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

Abstract

This invention discloses a method for preparing steel-aluminum pipe joints using a combination of interfacial coating and differential temperature hot pressing, belonging to the field of metal layered composite material preparation technology. The method includes the following steps: seamless steel pipes and seamless aluminum pipes are separately immersed in molten aluminum; the resulting seamless steel pipes with aluminum coatings and seamless aluminum pipes with aluminum coatings are heated separately and then assembled under pressure, followed by heat treatment, cooling, and machining to obtain the finished steel-aluminum pipe joint. This invention achieves the connection between seamless steel pipes and seamless aluminum pipes, greatly improving material yield, reducing production costs, enhancing interfacial bonding strength and sealing performance, and is beneficial for large-scale industrial production.

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 differential temperature hot pressing. Background Technology

[0002] With the widespread use of steel and aluminum pipelines in the manufacturing of modern liquefied natural gas (LNG) carriers and liquefied petroleum gas (LPG) carriers, effective connections between these two types of pipelines have become a key research focus. Due to significant differences in the thermodynamic and mechanical properties of steel and aluminum, traditional flange connections are prone to electrochemical corrosion and failure, while welded connections are susceptible to low bond strength and poor airtightness. To achieve an effective connection between steel and aluminum pipelines, a steel-aluminum transition joint has been proposed based on the principle of connecting steel and aluminum alloy structures using a steel-aluminum transition joint. This joint connects the aluminum pipe to the aluminum side of the joint and the steel pipe to the steel side of the joint, thus achieving an effective connection between the steel and aluminum pipelines and yielding good economic results.

[0003] However, the steel-aluminum transition pipe joints currently used in the market are mainly made by cutting thick-gauge steel / aluminum layered composite plates. This process utilizes explosive bonding to prepare the steel / aluminum layered composite plate of the required thickness, and then mechanically processes it to produce steel-aluminum transition pipe joints of different specifications. While this production process can produce steel-aluminum transition pipe joints that meet the requirements, it is complex, has a low yield, and is costly. Some scholars have proposed using casting to produce steel-aluminum transition pipe joints; however, due to the significant differences in properties between steel and aluminum, the performance indicators of the resulting steel-aluminum transition pipe joints are relatively low. Therefore, there is an urgent need for a simple, high-yield, and low-cost method for manufacturing high-quality steel-aluminum transition pipe joints to meet market demand. 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 differential temperature hot pressing.

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

[0006] A method for preparing steel-aluminum pipe joints by combining interface coating and differential temperature hot pressing includes the following steps: seamless steel pipe and seamless aluminum pipe are respectively immersed in molten aluminum liquid, and the resulting seamless steel pipe with aluminum coating and seamless aluminum pipe with aluminum coating are heated and then assembled under pressure, heat treated, cooled and machined to obtain the finished steel-aluminum pipe joint.

[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] The seamless steel pipe is made of any one of the following: steel for shipbuilding and marine engineering, ordinary steel, alloy steel, and stainless steel, with a wall thickness ≥3mm and in the O temper.

[0009] The seamless aluminum tube is made of any one of industrial pure aluminum, 3-series aluminum alloy, 5-series aluminum alloy, and 6-series aluminum alloy, with a wall thickness ≥3mm; in the O state.

[0010] 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.

[0011] Furthermore, before the seamless steel pipe is immersed in molten aluminum, a flux is coated on its surface; the flux is a chloride or a fluoride.

[0012] Furthermore, the specific steps for immersing the seamless steel pipe in molten aluminum are as follows: the seamless steel pipe to be composited is completely immersed in molten aluminum at 680-720℃ for 30-120 seconds, with an immersion depth not exceeding 5mm, and then subjected to micro-pressure treatment on a press at a pressure of 10-30MPa.

[0013] Furthermore, the specific steps for immersing the seamless aluminum tube in molten aluminum are as follows: the seamless aluminum tube to be composited is completely immersed in molten aluminum at 680-720℃ for 20-60 seconds, the immersion depth does not exceed 5mm, and micro-pressure treatment is performed on a press at a pressure of 10-15MPa.

[0014] Furthermore, the heating conditions for the seamless steel pipe with aluminum coating are: temperature 500-630℃, holding time 1 hour.

[0015] Furthermore, the heating conditions for the seamless aluminum tube with aluminum coating are: temperature 300-450℃, holding time 1 hour.

