Metal pipeline transition joint, expansion mechanism, welding device and welding method

Abstract

The invention discloses a metal pipeline transition joint and a welding device and method. The metal pipeline transition joint comprises an expansion sleeve, a mandrel, an axial supporting end and an axial pressing mechanism. The expansion sleeve is movably enclosed by a plurality of expansion sleeve sheets; the inner side of the rear portion of the expansion sleeve piece is of a wedge face structure, and the wedge face structure gradually becomes flat towards the rear end. The front part of the expansion sleeve sheet is mounted on the axial pressing mechanism; the middle of the mandrel is of a cone structure, and the outer side face of the cone structure is matched with the wedge face structure of the expansion sleeve in a complementary mode. The rear part of the core shaft is mounted on the axial supporting end; the expansion sleeve is sleeved on the outer side of the core shaft from the front part of the core shaft in a sliding manner; a metal pipeline arrangement area is arranged between the axial supporting end and the axial pressing mechanism, and a metal pipeline to-be-welded transition joint arrangement area is arranged on the corresponding outer side of the cone structure of the mandrel and the wedge face structure of the expansion sleeve. According to the invention, the transition joint with higher quality and better sealing performance can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a metal pipe transition joint, an expansion mechanism, a welding device and a welding method. Background Art

[0002] Aluminum alloy is light in weight, has good corrosion resistance, and has excellent low-temperature thermal conductivity. At present, aluminum alloy is widely used to manufacture low-temperature pressure vessels in aerospace, refrigeration, air separation, ethylene, LNG and other devices. Such aluminum alloy containers often require pipelines to be connected to the outside world, such as stainless steel, alloy steel and other pipeline connections. Because the thermophysical properties of aluminum and steel are very different (such as melting point, density, linear expansion coefficient, thermal conductivity and heat capacity, etc.) and brittle intermetallic compounds are easily generated between Al and Fe, the weldability of aluminum alloy and steel dissimilar materials is very poor and difficult to weld reliably.

[0003] In order to solve the connection problem of aluminum-steel dissimilar pipes, the explosion composite technology is currently commonly used to make aluminum-steel transition joints. However, the use of explosive composite technology to prepare aluminum-steel transition joints has technical bottlenecks, which limits the thickness of aluminum-steel. When the explosive composite aluminum-steel transition joint is welded to other pipes, the high welding temperature can easily cause the mechanical properties of the aluminum-steel transition joint to seriously deteriorate. The Institute of Metal Research, Chinese Academy of Sciences, has reported that aluminum and steel can be effectively connected through extrusion diffusion technology, but the implementation of this solution requires the use of larger extrusion equipment.

[0004] Other prior art, such as the invention patent application with patent publication number CN117961254A, discloses a method for manufacturing an aluminum alloy / stainless steel low-temperature metal pipe joint, which is prepared by a secondary explosion method to solve the problem of poor air tightness of explosion welding, but the process of this solution is relatively complicated, and flow resistance will be generated on the inner wall of the metal pipe, and the production cost is relatively high; the invention patent application with patent publication number CN106271028A discloses a method for connecting dissimilar metals by stir friction welding ring seam, which fixes the materials to be welded by a clamp, and uses the clamp to control the rotation of the rod for connection welding, but this solution does not take into account the internal support of the pipe wall at the welding position. Since the upsetting force during the stir friction welding process is very large, if there is no rigid support directly below the stirring tool, the inner pipe wall of the butt metal pipe is easily collapsed and deformed under the pressure of the stirring tool, destroying the integrity of the metal pipe. In severe cases, it will cause the entire metal pipe joint to be scrapped. At the same time, the collapsed and deformed position is likely to cause poor sealing of the joint, and the risk of leakage is very high. Therefore, this solution is less suitable for the processing of dissimilar metal pipes with high sealing requirements. Summary of the invention

[0005] The object of the present invention is to provide a metal pipe transition joint, an expansion mechanism, a welding device and a welding method, which can obtain a transition joint with higher quality and better sealing performance.

