A method for welding a cylindrical ring weld and applications thereof

Abstract

This invention provides a welding method and application for circumferential welds on cylindrical bodies, belonging to the field of pipeline welding. The welding method includes the following steps: 1) accessory preparation; 2) pre-welding preparation: including setting the assembly gap, opening the welding bevel, and opening the blunt edge; wherein, when the wall thickness t of the cylindrical body is 10mm≤t≤40mm, the assembly gap g is 3mm~10mm; when the wall thickness t>40mm, the assembly gap g is 0mm; opening a single V-groove or a double V-groove; the bevel angle θ of the single V-groove is 35°~40°; the upper bevel angle θ of the double V-groove is 30°~35°, and the lower bevel angle α is 35°~40°; 3) performing single-pass welding of the circumferential weld on the cylindrical body using gas electric welding; during the welding process, carbon dioxide gas shielded welding is used; 4) post-weld treatment. This invention uses gas electric welding and single-pass welding to reduce welding defects in the circumferential weld of the cylindrical body, improving welding quality and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of pipeline welding technology, and specifically relates to a welding method and application for circumferential welds on cylindrical bodies. Background Technology

[0002] Currently, for butt welding of pipes with thick walls and large diameters, CO2 gas shielded welding and submerged arc welding are commonly used for multi-layer, multi-pass welding. However, existing technologies have relatively low heat input, generally only reaching a maximum of 80 kJ / cm, resulting in a large welding workload, low efficiency, and long welding cycles. Furthermore, multi-layer, multi-pass welding leads to unstable welding quality, easily causing problems such as porosity, slag inclusions, and incomplete fusion.

[0003] Gas-fired welding is a widely used welding process that offers stable weld quality and high efficiency. Applying gas-fired welding to butt welding of thick-walled, large-diameter pipes can enhance competitiveness, improve overall efficiency, reduce material and energy consumption, and lower overall costs. Summary of the Invention

[0004] This invention provides a welding method and application for circumferential welds on cylindrical (or pipe) structures. The method employs gas-electric welding to perform single-pass welding on the circumferential weld of the cylindrical structure. This method is suitable for pipe connections with a diameter of 4 meters or more and a thickness of 10 mm or more. This welding method can be applied to various cylindrical steel structures, reducing operational difficulty, increasing welding efficiency, and achieving a high weld qualification rate. It reduces the probability of porosity, slag inclusions, and cracks. Except for the weld joint, single-pass welding can achieve a 100% qualification rate for a single weld.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

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

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

[0008] 2) Pre-welding preparation: The pre-welding preparation includes setting the assembly gap (or assembling the pipe butt joint), opening the welding bevel, and opening the blunt edge;

[0009] 3) Welding process: The circumferential weld of the cylinder is welded in a single pass using gas electric welding; during the welding process, carbon dioxide gas shielded welding is used.

[0010] 4) Post-weld treatment.

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

[0012] As an optional implementation, the welding materials include gas-electric welding wire and back-filled gas-shielded welding wire.

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

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

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

[0016] As an alternative implementation, the gas-electric welding wire and the back-filled gas-shielded welding wire can be made of the same material grade.

[0017] As an optional implementation, the inner annular liner is mainly made of ceramic, and the ceramic is reinforced with sheet metal on the outside; optionally, the curvature of the inner 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 cylindrical circumferential weld.

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

[0020] As an optional implementation, the main body of the double-sided welded internal arc-shaped slider is made of brass and is used for double-sided welding of the cylindrical circumferential 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-shaped slider or the double-sided welded internal arc-shaped slider adapts to the curvature of the cylinder, and its height is controlled at 55-60mm perpendicular to the arc surface tangent.

[0023] As an optional implementation, in step 2), during the assembly of the cylinder butt joint, the position of the cylinder butt joint is determined by installing a code plate on the back of the inner bevel of the cylinder.