[0016] Furthermore, during the pressure assembly process, the pressure value is 40-60 MPa, maintained for 10-30 minutes. During the hot-pressing composite process, the seamless aluminum tube is placed on top of the seamless steel tube to prevent excessive deformation of the aluminum tube.

[0017] Furthermore, the heat treatment refers to holding the assembled crude product at 350-450℃ for 60-120 minutes.

[0018] The present invention also provides a steel-aluminum pipe joint prepared using the method described above.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] This invention transforms the steel-aluminum interface composite into an aluminum-aluminum interface bond by utilizing a pre-fabricated aluminum layer, reducing the reduction required for interface bonding and improving the strength and reliability of the interface bond. Differential heating of the seamless steel pipe and seamless aluminum pipe increases their plasticity, reduces deformation resistance, and ensures connection strength. Furthermore, the steel-aluminum interface bond strength and airtightness are further enhanced by spraying a flux and hot-pressing after hot-dip galvanizing. Utilizing the oxidation resistance of the aluminum plating layer, seamless steel pipes and seamless aluminum pipes with aluminum plating can be heated without oxygen protection measures, and the micro-oxide layer is broken down into a reinforcing phase during the hot-pressing process, further improving the interface bond strength and airtightness.

[0021] This invention uses existing, mature seamless steel pipes and seamless aluminum pipes as base materials to achieve the connection between seamless steel pipes and seamless aluminum pipes, which greatly improves the material yield, reduces production costs, enhances the interface bonding strength and sealing performance, and is conducive to large-scale industrial production. Attached Figure Description

[0022] 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:

[0023] Figure 1 The flowchart of this invention is shown below; in the figure, 1-grinding device, 2-spraying device, 3-molten aluminum immersion plating tank, 4-base plate, 5-press, 6-box-type heating furnace, 7-cylindrical clamping mechanism. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] All raw materials used in the following embodiments of the present invention are commercially available.

[0030] A method for preparing steel-aluminum pipe joints by combining interface coating and high-temperature hot pressing, comprising the following steps:

[0031] 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 dry and let stand. Roughen the surfaces of seamless steel pipe A and seamless aluminum pipe B to be laminated. Apply flux to the surface of seamless steel pipe A to complete the pretreatment before immersion plating.

[0032] S2. Aluminum immersion treatment of the composite surface of seamless steel pipe A: The composite surface of seamless steel pipe A, which has been treated in step S1, is completely immersed in molten aluminum at 680-720℃ and kept for 30-120 seconds before being taken out. The immersion depth does not exceed 5mm. Micro-pressure treatment is performed on a press at a pressure of 10-30MPa to prepare seamless steel pipe A with aluminum coating.

[0033] S3. Aluminum immersion treatment of the composite surface of seamless aluminum tube B: The composite surface of seamless aluminum tube B, which has been treated in step S1, is completely immersed in molten aluminum liquid at 680-720℃ and kept for 20-60 seconds before being taken out. The immersion depth does not exceed 5mm. Micro-pressure treatment is performed on a press at a pressure of 10-15MPa to prepare seamless aluminum tube B with aluminum coating.

[0034] S4. Hot-pressing composite: The aluminum layer of the seamless steel pipe A with aluminum coating prepared in step S2 is cleaned, dried, and then roughened by grinding. It is then placed in a heating furnace and heated to 500-630℃ and held for 1 hour. At the same time, the seamless aluminum pipe B with aluminum coating prepared in step S3 is placed in a heating furnace and heated to 300-450℃ and held for 1 hour. After quickly removing the two, they are assembled into a blank to form an assembled pipe. The surfaces of the seamless steel pipe A with aluminum coating and the seamless aluminum pipe B with aluminum coating are in contact, and the coaxiality is ensured by a fixture. Pressure is applied to the assembled pipe by a press with a pressure value of 40-60MPa and held for 10-30 minutes to prepare the blank steel-aluminum pipe joint C.

[0035] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 350-450℃ for 60-120 minutes. After cooling, the blank steel-aluminum pipe joint C is subjected to finishing and polishing to produce the finished steel-aluminum pipe joint C.

[0036] In step S1 of some preferred embodiments of the present invention, the seamless steel pipe A is made of any one of shipbuilding and marine engineering steel, ordinary steel, alloy steel and stainless steel, and has a wall thickness greater than or equal to 3mm; the seamless aluminum pipe B is made of any one of industrial pure aluminum, 3-series aluminum alloy, 5-series aluminum alloy and 6-series aluminum alloy, and has a wall thickness greater than or equal to 3mm; both the seamless steel pipe A and the seamless aluminum pipe B are in the O state.

