A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing.

Abstract

This invention discloses a method for preparing steel-aluminum pipe joints using a combination of interfacial coating and corrugated hot pressing, belonging to the field of metal layered composite material preparation technology. The method includes the following steps: immersing a seamless steel pipe and a seamless aluminum pipe with corrugations into molten aluminum; then, pressure assembling the corrugated surface of the seamless steel pipe and the surface to be composited with the seamless aluminum pipe; followed by heat treatment, cooling, and machining to obtain the steel-aluminum pipe joint prepared by the combination of interfacial coating and corrugated hot pressing. The steel-aluminum pipe joint prepared using the method provided by this invention exhibits high interfacial bonding strength.

Description

Technical Field

[0001] This invention belongs to the field of metal layered composite material preparation technology, and particularly relates to a method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing. Background Technology

[0002] In response to global strategies for energy conservation and environmental protection, modern aerospace engineering, shipbuilding engineering, and rail transportation structural designs are placing increasingly higher demands on lightweighting, corrosion resistance, and service life. To achieve these goals, aluminum and aluminum alloy tubes are increasingly being used to meet the requirements of lightweighting and corrosion resistance in structural designs. This leads to the question of how to effectively connect traditional steel and aluminum alloy tubes. Due to the significant differences in the thermophysical, metallurgical, and chemical properties of steel and aluminum, direct welding between them is poor, and mechanical connections also present numerous problems. For example, early methods used flanges to connect steel and aluminum tubes, but this method easily leads to corrosion at the contact surfaces due to wear, requiring frequent maintenance, incurring high repair costs, and potentially causing leaks when airtightness is required. To address these issues, steel-aluminum transition pipe joints have been proposed. This structure effectively solves the problem of efficient connection between steel and aluminum tubes and has a wide range of applications.

[0003] Currently, steel-aluminum transition pipe joints are produced worldwide by cutting steel / aluminum composite plates prepared using the explosive bonding method. While this process solves the manufacturing challenges of steel-aluminum pipe joints, the cutting process results in a significant loss of the original composite plate, leading to extremely low yield and high cost. Furthermore, the composite plates prepared by the explosive bonding method suffer from poor performance stability and high residual stress, greatly hindering the efficient fabrication of steel-aluminum pipe joints. Some researchers have proposed using welding to fabricate steel-aluminum transition pipe joints. However, the significant differences in the coefficients of thermal expansion, thermal conductivity, and elastic modulus between steel and aluminum can cause uneven heating at the interface, resulting in substantial residual internal stress and a high susceptibility to cracking. Simultaneously, the substantial differences in density and melting point between steel and aluminum lead to uneven composition of the weld pool and inconsistent strength at the interface, posing a risk of fracture. Therefore, there is an urgent need to develop a production method that enables the efficient fabrication of high-performance steel-aluminum transition pipe joints. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing.

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

[0006] A method for preparing a steel-aluminum pipe joint by combining an interface coating and corrugated hot pressing includes the following steps: immersing a seamless steel pipe and a seamless aluminum pipe with corrugations into molten aluminum liquid, then assembling the corrugated surface of the seamless steel pipe and the surface to be composited with the seamless aluminum pipe under pressure, followed by heat treatment, cooling, and machining, thereby obtaining the steel-aluminum pipe joint prepared by combining an interface coating and corrugated hot pressing.

[0007] Furthermore, the seamless steel pipes and seamless aluminum pipes need to be cleaned of oil, rust, and oxide film, and roughened before use.

[0008] Furthermore, the aspect ratio of both the seamless steel pipe and the seamless aluminum pipe is ≤2, the wall thickness is ≥3mm, and both are in the O state; the material of the seamless steel pipe is steel for shipbuilding and marine engineering, ordinary steel, alloy steel, or stainless steel; the material of the seamless aluminum pipe is industrial pure aluminum, 3-series aluminum alloy, 5-series aluminum alloy, or 6-series aluminum alloy.

[0009] Furthermore, the method for preparing the corrugated seamless steel pipe is as follows: the surface of the seamless steel pipe to be composited is pressed into a corrugated shape using a press, and then cleaned, dried, and roughened by grinding to obtain a seamless steel pipe with a corrugated surface on one side.

[0010] Furthermore, the corrugation is a transverse / longitudinal sine curve, a transverse / longitudinal cosine curve, a cross corrugation, or a micro-knurled corrugation, with a corrugation height of 0.1-0.8 mm.

