Welding method for circumferential weld of barrel and application

Abstract

The invention provides a welding method for a circumferential weld of a barrel and application, and belongs to the field of pipeline welding. The welding method comprises the following steps: 1) preparing accessories; (2) preparation before welding is conducted, specifically, an assembling gap is set, a welding groove is formed, and a truncated edge is formed; wherein when the wall thickness t of the cylinder is larger than or equal to 10 mm and smaller than or equal to 40 mm, the assembly clearance g is 3-10 mm; wall thickness tgt; when the thickness is 40 mm, the assembly clearance g is 0 mm; a single V-shaped groove or a double V-shaped groove is formed; the groove angle theta of the single V-shaped groove ranges from 35 degrees to 40 degrees; the angle theta of an upper groove of the double-V-shaped groove is 30-35 degrees, and the angle alpha of a lower groove of the double-V-shaped groove is 35-40 degrees; (3) single-pass welding is conducted on the circumferential weld of the cylinder through a gas-electric welding method; in the welding process, carbon dioxide gas shielded welding is adopted for welding; and (4) post-welding treatment. Gas electric welding and single-pass welding are adopted, the welding defects of the circumferential weld of the cylinder are reduced, and the welding quality and efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline welding, and in particular relates to a welding method and application of a cylinder girth weld. Background Art

[0002] At present, for butt welding of thick-walled and large-diameter pipes, carbon dioxide gas shielded welding and submerged arc welding are usually used for multi-layer and multi-pass welding. However, the existing technology has a low heat input, generally only up to 80kJ / cm, and the welding workload is large while the efficiency is low and the welding cycle is long. In addition, the welding quality of multi-layer and multi-pass welding is unstable, and it is easy to have problems such as pores, slag inclusions, and incomplete fusion.

[0003] Gas-electric welding is a widely used welding process with stable welding quality and high welding efficiency. Applying gas-electric welding to butt welding of thick-walled and large-diameter pipes can improve competitiveness, help improve efficiency in terms of overall efficiency, reduce material and energy consumption, and reduce overall costs. Summary of the invention

[0004] The present invention provides a welding method and application of a cylinder (or pipeline) girth weld, wherein gas-electric welding is used to perform single-pass welding on the cylinder girth weld, and the method is suitable for butt jointing of pipelines with a diameter of more than 4 meters and a thickness of more than 10 mm. The welding method can be applied to various types of cylindrical steel structures, reduces the difficulty of operation, has high welding efficiency, and has a high welding pass rate, and can reduce the probability of pores, slag inclusions and cracks. In addition to welding joints, the single-pass welding can achieve a 100% pass rate of one-time welding.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions.

[0006] In a first aspect, the present invention provides a method for welding a cylinder girth weld, comprising the following steps:

[0007] 1) Accessories preparation: prepare the base material, welding materials and auxiliary materials of the cylinder, and prepare the internal annular gasket, surface arc slider and double-sided welded internal arc slider according to the size of the cylinder;

[0008] 2) Preparation before welding: The preparation before welding includes setting the assembly gap (or assembling the pipe joint), opening the welding groove and opening the blunt edge;

[0009] 3) Welding process: gas-electric welding is used to perform single-pass welding on the cylinder girth weld; in the welding process, carbon dioxide gas shielded welding is used for welding;

[0010] 4) Post-weld treatment.

[0011] As an optional implementation, when preparing the cylinder base material, a high-energy line welding test is performed on the cylinder base material to test the strength and low-temperature toughness value of the coarse-grained zone in the heat-affected zone of the joint after the cylinder base material is subjected to high-energy line heat input.

[0012] As an optional embodiment, the welding material includes gas-electric welding wire and back-filled gas shielded welding wire.

[0013] As an optional implementation, the material grades of the gas-electric welding wire or the back-filled gas shielded welding wire include 4Y and 5Y.

[0014] As an optional implementation manner, the 4Y includes any one of A-E, AH32-DH32, AH36-H36, Q235A-Q235D and Q355A-Q355D.

[0015] As an optional implementation manner, the 5Y includes any one of E, EH32-EH36, Q235E and Q355E.