[0037] In step S1 of some preferred embodiments of the present invention, the plating flux is a chloride (ZnCl2, NH4Cl, LiCl, NaCl) and a fluoride (KF, NaF, Na3AlF6), etc.

[0038] In step S2 of some preferred embodiments of the present invention, the molten aluminum liquid can be pure aluminum liquid or a mixture of molten aluminum and molten silicon with a volume ratio of 9:1.

[0039] In step S4 of some preferred embodiments of the present invention, the seamless aluminum tube B with a lower yield strength should be placed above the seamless aluminized steel tube A to prevent excessive deformation of the aluminum tube.

[0040] The following embodiments are further illustrations of the technical solution of the present invention.

[0041] Figure 1 This is a flowchart of the present invention.

[0042] Example 1

[0043] A method for preparing steel-aluminum pipe joints by combining interface coating and high-temperature 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:

[0044] S1. Pipe preparation: Prepare a seamless steel pipe A with a length of 15mm, a wall thickness of 3mm, and an outer diameter of 20mm, and a seamless aluminum pipe B with a length of 20mm, a wall thickness of 3mm, and an outer diameter of 20mm. Remove oil, rust, and oxide film from the seamless steel pipe A and the seamless aluminum pipe B, and then dry and let them stand. 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. Then, use spraying device 2 to spray 40ml of Na3AlF6 flux onto the surface of the seamless steel pipe A to complete the pretreatment before immersion plating.

[0045] S2. Aluminum immersion treatment of the composite surface of seamless steel pipe A: The composite surface of seamless steel pipe A, which has been treated in step S1, is completely immersed in molten pure aluminum liquid 3 at 680℃, kept for 30s and then taken out. The immersion depth is 3mm. Micro-pressure treatment is performed on press 5 at a pressure of 10MPa to prepare seamless steel pipe A with aluminum coating.

[0046] S3. Aluminum immersion treatment of the composite surface of seamless aluminum tube B: The composite surface of seamless aluminum tube B, which has been processed in step S1, is completely immersed in pure aluminum liquid in molten aluminum plating bath 3 at 680℃. After holding for 20 seconds, it is taken out and the immersion depth is 3mm. Micro-pressure treatment is performed on press 5 at a pressure of 10MPa to prepare seamless aluminum tube B with aluminum coating.

[0047] S4. Hot-pressing composite: The aluminum layer of the seamless steel pipe A with aluminum coating prepared in step S2 is cleaned and dried, then polished for 5 minutes, and then placed in a box furnace 6 and heated to 500°C for 1 hour; at the same time, the aluminum layer of the seamless aluminum pipe B with aluminum coating prepared in step S3 is cleaned and dried, then polished for 5 minutes, and then placed in a box furnace 6 and heated to 300°C for 1 hour; after quickly removing both, they are assembled into an assembled pipe with the aluminum pipe on top and the steel pipe on the bottom, so that the surfaces of the seamless steel pipe A with aluminum coating and the seamless aluminum pipe B with aluminum coating are in contact and the coaxiality is ensured by the cylindrical clamp mechanism 7. The assembled pipe is pressurized by the press 5 with a pressure of 40 MPa and held for 30 minutes to prepare the blank steel-aluminum pipe joint C;

[0048] 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 blank steel-aluminum pipe joint C is subjected to finishing and polishing to produce the finished steel-aluminum pipe joint C.

[0049] Example 2

[0050] A method for preparing steel-aluminum pipe joints by combining interface coating and high-temperature 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:

[0051] S1. Pipe preparation: Prepare a seamless steel pipe A with a length of 20mm, a wall thickness of 10mm, and an outer diameter of 40mm, and a seamless aluminum pipe B with a length of 40mm, 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, and then dry and let them stand. 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. Subsequently, spray 100ml of NaF flux onto the surface of the seamless steel pipe A using spraying device 2 to complete the pretreatment before immersion plating.

[0052] S2. Aluminum immersion treatment of the composite surface of seamless steel pipe A: The composite surface of seamless steel pipe A, which has been treated in step S1, is completely immersed in aluminum pool 3 at 700℃ with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 80 seconds, it is taken out and the immersion depth is 4mm. Micro-pressure treatment is performed on press 5 at a pressure of 20MPa to prepare seamless steel pipe A with aluminum coating.