[0011] Furthermore, when immersing the seamless aluminum tube into the molten aluminum liquid, the surface to be composited is completely immersed in the molten aluminum liquid and removed after 70-120 seconds;

[0012] When the corrugated seamless steel pipe is immersed in molten aluminum, the corrugated surface is completely immersed in the molten aluminum and removed after 20-30 seconds.

[0013] The temperature of the molten aluminum liquid is 720-750℃; the depth of aluminum immersion does not exceed 3mm.

[0014] Furthermore, the molten aluminum liquid is pure aluminum liquid or a mixture; the mixture is a mixture of molten aluminum and molten silicon with a volume ratio of 9:1.

[0015] Furthermore, the specific assembly method is as follows: the corrugated surface of the seamless steel pipe is assembled with the composite surface of the seamless aluminum pipe, the clamps are coaxial, the temperature of the composite surface reaches 500-600℃ within 5-10s, and then the pressing amount is controlled to be 0.2-1.6mm, and held for 20-30min to obtain the crude product.

[0016] Furthermore, the heat treatment refers to holding the assembled crude product at a temperature of 250-350℃ for 60-120 minutes.

[0017] The present invention also provides a steel-aluminum pipe joint prepared using the method described above.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] This invention employs a pre-corrugated process during aluminum immersion. This process is highly efficient, simple, requires no special equipment or instruments, and is easily industrialized. Furthermore, the pre-corrugated structure increases the contact area between the seamless aluminum tube and the molten aluminum during immersion plating, resulting in a more thorough metallurgical bond between the steel and aluminum dissimilar metals and improving the strength of the dissimilar metal interface. Simultaneously, during the subsequent assembly process to form the assembled tube, the easier bonding between aluminum and aluminum homometallic interfaces and the good plasticity of aluminum are utilized. The composite surface is inductively heated to achieve tube assembly, reducing the difficulty of interface bonding.

[0020] This invention employs hot-dip aluminizing technology. Hot-dip aluminizing technology has relatively simple equipment and processes, is easy to operate, has high production efficiency, and is easy to industrialize. In addition, the aluminum coating has strong adhesion, and hot-dip aluminizing technology enhances the bonding ability of dissimilar metals such as steel and aluminum. The high-temperature molten aluminum bath creates conditions for the metallurgical bonding of steel and aluminum, forming a composite coating with an inner layer of iron-aluminum metal compound and an outer layer of aluminum, enabling the billet tube to achieve more effective composite bonding and improving the bonding strength of the composite interface between the billet tube and the billet tube. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 The flowchart of this invention is shown in the figure. In the figure, 1-grinding device, 2-clamp, 3-press, 4-mold, 5-molten aluminum pool, 6-inductive heating device, 7-clamp mechanism. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] All raw materials used in the following embodiments of the present invention are commercially available.

[0029] A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing at high temperature includes the following steps:

[0030] S1. Pipe preparation: Prepare seamless steel pipe A and seamless aluminum pipe B with the same wall thickness and outer diameter. Remove oil, rust and oxide film from seamless steel pipe A and seamless aluminum pipe B, and then roughen them for later use.

[0031] S2. Pre-made corrugated morphology: The seamless steel pipe A is placed in the mold, and the surface of the seamless steel pipe A to be composited is pressed into a corrugated shape by a press. After cleaning, drying and roughening, a seamless steel pipe A with one corrugated side is prepared.

[0032] S3. Adding a coating: The side of the seamless steel pipe A with one corrugated surface prepared in step S2 to be composited is completely immersed in molten aluminum at 720-750℃ and kept for 70-120 seconds before being removed, thus preparing a seamless steel pipe A with one corrugated surface and an aluminum coating; The side of the seamless aluminum pipe B obtained in step S1 to be composited is completely immersed in molten aluminum at 720-750℃ and kept for 20-30 seconds before being removed, thus preparing a seamless aluminum pipe B with an aluminum coating.

[0033] S4. Hot-press composite: Take out the seamless steel pipe A with one side corrugated surface and aluminum coating prepared in step S3 and the seamless aluminum pipe B with aluminum coating to form an assembled pipe, and ensure coaxiality with a fixture; use an inductive heating device to heat the composite surface of the assembled pipe, so that the temperature of the composite surface reaches 500-600℃ within 5-10s, and use a press to apply pressure to the assembled pipe, with a reduction of 0.2-1.6mm, and hold for 20-30min to prepare the blank steel-aluminum pipe joint C;

[0034] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 250-350℃ for 60-120 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0035] In some preferred embodiments of the present invention, the seamless steel pipe A in step S1 is made of any one of shipbuilding and marine engineering steel, ordinary steel, alloy steel and stainless steel; the seamless aluminum pipe B is made of any one of industrial pure aluminum and 3-series aluminum alloy, 5-series aluminum alloy and 6-series aluminum alloy; both the seamless steel pipe A and the seamless aluminum pipe B are in the O state, and the length-to-diameter ratio does not exceed 2 and the wall thickness is not less than 3 mm.