[0006] The technical solution provided by the present invention is:

[0007] A first aspect of the present application provides a metal pipe transition joint welding expansion mechanism, comprising an expansion sleeve, a mandrel, an axial support end and an axial clamping mechanism;

[0008] The expansion sleeve is surrounded by a plurality of separate expansion sleeve pieces; the inner side of the rear part of the expansion sleeve piece is a wedge surface structure, and the wedge surface structure gradually flattens toward the rear end; the front part of the expansion sleeve piece is installed on the axial clamping mechanism;

[0009] The middle part of the mandrel is a conical structure, and the outer inclined surface of the conical structure is complementary to the inner wedge surface of the expansion sleeve; the rear part of the mandrel is installed on the axial support end, and the expansion sleeve is slidably sleeved on the outer side of the mandrel from the front part of the mandrel;

[0010] The area between the axial support end and the axial clamping mechanism is a metal pipe setting area, and the corresponding outer sides of the cone structure of the mandrel and the wedge surface structure of the expansion sleeve are metal pipe transition joint setting areas to be welded.

[0011] To optimize the above technical solutions, the specific measures taken also include:

[0012] The axial clamping mechanism includes a clamping platform, and the front end of the expansion sleeve is installed on the clamping platform. The axial clamping mechanism can drive the expansion sleeve to move backward relative to the core shaft and be clamped on the outside of the core shaft; the clamping platform has a central hole, and the front end of the core shaft has an external thread. After the front end of the core shaft passes through the central hole of the clamping platform, the front end of the core shaft is screwed onto the clamping platform through the first nut.

[0013] The central hole of the clamping platform is surrounded by small holes, and an adjustable bolt is arranged in the small hole, and the adjustable bolt is located in front of the front end face of the metal pipe to be welded; while the axial clamping mechanism drives the expansion sleeve to move backward relative to the core axis, the clamping platform can be tightened against the front end face of the metal pipe to be welded by tightening the adjustable bolt.

[0014] The clamping platform includes an upper clamping platform and a lower clamping platform. The small holes and adjustable bolts are both arranged on the upper clamping platform. The lower clamping platform is an annular platform arranged between the upper clamping platform and the metal pipe to be welded. The adjustable bolt presses against the front end surface of the metal pipe to be welded through the lower clamping platform.

[0015] The axial support end includes a support platform and a second nut. The support platform has a central hole, and the rear end of the core shaft has an external thread. After the rear end of the core shaft passes through the central hole of the support platform, the rear end of the core shaft is tightened on the support platform through the second nut.

[0016] The outer wall of the expansion sleeve is provided with a step, the outer wall of the expansion sleeve behind the step is higher than the outer wall of the expansion sleeve in front of the step, and the step is located in front of the expansion sleeve wedge surface structure.

[0017] The inclination of the outer side surface of the cone structure is the same as the inclination of the wedge surface of the expansion sleeve. The wedge surface of the expansion sleeve is pressed tightly around the outer side surface of the cone structure, and the outer surface of the expansion sleeve expands the inner wall surface of the metal pipe to be welded.

[0018] The second aspect of the present application provides a metal pipe transition joint welding method, the welding steps are as follows:

[0019] Install the front metal pipe and the rear metal pipe to be welded on the metal pipe transition joint welding expansion mechanism: make the transition joint between them be located at the corresponding outer sides of the cone structure of the expansion mechanism core shaft and the expansion sleeve wedge surface structure; form axial support and compression on the front metal pipe and the rear metal pipe through the axial support end and the axial compression mechanism, and form radial expansion and tightening on the front metal pipe and the rear metal pipe through the expansion sleeve and the core shaft;

[0020] A transition joint is welded on the circumferential surface where the joint between the front metal pipe and the rear metal pipe is located.

