Mechanical welding method for butt joint of close-packed pipe joints and pipes of header in narrow and small space

Abstract

The invention provides a mechanical welding method for butt joint of a close-packed pipe joint and a pipe of a header in a narrow and small space, and belongs to the technical field of welding methods. The problems of high labor intensity, low working efficiency, small welding operation space and high welding difficulty during welding of close-packed header pipe joints and pipes in a narrow space are solved. The high-frequency pulse argon arc welding device is provided with a high-frequency pulse argon arc welding power source so that the influence of heat accumulation on welding seam forming can be effectively reduced, and due to the fact that the inner diameter of the heat exchange pipe is small, existing equipment cannot achieve internal wire filling welding. According to the method, the base metal on the two sides and the embedded ring are heated and melted through the electric arc, the welding pool is formed to generate the welding metallurgical reaction, liquid metal in the pool is solidified to form the weld joint after the electric arc passes through, inner hole butt welding is achieved, and it can be guaranteed that the root of the weld joint is completely welded through the method. And after internal welding is completed, a welding joint is basically thoroughly welded, and the welding quality is ensured through external welding, so that the welding joint is attractive in molding and full-penetration of the welding joint is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of welding methods, and relates to a welding method for boilers and pressure vessels, and in particular to a mechanical welding method for butting close-packed pipe joints of a header in a narrow space with pipes. Background Art

[0002] Take the serpentine tube bundle assembly (referred to as the tube system) as an example. It is mainly composed of a header assembly, a serpentine tube bundle and a tube bundle support. When assembling the tube system, the header is fixed on the assembly platform in a vertical state, and the pipe rack is erected. The serpentine tube bundle is welded layer by layer from one end (bottom) of the header to the other end (top) along the circumference of the header. Due to structural limitations, the gap between each layer of serpentine heat exchange tubes is narrow, such as Figure 1-3 shown.

[0003] At present, manual argon arc welding is mainly used to weld the joints of closely packed headers in narrow spaces and pipes, using V-shaped welding grooves and wire welding. This method is not only labor-intensive and has poor working conditions, but also has blind spots during welding due to the small spacing between heat exchange tubes and fixed welding positions. The operation space is small, the welding is difficult, and the welding quality is greatly affected by the welder's level. Therefore, this method often has problems such as low welding efficiency and low welding qualification rate. Summary of the invention

[0004] In view of this, in order to solve the problems of high labor intensity, low work efficiency, small welding operation space, and great welding difficulty when welding closely spaced header pipe joints and pipes in a narrow space, the present invention proposes a mechanical welding method for connecting closely spaced header pipe joints and pipes in a narrow space.

[0005] To achieve the above object, the present invention adopts the following technical solution: a mechanical welding method for butt-jointing close-packed pipe joints and pipes in a narrow space header, suitable for welding heat exchange tubes with an inner diameter of ≥16mm and a wall thickness of 2.5-8mm to headers, specifically comprising the following steps:

[0006] S1. Welding groove adopts I-type groove;

[0007] S2. There are two docking methods: when the pipe wall thickness T is less than 3mm, the pipe is directly docked with the header pipe joint and fixed with a special tooling; when the pipe wall thickness T is greater than or equal to 3mm, the pipe is docked with the header pipe joint and the two are connected with an embedded ring;

[0008] S3. Use a high-frequency pulse tungsten electrode argon arc welding power source with a pulse value ≥10000Hz and an internal welding torch to perform full-position welding on the heat exchange tube and header, wherein the welding speed is 30-100mm / min, the tungsten electrode distance is 1.0-2.5mm, the preheating current is 80-150A, the preheating time is 2-5s, the current rise time is 0-2s, the welding pulse base current is 30-100A, the welding pulse peak current is 100-300A, the welding arc voltage is 9-15V, the advance ventilation time is 2-10s, the current start decay angle is 360-450°, the current decay time is 2-5s, the stop rotation angle is 365°-460°, the delayed gas stop time is 1-10s, the overlap length is ≥2mm, the shielding gas is argon, the flow rate is 2-16L / min, and the back shielding gas is argon, the flow rate is 6-12L / min;