[0053] S3. Aluminum immersion treatment of the composite surface of seamless aluminum tube B: The composite surface of seamless aluminum tube B, which has been processed in step S1, is completely immersed in pure aluminum liquid in molten aluminum plating bath 3 at 700℃. After holding for 40 seconds, it is taken out and the immersion depth is 4mm. Micro-pressure treatment is performed on press 5 at a pressure of 12MPa to prepare seamless aluminum tube B with aluminum coating.

[0054] S4. Hot-pressing composite: The aluminum layer of the seamless steel pipe A with aluminum coating prepared in step S2 is cleaned and dried, then polished for 10 minutes, and then placed in a box furnace 6 and heated to 570°C for 1 hour; at the same time, the aluminum layer of the seamless aluminum pipe B with aluminum coating prepared in step S3 is cleaned and dried, then polished for 10 minutes, and then placed in a box furnace 6 and heated to 400°C for 1 hour; after quickly removing both, they are assembled into an assembled pipe with the aluminum pipe on top and the steel pipe on the bottom, so that the surfaces of the seamless steel pipe A with aluminum coating and the seamless aluminum pipe B with aluminum coating are in contact and the coaxiality is ensured by the cylindrical clamp mechanism 7. The assembled pipe is pressurized by the press 5 with a pressure of 50 MPa and held for 20 minutes to prepare the blank steel-aluminum pipe joint C;

[0055] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 400℃ for 90 minutes. After cooling, the blank steel-aluminum pipe joint C is subjected to finishing and polishing to produce the finished steel-aluminum pipe joint C.

[0056] Example 3

[0057] A method for preparing steel-aluminum pipe joints by combining interface coating and high-temperature hot pressing, wherein the seamless steel pipe A is made of 430 stainless steel and the seamless aluminum pipe B is made of 6061 aluminum alloy. The specific steps are as follows:

[0058] S1. Pipe preparation: Prepare seamless steel pipe A with a length of 30mm, a wall thickness of 20mm, and an outer diameter of 80mm, and seamless aluminum pipe B with a length of 60mm, a wall thickness of 20mm, and an outer diameter of 80mm. Remove oil, rust, and oxide film from seamless steel pipe A and seamless aluminum pipe B, and then dry and let them stand. Grind the surfaces of seamless steel pipe A and seamless aluminum pipe B to be laminated for 15 minutes using grinding device 1. Subsequently, spray 150ml of ZnCl2 flux onto the surface of seamless steel pipe A using spraying device 2 to complete the pretreatment before immersion plating.

[0059] S2. Aluminum immersion treatment of the composite surface of seamless steel pipe A: The composite surface of seamless steel pipe A, which has been treated in step S1, is completely immersed in molten aluminum immersion bath 3 at 720℃ with a volume ratio of molten aluminum to molten silicon of 9:1. After holding for 120s, it is taken out and the immersion depth is 5mm. Micro-pressure treatment is performed on press 5 at a pressure of 30MPa to prepare seamless steel pipe A with aluminum coating.

[0060] S3. Aluminum immersion treatment of the composite surface of seamless aluminum tube B: The composite surface of seamless aluminum tube B, which has been processed in step S1, is completely immersed in molten pure aluminum liquid 3 at 720℃, kept for 60s and then taken out. The immersion depth is 5mm. Micro-pressure treatment is performed on press 5 at a pressure of 15MPa to prepare seamless aluminum tube B with aluminum coating.

[0061] S4. Hot-pressing composite: The aluminum layer of the seamless steel pipe A with aluminum coating prepared in step S2 is cleaned and dried, then polished for 15 minutes, and then placed in a box-type heating furnace 6 and heated to 630°C for 1 hour; at the same time, the aluminum layer of the seamless aluminum pipe B with aluminum coating prepared in step S3 is cleaned and dried, then polished for 15 minutes, and then placed in a box-type heating furnace 6 and heated to 450°C for 1 hour; after quickly removing both, they are assembled into an assembled pipe with the aluminum pipe on top and the steel pipe on the bottom, so that the surfaces of the seamless steel pipe A with aluminum coating and the seamless aluminum pipe B with aluminum coating are in contact and the coaxiality is ensured by the cylindrical clamp mechanism 7. The assembled pipe is pressurized by the press 5 with a pressure of 60 MPa and held for 10 minutes to prepare the blank steel-aluminum pipe joint C;

[0062] S5. Post-processing: The blank steel-aluminum pipe joint C prepared in step S4 is subjected to heat treatment at a temperature of 450℃ for 60 minutes. After cooling, the blank steel-aluminum pipe joint C is subjected to finishing and polishing to produce the finished steel-aluminum pipe joint C.