[0036] In some preferred embodiments of the present invention, the pre-made corrugations in step S2 are any one of transverse / longitudinal sine curves, transverse / longitudinal cosine curves, cross corrugations, and micro knurled corrugations, and the corrugation height is about 0.1-0.8 mm.

[0037] In some preferred embodiments of the present invention, the molten aluminum liquid in step S3 can be pure aluminum liquid or a mixture of molten aluminum and molten silicon with a volume ratio of 9:1; the immersion depth of aluminum does not exceed 3 mm;

[0038] In some preferred embodiments of the present invention, the fixture in step S4 should be able to ensure that the coaxiality level of the assembled tube is not lower than level 7.

[0039] The following embodiments are further illustrations of the technical solution of the present invention.

[0040] Figure 1 This is a flowchart of the present invention.

[0041] Example 1

[0042] A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing, wherein the seamless steel pipe A is made of Q235 steel and the seamless aluminum pipe B is made of 1060 industrial pure aluminum. The specific steps are as follows:

[0043] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 15mm, a wall thickness of 3mm, and an outer diameter of 15mm, and a seamless steel pipe A with a length of 10mm, a wall thickness of 3mm, and an outer diameter of 15mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 5 minutes using grinding device 1. Set aside for later use.

[0044] S2. Pre-made corrugated morphology: The seamless steel pipe A processed in step S1 is placed in the transverse sinusoidal corrugated mold 4 and fixed on the mold 4 with the clamp 2. The corrugation height is 0.1mm. The surface of the seamless steel pipe A to be composited is pressed into a transverse sinusoidal corrugated shape with the press 3 and the pressure is 3MPa. Then it is cleaned, dried and polished for 5 minutes by the polishing device 1 to prepare a seamless steel pipe A with one side corrugated surface.

[0045] S3. Adding a coating: The corrugated surface of the seamless steel pipe A prepared in step S2 is completely immersed in molten pure aluminum liquid 5 at 720°C. After holding for 70 seconds, it is taken out and the immersion depth is 0.2 mm to prepare a seamless steel pipe A with a corrugated surface and an aluminum coating. The corrugated surface of the seamless aluminum pipe B treated in step S1 is completely immersed in molten pure aluminum liquid 5 at 720°C. After holding for 20 seconds, it is taken out and the immersion depth is 0.2 mm to prepare a seamless aluminum pipe B with an aluminum coating.

[0046] S4. Hot-press composite: Take out the seamless steel pipe A with one side corrugated and aluminum-plated layer prepared in step S3 and the seamless aluminum pipe B with aluminum-plated layer to form an assembly pipe (that is, combine the corrugated and aluminum-plated surface of the seamless steel pipe A with the surface of the seamless aluminum pipe B to be composited), and ensure coaxiality through the clamp 7; use an inductive heating device 6 to heat the composite surface of the assembly pipe, so that the temperature of the composite surface reaches 500℃ within 10s, and use a press 3 to apply pressure to the assembly pipe, with a pressing amount of 0.2mm, and hold for 20min to prepare the blank steel-aluminum pipe joint C;

[0047] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 250℃ for 60 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0048] Example 2

[0049] A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing, wherein the seamless steel pipe A is made of 304 stainless steel and the seamless aluminum pipe B is made of 5083 aluminum alloy. The specific steps are as follows:

[0050] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 60mm, a wall thickness of 10mm, and an outer diameter of 40mm, and a seamless steel pipe A with a length of 20mm, a wall thickness of 10mm, and an outer diameter of 40mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 10 minutes using grinding device 1. Set aside for later use.

[0051] S2. Pre-made corrugated morphology: The seamless steel pipe A processed in step S1 is placed into the cross-corrugated mold 4 and fixed on the mold 4 with the clamp 2. The corrugation height is 0.5mm. The surface of the seamless steel pipe A to be composited is pressed into a cross-corrugated shape with the press 3 and the pressure is 7MPa. Then it is cleaned, dried and polished for 10 minutes by the polishing device 1 to prepare a seamless steel pipe A with one side corrugated surface.