[0009] S4. Use a high-frequency pulse tungsten electrode argon arc welding power supply with a pulse value ≥10000Hz and an external welding torch to perform full-position external welding of the heat exchange tubes and headers, with a welding speed of 60-150mm / min, a tungsten electrode distance of 0.8-2.5mm, a preheating current of 80-150A, a preheating time of 2-5s, a current rise time of 0-2s, a welding base current of 40-120A, a welding peak current of 100-200A, a welding voltage of 9-14V, a base time of 0.05-0.5s, a peak time of 0.05-0.5s, an advance ventilation time of 1-5s, a current start attenuation angle of 360-380°, a current attenuation time of 1-5s, a stop rotation angle of 365°-425°, a delayed gas stop time of 2-10s, an overlap angle ≥2°, and the shielding gas is argon with a flow rate of 4-15L / min.

[0010] Furthermore, in step S3, the welding direction of the internal welding gun is clockwise or counterclockwise.

[0011] Furthermore, in step S4, the welding direction of the external welding gun is clockwise or counterclockwise.

[0012] Furthermore, in step S4, the welding direction of the outer welding gun is opposite to the welding direction of the inner welding gun.

[0013] Furthermore, the shielding gas used in the internal welding and the external welding is argon gas with a purity of ≥99.99%, and the back shielding gas used in the internal welding is argon gas with a purity of ≥99.99%.

[0014] Furthermore, in step S3, the preheating current is 100-110A, the preheating time is 2s, the current rise time is 1s, the welding arc voltage is 10-13V, the advance ventilation time is 5-7s, the current start attenuation angle is 410°, the current decay time is 1s, the stop rotation angle is 410°, and the delayed gas stop time is 5s.

[0015] Furthermore, in step S4, the preheating current is 80-100A, the preheating time is 3s, the current rise time is 1s, the welding voltage is 10-13V, the base time is 0.1s, the pulse time is 0.1s, the advance ventilation time is 5s, the current start attenuation angle is 380°, the current attenuation time is 5s, the stop rotation angle is 400°, the delayed gas stop time is 10s, and the overlap angle is 20°.

[0016] Compared with the prior art, the mechanical welding method for butting close-packed pipe joints and pipes in a narrow space header described in the present invention has the following beneficial effects:

[0017] 1. The high-frequency pulse argon arc welding power supply of the present invention can effectively reduce the influence of heat accumulation on weld formation. Due to the small inner diameter of the heat exchange tube, the existing equipment cannot realize internal wire welding. Therefore, the method heats the parent materials and the embedded ring on both sides by electric arc and melts them to form a welding pool for welding metallurgical reaction. After the arc passes, the liquid metal in the molten pool solidifies to form a weld, realizing inner hole butt welding. This method can ensure that the root of the weld is fully penetrated. After the internal welding is completed, the weld joint is basically welded through, and then the weld quality is guaranteed by external welding, so that the weld is beautifully shaped and the weld joint is fully welded through. Therefore, the welding method of this method can effectively guarantee the welding quality of the joint, and can achieve complete penetration and defect-free joints.

[0018] 2. Compared with manual welding, the present invention greatly reduces the labor intensity of workers, increases the welding efficiency by about one time, has stable and reliable welding quality, beautiful weld formation and excellent performance, and realizes the mechanical welding of the closely spaced pipe joints of the header and the pipe in a narrow space. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 It is a schematic diagram of the serpentine high-pressure heater piping system and header mentioned in the background technology of the present invention;

[0021] Figure 2 It is a top view of the serpentine high pressure heating system mentioned in the background technology of the present invention;

[0022] Figure 3 It is a cross-sectional view of the serpentine high-pressure heater pipe system mentioned in the background technology of the present invention;

[0023] Figure 4 It is a schematic diagram of I-type groove;

[0024] Figure 5 This is a schematic diagram of the connection between the pipe and the header pipe joint when the pipe wall thickness T is less than 3mm;