[0016] As an optional implementation, the gas-electrode welding wire and the back-filling gas shielded welding wire may be made of the same material grade.

[0017] As an optional implementation, the internal annular liner is mainly made of ceramic, and the outside of the ceramic is reinforced with iron sheet; optionally, the curvature of the internal annular liner is consistent with the inner ring of the cylinder.

[0018] As an optional implementation, the main body of the surface arc-shaped slider is made of brass and is used for single-sided welding of the cylinder ring weld.

[0019] As an optional implementation, the curvature of the surface arc-shaped sliding block is consistent with the outer ring of the cylinder.

[0020] As an optional implementation, the main body of the double-sided welding internal arc-shaped slider is made of brass and is used for double-sided welding of the cylinder ring weld.

[0021] As an optional implementation, the curvature of the double-sided welded internal arc-shaped slider is consistent with the inner ring of the cylinder.

[0022] As an optional implementation, the surface arc slider or the double-sided welded internal arc slider adapts to the curvature of the cylinder, and the height is perpendicular to the arc surface section and is controlled at 55 to 60 mm.

[0023] As an optional implementation, in the step 2), during the process of assembling the butt joint of the cylinder, the position of the butt joint of the cylinder is determined by installing a code plate on the back side of the groove inside the cylinder.

[0024] As an alternative embodiment, in step 2), there are at least two code plates.

[0025] As an alternative embodiment, in step 2), the installation spacing between the code plates is 300 mm to 350 mm.

[0026] As an alternative embodiment, in step 2), the code plate is an "H"-shaped code.

[0027] As an alternative embodiment, in step 2), the assembly gap for assembling the butt joint of the cylinder body is set according to the wall thickness of the cylinder body.

[0028] Optionally, when the wall thickness t of the cylinder body is 10 mm ≤ t ≤ 40 mm, the assembly gap g is set to 3 mm to 10 mm.

[0029] Optionally, when the wall thickness t of the cylinder body > 40 mm, the assembly gap g is set to 0 mm.

[0030] As an alternative embodiment, in step 2), the welding groove is opened as a single V-groove or a double V-groove according to the wall thickness of the cylinder body, and a root face is opened at the narrow end of the welding groove.

[0031] As an alternative embodiment, in step 2), the groove angle θ of the single V-groove is 35° to 40° (for example, 35° or 38°).

[0032] As an alternative embodiment, in step 2), the double V-groove includes an upper groove angle θ and a lower groove angle α. The upper groove angle θ is 30° to 35° (for example, 30° or 35°), and the lower groove angle α is 35° to 40° (for example, 35° or 38°).

[0033] As an alternative embodiment, in step 2), when the wall thickness of the cylinder body is 10 mm ≤ t ≤ 28 mm (or 10 - 28 mm, for example, 12 mm, 15 mm, 20 mm, 22 mm, 25 mm or 27 mm), the shape of the welding groove is a single V-groove, the groove angle θ is 35° to 40° (for example, 36°, 37°, 38° or 39°), the assembly gap g is 3 mm to 10 mm (for example, 5 mm, 6 mm, 7 mm or 9 mm), and the root face height h is 0 to 1 mm (for example, 0.2 mm, 0.5 mm or 0.8 mm).

[0034] As an alternative embodiment, in step 2), when the wall thickness of the cylinder body is 28 mm < t ≤ 30 mm, the shape of the welding groove is a single V-groove, the groove angle θ is 35° to 40°, the assembly gap g is 3 mm to 10 mm, and the root face height h is 0 to 1.

[0035] As an optional implementation, in step 2), the wall thickness of the cylinder is 30mm<t≤40mm, the shape of the welding groove is a single V-shape, the groove angle θ is 25°~30°, the assembly gap g is 3mm~10mm, and the blunt edge height h is 0~1.

[0036] As an optional implementation, the wall thickness of the cylinder is t>40mm, the shape of the welding groove is double V-shaped, the groove angle θ is 30°~35°, the groove angle α is 35°~40°, the assembly gap g is 0, and the blunt edge h is 0~1mm.

[0037] As an optional implementation, the step 2) further includes the following steps: installing an arc-starting support plate, checking the error range during the installation process, groove processing, weld processing, and installing a gasket and a copper slider.

