A metal pipe transition joint, an expansion mechanism, a welding device and a welding method

Abstract

The application discloses a metal pipeline transition joint, a welding device and a method, which comprise a sleeve, a mandrel, an axial support end and an axial pressing mechanism; the sleeve is formed by a plurality of sleeve pieces; the rear inner side of the sleeve piece is a wedge surface structure, which is gradually flattened towards the rear end; the front part of the sleeve piece is installed on the axial pressing mechanism; the middle part of the mandrel is a conical body structure, the outer side surface of the conical body structure is complementary to the wedge surface structure of the sleeve; the rear part of the mandrel is installed on the axial support end, and the sleeve is slidably arranged outside the mandrel from the front part of the mandrel; the axial support end and the axial pressing mechanism are provided with a metal pipeline setting area, and the corresponding outer sides of the conical body structure of the mandrel and the wedge surface structure of the sleeve are provided with a metal pipeline transition joint setting area to be welded. The application can obtain a transition joint with higher quality and better sealing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a metal pipeline transition joint, an expansion mechanism, a welding device and a welding method. BACKGROUND

[0002] Aluminum alloy has the advantages of light weight, good corrosion resistance and excellent low-temperature thermal conductivity. At present, aluminum alloy is widely used to manufacture low-temperature pressure vessels in aerospace, refrigeration, air separation devices, ethylene devices, LNG devices and the like. Such aluminum alloy vessels often require connection with pipelines such as stainless steel and alloy steel pipelines. Because of the large difference in thermal physical properties (such as melting point, density, linear expansion coefficient, thermal conductivity and heat capacity) between aluminum and steel and the easy formation of brittle intermetallic compounds between Al and Fe, the weldability of aluminum alloy and steel dissimilar materials is poor, making it difficult to reliably weld.

[0003] In order to solve the connection problem of aluminum-steel dissimilar pipelines, the current common method is to use explosive composite technology to manufacture aluminum-steel transition joints. However, the use of explosive composite technology to prepare aluminum-steel transition joints has technical bottlenecks, limiting the thickness of aluminum-steel. When the explosive composite aluminum-steel transition joint is welded with other pipelines, the high temperature during welding can cause a serious decrease in the mechanical properties of the aluminum-steel transition joint. The Institute of Metal of the Chinese Academy of Sciences reported that aluminum and steel can be effectively connected through extrusion diffusion technology, but the implementation of this scheme requires the use of large extrusion equipment.

[0004] Other existing technologies, such as the patent application for an invention patent with the publication number CN117961254A, disclose a manufacturing method for an aluminum alloy / stainless steel low-temperature metal pipeline joint. The joint is prepared by a secondary explosion method to solve the problem of poor air tightness of explosive welding. However, the process of this scheme is relatively complex, and flow resistance can be generated on the inner wall of the metal pipeline, resulting in high production costs. The patent application for an invention patent with the publication number CN106271028A discloses a method for friction stir welding of ring seams to connect dissimilar metals. The method uses a clamp to fix the materials to be welded and controls the rotation of the bar material using the clamp control rod to connect and weld. However, this scheme does not consider the internal support of the pipe wall at the welding position. Because the upset force during friction stir welding is very large, if there is no rigid support directly below the stirring tool, the inner pipe wall of the butt joint metal pipe can easily collapse and deform under the pressure of the stirring tool, damaging the integrity of the metal pipe. In severe cases, it can cause the entire metal pipe joint to be scrapped. At the same time, the position of the collapsed deformation can easily cause poor sealing of the joint, resulting in a high risk of leakage. Therefore, this scheme is not suitable for the processing of dissimilar metal pipelines with high sealing requirements. SUMMARY

[0005] The purpose of the present application is to provide a metal pipeline transition joint, an expansion mechanism, a welding device and a welding method that can obtain a transition joint with higher quality and better sealing performance.

