite pipe to be processed including an end to be welded; an etching module for performing electrochemical etching on the end to be welded to obtain an etched end; a heating module for performing heating on the etched end to obtain a heated end, the heated end being in a viscous flow state; a sealing module for performing sealing on the heated end based on the viscous flow state to obtain a sealed steel-plastic composite pipe, the sealed steel-plastic composite pipe including a sealing portion corresponding to the sealing treatment; and a reinforcement coating module for performing reinforcement coating on the outer layer of the sealed portion to obtain a reinforced steel-plastic composite pipe.

[0018] On the other hand, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method provided in the embodiments of the present invention.

[0019] The present invention has at least the following technical effects through the technical solution provided by the present invention:

[0020] Electro-erosion pretreatment corrodes the ends of the steel strip skeleton, leaving only the pure polyethylene layer. After hot-melt sealing of this section of pure polyethylene, the steel skeleton can be effectively sealed inside the polyethylene layer. This allows the steel skeleton to not only reinforce the pipe and fittings but also prevent it from being corroded and failing due to contact with the medium being transported in the pipeline. It eliminates the physical barrier of intrusive welding, and the PE outer layer can achieve sufficient fusion depth, meeting the preset fusion depth requirements. The airtightness of the weld meets the sealing requirements, and the airtightness and watertightness of the joint can meet the high standard requirements of municipal water supply and drainage, gas transmission and other engineering applications.

[0021] After welding, a secondary injection molding process is used to coat the PE reinforcement layer, which increases the overall wall thickness of the welded area to a multiple of the original pipe wall thickness and the ring stiffness to a multiple of the original pipe material's ring stiffness. This effectively avoids the problem of a significant decrease in joint strength caused by traditional hollow welding methods. The tensile test fracture occurs in the original pipe material rather than at the weld.

[0022] The outer PE reinforcement layer completely covers the welding area, completely isolating the steel strip fracture from the external environment, eliminating the inducing conditions for pitting corrosion, crevice corrosion, and even stress corrosion cracking, and significantly improving the long-term operational safety of the welded joint.

[0023] The addition of the hot melt adhesive fusion layer forms a dual connection mechanism of chemical bonding and mechanical interlocking between the inner and outer PE layers. The interfacial shear strength reaches the preset shear strength, and the interfacial integrity can be maintained without peeling even under hot and cold cycling conditions. After multiple thermal cycles, the peeling rate remains within the preset peeling rate range.

[0024] Compared to chemical acid etching, electrochemical etching can accurately control the etching depth by precisely adjusting the current density and electrolysis time, achieving the preset accuracy requirements for repeatability. Moreover, the entire electrochemical etching process produces no chemical waste, meeting the requirements of green and environmentally friendly industrial production.

[0025] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 The flowchart illustrates the specific implementation of the processing method for sealing steel-plastic composite pipes and steel-reinforced pipe fittings provided in this embodiment of the invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this embodiment of the invention, the term "multiple" refers to two or more. Therefore, in this embodiment, "multiple" can also be understood as "at least two." "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / ", unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, it should be understood that in the description of this embodiment of the invention, terms such as "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or order.

[0030] The background technology of this invention will be introduced first below.

[0031] Existing pipe sealing technologies are primarily designed for plastic pipes. Specifically, they employ a hot-melt sealing process, where the ends of the pipes to be sealed are heated to a molten state, and then the two ends are fused together by compression. After sealing, any excess material at the seam is removed, completing the sealing operation. However, in practical applications, because steel-plastic composite pipes contain internal steel strips, traditional sealing methods, while heating the pipe ends to a molten state, leave the internal steel strips exposed. In this case, the compression sealing method is unable to penetrate due to the steel strips, leading to sealing failure and exposing the steel strips to the outside, thus failing to meet practical requirements.

[0032] On the other hand, even if the ends of the steel-plastic composite pipe are sealed with plastic through other methods, its strength is still greatly affected because the original steel strip structure is damaged, and it cannot meet the original structural strength requirements, thus greatly reducing its service life.

[0033] To resolve the above technical issues, please refer to Figure 1 This invention provides a method for sealing steel-plastic composite pipes and processing steel-reinforced pipe fittings, the method comprising:

[0034] S10, Obtain the steel-plastic composite pipe to be processed, wherein the steel-plastic composite pipe to be processed includes the end to be welded;

[0035] S20, perform electrochemical etching on the end to be welded to obtain the etched end;

[0036] S30, perform a heat treatment on the etched end portion to obtain a heated end portion, wherein the heated end portion is in a viscous flow state;

[0037] S40, based on the viscous flow state, the heated end is subjected to a sealing process to obtain a sealed steel-plastic composite pipe, wherein the sealed steel-plastic composite pipe includes a sealing portion corresponding to the sealing process;

[0038] S50, perform reinforcement coating treatment on the outer layer of the sealing part to obtain a reinforced steel-plastic composite pipe.