[0021] The welding exceeds one circle of the circumferential surface. After the circumferential surface welding is completed, the welding is not stopped, and the welding is continued to move to one side of the metal pipe so that the keyhole of the stir friction welding does not fall on the circumferential surface where the metal pipe transition joint is located.

[0022] A first inclined surface is arranged at the rear end of the front metal pipe, and a second inclined surface complementary to the first inclined surface of the front metal pipe is arranged at the front end of the rear metal pipe.

[0023] A third aspect of the present application provides a metal pipe transition joint, which is a welded transition joint formed by welding two sections of dissimilar metal pipes using the above method.

[0024] Preferably, one section of the metal pipe is a steel pipe, and the other section of the metal pipe is an aluminum pipe; after the circumferential surface welding is completed, the welding is not stopped, and the welding is continued to move toward one side of the aluminum pipe, and then the keyhole section of the aluminum pipe is cut off.

[0025] A fourth aspect of the present application provides a metal pipe transition joint welding device, comprising a clamping and rotating mechanism, a supporting wheel, a welding tool and the above-mentioned metal pipe transition joint welding expansion mechanism;

[0026] The metal pipe to be welded is arranged on the metal pipe transition joint welding expansion mechanism, and the clamping and rotating mechanism is arranged at the rear of the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism, and is used to clamp and drive the metal pipe and the metal pipe transition joint welding expansion mechanism to rotate;

[0027] The support wheel is arranged at the bottom of the metal pipe to be welded, and is used to support the metal pipe to be welded and the welding expansion mechanism of the metal pipe transition joint;

[0028] The welding tool is a friction stir welding device.

[0029] A fifth aspect of the present application provides a method for welding using the above-mentioned metal pipe transition joint welding device, comprising:

[0030] Install the front metal pipe and the rear metal pipe to be welded on the metal pipe transition joint welding expansion mechanism;

[0031] Install the rear end of the welding expansion mechanism of the metal pipe and the metal pipe transition joint to be welded on the clamping and rotating mechanism, so that the front lower end of the welding expansion mechanism of the metal pipe and the metal pipe transition joint is placed on the supporting wheel;

[0032] The clamping rotating mechanism is rotated to drive the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism to rotate, and the transition joint is welded along the circumferential surface of the joint between the front metal pipe and the rear metal pipe through the stir friction welding device.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The metal pipe transition joint welding expansion mechanism of the present invention comprises an expansion sleeve, a core shaft, an axial support end and an axial clamping mechanism, wherein the axial support end and the axial clamping mechanism are used for axial support and clamping, so that the contact ends of the metal pipes to be welded are tightly butted; the expansion sleeve and the core shaft are used for radial expansion, the wedge surface structure of the expansion sleeve and the outer side surface of the cone structure of the core shaft are complementary and adapted, the expansion sleeve is slidably sleeved on the outer side of the core shaft from the front part, and the transition joints to be welded of the connected metal pipes are located at the corresponding outer sides of the cone structure of the core shaft and the wedge surface structure of the expansion sleeve; the expansion sleeve and the core shaft cooperate with the axial support end and the axial clamping mechanism, so that the metal pipes to be welded maintain stable butt joint and tight combination during the entire welding process.

[0035] The welding expansion mechanism of the metal pipe transition joint of the present invention can adaptively adjust the uneven changes in the length of metal pipes within a certain range through the adjustable bolts of the axial clamping mechanism, thereby meeting the requirements for axial support and clamping of the metal pipe; the welding expansion mechanism of the metal pipe transition joint of the present invention can enable the axial clamping mechanism to drive the expansion sleeve to move backward relative to the core shaft and be clamped on the outside of the core shaft through the tightening of the nut, and can adaptively adjust the uneven changes in the diameters of metal pipes within a certain range of diameters, thereby meeting the requirements for radial tensioning of the metal pipe.