[0006] The technical scheme provided by the present application is:

[0007] The first aspect of the present application provides a metal pipe transition joint welding and expanding mechanism, which comprises a sleeve, a mandrel, an axial support end and an axial pressing mechanism.

[0008] The sleeve is composed of a plurality of sleeve pieces, and the inner side of the rear part of the sleeve piece is a wedge surface structure that gradually flattens towards the rear end.

[0009] The middle part of the mandrel is a conical structure, and the outer side of the conical structure is complementarily matched with the inner side wedge surface of the sleeve.

[0010] The axial support end and the axial pressing mechanism are provided with a metal pipe setting area, and the corresponding outer sides of the conical structure of the mandrel and the wedge surface structure of the sleeve are provided with a metal pipe transition joint setting area to be welded.

[0011] To optimize the above technical scheme, the following specific measures are taken:

[0012] The axial pressing mechanism comprises a pressing table, the front end of the sleeve piece is installed on the pressing table, the axial pressing mechanism can drive the sleeve piece to move backward relative to the mandrel and press on the outer side of the mandrel, the pressing table has a middle hole, the front end of the mandrel has external threads, and the front end of the mandrel passes through the middle hole of the pressing table and is screwed onto the pressing table by a first nut.

[0013] A plurality of small holes are arranged around the middle hole of the pressing table, an adjustable bolt is arranged in each small hole, and the adjustable bolt is located in front of the front end face of the metal pipe to be welded.

[0014] The pressing table comprises an upper pressing table and a lower pressing table, the small holes and the adjustable bolts are arranged on the upper pressing table, the lower pressing table is an annular table arranged between the upper pressing table and the metal pipe to be welded, and the adjustable bolts press the front end face of the metal pipe to be welded through the lower pressing table.

[0015] The axial support end comprises a support table and a second nut, the support table has a middle hole, the rear end of the mandrel has external threads, and the rear end of the mandrel passes through the middle hole of the support table and is screwed onto the support table by the second nut.

[0016] The outer wall of the expansion sleeve has 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 wedge surface structure of the expansion sleeve.

[0017] The outer side slope of the conical structure is the same as the wedge surface slope of the expansion sleeve, the wedge surface of the expansion sleeve is pressed against the outer side of the conical structure, and the outer surface of the expansion sleeve is expanded against the inner wall of the metal pipeline to be welded.

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

[0019] The front metal pipeline and the rear metal pipeline to be welded are installed on the metal pipeline transition joint welding expansion mechanism: the transition joint therebetween is located on the corresponding outer side of the conical structure and the wedge surface structure of the expansion mechanism mandrel; the front metal pipeline and the rear metal pipeline are axially supported and pressed by the axial support end and the axial pressing mechanism, and the front metal pipeline and the rear metal pipeline are radially expanded by the expansion sleeve and the mandrel;

[0020] The transition joint welding is performed on the circular surface where the joint between the front metal pipeline and the rear metal pipeline is located.

[0021] The welding is performed more than one circle of the circular surface, and after the welding on the circular surface is completed, the welding is not stopped, but is continuously moved to one side of the metal pipeline, so that the stir friction welding spoon hole is not located on the circular surface of the metal pipeline transition joint.

[0022] The rear end of the front metal pipeline is provided with a first inclined surface, and the front end of the rear metal pipeline is provided with a second inclined surface which is complementary and matched with the first inclined surface of the front metal pipeline.

[0023] The third aspect of the present application provides a metal pipeline transition joint, which is a welded transition joint formed by welding two metal pipelines of different materials by using the above method.

[0024] Preferably, one metal pipeline is a steel pipeline, and the other metal pipeline is an aluminum pipeline; after the welding on the circular surface is completed, the welding is not stopped, but is continuously moved to one side of the aluminum pipeline, and then the aluminum pipeline containing the spoon hole section is cut off.