[0039] In one possible implementation, the steel-plastic composite pipe to be processed is first obtained, and then the end of the steel-plastic composite pipe to be welded is treated. Specifically, the exposed steel strip skeleton at the end to be welded is subjected to electrochemical etching. Since electrolyte penetration during etching may damage the PE plastic layer, a protective agent needs to be applied to the exposed steel strip area at the end of the pipe to be welded during the electrochemical etching process. Specifically, a protective agent can be applied to the PE plastic layer area outside the exposed steel strip area at the end of the pipe to be welded, in a predetermined coverage area. This protective agent is, for example, liquid paraffin or insulating adhesive. In this embodiment of the invention, the protective agent completely covers at least 15mm to 25mm of the PE plastic layer area outside the exposed steel strip area to form an effective physical barrier. The coating thickness of the liquid paraffin protective layer is controlled to be 0.5mm to 2mm. After coating, the paraffin needs to be allowed to solidify naturally to form a dense protective film. The function of this protective layer is to prevent electrolyte penetration into the PE plastic layer during subsequent electrochemical etching, avoiding swelling or erosion damage to the PE material caused by the electrolyte.

[0040] At this point, the range of the steel strip to be etched is determined. For example, in one embodiment, it is necessary to etch the steel strip to a depth of 3 cm at the end to be welded. Therefore, based on the range of the steel strip to be etched, the total etching power required is determined, as well as the etching current required to ensure etching accuracy and etching speed. For example, in an embodiment of the present invention, the technician expects to complete the etching of the steel strip to this depth within half an hour. Therefore, based on the diameter of the steel-plastic composite pipe and the thickness of the steel strip, the etching power and etching current are determined.

[0041] The steel strip end, acting as the anode, and the stainless steel auxiliary electrode, acting as the cathode, are then immersed in an electrolytic cell containing the electrolyte. The electrode spacing between the anode and cathode is set to be between 15 mm and 25 mm. The electrolyte is a 10% to 15% sodium chloride solution or a neutral electrolyte, and the electrolyte temperature is controlled within the range of 15°C to 30°C, more preferably 20°C to 25°C. The electrolytic cell is made of corrosion-resistant materials, such as polypropylene or stainless steel lining, to prevent corrosion of the cell by the electrolyte. Then, the current density is controlled according to the etching charge and etching current to induce an electrochemical etching reaction at the steel strip end. For example, in this embodiment of the invention, the current density is 0.15 A / cm². 2 Up to 0.4A / cm 2 The range is more preferably 0.25 A / cm. 2 Up to 0.30A / cm 2 Under this current density condition, an electrochemical dissolution reaction occurs at the end of the steel strip:

[0042]

[0043] Fe atoms in the anodic region lose electrons and transform into Fe2+ Ions dissolve and enter the electrolyte, while hydrogen gas is released from water reduction at the cathode surface. Precise control of the etching depth is achieved by controlling the product of current intensity and electrolysis time (i.e., the charge Q) according to Faraday's law of electrolysis. During electrochemical etching, the electrolysis time is determined based on the target etching depth and current density parameters.

[0044] In this embodiment of the invention, the selection of current density, in addition to considering etching efficiency, also needs to take into account side reactions. When the current density exceeds 0.4 A / cm 2 At this time, the hydrogen evolution side reaction intensifies, which may disturb the PE protective layer; when the current density is below 0.15 A / cm 2 At that time, the etching efficiency was too low, and the economic efficiency of the process decreased.

[0045] In this embodiment of the invention, the method further includes: determining an etching efficiency based on the etching current magnitude; determining whether the etching efficiency is less than a preset efficiency value; if so, performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the etching current magnitude; otherwise, determining a hydrogen evolution rate based on the etching current magnitude; determining the disturbance effect of the electrochemical etching process on the plastic layer of the exposed area of ​​the steel strip based on the hydrogen evolution rate; if the disturbance effect is less than a preset disturbance value, performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the etching current magnitude; if the disturbance effect is greater than or equal to the preset disturbance value, determining a maximum etching current based on the preset disturbance value, and performing an electrochemical etching process on the exposed area of ​​the steel strip based on the etching charge and the maximum etching current.

[0046] In one possible implementation, after initially generating the etching current magnitude, the corresponding electrochemical etching process is not immediately performed. Instead, further analysis is conducted. Specifically, the etching efficiency is first determined based on the etching current magnitude. If the etching efficiency is lower than a preset efficiency value, it can be assumed that, on the one hand, the hydrogen evolution corresponding to the current magnitude at the current moment will not cause significant damage to the plastic layer, and on the other hand, that this efficiency is considered artificially determined to be low. Therefore, the aforementioned etching charge and etching current magnitude are still used to perform electrochemical etching processing on the exposed area of ​​the steel strip. If the etching efficiency is greater than or equal to the preset efficiency value, the excessively high hydrogen evolution efficiency may affect the plastic layer, so subsequent analysis is immediately performed.