[0038] As an optional implementation, the arc-starting support plate is installed at the arc-starting position of the cylinder body to establish a gas-electric welding molten pool.

[0039] As an optional implementation, the arc-striking support plate includes a flat plate structure at the bottom and a triangular cone structure at the top, the height of the triangular cone is the same as the wall thickness of the cylinder, and the angle of the triangular cone is the same as the angle of the V-shaped groove.

[0040] As an optional implementation, before welding, the arc-starting support plate is installed perpendicular to the groove at the starting point of welding, in contact with the copper slider to form a "bowl"-shaped space, providing conditions for the establishment of the molten pool.

[0041] As an optional implementation, the length L of the arc-striking support plate (including the height of the triangular pyramid and the height of the flat plate) is greater than 20% of the wall thickness of the cylinder.

[0042] As an optional implementation, the error range during the installation process includes the following aspects: the misalignment of the joint installation does not exceed 1.5mm, and the local wave deformation unevenness of the pipe surface on one side of the installation track does not exceed 2mm within 0.5m. That is, the unevenness is ≤2mm / 0.5m joint.

[0043] As an optional implementation, the groove treatment includes: cleaning the surface debris within 30 mm on both sides of the front of the groove to keep the part to be welded clean.

[0044] As an optional embodiment, the weld processing includes: ensuring that there is no obstacle on the cylinder surface on the left side or right side of the weld that would hinder the gas-electric welding equipment.

[0045] As an optional implementation, the installation of the liner should be positive to the center line of the groove, the liner should be tightly connected, and the assembly code and the welding holes on the back member should be used as support to tighten the liner with small pointed iron or pointed wood to make it close to the inner surface of the cylinder.

[0046] As an optional implementation, the installation of the slider should control the slider pressing pressure to be between 10 and 15 kgf (for example, 12 kgf).

[0047] As an optional implementation, in step 3), the welding process includes the following steps:

[0048] 31) Connect water, electricity and gas, and confirm that the water pressure and gas flow meet the usage requirements;

[0049] 32) Establish a molten pool and use carbon dioxide gas shielded welding for gas-electric welding.

[0050] As an optional implementation, in the step 3), the molten pool is established without the welding wire swinging.

[0051] As an optional embodiment, in step 3), after the molten pool is established, welding is performed by controlling the welding speed through the rolling speed of a rolling device under the swinging of the welding wire, wherein the rolling speed of the rolling device is selected according to the wall thickness of the cylinder to control the welding speed.

[0052] Optionally, when the cylinder wall thickness is 10 to 14 mm, the welding speed is 10 to 12 cm / min;

[0053] When the wall thickness of the cylinder is 14 to 20 mm (excluding 14 mm), the welding speed is 8 to 10 cm / min (excluding 10 cm / min);

[0054] When the wall thickness of the cylinder is 20-25 mm (excluding 20 mm), the welding speed is 6-8 cm / min (excluding 8 cm / min);

[0055] When the wall thickness of the cylinder is 25 to 35 mm (excluding 25 mm), the welding speed is 5 to 7 cm / min.

[0056] As an optional implementation, in step 3), the process parameters of gas-electric welding are selected according to the wall thickness of the cylinder.

[0057] Optionally, when the cylinder wall thickness is 10-14 mm, the welding current is 300-320 A (for example, 305 A, 310 A or 315 A), and the welding voltage is 32-34 V (for example, 33 V);

[0058] When the wall thickness of the cylinder is 14-20 mm (excluding 14 mm), the welding current is 340-360 A (for example, 345 A, 350 A or 355 A), and the welding voltage is 34-36 V (excluding 34 V);

[0059] When the wall thickness of the cylinder is 20-25 mm (excluding 20 mm), the welding current is 360-380 A (excluding 360 A), and the welding voltage is 36-40 V (excluding 36 V);

[0060] When the wall thickness of the cylinder is 25-30 mm (excluding 25 mm), the welding current is 380-400 A (excluding 380 A), and the welding voltage is 41-43 V;

[0061] When the wall thickness of the cylinder is 30-35 mm (excluding 30 mm), the welding current is 400-420 A (excluding 400 A), and the welding voltage is 43-45 V (excluding 43 V).