[0025] The fourth aspect of the present application provides a metal pipeline transition joint welding device, which comprises a clamping and rotating mechanism, a supporting wheel, a welding tool and the above-mentioned metal pipeline transition joint welding expansion mechanism.

[0026] The metal pipeline to be welded is arranged on the metal pipeline transition joint welding expansion mechanism, and the clamping and rotating mechanism is arranged at the rear part of the metal pipeline to be welded and the metal pipeline transition joint welding expansion mechanism, and is used for clamping and driving the metal pipeline and the metal pipeline transition joint welding expansion mechanism to rotate.

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

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

[0029] The fifth aspect of the present application provides a method for welding by using the metal pipeline transition joint welding device, comprising the following steps:

[0030] The front metal pipeline and the rear metal pipeline to be welded are installed on the metal pipeline transition joint welding expansion mechanism;

[0031] The rear end of the metal pipeline and the metal pipeline transition joint welding expansion mechanism to be welded is installed on the clamping and rotating mechanism, and the front lower end of the metal pipeline and the metal pipeline transition joint welding expansion mechanism is placed on the support wheel;

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

[0033] Compared with the prior art, the present application has the following advantages:

[0034] The metal pipeline transition joint welding expansion mechanism comprises a sleeve, a mandrel, an axial support end and an axial compression mechanism, the axial support end and the axial compression mechanism are used for axial support and compression, so that the contact ends of the metal pipelines to be welded are tightly butt-jointed, the sleeve and the mandrel are used for radial expansion, the wedge surface structure of the sleeve and the outer side surface of the conical structure of the mandrel are complementary and matched, the sleeve is sleeved outside the mandrel from the front of the mandrel, and the transition joint to be welded of the relatively connected metal pipelines is located at the corresponding outer side of the conical structure of the mandrel and the wedge surface structure of the sleeve; the sleeve and the mandrel are cooperated with the axial support end and the axial compression mechanism, so that the metal pipelines to be welded are kept stable butt-jointed and tightly combined during the whole welding process.

[0035] The metal pipeline transition joint welding expansion mechanism can be adaptively adjusted to the uneven change of the length of the metal pipeline within a certain range through the adjustable bolt of the axial compression mechanism, so as to meet the requirement of axial support and compression of the metal pipeline; the metal pipeline transition joint welding expansion mechanism can drive the sleeve to move backward relative to the mandrel and be compressed outside the mandrel through the screwing of the nut, so as to adaptively adjust the uneven change of the diameter of the metal pipeline within a certain range, and meet the requirement of radial expansion of the metal pipeline.

[0036] The two butt-jointed dissimilar metal pipe sections of the metal pipe transition joint can have a certain length, and when the metal pipe transition joint is welded with metal pipes at both ends respectively, because the weld distance is far from the dissimilar metal interface, the temperature rise at the dissimilar metal interface is limited, and therefore the mechanical properties of the dissimilar metal interface are not reduced in the case of continuous welding, which is superior to other existing dissimilar metal welding methods.

[0037] Tests show that the metal pipe transition joint has high tensile strength, good interface performance consistency, dense structure and good air tightness. The present application is particularly suitable for welding of metal pipe transition joints with high quality and good sealing performance. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The structure diagram of the expansion mechanism of the present application.

[0039] Figure 2 The structure diagram of the cross section of the expansion mechanism of the present application.

[0040] Figure 3 The structure diagram of the expansion sleeve and the expansion sleeve sheet of the present application.

[0041] Figure 4 The structure diagram of the cross section of the expansion sleeve of the present application.

[0042] Figure 5 The structure diagram of the mandrel of the present application.

[0043] Figure 6 The structure diagram of the axial compression mechanism of the present application.

[0044] Figure 7 The structure diagram of the metal pipe transition joint welding device of the present application.

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

[0046] Figure 9 The structure diagram of the metal pipe transition joint welding device from different perspectives.

[0047] Figure 10 The product diagram of the metal pipe transition joint after welding, with a spoon hole.