[0036] The two butted dissimilar metal pipe parts of the metal pipe transition joint of the present invention can both have a certain length. When the two ends of the metal pipe transition joint are respectively welded to the metal pipes, since the weld is far away from the dissimilar metal interface and the temperature rise at the dissimilar metal interface is limited, the mechanical properties of the dissimilar metal interface will not be reduced when continuous welding is implemented, which is superior to other existing dissimilar metal welding methods.

[0037] The metal pipe transition joint of the present invention has high tensile strength, good interface performance consistency, and the weld has dense structure and good air tightness after extrusion measurement. The present invention is particularly suitable for welding high-quality metal pipe transition joints with good sealing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : A schematic structural diagram of the expansion mechanism of the present invention.

[0039] Figure 2 : A schematic cross-sectional view of the expansion mechanism of the present invention.

[0040] Figure 3 : A schematic structural diagram of the expansion sleeve and the expansion sleeve sheet of the present invention.

[0041] Figure 4 : A schematic diagram of the cross-sectional structure of the expansion sleeve of the present invention.

[0042] Figure 5 : The structural schematic diagram of the mandrel of the present invention.

[0043] Figure 6 : A schematic structural diagram of the axial clamping mechanism of the present invention.

[0044] Figure 7 : A schematic structural diagram of a metal pipe transition joint welding device according to the present invention.

[0045] Figure 8 : Schematic diagram of the assembly of metal pipes on the metal pipe transition joint welding device.

[0046] Fig. 9 : Schematic diagram of the structure of the metal pipe transition joint welding device from various perspectives.

[0047] Fig.10 : Schematic diagram of the product after welding of the metal pipe transition joint, with keyhole.

[0048] Fig.11 : Schematic diagram of the metal pipe transition joint after welding, cutting and grinding, without keyhole.

[0049] In the figure: 1-expansion sleeve, 2-mandrel, 3-axial support end, 4-axial clamping mechanism, 5-expansion sleeve plate, 6-metal pipe transition joint setting area to be welded, 7-transition joint, 8-wedge surface structure, 9-clamping platform, 10-first nut, 11-adjustable bolt, 12-step, 13-clamping rotation mechanism, 14-support wheel, 15-base, 16-first inclined surface, 17-second inclined surface, 18-steel pipe, 19-aluminum pipe, 20-small hole, 21-support platform, 22-second nut, 23-first clamping platform, 24-second clamping platform, 25-conical structure, 26-front end of mandrel, 27-rear end of mandrel, 28-metal pipe. DETAILED DESCRIPTION

[0050] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0051] For the purpose of easy understanding, the orientation or position relationship in the present invention is: Figure 8 Representatively, Figure 8 The right side in the description is the outer side, that is, the outer end of the processing and welding overall equipment is the outer side; accordingly, Figure 8 The left side in the figure is the inner side of the description. The orientation or position relationship is based on the relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0052] In addition, terms such as "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on specific circumstances.

[0053] Example 1

[0054] A metal pipe transition joint welding expansion mechanism, such as Figure 1 , Figure 2 As shown, it includes an expansion sleeve 1, a core shaft 2, an axial support end 3 and an axial clamping mechanism 4;

[0055] The expansion sleeve 1 is surrounded by a plurality of separate expansion sleeve pieces 5, such as Figure 3 As shown; the inner side of the rear part of the expansion sleeve 5 is a wedge surface structure 8, which gradually flattens toward the rear end; the front part of the expansion sleeve 5 is mounted on the axial clamping mechanism 4; between the axial support end 3 and the axial clamping mechanism 4 is a metal pipe setting area.

[0056] The middle part of the mandrel 2 is a conical structure 25, such as Figure 5As shown, the outer side surface of the cone structure 25 is complementary to the wedge surface structure 8 of the expansion sleeve 1; the rear part of the core shaft 2 is installed on the axial support end 3, and the expansion sleeve 1 is slidably sleeved on the outer side of the core shaft 2 from the front part of the core shaft 2; the corresponding outer sides of the cone structure 25 of the core shaft and the wedge surface structure 8 of the expansion sleeve are the metal pipe transition joint setting area 6 to be welded.