[0024] As an optional implementation manner, in step 2), there are at least 2 code plates.

[0025] As an optional implementation manner, in step 2), the installation distance between the code plates is 300 mm to 350 mm.

[0026] As an optional implementation manner, in step 2), the code plate is an "H" - shaped code.

[0027] As an optional implementation manner, 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 be 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 be 0 mm.

[0030] As an optional implementation manner, in step 2), the welding groove is opened as a single V - shaped groove or a double V - shaped 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 optional implementation manner, in step 2), the groove angle θ of the single V - shaped groove is 35° to 40° (for example, 35° or 38°).

[0032] As an optional implementation manner, in step 2), 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° (for example, 30° or 35°), and the lower groove angle α is 35° to 40° (for example, 35° or 38°).

[0033] As an optional implementation manner, 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 - shaped 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 optional implementation manner, 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 - shaped 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 bevel is a single V-shape, the bevel 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 > 40 mm, the shape of the welding bevel is double V-shaped, the bevel angle θ is 30° to 35°, the bevel angle α is 35° to 40°, the assembly clearance g is 0, and the blunt edge h is 0 to 1 mm.

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

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

[0039] As an optional implementation, the arc-initiating support plate includes a bottom flat plate structure and an upper triangular pyramid structure. 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 bevel.

[0040] As an alternative implementation, before welding, the arc-starting plate is installed perpendicular to the bevel at the welding start point, in contact with the copper slider, forming a "bowl"-shaped space, which provides conditions for the establishment of the molten pool.

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

[0042] As an optional implementation method, the error range during installation 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 a range of 0.5m. That is, unevenness ≤ 2mm / 0.5m joint.

[0043] As an optional implementation, the beveling process includes cleaning surface debris within a 30mm radius on both sides of the bevel face to keep the area to be welded clean.

[0044] As an alternative implementation, the weld treatment includes ensuring that there are no obstructions on the left or right side of the cylinder surface that would hinder the gas welding equipment.

[0045] As an alternative implementation, the installation of the gaskets should be aligned with the center line of the bevel, the gaskets should be tightly connected, and the small pointed irons or pointed wooden pieces on the assembly brackets and back side components should be used as supports to tighten the gaskets so that they are tightly attached to the inner surface of the cylinder.

[0046] As an alternative implementation, the slider installation should control the slider clamping pressure to be between 10 and 15 kgf (e.g., 12 kgf).

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

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

[0049] 32) Establish a molten pool and perform gas electric welding using carbon dioxide gas shielded welding.

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

[0051] As an optional implementation, in step 3), after the molten pool is established, the welding speed is controlled by the rolling speed of the rolling device under the oscillation of the welding wire. 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 wall thickness of the cylinder is 10-14 mm, the welding speed is 10-12 cm / min;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0067] Air gouging is used to clean and repair the arc initiation and extinguishing points, as well as the intermediate arc initiation, extinguishing, and joint areas; and / or

[0068] Defects in the weld are removed by air gouging, and then repaired by carbon dioxide gas shielded welding.

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

[0070] As an optional implementation, the welding method is applicable to butt joint welding of wind turbine pipe sections and steel structure pipes with large wall thickness.

[0071] In this invention, the welding method can be applied to various cylindrical steel structures, such as low-carbon steel for TMCP.

[0072] In this invention, the above-mentioned technical features can be freely combined to form new technical solutions, provided they do not conflict with each other.

[0073] The beneficial effects of this invention are as follows:

[0074] (1) The welding method for the cylindrical circumferential weld provided by the present invention adopts gas electric welding, which has good welding quality. It changes the multi-layer and multi-pass welding to single-pass welding, thereby reducing the probability of defects, ensuring the welding quality of ship structure, and accelerating the upgrading and renewal of industry.