[0052] S3. Adding a coating: The corrugated surface of the seamless steel pipe A prepared in step S2 is completely immersed in an aluminum bath 5 at 730°C with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 100 seconds, the pipe is removed and the immersion depth is 0.7 mm. This produces a seamless steel pipe A with a corrugated surface and an aluminum coating. The corrugated surface of the seamless aluminum pipe B treated in step S1 is completely immersed in an aluminum bath 5 at 730°C with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 25 seconds, the pipe is removed and the immersion depth is 0.7 mm. This produces a seamless aluminum pipe B with an aluminum coating.

[0053] S4. Hot-press composite: Take out the seamless steel pipe A with one side corrugated and aluminum-plated layer prepared in step S3 and the seamless aluminum pipe B with aluminum-plated layer to form an assembly pipe (that is, combine the corrugated and aluminum-plated surface of the seamless steel pipe A with the surface of the seamless aluminum pipe B to be composited), and ensure coaxiality through the clamp 7; use an inductive heating device 6 to heat the composite surface of the assembly pipe, so that the temperature of the composite surface reaches 550℃ within 8s, and use a press 3 to apply pressure to the assembly pipe, with a pressing amount of 1mm, and hold for 25min to prepare the blank steel-aluminum pipe joint C.

[0054] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 300℃ for 90 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0055] Example 3

[0056] A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing, wherein the seamless steel pipe A is made of 403 stainless steel and the seamless aluminum pipe B is made of 6061 aluminum alloy. The specific steps are as follows:

[0057] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 80mm, a wall thickness of 20mm, and an outer diameter of 40mm, and a seamless steel pipe A with a length of 20mm, a wall thickness of 20mm, and an outer diameter of 40mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 20 minutes using grinding device 1. Set aside for later use.

[0058] S2. Pre-made corrugated morphology: The seamless steel pipe A treated in step S1 is placed into the micro-knurled corrugated mold 4 and fixed on the mold 4 with the clamp 2. The corrugation height is 0.8mm. The surface of the seamless steel pipe A to be composited is pressed into a micro-knurled corrugated shape with the press 3 and the pressure is 10MPa. Then it is cleaned, dried and polished for 20 minutes by the polishing device 1 to prepare a seamless steel pipe A with one side corrugated surface.

[0059] S3. Adding a coating: The corrugated surface of the seamless steel pipe A prepared in step S2 is completely immersed in an aluminum bath 5 at 750°C with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 120 seconds, the pipe is removed and the immersion depth is 1 mm. This produces a seamless steel pipe A with a corrugated surface and an aluminum coating. The corrugated surface of the seamless aluminum pipe B treated in step S1 is completely immersed in an aluminum bath 5 at 750°C with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 30 seconds, the pipe is removed and the immersion depth is 1 mm. This produces a seamless aluminum pipe B with an aluminum coating.

[0060] S4. Hot-press composite: Take out the seamless steel pipe A with one side corrugated and aluminum-plated layer prepared in step S3 and the seamless aluminum pipe B with aluminum-plated layer to form an assembly pipe (that is, combine the corrugated and aluminum-plated surface of the seamless steel pipe A with the surface of the seamless aluminum pipe B to be composited), and ensure coaxiality through the clamp 7; use an inductive heating device 6 to heat the composite surface of the assembly pipe, so that the temperature of the composite surface reaches 600℃ within 5s, and use a press 3 to apply pressure to the assembly pipe, with a reduction of 1.6mm, and hold for 30min to prepare the blank steel-aluminum pipe joint C;

[0061] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 350℃ for 120 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0062] Comparative Example 1

[0063] Same as Example 1, except that step S3 hot-dip aluminizing is not performed. The specific steps are as follows:

[0064] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 15mm, a wall thickness of 3mm, and an outer diameter of 15mm, and a seamless steel pipe A with a length of 10mm, a wall thickness of 3mm, and an outer diameter of 15mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 5 minutes using grinding device 1. Set aside for later use.

[0065] S2. Pre-made corrugated morphology: The seamless steel pipe A processed in step S1 is placed in the transverse sinusoidal corrugated mold 4 and fixed on the mold 4 with the clamp 2. The corrugation height is 0.1mm. The surface of the seamless steel pipe A to be composited is pressed into a transverse sinusoidal corrugated shape with the press 3 and the pressure is 3MPa. Then it is cleaned, dried and polished for 5 minutes by the polishing device 1 to prepare a seamless steel pipe A with one side corrugated surface.