[0063] Comparative Example 1

[0064] Same as Example 1, except that in step S4, the heating temperature of the seamless aluminum tube B is 500°C.

[0065] Performance testing:

[0066] 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 Example 1 of this invention was tested. The specific methods are as follows:

[0067] Pressure resistance test: Soap water was applied to the joint surfaces of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Example 1 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 joint surfaces of the four types of pipe joints.

[0068] Nitrogen Leakage Test: One end of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Example 1 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 at 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.

[0069] result:

[0070] Pressure resistance test: The steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Example 1 of this invention produced soap bubbles at the joint surface under pressures of 35MPa, 37MPa, 34MPa and 25MPa, respectively. This indicates that the pressure resistance of the steel-aluminum pipe joint prepared by Comparative Example 1, i.e., the steel-aluminum pipe joint prepared by heating at the same temperature, is lower than that of the steel-aluminum pipe joint prepared by heating at different temperatures.

[0071] Nitrogen leakage test: The nitrogen leakage rate of the steel-aluminum pipe joints prepared in Examples 1-3 and Comparative Example 1 was measured to be 9.3 × 10⁻⁶ under a working pressure of 25 MPa. -8 atm-cc / sec, 9.7×10 -8 atm-cc / sec, 9×10 -8 atm-cc / sec and 2.3×10 -4 atm-cc / sec indicates that, in Comparative Example 1, the airtightness of the steel-aluminum pipe joint obtained by heating at the same temperature is lower than that obtained by heating at different temperatures.

[0072] 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 differential temperature hot pressing, characterized in that, Includes the following steps: Seamless steel pipes and seamless aluminum pipes are respectively immersed in molten aluminum liquid. The resulting seamless steel pipes with aluminum coating and seamless aluminum pipes with aluminum coating are heated and then assembled under pressure, heat treated, cooled and machined to obtain finished steel-aluminum pipe joints. The specific steps for immersing the seamless steel pipe in molten aluminum are as follows: the seamless steel pipe to be composited is completely immersed in molten aluminum at 680-720℃ for 30-120 seconds, the immersion depth does not exceed 5mm, and micro-pressure treatment is performed on a press with a pressure of 10-30MPa. The specific steps for immersing the seamless aluminum tube in molten aluminum are as follows: the seamless aluminum tube to be composited is completely immersed in molten aluminum at 680-720℃ for 20-60 seconds, the immersion depth does not exceed 5mm, and micro-pressure treatment is performed on a press with a pressure of 10-15MPa. The heating conditions for the seamless steel pipe with aluminum coating are: temperature 500-630℃, holding time 1 hour; The heating conditions for the seamless aluminum tube with aluminum coating are: temperature 300-450℃, holding time 1 hour; During the pressure assembly process, the pressure value is 40-60 MPa and maintained for 10-30 minutes.

2. The method for preparing steel-aluminum pipe joints by combining interface coating and differential temperature 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. The seamless steel pipe is made of any one of the following: steel for shipbuilding and marine engineering, ordinary steel, alloy steel, and stainless steel, with a wall thickness ≥3mm and in the O temper. The seamless aluminum tube is made of any one of industrial pure aluminum, 3-series aluminum alloy, 5-series aluminum alloy, and 6-series aluminum alloy, with a wall thickness ≥3mm; in the O state. 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.

3. The method for preparing steel-aluminum pipe joints by combining interface coating and differential temperature hot pressing according to claim 1, characterized in that, Before being immersed in molten aluminum, the seamless steel pipe is coated with a flux; the flux is a chloride or a fluoride.

4. The method for preparing steel-aluminum pipe joints by combining interface coating and differential temperature hot pressing according to claim 1, characterized in that, The heat treatment refers to holding the assembled crude product at 350-450℃ for 60-120 minutes.

5. A steel-aluminum pipe joint prepared by the method according to any one of claims 1-4.

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