[0075] (2) The welding method of the present invention reduces the welding difficulty and improves the overall welding efficiency. Taking the butt welding of a cylinder with a wall thickness of 30mm as an example, the weld length is about 18 to 20m. Existing multi-layer and multi-pass welding requires 6 to 8 welds to fill the weld, the welding speed is about 6 to 8cm / min, and the total welding time is 2 to 3 days. The welding method of the present invention only requires 1 weld to fill the weld, and the total welding time is 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 consumption and significantly improve welding quality. Only one weld filler is required under the applicable thickness. Compared with the existing multi-layer and multi-pass welding, the weld joint and weld separation are reduced, thus reducing the probability of porosity and cracks. Attached Figure Description

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

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

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

[0080] Figure 4 This is a schematic diagram of the arc-initiating support plate in an embodiment of the present invention;

[0081] Figure 5 This diagram illustrates the installation structure of the gasket and slider during the welding process of the cylindrical circumferential weld in Embodiment 1 of the present invention.

[0082] Figure 6 This is a schematic diagram showing the internal structure of the cylindrical circumferential weld during the welding process in Embodiment 1 of the present invention.

[0083] in, Figure 1 The units for dimensions are in mm;

[0084] In the attached figures, t represents the thickness of the cylinder, θ represents the bevel angle, α represents the bevel angle, g represents the assembly clearance, h represents the height of the blunt edge, L represents the length of the arc-starting support plate, R represents the outer diameter of the cylinder, and r represents the inner diameter of the cylinder. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0086] Example 1

[0087] A welding method for a cylindrical circumferential weld seam includes the following steps.

[0088] S1: Accessory Preparation; Prepare the base material for the cylinder, welding materials, and auxiliary materials, and prepare the internal annular gasket, surface arc-shaped slider, and double-sided welded internal arc-shaped slider according to the cylinder dimensions. Among these,

[0089] The base material of the cylinder is low-carbon steel with TMCP, and a high heat input welding test should be conducted to test the strength and low-temperature toughness of the coarse-grained zone of the joint after the base material is subjected to high heat input, and acceptance should be carried out in accordance with the standard requirements.

[0090] 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 reinforced with sheet metal on the outside, with the curvature consistent with the inner ring of the cylinder. The surface arc-shaped slider is made of brass as the main body, with the curvature consistent with the outer ring of the cylinder. The double-sided welded internal arc-shaped slider is made of brass as the main body, with the curvature consistent with the inner ring of the cylinder. To adapt to the curvature of the cylinder, the height of the two types of sliders is controlled between 55 and 60 mm.

[0091] S2: Pre-welding preparation; the pre-welding preparation includes assembling the cylinder butt joint and opening the welding bevel. Specifically, it includes the following steps.

[0092] S21: During the assembly of the cylinder body butt joint, an "H"-shaped code plate shall be installed on the back of the inner bevel of the cylinder body. The center line of the groove of the "H"-shaped code plate must be aligned with the center of the bevel during installation. The "H"-shaped codes shall be installed at intervals of 300mm to 350mm, and at least two "H"-shaped assembly codes shall be fixed. The structure and dimensions of the code plate are as follows: Figure 1 As shown.

[0093] S22: When creating the welding bevel, select the welding bevel shape according to the wall thickness (or girth) of the cylinder (e.g., Figure 2 and Figure 3 (As shown), bevel angle, assembly clearance, and blunt edge, see Table 1.

[0094] Table 1. Bevel shape, bevel angle, assembly clearance, and blunt edge height for different cylinder thicknesses.