[0047] First, the hydrogen evolution rate is determined based on the etching current. The impact of this hydrogen evolution on the plastic layer in the exposed area of ​​the steel strip is then assessed. If the disturbance is found to damage the plastic layer, the electrochemical etching reaction process is immediately controlled according to the maximum etching current corresponding to the preset disturbance value. This ensures that the electrochemical etching process is performed as quickly as possible while keeping the damage to the plastic layer within acceptable limits, thus guaranteeing the service life of the steel-plastic composite pipe. Precise control of the etching depth is achieved through precise control of the current. After etching, the pipe end is removed from the electrolytic cell, and the etched area is rinsed with clean water to remove residual electrolyte and corrosion products. After cleaning, the pipe is dried. Then, the etching depth is checked and verified using a vernier caliper with an accuracy of 0.02 mm or a dedicated depth measuring instrument (such as an EDM device) to ensure that the etching depth meets the preset requirements. During the test, at least eight measurement points are evenly selected circumferentially along the end of the steel strip, and the average etching depth and uniformity deviation are calculated.

[0048] After electro-erosion, the ends of the steel-plastic composite pipe consist only of pure plastic and the voids left by the erosion of the steel strip. Heating the plastic to a molten state (i.e., a viscous flow state) effectively seals the steel skeleton within the anti-corrosion system provided by the plastic, preventing contact between the steel material and corrosive media. This effectively ensures the sealing performance of the welded steel-plastic composite pipe and improves its service life. Through this electro-erosion treatment, while preserving the integrity of the PE outer layer, the steel skeleton undergoes axial retraction at the ends, with the retraction distance comparable to the etching depth. This creates the necessary physical space for subsequent welding of the PE layer.

[0049] After electrochemical etching, the ends of the steel-plastic composite pipes to be processed are heated to a viscous flow state, preparing for subsequent sealing. For example, a hot air heating device can be used to heat the outer PE end face of the pipe to be welded to a viscous flow state. Under axial pressure, the two pipe end faces to be welded are pressed together, and pressure is maintained and cooled to solidify the molten PE to form a weld.

[0050] In this embodiment of the invention, the sealing process performed on the heated end portion based on the viscous flow state to obtain a sealed steel-plastic composite pipe includes: obtaining the diameter of the steel-plastic composite pipe to be processed, determining the pressing pressure based on the diameter; performing a pressing sealing process on the heated end portion based on the pressing pressure to obtain a sealed end portion; performing a pressure holding and cooling process on the sealed end portion to obtain a cooled end portion; performing a preliminary airtightness inspection on the cooled end portion, and determining that a sealed steel-plastic composite pipe has been obtained if the preliminary inspection result is qualified.

[0051] Specifically, first, inspect the end face condition of the steel-plastic composite pipes to be processed, ensuring that there is no residual electrolyte or rust products in the steel strip shrinkage area after electro-erosion pretreatment, and that the PE outer layer end face is flat and without defects. Then, fix the two steel-plastic composite pipes to be processed on the welding fixture, and adjust the coaxiality to make the axes of the two pipe sections coincide, with the coaxiality deviation controlled within 0.5mm. Install the hot air heating device, and adjust the position of the hot air gun so that its outlet is aimed at the PE outer layer end face of the pipe. At this time, the hot air heating device can be used to uniformly heat the PE outer layer end faces of the two pipes, with the heating temperature controlled in the range of 180℃ to 220℃, more preferably 200℃±10℃. The heating time is determined based on the thickness of the PE outer layer. When the wall thickness is between 6mm and 10mm, the heating time should be controlled between 30 and 60 seconds. The heating range should cover the entire thickness of the PE outer layer to ensure that the temperature at each point on the end face is uniform and reaches the viscous flow state. The air speed of the hot air gun should be controlled between 3m / s and 8m / s, and the heating distance can be controlled between 20mm and 40mm.

[0052] Once the PE outer layer reaches a viscous flow state, the heat source is immediately removed, and the sealing process is immediately initiated. This step is performed immediately after the electro-erosion pretreatment process has passed inspection to avoid secondary oxidation caused by prolonged exposure of the pipe ends to air. Specifically, first, the required sealing pressure is determined based on the diameter of the steel-plastic composite pipe to be processed. Then, the corresponding axial pressure is applied, and the two pipe ends to be welded are pressed together under the axial pressure. The axial pressure is controlled within the range of 0.1MPa to 0.3MPa, more preferably 0.2MPa. The pressing amount is controlled within the range of 3mm to 8mm. Since the steel strip skeleton has been electro-eroded and reduced, the PE outer layer can smoothly complete the pressing and melting process without obstruction. During the pressing process, the PE melt is extruded outwards under pressure to form a uniform molten ring.

[0053] After the initial insertion is complete, maintain the axial pressure and perform pressure holding and cooling. The pressure holding and cooling time should be controlled within the range of 30 to 60 seconds, preferably 45 seconds. During the pressure holding process, the molten PE gradually solidifies to form a weld. The PE melt at the weld should overflow evenly and be free of visible defects. After cooling is complete, release the pressure and remove the welded pipe section. Finally, the weld at the cooled end can be inspected using an electric spark tester. If the test results show good sealing performance, the sealed steel-plastic composite pipe can be confirmed.