[0066] S3. Hot-press composite: Take out the seamless steel pipe A and seamless aluminum pipe B with one side corrugated surface prepared in step S2 to form an assembled pipe (that is, combine the corrugated surface of the seamless steel pipe A with the surface of the seamless aluminum pipe B to be composited), and ensure coaxiality through the clamp 7; use an inductive heating device 6 to heat the composite surface of the assembled pipe so that the temperature of the composite surface reaches 500℃ within 10s, and use a press 3 to apply pressure to the assembled pipe with a reduction of 0.2mm, and hold for 20min to prepare the blank steel-aluminum pipe joint C;

[0067] S4. Post-processing: The blank steel-aluminum pipe joint C prepared in step S3 is subjected to heat treatment at a temperature of 250℃ for 60 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0068] Comparative Example 2

[0069] Same as Example 1, except that step S2, the pre-fabricated corrugation morphology processing, is not performed. The specific steps are as follows:

[0070] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 15mm, a wall thickness of 3mm, and an outer diameter of 15mm, and a seamless steel pipe A with a length of 10mm, a wall thickness of 3mm, and an outer diameter of 15mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 5 minutes using grinding device 1. Set aside for later use.

[0071] S2. Adding a coating: The surface of the seamless steel pipe A to be laminated prepared in step S1 is completely immersed in molten pure aluminum liquid 5 at 720°C, held for 70 seconds, and then removed. The immersion depth is 0.2 mm, thus preparing a seamless steel pipe A with an aluminum coating. The surface of the seamless aluminum pipe B to be laminated prepared in step S1 is completely immersed in molten pure aluminum liquid 5 at 720°C, held for 20 seconds, and then removed. The immersion depth is 0.2 mm, thus preparing a seamless aluminum pipe B with an aluminum coating.

[0072] S3. Hot-press composite: Take out the seamless steel pipe A with aluminum coating and the seamless aluminum pipe B with aluminum coating prepared in step S3 to form an assembled pipe (that is, combine the aluminum coating surface of the seamless steel pipe A with the surface to be composited of the seamless aluminum pipe B), and ensure coaxiality through the clamp 7; use an inductive heating device 6 to heat the composite surface of the assembled pipe so that the temperature of the composite surface reaches 500℃ within 10s, and use a press 3 to apply pressure to the assembled pipe with a reduction of 0.2mm, hold for 20min, and prepare the blank steel-aluminum pipe joint C;

[0073] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 250℃ for 60 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0074] Comparative Example 3 (Welding of Dissimilar Metals)

[0075] S1. Pipe preparation: Prepare a seamless aluminum pipe B with a length of 15mm, a wall thickness of 3mm, an outer diameter of 15mm, and a material of 1060 industrial pure aluminum, and a seamless steel pipe A with a length of 10mm, a wall thickness of 3mm, an outer diameter of 15mm, and a material of Q235 steel. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B. Grind the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated for 10 minutes using grinding device 1. Set aside.

[0076] S2. Hot pressing and bonding: The seamless steel pipe A prepared in step S1 is placed in a box furnace and heated to 450°C and held for 45 minutes; then the seamless steel pipe A is quickly removed and combined with the seamless aluminum pipe B prepared in step S1 to form an assembled pipe, so that the surfaces of the seamless steel pipe A and the seamless aluminum pipe B to be laminated are in contact and the coaxiality is ensured by a cylindrical clamping mechanism. Pressure is applied to the assembled pipe by a press with a pressure value of 20MPa.

[0077] S3. Welding: Place the Q235 steel welding rod at a vertical angle to the surface to be welded, and weld at a temperature of 1500℃ to prepare the blank steel-aluminum pipe joint C.

[0078] S4. Post-processing: The blank steel-aluminum pipe joint C prepared in step S3 is subjected to heat treatment at a temperature of 300℃ for 45 minutes. After cooling, the inner and outer walls and end faces of the blank steel-aluminum pipe joint C are machined to produce the finished steel-aluminum pipe joint C.

[0079] Performance testing:

[0080] Based on the airtightness and pressure resistance tests of the steel-aluminum transition joints, the performance of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Examples 1-3 of this invention was tested. The specific methods are as follows:

[0081] Pressure resistance test: Soap water was applied to the mating surfaces of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. One end of the steel-aluminum pipe joint was sealed, and the other end was filled with air and continuously pressurized. The gas pressure inside the pipe joint was recorded when soap bubbles were generated at the mating surfaces of the four types of pipe joints.