[0095]

[0096] In step S2, the pre-welding preparation also includes the following steps:

[0097] S23: Install an arc-starting plate: Install an arc-starting plate at the arc-starting position to establish the molten pool for gas-electric welding. The arc-starting plate should be aligned with the bevel angle of the butt joint, and its length L should be greater than 20% or 20mm of the cylinder wall thickness. The structure and dimensions of the arc-starting plate are as follows: Figure 4 As shown;

[0098] S24: Joint installation misalignment setting: The joint installation misalignment should not exceed 1.5mm. The local wavy deformation unevenness of the pipe surface on one side of the installation track should not exceed 2mm within 0.5m. If it exceeds the tolerance, it should be leveled. That is, unevenness ≤ 2mm / 0.5m joint; Beveling and weld treatment: There should be no burrs, transverse weld reinforcement, spatter, or other debris affecting the relative movement of the copper slider within 30mm on both sides of the beveling face, and the welding area should be cleaned; there should be no obstructions such as gas welding equipment on the left or right side of the cylinder surface of the weld.

[0099] S25: Install the pads and sliders: Press Figure 5 The structure shown includes a liner and a slider; the liner should be aligned with the bevel centerline, and the liner should be tightly connected, utilizing methods such as... Figure 1 The assembly brackets (or brackets) and the weld holes on the back side components are used as support for the small pointed iron or pointed wood to tighten the pads so that they are in close contact with the inner surface of the cylinder; control the clamping pressure of the copper slider to be 10-15 kgf.

[0100] S3: Welding process; single-pass welding of the cylindrical circumferential weld is performed using gas-electric welding; the welding process includes the following steps:

[0101] S31. Connect water, electricity, and gas, and confirm that the water pressure and gas flow rate meet the usage requirements. The cooling water pressure is generally adjusted to 4MPa to 4.5MPa.

[0102] S32. Adjust the arc voltage potentiometer, welding current potentiometer, and wire extension length control potentiometer to their predetermined positions. Adjust the welding torch angle to ensure the welding wire is perpendicular to the horizontal plane, generally at approximately 8° to the arc surface of the cylinder. The wire extension length should be 25mm–35mm. Figure 6 As shown in Table 2. Then press the start button to begin welding. First, establish the molten pool without oscillating the welding wire. After the molten pool is established, the welding speed is controlled by the rolling speed of the rolling device while the welding wire oscillates. The rolling speed of the rolling device is selected according to the wall thickness of the cylinder to control the welding speed, as shown in Table 2.

[0103] Table 2. Cylinder Wall Thickness and Welding Speed

[0104]

[0105] Note: *The numerical range here does not include the values ​​at the leading edge; **The numerical range here does not include the values ​​at the trailing edge.

[0106] During welding, the molten pool should be kept 2mm to 5mm below the lower end face of the carbon dioxide outlet. Simultaneously, pay attention to adjusting the centering of the welding torch, the copper slider, and the clamping position, as follows: Figure 6 As shown in Table 3 below, during the welding process, the welding torch head is kept stationary, and the cylinder is rotated using an automatic cylinder positioner to perform gas electric welding under carbon dioxide shielding gas.

[0107] Table 3 Welding parameters for gas electric welding

[0108]

[0109] Note: *The numerical range here does not include the values ​​at the leading edge; **The numerical range here does not include the values ​​at the trailing edge.

[0110] Furthermore, during the welding process, the alignment of the welding wire and the heat distribution of the weld are constantly observed based on the actual bevel and gap, and welding parameters are adjusted accordingly. The arc is constantly adjusted to the correct position using mechanical devices. During the welding process, the welding machine maintains a constant welding wire elongation by sensing changes in the welding conditions.

[0111] When welding stops, press the stop button and the swing stop button to first stop the positioner and wire feeding, 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 support.

[0112] Table 4 shows the relevant information of the welding materials and auxiliary materials used in this embodiment.

[0113] Table 4 Welding Materials and Auxiliary Materials

[0114]

[0115] S4: Post-weld treatment; including the following steps:

[0116] S41: The arc starting point, arc ending point, intermediate arc starting point, arc ending point, and joint should all be cleaned and repaired with air gouging, with a repair length of approximately 100mm.

[0117] S42: Repairs are performed using carbon dioxide gas shielded welding;

[0118] S43: Various defects in the weld, such as undercut, porosity, lack of fusion, and incomplete formation, are removed by air gouging and then repaired by carbon dioxide gas shielded welding.