[0025] Figure 6 This is a schematic diagram of the connection between the pipe and the header pipe joint when the pipe wall thickness T≥3mm;

[0026] Figure 7 Schematic diagram of the embedded ring shape;

[0027] Figure 8 is a cross-sectional view of the embedded ring;

[0028] Fig. 9 It is a schematic diagram of the internal welding equipment;

[0029] Fig.10 This is a schematic diagram of internal welding;

[0030] Fig.11 This is the main view of the internal welding process;

[0031] Fig.12 This is the left view of the internal welding process;

[0032] Fig.13 It is a schematic diagram of external welding equipment;

[0033] Fig.14 This is a schematic diagram of external welding;

[0034] Fig.15 This is the main view of the external welding;

[0035] Fig.16 This is the left view of external welding.

[0036] In the figure: 1-header cylinder, 2-header pipe joint, 3-serpentine tube bundle, 4-embedded ring, 5-tooling, 6-power supply, 7-internal welding gun, 8-control cabinet, 9-water tank, 10-ground wire, 11-tungsten electrode, 12-pipe, 13-external welding gun, 14-control cabinet and water tank, 15-power supply. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0038] See also Figure 4-16 The present embodiment is described as a mechanical welding method for butting a close-packed pipe joint of a header in a narrow space with a pipe, comprising the following steps:

[0039] S1. First, welding adopts I-type groove, such as Figure 4As shown, the heat exchange tubes and headers are placed and fixed according to the drawings, and the welding groove is an I-type groove. This type of groove not only saves the cost of processing the groove, but also reduces the amount of filler metal. When using an I-type groove, choose whether to use an insert ring according to the wall thickness of the tube, and the size of the insert ring should be processed according to the requirements of the article.

[0040] S2. There are two docking methods: When the pipe wall thickness T is less than 3mm, the pipe 12 can be directly docked with the header pipe joint 2 and fixed with the tooling 5. Figure 5 shown.

[0041] When the pipe wall thickness T≥3mm, the pipe 12 is butt-jointed with the header pipe joint 2, and the two are connected by an insert ring 4, such as Figure 6 The two sides of the embedded ring 4 are closely fitted with the pipe end and the header pipe joint 2, and the specific shape and size are selected according to the size of the pipe end and the header pipe joint.

[0042] The insert ring 4 is the key point of this method. The dimensions of each part of the insert ring are processed according to the given requirements. It can not only fix the pipe on the header pipe joint 2, play the role of assembly and fixing, but also avoid the excessive misalignment during assembly, ensure the concentricity of the header pipe joint 2 and the pipe 12, but also can be used as filler metal to ensure the metallurgical process of the welded joint is stable and alloyed during welding, and better guarantee the performance of the welded joint. At the same time, through the reasonable design of the insert ring structure, it can also ensure that the weld surface has a certain excess height, so that the weld is better formed and has higher strength. The appearance diagram of the insert ring 4 is as follows Figure 7-8 The dimensions of the insert ring are shown in Table 1. The material of the insert ring 4 is selected according to the welding material standard of the corresponding parent material.

[0043] Table 1 Insert ring size table

[0044]

[0045] S3, internal welding uses high-frequency pulse tungsten inert gas arc welding power supply 6, internal welding welding gun 7, water tank 9, control cabinet 8, etc., and internal welding equipment such as Fig. 9 shown.

[0046] Insert the internal welding torch 7 from the inside of the header cylinder 1 into the header pipe joint 2 to be welded, determine the position of the tungsten electrode 11, and connect and fix the pipe 12 to the header pipe joint 2 with the tooling 5. The internal welding diagram is as follows: Fig.10 shown.