[0048] Figure 11 The product diagram of the metal pipe transition joint after welding, cutting and polishing, without a spoon hole.

[0049] In the figure: 1-expansion sleeve, 2-core shaft, 3-axial support end, 4-axial pressing mechanism, 5-expansion sleeve plate, 6-metal pipe transition joint setting area to be welded, 7-transition joint, 8-wedge surface structure, 9-pressing 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 pressing platform, 24-second pressing platform, 25-conical structure, 26-front end of core shaft, 27-rear end of core shaft, 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. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention.

[0051] For ease of understanding, the orientation or position relationship in the present invention is: Figure 8 As a representative place, 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 orientations or positional relationships are based on the relationships shown in the drawings and are only for the purpose of facilitating and simplifying the description of the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be understood as limiting 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, they can understand the specific meanings of the above terms in the present invention 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 pressing mechanism 4;

[0055] The expansion sleeve 1 is surrounded by several 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 core shaft 2 is a conical structure 25, such as Figure 5As shown, the outer side of the conical structure 25 is complementarily fitted with the wedge surface structure 8 of the expansion sleeve 1; the rear part of the mandrel 2 is mounted on the axial support end 3, and the expansion sleeve 1 is sleeved on the outside of the mandrel 2 from the front part of the mandrel 2; the corresponding outer sides of the conical structure 25 of the mandrel and the wedge surface structure 8 of the expansion sleeve are the setting area 6 of the metal pipeline to be welded transition joint.

[0057] The metal pipeline 28 to be welded is arranged between the axial support end 3 and the axial pressing mechanism 4, and the transition joint 7 to be welded of the metal pipeline 28 is located on the corresponding outer sides of the conical structure 25 of the mandrel 2 and the wedge surface structure of the expansion sleeve 1.

[0058] The slope of the outer side of the conical structure 25 is the same as the slope of the wedge surface of the expansion sleeve 1, and when the wedge surface of the expansion sleeve 1 is pressed around the outer side of the conical structure 25, the outer surface of the expansion sleeve 1 is expanded to the inner wall surface of the metal pipeline to be welded.

[0059] The rear end of the metal pipeline is supported on the axial support end 3 and the outer periphery of the mandrel 2, and the front end of the metal pipeline is supported on the axial pressing mechanism 4 and the outer periphery of the expansion sleeve 1.

[0060] As shown, Figure 6 The axial pressing mechanism 4 includes a pressing table 9 and a first nut 10, and the expansion sleeve sheet 5 is mounted on the pressing table 9; the pressing table 9 has a middle hole, the front end 26 of the mandrel passes through the middle hole of the pressing table 9, the front end of the mandrel 2 has an external thread, and the front end of the mandrel 2 is screwed on the pressing table 9 through the first nut 10, so that the axial pressing mechanism 4 can drive the expansion sleeve 1 to move backward relative to the mandrel 2 and press on the outside of the mandrel 2.

[0061] A plurality of small holes 20 are arranged around the middle hole on the pressing table 9, an adjustable bolt 11 passing through the small hole 20 is arranged in the small hole 20, and the small hole 20 and the adjustable bolt 11 are located in front of the metal pipeline to be welded; while the axial pressing mechanism 4 drives the expansion sleeve 1 to move backward relative to the mandrel 2, the adjustable bolt 11 is tightened, so that the pressing table 9 tightly presses the metal pipeline to be welded.

[0062] In some embodiments, the pressing table 9 includes a first pressing table 23 and a second pressing table 24, the small holes 20 and the adjustable bolts 11 are arranged on the first pressing table 23, and the second pressing table 24 is an annular table arranged between the first pressing table 23 and the metal pipeline to be welded; the adjustable bolt 11 can make the metal pipeline end face be tightly pressed and uniformly stressed by tightly pressing the second pressing table 24 on the metal pipeline end face.