[0062] Optionally, when the wall thickness of the cylinder is 10-20 mm, the welding wire swing amplitude is 0 mm (ie, the welding wire does not swing).

[0063] Optionally, when the wall thickness of the cylinder is 20 to 25 mm (excluding 20 mm), the welding wire swing amplitude is 8 to 12 mm.

[0064] Optionally, when the wall thickness of the cylinder is 25 to 35 mm (excluding 25 mm), the welding wire swing amplitude is 12 to 15 mm (excluding 12 mm).

[0065] Optionally, when the cylinder wall thickness is 10 to 35 mm, the carbon dioxide gas flow rate is 25 to 30 L / min (for example, 28 L / min).

[0066] As an optional implementation, in step 4), the post-weld treatment includes the following steps:

[0067] Use air gouging to clean and repair the arc starting position, arc extinction position, intermediate arc starting, arc extinction and joints; and / or

[0068] Use air gouging to remove defects in the weld, and then use carbon dioxide gas shielded welding to repair it.

[0069] In a first aspect, the present invention provides as an optional embodiment that the welding method is suitable for butt joint of cylinders with a pipe diameter of more than 4m and a pipe wall thickness of more than 10mm. The automatic welding method does not require back-planing.

[0070] As an optional implementation, the welding method is suitable for butt-joint circumferential welding of wind power pipe sections and thick-walled steel structure pipes.

[0071] In the present invention, the welding method can be applied to various types of cylindrical steel structures, for example, low-carbon steel of TMCP.

[0072] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0073] The beneficial effects brought by the present invention are as follows:

[0074] (1) The welding method of the cylinder girth weld provided by the present invention adopts gas-electric welding, has good welding quality, and changes from multi-layer multi-pass welding to single-pass welding, thereby reducing the probability of defects, ensuring the welding quality of ship structures, and accelerating the upgrading of the industry;

[0075] (2) The welding method of the present invention reduces the difficulty of welding and improves the overall welding efficiency. Taking the butt welding of a cylinder with a wall thickness of 30 mm as an example, the weld length is about 18 to 20 m. The existing multi-layer multi-pass welding requires 6 to 8 welds to fill the welds, and the welding speed is about 6 to 8 cm / min. The welding time takes a total of 2 to 3 days. The welding method of the present invention only requires 1 weld to fill the welds, and the overall welding time takes only 4 to 6 hours, which improves the efficiency by 500% to 1000%;

[0076] (3) The welding method of the present invention can reduce energy usage and significantly improve welding quality. Only one weld is required to fill the applicable thickness. Compared with the existing multi-layer and multi-pass welding, the number of weld joints and weld separations is reduced, thereby reducing the probability of porosity and cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 A schematic diagram showing the structure and dimensions of a code plate in an embodiment of the present invention;

[0078] Figure 2 A schematic diagram showing the structure of a V-shaped welding groove in an embodiment of the present invention;

[0079] Figure 3 A schematic diagram showing the structure of a double V-shaped welding groove in an embodiment of the present invention;

[0080] Figure 4 A schematic diagram showing the structure of an arc starting support plate according to an embodiment of the present invention; Figure 5 A schematic diagram showing the installation structure of the gasket and the slider during the welding process of the cylinder ring weld in Example 1 of the present invention; Figure 6 A schematic diagram showing the internal structure of the cylinder ring weld during the welding process in Example 1 of the present invention.

[0081] in, Figure 1 The dimensions are in mm;

[0082] In the accompanying drawings, t is the thickness of the cylinder, θ is the groove angle, α is the groove angle, g is the assembly gap, h is the height of the blunt edge, L is the length of the arc-striking support plate, R is the outer diameter of the cylinder, and r is the inner diameter of the cylinder. DETAILED DESCRIPTION

[0083] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0084] Example 1

[0085] A welding method for a cylinder girth weld comprises the following steps.

[0086] S1: Preparation of accessories; prepare the base material, welding materials and auxiliary materials of the cylinder, and prepare the internal annular gasket, surface arc slider and double-sided welded internal arc slider according to the size of the cylinder.