[0054] In this embodiment of the invention, by performing further pressure holding and cooling treatment and electric spark sealing test on the sealed end, the sealed steel-plastic composite pipe is effectively ensured to have qualified sealing performance, thus guaranteeing the actual performance of the welded steel-plastic composite pipe and meeting the actual needs of enterprises.

[0055] Furthermore, although the sealed steel-plastic composite pipe possesses sufficient sealing performance, the physical structure of the original steel skeleton within the pipe is disrupted, resulting in a significant reduction in its strength and making it unsuitable for the actual use requirements of the welded steel-plastic composite pipe. Therefore, in this embodiment of the invention, further strength-enhancing treatment is applied.

[0056] In practical applications, because the material used to reinforce the sealing area is not manufactured at the same time (due to temperature differences) or is not the same material, if the sealing area is directly reinforced, the two layers of the steel-plastic composite pipe may delaminate. In subsequent use, if the steel-plastic composite pipe experiences significant shaking or swaying, gaps may form between the two layers, leading to a significant reduction in structural strength or the infiltration of corrosive liquids, thus greatly reducing the service life of the steel-plastic composite pipe and failing to meet actual requirements.

[0057] In this embodiment of the invention, the step of performing a reinforcing coating treatment on the outer layer of the sealed portion to obtain a reinforced steel-plastic composite pipe includes: roughening the outer surface of the sealed portion by grinding to obtain a roughened portion; determining the fusion layer coating thickness and the target injection molding thickness of the roughened portion; uniformly coating the fusion layer on the outer surface of the roughened portion based on the coating thickness to obtain a coated portion; and performing a high-pressure reinforcing injection molding operation on the coated portion based on the target injection molding thickness to obtain a reinforced steel-plastic composite pipe.

[0058] In one possible implementation, to ensure material adhesion, the outer surface of the sealing area is first roughened by grinding. The grinding area covers 30mm to 60mm on both sides of the weld area. Specifically, 80- to 120-grit sandpaper can be used for grinding, and the surface roughness after grinding is controlled to be in the range of Ra 6.3μm to 12.5μm. The purpose of the grinding operation is to remove the oxide layer and contaminants, while increasing the surface roughness to improve the adhesion of the subsequent fusion layer and injection molding layer. After grinding, the surface is wiped clean with a non-woven cloth soaked in ethanol to remove grinding debris and grease.

[0059] Then, determine the thickness of the fusion layer coating and the injection molding thickness of the polished area. In practical applications, the purpose of reinforcing the steel-plastic composite pipe with injection molding is to at least restore its original physical strength to meet its actual use requirements. However, if the injection molding is increased too much, it will lead to increased costs and fail to meet the actual needs of the enterprise. On the other hand, it will also lead to defects such as increased pipe size (which cannot meet the use requirements of specific application scenarios, such as diameter-limited wells) and increased weight (some pipes may need to be extended vertically for hundreds of meters in series, and the increase in weight will greatly increase the risk of tearing).

[0060] In this embodiment of the invention, determining the fusion layer coating thickness and target injection molding thickness of the polished portion includes: obtaining the physical strength index of the steel-plastic composite pipe to be processed; determining the minimum injection molding thickness of the polished portion based on the physical strength index; obtaining the weight index of the steel-plastic composite pipe to be processed; determining the maximum injection molding thickness of the polished portion based on the weight index; determining the target injection molding thickness based on the minimum and maximum injection molding thickness; and determining the fusion layer coating thickness based on the target injection molding thickness.

[0061] Furthermore, in this embodiment of the invention, determining the coating thickness of the fusion layer based on the target injection molding thickness includes: determining the tensile parameters of the fusion layer; determining the tensile requirement value based on the target injection molding thickness and a preset rated vibration index; and determining the coating thickness of the fusion layer based on the tensile parameters and the tensile requirement value.

[0062] In one possible implementation, to ensure the reinforced steel-plastic composite pipe achieves an optimal balance between thickness and reinforcement effect, the physical strength index of the steel-plastic composite pipe to be processed is first obtained. For example, this physical strength index is at least equal to that of the original steel-plastic composite pipe. This allows determination of the minimum injection molding layer thickness required to restore the physical strength of the sealed portion of the welded steel-plastic composite pipe to its original strength; that is, determining the minimum injection molding thickness after grinding. Based on this, the injection molding thickness can be further increased to further improve the physical strength of the sealed portion. To avoid exceeding the weight or thickness limits of the welded steel-plastic composite pipe, the weight index of the steel-plastic composite pipe to be processed is also obtained, and the maximum injection molding thickness is further determined to constrain the maximum value of the injection molding thickness, thereby determining the target injection molding thickness. For example, when the minimum injection thickness is less than the maximum injection thickness, the maximum injection thickness is used as the target injection thickness to maximize the physical strength of the sealing part while ensuring that its weight / size also meets the actual requirements; if the minimum injection thickness is greater than the maximum injection thickness, the minimum injection thickness is used as the target injection thickness to ensure that the steel-plastic composite pipe has basic physical strength.