[0063] The axial support end 3 includes a support table 21 and a second nut 22, the support table 21 has a middle hole, the rear end 27 of the mandrel passes through the middle hole of the support table 21, the rear end of the mandrel 2 has an external thread, and the rear end of the mandrel 2 is screwed on the support table 21 through the second nut 22.

[0064] In some embodiments, the outer wall of the expansion sleeve 5 has a step 12, as shown in the figure. Figure 4 As shown in the figure, 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 structure 8 of the expansion sleeve 1.

[0065] The step 12 is arranged to enable the expansion sleeve 1 to mainly apply the expansion effect on the corresponding side of the wedge structure 8 of the expansion sleeve 1, i.e. the position of the transition joint 7 of the metal pipe to be welded. Due to the arrangement of the step 12, the diameter of the front section of the expansion sleeve 1 is relatively smaller than the diameter of the rear section of the expansion sleeve 1, which can make it easier to take out the expansion sleeve 1 and the mandrel 2 inside the expansion sleeve 1 from the rear side of the metal pipe after the welding process is completed, reduce the difficulty of taking out, avoid damaging the product, and ensure the quality of the product.

[0066] Embodiment 2

[0067] A metal pipe transition joint welding device, as shown in the figure, Figure 7 , 8 , 9, comprises a clamping and rotating mechanism 13, a supporting wheel 14, a welding tool, and the metal pipe transition joint 7 welding expansion mechanism of embodiment 1.

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

[0069] The supporting wheel 14 is arranged at the bottom of the metal pipe to be welded 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] Embodiment 3

[0073] A metal pipe transition joint welding method, which adopts the metal pipe transition joint welding device of embodiment 2, and 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 side of the conical structure 25 of the mandrel 2 and the wedge 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 mandrel 2.

[0075] In operation, the front end of the mandrel 2 is screwed onto the pressing platform 9 by 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 press against the outer side of the mandrel 2; the adjustable bolt 11 on the axial pressing mechanism 4 is tightened to axially press the metal pipe to be welded against the rear end of the expansion sleeve;

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

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

[0078] The welding is performed beyond one circle (more than 360°), and after the circumferential surface welding is completed, the welding is not stopped, but is continued to move to one side of the metal pipe, so that the stir-frying hole is not located 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 complementary to the first inclined surface 16 of the front metal pipe, so that the assembly is more stable and the welding quality is improved.

[0080] Example 4

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

[0082] Wherein, one side of the metal pipe is a steel pipe 18, and the other side of the metal pipe is an aluminum pipe 19, forming 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, after the circumferential surface welding is completed, the welding is not stopped, but is continued to move to the aluminum pipe 19 to a certain distance and then cut off the aluminum pipe 19 containing the stir-frying hole segment, such as Figure 10 , so that the overall product does not contain the stir-frying hole, and after polishing, a perfect transition joint pipe can be formed, such as Figure 11 .

[0085] Example 5

[0086] Taking a specific test of the scheme in Example 4 as an example, wherein the length of the aluminum pipe part is 65 mm, the inner diameter is 33 mm, and the outer diameter is 45 mm, the length of the steel pipe part is 45 mm, the inner diameter is 33 mm, and the outer diameter is 45 mm, the actual product after welding is tested as follows:

[0087] (1) The aluminum steel transition joint pipe is applied to welding, and the temperature test at the aluminum steel interface is as follows:

[0088] When the steel end of the steel pipe part of the aluminum steel transition joint pipe is welded with other steel pipes, and the aluminum end of the aluminum pipe part is welded with other aluminum pipes, the weld of the re-welding is far away from the steel aluminum interface of the welding of the present application. It is determined that the temperature at the aluminum steel interface of the aluminum steel transition joint does not exceed 300 DEG C, and therefore the application to the welding has less influence on the aluminum steel interface. Even in the case of continuous welding, the mechanical properties of the aluminum steel interface will not be reduced. Therefore, the aluminum steel transition joint pipe can ensure the smooth construction when applied, and the influence of the construction on the quality of the aluminum steel transition joint does not need to be considered at all times.