[0082] Nitrogen Leakage Test: One end of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Examples 1-3 of this invention was sealed, and the other end was filled with nitrogen gas and continuously pressurized to the rated working pressure of 35 MPa and maintained. Subsequently, a leak detector was used to detect the nitrogen leakage rate at five points on the joint surface of the four types of steel-aluminum pipe joints, and the average value was taken as the gas leakage rate of the steel-aluminum pipe joint.

[0083] result:

[0084] Pressure resistance test: The steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention produced soap bubbles at the joint surface under pressures of 41MPa, 39MPa, 40MPa, 31MPa, 27MPa and 20MPa, respectively. This indicates that the pressure resistance of the steel-aluminum pipe joints prepared in Examples 1-3 of the present invention is significantly higher than that of Comparative Examples 1-3, that is, the pressure resistance of the steel-aluminum pipe joints obtained by hot-dip aluminized corrugated hot pressing is higher.

[0085] Nitrogen leakage test: The nitrogen leakage rate of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Examples 1-3 of this invention was measured to be 9.81 × 10⁻⁶ under a working pressure of 30 MPa. -8 atm-cc / sec, 9.37×10 -8 atm-cc / sec, 8.94×10 -8 atm-cc / sec, 2.97×10 -3 atm-cc / sec, 5.41×10 -5 atm-cc / sec and 1.56×10 -2The atm-cc / sec indicates that the airtightness of the steel-aluminum pipe joints prepared by Examples 1-3 of the present invention is significantly higher than that of other preparation methods, that is, the steel-aluminum pipe joints prepared by the examples of the present invention have excellent airtightness.

[0086] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing, characterized in that, The process includes the following steps: immersing a corrugated seamless steel pipe and a seamless aluminum pipe into molten aluminum, then assembling the corrugated surface of the seamless steel pipe and the surface of the seamless aluminum pipe to be composited under pressure, followed by heat treatment, cooling, and machining, to obtain a steel-aluminum pipe joint prepared by combining an interface coating and corrugated hot pressing. When the seamless aluminum tube is immersed in molten aluminum, the surface to be composited is completely immersed in the molten aluminum and removed after 70-120 seconds. When the corrugated seamless steel pipe is immersed in molten aluminum, the corrugated surface is completely immersed in the molten aluminum and removed after 20-30 seconds. The temperature of the molten aluminum liquid is 720-750℃; the immersion depth does not exceed 3mm; The specific assembly method is as follows: the corrugated surface of the seamless steel pipe is assembled with the composite surface of the seamless aluminum pipe, the clamps are coaxial, the temperature of the composite surface reaches 500-600℃ within 5-10s, and then the pressing amount is controlled to be 0.2-1.6mm, and held for 20-30min to obtain the crude product.

2. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 1, characterized in that, Before use, the seamless steel pipes and seamless aluminum pipes need to be cleaned of oil, rust, and oxide film, and roughened by grinding.

3. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 2, characterized in that, The seamless steel pipe and seamless aluminum pipe have an aspect ratio of ≤2 and a wall thickness of ≥3mm, and are both in the O state; the seamless steel pipe is made of shipbuilding and marine engineering steel, ordinary steel, alloy steel or stainless steel; the seamless aluminum pipe is made of industrial pure aluminum, 3-series aluminum alloy, 5-series aluminum alloy or 6-series aluminum alloy.

4. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 1, characterized in that, The method for preparing the corrugated seamless steel pipe is as follows: the surface of the seamless steel pipe to be composited is pressed into a corrugated shape using a press, and then cleaned, dried, and roughened by grinding to obtain a seamless steel pipe with a corrugated surface on one side.

5. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 4, characterized in that, The corrugations are horizontal / vertical sine curves, horizontal / vertical cosine curves, cross corrugations, or micro-knurled corrugations, with a corrugation height of 0.1-0.8 mm.

6. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 1, characterized in that, The molten aluminum liquid is pure aluminum liquid or a mixture; the mixture is a mixture of molten aluminum and molten silicon with a volume ratio of 9:

1.

7. The method for preparing steel-aluminum pipe joints by combining interface coating and corrugated hot pressing according to claim 1, characterized in that, The heat treatment refers to holding the assembled crude product at 250-350℃ for 60-120 minutes.

8. A steel-aluminum pipe joint prepared by the method according to any one of claims 1-7.

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