[0119] S5: Post-weld inspection; (taking a 40mm thick EH36 joint as an example)

[0120] S51: All test data must meet the requirements of the relevant classification society (taking DNV classification society requirements as an example).

[0121] S52: Bending test: The sample surface has no defects larger than 3mm, and the measured bending joint is qualified;

[0122] S53: Hardness test: Hardness value not greater than 350HV10, actual measured hardness value between 150 and 250HV10;

[0123] S54: Impact test: The impact value at -20℃ should be greater than 34J, and the measured impact value at -40℃ should be greater than 34J.

[0124] S55: Tensile test: The tensile strength is greater than the minimum requirement of the base material. The measured tensile strength is 515 MPa, which meets the standard requirements.

[0125] Example 2

[0126] The difference between this embodiment and embodiment 1 is that the wall thickness of the cylinder exceeds 40mm. Double-sided welding is used during welding. Welding is first performed on the outside of the cylinder. The internal clips are removed, and the root is cleaned by air gouging. The root inside the cylinder is filled (i.e., root pass welding) using a magnetic crawling trolley flux-cored welding wire gas shielded welding. 2 to 3 passes are filled, and the weld thickness is about 6 to 10mm. Then, gas electric vertical welding is performed.

[0127] The gas-electric vertical welding method is the same as that in Example 1.

[0128] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A welding method for a cylindrical circumferential weld, characterized in that, It includes the following steps: Step 1), fitting preparation: Prepare the cylinder base material, welding materials and auxiliary materials, and prepare the internal annular gasket and surface arc-shaped slider according to the size of the cylinder; Step 2), preparation before welding: The preparation before welding includes setting the assembly gap, opening the welding groove, and opening the root face at the narrow end of the welding groove; among which, Open a single V-shaped groove according to the wall thickness of the cylinder; among which, When 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° - 40°, the assembly gap g is 3 mm - 10 mm, and the root face height h is 0 - 1 mm; When 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° - 40°, the assembly gap g is 3 mm - 10 mm, and the root face height h is 0 - 1 mm; When 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° - 30°, the assembly gap g is 3 mm - 10 mm, and the root face height h is 0 - 1 mm; Step 2) also includes the following steps: Install the arc starting support plate, check the error range during the installation process, groove treatment, weld treatment, install the gasket and install the slider; the arc starting support plate includes a flat 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, the angle of the triangular pyramid is the same as the angle of the V-shaped groove, and the arc starting support plate is installed at the starting position of the cylinder for the establishment of the gas electric welding molten pool; Step 3), welding process: Use the gas electric welding method to carry out single-pass welding on the circumferential weld of the cylinder; during the welding process, use carbon dioxide gas shielded welding for welding; it includes the following steps: Step 3-1), Connect water, electricity, and gas, and confirm that the water pressure and gas flow reach the usage requirements; Step 3-2), Establish a molten pool without the wire oscillating and carry out gas electric welding; among which, after the molten pool is established, control the welding speed by the rolling speed of the rolling device while the wire is oscillating for welding; 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, the welding voltage is 32 - 34 V, and the welding speed is 10 - 12 cm / min; When the wall thickness of the cylinder is 14 - 20 mm and does not include 14 mm, the welding current is 340 - 360 A, the welding voltage is 34 - 36 V and does not include 34 V, and the welding speed is 8 - 10 cm / min and does not include 10 cm / min; When the wall thickness of the cylinder is 20 - 25 mm and does not include 20 mm, the welding current is 360 - 380 A and does not include 360 A, the welding voltage is 36 - 40 V and does not include 36 V, and the welding speed is 6 - 8 cm / min and does not include 8 cm / min; When the wall thickness of the cylinder is 25~30 mm (excluding 25 mm), the welding current is 380~400 A (excluding 380 A), the welding voltage is 41~43 V, and the welding speed is 5~7 cm / min. 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 20~25 mm (excluding 20 mm), the welding wire swing amplitude is 8~12 mm. When the wall thickness of the cylinder is 25~35 mm (excluding 25 mm), the welding wire swing is 12~15 mm (excluding 12 mm). When the wall thickness of the cylinder is 10~35 mm, the carbon dioxide gas flow rate is 25~30 L / min; Step 4), post-weld treatment.