[0057] A metal pipe 28 to be welded is arranged between the axial support end 3 and the axial clamping mechanism 4 . A transition joint 7 to be welded to the metal pipe 28 is located at the corresponding outer sides of the cone structure 25 of the core shaft 2 and the wedge surface structure of the expansion sleeve 1 .

[0058] The slope of the outer side surface of the cone structure 25 is the same as the slope of the wedge surface of the expansion sleeve 1. When the wedge surface of the expansion sleeve 1 is pressed tightly around the outer side surface of the cone structure 25, the outer surface of the expansion sleeve 1 tightens the inner wall surface of the metal pipe to be welded.

[0059] The rear end of the metal pipe is supported on the axial support end 3 and the outer periphery of the core shaft 2 , and the front end of the metal pipe is supported on the axial clamping mechanism 4 and the outer periphery of the expansion sleeve 1 .

[0060] like Figure 6 As shown, the axial clamping mechanism 4 includes a clamping platform 9 and a first nut 10, and the expansion sleeve 5 is installed on the clamping platform 9; the clamping platform 9 has a central hole, and the front end 26 of the core shaft passes through the central hole of the clamping platform 9, and the front end of the core shaft 2 has an external thread. The front end of the core shaft 2 is screwed onto the clamping platform 9 by the first nut 10, so that the axial clamping mechanism 4 can drive the expansion sleeve 1 to move backward relative to the core shaft 2 and be clamped on the outside of the core shaft 2.

[0061] The clamping platform 9 is provided with small holes 20 around the middle hole, and an adjustable bolt 11 passing through the small hole 20 is provided in the small hole 20. The small hole 20 and the adjustable bolt 11 are located in front of the metal pipe to be welded; while the axial clamping mechanism 4 drives the expansion sleeve 1 to move backward relative to the core shaft 2, the adjustable bolt 11 is tightened to make the clamping platform 9 press against the metal pipe to be welded.

[0062] In some embodiments, the clamping platform 9 includes a first clamping platform 23 and a second clamping platform 24, the small hole 20 and the adjustable bolt 11 are both provided on the first clamping platform 23, and the second clamping platform 24 is an annular platform provided between the first clamping platform 23 and the metal pipe to be welded. The adjustable bolt 11 presses the second clamping platform 24 against the end face of the metal pipe so that the end face of the metal pipe is subjected to uniform force when being pressed.

[0063] The axial support end 3 includes a support platform 21 and a second nut 22. The support platform 21 has a central hole, and the rear end 27 of the core shaft passes through the central hole of the support platform 21. The rear end of the core shaft 2 has an external thread, and the rear end of the core shaft 2 is tightened on the support platform 21 through the second nut 22.

[0064] In some embodiments, the outer wall of the expansion sleeve 5 has a step 12, such as Figure 4 As shown, the outer wall of the expansion sleeve 5 at the rear of the step 12 is higher than the outer wall of the expansion sleeve 5 at the front of the step 12, and the step 12 is located in front of the wedge surface structure 8 of the expansion sleeve 1.

[0065] The purpose of setting the step 12 is to make the tensioning effect of the expansion sleeve 1 on the metal pipe mainly applied to the corresponding side of the wedge surface structure 8 of the expansion sleeve 1, that is, the position of the transition joint 7 of the metal pipe to be welded; and because the step 12 is set to make the diameter of the front section of the expansion sleeve 1 relatively smaller than the diameter of the rear section of the expansion sleeve 1, after the welding process is completed, the expansion sleeve 1 and the core shaft 2 inside it can be more conveniently removed from the welded metal pipe from the rear side, reducing the difficulty of removal, avoiding damage to the product, and ensuring product quality.