[0089] (2) Tensile strength test:

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

[0091] (3) Extrusion test:

[0092] The weld is subjected to the extrusion test, and it is determined that the structure is compact.

[0093] (4) Air tightness test:

[0094] The weld is subjected to the helium detection test, and the helium detection qualified rate is more than 99.9%, and the air tightness reaches a high standard. The weld quality of the product of the present application is high, and especially the sealing property has a significant advantage, and is particularly suitable for high-tech fields such as aviation and high-end manufacturing.

[0095] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any person skilled in the art, without departing from the technical solution of the present application, according to the technical essence of the present application, any simple modification, equivalent replacement and improvement of the above embodiment, etc. still belongs to the protection scope of the technical solution of the present application.

Claims

1. A metal pipe transition joint welding and expanding mechanism, characterized by: The expansion sleeve, the mandrel, the axial support end and the axial compression mechanism are included. The expansion sleeve is formed by several expansion sleeve pieces. The middle part of the mandrel is a conical structure, and the outer side slope of the conical structure is complementary to the inner side wedge surface of the expansion sleeve. The axial support end and the axial compression mechanism are connected by a metal pipe setting area. The axial compression mechanism includes a compression platform. The front end of the expansion sleeve piece is installed on the compression platform. The middle hole of the compression platform is surrounded by a small hole.

2. The metal pipe transition joint weld-bushing mechanism of claim 1, wherein: The adjustable bolt is located in front of the front end face of the metal pipe to be welded.

3. The metal pipe transition joint weld-bushing mechanism of claim 1, wherein: The axial compression mechanism drives the expansion sleeve to move backward relative to the mandrel.

4. The metal pipe transition joint weld and swell mechanism of claim 1, wherein: The adjustable bolt is located in front of the front end face of the metal pipe to be welded.

5. A method of welding a metal pipe transition joint, characterized by: The axial compression mechanism drives the expansion sleeve to move backward relative to the mandrel. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end face of the metal pipe to be welded. The adjustable bolt is located in front of the front end 6. The method of claim 5, wherein: The welding is continued to the metal pipe on one side after the welding of the circumferential surface is finished, so that the stir friction welding spoon hole is not located on the circumferential surface of the metal pipe transition joint.

7. The method of claim 5, wherein: The rear end of the front metal pipe is provided with a first inclined surface, and the front end of the rear metal pipe is provided with a second inclined surface which is complementary to the first inclined surface of the front metal pipe.

8. A metal pipe transition joint characterized by: The welded transition joint formed by welding two sections of dissimilar metal pipes by the method of any one of claims 5-7.

9. A metal pipe transition joint welding apparatus characterized by: The metal pipe transition joint welding expansion mechanism comprises a clamping and rotating mechanism, a supporting wheel, a welding tool and the metal pipe transition joint welding expansion mechanism of any one of claims 1-4. 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 to clamp and drive the rotation of the metal pipe and the metal pipe transition joint welding expansion mechanism. The supporting wheel is arranged at the bottom of the metal pipe to be welded to support the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism. The welding tool is a stir friction welding device.

10. A method for welding by using the metal pipe transition joint welding device of claim 9, characterized in that: the front metal pipe and the rear metal pipe to be welded are arranged on the metal pipe transition joint welding expansion mechanism; the rear end of the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism is arranged on the clamping and rotating mechanism, and the front lower end of the metal pipe and the metal pipe transition joint welding expansion mechanism is arranged on the supporting wheel; the clamping and rotating mechanism is rotated to drive the rotation of the metal pipe to be welded and the metal pipe transition joint welding expansion mechanism, and the transition joint welding is performed along the circumferential surface of the joint between the front metal pipe and the rear metal pipe by the stir friction welding device.

Images