[0047] High-frequency pulse (≥10000Hz) tungsten inert gas arc welding power source and internal welding torch are used to perform clockwise internal welding on the heat exchange tube and header in all positions, wherein the welding speed is 30-100mm / min, the tungsten electrode distance is 1.0-2.5mm, the preheating current is 80-150A, the preheating time is 2-5s, the current rise time is 0-2s, the welding pulse base current is 30-100A, the welding pulse peak current is 100-300A, the welding arc voltage is 9-15V, the advance ventilation time is 2-10s, the current start decay angle is 360-450°, the current decay time is 1-5s, the stop rotation angle is 365°-460°, the delayed gas stop time is 1-10s, the overlap length is ≥2mm, the shielding gas is argon, the flow rate is 2-16L / min, the back shielding gas is argon, the flow rate is 6-12L / min, and the welding schematic diagram is as follows Figure 11-12 shown.

[0048] Use internal welding torch to weld pipes and headers, welding position is full position. Welding direction can be clockwise or counterclockwise.

[0049] The preferred solution is: use a high-frequency pulse (≥10000Hz) tungsten electrode argon arc welding power supply and an internal welding torch to perform clockwise internal welding on the heat exchange tube and the header, with a welding speed of 30-100mm / min, a tungsten electrode distance of 1.0-2.5mm, a preheating current of 100-110A, a preheating time of 2s, a current rise time of 1s, a welding pulse base current of 30-100A, a welding pulse peak current of 100-300A, a welding voltage of 10-13V, an advance ventilation time of 5-7s, a current start attenuation angle of 410°, a current attenuation time of 1s, a stop rotation angle of 410°, and a delayed gas stop time of 5s.

[0050] S4. After the internal welding is completed, external welding is used to ensure the welding quality. The external welding equipment includes a high-frequency pulse tungsten inert gas arc welding power supply 15, an external welding torch 13, a control cabinet and a water tank 14, etc. The equipment diagram is as follows Fig.13 shown.

[0051] According to the length of the pipe joint, adjust the front end top wire of the external welding torch 13 to ensure that the tungsten electrode 11 is positioned directly opposite the center of the embedded ring 4 during welding, and then install the external welding torch on the heat exchange tube after internal welding for welding. Fig.14 shown.

[0052] Use an external welding torch to perform full-position welding on the heat exchange tube and header, with a welding speed of 60-150 mm / min, a tungsten electrode distance of 0.8-2.5 mm, a preheating current of 80-150 A, a preheating time of 2-5 s, a current rise time of 0-2 s, a welding base current of 40-120 A, a welding peak current of 100-200 A, a welding voltage of 9-14 V, a base time of 0.05-0.5 s, a peak time of 0.05-0.5 s, an advance ventilation time of 2-5 s, a current start decay angle of 360-380°, a current decay time of 1-5 s, a stop rotation angle of 365°-425°, a delayed gas stop time of 2-10 s, an overlap angle ≥2°, and an argon gas with a flow rate of 4-15 L / min. The welding process is as follows: Figure 15-16 As shown, the welding direction can be clockwise or counterclockwise (preferably opposite to the internal welding direction).

[0053] The preferred solution is: use a high-frequency pulse tungsten electrode argon arc welding power supply and an external welding torch to perform counterclockwise external welding on the heat exchange tube and the header, with a welding speed of 60-150 mm / min, a tungsten electrode distance of 0.8-2.5 mm, a preheating current of 80-100 A, a preheating time of 3 s, a current rise time of 1 s, a welding base current of 40-120 A, a welding peak current of 100-200 A, a welding voltage of 10-13 V, a base time of 0.1 s, a pulse time of 0.1 s, an advance ventilation time of 5 s, a current start attenuation angle of 380°, a current attenuation time of 5 s, a stop rotation angle of 400°, a delayed gas stop time of 10 s, and an overlap angle of 20°.

[0054] The heat exchange tube and the header are externally welded using an external welding torch 13, and the welding position is full position. The welding direction can be clockwise or counterclockwise (preferably opposite to the internal welding direction).

[0055] To prevent weld oxidation, the shielding gases used in the internal and external welding are both argon with a purity ≥99.99%. The back shielding gas used in the internal welding is argon with a purity ≥99.99%. The gas flow rate of the shielding gas used in the internal and external welding is 2-12L / min, and the gas flow rate of the back shielding gas used in the internal welding is 6-12L / min.