[0063] Finally, the coating thickness of the fusion layer is determined based on the target injection molding thickness. The purpose of applying the fusion layer is to ensure that the fusion layer can effectively adhere to the original PE outer layer of the steel-plastic composite pipe and avoid delamination. If the coating thickness is too small, the steel-plastic composite pipe may experience excessive tensile force due to excessive vibration during use, which will cause the fusion layer to fail and the original PE layer and the coating layer to delaminate, thus failing to meet the actual requirements.

[0064] Therefore, in this embodiment of the invention, the tensile parameters of the fusion layer are further obtained, and the tensile requirement value is determined based on the target injection molding thickness and the preset rated vibration index. The preset rated vibration index is the maximum vibration index determined by technicians in advance based on the usage scenario of the steel-plastic composite pipe. Based on the above two parameters, the maximum tensile force experienced by the steel-plastic composite pipe during use can be determined, thereby determining the corresponding tensile requirement value. At this time, the coating thickness of the fusion layer can be determined based on the above tensile parameters and the tensile requirement value. For example, by obtaining the change curve of the tensile strength of the fusion layer at different thicknesses through the tensile parameters, it can be determined at what coating thickness of the fusion layer can meet the above requirements. After determining the coating thickness of the fusion layer and the target injection molding thickness, the coating operation of the fusion layer and the enhanced injection molding operation are further performed.

[0065] Specifically, at this point, a fusion layer is evenly applied to the roughened outer surface according to the required coating thickness. For example, EVA-based or PA-based hot melt adhesive granules are added to a melting device and heated at a temperature controlled 20°C to 30°C above their melting point; that is, EVA-based hot melt adhesive is heated to 140°C to 160°C, and PA-based hot melt adhesive is heated to 170°C to 190°C. After the hot melt adhesive has completely melted and become fluid, it is evenly applied to the outer surface of the welding area using a scraper, with a coating thickness controlled within the range of 0.5mm to 2mm. The fusion layer serves a dual purpose: firstly, it acts as an adhesive to fill the micropores and interface gaps between the original PE outer layer and the outer PE coating layer; secondly, it forms a dual connection with the outer PE coating layer during subsequent PE injection molding, involving both chemical bonding and mechanical interlocking.

[0066] At this point, the injection mold is further installed. For example, the injection mold can be assembled to the welding area. The inner cavity size of the mold is determined according to the outer diameter of the pipe and the designed coating thickness. After coating, the outer diameter exceeds the original pipe wall by 1.5 to 3 times. The mold adopts a split structure, consisting of an upper mold and a lower mold. The inner surface of the mold is coated with a release agent to facilitate subsequent demolding operations. When installing the mold, it is necessary to ensure that the mold axis coincides with the pipe axis and that the gap between the mold and the outer wall of the pipe is uniform. Finally, the PE raw material is heated to a molten state using an injection molding machine and injected into the mold under high pressure. Preferably, the material added to the injection molding machine is the same as the outer plastic material of the steel-plastic composite pipe. The injection material is filled and covered onto the surface of the welding area. The high pressure is controlled in the range of 15MPa to 40MPa, and the injection pressure is more preferably 25MPa. The thickness of the PE coating layer is controlled in the range of 3mm to 8mm, and it extends to cover the weld seam on one side in the range of 30mm to 60mm. This forms a composite reinforced coating structure consisting of the original pipe PE outer layer, the fusion layer, the weld seam area, and the outer PE reinforcement layer, which greatly improves the structural strength of the sealing part.

[0067] After injection molding, maintain pressure for 10 to 20 seconds. After pressure holding, proceed to the cooling and setting stage. The cooling time depends on the coating thickness and ambient temperature, generally not less than 60 seconds. After cooling, open the mold, remove the reinforced coating joint, and inspect the coating's appearance quality to ensure there are no bubbles, shrinkage marks, or warping. The PE reinforcement layer completely covers the outer wall of the welding area, forming a concentric circle structure with the original PE outer layer. At this point, the reinforcement coating process is complete, resulting in a reinforced steel-plastic composite pipe. The weld area is located at the joint surface of the two pipe ends, in a fused state with no obvious interface. The outer PE reinforcement layer covers the outside of the original PE outer layer, significantly increasing the wall thickness. The material is consistent with the original PE outer layer, and the coefficient of thermal expansion is matched.

[0068] In this embodiment of the invention, a high-strength, high-sealing welded connection of steel-plastic composite pipe is achieved through a systematic three-stage process. First, electrochemical etching technology is used to precisely process the ends of the steel strip skeleton to create welding space. Then, traditional hot melt insertion technology is used to achieve reliable fusion connection of the PE outer layer. Finally, secondary injection molding coating technology is used to restore and enhance the mechanical strength of the welded area. The three-stage process is interconnected and progressively advanced, ultimately forming an enhanced welded joint that combines reliable sealing, restored mechanical strength, and corrosion resistance.