[0066] Example 2

[0067] A metal pipe transition joint welding device, such as Figure 7 , 8 9, comprising a clamping and rotating mechanism 13, a supporting wheel 14, a welding tool and a welding and tightening mechanism for the metal pipe transition joint 7 of Example 1;

[0068] The metal pipe to be welded is arranged on the welding expansion mechanism of the metal pipe transition joint 7, and the clamping and rotating mechanism 13 is arranged at the rear of the metal pipe to be welded and the expansion mechanism, and is used to clamp and drive the metal pipe and the welding expansion mechanism of the metal pipe transition joint 7 to rotate;

[0069] The support wheel 14 is arranged at the bottom of the metal pipe to be welded, and is used to support the metal pipe to be welded;

[0070] The clamping and rotating mechanism 13 and the supporting wheel 14 are installed on the base 15 .

[0071] The welding tool is a friction stir welding device.

[0072] Example 3

[0073] A metal pipe transition joint welding method, using the metal pipe transition joint welding device of embodiment 2, the welding steps are as follows:

[0074] The front metal pipe and the rear metal pipe to be welded are installed on the expansion mechanism, so that the transition joint 7 therebetween is located at the corresponding outer sides of the cone structure 25 of the expansion mechanism core shaft 2 and the wedge surface structure 8 of the expansion sleeve 1; the metal pipe 28 is axially supported and compressed by the axial support end 3 and the axial compression mechanism 4, and the metal pipe 28 is radially expanded by the expansion sleeve 1 and the core shaft 2;

[0075] During operation, the front end of the mandrel 2 is screwed onto the pressing platform 9 through the first nut 10 of the axial pressing mechanism 4, so that the axial pressing mechanism 4 drives the expansion sleeve 1 to move backward relative to the mandrel 2 and presses on the outside of the mandrel 2; the adjustable bolt 11 on the axial pressing mechanism 4 is tightened so that its rear end axially presses the metal pipe to be welded;

[0076] Install the metal pipe to be welded and the rear end of the expansion mechanism on the clamping and rotating mechanism 13, so that the front lower end of the metal pipe and the expansion mechanism is placed on the supporting wheel 14;

[0077] The clamping rotating mechanism 13 is rotated to drive the metal pipe to be welded and the expansion mechanism to rotate, and the transition joint welding is performed along the circumferential surface of the metal pipe transition joint 7 by the stir friction welding device.

[0078] The welding is performed for more than one circle (more than 360°), and the welding is not stopped after the circumferential surface welding is completed, but the welding is continued to move toward the metal pipe on one side, so that the keyhole of the stir friction welding does not fall on the circumferential surface of the metal pipe transition joint 7.

[0079] The rear end of the front metal pipe is provided with a first inclined surface 16, and the front end of the rear metal pipe is provided with a second inclined surface 17 which complements and matches the first inclined surface 16 of the front metal pipe, so that the assembly is more stable and the quality of the weld is improved.

[0080] Example 4

[0081] A metal pipe transition joint 7 is a metal pipe transition joint 7 welded by the method in Example 3.

[0082] The metal pipe on one side is a steel pipe 18, and the metal pipe on the other side is an aluminum pipe 19, which is made into an aluminum-steel transition joint pipe.

[0083] Preferably, the length of the aluminum pipe 19 is greater than 60 mm, and the length of the steel pipe 18 is greater than 40 mm.

[0084] In some embodiments, welding is not stopped after the circumferential surface welding is completed, and the aluminum pipe 19 is continuously moved to the welding position until a certain distance is reached, and then the keyhole section of the aluminum pipe 19 is cut off. Fig.10 , so that the overall product does not contain keyholes, and after grinding, it can form a perfect transition joint pipe, such as Fig.11 .