[0056] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A mechanical welding method for butt joints between closely spaced pipe joints and pipes in a narrow space header, suitable for welding heat exchange tubes with an inner diameter of ≥16mm and a wall thickness of 2.5-8mm to headers, characterized in that: The specific steps include: S1. Welding groove adopts I-type groove; S2. There are two docking methods: when the pipe wall thickness T is less than 3mm, the pipe is directly docked with the header pipe joint and fixed with a tooling; when the pipe wall thickness T is greater than or equal to 3mm, the pipe is docked with the header pipe joint and the two are connected with an embedded ring; S3. Use a high-frequency pulse tungsten electrode argon arc welding power source with a pulse value of ≥10000Hz and an internal welding torch to perform full-position welding on the heat exchange tube and header, wherein the welding speed is 30-100mm / min, the tungsten electrode distance is 1.0-2.5mm, the preheating current is 80-150A, the preheating time is 2-5s, the current rise time is 0-2s, the welding pulse base current is 30-100A, the welding pulse peak current is 100-300A, the welding arc voltage is 9-15V, the advance ventilation time is 2-10s, the current start decay angle is 360-450°, the current decay time is 1-5s, the stop rotation angle is 365°-460°, the delayed gas stop time is 1-10s, the overlap length is ≥2mm, the shielding gas is argon, the flow rate is 2-16L / min, and the back shielding gas is argon, the flow rate is 6-12L / min; S4. Use a high-frequency pulse tungsten electrode argon arc welding power supply with a pulse value ≥10000Hz and an external welding torch to perform full-position external welding of the heat exchange tubes and headers, with a welding speed of 60-150mm / min, a tungsten electrode distance of 0.8-2.5mm, a preheating current of 80-150A, a preheating time of 2-5s, a current rise time of 0-2s, a welding base current of 40-120A, a welding peak current of 100-200A, a welding voltage of 9-14V, a base time of 0.05-0.5s, a peak time of 0.05-0.5s, an advance ventilation time of 2-5s, a current start attenuation angle of 360-380°, a current attenuation time of 1-5s, a stop rotation angle of 365°-425°, a delayed gas stop time of 2-10s, an overlap angle ≥2°, and the shielding gas is argon with a flow rate of 4-15L / min.

2. The mechanical welding method for butting close-packed pipe joints of a narrow space header and a pipe according to claim 1 is characterized in that: In step S3, the welding direction of the inner welding gun is clockwise or counterclockwise.

3. The mechanical welding method for butting close-packed pipe joints of a narrow space header and a pipe according to claim 1 is characterized in that: In step S4, the welding direction of the external welding gun is clockwise or counterclockwise.

4. The mechanical welding method for butting close-packed pipe joints of a narrow space header and a pipe according to claim 3 is characterized in that: In step S4, the welding direction of the outer welding gun is opposite to the welding direction of the inner welding gun.

5. The mechanical welding method for butting close-packed pipe joints of a narrow space header and a pipe according to claim 1 is characterized in that: The shielding gas used for internal welding and external welding is argon with a purity of ≥99.99%. The back shielding gas used for internal welding is argon with a purity of ≥99.99%.

6. The mechanical welding method for butting close-packed pipe joints of a narrow space header and a pipe according to claim 1 is characterized in that: In step S3, the preheating current is 100-110A, the preheating time is 2s, the current rise time is 1s, the welding arc voltage is 10-13V, the advance ventilation time is 5-7s, the current start decay angle is 410°, the current decay time is 1s, the stop rotation angle is 410°, and the delayed gas stop time is 5s.

7. The mechanical welding method for butting close-packed pipe joints of a narrow space header with a pipe according to claim 1 is characterized by: In step S4, the preheating current is 80-100A, the preheating time is 3s, the current rise time is 1s, the welding voltage is 10-13V, the base time is 0.1s, the pulse time is 0.1s, the advance ventilation time is 5s, the current start attenuation angle is 380°, the current attenuation time is 5s, the stop rotation angle is 400°, the delayed gas stop time is 10s, and the overlap angle is 20°.

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