2. The welding method for the circumferential weld of the cylinder according to claim 1, characterized in that, When preparing the base material for the cylinder, a high heat input welding test is conducted on the base material to test the strength and low-temperature toughness of the coarse-grained zone of the heat-affected zone of the joint after the base material is subjected to high heat input.

3. The welding method for the circumferential weld of the cylinder according to claim 1, characterized in that, The welding material includes gas-electric welding wire; the material grades of the gas-electric welding wire include 4Y and 5Y.

4. The welding method for the circumferential weld of the cylinder according to claim 3, characterized in that, The 4Y includes any one of A~E, AH32~DH32, AH36~H36, Q235A~Q235D, and Q355A~Q355D; The 5Y includes any one of E, EH32 to EH36, Q235E and Q355E.

5. The welding method for the circumferential weld of the cylinder according to claim 1, characterized in that, The internal annular liner is primarily made of ceramic, and the ceramic is reinforced with sheet metal; or / and The main body of the surface arc-shaped slider is made of brass and is used for single-sided welding of the cylindrical circumferential weld; or / and The curvature of the inner annular liner and the curvature of the surface arc-shaped slider are consistent with the inner ring of the cylinder. The surface arc-shaped slider adapts to the curvature of the cylinder, and its height is controlled at 55~60 mm perpendicular to the arc surface tangent.

6. The welding method for the circumferential weld of the cylinder according to claim 5, characterized in that, In step 2), during the assembly of the cylinder butt joint, the position of the cylinder butt joint is determined by installing a code plate on the back of the inner bevel of the cylinder; there are at least two code plates. The mounting distance between the code plates is 300 mm to 350 mm.

7. The welding method for the circumferential weld of the cylinder according to claim 6, characterized in that, The code plate is an "H" shaped code.

8. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, Before welding, the arc-starting plate is installed perpendicular to the bevel at the welding start point, in contact with the slider, forming a "bowl"-shaped space to provide conditions for the establishment of the molten pool.

9. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, The length L of the arc-initiating support plate is greater than 20% of the cylinder wall thickness; wherein, the length L of the arc-initiating support plate includes the height of the triangular pyramid and the height of the flat plate.

10. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, The error range during the installation process includes the following aspects: the misalignment of the joint installation does not exceed 1.5 mm, and the unevenness of the local wave deformation of the pipe surface on one side of the installation track does not exceed 2 mm within 0.5 m.

11. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, In the installation of the gasket, the gasket should be aligned with the center line of the bevel, the gaskets should be tightly connected, and the small pointed iron or pointed wood on the assembly bracket and the back side component should be used as support to tighten the gasket, so that the gasket is in close contact with the inner surface of the cylinder.

12. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, In the installation of the slider, the slider clamping pressure should be controlled at 10~15 kgf.

13. The welding method for the circumferential weld of the cylinder according to any one of claims 1-7, characterized in that, In step 4), the post-weld treatment includes the following steps: Air gouging is used to clean and repair the arc initiation and extinguishing points, as well as the intermediate arc initiation, extinguishing, and joint areas; and / or Defects in the weld are removed by air gouging, and then repaired by carbon dioxide gas shielded welding.

14. An application of a welding method for a cylindrical circumferential weld according to any one of claims 1-13, characterized in that, The welding method described herein is applicable to the butt joint circumferential welding of wind power pipe sections with a diameter of 4 m or more and a wall thickness of 10 mm or more, as well as steel structure pipes with large wall thickness.

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