[0069] In this embodiment of the invention, for a typical application scenario of connecting straight pipe sections of DN200 steel-plastic composite pipe, the pipe inner diameter is 200mm, the PE outer layer wall thickness is 8mm, the steel strip skeleton thickness is 2mm, and a double-sided steel strip structure is adopted. Specific process parameters are set as follows:

[0070] In the electro-erosion pretreatment process, the coating area is 20 mm, the liquid paraffin protective layer thickness is 1 mm; the electrolyte is a 12% NaCl solution, the temperature is 22℃; the electrode spacing is 20 mm; and the current density is 0.25 A / cm². 2 Electrolysis area 5cm² 2 The corresponding current intensity was 1.25A; the electrolysis time was 45 minutes; and the etching depth was controlled within the range of 12mm ± 0.5mm. Test results showed that the etching depth was 11.8mm, with a uniformity deviation of 0.3mm, meeting the process requirements.

[0071] In the infeed welding process, the heating temperature was 200℃±10℃, the heating time was 45 seconds, the axial pressure was 0.2MPa, the infeed depth was 5mm, the pressure holding and cooling time was 45 seconds, the initial airtightness test pressure was 0.4MPa, and there was no pressure drop after holding the pressure for 30 minutes. During the welding process, the PE melt overflowed evenly, and the weld formation was good.

[0072] In the reinforcement coating process, 80-grit sandpaper was used for polishing; PA-based hot melt adhesive was heated to 170℃ to melt; the fusion layer coating thickness was 1.5mm; the inner diameter of the injection mold was the outer diameter of the pipe plus 16mm, i.e., the thickness of the PE coating layer on one side was 8mm; the barrel temperature was 225℃, the mold temperature was 50℃, and the injection pressure was 25MPa; after holding the pressure for 15 seconds, it was cooled and shaped; the PE coating layer extended 45mm to each side of the weld. The final airtightness test passed at a pressure of 0.6MPa, and the tensile test showed that the fracture occurred in the original pipe rather than at the weld, indicating that the strength of the welded joint had been restored to a level superior to that of the original pipe.

[0073] In the above embodiments, the electro-erosion pretreatment process, the infeed welding process, and the reinforcement coating process form a complete process chain, and none of the three can be omitted. The electro-erosion pretreatment creates the necessary physical space for the infeed welding, the infeed welding achieves a reliable connection of the PE outer layer, and the reinforcement coating process fundamentally solves the problems of restoring the mechanical strength and improving the corrosion resistance of the welding area.

[0074] Example 2

[0075] To verify the effect of the fusion layer in enhancing the coating effect, the following comparative experiment was conducted. The experiment used the same pipe specifications and welding parameters, only changing the coating method of the fusion layer to create three different coating structures for comparison.

[0076] The coating structure of specimen one consisted of only a PE outer layer, without a fusion layer. The outer surface of the welded area was roughened by grinding before direct injection molding. The interfacial shear strength of this structure was 8.5 MPa, and the peeling rate after 50 thermal cycles (temperature range -30℃ to 80℃) was 12%. The analysis suggests that without a fusion layer, the connection between the original PE outer layer and the outer PE layer relies solely on physical contact and molecular diffusion, resulting in limited interfacial bonding. Under thermal cycling conditions, the slight difference in the thermal expansion coefficients of the two PE layers (typically 5 × 10⁻⁶) leads to insufficient bonding. -5 / ℃ to 8×10 -5 (℃), alternating shear stress is generated at the interface. After multiple cycles, the interface gradually undergoes micro-separation, which is manifested as the peeling rate increasing with the number of cycles.

[0077] The second specimen's covering structure consisted of a PE outer layer with an aluminum foil separator. An aluminum foil layer was sandwiched between the original PE outer layer and the outer PE layer, attempting to improve airtightness through the aluminum foil's barrier effect. However, test results showed that the interfacial shear strength of this structure was only 3.2 MPa, and an effective bond could not be formed between the aluminum foil and the PE material. During the thermal cycling test, the aluminum foil wrinkled and detached, making it impossible to complete the peel rate test.

[0078] Specimen 3 adopted the PE outer coating plus EVA fusion layer structure described in this invention. The EVA fusion layer was coated at 170℃, allowing it to fully contact and penetrate the surface of the original PE outer layer, filling micropores and forming a preliminary bond. During subsequent injection molding, the outer PE layer, in a high-temperature molten state, underwent molecular chain entanglement with the fusion layer, forming a dual connection of chemical bonding and mechanical interlocking. Test results showed that the interfacial shear strength of this structure reached 14.2 MPa, an increase of 67% compared to the specimen without the fusion layer; the peeling rate after 50 thermal cycles was only 0.5%, indicating that the addition of the fusion layer significantly improved the interfacial bonding strength and thermal cycling stability.