[0085] Example 5

[0086] Taking a specific test of the scheme of Example 4 as an example, the length of the aluminum tube part used is 65 mm, the inner diameter is 33 mm, and the outer diameter is 45 mm, and the length of the steel tube part is 45 mm, the inner diameter is 33 mm, and the outer diameter is 45 mm. The following test is performed on the actual product after welding:

[0087] (1) When the aluminum-steel transition joint pipe is used for welding, the temperature test at the aluminum-steel interface is:

[0088] When the steel end of the steel pipe part of the aluminum-steel dissimilar transition joint pipe is welded to other steel pipes, and the aluminum end of the aluminum pipe part is welded to other aluminum pipes respectively, since the re-welded weld is far away from the steel-aluminum interface welded in this application, it has been measured that the temperature at the aluminum-steel interface of the aluminum-steel dissimilar transition joint does not exceed 300°C. Therefore, the impact on the aluminum-steel interface when used for welding is small, and the mechanical properties of the aluminum-steel interface will not be reduced even in the case of continuous welding. Therefore, the aluminum-steel transition joint pipe can ensure the smooth construction when used, and there is no need to always consider the impact of construction on the quality of the aluminum-steel transition joint.

[0089] (2) Tensile strength test:

[0090] After the tensile strength test, the tensile strength of the aluminum-steel transition joint pipe exceeds 200MPa, and the interface performance consistency is good.

[0091] (3) Extrusion test:

[0092] The weld was subjected to extrusion testing and was found to have a dense structure.

[0093] (4) Air tightness test:

[0094] The weld has been tested by helium inspection, and the qualified rate of helium inspection is above 99.9%, and the airtightness reaches a high standard; the weld quality of the product of the present invention is high, especially the sealing has a significant advantage, and is particularly suitable for high-tech fields such as aviation and high-end manufacturing.

[0095] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention, may make any simple modifications, equivalent substitutions and improvements to the above embodiments, which are still within the protection scope of the technical solution of the present invention.

Claims

1. A metal pipe transition joint welding expansion mechanism, characterized in that: It includes an expansion sleeve, a core shaft, an axial support end and an axial clamping mechanism; The expansion sleeve is surrounded by a plurality of separate expansion sleeve pieces; the inner side of the rear part of the expansion sleeve piece is a wedge surface structure, and the wedge surface structure gradually flattens toward the rear end; the front part of the expansion sleeve piece is installed on the axial clamping mechanism; The middle part of the mandrel is a conical structure, and the outer inclined surface of the conical structure is complementary to the inner wedge surface of the expansion sleeve; the rear part of the mandrel is installed on the axial support end, and the expansion sleeve is slidably sleeved on the outer side of the mandrel from the front part of the mandrel; The area between the axial support end and the axial clamping mechanism is a metal pipe setting area, and the corresponding outer sides of the cone structure of the mandrel and the wedge surface structure of the expansion sleeve are metal pipe transition joint setting areas to be welded.

2. The metal pipe transition joint welding expansion mechanism according to claim 1 is characterized in that: The axial clamping mechanism includes a clamping platform, and the front end of the expansion sleeve is installed on the clamping platform. The axial clamping mechanism can drive the expansion sleeve to move backward relative to the core shaft and be clamped on the outside of the core shaft; the clamping platform has a central hole, and the front end of the core shaft has an external thread. After the front end of the core shaft passes through the central hole of the clamping platform, the front end of the core shaft is screwed onto the clamping platform through the first nut.

3. The metal pipe transition joint welding expansion mechanism according to claim 2 is characterized in that: The central hole of the clamping platform is surrounded by small holes, and an adjustable bolt is arranged in the small hole, and the adjustable bolt is located in front of the front end face of the metal pipe to be welded; while the axial clamping mechanism drives the expansion sleeve to move backward relative to the core axis, the clamping platform can be tightened against the front end face of the metal pipe to be welded by tightening the adjustable bolt.

4. The metal pipe transition joint welding expansion mechanism according to claim 3 is characterized in that: The clamping platform includes an upper clamping platform and a lower clamping platform. The small holes and adjustable bolts are both arranged on the upper clamping platform. The lower clamping platform is an annular platform arranged between the upper clamping platform and the metal pipe to be welded. The adjustable bolt presses against the front end surface of the metal pipe to be welded through the lower clamping platform.