[0087] The base material of the cylinder is low-carbon steel of TMCP, and a high-energy line welding test should be carried out to test the strength and low-temperature toughness of the coarse-grained zone in the heat-affected zone of the joint after the base material is subjected to high-energy line heat input, and acceptance should be carried out in accordance with standard requirements.

[0088] The internal annular liner and the surface arc-shaped copper slider are customized according to the size of the cylinder; specifically, the internal annular liner is made of ceramic as the main body and is reinforced with iron sheet on the outside, and the curvature is consistent with the inner ring of the cylinder; the main body of the surface arc-shaped slider is made of brass, and the curvature is consistent with the outer ring of the cylinder; the main body of the double-sided welded internal arc-shaped slider is made of brass, and the curvature is consistent with the inner ring of the cylinder; to adapt to the curvature of the cylinder, the height of the two sliders is controlled at 55-60mm.

[0089] S2: Preparation before welding: The preparation before welding includes assembling the butt joint of the cylinder and opening the welding groove. Specifically, it includes the following steps.

[0090] S21: During the assembly of the butt joint of the cylinder, an "H"-shaped code plate is installed on the back of the groove inside the cylinder. The center line of the groove of the "H"-shaped code plate must be aligned with the center of the groove during installation. The "H"-shaped code is installed at a distance of 300mm to 350mm and at least two "H"-shaped assembly codes are fixed. The structure and size of the code plate are as follows: Figure 1 shown.

[0091] S22: When opening the welding groove, select the welding groove shape (such as Figure 2 and Figure 3 As shown in Table 1), groove angle, assembly clearance and blunt edge.

[0092] Table 1 Groove shape, groove angle, assembly clearance and blunt edge height for different cylinder thicknesses

[0093]

[0094] In step S2, the pre-welding preparation further includes the following steps:

[0095] S23: Install the arc support plate: Install the arc support plate at the arc starting position to establish the gas-electric welding pool. The arc support plate should be consistent with the angle of the butt joint groove, and the length L of the arc support plate should be greater than 20% of the cylinder wall thickness or 20mm. The structure and size of the arc support plate are as follows: Figure 4 As shown;

[0096] S24: Set the misalignment of the joint installation: The misalignment of the joint installation should not exceed 1.5mm, and the local wave deformation unevenness of the pipe surface on one side of the installation track should not exceed 2mm within 0.5m. If there is an excess, it should be leveled. That is, the unevenness is ≤2mm / 0.5m joint; groove treatment and weld treatment: There should be no traces, transverse weld excess height and splashes on the surface within 30mm on both sides of the groove front, which may affect the relative movement of the copper slider, and the welding area should be cleaned; there should be no obstacles such as obstructions to gas and electric welding equipment on the left or right side of the weld;

[0097] S25: Install the gasket and slider: Press Figure 5 Install the liner and slider in the structure shown; the liner should be installed on the center line of the groove, the liner should be closely connected, and use the following method: Figure 1 The assembly code (or code plate) shown and the through-welding holes on the back member are used as supports to tighten the liner with a small pointed iron or pointed wood to make it close to the inner surface of the cylinder; the clamping pressure of the copper slider is controlled at 10 to 15 kgf.

[0098] S3: welding process; single-pass welding of the cylinder girth weld is performed by gas-electric welding; the welding process comprises the following steps:

[0099] S31. Connect water, electricity and gas, and confirm that the water pressure and gas flow meet the use requirements. The cooling water pressure is generally adjusted to 4MPa~4.5MPa.

[0100] S32. Adjust the arc voltage potentiometer, welding current potentiometer, and welding wire extension length control potentiometer to the preset positions. The welding gun angle is adjusted to keep the welding wire perpendicular to the horizontal plane, generally at an angle of about 8° to the arc surface of the cylinder. The welding wire extension length is 25mm to 35mm. Figure 6 Then press the start button to start welding, first build up a molten pool without the welding wire swinging, and after the molten pool is built up, the welding speed is controlled by the rolling speed of the rolling device under the swinging of the welding wire, wherein the rolling speed of the corresponding rolling device is selected according to the wall thickness of the cylinder, thereby controlling the welding speed, as shown in Table 2.