[0079] Based on the comparative test data above, it is evident that the addition of the fusion layer plays a crucial bridging role in the interfacial bonding mechanism. The melting point of EVA-based hot melt adhesive is 120℃ to 140℃, significantly lower than the melting temperature of PE. During injection molding, the fusion layer softens first and simultaneously fuses with both the original PE outer layer and the outer PE coating, forming a continuous and complete transition region. This transition region eliminates obvious interfacial delamination, resulting in a more uniform stress distribution and effectively improving the overall mechanical properties of the joint.

[0080] Example 3

[0081] To establish a quantitative relationship between electro-erosion parameters and etching depth, and to guide the optimization of process parameters in actual production, the following electro-erosion parameter calibration experiments were conducted.

[0082] According to Faraday's law of electrolysis, the relationship between the metal etching mass m and the electric charge Q is as follows:

[0083]

[0084] Where M is the molar mass of iron (56 g / mol), n is the change in oxidation state (2), and F is the Faraday constant (96485 C / mol). The charge Q is equal to the product of the current intensity I and the electrolysis time t, i.e., Q = I·t.

[0085] The electrolysis time required to etch to a depth of 12 mm using the steel strip material (grade Q235, thickness 2 mm) under different current densities was obtained through experimental calibration. The electrolysis area was fixed at 5 cm² in the experiment. 2 The etching depth was measured using a depth micrometer with an accuracy of 0.02 mm. Each parameter was tested three times and the average value was taken. The test calibration data are as follows:

[0086] The current density is 0.15 A / cm². 2 At this time, with a current intensity of 0.75A, the time required to etch to a depth of 12mm is 72 minutes; the current density is 0.20A / cm². 2At a current intensity of 1.00A, the time required to etch to a depth of 12mm is 54 minutes; the current density is 0.25A / cm². 2 At that time, with a current intensity of 1.25A, the time required to etch to a depth of 12mm was 43 minutes; the current density was 0.30A / cm². 2 At this time, with a current intensity of 1.50A, the time required to etch to a depth of 12mm is 36 minutes; the current density is 0.40A / cm². 2 At that time, with a current intensity of 2.00A, the time required to etch to a depth of 12mm is 27 minutes.

[0087] Analysis of the above data shows that etching time is inversely proportional to current density, which conforms to the basic law of Faraday's electrolysis. When the current density increases from 0.15 A / cm²... 2 Increased to 0.40 A / cm 2 At this rate, etching efficiency is increased by approximately 2.67 times. However, a side effect of high current density is the exacerbation of hydrogen evolution side reactions. When hydrogen evolves on the cathode surface, some bubbles adhere to the anode steel strip surface, forming a bubble shielding effect, which increases the micro-roughness of the etched surface and affects etching uniformity. More seriously, hydrogen bubbles accumulate at tiny defects at the interface between the PE protective layer and the steel strip, potentially causing localized peeling of the protective layer and increasing the risk of electrolyte penetration.

[0088] Taking into account etching efficiency, uniformity control, and protective layer safety, it is recommended to use 0.25 A / cm for actual production. 2 Up to 0.30A / cm 2 The current density range is within a certain range. Within this range, the etching efficiency is moderate, the etching depth repeatability is ±0.2mm, and the disturbance of the PE protective layer by side reactions is within an acceptable level. The electrolyte temperature also has a certain impact on the etching rate; for every 10°C increase in temperature, the etching rate increases by approximately 8% to 12%. It is recommended to control the electrolyte temperature within the range of 20°C to 25°C to obtain stable etching results.

[0089] In this embodiment of the invention, the PE fusion depth is ensured by electro-erosion pretreatment, the mechanical strength is enhanced by secondary injection molding and the steel strip fracture is completely covered, and the dual connection of chemical bonding and mechanical interlocking is achieved by hot melt adhesive fusion layer, thereby obtaining a welded joint that is airtight, reliable, has restored strength, and is corrosion resistant.

[0090] Furthermore, this embodiment of the invention also provides a processing system for sealing steel-plastic composite pipes and steel-reinforced pipe fittings. The system includes: a composite pipe acquisition module for acquiring a steel-plastic composite pipe to be processed, the steel-plastic composite pipe to be processed including an end to be welded; an etching module for performing electrochemical etching on the end to be welded to obtain an etched end; a heating module for performing heating on the etched end to obtain a heated end, the heated end being in a viscous flow state; a sealing module for performing sealing on the heated end based on the viscous flow state to obtain a sealed steel-plastic composite pipe, the sealed steel-plastic composite pipe including a sealing portion corresponding to the sealing treatment; and a reinforcement coating module for performing reinforcement coating on the outer layer of the sealed portion to obtain a reinforced steel-plastic composite pipe.

[0091] Furthermore, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the methods described in the embodiments of the present invention.

[0092] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0093] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0094] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0095] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A method for processing steel-plastic composite pipe sealing and steel-reinforced pipe fittings, characterized in that, The method includes: Obtain a steel-plastic composite pipe to be processed, wherein the steel-plastic composite pipe to be processed includes an end to be welded; Electrochemical etching is performed on the end to be welded to obtain the etched end. The etched end portion is subjected to a heat treatment to obtain a heated end portion, which is in a viscous flow state; Based on the viscous flow state, the heated end is subjected to a sealing process to obtain a sealed steel-plastic composite pipe, wherein the sealed steel-plastic composite pipe includes a sealing portion corresponding to the sealing process; The outer layer of the sealed portion is reinforced and coated to obtain a reinforced steel-plastic composite pipe.