5. The metal pipe transition joint welding expansion mechanism according to claim 1, characterized in that: The axial support end includes a support platform and a second nut. The support platform has a central hole, and the rear end of the core shaft has an external thread. After the rear end of the core shaft passes through the central hole of the support platform, the rear end of the core shaft is tightened on the support platform through the second nut.

6. The metal pipe transition joint welding expansion mechanism according to claim 1, characterized in that: The outer wall of the expansion sleeve is provided with a step, the outer wall of the expansion sleeve behind the step is higher than the outer wall of the expansion sleeve in front of the step, and the step is located in front of the expansion sleeve wedge surface structure.

7. The metal pipe transition joint welding expansion mechanism according to claim 1, characterized in that: The inclination of the outer side surface of the cone structure is the same as the inclination of the wedge surface of the expansion sleeve. The wedge surface of the expansion sleeve is pressed tightly around the outer side surface of the cone structure, and the outer surface of the expansion sleeve expands the inner wall surface of the metal pipe to be welded.

8. A metal pipe transition joint welding method, characterized in that: The metal pipe transition joint welding expansion mechanism according to any one of claims 1 to 7 is used, and the welding steps are as follows: Install the front metal pipe and the rear metal pipe to be welded on the metal pipe transition joint welding expansion mechanism: make the transition joint between them be located at the corresponding outer sides of the cone structure of the expansion mechanism core shaft and the expansion sleeve wedge surface structure; form axial support and compression on the front metal pipe and the rear metal pipe through the axial support end and the axial compression mechanism, and form radial expansion and tightening on the front metal pipe and the rear metal pipe through the expansion sleeve and the core shaft; A transition joint is welded on the circumferential surface where the joint between the front metal pipe and the rear metal pipe is located.

9. The metal pipe transition joint welding method according to claim 8, characterized in that: The welding exceeds one circle of the circumferential surface. After the circumferential surface welding is completed, the welding is not stopped, and the welding is continued to move to one side of the metal pipe so that the keyhole of the stir friction welding does not fall on the circumferential surface where the metal pipe transition joint is located.

10. The metal pipe transition joint welding method according to claim 8, characterized in that: A first inclined surface is arranged at the rear end of the front metal pipe, and a second inclined surface complementary to the first inclined surface of the front metal pipe is arranged at the front end of the rear metal pipe.

11. A metal pipe transition joint, characterized in that: A welded transition joint formed by welding two sections of dissimilar metal pipes using the method described in any one of claims 8 to 10.

12. A metal pipe transition joint welding device, characterized in that: It comprises a clamping and rotating mechanism, a supporting wheel, a welding tool and a metal pipe transition joint welding and tightening mechanism as claimed in any one of claims 1 to 7; The metal pipe to be welded is arranged on the metal pipe transition joint welding expansion mechanism, and the clamping and rotating mechanism is arranged at the rear of the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism, and is used to clamp and drive the metal pipe and the metal pipe transition joint welding expansion mechanism to rotate; The support wheel is arranged at the bottom of the metal pipe to be welded, and is used to support the metal pipe to be welded and the welding expansion mechanism of the metal pipe transition joint; The welding tool is a friction stir welding device.

13. A method for welding using the metal pipe transition joint welding device according to claim 12, characterized in that: Install the front metal pipe and the rear metal pipe to be welded on the metal pipe transition joint welding expansion mechanism; The rear end of the welding expansion mechanism of the metal pipe and the metal pipe transition joint to be welded is installed on the clamping and rotating mechanism, and the front lower end of the welding expansion mechanism of the metal pipe and the metal pipe transition joint is placed on the supporting wheel; The clamping rotating mechanism is rotated to drive the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism to rotate, and the transition joint is welded along the circumferential surface of the joint between the front metal pipe and the rear metal pipe through the stir friction welding device.

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