[0101] Table 2 Barrel wall thickness and welding speed

[0102]

[0103] Note: *The numerical range here does not include the front end point value; **The numerical range here does not include the back end point value.

[0104] During welding, the molten pool should be kept 2mm to 5mm below the lower end of the carbon dioxide outlet. At the same time, pay attention to adjusting the centering of the welding gun, the centering of the copper slider, and the clamping, as follows: Figure 6 During the welding process, the welding gun head is kept stationary, and the cylinder is rotated by the cylinder automatic positioner to perform gas-electric welding under carbon dioxide protective gas. The welding parameters are shown in Table 3 below.

[0105] Table 3 Gas-electric welding parameters

[0106]

[0107] Note: *The numerical range here does not include the front end point value; **The numerical range here does not include the back end point value.

[0108] In addition, during the welding process, the welding wire centering and weld heat distribution are observed at any time according to the actual groove and gap, and the welding parameters are corrected at any time. The arc is adjusted to the correct position at any time through mechanical devices. During the welding process, the welding machine maintains a constant wire extension state by sensing state changes.

[0109] When welding stops, press the stop button and the swing stop button to stop the positioner and wire feeding first, then extinguish the arc. After the molten pool solidifies, release the copper slider and remove the spatter on it, and remove the welding torch from the bracket.

[0110] Table 4 shows the relevant information of the welding materials and auxiliary materials used in this embodiment.

[0111] Table 4 Welding materials and auxiliary materials

[0112]

[0113] S4: Post-weld treatment; including the following steps:

[0114] S41: The arc starting position, arc extinction position, intermediate arc starting, arc extinction and joints should be cleaned and repaired with an air planer, and the repair length is about 100mm;

[0115] S42: Repair is done by carbon dioxide gas shielded welding;

[0116] S43: Various defects in the weld, such as undercut, pores, lack of fusion, and unformed, are removed with an air planer and then repaired with carbon dioxide gas shielded welding.

[0117] S5: Post-weld inspection; (taking 40mm thick EH36 joint as an example)

[0118] S51: All test data must meet the requirements of relevant classification societies (taking DNV classification society requirements as an example)

[0119] S52: Bending test: There is no defect larger than 3mm on the surface of the specimen, and the measured bending joint is qualified;

[0120] S53: Hardness test: The hardness value is not more than 350HV10, and the measured hardness value is between 150 and 250HV10;

[0121] S54: Impact test: The impact value at -20℃ should be greater than 34J, and the measured impact value at -40℃ is greater than 34J;

[0122] S55: Tensile test: The tensile strength is greater than the minimum requirement of the base material, and the measured tensile strength is 515MPa, which meets the standard requirements.

[0123] Example 2

[0124] The difference between this embodiment and embodiment 1 is that the wall thickness of the cylinder exceeds 40 mm, and double-sided welding is adopted during welding. Welding is first performed on the outside of the cylinder, the internal card code is removed, and the root is cleaned by air planing. The root of the inside of the cylinder is first filled with gas shielded welding using a magnetic crawling trolley flux-cored wire (i.e., base welding), and 2 to 3 passes are filled. The weld thickness is about 6 to 10 mm, and then gas-electric vertical welding is performed.

[0125] The gas-electric vertical welding method is the same as the method in Example 1.

[0126] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A welding method for a cylinder girth weld, characterized in that: The following steps are involved: 1) Accessories preparation: prepare the base material, welding materials and auxiliary materials of the cylinder, and prepare the internal annular gasket, surface arc slider and double-sided welded internal arc slider according to the size of the cylinder; 2) Preparation before welding: The preparation before welding includes setting the assembly gap, opening the welding groove, and opening a blunt edge at the narrow end of the welding groove; wherein, When the wall thickness t of the cylinder is 10mm≤t≤40mm, the assembly gap g is set to 3mm~10mm; When the wall thickness of the cylinder t>40mm, set the assembly gap g to 0mm; A single V-shaped groove or a double V-shaped groove is provided according to the wall thickness of the cylinder; wherein the groove angle θ of the single V-shaped groove is 35° to 40°; The double V-shaped groove includes an upper groove angle θ and a lower groove angle α, the upper groove angle θ is 30° to 35°, and the lower groove angle α is 35° to 40°; 3) Welding process: gas-electric welding is used to perform single-pass welding on the cylinder girth weld; in the welding process, carbon dioxide gas shielded welding is used for welding; 4) Post-weld treatment.