2. The method according to claim 1, characterized in that, The electrochemical etching process performed on the end to be welded to obtain the etched end includes: Determine the exposed area of ​​the steel strip at the end to be welded; A protective agent is applied to the exposed area of ​​the steel strip to obtain the coated end. Determine the range of the steel strip to be corroded and the desired corrosion efficiency, and determine the etching electrical parameters based on the range of the steel strip to be corroded and the desired corrosion efficiency, wherein the etching electrical parameters include the etching charge and the etching current. The coated end is used as the anode and the stainless steel auxiliary electrode is used as the cathode, and then immersed in the electrolyte. Based on the etching charge and the etching current, an electrochemical etching process is performed on the exposed area of ​​the steel strip to obtain the etched end.

3. The method according to claim 2, characterized in that, The method further includes: The etching efficiency is determined based on the magnitude of the etching current. Determine whether the etching efficiency is less than a preset efficiency value; If so, perform electrochemical etching treatment on the exposed area of ​​the steel strip based on the etching charge and the etching current magnitude; Otherwise, the hydrogen evolution rate is determined based on the magnitude of the etching current; The disturbance effect of the electrochemical etching process on the plastic layer in the exposed area of ​​the steel strip is determined based on the hydrogen evolution rate. If the disturbance effect is less than a preset disturbance value, an electrochemical etching process is performed on the exposed area of ​​the steel strip based on the etching charge and the etching current. If the disturbance effect is greater than or equal to the preset disturbance value, the maximum etching current is determined based on the preset disturbance value, and an electrochemical etching process is performed on the exposed area of ​​the steel strip based on the etching charge and the maximum etching current.

4. The method according to claim 1, characterized in that, The heating end, based on the viscous flow state, undergoes a sealing process to obtain a sealed steel-plastic composite pipe, comprising: Obtain the diameter of the steel-plastic composite pipe to be processed, and determine the insertion pressure based on the diameter; Based on the aforementioned pressing pressure, a sealing process is performed on the heated rear end to obtain a sealed rear end; The sealed end is subjected to pressure holding and cooling treatment to obtain a cooled end; The sealing effect of the cooled end is tested using an electrical spark detection device to obtain the sealing test result. If the sealing test results are satisfactory, the sealed steel-plastic composite pipe is obtained.

5. The method according to claim 1, characterized in that, The process of performing a reinforcing coating treatment on the outer layer of the sealed portion to obtain a reinforced steel-plastic composite pipe includes: The outer surface of the sealing portion is roughened by grinding to obtain the roughened portion; Determine the thickness of the fusion layer coating and the target injection molding thickness of the polished area; Based on the coating thickness, the fusion layer is uniformly coated on the outer surface of the polished area to obtain the coated area; Based on the target injection thickness, a high-pressure reinforcing injection molding operation is performed on the coated area to obtain a reinforced steel-plastic composite pipe.

6. The method according to claim 5, characterized in that, Determining the fusion layer coating thickness and target injection molding thickness of the polished area includes: Obtain the physical strength indicators of the steel-plastic composite pipe to be processed; The minimum injection molding thickness of the polished area is determined based on the physical strength index. Obtain the weight of the steel-plastic composite pipe to be processed; The maximum injection thickness of the polished area is determined based on the weight index. The target injection thickness is determined based on the minimum injection thickness and the maximum injection thickness; The thickness of the fusion layer is determined based on the target injection molding thickness.

7. The method according to claim 5, characterized in that, Determining the fusion layer coating thickness based on the target injection molding thickness includes: Determine the tensile parameters of the fusion layer; The tensile strength requirement value is determined based on the target injection thickness and the preset rated vibration index; The coating thickness of the fusion layer is determined based on the tensile parameters and the tensile requirement value.

8. The method according to claim 1, characterized in that, The injection molding material used in the high-pressure enhanced injection molding operation is the same as the body material of the steel-plastic composite pipe to be processed.

9. A processing system for sealing steel-plastic composite pipes and steel-reinforced pipe fittings, characterized in that, The system includes: A composite pipe acquisition module is used to acquire a steel-plastic composite pipe to be processed, wherein the steel-plastic composite pipe to be processed includes an end to be welded; An etching module is used to perform electrochemical etching on the end to be welded to obtain the etched end. A heating module is used to perform a heating treatment on the etched end portion to obtain a heated end portion, wherein the heated end portion is in a viscous flow state; A sealing module is used to perform a sealing process on the heated end based on a viscous flow state to obtain a sealed steel-plastic composite pipe, wherein the sealed steel-plastic composite pipe includes a sealing portion corresponding to the sealing process; The reinforcement coating module is used to perform reinforcement coating treatment on the outer layer of the sealing part to obtain a reinforced steel-plastic composite pipe.

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