2. The welding method of cylinder girth weld according to claim 1, characterized in that: When preparing the cylinder base material, a large line energy welding test is carried out on the cylinder base material to test the strength and low-temperature toughness value of the coarse-grained zone in the heat-affected zone of the joint after the cylinder base material is subjected to large line energy heat input.

3. The welding method of cylinder girth weld according to claim 1, characterized in that: The welding materials include gas-electric welding wire and back-filled gas shielded welding wire; Optionally, the material grades of the gas-electric welding wire or the back-filled gas shielded welding wire include 4Y and 5Y; Optionally, the 4Y includes any one of A to E, AH32 to DH32, AH36 to H36, Q235A to Q235D, and Q355A to Q355D; Optionally, the 5Y includes any one of E, EH32-EH36, Q235E and Q355E.

4. The welding method of cylinder girth weld according to claim 1, characterized in that: The inner annular liner is mainly made of ceramic, and the outer part of the ceramic is reinforced with iron sheet; or / and The main body of the surface arc-shaped slider is made of brass and is used for single-sided welding of the cylinder ring weld; or / and The main body of the double-sided welding internal arc-shaped slider is made of brass and is used for double-sided welding of the cylinder ring weld; Optionally, the curvature of the inner annular liner, the curvature of the surface curved slider, and the curvature of the double-sided welded inner curved slider are all consistent with the inner ring of the cylinder; Optionally, the surface arc slider or the double-sided welded internal arc slider adapts to the curvature of the cylinder, and the height is perpendicular to the arc surface section and is controlled at 55 to 60 mm.

5. The welding method of cylinder girth weld according to claim 4, characterized in that: In the step 2), during the process of assembling the butt joint of the cylinder, the position of the butt joint of the cylinder is determined by installing a code plate on the back of the groove inside the cylinder; Optionally, there are at least two code plates; Optionally, the installation spacing of the code plates is 300 mm to 350 mm; Optionally, the code plate is an "H" shaped code.

6. The welding method of cylinder girth weld according to claim 1, characterized in that: The wall thickness of the cylinder is 10 mm ≤ t ≤ 28 mm, the shape of the welding groove is single V-shaped, the groove angle θ is 35° to 40°, the assembly gap g is 3 mm to 10 mm, and the root face height h is 0 to 1 mm; The wall thickness of the cylinder is 28 mm < t ≤ 30 mm, the shape of the welding groove is single V-shaped, the groove angle θ is 35° to 40°, the assembly gap g is 3 mm to 10 mm, and the root face height h is 0 to 1 mm; The wall thickness of the cylinder is 30 mm < t ≤ 40 mm, the shape of the welding groove is single V-shaped, the groove angle θ is 25° to 30°, the assembly gap g is 3 mm to 10 mm, and the root face height h is 0 to 1 mm; When the wall thickness of the cylinder is t > 40 mm, the shape of the welding groove is double V-shaped, the groove angle θ is 30° to 35°, the groove angle α is 35° to 40°, the assembly gap g is 0, and the root face height h is 0 to 1 mm.

7. The welding method for the circumferential weld of the cylinder according to any one of claims 1-6, characterized in that Said step 2) further includes the following steps: Install the arc starting backing plate, check the error range during installation, groove treatment, weld treatment, install the backing and install the copper slider; Optionally, the arc starting backing plate is installed at the starting arc position of the cylinder for establishing the gas shielded arc welding molten pool; Optionally, the arc starting backing plate includes a flat plate structure at the bottom and a triangular pyramid structure at the upper part. The height of the triangular pyramid is the same as the wall thickness of the cylinder, and the angle of the triangular pyramid is the same as the angle of the V-shaped groove; Optionally, before welding, the arc starting backing plate is installed perpendicular to the groove at the welding starting point and contacts the copper slider to form a "bowl" - shaped space to provide conditions for establishing the molten pool; Optionally, the length L of the arc starting backing plate is greater than 20% of the wall thickness of the cylinder; wherein, the length L of the arc starting backing plate includes the height of the triangular pyramid and the height of the flat plate; Optionally, in the inspection of the error range during installation, the error range during installation includes the following aspects: the misalignment of the joint installation does not exceed 1.5 mm, and the unevenness of the local waviness deformation of the pipe surface on one side of the installation track does not exceed 2 mm within a range of 0.5 m; Optionally, in the installation of the backing, the installation of the backing should be aligned with the center line of the groove, the backing pads should be closely connected, and the assembly code and the through - welding holes on the back - side member are used as small pointed irons or pointed woods for support to tightly press the backing against the inner surface of the cylinder; Optionally, in the installation of the slider, the pressing pressure of the slider during installation should be controlled at 10 - 15 kgf.

8. The welding method for the circumferential weld of the cylinder according to any one of claims 1-6, characterized in that In said step 3), the welding process includes the following steps: 31) Connect water, electricity, and gas, and confirm that the water pressure and gas flow rate meet the usage requirements; 32) Establish the molten pool and perform gas shielded arc welding using carbon dioxide gas shielded welding; Optionally, in said step 3), the molten pool is established without the wire oscillating; Optionally, in said step 3), after the molten pool is established, the welding speed is controlled by the rolling speed of the rolling device with the wire oscillating for welding; wherein, When the wall thickness of the cylinder is 10 - 14 mm, the welding speed is 10 - 12 cm / min; When the wall thickness of the cylinder is 14 to 20 mm (excluding 14 mm), the welding speed is 8 to 10 cm / min (excluding 10 cm / min); When the wall thickness of the cylinder is 20 to 25 mm (excluding 20 mm), the welding speed is 6 to 8 cm / min (excluding 8 cm / min); When the wall thickness of the cylinder is 25 to 35 mm (excluding 25 mm), the welding speed is 5 to 7 cm / min; Optionally, the process parameters of gas-electric welding are selected according to the wall thickness of the cylinder; specifically, When the wall thickness of the cylinder is 10-14 mm, the welding current is 300-320 A and the welding voltage is 32-34 V; When the wall thickness of the cylinder is 14 to 20 mm (excluding 14 mm), the welding current is 340 to 360 A, and the welding voltage is 34 to 36 V (excluding 34 V); When the wall thickness of the cylinder is 20-25 mm (excluding 20 mm), the welding current is 360-380 A (excluding 360 A), and the welding voltage is 36-40 V (excluding 36 V); When the wall thickness of the cylinder is 25 to 30 mm (excluding 25 mm), the welding current is 380 to 400 A (excluding 380 A), and the welding voltage is 41 to 43 V; When the wall thickness of the cylinder is 30-35 mm (excluding 30 mm), the welding current is 400-420 A (excluding 400 A), and the welding voltage is 43-45 V (excluding 43 V); When the wall thickness of the cylinder is 10-20 mm, the welding wire swing amplitude is 0 mm; When the wall thickness of the cylinder is 20 to 25 mm (excluding 20 mm), the welding wire swing amplitude is 8 to 12 mm; When the wall thickness of the cylinder is 25 to 35 mm (excluding 25 mm), the welding wire swing amplitude is 12 to 15 mm (excluding 12 mm); When the cylinder wall thickness is 10-35 mm, the carbon dioxide gas flow rate is 25-30 L / min.

9. The welding method of cylinder girth weld according to claim 8, characterized in that: In the step 4), the post-weld treatment comprises the following steps: Use air gouging to clean and repair the arc starting position, arc extinction position, intermediate arc starting, arc extinction and joints; and / or Use air gouging to remove defects in the weld, and then use carbon dioxide gas shielded welding to repair it.

10. An application of the welding method for a cylinder girth weld according to any one of claims 1 to 9, characterized in that: The welding method is suitable for butt joint of cylinders with a pipe diameter of more than 4 m and a pipe wall thickness of more than 10 mm; it is particularly suitable for butt joint circumferential seam welding of wind power pipe sections and thick-walled steel structure pipes.

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